Effect of ferrous ion availability on growth of a corroding sulfate-reducing bacterium

Environmental conditions controlling growth and metabolic activity of the s ulfate-reducing bacterium (SRB), Desulforibrio gabonensis DSM 10636 which h ad been previously isolated from a corroded oil pipe, was investigated in a homogenous culture. The culture was conducted continuously in order to get steady-state conditions for growth. Several factors, such as stirring cond itions, and the flow rate of Nz injection into headspace of the culture, we re found to influence growth performances. The maximum growth rate was mark edly influenced by Fe2+ concentration in the medium. Surprisingly, removal of Fe2+ and replacement by a mild steel coupon allowed the strain to grow a t pH 6.0 but not at pH 7.4. A proposed biocorrosion mechanism by which the excretion of acidic products can promote Fe2+ availability for SRBs is put forward. Lowering the pH, metabolic products, such as acetic acid, increase s the level of corrosive sulfides (H2S. HS-). The latter, in turn, promote the attack of metallic iron which produces Fe2+. In such a way. acidic cond itions ensure Fe2+ for SBR growth acid can account for the persistency of c orrosion. (C) 2001 Elsevier Science Ltd. All rights reserved.