JPH0633504B2 - White treatment method for aluminum or aluminum alloy - Google Patents

Description

The present invention relates to a product made of aluminum or an aluminum alloy, for example, a building product such as an aluminum sash, a sliding door, a doorway, a showcase, daily necessities, a stepladder, a ladder, a decorative article,
The present invention relates to a whitening treatment method for aluminum or aluminum alloy used for parts such as castings, die castings, vehicles and ships.

(Prior Art) With the recent diversification of consumer lifestyles and demand preferences, products made of aluminum or aluminum alloys are also required to be colored in various colors. In particular, the color tone of the conventional coloring film applied to aluminum or an aluminum alloy is a shade that gives a cold impression based on a metal color such as gold or silver, so that the coloring film that gives a warm feeling based on white is used. Demand is increasing. In order to obtain such a colored film, several opaque white treatment methods have been conventionally proposed.

(Problems to be solved by the invention) However, in the conventional white treatment method, since the chemicals used are harmful substances, it is necessary to take measures to prevent pollution, and depending on the degree of the opaque white film obtained. Was sometimes unsuitable for practical use. Therefore, at present, the coating method is used.

Further, in order to solve such a problem, JP-A-60-
The following method has been proposed in Japanese Patent Laid-Open No. 197897. That is, it is a method in which a metal ion is introduced into the pores of the anodized film and then the introduced metal ion is reacted to produce a white or off-white compound.

However, in the above method, even when it is found that uneven deposition occurs when reacting metal ions to form a white compound, the amount of metal ions already introduced into the pores of the anodized film is Since it has been determined, the unevenness of precipitation cannot be corrected, and there is a problem that uneven coloring occurs.

Further, in the above method, when coloring a product having a complicated shape with irregularities such as a pot shape or a U-shape, the amount of metal ions introduced into the pores of the anodic oxide film is far from a portion close to the counter electrode. There is a problem in that unevenness in precipitation is likely to occur because it differs from the part.

Therefore, the applicant of the present application has already applied for the following invention (Japanese Patent Application No. 60-297590). That is, an anodic oxide film is formed on aluminum or an aluminum alloy, and then the pore size of the anodic oxide film is changed to inorganic acids such as phosphoric acid and sulfuric acid, organic acids such as sulfosalicylic acid and oxalic acid, or sodium hydroxide and potassium hydroxide. After expansion with an alkaline aqueous solution such as Ca, Ba, Ti, whose oxides are white,
White color of aluminum or aluminum alloy, characterized in that anodic oxidation treatment is carried out again in an aqueous solution of a metal such as Zn, Mg, Al, and a DC voltage or an AC voltage is applied with the anodic oxide film as a cathode in the same bath. It is a processing method.

By adopting the above treatment method, a white anodic oxide film having a uniform and warm color tone is produced. However, in the above treatment method, there is a possibility that decolorization may occur in the sealing treatment after the coloring treatment. In order to solve such defects,
After coloring, it is possible to perform a dipping treatment or an electrolytic treatment as a separate step in a bath containing alcohols, acetone and at least one of chelating agents. However, in that method, the number of steps is increased, and a decrease in productivity cannot be avoided.

INDUSTRIAL APPLICABILITY The present invention can form a white anodic oxide film having a uniform color tone and high whiteness on the surface of aluminum or an aluminum alloy, is durable, and does not discolor even when subjected to a sealing treatment. It is an object of the present invention to provide a white treatment method capable of forming a white anodized film.

(Means for Solving Problems) As a result of researching a method for solving the above problems in the case of coloring aluminum or an aluminum alloy white, at least one metal salt, alcohols and acetone In a bath of an aqueous solution containing at least one chelating agent, the anodized film is subjected to anodizing treatment, and then a DC voltage or an AC voltage is applied with the anodized film as a cathode in the bath. We have found that it is extremely effective to deposit a white compound in the pores of the anodized film, and have completed the present invention. In the bath of the aqueous solution, when a chelating agent is used, a complex salt formed by reacting with the metal salt is contained in a predetermined ratio based on the equilibrium constant of the chelating agent and the metal salt. ing.

