US20160376725A1 - Method for performing electropolishing treatment on aluminum material - Google Patents
Method for performing electropolishing treatment on aluminum material Download PDFInfo
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- US20160376725A1 US20160376725A1 US15/102,985 US201415102985A US2016376725A1 US 20160376725 A1 US20160376725 A1 US 20160376725A1 US 201415102985 A US201415102985 A US 201415102985A US 2016376725 A1 US2016376725 A1 US 2016376725A1
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- electropolishing
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- aluminum
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- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 262
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 262
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- 238000007254 oxidation reaction Methods 0.000 claims abstract description 37
- 206010040844 Skin exfoliation Diseases 0.000 claims abstract description 24
- 238000005868 electrolysis reaction Methods 0.000 claims abstract description 15
- 239000000243 solution Substances 0.000 claims description 109
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 82
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 38
- 238000005192 partition Methods 0.000 claims description 30
- 239000007864 aqueous solution Substances 0.000 claims description 20
- 150000001412 amines Chemical class 0.000 claims description 18
- 239000010407 anodic oxide Substances 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 229910000838 Al alloy Inorganic materials 0.000 claims description 11
- 238000007599 discharging Methods 0.000 claims description 10
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- IIACRCGMVDHOTQ-UHFFFAOYSA-N sulfamic acid Chemical compound NS(O)(=O)=O IIACRCGMVDHOTQ-UHFFFAOYSA-N 0.000 claims description 6
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 claims description 5
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- 238000012360 testing method Methods 0.000 description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 10
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- 238000003756 stirring Methods 0.000 description 7
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 6
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- 238000011161 development Methods 0.000 description 3
- 150000002222 fluorine compounds Chemical class 0.000 description 3
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
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- 238000007654 immersion Methods 0.000 description 3
- 230000001629 suppression Effects 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- BAVYZALUXZFZLV-UHFFFAOYSA-N Methylamine Chemical compound NC BAVYZALUXZFZLV-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 238000010306 acid treatment Methods 0.000 description 2
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- LNOPIUAQISRISI-UHFFFAOYSA-N n'-hydroxy-2-propan-2-ylsulfonylethanimidamide Chemical compound CC(C)S(=O)(=O)CC(N)=NO LNOPIUAQISRISI-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
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- WGYKZJWCGVVSQN-UHFFFAOYSA-N propylamine Chemical compound CCCN WGYKZJWCGVVSQN-UHFFFAOYSA-N 0.000 description 2
- 229910018134 Al-Mg Inorganic materials 0.000 description 1
- 229910018182 Al—Cu Inorganic materials 0.000 description 1
- 229910018467 Al—Mg Inorganic materials 0.000 description 1
- 229910018464 Al—Mg—Si Inorganic materials 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
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- 150000003973 alkyl amines Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- -1 ammonium ions Chemical class 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
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- NRNCYVBFPDDJNE-UHFFFAOYSA-N pemoline Chemical compound O1C(N)=NC(=O)C1C1=CC=CC=C1 NRNCYVBFPDDJNE-UHFFFAOYSA-N 0.000 description 1
- 231100000614 poison Toxicity 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-L sulfite Chemical compound [O-]S([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-L 0.000 description 1
- GRIPFENGMLEXMO-UHFFFAOYSA-N sulfuric acid Chemical compound OS(O)(=O)=O.OS(O)(=O)=O.OS(O)(=O)=O GRIPFENGMLEXMO-UHFFFAOYSA-N 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/16—Polishing
- C25F3/18—Polishing of light metals
- C25F3/20—Polishing of light metals of aluminium
-
- 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
- C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
-
- 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
- C25D11/18—After-treatment, e.g. pore-sealing
-
- 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
- C25D11/18—After-treatment, e.g. pore-sealing
- C25D11/20—Electrolytic after-treatment
-
- 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
- C25D11/18—After-treatment, e.g. pore-sealing
- C25D11/24—Chemical after-treatment
Abstract
Provided is a method of performing electropolishing treatment on an aluminum material, which is capable of easily producing an aluminum material having an excellent outer appearance with luster and uniformity on an industrial scale. The method of performing electropolishing treatment on an aluminum material includes immersing the aluminum material in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material, the method including: performing, as pretreatment for the electropolishing treatment, anodic oxidation treatment; performing, during the electropolishing treatment, bubble-diffusion-preventing treatment; and performing, as post-treatment for the electropolishing treatment, film peeling treatment for an electropolishing film.
Description
- The present invention relates to a method of performing electropolishing treatment on an aluminum material formed of aluminum or an aluminum alloy, and more particularly, to a method of performing electropolishing treatment on an aluminum material, which is suitable for producing an aluminum material having an excellent outer appearance with luster and uniformity.
- In electropolishing treatment of an aluminum material, a large amount of hydrogen gas is generated along with an electrolytic reaction of the aluminum material during the electropolishing treatment, and the hydrogen gas is formed into bubbles in an electrolytic solution to adhere to the surface of the aluminum material serving as a material to be treated. The bubbles adhering to the surface inhibit the electrolytic reaction on the surface of the aluminum material. As a result, portions to which the bubbles adhere become apparent as point-like defects after the electropolishing and impair luster, uniformity, and the like on the surface of the aluminum material after the electropolishing.
- In view of the foregoing, in order to obtain an aluminum material having an outer appearance excellent in luster and uniformity, it is necessary to prevent the bubbles from adhering to the surface of the aluminum material serving as the material to be treated during the electropolishing treatment or to remove the adhering bubbles. For example, there have been proposed an oscillation method for oscillating an aluminum material (Non Patent Literature 1), an electrolytic solution stirring method for stirring an electrolytic solution by shaking of an aluminum material or with an oscillating vane stirrer (Non Patent Literature 2), and the like.
- However, in the oscillation method and the electrolytic solution stirring method disclosed in
Non Patent Literatures 1 and 2, when the aluminum material has a complicated shape or a large area, it is difficult to completely prevent the adhesion of bubbles uniformly over the entire surface of the aluminum material and to completely remove the adhering bubbles. Further, the electropolishing treatment is performed through use of a concentrated acid, and hence it is necessary to manufacture a device configured to oscillate or shake the aluminum material or the oscillating vane stirrer with an expensive material excellent in acid resistance. Thus, considerable labor and cost are required also for maintaining and managing a facility. The methods are not preferred from the viewpoint of industry. - Further, when the electropolishing treatment is finished and current application is stopped, non-uniform dissolution occurs on the surface of the aluminum material after the electropolishing in an electropolishing solution having a strong dissolution ability, and the outer appearance and a mirror finishing property of the surface are impaired. Therefore, an anodic oxide film generated during the electropolishing treatment (hereinafter referred to as “electropolishing film”) is sometimes caused to remain intentionally. However, depending on the application, it may be necessary to remove the electropolishing film remaining on the surface of the aluminum material after the electropolishing.
