Method of obtaining a yellow gold alloy deposition by galvanoplasty without using toxic metals or metalloids

Abstract

The invention relates to an electrolytic deposition in the form of a gold alloy with a thickness of between 1 and 800 microns and which includes copper. According to the invention, the deposition includes indium as the third main compound. The invention concerns the field of electroplating methods.

Claims

1. A method for depositing a yellow gold alloy, wherein the method comprises the steps of: (a) forming a bath including: i. gold metal in a form of an alkaline aurocyanide; ii. organometallic components; iii. a wetting agent; iv. a complexing agent and free cyanide; v. copper metal in a form of a copper cyanide and potassium; and vi. indium metal in a form of a complex indium metal, (b) dipping an electrode to be coated in the bath; and (c) depositing by galvanoplasty a shiny reflective yellow gold alloy on the electrode, wherein the yellow gold alloy comprises gold, copper and indium as main components, wherein the bath does not contain zinc nor cadmium.

2. The method according to claim 1, wherein the complex indium metal is formed with an aminocarboxylic group and the indium metal or with an aminophosphonic group and the indium metal, wherein the amount of copper metal is from 30 to 80 g.Math.l.sup.1.

3. The method according to claim 2, wherein the bath includes the aminocarboxylic group in complex, in a concentration of between 0.1 g.Math.l.sup.1 to 20 g.Math.l.sup.1.

4. The method according to claim 1, wherein the bath includes from 1 to 10 g.Math.l.sup.1 of the gold metal.

5. The method according to claim 1, wherein the bath includes from 30 to 80 g.Math.l.sup.1 of the copper metal.

6. The method according to claim 1, wherein the bath includes from 10 mg.Math.l.sup.1 to 5 g.Math.l.sup.1 of the indium metal.

7. The method according to claim 1, wherein the bath includes from 15 to 35 g.Math.l.sup.1 of free cyanide.

8. The method according to claim 1, wherein a concentration of the wetting agent is between 0.05 and 10 ml.Math.l.sup.1.

9. The method according to claim 1, wherein the wetting agent is selected from the group consisting of polyoxyalkylenic, ether phosphate, lauryl sulphate, dimethyldodecylamine N oxide and dimethyldodecyl ammonium propane sulfonate.

10. The method according to claim 1, wherein the bath further includes an amine in a concentration of between 0.01 and 5 ml.Math.l.sup.1.

11. The method according to claim 1, wherein the bath further includes a depolarising agent in a concentration of between 0.1 mg.Math.l.sup.1 to 20 mg.Math.l.sup.1.

12. The method according to claim 1, wherein the bath further includes conductive salts selected from the group consisting of phosphates, carbonates, citrates, sulphates, tartrates, gluconates and phosphonates.

13. The method according to claim 1, wherein the temperature of the bath is maintained between 50 C. and 80 C.

14. The method according to claim 1, wherein the pH of the bath is maintained between 8 and 12.

15. The method according to claim 1, wherein the method is performed with a current density of between 0.2 A.Math.dm.sup.1 and 1.5 A.Math.dm.sup.2.

16. The method according to claim 1, wherein the complexing agent is an aminocarboxylic complexing agent.

17. The method according to claim 1, wherein a thickness of the shiny reflective yellow gold alloy on the electrode is between 1 and 800 microns and has a shiny colour that is between fields 1N and 3N.

18. A method for depositing a yellow gold alloy, wherein the method comprises the steps of: (a) forming a bath including: i. gold metal in a form of an alkaline aurocyanide; ii. organometallic components; iii. a wetting agent; iv. a complexing agent and free cyanide; v. copper metal in a form of a copper cyanide and potassium; vi. indium metal in a form of a complex indium metal; and vii. no more than negligible quantities of silver, zinc, and cadmium; (b) dipping an electrode to be coated in the bath; and (c) depositing by galvanoplasty a shiny reflective yellow gold alloy on the electrode, wherein the yellow gold alloy comprises gold, copper and indium as main components, wherein the bath does not contain zinc nor cadmium.