That is, according to the present invention, aluminum or an aluminum alloy is subjected to a first anodic oxidation treatment in a bath of a sulfuric acid aqueous solution to form a porous anodic oxide coating, and the anodic oxide coating is subjected to a phosphoric acid aqueous solution bath. A second anodic oxidation treatment is performed to expand the pore size of the porous anodic oxide film and to bind phosphate ions to the pore wall surface of the anodic oxide film, and then to form Al, C
a, Ba, Mg, Zn, and at least one metal salt, and at least one of alcohols, acetone, and a chelating agent, and when a chelating agent is used, the above metal salt. The anodized film is subjected to a third anodizing treatment in a bath of an aqueous solution containing a complex salt formed by the reaction at a predetermined ratio based on the equilibrium constant of the chelating agent and the metal salt, and the third anodizing is performed. The treatment is performed under the condition that the direct current voltage value higher than the voltage value at the time of the second anodizing treatment is boosted within 20 seconds and the voltage is held for 2 seconds or less.
After the third anodizing treatment, in the same bath as the third anodizing treatment, a DC voltage or an AC voltage is applied with the anodized film as a cathode to deposit a white compound in the pores of the anodized film. It is a characteristic white treatment method for aluminum or aluminum alloy.

Specifically, the first anodizing treatment includes direct current, alternating current,
The electrolysis is performed by the pulse wave, the PR wave, or the AC / DC superimposition method, and the second and third anodizing treatments are performed by the electrolysis by the direct current, the alternating current, and the pulse.

As the alcohols, methanol, ethanol,
Lower alcohols such as butanol are preferably used.

Examples of the chelating agent include ethylenediaminetetraacetic acid and its sodium salt, trans-1,2-cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid,
Ethylenediamine diacetic acid, 3,6-dioxa-1,8-
Polyaminocarboxylic acids such as octanediaminetetraacetic acid, N- (2-hydroxyethyl) iminodiacetic acid, triethylenetetraminehexaacetic acid, diamines such as ethylenediamine, triethanolamine, triethylenetetramine, etc. Amino compounds having amino groups, ethyl acetoacetate, nitrilotriacetic acid, formalin,
Oxalic acid, maleic acid, tartaric acid, malic acid, citric acid,
Examples include polybasic acids such as succinic acid, gluconic acid or glycine, and soluble metal salts thereof.

(Function) By the first anodizing treatment, an anodized film as shown in FIG. 1 is formed on the surface of aluminum or aluminum alloy. FIG. 1 is a schematic cross-sectional view of the obtained anodized film. In FIG. 1, 1 is an anodized film, 2
Are holes, 4 is a base material made of aluminum or an aluminum alloy, and 5 is a barrier layer. Since it is carried out in a bath of sulfuric acid, the diameter of the holes 2 is generally about 10 nm and is not so large.

By the second anodic oxidation treatment, the anodic oxide coating 1 shown in FIG. 1 has the diameter of the hole 2 enlarged as shown in FIG. The diameter a of the hole 2 is generally about 30 nm. In addition, it is preferable that the diameter of the hole 2 is increased to about 200 Å or more.

Since the second anodic oxidation treatment is carried out in a bath of phosphoric acid, the following formula (I) is applied to the pore walls of the anodic oxide coating 1 based on PO ₄ ³⁻ (phosphate ions) contained in the bath. , (II) based reaction occurs.

Al ³⁺ + PO ₄ ³⁻ AlPO ₄ (I) Al ³⁺ + SO ₄ ²⁻ Al ₂ (SO ₄ ) ₃ (II) The equilibrium constants of the reactions (I) and (II) are (I)> (II ), Al ₂ (SO ₄ ) ₃ generated in the first anodizing treatment is dissociated, SO ₄ ²⁻ is eluted in the solution, and Al ³⁺ is bonded with PO ₄ ³⁺ to anodize. Al containing phosphoric acid on the pore wall of coating 1
A wall of PO ₄ is created. Further, the wall surface thereof, present in excess to that PO ₄ ^3- is bound are attracted to the anodic oxide film 1 is charged positively in the bath. This PO ₄
^3- exerts a chelating action (“inorganic phosphorus chemistry”, 1
10 to 111, 1985, Kodansha Co., Ltd.), so that the white compound 3 (FIG. 3) generated in a later step is firmly fixed in the hole 2. That is, the metal used in the third anodizing treatment and the subsequent application of DC voltage or AC voltage is in the state of a complex ion of a metal hydrate in which water molecules are coordinate-bonded to the metal ion in the bath. These complex ions exist and are crosslinked by hydrolysis to have a plurality of metal ions. As the hydrolysis proceeds further, they precipitate as hydroxides, but they are in the state of complex ions. things, chelated by PO ₄ ^3- in migrating deposited into the pores 2 of the anodized layer 1 by applying a third DC voltage or AC voltage after the anodic oxidation treatment, that is secured to the wall. FIG. 11 is a graph showing the line analysis result of the finally colored anodic oxide film by EPMA. From FIG. 11, it is found that phosphoric acid is present in the pore walls of the anodic oxide film 1 and on the surface thereof. Recognize.

