· · Boron permanent magnet of a rare earth iron manufacturing method

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PROBLEM TO BE SOLVED : To prevent corrosion for a long term by sticking alkali silicate aqueous solution dispersed in metal fine particles on the surface of a magnet and forming a vitrescent protective layer. SOLUTION : The surface of a rare earth/iron/boron based permanent magnet is covered with a vitrescent protective layer in which metal fine particles are dispersed. The vitrescent protective layer is composed of alkali silicate such as water glass whose main component is Na2O and SiO2, potassium silicate and lithium silicate. Thickness of the vitrescent protective layer is set to be about 5 nm-50 μm. Metal constituting the metal fine particles is at least one kind selected out of Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo and Sn or these alloy or these compound. Mean grain diameter of the metal fine particles is set to be about 5 nm-50 μm. Rate of the metal fine particles in the glass type protective layer is set to be about 10-90 vol% to the whole volume.