Aluminum or aluminum alloy molten salt electroplating bath having good throwing power, electroplating method using the bath, and pretreatment method of the bath

A method for pretreating an aluminum or aluminum alloy molten salt plating bath which comprising:

• (A) an aluminum halide as a main component,
• (B) at least one further halide, wherein the further halide (B) is one or more compounds selected from the group consisting of N-alkylpyridinium halides, N-alkylimidazolium halides, N,N′-dialkylimidazolium halides, N-alkylpyrazolium halides, N,N′-dialkylpyrazolium halides, N-alkylpyrrolidinium halides, and N, N-dialkylpyrrolidinium halides, and
• no organic solvent,
• the method comprising:
• adding (C) a reducing compound which is one or more compounds selected from the group consisting of lithium aluminum hydride, lithium hydride, lithium sodium hydride, sodium hydride, sodium borohydride, dimethylamine borane, diethylamine borane, and trimethylamine borane to the plating bath, and
• followed by a heat treatment, wherein the heat treatment includes decomposing the reducing compound (C) by heating the plating bath at a temperature of 50 to 100° C. for 0.5 to 8 hours, and
• removing an impurity metal originating from the aluminum halide (A) in the plating bath,
• wherein the plating bath is for electrolytic applications.

A method for pretreating an aluminum or aluminum alloy molten salt plating bath which comprising:

• (A) an aluminum halide as a main component,
• (B) at least one further halide, wherein the further halide (B) is one or more compounds selected from the group consisting of N-alkylpyridinium halides, N-alkylimidazolium halides, N,N′-dialkylimidazolium halides, N-alkylpyrazolium halides, N,N′-dialkylpyrazolium halides, N-alkylpyrrolidinium halides, and N, N-dialkylpyrrolidinium halides, and
• no organic solvent,
• the method comprising:
• adding (C) a reducing compound which is one or more compounds selected from the group consisting of lithium aluminum hydride, lithium hydride, lithium sodium hydride, sodium hydride, sodium borohydride, dimethylamine borane, diethylamine borane, and trimethylamine borane to the plating bath, and
• followed by a heat treatment, wherein the heat treatment includes decomposing the reducing compound (C) by heating the plating bath at a temperature of 50 to 100° C. for 0.5 to 8 hours,
• wherein the plating bath is for electrolytic applications and the plating bath further comprises compounds (D) of one or more metals selected from the group consisting of Zr, Ti, Mo, W, Mn, Ni, Co, Sn, Zn, Si, Nd, and Dy in the amount of 0.1 to 100 g/l.