WO2021122932A1 - Electroplating composition and method for depositing a chromium coating on a substrate - Google Patents
Electroplating composition and method for depositing a chromium coating on a substrate Download PDFInfo
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- WO2021122932A1 WO2021122932A1 PCT/EP2020/086688 EP2020086688W WO2021122932A1 WO 2021122932 A1 WO2021122932 A1 WO 2021122932A1 EP 2020086688 W EP2020086688 W EP 2020086688W WO 2021122932 A1 WO2021122932 A1 WO 2021122932A1
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- WO
- WIPO (PCT)
- Prior art keywords
- electroplating composition
- electroplating
- substrate
- preferred
- present
- Prior art date
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- 238000009713 electroplating Methods 0.000 title claims abstract description 181
- 239000000203 mixture Substances 0.000 title claims abstract description 180
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 239000011651 chromium Substances 0.000 title claims abstract description 76
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 75
- 238000000576 coating method Methods 0.000 title claims abstract description 64
- 239000000758 substrate Substances 0.000 title claims abstract description 59
- 239000011248 coating agent Substances 0.000 title claims abstract description 58
- 238000000151 deposition Methods 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims description 69
- 150000002009 diols Chemical class 0.000 claims abstract description 56
- 239000000654 additive Substances 0.000 claims abstract description 36
- 229910001430 chromium ion Inorganic materials 0.000 claims abstract description 36
- 230000000996 additive effect Effects 0.000 claims abstract description 31
- 150000002334 glycols Chemical class 0.000 claims abstract description 21
- 239000008139 complexing agent Substances 0.000 claims abstract description 13
- KWIUHFFTVRNATP-UHFFFAOYSA-N Betaine Natural products C[N+](C)(C)CC([O-])=O KWIUHFFTVRNATP-UHFFFAOYSA-N 0.000 claims description 19
- KWIUHFFTVRNATP-UHFFFAOYSA-O N,N,N-trimethylglycinium Chemical compound C[N+](C)(C)CC(O)=O KWIUHFFTVRNATP-UHFFFAOYSA-O 0.000 claims description 19
- 229960003237 betaine Drugs 0.000 claims description 19
- 125000004432 carbon atom Chemical group C* 0.000 claims description 19
- -1 N-Oc- tadecyl-N Chemical compound 0.000 claims description 15
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- 125000001449 isopropyl group Chemical group [H]C([H])([H])C([H])(*)C([H])([H])[H] 0.000 claims description 5
- 125000004433 nitrogen atom Chemical group N* 0.000 claims description 4
- 230000005595 deprotonation Effects 0.000 claims description 3
- 238000010537 deprotonation reaction Methods 0.000 claims description 3
- 125000001273 sulfonato group Chemical group [O-]S(*)(=O)=O 0.000 claims description 3
- WKALLSVICJPZTM-UHFFFAOYSA-N 3-[decyl(dimethyl)azaniumyl]propane-1-sulfonate Chemical compound CCCCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O WKALLSVICJPZTM-UHFFFAOYSA-N 0.000 claims description 2
- QZRAABPTWGFNIU-UHFFFAOYSA-N 3-[dimethyl(octyl)azaniumyl]propane-1-sulfonate Chemical compound CCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O QZRAABPTWGFNIU-UHFFFAOYSA-N 0.000 claims description 2
- TUBRCQBRKJXJEA-UHFFFAOYSA-N 3-[hexadecyl(dimethyl)azaniumyl]propane-1-sulfonate Chemical compound CCCCCCCCCCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O TUBRCQBRKJXJEA-UHFFFAOYSA-N 0.000 claims description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 2
- BHATUINFZWUDIX-UHFFFAOYSA-N Zwittergent 3-14 Chemical compound CCCCCCCCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O BHATUINFZWUDIX-UHFFFAOYSA-N 0.000 claims description 2
- 150000007942 carboxylates Chemical group 0.000 claims description 2
- DVEKCXOJTLDBFE-UHFFFAOYSA-N n-dodecyl-n,n-dimethylglycinate Chemical compound CCCCCCCCCCCC[N+](C)(C)CC([O-])=O DVEKCXOJTLDBFE-UHFFFAOYSA-N 0.000 claims description 2
- 229920000642 polymer Polymers 0.000 claims description 2
- GYJNVSAUBGJVLV-UHFFFAOYSA-N 3-(dimethylazaniumyl)propane-1-sulfonate Chemical compound CN(C)CCCS(O)(=O)=O GYJNVSAUBGJVLV-UHFFFAOYSA-N 0.000 claims 1
- 235000012721 chromium Nutrition 0.000 description 67
- 229940107218 chromium Drugs 0.000 description 67
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 18
- 150000001875 compounds Chemical class 0.000 description 17
- 229910052751 metal Inorganic materials 0.000 description 14
- 239000002184 metal Substances 0.000 description 14
- 150000003839 salts Chemical class 0.000 description 12
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 229910052759 nickel Inorganic materials 0.000 description 9
- 229910052799 carbon Inorganic materials 0.000 description 8
- 238000002474 experimental method Methods 0.000 description 8
- 150000001408 amides Chemical class 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 6
- 125000000217 alkyl group Chemical group 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 229910052796 boron Inorganic materials 0.000 description 6
- 230000008021 deposition Effects 0.000 description 6
- 150000002148 esters Chemical class 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 125000001424 substituent group Chemical group 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- 238000005275 alloying Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- DNIAPMSPPWPWGF-UHFFFAOYSA-N monopropylene glycol Natural products CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 5
- 229910052717 sulfur Inorganic materials 0.000 description 5
- 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
- 229910000990 Ni alloy Inorganic materials 0.000 description 4
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 4
- 239000002518 antifoaming agent Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 4
- 150000001768 cations Chemical class 0.000 description 4
- GRWVQDDAKZFPFI-UHFFFAOYSA-H chromium(III) sulfate Chemical compound [Cr+3].[Cr+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O GRWVQDDAKZFPFI-UHFFFAOYSA-H 0.000 description 4
- 150000002894 organic compounds Chemical class 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- 229920001223 polyethylene glycol Polymers 0.000 description 4
- 229910052700 potassium Inorganic materials 0.000 description 4
- 239000011591 potassium Substances 0.000 description 4
- 239000002244 precipitate Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- CPELXLSAUQHCOX-UHFFFAOYSA-M Bromide Chemical compound [Br-] CPELXLSAUQHCOX-UHFFFAOYSA-M 0.000 description 3
- 229910000599 Cr alloy Inorganic materials 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 3
- 230000002378 acidificating effect Effects 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 3
- 239000004327 boric acid Substances 0.000 description 3
- 239000000788 chromium alloy Substances 0.000 description 3
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 238000004070 electrodeposition Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229920001515 polyalkylene glycol Polymers 0.000 description 3
- 229960004063 propylene glycol Drugs 0.000 description 3
- 235000013772 propylene glycol Nutrition 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- DNIAPMSPPWPWGF-GSVOUGTGSA-N (R)-(-)-Propylene glycol Chemical compound C[C@@H](O)CO DNIAPMSPPWPWGF-GSVOUGTGSA-N 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- 125000001931 aliphatic group Chemical group 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052729 chemical element Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 229940108928 copper Drugs 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 238000005187 foaming Methods 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 238000004442 gravimetric analysis Methods 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 239000003595 mist Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- DNIAPMSPPWPWGF-VKHMYHEASA-N (+)-propylene glycol Chemical compound C[C@H](O)CO DNIAPMSPPWPWGF-VKHMYHEASA-N 0.000 description 1
- 125000006732 (C1-C15) alkyl group Chemical group 0.000 description 1
- 125000003837 (C1-C20) alkyl group Chemical group 0.000 description 1
- 125000006527 (C1-C5) alkyl group Chemical group 0.000 description 1
- YPFDHNVEDLHUCE-UHFFFAOYSA-N 1,3-propanediol Substances OCCCO YPFDHNVEDLHUCE-UHFFFAOYSA-N 0.000 description 1
- 229940035437 1,3-propanediol Drugs 0.000 description 1
- CQZXCLFDXWOTOC-UHFFFAOYSA-N 3,3,4-trimethylundecane-2,2-diol Chemical compound CCCCCCCC(C)C(C)(C)C(C)(O)O CQZXCLFDXWOTOC-UHFFFAOYSA-N 0.000 description 1
- DIROHOMJLWMERM-UHFFFAOYSA-N 3-[dimethyl(octadecyl)azaniumyl]propane-1-sulfonate Chemical compound CCCCCCCCCCCCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O DIROHOMJLWMERM-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229910021555 Chromium Chloride Inorganic materials 0.000 description 1
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 1
- BDAGIHXWWSANSR-UHFFFAOYSA-M Formate Chemical compound [O-]C=O BDAGIHXWWSANSR-UHFFFAOYSA-M 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- VEQPNABPJHWNSG-UHFFFAOYSA-N Nickel(2+) Chemical compound [Ni+2] VEQPNABPJHWNSG-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 150000007933 aliphatic carboxylic acids Chemical class 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 229910001417 caesium ion Inorganic materials 0.000 description 1
- 150000001721 carbon Chemical group 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 description 1
- DSHWASKZZBZKOE-UHFFFAOYSA-K chromium(3+);hydroxide;sulfate Chemical compound [OH-].[Cr+3].[O-]S([O-])(=O)=O DSHWASKZZBZKOE-UHFFFAOYSA-K 0.000 description 1
- 229910000356 chromium(III) sulfate Inorganic materials 0.000 description 1
- 235000015217 chromium(III) sulphate Nutrition 0.000 description 1
- 239000011696 chromium(III) sulphate Substances 0.000 description 1
- 229940000425 combination drug Drugs 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000000536 complexating effect Effects 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- QUQFTIVBFKLPCL-UHFFFAOYSA-L copper;2-amino-3-[(2-amino-2-carboxylatoethyl)disulfanyl]propanoate Chemical compound [Cu+2].[O-]C(=O)C(N)CSSCC(N)C([O-])=O QUQFTIVBFKLPCL-UHFFFAOYSA-L 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 150000004665 fatty acids Chemical class 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- KLMCZVJOEAUDNE-UHFFFAOYSA-N francium atom Chemical compound [Fr] KLMCZVJOEAUDNE-UHFFFAOYSA-N 0.000 description 1
- 229910001418 francium ion Inorganic materials 0.000 description 1
- 125000003827 glycol group Chemical group 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 239000002608 ionic liquid Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- IZWSFJTYBVKZNK-UHFFFAOYSA-N lauryl sulfobetaine Chemical compound CCCCCCCCCCCC[N+](C)(C)CCCS([O-])(=O)=O IZWSFJTYBVKZNK-UHFFFAOYSA-N 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 229910003455 mixed metal oxide Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910001453 nickel ion Inorganic materials 0.000 description 1
- 229910052755 nonmetal Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 150000002891 organic anions Chemical class 0.000 description 1
- 229960003903 oxygen Drugs 0.000 description 1
- 229940093430 polyethylene glycol 1500 Drugs 0.000 description 1
- 229940113115 polyethylene glycol 200 Drugs 0.000 description 1
- 229940057847 polyethylene glycol 600 Drugs 0.000 description 1
- 229920000166 polytrimethylene carbonate Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- 229910001419 rubidium ion Inorganic materials 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 125000004434 sulfur atom Chemical group 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
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
- C25D3/04—Electroplating: Baths therefor from solutions of chromium
- C25D3/06—Electroplating: Baths therefor from solutions of chromium from solutions of trivalent chromium
-
- 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
- C25D3/04—Electroplating: Baths therefor from solutions of chromium
- C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used
Definitions
- the present invention relates to an electroplating composition and method for depositing a chromium coating on a substrate.
