EP2196563B1 - Process for inhibiting tarnishing of silver coatings - Google Patents
Process for inhibiting tarnishing of silver coatings Download PDFInfo
- Publication number
- EP2196563B1 EP2196563B1 EP08021571A EP08021571A EP2196563B1 EP 2196563 B1 EP2196563 B1 EP 2196563B1 EP 08021571 A EP08021571 A EP 08021571A EP 08021571 A EP08021571 A EP 08021571A EP 2196563 B1 EP2196563 B1 EP 2196563B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- metal
- palladium
- platinum
- group
- rhenium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims description 74
- 229910052709 silver Inorganic materials 0.000 title claims description 74
- 239000004332 silver Substances 0.000 title claims description 74
- 238000000034 method Methods 0.000 title claims description 32
- 238000000576 coating method Methods 0.000 title claims description 23
- 238000005494 tarnishing Methods 0.000 title claims description 12
- 230000002401 inhibitory effect Effects 0.000 title claims 2
- 229910052751 metal Inorganic materials 0.000 claims description 87
- 239000002184 metal Substances 0.000 claims description 87
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 70
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 60
- 229910052763 palladium Inorganic materials 0.000 claims description 35
- 239000003792 electrolyte Substances 0.000 claims description 33
- 229910052697 platinum Inorganic materials 0.000 claims description 30
- 229910052762 osmium Inorganic materials 0.000 claims description 27
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 claims description 27
- 229910052702 rhenium Inorganic materials 0.000 claims description 27
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 claims description 27
- 239000011248 coating agent Substances 0.000 claims description 20
- 239000000084 colloidal system Substances 0.000 claims description 14
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 12
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 9
- 239000003638 chemical reducing agent Substances 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 claims description 6
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 6
- 239000010949 copper Substances 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- -1 boron hydrogen compound Chemical class 0.000 claims description 5
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 4
- 229910052737 gold Inorganic materials 0.000 claims description 4
- 239000010931 gold Substances 0.000 claims description 4
- ORTRWBYBJVGVQC-UHFFFAOYSA-N hexadecane-1-thiol Chemical compound CCCCCCCCCCCCCCCCS ORTRWBYBJVGVQC-UHFFFAOYSA-N 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- QJAOYSPHSNGHNC-UHFFFAOYSA-N octadecane-1-thiol Chemical compound CCCCCCCCCCCCCCCCCCS QJAOYSPHSNGHNC-UHFFFAOYSA-N 0.000 claims description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims description 3
- 229910052797 bismuth Inorganic materials 0.000 claims description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 3
- 239000002253 acid Substances 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- 229910052732 germanium Inorganic materials 0.000 claims description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 2
- 150000002500 ions Chemical class 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000011133 lead Substances 0.000 claims description 2
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 claims description 2
- 239000011135 tin Substances 0.000 claims description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims 2
- 150000001335 aliphatic alkanes Chemical class 0.000 claims 1
- 229910052796 boron Inorganic materials 0.000 claims 1
- 229910052739 hydrogen Inorganic materials 0.000 claims 1
- 239000001257 hydrogen Substances 0.000 claims 1
- 238000000151 deposition Methods 0.000 description 17
- 230000008021 deposition Effects 0.000 description 15
- 239000000758 substrate Substances 0.000 description 13
- 150000002739 metals Chemical class 0.000 description 7
- 239000000080 wetting agent Substances 0.000 description 6
- 150000003839 salts Chemical class 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- 238000004070 electrodeposition Methods 0.000 description 3
- 238000005498 polishing Methods 0.000 description 3
- CMCBDXRRFKYBDG-UHFFFAOYSA-N 1-dodecoxydodecane Chemical compound CCCCCCCCCCCCOCCCCCCCCCCCC CMCBDXRRFKYBDG-UHFFFAOYSA-N 0.000 description 2
- 229910001316 Ag alloy Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- GEHMBYLTCISYNY-UHFFFAOYSA-N Ammonium sulfamate Chemical compound [NH4+].NS([O-])(=O)=O GEHMBYLTCISYNY-UHFFFAOYSA-N 0.000 description 2
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 235000011130 ammonium sulphate Nutrition 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910021538 borax Inorganic materials 0.000 description 2
- 150000001860 citric acid derivatives Chemical class 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000002845 discoloration Methods 0.000 description 2
- 229910000510 noble metal Inorganic materials 0.000 description 2
- 150000002898 organic sulfur compounds Chemical class 0.000 description 2
- 235000021317 phosphate Nutrition 0.000 description 2
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 2
- 229910052700 potassium Inorganic materials 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 235000010339 sodium tetraborate Nutrition 0.000 description 2
- 150000003464 sulfur compounds Chemical class 0.000 description 2
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 2
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 2
- BSVBQGMMJUBVOD-UHFFFAOYSA-N trisodium borate Chemical compound [Na+].[Na+].[Na+].[O-]B([O-])[O-] BSVBQGMMJUBVOD-UHFFFAOYSA-N 0.000 description 2
- 239000003981 vehicle Substances 0.000 description 2
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical compound FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910000927 Ge alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- BPYMJIZUWGOKJS-UHFFFAOYSA-N [Ge].[Ag] Chemical compound [Ge].[Ag] BPYMJIZUWGOKJS-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 210000000577 adipose tissue Anatomy 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 239000001166 ammonium sulphate Substances 0.000 description 1
- JXLHNMVSKXFWAO-UHFFFAOYSA-N azane;7-fluoro-2,1,3-benzoxadiazole-4-sulfonic acid Chemical compound N.OS(=O)(=O)C1=CC=C(F)C2=NON=C12 JXLHNMVSKXFWAO-UHFFFAOYSA-N 0.000 description 1
- 235000013361 beverage Nutrition 0.000 description 1
- 210000001124 body fluid Anatomy 0.000 description 1
- 239000010839 body fluid Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 239000007859 condensation product Substances 0.000 description 1
- 239000003599 detergent Substances 0.000 description 1
- 238000004870 electrical engineering Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003925 fat Substances 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 210000004185 liver Anatomy 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- PSZYNBSKGUBXEH-UHFFFAOYSA-N naphthalene-1-sulfonic acid Chemical compound C1=CC=C2C(S(=O)(=O)O)=CC=CC2=C1 PSZYNBSKGUBXEH-UHFFFAOYSA-N 0.000 description 1
- FTMKAMVLFVRZQX-UHFFFAOYSA-N octadecylphosphonic acid Chemical compound CCCCCCCCCCCCCCCCCCP(O)(O)=O FTMKAMVLFVRZQX-UHFFFAOYSA-N 0.000 description 1
- 125000001741 organic sulfur group Chemical group 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-N phosphinic acid Chemical class O[PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-N 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 239000011253 protective coating Substances 0.000 description 1
- 229910001379 sodium hypophosphite Inorganic materials 0.000 description 1
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 1
- 235000019345 sodium thiosulphate Nutrition 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 229910021653 sulphate ion Inorganic materials 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 150000003606 tin compounds Chemical class 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Images
Classifications
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- 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
- C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1655—Process features
- C23C18/1658—Process features with two steps starting with metal deposition followed by addition of reducing agent
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1655—Process features
- C23C18/166—Process features with two steps starting with addition of reducing agent followed by metal deposition
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1689—After-treatment
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/18—Pretreatment of the material to be coated
- C23C18/1803—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces
- C23C18/1824—Pretreatment of the material to be coated of metallic material surfaces or of a non-specific material surfaces by chemical pretreatment
- C23C18/1837—Multistep pretreatment
- C23C18/1841—Multistep pretreatment with use of metal first
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/31—Coating with metals
- C23C18/42—Coating with noble metals
- C23C18/44—Coating with noble metals using reducing agents
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/48—Coating with alloys
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/02—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material
- C23C28/023—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings only including layers of metallic material only coatings of metal elements only
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
- C23F11/16—Sulfur-containing compounds
- C23F11/161—Mercaptans
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- 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
- C25D3/567—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of platinum group metals
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- 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
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- 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
Definitions
- the present invention relates to a method for preventing the tarnishing of silver layers and silver layers with significantly improved tarnish protection.
