Introduction; Types of corrosion (pitting, inter granular ...
Transcript of Introduction; Types of corrosion (pitting, inter granular ...
Ch 8 Corrosion
bull Introduction bullTypes of corrosion (pitting inter granular crevice Galvanic etc)
bullCorrosion prevention methods (selection of materials heat treatment design)
bull casting method inhibitors etc
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bull High cost incurred by countries toward the protection of surface degradation
Cost of corrosion It is defined and dangerous enemybull in India ~ 5 of GDP gtgtgt $ 30 billion ( in 2013 data)bull In USA ~ $ 260 Billion
bull Drinking water and sewage system ~ $ 36 Billion
9142019
EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 2
Why to study surface damage (degradation)
DIRECT COST OF CORROSIONExpensive material applicationOver designCost of repair (replacement)Application of anti corrosion means treatments
INDIRECT COST OF CORROSIONPoor design and unrepairable damageCost of labourLoss of productivityCost of equipment used in relation to corrosion inspection and prevention activities
2016 IMPACT study in which it estimates the global cost of corrosion to be US$25 trillion equivalent to roughly 34 percent of the global Gross Domestic Product (GDP)
bullchemicals
bullgases
bullliquid metals
bullcorrosive media
bullWood damage
by termites
bullMicrobes
Physical interactionChemical interaction
Biological interaction
bullStress
bullHeat
bullRadiation
Physical + chemical interaction
o The fracture or deformation of
materials due to stress under sea water
Chemical + Biological
interaction
o Bacteria action on the
surface of materials
Physical + biological
interaction
o The fracture or
deformation of materials
implanted in the human
body
Surface Degradation
(damage)
Mechanisms
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 3
DAMAGED CAUSED BY CORROSION
bullWhy Study Corrosion Metals
bullTo understand of the mechanisms and causes of corrosion
Take measures to prevent them from occurringbullEnvironment (fluid velocity temperatureand composition) - controlbullMaterial - selectionbullMaterial - protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 4
Damage due to corrosion on the bridge
Corrosion failures
often relate to the
material selection
and the
environment
Understanding the mechanisms of corrosion is the key to the development of a knowledge-
based design of corrosion resistant alloys and to the prediction of the long-term behavior of
metallic materials in corrosive environments9142019 5EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
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Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
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Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
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15
Forms of Corrosion Uniform Attack
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Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
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Galvanic Cell
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Galvanic Corrosion
Recommend on the connection in the photo
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Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
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21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
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22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
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Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
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The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
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Forms of Corrosion Erosion corrosion
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Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
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Forms of corrosion Erosion
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Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
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Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
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Forms of Corrosion Fretting corrosion
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Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
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Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
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35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
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36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
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Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
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Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
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Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
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40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
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41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
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Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
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43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
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RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
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Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
