Corrosion of steel due to iron oxidizing bacteria

Purpose The purpose of this study is to investigate microbial influenced corrosion of steel because of iron oxidizing bacteria (IOB). Design/methodology/approach Carbon steel was selected for this study. Winogradsky media was used for isolation of IOB and as test solution for corrosion measurements. Electrochemical tests and immersion test were conducted to estimate the corrosion rate and extent of pitting. The corroded surface was analysed by SEM and corrosion products formed over the metal surface were identified by XRD and Fourier transformed infrared. Biofilm formed over the corroded metal was analysed by UV-visible spectroscopy for its extracellular polymeric substances (EPS) constituents. Findings Presence of IOB in Winogradsky medium enhances corrosion. Uniform and localized corrosion increases with increased bacterial concentration and EPS constituents of the biofilm. Iron sulphite formation as one of the corrosion products has been suggested to be responsible for increased corrosion attack in the inoculated media in comparison to control media where corrosion product observed is iron hydrogen phosphate which is protective in nature. Originality/value This work correlates increased corrosion of steel in the presence of bacteria with the nature of corrosion products formed over it in case of IOB. Formation of corrosion products is governed by various electrochemical reactions; hence, inhibition of such reactions may lead to reduce or stop the formation of such products which enhances corrosion and thereby may reduce the extent of microbial induced corrosion.