- Therefore, the electropolishing film remaining on the surface of the aluminum material after the electropolishing has hitherto been removed, and for example, film peeling treatment involving immersing the aluminum material after the electropolishing in a peeling solution, such as a sodium hydroxide aqueous solution, a mixed aqueous solution of phosphoric acid and chromic acid, or an aqueous solution of sulfuric acid or nitric acid and a fluorine compound, to thereby dissolve and remove the anodic oxide film remaining on the surface of the aluminum material is performed (Non Patent Literature 3).
- The film peeling treatment method involving using a peeling solution formed of a mixed aqueous solution of phosphoric acid and chromic acid or an aqueous solution of sulfuric acid or nitric acid and a fluorine compound is an excellent method because the electropolishing film can be selectively dissolved and removed. However, chromic acid and the fluorine compound that are main components are toxic substances from the viewpoint of environment sanitation, and currently, it is actually difficult to use these substances. Further, in the film peeling treatment method involving using a peeling solution formed of a sodium hydroxide aqueous solution, the sodium hydroxide aqueous solution dissolves aluminum or an aluminum alloy as a base material. Therefore, the base material is also inevitably dissolved along with the dissolution of the electropolishing film on the surface, and as a result, luster exhibited by the electropolishing treatment is traded off to some degree.
-
- [NPL 1] “Aluminum surface technology handbook,” p. 106, Oct. 17, 1980, issued by Light Metal Publishing Co., Ltd.
- [NPL 2] Aluminum finishing society of Kinki, No. 188, 1997, pp. 6-10
- [NPL 3] “Aluminum Encyclopedia”, p. 1017, Nov. 1, 1969, issued by Light Metal Syndicate
- In view of the foregoing, the inventors of the present invention have made extensive investigations regarding a method of performing electropolishing treatment on an aluminum material, which solves various problems caused by the electropolishing treatment of an aluminum material described above and which can easily produce an aluminum material having an excellent outer appearance with luster and uniformity on an industrial scale. The inventors of the present invention have also made the following investigations regarding a problem of point-like defects caused by the adhesion of bubbles generated along with chemical dissolution of the aluminum material at the start of and during the electropolishing treatment of the aluminum material and a problem involved in dissolution removal of an electropolishing film remaining on the surface of the aluminum material performed after the electropolishing of the aluminum material. As a result, the inventors of the present invention have developed the following method capable of solving the problems.
- First, the inventors of the present invention have made the following investigations and development regarding the problem of point-like defects caused by the adhesion of bubbles at the start of and during the electropolishing treatment of the aluminum material.
- Specifically, the inventors of the present invention have made detailed investigations on a generation mechanism of the point-like defects generated during the electropolishing treatment, and as a result, have found that the point-like defects generated on the surface of the aluminum material after the electropolishing are not pits (dents) as considered hitherto but protrusions. Further, the inventors of the present invention have found the following facts. Hydrogen gas that causes such point-like defects is not merely generated as a result of an electrolytic reaction during the electropolishing treatment under application of a current. When the aluminum material is immersed in an electrolytic treatment solution under no application of a current before the electropolishing treatment, the aluminum material is brought into contact with the electrolytic treatment solution to cause a chemical dissolution reaction. Hydrogen gas generated through the reaction is formed into bubbles to adhere to the surface of the aluminum material, and the adhering bubbles also inhibit the electrolytic reaction during the electropolishing treatment performed later, to thereby cause the point-like defects.
- Therefore, in the related-art oscillation method for oscillating an aluminum material serving as a material to be treated and the related-art electrolytic solution stirring method involving using the shaking of an aluminum material serving as a material to be treated or an oscillating vane stirrer, as compared to the case where the aluminum material is left to stand still without taking any measure, the problem of the point-like defects caused by the adhesion of bubbles during the electropolishing treatment of the aluminum material can be solved significantly. However, in the oscillation method and the electrolytic solution stirring method, a great deal of experience and a high degree of skill are required for adjusting the strength and magnitude of the oscillation, shaking, or stirring. Further, the inventors of the present invention have found the following facts. The adhesion of bubbles generated when the aluminum material is immersed in the electrolytic treatment solution under no application of a current at the beginning of the electropolishing treatment cannot be prevented. Further, it is difficult to completely remove the bubbles that have once adhered to the surface of the aluminum material by the oscillation method or the electrolytic solution stirring method during the electropolishing treatment. Further, the related-art methods are not applicable to a high-quality and excellent outer appearance with luster and uniformity, particularly as a mirror surface in which even slight defects are not accepted with respect to the surface of the aluminum material after the electropolishing.
- In view of the foregoing, the inventors of the present invention have focused attention on the following facts. During the electropolishing treatment of the aluminum material, in the electrolytic treatment solution having an extremely strong ability to dissolve the aluminum material, any one of an electrolytic reaction in which an electropolishing film is formed and a dissolution reaction in which metal aluminum is chemically dissolved in the electrolytic treatment solution occurs on the surface of the aluminum material. In an initial stage of the electropolishing treatment, in order to perform the electrolytic reaction in the electrolytic treatment solution having a strong dissolution ability, it is necessary to cause a large current to flow temporarily so that the electropolishing film is formed rapidly while overcoming the chemical dissolution of the metal aluminum. As a result, the inventors of the present invention have developed a method including performing, as pretreatment for the electropolishing treatment, anodic oxidation treatment under predetermined conditions so as to suppress the generation of hydrogen gas caused by the chemical dissolution of the surface of the aluminum material in the initial stage of the electropolishing treatment by an anodic oxide film formed in advance on the surface of the aluminum material, and utilizing the anodic oxide film as an electropolishing film required in the initial stage of the electropolishing treatment. Thus, the present invention has been completed.
- Further, the inventors of the present invention have made the following investigations and development regarding the problem of the point-like defects caused by the adhesion of bubbles at the start of and during the electropolishing treatment of the aluminum material.