- Objects made of silver, or objects silvered with corresponding silver layers tend to darken on contact with air. Depending on the duration of exposure, yellowish-brown to black deposits develop on the silver surfaces.
- the main cause of this problem is the formation of sulfides and oxides of silver by reaction with airborne organic sulfur compounds, or sulfur compounds derived from organic sources, such as food and beverages or body fluids and body fats.
- the GB 2 438 198 A describes silver alloys containing at least 80% by weight of silver, while mentioning that silver-germanium alloys prevent tarnishing of the metal.
- European patent application no. 0 116 173 A1 describes a silver mirror with a coating of alloyed noble metal and a process for its preparation. In this case, a gold layer is applied to the silver layer of the mirror in an electrochemical process or by vapor deposition.
- the GB 1 443 322 A describes a method to improve the resistance to tarnishing of a silver or silver alloy article.
- at least one layer of a noble metal is deposited on the object in an electrochemical process.
- This object is achieved with respect to the method by a method for preventing the tarnishing of silver layers, which is characterized in that on the silver layer, a layer of a metal from the group consisting of palladium, platinum, osmium and rhenium with a layer thickness of 5 nm to 100 nm is applied.
- the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium is applied to the silver layer by contacting the silver layer with an electrolyte containing ions of a corresponding metal.
- silver layers are deposited on substrate surfaces of cyanide-containing silver electrolytes.
- the electrolyte, with which the silver layer for depositing a metal of the group consisting of palladium, platinum, osmium and rhenium is brought into contact an acidic electrolyte, since acidic electrolytes against the eventual entry of cyanide by the upstream Silvering are insensitive.
- the deposition of a corresponding palladium, platinum, osmium or rhenium layer or a layer containing at least one of these metals can be carried out both galvanically and de-energized.
- the concentration of the metal of the group consisting of palladium, platinum, osmium and rhenium in the electrolyte may be between 0.5 g / l and 20 g / l, preferably between 1 g / l and 10 g / l and still more preferably between 1 g / l and 5 g / l.
- the electrolyte which can be used according to the invention for the electrodeposition of such a layer furthermore has a conductive salt in a concentration of between 10 g / l and 200 g / l and, for improving the substrate surface, a wetting agent in a concentration of between 1 g / l and 10 g / l ,
- Suitable conductive salts are, for example, alkanesulphonates, ammonium chloride, ammonium sulphate, ammonium sulphamate, as well as sulphates, citrates or phosphates of sodium or potassium.
- a suitable wetting agent is, for example, the wetting agent marketed under the name TamoINM and based on naphthalene sulphonic acid condensation products.
- a current density between 0.1 A / dm 2 and 4 A / dm 2 , preferably between 0.5 A / dm 2 and 3 A / dm 2 is set.
- the contact time ie the time for which a corresponding current density is set between the silver layer and the counterelectrode, varies between 1 second and 60 seconds, preferably between 1 second and 10 seconds.
- the silver layer is contacted with the corresponding electrolyte at a temperature between 20 ° C and 80 ° C.
- the preferred temperature for contacting is in a range between 40 ° C and 60 ° C.
- the substrate surface having a silver layer is contacted with an electrolyte comprising a metal from the group consisting of palladium, platinum, osmium and rhenium in a concentration between 0.5 g / l and 5 g / l has.
- an electrolyte comprising a metal from the group consisting of palladium, platinum, osmium and rhenium in a concentration between 0.5 g / l and 5 g / l has.
- the metal to be deposited in the form of a thin layer of the group consisting of palladium, platinum, osmium and rhenium in the form of a salt, such as sulphate, chloride or sulphonate, is added to the electrolyte.
- an electrolyte for the inventive autocatalytic deposition of a thin anti-tarnish layer proves a conductive salt in a concentration between 5 g / l and 50 g / l.
- Suitable conductive salts are, for example, sodium borate, ammonium chloride, ammonium sulfate, ammonium sulfamate, as well as sulfates, citrates or phosphates of sodium or potassium.
- a reducing agent in a concentration between 5 g / l and 20 g / l.
- particularly suitable reducing agents are hydrogen peroxide, hypophosphite, hydrazine, formaldehyde or borohydrocarbon compounds.
- An electrolyte as described above for autocatalytic deposition according to the invention may have a pH in the range between pH 5 and pH 9, with a range between pH 6 and pH 8 being preferred.
- the temperature of the electrolyte can be varied in the autocatalytic deposition in a range between 50 ° C and 80 ° C, with a range of 60 ° C to 70 ° C is preferred.
- the electrolyte may have a wetting agent in a concentration between 0.1 ml / l and 2 ml / l.
- Suitable wetting agents in this case are, for example, sodium lauryl ether.
