CA2908478C - Functional chromium layer with improved corrosion resistance - Google Patents
Functional chromium layer with improved corrosion resistance Download PDFInfo
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- CA2908478C CA2908478C CA2908478A CA2908478A CA2908478C CA 2908478 C CA2908478 C CA 2908478C CA 2908478 A CA2908478 A CA 2908478A CA 2908478 A CA2908478 A CA 2908478A CA 2908478 C CA2908478 C CA 2908478C
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- chromium layer
- functional chromium
- electroplating bath
- methane
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- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 43
- 239000011651 chromium Substances 0.000 title claims abstract description 43
- 230000007797 corrosion Effects 0.000 title abstract description 12
- 238000005260 corrosion Methods 0.000 title abstract description 12
- 238000009713 electroplating Methods 0.000 claims abstract description 37
- 150000003839 salts Chemical class 0.000 claims abstract description 23
- NARPMWPOFWHFDX-UHFFFAOYSA-N methanetrisulfonic acid Chemical compound OS(=O)(=O)C(S(O)(=O)=O)S(O)(=O)=O NARPMWPOFWHFDX-UHFFFAOYSA-N 0.000 claims abstract description 18
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims abstract description 11
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000000151 deposition Methods 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 21
- 239000000758 substrate Substances 0.000 claims description 21
- 239000004094 surface-active agent Substances 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 14
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 claims description 5
- OPUAWDUYWRUIIL-UHFFFAOYSA-N methanedisulfonic acid Chemical compound OS(=O)(=O)CS(O)(=O)=O OPUAWDUYWRUIIL-UHFFFAOYSA-N 0.000 claims description 5
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical class OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 claims description 4
- 150000003871 sulfonates Chemical class 0.000 claims description 4
- 150000001768 cations Chemical class 0.000 claims description 3
- AFAXGSQYZLGZPG-UHFFFAOYSA-N ethanedisulfonic acid Chemical compound OS(=O)(=O)CCS(O)(=O)=O AFAXGSQYZLGZPG-UHFFFAOYSA-N 0.000 claims description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 3
- FACKKNUWEJWKIC-UHFFFAOYSA-N propane-1,2,3-trisulfonic acid Chemical compound OS(=O)(=O)CC(S(O)(=O)=O)CS(O)(=O)=O FACKKNUWEJWKIC-UHFFFAOYSA-N 0.000 claims description 3
- KCXFHTAICRTXLI-UHFFFAOYSA-N propane-1-sulfonic acid Chemical compound CCCS(O)(=O)=O KCXFHTAICRTXLI-UHFFFAOYSA-N 0.000 claims description 3
- 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 claims description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 2
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 claims description 2
- CCIVGXIOQKPBKL-UHFFFAOYSA-M ethanesulfonate Chemical compound CCS([O-])(=O)=O CCIVGXIOQKPBKL-UHFFFAOYSA-M 0.000 claims description 2
- 229910000457 iridium oxide Inorganic materials 0.000 claims description 2
- 229940098779 methanesulfonic acid Drugs 0.000 claims description 2
- 229910052700 potassium Inorganic materials 0.000 claims description 2
- 239000011591 potassium Substances 0.000 claims description 2
- LJYOXSMOJRTHIL-UHFFFAOYSA-N propane-1,2-disulfonic acid Chemical compound OS(=O)(=O)C(C)CS(O)(=O)=O LJYOXSMOJRTHIL-UHFFFAOYSA-N 0.000 claims description 2
- MGNVWUDMMXZUDI-UHFFFAOYSA-N propane-1,3-disulfonic acid Chemical compound OS(=O)(=O)CCCS(O)(=O)=O MGNVWUDMMXZUDI-UHFFFAOYSA-N 0.000 claims description 2
- 229910052709 silver Inorganic materials 0.000 claims description 2
- 239000004332 silver Substances 0.000 claims description 2
- 229910052708 sodium Inorganic materials 0.000 claims description 2
- 239000011734 sodium Substances 0.000 claims description 2
- 229910019142 PO4 Inorganic materials 0.000 claims 1
- 150000003863 ammonium salts Chemical class 0.000 claims 1
- 239000011133 lead Substances 0.000 claims 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims 1
- 239000010452 phosphate Substances 0.000 claims 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 claims 1
- 239000003054 catalyst Substances 0.000 abstract description 5
- 229940107218 chromium Drugs 0.000 description 25
- 235000012721 chromium Nutrition 0.000 description 25
- 238000007747 plating Methods 0.000 description 23
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000011550 stock solution Substances 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- ZZTMMVAAULUFCS-UHFFFAOYSA-L disodium;methanedisulfonate Chemical compound [Na+].[Na+].[O-]S(=O)(=O)CS([O-])(=O)=O ZZTMMVAAULUFCS-UHFFFAOYSA-L 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- -1 chromium(VI) compound Chemical class 0.000 description 4
- 230000007935 neutral effect Effects 0.000 description 4
- 239000007921 spray Substances 0.000 description 4
- 150000007513 acids Chemical class 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- JWLDKEPWWPTYLJ-UHFFFAOYSA-K trisodium;methanetrisulfonate Chemical compound [Na+].[Na+].[Na+].[O-]S(=O)(=O)C(S([O-])(=O)=O)S([O-])(=O)=O JWLDKEPWWPTYLJ-UHFFFAOYSA-K 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 125000002467 phosphate group Chemical class [H]OP(=O)(O[H])O[*] 0.000 description 2