- the electroplating composition according to the present invention allows for the electrolytic deposi- tion of functional chromium coatings, also called hard chromium coatings, on a substrate, in particular on a ferrous substrate, in particular on a nickel or nickel alloy coated ferrous substrate.
- Functional chromium coatings usually have a much higher average coating thick- ness, typically from at least 1 pm up to several hundreds of micro meters, com pared to decorative chromium coatings, typically below 1 pm, and are character ized by excellent hardness and wear resistance.
- Typical chromium-based electroplating methods are described in the following prior art.
- WO 2015/110627 A1 refers to an electroplating composition for depositing chro mium and to a method for depositing chromium on a substrate using said elec troplating composition.
- US 2,748,069 relates to an electroplating solution of chromium, which allows ob taining very quickly a chromium coating of very good physical and mechanical properties.
- the chromium plating solution can be used for special electrolyzing methods, such as those known as spot or plugging or penciling galvanoplasty. In such special methods the substrate is typically not immersed into a respective electroplating solution.
- WO 2018/185154 A1 discloses a method for electrolytically depositing a chro mium or chromium alloy coating on a substrate.
- US 4,009,085 discloses lubricating compositions and a process for treating a metal sheet to impart lubricity and abrasion resistance thereto.
- US 3,432,408 A relates to the prevention of mist and spray in acidic hexavalent electroplating baths.
- US 2016/068983 A1 refers to methods and plating baths for electrodepositing a dark chromium layer on a workpiece, the bath for example comprising a diol.
- EP 0 100 133 A1 refers to zinc and nickel tolerant trivalent chromium plating baths and plating process, utilizing for example a betaine.
- CN 108034969 A refers to a sulfate-based trivalent chromium electroplating bath comprising for example a diol or polyethylene glycol.
- US 2018/245227 A1 relates to the use of ionic liquids in electroplating, and in particular for electroplating thick, hard chromium from trivalent salts.
- CCE cathodic current efficiencies
- the cathodic current efficiency (CCE) is based on Faraday’s law and is described as the percentage of metal actually deposited on the substrate during electroplat ing compared to the theoretical ideal case, when all, i.e.100%, of the metal pre sent in the electroplating composition could be deposited on the substrate.
- typical CCEs are between 20% and 25%, while in trivalent chromium-based methods for electroplating according to the prior art typical CCEs can be as low as 10%.
- An important factor, which can influence the CCEs in trivalent chromium-based methods for electroplating are inter alia the types and concentrations of complex- ing agents, which are used to stabilize the trivalent chromium ions in the electro- plating composition.
- Other factors, which can influence the CCEs in trivalent chro mium-based methods for electroplating are inter alia the types and concentra tions of further additives, which can be added to the electroplating composition.
- It was therefore the first objective of the present invention to provide an electro- plating composition comprising trivalent chromium ions and a respective method for depositing a chromium coating on a substrate with improved qualities of the coating (e.g. such as hardness and/or wear resistance).
- It was therefore the second objective of the present invention to provide an elec troplating composition comprising trivalent chromium ions and a respective method for depositing a chromium coating on a substrate resulting in an in creased cathodic current efficiency (CCE).
- CCE cathodic current efficiency
- an elec troplating composition for depositing a chromium coating on a substrate, the com position comprising:
- At least one complexing agent for the trivalent chromium ions at least one additive selected from the group consisting of betaines, poly meric glycols, monomeric diols, and mixtures thereof.
- the at least one complexing agent for the trivalent chromium ions By utilizing the at least one complexing agent for the trivalent chromium ions, a particularly effective stabilization of trivalent chromium ions in the electroplating composition can be achieved, which allows for an effective deposition of the chro- mium coating on the substrate during electroplating.
- composition comprising:
- At least one complexing agent for the trivalent chromium ions at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
- CCE cathodic current efficiency
- a sub strate with a surface wherein the surface of the substrate comprises a chromium coating obtained by a method for depositing according to the second aspect.
- the objectives mentioned above are solved according to a fourth aspect by a use of at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, for increasing the cathodic cur rent efficiency in an electroplating composition for depositing a chromium coating on a substrate.
- the term "at least one” or “one or more” denotes (and is exchangeable with) "one, two, three or more” and “one, two, three or more than three”, respectively.
- trivalent chromium refers to chromium with the oxidation number +3.
- trivalent chromium ions refers to Cr 3+ -ions in a free or complexed form.
- hexavalent chromium refers to chromium with the oxidation number +6.
- Cx-C y if used in the context of the present invention refers to a com pound comprising a total number from “x” carbon atoms to “y” carbon atoms.
- C1-C25 diols refers to diols comprising a total number from 1 carbon atom to 25 carbon atoms.
- CCE cathodic current efficiency
- the electroplating composition of the present invention comprises at least one additive selected from the group consisting of betaines, polymeric glycols, mon omeric diols and mixtures thereof.
- an electroplating composition of the present invention is preferred with the proviso that the at least one additive does not comprise polymeric gly cols.
- the electroplating composition is substantially free of or does not comprise polyethylene glycol, more preferably is substantially free of or does not comprise polyalkylene glycols, most preferably is substantially free of or does not comprise polymeric glycols.
- the electroplating composition of the present invention preferably comprises at least one additive selected from the group consisting of betaines, monomeric diols, and mixtures thereof.
- an electroplating composition of the present invention is pre ferred with the proviso that the at least one additive does not comprise monomeric diols.
- the electroplating composition is substantially free of or does not comprise ethanediol, more preferably is substantially free of or does not com prise alkanediols, even more preferably is substantially free of or does not com prise monomeric diols.
- the electroplating composition of the pre sent invention preferably comprises at least one additive selected from the group consisting of betaines, polymeric glycols, and mixtures thereof
- no hexavalent chro mium is intentionally added to the electroplating composition.
- the electro plating composition is substantially free of or does not comprise hexavalent chro mium (except very small amounts which may be formed anodically).
- the electroplating composition of the present invention is an aqueous electroplating composition comprising trivalent chromium ions.
- the electroplating composition comprises further additives and/or metal ions, more preferably iron ions, nickel ions, copper ions and/or zinc ions.
- the chromium coating comprises chro mium alloys, i.e. a coating comprising not only chromium but also alloying ele ments.
- metal alloying elements are preferred, preferably from metal ions as mentioned above. More typical and preferred are non-metal alloy ing elements, preferably carbon, nitrogen, and/or oxygen.
- the electroplating composition of the present invention is preferably used more than one time for depositing a chromium coating on a plurality of different sub strates, preferably during a continuous process.
- the electroplating composition is repeatedly utilized during electroplating, preferably for a usage of at least 100 Ah per liter electroplating composition, preferably at least 150 Ah per liter, more preferably at least 200 Ah per liter, most preferably at least 300 Ah per liter.
- an electroplating composition of the present invention wherein the betaines comprise at least 5 carbon atoms, more preferably at least 10 carbon atoms, and even more preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms.
- an electroplating composition of the present invention wherein the electroplating composition comprises at least one or more than one betaine, pref erably independently comprising at least 5 carbon atoms, more preferably at least 10 carbon atoms, and even more preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms. More preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises at least one or more than one betaine independently comprising at least 10 carbon atoms, preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms.
- the electroplating composition of the present invention must at least comprise a betaine, preferably with the number of carbon atoms as defined above.
- an electroplating composition of the present invention wherein the positively charged quaternary nitrogen atom has substituents such that said pos itive charge results, with the proviso that the substituents are not hydrogen.
- said substituents are independently selected from the group consisting of alkyl, ester, and amide.
- alkyl comprises C 1 -C 20 alkyl, more preferably C 1 -C 17 alkyl, most pref erably C 1 -C 15 alkyl.
- ester comprises C 8 -C 20 ester, more preferably C 9 -C 17 ester, most pref erably C10-C16 ester.
- ester comprises fatty acid esters, most preferably with a number of carbon atoms as defined above.
- amide comprises C8-C 20 amide, more preferably C9-C 17 amide, most preferably C 10 -C 16 amide.
- amide comprises fatty acid amides, most preferably with a number of carbon atoms as defined above for amide.
- at least one, preferably two, substituent is alkyl, preferably as defined above, most preferably a C 1 -C 5 alkyl, even more most preferably a Ci- C 3 alkyl, and in addition at least one substituent is ester, preferably as defined above, or amide, preferably as defined above.
- N-substituted-N,N-Dialkyl-ammonium sulfobetaines and the N-substituted-N,N- Dialkyl-N-alkyl ammonium sulfobetaines, respectively, is N-substituted with a substituent selected from the group consisting of alkyl, and amidoalkyl, wherein amidoalkyl is preferably cocoamidopropyl.
