What is the cause of fading or even blackening of zinc alloy die-casting parts after electroplating?
Electroplating processes and die cast surface quality can result in poor plating.
Mold castings should have good surface quality, no porosity, cracks, pores, bubbles, shrinkage holes, cold wires, pinholes, etc.; otherwise, the surface of the casting after electroplating is easy to foam, and the plating layer will be separated from the substrate.
When grinding and polishing before plating, be careful not to over-grind.
Due to the rapid cooling rate during the solidification process of Die casting, the die-casting surface becomes a dense hard layer, and the internal structure may have defects such as porosity and shrinkage.
Do not remove the fine surface during grinding, otherwise pitting and bubbles will occur during the plating process. In addition, the polishing wheel should not be pressed too tightly and overheated to prevent adhesion between the abrasive and the product, resulting in poor plating of the product.
Zinc is easily oxidized and forms an oxide film on the surface, which affects the performance of zinc.
Therefore, the oxide film is removed to have a reducing material, and the surface of the oxide film can be removed by an acid (e.g., hydrochloric acid) solution.
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