Classifications

• • 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

Definitions

• This invention relates to the electrodeposition of pink gold alloys and is concerned with an electroplating process and bath which can be used to obtain a pink gold alloy deposit. Such pink deposits are useful for decorative purposes, for example in the manufacture of spectacle frames.
• an aqueous cyanide-free electroplating bath for depositing a hard, bright gold alloy electrodeposit having a pink coloration, the bath comprising the following essential constituents:
• the pH of the bath should be in the range from 7 to 11-.5, advantageously 8.5 to 11.5 and preferably abot 9.5.
• an alkali for example potassium hydroxide
• a weak acid for example citric acid
• a process for electrodepositing a hard, bright gold alloy having a pink coloration on to a conductive substrate which comprises electroplating the conductive substrate as cathode in an aqueous cyanide-free electroplating bath as defined above at a cathode current density of from 0.1 to 1.5 amp/dm 2 (amperes per square decimetre) and a temperature of from 40 to 80°C.
• the cathode current density is about 0.5 amp/dm2 and the temperature about 60°C., whilst the cathode should be moderately agitated during the electroplating process.
• the gold is normally added in the form of an ammonium or alkali metal gold sulphite complex, for example potassium gold sulphite.
• the alloying element copper is normally added as a water-soluble salt or complex, for example copper sulphate, copper tartrate or copper citrate, whilst the alloying element palladium is normally added in the form of a water-soluble complex or salt, for example sodium, potassium, or ammonium palladium sulphite, palladium diammine dinitrite or palladium citrate.
• the free sulphite ion (SO ) may be added as an ammonium or alkali metal sulphite, for example sodium, potassium or ammonium sulphite.
• the buffering agent and/or conducting salt when present, may be selected from alkali metal, alkaline earth metal or ammonium phosphates, borates, sulphates, carbonates, acetates, citrates, gluconates and tartrates, and boric acid.
• the brightening element preferably arsenic, may be added as a soluble compound or complex, for example, arsenic trioxide which is advantageously added in the form of an aqueous solution, potassium antimony tartrate or thallium sulphate.
• the type of surface active agent present in the bath is not critical and any anionic, cationic or non-ionic surfactant effective within the stated pH range can be employed.
• the surfactant can be an alkyl phosphate ester or an alcohol alkoxylate.
• the anode employed is advantageously a platinum or platinised titanium anode.
• the bright, hard gold alloy deposit having a pink coloration which can be obtained by means of the invention is a gold/copper/palladium alloy in which the elements are present in parts by weight ranges of 86-94 Au - 8-2 Cu - 6-2 Pd, advantageously 88-90 Au - 8-7 Cu - 4-3 Pd. Generally the alloy will contain more copper than palladium.
• An electroplating bath was prepared by dissolving in demineralised water the following constituents:-
• Triton Q.S.-44 sold by Rohm and Haas (U.K.) Limited
• Triton Q.S.-44 is an anionic phosphate surfactant in free acid form.
• the pH of the bath was adjusted to a value of 9.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated to a thickness of i 3 microns in the foregoing bath at a temperature of 60°C. and a cathode current density of 0.5 amp/dm 2 , with moderate agitation and using a platinum coated titanium mesh anode.
• the deposit obtained was bright and pink, extremely hard (340 HV-Vickers hardness number), ductile and pore-free. Analysis showed the deposit to be the alloy 90 Au - 7 Cu - 3 Pd.
• Example 1 The procedure of Example 1 was repeated except that the Triton Q.S.-44 was replaced by the commercially available surface active agent Cu 84 (sold by LPW Neuss, West Germany), which is an alkyl phosphate ester.
• An electroplating bath was prepared by dissolving in demineralised water the following constituents:-
• the pH of the bath was adjusted to a value of 9.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated using the foregoing bath in the manner described in Example 1 to obtain a bright, pink, pore-free ductile and extremely hard deposit. Analysis showed the deposit to be the alloy 94 Au - 2 Cu - 4 Pd.
• An electroplating bath which contained no conducting salt or buffering agent, was made up by dissolving in demineralised water the following constituents:-
• the pH of the bath was adjusted to a value of 7-7.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated using the foregoing bath in the manner described in Example 1 to obtain a bright, pink, ductile and extremely hard deposit consisting of the alloy 91 Au - 4 Cu - 5 Pd.
• An electroplating bath was prepared by dissolving in demineralised water the following constituents:-
• the pH of the bath was adjusted to a value of 9.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated using the foregoing bath in the manner described in Example 1 to obtain a bright, pink, pore-free ductile and extremely hard deposit which on analysis was found to be the alloy 88 Au - 8 Cu - 4 Pd.
• An electroplating bath was prepared by dissolving in demineralised water the following constituents:-
• the pH of the bath was adjusted to a value of 9.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated using the foregoing bath in the manner described in Example 1 to obtain a bright, pink, pore-free ductile and extremely hard deposit which on analysis was found to be the alloy 88 Au - 8 Cu - 4 Pd.
• An electroplating bath was prepared by dissolving in demineralised water the following constituents:-
• the pH of the bath was adjusted to a value of 9.5 by the appropriate addition of potassium hydroxide or citric acid.
• a brass panel was electroplated using the foregoing bath in the manner described in Example 1 to obtain a bright, pink, pore-free ductile and extremely hard deposit which on analysis was found to be the alloy 88 Au - 8 Cu - 4 Pd.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating And Plating Baths Therefor (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Cited By (2)

Citations (4)

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• 1980
  • 1980-04-02 AU AU57112/80A patent/AU5711280A/en not_active Abandoned
  • 1980-04-15 FI FI801200A patent/FI801200A/fi not_active Application Discontinuation
  • 1980-04-15 FR FR8008379A patent/FR2455097A1/fr not_active Withdrawn
  • 1980-04-17 EP EP80301243A patent/EP0018753A1/en not_active Withdrawn
  • 1980-04-17 GB GB8012744A patent/GB2047749B/en not_active Expired
  • 1980-04-23 IT IT8067643A patent/IT8067643A0/it unknown
  • 1980-04-23 DK DK172980A patent/DK172980A/da active IP Right Grant
• 1984
  • 1984-04-05 HK HK310/84A patent/HK31084A/xx not_active IP Right Cessation

Patent Citations (4)

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