Biocorrosion and Its Impact on Carbon Steel API 5LX by Bacillus subtilis A1 and Bacillus cereus A4 Isolated From Indian Crude Oil Reservoir

Abstract

Biocorrosion is a frequent problem in oil and gas industry that occurs due to the ubiquitous nature of the microorganisms. The main objective of this study is to identify corrosive bacterial strains from crude oil reservoir samples and elucidation of their role in the biocorrosion of carbon steel API 5LX. Pure bacterial strains were identified using both biochemical and 16S rRNA gene sequencing methods. Identified dominant strains were subjected to weight loss and electrochemical studies. The Gram-positive bacteria Bacillus subtilis A1 and Bacillus cereus A4 were identified as dominant species. Corrosion rates were 0.743, 0.594 and 0.297 mm/year in the presence of strain B. subtilis A1, B. cereus A4 and abiotic control system, respectively. The charge transfer resistance values show a continuous decrease in the presence of bacterial culture indicating that formation of the heterogeneous biofilm and iron oxide over the metal surface leads to the corrosion phenomenon. Surface analysis techniques including X-ray diffraction, scanning electron microscopy and atomic force microscopy examination reveal the ability of bacteria to oxidize iron/manganese to their corresponding oxides, leading to the formation of thick biofilm on metal surface and accelerating the pitting corrosion of carbon steel.