Corrosion behavior of carbon steel in the presence of iron-oxidizing bacterium Pseudomonas sp. DASEWM1

The present study describes the microbiologically influenced corrosion (MIC) of carbon steel due to iron-oxidizing bacteria (IOB), isolated from the rust deposited on carbon steel’s surface exposed to river water. Bacterial isolates, meant for corrosion investigation, were identified as Pseudomonas sp. DASEWM1. In this work, corrosion tests were carried out to estimate the extent of corrosion. Corrosion products deposited on the steel’s surface were identified using X-ray diffraction and Fourier transformed infrared techniques. It is observed that the degree of corrosivity in inoculated nutrient broth (NB) depends upon bacterial concentration and the amount of the constituents of extracellular polymeric substances (EPS). The observance of a lesser amount of vivianite which is protective in nature, as corrosion product formed on corroded carbon steel exposed to inoculated NB, is suggested as an additional factor responsible for increased metal corrosion. Corrosion of steel in inoculated NB appears to be due to (1) oxidation of ferrous ions to ferric ions by iron-oxidizing bacteria (IOB), thereby decreasing the amount of ferrous ions available for vivianite formation, (2) some Fe3+ gets bound to EPS, thus offer electrons for the oxygen reduction reaction. Overall, this process leads to the increased alkalinity of NB. Lastly, a possible mechanism of MIC due to IOB has been proposed by considering the above mentioned reactions.