Causes and Solutions of Blistering in Zinc Alloy Plating
April 07 , 2022
Due to its convenient molding, strong plasticity, low cost and high processing efficiency, zinc alloy is widely used in bathroom, luggage, shoes and clothing accessories, but the blistering problem of zinc alloy (electroplating; spraying) has always troubled hardware factories and electroplating factories.
Compilation of the experience of zinc alloy foaming, the specific aspects are as follows:
1. At the beginning of the design of zinc alloy products, it is necessary to consider the feeding port, slag discharge port and exhaust setting of the mold. Because the flow path of the workpiece for feeding and slag discharge is smooth and does not contain air, no water stains, no dark bubbles, it directly affects whether the subsequent electroplating is foaming. No water marks.
2. The tonnage and pressure of the molding machine should also be considered in the mold development. We personally experienced a 20-30% blistering event after zinc alloy electroplating. A friend of a hardware factory received a large order of several million, and the mold was opened for 8 pieces. No matter how the pre-plating treatment was solved, there would always be 20-30% blistering. Finally, the mold was blocked by 4 pieces and changed to 4 pieces from one mold. No more bubbles after plating.
3. The roller polishing liquid, polishing paste, and oxide layer on the pre-treated surface have not been cleaned, and the workpiece after roller polishing and polishing has a bright surface. Many employees in the pickling process of the electroplating factory simply pickle it and lead to the surface. The attached roller polisher was not cleaned, and foaming appeared for a long time. In addition, the roller polishing agent selected by the roller polishing factory has a great relationship, and the surfactant in some roller polishing agents is extremely difficult to wash away.
4. There is still an oxide film (pickling film) on the surface of the workpiece before the product enters the alkali copper (a lot of hardware friends commonly known as copper bottom) to remove the wax and oil. , In the early years, anti-contamination salt could be used to remove it. Now environmental protection does not allow the discharge of wastewater containing anti-contamination salt. It is recommended to use LJ-D009 stripping powder, which has better effect than anti-contamination salt, and can also remove the nickel layer and COD discharge meets the requirements. international standard
5. The alkali copper plating tank contains organic matter, many impurities, and free cyanide is not in the range. Test the composition of the alkali copper tank to see if the sodium cyanide is too low or the sodium hydroxide is too high! The cleaning is very critical, it is recommended to carbon treatment once every 3-5 days
6. The conductivity of the alkali copper cylinder is also very important. Whether the anode is dissolved normally and whether the anode copper plate is sufficient will lead to foaming
7. The zinc alloy product foams after it comes out of the oven; it may be caused by the uneven temperature of the oven, that is, the temperature is too high. Because the die casting is not tight, the zinc alloy water stained trachoma is easy to enter the acid, and the acid and zinc are even on the surface. In the case of the coating, a chemical reaction will still occur, and a large amount of hydrogen H will be generated. When the pressure inside is higher than the atmospheric pressure to a certain extent, and high temperature will generate bubbles.
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