1. Definition of Corrosion
Corrosion is the deterioration of materials by chemical interaction with their environment.  The term corrosion is sometimes also applied to the degradation of plastics, concrete and wood, but generally refers to metals.

2. Anodic & Cathodic Reactions

4. Effects of corrosion Losses are economic and safety
Reduced mechanical properties
Downtime of equipment
Leak of fluids
Reduced value of goods

5. Uniform Corrosion: Rust!
FORMS OF CORROSION
Uniform Corrosion: Rust!
Prevention:
Paint
Cathodic Protection

6. FORMS OF CORROSION Galvanic Corrosion Causes: Dissimilar metals
Prevention:
Choose metals close in galvanic series
Have large anode/cathode ratios
Insulate dissimilar metals
Cathodic protection
Described by Galvanic Series

7. Pitting and Creviced Corrosion
FORMS OF CORROSION
Pitting and Creviced Corrosion
Causes: concentration gradients in electrolyte cause some areas high in ion concentrations that accelerate oxidation
Prevention:
Weld – don’t rivet
Use non-absorbing gaskets
Polish surfaces
Avoid stagnant water

8. FORMS OF CORROSION
Intergranular corrosion
Stress corrosion
Erosion

9. Corrosion prevention
Applied Voltage
Sacrificial Anode

10. Corrosion prevention Surface coatings & Passivation
Some materials, such as Aluminum or Stainless Steel, form oxide barrier coatings that prevent oxidation at active surface – this is called “passivation”
Surface can be coated with protective layers: painted, anodized, plated.

11. Corrosion prevention Design of structures Material selection
Control the environment
Inhibitors
Protective Coatings