Combining Thermodynamics and Kinetics to Investigate the Corrosion of 3Cr Steel and HP-13Cr Stainless Steel in Extreme Oil-Gas Environments Available to Purchase

The corrosion behavior of 3Cr steel and HP-13Cr stainless steel (SS) under high temperatures and CO₂ or H₂S pressure environments was investigated by immersion tests and multiple characterizations of corrosion films, and analyzed by combining the Pourbaix diagram and kinetic calculations. At 180°C/3.8 MPa CO₂, both 3Cr steel and HP-13Cr SS exhibited double-layered corrosion films, comprising a crystalline FeCO₃ outer layer and an inner Cr₂O₃ and Cr(OH)₃ layer. Furthermore, at 180°C/3.8 MPa H₂S, the corrosion films of both steels consist of an outer crystalline pyrrhotite and pyrite layer and an inner Cr₂O₃ and Cr(OH)₃ layer. The corrosion resistance of 3Cr in H₂S is inferior to that of HP-13Cr SS due to the influence of stress corrosion cracking but is close to that of HP-13Cr SS in CO₂. Therefore, 3Cr steel could be considered a cost-effective alternative to HP-13Cr SS in CO₂ environments.