Effect of H₂S partial pressure on stress corrosion cracking behavior of 13Cr stainless steel in annulus environment around CO₂ injection well

Electrochemical characteristics and stress corrosion cracking (SCC) behavior of 13Cr stainless steel were investigated by electrochemical measurements, U- bent specimen immersion test and surface analysis technique in an artificial solution with an autoclave, which aimed to simulate the annulus environment around CO₂ injection well. The results showed that annulus solution around injection well was a complicated H₂S-CO₂- Cl^- environment which generated the SCC of 13Cr stainless steel. The pitting breakthrough potential and SCC resistance of 13Cr stainless steel decreased obviously with increasing H₂S partial pressure, which is associated with the deterioration of surface film (passive film and corrosion products scales) on the steel. When the H₂S partial pressure exceeded 0.20 MPa (including 0.20), SCC occurred on 13Cr steel. Typical transgranular and intergranular fracture morphologies were observed, which indicated that the SCC process was mixed-controlled by both anodic dissolution and hydrogen-induced cracking.