KR101697468B1 - Aluminum-material anodization method - Google Patents

Abstract

A method of anodizing an aluminum material capable of forming a porous anodic oxidation film at a treatment voltage of 10 V or higher without changing the grain shape as much as possible, with respect to an aluminum material made of aluminum or an aluminum alloy. An anodic oxidation treatment method of an aluminum material for forming an anodic oxide film on a surface of an aluminum material by subjecting an aluminum material to an anodic oxidation treatment in a treatment bath containing a polybasic acid aqueous solution under a treatment condition of a target voltage of 10 V or higher, Anodic oxidation treatment is carried out in a treatment bath comprising an aqueous solution until the electric quantity reaches 0.05 C / cm 2 or more under the treatment conditions of a voltage of 6 V or less to form a pretreatment film on the surface of the aluminum material to be.

Description

{ALUMINUM-MATERIAL ANODIZATION METHOD}

The present invention relates to an anodic oxidation treatment method of an aluminum material that forms an anodized porous film on a surface by subjecting an aluminum material made of aluminum or an aluminum alloy to an anodization treatment under a predetermined voltage in a treatment bath made of an aqueous solution of polybasic acid, The present invention relates to an anodic oxidation treatment method of an aluminum material capable of suppressing current grain formation as much as possible by anodizing treatment.

In order to impart corrosion resistance and abrasion resistance to an aluminum material, aluminum itself is easily dipped in acid or alkali, and therefore, an aluminum material is supplied as an anode in an electrolyte solution, and a coating of aluminum oxide (Al ₂ O ₃ ) (Anodic oxidation film) is generally widely performed. For example, in the anodizing treatment using an aqueous solution of an acid such as sulfuric acid, oxalic acid, or phosphoric acid as an electrolyte, an anodic oxidation coating called a porous coating is formed by the anodic oxidation treatment. However, (Aluminum side) to be referred to as a porous layer, and a porous film formed on the outer side thereof and having a plurality of holes and referred to as a porous layer. In the initial stage of the anodic oxidation treatment, And then a plurality of holes are generated in the barrier layer, and these plural holes are grown to form a porous layer.

In the aluminum material before the anodic oxidation treatment, the shape (grain shape) caused by the crystal grains existing in the material can not be visually recognized. However, when the above anodic oxidation treatment is performed, And is now in the form of a crystal grain.

With respect to the shape of crystal grains in the aluminum material after the anodizing treatment, a technique has been proposed in which the shape of the crystal grains is intentionally determined to be highly decorative, For example, a housing member such as a door knob or a fence, a bicycle member such as a handle or a crank, a vehicle member such as a riding door frame or an inner panel, a decorative member such as an accessory or a wristwatch, In the applications such as a member for an optical product such as a camera, a printing roll, etc., the appearance and uniformity thereof are sometimes emphasized, and when such a crystal grain shape is remarkable, it is sometimes judged that the appearance is poor.

The problem of the grain shape of the aluminum material after the anodizing treatment is that the grain size becomes larger when the aluminum purity (Al purity) in the aluminum material is high and becomes more current, and the surface of the aluminum material is varnished Or the like is subjected to mirror-surface processing by means of mirror-surface processing such as cutting, buffing, electrolytic polishing, or chemical polishing.

As a method for making it impossible to visually observe the crystal grain shape on the surface of the aluminum material after the anodizing treatment as described above, there is a method in which the cooling rate is controlled during the casting of the aluminum material before the anodizing treatment, (Approximately 100 mu m) so that the size of the crystal grains existing in the aluminum material can be visually confirmed, thereby making it possible to make the apparent grain shape less conspicuous.

However, depending on the product, the processing method of aluminum is limited. Therefore, there is a limit in reducing the size of crystal grains. Particularly, in a material in which the aluminum material has a high Al purity or a material requiring heat treatment at the time of its production, It is technically difficult to reduce the size to 100 占 퐉 or less. In addition, even if the size of the crystal grains can be made small, when the crystal grains are agglomerated in the aluminum material, , It is difficult to obtain a uniform appearance.

