Provided herein is an electric Al—Zr—Mn alloy-plating bath which comprises (A) an aluminum halide; (B) one or at least two kinds of compounds selected from the group consisting of N-alkylpyridinium halides, N-alkylimidazolium halides, N,N′-dialkyl-imidazolium halides, N-alkyl-pyrazolium halides, N,N′-dialkyl-pyrazolium halides, N-alkylpyrrolidinium halides and N,N-dialkyl-pyrrolidinium halides; (C) a zirconium halide; and (D) a manganese halide, in which the molar ratio of the aluminum halide (A) to the compound (B) ranges from 1:1 to 3:1. The plating bath never involves any risk of causing an explosion and can provide a smooth and fine Al—Zr—Mn alloy-plated film. Moreover, the resulting film has high resistance to corrosion even when it does not contain any chromium and therefore, it is quite suitable from the viewpoint of the environmental protection and it can thus be used in a wide variety of applications including the plating of parts for motorcars, and the plating of parts for electrical appliances.
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