- Specifically, the inventors of the present invention have made further investigations regarding how the generation and adhesion of bubbles occur during the electropolishing treatment of the aluminum material. As a result, the inventors of the present invention have found that, during the electropolishing treatment after the start of application of a current, the generation of the hydrogen gas hardly occurs on an aluminum material side serving as an anode, and the generation of the hydrogen gas occurs mainly on a cathode side serving as a counter electrode of the aluminum material. Further, the inventors of the present invention have found that the bubbles of the hydrogen gas generated on the cathode side diffuse to the aluminum material side serving as the anode, and the diffusing bubbles adhere to the surface of the aluminum material, to thereby cause the problem of the point-like defects.
- In view of the foregoing, the inventors of the present invention have made various investigations regarding a method of preventing the bubbles of the hydrogen gas generated on the cathode side from diffusing to the aluminum material side serving as the anode. As a result, the inventors of the present invention have found that the bubbles of the hydrogen gas generated on the cathode can be effectively prevented from diffusing to the aluminum material side serving as the anode by forming a cathode partition chamber formed of a liquid-permeable material which is non-permeable to the bubbles to be generated in an electrolytic treatment layer (non-permeable to bubbles) and is permeable to the electrolytic treatment solution so that conductivity between the electrodes can be ensured, and arranging the cathode in the cathode partition chamber. Thus, the present invention has been completed.
- Further, the inventors of the present invention have made the following investigations and development regarding the problem involved in dissolution removal of the electropolishing film remaining on the surface of the aluminum material performed after the electropolishing of the aluminum material.
- Specifically, in the electropolishing treatment of the aluminum material, when the aluminum material is kept immersed in the electrolytic treatment solution after the completion of the treatment, the surface of the aluminum material is chemically dissolved with the electrolytic treatment solution, and non-uniform chemical dissolution occurs at this time to form local convex portions, which cause the point-like defects. Therefore, it is necessary to remove the aluminum material after the electropolishing from the electrolytic treatment solution immediately after the completion of the treatment. However, the electropolishing treatment is a method in which a porous electropolishing film is dissolved at high speed while the porous electropolishing film is formed, and hence the electrolytic treatment solution has a strong ability to dissolve the aluminum material, and the chemical dissolution of the surface of the aluminum material starts immediately after application of a current is stopped. Therefore, it is difficult to prevent non-uniform chemical dissolution immediately after the completion of the electropolishing treatment while achieving an excellent mirror finishing property by keeping the electrolytic reaction and the chemical dissolution reaction during the electropolishing treatment in a satisfactory state.
- In view of the foregoing, as a method of solving the problem caused by the chemical dissolution after the electropolishing, the electropolishing film is caused to remain intentionally on the surface of the aluminum material after the electropolishing, and the electropolishing film remaining on the surface is dissolved and removed after the electropolishing. However, as described above, the dissolution removal of the electropolishing film to be performed after the electropolishing has a problem.
- In view of the foregoing, the inventors of the present invention have made further investigations regarding the dissolution removal of the electropolishing film on the surface of the aluminum material after the electropolishing, and have focused attention on the following facts. The dissolution of the electropolishing film (oxide) is a chemical dissolution reaction not involving the movement of a charge. In contrast, the dissolution of a base material (metal) is an electrochemical reaction involving the movement of a charge. Then, the inventors of the present invention have made investigations so as to develop a post-treatment solution excellent in such selective dissolution ability as to accelerate the chemical dissolution reaction while suppressing the electrochemical reaction, and have attained a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine. Thus, the present invention has been completed.
- Thus, an object of the present invention is to provide a method of performing electropolishing treatment on an aluminum material, which can easily produce an aluminum material having an excellent outer appearance with luster and uniformity on an industrial scale.
- Specifically, the present application provides the following first to fourth inventions, and the first to fourth inventions are sometimes referred to as “the present invention” collectively.
- According to a first invention of the present application, there is provided a method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
- the method including, as pretreatment for the electropolishing treatment, performing anodic oxidation treatment including subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material.
- Further, according to a second invention of the present application, there is provided a method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
- the electrolytic treatment tank including a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank,
- the method including, during the electropolishing treatment of the aluminum material, performing bubble-diffusion-preventing treatment including: preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side; and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port.
- Further, according to a third invention of the present application, there is provided a method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
- the method including, as post-treatment for the electropolishing treatment, performing film peeling treatment including immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove an electropolishing film present on the surface of the aluminum material.
- Further, according to a fourth invention of the present application, there is provided a method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
- the method including performing two kinds or three kinds of the treatments selected from the anodic oxidation treatment as the pretreatment of the first invention, the bubble-diffusion-preventing treatment during the electropolishing treatment of the second invention, and the film peeling treatment of the electropolishing film as the post-treatment of the third invention.
- In the present invention, there is no particular limitation on the aluminum material formed of aluminum or an aluminum alloy to be subjected to the electropolishing treatment, and various aluminum materials required to be mirror-finished by the electropolishing treatment are applicable. Examples of the aluminum material include Al—Cu-based 2000-based materials, Al—Mg-based 5000-based materials, and Al—Mg—Si-based 6000-based materials. Of those, in particular, as an aluminum material having a high aluminum purity (Al purity) and required to be highly mirror-finished, there may be given, for example, a high-purity aluminum material having a purity of 99.99% or more, a pure aluminum-based 1000-based material (such as A1050 material), and the like.
- Further, in the aluminum material, the surface thereof may be subjected to preliminary mirror-finishing treatment in advance by means of buffing, cutting work, or chemical polishing, and the present invention is also effective for an aluminum material having a surface subjected to such preliminary mirror-surface finishing in advance.
- Further, in the present invention, the treatment conditions for the electropolishing treatment of the aluminum material in the electrolytic treatment solution in the electrolytic treatment tank do not particularly differ from the conditions of related-art electropolishing treatment of an aluminum material, and treatment conditions for the related-art electropolishing treatment can be directly adopted with regard to the composition of the electrolytic treatment solution, the electrolysis voltage, the treatment temperature, the treatment time, the inrush current at the start of the electropolishing treatment, and other conditions. Herein, as the electrolytic treatment solution, there may be given, for example, a solution having a composition of phosphoric acid and sulfuric acid (volume ratio: 7:3), a composition of phosphoric acid and sulfuric acid (volume ratio: 1:1), and the like.