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DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
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Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
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Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
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Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
bull High cost incurred by countries toward the protection of surface degradation
Cost of corrosion It is defined and dangerous enemybull in India ~ 5 of GDP gtgtgt $ 30 billion ( in 2013 data)bull In USA ~ $ 260 Billion
bull Drinking water and sewage system ~ $ 36 Billion
9142019
EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 2
Why to study surface damage (degradation)
DIRECT COST OF CORROSIONExpensive material applicationOver designCost of repair (replacement)Application of anti corrosion means treatments
INDIRECT COST OF CORROSIONPoor design and unrepairable damageCost of labourLoss of productivityCost of equipment used in relation to corrosion inspection and prevention activities
2016 IMPACT study in which it estimates the global cost of corrosion to be US$25 trillion equivalent to roughly 34 percent of the global Gross Domestic Product (GDP)
bullchemicals
bullgases
bullliquid metals
bullcorrosive media
bullWood damage
by termites
bullMicrobes
Physical interactionChemical interaction
Biological interaction
bullStress
bullHeat
bullRadiation
Physical + chemical interaction
o The fracture or deformation of
materials due to stress under sea water
Chemical + Biological
interaction
o Bacteria action on the
surface of materials
Physical + biological
interaction
o The fracture or
deformation of materials
implanted in the human
body
Surface Degradation
(damage)
Mechanisms
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 3
DAMAGED CAUSED BY CORROSION
bullWhy Study Corrosion Metals
bullTo understand of the mechanisms and causes of corrosion
Take measures to prevent them from occurringbullEnvironment (fluid velocity temperatureand composition) - controlbullMaterial - selectionbullMaterial - protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 4
Damage due to corrosion on the bridge
Corrosion failures
often relate to the
material selection
and the
environment
Understanding the mechanisms of corrosion is the key to the development of a knowledge-
based design of corrosion resistant alloys and to the prediction of the long-term behavior of
metallic materials in corrosive environments9142019 5EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 6
Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
bullchemicals
bullgases
bullliquid metals
bullcorrosive media
bullWood damage
by termites
bullMicrobes
Physical interactionChemical interaction
Biological interaction
bullStress
bullHeat
bullRadiation
Physical + chemical interaction
o The fracture or deformation of
materials due to stress under sea water
Chemical + Biological
interaction
o Bacteria action on the
surface of materials
Physical + biological
interaction
o The fracture or
deformation of materials
implanted in the human
body
Surface Degradation
(damage)
Mechanisms
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 3
DAMAGED CAUSED BY CORROSION
bullWhy Study Corrosion Metals
bullTo understand of the mechanisms and causes of corrosion
Take measures to prevent them from occurringbullEnvironment (fluid velocity temperatureand composition) - controlbullMaterial - selectionbullMaterial - protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 4
Damage due to corrosion on the bridge
Corrosion failures
often relate to the
material selection
and the
environment
Understanding the mechanisms of corrosion is the key to the development of a knowledge-
based design of corrosion resistant alloys and to the prediction of the long-term behavior of
metallic materials in corrosive environments9142019 5EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 6
Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
DAMAGED CAUSED BY CORROSION
bullWhy Study Corrosion Metals
bullTo understand of the mechanisms and causes of corrosion
Take measures to prevent them from occurringbullEnvironment (fluid velocity temperatureand composition) - controlbullMaterial - selectionbullMaterial - protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 4
Damage due to corrosion on the bridge
Corrosion failures
often relate to the
material selection
and the
environment
Understanding the mechanisms of corrosion is the key to the development of a knowledge-
based design of corrosion resistant alloys and to the prediction of the long-term behavior of
metallic materials in corrosive environments9142019 5EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 6
Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Damage due to corrosion on the bridge
Corrosion failures
often relate to the
material selection
and the
environment
Understanding the mechanisms of corrosion is the key to the development of a knowledge-
based design of corrosion resistant alloys and to the prediction of the long-term behavior of
metallic materials in corrosive environments9142019 5EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 6
Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
CORROSION FUNDAMENTALS
Scientific definition
bull Electrochemical deterioration of materials by chemical interaction with their environmentbull The term corrosion is sometimes also applied to the degradation of plastics
concrete and wood but generally refers to metals
bull Degradation implies deterioration of physical properties of the material
o weakening of the material due to a loss of cross-sectional area
