Effect of Electrotess Zinc Plating Process on Al-Zn Composite Coating on Magnesium Alloy Surface

In order to improve the corrosion resistance of magnesium alloys, an Al-Zn composite coating was prepared on the alloy surface by the process of electroplating aluminum-electroless zinc plating. Composition and structure of the coating were investigated through observation of coating morphology and phase analysis. The influence of main salt concentrations, complexing agent concentrations and bath temperature on the corrosion resistance of the coating was studied by electrochemical methods. The results showed that the Al-Zn composite coating obtained by the process of electroplating aluminum-electroless zinc plating had excellent flatness and uniformity, and the coating was firmly bonded to the substrate. The optimal plating process parameters were ZnSO₄·7H₂O with a mass concentration of 40 g/L, K₄P₂O₇·3H₂O with a mass concentration of 150 g/L, and the temperature of the electroless plating solution was 50 ℃. Compared with the base sample, the corrosion rate of the sample was greatly reduced after plating under the best process parameter conditions. This process could achieve good electroplating effect and anti-corrosion performance, and had certain industrial value.