Stress Corrosion Sensitivity of Martensitic Stainless Steel in H₂S Environment

In CO₂/H₂S coexisting environment simulating oil field, the stress corrosion sensitivity of 13Cr stainless steel under the interaction of stress and crevice in simulated oilfield environment was evaluated by means of high temperature and high pressure simulation test, four-point bending stress loading method and scanning electron microscopy. The results show that under stress-free condition in CO₂ and H₂S environments the 13Cr stainless steel had stable anodic passivation zones. But the corrosion potential was significantly reduced when H₂S occurred in the environment, the corrosion rate and pitting corrosion sensitivity were relatively increased, and the passivation state of the material surface was unstable after loading stress (80% σ_s). In a high temperature and high pressure environment at H₂S partial pressure of 0.1 MPa and under the interaction of 80% σ_s stress and 0.1 mm crevice, pitting corrosion appeared in the crevices on the surface of 13Cr stainless steel, but did not expand to cause stress corrosion cracking. When the partial pressure of H₂S increased to 0.5 MPa, stress corrosion cracking occurred when stress of 80% σ_s was loaded. The presence of H₂S increased the activity of the material surface and accelerated the corrosion damage.