US3862892A - Aluminium object with anodic oxide surface - Google Patents

Aluminium object with anodic oxide surface Download PDF

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Publication number
US3862892A
US3862892A US325765A US32576573A US3862892A US 3862892 A US3862892 A US 3862892A US 325765 A US325765 A US 325765A US 32576573 A US32576573 A US 32576573A US 3862892 A US3862892 A US 3862892A
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Prior art keywords
shaped object
aluminium
aluminum
current density
weakly
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Expired - Lifetime
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US325765A
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Werner Lautenschlager
Siegfried Pahlke
Gunther Tolg
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Max Planck Gesellschaft zur Foerderung der Wissenschaften
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Max Planck Gesellschaft zur Foerderung der Wissenschaften
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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
    • 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
    • C25D11/026—Anodisation with spark discharge

Definitions

  • ABSTRACT There is provided an aluminium shaped object with an oxidised surface, characterised by an elastic aluminium oxide surface layer with a thickness of between I and 20 ,um, preferably of 2 to 10 pm, with a spongy structure of granular structural elements having an average diameter of between 1 and 10 um, preferably of 3 to 8 am.
  • Aluminium shaped objects with oxide coatings are known. They are usually produced by anodic oxidation in acidic electrolytes, for example, in chromic acid. sulphuric acid, oxalic acid or the like by the so-called eloxal process.
  • a disadvantage of the layers produced by this process is their brittleness which. in the case of subsequent working up, leads to a cracking and flaking off of the oxide layer.
  • the structure of the oxide layers is smooth so that they are unsuitable for many purposes, for example, as carrier materials for chromatographic separations.
  • the present invention provides an aluminium shaped object with an oxidised surface, which is characterised by an anodically produced, elastic aluminium oxide surface layer with a thickness of between 1 and 20 um, preferably of 5 to 6 pm, and with a spongy structure of granule-like structural elements with an average diameter of between 1 and 10 um, preferably of 3 to 8 pm.
  • the aluminium shaped object according to the present invention can have any desired shape but is preferably in the form ofa sheet, plate, foil, wire or rod.
  • the production of the aluminium shaped object according to the present invention by anodic oxidation in an electrolyte is carried out by contacting the surface of the aluminium shaped object in a weakly acidic to alkaline bath by sparkovers at high voltages and very high current densities. By means of this contacting or rastering off, each sparkover results in the formation of an insulated, oxidised burnt spot on the aluminium surface so that the next spark flashes over to a still unoxidised spot.
  • the voltages used are preferably between 100 and 200 V., the lower limit of the striking voltage being regarded as being about 80 to 90 V.
  • the striking voltage depends upon and is inversely proportional to the temperature.
  • the current density used is preferably within the range of 5 to 40 A/dm.
  • electrolytes used is of minor importance. In principle, an electrolyte can be tested, without great difficulty, for its suitability in preliminary experiments so long as it is borne in mind that it must lead to the spark oxidation of the aluminium surface. It is preferred to use neutral to weakly alkaline electrolytes which generally give better surfaces than acidic electrolytes, which can, however, also be used. Weakly acidic electrolytes are, according to the present invention, those with a pH value above 4. Of the neutral to weakly alkaline electrolytes, i.e., electrolytes in the pH range of about 6 to 10, those based on sodium ions have proved to be better than, for example, those based on potassium ions. Especially good results have been obtained with weakly basic sodium salts, for example, sodium carbonate or sodium acetate, in admixture with sodium fluoride.
  • weakly basic sodium salts for example, sodium carbonate or sodium acetate
  • the surfaces of the aluminium shaped objects according to the present invention have a spongy structure of granular structural elements, the average diameter of which can be between 1 and 10 um, preferably between 3 and 8 pm.
  • the average layer thickness of about 5 um, the dimension of which is only slightly dependent upon the voltage used.
  • FIGS. 1, 2 and 3 typical raster-microscopic pictures of the surface at enlargements of 100, 300 and 1,000 fold.
  • the layers were obtained at a temperature of between about l and 5C. and a voltage of 150 V with an electrolyte which consisted of an aqeuous 2M sodium carbonate and 1M sodium fluoride solution.
  • the extraordinarily uniform spongy structure can easily be seen.
  • An especial advantage of the present invention is that, in contradistinction to thin layer chromatography on plates, which is the conventional technique, it is now possible to employ wires, strips and other shapes for the aluminium carrier.
  • the use of carriers in the form of wires provides an interesting and new separation technique. After the chromatographic separation has taken place, the substances of interest can then be recovered without loss merely by cutting out the appropriate sections of the wire and dissolving them in, for example, an acid or lye, or the substances of interest can be dissolved off from the carrier with an appropriate solvent.
  • the product according to the present invention can also be used in electrophoretic, gas chromatographic and partition chromatographic separations as carrier and/or separation materials.
  • they can be used for liquid-liquid partition chromatography.
  • an aluminium shaped object according to the present invention can, for example, be introduced, in wire form, into a synthetic resin tube, for example into a tube of TEFLON, to form a stationary phase which can be used for the separation of extremely small amounts of substances.
