Microbially initiated pitting on 316L stainless steel

Pitting corrosion of 316L stainless steel ennobled in the presence of manganese-oxidizing bacteria, Leptothrix discophora, was studied in a low-concentration sodium chloride solution. Corrosion coupons were first exposed to the microorganisms in a batch reactor until ennoblement occurred, then sodium chloride was added, which initiated pitting. The pits had aspect ratios (length divided by width) and shapes closely resembling the aspect ratio and the shape of the bacteria, which suggested that the microorganisms were involved in pit initiation.