- the betaines comprise one or more of N,N-Dimethyl-N-(3-cocoamidopropyl)-N-(2-hy- droxy-3-sulfopropyl) ammonium betaine, N-Dodecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate, N-Octyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N- Decyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N-Tetradecyl-N,N-dime- thyl-3-ammonio-1-propanesulfonate, N-Hexadecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate, N-Octadecyl-N,N-dimethyl-3-ammonio-1-propanes,
- CCE cathodic current efficiency
- an electroplating composition of the present invention is preferred, wherein the electroplating composition com prises at least one betaine and preferably in addition one or more than one of polymeric glycols and/or monomeric diols.
- an electroplating composition of the present invention wherein the electroplating composition comprises at least one betaine and in ad dition one or more than one monomeric diol.
- an electroplating composition of the present invention wherein the electroplating composition comprises the betaines in a total concentration in a range from 0.0005 g/L to 1 g/L, based on the total volume of the electroplating composition, preferably from 0.001 g/L to 0.5 g/L, more preferably from 0.005 g/L to 0.3 g/L, and most preferably from 0.01 g/L to 0.2 g/L.
- the polymeric glycols are polyalkylene glycols, preferably polyethylene glycols.
- the polyalkylene glycols preferably the polyethylene glycols
- the polyalkylene glycols have an av erage molecular weight in a range from 150 Da to 5000 Da, preferably from 200 Da to 2500 Da.
- polymeric glycols selected from the group consisting of polyethylene glycol 200, polyethylene glycol 600, and polyethylene glycol 1500.
- the electroplating composition comprises the polymeric glycols in a total concentra tion in a range from 0.01 g/L to 50 g/L, based on the total volume of the electro plating composition, preferably from 0.05 g/L to 35 g/L, more preferably from 0.1 g/L to 20 g/L, most preferably from 0.15 g/L to 25 g/L.
- CCE cathodic current efficiency
- an electroplating composition of the present inven tion wherein the monomeric diols comprise one or more than one C1-C10 diol, preferably one or more than one C2-C8 diol, more preferably one or more than one C2-C6 diol, even more preferably one or more than one C2-C5 diol, most pref erably one or more than one C2-C4 diol, even most preferably the monomeric diol comprises 1 ,2-propane diol and/or 1 ,3-propane diol. Most preferably in combina tion with one or more than one betaine.
- an electroplating composition of the present inven tion wherein the monomeric diols comprise, in addition to the C1-C10 diols and its preferred variants, or alternatively to the C1-C10 diols, and its preferred variants, preferably in addition, one or more than one C11-C25 diol, preferably one or more than one C12-C23 diol, more preferably one or more than one C13-C21 diol, even more preferably one or more than one C 14 -C 20 diol, most preferably one or more than one C 15 -C 19 diol, even most preferably one or more than one C 16 -C 18 diol, most preferably in combination with one or more than one betaine.
- the monomeric diols comprise, in addition to the C1-C10 diols and its preferred variants, or alternatively to the C1-C10 diols, and its preferred variants, preferably in addition, one or more than one C11-C25 diol
- an electroplating composition of the present invention wherein the one or more than one C11-C25 diol, and its preferred variants, comprises an anti foam compound.
- the one or more than one C11-C25 diol, and its preferred variants comprises an anti foam compound.
- C11-C25 diols have the potential to function as an anti-foam compound.
- Ci to C10 diols are often excellent solvents for aforementioned anti-foam compounds.
- the electroplating composition comprises the monomeric diols in a total concentration in a range from 0.001 g/L to 60 g/L, based on the total volume of the electroplating composition, preferably from 0.1 g/L to 50 g/L, more preferably from 1.0 g/L to 40 g/L, even more preferably from 5.0 g/L to 35 g/L, most preferably from 15 g/L to 30 g/L.
- an electroplating composition of the present invention wherein the electroplating composition comprises the monomeric diols in a total concentration in a range from 0.001 g/L to 10 g/L, based on the total volume of the electroplating composition, preferably from 0.01 g/L to 8.0 g/L, more preferably from 0.1 g/L to 6.0 g/L, even more preferably from 0.5 g/L to 4.0 g/L, most preferably from 1 .0 g/L to 3.0 g/L.
- the electroplating composition of the present invention comprises one or more than one betaine, most preferably if the electroplating composition of the present invention comprises one or more than one betaine and one or more than one C11-C25 diol, and its preferred variants.
- an electroplating composition of the present invention wherein the electroplating composition comprises trivalent chromium ions in a total concen tration from 10 g/L to 30 g/L, based on the total volume of the electroplating com position, preferably from 14 g/L to 27 g/L, and most preferably from 17 g/L to 24 g/L.
- the concentration range of the trivalent chromium ions in the electroplating composition a particular effective deposition of the chro mium coating on the substrate can be achieved. If the total amount of trivalent chromium ions is significantly below 10 g/L in many cases an insufficient deposi tion is observed, and the deposited chromium is usually of low quality. If the total amount is significantly above 30 g/L, the electroplating composition is not any longer stable, which includes formation of undesired precipitates.
- the at least one complexing agent for the trivalent chromium ions is selected from the group consisting of organic complexing agents and salts thereof, preferably car boxylic acids and salts thereof, more preferably aliphatic carboxylic acids and salts thereof, most preferably aliphatic mono-carboxylic acids and salts thereof.
- Preferred aliphatic mono-carboxylic acids and salts thereof are C1-C10 aliphatic mono-carboxylic acids and salts thereof, preferably Ci-Cs aliphatic mono-carbox- ylic acids and salts thereof, more preferably C1-C6 aliphatic mono-carboxylic ac ids and salts thereof, most preferably C1-C3 aliphatic mono-carboxylic acids and salts thereof.
- the electroplating composition comprises the at least one complexing agent in a total concentration in a range from 50 g/L to 350 g/L, based on the total volume of the composition, preferably from 100 g/L to 300 g/L, even more preferably from 150 g/L to 250 g/L.
- the trivalent chromium ions can be efficiently stabilized in the electroplat ing composition by the complexing agents
- an electroplating composition of the present invention wherein the electroplating composition has a pH in a range from 4.1 to 7.0, preferably from 4.5 to 6.5, more preferably from 5.0 to 6.0, and most preferably from 5.3 to 5.9.
- the preferred acidic pH ranges are in particular beneficial for effectively deposit ing a chromium coating on the substrate having the desired qualities.
- an electroplating composition of the present invention wherein the electroplating composition comprises one or more than one betaine and one or more than one monomeric diol, with the proviso that the one or more than one monomeric diol comprises one or more than one C11-C25 diol comprising one, two or more than two iso-propyl moi eties.
- electroplating composition of the present invention wherein the electroplating composition comprises one or more than one betaine and more than one monomeric diol, with the proviso that - at least one of the more than one monomeric diol comprises one or more than one C 11 -C 25 diol (or another preferred diol among the C 11 -C 25 diol as mentioned above) comprising one, two or more than two iso-propyl moieties, and
- the more than one monomeric diol comprises one or more than one C 2 -C 8 diol (or another preferred diol among the C 2 -C 8 diol as mentioned above).
- electroplating composition of the present invention wherein the electroplating composition is essentially free of or does not comprise boric acid, preferably is essentially free of or does not comprise boron-containing com pounds.
- the elec troplating composition of the present invention is preferably essentially free of or does not comprise boron-containing compounds. Surprisingly, the electroplating composition of the present invention performs very well without boron-containing compounds, in particular in the above-mentioned preferred pH ranges.
- electroplating composition of the present invention wherein the electroplating composition is essentially free of or does not comprise organic compounds containing divalent sulfur, preferably is essentially free of or does not comprise sulfur-containing compounds with a sulfur atom having an oxidation number below +6.
- Omitting organic compounds containing divalent sulfur from the electroplating composition is particularly advantageous when employing the electroplating com position for deposition of hard, functional chromium coatings.
- the term "does not comprise” typically denotes that respective compounds and/or ingredients are not intentionally added to e.g. the electroplating composi tion. This does not exclude that such compounds are dragged in as impurities of other chemicals. However, typically the total amount of such compounds and in gredients is below the detection range and therefore is not critical in the various aspects of the present invention.
- an electroplating composition furthermore comprising one or more than one compound selected from the group consisting of
- halogen ions preferably bromide
- alkaline metal cations preferably sodium and/or potassium
- the deposition of chromium during an electroplating process can be improved, most preferably dur ing the method of the present invention.
- the electroplating composition of the present invention comprises one or more than one type of halogen ions, preferably bromide, in a concentration of at least 0.06 mol/L, based on the total volume of the electroplating composition, more preferably at least 0.1 mol/L, even more preferably at least 0.15 mol/L.
- bromide anions effectively suppress the formation of hexavalent chro mium species at the at least one anode.
- the electroplating composition comprises one or more than one type of alkaline metal cations, preferably sodium and/or potassium, in a total concen tration ranging from 0 mol/L to 0.5 mol/L, based on the total volume of the elec troplating composition, more preferably from 0 mol/L to 0.3 mol/L, even more preferably from 0 mol/L to 0.1 mol/L, and most preferably from 0 mol/L to 0.08 mol/L.
- alkaline metal cations preferably sodium and/or potassium
- the one or more than one type of alkaline metal cations includes metal cations of lithium, sodium, and potassium, mostly sodium and potassium.
- the trivalent chromium ions of the electroplating composition are obtained from a sol uble, trivalent chromium ion containing source, typically a water-soluble salt com prising said trivalent chromium ions.
- the soluble, trivalent chromium ion containing source comprises alkali metal cations in a total amount of 1 wt.-% or less, based on the total weight of said source. In some cases, preferably, such a source is utilized for replenishing trivalent chromium ions if the method is oper ated continuously.
- a preferred water-soluble salt comprising said trivalent chro mium ions is alkali metal free trivalent chromium sulfate or alkali metal free triva lent chromium chloride.
- the electroplating com position of the present invention contains sulfate ions, preferably in a total amount in the range from 50 g/L to 250 g/L, based on the total volume of the electroplating composition.
