Neodymium-iron-boron plating is mainly nickel and zinc plating.
Nickel plating can be divided into single nickel, double nickel, nickel-copper-nickel, etc. according to the structure of the coating, and dark nickel, semi-bright nickel and bright nickel according to their appearance and luster. Generally, bright nickel and semi-bright nickel are the most common nickel plating layers. The advantages of nickel plating are wear resistance and good environmental resistance. The worse one is that nickel layer is ferromagnetic material. Magnets have certain influence on magnetic properties, especially on thin and small products. The improvement method is to replace some copper layer. Ferromagnetism of electroless nickel and electroplated nickel-phosphorus alloy is weak, but it is difficult to strip, which is generally not used as the mainstream coating.
Chemical nickel is more uniform than electroplated Nickel-Nickel layer, but it can not be directly plated on Nd-Fe-B matrix at present. Moreover, chemical nickel uses a large number of complexing agents and reducing agents, and the bath life is short, the driving force of plating is low, and the energy consumption is high, so it can not be used as mainstream coating.
After nickel plating products, according to the requirements of the coating, can also be plated with gold, silver, tin, chromium substitutes, imitation gold, black nickel and other coatings.
Generally speaking, chloride zinc plating is used for NdFeB zinc plating. In terms of domestic production, zinc plating is the largest one, especially for the magnetic steel of electric bicycle. The advantages of the coating are cheap, convenient and the zinc layer is not ferromagnetic. The disadvantage is that the wear resistance and weatherability are not as good as nickel plating. After galvanizing, the coating is usually passivated. Because hexavalent chromium passivation has been eliminated, trivalent chromium blue-white passivation and Trivalent Chromium Color Passivation are commonly used at present. Of course, galvanized passivation can also be as rich as hardware; however, at present, the mainstream is trivalent chromium blue-white passivation. Zinc-nickel alloy has been used in electroplating, but it can not be a conventional kind of Nd-Fe-B electroplating.
Secondly, conversion film
Neodymium iron boron conversion film mainly includes phosphorus and passivation film. Because the conversion film belongs to workshop protective film and so on, for a long time, many products will have flashover rust and other phenomena.
The coatings referred to here refer to the electrophoretic, spraying, brushing and dipping processes, excluding vapor-phase coatings. At present, epoxy coatings are the most common coatings, followed by Everlube coatings, Teflon coatings and chromium-free Dacromet coatings. The salt spray test, hardness and color of epoxy coatings are different due to the different kinds of coatings. Everlube coatings are usually golden yellow with metallic luster, which is an improvement of a solid lubrication film produced in the United States. The comprehensive performance of the coatings is excellent and has been commercialized. Teflon coatings have also been commercialized. Advanced chromium-free Dacromet is also a promising alternative to electroplating. Vapor deposition includes physical vapor deposition (PVD). Physical vapor deposition can be divided into evaporation, sputtering and ion plating. Magnets can form coatings of Al, Zn and Cr. Chemical vapor deposition (CVD) can form coatings of nitride and carbide such as Ti and Cr. Chemical vapor deposition (CVD) can form coatings of polymer such as Perrin.