Effects of ferrous ion concentration on microbiologically influenced corrosion of carbon steel by sulfate reducing bacterium Desulfovibrio vulgaris.

• More Fe2+ leads to better planktonic and sessile Desulfovibrio vulgaris growth. • More Fe2+ increases dissolved H 2 S concentration despite increased FeS precipitation. • More Fe2+ in the culture medium increases carbon steel weight loss and pit depth. • With more Fe2+, increased corrosion is primarily attributed to more sessile cells. • Electrochemical measurements corroborate weight loss and pit depth data. Ferrous ion (Fe2+) in a sulfate reducing bacteria (SRB) culture medium is known to enhance microbiologically influenced corrosion (MIC) of carbon steel, but the underlining mechanism is controversial. This work showed that it was due to better sessile cell growth that was likely attributed to Fe2+ detoxification of H 2 S. Two hundred ppm (w/w) initial Fe2+ in the ATCC 1249 medium achieved a 4.7 times higher Desulfovibrio vulgaris sessile cell count and 5.0 times higher C1018 carbon steel weight loss, compared to 20 ppm. Linear polarization resistance, electrochemical impedance spectroscopy and potentiodynamic polarization measurements corroborated weight loss and pitting data trends. [ABSTRACT FROM AUTHOR]