The effect of a sulphate-reducing bacteria on the rate of corrosion of steel alloys

In this article, we investigate the effect of micro-organisms on the rate of corrosion of stainless steel and mild steel alloys. The three analytical techniques we will employ in measuring the rate of corrosion are the electrochemical impedance spectroscopy, cyclic polarization and the mass loss method. The test material used is the 316L stainless steel and the mild steel coupons. The microorganism we are going to use for this investigation is the sulphate-reducing bacteria (SRB). The scope of the study will cover the cultivation of the micro-organism, cell count, electrochemical testing, cyclic polarization testing, analysis of corrosion product, mass loss and the pitting morphology consistent with the microbiologically induced corrosion mechanism. Our results show that the chemical composition of the mild steel and stainless steel test material conformed to SAE1020 and Type 316L stainless steel respectively. We also found that the corrosion rate of mild steel in both biotic and abiotic systems was significantly higher than that of the 316L stainless steel. The biotic system was more corrosive for both the mild steel and the 316L stainless steel. The biotic system showed a substantial corrosion effect in two days while the abiotic system showed the same effect after seven days. The cell count procedure confirmed the presence of sulphate-reducing bacteria throughout the test.