R-T-B-BASED RARE EARTH PERMANENT MAGNET AND PRODUCTION METHOD THEREFOR

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PROBLEM TO BE SOLVED : To provide an R-T-B rare earth permanent magnet which shows superior stability in harsh working conditions of being exposed to water and/or a highly chemically active gas and/or a refrigerant and lubricant for a long period of time, and shows high corrosion resistance in a highly chemically active atmosphere such as in ammonia or hydrogen, and to provide a production method therefor. SOLUTION : The R-T-B rare earth permanent magnet is used in an environment containing water and/or the highly chemically active gas and/or the refrigerant and lubricant, and has a corrosion-resistant coating film which comprises a metal oxide layer formed on a nickel-plated layer and has a thickness of 40 nm or more. The production method includes forming a new protective coating film on the surface of a nickel-plated R-T-B rare earth permanent magnet by heat-treating the nickel-plated R-T-B rare earth permanent magnet in a controlled oxygen atmosphere; and can easily and inexpensively provide a nickel-plated R-T-B rare earth permanent magnet which shows the superior corrosion resistance and further hydrogen barrier properties even in a high-temperature and high-pressure atmosphere containing the extremely highly chemically active ammonium refrigerant or hydrogen and the lubricant, and shows an extremely high utility value for industry. COPYRIGHT : (C)2008, JPO&INPIT