Method of producing AuCuGa alloy coating using electrolysis, and alloys produced by such a method
The present invention relates to a method of producing a gold-copper-gallium (AuCuGa) alloy coating by electrodeposition on a substrate (2), using an aqueous electrolytic bath. The method is characterized in that the aqueous electrolytic bath comprises potassium aurocyanide (KAu(CN)2), copper cyanide (CuCN), potassium cyanide (KCN) or sodium cyanide (NaCN), and a gallium salt (e.g. gallium sulfate Ga2(SO4)3). In particular, the molar concentration of gold cations (ÄAu<+>Ü), copper cations (ÄCu<+>Ü) and gallium cations (ÄGa<3+>Ü) in the electrolytic bath is respectively comprised within the following ranges: 0,19 g/l ≤ ÄAu<+>Ü ≤ 2,17 g/l (0,1.10<-2> mol/l ≤ ÄAu<+>Ü ≤ 1,1.10<-2> mol/l); 0,31 g/l ≤ Äcu<+>Ü ≤ 1,59 g/l (0,5.10<-2> mol/l ≤ ÄCu<+>Ü ≤ 2,5.10<-2> mol/l); and 0,69 g/l ≤ ÄGa<3+>Ü ≤ 2,79 g/l (1.10<-2> mol/l ≤ ÄGa<3+>Ü ≤ 4.10<-2> mol/l). Such a method allows to provide an AuCuGa alloy coating having brightness and ductility properties which are equivalent to those of the prior art AuCuCd alloy coatings.