A novel process for electroless nickel plating on anodized magnesium alloy

In this paper, a novel palladium-free activation electroless nickel (EN) plating process, by which a TiB2 powders contained intermediate film was used as catalyst, was introduced for anodized magnesium alloy AZ91D. The corrosion behavior of AZ91D without and with coating was compared and the bonding strength of the EN plating to the substrate was also measured. The results showed that the EN plating could easily take place on the intermediate catalytic layer, directly on which a smooth and compact Ni-P alloy layer without obvious flaws, about 20 μm thickness, was successfully deposited. The catalytic function was principally from TiB2 powder. The adhesive tensile test indicated a good bonding strength of about 11 MPa between the substrate and the catalytic layer. An obvious passivation range and higher Ecorr (−0.323 V) for the EN plating during anodic polarization in 3.5 wt.% NaCl solution, implied a typical character of a compact Ni-P alloy layer, with an effective protection for the substrate.