Electrodeposition of zinc-nickel coating on AZ31 magnesium alloy

Although magnesium and its alloys have excellent physical and mechanical properties, they are highly susceptible to corrosion to hinder their widespread use in many applications. In this paper, zinc-nickel coating is directly electrodeposited on AZ31 magnesium alloy using an aqueous solution containing zinc fluoride, basic nickel carbonate, and citrate. Various parameters such as pH value, additive, complexing agent, current density, and electrodepositing temperature are studied to understand electrodepositing zinc-nickel coating on AZ31 magnesium alloy. SEM observation shows that the morphology of zinc-nickel coating is typical dense nodular structure, and the coating compositions are found to be 86 wt% zincs and 14 wt% nickels. Adhesion strength result shows that there is not peeling for zinc-nickel coating with the grid of 1 × 1 cm treated by the adhesive tape. The immersion test in 5% NaCl solution reveals that the zinc-nickel coating has good dense property.