The influence of surface features on bacterial colonization and subsequent substratum chemical changes of 316L stainless steel

Biofilm-forming bacteria were found to selectively colonize specific surface features of unpolished 316L stainless steel exposed to flowing aqueous media. Depending on the types of bacteria present, selective colonization resulted in significant depletion of Cr and Fe relative to Ni in the surface film at these features. No such depletion was observed on uncolonized surfaces exposed to sterile flowing aqueous medium. The results demonstrate that non-random, initial colonization of 316L stainless steel surfaces by these bacteria leads to changes in alloy elemental composition in the surface film that are enhanced with time. These chemical changes may be a critical step that weakens the oxide film at specific locations, allowing halides such as Cl- ions greater access to the underlying bulk alloy, and thereby facilitates localized attack and pit formation and propagation.