Effect of H₂S Content on the Corrosion Behavior of 3Cr Steel in Oil and Gas Environments

In order to study the corrosion behavior and evolution process of corrosion products of 3Cr steel in solutions containing different amounts of H₂S, immersion tests were conducted on 3Cr steel in simulated oilfield produced water containing different amounts of H₂S for different times (6, 12, 24, 72 h), and the corrosion rates were tested. SEM, EDS, and XPS were used to analyze the surface morphology, elemental composition, and corrosion product composition of 3Cr steel. The results indicate that with the increase of H₂S content, the corrosion rate of 3Cr steel showed a trend of first increasing and then decreasing. Among them, the increase in corrosion rate was due to the dissociation of dissolved H₂S to produce H⁺, which increased the corrosiveness of the solution. When the mass concentration of H₂S exceeded 6.8 mg/L, there was an increase in surface corrosion products, which inhibited further corrosion of 3Cr steel. On the other hand, as the corrosion temperature increased from 60 ℃ to 120 ℃, the corrosion rate of 3Cr steel increased, and the corrosion products transformed from FeS to FeCO₃. The main reason was that increasing the temperature reduced the solubility of FeCO₃. In addition, the increase of temperature significantly increased the content of Fe²⁺ and promoted the precipitation of FeCO₃ crystals.