Role of inorganic and organic medium in the corrosion behavior of bacillus megaterium and pseudomonas sp. in stainless steel SS 304

Abstract

The production of extracellular polysaccharides (EPS) forms a layer on a metal surface that may either inhibit or accelerate corrosion. In the present study, the biocorrosion behavior of stainless steel 304 in the presence of aerobic bacteria Bacillus megaterium and Pseudomonas sp. was investigated in different growth media; an inorganic medium and an organic medium with 3.5% sodium chloride as the electrolyte. Biocorrosion was evaluated using potentiodynamic anodic and cathodic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy-energy dispersive spectrum analysis (SEM-EDAX), and Fourier transform infrared spectroscopy (FTIR). The corrosion potential (Ecorr) and pitting potential (Epit) were lower in the presence of both bacteria in the inorganic medium when compared to the organic medium. The inorganic medium consisted of inorganic nitrates and phosphates which accelerated the production of bacterial metabolites and enhanced corrosion resistance through the formation of a passive layer which inhibited the corrosion. Exposure of the metal in organic medium however caused both bacteria to shift the corrosion potential (Ecorr) toward the negative direction, thus causing the metal to undergo severe pitting attack. Electrochemical measurements showed that both the bacteria enhanced pitting corrosion in the organic medium. © 2011 American Chemical Society.