US2630407A - Electrodeposition of chromium - Google Patents

Electrodeposition of chromium Download PDF

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Publication number
US2630407A
US2630407A US201487A US20148750A US2630407A US 2630407 A US2630407 A US 2630407A US 201487 A US201487 A US 201487A US 20148750 A US20148750 A US 20148750A US 2630407 A US2630407 A US 2630407A
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chromium
solution
parts
chromic acid
electrodeposition
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US201487A
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Hackerman Norman
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Research Corp
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Research Corp
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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
    • C25D3/04—Electroplating: Baths therefor from solutions of chromium

Definitions

  • Chromium plate electrically deposited on other metals provides a bright decorative finish and an extremely hard surface.
  • the chromium film is very corrosion resistant since it generally is in the passive state.
  • chromium electroplate alone does not protect the base metal from corrosion due to the presence of a crack network in the chromium plate, the cause of which has not been ascertained.
  • the crack network in electrodeposited chromium can be greatly reduced or eliminated by the electrodeposition of chromium from a bath containing a salt of indium.
  • the plated metal film produced in this way has all of the advantages of chromium plate and in addition provides greatly increased protection of the base metal, such as copper or steel, against corrosion.
  • the indium salt may be added to the chromic acid-sulfuric acid plating solutions commonly used for chromium plating, advantageously in the form of indium sulfate.
  • chromic acid-sulfuric acid plating solutions commonly used for chromium plating, advantageously in the form of indium sulfate.
  • Plating from such solutions may be efiected at voltages of from 2.5 to 4.0 volts and at current densities of from 6 to 18 ampa/dm. at about 30 C.
  • the voltage is maintained between about 3.2 and about 3.5.
  • the optimum current density will vary with the concentrations of the bath components.
  • a hard, bright plate substantially free from cracks and providing a high protection against corrosion may be obtained by the following procedure which is illustrative of the principles of the invention:
  • a steel or copper article is plated from a bath containing 250 g./liter of Cl'Os, 2.5 g./liter of H2804 and 38.7 g./liter of indium sulfate at a current density of 13 to 15.5 amps/dm. and a voltage of 3.2 to 3.5 using lead anodes and continuing the plating for about twelve hours at 1
  • a chromium oxide-sulfuric acid plating solution of the composition given in the example it is desirable to use at least about 17 grams per liter of indium sulfate. Improved brightness of the plate and substantial freedom from cracks is obtained with higher amounts of the indium salt of the order of 35 to 40 grams per liter.
  • the bright, substantially crack-free, plate is much less brittle than the chromium plate obtained in the absence of indium as shown by bend tests.
  • the method of electrodepositing bright, smooth, adherent films of chromium upon a cathodic workpiece which comprises immersing the cathode workpiece in an aqueous solution of chromic acid and sulfuric acid containing from about 14 to about 16 parts of indium sulfate to each parts of chromic acid and passing an electric current through said solution between the cathodic workpiece and an anode immersed in said solution.
  • the method of electrodepositing bright, smooth, adherent films of chromium 'upon a cathodic workpiece which comprises immersing the cathodic workpiece in an aqueous solution of chromic acid and sulfuric acid containing from about 14 to about 16 parts of indium sulfate to each 100 parts of chromic acid and passing an electric current at a current density of from about 13 to about 15.5 amp./dm. through said solution between the cathodic workpiece and an anode immersed in said solution.

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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 Methods And Accessories (AREA)
  • Electroplating And Plating Baths Therefor (AREA)