o shattering of a metal due to hydrogen embrittlement
o cracking of a polymer due to sunlight exposure
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 6
Practical definition Tendency of metal to reverting back to its natural startPure iron (Fe) to iron ore (Fe2O3)
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Causes of Corrosion
bull It involves four factors
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 7
Mechanical factor (Stress)
Thermodynamics factor (Material)
Metallurgical factor (Material)
Electrochemical factor(rate)
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Causes of Corrosion
bull Three conditions must exist simultaneously in order for the corrosion to occur
1 The presence of an anode and a cathode This occur when two dissimilar metals or two regions of differential electrolyte concentration create a difference in electrical potential
2 A metallic connector between the anode and the cathode
3 An electrolyte such as water
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 8
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
How corrosion occurbull The source of all corrosion is an electrochemical cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 9
electrochemical cell
930min ndash 1955min
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Corrosion - Classifications
bull Direct chemical attack
bull Battery acid residual flux deposits entrapped caustic cleaning solutions
bull Electrochemical attack
bull Requires a medium (usually water) that conducts tiny current of electricity
bull More active metal becomes anodic amp less active metal becomes cathodic
bull The greater the difference in electrical potential (dissimilar metals) the greater the corrosion
bull Most common cause of corrosion
bull Environment causing degradation
bull Gas and Vapor environment
bull Aqueous environment
bull Stress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 10
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Environmental severity factors that influence corrosion
These include but are not limited to
bullTemperature
bullTime-of-Wetness
bullPresence of chloride
bullPH
bull Industrial pollutants
bullUV radiation
bullMicrobiological activity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 11
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Corrosion classification Manner in which it is manifest
bull Metallic corrosion is sometimes classified into eight forms
bulluniform
bullPitting
bullcrevice
bullgalvanic
bull intergranular
bullselective leaching
bullerosionndashcorrosion and
bullstress corrosion9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 12
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 13
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 14
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
15
Forms of Corrosion Uniform Attack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Galvanic
bull Two metals or alloys having different compositions are electrically coupled while exposed to an electrolyte
bull The less noble or more reactive anode in the particular environment will experience corrosion
bull The more inert metal the cathode will be protected from corrosion
bull Eg Steel screws corrode when in contact with brass in a marine environment
Copper and steel tubing are joined in a domestic water heater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 16
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Galvanic Cell
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 17
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 18
Galvanic Corrosion
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Recommend on the connection in the photo
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 19
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Galvanic Corrosion Demetallification amp Concentration Cell
bull Alloy or a metal containing impurities
bull Brass Zinc = anode Copper = cathodebull Zinc corrode [Dezincification]
bull Pearlitic steel Ferrite = anode Cementite=cathodebull Ferrite corroded
bull Cast Iron iron = anode graphite = cathodebull Iron corroded [Graphitisation]
Drop of
H2O
Greatest
amount of
dissolved
oxygen
AnodeCathode
bull More concentrated electrolyte
bull Least concentration of oxygen
bull Dilute electrolyte
bull High concentration of oxygen
Demetallification
Concentration Cell
bullAnode end
bullCathode end
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 20
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
21
Forms of Corrosion Pitting corrosion
bull Localized nature
bull Coring mixture of phases and residual stress
bull Different electrical potential occur at metal surface
bull Thus presence of electrolyte established galvanic cell with more anodic portion of the surface is attacked at localized site
Corrosion pits can also be harmful by acting as
stress risers Fatigue and stress corrosion cracking
may initiate at the base of corrosion pits
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
22
Forms of Corrosion Pitting
Pitting Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Microscopic Image of Pitting corrosion Once the corrosion products are cleaned away from the metal surface
It has a great impact on the structural integrity
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 23
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Crevice
bull Describes two modes of localized corrosionsbull 1The physical situation where electrolyte
is trapped and not drained out
bull 2 Difference in the concentration of ions in the electrolyte
consequence of concentration
differences of ions or dissolved
gases in the electrolyte solution and
between two regions of the same
metal piece
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 24
