US20100155256A1 - Electroplating Process for Using Trivalent Chromium Electroplating Solution - Google Patents
Electroplating Process for Using Trivalent Chromium Electroplating Solution Download PDFInfo
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- US20100155256A1 US20100155256A1 US12/704,137 US70413710A US2010155256A1 US 20100155256 A1 US20100155256 A1 US 20100155256A1 US 70413710 A US70413710 A US 70413710A US 2010155256 A1 US2010155256 A1 US 2010155256A1
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- trivalent chromium
- electroplating
- workpiece
- chromium
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- 238000009713 electroplating Methods 0.000 title claims abstract description 81
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 72
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 72
- 239000011651 chromium Substances 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 24
- 150000001844 chromium Chemical class 0.000 claims abstract description 15
- 239000000243 solution Substances 0.000 claims description 30
- 150000003839 salts Chemical class 0.000 claims description 19
- 239000000203 mixture Substances 0.000 claims description 12
- 239000000654 additive Substances 0.000 claims description 9
- 230000000996 additive effect Effects 0.000 claims description 9
- 239000003795 chemical substances by application Substances 0.000 claims description 9
- IOLCXVTUBQKXJR-UHFFFAOYSA-M potassium bromide Chemical compound [K+].[Br-] IOLCXVTUBQKXJR-UHFFFAOYSA-M 0.000 claims description 8
- JHJLBTNAGRQEKS-UHFFFAOYSA-M sodium bromide Chemical compound [Na+].[Br-] JHJLBTNAGRQEKS-UHFFFAOYSA-M 0.000 claims description 8
- 150000004677 hydrates Chemical class 0.000 claims description 7
- 239000006172 buffering agent Substances 0.000 claims description 6
- 229910021555 Chromium Chloride Inorganic materials 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 4
- SWLVFNYSXGMGBS-UHFFFAOYSA-N ammonium bromide Chemical compound [NH4+].[Br-] SWLVFNYSXGMGBS-UHFFFAOYSA-N 0.000 claims description 4
- QSWDMMVNRMROPK-UHFFFAOYSA-K chromium(3+) trichloride Chemical compound [Cl-].[Cl-].[Cl-].[Cr+3] QSWDMMVNRMROPK-UHFFFAOYSA-K 0.000 claims 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 claims description 4
- 239000013527 degreasing agent Substances 0.000 claims description 4
- 238000005237 degreasing agent Methods 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 4
- 230000003213 activating effect Effects 0.000 claims description 3
- 238000005238 degreasing Methods 0.000 claims description 3
- 238000005406 washing Methods 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- 239000012670 alkaline solution Substances 0.000 claims description 2
- 230000005611 electricity Effects 0.000 claims description 2
- 229910002804 graphite Inorganic materials 0.000 claims description 2
- 239000010439 graphite Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- 239000007800 oxidant agent Substances 0.000 claims description 2
- 230000001590 oxidative effect Effects 0.000 claims description 2
- 229910052697 platinum Inorganic materials 0.000 claims description 2
- 229910001220 stainless steel Inorganic materials 0.000 claims description 2
- 239000010935 stainless steel Substances 0.000 claims description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims 2
- 238000004381 surface treatment Methods 0.000 claims 1
- 229910052719 titanium Inorganic materials 0.000 claims 1
- 239000010936 titanium Substances 0.000 claims 1
- 231100000331 toxic Toxicity 0.000 abstract description 8
- 230000002588 toxic effect Effects 0.000 abstract description 8
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 abstract description 3
- 239000011247 coating layer Substances 0.000 abstract description 2
- 235000002639 sodium chloride Nutrition 0.000 description 20
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 14
- 235000013877 carbamide Nutrition 0.000 description 7
- 239000004202 carbamide Substances 0.000 description 7
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 6
- 229910001430 chromium ion Inorganic materials 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- AEMRFAOFKBGASW-UHFFFAOYSA-N Glycolic acid Chemical compound OCC(O)=O AEMRFAOFKBGASW-UHFFFAOYSA-N 0.000 description 4
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 4
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 4
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 description 4
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 3
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 3
- 235000019253 formic acid Nutrition 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 238000007747 plating Methods 0.000 description 3
