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
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/58—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of copper
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12785—Group IIB metal-base component
  • Y10T428/12792—Zn-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12903—Cu-base component

Definitions

• Electrodeposition of brass from cyanide solutions as practiced heretofore has been characterized by being somewhat more diflicmt than the plating of a single metal such as zinc or copper.
• the electroplater In the electrodeposition of the zinc-copper alloys the electroplater combines the electrodeposition of two difierent metals, each of which requires diiferent conditions for optimum practical results.
• current efiiciencies are usually relatively low, relatively low current densities must be used and-considerab'e difilculty is usually encountered in maintaining a constant composition of the alloy in the cathode deposit.
• the composition of the cathode deposit varies widely with changes in the bath composition and with varying operating conditions.
• An increase of the temperature of the plating bath usually greatly increases the copper content of the cathode deposit.
• the cathode composition also changes materially when the current density is changed by relatively small amounts.
• thermostat control In a commercial electroplating operation it is relatively easy to maintain constant bath composition and constant bath temperatures may be readily obtained by thermostat control.
• the current density will vary for difl'erent shapes and sizes of work and moreover, different current densities often will appear at difierent portions of the same article.
• An object of the present invention is to provide an improved method for plating zinc-copper alloys, by means of which method the composition of the alloy electrodeposit can be more closely controlled than in the methods known heretofore.
• a further object isto provide a means of electroplating zinc-copper alloys at substantially constant composition under varied current density conditions.
• My invention also includes a novel type of electrodeposited zinccopper alloy which I term white brass, as described hereinafter. Other objects will be apparent from the following description of my invention.
• I may apply various current densities over a wide range without materially changing the composition of the cathode deposit.
• the bath is excellently adapted for commercial plating of a variety of articles of various shapes and sizes in the same installation and, if a reasonably constant bath temperature is maintained, all of the articles coming from the plating bath are identical in color. Since the only control necessary is to control the bath temperature and bath composition, my improved bath is easily controlled.
• a white zinccopper alloy containing about 19 to 31%- of cop'- per can be plated by the method of the hereinafter described invention with excellent control of the cathode composition.
• This white alloy which I term white brass” has been found to have excellent resistance to corrosion and is well adapted for plating on steel, brass or other base metal, both for the purpose of protection against corrosion and for decorative purposes.
• the white brass electrodeposit plated according to my method' is white and semi-bright and is easily buffed to form a highly polished plate of pleasing appearance.
• brass similar to polished metal also may be obtained by purifying the bath to remove heavy metal compounds therefrom, for example, the addition of a small amount of an alkali sulphide and bright dipping the resulting in acidic oxidizing solutionsuch as nitric acid, chromic acid, acidic hydrogen peromde or the like.
• Bright deposits may also be obtained by the addition of various mown brightening agents in the bath.
• suflicient sulfide or otherwise treat the solution to substantially completely precipitate the traces of heavy metal impurities usually present in the bath, e. g., lead salts.
• Various methods, alternative to sulfide addition may be utilized for such bath purification.
• various reducing agents e. g., zinc dust, may be added to the bath.
• Another effective method consists in allowing the bath to stand over night with zinc anodes placed therein.
• the herein described white brass is especially well adapted as an undercoat for nickel and chromium plating. It has the same advantages as those possessed by yellow or red brass for this purpose. In addition the color of the white brass is close to that of nickel or chromium, so that very s amounts of the nickel or chromium can be plated with no danger of a yellow cast showing through.
• the copper-cyanide concentration preferably is much greater than that of the zinc cyanide.
• the following formula is suitable for plating yellow brass according to my invention:
• the anodes used preferably are of approximately the same composition as the desired. alloy electrodeposit. If desired, combinations of copper and zinc anodes may be used, as in known methods. I prefer to use alloyanodes.
• the ratio of zinc cyanide to caustic soda may be varied between the approximate limits of 2:3 to 2:1 (0.66 to 2.0) That is, the weight of caustic soda may be equal to 50 to 150% of the weight of the zinc cyanide.
• the range over which the zinc cyanide-caustic ratio may vary also increases. For example, in a bath containing 8 grams per liter of zinc cyanide, the
• .ratio Zn(CN)-z:NaOH may vary from 2:4 to 4:3
• the ratio may vary from 2:3 to 2:1 (0.66 to 2.0). In a bath containing only 6 grams per liter of zinc cyanide, the ratio-must be within the range 3:4 to 5:4 (0.75 to 1.25). However, it is preferable to maintain this ratio as close to 1:1 as operating conditions will permit, because any substantial deviation from the 1: 1 ratio correspondingly decreases the effectiveness of the control of the cathode composition.
• the anodes will contain about 30% copper to 70% zinc and may be of the conventional forms known to the plating art.
• the anodes are enclosed in cotton bags or the like to prevent solid impurities on the anodes from entering the bath.
• Copper clon- Cathode current density fg g deposit Perceniz9 1 20 am also. it 30 amga/sq. it 27. 1 40 amps/sq. it 28. 8
• the cathode current efliciencies varied from 72.4% to 89.7%.
• a process for electroplating brass comprising electrolyzing a solution containing zinc and copper cyanides and caustic soda, the ratio of the concentration of zinc cyanide to the concentration of the caustic soda in said solution being maintained within the range of 2:3 to 2:1,
• a process for electroplating white brass comprising preparing a solution containing copper cyanide and an amount of zinc cyanide greater than the amount of copper cyanide present, while maintaining in said solution that amount of caustic soda which is approximately equal to the weight of the zinc cyanide in said solution and maintaining said solution at a reasonably constant temperature, so as to maintain a substantially constant composition of electrodeposit when changes occur in the current density.

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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)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22389510

Family Applications (1)

Country Status (2)

Cited By (9)

• 1937
  • 1937-01-12 US US120315A patent/US2181773A/en not_active Expired - Lifetime
• 1938
  • 1938-01-13 DE DEP76556D patent/DE685630C/de not_active Expired

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