As described above, according to the present invention, the first anodizing treatment is carried out in the bath of the sulfuric acid aqueous solution and the second anodizing treatment is carried out in the bath of the phosphoric acid aqueous solution. The reason why the anodic oxidation treatment is not performed is as follows.
That is, (i) to conform to the JIS standard, and (ii) to ensure practical durability. That is, in (i) JIS standard, H9500 indicates an anodizing operation standard for aluminum and aluminum alloys, and the anodizing electrolysis conditions in this standard are two types: a sulfuric acid method and an oxalic acid method. On the other hand, H8601, 86
02 specifies the physical properties of the anodized film obtained according to H9500. That is, it is essential to use sulfuric acid or oxalic acid in order to comply with the JIS standard. Therefore, in the present invention, first, the anodic oxidation treatment is performed using sulfuric acid to comply with the JIS standard.

(ii) The film obtained by anodizing only with phosphoric acid becomes very thin and impractical in terms of durability. This is, for example, in Japanese Patent Publication No. 57-819.
Understood from 8. That is, the application includes an example of anodizing only with phosphoric acid, an example of anodizing with sulfuric acid, and in the example of sulfuric acid, "the thickness of the film is a film necessary to maintain durability depending on the application. Pressure. " That is, it is shown that a durable film cannot be obtained with phosphoric acid, and a durable film can be obtained with sulfuric acid. In the case of phosphoric acid, the film thickness seems to be 1 μm or less.

Further, the reason why the anodizing treatment is not performed only with the sulfuric acid aqueous solution is that the action effect based on phosphoric acid in the above-described second anodizing treatment cannot be obtained. That is, the whiteness can be increased based on the enlarged pore diameter, and the adhesion of the white compound is improved based on the binding of phosphate ions to the pore wall surface to improve the durability of the colored anodized film. The effect of being able to be obtained cannot be obtained.

At least one of alcohols, acetone, and a chelating agent is contained in the bath of the aqueous solution for performing the third anodic oxidation treatment.
The seeds are included, and the conditions for the third anodizing treatment are that the DC voltage value is higher than the voltage value at the time of the second anodizing treatment, and that the boosting time is within 20 seconds.
Since the holding time is within 2 seconds, if a DC voltage or an AC voltage is applied with the anodic oxide film 1 as the cathode in the next step, it will be evenly distributed over the entire anodizing process 1 regardless of the distance from the counter electrode. Therefore, a sufficient amount of current flows, so that the anodic oxide coating 1 is colored uniformly and with high whiteness as described later. That is, by satisfying the above conditions, the barrier layer 5 of the anodic oxide film 1 is surely changed, and due to the anodic oxidation reaction based on alcohols, acetone, or a chelating agent, the barrier layer 5 is changed to the counter electrode. The thicker the part is, the thinner the part is. If the above conditions are not satisfied, that is, if the pressurization time is longer than 20 seconds, the barrier layer 5 becomes too thick, and it becomes difficult for current to flow, so that the amount of the white compound 3 deposited decreases.
The whiteness is low. When the above condition is not satisfied, that is, when the holding time is longer than 2 seconds, the whiteness is low as in the case where the above condition is not satisfied.

