US1936058A - Production of corrosion-resistant coatings on aluminum and aluminum alloys - Google Patents

Production of corrosion-resistant coatings on aluminum and aluminum alloys Download PDF

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Publication number
US1936058A
US1936058A US646978A US64697832A US1936058A US 1936058 A US1936058 A US 1936058A US 646978 A US646978 A US 646978A US 64697832 A US64697832 A US 64697832A US 1936058 A US1936058 A US 1936058A
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US
United States
Prior art keywords
aluminum
coatings
production
corrosion
chromic acid
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US646978A
Inventor
Jenny Alexander
Budiloff Nikolai
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Siemens and Halske AG
Siemens AG
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Siemens AG
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Publication date
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/024—Anodisation under pulsed or modulated current or potential
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/14—Producing integrally coloured layers
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/30—Anodisation of magnesium or alloys based thereon

Definitions

  • the present invention relates to the production of corrosion-resistant coatings on aluminum and aluminum alloys by passage of an alternating current in acid baths, especially saturated chromic acid baths.
  • an object of aluminum or an aluminum alloy, already provided with a protective coating is used as often as desired as counter-electrode in producing a protective coating on a second object of aluminum or of an alu- 1 minum alloy.
  • relatively low concentrations of chromic acid for instance 0,05% or 3% chromic acid solutions there is the possibility of producing uniformly colored protective coatings in many cases but the use of saturated solu- 1 tions is more advantageous.
  • the invention provides a method, in which a saturated chromic acid solution is used for obtaining a coating of oxide on the counter-electrode by passage of an alternating current and advantageously also for obtaining a protective coating .on untreated objects oi! aluminum and aluminum alloys.
  • the protective coatings can be produced by employing a bath temperature ranging between about and 60 C. and by employing voltages oi. alternating current between about 40 and 60 volts for a period of about 20 minutes.
  • a chromic acid solution saturated at room temperature (20 C.) which contained about 102 g of solid chromic acid '(CrOa) in 100 com of water and had a specific weight of about 1.71 was used for the production of oxide containing coatings on two plates of Duralumin. The temperature of the solution was maintained at 50 C. and an alternating voltage of 50 volts was employed. After about 20 minutes one of the two" plates had a hard, nearly colorless, glass-like coating and on the other plate was deposited a pearl-grey coating.
  • chromic acid solutions saturated at room temperature (20 C.) can be used but also chromic acid solutions saturated at the working temperature (40450" C.).
  • the formation of the saturated chromic acid solutions advantageously takes place by dissolving crystalline chromicacid (CrOa) in water which is heated to a higher temperature than the desired temperature of saturation and by cooling the resulting solution to the temperature 01' saturation afterwards.
  • CrOa crystalline chromicacid
  • Such "a quantity of crystalline chromic acid must be employed that a portion of the chromic acid remains on the bottom of the solution vessel in solid state.

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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)
  • Inorganic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Description

