| 摘要 |
PROBLEM TO BE SOLVED: To improve mechanical strength and corrosion resistance, by a method wherein etching treatment is conducted using an acidic solution having pH in a specific range in order to remove the modified layer formed on the surface of a magnet body during mechanical processing, and after removal of the generated smut, a resin film in a specific thickness is provided. SOLUTION: The surface of this rare-earth permanent magnet is etched using an acidic solution of pH 1 to 4. When etching treatment is conducted in the range of pH 1 to 4 as shown in the diagram, the corrosion resisting effect of the enchant is improved by about 20 times, but the corrosion resisting effect is only about twice with pH 5. Then, the smut on the surface is removed by conducting ultrasonic washing in the aqueous solution which is mainly composed of sodium hydroxide. After wishing by a solvent if necessary, an oxidation resistant resin layer is covered on the surface of the magnet. The practically desirable thickness of this layer is 5 to 80μm. As a result, the permanent magnet can be used for the field where high corrosion resistance is required. |
