Method of obtaining a yellow gold alloy deposition by galvanoplasty without using toxic materials

Abstract

A method of galvanoplastic deposition of a gold alloy on an electrode dipped into a bath including metal gold in alkaline aurocyanide form, organometallic compounds, a wetting agent, a sequestering agent and free cyanide, where the alloy metals are copper, in double copper and potassium cyanide form, and silver in cyanide form, allowing a mirror bright yellow gold alloy to be deposited on the electrode.

1 : A method for the galvanoplastic deposition of a gold alloy on an electrode, the method comprising:
 (a) dipping an electrode into a bath, wherein the bath comprises:
 gold metal in alkaline aurocyanide form, 
 copper metal in copper and double potassium cyanide form, 
 silver metal in cyanide form, 
 organometallic compounds, 
 a wetting agent, 
 a sequestering agent, and 
 free cyanide, 
 wherein the bath has a proportion of 9.08% gold, 90.85% copper, and 0.07% silver, and the bath does not comprise cadmium or zinc; and then, 
   (b) galvanoplastically depositing a bright 3N colour gold alloy made of 75% gold, 21% copper, and 4% silver on the electrode, wherein the gold alloy has a thickness of 200 to 800 μm.   
     
     
         2 : The method according to  claim 1 , wherein the bath comprises 5.5 g·l −1  of gold metal in alkaline aurocyanide form, 55 g·l −1  of copper metal in copper and double alkaline cyanide form, and 40 mg·l −1  of silver metal in cyanide form. 
     
     
         3 : The method according to  claim 2 , wherein the bath comprises from 15 to 35 g·l −1  of cyanide. 
     
     
         4 : The method according to  claim 1 , wherein a concentration of the wetting agent is between 0.05 and 10 ml·l −1 . 
     
     
         5 : The method according to  claim 1 , wherein the wetting agent is selected from the group consisting of poly-oxy-alkenic, ether phosphate, lauryl sulphate, dimethyldodecylamine-N-oxide, and a dimethyl(dodecyl) ammonium propane sulfonate. 
     
     
         6 : The method according to  claim 1 , wherein the bath further comprises an amine, and wherein a concentration of the amine is between 0.01 and 5 ml·l −1 . 
     
     
         7 : The method according to  claim 1 , wherein the bath further comprises a depolariser, and wherein a concentration of the depolariser is between 0.1 mg·l −1  to 20 mg·l −1 . 
     
     
         8 : The method according to  claim 1 , wherein the bath further comprises at least one conductive salt selected from the group consisting of a phosphate, a carbonate, a citrate, a sulphate, a tartrate, a gluconate, and a phosphonate conductive salt. 
     
     
         9 : The method according to  claim 1 , wherein the temperature of the bath is kept between 50 and 80° C. 
     
     
         10 : The method according to  claim 1 , wherein the pH of the bath is kept between 8 and 12. 
     
     
         11 : The method according to  claim 1 , wherein the galvanoplastically depositing (b) is performed at a current density of between 0.3 A·dm −2 . 
     
     
         12 - 13 . (canceled)