With reference to corrosion processes

(a) Explain the mechanism of: (8)

(i) Stress corrosion:

(ii) Corrosion fatigue.

(b) State where the following types of corrosion may occur, and the materials commonly involved in each case. (8)

(i) Fretting corrosion;

(ii) Impingement corrosion;

(iii) Galvanic corrosion;

(iv) Crevice corrosion;