EP0156591A2 - Anodisierungsverfahren zur Herstellung von hoch reflektierenden Aluminiummaterialien - Google Patents

Anodisierungsverfahren zur Herstellung von hoch reflektierenden Aluminiummaterialien Download PDF

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Publication number
EP0156591A2
EP0156591A2 EP85301754A EP85301754A EP0156591A2 EP 0156591 A2 EP0156591 A2 EP 0156591A2 EP 85301754 A EP85301754 A EP 85301754A EP 85301754 A EP85301754 A EP 85301754A EP 0156591 A2 EP0156591 A2 EP 0156591A2
Authority
EP
European Patent Office
Prior art keywords
aluminum
anodizing
sulfuric acid
highly reflective
anodized
Prior art date
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.)
Withdrawn
Application number
EP85301754A
Other languages
English (en)
French (fr)
Other versions
EP0156591A3 (de
Inventor
John H. Powers
Hang T Dang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Howmet Aerospace Inc
Original Assignee
Aluminum Company of America
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from US06/590,323 external-priority patent/US4483750A/en
Application filed by Aluminum Company of America filed Critical Aluminum Company of America
Publication of EP0156591A2 publication Critical patent/EP0156591A2/de
Publication of EP0156591A3 publication Critical patent/EP0156591A3/de
Withdrawn legal-status Critical Current

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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
    • 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
    • C25D11/04—Anodisation of aluminium or alloys based thereon

Definitions

  • This invention relates to anodizing aluminum. More particularly, this invention relates to improvements in the anodizing to produce highly reflective surfaces on aluminum materials.
  • Highly reflective surfaces may be produced on an aluminum material by proper selection of the alloy constituents, bright rolling or mechanical polishing of the aluminum surface and processing of the highly polished or bright rolled surface in a brightening bath which may comprise either electrobrightening or chemical brightening.
  • the highly reflective surface so produced is then protected by anodizing the aluminum to provide a thin, transparent, protective layer of aluminum oxide on the surface as is well known to those skilled in the art.
  • Various attempts at improving the reflectivity of the product have been proposed through the years.
  • One approach is to vary the type of brightener used to treat the aluminum surface prior to anodizing. Typical of such an approach is the aluminum phosphate chemical brightening bath disclosed in U.S.
  • Patent 3,530,0.48 d hich uses a combination of aluminum phosphate, nitric acid, phosphoric acid and copper sulfate.
  • the brightened aluminum surface according to the patentees, is then anodized in a sulfuric acid bath having a concentration of from 12 to 20 wt.% at a temperature of 70 to 80°F. ising a current of about 10 to 15 amperes per square ioot.
  • U.S. Patent 3,720,508 discloses an aluminum alloy used in the production of a highly reflective aluminum surface which contains from 0.5 to 3% magnesium, from 0.2 to 0.5% silver, from 0.001 to 0.2% iron and from 0.001 to 0.15% silicon.
  • U.S. Patent 3,671,333 provides for the addition of a natural or synthetic hydrophilic colloid to the reflective aluminum surface during anodizing of the aluminum by adding the colloid to the anodizing bath.
  • Surface coatings produced during the anodization are alleged to be much thinner and apparently more compact than previous anodized aluminum coatings which the patentees allege is believed to be due to the larger molecule of the colloid forming as a colloidate on the reflective surface which apparently compacts the aluminum oxide formed.
  • the thinner coating is then alleged to provide better reflectivity while eliminating the disadvantages of a thin normal anodized coating.
  • an improved process for the production"of aluminum reflective material having a higher total reflectance value comprises controlling the anodizing conditions of an aluminum alloy which preferably has been subjected to bright rolling or other mechanical brightening by immersing the alloy in a DC anodizing bath containing at least 26 wt.% sulfuric acid and anodizing the sheet at a current density of at least 18 amperes per square foot at a temperature of at least 60°F.
  • an improved anodizing process for the production of highly reflective aluminum material from an aluminum alloy.
  • the alloy is either bright rolled at the plant or else is first mechanically finished or polished to provide a smooth surface.
  • the material may then be treated in a brightening bath which may comprise a chemical brightener or an electro brightener.
  • a brightening bath may comprise a chemical brightener or an electro brightener.
  • the use of a brightening bath is not necessary when the surface is anodized in accordance with the invention.
  • the bright rolled or polished aluminum surface is then anodized in accordance with the invention to provide the desired highly reflective surface.
  • the process of the invention may be successfully utilized using any of the conventional aluminum alloys normally used in the production of reflectorized aluminum materials, such as aluminum reflector sheet or the like, preferably the aluminum alloy comprises 0 to 2.5% Mg, 0 to 1% Fe, 0 to .2% Cu and 0 to .2% Mn.
  • the aluminum alloy material used to form the highly reflective product may comprise as-rolled or bright rolled sheet or may be subjected to any conventional mechanical polishing techniques as are well . known to those skilled in the art.
  • a conventional brightening step it may, for example, comprise a treatment with a chemical brightener, such as the Alcoa 5 chemical brightening treatment.
  • This treatment comprises the use of a hot mixture of 85% phosphoric acid and 70% nitric acid which is initially mixed in a 19:1 volumetric ratio, although this ratio will change during use due to accumulation of aluminum phosphate in the solution.
  • a sulfuric acid bath having a concentration of from 26 to 32 wt.% sulfuric acid, preferably 28 to 32 wt.% sulfuric acid.
  • the temperature of the bath during anodizing is maintained, in accordance with the invention, at from about 60 to 84°F., preferably 67 to 84°F., and most preferably about 73 to 75°F.
  • the reflective aluminum material is subjected to D C anodizing, i.e. anodizing using direct current with the reflective aluminum material serving as the anode, while maintaining a current density of at least 18 amperes per square foot, preferably from 27 to 72 amperes per square foot, and most preferably, from 30 to 45 amperes per square foot during the time of anodizing.
  • the reflector material is rinsed in deionized water and the anodized coating is sealed by immersion in hot (95°C.) water or a nickel acetate solution for 5 minutes and then removed and dried.
  • hot (95°C.) water or a nickel acetate solution for 5 minutes and then removed and dried.
  • Other, more involved, sealing techniques may be used, but may not be necessary.
  • the total reflectance of the anodized reflector may then be measured using an integrating sphere type total reflectometer such as Dianos TRI Reflectometer which was used to produce the data in the examples below.
  • Reflective materials, anodized in accordance with the invention have total reflectance values usually over 80%, and in some instances, over 85%.
  • Table I shows the descending order of total reflectance values of the as-processed samples, corrected coating weight and corrected coating thickness values correlated with the processing parameters. Since variations in anodizing parameters cause differences in coating weight or thickness that have a known effect on reflectance, it was necessary to correct the data to a constant coating weight or thickness to eliminate this variable.
  • Example II To further illustrate the process of the invention, a number of samples similar to those used in Example I were brightened as in Example I and then DC anodized in a 32 wt.% sulfuric acid bath at various temperatures and current densities. As shown in Table II, at this acid concentration, every sample had a total reflectance of at least 81.3%.
  • the invention provides an improved process for the production of highly reflective aluminum whereby control and adjustment of the anodizing parameters can be made to maximize the total reflectance of the product.
  • samples of AA3002 and AA5005 type alloys were treated as provided in Table IV and percent total reflectance measured.
  • Samples of AA3002 and AA5005 type alloys, with and without being subject to a brightening process, were anodized using conventional and the improved anodizing.
  • the results in Table IV show that bright rolled samples not subject to a chemical brightening process but anodized in accordance with the improved process in accordance with the present invention had a high level of reflectance.
  • the invention provides an improved process for the production of highly reflective aluminum whereby control and adjustment of the anodizing parameters can be made to maximize the total reflectance of the product.