- UUEFNRLFBIHJFY-UHFFFAOYSA-K trisodium propane-1,2,3-trisulfonate Chemical compound [Na+].[Na+].[Na+].[O-]S(=O)(=O)CC(CS([O-])(=O)=O)S([O-])(=O)=O UUEFNRLFBIHJFY-UHFFFAOYSA-K 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000003377 acid catalyst Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- CCIVGXIOQKPBKL-UHFFFAOYSA-N ethanesulfonic acid Chemical compound CCS(O)(=O)=O CCIVGXIOQKPBKL-UHFFFAOYSA-N 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- FWFGVMYFCODZRD-UHFFFAOYSA-N oxidanium;hydrogen sulfate Chemical compound O.OS(O)(=O)=O FWFGVMYFCODZRD-UHFFFAOYSA-N 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- C25D3/10—Electroplating: Baths therefor from solutions of chromium characterised by the organic bath constituents used
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
- C25D17/10—Electrodes, e.g. composition, counter electrode
-
- 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
- C25D3/08—Deposition of black chromium, e.g. hexavalent chromium, CrVI
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D3/00—Electroplating: Baths therefor
- C25D3/02—Electroplating: Baths therefor from solutions
- C25D3/56—Electroplating: Baths therefor from solutions of alloys
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electroplating And Plating Baths Therefor (AREA)
- Electroplating Methods And Accessories (AREA)
Abstract
The aqueous electroplating bath according to the present invention comprises chromium(VI) ions, sulfate ions and methane-trisulfonic acid or a salt thereof as the catalyst. The functional chromium layer deposited from the aqueous electroplating bath according to the present invention has an increased corrosion resistance.
Description
Functional chromium layer with improved corrosion resistance Field of the Invention The present invention relates to plating bath compositions and a process for depositing functional chromium layers by electroplating.
Backs:1round of the Invention Functional chromium layers deposited by electroplating are used to improve wear and corrosion resistance of products such as shock absorbers, hydraulic pistons and the like.
The plating bath compositions used comprise chromic acid, sulfate ions, water and an alkyl-sulfonic acid or salt thereof.
Alkyl-sulfonic acid catalysts having a molar ratio S : C 1 :
3 are disclosed in EP 0 196 053 B1. Examples of suitable alkyl-sulfonic acids are methyl-sulfonic acid, ethyl-sulfonic acid, propyl-sulfonic acid, methane-disulfonic acid and 1,2-ethane-disulfonic acid. Said alkyl-sulfonic acids improve the cathodic current efficiency during plating.
The use of alkyl-polysulfonic acids, halogenated alkyl-polysulfonic acids and corresponding salts such as methane-disulfonic acid for reducing the corrosion of lead anodes during plating is disclosed in EP 0 452 471 B1.
Aromatic-trisulfionic acids as an additive in plating bath compositions for depos-iting functional chromium layers are disclosed in US 2,195,409. The chromium layers obtained from such plating bath compositions are bright and uniform.
Backs:1round of the Invention Functional chromium layers deposited by electroplating are used to improve wear and corrosion resistance of products such as shock absorbers, hydraulic pistons and the like.
The plating bath compositions used comprise chromic acid, sulfate ions, water and an alkyl-sulfonic acid or salt thereof.
Alkyl-sulfonic acid catalysts having a molar ratio S : C 1 :
3 are disclosed in EP 0 196 053 B1. Examples of suitable alkyl-sulfonic acids are methyl-sulfonic acid, ethyl-sulfonic acid, propyl-sulfonic acid, methane-disulfonic acid and 1,2-ethane-disulfonic acid. Said alkyl-sulfonic acids improve the cathodic current efficiency during plating.
The use of alkyl-polysulfonic acids, halogenated alkyl-polysulfonic acids and corresponding salts such as methane-disulfonic acid for reducing the corrosion of lead anodes during plating is disclosed in EP 0 452 471 B1.
Aromatic-trisulfionic acids as an additive in plating bath compositions for depos-iting functional chromium layers are disclosed in US 2,195,409. The chromium layers obtained from such plating bath compositions are bright and uniform.
2 A plating bath composition for depositing a functional chromium layer with an improved cathodic current efficiency comprising propane-1,2,3-trisulfonic acid is disclosed in DE 43 05 732 A1.
Obiective of the present Invention The objective of the present invention is to provide a plating bath composition and a process utilizing said plating bath composition for depositing functional chromium layers having an improved corrosion resistance.
Summary of the Invention This objective is solved with an aqueous electroplating bath for depositing a functional chromium layer, comprising (i) a source for chromium(VI) ions, (ii) a source for sulfate ions and (iii) methane-trisulfonic acid or a salt thereof.
