Pit initiation on 316l stainless steel in the presence of bacteria leptothrix discophora

Abstract

Ennoblement of stainless steel by microbially deposited manganese oxides can cause pitting corrosion of the SS in natural waters at low chloride concentrations, leading to unexpected material failures. To study the effects of microbially deposited manganese oxides on pit initiation, we exposed 316L stainless steel to manganese oxidizing bacteria Leptothrix descophora under well-defined laboratory conditions. We then placed the ennobled coupons in a solution of low concentration sodium chloride until pitting initiated. The pits had different morphologies that those initiated by electrochemical polarization, hypothetically indicating a direct involvement of the bacteria in pit initiation.