- 238000004626 scanning electron microscopy Methods 0.000 description 3
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 2
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 2
- 235000011130 ammonium sulphate Nutrition 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 2
- 239000004327 boric acid Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- GICLSALZHXCILJ-UHFFFAOYSA-N ctk5a5089 Chemical compound NCC(O)=O.NCC(O)=O GICLSALZHXCILJ-UHFFFAOYSA-N 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 229960004275 glycolic acid Drugs 0.000 description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 description 2
- 235000011147 magnesium chloride Nutrition 0.000 description 2
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 2
- 235000019341 magnesium sulphate Nutrition 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000001103 potassium chloride Substances 0.000 description 2
- 235000011164 potassium chloride Nutrition 0.000 description 2
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 2
- 229910052939 potassium sulfate Inorganic materials 0.000 description 2
- 235000011151 potassium sulphates Nutrition 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 239000004471 Glycine Substances 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910001315 Tool steel Inorganic materials 0.000 description 1
- OJMOMXZKOWKUTA-UHFFFAOYSA-N aluminum;borate Chemical compound [Al+3].[O-]B([O-])[O-] OJMOMXZKOWKUTA-UHFFFAOYSA-N 0.000 description 1
- 230000003139 buffering effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229960002449 glycine Drugs 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
Images
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
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
Definitions
- the present invention relates to an electroplating bath contained with low toxic trivalent chromium ions to obtain chromium deposit through electroplating.
- the chromium deposit is commonly used in industrial applications.
- the chromium deposit is mainly obtained from the plating bath containing hexavalent chromium ion which is highly toxic in nature.
- the plating bath with low toxic trivalent chromium ions could be a suitable alternative electroplating method for obtaining chromium deposit.
- lack of stability and difficult to obtain thick chromium deposit are presently the main drawbacks for trivalent chromium electroplating.
- a stable trivalent chromium electroplating bath and its electroplating process will be stressed.
- the main objective of this invention is to provide a low toxic trivalent chromium electroplating bath, which can be used to achieve chromium deposit by electroplating with high current efficiency and high electroplating current density; meanwhile, an electroplating process for using the trivalent chromium electroplating solution is provided.
- the trivalent chromium electroplating bath comprises an aqueous solution added with trivalent chromium salt, a complex agent, conductive salt, a buffering agent, and an additive, wherein the additive is a mixture of ammonium bromide, sodium bromide, and potassium bromide.
- the electroplating process comprises the steps of: (a) degreasing the workpiece; (b) washing the workpiece; (c) surface activating to enhance the binding ability between the surface and workpiece; (d) trivalent chromium electroplating on the workpiece; and (e) post drying.
- FIG. 1 demonstrates the flow chart of an electroplating process using the trivalent chromium electroplating solution in accordance with the present invention
- FIG. 2 shows a SEM (Scanning Electron Microscopy) micrograph of a chromium layer on steel surface by using above-mentioned electroplating process with the trivalent chromium electroplating solution;
- FIG. 3 is an EDS (Energy Dispersive X-ray Spectrometer) spectrum of the chromium layer obtained from the electroplating process with the trivalent chromium electroplating bath;
- FIG. 4 is a SEM micrograph of cross-sectional chromium layer obtained from the electroplating process with the trivalent chromium electroplating solution.
- FIG. 5 presents the figure showing the current efficiency of the trivalent chromium electroplating at different temperatures and electroplating current densities.
- a trivalent chromium electroplating solution in accordance with the present invention contains at least one trivalent chromium salt for electroplating a chromium deposit on a workpiece.
- electroplating is conducted with the bath containing low toxic trivalent chromium ions to substitute the bath with highly toxic hexavalent chromium ions. Therefore, the electroplating process of the present trivalent chromium electroplating bath is an environmental friendly method.