This objective is further solved with a process for depositing a functional chro-mium layer onto a metallic substrate, comprising, in this order, the steps of (i) providing a metallic substrate, (ii) contacting said substrate with an aqueous electroplating bath comprising a source for chromium(VI) ions, a source for sulfate ions and methane-trisulfonic acid or a salt thereof and (iii) applying an external current to said substrate as the cathode and thereby depositing a functional chromium layer onto said sub-strate.
Obiective of the present Invention The objective of the present invention is to provide a plating bath composition and a process utilizing said plating bath composition for depositing functional chromium layers having an improved corrosion resistance.
Summary of the Invention This objective is solved with an aqueous electroplating bath for depositing a functional chromium layer, comprising (i) a source for chromium(VI) ions, (ii) a source for sulfate ions and (iii) methane-trisulfonic acid or a salt thereof.
This objective is further solved with a process for depositing a functional chro-mium layer onto a metallic substrate, comprising, in this order, the steps of (i) providing a metallic substrate, (ii) contacting said substrate with an aqueous electroplating bath comprising a source for chromium(VI) ions, a source for sulfate ions and methane-trisulfonic acid or a salt thereof and (iii) applying an external current to said substrate as the cathode and thereby depositing a functional chromium layer onto said sub-strate.
3 The functional chromium layers deposited from the aqueous plating bath and by the process according to the present invention have an increased corrosion re-sistance compared to functional chromium layers deposited from conventional electroplating bath compositions comprising known alkyl-sulfonic acid.
Detailed Description of the Invention The aqueous electroplating bath according to the present invention comprises a source for chromium(VI) ions, sulfate ions, methane-trisulfonic acid, or a salt thereof, and optionally a surface active agent.
The source for chromium(VI) ions is preferably a chromium(VI) compound solu-ble in the plating bath such as Cr03, Na2Cr207 and K2Cr207, most preferably Cr03. The concentration of chromium(VI) ions in the electroplating bath accord-ing to the present invention preferably ranges from 80 to 600 g/I, more prefera-bly from 100 to 200 g/I.
Sulfate ions present in the electroplating bath are preferably added in form of sulfuric acid or a plating bath soluble sulfate salt such as Na2SO4. The concen-tration of sulfate ions in the electroplating bath preferably ranges from 1 to 15 g/I, more preferably from 2 to 6 g/I.
The ratio of the concentration in wt.-% of chromic acid to sulfate preferably ranges from 25 to 200, more preferably from 60 to 150.
The alkyl-sulfonic acid in the electroplating bath is either methane-trisulfonic acid (HC(S020H)3) or a mixture of methane-trisulfonic acid and one or more other alkyl-sulfonic acids. Suitable other alkyl-sulfonic acids in mixtures with methane-trisulfonic acid comprise methane-sulfonic acid, methane-disulfonic acid, ethane-sulfonic acid, 1,2-ethane-disulfonic acid, propyl sulfonic acid, 1,2-propane-disulfonic acid, 1,3-propane-disulfonic acid and 1,2,3-propane-trisulfonic acid. Corresponding salts such as sodium, potassium and ammonium
Detailed Description of the Invention The aqueous electroplating bath according to the present invention comprises a source for chromium(VI) ions, sulfate ions, methane-trisulfonic acid, or a salt thereof, and optionally a surface active agent.
The source for chromium(VI) ions is preferably a chromium(VI) compound solu-ble in the plating bath such as Cr03, Na2Cr207 and K2Cr207, most preferably Cr03. The concentration of chromium(VI) ions in the electroplating bath accord-ing to the present invention preferably ranges from 80 to 600 g/I, more prefera-bly from 100 to 200 g/I.
Sulfate ions present in the electroplating bath are preferably added in form of sulfuric acid or a plating bath soluble sulfate salt such as Na2SO4. The concen-tration of sulfate ions in the electroplating bath preferably ranges from 1 to 15 g/I, more preferably from 2 to 6 g/I.
The ratio of the concentration in wt.-% of chromic acid to sulfate preferably ranges from 25 to 200, more preferably from 60 to 150.
The alkyl-sulfonic acid in the electroplating bath is either methane-trisulfonic acid (HC(S020H)3) or a mixture of methane-trisulfonic acid and one or more other alkyl-sulfonic acids. Suitable other alkyl-sulfonic acids in mixtures with methane-trisulfonic acid comprise methane-sulfonic acid, methane-disulfonic acid, ethane-sulfonic acid, 1,2-ethane-disulfonic acid, propyl sulfonic acid, 1,2-propane-disulfonic acid, 1,3-propane-disulfonic acid and 1,2,3-propane-trisulfonic acid. Corresponding salts such as sodium, potassium and ammonium
4 salts of the aforementioned sulfonic acids can also be employed instead of or as a mixture with the free alkyl-sulfonic acids.
A precursor of methane-trisulfonic acid or a salt thereof which is oxidized in the electroplating bath according to the present invention to methane-trisulfonic acid or a salt thereof may be used as part or sole source of methane-trisulfonic acid or a salt thereof.
