Electroplating

What are the types of electroplating plating?

Electroplating is the process of using the principle of electrolysis to deposit a thin layer of other metals or alloys on certain metal surfaces. According to the composition of the coating, cadmium electroplating process can be divided into eight categories: chromium plating, copper plating, cadmium plating, tin plating, zinc alloy electroplating, copper nickel electroplating, gold electroplating service, and silver electroplating service.

Chrome plating

Chromium is a silver white metal with a slight sky blue hue. It has strong passivation performance and quickly passivates in the atmosphere, showing properties of precious metals. Therefore, the chromium plating layer on iron parts is a cathodic coating. The chromium layer is very stable in the atmosphere and can maintain its luster for a long time. It is very stable in corrosive media such as alkali, nitric acid, sulfide, carbonate, and organic acid, but soluble in hydrochloric acid and other hydrogen halide acids and hot concentrated sulfuric acid.

The chromium layer has high hardness, good wear resistance, strong reflective ability, and good heat resistance. There is no significant change in gloss and hardness below 500 ° C; Oxidation and discoloration begin when the temperature exceeds 500 ° C; It only begins to soften when it exceeds 700 ° C. Due to the excellent performance of the chrome plating layer, it is widely used as the outer layer and functional coating of the protective decorative coating system.

Copper plating

The copper plating layer is pink in color, soft in texture, and has good ductility, conductivity, and thermal conductivity, making it easy to polish. After appropriate chemical treatment, decorative colors such as antique copper, copper green, black, and natural colors can be obtained. Copper plating is prone to losing its luster in the air and reacts with carbon dioxide or chloride to form a basic copper carbonate or chloride film on the surface. When exposed to sulfides, it can produce brown or black copper sulfide. Therefore, as a decorative copper plating layer, an organic covering layer needs to be coated on the surface.

Cadmium plating

Cadmium is a silver white, glossy, soft metal that is harder than tin and softer than zinc. It has good plasticity and is easy to forge and roll. Cadmium has chemical properties similar to zinc, but it does not dissolve in alkaline solution, dissolves in nitric acid and ammonium nitrate, and dissolves slowly in dilute sulfuric acid and hydrochloric acid. The vapor and soluble cadmium salts of cadmium are both toxic and must be strictly prevented from cadmium pollution. Due to the significant harm and high cost of cadmium pollution, galvanized or alloy coatings are usually used to replace cadmium plating. The commonly used types of cadmium plating solutions in domestic production include ammonia carboxyl complex cadmium plating, acid sulfate cadmium plating, and cyanide cadmium plating. In addition, there are also cadmium plating with pyrophosphate, alkaline triethanolamine, and HEDP.

Tin plating

Tin has a silver white appearance, an atomic weight of 118.7, a density of 7.3g/cm3, a melting point of 231.89 ℃, and atomic valences of divalent and tetravalent. Therefore, its electrochemical equivalents are 2.12g/A · h and 1.107g/A · h, respectively. Tin has advantages such as corrosion resistance, non toxicity, easy soldering, softness, and good ductility.