  • Further possibilities of use as sample carriers include solution X-ray fluorescent analysis and special sampling techniques, for example by the corundum rodlet method.
  • Very thin layers for thin layer chromatography are already known. These layers are produced by the vapour deposition of metallic oxides, for example of indium oxide or of bismuth oxide, on substrates of, for example, glass.
  • metallic oxides for example of indium oxide or of bismuth oxide
  • these thin films have a limited absorptive ability, are less homogeneous and are difficult to produce.
  • the product according to the present invention when used in thin film chromatography, not only possesses the above-mentioned advantages but also overcomes the difficulties which, in the case of normal thin layer chromatography, arise in connection with the handling and production of the very sensitive layers. These advantages are, to a large extent, also applicable in the case of the use in other chromatographic and electrophoretic methods.
  • the product according to the present invention also has surface properties which make it of extreme interest in other technical fields.
  • an aluminium shaped object such as an aluminium sheet, eloxated in known manner, has a hard, brittle, crystalline aluminium oxide layer which, in the case of subsequent working up, forms cracks and fissures so that the desired surface protective action is no longer retained.
  • This defect has excluded the use of the eloxal process for surface protection in many technical fields in which a subsequent working up is necessary, for example, in aircraft technology. In these technical fields, the desired corrosion protective action must be achieved by coating with lacquer.
  • products according to the present invention possess aluminium surfaces which are very elastic and can, without diffieulty, withstand a subsequent working up. Furthermore, they also provide an outstanding adhesive substrate for lacquers and colouring materials and, in this regard, too, are also superior to the previously known eloxal layers.
  • the surfaces of the products according to the present invention are also outstanding insulators. This property enables them to he used for condensers and other electrical constructional elements in which an insulating layer over a conductive substrate material based on aluminium is desired.
  • An especial advantage for this field of use is also the formability of the products according to the present invention.
  • EXAMPLE 1 Production a. There was used an electrolysis vessel equipped with a stirrer, the temperature of which could be regulated by means ofa thermostat. As cathode, there was used an aluminium plate and as anode an aluminium shaped piece, with the shape shown in the following diagram:
  • the anode was supplied with current via the narrow part thereof.
  • the broad part was completely immersed in the electrolytes used.
  • the cathode to anode surface ratio was 4:1 and the distance between the cathode and the anode was 10 cm.
  • the surface of the anode was cleaned by immersion for 20 seconds in a 15% aqueous sodium hydroxide solution at C., followed by rinsing with distilled water.
  • the electrolyte solution used was 2 molar with regard to sodium carbonate and 0.25 molar with regard to sodium fluoride.
  • the whole of the oxidised aluminium sheet had a very uniform surface layer which had outstanding properties when used as a carrier for thin film chromatographic separation processes.
  • Example 1(a) The process according to Example 1(a) was repeated but with the difference that the electrolyte used was 1 molar with regard to sodium fluoride. Here, too. there was obtained a surface layer with outstanding properties.
  • Example 1(a) Under otherwise the same conditions as in Example 1(a), instead of a rectangular aluminium anode. there was used a length of aluminium wire (length 10 cm., diameter 1 mm.). After 3 minutes, the wire was uniformly coated with an oxide layer. There was no difficulty in transporting a wire continuously over a spool system, at a constant velocity, through the electrolyte so that the residence time was just sufficient for the complete oxidation of the section of wire present in the bath.
  • the layers produced according to Example l(a) and (b) had an average thickness of 5 am. Pictures taken with an electron raster microscope enabled a spongy structure of the layer to be recognised with an average grain size of about 5 am.
  • Example 1(a) On to a plate produced according to Example 1(a), there was applied a solution of a dyestuff test mixture
  • the detection limit for the above-mentioned organic coloured materials was found to be 0.1 rig. for all of ,them, except titan yellow, the detection limit of which was about 1 ng.
  • EXAMPLE 3 Use of a shaped body according to the present invention for the chromatographic separation of metal dithi zonates in the ng. range.
  • thymol blue and titan yellow using an ultrami-v cropipette, application being in the form of spots on a starting line on one end of the plate.
  • the plate was developed upwardly in the usual manner in a small ground glass vessel, the lid of which was firmly closed.
  • eluant I there was used actone:isopropanol:- chloroform in a volume ratio of4:3:2. 15 to seconds after application of the eluant, the substances were already separated. For a running distance ofabout 2 cm., a running time of 1 to 2 minutes was necessary.
  • Examples 2 and 3 show that, with the spaed objects according to the present invention, it is possible to carry out extremely rapid chromatographic separations 0 of extremely small amounts of substances.
  • the method can also be applied to the separation of small amounts of substances such as are usually carried out with aluminium oxide adsorbents.
  • Process for the production of an aluminum shaped object having an oxidized surface by anodic oxidation in an electrolyte which process comprises contacting the surface of an aluminum shaped object in a weakly acidic to alkaline electrolyte bath containing sodium carbonate and sodium fluoride with sparkovers at a spark voltage of more than 80 V. and very high 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)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Electrochemical Coating By Surface Reaction (AREA)
  • Agricultural Chemicals And Associated Chemicals (AREA)
US325765A 1972-01-25 1973-01-22 Aluminium object with anodic oxide surface Expired - Lifetime US3862892A (en)