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
The chronology of a Crevice
Stage One induction
At time zero the oxygen
content in the water
occupying a crevice is equal
to the level of soluble
oxygen and is the same
everywhere
Stage Two Restricted Convection
Difficult access caused by the crevice
geometry oxygen consumed by
normal uniform corrosion is very soon
depleted in the crevice The corrosion
reactions now specialize in the crevice
(anodic) and on the open surface
(cathodic)
Stage Three Obstruction
and Electro migration
bullThe metal ions produced by the
anodic corrosion reaction readily
hydrolyze giving off protons (acid)
and forming corrosion products
The pH in a crevice can reach
very acidic values sometimes
equivalent to pure acids 9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 25
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of corrosion Erosion
bull Flow removes protective layer
bull New protective layer forms using up metal
bull Promoted bybull High flow
bull Turbulent conditions
bull Particulates in fluid
bull Erosionndashcorrosion is commonly found in piping especially at bends elbows and abrupt changes in pipe diametermdashpositions where the fluid changes direction or flow suddenly becomes turbulent
bull Propellers turbine blades valves and pumps are also susceptible to this form of corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 26
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Erosion corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 27
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of corrosion Erosion
bull Four Categories
bull 1 Solid particle erosion
bull Solid particle carried by gas
bull Corrosion rate = f(velocity size shape strike angle) of particle
bull Ductile materials 20 to 30 OC
bull Brittle materials 90 OC
bull 2 Slurry erosion
bull Liquid stream carry particle against metal surface
bull 3 Liquid droplet erosion
bull Liquid droplets striking metal surface causing plastic depressions
bull Stream turbines and AC flying at high speed through rainstorm
bull 4 Cavitation
bull Propellers and impellers turbine blades valves and pumps at (suction end) also susceptible to this form of corrosion
Sever deterioration
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 28
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of corrosion Erosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 29
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Cavitation Erosion
Cavitation occurs when a fluids
operational pressure drops below its
vapor pressure causing gas pockets
and bubbles to form and collapse
This form of corrosion will eat out the volutes and impellers of centrifugal
pumps amp valve seats It will contribute to other forms of erosion corrosion
such as found in elbows and tees
Cavitation should be designed out by reducing hydrodynamic pressure
gradients and designing to avoid pressure drops below the vapor pressure of
the liquid and air ingress
bull Mechanically Aided Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 30
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Fretting corrosion
bull It refers to corrosion damage at the asperities under the category of erosion corrosion
bull of contact surfaces
bullMechanically Aided Corrosion
bullOccurs when mating parts have little relative motion
bullSplined shaft Keyed shaft pressed fittings
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 31
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Fretting corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 32
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Intergranular
bullDue to difference in the electrical potential with in the metal itself ( Similar to pitting)
bullThe electrical difference is between the grain boundary and the grain ndash causing the higher corrosion rate at the grain boundaries
bullThis potential difference is because of difference in composition between the two areas
bull Improperly heat treated stainless steel
bullMore chromium precipitation at the grain boundary and not enough chromium within the grain
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 33
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Forms of Corrosion Intergranular Corrosion
Intergranular Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 34
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
35
SL = Short longitudinal
ST = Short transverse
LT = Longitudinal transverse
Wrought
aluminum
alloys
Forms of Corrosion Intergranular
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
36
Forms of Corrosion Intergranular
Intergranular corrosion is an especially severe problem in the
welding of stainless steels when it is often termed weld decay
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Selective leaching
bull Is found in solid solution alloys and occurs when one element or constituent is preferentially removed as a consequence of corrosion processes
bullDealloying
bull intragranular Dealloying
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 37
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Environmental cracking
bull A corrosion cracking caused by a combination of conditions
bull Stress Corrosion Cracking (SCC) - Results from the combined action of an applied tensile stress and a corrosive environment
bull SCC = Tensile stress + corrosive environment bull Corrosion fatigue - Result of the combined action of an alternating or
cycling stresses and a corrosive environmentbull Hydrogen embrittlement
bull Stress that cause environmental cracking arise from
bull Residual cold work welding grinding thermal treatment or may be externally applied during service and to be effective must be tensile (as opposed to compressive)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 38
