Zinc-aluminum die casting is a powder die-casting part with zinc as the main component. This kind of part has a dense surface layer on the outside and a dispersed porous structure on the inside. Acidic degreasers cannot be used, but alkaline degreasers can only be used for degreasing.
Most of the zinc and aluminum parts require copper-nickel-chromium multi-layer plating, which requires higher decoration. Before degreasing, it is mechanically polished. So dewaxing (the polishing paste is rich in white wax) is the first step, followed by chemical degreasing and electrolytic degreasing.
Because the melting point of white wax is above 70%, in order to emulsify white wax, the temperature of the wax removal water is higher than 70°C. In the past, people only used ordinary chemical degreasing fluid to increase the temperature to Zinc die casting parts remove wax. This method has a long time and low power. Nowadays, there is a special supply of dewaxing water, the time is shortened, and the effect is better. If you use ultrasound, the effect is very good. Usually, the wax removal water only removes wax but not degreasing, and then chemical degreasing is required. The chemical activity of zinc alloy is very strong, and the alkalinity of the chemical degreasing solution should not be too strong, otherwise it will corrode the appearance. The temperature is usually controlled between 50 and 70°C for 3 to 5 minutes. The products on the market also have degreasing agents that combine degreasing and wax removal, and they work well with ultrasound.
The composition of the electrolytic degreasing agent for zinc alloy parts is similar to that of the chemical degreasing agent. But it is necessary to be rich in complexing agents to be able to use it. During electrolytic degreasing, the zinc alloy die-casting should be placed on the cathode for degreasing at a temperature of 50-70°C, a current density of 3-5A/dm2, and a time of 1-2min.
When selecting the two-in-one process of wax removal and degreasing, a brown corrosion film sometimes occurs on the surface of die castings under the effect of ultrasonic waves. This degreaser is not suitable for use. Degreasing agents dedicated to zinc die castings should be replaced. This point should be paid special attention.