- the silver layer is brought into contact with an electrolyte which comprises a metal of the group consisting of palladium, platinum, osmium and rhenium in the form of a metal / metal colloid with the metal of said group as the core metal and a colloid metal surrounding said core ,
- an electrolyte which comprises a metal of the group consisting of palladium, platinum, osmium and rhenium in the form of a metal / metal colloid with the metal of said group as the core metal and a colloid metal surrounding said core
- suitable colloidal metals according to the invention are, for example, iron, tin, lead, cobalt or germanium.
- Such metal / metal colloid systems are for example from EP 0 538 006 A1 known and are used for the metallization of plastic surfaces.
- the silver layer Following the treatment of the silver layer with the aforementioned electrolytes, it is contacted with a treating solution comprising a reducing agent or a metal reducible by the colloidal metal.
- hydrogen peroxide, hypophosphites, hydrazine, formaldehyde or hydrobromic compounds can be used here as reducing agents.
- Suitable metals which are reducible by the colloidal metal are, for example, silver, gold, nickel, palladium, platinum, bismuth or mixtures of these. These metals, which can be reduced by the colloidal metal, are ionogenic in the treatment solution to be used according to the invention.
- the metal reducible by the colloid metal can advantageously also be deposited on the silver layer.
- the treatment solution to be used according to the invention also has suitable complexing agents to prevent precipitation of the released colloidal metals.
- the metal / metal colloid-containing electrolyte has a metal / metal colloid with palladium as the core metal and tin as the colloidal metal, and the treatment solution has palladium in ionic form as metal reducible by the colloidal metal.
- SAMs self-assembling molecules
- SAMs self-assembling molecules
- These self-organizing molecules then form on the silver layer a further layer which prevents or at least reduces the tarnishing of the silver layer.
- another metal such as copper and / or nickel
- the metal of the group consisting of palladium, platinum, osmium and rhenium can be deposited with the metal of the group consisting of palladium, platinum, osmium and rhenium.
- the mechanical or electrical properties of the deposited as tarnish protection metal layer can be influenced in an advantageous manner.
- the co-deposition of copper leads to higher ductility of the coatings and to a cost reduction by mitabedorfenen copper content.
- the deposition of nickel also leads to a higher ductility of the layer, but at the same time reduces pore formation and improves corrosion resistance.
- the co-deposited metal may be contained by the process of the invention in electrolytes in a concentration between 0.1 g / l and 5 g / l, preferably between 0.5 g / l and 3 g / l.
- a current pulse is applied between the silver layer and a counterelectrode, which serves to initialize a subsequent electroless deposition of said metal on the silver layer.
- the object according to the invention is achieved by a silver coating, which is characterized in that the silver coating also has a layer comprising a metal of the group consisting of palladium, platinum, osmium and rhenium with a layer thickness of 5 nm to 100 nm is.
- a metal of the group consisting of copper, nickel, gold, platinum, bismuth or mixtures thereof can be deposited.
- a layer of a self-organizing molecule such as, for example, hexadecanethiol and / or octadecanethiol, can be applied to the silver coating according to the invention.
- FIG. 12 shows the relationship between the selected concentration of the metal of the group consisting of palladium, platinum, osmium and rhenium in an electrolyte to be used in the present invention and the current density to be set and the contact time to obtain a silver layer tarnish prevention layer according to the present invention.
- a deposition metal concentration of 8 g / l in the electrolyte and a set mean current density of 1.5 A / dm 2 a layer thickness of 5 nm to 100 nm according to the invention can be achieved within a contact time of 1 second. The lower the set average current density, the longer the contact time must be.
- a correspondingly reduced concentration of the deposition metal in the electrolyte such as 1 g / l deposition metal is at a relatively high average current density of 2.5 A / dm 2, a contact time of at least 5 seconds to achieve a layer thickness of 5 nm to 100 nm according to the invention provided.
- a previously silver-coated substrate is contacted with an electrolyte containing 1 g / L of palladium sulfate, 100 g / L of an alkanesulfonate, and 3 g / L of a surfactant type TamolNM at a temperature of 40 ° C.
- a current density of 0.5 A / dm 2 is set for a time of 5 seconds.
- the substrate surface obtained under these conditions is mirror-polished and shows no tendency to run even after a long time.
- a tarnish protection is applied autocatalytically.
- the substrate with an electrolyte, which 1 g / l of palladium sulfate, 8 g / l sodium borate, 10 g / l of sodium hypophosphite and 0.5 ml / l of a wetting agent (sodium lauryl ether) at a temperature of 65 ° C and a set pH of 7.5 for 3 minutes in contact.
- a wetting agent sodium lauryl ether
- a previously coated with a silver layer substrate with an as in this example previously described electrolyte was brought into contact, wherein at the beginning of the deposition, a short current pulse of about 1 second at a set current density of about 0.1 A / dm 2 was created.
- the contact time could be shortened to 1 minute. Also in this case a mirror-like substrate surface was obtained, which shows no tendency to tarnish even after a long time.
- the substrate obtained in Example 1 and in Example 2 was contacted with an alkyl phosphonic acid or an alkyl phosphonic acid derivative (eg hexadecyl-, octadecylphosphonic acid, or mixtures thereof).
- an alkyl phosphonic acid or an alkyl phosphonic acid derivative eg hexadecyl-, octadecylphosphonic acid, or mixtures thereof.
- an improved start-up behavior and increased corrosion protection were achieved compared to the substrates obtained from Examples 1 and 2.
- the treated layers showed after one Treatment with Sulfur Liver (Universal Oxide ECTH B-48) did not show any discoloration after exposure for 1 s or for 10 s exposure time, whereas untreated silver layers showed a spontaneous intense black discoloration even with a short exposure time.
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Description
Die vorliegende Erfindung betrifft ein Verfahren zur Verhinderung des Anlaufens von Silberschichten sowie Silberschichten mit deutlich verbessertem Anlaufschutz.The present invention relates to a method for preventing the tarnishing of silver layers and silver layers with significantly improved tarnish protection.
Gegenstände aus Silber, oder mit entsprechenden Silberlagen versilberte Gegenstände neigen bei Kontakt mit Luft dazu, allmählich dunkel anzulaufen. Je nach Dauer der Exposition bilden sich gelblich-braune bis schwarze Beläge auf den Silberoberflächen aus. Hauptursache für dieses Anlaufen ist die Ausbildung von Sulfiden und Oxiden des Silbers durch Reaktion mit in der Luft enthaltenen organischen Schwefelverbindungen, oder Schwefelverbindungen, die aus organischen Quellen stammen, wie beispielsweise Speisen und Getränke oder auch Körperflüssigkeiten und Körperfette.Objects made of silver, or objects silvered with corresponding silver layers tend to darken on contact with air. Depending on the duration of exposure, yellowish-brown to black deposits develop on the silver surfaces. The main cause of this problem is the formation of sulfides and oxides of silver by reaction with airborne organic sulfur compounds, or sulfur compounds derived from organic sources, such as food and beverages or body fluids and body fats.
