According to the different coating structures, Nickel plating is divided into single nickel, double nickel, nickel copper-nickel, etc.; according to the different appearance and color, it is divided into dark nickel, semi-bright nickel, and light nickel. Generally, the nickel-plated coating of nickel copper-nickel is mostly bright nickel and semi-bright nickel. The advantage of nickel plating is that the coating is more wear-resistant and environmentally resistant. The worse is that the nickel coating is a ferromagnetism substance. The magnet has a certain influence on the magnetism, especially for thin and small products, the improvement method is using part of the copper coating to replace it. neodymium bar magnets chemical plating and electroplated nickel-phosphorus alloy have weak ferromagnetism, but deplating is more troublesome and generally not used as mainstream plating.
The nickel coating of chemical plating is relatively more uniform than those of electroplated nickel. However, it is currently not possible to directly plate on the matrix of neodymium bar magnets, and chemical plating uses a large amount of complexing agents and reducing agents, and the life of the electroplating liquid is short, the impetus for plating is low and the energy consumption is high, so it cannot be used as mainstream plating. Products after nickel plating can also be plated with gold, silver, tin, chromium, imitation gold, black nickel, and other plating layers according to the requirements of the plating.
Neodymium bar magnets are generally galvanized with chloride. The advantages of the coating are cheap and convenient, and the zinc coating is not ferromagnetic. The disadvantage is that the wear resistance and weather resistance are not as good as the nickel-plated coating. The coating of neodymium bar magnets generally needs to be passivated after electro galvanization. Because hexavalent chromium passivation is eliminated, the commonly used passivations are trivalent chromium blue-white passivation and trivalent chromium color passivation. Of course, the passivation of the galvanized coating can be as rich as hardware; however, the current mainstream is trivalent chromium blue-white passivation. Some people have used zinc-nickel alloys for electroplating. However, it has not yet become a conventional plating species for NdFeB electroplating.
The conversion coating of neodymium bar magnets mainly includes phosphating and passivation coatings. Since the conversion coating belongs to the protective coating in the workshop, it is used for a long time, and many products will have flash rust and other phenomena.
The coating referred to here refers to the coating by electrophoresis, spray coating, brush coating, and dip coating, excluding vapor coating. At present, the most common coatings are epoxy paint coatings, followed by Everlube coatings, Teflon coatings, and chromium-free Dacromet coatings.
Due to different types of coatings, epoxy coatings vary in salt spray test, hardness, color, etc. The coating of the neodymium bar magnet is generally metallic golden yellow. It is an improvement of a solid lubricating film produced in the United States. The overall performance of the coating is very good and it has been commercialized. Teflon coating has also been commercialized. And there are custom shaped neodymium magnets. Advanced chromium-free Dacromet is also a kind of coating that is expected to replace electroplating.
Vapor coating includes physical vapor deposition. Physical vapor deposition technology is mainly divided into evaporation coating, sputtering coating, and ion coating. Magnets can form Al, Zn, Cr, and other coatings; chemical vapor deposition can form Ti, Cr, and other nitrides, carbide coating; chemical vapor deposition polymer coating Parylene, etc.
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