Investigating the corrosion resistance of Cu-doped Ni-Mo low alloy steel through electrochemical tests

Corrosion resistance of Cu-doped Ni-Mo low alloy steel (Ni-Mo steel) in marine environments was systematically investigated through microstructure observation and galvanostatic polarization tests. Results show that solid solution Cu improved the corrosion thermodynamic stability of steel. The increasing Cu content promoted the formation of Cu-rich precipitates, martensite-austenite island, granular bainitic and high angle grain boundary, increasing the surface potential difference and the occurrence probability of local galvanic corrosion on steel surface. The addition of Cu improved the protectiveness of corrosion product film after galvanostatic polarization tests relying on the functions of CuFeO₂ and CuO, whose formation was mainly related to the solid solution Cu in Ni-Mo steel.