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Environmental cracking
Stress Corrosion Cracking
Fatigue stress
corrosion Cracking
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 39
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
40
Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
41
Hydrogen embrittlement
bull Hydrogen-induced cracking and hydrogen stress cracking
bull Various metal alloys specifically some steels experience a significant reduction in ductility and tensile strength when atomic hydrogen (H) penetrates into the material
bull Hydrogen in its atomic form (H) diffuses interstitially through the crystal lattice
bull Concentrations as low as several parts per million can lead to cracking
bull Hydrogen embrittlement does not affect all metallic materials equally The most vulnerable are high-strength steels titanium alloys and aluminium alloys
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Hydrogen embrittlement
bull Favorable conditions
bull pickling of steels in sulfuric acid
bull electroplating
bull presence of hydrogen-bearing atmospheres (including water vapor) at elevated temperatures such as during welding and heat treatments
bull presence of what are termed ldquopoisonsrdquo such as sulfur (ieH2S) and arsenic compounds
bull these substances retard the formation of molecular hydrogen and thereby increase the residence time of atomic hydrogen on the metal surface
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 42
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
43
RECAP Fatigue limit load in corrosion-assisted fatigue
bull Fracture is brittle and the cracks are most often transgranular as in stress-corrosion cracking but not branched
Corrosion-fatigue crack
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
RECAPhellipMain
forms of corrosion regrouped
by their ease of
recognition
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 44
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
gtgtgtgt GROUP ASSIGNMENT 01
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 45
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
bull Pitting helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR1
bull crevice helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR2
bull galvanichelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR3
bull intergranularhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR4
bull erosionndashcorrosion helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR5
bull Cavitation helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR6
bull FrettinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR7
bull stress corrosionhelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR8
bull selective leachinghelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR9
bull uniform helliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphelliphellipGR10
GROUP ASSIGNMENT 04 Sub date 21st September 19Write short note with practical example from the industryManner in which the corrosion is manifest and prevention methods
DIRECT COPY AND PASTE FROM ANY SOURCE9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 46
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Corrosion Prevention method
1 Selection of appropriate material for the environment concerned
bull Dissimilar metals not to form a cellbull Sacrificial protection ndash Mg or Zn
2 Selection of appropriate designbull Avoid potential crevicesbull Avoid Stress concentration
3 Modification of the environmentbull Corrosion inhibitors in liquids (chromate or phosphate
ions)bull Removing residual water vapor in packagebull include desiccant such as Silica gel within package
4 Use of protective coatingsbull Paintsbull Metallic coatings ndash Zinc coated steelbull Electroplating ndash Cr or Ni plating
Mg++
Fe pipeMg
e-
concrete
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 47
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Prevention of Corrosion-Related Failures of Metals
bull Material Selection
bull Corrosion allowance
bull Change in the environment
bull Change in the alloy or heat treatment
bull Design change
bull Use of galvanic protection (cathodic protection amp anodic potection)
bull Use of inhibitors
bull Use of nonmetallic coatings and liners
bull Application of metallic coatings
bull Use of surface treatments thermal spray or other surface modifications
bull Corrosion monitoring9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 48
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
bull R amp D on corrosion focus o four area of corrosion pretension control methods
1 Prevent ndash The chance of occurrence 2 Detect ndash Analyze the type of corrosion3 Predict - Intensity of damage4 Manage ndash take corrective action accordingly
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 49
Prevention of Corrosion
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 50
Prevention of Corrosion-Retard corrosion (Stop corrosion cell activity)
Use of inhibitors
Materialselection
Highly resistance to
corrosion
Design system
Any of the corrosion cell can not exist
New material
Manufacturing
method
Surface treatment
bullPaints
bullCPC
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Corrosion Prevention method Cathodic Protection
One of the most common methods of corrosion mitigation in the pipeline and storage tank industry mitigates corrosion by eliminating all anodic areas on an underground metallic structure
bull Two methodsbull Connect a
sacrificial metal bull Impressed current
cathodic protection
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 51