Auch die durch unterschiedliche Ursachen in die Umwelt eingebrachten Schwefelverbindungen, wie sie beispielsweise durch Verbrennung fossiler Brennstoffe entstehen, können zum Anlaufen von Silberschichten führen.The sulfur compounds introduced into the environment through various causes, such as those caused by the combustion of fossil fuels, can lead to tarnishing of silver layers.
Insbesondere bei Silberschmuck oder Silberbesteck tritt ein solches Anlaufen durch den intensiven Kontakt mit Speisen und Getränken oder auch Körperfetten auf. Im Falle der Silberbestecke wird das Anlaufen beim Reinigen der Bestecke in Spülmaschinen unter Zusatz der handelsüblichen Detergenzien noch verstärkt, so dass häufig eine Nachbehandlung des Silbers nach dem Spülen mittels Polieren notwendig ist.Especially with silver jewelery or silver cutlery, such tarnishing occurs through intensive contact with food and drink or even body fat. In the case of silver flatware, tarnishing when cleaning the cutlery in dishwashers with the addition of commercial detergents is enhanced, so that a post-treatment of the silver after polishing by polishing is often necessary.
Im Bereich der Elektrotechnik werden vielfach versilberte Kontaktflächen für elektrische Steckverbindungen genutzt. Diese unterliegen jedoch bei Umwelteinflüssen ebenfalls einem entsprechenden Anlaufen, was die Leitfähigkeit deutlich verringert und so zu Kontaktschwierigkeiten führen kann.In the field of electrical engineering many silvered contact surfaces are used for electrical connectors. However, these are also subject to environmental influences a corresponding start, which significantly reduces the conductivity and thus can lead to contact difficulties.
Während im Bereich des Silberschmucks und des Silberbestecks es bekannt ist, die ausgebildeten Sulfid- und/oder Oxidschichten durch Polieren mit Natriumthiosulfat, Thioharnstoff oder ammoniakhaltigen Mitteln zu entfernen, ist dies vielfach bei den Kontaktflächen von elektrischen Steckverbindungen nicht möglich.While it is known in the field of silver jewelry and silverware to remove the formed sulfide and / or oxide layers by polishing with sodium thiosulfate, thiourea or ammonia-containing agents, this is often not possible at the contact surfaces of electrical connectors.
Insbesondere im Bereich der Automobilindustrie werden jedoch aufgrund der immer mehr zunehmenden Automatisierung der Kraftfahrzeugtechnik immer geringere Ströme in den elektronischen Systemen der Kraftfahrzeuge verwendet, so dass hier sichere und gut leitfähige Kontakte benötigt werden. Hierzu bieten sich Silberkontakte oder versilberte Kontaktflächen an, die jedoch aufgrund der Exposition gegenüber organischen Schwefelverbindungen insbesondere im Motorraum dazu neigen, anzulaufen und entsprechend gering leitfähige Sulfidschichten auf der Oberfläche auszubilden.Particularly in the automotive industry, however, due to the ever-increasing automation of motor vehicle technology, ever lower currents are used in the electronic systems of motor vehicles, so that safe and highly conductive contacts are required here. For this purpose, silver contacts or silvered contact surfaces offer, but due to the exposure to organic sulfur compounds, especially in the engine compartment tend to tarnish and form correspondingly low-conductivity sulfide layers on the surface.
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Dies berücksichtigend ist es die aufgabe der vorliegenden Erfindung, ein Verfahren anzugeben, mit welchem es möglich ist, Silberoberflächen langfristig vor einem Anlaufen zu schützen oder zumindest die Neigung zum Anlaufen deutlich zu verringern, ohne das Aussehen der Silberoberfläche oder deren elektrischen Eigenschaften nachhaltig zu beeinflussen. Darüber hinaus ist es die Aufgabe der vorliegenden Erfindung, eine entsprechende Silberschicht anzugeben, welche eine geringe Neigung zum Anlaufen aufweist. With this in mind, it is the object of the present invention to provide a method with which it is possible to protect silver surfaces against tarnishing in the long term or at least to significantly reduce the tendency to tarnish without sustainably influencing the appearance of the silver surface or its electrical properties. Moreover, it is the object of the present invention to provide a corresponding silver layer, which has a low tendency to tarnish.
Gelöst wird diese Aufgabe hinsichtlich des Verfahrens durch ein Verfahren zur Verhinderung des Anlaufens von Silberschichten, welches dadurch gekennzeichnet ist, dass auf die Silberschicht eine Schicht eines Metalls aus der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium mit einer Schichtdicke von 5 nm bis 100 nm aufgebracht wird. This object is achieved with respect to the method by a method for preventing the tarnishing of silver layers, which is characterized in that on the silver layer, a layer of a metal from the group consisting of palladium, platinum, osmium and rhenium with a layer thickness of 5 nm to 100 nm is applied.
In einer Ausgestaltung des erfindungsgemäßen Verfahrens wird die Schicht eines Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium durch in Kontaktbringen der Silberschicht mit einem Elektrolyten, welcher Ionen eines entsprechenden Metalls enthält, auf die Silberschicht aufgebracht.In one embodiment of the method according to the invention, the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium is applied to the silver layer by contacting the silver layer with an electrolyte containing ions of a corresponding metal.
Häufig werden Silberschichten auf Substratoberflächen aus cyanidhaltigen Silberelektrolyten abgeschieden. In einer vorteilhaften Ausgestaltung des Verfahrens ist der Elektrolyt, mit dem die Silberschicht zur Abscheidung eines Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium in Kontakt gebracht wird, ein saurer Elektrolyt, da saure Elektrolyte gegen den eventuellen Eintrag von Cyanid durch die vorgeschaltete Versilberung unempfindlich sind.Frequently, silver layers are deposited on substrate surfaces of cyanide-containing silver electrolytes. In an advantageous embodiment of the method, the electrolyte, with which the silver layer for depositing a metal of the group consisting of palladium, platinum, osmium and rhenium is brought into contact, an acidic electrolyte, since acidic electrolytes against the eventual entry of cyanide by the upstream Silvering are insensitive.
