KR20120021616A - Surface treatment method of mother metal - Google Patents

Abstract

PURPOSE: A method for treating surface of metal base material is provided to form an oxide coating through two oxidizing processes on the surface of metal base with aluminum material, and to improve plasma-resistance, crack-resistance and corrosion-resistance according to the control of porous characteristics of the coating. CONSTITUTION: A method for treating surface of metal base material comprises: a step of forming a first positive electrode oxide coating through a first oxidizing process to a metal base material consisting of aluminum or alloy thereof at first electrolyte; and a step of forming a second positive electrode oxide coating through a second oxidizing process at second electrolyte. The first electrolyte is sulfuric acid aqueous solution with the density of 15-18 weight%. In the first positive electrode oxide coating, the voltage of 0.1-100 V is applied, and the first positive electrode oxide coating is conducted at the temperature of 5-100°C for 0.5-5 hours. The second electrolyte is aqueous solution consisting of oxalic acid, citric acid, formic acid and boric acid. In the second positive electrode oxide coating, the voltage of 0.1-100 V is applied, and the second positive electrode oxide coating is conducted at the temperature of 5-100°C for 0.5-5 hours.

Description

Surface treatment method of metal base material {SURFACE TREATMENT METHOD OF MOTHER METAL}

The present invention is used in the surface treatment of various subsidiary materials such as heaters and shower heads (diffusers) used in vacuum chambers and vacuum chambers of semiconductor and TFT-LCD manufacturing equipment, and thus, the plasma resistance, thermal crack resistance, and corrosion resistance It is related with the surface treatment method of the metal base material which can be improved.

At present, due to the technological development of semiconductor and TFT-LCD processes, each process requires an ultra-clean process environment, and the damage caused by product damage due to the generation of some pollutants during the process is very large. Contaminants generated in these processes include particles coming in from the outside or particles coming back during the process cycle.

However, the largest source of pollutants at present is the components used in the process. If the process parts are continuously exposed to the process environment, the surface is damaged and the coating film or the oxide film is destroyed, resulting in outgassing or particles. Accordingly, technologies for treating the surface of the aluminum subsidiary materials in various ways have been proposed to have plasma resistance and thermal crack resistance to withstand the harsh atmosphere in the vacuum chamber.

U. S. Patent No. 5,641, 375 discloses a technique for forming an anodized film by performing anodization to reduce plasma corrosion and wall wear of an aluminum chamber wall.

Korean Patent Publication No. 2005-65497 discloses an oxide film layer on the surface of an aluminum alloy using an electrolyte composed of 0.5-10% citric acid and 0.2-10% oxalic acid, wherein the oxide film layer has a fine porous structure. It is said to have pores.

Republic of Korea Patent Registration No. 10-081918 is an anodized surface of an aluminum substrate using an electrolyte consisting of 13-17% by weight sulfuric acid, 0.01-1% by weight oxalic acid and deionized water in the production of electrophotographic aluminum drum The film was formed to improve the physical properties.

However, the oxide film layer formed through the anodic oxidation process is able to secure some degree of plasma resistance or thermal crack resistance by its own micropores, but a serious problem such as film damage due to corrosion by plasma gas has occurred.

United States Patent No. 5,641,375 Republic of Korea Patent Publication No. 2005-65497 Republic of Korea Patent Registration No. 10-081918

It is an object of the present invention to provide a method for surface treatment of a metal base material which can improve not only plasma resistance or thermal crack resistance but also corrosion resistance to improve product life.

In order to achieve the above object,

A first anodic oxidation film is formed by performing a first anodic oxidation process on a metal base material made of aluminum or an alloy thereof, in a first electrolyte solution,

It provides a method for surface treatment of a metal base material comprising performing a secondary anodic oxidation process in a second electrolyte solution to form a second anodized film.

According to the present invention, anodization process is performed on the surface of an aluminum metal base material to form an anodized film, and the porosity of the film is controlled to improve plasma resistance, thermal crack resistance, and corrosion resistance of the metal. Let's do it.

