Influence of dissolved oxygen content on the bacteria-induced ennoblement of stainless steels in seawater and consequence on the localized corrosion risk.

The open circuit potential of stainless steel typically increase by +300mV in aerated seawater in a phenomenon called ennoblement. That shift of potential increases the risk of localized corrosion for stainless steel. In this study, we tried to infer the fraction of the bacterial community responsible for the ennoblement with the use of control non-conductive glass coupon and anaerobic condition. We exposed coupons of stainless steel and glass for a week in renewed seawater tanks heated at 30°C for a week. The dissolved oxygen content (DOC) of the tanks were controlled and two conditions were used: fully aerated seawater (6ppm) and very low DOC (<20ppb). Under aerobic condition, the open circuit potential of the stainless steel increased by +300 mV in a phenomenon called "Ennoblement".