Different types of corrosion are:
1. Differential metal corrosion or Galvanic Corrosion
2. Differential Aeration corrosion
3. Stress Corrosion
1. Differential metal corrosion:
When two metals of different electrode potential or two dissimilar metals are in contact, the metal with lower electrode potential or more reactive metal act as anode and undergoes corrosion. Potential difference between the metals causes the corrosion.
The factors determining the rate of corrosion
2. Differential aeration corrosion:
Difference in the concentration of oxygen on the surface of oxygen causes the differential aeration corrosion. The part of metal over which oxygen concentration is less becomes anode and gets corroded. The metal surface over which oxygen concentration is high becomes cathode, because cathodic reaction involves consumption of oxygen.
3. Stress Corrosion:
The corrosion taking place at stress points of metals formed due to welding, hammering, bending, etc. the atoms under stressed part get high energy and get higher oxidation potential than that of stress free part. hence stressed part becomes anode and stress free part becomes cathode and corrosion takes place.