The passivation of iron-carbon alloys in acidic phosphate solution and its relation to stress corrosion cracking

Abstract

Anodic dissolution and passivation of FeC alloys were examined in 1M NaH 2PO 4 of pH 4.0 at 25°C. Carbon retarded the passivation of iron and decreased the protectiveness and stability of the passivating film, but it promoted the growth of oxide layers, especially of magnetite. It is suggested that intergranular and transgranular stress corrosion cracking of mild steel in the phosphate solution is largely associated with the deterioration of the passivating film by carbon at grain boundaries and at slip steps, respectively.