However, in Patent Document 2, in order to prevent uneven treatment in the rough state called folding stripe or surface irregularity called "strick" which is likely to occur at the time of chemical etching due to the orientation difference of crystal grains, (1) a preliminary electrochemical roughening treatment in an electric quantity of 1 to 300 C / dm 2, which is carried out using desmut treatment, (2) an alternating flow of a predetermined frequency in an aqueous hydrochloric acid solution, and (3) And (4) a predetermined amount of etching treatment and / or a desmutting treatment in an aqueous hydrochloric acid solution to prepare an aluminum support for an improved flat plate surface. However, the preliminary electrochemical roughening treatment performed by this method is an etching treatment that electrochemically dissolves aluminum in a monobasic acid to roughen the surface, and does not form a porous anodic oxidation coating by anodic oxidation treatment.

Japanese Patent Application Laid-Open No. 2005-097,735 Japanese Patent Application Laid-Open No. 2001-011,699

Thus, the present inventors, as a result, the aluminum metal in the aluminum material after the anodic oxidation treatment in detail repeated investigation examined the cause of the grain shape is actualized by the anodizing treatment (Al) / barrier layer (Al ₂ O ₃ ) Is different for each crystal grain whose orientation is different from each other. That is, according to a study made by the inventors of the present invention, in the anodic oxidation treatment, the barrier layer is first formed at the beginning of film formation, and holes are opened in the film formed thereafter. However, (Al) / barrier layer (Al ₂ O ₃ ) due to the difference in orientation between the aluminum metal (Al) and the barrier layer (Al ₂ O ₃ ) And a minute difference in the plurality of formed holes is reflected also in the porous layer formed by growing a plurality of holes thereafter. The minute difference in the number of holes of the anodized film formed in this manner is emphasized when light is applied to the surface and becomes present as a crystal grain shape even if the difference is extremely remarkable. So that a uniform appearance can not be formed.

Based on the result of the examination, the inventors of the present invention have found that, regardless of the orientation of crystal grains, the inventors of the present invention have proposed a method for making as many pores as possible in the interface of aluminum metal (Al) / barrier layer (Al ₂ O ₃ ) As a result, it has been found that, prior to the anodic oxidation treatment at a target voltage of 10 V or higher, an anodic oxidation treatment is performed in advance at a low voltage to a predetermined amount of electricity, It is possible to form a porous layer having pores having a uniform shape in the anodizing treatment at the subsequent target voltage and to prevent the crystal grain shape from being present in the aluminum material after the anodizing treatment as much as possible And completed the present invention.

Accordingly, an object of the present invention is to provide an aluminum material made of aluminum or an aluminum alloy, which is capable of forming a porous anodized film of a porous type at a processing voltage of 10 V or higher, Method.

That is, the present invention relates to an anodic oxidation treatment of an aluminum material made of aluminum or an aluminum alloy in a treatment bath made of a polybasic acid aqueous solution under a treatment condition of a target voltage of 10 V or higher and anodic oxidation of an aluminum material forming a porous anodic oxide coating on the surface of the aluminum material Wherein an anodic oxidation treatment is carried out in a treatment bath comprising an aqueous solution of polybasic acid as a pretreatment of the anodizing treatment until the electric quantity reaches 0.05 C / cm 2 or more under the treatment condition of a voltage of 6 V or less, Thereby forming a coating film on the surface of the aluminum material.