- The first invention of the present application is the method of performing electropolishing treatment on an aluminum material, the method including, as pretreatment for the electropolishing treatment, performing anodic oxidation treatment including subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank to be used in the electropolishing treatment at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material.
- In this case, it is important in the anodic oxidation treatment as the pretreatment to perform the anodic oxidation treatment in the pretreatment tank arranged separately from the electrolytic treatment tank. Further, it is important in the anodic oxidation treatment to subject the aluminum material to the anodic oxidation at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of the pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution during the electropolishing treatment. With this, an intended anodic oxide film can be formed easily on the surface of the aluminum material during the pretreatment. Further, through adoption of such anodic oxidation treatment as the pretreatment, a power source specification during the electropolishing treatment can be directly utilized, and hence it is not necessary to separately prepare a dedicated power source. Further, it is not necessary to form the anodic oxide film on the surface of the aluminum material by causing a large current to flow in an initial stage of the electropolishing treatment, and hence the capacity of the power source during the electropolishing treatment can be reduced, with the result that a relatively small and inexpensive power source device can be adopted.
- Further, as the pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution during the electropolishing treatment to be used in the anodic oxidation treatment as the pretreatment, specifically, there are given, for example, a sulfuric acid aqueous solution having a composition of a sulfuric acid concentration of 15 mass %, an oxalic acid aqueous solution having a composition of an oxalic acid concentration of 2 mass %, and the like. When the electrolytic treatment solution and the pretreatment solution use the same acid, for example, when the acid is sulfuric acid, a sulfuric acid aqueous solution having a sulfuric acid concentration lower than that of the electrolytic treatment solution or having a pH value higher than that of the electrolytic treatment solution is used as the pretreatment solution. Further, the treatment conditions for the anodic oxidation treatment as the pretreatment do not differ from the treatment conditions for ordinary anodic oxidation treatment.
- Further, in the anodic oxidation treatment as the pretreatment, the thickness of the anodic oxide film to be formed on the surface of the aluminum material maybe the thickness formed by general anodic oxidation treatment. There is no particular limitation on the thickness, and the thickness is generally from about several tens of nanometers to about several tens of micrometers.
- Further, the second invention of the present application is the method of performing electropolishing treatment on an aluminum material, the electrolytic treatment tank including a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank,
- the method including, during the electropolishing treatment of the aluminum material, performing bubble-diffusion-preventing treatment including: preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side; and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port.
- In this case, it is sufficient that the cathode partition chamber configured to partition the cathode from the aluminum material serving as the anode be formed of at least a material non-permeable to bubbles and permeable to a liquid, include a partition wall for partitioning the cathode and the aluminum material and the discharge port for the hydrogen gas, and be able to discharge the hydrogen gas generated in the cathode partition chamber out of the tank through the discharge port. Further, as a material for forming the cathode partition chamber, there may be given, for example, a porous film made of Teflon (trademark), a glass sintered filter, and a filter medium formed of glass, such as glass fibers.
- Further, the third invention of the present application is the method of performing electropolishing treatment on an aluminum material, the method including, as post-treatment for the electropolishing treatment, performing film peeling treatment including immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove an electropolishing film present on the surface of the aluminum material.
- As the post-treatment solution to be used in the film peeling treatment as the post-treatment, the sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine is used. It is desired that the sulfuric acid solution contain at least sulfate ions and/or sulfite ions and ammonium ions derived from the amine in the aqueous solution, and the pH of the sulfuric acid solution be generally 2 or less, preferably 1.5 or less. When the pH value of the sulfuric acid solution is more than 2, there is a risk in that the dissolution of the film may hardly proceed. Such post-treatment solution is desirably a sulfuric acid solution obtained by dissolving a sulfate of an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid and an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid, an amine, and a sulfate of an amine in water, or a sulfuric acidic solution obtained by dissolving amidosulfuric acid (sulfamic acid) or an amidosulfuric acid salt thereof, such as an ammonium salt thereof, in water, more preferably an aqueous solution of amidosulfuric acid. Further, examples of the amine for preparing the sulfuric acid solution as the post-treatment solution may include ammonia, and an alkylamine, such as methylamine or propylamine.
- As a specific example of the film peeling treatment performed in the third invention, for example, in the case of using a 3 mass % sulfamic acid aqueous solution as the post-treatment solution, there is given a method involving immersing the aluminum material in the solution under the treatment conditions of 70° C. and 10 minutes.
- Further, the fourth invention of the present application is the method of performing electropolishing treatment on an aluminum material, the method including performing two kinds or three kinds of the treatments selected from the anodic oxidation treatment as the pretreatment of the first invention, the bubble-diffusion-preventing treatment during the electropolishing treatment of the second invention, and the film peeling treatment of the electropolishing film as the post-treatment of the third invention.
- In the fourth invention, when two kinds of the treatments are combined, the treatments of the first invention, the second invention, and the third invention described above may be combined arbitrarily. In the electropolishing treatment of the aluminum material, for example, the anodic oxidation treatment of the first invention and the bubble-diffusion-preventing treatment of the second invention may be combined. Further, the anodic oxidation treatment of the first invention and the coating peeing treatment of the third invention may be combined. Further, the bubble-diffusion-preventing treatment of the second invention and the film peeling treatment of the third invention may be combined. Further, when three kinds of the treatments are combined, the anodic oxidation treatment of the first invention, the bubble-diffusion-preventing treatment of the second invention, and the film peeling treatment of the third invention are combined to perform the electropolishing treatment of the aluminum material.
- When those two kinds or three kinds of the treatments are combined to perform the electropolishing treatment of the aluminum material, the effects obtained in each treatment can be attained in each step of the pretreatment, the electropolishing treatment, and the post-treatment. Therefore, it is desired that those two kinds or three kinds of the treatments be performed in combination in accordance with the requirements for the outer appearance, such as luster and uniformity, required for the aluminum material to be subjected to the electropolishing treatment.
- According to the first invention, when the electropolishing treatment of the aluminum material is performed, particularly, when the aluminum material is immersed in the electrolytic treatment solution in the electrolytic treatment tank, the generation of the hydrogen gas caused by the chemical dissolution reaction on the surface of the aluminum material can be suppressed, the point-like defects caused by the adhesion of bubbles can be reduced significantly, and the outer appearance excellent in luster and uniformity can be achieved in the aluminum material after the electropolishing. Further, it is not necessary to cause a large current to flow in an initial stage of the electropolishing treatment, and thus a power source facility can also be downsized.
