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CORROSION The Best Kept Secret in the Western World Terry May President, NACE Foundation Slide 2 Corrosion & Society Slide 3 Slide 4 Slide 5 Cost of Corrosion in 1998 GNP Slide 6 Money To put in perspective the annual cost of all the natural disasters in the USA. (Hurricanes, tornadoes, tropical storms, floods, fires etc) $17 Billion Corrosion Costs the US economy $276 Billion per Year or 16 times as much as all the natural disasters combined More than $1000/year/person Slide 7 Money 25+% could be saved using existing technologies Slide 8 Environment Slide 9 Slide 10 Safety Slide 11 Slide 12 Slide 13 Slide 14 Application to Various Industries Pipelines Underground Storage Tanks Industrial Plants Power Generation Transportation Marine Waterworks Petrochemical Plants Pulp and Paper Real Estate Private Homes Slide 15 Slide 16 Slide 17 Slide 18 Slide 19 Slide 20 What is Corrosion? Corrosion is an electrochemical reaction between a metal and its environment Corrosion is the tendency of a metal to return to its original state Corrosion involves the flow of DC current Corrosion is a natural process Slide 21 What causes Corrosion? Dissimilar metal Differential Aeration Environment concentration differences Bacteria Stress Erosion Temperature effects Slide 22 What does Corrosion look like? Uniform Pitting Stress Cracking Intergranular Crevice Attack Erosion-Corrosion Slide 23 General Corrosion Slide 24 Pitting Slide 25 Crevice Corrosion Slide 26 Galvanic Corrosion Slide 27 Practical Galvanic Series Magnesium-1.6 Volts Zinc-1.1 Aluminum-1.05 Steel (clean or shiny)-0.5 to -0.8 Steel (rusty) -0.2 to -0.5 Cast Iron-0.5 Lead-0.5 Copper or brass-0.2 Mill scale on steel-0.2 Carbon or graphite+0.3 ACTIVE PASSIVE Slide 28 Flashlight Battery An engineered corrosion reaction Zinc/Carbon cell connected with a conductive electrolyte Life depends on current load Slide 29 Pitch Seal Air Space Carbon rod Protective casing Electrolyte paste (ammonium chloride and zinc chloride) Zinc Separator Negative terminal Graphite-Zinc Battery Slide 30 What conditions are required for corrosion to occur? An anode and a cathode locations with a difference in electrical potential (voltage) between them A metallic connection between the two points Both locations exposed to the same environment Slide 31 Four Conditions of a Corrosion Cell Anode - where oxidation occurs Cathode - where reduction occurs Electrolyte - where ion migration occurs Metallic path - where electrons migrate from the anode to the cathode Slide 32 Single Corrosion Cell e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Fe ++ OH - Fe(OH) 2 H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H H H CATHODIC SITE ANODIC SITE Microscopic View Fe ++ e-e- Slide 33 The Corrosion Cell Metallic corrosion is an electrochemical reaction which involves : a transfer of electrons oxidation - loss of electrons (corrosion) reduction - gain of electrons (protection) migration of ions Slide 34 ee CuFe e e e e Metallic Path CathodeAnode Electrolyte Fe ++ H+H+ H+H+ H + OH Corrosion Cell Slide 35 Practical Case Showing Conventional Current Flow Corrosion Current Electrolyte (soil) Anode Cathode Structure (metallic path) E Slide 36 Electrochemical Reactions Anode: (Oxidation) Fe Fe++ + 2e Cathode : (reduction) 2H+ + 2e H2 3O2 + 6H2O + 12e 12OH O2 + 4H+ + 4e 2H2O Electrolyte H2O H+ + OH Slide 37 Fe ++ Fe ++ Fe ++ Fe ++ Fe ++ Fe ++ Fe ++ Fe ++ Fe ++ e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - ANODE Oxidation Reaction ELECTROLYTE Anodic Process Slide 38 H + e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - e - CATHODE H H + H + H + H + H + H H H + H + H + H + H + H + H + H H H Reduction Reaction ELECTROLYTE Cathodic Process Slide 39 Current Flow in a Basic Galvanic Cell Slide 40 Methods of Corrosion Control Coating Cathodic Protection Environment Control Material Selection Design Slide 41 Anode Cathode Microscopic Corrosion Cell on the Surface of a Pipeline Microscopic View of a Corrosion Cell Slide 42 Anode Cathode Metallic Connection Electrolyte Cathodic Protection Anode Cathodic Protection Current Applied Cathodic Protection on a Structure (Macroscopic view) Slide 43 Typical Application of Cathodic Protection Underground pipelines Underground storage tanks Bottoms of on grade storage tanks Interiors of water storage tanks Condenser and heat exchanger water boxes Reinforced concrete Doesnt work in the atmosphere (Automobiles) Slide 44 Preserving the Past Slide 45 Slide 46 Slide 47 Statue of Liberty Slide 48 Just Flying along, enjoying the ride.... what's so cool is they actually pay me to do this! Slide 49 Hmmm. Strange sound. Something feels different. Slide 50 Hey, why am I looking up.?? Slide 51 Whoa here, what the hell? Controls aren't working Slide 52 Time for a mirror check. Hey, where's the rest of my F-15.? Slide 53 Uh oh, it's over there. I think I've got a definite "Aw, sh*t" going here... Slide 54 I gotta wonder, am I the first guy to ever experience " cockpit-airframe separation anxiety". Slide 55 I'm outta here. But first the canopy has to go. Slide 56 Hey GREAT! That worked as advertised. Things are looking up! Slide 57 OK, now it's my turn to go. I'm gone - soon as I find the eject handle. Slide 58 Oh yeah, that's what I'm talking about. Looks like it's going to be just another "average day at the office." Slide 59