Electrochemical investigation of the “double-edged” effect of low-dose biocide and exogenous electron shuttle on microbial corrosion behavior of carbon steel and copper in enriched seawater

Abstract

The microbiologically influenced corrosion (MIC) behavior of carbon steel and copper induced by SRB was investigated by low levels of the biocide tetrakis hydroxymethyl phosphonium sulphate (THPS) and the environmental electron shuttle riboflavin in early incubation and harsh conditions. After 7 days of incubation, riboflavin weakened the inhibition for SRB by THPS in the carbon steel system, but did not apply to the copper. Thirty ppm THPS inhibited planktonic cell proliferation, but still formed visual biofilms on carbon steel and copper surfaces. In the co-existence of THPS and riboflavin, higher corrosion rates were obtained in carbon steel, while the MIC of copper was mitigated. For the harsh biotic systems, thirty ppm THPS was ineffective against the SRB-MIC of the harsh systems. Riboflavin was the icing on the cake for carbon steel under this condition, accelerating the SRB-MIC process. Electrochemical noise currents were used to monitor the effects of chemical injection in harsh conditions.