| 简介 |
PROBLEM TO BE SOLVED : To provide a highly anticorrosive permanent magnet which can maintain a beautiful appearance and a high anticorrosiveness for a long time even when the magnet is composed of an extremely thin film, by forming a chromate film having a chromium composition adjusted to a specific ratio and a specific thickness on the surface of an R-T-B permanent magnet. SOLUTION : One, two, or more kinds of rare-earth elements including Y are used as the R of an R-T-B permanent magnet and Fe or Fe and Co are used as the T of the magnet. The magnet is coated with a chromate film. The abundance ratio between trivalent chromium and hexavalent chromium, namely, Cr /Cr in the chromate film is adjusted to >=10. In addition, the thickness of the chromate film is set to between about 1 nm and about 100 nm. As a result, the permanent magnet can maintain a beautiful appearance and a high corrosion resistance for a long time, even if the magnet is composed of an extremely thin film. |
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