Electroplating Quality And Electroplating Process Of Faucet

1. Material selection

The electroplating quality of water nozzle not only depends on the electroplating process, but also involves the base material of water nozzle, casting process, electroplating pretreatment and so on. The faucet valve body is the main component of the faucet. It is made of cast brass. Zcu40znpb2 is the most common brand, and the average wall thickness of the casting is 3mm. The valve body, handle and bonnet of a good faucet are all refined with brass. After casting, processing, surface grinding and polishing, they are electroplated with nickel, decorative chromium or chromium nickel alloy. If such products are well treated in casting, electroplating pretreatment and electroplating process, they are generally corrosion-resistant. In order to enhance the corrosion resistance and improve the grade of products, multi-layer nickel plating process is also adopted. However, in order to save the production cost, some enterprises add a large amount of waste copper into the cast brass, so that the cast brass contains a large amount of impurities. The surface of the product is loose, contains more sand holes and is not corrosion resistant. After the acid salt spray test, there are pitting and pitting corrosion. Some manufacturers even use obsolete cast iron and zinc alloy as raw materials. Because cast iron is easy to rust and zinc alloy is not corrosion-resistant, the water nozzle made of these raw materials is easy to appear rust spots. After 2H acid salt spray test, a large number of rust spots, pits and other defects appear on the valve body. In other manufacturers, the nozzle valve body is made of brass, while the handle and valve cover are made of cast iron, plastic and other inferior materials. After the 24h acid salt spray test, the valve body is often not corroded, while the handle and valve cover are seriously corroded, resulting in unqualified products and reducing the grade of the product.

2. Casting process

The nozzle valve body is the main component of the nozzle, and its production method is generally sand casting and metal casting. Due to the high surface quality requirements of the nozzle, there shall be no visible pores, cracks, looseness and inclusions on the outer surface of the casting before electroplating; The nozzle body with metal mold casting has compact structure, good surface quality and high yield, and may also avoid the environmental pollution caused by sand mold casting. Therefore, at present, most manufacturers adopt metal mold casting technology. However, when the nozzle valve is cast in metal mold, its outer surface is formed by metal mold and its inner cavity is formed by coated sand core. When the liquid copper is poured into the metal mold cavity, the external cooling rate is fast and the casting structure is dense; The inner cavity is surrounded by sand core, and the cooling rate is slow, which is easy to produce shrinkage and porosity defects. Although some manufacturers use cast brass with good material, after 24h acid salt spray test, the valve body still has light loss and rust spots. The reason is that the casting process is not handled well during the casting of water nozzle body. Therefore, only by strengthening the design of casting mold, alloy melting and pouring, casting process control and cleaning of falling sand, can we cast qualified nozzle body castings.

3. Polishing and cleaning before plating. Qualified nozzle castings need to go through machining, grinding and polishing processes before plating.

Machining and polishing are the shaping of products. Grinding and polishing mainly flatten the product surface, reduce the roughness of castings, and eliminate minor sand holes, burrs and other defects caused by casting. As the appearance quality requirements of the water nozzle are relatively high, the coating on the outer surface of the water nozzle shall be well combined, the organization shall be fine, smooth and uniform, the color shall be uniform, the polished outer surface shall be bright, and there shall be no appearance defects such as bubbles, charring, separation, scratches and so on. Polishing quality is the key factor to ensure electroplating quality, improve surface brightness and eliminate defects. Faucets are decorative products. It is very sensitive to inclusions and slag inclusion. Even very fine impurities may cause defects such as burrs, pits or pinholes on the plated surface, and even scorch, blister and peeling of the coating. For example, after 24h acid salt spray test, there will be loss of light and rust, even bubbling and overall corrosion, so pretreatment is very important. The sand and carbonized resin in the inner cavity after casting, the grease, copper chips and copper powder left after machining, and the polishing paste after polishing must be cleaned, so as to ensure the quality of electroplating. The existence of pollutants is the main factor of burr and pitting in electroplating.

4. Control of electroplating process

The surface of the water nozzle is mainly plated with nickel chromium. The nickel chromium electroplating process has a history of many years. The electroplating process is very mature, with high purity of chemical raw materials and additives and less impurities; Moreover, the electroplating equipment is advanced. In the electroplating process, as long as the process management is strict and the bath solution, rinsing water, equipment and production environment are kept clean, there are generally few electroplating quality problems. The non-corrosion phenomenon found in the test is mainly that in order to reduce the cost, some manufacturers reduce the electroplating time and the coating is thin, which can not completely make up for the pores of the coating. The corrosive solution corrodes to the matrix through the pores, resulting in a large number of rust spots.

5. Conclusion

1) The valve body, handle and bonnet of the water nozzle shall be cast brass or copper alloy with good quality, and the materials such as easily rusty cast iron and non-corrosion zinc alloy shall be discarded;

2) Adopt metal mold to cast the water nozzle valve body, and pay attention to the casting process;

3) Grinding and polishing shall be complete, and pre plating treatment shall be done well;

4) Strictly implement the nickel chromium plating process specification, strengthen process management and ensure the coating thickness.