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

• the thickness of the gold coating is limited to a maximum of about 0.0003 to 0.0005 inches if satisfactory slip ring properties (i.e., the lack of brittleness and flaking caused by the buildup of internal stresses) are to be maintained. Since it is exceedingly difficult, if not impossible, to subject coatings of such thicknesses to machining operations, it is required, in the manufacture of slip rings, to employ coatings having thicknesses to about 0.003 to 0.040.
• a patent to Spreter et al. (2,724,687) discloses the addition, to an alkaline aurocyanide bath, of a metal to be alloyed with the gold in he form of its ethylenediaminotetraacetic acid salt.
• This bath contains no free alkali cyanide and unlike the process of the present invention the ethylenediaminotetraacetic acid is added in the form of a metal salt.
• Spreter et al. teach that the advantage of this addition is that the bath does not age, as is the case with previously disclosed baths.
• electroplating baths which allow the deposition of thicknesses of gold of up to about 0.04 inches.
• the present invention allows the production of suitably heavy gold deposits while at the same time greatly simplifying the plating process in that no machining of preliminary basis coatings is required.
• the baths of the present invention are alkaline cyanide electroplating baths designed for the electrodeposition of an alloy comprising gold and silver.
• Electrolyte solutions comprising the electroplating baths of this invention comprise the following components in the proportions set forth below, all proportions being set forth in grams per liter:
• Further embodiments of the present invention are electroplating baths designed to produce alloys of gold, silver, and indium.
• the components of these baths and their proportions (in grams per liter) are set forth below:
• indium to the baths of this invention as set forth above results in deposits possessing higher hardness and built-in" lubricating properties to the surface of coating. These properties are particularly advantageous, for example in the production of the slip rings mentioned above.
• the plating bath of this invention may be operated at a current density of from 2 to 22 amperes per square foot of cathode surface, although it is preferable to operate at a current density of 10:5 amperes per square foot.
• the process of this invention operates at an efficiency of approximately percent-l00 percent.
• the range of operating temperature for the baths of the present invention is about F. to about 130 F., preferably about 1 15 F. to about F.
• the pH of the bath is automatically maintained at about 12.2 by the potassium carbonate present.
• the baths of this invention are formed by dissolving the appropriate amounts of potassium aurocyanide, free potassium cyanide, and potassium carbonate in water.
• the silver is added during the course of the electroplating process as a mixture of potassium silver cyanide and EDTA.
• the deposition normally takes place over a period of about 20 hours, although a period of about 0.5 to about 50 hours is contemplated.
• a slip ring is a mechanical device that is used to transmit electrical information from a stationary member to a rotating member or vice versa.
• the slip ring of this Example Prior to the deposition of metal, the slip ring of this Example consists of cured epoxy resin and in machined to effect latitudinal grooves.
• Various copper leads extend from the core of the device and are separately exposed at the bottom of each groove.
• the bottom of the groove is coated with a conductive paint, which is removed from the end of the copper lead with a dental burr.
• the slip ring is then subjected to a preplate cleaning cycle e.g. pickling) and electrodeposited by immersion in an electrolyte having the following composition (in grams/liter) Gold (as metal) 33.0 Free potassium cyanide 30.0 Potassium carbonate 300 Silver (as metal) 0.02 EDTA 5.0
• the gold and silver were added to the bath in the form of potassium metal salts.
• the conditions of treatment were as follows:
• Example II The procedure of Example I was followed except that the electrolyte solutions contained, in addition, indium in the amount of 0.02 grams/liter (added as potassium indium cyanide and EPTA was present in the amount of 10.0 grams/liter. A bright deposit was obtained in a thickness of 0.033 inches and possessed a hardness of 155 Knoop.
• Deposits produced in accordance with the present invention meet the specifications of MIL-G-45204 B with respect to thickness, hardness and purity. This fact is extremely important, since the reliability of such products as slip rings depends, in great measure, upon the purity of the gold deposit coupled with good wearing qualities.
• the baths of the present invention produce gold deposits which possess this particular combination of properties and hence are particularly suited to be employed in the production of slip rings.
• An aqueous alkaline cyanide gold-plating bath comprising from about 28.8 to g./l. of gold, added as potassium gold cyanide, about 0.0l3 to about 0.04 g./l. of silver, added as potassium silver cyanide, about 0.75 to about 30.0 g./l. of free potassium cyanide, about 14.9 to about 75 g/l of potassium carbonate, and about 2.0 to about 15.0 g./l. of ethylenediaminetetraacetic acid.
• a process of producing a gold alloy coating which comprises electroplating the alloy from an aqueous alkaline cyanide gold-plating baths as set forth in claim 1.
• a process of producing a gold alloy coating which comprises electroplating the alloy from an aqueous alkaline cyanide gold-plating bath as set forth in claim 4.

Landscapes

• 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 (1)

Publications (1)

Family

ID=25288049

Family Applications (1)

Country Status (4)

Cited By (1)

• 1969
  • 1969-07-17 US US842704A patent/US3607682A/en not_active Expired - Lifetime
• 1970
  • 1970-07-08 DE DE19702033970 patent/DE2033970A1/de active Pending
  • 1970-07-15 FR FR7026921A patent/FR2051823A1/fr not_active Withdrawn
  • 1970-07-17 BE BE753613D patent/BE753613A/fr unknown

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