JP2007314840A - Surface treatment method for imparting aluminum alloy superior hydrophilicity - Google Patents

Surface treatment method for imparting aluminum alloy superior hydrophilicity Download PDF

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JP2007314840A
JP2007314840A JP2006146193A JP2006146193A JP2007314840A JP 2007314840 A JP2007314840 A JP 2007314840A JP 2006146193 A JP2006146193 A JP 2006146193A JP 2006146193 A JP2006146193 A JP 2006146193A JP 2007314840 A JP2007314840 A JP 2007314840A
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aluminum alloy
titanium
film
range
surface treatment
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JP2006146193A
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Japanese (ja)
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Takamasa Akechi
Hiroaki Goto
宏顕 後藤
孝将 明地
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Aisin Keikinzoku Co Ltd
アイシン軽金属株式会社
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment method which imparts superior corrosion resistance and long sustainable hydrophilicity to an aluminum alloy while keeping the design characteristics of the aluminum alloy. <P>SOLUTION: This surface treatment method comprises the steps of: forming an anodic oxide coating 2 on the aluminum alloy 1; subsequently immersing the anodized aluminum alloy in an aqueous solution containing a water-soluble titanium compound; and then forming a silicon dioxide coating 7 on the anodized aluminum alloy. The titanium film layer 4 has a coating weight in a range from 10 to 150 mg/m<SP>2</SP>in titanium terms. The silicon dioxide coating 7 has a coating weight in a range from 0.1 to 2.0 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface treatment applied to an aluminum alloy, and a method for producing an aluminum alloy excellent in corrosion resistance having a high surface hardness by an anodized film and a silicon dioxide film and having photocatalytic performance with emphasis on hydrophilic properties About.

A member made of an aluminum alloy has excellent features such as light weight and good workability, and is widely used in building materials such as aluminum sashes, vehicles, machine parts, and housings of various electric products.
In particular, metal parts such as automobiles, buildings, and housing construction materials, especially those that want to be maintenance-free, such as those that are installed in places exposed to wind and rain at high places, have been attracting attention to the provision of dirt prevention functions. Therefore, a self-cleaning (self-cleaning) member having a photocatalytic function excellent in hydrophilic properties is demanded.

Conventionally, a method of applying a photocatalyst to an aluminum alloy member has been considered promising. For example, as disclosed in JP-A-2002-285357 and JP-A-2002-285036, a titanium dioxide solution is applied and heated to form a titanium dioxide film. However, since the adhesion to the member is weak, there are problems such as peeling due to expansion and contraction due to temperature change.
In order to solve such a problem, a method of improving the adhesion by providing an organic base is conceivable. However, since the organic substance is decomposed by the photocatalytic function, long-term outdoor use is difficult.

  Further, as described in JP-A-10-195694, a photocatalytic film made of 1 μm semiconductor particles supported in the pores of the anodized film is obtained by immersing the anodized product in a titanium oxide sol. Although there is a method, in practice, it is difficult to obtain a uniform film, and the effect is insufficient.

  Further, as described in JP-A-2001-329396, there is a method of obtaining a photocatalytic function by subjecting an aluminum alloy member to anodization treatment and immersing it in hot water containing a titanium compound. There was a possibility that the coating property would be impaired due to excessive coating and powder spraying, and that the titanium coating hindered the sealing treatment and the corrosion resistance of the anodic oxide coating could be lowered.

JP 2002-285357 A JP 2002-285036 A Japanese Patent Laid-Open No. 10-195694 JP 2001-329396 A

  An object of the present invention is to provide a novel surface treatment method that is excellent in corrosion resistance and can maintain hydrophilic performance over a long period of time while ensuring the design properties of an aluminum alloy in view of the technical problems of the background art.

