Understand the structural characteristics of zinc alloy die castings
      Like steamed bun zinc alloy die casting surfaces with a layer thickness of 0.02 ~ 0.10mln, smooth dense metal layer, in which the bottom is loose, porous structure. Therefore, when mechanical polishing, polishing prevent wear their smooth dense layer, avoid loose, porous material exposed inside, causing the coating to produce blistering, peeling and other undesirable phenomena.
Master chemical properties of zinc alloy die castings
      In the die-casting process, the impact of process factors can cause produce zinc and aluminum-rich site with a zinc alloy die part. Alkali preferentially dissolve the Al-rich phase, acid is preferentially dissolved zinc phase. If degreasing or etching process using alkali or acid, in the plating will cause coating blistering and peeling, seriously affecting the yield. For this reason, zinc alloy die castings are not in strong acid or alkali degreasing and etching.
Zinc Alloy Die Casting meet the dimensional requirements of the pre-coating
       Zinc Alloy Die Casting after completion of treatment before plating, to the pre-plated underlayer. Generally in the absence of NaOH copper cyanide plating bath, or in a neutral nickel plating nickel plating baths. Tubular parts should be deposited pyrophosphate plating solution.
Its coating thickness not less than 61, or very thin copper layer will soon spread to the zinc alloy, forming a layer of very brittle copper-zinc alloy, affect coating quality. The thinner the copper layer, the copper-zinc alloy, the faster the rate of diffusion within.
       Matrix properties of the workpiece itself and form a special processing have a significant impact on the plating.
1) Material zinc alloy die casting an aluminum alloy, are lively amphoteric metal. And again the two metals aluminum plating pretreatment and treatment of the most difficult, it is necessary to control the aluminum content, the content (mass fraction) materials are generally rust plated zinc alloy die casting, aluminum should not exceed 4%, aluminum content too, will make plating difficult normally.
2) the part design to be reasonable, casting shape plating coverage should be considered to minimize blind hole, so water is not easy to carry solution. Reduce sharp corners and other parts, so that when the power line distribution plating.
3) die-casting process, die-casting mold design is reasonable, so that casting does not produce shrinkage, defects such as pinholes and loose, the defect will affect coating adhesion.
4) die-casting process, to minimize segregation. As some parts of the aluminum segregation, in the degreasing, aluminum that is first dissolved happen, it will produce the casting surface pores, pinholes and can not be cleaned, resulting in poor adhesion. Cause coating blistering and peeling.
5) grinding the polishing process should pay attention to propriety, a dense layer of 0.05 ~ 0.1mm casting surface of the cooling process of the formation of the plating is very important to minimize losses when the dense layer of grinding polishing, grinding If this layer throw away, exposing the porous structure will be, in this layer will not be good plating layer.
6) copper-nickel-chrome plating layer formed by a plurality of types of plating, in terms relative to the base plate of the coating is female, only mechanical protection, and zinc alloy parts in moist air that is corrosive, it is necessary to ensure a non-porous coating . Otherwise corrosion products of zinc alloy coating will blister. With respect to steel parts in terms of the coating should be thicker two more, in order to apply zinc alloy die castings.
7) Diecast residue member die-casting and machining process, should be cleaned after machining. Because the residue is lively metal, any one operation in the plating will react with the solution, and damage the bath, the impact on the quality of the plating.