US3772167A - Electrodeposition of metals - Google Patents

Electrodeposition of metals Download PDF

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Publication number
US3772167A
US3772167A US00175771A US3772167DA US3772167A US 3772167 A US3772167 A US 3772167A US 00175771 A US00175771 A US 00175771A US 3772167D A US3772167D A US 3772167DA US 3772167 A US3772167 A US 3772167A
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percent
chromium
concentration
ions
water
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N Bharucha
J Ward
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • 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
    • 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

  • ABSTRACT The specification discloses an improved method and A 9 Claims, No Drawings ELECTRODEPOSKTKON F METALS This is a continuation-in-part of our copending applications Ser. Nos. 840,823 filed July 10, 1968 and 718,234 filed Apr. 2, 1968, both now abandoned. This invention is directed to the electrodeposition of metal coatings and to electrolyte solutions suitable for the depositions of metallic coatings.
  • Chrome nickel alloy coatings have excellent resistance to oxidation and corrosion.
  • Prior methods of applying such coatings have involved electrophoresis or cladding of a layer of the alloy to the metal object to be coated.
  • Methods for applying such coatings by electrodeposition have been put forward, but have not been satisfactory, due, as is the case with chromium plating, to the fact that, at the pH range at which nickel is readily deposited, chromic acid solutions do not readily deposit coherent chromium coatings and solutions of trivalent chromium evolve excessive amounts of hydrogen.
  • chromic acid solutions do not readily deposit coherent chromium coatings and solutions of trivalent chromium evolve excessive amounts of hydrogen.
  • the general object of this invention is to provide an improved process for the electrodeposition of metallic coatings and to provide improved plating baths for use in electroplating processes.
  • a particular object of the invention is to provide improved electrolyte solutions for the deposition of metallic coatings by electrolytic techniques.
  • a further object of the invention is to provide metallic coatings which are characterized by improved corrosion resistance.
  • Another object of the invention is to provide metallic coatings by a method characterized by improved current efficiency and throwing power.
  • a further object of the invention is to provide a method for the deposition of metallic coatings by an electrolytic process characterized by reduced hydrogen evolution at the cathode during deposition.
  • a still further object of the invention is to satisfy the need for chromium plating solutions capable of providing crack free deposits over a wide range of current densities and to provide chromium plating baths capable of depositing a suitable chromium deposit under conditions of adequate current efficiency, improved covering characteristics, and improved throwing power.
  • a still further object of the invention is to provide an electrolyte solution for the plating of chromium nickel alloy and nickel metallic coatings.
  • a still further object of the invention is to provide a method by which significantly improved coatings can be deposited upon articles of complex shape.
  • the instant invention is directed to the plating of any metal which can be electroplated or deposited from solution by passing an electric current through a solution containing ions of the metal to be deposited.
  • metals include chromium, manganese, iron, zinc, copper, lead, nickel, cobalt, tin, and cadmium. Chromium is of particular interest in view of its desirable appearance and high resistance to tarnish and corrosion under varied indoor and outdoor environmental conditions.
  • metallic deposits particularly chromium deposits, having greatly improved corrosion resistance and exhibiting a very good appearance
  • electrolytic techniques through the use of a plating bath containing chromium ions, particularly trivalent chromium ions, ammonium ions, halide ions and a homogeneous mixture of water and a dipolar organic solvent, the molecules of which contain a highly electronegative oxygen atom as hereinafter defined.
  • the plating baths of this invention comprise a homogeneous mixture of water and a dipolar organic solvent, preferably a dipolar aprotic organic solvent, ammonium ions, and halide ions in addition to the ions of the metal to be deposited.
  • a dipolar organic solvent preferably a dipolar aprotic organic solvent, ammonium ions, and halide ions in addition to the ions of the metal to be deposited.
  • the proportion of water in the electrolyte solvent can range from about 20 to about 60 percent by volume and the amount of organic solvent can range from about 40 to about percent by volume.
  • the preferred ratio of water to dipolar organic solvent is from 45 55 to about 55 45 by volume.
  • dipolar organic solvent refers to an organic liquid which is capable of dissolving a substantial amount of a salt of the metal to be deposited and which does not donate a substantial amount or quantity of hydrogen ions. it is to be understood that the solvent must permit ionization of the dissolved metal salts in the bath.
  • the dipolar organic molecule must contain at least one highly electronegative oxygen atom.
  • suitable dipolar organic solvents include dimethylsulphoxide and tetrahydrothiophen dioxide. The oxygen atoms of these materials are activated by the electron donating prop erties of the sulphur atoms.
  • a ketonic oxygen atom is not generally sufficiently electronegative to constitute a suitable dipolar organic solvent unless there is present an activating group adjacent to the carbon atom, for example, an amino group.
  • compounds such as tetramethylurea, tertiary butyl formamide, and compounds of the formula R,R N.OCR wherein R R and R may be the same or different members selected from the group consisting of hydrogen atoms, aryl groups, e.g., phenyl, or alkyl groups, preferably lower alkyl, are suitable.
