US3551303A - Method for forming anodic oxide film on aluminum or aluminum alloy - Google Patents

Method for forming anodic oxide film on aluminum or aluminum alloy Download PDF

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Publication number
US3551303A
US3551303A US663628A US3551303DA US3551303A US 3551303 A US3551303 A US 3551303A US 663628 A US663628 A US 663628A US 3551303D A US3551303D A US 3551303DA US 3551303 A US3551303 A US 3551303A
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film
thickness
aluminum
cracks
anodic oxide
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US663628A
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English (en)
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Takashi Suzuki
Takesi Hamabe
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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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
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S205/00—Electrolysis: processes, compositions used therein, and methods of preparing the compositions
    • Y10S205/917—Treatment of workpiece between coating steps

Definitions

  • a method for forming an anodic oxide film of a desired thickness on an aluminum or an aluminum alloy which has an improved withstand voltage when a bending stress is applied which comprises forming an anodic oxide film thinner than a desired thickness, cracking said film in a suitable manner, then conducting an anodic oxidation again and, if necessary, repeating said cracking and said anodic oxidation, whereby there is formed an anodic oxide film on an aluminum or an aluminum alloy.
  • the present invention relates to a method for treating the surfaces of an aluminum and its alloy to obtain an insulating film which has a high bending resistance.
  • an anodic oxide film obtained by conducting an anodic oxidation on an aluminum or its alloy is excellent in insulating property, it is used for a surface insulating material on a linear-or strip-type electrical conductor made of aluminum or aluminum alloy (this will be described as a conductor hereinafter).
  • an anodic oxide film obtained by the generally known method for anodic oxidation does scarcely show flexibility and is cracked with an elongation of only 0.4-5 That is when a conductor having a surface subjected to anodic oxidation is 'bended with a curvature smaller than a certain value, a tensile stress comes to be applied on the film of outer surface, so that cracks occur running in the direction perpendicular to that of bending.
  • the conductor having an anodic oxide film formed by the ordinary method has advantages that the thermal durability and the adhesive property of the film are excellent, it has a serious disadvantage that the withstand voltage of the film becomes lower when the conductor is bended with a curvature not larger than about 20 times as large as its diameter or thickness, so that with a smaller curvature than said value it can not be substantially employed.
  • some methods for improving the fiexibility of film by varying electrolytes or electrolitic conditions for the anodic oxidation were not able to largely improve the resistance to bending.
  • a crack density (the number of cracks per unit length in a bending direction breaking out in the outer surface of a conductor) is increased with the same film thickness and the same bending curvature.
  • the present invention has been accomplished on the basis of this consideration and "ice the experimental result that with the same quality of film, the crack density is reduced with the same elongation rate, as the film thickness is increased.
  • anodic oxide film whose bending resistance is improved, on an alurninum and an alurninum alloy.
  • an anodic oxide film whose insulating property at the time of applying a tensile stress is improved, on an aluminum or an alurninum alloy, characterized by forming an anodic oxide film having a thickness thinner than a desired value on the surface of an aluminum or an aluminum alloy, then elongating said anodic oxide film so as to break out cracks over all region of said' film, then again conductng an anodic oxidation on said aluminum or aluminum alloy so as to increase the thickness of said whole anodic oxide film and, if necessary, repeating the above Operations, whereby an anodic oxide film of a desired thickness is formed.
  • FIG. 1a shows schematically a state of crack formation in an anodic oxide film prepared in accordance with the present invention
  • FIG. 1b shows schematically a state of crack formation in an anodic oxide film formed by the conventional method
  • FIG. 2 shows graphically the results of experiment regarding the relation between the thickness of anodic oxide film and the density of cracks (the number of cracks per unit length in elongation direction) formed in the oxide film at the time of giving a predetermined elongation.
  • d1 and dz mean sizes of the crack apertures respectively, where d1 d2. That is, dl in the case that a density of cracks formed in the film 2 is larger (FIG. la) is smaller than dz in the case of a smaller density (FIG. 1b).