In the present invention, there is no particular limitation on the aluminum material to be subjected to the anodic oxidation treatment, and the aluminum material to be subjected to the anodic oxidation treatment is anodic oxidation treatment at a treatment condition of a target voltage of 10 V or higher in a treatment bath comprising a polybasic acid aqueous solution, When the anodic oxidation film of the Al type is formed, the shape of the crystal grains is present due to the crystal grains existing in the aluminum material. In particular, the Al purity is high and the size of the crystal grains existing in the material is 100 탆 or more, For example, a high-purity aluminum material having a high purity of 99.99% or more, and the like. In addition, since the surface of the aluminum material is susceptible to a crystal grain shape even when the surface thereof is mirror-finished by a mirror-surface processing means such as buff polishing, electrolytic polishing, cutting, and chemical polishing, It is also effective for a mirror finished aluminum surface.

In the present invention, the term "target voltage" as the treatment condition of the anodizing treatment refers to, for example, by using a treatment bath composed of 10 to 20 wt% -sulfuric acid aqueous solution as a polybasic acid aqueous solution, A dyestuff film, a decorative film or the like is formed, a direct current voltage of about 10 to 20 V is applied, and a treatment bath composed of an aqueous solution of 0.01 to 4 wt% of oxalic acid as an aqueous solution of polybasic acid is used to form an anti- In the case of forming the abrasion-resistant film, the decorative film, etc., a direct current voltage of about 10 to 600 V is applied, but this refers to a voltage to be applied during the anodizing treatment which is carried out using a predetermined treatment bath for a predetermined purpose.

In the present invention, the size of the crystal grains existing in the aluminum material can be determined, for example, by polishing the surface of the aluminum material (for example, buffing) And the surface of the cross section of the sample is melted so that the crystal grains can be seen by the eye. Thereafter, the cross section is photographed by a microscope or an inverted microscope, and three or more, for example, A value of L / N is obtained by dividing the line length L by the number (N) of crystal grains, by counting the number of crystal grains on the line segment by drawing a line of a predetermined length (e.g., 50 mm, 20 mm) , And the value of the obtained L / N is defined as the size (length) of the crystal grain and is generally referred to as "cutting method".

In the pretreatment carried out before the anodic oxidation treatment at the target voltage in the present invention, the anodic oxidation treatment is carried out in the treatment bath of the aqueous solution of the polybasic acid until the electric quantity reaches 0.05 C / , And a pre-coating is formed on the surface of the aluminum material.

Examples of the polybasic acid constituting the treatment bath include inorganic acids such as sulfuric acid, phosphoric acid and chromic acid, and organic acids such as oxalic acid, tartaric acid and malonic acid, preferably sulfuric acid and phosphoric acid having a high treating rate, The concentration of the polybasic acid in the treatment bath (aqueous solution of polybasic acid) using a treating bath (aqueous solution of polybasic acid) may be the same as that used in the conventional anodizing treatment. For example, in the case of sulfuric acid, Or more and 18 weight% or less.

In the pretreatment of the present invention, the anodic oxidation treatment must be performed until the voltage is maintained at 6 V or lower and the electricity quantity becomes 0.05 C / cm 2 or higher. When the voltage becomes higher than 6 V, It is difficult to suppress the difference in the opening start of the hole due to the difference in orientation. As a result, when the anodic oxidation treatment is performed with a target voltage of 10 V or higher thereafter, In this pretreatment, even if the voltage is maintained at 6 V or lower, if the electric quantity between the pretreatments is not satisfied at 0.05 C / cm 2, a large number of thin and uniform holes may not be formed in the formed prepreg film, When the anodic oxidation treatment is performed with a target voltage of 10 V or higher, the crystal grain shape can not be prevented from becoming current. Here, although there is no particular lower limit for the voltage at the time of the pretreatment, if the voltage is 1 V or less through the entire pretreatment, it may take a long time to form the pre-coating. Although there is no particular upper limit for the amount of electricity, the effect is almost the same even if the amount of electricity is greatly increased. For example, the film thickness of the prepreg film may become several micrometers or more at an electrical quantity exceeding 5 C / In the case of removing the pre-coating film in the process, it is not preferable because the process time is lost.

