Stress corrosion cracking of 2205 duplex stainless steel in H₂S–CO₂ environment

Stress corrosion cracking (SCC) behavior of 2205 duplex stainless steel (DSS) in H₂S–CO₂ environment was investigated by electrochemical measurements, slow strain rate test (SSRT), and scanning electron microscopy (SEM) characterization. Results demonstrated that the passive current density of steel increases with the decrease of solution pH and the presence of CO₂. When solutions pH was 2.7, the steel SCC in the absence and presence of CO₂ is expected to be a hydrogen-based process, i.e., hydrogen-induced cracking (HIC) dominates the SCC of the steel. The presence of CO₂ in solution does not affect the fracture mechanism. However, the SCC susceptibility is enhanced when the solution is saturated simultaneously with H₂S and CO₂. With elevation of solution pH to 4.5, the hydrogen evolution is inhibited, and dissolution is involved in cracking process. Even in the presence of CO₂, the additional cathodic reduction of H₂CO₃ would enhance the anodic reaction rate. Therefore, in addition to the hydrogen effect, anodic dissolution plays an important role in SCC of duplex stainless steel at solution pH of 4.5.