Abstract
Stainless steel (SS), the workhorse material for diverse industrial applications is susceptible to localized corrosion, and failures of components occur with through wall pitting even in low chloride environments especially under the influence of biofilms. An attempt was made to look into this age-old problem using metallurgical and microbiological approach to come up with a Metal-Microbe Synergy (MMS) mechanism for the localized corrosion aspect of SS. Localized corrosion initiation of AISI 316L SS and 202 SS under the influence of natural biofilms and biofilms of manganese oxidizing Bacillus flexus was studied and correlated with Mn content in the alloy. The effect of microstructure on microbial adhesion, growth rate, diversity and biofilm formation was evaluated. The pitting susceptibility under the influence of biofilm was characterized by potentiostatic and potentiodynamic polarization studies. Confocal Laser Scanning Microscope imaging was used to analyze the three dimensional biofilm architecture and pit morphology. X-ray photoelectron spectroscopy was used to characterize the changes in the passive film under the influence of biofilms. The presentation makes a fresh look at this age-old problem using advanced chemical, microbiological and metallurgical techniques, and provides a deeper understanding of metal-microbe synergy on the localized corrosion of stainless steels.
