Effect of Service Environmental Parameters on Electrochemical Corrosion Behavior of L80 Casing Steel

The corrosion behavior of L80 casing steel was studied in a simulating annulus environment using the electrochemical measurement method, immersion test, and tensile test under a high-temperature and high-pressure H₂S/CO₂ environment. The partial pressure of CO₂ ($P_{{\mathrm{CO}}_2}$), the partial pressure of H₂S ($P_{{\mathrm{H}}_2\mathrm{S}}$), water content, and preloading stress remarkably affected the corrosion behavior of L80 steel. The influence of $P_{{\mathrm{CO}}_2}$ on stress corrosion cracking (SCC) susceptibility has an inflection point of approximately 1.1 MPa. The SCC susceptibility reaches the maximum when the $P_{{\mathrm{CO}}_2}$ is about 1.1 MPa. The SCC susceptibility has a positive correlation to $P_{{\mathrm{H}}_2\mathrm{S}}$ and water content. The higher water content of the corrosion medium can increase the electrical conductivity of the corrosion medium and promote the corrosion of L80 steel, which can improve the diffusion of hydrogen into steel and promote the SCC of L80 steel. Preloading stress can promote local corrosion, thereby promoting SCC of steel under stress. The dislocation emergence point caused by preloading stress can accelerate the diffusion of hydrogen into steel and increase SCC susceptibility.