- Further, according to the second invention, the hydrogen gas to be generated on the cathode serving as a counter electrode of the aluminum material does not diffuse to form bubbles on the surface of the aluminum material. Therefore, the point-like defects caused by the adhesion of the bubbles can be prevented, and the outer appearance excellent in luster and uniformity can be achieved in the aluminum material after the electropolishing.
- Further, according to the third invention, the electropolishing film remaining on the aluminum material after the electropolishing can be selectively dissolved and removed by the film peeling treatment, and the outer appearance excellent in luster and uniformity can be achieved in the aluminum material after the electropolishing.
- Still further, according to the fourth invention, through combination of the treatments of the first invention, the second invention, and the third invention described above, the outer appearance excellent in luster and uniformity can be achieved in the aluminum material after the electropolishing.
-
FIG. 1 are each an explanatory view for illustrating a concept of the first invention.FIG. 1(a) is an illustration of an anodic oxidation treatment step as pretreatment, andFIG. 1(b) is an illustration of an electropolishing treatment step. -
FIG. 2 are each an explanatory view for illustrating a concept of the second invention.FIG. 2(A) is an illustration of a related-art electropolishing treatment step, andFIG. 2(B) is an illustration of an electropolishing treatment step of the second invention. - Now, an embodiment of a first invention is described with reference to the conceptual views of the invention illustrated in
FIGS. 1 . Further, an embodiment of a second invention is described with reference to the conceptual views of the invention illustrated inFIGS. 2 . Further, a preferred embodiment of a third invention is described. -
FIG. 1 are each an explanatory view for illustrating a concept of a method of performing electropolishing treatment on an aluminum material according to the first invention, and a treatment process including an anodic oxidation treatment step (a) as pretreatment and an electropolishing treatment step (b) is illustrated. - In
FIG. 1 , in the anodic oxidation treatment step (a), apretreatment solution 3 for anodic oxidation treatment to be performed as pretreatment is filled into apretreatment tank 2 arranged separately from an electrolytic treatment tank 1 in the electropolishing treatment step (b). Analuminum material 4 serving as a material to be treated is set as an anode, and a DC voltage is applied between the anode and acathode 5 serving as a counter electrode of thealuminum material 4 to form ananodic oxide film 6 on the surface of the aluminum material. - Next, in the electropolishing treatment step (b) of
FIG. 1 , anelectrolytic treatment solution 7 is filled into the electrolytic treatment tank 1, and then, thealuminum material 4 serving as the material to be treated, in which theanodic oxide film 6 has been formed on the surface in the anodic oxidation treatment step (a) as the pretreatment, is immersed in theelectrolytic treatment solution 7. After that, thealuminum material 4 is set as an anode, and a DC voltage is applied between the anode and acathode 8 serving as a counter electrode of thealuminum material 4 to perform electropolishing treatment on the surface of thealuminum material 4. - In the electropolishing treatment step (b), at the time of immersion (S1) of the
aluminum material 4 in theelectrolytic treatment solution 7, thealuminum material 4 serving as the material to be treated is immersed in theelectrolytic treatment solution 7 under no application of a current. However, theanodic oxide film 6 has been formed on the surface of thealuminum material 4, and hence a metal surface of thealuminum material 4 is not brought into direct contact with theelectrolytic treatment solution 7 at the time of the immersion (S1) under no application of a current. Further, theanodic oxide film 6 on the surface of thealuminum material 4, which is brought into direct contact with theelectrolytic treatment solution 7, is gradually dissolved into theelectrolytic treatment solution 7, and hydrogen gas is not generated at this time. - Further, in the electropolishing treatment step (b), when a DC voltage is applied between the
aluminum material 4 serving as the anode and thecathode 8 to start the electropolishing treatment, theanodic oxide film 6 on the surface of thealuminum material 4 is gradually dissolved into theelectrolytic treatment solution 7 to be eliminated at the time of electrolytic treatment (S2) of thealuminum material 4. Further, the generation of anelectropolishing film 9 and the chemical dissolution of metal aluminum occur on the surface of thealuminum material 4, and as a result, theanodic oxide film 6 is gradually dissolved to be eliminated. Further, the surface of thealuminum material 4 is subjected to electropolishing. - After the electropolishing treatment is completed as described above, the application of a current is stopped, and the
aluminum material 4 after the electropolishing is immediately pulled up from the electrolytic treatment tank 1. Then, thealuminum material 4 is washed with pure water and dried with air to provide the aluminum material after the electropolishing. - In this case, as illustrated in
FIG. 1 , when theelectropolishing film 9 is caused to remain intentionally on the surface of thealuminum material 4 after the electropolishing at the time of completion of the application of a current (S3) in the electropolishing treatment, and thereafter, theelectropolishing film 9 remaining on the surface is removed, the third invention is performed successively. The third invention described below is a method effective for selectively dissolving and removing the electropolishing film on the surface of the aluminum material generated by the electropolishing treatment. Therefore, the third invention does not need to be performed successively after the first invention, and needless to say, may be performed successively after related-art electropolishing treatment. - In the third invention, coating peeing treatment including immersing the aluminum material after the electropolishing, which has been pulled up from the electropolishing solution at the time of completion of the electropolishing treatment, in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby selectively dissolve and remove the electropolishing film remaining on the surface of the aluminum material after the electropolishing.
- After the film peeling treatment is completed, the aluminum material after the electropolishing is pulled up from a post-treatment tank. Then, the aluminum material is immediately washed with pure water and dried with air to provide the aluminum material after the electropolishing as a product.