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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)
  • Optical Elements Other Than Lenses (AREA)
  • Physical Vapour Deposition (AREA)
EP85301754A 1984-03-16 1985-03-14 Anodisierungsverfahren zur Herstellung von hoch reflektierenden Aluminiummaterialien Withdrawn EP0156591A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US06/590,323 US4483750A (en) 1984-03-16 1984-03-16 Process for anodizing highly reflective aluminum materials
US590323 1984-03-16
US65191284A 1984-09-19 1984-09-19
US651912 1984-09-19

Publications (2)

Publication Number Publication Date
EP0156591A2 true EP0156591A2 (de) 1985-10-02
EP0156591A3 EP0156591A3 (de) 1985-12-04

Family

ID=27080817

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85301754A Withdrawn EP0156591A3 (de) 1984-03-16 1985-03-14 Anodisierungsverfahren zur Herstellung von hoch reflektierenden Aluminiummaterialien

Country Status (3)

Country Link
EP (1) EP0156591A3 (de)
AU (1) AU3908585A (de)
ES (1) ES8608592A1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11421318B2 (en) * 2018-05-04 2022-08-23 Applied Materials, Inc. Methods and apparatus for high reflectivity aluminum layers

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4225399A (en) * 1979-04-25 1980-09-30 Setsuo Tomita High speed aluminum anodizing
JPS56142896A (en) * 1980-04-09 1981-11-07 Matsushita Electric Ind Co Ltd Preparation of reflective type screen

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4225399A (en) * 1979-04-25 1980-09-30 Setsuo Tomita High speed aluminum anodizing
JPS56142896A (en) * 1980-04-09 1981-11-07 Matsushita Electric Ind Co Ltd Preparation of reflective type screen

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, vol. 96, no. 10, March 1982, page 520, no. 76524b, Columbus, Ohio, US; & JP - A - 81 142 896 (MATSUSITA ELECTRIC INDUSTRIAL CO., LTD.) 07-11-1981 *
S. WERNICK et al.: "The surface treatment and finishing of aluminium and its alloys", 4th edition, vol. 2, 1972, pages 848-858, Robert Draper Ltd., Teddington, GB. *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11421318B2 (en) * 2018-05-04 2022-08-23 Applied Materials, Inc. Methods and apparatus for high reflectivity aluminum layers

Also Published As

Publication number Publication date
AU3908585A (en) 1985-09-19
EP0156591A3 (de) 1985-12-04
ES541335A0 (es) 1986-06-16
ES8608592A1 (es) 1986-06-16

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Inventor name: POWERS, JOHN H.

Inventor name: DANG, HANG T