The concentration of methane-trisulfonic acid or a salt thereof in the plating bath according to the present invention preferably ranges from 2 to 80 mmo1/1, more preferably from 4 to 60 mmo1/1.
The overall concentration of methane-trisulfonic acid and other alkyl-sulfonic acids or salts of the aforementioned in case a mixture of methane-trisulfonic acid with other alkyl-sulfonic acids is employed preferably ranges from 4 to 160 mmo1/1, more preferably from 12 to 120 mmo1/1.
A high number of micro-cracks inside the functional chromium layer deposited is desired because thereby a high corrosion resistance and desirable mechanical properties such as a reduced internal stress are achieved. Micro-cracks in con-trast to macro-cracks within a functional chromium layer do not extend to the surface of the underlying substrate and thus do not result in corrosion of the underlying substrate material, which usually is steel.
Methane-trisulfonic acid or a salt thereof or constituent of a mixture with other alkyl-sulfonic acid(s) enables a high number of desired micro-cracks in the range of 200 to 1000, more preferably 450 to 750 micro-cracks per cm of the functional chromium layer surface as determined after etching in an aqueous solution containing sodium hydroxide and K3[Fe(CN)6] with an optical micro-scope. The number of micro-cracks along lines is counted and the number of micro-cracks per cm is then calculated with the formula Micro-cracks per cm = (average number of cracks per line) : (length if line in cm) The number of micro-cracks and the corrosion resistance is increased with me-thane-trisulfonic acid or a salt thereof as the catalyst compared with methane-disulfonic acid sodium salt or propane-1,2,3-trisulfonic acid sodium salt as the
A precursor of methane-trisulfonic acid or a salt thereof which is oxidized in the electroplating bath according to the present invention to methane-trisulfonic acid or a salt thereof may be used as part or sole source of methane-trisulfonic acid or a salt thereof.
The concentration of methane-trisulfonic acid or a salt thereof in the plating bath according to the present invention preferably ranges from 2 to 80 mmo1/1, more preferably from 4 to 60 mmo1/1.
The overall concentration of methane-trisulfonic acid and other alkyl-sulfonic acids or salts of the aforementioned in case a mixture of methane-trisulfonic acid with other alkyl-sulfonic acids is employed preferably ranges from 4 to 160 mmo1/1, more preferably from 12 to 120 mmo1/1.
A high number of micro-cracks inside the functional chromium layer deposited is desired because thereby a high corrosion resistance and desirable mechanical properties such as a reduced internal stress are achieved. Micro-cracks in con-trast to macro-cracks within a functional chromium layer do not extend to the surface of the underlying substrate and thus do not result in corrosion of the underlying substrate material, which usually is steel.
Methane-trisulfonic acid or a salt thereof or constituent of a mixture with other alkyl-sulfonic acid(s) enables a high number of desired micro-cracks in the range of 200 to 1000, more preferably 450 to 750 micro-cracks per cm of the functional chromium layer surface as determined after etching in an aqueous solution containing sodium hydroxide and K3[Fe(CN)6] with an optical micro-scope. The number of micro-cracks along lines is counted and the number of micro-cracks per cm is then calculated with the formula Micro-cracks per cm = (average number of cracks per line) : (length if line in cm) The number of micro-cracks and the corrosion resistance is increased with me-thane-trisulfonic acid or a salt thereof as the catalyst compared with methane-disulfonic acid sodium salt or propane-1,2,3-trisulfonic acid sodium salt as the
5 sole alkyl-sulfonic acid. This is shown in Examples 1 to 3.
Furthermore, an increased number of desired micro-cracks is also obtained at higher current densities (Example 3) whereas the number of micro-cracks is decreasing at higher current densities in case of known alkyl-sulfonic acids such as methane-disulfonic acid (Example 1). Higher current density values during plating are desired because the plating speed is increased thereby.
The electroplating bath according to the present invention optionally further comprises a surface active agent which reduces formation of undesired foam on top of the plating liquid. The surface active additive is selected from the group comprising perfluorinated sulfonate tenisdes, perfluorinated phosphate ten-sides, perfluorinated phosphonate tensides, partially fluorinated sulfonate ten-sides, partially fluorinated phosphate tensides, partially fluorinated phosphonate tensides and mixtures thereof.
The concentration of the optional surface active agent preferably ranges from 0.05 to 4 g/I, more preferably from 0.1 to 2.5 g/I.
The current density applied during plating preferably ranges from 10 to 250 A/dm2, more preferably from 40 to 200 A/dm2. The substrate to be plated with a functional chromium layer serves as the cathode during electroplating.
Cathodic current efficiency is the percentage of current, which is actually used for the deposition of the metal (chromium) at the cathode during electroplating of the functional chromium layer.
Furthermore, an increased number of desired micro-cracks is also obtained at higher current densities (Example 3) whereas the number of micro-cracks is decreasing at higher current densities in case of known alkyl-sulfonic acids such as methane-disulfonic acid (Example 1). Higher current density values during plating are desired because the plating speed is increased thereby.