  • Such solvents include dimethylformamide (DMF) and dimethylacetamide (DMAC). It will be appreciated that mixtures of several of the above-mentioned organic solvents may be employed.
  • dipolar organic solvents are the dipolar aprotic organic solvents.
  • aprotic solvents include dimethylsulphoxide, tetrahydrothiophen dioxide, tetramethylurea, dimethylacetamide and dimethylformamide.
  • dimethylformamide is especially convenient. Dirnethylformamide, in addition to possessing an excellent balance of physical, chemical, toxicological, and economic properties, has shown excellent electroplating properties. Dimethylformamide is characterized by a relatively wide liquid range, a boiling point of 150 C., a high dielectric constant of about 37.5, a low vapor pressure of about 3.6 millimeters of mercury at 25 C.
  • Dimethylforrnamide is also completely miscible with water in all proportions and has the ability to dissolve substantial amounts of metal salts, e.g., about 450 grams per liter of hexahydratecl chromium trichloride. Dimethylformamide also interacts with such salts to form stable complexes of the type CrCl .6DMF and CrCl .4DMF. It is important to note that because of the ability of the DMF to function as a complexing agent, no other complexing agent need be utilized.
  • the metal to be deposited can be conveniently incorporated in the plating bath in a form of a metal salt which is soluble in the water-organic solvent mixture.
  • Halide salts such as bromides, chlorides, or iodides, nitrates, acetates, formates, oxalates, and sulfates are suitable.
  • the bromides, chlorides, and iodides with their characteristic water of hydration are preferable due to the rather limited solubility of the acetates, for mates, oxalates, sulfates, and chrome alums in the dipolar solvents.
  • soiubility can be increased by the use of water concentra tions near the upper end of the ranges above mentioned.
  • the physical characteristics of the solution e.g., color, pH, and viscosity, have been found to change during storage and the color and adhesion of successive metal deposits from the same bath may deteriorate.
  • plating baths containing low concentrations of water have a relatively low conductivity, while solutions with higher concentration of water tend to evolve excessive amounts of hydrogen at the cathode during plating. it has been found that the presence of an ammonium salt improves the stability of the solution and reduces the tendency of the bath to evolve hydrogen at high water content.
  • ammonium salts have been found to significantly reduce the effect of changes in pl-l on the lower limiting plating current density.
  • the ammonium ion should be present at a concentration of at least about 0.2 molar and preferably from about 0.6 to about 1 molar.
  • Solutions containing over percent by volume of dimethylformamide provide limited solubility for ammonium salts. it is therefore necessary to provide sufficient water to dissolve the required amount of ammonium salt.
  • the use of about 20 percent by volume of added water and about 80 percent by volume of dimethylformamide allows solutions containing about 1 molar concentrations of ammonium ions to be prepared at 55 C.
  • the preferred proportion by volume of added water to dipolar organic compound is from 10 to 5G S0.
  • a prerequisite of successful chromium, chromium nickel, and nickel plating from a dipolar organic solvent is that the trivalent chromium and nickel ions shall form small moderately stable complexes with the solvent molecule. lf there is no complex formation, then the chromic and nickel salts are unlikely to be sufficiently soluble. If the complexes formed are excessively stable, then electrodeposition may be difficult. It is believed that the highly electronegative oxygen atoms which characterize the dipolar organic compounds of this invention may act as covalent links in the formation of complexes between the chromic ions and the organic molecules. Such solutions by themselves do not, however, give smooth coherent metallic deposits.
  • the addition of water probably generates the polynuclear olated and oxalated chromic species usually found in solutions of trivalent chromium compounds, which again do not readily give good chromium deposits.
  • the effect of the ammonium ion may be attributed to its structure-disordering properties simplifying the nature of the trivalent chromium and nickel species in solution, possibly with the formation of mononuclear Cr +DMF-H O complexes.
  • the water may be pre vented from showing its full protic tendencies by reason of the formation of complexes with the dipolar or ganic molecules.
  • the halogen ions may be partly solvated, although the ready evolution of chlorine at the anode indicates solvation is not complete.
  • the pH of the solution should be from i to 3.5 and preferably about 2. If the pH is too low, hydrogen tends to be evolved at the cathode in preference to chromium. if the pH is too high, basic chromium compounds are liable to precipitate out.
  • the pH can be adjusted by the use of hydrochloric acid or sodium hydroxide as required.
  • the current efficiency of the solution may be improved by the addition of boric acid, preferably to a concentration of at least OlM.
  • Boric acid is not normally soluble to the extent of more than about 0.2M.
  • electroplating baths of the present invention contain a sodium halide which has been found to increase the plating range and current efficiency.
  • Sodium halides are also beneficial in that they enhance the covering power of the bath. It is preferred that the sodium halide be present in a concentration of at least about 0.8 molar.
  • the concentration of chromium in the solution is not critical, and is preferably about from 0.8M to 1.3M, particularly about 1M.
  • Nickel ions should be present in the solution at a concentration of at least 0.05M, and a preferred concentration range is about 0.8M to 1.2M.