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Impressed current cathodic protection(ICCP)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 52
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
53
Corrosion-Preventive Maintenance
bullAn adequate cleaning
bullDetailed inspection for corrosion and failure of protective systems
bullPrompt treatment of corrosion and touchup of damaged paint areas
bullKeeping drain holes free of obstruction
bullDaily wipe down of exposed critical areas
bullMaking maximum use of protective covers
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Corrosion ndash Preventive Maintenance
bullElectroplating
bullMetal Spraying (Metallizing)
bullParco Lubrizing
bullAnodizing
bullAnodized surfaces
bullAlodizing
bullSurface Treatment
bullProtective paint finishes
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 54
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 55
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 56
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 57
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Design and assembly can affect localized corrosion by creating crevices and traps where corrosive liquids can accumulate
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 58
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Constructive Uses of Corrosion
bullElectrochemical Machining ndash EDM
bullElectropolishing
bullSacrificial Metal (Cathodic) protection
Corrosion prevents corrosion
bullGalvanic corrosion - used in batteries
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 59
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Validation of corrosion damage in pipes
bull Around 2000 the Royal shell company has launched a program of ldquointelligent pig runsrdquo An intelligent pig is a device that can be sent through a large-diameter pipe to measure corrosion defects
bull The Oil amp gas company is interested in using these runs to calibrate the failure model so that the model can be used to support the selection of pipes to be pigged in the future
bull The data consist of list of defects their position on the pipe and their depth( of wall thickness removed)
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 60
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 61
Fatigue failure
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Fatigue failure
bull Less than 10 of bearing reach their designed lifetime
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 62
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 63
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
DRILL 1 Below is a picture representing one of the corrosion protection
method Discuss in brief what you know about it
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 64
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Drill 2 Galvanic corrosion
If the use of undesirable couple of metal can not be avoided what can be done to minimize the
galvanic corrosion that may result
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 65
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
DRILL 3 Discuss on the sketch below
Galvanic coupling caused by riveting plates9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 66
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
DRILL 3A GALVANIC CORROSION
bull If aluminum rivets were used on steel plates the rivets would corrode extremely rapidly Explain
bull Which one of the following riveting system is advisable Why
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 67
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Drill 4 Forms of corrosion
Discuss what will happen in the fitting
Steel
Copper
Zinc coating
H2O
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 68
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Drill 5 Observe the picture shown below Discuss the type of
failure and the remedial actions
ldquohorseshoerdquo
shape using a
nut-and bolt
assembly-
While
immersed in
seawater
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 69
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
70
DRILL 6 Discuss on the figure shown below
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
RECAP corrosionThe science of corrosion
bull A Silent Pervasive Enemy that destroys the very item we count on every day
bull It occurs naturally (Simple law of physical science)
bull Examplesbull Brake failure in transport systembull Overhead crane cable failure
Cost of corrosionbull Direct costbull Indirect costbull gtgt investing in the prevention of corrosion
reduces total cost by ~ 40USA in 2002 congress director of department of defense developed a program corrosion prevention and controlgtgtgt corrosion education at the university level
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 85
Corrosion Protection
bull Material selection in the designed stage (might not be possible in all cases)
bull Engineers unintentional design and use a manufacturing methods that might promote corrosion
bull Initial corrosion protection procedures and designs might be more costly than the life time maintenance cost of equipment
bull Inspectionbull Treatmentbull Repairsbull combat
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
Todayrsquos challenge
bull Aging infrastructures
bull Simulation of the real corrosion environment to demonstrate in the research area
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 86
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-
EXAMPLES
9142019 EMeng 1081- Sem III 2019 AYLECTURER FANUEAL SAMSON 87
Zn
HCL
CASE 1 NO DISOLVED OXYGEN PURE HCL
Reaction Zn + 2HCL ZnCl2 + H2
Zn Zn ++
Oxidation (anodic reaction)
Two Half cell
Reaction2H++ 2H = H2
reduction (Cathodic reaction)
- 2e-
+ 2e-