When a DC voltage or an AC voltage is applied with the anodic oxide coating 1 as a cathode, complex ions of Al, Ca, Ba, Mg, or Zn are deposited in the pores 2 of the anodic oxide coating 1 as described above and white. It becomes a hydroxide, and a white compound is produced in a state of being fixed by PO ₄ ³⁻ , and as shown in FIG. 3, the white compound 3 is deposited in the pores 2 of the anodized film 1. As a result, the anodized film 1 is colored white.
Since the diameter of the hole 2 is enlarged, the white compound 3 is smoothly and largely deposited in the hole 2. Since this step is performed in the same bath as the third anodic oxidation treatment, the treatment step is simplified and the productivity is improved. When a chelating agent is used as the bath composition of the aqueous solution, the above-mentioned metal used in applying a DC voltage or an AC voltage reacts with the chelating agent based on the equilibrium constant of both to form a complex salt. That is, the metal, the chelating agent and the complex salt are present in the bath, but this does not affect the precipitation reaction of the white compound.

Further, since the electrolytic bath contains at least one of alcohols, acetone and a chelating agent, the white compound 3 deposited in the pores 2 of the anodic oxide film 1 is the same as the alcohols and acetone used. Alternatively, it becomes strongly insoluble in hot water by the chelating agent. Therefore, even if the sealing treatment is performed, the color is not decolorized.

(Effects of the Invention) (1) According to the present invention, the diameter of the pores 2 of the anodized film 1 is enlarged by the second anodizing treatment, so that the white compound 3 can be smoothly and in large amounts in the pores 2. It can be deposited. Therefore, the whiteness can be increased.

(2) According to the present invention, since the second anodic oxidation treatment is performed in a bath of phosphoric acid, the white compound 3 can be firmly fixed by the phosphate ions bonded to the pore wall surface of the anodic oxide coating 1. Therefore, the adhesion of the white compound 3 can be improved, and the durability of the colored anodized film 1 can be improved.

(3) According to the present invention, the thickness of the barrier layer 5 of the anodized film 1 can be surely made different between a portion close to the counter electrode and a portion far from it by the third anodic oxidation treatment. Since the thickness of the barrier layer 5 can be set to an appropriate thickness so that current can easily flow, when a DC voltage or an AC voltage is applied with the anodic oxide film 1 as a cathode in the next step, regardless of the distance from the counter electrode, An electric current can be evenly and sufficiently applied to the entire anodized film 1. Therefore, even if the shape of the sample made of aluminum or aluminum alloy is complicated,
The white compound 3 can be evenly and sufficiently deposited on the entire anodized film 1, and the entire anodized film 1 can be colored with a uniform tone of high whiteness. That is, uneven coloring can be prevented.

(4) According to the present invention, since at least one of alcohols, acetone, and a chelating agent is used in the third anodic oxidation treatment and the subsequent application of DC voltage or AC voltage, the white compound is used. 3 can be strongly insoluble in hot water. Therefore, it is possible to prevent decolorization due to the sealing treatment.

(5) According to the present invention, application of a DC voltage or an AC voltage with the anodized film 1 as a cathode is performed in the same bath as the third anodizing treatment, so that the treatment process is simple. Therefore, productivity can be improved.

(6) As described above, according to the present invention, on the surface of aluminum or aluminum alloy, it is possible to form a white anodic oxide film having a uniform color tone and high whiteness, and also, durability, and It is possible to form a white anodic oxide film that does not discolor even when the sealing treatment is performed. Therefore, according to the present invention, it is possible to meet the demands of various markets.

(Example) The examples described below were carried out using aluminum or an alloy as a sample, but it goes without saying that the same can be done using aluminum.

First, as shown in FIG. 4 and FIG. 5 which is a side view of FIG. 4, a flat plate-shaped sample 10 made of an aluminum alloy (A6063S-T5 material) is hung on the electrolytic rod 14 of the electrolytic frame 12 and the sample 10 is suspended. Was subjected to anodization treatment in a 170 g / l H ₂ SO ₄ bath to form an anodized film having a film thickness of 9 μm on the surface of the sample 10.

Next, using carbon as a counter electrode on the anodized film, 2
The pore size of the anodized film was enlarged by performing anodizing treatment in a 100 g / l phosphoric acid bath at 0 ° C. The anodic oxidation treatment was performed by applying a DC voltage of 16 V for 10 minutes.

Next, the anodized film with the enlarged pore size was treated as in the following first to fifth examples.

