How to ensure the quality of zinc alloy die casting coating?
Zinc alloy die castings must be pre-coated with an excellent, well-preserved metal in a solution with a small corrosive effect on the parts to ensure the quality of the coating.
(1) pre-plating nickel. It can also be chemically impregnated with nickel.
(2) pre - plated brass. It is very good to use cyanide pre - plated brass to replace cyanide precoated copper. The precoated copper layer should not be less than 7 microns, and the copper layer is too thin to disperse to the zinc base, forming the middle layer of zinc-copper alloy and affecting the contact force.
(3) chemical immersion nickel. The chemical immersion (plating) nickel is acidic and alkaline, the zinc alloy die casting is the alkaline chemical dip (plating) nickel is better than the acid, the acid is easy to corrode the matrix, and the nickel layer is presented.
(4) precoated copper. Zinc alloy die casting precoated copper is usually carried out in cyanide solution. The copper content in the pre-copper solution is low, and the free sodium cyanide is high, and the large current shock is selected to ensure that the deep concave can be plated with copper and the tank is charged.
In order to ensure the bonding of zinc alloy die casting substrate and coating, it can be used to pre-plating cyanide copper, and then pre-plating neutral nickel. The zinc alloy die casting parts can be coated with copper or nickel plating on the normal technology after the pre-coating of a qualified coating, and other metals are electroplated according to the general technology.
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