The electroplating bath according to the present invention optionally further comprises a surface active agent which reduces formation of undesired foam on top of the plating liquid. The surface active additive is selected from the group comprising perfluorinated sulfonate tenisdes, perfluorinated phosphate ten-sides, perfluorinated phosphonate tensides, partially fluorinated sulfonate ten-sides, partially fluorinated phosphate tensides, partially fluorinated phosphonate tensides and mixtures thereof.
The concentration of the optional surface active agent preferably ranges from 0.05 to 4 g/I, more preferably from 0.1 to 2.5 g/I.
The current density applied during plating preferably ranges from 10 to 250 A/dm2, more preferably from 40 to 200 A/dm2. The substrate to be plated with a functional chromium layer serves as the cathode during electroplating.
Cathodic current efficiency is the percentage of current, which is actually used for the deposition of the metal (chromium) at the cathode during electroplating of the functional chromium layer.
6 The preferred current efficiency of the process according to the present inven-tion is 22 % at a current density of 50 A/dm2.
The temperature of the electroplating bath according to the present invention is held during plating preferably in a range of 10 to 80 C, more preferably in a range of 45 to 70 C and most preferably from 50 to 60 C.
Inert anodes are preferably applied in the process according to the present in-vention.
Suitable inert anodes are for example made of titanium or a titanium alloy coat-ed with one or more platinum group metal, alloys thereof and/or oxides thereof.
The coating preferably consists of platinum metal, iridium oxide or a mixture thereof. Such inert anodes enable higher current densities during electroplating and thereby a higher plating rate compared to lead anodes.
The plating bath according to the present invention can also be operated with conventional lead anodes.
Chromium(III) ions are formed when using such inert anodes. Methane-trisulfonic acid and/or a salt thereof as the alkyl-sulfonic acid in a chromium(VI) ion based functional chromium electroplating bath is very sensitive to chromi-um(III) ions.
In a preferred embodiment of the present invention, cations of a further metal such as silver ions, lead ions and mixtures thereof are added to the electroplat-ing bath. Thereby, the negative impact of chromium(III) ions can be minimized.
The concentration of ions of a further metal preferably ranges from 0.005 to 5 g/I, more preferably from 0.01 to 3 g/I.
The present invention provides a functional chromium electroplating bath and a process for depositing a functional chromium layer onto a substrate having an increased corrosion resistance which is also obtained at high current densities.
The temperature of the electroplating bath according to the present invention is held during plating preferably in a range of 10 to 80 C, more preferably in a range of 45 to 70 C and most preferably from 50 to 60 C.
Inert anodes are preferably applied in the process according to the present in-vention.
Suitable inert anodes are for example made of titanium or a titanium alloy coat-ed with one or more platinum group metal, alloys thereof and/or oxides thereof.
The coating preferably consists of platinum metal, iridium oxide or a mixture thereof. Such inert anodes enable higher current densities during electroplating and thereby a higher plating rate compared to lead anodes.
The plating bath according to the present invention can also be operated with conventional lead anodes.
Chromium(III) ions are formed when using such inert anodes. Methane-trisulfonic acid and/or a salt thereof as the alkyl-sulfonic acid in a chromium(VI) ion based functional chromium electroplating bath is very sensitive to chromi-um(III) ions.
In a preferred embodiment of the present invention, cations of a further metal such as silver ions, lead ions and mixtures thereof are added to the electroplat-ing bath. Thereby, the negative impact of chromium(III) ions can be minimized.
The concentration of ions of a further metal preferably ranges from 0.005 to 5 g/I, more preferably from 0.01 to 3 g/I.
The present invention provides a functional chromium electroplating bath and a process for depositing a functional chromium layer onto a substrate having an increased corrosion resistance which is also obtained at high current densities.
7 Examples The invention will now be illustrated by reference to the following non-limiting examples.
The number of micro-cracks was determined with an optical microscope after etching the surface of the chromium layer in an aqueous solution containing sodium hydroxide and K3[Fe(CN)6]. The number of micro-cracks along several lines having the same length is determined from which the average number of micro-cracks is calculated and then divided by the line length given in cm to provide the "average number of micro-cracks" in cracks/cm.
The corrosion resistance of the functional chromium layers was determined ac-cording ISO 9227 NSS (neutral salt spray test).
An aqueous electroplating bath stock solution containing 250 g/I Cr03, 3.2 g/I
sulfate ions and 2 m1/I of a surface active agent was used throughout examples 1 to 3. Different amounts of alkyl-sulfonic acids were added to this stock solu-tion prior to depositing the functional chromium layers.
Example 1 (comparative) The alkyl-sulfonic acid was methane-disulfonic acid disodium salt added to the stock solution in a concentration of 2 to 12 g/I (7.6 to 45.4 mmo1/1). This alkyl-sulfonic acid is disclosed in EP 0 452 471 B1.
Table 1 summarizes the average number of micro-cracks determined at differ-ent concentrations of methane-disulfonic acid disodium salt as the sole alkyl-sulfonic acid (plating bath temperature: 58 C, current density: 50 A/dm2).