Here, as for the voltage between the pretreatment of the present invention, a constant voltage of 6 V or less may be applied from the beginning to the end of the pretreatment, or the voltage may be gradually increased within the range of 6 V or less from the beginning to the end of the pretreatment, The treatment time of the pretreatment may be gradually lowered until the amount of electricity between the pretreatment reaches 0.05 C / cm < 2 > and the treatment temperature at the time of pretreatment May be in the range of 5 占 폚 or more and 35 占 폚 or less in the case of sulfuric acid, for example, in the same manner as the ordinary anodizing treatment.

The pre-coating formed in the pretreatment of the present invention has a larger number of holes and a smaller thickness and a uniform hole shape as compared with the anodic oxidation coating formed by the anodic oxidation treatment at the target voltage, For example, about 25 nm or more when a 15 wt% -sulfuric acid aqueous solution is used as an aqueous solution of polybasic acid, depending on the type and concentration of the polybasic acid in the polybasic acid aqueous solution used as the bath.

In the present invention, the pre-coating formed in the pre-treatment is thinner and more numerous than the anodic oxidation coating formed by the anodic oxidation treatment at the target voltage, and the aluminum metal (Al) / oxidation Since the irregularities at the aluminum (Al ₂ O ₃ ) interface are suppressed to a low level and the number of holes is reduced to suppress the irregularities, the shape and size of the holes formed in the prefilm become uniform and uniform irrespective of the orientation of the crystal grains, It is possible to form an anodic oxide film having relatively uniform pores in the anodic oxidation treatment at a later target voltage (10 V or more), and it is possible to suppress the current state of the grain shape due to the difference in orientation of the grain as much as possible.

In the present invention, the anodizing treatment at a voltage of 10 V or higher, which is performed after the pretreatment, can be carried out in the same manner as the conventional anodizing treatment for forming a porous anodizing film, The treatment conditions can be the same as those of the conventional anodic oxidation treatment, and a uniform anodic oxide film having relatively uniform pores in the anodic oxidation treatment at the target voltage (10 V or higher) and having no crystal grain shape can be formed.

In the present invention, the treatment bath used in the pretreatment and the treatment bath used in the anodic oxidation treatment may be the same aqueous solution of a polybasic acid, or may be an aqueous solution of another polybasic acid, and the polybasic acid concentration May be the same or different. Use of a polybasic acid aqueous solution of the same kind and the same concentration in the pre-treatment and the anodic oxidation treatment has an advantage in that it is not necessary to exchange the treatment bath when the transition from the pre-treatment to the anodic oxidation treatment is carried out. Or more), it is necessary to use a polybasic acid aqueous solution of a different kind and / or a different concentration, and at this time, as a treatment bath for pretreatment, By using a rapid aqueous solution of polybasic acid, the entire treatment time can be shortened.

Further, in the present invention, when an anodic oxidation treatment is performed on an aluminum material at a target voltage (10 V or higher), if necessary, during or after the anodizing treatment, a pre-coating film Removal processing may be performed.

Here, as the pretreatment film removing treatment to be carried out during the anodizing treatment, for example, anodizing treatment of an aluminum material after the pretreatment is preferably carried out at an anodic oxidation of not less than 50 times, preferably not less than 80 times, A method of dissolving and removing the porous prepreg formed in the pretreatment in the treatment bath of the anodizing treatment can be exemplified. In this method, if the amount of electricity in the anodizing treatment is lower than 50 times, the dissolution of the prepreg in the anodizing treatment is insufficient, and the porous prepreg may remain on the surface and remain.

The pretreatment film removing treatment after the anodizing treatment may be carried out, for example, by immersing the aluminum material after the anodizing treatment in an aqueous solution of an acid or an alkali and chemically treating the porous film remaining on the surface during the anodizing treatment Followed by dissolving and removing it.

Thus, by removing the porous film formed in the pretreatment during or after the treatment of the anodic oxidation treatment, the intended pore diameter is uniform when viewed from the surface, and uniformly from the bottom to the top of the hole There arises an advantage that a coating film in which porous holes are opened can be obtained, that is, the same film can be obtained as in the case where the structure of the film is treated with only the target voltage (normal anodization treatment).