  • the invention also provides a method of electrodepositing a chromium nickel alloy, which method comprises providing a cathode in the solution described above, and an anode, and passing an electric current through the solution so as to deposit a chromium nickel alloy on the cathode.
  • Electroplating baths as described herein have useful current density ranges of from 0.5 to about 20 amperes per square decimeter, depending on the composition and temperature of the particular solution and on the desired composition of the deposited metal. Optimum current densities are generally within the range from about 6 to about amperes per square decimeter.
  • the useful plating current range for a particular plating solution varies with temperature, being larger at lower temperatures. Above about 30 C. narrower plating ranges are encountered.
  • the amount of organic solvent in the bath influences the plating range and the temperature at which optimum plating occurs. For example, a solution containing a high ratio of dimethylformamide to water provides suitable plating at temperatures of about 50 C. Preferred plating temperatures are in the range of 40 to 80 C.
  • the composition of the alloy deposited depends on the composition of the plating solution, on the temperature and on the plating current density. in general, the higher the current density, the greater is the percentage of chromium in the alloy deposited, and the lower the current density, the greater is the percentage of nickelin the alloy deposited. This may be due to the fact that the threshold current density for plating with the two separate metals differs.
  • the anode of the electroplating apparatus may be immersed in a chromium or chromium nickel solution, it is preferred that the anode be of graphite or titanium or of some other similar inert material.
  • the use of graphite anodes is disadvantageous because of the evolution of chlorine gas at the anode. Since chlorine is very soluble in some of the organic solvents, particularly dimethylformamide, large concentrations of chlorine can build up in the solution.
  • the use of a nickel chromium anode prevents chlorine formation, but the chromium may dissolve off as chromic acid which is liable to oxidize the DMF.
  • a suitable aqueous anolyte comprises a molar solution of ammonium or sodium acetate separated from the plating solution by a porous ceramic diaphragm.
  • EXAMPLE 1 Bright nickel plated copper cathodes were plated with chromium in a bath comprising 240 grams per liter of chromic chloride hexahydrate, 58 grams per liter of sodium chloride, 50 grams per liter ammonium chloride, and 8 grams per liter of boric acid, the solvent being a 50 percent by volume mixture of water and dimethylformamide (DMF).
  • the bath was operated at temperatures from to 30 C., a current density of from 1 to amperes per square decimeter, and a pH from 1 to 3. Current efficiencies of up to 50 percent M Li+ (1 M ammonium acetate anolyte) tam the relative concentrations of mckel and chro- 45 were achieved.
  • Plating range ratio 9.5.
  • the plating performance of a triva- 1O lent organic solution according to the invention is corn- EXAMPLE 32 pared with a conventional hexavalent aqueous bath.
  • DMAC Dimethylacetamide
  • Plating range LS-22.5 ajdm. Plating range ratio: 5
  • EXAMPLE 31 EXAMPLE 34 P 2 40 Percem DMF Solution 60
  • This solution yields a dark deposit containing, approximately 20 percent chromium, 80 percent nickel.
  • EXAMPLE 37 Composition Operating Conditions 1 M CrCl .6H O .0 40 l M NiCl .6H O Temperature 25C. 25 g/l Nl-LCl Current Density 100 A/Sq.ft.
  • EXAMPLE 39 The invention also encompasses electrolyte solutions for nickel plating.
  • electroforming applications e.g.,
  • An electrolyte solution for electrodeposition of a chromium-nickel alloy on a substrate comprising at least about 40 percent of an organic dipolar aprotic solvent selected from the group consisting of dimethylformamide, dimethylsulphoxide, dimethylacetamide, tetrahydrothiophen dioxide, propylene carbonate, tetramethyl urea, and hexamethyl phosphoramide, trivalent chromium ions in a concentration of at least about 0.8M, nickel ions in a concentration of at least about 0.05M, and at least about 20 percent water.
  • an organic dipolar aprotic solvent selected from the group consisting of dimethylformamide, dimethylsulphoxide, dimethylacetamide, tetrahydrothiophen dioxide, propylene carbonate, tetramethyl urea, and hexamethyl phosphoramide, trivalent chromium ions in a concentration of at least about 0.8M, nickel ions in a concentration of at least about 0.05M,
  • An electrolyte solution according to claim 1 containing at least 0.2M ammonium ions, and a complexing agent which consists essentially of said organic dipolar aprotic solvent.
  • An electrolyte solution according to claim 7 containing at least 0.8 M sodium chloride.
  • a method for electrodepositing a chromium-nickel alloy on a substrate which comprises immersing said substrate in an electrolyte solution comprising at least about 40 percent of a dipolar aprotic organic solvent selected from the group consisting of dimethylformamide, dimethylsulphoxide, dimethylacetamide, tetrahydrothiophen dioxide, propylene carbonate, tetramethyl urea, and hexamethyl phosphoramide, trivalent chromium ions in a concentration of at least about 0.8M, nickel ions in a concentration of at least about 0.05M, ammonium ions in a concentration of at least 0.2M, from about 20 percent to about 60 percent water, and a complexing agent which consists essentially of said dipolar aprotic solvent, the pH of the solution being from about 1 to about 3.5, said solution being free of other complexing agents, and passing an electric current through said solution thereby to deposit said metal ions on a substrate in the form of a metallic coating.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
US00175771A 1967-04-03 1971-08-27 Electrodeposition of metals Expired - Lifetime US3772167A (en)