- chromium coating is widely used for surface finish of precision mechanical parts, moulds, and surgical tools. According to the thickness, two types of chromium deposits could be classified. The first type is decorative chromium deposit and the other type is hard chromium deposit.
- the decorative chromium deposit usually has a thickness of about 0.1-0.5 ⁇ m.
- the decorative chromium is mainly used for decoration and protection because of its varnish appearance.
- the hard chromium deposit has a thickness higher than 1 ⁇ m and is used for wear and corrosion resistance.
- the trivalent chromium electroplating bath and its electroplating process in the present invention can be applied to obtain both the decorative and hard chromium deposits through electroplating.
- the trivalent chromium electroplating solution substantially comprises:
- trivalent chromium salt 0.2-1.4 mole/L of trivalent chromium salt that is selected from the group consisting of chromium chloride, chromium sulfate and hydrates of the foregoing components;
- (b) complex agent 0.2-4.2 mole/L of the complex agent that is selected from the group consisting of urea (carbamide), glycine (aminoacetic acid), hydroxyacetic acid, formic acid, dissoluble salts of acids, and dissoluble salts of urea;
- conductive salt 1.0-3.0 mole/L of the conductive salt component that is a mixture having at least two components selected from the group consisting of ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate;
- buffering agent 0.1-0.8 mole/L of the buffering agent that is selected from the group consisting of boric acid, aluminum chloride, aluminum sulfate, and hydrates of foregoing components; and
- (e) additive 0.01-0.25 mole/L of the additive that is selected from the group consisting of ammonium bromide, sodium bromide, potassium bromide, and a mixture of the foregoing components.
- compositions of the trivalent chromium electroplating solution in number of 6, 8, 10, 12, 15, 18, 21 and 24 in the table are mostly preferred.
- an electroplating process is demonstrated and adopted to electroplate a chromium deposit on a workpiece, for example harden high-carbon tool steel, by using the trivalent chromium electroplating solution in the present invention.
- the electroplating process comprises steps of:
- the prepared workpiece is degreased with a degreasing agent to remove oil and dirt from its surface.
- the prepared workpiece is washed to remove the degreasing agent and to keep the surface clean.
- the workpiece is dipped into acid or alkaline solution to activate the surface by adding oxidant or providing electricity so as to enhance the binding efficiency between the surface of the workpiece and the chromium deposit.
- the workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution are set in a cell tank. A fixed current is applied across the workpiece and the auxiliary electrodes by an additional power supply to start electroplating operation. No extra membrane, for example Nafion, is necessary to separate electroplating solutions between cathode and anode.
- the auxiliary electrodes are made of material selected from the group comprising with the platinized Ti mesh or plate, platinum, graphite and stainless steel.
- the fixed current provided by the additional power supply has a range from 5 to 95 ampere per square decimeter.
- the temperature for the trivalent chromium electroplating on the workpiece is in the range of 1 to 60° C.
- FIG. 1 a preferred flowchart of an electroplating process to achieve the trivalent chromium deposit is shown.
- the workpiece is prepared ( 10 ), degreased ( 11 ) and washed ( 12 ) to make its surface clean. Then, the surface of the workpiece is activated ( 13 ) and washed ( 14 ) again. After inputting the workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution into a tank, electroplating is mechanically stirred ( 15 ).
- the ions of chromium complex By applying a fixed current from an additional power supply, the ions of chromium complex obtain electrons to reduce and deposit on the surface of the workpiece so that the workpiece obtains a uniform chromium deposit. After electroplating, the workpiece is washed ( 16 ) again and dried ( 17 ) to obtain the final product.
- the final product is observed by Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray Spectrometer (EDS) to exam the surface and a cross-section of the deposited workpiece. According to those figures, the workpiece indeed obtains a uniform chromium deposit on the surface thereof.
- SEM Scanning Electronic Microscopy
- EDS Energy Dispersive X-ray Spectrometer
- the graph shows that deposition rate of the chromium coating layer is influenced by the temperature and the plating current density.
