How To Degrease Zinc And Aluminum Die Castings
Keganhirl > 07-10-2019, 09:20 AM
Zn-al die casting is a kind of powder die casting parts with zinc as the main component. The surface of this part is a very dense layer, inside is a dispersed porous structure. Instead of using an acidic degreaser, only an alkaline degreaser can be used for degreasing.
Most zinc-aluminum parts require copper-nickel-chromium multilayer coating, which has higher requirements for decoration. It is mechanically polished before degreasing. So waxing (the waxing cream is rich in white wax) is a step forward, followed by chemical degreasing and electrolytic degreasing.
Because the melting point of white wax is above 70%, in order to emulsify white wax, dewaxing water temperature above 70℃ is useful. In the past, we only used ordinary chemical degreasing liquid to remove wax. This method has long time and low power. Now there is a special wax removal water supply, time to shorten, the effect is better. If apply ultrasonic effect very good. Usually wax removal water only wax removal without degreasing, but also chemical degreasing. The chemical activity of zinc alloy is very strong, the alkalinity of chemical degreasing liquid should not be too strong, or it will corrode the appearance. The temperature is usually controlled between 50 and 70℃ for 3 to 5 minutes. The product that supplies on the market also has the degreasing agent that combines degreasing and removing wax for one, cooperate ultrasonic effect very good.
The composition of electrolytic degreaser of zinc alloy is similar to that of chemical degreaser. But it is necessary to enrich the complex agent ability to use. In electrolytic degreasing, zinc alloy die casting parts should be placed in cathodic degreasing, temperature 50 ~ 70℃, current density 3 ~ 5A/dm2, time 1 ~ 2min.
When selecting the two-in-one process of wax removal and degreasing, brown corroded film will sometimes occur on the surface of casting under ultrasonic effect. This degreasing agent should not be used. Degreasing agents for zinc die castings should be replaced. Special attention should be paid to this.