1 is a flow chart showing a coating method of a metal base material according to an embodiment of the present invention.
Figure 2 is a schematic diagram showing a coating method of a metal base material according to an embodiment of the present invention.
3 is a SEM photograph showing the surface of the substrate (a) subjected to the first anodization and the substrate (b) subjected to the second anodization in Example 1 (100,000 magnification).
4 and 5 are graphs showing the breakdown voltage characteristics of the substrate (a) subjected to the first anodization and the substrate (b) subjected to the second anodization in Example 1. FIG.
FIG. 6 is a graph illustrating chemical resistance of substrates subjected to first and second anodic oxidations in Example 1. FIG.
FIG. 7 is a SEM photograph showing plasma characteristics of (a) reference, the substrate (b) subjected to the first anodization and the substrate (c) subjected to the second anodization in Example 1. FIG.
FIG. 8 is a graph showing plasma characteristics of a substrate subjected to first and second anodization in Example 1. FIG.
FIG. 9 is a SEM photograph showing the corrosion resistance characteristics of the substrate (b) subjected to the first anodization and the substrate (c) subjected to the second anodic oxidation in (a) Reference Example 1. FIG.
(A) of FIG. 10 and FIG. 11 show the surface of the board | substrate obtained in Example 1, (b) shows the surface of the board | substrate obtained in Comparative Example 1, and (c).
(A) is a scanning electron microscope photograph which shows the surface of the board | substrate obtained in Example 1, (b) shows the surface of the board | substrate obtained in Comparative Example 1 and (c).

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. It is preferable to understand that the shape and the like of the elements in each drawing are exaggerated in order to emphasize a more clear description. In this case, elements denoted by the same reference numerals in the drawings mean the same elements. In addition, where a layer is described as being "on" another layer, the layer may exist in direct contact with the other layer, or a third layer may be interposed therebetween.

1 is a flow chart showing a coating method of a metal base material according to an embodiment of the present invention, Figure 2 (a) to (d) is a schematic diagram thereof.

First, a metal base material 11 made of aluminum or aluminum alloy is prepared (see FIG. 2A).

The metal base material 11 is subjected to a pretreatment step consisting of a degreasing step, a water washing step, an etching step, and an electrolytic degreasing step.

First, in order to remove the grease on the surface of the metal base material 11 in order to form a film well as a pre-treatment process, it performs a degreasing (Cleaning, Degreesing) process, and then degreasing solution and foreign matter In order to remove the water, washing processes such as air stirring, forced convection, hot water washing and spray washing are performed.

Next, an etching process is performed to increase the surface area, and electrolytic degreasing is performed. This pretreatment process may be used in addition to or in addition to the known pretreatment processes such as ultrasonic application.

Next, the first anodic oxidation film 13 is formed by performing a first anodic oxidation process on the metal base material 11 made of aluminum or an alloy thereof (see FIG. 2B).

In the anodic oxidation process, the metal base material 11 made of aluminum is used as a positive electrode, which is immersed in the first electrolyte solution, and then voltage is applied to cause anodization.

At this time, the metal base material 11 is electrically oxidized from the surface by the applied voltage, and the surface of the metal base material 11 is converted into the aluminum oxide film Al ₂ O ₃ , which is the first anodized film 13. Subsequently, when voltage is continuously applied, pores are formed in the first anodized film 13 in a direction perpendicular to the metal base material 11.

It is preferable that 15-18 weight% of sulfuric acid aqueous solution is used for the 1st electrolyte solution used for a primary anodic oxidation process.

In the first anodic oxidation process, the voltage is applied at 0.1 to 100V, preferably 10 to 40V. If the voltage is less than the above range, sufficient anodic oxidation may not be performed or the anodization process may be performed for a long time. On the contrary, if the voltage exceeds the above range, the fine pores of the anodized film formed due to sudden oxidation are greatly degraded and fine. Pore size distribution also causes a problem.

The temperature of the primary anodic oxidation process is carried out at -5 ~ 100 ℃, preferably 25 ~ 50 ℃. If the temperature is less than the above range, the anodic oxidation rate is lowered. On the contrary, if the temperature exceeds the above range, the concentration of the electrolyte is changed (near the boiling point of water), resulting in the formation of a nonuniform anodic oxide film.

In addition, the primary anodic oxidation process is carried out for 0.5 to 5 hours, preferably 1 to 2 hours. If the time is less than the above range, the time is short and sufficient anodic oxidation cannot be achieved. On the contrary, if the time exceeds the above range, the thickness of the aluminum material under the anodic oxide film is excessively reduced due to excessive anodization, which causes problems in product application.

The conditions of the anodic oxidation process can be sufficiently changed by those skilled in the art within the above range in consideration of various factors such as the diameter and the degree of alignment of the fine pores, the thickness of the anodized film and the like.

The first anodic oxide film 13 thus formed is amorphous Al ₂ O ₃ The film has a number of fine pores.