In the anodic oxidation treatment of the aluminum material after the pretreatment, a partial dissolution treatment of the pre-coating film may be performed in which the porous prepreg film formed on the aluminum material after the pretreatment is dissolved in a treatment condition in which 10% or more of the wall thickness remains As a partial dissolution treatment of the pre-coating, for example, a test sample substantially the same as that of the aluminum material after the pretreatment is prepared, and the treatment conditions in which the thickness of the inter-hole wall thickness of the pre- , And a method of treating the aluminum material after the pretreatment with the previously obtained treatment conditions can be exemplified. Thus, a porous anodic oxide film in which the pre-coat is not left on the surface and the porous layer is uniformly formed can be obtained by performing a partial dissolution treatment of the pre-coat in advance to adjust the thickness of the inter-hole wall of the pre-coat.

In the dissolving treatment of a part of the porous pre-coating, if the thickness of the inter-hole wall of the pre-coating is dissolved to less than 10% of the inter-hole wall thickness when the pre-coating is formed in the pretreatment, the porous pre- , Anodic oxidation may occur preferentially at a portion where the substrate is exposed, and a uniform anodized film may not be formed.

According to the method of the present invention, since the porous anodic oxide film can be formed at a treatment voltage of 10 V or higher, the grain shape can not be visually recognized for the aluminum material made of aluminum or aluminum alloy, It is possible to industrially easily manufacture an anodized aluminum material used for a housing member, a bicycle member, a vehicle member, a decoration member, an optical product member, a printing roll, etc., in which the uniformity of appearance is important.

Fig. 1 is a SEM photograph (upper photograph) in which the upper section of the test piece obtained in Example 1 was observed at a magnification of 3,000 times (upper photograph), and an SEM photograph )to be.
Fig. 2 is a graph showing the results of the evaluation of the results obtained in Example 14 when the anodic oxidation treatment of the pre-treated aluminum material obtained by forming the pretreatment film in the pretreatment and the anodic oxidation treatment at 1 minute after the initiation of the anodic oxidation treatment was stopped, It is a SEM photograph taken on a ship.

Hereinafter, preferred embodiments of the present invention will be described more specifically based on examples and comparative examples.

[Examples 1 to 20]

An aluminum piece having a size of 50 mm x 50 mm x 10 mm was cut out from these plate materials and the surface roughness Rt The aluminum pieces obtained after the mirror-finishing treatment were pretreated with a polybasic acid aqueous solution shown in Table 1 and a treatment condition to form a porous prepreg, And subjected to an anodic oxidation treatment, followed by washing with water to obtain aluminum pieces (test pieces) after the anodic oxidation treatment of each of Examples 1 to 20.

[Evaluation of crystal grain shape by surface observation]

The specimens obtained in Examples 1 to 20 were evaluated as having a grain shape when observed with a naked eye under a fluorescent lamp having an illuminance of 1500 Lux or more and 2,500 Lux or less and rated as X and under a fluorescent lamp having an illuminance of 1500 Lux or more and 2,500 Lux or less, A surface observation was conducted in which no crystal grain shape was observed when the observation was performed, and when the observation was made by visual observation under the video light having an illuminance of 15,000 Lux or more and 20,000 Lux or less, the crystal grain shape was not observed. Was evaluated.

The results are shown in Table 1.

[State of Precursor Film and Anodic Oxide Film Observed by SEM]

1, an upper photograph is an SEM photograph of an upper section of the test piece obtained in Example 1 by SEM at a magnification of 3,000, and the lower photograph shows anodic oxidation of the test piece obtained in Example 1 The SEM image of the top of the cross section of the coating film was observed at a magnification of 50,000 times. The pre-coating film was dissolved and disappeared during the anodic treatment, and a uniform porous anodic oxide coating film was formed.

