Influence of zincate pretreatment on adhesion strength of a copper electroplating layer on AZ91 D magnesium alloy

►Zn is mainly deposited on the α-phase surface rather than on the β-phase surface. ►Ultrasonic agitation improves the coverage of Zn deposits on the β-phase surface. ►Addition of H3BO3 to the plating bath improves the smoothness of Cu deposits. ►Zn layer deposited on the α-phase determine adhesion strength of the plating layer. ►Adhesion strength of the Cu coat is determined by the quality of a Zn-Cu mixed layer.