Corrosion of Mild Steel by Sulphate-reducing Bacteria: An Alternative Mechanism

Studies of cathodic polarisation of steel in sulphate-reducing bacteria growing without sulphate metabolism, but in the presence or absence of chemically prepared suspensions of ferrous sulphide, indicate that two distinct mechanisms of depolarisation can occur. In addition to utilisation of polarising hydrogen by the bacterial hydrogenase system, there is evidence for depolarisation of the cathode by solid ferrous sulphide. The form of the cathodic polarisation curves and the results of complementary weightloss experiments indicate that the second (sulphide) mechanism may make a major contribution to the overall corrosion.