- Next,
FIG. 2 are each an explanatory view for illustrating a concept of a method of performing electropolishing treatment on an aluminum material according to the second invention.FIG. 2(A) is an explanatory view for illustrating a related-art electropolishing treatment step using an electrolytic treatment tank, and further,FIG. 2B is an explanatory view for illustrating an electropolishing treatment step using an electrolytic treatment tank according to the second invention. - In
FIG. 2(A) in which the electrolytic treatment tank 1 of the related-art is illustrated, theelectrolytic treatment solution 7 is filled into the electrolytic treatment tank 1, and thealuminum material 4 serving as the material to be treated is immersed in theelectrolytic treatment solution 7. After that, thealuminum material 4 is set as an anode, and a DC voltage is applied between the anode and thecathode 8 serving as a counter electrode of thealuminum material 4 to perform the electropolishing treatment on the surface of thealuminum material 4. Then, in the related-art electropolishing treatment using the electrolytic treatment tank 1, during the electropolishing treatment, bubbles 10 of hydrogen gas are generated on thecathode 8 side and diffuse into theelectrolytic treatment solution 7. Most of thebubbles 10 fly into the atmosphere from a liquid surface of theelectrolytic treatment solution 7. However, part of thebubbles 10 diffuses to thealuminum material 4 side serving as the anode to adhere to the surface of thealuminum material 4, which causes the generation of point-like defects on the surface of the aluminum material after the electropolishing. - In contrast, in the second invention, as illustrated in
FIG. 2B , acathode partition chamber 11 is formed in the electrolytic treatment tank 1. Thecathode partition chamber 11 is formed of a material which is non-permeable to thebubbles 10 of the hydrogen gas generated on thecathode 8 serving as the counter electrode of thealuminum material 4 and is permeable to a liquid. Thecathode partition chamber 11 is configured to partition thecathode 8 from thealuminum material 4 and includes adischarge port 12 for discharging the generated bubbles 10 out of the tank. During the electropolishing treatment of thealuminum material 4, thebubbles 10 generated on thecathode 8 in thecathode partition chamber 11 are prevented from diffusing to thealuminum material 4 side and are discharged out of the tank through thedischarge port 12. By virtue of the bubble-diffusion-preventing treatment, thebubbles 10 of the hydrogen gas generated on thecathode 8 during the electropolishing treatment can be prevented from adhering to the surface of thealuminum material 4. - Now, a method of performing electropolishing treatment on an aluminum material of the present invention is described on the basis of Examples and Comparative Examples.
- A plate material having an Al purity of 99.99 mass % was used as an aluminum material, and an aluminum piece having dimensions of 50 mm×50 mm×10 mm was cut out from the plate material. The aluminum piece was subjected to anodic oxidation treatment as pretreatment under treatment conditions (voltage, electrical quantity, and temperature) shown in Table 1 through use of a pretreatment solution shown in Table 1. The resultant aluminum piece was washed with water and dried to provide a pretreated aluminum piece of each of Examples 1 to 3.
- The pretreated aluminum piece of each of Examples and Comparative Example thus obtained was subjected to electropolishing treatment under treatment conditions (temperature, voltage, time, and inrush current) shown in Table 1 through use of an electrolytic treatment solution shown in Table 1. The resultant aluminum piece was immediately washed with water and dried to provide an aluminum piece (test piece) after the electropolishing of each of Examples 1 to 3.
- The same aluminum piece as that used in each of Examples 1 to 3 described above was used to be subjected to electropolishing treatment under treatment conditions (temperature, voltage, time, and inrush current) shown in Table 1 through use of an electrolytic treatment solution shown in Table 1 without being subjected to anodic oxidation treatment as pretreatment. The resultant aluminum piece was immediately washed with water and dried to provide an aluminum piece (test piece) after the electropolishing of Comparative Example 1.
- [Evaluation of Bubble Adhesion-Suppressing Property During Treatment]
- During the electropolishing treatment in Examples 1 to 3 and Comparative Example 1 described above, the surface of the aluminum piece was visually observed from outside of a treatment tank made of glass, and bubbles of hydrogen gas adhering to the surface of the aluminum piece of each of Examples and Comparative Example were examined. Then, a suppression effect on bubble adhesion during the electropolishing treatment (bubble adhesion-suppressing property during treatment) was evaluated based on the following criteria: ◯: no adhesion of bubbles; Δ: adhesion of two or less bubbles (per 1 cm2); and x: adhesion of three or more bubbles (per 1 cm2).
- The results are shown in Table 1.
- [Evaluation of Outer Appearance Observation]
- Further, each of the test pieces obtained in Examples 1 to 3 and Comparative Example 1 described above was visually observed for the following outer appearance, and examined and evaluated for mirror luster, point-like defects, and presence or absence of interference color.
- Regarding the mirror luster, the degree of bubble adhesion during the electropolishing treatment was evaluated by visually observing how an object is reflected on a sample based on the following criteria: ◯: the object is reflected on the sample clearly without being distorted; Δ: the object is reflected on the sample clearly but is partially distorted; and x: the object is distorted significantly and is not reflected on the sample.
- Further, regarding the point-like defects, the surface of each of the test pieces was visually observed under a fluorescent lamp, and the number of visually recognized point-like defects was counted and evaluated based on the following criteria: ◯: 0 pieces/cm2; Δ: 1 piece/cm2 or more and less than 3 pieces/cm3; and x: 3 pieces/cm2 or more.
- Regarding the presence or absence of interference color, each of the test pieces was tilted by 70° under a fluorescent lamp, and the surface thereof was visually observed. Then, interference color caused by an electropolishing film was confirmed and evaluated based on the following criteria: ◯: no interference color is seen; Δ: interference color is seen in part of the sample; and x: an interference pattern is seen over the entire sample.
- The results are shown in Table 1.
-
TABLE 1 Example Comparative 1 2 3 Example 1 Pretreatment Pretreatment 15 mass % 2 mass % oxalic 5 mass % tartaric — (anodic oxidation solution sulfuric acid acid acid treatment) Temperature (° C.) 20 20 20 — Voltage (V) 15 30 30 — Electrical 0.1 0.1 0.1 — quantity (C/cm2) Electropolishing Electrolytic Sulfuric Sulfuric Sulfuric Sulfuric treatment treatment acid-phosphoric acid-phosphoric acid-phosphoric acid-phosphoric solution acid acid acid acid (mass ratio) (1:5) (1:5) (1:5) (1:5) Temperature (° C.) 60 60 60 60 Voltage (V) 30 30 30 30 Time (min) 5 5 5 5 Inrush current 20 15 15 30 (A/dm2) Bubble adhesion-suppressing property Δ Δ Δ x during treatment Outer appearance Point-like defect 1 1 1 8 observation (piece(s)/cm2) evaluation Mirror luster ∘ ∘ ∘ x - In a tank for electropolishing treatment, a cathode partition chamber which was configured to partition a cathode from an anode (aluminum material) and included a discharge port for discharging bubbles of hydrogen gas to be generated during the electropolishing treatment out of the window was formed through use of a porous filter made of Teflon (trademark) (Example 4) or a filter made of glass fibers (Example 5), Teflon and the glass fibers being each a material non-permeable to bubbles of hydrogen gas and permeable to a liquid, to thereby constitute an electrolytic treatment tank.