[First Example] As a result of applying the voltage shown in FIG. 6 in a bath of 10 g / l MgSO ₄ and 5% methanol, the central portion 10a and the end portion 10b of the sample 10 (see FIGS. (Fig.) In both cases, a white anodized film with a uniform color tone was obtained. According to the Hunter system, the whiteness of the obtained film was 92.5, which was high. The voltage shown in FIG. 6 means a DC voltage E = 2
4 V, AC voltage V = 20 V, DC voltage E boosting time t ₁ = 20 seconds, holding time t ₂ = 2 seconds, AC voltage V boosting time t ₃ = 5 seconds, holding time t ₄ = It is 300 seconds.

Furthermore, as a sealing treatment, a 7 g / l nickel acetate-based sealing aid (trade name "Sealing Salt AS", manufactured by Sand Co.)
Immersion treatment was performed for 20 minutes at 90 ° C. in the bath No. 10 of the sample 10 at the central portion 10a and the end portion 10b (see FIGS. 4 and 5).
None of these) did not decolorize at all.

On the other hand, when the same treatment as above was carried out in a bath containing no 5% methanol, a white anodic oxide film with a uniform color tone could be obtained before the sealing treatment, but it was decolorized by the sealing treatment. Occurred, and the whiteness by the Hunter system dropped to 71.5 in all parts.

Second Example The voltage shown in FIG. 7 was applied in a bath of 5 g / l BaCO ₃ and 1% acetone.
A white anodic oxide coating having a uniform color tone was obtained on both a and the end portion 10b (FIGS. 4 and 5). The whiteness of the obtained film is
According to the Hunter system, it was 89.2, which was high. The voltage shown in FIG. 7 means a voltage of positive polarity E ₁ = 20
Volts, negative polarity voltage E ₂ = 18 volts, positive polarity voltage E ₁ boosting time t ₁ = 15 seconds, holding time t ₂ = 1
Seconds, the boosting time t _{3 of} the negative polarity voltage E ₂ is 30 seconds, and the holding time t _{4 is} 180 seconds.

Furthermore, as a sealing treatment, a 7 g / l nickel acetate-based sealing aid (trade name "Sealing Salt AS", manufactured by Sand Co.)
Immersion treatment was performed for 20 minutes at 90 ° C. in the bath No. 10 of the sample 10 at the central portion 10a and the end portion 10b (see FIGS. 4 and 5).
None of these) did not decolorize at all.

On the other hand, when the same treatment as above was performed in a bath containing no 1% acetone, a white anodic oxide film with a uniform color tone could be obtained before the pore-sealing treatment. Decolorization occurred, and the whiteness by the Hunter system decreased to 79.3 in all parts.

Third Example 2 g / l Zn (NO ₃ ) ₂ and 10 g / l Al ₂ (S
As a result of applying the voltage shown in FIG. 8 in a bath of O ₄ ) ₃ , 2 g / l of EDTA, both the central portion 10a and the end portion 10b (FIGS. 4 and 5) of the sample 10 had a uniform color tone. To obtain a white anodic oxide film. According to the Hunter system, the whiteness of the obtained film was 91.5, which was high. 8th
The voltage shown in the figure means a positive polarity voltage E ₁ = 18 volts,
Negative polarity voltage E ₂ = 18 volts, positive polarity voltage E ₁
Boosting time t ₁ = 10 seconds, holding time t ₂ = 2 seconds, boosting time t _{3 of} negative polarity voltage E ₂ = 10 seconds, holding time t ₄ =
The number of repetitions is n = 30 with 5 seconds and a pause time t ₅ = 1 second.

Furthermore, as a sealing treatment, a 7 g / l nickel acetate-based sealing aid (trade name "Sealing Salt AS", manufactured by Sand Co.)
Immersion treatment was performed for 20 minutes at 90 ° C. in the bath of No. 10, but the central portion 10a and the end portion 10b of the sample 10 (see FIGS.
None of these) did not decolorize at all.

On the other hand, when the same treatment as described above was performed in a bath containing no 2 g / l of EDTA, a white anodic oxide film having a uniform color tone could be obtained before the pore-sealing treatment. Decolorization occurred, and the whiteness by the Hunter system decreased to 80.6 in any part.