Die Abscheidung einer entsprechenden Palladium-, Platin-, Osmium- oder Rheniumschicht beziehungsweise einer Schicht, die wenigstens eins dieser Metalle enthält, kann sowohl galvanisch als auch stromlos erfolgen.The deposition of a corresponding palladium, platinum, osmium or rhenium layer or a layer containing at least one of these metals can be carried out both galvanically and de-energized.
Im Fall der galvanischen Abscheidung einer solchen Schicht wird die zwischen der Silberschicht und einer Gegenelektrode zumindest kurzzeitig ein Strom angelegt. In einem solchen Fall kann erfindungsgemäß die Konzentration des Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium in dem Elektrolyten zwischen 0,5 g/l und 20 g/l, vorzugsweise zwischen 1 g/l und 10 g/l und noch bevorzugter zwischen 1 g/l und 5 g/l liegen. Der erfindungsgemäß einsetzbare Elektrolyt zur galvanischen Abscheidung einer solchen Schicht weist darüber hinaus ein Leitsalz in einer Konzentration zwischen 10 g/l und 200 g/l, sowie zur Verbesserung der Substratoberfläche ein Netzmittel in einer Konzentration zwischen 1 g/l und 10 g/l auf. Geeignete Leitsalze sind beispielsweise Alkansulphonate, Ammoniumchlorid, Ammoniumsulfat, Ammoniumsulfamat, sowie Sulfate, Citrate oder Phosphate des Natriums oder Kaliums. Ein geeignetes Netzmittel ist beispielsweise das unter dem Namen TamoINM vertriebene Netzmittel auf Basis von Naphthalensulphonsäurekondensationsprodukten.In the case of the electrodeposition of such a layer, the current between the silver layer and a counterelectrode is at least briefly applied. In such a case, according to the invention, the concentration of the metal of the group consisting of palladium, platinum, osmium and rhenium in the electrolyte may be between 0.5 g / l and 20 g / l, preferably between 1 g / l and 10 g / l and still more preferably between 1 g / l and 5 g / l. The electrolyte which can be used according to the invention for the electrodeposition of such a layer furthermore has a conductive salt in a concentration of between 10 g / l and 200 g / l and, for improving the substrate surface, a wetting agent in a concentration of between 1 g / l and 10 g / l , Suitable conductive salts are, for example, alkanesulphonates, ammonium chloride, ammonium sulphate, ammonium sulphamate, as well as sulphates, citrates or phosphates of sodium or potassium. A suitable wetting agent is, for example, the wetting agent marketed under the name TamoINM and based on naphthalene sulphonic acid condensation products.
Zwischen der Silberschicht und einer geeigneten Gegenelektrode, wie beispielsweise einer Elektrode aus platiniertem Titan wird eine Stromdichte zwischen 0,1 A/dm2 und 4 A/dm2, bevorzugt zwischen 0,5 A/dm2 und 3 A/dm2 eingestellt.Between the silver layer and a suitable counterelectrode, such as an electrode of platinized titanium, a current density between 0.1 A / dm 2 and 4 A / dm 2 , preferably between 0.5 A / dm 2 and 3 A / dm 2 is set.
In Abhängigkeit der Konzentration des auf der Silberschicht abzuscheidenden Metalls im Elektrolyten und der eingestellten Stromdichte variiert die Kontaktzeit, also die Zeit für die zwischen der Silberschicht und der Gegenelektrode eine entsprechende Stromdichte eingestellt wird, zwischen 1 Sekunde und 60 Sekunden, vorzugsweise zwischen 1 Sekunde und 10 Sekunden.Depending on the concentration of the metal to be deposited on the silver layer in the electrolyte and the current density set, the contact time, ie the time for which a corresponding current density is set between the silver layer and the counterelectrode, varies between 1 second and 60 seconds, preferably between 1 second and 10 seconds.
Im Fall der galvanischen Abscheidung einer Schicht eines Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium mit einer Schichtdicke von 5 nm bis 100 nm wird die Silberschicht mit dem entsprechenden Elektrolyten bei einer Temperatur zwischen 20°C und 80°C kontaktiert.In the case of the electrodeposition of a layer of a metal of the group consisting of palladium, platinum, osmium and rhenium with a layer thickness of 5 nm to 100 nm, the silver layer is contacted with the corresponding electrolyte at a temperature between 20 ° C and 80 ° C.
Die bevorzugte Temperatur zur Kontaktierung liegt in einem Bereich zwischen 40°C und 60°C.The preferred temperature for contacting is in a range between 40 ° C and 60 ° C.
Im Fall der stromlosen Abscheidung einer erfindungsgemäßen dünnen anlaufverhindernden Schicht wird die eine Silberschicht aufweisende Substratoberfläche mit einem Elektrolyten kontaktiert, welcher ein Metall aus der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium in einer Konzentration zwischen 0,5 g/l und 5 g/l aufweist. Vorzugsweise wird das in Form einer dünnen Schicht abzuscheidende Metall der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium in Form eines Salzes, wie beispielsweise als Sulphat, Chlorid oder Sulphonat dem Elektrolyten zugegeben. Desweiteren beweist ein solcher Elektrolyt zur erfindungsgemäßen autokatalytischen Abscheidung einer dünnen anlaufverhindernden Schicht ein Leitsalz in einer Konzentration zwischen 5 g/l und 50 g/l auf. Geeignete Leitsalze sind beispielsweise Natriumborat, Ammoniumchlorid, Ammoniumsulfat, Ammoniumsulfamat, sowie Sulfate, Citrate oder Phosphate des Natriums oder Kaliums. Zur autokatalytischen Abscheidung der zuvor genannten Metalle weist ein solcher Elektrolyt ein Reduktionsmittel in einer Konzentration zwischen 5 g/l und 20 g/l auf. Hierbei sind neben anderen besonders geeignete Reduktionsmittel Wasserstoffperoxid, Hypophosphit, Hydrazin, Formaldehyd oder Borwasserstoffverbindungen.In the case of the electroless deposition of a thin anti-tarnish layer according to the invention, the substrate surface having a silver layer is contacted with an electrolyte comprising a metal from the group consisting of palladium, platinum, osmium and rhenium in a concentration between 0.5 g / l and 5 g / l has. Preferably, the metal to be deposited in the form of a thin layer of the group consisting of palladium, platinum, osmium and rhenium in the form of a salt, such as sulphate, chloride or sulphonate, is added to the electrolyte. Furthermore, such an electrolyte for the inventive autocatalytic deposition of a thin anti-tarnish layer proves a conductive salt in a concentration between 5 g / l and 50 g / l. Suitable conductive salts are, for example, sodium borate, ammonium chloride, ammonium sulfate, ammonium sulfamate, as well as sulfates, citrates or phosphates of sodium or potassium. For autocatalytic deposition of the aforementioned metals, such an electrolyte has a reducing agent in a concentration between 5 g / l and 20 g / l. Among others, particularly suitable reducing agents are hydrogen peroxide, hypophosphite, hydrazine, formaldehyde or borohydrocarbon compounds.
