According to the use of the coating coating can be divided into three categories, namely the protective coating, protective decorative coatings and functional coatings.
(1) and protective coatings. This kind of coating is mainly used for the corrosion protection of metal parts. Zinc plating, cadmium plating, tin and zinc based alloy (Zn-Fe.Zn-Co.Zn-Ni) coatings are belong to this type of coating. Black metal parts in the general atmospheric conditions commonly used galvanized layer to protect, in marine climate conditions commonly used cadmium plating layer to protect the requirements; when the coating is thin and resist ability, can be used to replace tin cadmium alloys cadmium plating; copper alloy manufacture navigation instrument, can use silver cadmium and Jin Baohu; for black metal the parts contact with organic acid, such as food containers, with tin coating to protect, it not only corrosion ability is strong, and the corrosion product is harmless to the human body.
(2) a decorative coating protection. For many metal parts, both to prevent corrosion, but also requires constant appearance, it requires applying a decorative coating protection. This kind of coating used multilayer electroplating, firstly on the substrate plating "bottom" layer, and then plated "table", sometimes "intermediate" layer plating. For example, the usual Cu-Ni-Cr multilayer electroplating is a typical protection a decorative coating, used on bicycles, sewing machines, the exposed parts of the car. Currently popular color plating, plating black and gold imitation plating also belongs to this kind of coating.
(3) functional coatings. In order to meet the need of special physical properties of optical, electric, magnetic, heat, wear resistance of the deposited coatings called functional coatings, at present more varieties.
The wear resistance and antifriction coating: wear resistant coating is plated with a layer of high hardness to parts of metal to increase its wear resistance ability. Such as hard chrome plating, hardness can reach 1000-1200HV, for direct axis or crankshaft journal, embossing roll surface, stamping die cavity, guns and cannon pipe etc.. Connector for some instruments, should have not only high conductive ability, and abrasion resistance, often using hard silver, gold, germanium and so hard.
Antifriction coating used for sliding contact surface, lubrication, reducing the coefficient of sliding friction, prolong the service life of parts. As antifriction coating metal tin, tin alloy, lead, tin and indium alloy of copper and lead antimony tin three element alloy etc..
Coating with heat processing: a surface for improving the physical properties of mechanical parts, often by heat treatment. But to a component, only local changes to the original performance, this required before heat treatment, the first does not need to change the properties of the site protection. Such as industrial production, in order to prevent local carburizing nitriding to prevent local to copper, tin, which is using the characteristic of carbon or nitrogen to diffusion in these metals to achieve.
The conductive coating: in electrical, radio and communication equipment, in order to improve the conductivity of the part surface, use a lot of this kind of coating, commonly used are copper, silver, gold, etc.. If the wear resistance, can be silver antimony alloy, gold cobalt alloy, gold antimony alloy etc..
Magnetic coating: tape recorder, computer and other equipment, the tape, magnetic disk, drum line, such as storage devices are required to magnetic materials, commonly used with cobalt nickel, nickel iron, cobalt and nickel phosphorus alloy coating as magnetism; magneto-optical recording materials, with samarium cobalt etc.. Production, when changing the plating process conditions, the change characteristics of magnetic coating, it should strictly control the construction conditions.
The repair coating: important machine parts wear, can be repaired by electroplating method. Such as the crankshaft, camshaft, automobile and tractor gears, splines, textile machine roller, deep well pump shaft available hard chromium electroplating, plating iron (or composite plating iron) to repair; some parts of printing and dyeing, paper making, film industry also available copper plating, chrome plating to repair; matrix or die used for printing available iron plating to repair.
In addition, with the development of science and technology, electroplating and electro deposition can also be used for nano material, high performance material thin film preparation, such as superconducting oxide films, electrochromic oxide thin films, the metal compound semiconductor thin film, the film of shape memory alloy, gradient material films. Use of electroplating in the field of functional materials is very extensive. |