[Fourth Example] In a bath of 10 g / l TiOSO ₄ , 5% dimethylformamide, and 5 g / l glycine, the voltage shown in FIG. 1
0b (FIGS. 4 and 5), a white anodic oxide film having a uniform color tone was obtained. According to the Hunter system, the whiteness of the obtained film was 92.3, which was high. The voltages shown in FIG. 9 are DC voltage E = 26 V, AC voltage V = 20 V, and DC voltage E boosting time t ₁ = 15.
Second, holding time t ₂ = 2 seconds, boosting time t ₃ of AC voltage V
= 10 seconds, the holding time _t 4 = 300 seconds.

Furthermore, as a sealing treatment, a 7 g / l nickel acetate-based sealing aid (trade name "Sealing Salt AS", manufactured by Sand Co.)
Immersion treatment was performed for 20 minutes at 90 ° C. in the bath No. 10 of the sample 10 at the central portion 10a and the end portion 10b (see FIGS. 4 and 5).
None of these) did not decolorize at all.

In contrast, 5% dimethylformamide and 5 g / l
When a treatment similar to the above was performed in a bath containing no glycine, a white anodic oxide film with a uniform color tone could be obtained before the sealing treatment, but decolorization occurred due to the sealing treatment and Whiteness dropped to 73.7 in all areas.

[Fifth Example] 10 g / l Al ₂ (SO ₄ ) ₃ and 2 g / l CaSO
₄ and 1% gluconic acid in the bath, the voltage shown in FIG.
0b (FIGS. 4 and 5), a white anodic oxide film having a uniform color tone was obtained. The whiteness of the obtained film was 90.7 according to the Hunter system, which was high. Voltages shown in FIG. 10 are positive polarity voltage E ₁ = 18 volts, negative polarity voltage E ₂ = 18 volts, positive polarity voltage E ₁ boosting time t ₁ = 10 seconds, holding time t. ₂ = 1 second, negative voltage E ₂ boosting time t ₃ = 30 seconds, holding time t ₄ = 1
80 seconds. FIG. 11 is a graph showing the line analysis result by EPMA of the cross section of the obtained white anodic oxide film.

Furthermore, as a sealing treatment, a 7 g / l nickel acetate-based sealing aid (trade name "Sealing Salt AS", manufactured by Sand Co.)
Immersion treatment was performed for 20 minutes at 90 ° C. in the bath No. 10 of the sample 10 at the central portion 10a and the end portion 10b (see FIGS. 4 and 5).
None of these) did not decolorize at all.

On the other hand, when the same treatment as above was performed in a bath containing no 1% gluconic acid, a white anodic oxide film with a uniform color tone could be obtained before the sealing treatment, but the sealing treatment Decolorization occurred, and whiteness by the Hunter system decreased to 81.2.

As described above, according to the first to fifth examples, it was possible to obtain a white anodic oxide film having a uniform color tone regardless of the distance from the counter electrode. Moreover, the white anodic oxide film is
It had a high degree of whiteness, and did not decolorize even after the sealing treatment.

Methanol of the first embodiment, acetone of the second embodiment, third
The white anodic oxide film obtained by the treatment in the bath containing neither EDTA of the example, dimethylformamide and glycine of the fourth example, nor gluconic acid of the fifth example was decolorized by the sealing treatment. . From this, it is understood that at least one of alcohols, acetone, and a chelating agent is necessary in order to obtain a white anodic oxide film which is not discolored even if the sealing treatment is performed.

Furthermore, an example in which the condition of the third anodizing treatment is not satisfied is Comparative Example 1
~ 3. The conditions for the third anodizing treatment are that the direct current voltage value is higher than the voltage value during the second anodizing treatment, and that the boosting time is within 20 seconds.
The holding time is within 2 seconds, Comparative Example 1 is an example out of the above conditions, Comparative Example 2 is an example out of the above conditions, and Comparative Example 3 is an example out of the above conditions. .

[Comparative Example 1] -When E = 14V in the first embodiment.