Description

Patented Mar. 3, 1953 ELECTRODEPOSITION F CHROMIUM Norman Hackerman, Austin, Tex., assignor to Research Corporation, New York, N. Y., a corporation of New York No Drawing. Application December 18, 1950, Serial No. 201,487
2 Claims. (Cl. 20451) Thi invention relates to the electrodeposition of chromium.
Chromium plate electrically deposited on other metals provides a bright decorative finish and an extremely hard surface. The chromium film is very corrosion resistant since it generally is in the passive state. However, chromium electroplate alone does not protect the base metal from corrosion due to the presence of a crack network in the chromium plate, the cause of which has not been ascertained.
It has now been found that the crack network in electrodeposited chromium can be greatly reduced or eliminated by the electrodeposition of chromium from a bath containing a salt of indium. The plated metal film produced in this way has all of the advantages of chromium plate and in addition provides greatly increased protection of the base metal, such as copper or steel, against corrosion.
The indium salt may be added to the chromic acid-sulfuric acid plating solutions commonly used for chromium plating, advantageously in the form of indium sulfate. Preferably from about 14 to about 16 parts of indium sulfate should be present for each 100 parts of chromic acid in the plating solution. Plating from such solutions may be efiected at voltages of from 2.5 to 4.0 volts and at current densities of from 6 to 18 ampa/dm. at about 30 C. Preferably the voltage is maintained between about 3.2 and about 3.5. The optimum current density will vary with the concentrations of the bath components.
A hard, bright plate substantially free from cracks and providing a high protection against corrosion may be obtained by the following procedure which is illustrative of the principles of the invention:
A steel or copper article is plated from a bath containing 250 g./liter of Cl'Os, 2.5 g./liter of H2804 and 38.7 g./liter of indium sulfate at a current density of 13 to 15.5 amps/dm. and a voltage of 3.2 to 3.5 using lead anodes and continuing the plating for about twelve hours at 1 In general, in a chromium oxide-sulfuric acid plating solution of the composition given in the example, it is desirable to use at least about 17 grams per liter of indium sulfate. Improved brightness of the plate and substantial freedom from cracks is obtained with higher amounts of the indium salt of the order of 35 to 40 grams per liter.
The bright, substantially crack-free, plate is much less brittle than the chromium plate obtained in the absence of indium as shown by bend tests.
I claim:
1. The method of electrodepositing bright, smooth, adherent films of chromium upon a cathodic workpiece which comprises immersing the cathode workpiece in an aqueous solution of chromic acid and sulfuric acid containing from about 14 to about 16 parts of indium sulfate to each parts of chromic acid and passing an electric current through said solution between the cathodic workpiece and an anode immersed in said solution.
2. The method of electrodepositing bright, smooth, adherent films of chromium 'upon a cathodic workpiece which comprises immersing the cathodic workpiece in an aqueous solution of chromic acid and sulfuric acid containing from about 14 to about 16 parts of indium sulfate to each 100 parts of chromic acid and passing an electric current at a current density of from about 13 to about 15.5 amp./dm. through said solution between the cathodic workpiece and an anode immersed in said solution.
NORMAN HACKERMAN.
REFERENCES CITED The following references are of record. in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,802,463 Fink Apr. 28, 1931 2,358,029 Phillips et al. Sept. 12, 19M

Claims (1)

1. THE METHOD OF ELECTRODEPOSITING BRIGHT, SMOOTH, ADHERENT FILMS OF CHROMIUM UPON A CATHODIC WORKPIECE WHICH COMPRISES IMMERSING THE CATHODIC WORKPIECE IN AN AQUEOUS SOLUTION OF CHROMIC ACID AND SULFURIC ACID CONTAINING FROM ABOUT 14 TO ABOUT 16 PARTS OF INDIUM SULFATE TO EACH 100 PARTS OF CHROMIC ACID AND PASSING AN ELECTRIC CURRENT THROUGH SAID SOLUTION BETWEEN THE CATHODIC WORKPIECE AND AN ANODE IMMERSED IN SAID SOLUTION .
US201487A 1950-12-18 1950-12-18 Electrodeposition of chromium Expired - Lifetime US2630407A (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1802463A (en) * 1925-09-19 1931-04-28 Chemical Treat Company Inc Process of producing chromium-plated articles with mirrorlike, scratchfinish, or the like surfaces
US2358029A (en) * 1940-03-02 1944-09-12 American Smelting Refining Process of electrodepositing indium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1802463A (en) * 1925-09-19 1931-04-28 Chemical Treat Company Inc Process of producing chromium-plated articles with mirrorlike, scratchfinish, or the like surfaces
US2358029A (en) * 1940-03-02 1944-09-12 American Smelting Refining Process of electrodepositing indium

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