The stress corrosion cracking behavior of high-strength mooring chain steel in SO₂-polluted coastal atmosphere

21Cr2NiMo steel is widely used to stabilize offshore oil platforms, however, it suffers from stress corrosion cracking (SCC). Herein, we studied the SCC behavior of 21Cr2NiMo steel in SO₂-polluted coastal atmospheres. Electrochemical tests revealed that the addition of SO₂ increases the corrosion current. Rust characterization showed that the SO₂ addition densities the corrosion products and promotes pitting. Furthermore, the slow strain rate tests demonstrated high susceptibility to SCC at high SO₂ contents. Fracture morphologies revealed that the stress-corrosion cracks initiated at corrosion pits and the crack propagation showed transgranular and intergranular cracking modes. In conclusion, the SCC is mix-controlled by anodic dissolution and hydrogen embrittlement mechanisms.