Under-deposit microbial corrosion of X65 pipeline steel in the simulated shale gas production environment

The synergistic effect of sand deposit and sulfate-reducing bacteria on the X65 pipeline steel was investigated in the simulated shale gas production environment, by means of weight loss tests, EIS, SEM and EDS. The results indicated that the coexistence of sand deposit and sulfate reducing bacteria (SRB) resulted in 63% reduction in uniform corrosion, but 183% increase in localized corrosion rate. The EIS results revealed that the formation of biofilm altered the protectiveness of the surface mixed layer and showed a trend related to the bacterial growth curve. The mixed layer was also clarified from the cross-section morphology and EDS analysis. This mixed layer may hinder the diffusion of substances to the deposit/steel interface, thus creating a microenvironment at the deposit/steel interface that promotes localized corrosion.