- the soluble, trivalent chromium ion containing source comprises or is chromium sulfate, more preferably acidic chromium sulfate, even more preferably chromium sulfate with the general formula Cr2(S04)3 and a molecular weight of 392 g/mol.
- a soluble, trivalent chromium ion containing source is preferred, wherein the anion is an organic anion, preferably an organic acid anion, most preferably formate and/or acetate.
- the present invention according to the second aspect provides a method for de positing a chromium coating on a substrate, the method comprising the following steps: (a) providing the substrate,
- At least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
- the aforementioned regarding the electroplating composition of the present invention applies likewise to the method of the present invention (preferably a method as described below as being preferred).
- Preferred is a method of the present invention, wherein in step (c) the electrical current is a direct current.
- the direct current (DC) is a direct current without interruptions during the electroplating, wherein more preferably the direct current is not pulsed (non- pulsed DC). Furthermore, the direct current preferably does not include reverse pulses.
- the electrical current has a cathodic current density of at least 18 A/dm 2 , preferably of at least 20 A/dm 2 , more preferably of at least 25 A/dm 2 , even more preferably of at least 30 A/dm 2 , most preferably of at least 39 A/dm 2 .
- the cathodic current density is in a range from 18 A/dm 2 to 60 A/dm 2 , more preferably from 25 A/dm 2 to 55 A/dm 2 , most preferably from 30 A/dm 2 to 50 A/dm 2 .
- the substrate provided during the method of the present invention is the cathode during the electroplating process (i.e. in step (c)).
- the substrate provided during the method of the present invention is the cathode during the electroplating process (i.e. in step (c)).
- more than one substrate is provided simultaneously in step (c) of the method of the present invention.
- step (c) at least one anode is provided, wherein the at least one anode is independently selected from the group consisting of graphite anodes and mixed metal oxide on titanium an odes.
- the at least one anode has shown to be sufficiently resistant in the electroplating composition of the present invention.
- the at least one anode does not comprise any lead or chromium.
- a chromium coating is depos ited, either a pure one or an alloy.
- the chromium coating is an alloy.
- Preferred alloying elements are carbon, nitrogen, and oxygen, preferably carbon and oxygen. Carbon is typically present because of organic compounds usually present in the electroplating composition.
- the chromium coating does not comprise one, more than one or all elements selected from the group consisting of sulphur, nickel, copper, aluminium, tin and iron. More preferably, the only alloying ele ments are carbon, nitrogen, and/or oxygen, more preferably carbon and/or oxy gen, most preferably carbon and oxygen.
- the chromium coating con tains 90 weight percent chromium or more, based on the total weight of the chro mium coating, more preferably 95 weight percent or more.
- step (c) the electroplat ing composition has a temperature in a range from 20°C to 90°C, preferably from 30°C to 70°C, more preferably from 40°C to 60°C, most preferably from 45°C to 58°C.
- the chromium coating is optimally deposited in step (c). If the temper ature significantly exceeds 90 °C, an undesired vaporization occurs, which can negatively affect the concentration of the composition components. Furthermore, the undesired anodic formation of hexavalent chromium is significantly less sup pressed. If the temperature is significantly below 20 °C the electrodeposition is insufficient.
- step (c) is performed for a time period from 10 min to 100 min, preferably from 20 min to 90 min, more preferably from 30 min to 60 min.
- step (c) the electroplat ing composition is stirred, preferably with a stirring rate in a range from 100 rpm to 500 rpm, most preferably from 200 rpm to 400 rpm.
- step (c) By performing the method step (c) in the abovementioned preferred temperature ranges and/or (preferably and) for the preferred time periods and/or (preferably and) with the preferred stirring rates, particularly advantageous electrodeposition kinetics during step (c) can be ensured.
- step (d) heat-treating the chromium-coated substrate obtained from step (c).
- step (d) the heat-treat ing is carried out at a temperature in a range from 100°C to 250°C, preferably from 120°C to 240°C, more preferably from 150°C to 220°C, most preferably from 170°C to 200°C.
- step (d) the heat-treat ing is carried out for a time period from 1 h to 10 h, preferably from 2 h to 4 h.
- the properties of the chromium coating can be further improved in some cases (e.g. hardness).
- step (c) the cathodic current efficiency (CCE) is 11 % or more, preferably 12% or more, most preferably 13% or more. This most preferably applies, if an identical method with the only exception that the electroplating composition does not comprise an additive, is carried out.
- CCE cathodic current efficiency
- CCE cathodic current efficiency
- the substrate comprises a metal or metal alloy, preferably comprises one or more than one metal selected from the group consisting of copper, iron, nickel and aluminum, more preferably comprises one or more than one metal selected from the group consisting of cop per, iron, and nickel, most preferably comprises at least iron.
- a substrate comprising a pre-coating, the pre-coating preferably being a nickel or nickel alloy coating, most preferably a semi-bright nickel coating, on which the chromium coating is applied to during step (c) of the method of the present invention.
- the pre-coating preferably being a nickel or nickel alloy coating, most preferably a semi-bright nickel coating, on which the chromium coating is applied to during step (c) of the method of the present invention.
- a steel substrate pre coated with a nickel or nickel alloy coating preferably other pre-coat ings are alternatively or additionally present.
- such a pre-coating significantly increases corrosion resistance compared to a metal substrate with out such a pre-coating.
- the substrates are not suscepti ble to corrosion due to a corrosion inert environment (e.g. in an oil composition).
- a pre-coating preferably a nickel or nickel alloy pre-coating
- the chromium coating has a thickness in a range from 1.1 pm to 500 pm, preferably from 2 pm to 450 pm, more preferably from 4 pm to 400 pm, even more preferably from 6 pm to 350 pm, yet even more preferably from 8 pm to 300 pm, and most preferably from 10 pm to 250 pm.
- step (c) the chromium coating has a thickness of 0.5 pm or more, preferably of 0.75 pm or more, more preferably of 0.9 pm or more, even more preferably of 1 .0 pm or more, yet even more preferably of 1 .5 pm or more, and most preferably of 2.0 pm or more.
- step (c) the chromium coating has a thickness of 15 pm or more, pref erably of 20 pm or more.
- step (c) the concentra tion of the at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof (preferably at least of the betaines), is continually or semi-continually monitored, wherein
- the monitored concentration is compared to a target concentration of said at least one additive (preferably of said betaines), and
- the at least one additive preferably the betaines
- the present invention according to the third aspect provides a substrate with a surface, wherein the surface of the substrate comprises a chromium coating ob tained by a method for depositing according to the second aspect.
- the chromium-coated substrate comprises or is a metal rod.
- the aforementioned regarding the electroplating composition of the present in vention preferably an electroplating composition as described as being pre ferred
- the aforementioned regarding the method of the present invention preferably a method for depositing as described as being preferred
- preferred embodiments of the electroplating composition of the first aspect and preferred embodiments of the method for depositing according to the second aspect are also preferred embodiments for the substrate according to the third aspect. This applies in particular and most preferably to the characteristics of the chromium coating.
- the present invention according to the fourth aspect provides a use of at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, for increasing the cathodic current effi ciency in an electroplating composition for depositing a chromium coating on a substrate.
- the aforementioned regarding the electroplating composition of the present in vention preferably an electroplating composition as described as being pre ferred
- the aforementioned regarding the method of the present invention preferably a method for depositing as described as being preferred
- the present invention is described in more detail by the following non-limiting examples.
- test electroplating compositions were prepared (volume: appr. 850 ml_) comprising 10 g/L to 30 g/L trivalent chromium ions (source: basic chromium sulfate), 50 g/L to 250 g/L sulfate ions, at least one organic complexing compound (an aliphatic mono carboxylic organic acid), am monium ions, and bromide ions.
- source basic chromium sulfate
- organic complexing compound an aliphatic mono carboxylic organic acid
- am monium ions and bromide ions.
- the compositions did not contain boric acid nor any boron-containing compounds and no organic compounds with divalent sulfur.
- the pH was in a range from 5.4 to 5.7.
- the respective electroplating composition was subjected to electro plating in order to obtain a chromium coating on a substrate (mild steel rod with 10 mm diameter).
- a graphite anode was used as anodes. Electrodeposition was carried out at 40 A/dm 2 for 45 minutes at 50°C under mild stirring. CCE was determined based on the Faraday law and gravimetric analysis.
- foaming was limited by adding an anti-foam compound (a tetramethyl- decandiol comprising two iso-propyl moieties (a monomeric C11-C25 diol), solubil ized in propylene glycol (a monomeric C3 diol) prior to addition (total amount of diols in the electroplating composition below 4.0 g/L).
- an anti-foam compound a tetramethyl- decandiol comprising two iso-propyl moieties (a monomeric C11-C25 diol), solubil ized in propylene glycol (a monomeric C3 diol) prior to addition (total amount of diols in the electroplating composition below 4.0 g/L).
- sulfobetaines as utilized in experiments 13 and 16 were tested in a hexavalent chromium electro plating composition (55°C, 50 A/dm 2 ).
- the CCE was appr. 25% without additive
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Abstract
The present invention refers to an electroplating composition for depositing a chromium coating on a substrate, the composition comprising: (i) trivalent chromium ions, (ii) at least one complexing agent for the trivalent chromium ions, and (iii) at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
Description
ELECTROPLATING COMPOSITION AND METHOD FOR DEPOSITING A CHROMIUM COATING ON A SUBSTRATE
Field of the Invention
The present invention relates to an electroplating composition and method for depositing a chromium coating on a substrate. In particular the electroplating composition according to the present invention allows for the electrolytic deposi- tion of functional chromium coatings, also called hard chromium coatings, on a substrate, in particular on a ferrous substrate, in particular on a nickel or nickel alloy coated ferrous substrate.
Background of the Invention
Functional chromium coatings usually have a much higher average coating thick- ness, typically from at least 1 pm up to several hundreds of micro meters, com pared to decorative chromium coatings, typically below 1 pm, and are character ized by excellent hardness and wear resistance.
Functional chromium coatings obtained from a chromium electroplating compo sition containing hexavalent chromium are known in the prior art and are a well- established standard.