- Further, as the aluminum material, the same aluminum piece having an Al purity of 99.99 mass % as that used in each of Examples 1 to 3 described above was used.
- Next, an electrolytic treatment solution (solution containing sulfuric acid and phosphoric acid in a mass ratio of 1:5) shown in Table 2 was loaded into the electrolytic treatment tank, and the aluminum piece was subjected to electropolishing treatment while bubble-diffusion-preventing treatment was performed with the cathode partition chamber under treatment conditions (temperature, voltage, time, and inrush current) shown in Table 2. The resultant aluminum piece was immediately washed with water and dried to provide an aluminum piece (test piece) after the electropolishing of each of Examples 4 and 5.
- The test pieces of Examples 4 and 5 thus obtained were examined and evaluated for a bubble adhesion-suppressing property during treatment, mirror luster, point-like defects, and presence or absence of interference color in the same manner as in Examples 1 to 3 described above.
- The results are shown in Table 2 together with those of Comparative Example 1 described above without the bubble-diffusion-preventing treatment.
-
TABLE 2 Example Comparative 4 5 Example 1 Electropolishing Presence or absence of Present Present Absent treatment bubble-diffusion-preventing treatment (cathode partition chamber) Electrolytic treatment Sulfuric Sulfuric Sulfuric solution acid-phosphoric acid-phosphoric acid-phosphoric (mass ratio) acid acid acid (1:5) (1:5) (1:5) Temperature (° C.) 60 60 60 Voltage (V) 30 30 30 Time (min) 5 5 5 Inrush current (A/dm2) 30 30 30 Bubble adhesion-suppressing Δ Δ x property during treatment Suppression effect on bubble generation ∘ ∘ x Outer appearance Point-like defect 1 1 7 observation (piece(s)/cm2) evaluation Mirror luster ∘ ∘ Δ - After the electropolishing treatment was performed in the same manner as in Comparative Example 1 described above, film peeling treatment involving immersing the aluminum piece in a post-treatment solution under conditions shown in Table 3, to thereby peel the electropolishing film, was performed as post-treatment through use of a post-treatment solution shown in Table 3 to provide an aluminum piece (test piece) after the electropolishing of each of Examples 6 and 7 and Comparative Examples 2 and 3.
- The test pieces of Examples 6 and 7 and Comparative Examples 2 and 3 thus obtained were examined and evaluated for a bubble adhesion-suppressing property during treatment, mirror luster, point-like defects, and presence or absence of interference color in the same manner as in Examples 1 to 3 described above.
- The results are shown in Table 3.
-
TABLE 3 Example Comparative Example 6 7 2 3 Electropolishing Electrolytic Sulfuric Sulfuric Sulfuric Sulfuric treatment treatment acid-phosphoric acid-phosphoric acid-phosphoric acid-phosphoric solution acid acid acid acid (mass ratio) (1:5) (1:5) (1:5) (1:5) Temperature 60 60 60 60 (° C.) Voltage (V) 30 30 30 30 Time (min) 5 5 5 5 Inrush current 30 30 30 30 (A/dm2) Post-treatment Post-treatment 3 mass % Sulfuric NaOH Dry blasting (film peeling solution amidosulfuric acid + triethanol etching treatment) acid (pH = 0.9) amine (pH = 1.7) (pH = 13.0) Temperature 70 60 20 Room (° C.) temperature Time (min) 10 7 5 3 min Bubble adhesion-suppressing x x x x property during treatment Outer appearance Point-like 5 5 Large Large number observation defect number evaluation (piece(s)/cm2) Mirror luster Δ Δ x x - The pretreatment (anodic oxidation treatment) of Example 1, the bubble-diffusion-preventing treatment of Example 4, and/or the post-treatment (film peeling treatment) of Example 6 were performed as shown in Table 4 through use of the same aluminum piece having an Al purity of 99.99 mass % as that used in each of Examples 1 to 3 described above as the aluminum material, to thereby provide an aluminum piece (test piece) after the electropolishing of each of Examples 8 to 11.
- The test pieces of Examples 8 to 11 thus obtained were examined and evaluated for a bubble adhesion-suppressing property during treatment, mirror luster, point-like defects, and presence or absence of interference color in the same manner as in Examples 1 to 3 described above. Further, total evaluation was performed by defining, in those evaluation items, the case where all the items were satisfactory (test piece had mirror luster in which no interference color was observed and no defects were recognized over a wide area) to be ⊚, and the case where any two or three items were satisfactory to be ◯.
- The results are shown in Table 4.
-
TABLE 4 Example 8 9 10 11 Pretreatment Pretreatment 15 mass % 15 mass % 15 mass % — (anodic oxidation solution sulfuric acid sulfuric acid sulfuric acid treatment) Temperature (° C.) 20 20 20 — Voltage (V) 15 15 15 — Electric charge 0.1 0.1 0.1 — (C/cm2) Electropolishing Presence or Present Present Absent Present treatment absence of cathode partition chamber Electrolytic Sulfuric Sulfuric Sulfuric Sulfuric treatment solution acid-phosphoric acid-phosphoric acid-phosphoric acid-phosphoric (mass ratio) acid acid acid acid (1:5) (1:5) (1:5) (1:5) Temperature (° C.) 60 60 60 60 Voltage (V) 30 30 30 30 Time (min) 5 5 5 5 Inrush current 20 20 20 30 (A/dm2) Post-treatment Post-treatment 3 mass % — 3 mass % 3 mass % (film peeling solution amidosulfuric amidosulfuric amidosulfuric treatment) acid acid acid (pH = 0.9) (pH = 0.9) (pH = 0.9) Temperature (° C.) 70 — 70 70 Time (min) 10 — 10 10 Bubble adhesion-suppressing property ◯ ◯ X ◯ during treatment Suppression effect on bubble generation ◯ ◯ ◯ X Outer appearance Point-like defect ◯ ◯ Δ Δ observation (piece/cm2) evaluation Mirror luster ◯ ◯ ◯ ◯ Interference color ◯ X ◯ ◯ Total evaluation ⊚ ◯ ◯ ◯ - a . . . anodic oxidation treatment step, b . . . electropolishing treatment step, S1 . . . time of immersion under no application of current in electropolishing treatment, S2 . . . time of electrolytic treatment in electropolishing treatment, S3 . . . time of completion of application of current in electropolishing treatment, 1 . . . electrolytic treatment tank, 2 . . . pretreatment tank, 3 . . . pretreatment solution, 4 . . . aluminum material (material to be treated), 5, 8 . . . cathode, 6 . . . anodic oxide film, 7 . . . electrolytic treatment solution, 9 . . . electropolishing film, 10 . . . bubbles of hydrogen gas, 11 . . . cathode partition chamber, 12 . . . discharge port.
