Classification of Corrosion Process
Depending upon the nature of corrosion, and the factors affecting it, the corrosion may be classified as follows.
(i) Chemical corrosion : Such corrosion, generally takes place when
(a) Reactive gases come in contact with metals at high temperatures e.g., corrosion in chemical industry.
(b) Slow dissolution of metal takes place when kept in contact with non conducting media containing organic acids.
(ii) Bio-chemical corrosion or Bio-corrosion: This is caused by the action of microorganisms. Soils of definite composition, stagnant water and certain organic products greatly favour the bio-corrosion.
(iii) Electrochemical corrosion : It occurs in a gaseous atmosphere in the presence of moisture, in soils and in solutions.