During recent decades, hexavalent chromium-based methods are more and more replaced by trivalent chromium-based methods, which are much more health- and environment friendly.
Typical chromium-based electroplating methods are described in the following prior art.
WO 2015/110627 A1 refers to an electroplating composition for depositing chro mium and to a method for depositing chromium on a substrate using said elec troplating composition.
US 2,748,069 relates to an electroplating solution of chromium, which allows ob taining very quickly a chromium coating of very good physical and mechanical properties. The chromium plating solution can be used for special electrolyzing methods, such as those known as spot or plugging or penciling galvanoplasty. In such special methods the substrate is typically not immersed into a respective electroplating solution.
WO 2018/185154 A1 discloses a method for electrolytically depositing a chro mium or chromium alloy coating on a substrate.
US 4,009,085 discloses lubricating compositions and a process for treating a metal sheet to impart lubricity and abrasion resistance thereto.
US 3,432,408 A relates to the prevention of mist and spray in acidic hexavalent electroplating baths.
US 2016/068983 A1 refers to methods and plating baths for electrodepositing a dark chromium layer on a workpiece, the bath for example comprising a diol.
EP 0 100 133 A1 refers to zinc and nickel tolerant trivalent chromium plating baths and plating process, utilizing for example a betaine.
CN 108034969 A refers to a sulfate-based trivalent chromium electroplating bath comprising for example a diol or polyethylene glycol.
US 2018/245227 A1 relates to the use of ionic liquids in electroplating, and in particular for electroplating thick, hard chromium from trivalent salts.
However, when using trivalent chromium-based methods for electroplating ac cording to the prior art, the cathodic current efficiencies (CCE) observed are typ ically smaller compared to the cathodic current efficiencies observed when using hexavalent chromium-based methods for electroplating.
The cathodic current efficiency (CCE) is based on Faraday’s law and is described as the percentage of metal actually deposited on the substrate during electroplat ing compared to the theoretical ideal case, when all, i.e.100%, of the metal pre sent in the electroplating composition could be deposited on the substrate. In hexavalent chromium-based methods for electroplating according to the prior art typical CCEs are between 20% and 25%, while in trivalent chromium-based methods for electroplating according to the prior art typical CCEs can be as low as 10%.
An important factor, which can influence the CCEs in trivalent chromium-based methods for electroplating are inter alia the types and concentrations of complex- ing agents, which are used to stabilize the trivalent chromium ions in the electro- plating composition. Other factors, which can influence the CCEs in trivalent chro mium-based methods for electroplating are inter alia the types and concentra tions of further additives, which can be added to the electroplating composition.
Objective of the present Invention
It was therefore the first objective of the present invention to provide an electro- plating composition comprising trivalent chromium ions and a respective method for depositing a chromium coating on a substrate with improved qualities of the coating (e.g. such as hardness and/or wear resistance).
It was therefore the second objective of the present invention to provide an elec troplating composition comprising trivalent chromium ions and a respective method for depositing a chromium coating on a substrate resulting in an in creased cathodic current efficiency (CCE).
Summary of the Invention
The objectives mentioned above are solved according to a first aspect by an elec troplating composition for depositing a chromium coating on a substrate, the com position comprising:
(i) trivalent chromium ions,
(ii) at least one complexing agent for the trivalent chromium ions, and (iii) at least one additive selected from the group consisting of betaines, poly meric glycols, monomeric diols, and mixtures thereof.
By utilizing the at least one complexing agent for the trivalent chromium ions, a particularly effective stabilization of trivalent chromium ions in the electroplating composition can be achieved, which allows for an effective deposition of the chro- mium coating on the substrate during electroplating.
It has been surprisingly found that using at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, a significant increase of the cathodic current efficiency (CCE) during elec troplating is observed, while on the other hand a coating with high quality is ob- tained.
The objectives mentioned above are solved according to a second aspect by a method for depositing a chromium coating on a substrate, the method comprising the following steps:
(a) providing the substrate, (b) providing an electroplating composition for depositing a chromium coating on the substrate, the composition comprising:
(i) trivalent chromium ions,
(ii) at least one complexing agent for the trivalent chromium ions, and
(iii) at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
(c) contacting the substrate with said electroplating composition and applying an electrical current such that the chromium coating is deposited on at least one surface of said substrate.
By having the at least one additive as defined above in the electroplating compo sition, a comparatively high cathodic current efficiency (CCE) is obtained during step (c).
The objectives mentioned above are solved according to a third aspect by a sub strate with a surface, wherein the surface of the substrate comprises a chromium coating obtained by a method for depositing according to the second aspect.
The objectives mentioned above are solved according to a fourth aspect by a use of at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, for increasing the cathodic cur rent efficiency in an electroplating composition for depositing a chromium coating on a substrate.
Brief description of the Table
In Table 1 , correlations between varying concentrations of different additives in respective electroplating compositions, represented as the total amount of addi tive in g/L, based on the total volume of the respective electroplating composition, in respect to the resulting cathodic current efficiency (CCE) are shown. Each bar (C1 ) to (18) represents a specific electroplating composition. Further details are given in the "Examples" section below in the text.
Detailed Description of the Invention
In the context of the present invention, the term "at least one" or “one or more” denotes (and is exchangeable with) "one, two, three or more” and “one, two, three or more than three", respectively. Furthermore, "trivalent chromium" refers to
chromium with the oxidation number +3. The term "trivalent chromium ions" refers to Cr3+-ions in a free or complexed form. Furthermore, "hexavalent chromium" refers to chromium with the oxidation number +6.
The term Cx-Cy if used in the context of the present invention refers to a com pound comprising a total number from “x” carbon atoms to “y” carbon atoms. For example, the term C1-C25 diols refers to diols comprising a total number from 1 carbon atom to 25 carbon atoms.
The cathodic current efficiency (CCE) is determined as described in the text above and is based on gravimetric analysis (see examples below in the text).
The electroplating composition of the present invention comprises at least one additive selected from the group consisting of betaines, polymeric glycols, mon omeric diols and mixtures thereof.
In rare cases an electroplating composition of the present invention is preferred with the proviso that the at least one additive does not comprise polymeric gly cols. Preferably, the electroplating composition is substantially free of or does not comprise polyethylene glycol, more preferably is substantially free of or does not comprise polyalkylene glycols, most preferably is substantially free of or does not comprise polymeric glycols. In such a case, the electroplating composition of the present invention preferably comprises at least one additive selected from the group consisting of betaines, monomeric diols, and mixtures thereof.
In very rare cases an electroplating composition of the present invention is pre ferred with the proviso that the at least one additive does not comprise monomeric diols. Preferably, the electroplating composition is substantially free of or does not comprise ethanediol, more preferably is substantially free of or does not com prise alkanediols, even more preferably is substantially free of or does not com prise monomeric diols. In such a case, the electroplating composition of the pre sent invention preferably comprises at least one additive selected from the group consisting of betaines, polymeric glycols, and mixtures thereof
In the electroplating composition of the present invention no hexavalent chro mium is intentionally added to the electroplating composition. Thus, the electro plating composition is substantially free of or does not comprise hexavalent chro mium (except very small amounts which may be formed anodically).
Preferably, the electroplating composition of the present invention is an aqueous electroplating composition comprising trivalent chromium ions. Preferably, the electroplating composition comprises further additives and/or metal ions, more preferably iron ions, nickel ions, copper ions and/or zinc ions.
In the context of the present invention, the chromium coating comprises chro mium alloys, i.e. a coating comprising not only chromium but also alloying ele ments. In very rare cases, metal alloying elements are preferred, preferably from metal ions as mentioned above. More typical and preferred are non-metal alloy ing elements, preferably carbon, nitrogen, and/or oxygen.
The electroplating composition of the present invention is preferably used more than one time for depositing a chromium coating on a plurality of different sub strates, preferably during a continuous process. Preferably, the electroplating composition is repeatedly utilized during electroplating, preferably for a usage of at least 100 Ah per liter electroplating composition, preferably at least 150 Ah per liter, more preferably at least 200 Ah per liter, most preferably at least 300 Ah per liter.
Basically, preferred is an electroplating composition of the present invention, wherein the betaines comprise at least 5 carbon atoms, more preferably at least 10 carbon atoms, and even more preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises at least one or more than one betaine, pref erably independently comprising at least 5 carbon atoms, more preferably at least 10 carbon atoms, and even more preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms.
More preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises at least one or more than one betaine independently comprising at least 10 carbon atoms, preferably at least 15 carbon atoms. Preferable not having more than 50 carbon atoms.
This all means that out of the selection from betaines, polymeric glycols, mono meric diols, and mixtures thereof, the electroplating composition of the present invention must at least comprise a betaine, preferably with the number of carbon atoms as defined above.
Preferred is an electroplating composition of the present invention, wherein the betaines independently comprise (or betaines at least denote):
- a positively charged quaternary nitrogen atom, and
- a negatively charged sulfonate group and/or negatively charged carboxylate group, with the proviso that the positive charge cannot be removed by deprotonation.
Preferred is an electroplating composition of the present invention, wherein the betaines have a neutral net charge.
Preferred is an electroplating composition of the present invention, wherein the betaines are linear betaines.
Preferred is an electroplating composition of the present invention, wherein the betaines do not comprise an aromatic ring structure, preferably do not comprise a ring structure.
Preferred is an electroplating composition of the present invention, wherein the positively charged quaternary nitrogen atom has substituents such that said pos itive charge results, with the proviso that the substituents are not hydrogen. Pref erably, said substituents are independently selected from the group consisting of alkyl, ester, and amide.
Preferably, alkyl comprises C1-C20 alkyl, more preferably C1-C17 alkyl, most pref erably C1-C15 alkyl.
Preferably, ester comprises C8-C20 ester, more preferably C9-C17 ester, most pref erably C10-C16 ester.
Preferably, ester comprises fatty acid esters, most preferably with a number of carbon atoms as defined above.
Preferably, amide comprises C8-C20 amide, more preferably C9-C17 amide, most preferably C10-C16 amide.