- the trivalent chromium electroplating bath is an aqueous solution added with a trivalent chromium salt, a complex agent, a conductive salt, a buffering agent, and an additive, wherein the additive is a mixture of ammonium bromide, sodium bromide or potassium bromide.
- the additive is of 0.01 to 0.25 mole/L in the trivalent chromium electroplating solution.
- the buffering agent is selected from the group consisting of boric acid, aluminum salt, dissolvable salt of foregoing components, a mixture of at least two of the foregoing components, and the dissolvable salt.
- boric acid and/or the dissolvable salt are of 0.1-0.8 mole/L in the trivalent chromium electroplating solution.
- the aluminum salt is selected from the group consisting of aluminum chloride, aluminum sulfate, and hydrates of the foregoing components.
- the aluminum salt and/or the hydrates of the aluminum salt are of 0.1-0.6 mole/L in the trivalent chromium electroplating solution.
- the complex agent is selected from the group consisting of urea (carbamide), glycine (aminoacetic acid), formic acid, dissoluble salts of urea, and dissoluble salts of acids.
- urea and/or its dissoluble salt are of 0.2-4.2 mole/L in the trivalent chromium electroplating solution.
- glycine and/or its dissoluble salt are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution.
- hydroxyacetic acid and/or its dissoluble salt are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution.
- formic acid and/or its dissoluble salt are of 0.1-1.4 mole/L in the trivalent chromium electroplating solution.
- the conductive salt composition is a mixture having at least two components selected from the group consisting of ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate.
- the conductive salt composition is of 1.0-3.0 mole/L in the trivalent chromium electroplating solution.
- the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components.
- the trivalent chromium salt and/or its hydrate are of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.
Abstract
A trivalent chromium electroplating solution in accordance with the present invention contains at least one trivalent chromium salt for electroplating a chromium coating layer on a workpiece. By using the low toxic trivalent chromium to substitute highly toxic hexavalent chromium, an electroplating process of the present trivalent chromium electroplating solution has less pollution.
Description
- The present application is a division of U.S. patent application Ser. No. 11/654,265, filed on Jan. 17, 2007, titled Trivalent Chromium Electroplating Solution and an Electroplating Process with the Solution, listing Ching-An Huang, Chun-Ching Hsu and Ui-Wei Leu as inventors.
- 1. Field of the Invention
- The present invention relates to an electroplating bath contained with low toxic trivalent chromium ions to obtain chromium deposit through electroplating.
- 2. Description of the Prior Art
- Because of high hardness, excellent wear and oxidation resistance, the chromium deposit is commonly used in industrial applications. Nowadays, the chromium deposit is mainly obtained from the plating bath containing hexavalent chromium ion which is highly toxic in nature. Thus, to develop alternative surface coatings for replacement of hard and decorative chromium deposits has been much attracted in recent years. The plating bath with low toxic trivalent chromium ions could be a suitable alternative electroplating method for obtaining chromium deposit. However, lack of stability and difficult to obtain thick chromium deposit are presently the main drawbacks for trivalent chromium electroplating. In this invention, a stable trivalent chromium electroplating bath and its electroplating process will be stressed.
- The main objective of this invention is to provide a low toxic trivalent chromium electroplating bath, which can be used to achieve chromium deposit by electroplating with high current efficiency and high electroplating current density; meanwhile, an electroplating process for using the trivalent chromium electroplating solution is provided.
- To achieve foregoing main objective, the trivalent chromium electroplating bath comprises an aqueous solution added with trivalent chromium salt, a complex agent, conductive salt, a buffering agent, and an additive, wherein the additive is a mixture of ammonium bromide, sodium bromide, and potassium bromide.
- The electroplating process comprises the steps of: (a) degreasing the workpiece; (b) washing the workpiece; (c) surface activating to enhance the binding ability between the surface and workpiece; (d) trivalent chromium electroplating on the workpiece; and (e) post drying.
- Benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.
-
FIG. 1 demonstrates the flow chart of an electroplating process using the trivalent chromium electroplating solution in accordance with the present invention; -
FIG. 2 shows a SEM (Scanning Electron Microscopy) micrograph of a chromium layer on steel surface by using above-mentioned electroplating process with the trivalent chromium electroplating solution; -
FIG. 3 is an EDS (Energy Dispersive X-ray Spectrometer) spectrum of the chromium layer obtained from the electroplating process with the trivalent chromium electroplating bath; -
FIG. 4 is a SEM micrograph of cross-sectional chromium layer obtained from the electroplating process with the trivalent chromium electroplating solution; and -
FIG. 5 presents the figure showing the current efficiency of the trivalent chromium electroplating at different temperatures and electroplating current densities. - A trivalent chromium electroplating solution in accordance with the present invention contains at least one trivalent chromium salt for electroplating a chromium deposit on a workpiece. To obtain the chromium deposit on a workpiece, electroplating is conducted with the bath containing low toxic trivalent chromium ions to substitute the bath with highly toxic hexavalent chromium ions. Therefore, the electroplating process of the present trivalent chromium electroplating bath is an environmental friendly method.
- Owing to its high hardness, superior oxidation and wear resistance, chromium coating is widely used for surface finish of precision mechanical parts, moulds, and surgical tools. According to the thickness, two types of chromium deposits could be classified. The first type is decorative chromium deposit and the other type is hard chromium deposit. The decorative chromium deposit usually has a thickness of about 0.1-0.5 μm. The decorative chromium is mainly used for decoration and protection because of its varnish appearance. The hard chromium deposit has a thickness higher than 1 μm and is used for wear and corrosion resistance. The trivalent chromium electroplating bath and its electroplating process in the present invention can be applied to obtain both the decorative and hard chromium deposits through electroplating.
- The trivalent chromium electroplating solution substantially comprises:
- (a) trivalent chromium salt: 0.2-1.4 mole/L of trivalent chromium salt that is selected from the group consisting of chromium chloride, chromium sulfate and hydrates of the foregoing components;
- (b) complex agent: 0.2-4.2 mole/L of the complex agent that is selected from the group consisting of urea (carbamide), glycine (aminoacetic acid), hydroxyacetic acid, formic acid, dissoluble salts of acids, and dissoluble salts of urea;
- (c) conductive salt: 1.0-3.0 mole/L of the conductive salt component that is a mixture having at least two components selected from the group consisting of ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate;
- (d) buffering agent: 0.1-0.8 mole/L of the buffering agent that is selected from the group consisting of boric acid, aluminum chloride, aluminum sulfate, and hydrates of foregoing components; and
- (e) additive: 0.01-0.25 mole/L of the additive that is selected from the group consisting of ammonium bromide, sodium bromide, potassium bromide, and a mixture of the foregoing components.
