ELECTROLESS Ni-P PLATING ON THE AZ91D MAGNESIUM ALLOY

Direct electroless Ni-P plating on the AZ91D magnesium alloy from a plating bath containing sulfate nickel was investigated.The morphology and microstructure of the electroless Ni-P coating was studied by using SEM and XRD.The electroless Ni-P coating was compact and no obvious defects.The hardness values of the Ni-P coatings were about 660 VHN and the phosphorus content of this coating was about 3.72 mass%.The deposition rate of the electroless Ni-P alloy was about 23 μm/h.The acid pickle pretreatment on the AZ91D magnesium alloy substrate provides surface pits to act as sites for mechanical interlocking to improve adhesion of the coating and the substrate.