In recent years RFeB based magnets have derived wide range attraction and popularity due to their excellent magnetic properties such as high remanence, coercivity and large energy product. However, the sintered NdFeB magnets are sensitive to temperature and corrosiveness of the working environment due to the electrochemically active phases in their microstructure, that deteriorate their efficiency as they corrode during exposure to humid or moist environments.  The low corrosion resistances and Curie temperature of these magnets have strictly limited their wide application in many industrial cases.

The paper describes the recent developments, microstructure, magnetic properties and corrosion resistance of sintered ReFeB permanent magnets with and without coatings. An innovative composite coating composed of an undercoat of electrodeposited nickel and a top layer of CAPVD Ti₂N ceramic coating was successfully employed for corrosion protection of sintered NdFeB permanent magnets. The electrochemical corrosion studies indicate that noval composite coating significantly enhanced the corrosion resistance of sintered RFeB magnets in simulated marine and industrial environments without affecting the magnetic properties.