Effect of imidazoline inhibitor on stress corrosion cracking of P110 steel in simulated annulus environments of CO2 injection well

In this study, the effect of imidazoline inhibitor on the stress corrosion cracking (SCC) behavior of P110 steel in a simulated annulus environment in CO2 injection wells was investigated by immersion tests on three-point bending specimens, electrochemical measurements, and corrosion morphology analysis. Results show that the addition of imidazoline inhibitor may lead to a high sensitivity of SCC for P110 steel. In the absence of tensile stress, P110 steel gains effective protection when the corrosion inhibitor concentration is less than 1000 mg/L. However, under various tensile loadings, the SCC susceptibility, which in the presence of the inhibitor is higher than that in the absence of the inhibitor, increases with an increase in the concentration of the inhibitor (when the inhibitor concentration is less than 1000 mg/L). The SCC sensitivity starts to reduce if the inhibitor is added continuously; when the inhibitor concentration reaches 2000 mg/L, SCC becomes markedly suppressed. The above phenomenon manifests that the addition of an inhibitor needs careful consideration and the SCC test must be introduced to evaluate the efficiency of the inhibitors; electrochemical analysis and immersion tests of non-SCC samples alone are insufficient to assess the controlling efficiency of inhibitors.