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
  • C25D3/46—Electroplating: Baths therefor from solutions of silver

Definitions

• the present invention relates to a cyanide-free electrolyte composition for depositing a silver or silver alloy layer on a substrate. Moreover, the present invention relates to a method for depositing such layers using the cyanide-free electrolyte composition of the present invention.
• Galvanic electrolyte compositions for the deposition of silver or silver alloy layers are known both for use in the field of decorative surfaces and in the technical field. It is customary in the prior art to use soluble silver compounds, usually in the form of cyanide compounds such as potassium silver cyanide or in the form of sulfur-containing complexes such as sulfite, thiosulfate or thiocyanate and ammonium complexes.
• soluble silver compounds usually in the form of cyanide compounds such as potassium silver cyanide or in the form of sulfur-containing complexes such as sulfite, thiosulfate or thiocyanate and ammonium complexes.
• electrolyte compositions are generally unstable without the addition of other complexing or stabilizing agents, it is customary to use the complexing agent components in excess, so that such electrolyte compositions often have very high cyanide, sulfur-containing complexing agent or ammonium concentrations.
• the electrolyte compositions produced in this way are characterized by a wide range of applications. Cyanidic compositions are stable but toxic and therefore of environmental concern. The others mentioned have a lower risk potential, but tend to instability. Despite the significantly lower risk potential with respect to cyanides, the environmental relevance contained in such electrolyte compositions is not negligible and, because of their allergenic potential, can pose a threat to persons working with these electrolyte compositions.
• DE 199 28 47 A1 discloses a low-pollutant to unpolluted aqueous electrolyte composition for the electrodeposition of noble metals and noble metal alloys comprising the noble metal to be deposited and the alloy metals to be used in the form of water-soluble compounds of protein amino acids or their salts or in the form of sulfonic acid compounds.
• these have water-soluble nitro compounds. These may be, for example, 3-nitrophthalic acid, 4-nitrophthalic acid or m-nitrobenzenesulfonic acid.
• these may include organic acids such as nicotinic acid or succinic acid.
• No. 4,126,524 A1 discloses cyanide-free electrolyte compositions for depositing silver or silver alloys which have silver in the form of imides of organic dicarboxylic acids.
• the reaction products of water-soluble silver salts with pyrrolidinediones may serve as silver sources in corresponding electrolyte compositions.
• silver can be used in the form of succinimides or maleimides.
• U.S. Patent No. 4,246,077 discloses the use of silver in the form of pyrrolidinediones as a silver source in corresponding electrolyte compositions for depositing silver or silver alloy layers.
• U.S. Patent No. 5,601,696 discloses the use of hydantoin as a complexing agent in electrolyte compositions for depositing silver or silver alloy layers on substrates.
• hydantoin for example, 1-methylhydantoin, 1, 3-dimethylhydantoin, 5,5-dimethylhydantoin, 1-methanol-5,5-dimethylhydantoin or also 5,5-diphenylhydantoin can be used as complexing reagents.
• WO 2005/083156 discloses a hydantoin-containing electrolyte composition for depositing mirror-finished silver or silver alloy layers.
• these electrolyte compositions have other environmentally harmful compounds such as 2,2'-bipyridine.
• 2,2'-bipyridine can lead to an inhibition of carboxypeptidases, which play a crucial role, for example, in the digestion of proteins in the small intestine, which justifies the toxicity of this class of compounds and requires extremely careful handling of these compounds.
• a cyanide-free electrolyte composition for depositing a silver or silver alloy layer on a substrate comprising at least a silver ion source, a sulfonic acid and / or a derivative of a sulfonic acid, a wetting agent and a hydantoin of the general formula
• Ri and R 2 independently of one another may be an H, an alkyl group having 1 to 5 carbon atoms or a substituted or unsubstituted aryl group.
• the electrolyte composition according to the invention comprises the sulfonic acid and / or a derivative of a sulfonic acid in a concentration between 50 g / l and 500 g / l, preferably between 100 g / l and 300 g / l, more preferably between 130 g / l and 200 g / l ,
• the electrolyte composition according to the invention preferably comprises potassium methanesulfonate.
• methanesulfonates such as, for example, sodium methanesulfonate, but also sulfates and other compounds suitable as electrolyte salt are suitable for use in the electrolyte composition according to the invention.
• the electrolyte composition of the present invention may have a silver concentration of from 10 to 50 g / L, preferably from 20 to 40 g / L, more preferably from 25 to 35 g / L.
• the electrolyte composition of the present invention has at least one silver salt of a sulfonic acid.
• other silver ion sources may include inorganic silver salts selected from the group consisting of silver oxide, silver nitrate and silver sulfate in the electrolyte composition.
