Zinc aluminum die casting parts is a kind of powder die-casting parts with zinc as the main component. This kind of parts is a very dense surface layer on the outside and a dispersed porous structure on the inside. Acid degreaser can not be used, but only alkaline degreaser can be used for degreasing.
Most of the Zinc aluminum die casting parts are required to be plated with copper, nickel and chromium multi-layer coating, which requires high decoration. Before degreasing, they are all 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 more than 70%, in order to emulsify white wax, the temperature of dewaxing water is higher than 70 ℃. In the past, we only used ordinary chemical degreasing solution to improve the temperature to remove wax. This method has a long time and low power. Now there is a special supply of dewaxing water, which is shortened at any time, and the effect is better. If use ultrasonic wave effect is very good. Generally, the dewaxing water only removes the wax and does not degrease, but also carries on the chemical degreasing. The chemical activity of zinc alloy is very strong, and the basicity of chemical degreasing solution cannot be too strong, otherwise it will corrode the surface. The temperature is usually controlled between 50-70 ℃ for 3-5min. The products supplied on the market also have degreaser which combines degreasing and wax removal, and the effect of ultrasonic cooperation is very good.
The composition of electrolytic degreaser for zinc alloy parts is similar to that of chemical degreaser. However, it is necessary to be rich in complexing agents. During electrolytic degreasing, the Zinc aluminum die casting parts should be placed on the cathode for degreasing, the temperature is 50-70 ℃, the current density is 3-5a / DM2, and the time is 1-2min.
In the selection of wax removal and degreasing two in one process, under the effect of ultrasonic, sometimes there is brown corrosion film on the surface of die casting. This degreaser is not suitable for use. Degreaser for zinc die casting shall be replaced. Special attention should be paid to this.