The technical gist of the present invention is that, as a surface treatment method for an aluminum alloy, a step of forming an anodized film on the aluminum alloy, a step of immersing in an aqueous solution containing a water-soluble titanium compound, It includes a step of forming a silicon film.
Here, the adhesion amount as titanium is preferably in the range of 10 to 150 mg / m 2 , the titanium concentration is in the range of 5 to 300 mg / L, the pH is in the range of 2.5 to 5.0, and the temperature is 10 to 50 ° C. It is good to immerse in the range for 0.5 to 10 minutes in the aqueous solution containing the water-soluble titanium compound adjusted to the range.
Further, sealing treatment is preferably performed, and a polysilazane solution is applied and dried to form a silicon dioxide film, and the silicon dioxide film is preferably in the range of 0.1 to 2.0 μm.

When an aluminum alloy is anodized, a porous oxide film is formed.
In the present invention, when immersed in an aqueous solution containing a water-soluble titanium compound, as shown in the schematic diagram of FIG. 1, the barrier layer 3 of the anodized film 2 formed on the aluminum 1 is included (pores). It was clarified by the cross-sectional analysis or the like that the titanium film layer 4 is formed on the surface 5.
Thus, the corrosion resistance of the anodized film itself was improved by filling the electrolytic holes with titanium oxide. Further, hydrophilicity and photocatalytic property were imparted by the titanium coating layer 6 exposed on the surface.

After the step of immersing in an aqueous solution containing a water-soluble titanium compound, sealing treatment is performed, and a polysilazane solution is applied and dried. As shown in FIG. 2, a schematic view of a silicon dioxide film (silica film) 7 To form a composite film.
This silica film improved corrosion resistance and hydrophilicity. Moreover, by irradiating light, an electron and a hole are photoexcited. Due to the polarity, the hydroxyl group formed by the reaction with water was adsorbed on the surface, and the hydrophilicity was further improved.

  Here, the titanium compound is preferably a water-soluble fluoride or phosphate compound.

  In the present invention, after forming a porous anodic oxide film on the surface of the aluminum alloy, by forming a composite film composed of a titanium oxide layer and silicon dioxide, the surface can be maintained hydrophilic, A self-cleaning function can be maintained for a long time.

  In the present invention, after finishing the surface of the aluminum alloy material, following the pretreatment such as degreasing, etching, chemical polishing, electropolishing and smut removal, a fold oxidation treatment is performed and immersed in an aqueous solution containing a water-soluble titanium compound. After that, the sealing process is performed, and the top coat is performed.

  In the surface treatment method of the present invention, before the sealing treatment or the like is performed on the anodized film applied to aluminum or the aluminum alloy, the surface treatment method is performed by immersing and washing in an aqueous solution mainly containing fluoride. A film is formed on an infinite number of electrolytic holes and on a barrier layer, and further, a silicon dioxide film is formed after sealing treatment, thereby having hydrophilic performance and dramatically improving film performance such as corrosion resistance.

Anodizing is a method of applying an electric voltage to aluminum as an anode in an electrolytic solution to obtain an oxide film, and forming a porous anodized film on the surface of an aluminum alloy to ensure film performance such as design and corrosion resistance. Is the purpose.
Therefore, usually, the surface of the aluminum alloy is subjected to buffing or the like after degreasing and cleaning, alkali etching or chemical polishing, and pickling treatment as necessary. This is used as an anode, graphite or the like is used as a cathode, and electrolysis is performed with a direct current or a pulse waveform.

As the electrolytic solution used here, sulfuric acid, oxalic acid, phosphoric acid, aromatic sulfonic acid and the like are widely known.
After the anodizing treatment, an electrolytic coloring treatment or a dyeing treatment may be performed as necessary. In order to impart photocatalytic performance, it is desirable to use an inorganic pigment.
In the treatment for immersing a water-soluble solution containing a titanium compound after the anodizing treatment, a chemical conversion film containing titanium as a main component is formed in an infinite number of electrolytic pores (pores) in the anodized film and in the barrier layer.

As the titanium compound, a water-soluble fluoride or a phosphoric acid compound is preferable, and a water-soluble complex fluoride containing titanium and a phosphorus compound are the main components. The concentration of the aqueous solution and the treatment conditions (treatment temperature, immersion time) so that the amount of titanium deposited on the anodized film is 10 to 150 mg / m 2 , preferably 20 to 100 mg / m 2. Adjust the process.
When the coating amount is less than 10 mg / m 2 , the photocatalytic effect is slight and the self-cleaning effect due to hydrophilicity cannot be obtained.
On the other hand, when the coating amount is 150 mg / m 2 or more, excessive titanium is deposited on the surface of the anodized film, resulting in a non-uniform appearance, which is economically disadvantageous.

