Neodymium magnet is an efficient energy conversion medium. NdFeB materials are popular for their superior magnetic properties, abundant raw material resources and low price. However, because of its poor corrosion resistance, the application of it is limited. The corrosion resistance of neodymium magnets is related to the multiphase structure of magnets. Besides, it is also related to the difference of electrochemistry degrees between different phases. To improve the corrosion resistance of NdFeB magnets, there are two ways: firstly, to improve the corrosion resistance of the magnet itself. By adding elements and changing the distribution of neodymium, the chemical activity of Nd rich phase can be reduced and the intergranular corrosion propagation channel can be narrowed. So it can help reduce corrosion current and achieve the purpose of reducing the electrochemical corrosion rate; secondly, making some treatments on the surface of magnets through the coatings in order to avoid corrosion. In the aspect of NdFeB protective coatings, many kinds of protective coatings have been developed, such as metal coatings and organic coatings. Among these, the rubber coating has been widely used for its simple technology, low cost and good protection performance. Compared with other coatings, the insulating current of the rubber coating is formed to protect the inner magnet metals from corrosion, thus slowing the corrosion of the electrolyte to the matrix, which makes the rubber coating shown much better corrosion resistance. Compared with other plating methods, such as nickel plating, the electric potential of nickel coating itself is higher than that of NdFeB matrix. So once the external liquid penetrates into the coating, the coating and the substrate will form the corrosion source battery. On the contrary, it accelerates corrosion. Because the corrosion resistance of the matrix will directly affect the adhesion and corrosion resistance of the coating. In conclusion, the neodymium magnet with rubber coating is an ideal coating way.
