The invention relates to an electrolytic deposition in the form of a thick gold alloy layer and the manufacturing method thereof
In the field of decorative plating, methods are known for producing gold electrolytic depositions that are yellow with a fineness greater than or equal to 9 carats, ductile with a thickness of 10 microns, and with a high level of tarnish resistance. These depositions are obtained by electrolysis in an alkaline galvanic bath containing 0.1 to 3 g/1 of cadmium, in addition to gold and copper. The depositions obtained via these known methods have however cadmium levels of between 1 and 10%. Cadmium facilitates the deposition of thick layers, i.e. between 1 and 800 microns and provides a yellow alloy by reducing the quantity of copper contained in the alloy, however, cadmium is extremely toxic and prohibited in some countries.
Other known yellow depositions are alloys comprising gold and silver.
18 carat gold alloys containing copper and zinc and no cadmium are also known. However, these depositions are too pink (fineness too copper rich). Finally, these depositions have poor resistance to corrosion which means that they tarnish quickly.
It is an object of this invention to overcome all or part of the aforementioned drawbacks by proposing a method for depositing a thick gold alloy layer that is yellow and has neither zinc nor cadmium as main components.
The invention thus relates to an electrolytic deposition in the form of a gold alloy, whose thickness is comprised between 1 and 800 microns and includes copper, characterized in that it includes indium as the third main component.
According to other advantageous features of the invention:
The invention also relates to a method for the galvanoplasty deposition of a gold alloy on an electrode dipped in a bath including gold metal in the form of aurocyanide alkaline, organometallic components, a wetting agent, a complexing agent and free cyanide, characterized in that the alloy metals are copper in the form of the copper II cyanide and potassium, and indium in complex aminocarboxylic or aminophosphoric form for depositing a shiny reflective? yellow type gold alloy.
According to other advantageous features of the invention:
The electrolysis is preferably followed by a thermal treatment at at least 450 degrees Celsius for at least 30 minutes in order to obtain optimum deposition quality.
The bath may also contain a brightener. The brightener is preferably a butynediol derivative, a pyridinio-propane sulfonate or a mixture of the two, a tin salt, sulfonated castor oil, methylimidazole, dithiocarboxylic acid, such as thiourea, thiobarbituric acid, imidazolidinthione or thiomalic acid.
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.
This deposition is obtained by electrolysis in an electrolytic bath of the following type:
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
Under such conditions, cathodic efficiency of 62 mg·A·min−1 can be obtained, with a deposition speed of 1 μm in 3 minutes in example 1 and, in example 2, a shiny deposition of 10 μm in 30 minutes.
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.
Number | Date | Country | Kind |
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01494/07 | Sep 2007 | CH | national |
This is a Divisional Patent Application of U.S. patent application Ser. No. 12/678,984 filed on Mar. 18, 2010, which is a National Phase Application in the United States of International Patent Application PCT/EP 2008/062042 filed Sep. 11, 2008, which claims priority on Swiss Patent Application No. 01494/07 of Sep. 21, 2007. The entire disclosures of the above patent applications are hereby incorporated by reference.
Number | Date | Country | |
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Parent | 12678984 | Mar 2010 | US |
Child | 14244071 | US |