Highly corrosion-resistant rare-earth-iron magnets

摘要

A highly corrosion-resistant rare-earth-iron magnet has a paraxylylene polymer film or a chloropara-xylylene polymer film formed thereon. The substrate magnet surface has a roughness Ra of no more than one micron. The magnet has a plasma polymer film formed beforehand or afterwards. The plasma polymer film has a protective film consists of only carbon and hydrogen, with a refractive index decreasing from the boundary surface between the film and the magnet toward the exposed surface. The protective coating has a thickness about three times the surface roughness of the substrate magnet.