Permanent rare-earth magenets: the need to protect them against corrosion

The RE-Fe-B permanent magnets have a complex microstructure and they are suscep-tible to corrosion process. In this paper, the commercial nickel coatings adhesion was investigated. The microstructure of the RE-Fe-B without coating was analyzed by scanning electronic microscopy and electrochemical techniques. The interface mag-net/coating was studied by scanning electron microscopy and the nickel-plated Nd-Fe-B commercial magnets were tested in a salt spray chamber. The ferromagnetic and RE-rich phases were observed. After the anodic polarization curve, a strong inter-granular corrosion was observed and the RE-rich phase was preferentially attacked. The interface magnet/Ni coating presented intergranular corrosion that can affect the nickel coating adherence. This attack had probably occurred during the electrodeposi-tion process. Not all the samples suffered localized corrosion during the salt spray tests and the Ni triple-layer coating presented a few corrosion points. RE-Fe-B alloy mag-nets need to be protected with appropriate coatings to each environment to which they will be exposed and the protective coating must not be damage.

SANTOS, Célia Aparecida Lino dos; PANOSSIAN, Zehbour. Permanent rare-earth magenets: the need to protect them against corrosion. Advances in Aerospace Science Technology, v.10, n.4, 2019. 11 p.

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