Ein wie zuvor beschriebener Elektrolyt zur erfindungsgemäßen autokatalytischen Abscheidung kann einen pH-Wert im Bereich zwischen pH 5 und pH 9 aufweisen, wobei ein Bereich zwischen pH 6 und pH 8 bevorzugt ist. Die Temperatur des Elektrolyten kann bei der autokatalytischen Abscheidung in einem Bereich zwischen 50°C und 80°C variiert werden, wobei ein Bereich von 60°C bis 70°C bevorzugt ist.An electrolyte as described above for autocatalytic deposition according to the invention may have a pH in the range between
Zur Verbesserung der Benetzung des Substrates kann der Elektrolyt ein Netzmittel in einer Konzentration zwischen 0,1 ml/l und 2 ml/l aufweisen. Geeignete Netzmittel sind in diesem Fall beispielsweise Natriumlauryläther.To improve the wetting of the substrate, the electrolyte may have a wetting agent in a concentration between 0.1 ml / l and 2 ml / l. Suitable wetting agents in this case are, for example, sodium lauryl ether.
Im erfindungsgemäßen Verfahren wird die Silberschicht mit einem Elektrolyten in Kontakt gebracht, welcher ein Metall der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium in Form eines Metall/Metall-Kolloids mit dem Metall der genannten Gruppe als Kernmetall und einem diesen Kern umgebenden Kolloidmetall aufweist. Hierbei sind erfindungsgemäß geeignete Kolloidmetalle beispielsweise Eisen, Zinn, Blei, Kobalt oder Germanium. Solche Metall-/Metall-Kolloidsysteme sind beispielsweise aus der
Im Anschluss an die Behandlung der Silberschicht mit den zuvor genannten Elektrolyten wird diese mit einer Behandlungslösung in Kontakt gebracht, welche ein Reduktionsmittel oder ein durch das Kolloidmetall reduzierbares Metall aufweist.Following the treatment of the silver layer with the aforementioned electrolytes, it is contacted with a treating solution comprising a reducing agent or a metal reducible by the colloidal metal.
Erfindungsgemäß sind hier als Reduktionsmittel beispielsweise Wasserstoffperoxid, Hypophosphite, Hydrazin, Formaldehyd oder Borwasserstoffverbindungen einsetzbar.According to the invention, for example, hydrogen peroxide, hypophosphites, hydrazine, formaldehyde or hydrobromic compounds can be used here as reducing agents.
Geeignete Metalle, welche durch das Kolloidmetall reduzierbar sind, sind beispielsweise Silber, Gold, Nickel, Palladium, Platin, Bismut oder Mischungen dieser. Diese durch das Kolloidmetall reduzierbaren Metalle liegen in der erfindungsgemäß einzusetzenden Behandlungslösung ionogen vor. Durch das Kontaktieren der zuvor mit einer metall/metall-kolloidhaltigen Lösung behandelten Silberschicht mit einer ein Reduktionsmittel oder ein durch das Kolloidmetall reduzierbares Metall aufweisenden Behandlungslösung werden die Kernmetall des Metall/Metall-Kolloides freigelegt und lagern sich auf der Silberschicht ab.Suitable metals which are reducible by the colloidal metal are, for example, silver, gold, nickel, palladium, platinum, bismuth or mixtures of these. These metals, which can be reduced by the colloidal metal, are ionogenic in the treatment solution to be used according to the invention. By contacting the silver layer previously treated with a metal / metal colloid-containing solution with a treatment solution comprising a reducing agent or a metal reducible by the colloidal metal, the metallo-metal colloid core metal is exposed and deposited on the silver layer.
In der Ausgestaltung des erfindungsgemäßen Verfahrens, in welcher die Behandlungslösung ein durch das Kolloidmetall reduzierbares Metall aufweist, kann in vorteilhafter Weise auch das durch das Kolloidmetall reduzierbare Metall auf der Silberschicht abgelagert werden.In the embodiment of the method according to the invention, in which the treatment solution has a metal which can be reduced by the colloidal metal, the metal reducible by the colloid metal can advantageously also be deposited on the silver layer.
In einem solchen Fall weist die erfindungsgemäß einzusetzende Behandlungslösung auch noch geeignete Komplexbildner auf, um ein Ausfallen der freigesetzten Kolloidmetalle zu verhindern.In such a case, the treatment solution to be used according to the invention also has suitable complexing agents to prevent precipitation of the released colloidal metals.
In einer besonderen Ausgestaltung des erfindungsgemäßen Verfahrens weist der metall/metall-kolloidhaltige Elektrolyt ein Metall/Metall-Kolloid mit Palladium als Kernmetall und Zinn als Kolloidmetall auf, und die Behandlungslösung weist Palladium in ionogener Form als durch das Kolloidmetall reduzierbares Metall auf.In a particular embodiment of the method according to the invention, the metal / metal colloid-containing electrolyte has a metal / metal colloid with palladium as the core metal and tin as the colloidal metal, and the treatment solution has palladium in ionic form as metal reducible by the colloidal metal.
Unabhängig davon, wie die Schicht eines Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium auf die Silberschicht aufgebracht wurde, kann es erfindungsgemäß vorgesehen sein, auf eine solche Metallschicht eine Schicht aus selbstorganisierenden Molekülen (sogenannten SAMs) aufzubringen. Insbesondere geeignete Self-Assembling-Molecules (SAMs) sind beispielsweise Hexadecanthiol, Octadecanthiol und/oder Alkanphosphorsäuren und deren Derivate.Regardless of how the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium was applied to the silver layer, it can be provided according to the invention to apply a layer of self-assembling molecules (so-called SAMs) to such a metal layer. Particularly suitable self-assembling molecules (SAMs) are, for example, hexadecanethiol, octadecanethiol and / or alkanephosphoric acids and derivatives thereof.
Diese selbstorganisierenden Moleküle bilden dann auf der Silberschicht eine weitere, das Anlaufen der Silberschicht verhindernde oder zumindest reduzierende Schicht aus.These self-organizing molecules then form on the silver layer a further layer which prevents or at least reduces the tarnishing of the silver layer.
