Sink faucet, also known as water tap, is widely used in our daily life, from household to restaurant, hotel. With living standards rising, the continuous improvement of housing conditions, the demand for faucets is increasing. So the requirements for the metal plating quality of faucets are also higher. In view of the quality problem of faucet electroplating, the author consulted a lot of relevant information and conducted acid salt spray tests on some products. Regarding the electroplating quality of the faucet, let us talk about the following issues at first.
The quality of faucet plating not only depends on the plating process but also involves basic materials, casting process, plating pretreatment and other aspects. The faucet body and valve core are the main components of the faucet. The body, valve core, handle and valve cover of a good faucet are all made of brass. After casting, processing, surface grinding, and polishing, electroplating nickel, decorative chromium or chromium-nickel alloy, if such products are well handled and generally more corrosion resistant. In order to enhance the corrosion resistance of the product and advance the product level, a multilayer nickel plating process is also selected.
The faucet body and valve are the main components of the faucet, and its production method generally includes sand casting and metal casting. Due to the high requirements for the surface quality of the faucet, the surface of the casting before electroplating must not have any visible pores, cracks, looseness and impurities. The faucet with metal casting has a fine structure, good surface quality, and high yield. It is possible to avoid the environmental pollution caused by sand casting, so most manufacturers now choose metal casting technology. However, the metal casting faucet surface is formed by a metal mold, 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 faster, and the casting structure is fine. The cavity is surrounded by sand cores, the cooling rate is slow, and shrinkage defects are more likely to occur. Although some manufacturers choose cast brass with better quality, after 24h acid salt spray test, the valve body still shows loss of gloss and rust spots. Why did this happen? It’s because the casting process of the faucet body is not handled properly. Therefore, as long as the design of the casting mold, the smelting and pouring of the alloy, the control of the casting process and the finishing of the falling sand are strengthened, the qualified faucet can be completed.
Pre-plating polishing and cleaning
Qualified faucet needs to go through machining, grinding and polishing processes before electroplating. Machining and grinding are the shapings of the product. Grinding and polishing mainly flatten the surface of the product, reduce the roughness of the casting. At the same time eliminate the fine sand holes, burrs and other defects caused by casting. Since the appearance quality of the faucet is relatively high, the electroplating layer on the surface of the faucet should be smooth and fine, with uniform color and luster, the polished surface should be bright. There should be no appearance defects such as bubbles, burns, detachment, and scratches. Polishing quality is a key factor to ensure the quality of electroplating, increase surface brightness and eliminate defects. It is very sensitive to mixing impurities since the faucet is a decorative product. Even small impurities may cause defects such as burrs, pits or pinholes on the electroplating surface, and even charring, blistering and peeling of the coating. For example, after passing the 24h acid salt spray test, there will be loss of bright and rust spots and even bubbling, etc., So the pretreatment of electroplating is very important. After casting, the sand and carbonized resin in the inner cavity, the grease, copper chips and copper powder left after machining, and the polishing paste after polishing should be cleaned to ensure the quality of electroplating. The presence of contaminants is the primary cause of burrs and pitting in electroplating.
Control of electroplating process
The surface of the faucet is mainly electroplated with nickel or chrome. The nickel or chromium electroplating process has a history of many years. The electroplating process is very sophisticated, the purity of chemical materials and additives is high, and the impurities are low. The electroplating equipment is advanced, and only severe process treatment is required during the electroplating process. With the cleanliness of the production environment, there are generally fewer problems with electroplating quality. The phenomenon of non-corrosion resistance found in the inspection is mainly due to some manufacturers in order to reduce the cost, the electroplating time is reduced, the coating is thin, and the pores of the coating cannot be compensated.
1) The valve, handle and valve cover of the faucet should be made of brass or copper alloy with good quality, while iron that is easy to rust, zinc alloy that is not corrosion-resistant and other materials are thrown away.
2) Select the metal mold to cast the faucet body and pay attention to the casting process.
3) Grinding and polishing should be comprehensive, and pre-plating treatment should be done well.
4) Strictly implement the nickel-chromium electroplating process standards, strengthen the process treatment, and ensure the thickness of the plating.