Characterizing Pitting Corrosion Caused by a Long-Term Starving Sulfate-Reducing Bacterium Surviving on Carbon Steel and Effects of Surface Roughness Available to Purchase

Sulfate-reducing bacteria (SRB) are known as potential promoters for microbiologically influenced corrosion (MIC). Many researchers have studied the SRB-induced corrosion in the presence of organic nutrients. However, SRB-metabolizable organics are not constantly present in corroding environments. In this study, pitting and weight loss of carbon steel (CS) coupons due to corrosion caused by a SRB culture were examined over a 40-day period after the organic substrate had been exhausted. The extents of pitting corrosion on the polished and unpolished sides of the coupons were also compared to investigate the effect of roughness. The study was done in reactors with constant bubbling of nitrogen to ensure the anoxic condition (verified by the redox indicator resazurin). The surface structure of biofilm was observed using scanning electron microscopy (SEM). Pit depth, density, and morphology were examined using infinite focus microscopy (IFM). The SRB, surviving through the 40-day starvation of an organic energy source, caused severe pitting corrosion with a maximum pit depth of 46 μm. On the rougher surface the pitting initiated earlier and reached a much higher pit density. The finding of SRB's ability to cause severe pitting corrosion under the condition of no organic energy source is important to the understanding of SRB activities in corroding environments.