The fitness and corrosion mechanisms of high-strength steel in corrosive oil–water environment at high temperature

This work investigated the mechanical decay mechanism and high-temperature corrosion mechanism of high-strength steel via high-temperature mechanical experiments, and corrosion and stress corrosion cracking tests were performed in simulated working conditions where water, oil, H₂S, and CO₂ coexist. The results show that the tensile strength and yield strength of high-strength steel decrease with increasing temperature; the tensile strength and yield strength at 350°C reduce 11.91% and 19.08%, respectively, compared with 25°C. Moreover, the corrosion rate of high-strength steel gradually increased from 0.0914 mm/a at 150°C to 1.2288 mm/a at 350°C. In addition, the influence of high temperature on the corrosion mechanism was inferred through thermodynamic calculations, and the reason for the presence of Fe₃O₄ in the corrosion products at 350°C was analyzed. At 350°C, stress corrosion cracking was observed in high-strength steels when the applied stress reached 90% of the yield strength. Based on the aforementioned studies, the relevant mechanisms related to the decay of mechanical properties, corrosion, and stress corrosion cracking are also proposed.