Preparation and Performance of Electroless Nickel on AZ91D Magnesium Alloy

The corrosion of magnesium alloy in different plating solutions was researched. The results demonstrated that corrosive condition of the alloy immersed in nickel chloride solution and nickel sulfate solution is serious and in nickel acetate solution and nickel nitrate solution is less. Magnesium alloy was handled with four acid pickling formulas and two activation formulas and the effects of different pickling formulas and activation formulas were researched through comparative experiment. The experimental results indicated that after handed with pickling formula about 500mL L-1 H3PO4 (85%), 110mL L-1 HNO3 (68%), room temperature for 30s and activation formula about 375mL L-1 HF (40%), room temperature for 10min, magnesium alloy could realize electroless nickel plating directly and the performance of the prepared plating was much better. The properties of the nickel-plating coating were researched by electrochemical workstation, scanning electron microscope, and X-ray diffraction. The results demonstrated that this Ni-P coating was very uniform and meticulous; the structure of Ni-P coating was amorphous; and comparing with magnesium alloy, the corrosion potential of this plating increased about 799V and the corrosion current density declined obviously. The nickel-plating coating effectively improved the anticorrosion performance of magnesium alloy.