Electroless nickel-plating on die cast magnesium alloy AZ91D
(1. School of Materials Science and Engineering, Changchun University of Technology, Changchun 130012, China;
2. Key Laboratory of Automobile Materials, Ministry of Education, Jilin University, Changchun 130025, China)
2. Key Laboratory of Automobile Materials, Ministry of Education, Jilin University, Changchun 130025, China)
Abstract: Electroless nickel-plating on die cast magnesium alloy AZ91D was investigated. Growth of the electroless nickel-plating coating was characterized using scanning electron microscopy. Corrosion resistance of the coating was evaluated by open circuit potential and potentiodynamic polarization curves in 3.5% (mass fraction) NaCl solution. The results show that plating deposition is initiated on the crevices and then spread onto primary α phase. The corrosion potentials for die cast magnesium alloy AZ91D and nickel-plating coating are about −1.45 V and −0.36 V (vs. SCE), respectively. No discoloration, cracks, blisters, or peeling appear by heat-quench test. The results show that the corrosion potential of Ni-P coating is increased by 1 000 mV and corrosion resistance for die cast magnesium alloy AZ91D is improved. The adhesion between the coating and the substrate is excellent. Electroless nickel plating is a promising method to enhance magnesium alloys resistance for attacking.
Key words: electroless nickel-plating; die cast magnesium alloy; corrosion resistance; polarization