The number of micro-cracks was determined with an optical microscope after etching the surface of the chromium layer in an aqueous solution containing sodium hydroxide and K3[Fe(CN)6]. The number of micro-cracks along several lines having the same length is determined from which the average number of micro-cracks is calculated and then divided by the line length given in cm to provide the "average number of micro-cracks" in cracks/cm.
The corrosion resistance of the functional chromium layers was determined ac-cording ISO 9227 NSS (neutral salt spray test).
An aqueous electroplating bath stock solution containing 250 g/I Cr03, 3.2 g/I
sulfate ions and 2 m1/I of a surface active agent was used throughout examples 1 to 3. Different amounts of alkyl-sulfonic acids were added to this stock solu-tion prior to depositing the functional chromium layers.
Example 1 (comparative) The alkyl-sulfonic acid was methane-disulfonic acid disodium salt added to the stock solution in a concentration of 2 to 12 g/I (7.6 to 45.4 mmo1/1). This alkyl-sulfonic acid is disclosed in EP 0 452 471 B1.
Table 1 summarizes the average number of micro-cracks determined at differ-ent concentrations of methane-disulfonic acid disodium salt as the sole alkyl-sulfonic acid (plating bath temperature: 58 C, current density: 50 A/dm2).
8 Catalyst concentration Current efficiency (%) Average number of mi-(mmo1/1) cro-cracks (crack/cm) 7.6 24.6 600 15.2 24.3 820 22.7 22.2 820 30.3 19.7 660 37.9 20.3 530 45.4 18.9 440 A high number of desired micro-cracks is only obtained when a narrow concen-tration range of the catalyst methane-disulfonic acid disodium salt is used in the stock solution.
Table 2 summarizes the average number of micro-cracks determined at differ-ent current densities for an electroplating bath composition with 18.9 mmo1/1 (5 g/1) methane-disulfonic acid disodium salt as the sole alkyl-sulfonic acid.
Current density Current efficiency Average number of micro-cracks (A/d m2) (%) (crack/cm) 30 21.7 730 40 23.7 660 50 24.4 630 60 25.3 620 70 25.9 580 The number of desired micro-cracks is declining with increased current density.
Formation of undesired red rust was determined after 192 h of neutral salt spray test according to ISO 9227 NSS (>0.1 % of the surface area covered with red rust after 192 h).
Example 2 (comparative) The alkyl-sulfonic acid was propane-1,2,3-trisulfonic acid trisodium salt added to the stock solution in a concentration of 14.3 mmo1/1 (5 g/l). This alkyl-disulfonic acid is disclosed in DE 43 05 732 A1.
Table 2 summarizes the average number of micro-cracks determined at differ-ent current densities for an electroplating bath composition with 18.9 mmo1/1 (5 g/1) methane-disulfonic acid disodium salt as the sole alkyl-sulfonic acid.
Current density Current efficiency Average number of micro-cracks (A/d m2) (%) (crack/cm) 30 21.7 730 40 23.7 660 50 24.4 630 60 25.3 620 70 25.9 580 The number of desired micro-cracks is declining with increased current density.
Formation of undesired red rust was determined after 192 h of neutral salt spray test according to ISO 9227 NSS (>0.1 % of the surface area covered with red rust after 192 h).
Example 2 (comparative) The alkyl-sulfonic acid was propane-1,2,3-trisulfonic acid trisodium salt added to the stock solution in a concentration of 14.3 mmo1/1 (5 g/l). This alkyl-disulfonic acid is disclosed in DE 43 05 732 A1.
9 The current efficiency at 50 A/dm2 and a plating bath temperature of 55 C is 17.4 % and the number of micro-cracks in the chromium layer deposited under these conditions is 160 cracks/cm.
Formation of undesired red rust was already determined after 24 h of neutral salt spray test according to ISO 9227 NSS (>0.1 % of the surface area covered with red rust after 24 h).
Example 3 (invention) The alkyl-sulfonic acid was methane-trisulfonic acid trisodium salt added to the stock solution in concentrations of 6.2 to 37.2 mmo1/1 (2 to 12 g/l).
Table 3 summarizes the average number of micro-cracks determined at differ-ent concentrations of methane-trisulfonic acid trisodium salt as the sole alkyl-sulfonic acid (plating bath temperature: 58 C, current density: 50 A/dm2).
Catalyst concentrationAverage number of mi-Current efficiency (%) (mmo1/1) cro-cracks (crack/cm) 6.2 23.6 270 12.4 24.5 670 18.6 24.3 950 24.8 23.7 1020 31.0 23.8 920 37.2 22.9 1020 Table 4 summarizes the average number of micro-cracks determined at differ-ent current densities for an electroplating bath composition with 24.8 mmo1/1 (8 g/l) methane-trisulfonic acid trisodium salt as the sole alkyl-sulfonic acid.
Current density Current efficiency Average number of micro-cracks (A/dm2) (%) (crack/cm) 30 19.4 810 40 23.2 780 50 24.8 860 60 26.0 850 70 27.2 840 A high number of desired micro-cracks was obtained in the whole current densi-ty range applied.
