A manufacturing method of a high corrosion-resistant permanent magnet

PROBLEM TO BE SOLVED : To provide a highly anticorrosive permanent magnet which is capable of maintaining a beautiful appearance for a long time and can be easily surface-treated, even if the magnet has such a shape that is difficult to be surface-treated by a surface treating method, by forming an oxidation-resistant film composed mainly of chromium chromate on the surface of an R-Fe-Co-B permanent magnet. SOLUTION : One, two, or more kinds of rare-earth elements including Y are used as the R of an R-Fe-Co-B permanent magnet. After the surface of the magnet has been pickled, the magnet is successively subjected to ultrasonic cleaning which is performed in pure water containing a corrosion inhibitor, cleaning with pure water, and dipping in a treating solution containing hexavalent chromium. PH and hexavalent chromium concentration of the treating solution are respectively adjusted between 1 and 3 and between about 1 g/l to 25 g/l. In addition, the treating temperature and time are respectively set between about 20 deg.C and about 70 deg.C and between about 1 minute and 20 minutes. After dipping, the magnet is sufficiently washed with water and dried. The drying temperature is adjusted to about 60 deg.C or lower. It is possible to dip the magnet in a water-soluble solvent, such as methanol, etc., and to dry the dipped magnet with air.