Fig. 2 is a graph showing the results of a comparison between the results of SEM measurement of a reference specimen obtained by stopping the anodizing treatment for one minute after the initiation of the anodizing treatment and the pretreatment aluminum material obtained by forming the pretreatment film in the pretreatment in Example 14, The SEM image of the upper surface of the cross section was observed at a magnification of 100,000 times, and the remaining pre-coating film was observed on the upper surface of the porous anodic oxide coating. Further, in the test piece obtained in Example 14 in which the anodic oxidation treatment was performed under the condition of the treatment time of 45 minutes, no residual pre-coating film on the upper surface of the anodized film was observed.

[Example 21]

As in the case of Examples 1 to 20, a porous prepreg was formed as a pretreatment under the conditions of a voltage of 5 V and an electric quantity of 0.1 C / cm 2 in a treatment bath of 15 wt% -sulfuric acid (18 ° C) A porous anodic oxide film was formed under the conditions of a voltage of 15 V and an electric quantity of 6 C / cm 2 (corresponding to a film thickness of 3 탆) in a treatment bath of% - sulfuric acid (18 캜) An aluminum piece (test piece) after the oxidation treatment was obtained.

The obtained test pieces were evaluated in terms of grain shape by surface observation in the same manner as in Examples 1 to 20. The results are shown in Table 1.

Further, when the cross section of the obtained test piece was observed by SEM, it was confirmed that the pre-coat did not remain in the upper portion of the coat, and it was confirmed that the coat structure was uniform. As for Example 1 in which the pre-coating film remained, a large difference in appearance was not observed.

[Example 22]

As in the case of Examples 1 to 20, a porous prepreg was formed as a pretreatment under the conditions of a voltage of 5 V and an electric quantity of 0.1 C / cm 2 in a treatment bath of 15 wt% -sulfuric acid (18 ° C) A porous anodic oxide film was formed under the conditions of a voltage of 15 V and an electric quantity of 2 C / cm 2 in a treatment bath of% - sulfuric acid (18 캜). After the amount of electricity reached 2 C / cm < 2 >, the sample was immersed in the same bath for 15 minutes (a pretreating process) .

The obtained test pieces were evaluated in terms of grain shape by surface observation in the same manner as in Examples 1 to 20. The results are shown in Table 1.

When the cross section of the obtained test piece was observed by SEM, it was confirmed that the pre-coat did not remain in the upper portion of the coat, and the coat structure was confirmed to be uniform. The appearance was almost the same as in the case where the pre-coating removing process was not performed.

[Example 23]

As in the case of Examples 1 to 20, the mirror-finished aluminum pieces subjected to the same mirror-surface treatment were subjected to the same pretreatment under the conditions of a voltage of 5 V and an electric quantity of 0.1 C / cm 2 in a treatment bath of 15 wt% Two preliminary aluminum pieces having a porous prepreg formed thereon were prepared.

One surface of the obtained aluminum piece after the pretreatment was used as a test sample. The test sample was immersed in a 10 wt% -phosphoric acid aqueous solution (20 ° C) for 2 minutes (partial dissolution treatment of the pretreatment film) and observed by an electron microscope. It was confirmed that the thickness of the inter-hole wall of the pre-coating was reduced to 15% with respect to the aluminum piece after the pretreatment without treatment.

Next, the aluminum piece after the pretreatment without any dissolution treatment was subjected to partial dissolution treatment of the pretreatment film under exactly the same conditions as above, and then, without confirming the thickness of the hole between the holes of the pretreatment film, 15 wt% A porous anodized film was formed under the conditions of a voltage of 15 V and an electric quantity of 2 C / cm 2 in sulfuric acid (18 캜) to obtain an aluminum piece (test piece) after the anodizing treatment of Example 23.

The obtained test pieces were evaluated in terms of grain shape by surface observation in the same manner as in Examples 1 to 20. The results are shown in Table 1.