Formation of undesired red rust was not determined until 552 h of neutral salt spray test according to ISO 9227 NSS.
Formation of undesired red rust was already determined after 24 h of neutral salt spray test according to ISO 9227 NSS (>0.1 % of the surface area covered with red rust after 24 h).
Example 3 (invention) The alkyl-sulfonic acid was methane-trisulfonic acid trisodium salt added to the stock solution in concentrations of 6.2 to 37.2 mmo1/1 (2 to 12 g/l).
Table 3 summarizes the average number of micro-cracks determined at differ-ent concentrations of methane-trisulfonic acid trisodium salt as the sole alkyl-sulfonic acid (plating bath temperature: 58 C, current density: 50 A/dm2).
Catalyst concentrationAverage number of mi-Current efficiency (%) (mmo1/1) cro-cracks (crack/cm) 6.2 23.6 270 12.4 24.5 670 18.6 24.3 950 24.8 23.7 1020 31.0 23.8 920 37.2 22.9 1020 Table 4 summarizes the average number of micro-cracks determined at differ-ent current densities for an electroplating bath composition with 24.8 mmo1/1 (8 g/l) methane-trisulfonic acid trisodium salt as the sole alkyl-sulfonic acid.
Current density Current efficiency Average number of micro-cracks (A/dm2) (%) (crack/cm) 30 19.4 810 40 23.2 780 50 24.8 860 60 26.0 850 70 27.2 840 A high number of desired micro-cracks was obtained in the whole current densi-ty range applied.
Formation of undesired red rust was not determined until 552 h of neutral salt spray test according to ISO 9227 NSS.
Claims (15)
1. An aqueous electroplating bath for depositing a functional chromium layer, comprising (i) a source for chromium(VI) ions, (ii) a source for sulfate ions and (iii) methane-trisulfonic acid or a salt thereof.
2. The aqueous electroplating bath for depositing a functional chromium layer according to claim 1 wherein the concentration of chromium(VI) ions ranges from 80 to 600 g/l.
3. The aqueous electroplating bath for depositing a functional chromium layer according to claim 1 or claim 2 wherein the concentration of sulfate ions ranges from 1 to 15 g/l
4. The aqueous electroplating bath for depositing a functional chromium layer according to any one of claims 1 to 3 wherein the salt of methane-trisulfonic acid is selected from sodium, potassium and ammonium salts.
5. The aqueous electroplating bath for depositing a functional chromium layer according to any one of claims 1 to 4 wherein the concentration of methane-trisulfonic acid or a salt thereof ranges from 2 to 80 mmol/l.
6. The aqueous electroplating bath for depositing a functional chromium layer according to any one of claims 1 to 5 wherein the aqueous electro-plating bath further comprises one or more other alkyl-sulfonic acids se-lected from the group consisting of methane-sulfonic acid, methane-disulfonic acid, ethane-sulfonic acid, 1,2-ethane-disulfonic acid, propyl sulfonic acid, 1,2-propane-disulfonic acid, 1,3-propane-disulfonic acid and 1,2,3-propane-trisulfonic acid
7. The aqueous electroplating bath for depositing a functional chromium layer according to any one of claims 1 to 6 wherein the aqueous electro-plating bath further comprises a surface active agent which is selected from the group consisting of perfluorinated sulfonate tenisdes, perfluori-nated phosphate tensides, perfluorinated phosphonate tensides, partially fluorinated sulfonate tensides, partially fluorinated phosphate tensides, partially fluorinated phosphonate tensides and mixtures thereof.
8. The aqueous electroplating bath for depositing a functional chromium layer according to claim 7 wherein the concentration of the surface active agent ranges from 0.05 to 4 g/l.
9. A process for depositing a functional chromium layer onto a metallic sub-strate comprising, in this order, the steps of (i) providing a metallic substrate, (ii) contacting said substrate with the aqueous electroplating bath ac-cording to any one of claims 1 to 8 and (iii) applying an external current to said substrate as a cathode and thereby depositing a functional chromium layer onto said sub-strate.
10.The process for depositing a functional chromium layer onto a metallic substrate according to claim 9 wherein the aqueous electroplating bath is held at a temperature in the range of 10 to 80 °C during use.
11.The process for depositing a functional chromium layer onto a metallic substrate according to claim 9 or claim 10 wherein a current density in the range of 10 to 250 A/dm2 is applied to the metallic substrate during use.
12 The process for depositing a functional chromium layer onto a metallic substrate according to any one of claims 9 to 11 wherein an inert anode is used in step (iii).
13.The process for depositing a functional chromium layer onto a metallic substrate according to claim 12 wherein the inert anode has a surface selected from the group consisting of platinum metal, iridium oxide and mixtures thereof.
14.The process for depositing a functional chromium layer onto a metallic substrate according to claim 12 or claim 13 wherein the aqueous electro-plating bath further comprises cations of an additional metal selected from the group consisting of silver, lead and mixtures thereof.
