Study on the Preparation and Property of Coatings on AZ91 Magnesium Alloy by Electroless Nickel Plating

The process of direct electroless nickel plating on the surface of AZ91 magnesium alloy and the performances of nickel coat were studied.The morphology of plating has been observed by SEM;The chemical compositions and phases have been analyzed by EDS and XRD;The adhesive force between the coating and the magnesium substrate has been estimated by using scribe test.It is showed that a Ni coating with good combination force and high hardness can be obtained.The results of XRD and EDS indicate that owing to the oxidation-reduction reaction of NaH2PO2,a little P exists in the layer.By static corrosion test in 3.5% NaCl solution,it can be seen that the corrosion resistance of the plating is approved and the protection for the magnesium alloy matrix is optimal.