CORROSION THEORY

What Is Corrosion?Why Does Corrosion Happen?How Does Corrosion Happen?What are some different types?

To Make a Metal

Open Pit Butte, MT

Cu Copper Element Copper Wire

What is Corrosion?

Deterioration of a metal as it reacts to its environment……… in an attempt to return to its natural state

Why Corrosion Happens

Most Metals Not Stable in Normal Environments

They Want to Revert to a More Stable Condition

TermsChemical Properties:The way matter behaves when it is placed in contact with other kinds of matter

Physical Properties:Color, Odor, Taste, Density, Freezing

Oxidation & Reduction: 1 Substance is being oxidized = Another substance is being reduced Happens Simultaneously

Corrosion Cell:Anode + Cathode + Metal Path + Electrolyte

How Do Metals Corrode?

Electrochemical Reaction

Chemical Change + Production of Electrical Energy

Direct Chemical Attack

or

Direct Chemical Attack

Uniform Surface Corrosion

Salts Deposited From Coastal Waters Urine Spray Battery Acid Spillage Gases Absorbed From Environment

Pitting Corrosion

Localized Attacks

Electrochemical Reaction

Cathode: Passive Metal Less Likely to Corrode Than Anode

Anode: Active (weak) Metal

Electrolyte: Any Liquid PathMetal Path:

Conductor Carries Flow of Electrons From Anode To Cathode Usually Metal-to-Metal Contact – Fasteners in Metal

Galvanic Corrosion

DevelopmentAll Corrosive Attacks Start on Surface

Penetrates Into Granular Structure

Protect Surface or Remove 1 Condition = Stop Corrosion

Results in Extensive Surface & Structural Damage

Intergranular Corrosion Exfoliation Stress Cracking Fatigue

Uniform Surface Corrosion Pitting Galvanic

Destructive Corrosion

Exfoliation Stress Cracking

Fatigue Failure

Corrosion Video

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Corrosion & Rust

Corrosion Review

Why Does Metal Corrode?

What is Corrosion?

How Does Metal Corrode?

What are Some Different Kinds of Corrosion?