Effect of thermophilic sulphate-reducing bacteria (Desulfotomaculum geothermicum) isolated from Indian petroleum refinery on the corrosion of mild steel

The role of thermophilic sulphate-reducing bacteria (SRB) Desulfotomaculum geothermicum in mild steel corrosion was evaluated by electrochemical study and surface analysis technique. In the presence of D. geothermicum, the corrosion rate was 0.0698 mmpy at 50°C, which was higher when compared to control. Polarization study revealed that the bacteria enhanced cathodic reaction and suppressed anodic reaction. XRD data revealed that the presence of FeS enhanced the cathodic reaction by the formation of a protective film on the metal surface. Pitting was observed by confocal microscopy, which may be due to cathodic depolarization. The study implicates the importance of D. geothermicum in the corrosion of cooling towers of the petroleum refinery.