- According to above description, some preferred compositions of the trivalent chromium electroplating solution are shown in the following table:
-
component Complex Conductive salt Buffering Num. Cr+3 agent composition agent Addative 1 1.2 mole/L 4.8 mole/L 1.5 mole/L 0.8 mole/L 0.3 mole/ L 2 0.1 mole/L 0.4 mole/L 1.0 mole/L 0.4 mole/L 0.05 mole/ L 3 0.2 mole/L 2.4 mole/L 2.0 mole/L 0.6 mole/L 0.25 mole/ L 4 0.8 mole/L 0.4 mole/L 1.0 mole/L 0.5 mole/L 0.05 mole/L 5 0.6 mole/L 4.0 mole/L 1.2 mole/L 0.8 mole/L 0.2 mole/ L 6 0.8 mole/L 2.4 mole/L 1.5 mole/L 0.8 mole/L 0.1 mole/L 7 1.1 mole/L 3.8 mole/L 2.4 mole/L 0.8 mole/L 0.3 mole/L 8 0.6 mole/L 1.2 mole/L 1.2 mole/L 0.6 mole/L 0.05 mole/ L 9 0.5 mole/L 2.4 mole/L 1.8 mole/L 0.8 mole/L 0.1 mole/ L 10 1.0 mole/L 1.8 mole/L 1.5 mole/L 0.6 mole/L 0.2 mole/ L 11 0.9 mole/L 0.5 mole/L 0.8 mole/L 0.4 mole/L 0.15 mole/ L 12 0.4 mole/L 0.8 mole/L 1.2 mole/L 0.7 mole/L 0.05 mole/ L 13 1.6 mole/L 5.4 mole/L 1.2 mole/L 0.8 mole/L 0.3 mole/ L 14 0.7 mole/L 2.4 mole/L 0.8 mole/L 0.3 mole/L 0.15 mole/ L 15 0.5 mole/L 1.05 mole/L 1.0 mole/L 0.8 mole/L 0.1 mole/ L 16 1.4 mole/L 4.2 mole/L 3.0 mole/L 0.8 mole/L 0.2 mole/ L 17 0.6 mole/L 3.6 mole/L 2.1 mole/L 0.8 mole/L 0.1 mole/L 18 0.3 mole/L 0.6 mole/L 1.5 mole/L 0.7 mole/L 0.05 mole/L 19 1.5 mole/L 1.5 mole/L 1.5 mole/L 0.8 mole/L 0.1 mole/ L 20 1.1 mole/L 3.0 mole/L 2.4 mole/L 0.7 mole/L 0.25 mole/L 21 0.7 mole/L 1.8 mole/L 1.8 mole/L 0.8 mole/L 0.15 mole/L 22 1.3 mole/L 0.8 mole/L 1.0 mole/L 0.5 mole/L 0.25 mole/L 23 0.4 mole/L 2.4 mole/L 1.8 mole/L 0.6 mole/L 0.1 mole/L 24 0.9 mole/L 1.35 mole/L 1.2 mole/L 0.8 mole/L 0.15 mole/L 25 1.0 mole/L 4.0 mole/L 2.4 mole/L 0.6 mole/L 0.1 mole/L - Compositions of the trivalent chromium electroplating solution in number of 6, 8, 10, 12, 15, 18, 21 and 24 in the table are mostly preferred.
- With reference to
FIG. 1 , an electroplating process is demonstrated and adopted to electroplate a chromium deposit on a workpiece, for example harden high-carbon tool steel, by using the trivalent chromium electroplating solution in the present invention. The electroplating process comprises steps of: - (a). degreasing:
- The prepared workpiece is degreased with a degreasing agent to remove oil and dirt from its surface.
- (b). washing:
- The prepared workpiece is washed to remove the degreasing agent and to keep the surface clean.
- (c) surface activating:
- The workpiece is dipped into acid or alkaline solution to activate the surface by adding oxidant or providing electricity so as to enhance the binding efficiency between the surface of the workpiece and the chromium deposit.
- (d) trivalent chromium electroplating:
- The workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution are set in a cell tank. A fixed current is applied across the workpiece and the auxiliary electrodes by an additional power supply to start electroplating operation. No extra membrane, for example Nafion, is necessary to separate electroplating solutions between cathode and anode.
- (e) drying:
- After electroplating, residual electroplating solution is removed from the surface of the workpiece by clean agent dipping and hot-air blaster drying.
- Wherein, the auxiliary electrodes are made of material selected from the group comprising with the platinized Ti mesh or plate, platinum, graphite and stainless steel.
- Wherein, the fixed current provided by the additional power supply has a range from 5 to 95 ampere per square decimeter.
- Wherein, the temperature for the trivalent chromium electroplating on the workpiece is in the range of 1 to 60° C.
