Improving resistance of E690 steel to stress corrosion cracking in high Cl⁻ environments through Sn microalloying

A series of Sn microalloying high-strength low-alloy (HSLA) steels were prepared through vacuum melting and hot rolling. Their stress corrosion cracking (SCC) behavior under high Cl⁻ environments was investigated using U-bend immersion, slow strain rate testing, electrochemical methods, and novel SCC sensor. Results revealed that HSLA steel microalloying with 0.1 wt.% Sn demonstrated superior SCC resistance, primarily attributed to the effective inhibition of the anodic dissolution mechanism. Fracture morphology revealed a transformation in fracture mode from brittle to a mixture of brittle-ductile characteristics, accompanied by the formation of a protective SnO₂ oxide film on the steel surface. However, excessive Sn content exacerbated SCC susceptibility due to the increased hydrolysis of Sn²⁺, leading to localized pitting and crack initiation. The critical role of optimal Sn content was highlighted in balancing mechanical properties and corrosion resistance, suggesting potential applications in industries where materials face harsh chloride environments.