Permanent magnet having high corrosion resistance, a process for making the same and a process for making a bonded magnet having high corrosion resistance

摘要

A sintered or bonded permanent magnet formed from a material consisting mainly of iron, particularly a Nd-Fe-B alloy, and having a high corrosion resistance has a surface coated with a resin obtained by the polycondensation of tannic acid, phenols and aldehydes. A bonded magnet is also made from a powder of any such material composed of particles coated with any such resin.