The main components in the aqueous solution used here include potassium potassium oxalate, potassium titanium fluoride, ammonium ammonium fluoride ((NH 4 ) 2 TiF 6 ), titanium hydrofluoric acid (H 2 TiF 6 ), titanium phosphate, and the like. The concentration of the aqueous solution is 5 to 300 mg / L, preferably 10 to 200 mg / L, as the titanium concentration.
The pH of the aqueous solution affects the formation state of the film. In other words, if the pH is too low, the film formation is promoted too much, so that processing unevenness is likely to occur. If the pH is high, titanium in the aqueous solution is precipitated and the liquid composition is destroyed, so the pH is 2.5-5. A range of is desirable.

Processing temperature is 10-50 degreeC, Preferably it is 15-45 degreeC. The immersion time is 0.5 to 10 minutes, preferably 1 to 8 minutes. In any case, when the treatment is performed under conditions other than the range of conditions, the amount of the obtained film is reduced, or the amount of the film is excessive and a uniform film cannot be obtained.
After immersion / cleaning treatment with an aqueous solution containing fluoride as a main component, the surface may be washed with water, but then the surface may be dried by performing warm water or hot water washing at about 80 ° C. .

  For the sealing treatment, in order to form a hydrate layer by sealing treatment in the electrolytic layer existing innumerably in the anodized film, and further on the surface layer portion of the titanium film formed on the barrier layer, A method using a commercially available sealing agent for anodized film containing nickel acetate or the like may be used.

About the method of forming a silicon dioxide film, the application method of the polysilazane solution is not particularly limited, and is applied by a spray coating method, a flow coating method, a roll coating method, etc., and dried in a drying oven at 80 ° C. A silicon dioxide film of 2 μm or less can be formed and fixed to the substrate.
When the silicon dioxide film is made thick, the titanium film is completely covered, the photocatalytic function cannot be maintained, and cracks are generated in the silicon dioxide film. Therefore, the film thickness is preferably 2 μm or less. Is preferably 1 μm or less.

The extruded shape of aluminum alloy A6063-T5 (JIS) (55 mm × 200 mm × 2 mm) is degreased at 60 ° C. for 5 minutes with a 50 g / L solution of a weak alkaline degreasing agent (FC-315: manufactured by Nihon Parkerizing). , Washed with water.
Alkaline etching was performed by immersing in a 100 g / L sodium hydroxide solution at 50 ° C. for 3 minutes, washing with water, and removing smut with a 15% nitric acid solution.
Thereafter, an anodized film having a film thickness of 10 μm was formed by performing anodization treatment at a current density of 100 A / m 2 using a 150 to 200 g / L sulfuric acid aqueous solution.

Next, using PT-3753 (manufactured by Nihon Parkerizing Co., Ltd.) containing titanium hydrofluoric acid as a main component, immersion treatment was performed in an aqueous solution with a titanium concentration of 100 g / L and a pH adjusted to 3 to 3.5 with ammonia water. It was.
As immersion treatment conditions, when the treatment temperature was 30 ° C. and the immersion time was 5 minutes, a titanium coating amount of 60 mg / m 2 was obtained.

After the immersion treatment, the anodized film was sealed with a 7 g / L solution of a nickel-based sealing agent (DX-200: manufactured by Okuno Seiyaku).
As sealing treatment conditions, immersion was performed at 90 ° C. for 20 minutes. This was done as Example 1.
As the top coat, NP140 (manufactured by Clariant Japan) containing 1% of a polysilazane solution as a main component was used, and a film having a thickness of 0.5 μm was obtained by a flow coating method and drying at 80 ° C. × 2 hr.

