Unraveling the effect of O2, NO2 and SO2 impurities on the stress corrosion behavior of X65 steel in water-saturated supercritical CO2 streams

The stress corrosion behavior of X65 steel in water-saturated supercritical CO 2 streams with various impurities was explored. The stress demonstrates a significant acceleration effect on the corrosion, especially the localized corrosion, which mostly depends on impurity type. O 2 scarcely raises the SCC susceptibility of X65 steel, whereas SO 2 and NO 2 greatly enhance its SCC susceptibility due to their strong corrosion effects. The SCC process of X65 steel in SO 2 -containing environment is dominated collectively by local anodic dissolution, hydrogen embrittlement and stress, while the couple effect of local anodic dissolution and stress plays a leading role in SCC in NO 2 -containing environment. • The contribution of stress to enhanced corrosion is closely related to impurity type. • The stress has an obvious acceleration effect on the localized corrosion of X65 steel. • X65 steel is highly susceptible to SCC in SO 2 - and NO 2 -containing wsCO 2 streams. • Hydrogen permeation effect induced by SO 2 is much more significant than that by NO 2 . • The role of impurity in SCC process of X65 steel in impure wsCO 2 streams is unmasked.