Surface treatment for iron-based permanent magnet including rare-earth element

A surface treatment for R-TM-X permanent magnet material comprising the following steps after mechanical working and degreasing treatment,

• (1) etching the magnet material in a first solution comprising nitric acid having a concentration of 0.2 to 10 vol %,
• (2) etching the magnet material in a second solution comprising a mixture of oxygenated water having a hydrogen peroxide concentration of 0.2 to 10 vol %, and acetic acid having a concentration of 10 to 30 vol %,
• (3) copper plating to form a 0.5 to 15 .mu.m thick copper layer on the magnet material, and
• (4) nickel plating to form a 1 to 100 .mu.m thick nickel layer on the copper layer,
• where the magnet material consists essentially of 5-40% by weight of R, 50-90% by weight of TM and 0.2 to 8.0% by weight of X, and
• where R consists of yttrium or one or more rare earth elements or mixtures thereof, TM consists of iron as its main component and one or more transition metals other than iron, said one or more transition metals being partially replaceable with one or more other elements, and X consists of at least one non-metallic element or metalloid element or mixture thereof to enhance the coercive force of the magnet material.