  • FIG. 2 shows the relation between the crack density and the thickness of film obtained from an experiment. This relation was obtained with a given quality and Shape of aluminum specimens, a given anodic oxidation condition and a given elongation rate of the film. The Variation of the thickness of the film was efiected by changing time or voltage for anodic oxidation.
  • an anodic oxide film having a thickness of a When an anodic oxide film having a thickness of a is to be formed on a conductor, such a thickness should not be attained at a time, but at first a film having a thickness of b (where b a) should be formed. Then the film is elongated to produce cracks over all region of the film. After that, again an anodic oxidation is conducted and stopped when the thickness of film comes to be a. It has been found that the film formed in such a manner has a tendency that when elongated, cracks break out at the same points where the cracks were formed previously, and that density of the newly formed cracks is almost equal to that of cracks in the case of the film thickness of b.
  • the film thickness b in order to increase the density of cracks, it is preferable to make the film thickness b as small as possible. If a difference between the film thickness b and the final film thickness a is too large, however, after forming the film subsequently up to the thickness of a, cracks break out by elongating the film at points independent of those, where cracks Were formed at the time of the film thickness of b, only in the same state as in the case a film of a in thickness is formed from the beginning at a setting. In other words, the density of cracks does not become m but l. Therefore, there is a limitation in a ratio of the film thickness of b to that of a.
  • a film of cl in thickness is formed and cracked.
  • the crack density at this time is designated as nl.
  • an anodic oxidation is conducted again to make the fihn thickness C2 of about 5 times as large as cl, followed by breaking out cracks again.
  • the density of cracks does not become n2, but nl.
  • the thickness of the film is increased to C3, c., with reaching finally a.
  • the thus produced film shows, in spite of the thickness of a, a density of cracks formed by its elongation almost equal to that in the case of the film thickness of C1, that is, nl.
  • liquids such as sulfuric acid, oxalic acid, phosphoric acid, chromic acid and sulfamic acid forming a porous film are suitable. Further, liquids such as boric acid and ammonium borate may be employed. In this case increasing of the film thickness is eifected by increasing a forming voltage.
  • methods for breaking out cracks that is, methods for elongating a film
  • the conductor, on the surface of which a film is formed is rolled on rolls of a suitable diameter having smooth surfaces or having ribbed surfaces
  • a rapid temperature change is applied to the conductor having a film formed by using a difference between the thermal expansion coefiicient of aluminum or aluminum alloy and that of anodic oxide film (for example, at a temperature range of -30, C., the thermal expansion coeflicient of aluminum is 24.5 10-6/ C., while that of the film is 4.5 10 6/ C).
  • Crack formation may be carried out in air after taking out a conductor from a electrolytic bath and washing the same with water, but it can be also conducted in the electrolytic bath. In the latter, only one of the electrolytic bath is required and water-washing is not necessary more than once after all the anodic oxidations are finished.
  • Example An anodic oxidation was conducted on an aluminum foil of 100p. in thickness and 85 mm. in width having an aluminum purity of 99.4% in a 10% sulfuric acid solution at a current density of 0.8 a./dm.2 to form a film on the surface.
  • the final film thickness was made to 10a.
  • the sample A in which a film of 10a in thickness was formed at a time
  • the sample B in which a film of 10a in thickness was formed by re- Peating a process ef anodic oxidaton and crack forma- TABLE 2.
  • -RESULTS OF BENDING-RESISTANCE TESTS As is clear from Table 2, the anodic oxide film prepared in accordance with the present invention shows an extremely smaller reduction of its insulating characteristic at the time of application of a tensile stress comparing with that in accordance with the conventional process. Moreover, the method of the present invention can be easily carried out with an ordinary apparatus for anodic oxidation and, therefore, has an extremely large advantage in the industry.
  • a method for forming an anodically oxidized film on the surface of aluminum or an alloy thereof comprising the steps of elongating an anodically oxidized film formed on the surface of aluminum or an alloy thereof to break out cracks over the whole regions of said film, and then anodically oxidizing the resultant film to increase the film thickness to break out further cracks when the film is again elongated, said increased film thickness being in the range of less than 10 times the thickness of the initially formed film and repeating said process a plurality of times to form a film having a density of cracks of more than 60 cracks/ mm. broken out in the direction of elongation.

