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

Abstract

A galvanic bath, containing: gold metal in the form of alkaline aurocyanide; organometallic components; a wetting agent; a complexing agent; free cyanide; copper metal in the form of copper II cyanide and potassium; and indium metal in the form of a complex indium metal, where the galvanic bath does not contain cadmium and zinc, and where the galvanic bath deposits a yellow gold alloy comprising gold, copper, and indium as main components.

Claims

1. A galvanic bath, comprising: gold metal in the form of alkaline aurocyanide; organometallic components; a wetting agent; a complexing agent; free cyanide; copper metal in the form of copper II cyanide and potassium; and indium metal in the form of a complex indium metal, wherein the galvanic bath does not comprise cadmium and zinc, wherein the galvanic bath may optionally comprise silver only in negligible quantity, and wherein the galvanic bath deposits a yellow gold alloy comprising gold, copper, and indium as main components.

2. The galvanic bath according to claim 1, wherein the complex indium metal comprises an aminocarboxylic group or an aminophosphonic group.

3. The galvanic bath according to claim 2, wherein the aminocarboxylic group, in complex form, is present in the galvanic bath at a concentration of between 0.1 g.Math.l.sup.1 to 20 g.Math.l.sup.1.

4. The galvanic bath according to claim 1, wherein the galvanic bath comprises from 30 to 80 g.Math.l.sup.1 of copper metal in the form of the copper II cyanide and potassium.

5. The galvanic bath according to claim 1, wherein the galvanic bath comprises from 10 mg.Math.l.sup.1 to 5 g.Math.l.sup.1 of the complex indium metal.

6. The galvanic bath according to claim 1, wherein the galvanic bath comprises from 15 to 35 g.Math.l.sup.1 of the free cyanide.

7. The galvanic bath according to claim 1, wherein the wetting agent is present in the galvanic bath at a concentration of between 0.05 to 10 ml.Math.l.sup.1.

8. The galvanic bath according to claim 7, wherein the wetting agent is selected from the group consisting of: polyoxyalkylenic, ether phosphate, lauryl sulphate, dimethyldodecylamine N oxide and dimethyldodecyl ammonium propane sulfonate.

9. The galvanic bath according to claim 1, wherein the galvanic bath further comprises an amine concentration of between 0.01 and 5 ml.Math.l.sup.1.

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

11. The galvanic bath according to claim 1, wherein the galvanic bath further comprises conductive salts selected from the group consisting of: phosphates, carbonates, citrates, sulphates, tartrates, gluconates and phosphonates.

12. The galvanic bath according to claim 1, wherein the galvanic bath comprises from 1 to 10 g.Math.l.sup.1 of the gold metal in the form of alkaline aurocyanide.

13. The galvanic bath according to claim 1, wherein the galvanic bath further comprises an additional metal selected from the group consisting of: Zr, Se, Te, Sb, Sn, Ga, As, Sr, Be and Bi, wherein the individual weight concentrations of gold, copper and indium in the galvanic bath are each greater than the weight concentration of the additional metal.

14. The galvanic bath according to claim 1, wherein the galvanic bath does not comprise silver.

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

(4) Cu: 45 g.Math.l.sup.1

(5) In: 0.1 g.Math.l.sup.1

(6) KCN: 22 g.Math.l.sup.1

(7) pH: 10.5

(8) Temperature: 65 C.

(9) Current density: 0.5 A.Math.dm.sup.2

(10) Wetting agent: 0.05 ml.Math.l.sup.1 NN-Dimethyldodecyl N Oxide

(11) Iminodiacetic: 20 g.Math.l.sup.1

(12) Ethylenediamine: 0.5 ml.Math.l.sup.1

(13) Potassium selenocyanate: 1 mg.Math.l.sup.1

Example 2

(14) Au: 6 g.Math.l.sup.1

(15) Cu: 60 g.Math.l.sup.1

(16) In: 2 g.Math.l.sup.1

(17) KCN: 30 g.Math.l.sup.1

(18) NTA: 4 g.Math.l.sup.1

(19) Ag: 10 mg.Math.l.sup.1

(20) Diethylentriamine: 0.2 ml.Math.l.sup.1

(21) Gallium, selenium or tellurium: 5 mg.Math.l.sup.1

(22) Sodium hypophosphite: 0.1 g.Math.l.sup.1

(23) Thiomalic acid: 50 mg.Math.l.sup.1

(24) Current density: 0.5 A.Math.dm.sup.2

(25) Temperature: 70 C.

(26) pH: 10.5

(27) Wetting agent: 2 ml.Math.l.sup.1 ether phosphate

(28) 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.

(29) 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 30 minutes in example 1 and, in example 2, a shiny deposition of 10 m in 30 minutes.

(30) 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.

(31) 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.