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
  • C25D3/48—Electroplating: Baths therefor from solutions 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
  • 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

• acids which may be employed are formic, acetic, citric, tartaric, lactic, kojic, or similar acidsandl mixtures of these acids.
• the acid should be present in proportions of about 10 to 150 grams per liter and may be partially neutralized with ammonium or alkali hydroxide to give a pH of about 3-5. It is this weak organic acid and the procedure of maintaining the bath within a limited pH range that produces the desired eifect of a gold alloy deposition.
• the gold may be added as the double cyanide of gold and an alkali metal, potassium gold cyanide for example, and may be present in proportions of about 1 gram per liter to 15 grams per liter of gold.
• Base metal salts which may be added comprise the sulfates, sulfamates, formates, acetates, citrates, lactates, tartrates, fluoborate-s, borates, phosphates, etc., of nickel, zinc, cobalt, indium, iron, manganese, antimony, copper, etc. These metal salts are added in the proportion of from 1 to 50 grams per liter. Very satisfactory results are obtained when two of such base metal salts are included in the bath. Although the addition of base metal salt is necessary, it does not matter which salt or mixture of salts is added as long as the added salts are soluble and. compatible with all other bath ingredients.
• the bath may be operated at a current density of l to 100 amperes per square foot. Moderate to rapid agita-- tion improves the operation.
• the bath may be operatedv at normal room temperature (70 F.) which is advanta-- geous in that no themostatic regulation is necessary but: higher or lower temperatures of from 50 to 120 F.. may be employed.
• the maximum cathode/anode ratio should be about 4:1.
• the deposits obtained have a pale yellow color of pure gold, but depending upon which base metal is added the deposit may have a greenish or yellow-orange tinge.
• The: gold deposits are from about 21 to 23 karat gold.
• Citric acid plus sodium citrate Gold (as potassium gold cyanide) t 8 Nickel (as nickel sulfamate) 3 Zinc (as zinc acetate) 0.5 Water Remainder
• The. amount of sodium citrate is adjusted by adding it until the bath has a pH of 4 to 5.
• a clean and polished steel or other metal body is made the cathode in said bath, at a current density of 10 amperes per square foot, while the bath is maintained at a temperature of about 70 F.
• the deposit obtained from this bath is hard, corrosionresistant with a uniform, br'lliant, pale yellow-green coloration.
• the gold deposits assay 23 karat gold. Deposits of thicknesses of 25 to 50 microns are readily obtained from this bath.
• Example 2 An electrolytic bath is made by dissolving the following components:
• Example 3 An electrolytic bath is made by dissolving the following components:
• Citric acid and sodium citrate 80 Gold (as potassium gold cyanide) 8 Indium (as sulfate) 5 Water Remainder The pH of the bath is adjusted to 3-4 by addition of more acid or alkali.
• the deposit obtained from this bath under conditions such as specified in Example 1 is hard, corrosion-resistant, and uniformly pale yellow in color. The fineness of the deposit is 21 karat.
• tartaric acid, lactic acid, kojic acid, formic acid or similar organic acids may be substituted for the acetic or citric acid specified.
• Such baths are brought to the proper pH by the addition of an alkali or the acid in use.
• a method of electrodepositing bright gold which comprises electrolyzing a solution consisting of 10-150 g./liter of a weak, stable, organic acid, partially neutralized with alkali to provide a pH of 3-5, 1-15 g./liter of gold added as a gold cyanide, and 1-50 g./liter of at least one soluble base metal salt.
• a method as claimedinclaim 1 in which said base metal salt comprises a mixture of a cobaltsalt and an acid partially neutraliaed with alkalito provide a pH of 3-5, 1-15 g./liter of gold added as a gold cyanide and l-SOgI/litr bf at least one soluble base metal salt.
• An electrol yte for depositing bright gold coatings 'witli agreenish tinge consisting of about 80 g./liter of citrate radical neutralized with alkali to proyide apH of 4-5, about 1-15 g./liter of gold as potassium gold cyanide, about 3 g./ liter of nickel as nickel snlfamate, and
• electrolyte for depositing bright pale yellow gold coatings consisting of about 50 g./liter of weak organic acid radical partially neutralized with alkali to provide a pH of 3-4, 1-15 g./ liter of gold as cyanide gold, about 5 g./ liter of indium as indium sulfate, and about 3 g./ liter of cobalt as cobalt sulfate.
• a method of electrodepositing bright gold which comprises electrolyzing a solution consisting of -150 g./ liter of citricacid, partially neutralized with alkali to provide a pH of 3-5, 1-15 g./liter of gold added as a gold cyanide, and 1-50 g./liter of at least onesoluble base'metal salt.
• a method of electrodepositing bright gold which comprises electrolyzing a solution consisting of 10-150 g./liter of acetic' acid, partially neutralized with alkali to provide a pH of 3-5, 1-15 g./liter of gold added as a gold cyanide, and 1-50 g./ liter of at least one soluble base metal salt.
• An electrolyte for depositing bright gold coatings consisting of 10-150 g./literof citric acid partially neutralized with alkali to provide a pH of 3-5, 1-15 g./liter of gold added as a gold cyanide and 1-50 g./ liter of at least one soluble base metal salt.
• An electrolyte for depositing bright gold coatings consisting of 10-150 g./liter of acetic acid partially neutralized with alkali to provide a pH of 3-5, l-l5 g./liter of gold added as a gold cyanide and 1-50 g./1iter of at least one soluble base metal salt.

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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)

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Cited By (27)

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Citations (4)

• 0
  • NL NL230397D patent/NL230397A/xx unknown
  • BE BE570261D patent/BE570261A/xx unknown
  • NL NL112916D patent/NL112916C/xx active
• 1957
  • 1957-08-13 US US677818A patent/US2905601A/en not_active Expired - Lifetime
• 1958
  • 1958-08-07 FR FR1201185D patent/FR1201185A/fr not_active Expired
  • 1958-08-08 CH CH6272358A patent/CH384972A/de unknown
  • 1958-08-11 GB GB25764/58A patent/GB851973A/en not_active Expired

Patent Citations (4)

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