After the first anodic oxidation process, a washing process is performed for subsequent processes.

Next, the second anodic oxide film 15 is formed by performing a secondary anodic oxidation process on the metal base material 11 on which the first anodized film 13 is formed in the second electrolyte (FIG. 2C). ) Reference).

In the present invention, the second anodic oxidation film 15 is formed by performing a second anodic oxidation process to minimize the number of fine pores of the first anodic oxide film 13 and having a low porosity. The second anodization film 15 not only improves the plasma resistance and thermal crack resistance of the metal base material 11 made of aluminum, but also suppresses corrosion due to inflow of chemicals or gases due to low porosity. 11) has the effect of improving the corrosion resistance.

The formation of the second anodic oxide film 15 is formed by a secondary anodic oxidation process (that is, the first anodic oxide film is converted), which is most affected by the composition of the electrolyte solution in the process conditions performed at this time.

According to Experimental Example 1 of the present invention, as a result of forming an anodic oxide film using the electrolyte solution and sulfuric acid or oxalic acid proposed by the present invention as an electrolyte solution, as shown in FIG. It can be seen that there is a big difference in the number.

The second electrolyte solution used in the present invention uses an aqueous solution consisting of oxalic acid, citric acid, formic acid and boric acid, preferably oxalic acid (5-30 g / l), citric acid (5-30 g / l), formic acid (5-30 g / l). l) and boric acid (5-30 g / l), more preferably oxalic acid (15-25 g / l), citric acid (15-25 g / l), formic acid (15-25 g / l) and boric acid (15-25 g / l) Use an aqueous solution consisting of). As the secondary anodic oxidation process is performed using the second electrolyte having the composition, the number of pores of the first anodic oxide film 13 can be significantly reduced.

In the secondary anodic oxidation process, the voltage is applied at 0.1 to 100V, preferably 10 to 40V. If the voltage is less than the above range, sufficient anodic oxidation is not achieved, and thus the second anodized film 15 is formed on the first anodized film 13. It is not easy to control the size and porosity of the fine pores of the two anodized film 15.

The temperature of the secondary anodic oxidation process is carried out at -5 ~ 100 ℃, preferably 25 ~ 50 ℃. If the temperature is less than the above range, the rate of anodic oxidation is low, so the transition to the second anodic oxide film is too slow. On the contrary, if the temperature is exceeded, the concentration of the electrolyte is changed (near the boiling point of water), so that the fineness of the second anodic oxide film 15 is reduced. Pore size and porosity control is not easy.

In addition, the secondary anodic oxidation process is carried out for 0.5 to 5 hours, preferably 1 to 2 hours. If the time is less than the above range, the time is short to achieve a sufficient secondary anodic oxidation process. On the contrary, if the time exceeds the above range, the thickness of the aluminum material under the second anodic oxide film 15 is excessively reduced due to excessive anodic oxidation. Problems with product application.

The conditions of the secondary anodization process are conventional in this field within the above range in consideration of each condition in the direction of minimizing the number of pores in the first anodizing film 13 and reducing the diameter of the pores to improve corrosion resistance. Fully changeable by knowledgeable ones.

The second anodic oxide film 15 thus formed is amorphous Al ₂ O ₃ The film almost eliminates micropores.

After forming the second anodic oxide film by the secondary anodic oxidation process, a washing process and a drying process are performed.

In addition, a post-treatment process consisting of a sealing process, a water washing process, and a drying process is performed after the secondary anodic oxidation treatment.

The sealing is a work for sealing the aluminum, the sealing film (not shown) by depositing a high temperature sealing agent (product name DN1508) for about 30 minutes at a high temperature of 4 ~ 6 g / ℓ, a temperature of 85 ~ 90 ℃ Form.

The washing and drying are carried out in a conventional manner.

Through the above steps, the present invention forms an anodized film having a significantly reduced pore number on the surface of the metal base material.

The surface treatment of the metal base material according to the present invention is applied to the surface treatment of various subsidiary materials, such as a vacuum chamber and a heater and a shower head (diffuser) used in the semiconductor and TFT-LCD manufacturing equipment.

The subsidiary material is mainly composed of aluminum or aluminum alloy, the surface of the subsidiary material has the effect of improving the corrosion resistance, plasma resistance and thermal crack resistance due to the second anodic oxide film to improve the life of the above-mentioned equipment Increase.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the examples.

[Example]

Example  One

The aluminum substrate was pretreated by degreasing, washing with water, etching and electrolytic degreasing by a known method.