Preferably, amide comprises fatty acid amides, most preferably with a number of carbon atoms as defined above for amide. Most preferably, at least one, preferably two, substituent is alkyl, preferably as defined above, most preferably a C1-C5 alkyl, even more most preferably a Ci- C3 alkyl, and in addition at least one substituent is ester, preferably as defined above, or amide, preferably as defined above.
Preferred is an electroplating composition of the present invention, wherein the betaines independently comprise a positively charged quaternary nitrogen atom and a negatively charged sulfonate group, with the proviso that the positive charge cannot be removed by deprotonation.
Preferred is an electroplating composition of the present invention, wherein the betaines are selected from the group consisting of N-substituted-ammonium sul- fobetaines and N-substituted-ammonium carboxybetaines.
Preferred is an electroplating composition of the present invention, wherein the betaines are selected from the group consisting of N-substituted-N,N-Dialkyl-am- monium sulfobetaines, preferably N-substituted-N,N-Dialkyl-N-alkyl ammonium sulfobetaines.
Preferred is an electroplating composition of the present invention, wherein the N-substituted-N,N-Dialkyl-ammonium sulfobetaines and the N-substituted-N,N- Dialkyl-N-alkyl ammonium sulfobetaines, respectively, is N-substituted with a substituent selected from the group consisting of alkyl, and amidoalkyl, wherein amidoalkyl is preferably cocoamidopropyl.
Preferred is an electroplating composition of the present invention, wherein the betaines comprise one or more of N,N-Dimethyl-N-(3-cocoamidopropyl)-N-(2-hy- droxy-3-sulfopropyl) ammonium betaine, N-Dodecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate, N-Octyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N- Decyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N-Tetradecyl-N,N-dime- thyl-3-ammonio-1-propanesulfonate, N-Hexadecyl-N,N-dimethyl-3-ammonio-1- propanesulfonate, N-Octadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, and N,N-Dimethyl-N-dodecylglycine betaine.
By selecting the preferred betaines a particular advantageous cathodic current efficiency (CCE) is achieved, preferably along with a foam formation for mist sup pression during electroplating. Advantageously, the concentration of betaines can be comparatively low (see examples).
Regarding the at least one additive, in some cases an electroplating composition of the present invention is preferred, wherein the electroplating composition com prises at least one betaine and preferably in addition one or more than one of polymeric glycols and/or monomeric diols.
In particular preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises at least one betaine and in ad dition one or more than one monomeric diol.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises the betaines in a total concentration in a range from 0.0005 g/L to 1 g/L, based on the total volume of the electroplating composition, preferably from 0.001 g/L to 0.5 g/L, more preferably from 0.005 g/L to 0.3 g/L, and most preferably from 0.01 g/L to 0.2 g/L.
Preferred is an electroplating composition of the present invention, wherein the polymeric glycols are polyalkylene glycols, preferably polyethylene glycols. Pref erably, the polyalkylene glycols, preferably the polyethylene glycols, have an av erage molecular weight in a range from 150 Da to 5000 Da, preferably from 200 Da to 2500 Da. Most preferred are polymeric glycols, selected from the group consisting of polyethylene glycol 200, polyethylene glycol 600, and polyethylene glycol 1500.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises the polymeric glycols in a total concentra tion in a range from 0.01 g/L to 50 g/L, based on the total volume of the electro plating composition, preferably from 0.05 g/L to 35 g/L, more preferably from 0.1 g/L to 20 g/L, most preferably from 0.15 g/L to 25 g/L.
Also, when using polymeric glycoles as a representative of the at least one addi tives a beneficial increase in the cathodic current efficiency (CCE) is obtained.
Preferred is an electroplating composition of the present invention, wherein the monomeric diols are C1-C25 diols, preferably C2-C23 diols, more preferably C2-C21 diols, even more preferably C2-C19 diols, most preferably C2-C18 diols.
In some cases, preferred is an electroplating composition of the present inven tion, wherein the monomeric diols comprise one or more than one C1-C10 diol, preferably one or more than one C2-C8 diol, more preferably one or more than one C2-C6 diol, even more preferably one or more than one C2-C5 diol, most pref erably one or more than one C2-C4 diol, even most preferably the monomeric diol comprises 1 ,2-propane diol and/or 1 ,3-propane diol. Most preferably in combina tion with one or more than one betaine.
In some cases, preferred is an electroplating composition of the present inven tion, wherein the monomeric diols comprise, in addition to the C1-C10 diols and its preferred variants, or alternatively to the C1-C10 diols, and its preferred variants, preferably in addition, one or more than one C11-C25 diol, preferably one or more than one C12-C23 diol, more preferably one or more than one C13-C21 diol, even
more preferably one or more than one C14-C20 diol, most preferably one or more than one C15-C19 diol, even most preferably one or more than one C16-C18 diol, most preferably in combination with one or more than one betaine.
Preferred is an electroplating composition of the present invention, wherein the one or more than one C11-C25 diol, and its preferred variants, is selected from the group of saturated and unsaturated C11-C25 diols, preferably saturated C11-C25 diols.
Preferred is an electroplating composition of the present invention, wherein the one or more than one C11-C25 diol, and its preferred variants, is branched.
Preferred is an electroplating composition of the present invention, wherein the one or more than one C11-C25 diol, and its preferred variants, comprises one, two or more than two iso-propyl moieties.
Preferred is an electroplating composition of the present invention, wherein the one or more than one C11-C25 diol, and its preferred variants, comprises an anti foam compound. In many cases, such C11-C25 diols have the potential to function as an anti-foam compound. Furthermore, in many cases Ci to C10 diols are often excellent solvents for aforementioned anti-foam compounds.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises the monomeric diols in a total concentration in a range from 0.001 g/L to 60 g/L, based on the total volume of the electroplating composition, preferably from 0.1 g/L to 50 g/L, more preferably from 1.0 g/L to 40 g/L, even more preferably from 5.0 g/L to 35 g/L, most preferably from 15 g/L to 30 g/L.
In a few specific cases, preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises the monomeric diols in a total concentration in a range from 0.001 g/L to 10 g/L, based on the total volume of the electroplating composition, preferably from 0.01 g/L to 8.0 g/L, more preferably from 0.1 g/L to 6.0 g/L, even more preferably from 0.5 g/L to 4.0
g/L, most preferably from 1 .0 g/L to 3.0 g/L. This most preferable selection pref erably applies if the electroplating composition of the present invention comprises one or more than one betaine, most preferably if the electroplating composition of the present invention comprises one or more than one betaine and one or more than one C11-C25 diol, and its preferred variants.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition is substantially free of or does not comprise hexava- lent chromium ions.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises trivalent chromium ions in a total concen tration from 10 g/L to 30 g/L, based on the total volume of the electroplating com position, preferably from 14 g/L to 27 g/L, and most preferably from 17 g/L to 24 g/L.
With the preferred selections of the concentration range of the trivalent chromium ions in the electroplating composition, a particular effective deposition of the chro mium coating on the substrate can be achieved. If the total amount of trivalent chromium ions is significantly below 10 g/L in many cases an insufficient deposi tion is observed, and the deposited chromium is usually of low quality. If the total amount is significantly above 30 g/L, the electroplating composition is not any longer stable, which includes formation of undesired precipitates.
Preferred is an electroplating composition of the present invention, wherein the at least one complexing agent for the trivalent chromium ions is selected from the group consisting of organic complexing agents and salts thereof, preferably car boxylic acids and salts thereof, more preferably aliphatic carboxylic acids and salts thereof, most preferably aliphatic mono-carboxylic acids and salts thereof. Preferred aliphatic mono-carboxylic acids and salts thereof are C1-C10 aliphatic mono-carboxylic acids and salts thereof, preferably Ci-Cs aliphatic mono-carbox-
ylic acids and salts thereof, more preferably C1-C6 aliphatic mono-carboxylic ac ids and salts thereof, most preferably C1-C3 aliphatic mono-carboxylic acids and salts thereof.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises the at least one complexing agent in a total concentration in a range from 50 g/L to 350 g/L, based on the total volume of the composition, preferably from 100 g/L to 300 g/L, even more preferably from 150 g/L to 250 g/L.
By utilizing in particular the above-mentioned preferred selection of complexing agents, the trivalent chromium ions can be efficiently stabilized in the electroplat ing composition by the complexing agents
Preferred is an electroplating composition of the present invention, wherein the electroplating composition has a pH in a range from 4.1 to 7.0, preferably from 4.5 to 6.5, more preferably from 5.0 to 6.0, and most preferably from 5.3 to 5.9.
The preferred acidic pH ranges are in particular beneficial for effectively deposit ing a chromium coating on the substrate having the desired qualities.
In particular preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises one or more than one betaine and one or more than one monomeric diol, with the proviso that the one or more than one monomeric diol comprises one or more than one C11-C25 diol comprising one, two or more than two iso-propyl moi eties.
Even more preferred is an electroplating composition of the present invention, wherein the electroplating composition comprises one or more than one betaine and more than one monomeric diol, with the proviso that
- at least one of the more than one monomeric diol comprises one or more than one C11-C25 diol (or another preferred diol among the C11-C25 diol as mentioned above) comprising one, two or more than two iso-propyl moieties, and
- at least one of the more than one monomeric diol comprises one or more than one C2-C8 diol (or another preferred diol among the C2-C8 diol as mentioned above).
Preferred is an electroplating composition of the present invention, wherein the electroplating composition is essentially free of or does not comprise boric acid, preferably is essentially free of or does not comprise boron-containing com pounds.
Boron-containing compounds are not desired because they are environmentally problematic. When using boron-containing compounds, waste water treatment is expensive and time consuming. Furthermore, boric acid typically shows poor sol ubility and therefore has the tendency to form precipitates. Although such precip itates can be solubilized upon heating, a respective electroplating composition cannot be utilized for electroplating during this time. There is a significant risk that such precipitates facilitate a reduced chromium coating quality. Thus, the elec troplating composition of the present invention is preferably essentially free of or does not comprise boron-containing compounds. Surprisingly, the electroplating composition of the present invention performs very well without boron-containing compounds, in particular in the above-mentioned preferred pH ranges.
