Zinc alloy is widely used in bathroom, luggage, shoes and clothing accessories due to its convenient molding, strong plasticity, low cost, and high processing efficiency. However, the foaming problem (electroplating; spraying) of zinc alloy has always troubled friends from hardware factories and electroplating factories.
Author: Marisa
Zinc alloy is widely used in bathroom, luggage, shoes and clothing accessories due to its convenient molding, strong plasticity, low cost, and high processing efficiency. However, the foaming problem (electroplating; spraying) of zinc alloy has always troubled friends from hardware factories and electroplating factories.
Compile the experience of zinc alloy foaming from multiple hardware and electroplating factories that have provided summary services, including the following aspects:
1.At the beginning of the design of zinc alloy products, the feeding port, slag discharge port, and exhaust setting of the mold should be considered. Because the flow path of the workpiece for feeding and slag discharge is smooth and free of air, there are no water stains or dark bubbles, which directly affects whether the subsequent electroplating will produce bubbles. Qualified feeding and slag discharge molds can cast workpieces with a smooth, white and bright surface, and no water stains.
2.In mold development, the tonnage and pressure of the molding machine should also be considered. We personally experienced a 20-30% foaming event after zinc alloy electroplating. A friend of a hardware factory received a large order of several million yuan, and 8 pieces of molds were opened. No matter how to solve the problem before electroplating, there were always 20-30% blisters. Finally, 4 pieces of molds were blocked, and 4 pieces of the first mock examination were opened. After electroplating, there would be no blisters.
3. The surface polishing solution, polishing paste, and oxide layer on the pre-treatment surface were not cleaned thoroughly, resulting in rolling and polishing. After rolling and polishing, the surface of the workpiece became shiny. Many employees in the electroplating factory's pickling process casually pickled it, causing the rolling agent attached to the surface to not be cleaned thoroughly, resulting in the appearance of bubbles. The relationship between the rolling agent selected by the rolling and polishing factory is also significant, as some surface active agents in the rolling agent are extremely difficult to remove.
4. Before the product enters the alkaline copper plating tank (commonly known as copper base by many hardware friends), there is still an oxide film (acid washed film) on the surface of the workpiece, and the wax and oil removal films have not been completely treated. Therefore, film removal is very important. In earlier years, anti dye salts could also be used for removal. Nowadays, environmental protection does not allow the discharge of wastewater containing anti dye salts. It is recommended to use LJ-D009 film removal powder, which has better effect than anti dye salts, can remove the nickel layer, and COD emissions meet international standards
5. The alkaline copper plating tank contains organic matter with many impurities and free cyanide is not within the range. Analyze the composition of the alkaline copper tank to see if the sodium cyanide is too low or the sodium hydroxide is too high! Be careful when adding brighteners. If the brightener is too high, cleaning the alkali copper tank is crucial. It is recommended to carbon treat it once every 3-5 days
6. The conductivity of the alkaline copper cylinder is also important. Whether the anode dissolves normally and whether the anode copper plate is sufficient will lead to foaming
7. Zinc alloy products will bubble after coming out of the oven; It may be due to uneven temperature distribution in the oven, resulting in excessively high temperatures Due to the lack of tightness during die-casting, zinc alloy water stains and sand holes are prone to acid ingress. Even with surface coatings, acid and zinc still undergo chemical reactions, producing a large amount of hydrogen gas. When the pressure inside exceeds atmospheric pressure to a certain extent and high temperature is added, bubbles will be generated