Dongguan zinc alloy die castings (a zinc alloy material with about 4% aluminum) have the advantages of high precision, no cutting or less cutting during processing, low density, and certain mechanical strength. Therefore, in the industry: zinc alloy die castings are widely used for structures and decorations with little force and complicated shapes. Zinc alloy is easy to be corroded, so electroplating layer is often used as protective layer or protective decorative layer, and pre-plating copper is required before electroplating. The surface adjustment process consists of activation and pre-plating.
After polishing, polishing and degreasing the zinc alloy die castings, there is a very thin oxide mold on the surface. In order to ensure the bonding strength of the coating, a 1%-3% hydrofluoric acid solution is usually used for immersion activation for 3-5s. When the surface shows uniform small bubbles or slight discoloration, immediately go out of the tank for cleaning. It is also possible to use 15-20m1./I. fluoroboric acid solution to corrode and activate the workpiece for 3-5s. After activation, the workpiece can be cyanide pre-copper-plated.
In order to ensure that zinc alloy die-casting parts with complex shapes have good electroplating dispersion and covering power, and to prevent the replacement of zinc with metal ions in the electroplating solution, which affects the bonding force of the coating, zinc alloy die-casting parts should be After charging into the tank, use 2--3A, %d㎡ high current impulse electroplating for 1 to 3 minutes, so as to quickly coat a layer of dense copper with a complete layer of less pores. Then the normal current density is restored. When the cathode is used to move the electrodeposited copper, a fine and smooth copper coating can be obtained. The thickness of the pre-plated copper bottom layer should be no less than 5um, preferably over 8-1Cum. The pre-plated copper is too thin, and it is not enough to prevent the zinc alloy from being etched by the solution when the acid copper or nickel plating is carried out after twisting. In addition, the thinner the pre-plated copper, the faster the diffusion of copper to the zinc alloy, because the surface coating and the zinc alloy The electrochemical corrosion caused by the potential difference of the substrate is also extremely serious. Zinc alloy die castings with less complex shapes can also be pre-plated with neutral nickel plating solution.
What are the important features of zinc alloy die casting machine accessories?
Zinc alloy die-casting machine accessories are alloys based on zinc with various elements added. The alloying elements that manufacturers usually add are aluminum, copper, magnesium, cadmium, lead, titanium and other low-temperature zinc alloys, zinc alloy die-casting Machine parts, zinc alloy has a low melting point, good fluidity, easy to weld, braze and plastic process, corrosion resistance in the atmosphere, and easy recycling and remelting of residual waste; but the creep strength is low, and natural aging is easy to cause dimensional changes. Prepared by melting method, die-casting or pressure-processed into material. According to the manufacturing process, it can be divided into cast zinc alloy and wrought zinc alloy. Important features of zinc alloy die-casting machine accessories: high specific gravity; zinc alloy die-casting machine accessories, good casting performance, can die-cast precision parts with complex shapes and thin walls, and smooth casting surfaces; surface treatment: electroplating, spraying, painting; melting and When die-casting, it does not absorb iron, does not corrode the molding, and does not stick to the mold; it has good mechanical properties and wear resistance at room temperature; it has a low melting point and melts at 385°C, making it easy to die-casting.
