September 7, 2023
Copper plating: the copper plating layer is pink, soft, has good ductility, electrical conductivity and thermal conductivity, and is easy to polish. After proper chemical treatment, decorative colors such as bronze, copper green, black and natural colors can be obtained. Copper plating is easy to lose its luster in the air, and reacts with carbon trioxide or chloride to form a layer of basic copper carbonate or copper chloride film on the surface, which will generate brown or black copper sulfide under the action of sulfide. Therefore, as decorative copper plating requires an organic coating on the surface.
Cadmium plating: cadmium is a silvery white shiny soft metal, its hardness is harder than tin, softer than zinc, good plasticity, easy forging and rolling. The chemical properties of cadmium are similar to zinc, but it is insoluble in lye, soluble in nitric acid and ammonium nitrate, and dissolves very slowly in dilute sulfuric acid and dilute hydrochloric acid. Both cadmium vapor and soluble cadmium salts are toxic, and cadmium pollution must be strictly prevented. Because cadmium pollution is very harmful and expensive, zinc plating or alloy plating is usually used to replace cadmium plating. At present, the types of cadmium plating solutions widely used in domestic production include: ammonia carboxyl complex cadmium plating, acid sulfate cadmium plating and cyanide cadmium plating. In addition, there are pyrophosphate cadmium plating, alkaline triethanolamine cadmium plating and HEDP cadmium plating.
Tin plating: tin has a silver-white appearance, an atomic weight of 118.7, a density of 7.3g/cm3, a melting point of 2320C, and atomic valences of divalent and tetravalent, so the electrochemical equivalents are 2.12g/A.h and 1.107g/A.h respectively. Tin has the advantages of corrosion resistance, non-toxicity, easy iron welding, softness and good ductility. Tin plating has the following characteristics and uses: 1. High chemical stability. 2. In the electrochemical sequence, the standard potential of tin is higher than that of iron. For steel, it is a cathodic plating. The substrate can be effectively protected only when the coating has no pores. 3. Tin has good electrical conductivity and is easy to solder. 4. Tin begins to mutate when it crystallizes from -130C, and it will completely transform into a crystal form of isomers at -300C, commonly known as "tin plague". Completely lose the nature of tin. 5. tin, like zinc and cadmium plating, can grow into whiskers under high temperature, humidity and airtight conditions, which is called long hair. 6. after tin plating, re-dissolve in hot oil above 2320C a glossy patterned tin layer can be obtained, which can be used as a decorative coating for daily necessities.
In terms of single metal plating, there are lead plating, iron plating, silver plating, gold plating, etc.
Electroplating alloys include: electroplated copper-based alloy, electroplated zinc-based alloy, electroplated cadmium-based, indium-based alloy, electroplated lead-based, tin-based alloy, electroplated nickel-based, cobalt-based alloy, electroplated palladium-nickel alloy, etc.
Composite electroplating includes: nickel-based composite electroplating, zinc-based composite electroplating, silver-based composite electroplating, and diamond inlaid composite electroplating.