CORROSIVE PERMANENT MAGNET

PURPOSE:To enable the film thickness of a protection layer to be uniform, to reduce residual stress, and improve corrosion resistance by providing an N-P alloy protection layer in two-layer laminated state of different P content in amorphous structure which is formed on the surface of a sintered permanent magnetic body by the electroless plating method. CONSTITUTION:An R (R is one or more types of rare-earth elements including Y)-Fe-B family is used as a sintered permanent magnet body 2. A protection layer 3 is formed by the electroless plating method. The protection layer 3 by the electroless plating method changes from a crystal to an amorphous as the content of phosphor increases and becomes nearly perfect amorphous structure with phosphorus being equal to or more than 8wt.%. Then, in the case of the protection layer 3 in amorphous structure, there is no regularity in the growth direction of crystal, thus enabling it difficult to generate pin holes. In the sintered permanent magnetic body 2, an electroless deposition reaction is hard to occur within an acid solution and a first layer 3a with less content of phosphorus is formed using an alkali plating bath (pH7 or more). With pH of the plating bath being 6.5 or more, a complete amorphous structure is formed as a second layer 3b.