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DE19722203445 DE2203445A1 (de) 1972-01-25 1972-01-25 Aluminiumformgegenstand mit oxidoberflaeche

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JP (1) JPS4883042A (enrdf_load_html_response)
CH (1) CH594070A5 (enrdf_load_html_response)
DE (1) DE2203445A1 (enrdf_load_html_response)
FR (1) FR2169259B1 (enrdf_load_html_response)
IT (1) IT978434B (enrdf_load_html_response)
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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5385662A (en) * 1991-11-27 1995-01-31 Electro Chemical Engineering Gmbh Method of producing oxide ceramic layers on barrier layer-forming metals and articles produced by the method
US5487825A (en) * 1991-11-27 1996-01-30 Electro Chemical Engineering Gmbh Method of producing articles of aluminum, magnesium or titanium with an oxide ceramic layer filled with fluorine polymers
US5720866A (en) * 1996-06-14 1998-02-24 Ara Coating, Inc. Method for forming coatings by electrolyte discharge and coatings formed thereby
US6027629A (en) * 1994-11-16 2000-02-22 Kabushiki Kaisha Kobe Seiko Sho Vacuum chamber made of aluminum or its alloys, and surface treatment and material for the vacuum chamber
US6197178B1 (en) 1999-04-02 2001-03-06 Microplasmic Corporation Method for forming ceramic coatings by micro-arc oxidation of reactive metals
US6245436B1 (en) 1999-02-08 2001-06-12 David Boyle Surfacing of aluminum bodies by anodic spark deposition
US20060207884A1 (en) * 2005-03-17 2006-09-21 Volodymyr Shpakovsky Method of producing corundum layer on metal parts
US20140083843A1 (en) * 2012-09-25 2014-03-27 Southern Taiwan University Of Science And Technology Preparation apparatus for porous alumina template
EP2832898A1 (de) * 2014-02-05 2015-02-04 ThyssenKrupp Steel Europe AG Plasmaelektrolytisch veredeltes Bauteil und Verfahren zu seiner Herstellung
EP3061128A1 (en) * 2013-10-24 2016-08-31 Rogers Corporation Thermal management circuit materials, method of manufacture thereof, and articles formed therefrom
CN112345691A (zh) * 2020-12-07 2021-02-09 武汉海斯普林科技发展有限公司 一种铝电解电容器电解液溶质的氯离子含量检测方法