-Results ... The whiteness of the central portion 10a of the material 10 was 85.2 and the whiteness of the end portion 10b was 92.7. That is,
It was not uniformly colored. This is because the treatment voltage is lower than the voltage (DC voltage 16V) at the time of the second anodizing treatment, so that the barrier layer 5 formed by the second anodizing treatment does not change, and therefore the third anodizing treatment is performed. This is because, in the electrolytic coloring treatment after the anodizing treatment, the electric current is concentrated on the end portion rather than the central portion due to so-called “end portion concentration”, and a large amount of the white compound is deposited on the end portion.

[Comparative Example 2] In the first example, t ₁ = 30 seconds and t ₂ = 2 seconds.

-Result ... Both the central part 10a and the end part 10b have a whiteness of 7
It was 7.5. That is, although it was uniformly colored, the whiteness was low. This is because the barrier layer 5 became too thick because t ₁ was too long, and it became difficult for current to flow in the electrolytic coloring treatment after the third anodizing treatment, and therefore the amount of white compound deposited was reduced. .

[Comparative Example 3] -When t ₁ = 20 seconds and t ₂ = 5 seconds in the first example.

-Result ... Same as Comparative Example 2. This is also because, as in Comparative Example 2, the barrier layer 5 became too thick, and therefore the amount of white compound deposited was reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an anodized film obtained by the first anodizing treatment, FIG. 2 is a schematic sectional view of an anodized film obtained by the second anodizing treatment, and FIG. 3 is a hole. FIG. 4 is a schematic cross-sectional view of an anodized film in which a white compound is deposited on FIG. 4, FIG. 4 is a schematic front view of a sample attached to a hanging tool used in Examples 1 to 5, and FIG. 5 is a side view of FIG. 6 is a graph showing the voltage applying method of the first embodiment, FIG. 7 is a graph showing the voltage applying method of the second embodiment, FIG. 8 is a graph showing the voltage applying method of the third embodiment, and FIG. FIG. 10 is a graph showing the voltage applying method of the fourth embodiment, FIG. 10 is a graph showing the voltage applying method of the fifth embodiment, and FIG. 11 is a line by EPMA of the cross section of the white film obtained in the fifth embodiment. It is a graph which shows an analysis result.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Ohnaka, 3-9-39, Mikuni Honcho, Yodogawa-ku, Osaka City, Osaka Prefecture Japan Aluminum Industry Co., Ltd. (72) Shinichi Ishida, Mikuni-honcho, Yodogawa-ku, Osaka 3-939 Japan Aluminum Industry Co., Ltd. (72) Inventor Seiji Hagino 3-939 Mikunihonmachi, Yodogawa-ku, Osaka City, Osaka Prefecture Japan Aluminum Industry Co., Ltd. (72) Inventor Shiro Manaka Osaka Prefecture Fujita Shoji Co., Ltd., 23, Hashizume-cho, Higashi-ku, Higashi-ku, Japan (56) References JP-A-57-92194 (JP, A)

Claims (2)

[Claims] 1. A first anodic oxidation treatment is performed on aluminum or an aluminum alloy in a bath of sulfuric acid aqueous solution to form a porous anodic oxide coating, and the anodic oxide coating is treated in a bath of phosphoric acid aqueous solution. 2 is anodized to expand the pore size of the porous anodic oxide coating and to bind phosphate ions to the pore wall surface of the anodic oxide coating. Then, among the salts of Al, Ca, Ba, Mg and Zn, When a chelating agent is used, a complex salt formed by reacting with at least one metal salt and at least one of alcohols, acetone, and a chelating agent is used as a chelating agent. The anodized film is subjected to a third anodizing treatment in a bath of an aqueous solution containing a predetermined ratio based on the equilibrium constant with the metal salt, and the third anodizing treatment is performed by applying a voltage during the second anodizing treatment. DC voltage value higher than the value Under a condition that the voltage is raised within 20 seconds and the voltage is maintained for a time within 2 seconds. After the third anodizing treatment, in the same bath as the third anodizing treatment, the anodized film is used as a cathode and the direct current is applied. A white treatment method for aluminum or an aluminum alloy, which comprises applying a voltage or an alternating voltage to deposit a white compound in the pores of the anodized film. 2. The white color of aluminum or aluminum alloy according to claim 1, wherein the chelating agent is a polyaminocarboxylic acid, a polybasic acid, or an amino compound having two or more amino groups in one molecule. Processing method.