In einer weiteren Ausgestaltung des erfindungsgemäßen Verfahrens kann mit dem Metall der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium ein weiteres Metall, wie beispielsweise Kupfer und/oder Nickel, abgeschieden werden. Hierdurch lassen sich in vorteilhafter Weise die mechanischen oder elektrischen Eigenschaften der als Anlaufschutz abgeschiedenen Metallschicht beeinflussen. So führt beispielsweise die Mitabscheidung von Kupfer zu höherer Duktilität der Überzüge sowie zu eine Kostenreduzierung durch den mitabgeschiedenen Kupferanteil. Die Abscheidung von Nickel führt ebenfalls zu einer höheren Duktilität der Schicht, verringert aber gleichzeitig die Porenbildung und verbessert die Korrosionsbeständigkeit.In a further embodiment of the method according to the invention, another metal, such as copper and / or nickel, can be deposited with the metal of the group consisting of palladium, platinum, osmium and rhenium. As a result, the mechanical or electrical properties of the deposited as tarnish protection metal layer can be influenced in an advantageous manner. For example, the co-deposition of copper leads to higher ductility of the coatings and to a cost reduction by mitabeschiedenen copper content. The deposition of nickel also leads to a higher ductility of the layer, but at the same time reduces pore formation and improves corrosion resistance.
Das mitabzuscheidende Metall kann nach dem erfindungsgemäßen Verfahren in Elektrolyten in einer Konzentration zwischen 0,1 g/l und 5 g/l, vorzugsweise zwischen 0,5 g/l und 3 g/l enthalten sein.The co-deposited metal may be contained by the process of the invention in electrolytes in a concentration between 0.1 g / l and 5 g / l, preferably between 0.5 g / l and 3 g / l.
In einer weiteren Ausgestaltung des erfindungsgemäßen Verfahrens wird zu Beginn der Abscheidung eines Metalls der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium ein Stromimpuls zwischen der Silberschicht und einer Gegenelektrode angelegt, welcher zur Initialisierung einer nachfolgenden stromlosen Abscheidung der genannten Metall auf der Silberschicht dient.In a further embodiment of the method according to the invention, at the beginning of the deposition of a metal of the group consisting of palladium, platinum, osmium and rhenium, a current pulse is applied between the silver layer and a counterelectrode, which serves to initialize a subsequent electroless deposition of said metal on the silver layer.
Hinsichtlich der Silberbeschichtung wird die erfindungsgemäße Aufgabe durch eine Silberbeschichtung gelöst, welche dadurch gekennzeichnet ist, dass auch die Silberbeschichtung eine Schicht, welche ein Metall der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium aufweist, mit einer Schichtdicke von 5 nm bis 100 nm aufgebracht ist.With regard to the silver coating, the object according to the invention is achieved by a silver coating, which is characterized in that the silver coating also has a layer comprising a metal of the group consisting of palladium, platinum, osmium and rhenium with a layer thickness of 5 nm to 100 nm is.
In einer Ausgestaltung der erfindungsgemäßen Silberbeschichtung kann neben den Metallen der Gruppe bestehend aus Palladium, Platin, Osmium und Rhenium ein Metall der Gruppe bestehend aus Kupfer, Nickel, Gold, Platin, Bismut oder Mischungen dieser abgeschieden werden.In one embodiment of the silver coating according to the invention, in addition to the metals of the group consisting of palladium, platinum, osmium and rhenium, a metal of the group consisting of copper, nickel, gold, platinum, bismuth or mixtures thereof can be deposited.
Auf die erfindungsgemäße Silberbeschichtung kann in einer Ausgestaltung der Erfindung eine Schicht eines selbstorganisierenden Moleküls, wie beispielsweise Hexadecanthiol und/oder Octadecanthiol, aufgebracht sein.In one embodiment of the invention, a layer of a self-organizing molecule, such as, for example, hexadecanethiol and / or octadecanethiol, can be applied to the silver coating according to the invention.
Die vorliegende Erfindung wird nachfolgend anhand von Ausführungsbeispielen exemplarisch dargestellt, ohne dass sich die Erfindung jedoch auf diese Ausführungsbeispiele beschränken lässt.The present invention is illustrated by way of example with reference to exemplary embodiments, but without the invention being limited to these exemplary embodiments.
Ein zuvor mit einer Silberschicht beschichtetes Substrat wird mit einem Elektrolyten, aufweisend 1 g/l Palladiumsulfat, 100 g/l eines Alkansulfonats, sowie 3 g/l eines Netzmittels Typ TamolNM bei einer Temperatur von 40°C in Kontakt gebracht. Es wird eine Stromdichte von 0,5 A/dm2 für eine Zeit von 5 Sekunden eingestellt. Die unter diesen Bedingungen erhaltene Substratoberfläche ist spiegelglänzend und zeigt auch nach längerer Zeit keine Tendenzen anzulaufen.A previously silver-coated substrate is contacted with an electrolyte containing 1 g / L of palladium sulfate, 100 g / L of an alkanesulfonate, and 3 g / L of a surfactant type TamolNM at a temperature of 40 ° C. A current density of 0.5 A / dm 2 is set for a time of 5 seconds. The substrate surface obtained under these conditions is mirror-polished and shows no tendency to run even after a long time.
Auf ein zuvor mit einer Silberschicht beschichteten Substrat wird autokatalytisch ein erfindungsgemäßer Anlaufschutz aufgebracht. Zu diesem Zweck wird das Substrat mit einem Elektrolyten, welcher 1 g/l Palladiumsulfat, 8 g/l Natriumborat, 10 g/l Natriumhypophosphit sowie 0,5 ml/l eines Netzmittels (Natriumlauryläther) bei einer Temperatur von 65°C und einem eingestellten pH-Wert von 7,5 für 3 Minuten in Kontakt gebracht.On a substrate previously coated with a silver layer, a tarnish protection according to the invention is applied autocatalytically. For this purpose, the substrate with an electrolyte, which 1 g / l of palladium sulfate, 8 g / l sodium borate, 10 g / l of sodium hypophosphite and 0.5 ml / l of a wetting agent (sodium lauryl ether) at a temperature of 65 ° C and a set pH of 7.5 for 3 minutes in contact.
Unter diesen Bedingungen wird eine spiegelglänzende Substratoberfläche erhalten, welche auch nach längerer Zeit keinerlei Anlauftendenz zeigt.Under these conditions, a mirror-like substrate surface is obtained, which shows no tendency to tarnish even after a long time.
