Extracellular electron transfer corrosion mechanism of two marine structural steels caused by nitrate reducing Halomonas titanicae.

The extracellular electron transfer (EET) mechanism for corrosion of EH36 steel (with copper) and Q235 steel (without copper) caused by Halomonas titanicae was investigated. Due to copper cytotoxicity, the sessile H. titanicae cells on the EH36 surface was only 18% of that on Q235. This led to its lower EET rate, resulting in EH36 corrosion being 0.67 times of Q235 corrosion. The EET corrosion mechanism was further proven by the increased corrosion of the two steels after injection to the H. titanicae broth of 20 ppm (w/w) (in the broth) riboflavin, an electron mediator known to accelerate EET. • H. titanicae causes EH36 and Q235 MIC in anaerobic environments. • EH36 ship steel is more resistant to nitrate reducing H. titanicae than Q235 steel. • Copper cytotoxicity on EH36 leads to a much lower sessile cell count. • Fewer sessile H. titanicae cells on EH36 leads to less severe MIC. • MIC mechanism is confirmed as extracellular electron transfer-MIC using riboflavin. [ABSTRACT FROM AUTHOR]