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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)
  • Laminated Bodies (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Printing Plates And Materials Therefor (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Formation Of Insulating Films (AREA)
US663628A 1966-09-05 1967-08-28 Method for forming anodic oxide film on aluminum or aluminum alloy Expired - Lifetime US3551303A (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP5910866 1966-09-05
JP6469966 1966-09-30
JP8341866 1966-12-16
JP1353267 1967-03-01

Publications (1)

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US3551303A true US3551303A (en) 1970-12-29

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US (1) US3551303A (de)
CH (1) CH490508A (de)
DE (1) DE1621114C3 (de)
GB (1) GB1169647A (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4177299A (en) * 1978-01-27 1979-12-04 Swiss Aluminium Ltd. Aluminum or aluminum alloy article and process
US5158663A (en) * 1991-08-12 1992-10-27 Joseph Yahalom Protective coatings for metal parts to be used at high temperatures
US5202013A (en) * 1991-10-15 1993-04-13 Alcan International Limited Process for coloring metal surfaces
US20100001629A1 (en) * 2007-05-16 2010-01-07 Eden J Gary Arrays of microcavity plasma devices and electrodes with reduced mechanical stress
US8362699B2 (en) 2007-10-25 2013-01-29 The Board Of Trustees Of The University Of Illinois Interwoven wire mesh microcavity plasma arrays
US8404558B2 (en) 2006-07-26 2013-03-26 The Board Of Trustees Of The University Of Illinois Method for making buried circumferential electrode microcavity plasma device arrays, and electrical interconnects
US8547004B2 (en) 2010-07-27 2013-10-01 The Board Of Trustees Of The University Of Illinois Encapsulated metal microtip microplasma devices, arrays and fabrication methods
US8968668B2 (en) 2011-06-24 2015-03-03 The Board Of Trustees Of The University Of Illinois Arrays of metal and metal oxide microplasma devices with defect free oxide
US9659737B2 (en) 2010-07-29 2017-05-23 The Board Of Trustees Of The University Of Illinois Phosphor coating for irregular surfaces and method for creating phosphor coatings

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2714394C3 (de) * 1977-02-03 1981-01-15 Schweizerische Aluminium Ag, Chippis (Schweiz) Verwendung von Aluminium oder Aluminiumlegierungen mit darauf anodisch erzeugten Oxidschichten für den Thermotransferdruck
DE59009223D1 (de) * 1989-03-16 1995-07-20 Alusuisse Lonza Services Ag Verfahren zur Erzeugung einer strukturierten Oberfläche auf einem Gegenstand aus Aluminium oder einer Aluminiumlegierung.
EP3445896B1 (de) 2016-04-18 2023-10-18 Fokker Aerostructures B.V. Verfahren zur anodisierung eines artikels aus aluminium oder einer legierung davon

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4177299A (en) * 1978-01-27 1979-12-04 Swiss Aluminium Ltd. Aluminum or aluminum alloy article and process
US5158663A (en) * 1991-08-12 1992-10-27 Joseph Yahalom Protective coatings for metal parts to be used at high temperatures
EP0531183A2 (de) * 1991-08-18 1993-03-10 Joseph Yahalom Schutzbeschichtungen für Metallteile, die bei hohen Temperaturen verwendet werden
EP0531183B1 (de) * 1991-08-18 1998-04-01 Joseph Yahalom Schutzbeschichtungen für Metallteile, die bei hohen Temperaturen verwendet werden
US5202013A (en) * 1991-10-15 1993-04-13 Alcan International Limited Process for coloring metal surfaces
US8404558B2 (en) 2006-07-26 2013-03-26 The Board Of Trustees Of The University Of Illinois Method for making buried circumferential electrode microcavity plasma device arrays, and electrical interconnects
US8159134B2 (en) 2007-05-16 2012-04-17 The Board Of Trustees Of The University Of Illinois Arrays of microcavity plasma devices and electrodes with reduced mechanical stress
EP2153454A4 (de) * 2007-05-16 2011-02-23 Univ Illinois Arrays von mikrokavitäts-plasmageräten und elektroden mit reduzierter mechanischer belastung
EP2153454A1 (de) * 2007-05-16 2010-02-17 The Board Of Trustees Of The University Of Illinois Arrays von mikrokavitäts-plasmageräten und elektroden mit reduzierter mechanischer belastung
US20100001629A1 (en) * 2007-05-16 2010-01-07 Eden J Gary Arrays of microcavity plasma devices and electrodes with reduced mechanical stress
US8535110B2 (en) 2007-05-16 2013-09-17 The Board Of Trustees Of The University Of Illinois Method to manufacture reduced mechanical stress electrodes and microcavity plasma device arrays
US8362699B2 (en) 2007-10-25 2013-01-29 The Board Of Trustees Of The University Of Illinois Interwoven wire mesh microcavity plasma arrays
US8547004B2 (en) 2010-07-27 2013-10-01 The Board Of Trustees Of The University Of Illinois Encapsulated metal microtip microplasma devices, arrays and fabrication methods
US8870618B2 (en) 2010-07-27 2014-10-28 The Board Of Trustees Of The University Of Illinois Encapsulated metal microtip microplasma device and array fabrication methods
US9659737B2 (en) 2010-07-29 2017-05-23 The Board Of Trustees Of The University Of Illinois Phosphor coating for irregular surfaces and method for creating phosphor coatings
US8968668B2 (en) 2011-06-24 2015-03-03 The Board Of Trustees Of The University Of Illinois Arrays of metal and metal oxide microplasma devices with defect free oxide
US9579624B2 (en) 2011-06-24 2017-02-28 The Board Of Trustees Of The University Of Illinois Gas reactor devices with microplasma arrays encapsulated in defect free oxide

Also Published As

Publication number Publication date
GB1169647A (en) 1969-11-05
DE1621114B2 (de) 1977-07-28
DE1621114A1 (de) 1971-05-13
DE1621114C3 (de) 1978-03-23
CH490508A (de) 1970-05-15

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