As a comparative example, in the immersion treatment performed after the oxidation treatment, the concentration of the aqueous solution mainly containing titanium hydrofluoric acid and the immersion treatment conditions were changed, and the others were the same as those in Example 1. In Comparative Example 1, the concentration was 5 mg / L, the treatment temperature was 10 ° C., and the time was 0.3 minutes, and the film amount was 5 mg / m 2 . In Comparative Example 2, the concentration was 300 mg / L, the processing temperature was 70 ° C. × time was 10 minutes, and a coating amount of 170 mg / m 2 was obtained.
Further, as Comparative Example 3, the same steps as in Example 1 were performed until the titanium film was formed, and the top coat performed after the sealing treatment was not performed.

Table 1 shows the evaluation results of Example 1 and Comparative Examples 1 to 3.
In the table, the appearance was evaluated as ◯ without treatment unevenness and x with treatment unevenness.
Hydrophilicity is evaluated by measuring the contact angle of water droplets after UV irradiation by irradiating UV rays for 24 hours, dropping water and measuring the contact angle with a contact angle measuring device (CA-X manufactured by Kyowa Interface Science Co., Ltd.). did. The contact angle is preferably 10 degrees or less.
The decomposition performance was evaluated by a magic ink decomposition test. BLB (FL6BLB 6W TOSHIBA) was used as a light source, and light was irradiated for 48 hours at an intensity of 1 mW / cm 2 .

Corrosion resistance was evaluated by a rating number (RN) after a spray test for 48 hours by a method based on a cast test (JIS Z 2371).
As shown in Table 1, the surface-treated product according to the present invention is excellent in appearance design, photocatalytic properties, and corrosion resistance.

The schematic diagram (after sealing) of the processing method in this invention is shown. The schematic diagram (after topcoat) of the processing method in this invention is shown.

Explanation of symbols

1 Aluminum 2 Anodized film 3 Barrier layers 4 and 6 Titanium film layer 5 Micropores
7 Silicon dioxide film (silica film)
8 Sealing part (hydrate)

Claims (3)

  1. It includes a step of forming an anodic oxide film on an aluminum alloy, a step of immersing in an aqueous solution containing a water-soluble titanium compound, and a step of forming a silicon dioxide film thereafter, and the amount of adhesion as titanium is 10 A surface treatment method for an aluminum alloy excellent in hydrophilicity, characterized in that it is in the range of ˜150 mg / m 2 and the silicon dioxide film is in the range of 0.1 to 2.0 μm.
  2. Forming an anodized film on the aluminum alloy;
    Next, an aqueous solution containing a water-soluble titanium compound in which the titanium concentration is in the range of 5 to 300 mg / L, the pH is in the range of 2.5 to 5.0, and the temperature is in the range of 10 to 50 ° C. is 0.5. Dipping in a range of 10 minutes;
    Then, the surface treatment method of the aluminum alloy excellent in hydrophilicity characterized by including the process of performing a sealing process and apply | coating and drying a polysilazane solution.
  3. The surface treatment method for an aluminum alloy having excellent hydrophilicity according to claim 1 or 2, wherein the titanium compound is a water-soluble fluoride or phosphate compound.

JP2006146193A 2006-05-26 2006-05-26 Surface treatment method for imparting aluminum alloy superior hydrophilicity Pending JP2007314840A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102703950A (en) * 2012-06-27 2012-10-03 湖南迈迪科新材有限公司 Electrochemical preparation method for medical external use aluminum alloy multifunctional coating
CN105492662A (en) * 2013-09-27 2016-04-13 苹果公司 Methods for forming white anodized films by metal complex infusion
US9359946B2 (en) 2011-09-12 2016-06-07 Toyota Jidosha Kabushiki Kaisha Internal combustion engine and method for manufacturing the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9359946B2 (en) 2011-09-12 2016-06-07 Toyota Jidosha Kabushiki Kaisha Internal combustion engine and method for manufacturing the same
CN102703950A (en) * 2012-06-27 2012-10-03 湖南迈迪科新材有限公司 Electrochemical preparation method for medical external use aluminum alloy multifunctional coating
CN105492662A (en) * 2013-09-27 2016-04-13 苹果公司 Methods for forming white anodized films by metal complex infusion
JP2016531208A (en) * 2013-09-27 2016-10-06 アップル インコーポレイテッド Method for forming white anodic oxide film by injection of metal complex

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