The main elements of zinc alloy are zinc and alloy, they are both amphoteric metals which has poor chemical stability, easily oxidize and corrode, so zinc alloy cast needs to be electroplated or coated. When it comes to those that don't require a lot of pressure and have complicated shapes, we always use zinc alloy to replace copper, iron or other metal materials. Because zinc alloy is easy to die cast and has low cost and processing cost.
The quality control of the surface of zinc alloy die cast
The designs for geometrical shapes of die casting
You should avoid the structure of deep blind hole when designing the geometrical shapes of zinc alloy die cast. So there should be a fabrication hole for liquor and gas to flow when designing the parts. In this way, you can not only plate the cast, but also reduce the plating solution contamination.
The mold design for die cast and the die casting technique
Zinc alloy die cast surface is a compact layer, the inner structure is loose and porous, and the thickness is 0.1mm. In order to reduce the die casting defect of the crack, air hole, trimming and burr, you should try to make the surface smooth when using the technology of mold design and die cast. It is necessary to clean the machine and avoid damage of the surface compact layer, in order to prevent porous substrate and showing porous matrix. Porous matrix can make the electroplating to be difficult and affect the quality as well. We often use mold release in die casting
process, we should pay certain attention to its use and removing, for it is one of the reasons which influences the adhesion of the firm.
The selection for die casting materials
The common zinc alloy materials that are used for electroplating are 2ZnAl43, 2ZnAl41, 2ZnAl40.5 and 2ZnAl4, the frequently used grade is ZnAl925, ZnAl903, though ZnAl903 is better than ZnAl925.
In addition, we always use a part of recycled materials when die casting, the amount should be controlled under 15%, better not to exceed 20%. Because the recycled materials are mix with other component such as silicon,which will affect the adhesion of the firm. If you use a lot recycled materials in die casting, you'd better use hydrofluoric acid to activate them when electroplating.