Pitting corrosion behavior of 316L stainless steel in the media of sulphate-reducing and iron-oxidizing bacteria

Pitting corrosion behavior of 316L SS was investigated in the presence of aerobic and anaerobic bacteria isolated from cooling water system in oil refinery using polarization measurement, electrochemical impedance spectroscopy, scanning electron microscopy examinations and energy dispersive spectrum analysis. The results show the corrosion potential (Ecorr), pitting potential (Epit) and polarization resistance (RP) of 316L SS had a distinct decrease in the presence of bacteria, in comparison with those observed in the sterile medium for the same exposure time interval. Micrometer-scale pitting was observed on the 316L SS surface in the presence of bacteria. The combination of SRB and IOB demonstrated higher corrosion rates than SRB or IOB alone. The synergy of 0.01 M NaCl + SRB + IOB yielded the highest corrosion rate. The synergies between the metal surface, abiotic corrosion products, chloride anion, and bacterial cells and their metabolic products increased the corrosion damage degree of the passive film and accelerated pitting propagation.