19. The method according to claim 18, wherein the bath includes no more than negligible quantities of metals selected from the group consisting of Se, Te, Sb, Sn, Ga, As, Sr, Be and Bi.

20. The method according to claim 18, wherein the complexing agent is an aminocarboxylic complexing agent.

21. The method according to claim 18, wherein the bath does not contain arsenic.

22. A method for depositing a yellow gold alloy, wherein the method comprises the steps of: (a) forming a bath consisting essentially of: i. gold metal in a form of an alkaline aurocyanide; ii. organometallic components; iii. a wetting agent; iv. a complexing agent and free cyanide; v. copper metal in a form of a copper cyanide and potassium; and vi. indium metal in a form of a complex indium metal, (b) dipping an electrode to be coated in the bath; and (c) depositing by galvanoplasty a shiny reflective yellow gold alloy on the electrode, wherein the yellow gold alloy comprises gold, copper and indium as main components, wherein the bath does not contain zinc nor cadmium.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) In an example deposition, there is a gold alloy, free of toxic metals or metalloids, in particular free of cadmium, with a 2N yellow colour, a thickness of 200 microns, excellent brilliance and highly wear and tarnish resistant.

(2) This deposition is obtained by electrolysis in an electrolytic bath of the following type:

Example 1

(3) Au: 3 g.Math.l.sup.1 Cu: 45 g.Math.l.sup.1 In: 0.1 g.Math.l.sup.1 KCN: 22 g.Math.l.sup.1 pH: 10.5 Temperature: 65 C. Current density: 0.5 A.Math.dm.sup.2 Wetting agent: 0.05 ml.Math.l.sup.1 NN-Dimethyldodecyl N Oxide Iminodiacetic: 20 g.Math.l.sup.1 Ethylenediamine: 0.5 ml.Math.l.sup.1 Potassium selenocyalate: 1 mg.Math.l.sup.1

Example 2

(4) Au: 6 g.Math.l.sup.1 Cu: 60 g.Math.l.sup.1 In: 2 g.Math.l.sup.1 KCN: 30 g.Math.l.sup.1 NTA: 4 g.Math.l.sup.1 Ag: 10 mg.Math.l.sup.1 Diethylentriamine: 0.2 ml.Math.l.sup.1 Gallium, selenium or tellurium: 5 mg.Math.l.sup.1 Sodium hypophosphite: 0.1 g.Math.l.sup.1 Thiomalic acid: 50 mg.Math.l.sup.1 Current density: 0.5 A.Math.dm.sup.2 Temperature: 70 C. pH: 10.5 Wetting agent: 2 ml.Math.l.sup.1 ether phosphate

(5) In these examples, the electrolytic bath is contained in a polypropylene or PVC bath holder with heat insulation. The bath is heated using quartz, PTFE, porcelain or stabilised stainless steel thermo-plungers. Proper cathodic agitation and electrolyte flow must be maintained. The anodes are made of platinum plated titanium, stainless steel, ruthenium, iridium or alloys thereof.

(6) Under such conditions, cathodic efficiency of 62 mg.Math.A.Math.min.sup.1 can be obtained, with a deposition speed of 1 m in 3 minutes in example 1 and, in example 2, a shiny deposition of 10 m in 30 minutes.

(7) Of course, this invention is not limited to the illustrated example, but is capable of various variants and alterations, which will be clear to those skilled in the art. In particular, the bath may contain negligible quantities of the following metals: Ag, Cd, Zr, Se, Te, Sb, Sn, Ga, As, Sr, Be, Bi. Moreover, the wetting agent may be of any type able to wet in an alkaline cyanide medium.

(8) Most generally, the invention concerns the field of electroplating methods, and relates to an electrolytic deposition in the form of a gold alloy with a thickness of between 1 and 800 microns and that includes copper. According to the invention, the deposition includes indium as a third main compound.