Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D1/00—Electroforming
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C5/00—Alloys based on noble metals
  • C22C5/02—Alloys based on gold
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/62—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of gold
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/18—Electroplating using modulated, pulsed or reversing current
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/48—After-treatment of electroplated surfaces
  • C25D5/50—After-treatment of electroplated surfaces by heat-treatment
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/60—Electroplating characterised by the structure or texture of the layers
  • C25D5/615—Microstructure of the layers, e.g. mixed structure
  • C25D5/617—Crystalline layers
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/627—Electroplating characterised by the visual appearance of the layers, e.g. colour, brightness or mat appearance

Definitions

• the present invention relates to an electroforming process for making gold-alloy-based parts or layers containing zinc, copper and / or silver, as well as parts or layers obtained by this process. . More particularly, the invention relates to such a method for depositing on substrates thick layers of said alloy, typically of the order of 300 microns.
• Gold alloy electrodeposition processes are already known by electrolysis in an alkaline galvanic bath containing, in addition to gold and copper, cadmium. As cadmium is a toxic metal, it is now banned from use by many laws.
• the main purpose of the present invention is therefore to provide a process for electroforming a part or a layer based on a cadmium-free alloy of gold, zinc and copper, having thicknesses of several hundred millimeters. microns.
• the present invention also aims to provide such a method for producing such layers having improved hardness while maintaining good ductility.
• the subject of the invention is a process for electroforming a layer of a gold alloy comprising 88 to 94% by weight of gold, x% of copper and / or silver by weight, and 2x% zinc by weight, x being between 2 and 4 consisting of:
• an alkaline electrolytic bath containing an anode, said bath containing at least gold salts in the form of cyanide gold and potassium, copper salts in the form of copper cyanide, zinc salts in the form of zinc oxide and / or silver salts in the form of silver oxide, sodium cyanide, sodium hydroxide, acid, for example tetraethylene diamino acetate acid and a surfactant, said substrate forming a cathode,
• the voltage is varied during the electroforming step of said layer, which makes it possible to obtain a crystallization of the ⁇ phase of the inhomogeneous gold in the layer at the time of deposition.
• This inhomogeneity makes it possible in particular to reduce the surface defects of the layer deposited by a crystalline superstructure.
• the voltage between the anode and the cathode is reduced in the final phase of the electroforming step to increase the gold concentration of the superficial zone of the deposited layer and thus enhance the golden color of the deposited layer.
• the electroforming step is followed by an annealing heat treatment of between 300 ° and 700 ° C. for at least 30 minutes and rapid quenching.
• the subject of the invention is also an electroformed piece made of gold alloy, characterized in that the gold alloy is composed of 88 to 94% by weight of gold, x% of copper and / or silver in weight, and 2x% zinc by weight, x being between 2 and 4.
• the alloy is composed of 88% by weight of gold, 8% by weight of zinc and 4% by weight of copper.
• the electroforming is carried out at a temperature of between 40 ° and 80 ° C. 0 C.
• the surfactant used is a phosphatidic ester of an alkyl polyglycol alcohol.
• an electrolysis is carried out in an alkaline galvanic bath having a pH of between 8 and 10 containing approximately 7 to 15 g / l of gold in the form of gold and potassium cyanide, approximately 1, 5 to 5 g / l of zinc in the form of zinc oxide, about 1.5 to 3 g / l of copper or silver in the form of copper cyanide or silver oxide respectively, sodium cyanide, sodium hydroxide, tetraethylene diamino acetate acid and its potassium salt and a surfactant.
• This electrolysis step is followed by a heat treatment at least 300 ° C for at least 30 minutes.
• This heat treatment is preferably carried out under a reducing atmosphere to reduce zinc oxide.
• the electroplating bath further contains a brightener.
• a brightener is preferably a potassium antimony tartrate combined with potassium hypophosphite or potassium selenocyanate.
• the surfactant is preferably a phosphatidic ester of butyl or nonyl phenolpolyglycol.
• the electrolysis is preferably carried out at a temperature between 60 and 75 ° C in an acidic galvanic bath whose pH is between 8 and 10.
• the electrolysis can be carried out with a current density of typically of the order 1, 0 A / dm 2 .
• the electrolysis is followed by a heat treatment carried out at a temperature above 300 ° C. for a time typically comprised between 30 minutes and 1 hour.
• This heat treatment comprises rapid cooling in air, which can be obtained for example in a belt furnace.
• This heat treatment is carried out under a reducing atmosphere.
• an 18-carat gold alloy free of toxic metals or metalloids, in particular free of cadmium, of pale yellow 2N tint, of hardness of between 200 and 300 HV 0.005, particularly ductile for thicknesses between 40 and 350 microns, excellent gloss and having a very high resistance to wear and tarnishing.
• This deposit is obtained by electrolysis in an electrolytic bath followed by heat treatment at 300 ° C. for 30 minutes under a reducing atmosphere. This electrolysis is carried out in an electrolytic bath containing the following compounds:
• the electrolytic bath contained in a polypropylene or PVC tank with heat-insulating coating, has a pH between 8 and 10 and its temperature is 70 ° C.
• the heating of the bath is carried out thanks to thermo-plungers made of quartz, PTFE, porcelain or stabilized stainless steel. Its density is between 16 and 30 ° g / cm 3 at 20 ° C. Good cathodic stirring as well as a circulation of the electrolyte must be maintained.
• the anodes are in platinum titanium or stainless steel.
• the present invention is not limited to the illustrated example but is susceptible of various variations and modifications that will occur to those skilled in the art.
• the bath may contain silver and the following metals In, Cd, Zr, Se, Te, Sb, Sn, Ga, As, Sr, Be, Bi in negligible amount.
• the wetting agent may be of any type capable of wetting in alkaline cyanide medium.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrochemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mechanical Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Electroplating Methods And Accessories (AREA)
• Laminated Bodies (AREA)
• Adornments (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Cites Families (31)

• 2006
  • 2006-10-03 CH CH01583/06A patent/CH714243B1/fr unknown
• 2007
  • 2007-10-03 EP EP07820883A patent/EP2079859A2/de not_active Withdrawn
  • 2007-10-03 CN CNA2007800368276A patent/CN101611176A/zh active Pending
  • 2007-10-03 JP JP2009530878A patent/JP2010506040A/ja active Pending
  • 2007-10-03 US US12/444,046 patent/US20100024930A1/en not_active Abandoned
  • 2007-10-03 WO PCT/EP2007/060506 patent/WO2008040761A2/fr active Search and Examination
  • 2007-10-03 KR KR1020097008807A patent/KR101326883B1/ko not_active IP Right Cessation

Non-Patent Citations (1)

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