The copper plating film formed on the surface of the rare-earth permanent magnet

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An objective of the invention is to provide a method for producing a rare earth metal-based permanent magnet having on the surface thereof a copper plating film by using a novel plating solution for use in a copper electroplating treatment capable of forming a copper plating film having excellent adhesiveness on the surface of a rare earth metal-based permanent magnet. As a means for solving the problem, the method for producing a rare earth metal-based permanent magnet having a copper plating film on the surface thereof according to the invention is characterized in that the production method comprises forming a copper plating film on the surface of the rare earth metal-based permanent magnet by applying a copper electroplating treatment using a plating solution whose pH is adjusted to a range from 9.0 to 11.5 and containing at least : (1) Cu2+ ions, (2) an organic phosphoric acid having two or more phosphorus atoms and/or a salt thereof, (3) gluconic acid and/or a salt thereof, (4) a sulfate and/or a nitrate, and (5) at least one organic carboxylic acid selected from oxalic acid, tartaric acid, citric acid, malonic acid, and malic acid, and/or a salt thereof; provided that a copper salt is excluded from the components (2) to (5).