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60159195A (ja) * 1984-01-30 1985-08-20 Pentel Kk 酸化アルミニウム薄膜体
JPS60181295A (ja) * 1984-02-27 1985-09-14 Pentel Kk 酸化皮膜を有するアルミニウムまたはアルミニウム合金基体の製造方法
JPS62199797A (ja) * 1986-02-25 1987-09-03 Deitsupusoole Kk 可撓性金属−セラミツクス複合材料とその製造方法
DE4104847A1 (de) * 1991-02-16 1992-08-20 Friebe & Reininghaus Ahc Verfahren zur keramisierung von metalloberflaechen
DE102007046775A1 (de) * 2007-09-27 2009-04-02 Friedrich-Schiller-Universität Jena Verfahren zur Generierung von nanokristallinen oder nanokristallinhaltigen Metalloxid- und Metallmischoxidschichten auf sperrschichtbildenden Metallen

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2346658A (en) * 1938-12-02 1944-04-18 Brennan Corrosion resistant coating
US3293158A (en) * 1963-09-17 1966-12-20 Mcneill William Anodic spark reaction processes and articles
US3531385A (en) * 1968-12-13 1970-09-29 Matsushita Electric Ind Co Ltd Method of forming electrical insulating film on aluminium metals

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1595008A (enrdf_load_html_response) * 1968-12-11 1970-06-08

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2346658A (en) * 1938-12-02 1944-04-18 Brennan Corrosion resistant coating
US3293158A (en) * 1963-09-17 1966-12-20 Mcneill William Anodic spark reaction processes and articles
US3531385A (en) * 1968-12-13 1970-09-29 Matsushita Electric Ind Co Ltd Method of forming electrical insulating film on aluminium metals

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5385662A (en) * 1991-11-27 1995-01-31 Electro Chemical Engineering Gmbh Method of producing oxide ceramic layers on barrier layer-forming metals and articles produced by the method
US5487825A (en) * 1991-11-27 1996-01-30 Electro Chemical Engineering Gmbh Method of producing articles of aluminum, magnesium or titanium with an oxide ceramic layer filled with fluorine polymers
US6027629A (en) * 1994-11-16 2000-02-22 Kabushiki Kaisha Kobe Seiko Sho Vacuum chamber made of aluminum or its alloys, and surface treatment and material for the vacuum chamber
US5720866A (en) * 1996-06-14 1998-02-24 Ara Coating, Inc. Method for forming coatings by electrolyte discharge and coatings formed thereby
US6245436B1 (en) 1999-02-08 2001-06-12 David Boyle Surfacing of aluminum bodies by anodic spark deposition
US6197178B1 (en) 1999-04-02 2001-03-06 Microplasmic Corporation Method for forming ceramic coatings by micro-arc oxidation of reactive metals
US20060207884A1 (en) * 2005-03-17 2006-09-21 Volodymyr Shpakovsky Method of producing corundum layer on metal parts
US20140083843A1 (en) * 2012-09-25 2014-03-27 Southern Taiwan University Of Science And Technology Preparation apparatus for porous alumina template
EP3061128A1 (en) * 2013-10-24 2016-08-31 Rogers Corporation Thermal management circuit materials, method of manufacture thereof, and articles formed therefrom
EP2832898A1 (de) * 2014-02-05 2015-02-04 ThyssenKrupp Steel Europe AG Plasmaelektrolytisch veredeltes Bauteil und Verfahren zu seiner Herstellung
CN112345691A (zh) * 2020-12-07 2021-02-09 武汉海斯普林科技发展有限公司 一种铝电解电容器电解液溶质的氯离子含量检测方法
CN112345691B (zh) * 2020-12-07 2022-08-19 武汉海斯普林科技发展有限公司 一种铝电解电容器电解液溶质的氯离子含量检测方法

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FR2169259A1 (enrdf_load_html_response) 1973-09-07
NO133455C (enrdf_load_html_response) 1976-05-05
DE2203445A1 (de) 1973-08-02
JPS4883042A (enrdf_load_html_response) 1973-11-06
IT978434B (it) 1974-09-20
CH594070A5 (enrdf_load_html_response) 1977-12-30
NO133455B (enrdf_load_html_response) 1976-01-26
FR2169259B1 (enrdf_load_html_response) 1976-04-09

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