The purpose of scientific thought is to predict what will happen in given experimental...

The purpose of scientific thought is to predict what will happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

– Feynman

The purpose of scientific thought is to predict what will happen in given experimental circumstances. All the philosophical discussion is an evasion of the point.

– Feynman

Last class -

More corrosion - micro cellsWelding HAZSensitization

Ol' Harold's story

Last class -

More corrosion - micro cellsWelding HAZSensitization

Ol' Harold's story

Today -

Suppressing corrosionCorrosion examples

Today -

Suppressing corrosionCorrosion examples

Suppressing corrosion Suppressing corrosion

Components of a cell:

anode cathode electrolyte connection

Components of a cell:

anode cathode electrolyte connection


Occlude electrolyte - coatingsOcclude electrolyte - coatings

asphaltgreases, oilspaintspolymersceramic coatings"noble" metals

asphaltgreases, oilspaintspolymersceramic coatings"noble" metals


Occlude electrolyte - coatingsOcclude electrolyte - coatings

"noble" metals:

unless scratch heals, a galvanic cell is set up

"noble" metals:

unless scratch heals, a galvanic cell is set up


Cathodic protectionCathodic protection

galvanizing:

Zn coating applied by

hot-dipping electroplating

galvanizing:

Zn coating applied by

hot-dipping electroplating



galvanizing:

presence of scratch does not promote corrosion of protected metal

galvanizing:

presence of scratch does not promote corrosion of protected metal

but steel helps Zn corrodebut steel helps Zn corrode



set up cell by adding metal which ismore anodic thanmetal or alloy tobe protected

set up cell by adding metal which ismore anodic thanmetal or alloy tobe protected



example:

protecting ship plate

example:

protecting ship plate



example:

protecting hot water heater tanks

example:

protecting hot water heater tanks

Suppressing corrosion Suppressing corrosion Cathodic protectionCathodic protection

Problem:

steel fermentation tank in brewery

Problem:

steel fermentation tank in brewery

sacrificial anodes add metallic ions to electrolyte

sacrificial anodes add metallic ions to electrolyte


Different approach:

Impose a voltage across cell formed by tank (cathode) and an inert anode

Different approach:

Impose a voltage across cell formed by tank (cathode) and an inert anodechoice of anode material:

very inert material like Pt

choice of anode material:

very inert material like Ptbut oxygen gas produced at anodebut oxygen gas produced at anode


Different approach:

Impose a voltage across cell formed by tank (cathode) and an inert anode

Different approach:

Impose a voltage across cell formed by tank (cathode) and an inert anodechoice of anode material:

use carbon - inert

C + O2 CO2

choice of anode material:

use carbon - inert

C + O2 CO2


"…..join in a planned discussion of whether it is best to use copper tubing coils or stainless steel tubing coils inside of a stainless steel beer fermenter, the coils being used as a chiller? There has been a discussion in another brewing forum about competing concerns between the two, i.e., copper conducts heat better and is easier to bend, versus copper will slowly dissolve in the acidic environment of beer"

"…..join in a planned discussion of whether it is best to use copper tubing coils or stainless steel tubing coils inside of a stainless steel beer fermenter, the coils being used as a chiller? There has been a discussion in another brewing forum about competing concerns between the two, i.e., copper conducts heat better and is easier to bend, versus copper will slowly dissolve in the acidic environment of beer"

Suppressing corrosion Suppressing corrosion Use passivated materialsUse passivated materials

Ni - NiO

Ti - TiO2

Al - Al2O3

Ni - NiO

Ti - TiO2

Al - Al2O3

COR-TEN:

0.19% C 0.30% Cu 0.40% Ni 0.50% Cr 0.05% V

COR-TEN:

0.19% C 0.30% Cu 0.40% Ni 0.50% Cr 0.05% V

Suppressing corrosion Suppressing corrosion AnodizingAnodizing

Al & other materials can be anodized

very thick oxide coating formed (8-50 microns)

Al & other materials can be anodized

very thick oxide coating formed (8-50 microns)

Suppressing corrosion Suppressing corrosion Thinking again of noble metal coatings, what about Cr plating?Thinking again of noble metal coatings, what about Cr plating?

Cr plating usually filled w/ microcracks due to stresses in plating

Cr plating usually filled w/ microcracks due to stresses in plating

540x 2300x


Cr plating frequently a series of layers Cr plating frequently a series of layers

Corrosion examples in shuttle mat'ls Corrosion examples in shuttle mat'ls

1x1x 60x60x

235x235x 1180x1180x

Corrosion examples in shuttle mat'ls Corrosion examples in shuttle mat'ls

Corrosion area effectCorrosion area effect

Area effect:

large cathode & small anode - corrosion accelerated

Area effect:

large cathode & small anode - corrosion accelerated

electrochemical cell current density highelectrochemical cell current density high

try to keep potential anodic areas large relative to cathode

try to keep potential anodic areas large relative to cathode

Polymers - the nightmare beginsPolymers - the nightmare begins

I am inclined to think that the development of polymerization is, perhaps, the biggest thing that chemistry has done, where it has the biggest effect on everyday life

I am inclined to think that the development of polymerization is, perhaps, the biggest thing that chemistry has done, where it has the biggest effect on everyday life

LORD TODDPresident of the RoyalSociety of London

LORD TODDPresident of the RoyalSociety of London

What are polymers?Why important ?

What are polymers?Why important ?

• Long chain molecules

• Extraordinary range of physical properties

• Many (not all) are cheap

• Low densities

• Long chain molecules

• Extraordinary range of physical properties

• Many (not all) are cheap

• Low densities

Assignment:

Review today's classnotesa. coatingsb. cathodic protectionc. passivationd. anodizinge. Cr platingf. corrosion examplesg. area effect h. what is a polymer?

Read: pp 569-585, 589-591, chapter 14

Assignment:

Review today's classnotesa. coatingsb. cathodic protectionc. passivationd. anodizinge. Cr platingf. corrosion examplesg. area effect h. what is a polymer?

Read: pp 569-585, 589-591, chapter 14

The purpose of scientific thought is to predict what will happen in given experimental...

Documents

Transcript of The purpose of scientific thought is to predict what will happen in given experimental...