Distinct beneficial effect of Sn on the corrosion resistance of Cr–Mo low alloy steel

In this work, the beneficial effect of Sn addition on the corrosion resistance mechanism of Cr–Mo low alloy steel was studied. Results demonstrated that Sn improves the corrosion resistance of the steel matrix mainly by influencing the microstructural transformation. Sn addition and the synergistic effect of Sn, Cr, and Mo promote the formation of α-FeOOH, SnO2, SnO, Cr(OH)3, and molybdates, lead to the improved protection and stability of the rust layer. This synergistic effect also endows the inner rust layer with cation selectivity, preventing the further penetration of Cl− and inhibiting the localized corrosion of steel.