Subsequently, it was immersed in an aqueous solution of 15% sulfuric acid, and then used as an anode to supply 0.2 A / cm 2 of current at 28 ° C. for 60 minutes to form a first anodic oxide film.

The obtained substrate was washed with deionized water and immersed in an aqueous solution containing oxalic acid (20 g / l), citric acid (20 g / l), formic acid (20 g / l), and boric acid (20 g / l), and then 0.2 was used as an anode. A / cm 2 current was supplied at 28 ° C. for 60 minutes to form a second anodic oxide film.

Subsequently, after washing with deionized water, 5 g / l, the temperature was immersed in a high temperature sealing agent (product name DN1508) for 30 minutes at 85 ℃ to perform a sealing process. Again washed with deionized water and dried for 1 hour at room temperature.

Experimental Example  One

In order to examine the improvement of the physical properties of the substrate treated by the second anodic oxidation process according to the present invention, SEM photographs, voltage resistance, chemical resistance, plasma resistance, and corrosion resistance tests were performed, and the obtained results are shown below. It was.

(One) SEM  Photo observation

3 is a SEM photograph showing the surface of the substrate (a) subjected to the first anodization and the substrate (b) subjected to the second anodization in Example 1 (100,000 magnification).

Referring to FIG. 3, when only the first anodic oxidation is performed, the pore depth and distribution are very large, but as a result of the second anodic oxidation treatment, most of the pores are removed and only the shape of the pores remains, so the depth is not deep. It is judged to be very excellent in characteristics.

(2) withstand voltage characteristics

4 and 5 are graphs showing the breakdown voltage characteristics of the substrate (a) subjected to the first anodization and the substrate (b) subjected to the second anodization in Example 1. FIG.

Referring to FIGS. 4 and 5, it can be seen that insulation breakdown caused by pores occurs more easily than the second anodized substrate as a result of the breakdown voltage measurement of the first anodized substrate.

That is, referring to FIG. 4, when the anodic oxidation is performed using the sulfuric acid electrolyte, the electrical insulation property is low due to a plurality of pores present on the surface of the substrate, and when the anodic oxidation is performed by the present invention, the sulfuric acid electrolyte is used. Since the pores of the formed substrate are hardly present, the electrical insulating properties are about 1.5 to 2 times higher than the case of using only sulfuric acid electrolyte.

In addition, FIG. 5 is an experimental result measured to observe how the sample is changed when the same process influence is applied to each sample on the basis of the insulation characteristics indicated when the component used in the TFT-LCD process is damaged. Referring to FIG. 5, the parts made using the actual sulfuric acid electrolyte were damaged as in the conventionally used parts, but the first and second anodic oxidation processes according to the present invention did not reach the damage reference point. Can be.

(3) chemical resistance analysis

FIG. 6 is a graph illustrating chemical resistance of substrates subjected to first and second anodic oxidations in Example 1. FIG. The chemical resistance test was performed to observe the result of artificial damage to the oxide film with HCl gas generated using pure 100% HCl in the container. At this time, the arrow at the top of the graph is the result of evaluation by taking a sample from the part used in the actual process, the middle arrow is the result of the experiment on the sample made using sulfuric acid electrolyte, and finally the second anodic oxidation according to the present invention. Shows the result of

Referring to FIG. 6, it can be seen that chemical resistance is further improved when the second anodic oxidation is performed according to the present invention.

(4) Plasma resistance  analysis

FIG. 7 is a SEM photograph showing plasma characteristics of (a) reference, the substrate (b) subjected to the first anodization and the substrate (c) subjected to the second anodization in Example 1. FIG. Plasma resistance of the substrate was injected into a PECVD chamber, and plasma was generated using NF ₃ gas at 380 ° C. and measured by SEM camera.

Referring to FIG. 7, it can be seen that plasma resistance is further improved by performing the second anodic oxidation according to the present invention.

FIG. 8 is a graph showing plasma characteristics of a substrate subjected to first and second anodization in Example 1. FIG. Specifically, as an experiment to evaluate the degree of damage caused by plasma in the TFT-LCD process, the arrow at the top in Figure 8 shows the result of the plasma effect by taking a sample from the parts used in the actual process, the middle arrow When the sulfuric acid electrolyte is used, the last arrow shows the characteristics when the second anodic oxidation according to the present invention is carried out.