Preferred is an electroplating composition of the present invention, wherein the electroplating composition is essentially free of or does not comprise organic compounds containing divalent sulfur, preferably is essentially free of or does not comprise sulfur-containing compounds with a sulfur atom having an oxidation number below +6.
Omitting organic compounds containing divalent sulfur from the electroplating composition is particularly advantageous when employing the electroplating com position for deposition of hard, functional chromium coatings.
The term "does not comprise" typically denotes that respective compounds and/or ingredients are not intentionally added to e.g. the electroplating composi tion. This does not exclude that such compounds are dragged in as impurities of other chemicals. However, typically the total amount of such compounds and in gredients is below the detection range and therefore is not critical in the various aspects of the present invention.
Preferred is an electroplating composition furthermore comprising one or more than one compound selected from the group consisting of
- one or more than one type of halogen ions, preferably bromide,
- one or more than one type of alkaline metal cations, preferably sodium and/or potassium,
- sulfate ions, and
- ammonium ions.
By adding one or more of the above-mentioned compounds the deposition of chromium during an electroplating process can be improved, most preferably dur ing the method of the present invention.
Preferably, the electroplating composition of the present invention comprises one or more than one type of halogen ions, preferably bromide, in a concentration of at least 0.06 mol/L, based on the total volume of the electroplating composition, more preferably at least 0.1 mol/L, even more preferably at least 0.15 mol/L. In particular bromide anions effectively suppress the formation of hexavalent chro mium species at the at least one anode.
Preferably, the electroplating composition comprises one or more than one type of alkaline metal cations, preferably sodium and/or potassium, in a total concen tration ranging from 0 mol/L to 0.5 mol/L, based on the total volume of the elec troplating composition, more preferably from 0 mol/L to 0.3 mol/L, even more
preferably from 0 mol/L to 0.1 mol/L, and most preferably from 0 mol/L to 0.08 mol/L.
Typically, rubidium, francium, and caesium ions are not utilized in an electroplat ing composition comprising trivalent chromium ions. Thus, preferably the one or more than one type of alkaline metal cations includes metal cations of lithium, sodium, and potassium, mostly sodium and potassium.
Preferred is an electroplating composition of the present invention, wherein the trivalent chromium ions of the electroplating composition are obtained from a sol uble, trivalent chromium ion containing source, typically a water-soluble salt com prising said trivalent chromium ions. Preferably, the soluble, trivalent chromium ion containing source comprises alkali metal cations in a total amount of 1 wt.-% or less, based on the total weight of said source. In some cases, preferably, such a source is utilized for replenishing trivalent chromium ions if the method is oper ated continuously. A preferred water-soluble salt comprising said trivalent chro mium ions is alkali metal free trivalent chromium sulfate or alkali metal free triva lent chromium chloride. In some cases it is preferred that the electroplating com position of the present invention contains sulfate ions, preferably in a total amount in the range from 50 g/L to 250 g/L, based on the total volume of the electroplating composition.
Preferably, the soluble, trivalent chromium ion containing source comprises or is chromium sulfate, more preferably acidic chromium sulfate, even more preferably chromium sulfate with the general formula Cr2(S04)3 and a molecular weight of 392 g/mol.
More preferably, for replenishing, a soluble, trivalent chromium ion containing source is preferred, wherein the anion is an organic anion, preferably an organic acid anion, most preferably formate and/or acetate.
The present invention according to the second aspect provides a method for de positing a chromium coating on a substrate, the method comprising the following steps:
(a) providing the substrate,
(b) providing an electroplating composition (preferably as described above, most preferably as above described as being preferred) for depositing a chromium coating on the substrate, the composition comprising:
(i) trivalent chromium ions, (ii) at least one complexing agent for the trivalent chromium ions, and
(iii) at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
(c) contacting the substrate with said electroplating composition and applying an electrical current such that the chromium coating is deposited on at least one surface of said substrate.
Preferably, the aforementioned regarding the electroplating composition of the present invention (preferably as described above as being preferred), applies likewise to the method of the present invention (preferably a method as described below as being preferred). Preferred is a method of the present invention, wherein in step (c) the electrical current is a direct current.
Preferably, the direct current (DC) is a direct current without interruptions during the electroplating, wherein more preferably the direct current is not pulsed (non- pulsed DC). Furthermore, the direct current preferably does not include reverse pulses.
Preferred is a method of the present invention, wherein in step (c) the electrical current has a cathodic current density of at least 18 A/dm2, preferably of at least 20 A/dm2, more preferably of at least 25 A/dm2, even more preferably of at least 30 A/dm2, most preferably of at least 39 A/dm2. Preferably, the cathodic current
density is in a range from 18 A/dm2 to 60 A/dm2, more preferably from 25 A/dm2 to 55 A/dm2, most preferably from 30 A/dm2 to 50 A/dm2.
Typically, the substrate provided during the method of the present invention is the cathode during the electroplating process (i.e. in step (c)). Preferably, more than one substrate is provided simultaneously in step (c) of the method of the present invention.
Preferred is a method of the present invention, wherein in step (c) at least one anode is provided, wherein the at least one anode is independently selected from the group consisting of graphite anodes and mixed metal oxide on titanium an odes. Such anodes have shown to be sufficiently resistant in the electroplating composition of the present invention. Preferably, the at least one anode does not comprise any lead or chromium.
In step (c) of the method of the present invention a chromium coating is depos ited, either a pure one or an alloy. Preferably, the chromium coating is an alloy. Preferred alloying elements are carbon, nitrogen, and oxygen, preferably carbon and oxygen. Carbon is typically present because of organic compounds usually present in the electroplating composition. In many cases preferred is a method of the present invention, wherein the chromium coating does not comprise one, more than one or all elements selected from the group consisting of sulphur, nickel, copper, aluminium, tin and iron. More preferably, the only alloying ele ments are carbon, nitrogen, and/or oxygen, more preferably carbon and/or oxy gen, most preferably carbon and oxygen. Preferably, the chromium coating con tains 90 weight percent chromium or more, based on the total weight of the chro mium coating, more preferably 95 weight percent or more.
Preferred is a method of the present invention, wherein in step (c) the electroplat ing composition has a temperature in a range from 20°C to 90°C, preferably from 30°C to 70°C, more preferably from 40°C to 60°C, most preferably from 45°C to 58°C.
In the preferred temperature range (in particular in the most preferred tempera ture range) the chromium coating is optimally deposited in step (c). If the temper ature significantly exceeds 90 °C, an undesired vaporization occurs, which can negatively affect the concentration of the composition components. Furthermore, the undesired anodic formation of hexavalent chromium is significantly less sup pressed. If the temperature is significantly below 20 °C the electrodeposition is insufficient.
Preferred is a method of the present invention, wherein step (c) is performed for a time period from 10 min to 100 min, preferably from 20 min to 90 min, more preferably from 30 min to 60 min.
Preferred is a method of the present invention, wherein in step (c) the electroplat ing composition is stirred, preferably with a stirring rate in a range from 100 rpm to 500 rpm, most preferably from 200 rpm to 400 rpm.
By performing the method step (c) in the abovementioned preferred temperature ranges and/or (preferably and) for the preferred time periods and/or (preferably and) with the preferred stirring rates, particularly advantageous electrodeposition kinetics during step (c) can be ensured.
Preferred is a method of the present invention further comprising after step (c) step
(d) heat-treating the chromium-coated substrate obtained from step (c).
Preferred is a method of the present invention, wherein in step (d) the heat-treat ing is carried out at a temperature in a range from 100°C to 250°C, preferably from 120°C to 240°C, more preferably from 150°C to 220°C, most preferably from 170°C to 200°C.
Preferred is a method of the present invention, wherein in step (d) the heat-treat ing is carried out for a time period from 1 h to 10 h, preferably from 2 h to 4 h.
By preferably performing a heat-treatment of the substrate, more preferably at the preferred temperatures and/or for the preferred time periods, the properties of the chromium coating can be further improved in some cases (e.g. hardness).
Preferred is a method of the present invention, wherein in step (c) the cathodic current efficiency (CCE) is 11 % or more, preferably 12% or more, most preferably 13% or more. This most preferably applies, if an identical method with the only exception that the electroplating composition does not comprise an additive, is carried out.
By significantly increasing the cathodic current efficiency (CCE) to 11 % or more, the entire method is more effective and economical. Furthermore, less energy is wasted and less hydrogen gas is produced during step (c).
Preferred is a method of the present invention, wherein the substrate comprises a metal rod.
Preferred is a method of the present invention, wherein the substrate comprises a metal or metal alloy, preferably comprises one or more than one metal selected from the group consisting of copper, iron, nickel and aluminum, more preferably comprises one or more than one metal selected from the group consisting of cop per, iron, and nickel, most preferably comprises at least iron.
In many cases preferred is a substrate comprising a pre-coating, the pre-coating preferably being a nickel or nickel alloy coating, most preferably a semi-bright nickel coating, on which the chromium coating is applied to during step (c) of the method of the present invention. In particular preferred is a steel substrate pre coated with a nickel or nickel alloy coating. However, preferably other pre-coat ings are alternatively or additionally present. In many cases such a pre-coating significantly increases corrosion resistance compared to a metal substrate with out such a pre-coating. However, in some cases the substrates are not suscepti ble to corrosion due to a corrosion inert environment (e.g. in an oil composition). In such a case a pre-coating, preferably a nickel or nickel alloy pre-coating, is not necessarily needed.
Generally, preferred is a method of the present invention, wherein in step (c) the chromium coating has a thickness in a range from 1.1 pm to 500 pm, preferably from 2 pm to 450 pm, more preferably from 4 pm to 400 pm, even more preferably from 6 pm to 350 pm, yet even more preferably from 8 pm to 300 pm, and most preferably from 10 pm to 250 pm.
In some cases, preferred is a method of the present invention, wherein in step (c) the chromium coating has a thickness of 0.5 pm or more, preferably of 0.75 pm or more, more preferably of 0.9 pm or more, even more preferably of 1 .0 pm or more, yet even more preferably of 1 .5 pm or more, and most preferably of 2.0 pm or more. In some further cases a method of the present invention is preferred, wherein in step (c) the chromium coating has a thickness of 15 pm or more, pref erably of 20 pm or more.