Patented Nov. 21, 1933 I UNITED STATES PRODUCTION OF CORROSION-RESISTANT COATINGS N ALUMINUM AND ALUMINUM ALLOYS Alexander Jenny, Berlin-Charlottenburg, and Nikolai Budiloil', Berlin-Friedenau, Germany, assignors to Siemens & Halske, Aktiengesellschaft, Siemensstadt, near Berlin, Germany, a
corporation of Germany No Drawing. Application December 13, 1932, Serial No. 646,978, and in Germany December t Claims.
The present invention relates to the production of corrosion-resistant coatings on aluminum and aluminum alloys by passage of an alternating current in acid baths, especially saturated chromic acid baths. In this process an object of aluminum or an aluminum alloy, already provided with a protective coating, is used as often as desired as counter-electrode in producing a protective coating on a second object of aluminum or of an alu- 1 minum alloy. When using relatively low concentrations of chromic acid, for instance 0,05% or 3% chromic acid solutions there is the possibility of producing uniformly colored protective coatings in many cases but the use of saturated solu- 1 tions is more advantageous.
In testing this process by using different aluminum alloys, there was found that in some cases irregularities in the color of the protective coatings occurred, especially in the production 2 of black coatings on aluminum alloys, known under the name Lautal and Duralumin". To avoid this drawback, the invention provides a method, in which a saturated chromic acid solution is used for obtaining a coating of oxide on the counter-electrode by passage of an alternating current and advantageously also for obtaining a protective coating .on untreated objects oi! aluminum and aluminum alloys. The protective coatings can be produced by employing a bath temperature ranging between about and 60 C. and by employing voltages oi. alternating current between about 40 and 60 volts for a period of about 20 minutes.
A chromic acid solution, saturated at room temperature (20 C.) which contained about 102 g of solid chromic acid '(CrOa) in 100 com of water and had a specific weight of about 1.71 was used for the production of oxide containing coatings on two plates of Duralumin. The temperature of the solution was maintained at 50 C. and an alternating voltage of 50 volts was employed. After about 20 minutes one of the two" plates had a hard, nearly colorless, glass-like coating and on the other plate was deposited a pearl-grey coating.
Then the so treated plates were used as countective coatings on Lautal was similar to that of tor. sot-1)- coating of the second counter-electrode, howeve. remained practically unchanged.
It was observed that increases or decreases voltage of not more than about 10 volts and variations in bath temperature of not more t about 1%" C. had no essential influence on qualities of the coatings, especially on the c and the protective action. The coating proces could be extended to 30 minutes when a voltage of 40 volts. The best coatings were produced with a temperature of C. and an alternating voltage of 50 volts in a coating period of 20 minutes. At volts unsatisfactory coatings were obtained.
Almost the same results were found to be produced with plates of Lautal. The same chromic acid solutions and substantially the same bath temperatures and bath voltages could be used for producing good coatings. The color of the prothe above mentioned coatings on Duralumin; only on the white surface of Lautal the coatings had a somewhat gloomy aspect.
On objects of pure aluminum there are always deposited by the above described process dark brownish glass-like coatings on one electrode and bright grey coatings on the other electrode.
In order to dye the coatings produced on aluminum or on an aluminum alloy it is advantageous to dip the coatings immediately after their production and after washing with water into suitable organic dye solutions or to paint or flow such solutions upon the described coatings.
It will be understood that, in executing the new method, not only chromic acid solutions saturated at room temperature (20 C.) can be used but also chromic acid solutions saturated at the working temperature (40450" C.). The formation of the saturated chromic acid solutions advantageously takes place by dissolving crystalline chromicacid (CrOa) in water which is heated to a higher temperature than the desired temperature of saturation and by cooling the resulting solution to the temperature 01' saturation afterwards. Such "a quantity of crystalline chromic acid must be employed that a portion of the chromic acid remains on the bottom of the solution vessel in solid state.
.comprises immersing such articles in a saturated solution of chromic acid and passing alternating no current between said articles through said solution.
2. The process of claim 1 wherein a previously coated article is employed as a counter electrode 5 to the article which is being coated.
3. The process of claim 1 wherein the temperature of the bath is maintained between about 40 to C. and an alternating current voltage of about 40to 60 volts is employed.
emxmnm my. mom nonnorr.
US646978A 1929-09-16 1932-12-13 Production of corrosion-resistant coatings on aluminum and aluminum alloys Expired - Lifetime US1936058A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DES93945D DE600046C (en) 1929-09-16 1929-09-16 Process for the production of corrosion-resistant protective coatings on aluminum or aluminum alloys
DE562615T 1930-07-02
DE390110X 1931-12-10

Publications (1)

Publication Number Publication Date
US1936058A true US1936058A (en) 1933-11-21

Family

ID=34577269

Family Applications (2)

Application Number Title Priority Date Filing Date
US482368A Expired - Lifetime US1923539A (en) 1929-09-16 1930-09-16 Production of anticorrosive protective coatings on light metals
US646978A Expired - Lifetime US1936058A (en) 1929-09-16 1932-12-13 Production of corrosion-resistant coatings on aluminum and aluminum alloys

Family Applications Before (1)

Application Number Title Priority Date Filing Date
US482368A Expired - Lifetime US1923539A (en) 1929-09-16 1930-09-16 Production of anticorrosive protective coatings on light metals

Country Status (6)

Country Link
US (2) US1923539A (en)
AT (1) AT133115B (en)
BE (1) BE373447A (en)
DE (2) DE600046C (en)
FR (2) FR702266A (en)
GB (2) GB371213A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3091676A (en) * 1959-12-18 1963-05-28 Arthur H Koster Fluid level control system

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL56499C (en) * 1938-09-22
BE467056A (en) * 1939-01-31
US2578400A (en) * 1947-03-29 1951-12-11 Charles C Cohn Method for providing oxide coating on aluminum and its alloys
US2574225A (en) * 1948-07-28 1951-11-06 Benzol Products Company Process for rendering metal surfaces antiseptic and products therefrom
US2700212A (en) * 1948-10-15 1955-01-25 Gen Electric Electrical conductor
US2607825A (en) * 1948-10-20 1952-08-19 Eisler Paul Electric capacitor and method of making it
US2666023A (en) * 1948-12-30 1954-01-12 Siegfried Junghans Anodic coating of aluminum
US2930951A (en) * 1957-07-08 1960-03-29 Gen Electric Electrical capacitor
US3382160A (en) * 1960-03-31 1968-05-07 Asada Tahei Process for inorganically coloring aluminum
US4104136A (en) * 1974-09-22 1978-08-01 Reynolds Metals Company Process for applying thin molybdenum containing coatings on aluminum for solar energy absorption

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3091676A (en) * 1959-12-18 1963-05-28 Arthur H Koster Fluid level control system

Also Published As

Publication number Publication date
GB390110A (en) 1933-03-30
FR42676E (en) 1933-09-01
AT133115B (en) 1933-05-10
US1923539A (en) 1933-08-22
DE600046C (en) 1934-07-13
DE562615C (en) 1932-10-27
FR702266A (en) 1931-04-03
GB371213A (en) 1932-04-21
BE373447A (en)

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