Faucet plating quality and plating process problems

Release time:09-06-2019

1. Material selection The quality of the nozzle plating […]

1. Material selection

The quality of the nozzle plating depends not only on the plating process, but also on the faucet base material, the casting process, and the pre-plating treatment. The nozzle body is the main component of the faucet. The material is cast brass. The ZCu40ZnPb2 grade is the most common. The wall thickness of the casting is 3mm on average. The valve body, handle and bonnet of a good faucet are all made of brass. After casting, processing, surface grinding and polishing, nickel plating, decorative chrome or chrome-nickel alloy, such products are processed before casting, plating, plating. The process is well treated and generally resistant to corrosion. In order to enhance the corrosion resistance of the product and improve the grade of the product, a multi-layer nickel plating process is also adopted. However, in order to save production costs, some enterprises incorporate a large amount of waste copper into the cast brass, which causes the cast brass to contain a large amount of impurities. The finished product has a loose surface, contains a lot of sand holes, and is resistant to corrosion. Pitting and pitting occurred after the acid salt spray test. Some manufacturers even use cast iron and zinc alloys that have been eliminated as raw materials. Since cast iron is easy to rust and zinc alloy is not resistant to corrosion, the nozzles made from these raw materials are prone to rust spots. After 2 hours of acid salt spray test, the valve body There are a lot of defects such as rust spots and pitting. There are also manufacturers of faucet valve body made of brass, and the handle and bonnet are made of inferior materials such as cast iron and plastic. After 24 hours of acid salt spray test, this product is often not corroded by the valve body, but the handle and valve The cover has more serious corrosion, which leads to product failure and lowers the grade of the product.

2. Casting process

The nozzle body is the main component of the nozzle, and the production method is generally sand casting and metal casting. Since the surface quality of the nozzle is very high, the outer surface of the casting before plating cannot have any visible pores, cracks, looseness and inclusions; the nozzle of the metal casting has dense structure, good surface quality and high yield, and It is also possible to avoid environmental pollution caused by sand casting, so most manufacturers currently use metal casting technology. However, the metal-type casting nozzle valve has a metal surface formed by an outer surface, and the inner cavity is formed by a coated sand core. When the copper liquid is poured into the metal cavity, the surface cooling rate is fast, and the casting structure is dense; The cavity is surrounded by the sand core, and the cooling rate is slower, which is more likely to cause shrinkage defects. Some manufacturers use cast brass with better material quality. After 24 hours of acid salt spray test, the valve body still has light loss and rust spots. The reason is that the casting process has not been processed. Therefore, only the enhanced casting mold design, the alloy smelting and casting, the casting process control and the falling sand cleaning can be used to cast qualified nozzle castings.

3. The faucet castings that have been polished and cleaned before plating need to be machined, polished and polished before plating.

Machining and grinding are the shaping, grinding and polishing of the product to level the surface of the product, reducing the roughness of the casting, while also eliminating the slight blisters, burrs and other defects caused by casting. Since the appearance quality of the faucet is relatively high, the coating on the outer surface of the faucet should be well combined, the structure should be fine, smooth and uniform, and the color should be uniform. The polished outer surface should be bright, and there should be no appearance defects such as bubbles, scorching, detachment and scratching. . Polishing quality is a key factor in ensuring plating quality, increasing surface brightness and eliminating enthalpy. The faucet is a decorative product. It is very sensitive to inclusions and inclusions. Even extremely fine impurities may cause defects such as burrs, pitting or pinholes on the plating surface, and even burnt, blistering and peeling of the coating. After 24h acid salt spray test, there will be light loss and rust spots, even bubbling and general corrosion, so pretreatment is very important. The sand and carbonized resin in the inner cavity after casting, the grease, copper scrap and copper powder left after machining, and the polishing paste after polishing must be cleaned, so as to ensure the quality of plating. The presence of contaminants is a major factor in the occurrence of burrs and pitting in electroplating.

4. Control of electroplating process

The surface of the nozzle is mainly electroplated with nickel and chromium. The electroplating nickel-chromium process has been in the past many years, the electroplating process is very mature, the chemical raw materials and additives have high purity and less impurities; and the electroplating equipment is advanced, as long as strict process management in the electroplating process, keeping the bath liquid, rinse water, equipment and production The environment is clean and there are generally fewer plating quality problems. In the detection, the non-corrosion phenomenon is mainly caused by some manufacturers in order to reduce the cost, the plating time is reduced, the plating layer is thin, and the pores of the plating layer cannot be completely compensated. The etching liquid corrodes to the substrate through the fine pores, and a large amount of rust spots appear.

5 Conclusion

1) The valve body, handle and bonnet of the faucet should be made of cast brass or copper alloy with good quality, and the rust-resistant cast iron and non-corrosive zinc alloy should be discarded;

2) The metal casting nozzle body is used, and the casting process is emphasized;

3) Grinding and polishing should be thorough, and pre-plating treatment;

4) Strictly implement the electroplated nickel and chromium process specifications, strengthen process management, and ensure coating thickness.
The reason for the leakage of the faucet and the solution recommended