PURPOSE:To form an oxidation-resistant coating film with the glossiness and adhesion improved by incorporating specified boric acid compd., alkali metal and tetraalkylammonium salt to the org. solvent electroplating soln. for a plating film as the supporting salt. CONSTITUTION:A plating film is formed with the org. solvent electroplating soln. on the surface of an R2T14B intermetallic compd. permanent magnet material (R is the rare-earth elements including Y, and T is transition metals). At least one kind among the boric acid compd. contg. =1 kind among R'3BO3, MBO2, M'BO3 and M'2BxO (R' is H or an alkyl group, M is H or an alkali metal, M' is an alkali metal and x=2), an alkali metal contg. either M'XO4 (X is a halogen) or R'4NXO4 or the XO4- salt of a tetraalkylamine, the BX4- salt (or PX6- salt) of an alkali metal and a tetraalkylamine and the R'COO- salt of an alkali metal is added to the plating soln. as the supporting salt.
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