1. General
   1. Atmospheric
      1. Dry
      2. Damp
         1. moisture involved
   2. Galvanic
      1. Galvanic series
         1. dissimilar metals with an electro potential difference >0.4mV
      2. Polarisation
         1. current flow
            1. potential shift
      3. Surface Area
         1. between anode and cathode
      4. Distance between the metals
   3. Stray Current
      1. Electrical
   4. High Temperature
      1. Oxidising gases
      2. Sulfidation
         1. sulphides
      3. Carburization
         1. carbides
2. Localised
   1. Pitting
      1. Low Oxygen
      2. High chlorides
      3. Stress
   2. Crevice
      1. Localised
         1. In boundaries
         2. oxygen differential cells
         3. chloride concentration
   3. Microbial
      1. Bacteria
         1. Low oxygen
            1. Sulphate reducing
         2. High oxygen
         3. Type of bacteria
            1. iron bacteria - Gallionella
            2. iron/manganese- Siderocapsa
            3. aluminum- Pseudomonas, Cladosporium, Desulfovibrio
            4. copper- Thiobacilluis thiooxidans
            5. Sulphate reducers
            6. Desulfovibrio
            7. Desulfomonas
            8. Desulfotomaculum
            9. Other anaerobic
            10. Thiobacillus thiooxidans
            11. Clostridium
            12. Acid producers
            13. Metal depositors
            14. Slime formers
   4. Filiform
      1. On coated steels
         1. humidity
            1. thin organic film
            2. coating cracks/bulges
            3. ingress of salts/chlorides
3. Metallurgically
   1. Intergranular
   2. Dealloying
      1. Alloys
         1. grain boundaries
         2. leaching of one constituent
         3. graphitic on gray iron
   3. Temperature
      1. stainless steels, T >1035C chromium carbides dissolve austenitic SS
4. Mechanically Assisted
   1. Erosion
      1. Soft metals
      2. Velocity of fluid flow
      3. Dissolved/suspended solids
   2. Impingement
      1. cavitation
      2. water drop impingement
   3. Fretting
      1. combined wear and corrosion process(usually oxidation)
   4. Corrosion fatigue
5. Environmentally Induced Cracking
   1. Stress corrosion cracking
   2. Hydrogen damage
   3. Liquid Metal embrittlement
   4. Solid metal Induced Embrittlement
6. Protection
   1. Sacrificial Anodes
   2. Cathodic protection
   3. Protective Coatings
   4. Anodization
   5. Reactive Coatings- corrosion inhibitors