- As presented in
FIG. 1 , a preferred flowchart of an electroplating process to achieve the trivalent chromium deposit is shown. Before electroplating of trivalent chromium, the workpiece is prepared (10), degreased (11) and washed (12) to make its surface clean. Then, the surface of the workpiece is activated (13) and washed (14) again. After inputting the workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution into a tank, electroplating is mechanically stirred (15). By applying a fixed current from an additional power supply, the ions of chromium complex obtain electrons to reduce and deposit on the surface of the workpiece so that the workpiece obtains a uniform chromium deposit. After electroplating, the workpiece is washed (16) again and dried (17) to obtain the final product. - With reference to
FIGS. 2 , 3 and 4, the final product is observed by Scanning Electronic Microscopy (SEM) and Energy Dispersive X-ray Spectrometer (EDS) to exam the surface and a cross-section of the deposited workpiece. According to those figures, the workpiece indeed obtains a uniform chromium deposit on the surface thereof. - With reference to
FIG. 5 , the graph shows that deposition rate of the chromium coating layer is influenced by the temperature and the plating current density. - In summary, the trivalent chromium electroplating bath is an aqueous solution added with a trivalent chromium salt, a complex agent, a conductive salt, a buffering agent, and an additive, wherein the additive is a mixture of ammonium bromide, sodium bromide or potassium bromide.
- Wherein, the additive is of 0.01 to 0.25 mole/L in the trivalent chromium electroplating solution.
- Wherein, the buffering agent is selected from the group consisting of boric acid, aluminum salt, dissolvable salt of foregoing components, a mixture of at least two of the foregoing components, and the dissolvable salt.
- Wherein, boric acid and/or the dissolvable salt are of 0.1-0.8 mole/L in the trivalent chromium electroplating solution.
- Wherein, the aluminum salt is selected from the group consisting of aluminum chloride, aluminum sulfate, and hydrates of the foregoing components.
- Wherein, the aluminum salt and/or the hydrates of the aluminum salt are of 0.1-0.6 mole/L in the trivalent chromium electroplating solution.
- Wherein, the complex agent is selected from the group consisting of urea (carbamide), glycine (aminoacetic acid), formic acid, dissoluble salts of urea, and dissoluble salts of acids.
- Wherein, urea and/or its dissoluble salt are of 0.2-4.2 mole/L in the trivalent chromium electroplating solution.
- Wherein, glycine and/or its dissoluble salt are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution.
- Wherein, hydroxyacetic acid and/or its dissoluble salt are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution.
- Wherein, formic acid and/or its dissoluble salt are of 0.1-1.4 mole/L in the trivalent chromium electroplating solution.
- Wherein, the conductive salt composition is a mixture having at least two components selected from the group consisting of ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate.
- Wherein, the conductive salt composition is of 1.0-3.0 mole/L in the trivalent chromium electroplating solution.
- Wherein, the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components.
- Wherein, the trivalent chromium salt and/or its hydrate are of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.
- Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.
Claims (9)
1-12. (canceled)
13. An electroplating process for using a trivalent chromium electroplating solution comprising:
(a) degreasing, wherein a prepared workpiece is degreased with a degreasing agent to remove oil and dirt from the surface of the workpiece;
(b) washing, wherein the prepared workpiece is washed to remove the degreasing agent and to keep the cleaned surface of the workpiece;
(c) surface activating, wherein the workpiece is dipped into one of acid and alkaline solution to activate the surface by adding oxidant or providing electricity so as to enhance the binding efficiency of the surface of the workpiece;
(d) trivalent chromium electroplating, wherein the workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution are set in a tank and a fixed current is applied across between the workpiece and auxiliary electrodes by an additional power supply to start electroplating operation; and
(e) drying.
14. The electroplating process as claimed in claim 13 , wherein the auxiliary electrodes are made of material selected from the group comprising plantized titanium mesh, titanium plate, platinum, graphite, and stainless steel.
15. The electroplating process as claimed in claim 13 , wherein the fixed current provided by the additional power supply has a range from 5 to 95 ampere per square decimeter.
16. The operational method as claimed in claim 13 , wherein the temperature for a surface treatment of the workpiece is in a range of 1 to 60° C.
