Abstract
In the present study, the effects of the corrosive bacterial community and the biofilm on cooling water systems made from mild steel (MS) and brass (BR) were studied under field exposure conditions using electrochemical impedance spectroscopy measurements, scanning electron microscope, and X-ray diffraction methods. Results froml6S rRNA gene sequences showed that the predominant bacteria species detected in the biofilm of MS and BR metals during 360 days of exposure were Bacillus cereus EN14, Achromobacter xylosoxidans EN1S, A. xylosoxidans EN16, and B. cereus EN17. The weight loss results revealed that a higher corrosion rate was observed in MS (0.7 +/- 0.1 mm/y) compared with that in BR (0.17 +/- 0.05 mm/y) at the end of the exposure period. This can be explained by the bacterial communities enhancing the corrosion rates by creating a local corrosive environment. Scanning electron microscope images revealed the adsorption of biofilm on the MS and BR surfaces following180 days of exposure. From the electrochemical impedance study, a higher charge transfer resistance (R-ct) was obtained for BR (119.6 Omega cm(2)) when compared with that of MS (43.4 Omega cm(2)). This study explains the role of bacterial communities and their mechanisms in the corrosion of MS and BR in cooling water systems.