Desulfovibrio desulfuricans induced corrosion of welded joint in X80 pipeline steel below delaminated coating

Buried pipelines are an important tool for long-distance oil and gas transportation. Welded joints are the weak components of buried pipelines. Interestingly, the biocorrosion degree of the heat affected zone (HAZ) of the welded joint is the lowest in mediums. However, there is no report on the biocorrosion of the welded joints when the protective coating is delaminated. In this paper, sulfate-reducing bacteria (SRB) corrosion of X80 steel welded joint was studied below delaminated coating. Results showed that SRB corrosion of the welded joint was selective at the opening of the delaminated coating, and such selected SRB corrosion gradually faded along the direction from the opening to the far end. At the far end below the delaminated coating, the corrosion of the welded joint was related more to its microstructural characteristics rather than to the SRB metabolism process. The concentration decrease of the SRB cells was responsible for the gradual decrease of the SRB corrosion of the welded joint below the delaminated coating.