Effect of iron exposure in SRB media on pitting initiation

Pitting corrosion of iron (99.9%) in Sulphate-reducing bacteria (SRB) media containing 0.09–0.30 g/l sulphides and 0.1–5.0 g/l [Cl−] was studied. Iron electrode immersed in SRB media undergoes fast activation and numerous active sites formed on the surface. Depending on exposure time, pitting was initiated at different potentials. After short period (<2 h) in open circuit potential, when active sites were still exist on the surface, pitting occurred at the potential range of −0.60 to −0.55 V (SCE). Extended exposures resulted in more stable passivity of iron and the pitting potential shifted to positive values. Pit initiation mechanism at the various exposure periods is discussed.