Zinc-aluminum die-casting is a kind of die-casting part with zinc as the main component. The surface of this part has a very dense surface layer, inside which is an evacuated porous structure and a lively amphoteric metal. Therefore, only by adopting appropriate pre-treatment methods and electroplating processes can the coating layer on the zinc alloy be well adhered to meet the requirements of qualified products.
The zinc alloy materials commonly used for electroplating are: 3.5% to 4.5% aluminum, 0.75% to 1.25% copper, 0.03% to 0.08% magnesium, the balance being zinc, and the total impurity is ≤0.2%. The 925 grade zinc alloy has a high copper content and is easy to plate. Generally, the zinc alloy has a density of 6.4 to 6.5 g/cm3, and if the density is <6.4 g/cm3, foaming and pitting may occur after plating. In short, the selection must be strictly controlled. In addition, the mold must be designed properly during die casting to avoid inadvertent defects (such as pitting).
