For the appearance of fasteners to be more beautiful and beautiful, the surface treatment of screw fasteners will be done in many ways. The process of forming a covering layer on the surface of the workpiece by a certain method, the purpose of which is to give the surface of the workpiece a beautiful and anti-corrosion effect!
Today we talk about electroplating. When talking about the identification of pressure riveting fasteners, we mentioned the suffix codes of the surface treatment. These codes represent the type of electroplating on the surface.
Electroplating is to plate a metal coating on the fastener to change its surface properties and make it not easy to oxidize and corrode. The coating metal generally uses corrosion-resistant metal. Electroplating can not only enhance the corrosion resistance of fasteners, but also increase the hardness to prevent wear, improve conductivity, heat resistance, and make the surface smoother and more beautiful.
Electroplating is a process that uses electrolysis to attach a metal film to the surface of a metal or other material. The following briefly introduces some commonly used coatings for fasteners.
NO.1 electro galvanized
Electro-galvanizing is the most commonly used coating for fasteners. It looks good and is relatively cheap. There are white zinc, blue zinc, color zinc, black zinc and other colors. Compared with other metal coatings, zinc is relatively cheap and easy to be electroplated. However, its anti-corrosion performance is general. The neutral salt spray test of electro-galvanized zinc is within 72 hours. Of course, special sealants are also used to make the medium The salt spray test lasts for more than 200 hours, but the price is 5-8 times that of general galvanizing.
NO.2 Plating nickel
Electroplated nickel fasteners are generally used in places where both high corrosion resistance and good electrical conductivity are required. The stability of the electroplated nickel layer in the air is very high. Because the metal nickel has a strong passivation ability, a very thin passivation film can be quickly formed on the surface, which can resist the corrosion of the atmosphere, alkali and certain acids. Electroplated nickel has excellent polishing performance, and its gloss can be maintained for a long time after polishing, and the higher hardness of the nickel plating can improve the wear resistance of fasteners.
Black oxide + oil is a popular coating for industrial fasteners because it is the cheapest and looks good before the oil runs out. The neutral salt spray test can only reach 3 to 5 hours in the presence of oil. Blackened fastener torque-preload consistency is also poor. If you need to improve, you can apply grease to the inner thread during assembly and then screw it on.
NO.4 Chrome plating
Chrome plating on fasteners is generally used for decoration. The chromium coating is very stable in the atmosphere, is not easy to change color and lose its luster, has high hardness and good wear resistance. To prevent corrosion, copper and nickel should be plated before chromium plating. Chromium plating can withstand high temperatures of 650℃, but it has the same hydrogen embrittlement problem as electro-galvanized.