Fabrication of low-cost Ni-P composite coating on Mg alloys with a significant improvement of corrosion resistance: Critical role of mitigating the galvanic contact between the substrate and the coating

High galvanic corrosion susceptibility and expensive Pd-activation process are two critical obstacles for the application of electroless nickel (EN) plating on Mg alloy. In this work, the plasma electrolytic oxidation (PEO) coating was sealed by chemical conversion post-treatment to obtain an intermediate layer with high electrical resistance, aiming to minimize the susceptibility of galvanic corrosion. A low-cost Ag-activation technique was proposed to catalyze the EN plating process. Results indicate a dramatic improvement of corrosion resistance of EN composite coating. In addition, the composite coating also exhibits high adhesion, hardness, electrical conductivity and low magnetism.

Automated summary

The high galvanic corrosion susceptibility and expensive Pd-activation process are critical obstacles for the application of electroless nickel (EN) plating on Mg alloy. In this study, a plasma electrolytic oxidation (PEO) coating was post-treated with chemical conversion to obtain an intermediate layer with high electrical resistance, aiming to reduce galvanic corrosion susceptibility. A low-cost Ag-activation technique was proposed to catalyze the EN plating process, leading to significant improvement in corrosion resistance of the EN composite coating. Additionally, the composite coating demonstrated high adhesion, hardness, electrical conductivity, and low magnetism.