I've heard that NdFeB is very easy to corrode. Is that true?
The bonded magnet is isotropic, i.e. whether the magnetization along any direction, the strength of the magnetic field are the same (and shape), and sintered magnet is anisotropic, in the production process of sintered magnets, a procedure called the magnetic field orientation, then only when magnetizing orientation along the magnetizing direction only high magnetic field strength the other direction, there is no magnetic magnetization. Theoretically, the magnetic remanence of the isotropic is 1/2 of the residual magnetic anisotropy, and since the magnetic energy product is proportional to the square of the remanence, the isotropic magnetic property is only 1/4 of the anisotropy.
This statement is true, because the NdFeB magnetic material is neodymium, iron oxide and other alloy, also called magnetic steel containing neodymium and iron, in a large number of NdFeB material is easy to rust, so NdFeB magnets must be surface coating treatment.
Because of the adhesive, the density of bonded magnet is only 80% of the theoretical density. Therefore, the magnetic property of the bonded magnet will decrease by about 30%. The density of sintered magnet is close to theoretical density, and the attenuation is very small.
The magnetism of bonded NdFeB magnets is only about 1/5 of that of sintered magnets. At present, the magnetic energy product of sintered NdFeB magnets can reach more than 50M, while the bonded magnets are generally below 10M, and the best is only 12M. The properties of magnetic particles used for bonded magnets are generally 15M, and the maximum is only 10.5M when bonded magnets are made.