15. The process for depositing a functional chromium layer onto a metallic substrate according to claim 14 wherein the concentration of the cations of an additional metal ranges from 0.005 to 5 g/l.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP13164188.8 | 2013-04-17 | ||
| EP13164188.8A EP2792770B1 (en) | 2013-04-17 | 2013-04-17 | Functional chromium layer with improved corrosion resistance |
| PCT/EP2014/051251 WO2014170037A1 (en) | 2013-04-17 | 2014-01-22 | Functional chromium layer with improved corrosion resistance |
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| CA2908478A1 CA2908478A1 (en) | 2014-10-23 |
| CA2908478C true CA2908478C (en) | 2020-12-15 |
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| US (1) | US20160024674A1 (en) |
| EP (1) | EP2792770B1 (en) |
| JP (1) | JP6388913B2 (en) |
| KR (1) | KR102194114B1 (en) |
| CN (1) | CN105102686B (en) |
| CA (1) | CA2908478C (en) |
| ES (1) | ES2546007T3 (en) |
| PL (1) | PL2792770T3 (en) |
| TW (1) | TWI645078B (en) |
| WO (1) | WO2014170037A1 (en) |
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| KR101646160B1 (en) * | 2015-11-13 | 2016-08-08 | (주)에스에이치팩 | Chrome plating solution having excellent corrosion resistance |
| KR102012726B1 (en) * | 2018-12-06 | 2019-08-21 | 주식회사 에이엔씨코리아 | Hexavalent Chrome Plating Solution And Crack Free Pulse-Reverse Electroplating Method Using of The Same |
Family Cites Families (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1589988A (en) * | 1924-11-11 | 1926-06-22 | Chromium Products Corp | Chromium plating |
| US2195409A (en) | 1936-07-31 | 1940-04-02 | Nat Aniline & Chem Co Inc | Electrodeposition |
| JPS5161492A (en) * | 1974-11-27 | 1976-05-28 | Hishe Kagaku Kk | Kafuruorokashibozokukagobutsuno suiyokakaizenhoho |
| DE3402554A1 (en) | 1984-01-26 | 1985-08-08 | LPW-Chemie GmbH, 4040 Neuss | DEPOSITION OF HARD CHROME ON A METAL ALLOY FROM AN AQUEOUS ELECTROLYTE CONTAINING CHROME ACID AND SULFURIC ACID |
| JPS6179796A (en) * | 1984-09-26 | 1986-04-23 | Kiyoteru Takayasu | Method for electrodepositing chromium |
| US4588481A (en) * | 1985-03-26 | 1986-05-13 | M&T Chemicals Inc. | Chromium plating bath for producing non-iridescent, adherent, bright chromium deposits at high efficiencies and substantially free of cathodic low current density etching |
| JPH0347985A (en) * | 1989-07-13 | 1991-02-28 | Nippon M & T Kk | Chromium plating method |
| CA2054201C (en) | 1989-11-06 | 2000-04-11 | Kenneth Russ Newby | Protection of lead-containing anodes during chromium electroplating |
| US5453175A (en) * | 1989-11-06 | 1995-09-26 | Elf Atochem N. A., Inc. | Protection of lead-containing anodes during chromium electroplating |
| DE4305732A1 (en) | 1993-02-22 | 1994-09-22 | Trinova Chemie Gmbh | Electroplating chromium bath, and method for hard chromium plating with high current efficiencies |
| JP4299253B2 (en) * | 2004-10-08 | 2009-07-22 | ダイソー株式会社 | Hexavalent chromium plating method |
| DE102009013380A1 (en) * | 2009-03-09 | 2010-09-16 | Hansgrohe Ag | Process for the decomposition of partially fluorinated and perfluorinated surfactants |
| JP2011063839A (en) * | 2009-09-16 | 2011-03-31 | Mazda Motor Corp | Sliding member |
-
2013
- 2013-04-17 EP EP13164188.8A patent/EP2792770B1/en active Active
- 2013-04-17 PL PL13164188T patent/PL2792770T3/en unknown
- 2013-04-17 ES ES13164188.8T patent/ES2546007T3/en active Active
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- 2014-01-22 JP JP2016508048A patent/JP6388913B2/en active Active
- 2014-01-22 WO PCT/EP2014/051251 patent/WO2014170037A1/en active Application Filing
- 2014-01-22 US US14/765,609 patent/US20160024674A1/en not_active Abandoned
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| KR102194114B1 (en) | 2020-12-23 |
| ES2546007T3 (en) | 2015-09-17 |
| EP2792770A1 (en) | 2014-10-22 |
| CN105102686A (en) | 2015-11-25 |
| EP2792770B1 (en) | 2015-06-24 |
| JP6388913B2 (en) | 2018-09-12 |
| US20160024674A1 (en) | 2016-01-28 |
| KR20150140653A (en) | 2015-12-16 |
| WO2014170037A1 (en) | 2014-10-23 |
| JP2016519219A (en) | 2016-06-30 |
| TWI645078B (en) | 2018-12-21 |
| CN105102686B (en) | 2017-03-08 |
| CA2908478A1 (en) | 2014-10-23 |
| PL2792770T3 (en) | 2015-11-30 |
| TW201500597A (en) | 2015-01-01 |
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