Claims (6)
1. A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
the method comprising, as pretreatment for the electropolishing treatment, performing anodic oxidation treatment including subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material.
2. A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
the electrolytic treatment tank comprising a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank,
the method comprising, during the electropolishing treatment of the aluminum material, performing bubble-diffusion-preventing treatment including: preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side; and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port.
3. A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
the method comprising, as post-treatment for the electropolishing treatment, performing film peeling treatment including immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove an electropolishing film present on the surface of the aluminum material.
4. A method of performing electropolishing treatment on an aluminum material including immersing an aluminum material formed of aluminum or an aluminum alloy in an electrolytic treatment solution in an electrolytic treatment tank, and applying an electrolysis voltage through use of the aluminum material as an anode, to thereby perform electropolishing treatment on a surface of the aluminum material,
the method comprising performing two or three treatments selected from the group consisting of i) an anodic oxidation treatment as a pretreatment, ii) a bubble-diffusion-preventing treatment during the electropolishing treatment, and iii) a film peeling treatment of an electropolishing film as a post-treatment, wherein
i) the anodic oxidation treatment includes subjecting the aluminum material to anodic oxidation in a pretreatment tank arranged separately from the electrolytic treatment tank at a voltage lower than the electrolysis voltage during the electropolishing treatment through use of a pretreatment solution formed of a polybasic acid aqueous solution having a weak ability to dissolve the aluminum material as compared to the electrolytic treatment solution, to thereby form an anodic oxide film on the surface of the aluminum material;
ii) the electrolytic treatment tank comprising a cathode partition chamber which is formed of a material non-permeable to bubbles of hydrogen gas to be generated on a cathode serving as a counter electrode of the aluminum material and permeable to a liquid, is configured to partition the cathode from the aluminum material, and includes a discharge port for discharging the hydrogen gas out of the electrolytic treatment tank, and
the bubble-diffusion-preventing treatment includes preventing the bubbles of the hydrogen gas generated on the cathode in the cathode partition chamber from diffusing to an aluminum material side, and discharging the hydrogen gas out of the electrolytic treatment tank through the discharge port; and
iii) the film peeling treatment includes immersing the aluminum material after the electropolishing treatment in a post-treatment solution formed of a sulfuric acid solution having a pH of 2 or less and containing sulfuric acid and an amine, to thereby dissolve and remove the electropolishing film present on the surface of the aluminum material.
5. A method of performing electropolishing treatment on an aluminum material according to claim 3 or 4 , wherein the post-treatment solution comprises a sulfuric acid solution obtained by dissolving a sulfate of an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid and an amine in water, a sulfuric acid solution obtained by dissolving sulfuric acid, an amine, and a sulfate of an amine in water, or a sulfuric acid solution obtained by dissolving amidosulfuric acid or an ammonium salt thereof in water.
6. A method of performing electropolishing treatment on an aluminum material according to claim 5 , wherein the sulfuric acid solution to be used as the post-treatment solution comprises an aqueous solution of amidosulfuric acid.
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JP2013-262340 | 2013-12-19 | ||
JP2013262340A JP6078851B2 (en) | 2013-12-19 | 2013-12-19 | Method for electrolytic polishing of aluminum material |
PCT/JP2014/079045 WO2015093159A1 (en) | 2013-12-19 | 2014-10-31 | Method for performing electropolishing treatment on aluminum material |
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JP (1) | JP6078851B2 (en) |
KR (1) | KR20160100343A (en) |
CN (3) | CN107858743A (en) |
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US20180298512A1 (en) * | 2017-04-13 | 2018-10-18 | General Electric Company | Electropolishing and anodizing method for brush holder apparatus |
CN111088503A (en) * | 2019-12-31 | 2020-05-01 | 中山市皓祥模具五金有限公司 | Surface treatment process for aluminum product |
CN111235579A (en) * | 2019-12-31 | 2020-06-05 | 南方科技大学 | Metal polishing method |
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CN1006000B (en) * | 1985-04-23 | 1989-12-06 | 东北工学院 | Method to produce white film on surface of aluminum or aluminum alloys |
EP1046514B1 (en) * | 1999-04-22 | 2005-07-06 | Fuji Photo Film Co., Ltd. | Method for producing aluminium support for lithographic printing plate |
JP4703803B2 (en) * | 1999-10-08 | 2011-06-15 | 株式会社アルバック | Method for electrolytic polishing of aluminum material |
KR100371564B1 (en) * | 2000-10-27 | 2003-02-07 | 삼성테크윈 주식회사 | Metal finishing apparatus and metal finishing method using the same |
DE10149928C1 (en) * | 2001-10-10 | 2002-12-12 | Wkw Erbsloeh Automotive Gmbh | Process for treating the surface of a workpiece made from aluminum or aluminum alloy used in the manufacture of car trims comprises polishing the workpiece in an aqueous electrolyte by applying an electrical direct voltage |
JP4929679B2 (en) * | 2005-10-26 | 2012-05-09 | 日本ケミコン株式会社 | Method for producing aluminum etching foil |
CN102649209B (en) * | 2011-02-23 | 2015-08-12 | 汉达精密电子(昆山)有限公司 | A kind of preparation method of aluminum alloy appearance part |
CN103122475B (en) * | 2011-11-21 | 2015-11-25 | 比亚迪股份有限公司 | A kind of aluminium alloy electric chemical brightening solution and a kind of aluminium alloy electric chemically polishing method |
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WO2015093159A1 (en) | 2015-06-25 |
CN108060452A (en) | 2018-05-22 |
KR20160100343A (en) | 2016-08-23 |
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JP2015117418A (en) | 2015-06-25 |
TWI636160B (en) | 2018-09-21 |
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