| 摘要 |
PROBLEM TO BE SOLVED: To enable inexpensive processing and realize maintenance of good appearance for a long period of time, by impregnating a permanent magnet made from one kind of yttrium-containing rare-earth element, iron and boron, or coating the surface of the permanent magnet, with a processing solution made from an alkaline silicate aqueous solution and a water-soluble or resin emulsion, and then heating the permanent magnet to form a composite anticorrosive film including a vitreous film and a resin film. SOLUTION: An alkaline silicate aqueous solution is expressed by a general formula, M2 O.nSiO2 [(M=alkaline metal, n=SiO2 /M2 O (molar ratio)], and the concentration is adjusted by adding ion-exchange water so that (n) falls within a range of 1.5-2.00. Lithium silicate, which provides the highest water resisting property for a dry film, is used. In order further improve the water resisting property of the anticorrosive film, a water-soluble resin, a liquid resin emulsion or a solid resin emulsion is added to an adjusted alkaline silicate aqueous solution, thus forming a processing solution. In heating processing after impregnation or coating with the processing solution, a range of 120-300 deg.C is desired for evaporation of moisture, dehydration condensation of silanol groups, and condensation reaction of the watersoluble resin. |