Referring to FIG. 8, it can be seen that plasma resistance is much superior to the case of using only sulfuric acid electrolyte when the second anodic oxidation is performed according to the present invention.

(5) Corrosion resistance  analysis

FIG. 9 is a SEM photograph showing the corrosion resistance characteristics of the substrate (b) subjected to the first anodization and the substrate (c) subjected to the second anodic oxidation in (a) Reference Example 1. FIG. Corrosion resistance of the substrate was measured by SEM cameras on the surface of the substrate in which the substrate was immersed in an HCl 10% solution (25 ° C.).

Referring to FIG. 9, it can be seen that the corrosion resistance property is further improved by performing the second anodic oxidation according to the present invention.

Experimental Example  2

In order to confirm the characteristics according to the type of electrolyte, the order of the process and the number of processes in the anodic oxidation process, the surface treatment of the aluminum substrate was performed using the composition shown in Table 1 below. Except for the composition of the electrolyte, the rest of the process was carried out in the same manner as in Example 1.

First electrolyte (primary anodic oxidation) Second Electrolyte (Secondary Anodic Oxidation) Example 1 Sulfuric acid Oxalic acid / citric acid / formic acid / boric acid Comparative Example 1 Sulfuric acid Sulfuric acid Comparative Example 2 Sulfuric acid Oxalic acid Comparative Example 3 Oxalic acid / citric acid / formic acid / boric acid Sulfuric acid Comparative Example 4 Sulfuric acid - Comparative Example 5 Oxalic acid / citric acid / formic acid / boric acid -

(One) SEM  Photo analysis

The surface of the aluminum substrate treated with the composition of Table 1 was measured by SEM, and the results obtained are shown in FIG. 10, and its three-dimensional schematic diagram is shown in FIG. 11.

(A) of FIG. 10 and FIG. 11 show the surface of the board | substrate obtained in Example 1, (b) shows the surface of the board | substrate obtained in Comparative Example 1, and (c). Referring to FIGS. 10 and 11, in the case of anodizing only with sulfuric acid (Comparative Examples 1 and b), relatively large pores were formed on the substrate, followed by secondary anodizing with oxalic acid (Comparative Examples 2 and c). ) The pores tended to decrease. However, pores were still identified on the substrate, and when the second anodic oxidation was performed with oxalic acid / citric acid / formic acid / boric acid according to the present invention (Example 1), it was confirmed that the pores were minimized on the substrate.

Although not attached, the substrates of Comparative Examples 3 and 4, which were anodized with sulfuric acid, oxalic acid, and the like, had relatively large pores, and primary anodic oxidation with oxalic acid / citric acid / formic acid / boric acid of Comparative Example 5 was performed. In one case it was confirmed that the fine pores are formed.

(2) Thermal crack resistance  analysis

To measure the thermal crack resistance of the substrate After heating to 500 ° C and cooling the water at room temperature 10 times, the surface was measured by a scanning electron microscope to confirm the degree of cracking, and the results obtained are shown in Table 2 below.

crack Example 1 Not occurring Comparative Example 1 Occur Comparative Example 2 Occur Comparative Example 3 Occur Comparative Example 4 Occur Comparative Example 5 Occur

Referring to Table 2, except for the substrate of Example 1, cracks occurred in the case of the substrates of Comparative Examples 1 to 5.

(3) chemical resistance analysis

Chemical resistance of the substrate In order to measure the corrosion degree over time after immersion in HCl 10% solution (25 ℃), the obtained results are shown in Table 3 below.

corrosion Example 1 Not occurring Comparative Example 1 Occur Comparative Example 2 Occur Comparative Example 3 Occur Comparative Example 4 Occur Comparative Example 5 Occur

Referring to Table 3, except for the substrate of Example 1, the corrosion of the substrates of Comparative Examples 1 to 5 occurred.

(4) Plasma resistance  analysis

After the injection into the PECVD chamber to measure the plasma resistance of the substrate to determine the surface damage by generating a plasma using NF ₃ gas at 380 ℃, the results are shown in Table 4 below.

24 hours 48 hours 96 hours Example 1 No damage No damage No damage Comparative Example 1 No damage Slight damage Slight damage Comparative Example 2 No damage Slight damage Slight damage Comparative Example 3 No damage Slight damage Serious damage Comparative Example 4 Slight damage Serious damage Serious damage Comparative Example 5 Slight damage Serious damage Serious damage

Referring to Table 4, except for the substrate of Example 1 according to the present invention, damage occurred in the case of the substrates of Comparative Examples 1 to 5.