• the electrolyte composition of the present invention may have corresponding sources of alloy metal ions.
• corresponding alloying metals are used in the form of their sulfonic acid salts, oxides, nitrates or sulfates.
• the electrolyte composition according to the invention may for example comprise a naphthalenesulfonic acid-formaldehyde polycondensate and / or a sulfopropylated polyalkoxylated naphthol.
• the electrolyte composition may comprise other wetting agents or surfactants.
• an alkali bromide for improving the deposition result may be added to the electrolyte composition of the present invention.
• the addition of potassium bromide has proven particularly suitable.
• the addition of alkali bromides, in particular potassium bromide leads to a uniform deposition of the silver layer on the substrate surface.
• the addition of potassium bromide leads to a uniform matting effect of the deposited layer.
• more uniform deposition results by the addition of alkali bromides such. B. reached potassium bromide.
• the addition of 50 to 500 mg / 1 alkali bromide, preferably 100 to 200 mg / l Alkalibromid be provided in order to achieve the above-described improved deposition results.
• the layers deposited in this way are virtually free of internal stresses and show very good soldering properties.
• the electrolyte composition according to the invention has a thiosulfate.
• the Electrolyte composition an alkali metal thiosulfate, particularly preferably sodium thiosulfate.
• the thiosulfate is contained in a concentration between 50 mg / l and 500 mg / l, preferably 100 mg / l to 200 mg / l in the electrolyte composition.
• the thiosulfate does not serve as a complexing agent for the silver to be deposited, but as a matting agent.
• the silver layers deposited from such an electrolyte composition are uniformly matt and almost free from internal stress. In addition, the layers show very good soldering properties.
• this has both an alkali bromide and a thiosulfate.
• the total concentration of alkali bromide and thiosulfate in the electrolyte composition is 50 mg / l to 500 mg / l, preferably 100 mg / l to 200 mg / l.
• the layers deposited from such an electrolyte composition are uniformly matt, virtually stress-free and show very good soldering properties.
• the pH of the electrolyte composition of the invention is between pH 8 and pH 14, preferably between pH 9.0 and pH 12.5, more preferably between pH 9.5 and pH 12.0.
• the object is achieved by a method for depositing a silver or silver alloy layer on a substrate, wherein the substrate to be coated at a set current density between 0.1 and 2 A / dm 2 , preferably 0.3 to 1, 5 A / dm 2 is contacted with the electrolyte composition according to the invention.
• the cyanide-free electrolyte compositions according to the invention exhibit a hitherto unknown stability for a cyanide-free silver deposition electrolyte which is comparable to the stability of cyanidic baths.
• the electrolyte compositions of the invention show a bath stability of> 100 Ah / l.
• the electrolyte compositions according to the invention can thus be used in corresponding silver deposition baths with a service life of over one year, which is too large in terms of cost and environmental impact Advantages over the previously known from the prior art cyanide electrolyte compositions leads.
• the deposition of lustrous, ductile silver or silver alloy layers in a wide range of applications is possible.
• layers for applications in the jewelery, electronics or automotive industry can be deposited with the aid of the electrolyte composition according to the invention.
• inventive method and the electrolyte composition of the invention are particularly applicable to suitable substrates such as gold-plated, nickel-plated and other, not prone to sedimentation sheets.
• a gilded brass sheet was contacted at an adjusted current density of 0.5 A / dm 2 for 15 minutes with an electrolyte composition having the following composition:
• a gilded brass sheet was contacted at an adjusted current density of 0.5 A / dm 2 for 15 minutes with an electrolyte composition having the following composition:
• a gilded brass sheet was contacted at an adjusted current density of 0.5 A / dm 2 for 15 minutes with an electrolyte composition having the following composition:
• a gilded brass sheet was contacted at an adjusted current density of 0.5 A / dm 2 for 15 minutes with an electrolyte composition having the following composition:

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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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• 2006
  • 2006-10-09 EP EP06021174A patent/EP1918426A1/de not_active Withdrawn
• 2007
  • 2007-10-09 KR KR1020097009568A patent/KR101409701B1/ko active Active
  • 2007-10-09 EP EP07818853.9A patent/EP2089561B1/de active Active
  • 2007-10-09 JP JP2009531764A patent/JP5439181B2/ja active Active
  • 2007-10-09 CN CN2007800454144A patent/CN101627150B/zh active Active
  • 2007-10-09 WO PCT/EP2007/008780 patent/WO2008043528A2/de not_active Ceased
  • 2007-10-09 US US12/445,049 patent/US9212427B2/en active Active
• 2015
  • 2015-12-08 US US14/962,863 patent/US9657402B2/en active Active

Patent Citations (6)

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