How to degrease zinc and aluminum die castings

Zinc aluminum die casting is a powder die casting with zinc as the main component. This part has a dense surface layer on the outside and a dispersed porous structure on the inside. Acidic degreasing agents cannot be used, but only alkaline degreasing agents can be used for degreasing.

Most zinc and aluminum parts require copper-nickel-chromium multi-layer plating, which requires higher decorativeness. Before degreasing, it is mechanically polished. Therefore, dewaxing (the polishing paste is rich in white wax) is the first step, followed by chemical degreasing and electrolytic degreasing.

Since the melting point of white wax is above 70%, in order to emulsify white wax, the temperature of the dewaxing water must be higher than 70°C. In the past, people only used ordinary chemical degreasing fluids to raise the temperature to remove wax. This method has a long time and low power consumption. Nowadays, there is a special supply of dewaxing water, the time is shortened and the effect is better. If the ultrasonic effect is good. Usually, the dewaxing water only removes the wax but not the oil, and also removes the chemical oil. 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 dewaxing, 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 must be rich in complexing agents to use it. In the electrolytic degreasing process, the zinc alloy die casting should be placed on the cathode to degreasing at a temperature of 50 to 70°C, a current density of 3 to 5A/dm2 and a time of 1 to 2 minutes.

When the two-in-one process of dewaxing and degreasing is selected, under the action of ultrasonic waves, a brown corrosion film sometimes appears on the surface of the die casting. This degreaser is not suitable for use. The degreaser dedicated to zinc die castings should be replaced. Special attention should be paid.