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

Abstract

The invention relates to 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. According to the invention, 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. The invention concerns the field of galvanic depositions.

1 . A method for the galvanoplastic deposition of a gold alloy on an electrode dipped into a bath including gold metal in alkaline aurocyanide form, organometallic compounds, a wetting agent, a sequestering agent and free cyanide, the alloy metals being 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 wherein the bath respects a proportion of 9.08% gold, 90.85% copper and 0.07% silver containing neither cadmium nor zinc. 
     
     
         2 . The method according to  claim 1 , wherein the bath includes 5.5 g·l −1  of gold metal in alkaline aurocyanide form, 55 g·l −1  of copper metal in double alkaline cyanide form and 40 mg·l −1  of silver metal in complex form. 
     
     
         3 . The method according to  claim 2 , wherein the bath includes from 15 to 35 g·l −1 of cyanide. 
     
     
         4 . The method according to  claim 1 , wherein the wetting agent includes a concentration of between 0.05 and 10 ml·l −1 . 
     
     
         5 . The method according to  claim 1 , wherein the wetting agent is chosen from among poly-oxy-alkenic, ether phosphate, lauryl sulphate, dimethyldodecylamine-N-oxide, dimethyl(dodecyl) ammonium propane sulfonate types. 
     
     
         6 . The method according to  claim 1 , wherein the bath includes a concentration of amine of between 0.01 and 5 ml·l −1 . 
     
     
         7 . The method according to  claim 1 , wherein the bath includes a concentration of depolariser of between 0.1 mg·l −1  to 20 mg·l −1 . 
     
     
         8 . The method according to  claim 1 , wherein the bath includes phosphate, carbonate, citrate, sulphate, tartrate, gluconate and/or phosphonate type conductive salts. 
     
     
         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 method is performed at a current density of between 0.3 A·dm −2 . 
     
     
         12 . An electrolytic deposition in the form of a gold alloy obtained from a method according to  claim 1 , the thickness of which is between 1 and 800 microns and which includes copper, wherein it includes silver as the third main compound allowing a bright 3N colour to be obtained. 
     
     
         13 . An electrolytic deposition in the form of a gold, cupper and silver alloy wherein the deposition is made of 75% gold, 21% copper and 4% silver, allowing a bright 3N colour to be obtained.