The combined effect of sulfate-reducing bacteria (SRB) and a microstructure on the stress corrosion behavior of heat-affected zones (HAZs) in pipeline steel for shale gas field applications was investigated. The results show that when the peak heating temperature reached 1020 °C, a coarse microstructure formed during multiple thermal cycles (MTCs), and Widmanstätten structures appeared in the HAZ. In the simulated environment, SRB intensified localized pitting corrosion of both the base metal and the HAZ. The welding HAZ was softened by the MTCs, and significant microcrack growth was observed in the presence of SRB. Among all subzones, the coarse-grained HAZ (CGHAZ) was the most susceptible to stress corrosion cracking (SCC) under shale gas service conditions. Cracks initiated at the metal surface and propagated vertically into the material. SRB activity further increased the SCC sensitivity of the CGHAZ.

The corrosion of steel caused by sulfate reducing bacteria (SRB) in shale gas environment is one of the big factors leading to the service failure of pipeline steel. However, the related studies of SRB corrosion especially at a high temperature are still poor. This paper aims to investigate the effects of SRB on the corrosion behavior of N80 steel in CO₂-saturated simulated shale gas produced water at 60°C by weight loss, 3D microscope,electrochemical impedance spectroscopy (EIS) and polarization curves and so on. Results showed that the corrosion rate of N80 steel in the presence of SRB was greater than that of the abiotic control specimen. SRB cells and the inhibitive organics could have a competitive adsorption on the steel surface. The adsorption of inhibitive organics on steel in the abiotic condition caused a slight corrosion of the control specimen. While the adsorption of SRB cells as well as the subsequent formation of biofilm have accelerated the localized corrosion of specimen. Therefore, steel corrosion is accelerated in the presence of SRB at a high temperature.