Further, when the cross section of the coating film of the test piece after the anodic oxidation treatment was confirmed by an electron microscope, the coating film confirmed in the test piece of Example 1 was not found on the coating film, and it was confirmed that the coating film structure was uniform.

[Comparative Examples 1 to 10]

Aluminum pieces having a size of 50 mm x 50 mm x 10 mm were cut out of these plate materials using Al purity plate materials or kinds of plate materials shown in Table 2 as the aluminum materials and the mirror surface processing means (puff polishing) To the surface roughness Rt < 200 nm, and the obtained aluminum pieces after the mirror-finishing treatment were subjected to pretreatment for forming a pretreatment film under the treatment conditions shown in Table 2, Anodic oxidation treatment, and further washing with water to obtain aluminum pieces (test pieces) after anodizing treatment of Comparative Examples 1 to 10.

[Evaluation of crystal grain shape by surface observation]

With respect to the test pieces obtained in Comparative Examples 1 to 10, the shape of crystal grains was evaluated by surface observation in the same manner as in each of the above-mentioned Examples.

The results are shown in Table 2.

Claims (12)

An anodic oxidation treatment method of an aluminum material for forming an anodic oxide film on a surface of an aluminum material by subjecting an aluminum material made of aluminum or an aluminum alloy to an anodic oxidation treatment in a treatment bath comprising a polybasic acid aqueous solution under a treatment condition of a target voltage of 10 V or higher,
As the pretreatment of the anodic oxidation treatment, an anodic oxidation treatment is carried out in a treatment bath comprising a polybasic acid aqueous solution until the electric quantity between pre-treatments reaches 0.05 C / cm 2 under a treatment condition of a voltage of 6 V or less, Wherein the pre-coating is formed on the surface of the aluminum material. The method according to claim 1, wherein the aluminum material has a grain size of 100 mu m or more existing in the material. The method of anodizing aluminum material according to claim 1 or 2, wherein the aluminum material has a mirror-finished surface. 4. The method of claim 3, wherein the mirror surface treatment is performed by mirror surface processing selected from buffing, electrolytic polishing, cutting, and chemical polishing. The method for anodizing aluminum material according to claim 1 or 2, wherein the treatment bath used in the pretreatment and the treatment bath used in the anodic oxidation treatment are the same aqueous solution of polybasic acid. The method for anodizing aluminum material according to claim 1 or 2, wherein the treating bath used in the pretreatment and the treating bath used in the anodizing treatment are different aqueous solutions of polybasic acid. The method of anodizing aluminum material according to claim 1 or 2, wherein, when carrying out the anodic oxidation treatment of the aluminum material, a pretreatment film removing treatment for removing the porous prepreg formed in the pretreatment is carried out. 8. The method of claim 7, wherein the pre-coating removing process is performed during or after the anodizing process. The pretreatment film removing method according to claim 8, wherein, in the anodic oxidation treatment of the aluminum material after the pretreatment, an anodic oxidation treatment at least 50 times the electricity applied at the pretreatment is carried out, Wherein the formed porous film is dissolved and removed in a treatment bath of an anodizing treatment. 9. The method according to claim 8, wherein the pretreatment film removal treatment after the anodizing treatment is performed by immersing the aluminum material after the anodizing treatment in an aqueous acid or alkali solution, chemically removing the porous film remaining on the surface during the anodizing treatment Wherein the anodic oxidation treatment is carried out by dissolving the aluminum material. The pretreatment method according to any one of claims 1 to 3, further comprising, in the anodic oxidation treatment of the aluminum material after the pretreatment, a pretreatment step of dissolving the porous prepreg film formed on the aluminum material after the pretreatment in a treatment condition in which 10% A method for anodization of an aluminum material, in which a partial dissolution process is performed. The method according to claim 11, wherein the dissolving treatment of the porous pre-coating is performed by preparing a test sample which is substantially the same as the aluminum material after the pretreatment, and using the test sample to leave at least 10% And an aluminum material after the pretreatment is treated with the pre-determined processing conditions.

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