Exploring the influence of Cu addition on the microstructure and substance transformation in corrosion product layer of X80 steel

The influence of Cu addition on the microstructure evolution and substance transformation in corrosion product layer was explored through comprehensive microscopic characterization and immersion test. The Cu lowers the Ar3 and Ms temperatures of X80 steel, facilitating the Granular Bainite formation while impeding the development of Polygonal Ferrite. Furthermore, the Cu facilitates the development of stable corrosion products, leading to an increased proportion of these substances in corrosion product layer and a reduction in their dissolution and detachment during rust formation. And the formed oxide (CuO) not only enhances the stability of the corrosion product layer but also provides nucleation sites for CuFeO2 production. CuFeO2 carries a negative charge, which enhances the Cl- blocking ability of the corrosion product layer. The inclusion of these substances in corrosion product layer enhances its resistance to corrosive media. The corrosion product layer offers the best protection for the steel when the Cu addition is 1.5 wt%.