Rare earth permanent magnet of high corrosion resistance
US6224986A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 22, 1999 |
| Grant date | May 1, 2001 |
| Priority date | — |
| Expiry date | Jul 22, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01F1/0577
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A neodymium/iron/boron permanent magnet is provided with high corrosion resistance by forming a coating layer of a vitrified sodium silicate on the surface. The vitreous coating layer of sodium silicate is formed by coating the surface of the permanent magnet with an aqueous coating solution of water glass followed by drying of the coating layer and vitrification of the dried coating layer by a heat treatment under specified conditions. Characteristically, the thus formed vitreous coating layer of sodium silicate is subjected to a leaching treatment with water at a specified temperature for a specified length of time in order to remove away residual sodium content leachable in water so that the troubles due to absorption of moisture by the alkali constituent in the sodium silicate coating layer can be largely dissolved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.