17. The electroplating process as claimed in claim 13 , wherein the trivalent chromium electroplating solution comprises an aqua solution added with trivalent chromium salt, a complex agent, conductive salt, a buffering agent, and an additive,
wherein the additive is a mixture of ammonium bromide, sodium bromide and potassium bromide.
18. The electroplating process as claimed in claim 17 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components; and
the trivalent chromium salt and a hydrate of the trivalent chromium salt are of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.
19-24. (canceled)
25. The electroplating process as claimed in claim 17 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components;
one of the trivalent chromium salt and a hydrate of the trivalent chromium salt is of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.
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US12/704,137 US20100155256A1 (en) | 2007-01-17 | 2010-02-11 | Electroplating Process for Using Trivalent Chromium Electroplating Solution |
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US11/654,265 US20080169199A1 (en) | 2007-01-17 | 2007-01-17 | Trivalent chromium electroplating solution and an electroplating process with the solution |
US12/704,137 US20100155256A1 (en) | 2007-01-17 | 2010-02-11 | Electroplating Process for Using Trivalent Chromium Electroplating Solution |
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ES2669050T3 (en) * | 2006-03-31 | 2018-05-23 | Atotech Deutschland Gmbh | Crystalline Chrome Deposit |
EP1970470B1 (en) * | 2007-03-05 | 2011-05-11 | ATOTECH Deutschland GmbH | Chrome(VI)-free black passivates for surfaces containing zinc |
JP5570423B2 (en) * | 2007-10-02 | 2014-08-13 | アトテック・ドイチュラント・ゲーエムベーハー | Crystalline chromium alloy deposits |
US9765437B2 (en) * | 2009-03-24 | 2017-09-19 | Roderick D. Herdman | Chromium alloy coating with enhanced resistance to corrosion in calcium chloride environments |
KR101198353B1 (en) * | 2010-07-29 | 2012-11-09 | 한국기계연구원 | Trivalent chromium plating solution and plating method using the same |
AT510422B1 (en) | 2010-11-04 | 2012-04-15 | Univ Wien Tech | METHOD FOR THE DEPOSITION OF HARTCHROM FROM CR (VI) - FREE ELECTROLYTES |
CN102766885B (en) * | 2012-08-09 | 2014-12-10 | 哈尔滨工业大学(威海) | Method for preparing high-purity chromium powder through electrochemical reduction of trivalent chromium by using ionic exchange membrane cell |
RU2660478C2 (en) * | 2012-11-21 | 2018-07-06 | Тата Стил Эймейден Б.В. | Chromium-chromium oxide coatings applied to steel substrates for packaging applications and method for producing said coatings |
EP2899299A1 (en) * | 2014-01-24 | 2015-07-29 | COVENTYA S.p.A. | Electroplating bath containing trivalent chromium and process for depositing chromium |
CO7190036A1 (en) * | 2014-02-11 | 2015-02-19 | Garcia Carlos Enrique Muñoz | Continuous trivalent chrome plating process |
JP6373185B2 (en) * | 2014-12-15 | 2018-08-15 | 株式会社Jcu | Trivalent chromium plating solution and trivalent chromium plating method |
GB2534883A (en) * | 2015-02-03 | 2016-08-10 | Univ Leicester | Electrolyte for electroplating |
CN107313078A (en) * | 2016-04-27 | 2017-11-03 | 中国科学院金属研究所 | A kind of trivalent chromium plating solution and preparation method thereof |
US20170314153A1 (en) * | 2016-05-02 | 2017-11-02 | The Boeing Company | Trivalent chromium plating formulations and processes |
CN107254693A (en) * | 2017-06-28 | 2017-10-17 | 合肥博之泰电子科技有限公司 | A kind of chromium electro-plating method of ornamental strip |
CN108456898B (en) * | 2018-06-25 | 2020-06-16 | 厦门大学 | Low-concentration sulfate trivalent chromium rapid chromium plating electroplating solution and preparation method thereof |
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