In einer weiteren Ausgestaltung der Erfindung wurde ein zuvor mit einer Silberschicht beschichtetes Substrat mit einem wie in diesem Beispiel zuvor beschriebenen Elektrolyten in Kontakt gebracht, wobei zu Beginn der Abscheidung ein kurzer Stromimpuls von ca. 1 Sekunde bei einer eingestellten Stromdicht von ca. 0,1 A/dm2 angelegt wurde. Durch die so initiierte Abscheidung konnte die Kontaktzeit auf 1 Minute verkürzt werden. Auch in diesem Fall wurde eine spiegelglänzende Substratoberfläche erhalten, welche auch nach längerer Zeit keinerlei Anlauftendenzen zeigt.In a further embodiment of the invention, a previously coated with a silver layer substrate with an as in this example previously described electrolyte was brought into contact, wherein at the beginning of the deposition, a short current pulse of about 1 second at a set current density of about 0.1 A / dm 2 was created. Through the so initiated deposition, the contact time could be shortened to 1 minute. Also in this case a mirror-like substrate surface was obtained, which shows no tendency to tarnish even after a long time.
Das in Beispiel 1 sowie in Beispiel 2 erhaltene Substrat wurde im Anschluss an die Abscheidung der dünnen Palladiumschicht mit einer Alkyl-phosphonsäure oder einem Alkyl-phosphonsäurederivat (z. B. Hexadecyl-, Octadecylphosphonsäure, oder Mischungen dieser) kontaktiert. Nach dem Abtrocknen der Schicht wurde ein noch gegenüber den aus den Beispielen 1 und 2 erhaltenen Substraten verbessertes Anlaufverhalten und ein erhöhter Korrosionsschutz erzielt. So zeigten die behandelten Schichten nach einer Behandlung mit Schwefelleber (Universal Oxide ECTH B-48) sowohl nach einer Expositionszeit von 1 s als auch nach einer Expositionszeit von 10 s keinerlei Verfärbungen, während nicht behandelte Silberschichten bereits bei kurzer Expositionszeit eine spontane intensive Schwarzverfärbung zeigten.Following the deposition of the thin palladium layer, the substrate obtained in Example 1 and in Example 2 was contacted with an alkyl phosphonic acid or an alkyl phosphonic acid derivative (eg hexadecyl-, octadecylphosphonic acid, or mixtures thereof). After the layer had dried, an improved start-up behavior and increased corrosion protection were achieved compared to the substrates obtained from Examples 1 and 2. Thus, the treated layers showed after one Treatment with Sulfur Liver (Universal Oxide ECTH B-48) did not show any discoloration after exposure for 1 s or for 10 s exposure time, whereas untreated silver layers showed a spontaneous intense black discoloration even with a short exposure time.
Claims (16)
- A method for inhibiting tarnishing of silver coatings,
characterized in that
a layer of a metal of the group consisting of palladium, platinum, osmium and rhenium having a layer thickness comprised between 5 nm and 100 nm is applied onto the silver coating,
wherein the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium is applied by bringing the silver coating into contact with an electrolyte which contains ions of a metal or a metal in form of a metal/metal colloid of the group consisting of palladium, platinum, osmium and rhenium and
wherein a layer of a self-organizing molecule is applied onto the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium. - A method according to claim 1, wherein the silver coating is brought into contact with an acid electrolyte.
- A method according to claim 1 or 2, characterized in that a current for producing the layer of a metal of the group consisting of palladium, platinum, osmium and rhenium is applied between the silver coating and a counter-electrode for a period of time comprised between 1 second and 60 seconds.
- A method according to one of the claims 1 through 3, wherein the silver coating is brought into contact with an electrolyte comprises a metal of the group consisting of palladium, platinum, osmium and rhenium in form of a metal/metal colloid with the metal of the mentioned group being the core metal and a colloid metal which encompasses this core.
- A method according to claim 4, wherein the silver coating is brought into contact with an electrolyte which comprises iron, tin, lead, cobalt or germanium as colloid metal.
- A method according to one of the claims 1 through 5, wherein the silver coating is brought into contact with a treatment solution which comprises a reducing agent or a metal reducible by the colloid metal after having brought the silver coating into contact with an electrolyte which contains a metal of the group consisting of palladium, platinum, osmium and rhenium.
- A method according to claim 6, wherein the silver coating is brought into contact with a treatment solution which comprises hydrogen peroxide, a hypophosphite, a hydrazine, formaldehyde or a boron hydrogen compound as reducing agent.
- A method according to claim 6, wherein the silver coating is brought into contact with a treatment solution which comprises silver, gold, nickel, palladium, platinum, bismuth or mixtures thereof as a metal reducible by the colloid metal.
- A method according to claim 3 or 4, wherein the electrolyte comprises a concentration comprised between 0.5 g/l and 20 g/l, preferably between 1 g/l and 10 g/l of the metal of the group consisting of palladium, platinum, osmium and rhenium.
- A method according to claim 9, wherein a current density comprised between 0.1 A/dm2 and 4 A/dm2, preferably between 0.5 A/dm2 and 3 A/dm2 is set between the silver coating and a counter-electrode.
- A method according to claims 3, 9 or 10, wherein the current is applied for a period of time comprised between 1 s and 60 s, preferably between 1 s and 10 s.
- A method according to one of the claims 9 through 11, wherein the period of time in which a current is applied is determined in dependence on the current density and the concentration of the metal of the group consisting of palladium, platinum, osmium and rhenium in the electrolyte with the aim to obtain a layer thickness of the metal to be deposited comprised between 5 nm and 100 nm.
- A method according to one of the claims 1 through 12, characterized in that hexadecanethiol and/or octadecanethiol and/or an alkane phosphoric acid or a derivate of these ones is used as self-organizing molecules.
- A method according to one of the preceding claims, wherein a metal of the group consisting of palladium, platinum, osmium and rhenium is deposited together with copper and/or nickel.
- A silver coating characterized in that a layer which comprises a metal of the group consisting of palladium, platinum, osmium and rhenium and has a layer thickness comprised between 5 nm and 100 nm is applied onto the silver coating and a layer of a self-organizing molecule is applied onto the layer which comprises a metal of the group consisting of palladium, platinum, osmium and rhenium.
- A silver coating according to claim 15, wherein the self-organizing molecule is hexadecanethiol and/or octadecanethiol and/or an alkyl phosphoric acid or a derivate of these ones.
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