Preferred is a method of the present invention, wherein in step (c) the concentra tion of the at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof (preferably at least of the betaines), is continually or semi-continually monitored, wherein
- the monitored concentration is compared to a target concentration of said at least one additive (preferably of said betaines), and
- if the monitored concentration is below the target concentration than the at least one additive (preferably the betaines) is added to the electroplating composition.
In particular the aforementioned regarding the betaines in the electroplating com position applies likewise to the method of the present invention.
The present invention according to the third aspect provides a substrate with a surface, wherein the surface of the substrate comprises a chromium coating ob tained by a method for depositing according to the second aspect.
Preferred is a substrate of the present invention, wherein the chromium-coated substrate comprises or is a metal rod.
The aforementioned regarding the electroplating composition of the present in vention (preferably an electroplating composition as described as being pre ferred) and the aforementioned regarding the method of the present invention (preferably a method for depositing as described as being preferred) preferably applies likewise to the substrate of the present invention. In particular, preferred embodiments of the electroplating composition of the first aspect and preferred embodiments of the method for depositing according to the second aspect are also preferred embodiments for the substrate according to the third aspect. This applies in particular and most preferably to the characteristics of the chromium coating. The present invention according to the fourth aspect provides a use of at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, for increasing the cathodic current effi ciency in an electroplating composition for depositing a chromium coating on a substrate. The aforementioned regarding the electroplating composition of the present in vention (preferably an electroplating composition as described as being pre ferred) and the aforementioned regarding the method of the present invention (preferably a method for depositing as described as being preferred) preferably applies likewise to the use of the present invention. The present invention is described in more detail by the following non-limiting examples.
Examples
For a number of experiments, respective test electroplating compositions were prepared (volume: appr. 850 ml_) comprising 10 g/L to 30 g/L trivalent chromium ions (source: basic chromium sulfate), 50 g/L to 250 g/L sulfate ions, at least one organic complexing compound (an aliphatic mono carboxylic organic acid), am monium ions, and bromide ions. The compositions did not contain boric acid nor
any boron-containing compounds and no organic compounds with divalent sulfur. The pH was in a range from 5.4 to 5.7.
In a reference electroplating composition (C1 ) no additive was contained, defining the reference cathodic current efficiency (CCE). In a number of further experi ments, various additives in a number of concentrations were tested (see Table 1 below).
In each test, the respective electroplating composition was subjected to electro plating in order to obtain a chromium coating on a substrate (mild steel rod with 10 mm diameter). As anodes a graphite anode was used. Electrodeposition was carried out at 40 A/dm2 for 45 minutes at 50°C under mild stirring. CCE was determined based on the Faraday law and gravimetric analysis.
Table 1: Cathodic current efficiency determined on the basis of various additives
Very similar results were obtained with 1 ,2-propanediol, diethyleneglycol and tri ethyleneglycol (data not shown), confirming the results shown in Table 1.
The results in Table 1 show that the tested compound increases the CCE up to 40% compared to the CCE of the reference experiment. Furthermore, according to experiments 1 to 12 a comparatively high additive concentration is required compared to the additive utilized in experiments 13 to 18. Thus, betaines allow to significantly increase the CCE at comparatively low concentrations. It was fur- thermore observed that experiments 13 to 18 showed foaming. In further experi ments foaming was limited by adding an anti-foam compound (a tetramethyl- decandiol comprising two iso-propyl moieties (a monomeric C11-C25 diol), solubil ized in propylene glycol (a monomeric C3 diol) prior to addition (total amount of diols in the electroplating composition below 4.0 g/L). In further comparative examples and in view of US 3,432,408, sulfobetaines as utilized in experiments 13 and 16 were tested in a hexavalent chromium electro plating composition (55°C, 50 A/dm2). The CCE was appr. 25% without additive and appr. 25% with 0.04 g/L additive. Thus, no significant increase in the CCE was observed, confirming that the positive effect of CCE increase is limited to electroplating compositions comprising trivalent chromium ions.
Claims
1. An electroplating composition for depositing a chromium coating on a sub strate, the composition comprising:
(i) trivalent chromium ions,
(ii) at least one complexing agent for the trivalent chromium ions, and (iii) at least one additive selected from the group consisting of betaines, poly meric glycols, monomeric diols, and mixtures thereof.
2. The electroplating composition according to claim 1 , wherein the electro plating composition comprises at least one or more than one betaine inde pendently comprising at least 10 carbon atoms, preferably at least 15 car- bon atoms.
3. The electroplating composition according to claim 1 or 2, wherein the beta ines independently comprise:
- a positively charged quaternary nitrogen atom, and
- a negatively charged sulfonate group and/or negatively charged carbox- ylate group, with the proviso that the positive charge cannot be removed by deprotona tion.
4. The electroplating composition according to any one of the preceding claims, wherein the betaines are selected from the group consisting of N- substituted-N,N-Dialkyl-ammonium sulfobetaines, preferably N-substituted-
N, N-Dialkyl-N-alkyl ammonium sulfobetaines.
5. The electroplating composition according to any one of the preceding claims, wherein the betaines comprise one or more of N,N-Dimethyl-N-(3-
cocoamidopropyl)-N-(2-hydroxy-3-sulfopropyl) ammonium betaine, N-Do- decyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N-Octyl-N,N-dimethyl- 3-ammonio-1-propanesulfonate, N-Decyl-N,N-dimethyl-3-ammonio-1-pro- panesulfonate, N-Tetradecyl-N,N-dimethyl-3-ammonio-1-propanesul- fonate, N-Hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, N-Oc- tadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate, and N,N-Dimethyl- N-dodecylglycine betaine.
6. The electroplating composition according to any one of the preceding claims, wherein the electroplating composition comprises at least one beta ine and in addition one or more than one monomeric diol.
7. The electroplating composition according to any one of the preceding claims, wherein the electroplating composition comprises the betaines in a total concentration in a range from 0.0005 g/L to 1 g/L, based on the total volume of the electroplating composition, preferably from 0.001 g/L to 0.5 g/L, more preferably from 0.005 g/L to 0.3 g/L, and most preferably from 0.01 g/L to 0.2 g/L.
8. The electroplating composition according to any one of the preceding claims, wherein the electroplating composition has a pH in a range from 4.1 to 7.0, preferably from 4.5 to 6.5, more preferably from 5.0 to 6.0, and most preferably from 5.3 to 5.9.
9. The electroplating composition according to any one of the preceding claims, wherein the electroplating composition comprises one or more than one betaine and one or more than one monomeric diol, with the proviso that the one or more than one monomeric diol comprises one or more than one C11-C25 diol comprising one, two or more than two iso-propyl moieties.
10. A method for depositing a chromium coating on a substrate, the method comprising the following steps:
(a) providing the substrate,
(b) providing an electroplating composition for depositing a chromium coating on the substrate, the composition comprising: (i) trivalent chromium ions,
(ii) at least one complexing agent for the trivalent chromium ions, and
(iii) at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof.
(c) contacting the substrate with said electroplating composition and applying an electrical current such that the chromium coating is deposited on at least one surface of said substrate.
11. The method of claim 9, wherein in step (c) the cathodic current efficiency (CCE) is 11% or more, preferably 12% or more, most preferably 13% or more.
12. The method of claim 9 or 10, wherein in step (c) the chromium coating has a thickness in a range from 1.1 pm to 500 pm, preferably from 2 pm to 450 pm, more preferably from 4 pm to 400 pm, even more preferably from 6 pm to 350 pm, yet even more preferably from 8 pm to 300 pm, and most pref erably from 10 pm to 250 pm.
13. The method of any one of claims 9 to 11 , wherein in step (c) the concentra tion of the at least one additive selected from the group consisting of beta ines, polymeric glycols, monomeric diols, and mixtures thereof, is continu ally or semi-continually monitored, wherein
- the monitored concentration is compared to a target concentration of said at least one additive, and
- if the monitored concentration is below the target concentration than the at least one additive is added to the electroplating composition.
14. A substrate with a surface, wherein the surface of the substrate comprises a chromium coating obtained by a method for depositing according to any one of claims 10 to 13.
15. A use of at least one additive selected from the group consisting of betaines, polymeric glycols, monomeric diols, and mixtures thereof, for increasing the cathodic current efficiency in an electroplating composition for depositing a chromium coating on a substrate.
Priority Applications (5)
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| KR1020227023495A KR20220116477A (en) | 2019-12-18 | 2020-12-17 | Electroplating compositions and methods for depositing chromium coatings on substrates |
| US17/785,114 US20230015534A1 (en) | 2019-12-18 | 2020-12-17 | Electroplating composition and method for depositing a chromium coating on a substrate |
| CN202080087415.0A CN114829677A (en) | 2019-12-18 | 2020-12-17 | Electroplating composition and method for depositing chromium coating on substrate |
| JP2022537718A JP2023507017A (en) | 2019-12-18 | 2020-12-17 | Electroplating composition and method for depositing a chromium coating on a substrate |
| EP20838402.4A EP4077770A1 (en) | 2019-12-18 | 2020-12-17 | Electroplating composition and method for depositing a chromium coating on a substrate |
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| EP19217662 | 2019-12-18 | ||
| EP19217662.6 | 2019-12-18 |
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| PCT/EP2020/086688 WO2021122932A1 (en) | 2019-12-18 | 2020-12-17 | Electroplating composition and method for depositing a chromium coating on a substrate |
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| US (1) | US20230015534A1 (en) |
| EP (1) | EP4077770A1 (en) |
| JP (1) | JP2023507017A (en) |
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- 2020-12-17 JP JP2022537718A patent/JP2023507017A/en active Pending
- 2020-12-17 US US17/785,114 patent/US20230015534A1/en active Pending
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| Publication number | Publication date |
|---|---|
| EP4077770A1 (en) | 2022-10-26 |
| CN114829677A (en) | 2022-07-29 |
| JP2023507017A (en) | 2023-02-20 |
| KR20220116477A (en) | 2022-08-23 |
| US20230015534A1 (en) | 2023-01-19 |
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