Experimental Example  3

In order to confirm the characteristics according to the process conditions of the secondary anodic oxidation process, the surface treatment of the aluminum substrate was performed using the composition shown in Table 5 below. At this time, except for the following Table 5 was carried out in the same manner as in Example 1.

Second electrolyte composition Voltage Temperature time Example 1 Oxalic acid / citric acid / formic acid / boric acid 5 V 25 30 seconds Comparative Example 6 Oxalic acid / citric acid / formic acid / boric acid 120 V 10 30 seconds Comparative Example 7 Oxalic acid / citric acid / formic acid / boric acid 5 V -10 30 seconds Comparative Example 8 Oxalic acid / citric acid / formic acid / boric acid 5 V 25 10 sec Comparative Example 9 Oxalic acid / citric acid / formic acid / boric acid 50 50 6 hours Comparative Example 10 Oxalic acid / citric acid / formic acid / boric acid
(High concentration) 5 V 25 30 seconds

(One) Thermal crack resistance  analysis

To measure the thermal crack resistance of the substrate After heating to 500 ° C and cooling the water at room temperature 10 times, the surface was measured by a scanning electron microscope to confirm the degree of cracking, and the results obtained are shown in Table 6 below.

crack Example 1 Not occurring Comparative Example 6 Occur Comparative Example 7 Occur Comparative Example 8 Occur Comparative Example 9 Occur Comparative Example 10 Occur

Referring to Table 6 above, except for the substrate of Example 1, cracks occurred in the substrates of Comparative Examples 6 to 10.

(2) chemical resistance analysis

Chemical resistance of the substrate After immersion in HCl 10% solution (25 ℃) to measure the degree of corrosion over time was measured, the results obtained are shown in Table 7.

corrosion Example 1 Not occurring Comparative Example 6 Occur Comparative Example 7 Occur Comparative Example 8 Occur Comparative Example 9 Occur Comparative Example 10 Occur

Referring to Table 7, except for the substrate of Example 1, the corrosion of the substrate of Comparative Examples 6 to 10 occurred.

(3) Plasma resistance  analysis

After the injection into the PECVD chamber to measure the plasma resistance of the substrate to determine the surface damage by generating a plasma using NF ₃ gas at 380 ℃, the obtained results are shown in Table 8 below.

24 hours 48 hours 96 hours Example 1 No damage No damage No damage Comparative Example 6 No damage Slight damage Slight damage Comparative Example 7 No damage Slight damage Slight damage Comparative Example 8 No damage Slight damage Serious damage Comparative Example 9 Slight damage Serious damage Serious damage Comparative Example 10 Slight damage Serious damage Serious damage

Referring to Table 8, damage was generated in the case of the substrates of Comparative Examples 6 to 10, except for the substrate of Example 1 according to the present invention.

The surface treatment method according to the present invention is applied to the surface treatment of various subsidiary materials such as heaters and shower heads (diffusers) used in vacuum chambers and vacuum chambers of semiconductor and TFT-LCD manufacturing equipment.

11: metal base material 13: first anodized film
15: second anodic oxide film

Claims (7)

A first anodic oxidation film is formed by performing a first anodic oxidation process on a metal base material made of aluminum or an alloy thereof, in a first electrolyte solution,
A method of surface treatment of a metal base material comprising performing a secondary anodic oxidation process in a second electrolyte to form a second anodized film. The method of claim 1, wherein the first electrolyte solution is an aqueous sulfuric acid solution having a concentration of 15 to 18% by weight. The method of claim 1, wherein the first anodic oxidation process is performed at a voltage of 0.1 to 100 V and is performed at a temperature of −5 to 100 ° C. for 0.5 to 5 hours. The method of claim 1, wherein the second electrolyte is an aqueous solution consisting of oxalic acid (5-30 g / l), citric acid (5-30 g / l), formic acid (5-30 g / l) and boric acid (5-30 g / l). Surface treatment method of a metal base material. The method of claim 1, wherein the second anodic oxidation process is performed at a voltage of 0.1 to 100 V and is performed at a temperature of −5 to 100 ° C. for 0.5 to 5 hours. The surface treatment method of a metal base material according to claim 1, wherein a pretreatment comprising degreasing, washing, etching, and electrolytic degreasing is performed before the first anodic oxidation process. The surface treatment method of the metal base material of Claim 1 which performs the post-processing which consists of a sealing, a water washing, and a drying process after the said secondary anodic oxidation process.

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