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GB1523767 1967-04-03
GB3297668A GB1213556A (en) 1966-10-31 1968-07-10 Electrodeposition of chromium/nickel alloys

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184929A (en) * 1978-04-03 1980-01-22 Oxy Metal Industries Corporation Trivalent chromium plating bath composition and process
EP0040461A1 (en) * 1980-04-16 1981-11-25 Rolls-Royce Plc Electroplating of titanium and titanium alloy
US4376685A (en) * 1981-06-24 1983-03-15 M&T Chemicals Inc. Acid copper electroplating baths containing brightening and leveling additives
US4686017A (en) * 1981-11-05 1987-08-11 Union Oil Co. Of California Electrolytic bath and methods of use
US4755265A (en) * 1985-06-28 1988-07-05 Union Oil Company Of California Processes for the deposition or removal of metals
US4801511A (en) * 1985-06-28 1989-01-31 Union Oil Company Of California Battery cell electrolyte
US20220042195A1 (en) * 2019-08-09 2022-02-10 Changzhou University Method for preparing copper-based graphene/aluminum composite wire with high electrical conductivity

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB189822622A (en) * 1898-10-27 1899-10-27 Quintin Marino Improvements in or relating to Electrolytic Baths.
US2693444A (en) * 1951-02-12 1954-11-02 Battelle Development Corp Electrodeposition of chromium and alloys thereof
US3131134A (en) * 1961-08-03 1964-04-28 Grumman Aircraft Engineering C Electroplating from an organic electrolytic solution
US3336658A (en) * 1963-12-06 1967-08-22 Rca Corp Superconductive articles

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB189822622A (en) * 1898-10-27 1899-10-27 Quintin Marino Improvements in or relating to Electrolytic Baths.
US2693444A (en) * 1951-02-12 1954-11-02 Battelle Development Corp Electrodeposition of chromium and alloys thereof
US3131134A (en) * 1961-08-03 1964-04-28 Grumman Aircraft Engineering C Electroplating from an organic electrolytic solution
US3336658A (en) * 1963-12-06 1967-08-22 Rca Corp Superconductive articles

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
R. D. Blue et al., Trans. Electrochemical Soc., Vol. 43, pp. 231 238, (1933). *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4184929A (en) * 1978-04-03 1980-01-22 Oxy Metal Industries Corporation Trivalent chromium plating bath composition and process
EP0040461A1 (en) * 1980-04-16 1981-11-25 Rolls-Royce Plc Electroplating of titanium and titanium alloy
US4376685A (en) * 1981-06-24 1983-03-15 M&T Chemicals Inc. Acid copper electroplating baths containing brightening and leveling additives
US4686017A (en) * 1981-11-05 1987-08-11 Union Oil Co. Of California Electrolytic bath and methods of use
US4755265A (en) * 1985-06-28 1988-07-05 Union Oil Company Of California Processes for the deposition or removal of metals
US4801511A (en) * 1985-06-28 1989-01-31 Union Oil Company Of California Battery cell electrolyte
US20220042195A1 (en) * 2019-08-09 2022-02-10 Changzhou University Method for preparing copper-based graphene/aluminum composite wire with high electrical conductivity

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