Severe pitting corrosion caused by a starving sulfate-reducing bacterium surviving on carbon steel and effect of surface roughness
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Sulfate reducing bacteria (SRB) are known as potential promoters for microbiologically influenced corrosion (MIC). Many researchers have studied the SRB-induced corrosion with supplemented organic nutrients. However, many corroding environments do not always contain organic substrates that can be metabolized by SRB. In this study, the pitting and weight loss of carbon steel coupons due to corrosion caused by a SRB culture were examined over a 40-day period after organic substrates had been exhausted. The extents of pitting corrosion on polished and unpolished sides of steel coupons were also compared for the effect of roughness. The study was done in sterilized batch containers with constant purge of nitrogen to ensure the anoxic conditions. The surface structure of biofilm was observed by scanning electron microscopy (SEM). Pit depth, density and morphology were determined by infinite focus microscopy (IFM). The SRB was found to survive through the 40-day starvation and cause severe pitting corrosion with a maximum pit depth of 46 m. The rougher surface showed earlier pitting initiation and higher pit density. The finding of SRB's ability to live and cause severe pitting corrosion under condition of no organic nutrients is very important to the understanding of SRB activities in corroding environments. 2013 by NACE International.
