JP5265181B2 - Protective film manufacturing method - Google Patents

Abstract

Disclosed is a method for forming a protective film having high corrosion resistance. The method comprises bringing warm water (46) having a temperature of 70°C or above and 90°C or below (first temperature) into contact with an anode oxide film (12) to form a discontinuous face on the surface of the anode oxide film (12) and then bringing hot water having a second temperature, which is above the first temperature, or a water vapor having the second temperature into contact with the film. The hot water or the water vapor is introduced through the surface of the anode oxide film (12) into the inside of the anode oxide film (12). Accordingly, voids on the surface portion in the anode oxide film (12) are clogged by a hydrate formed upon the contact of the voids with the hot water or the water vapor. Therefore, a protective film formed of a dense layer can be reliably formed on the surface of the anode oxide film (12).

Description

  The present invention relates to a method for producing a protective film of an aluminum material, and more particularly to a method for forming a dense layer (protective film) on an anodic oxide film of aluminum.

Aluminum and aluminum alloys are widely used as an inner wall member of a vacuum chamber of a vacuum processing apparatus because they are lighter and have better thermal conductivity than stainless steel and are not affected by heavy metal contamination such as chromium.
Conventionally, anodizing treatment called anodizing treatment has been widely used for corrosion treatment of aluminum or aluminum alloy.

  However, even in a vacuum processing apparatus, particularly a reactive gas, or an apparatus (such as a CVD apparatus or an etching apparatus) that uses plasma or radical thereof requires high corrosion resistance, and the conventional anodic oxidation process is insufficient.

  In the anodic oxidation treatment, an aqueous solution of sulfuric acid, oxalic acid or the like is used as an electrolytic solution, and the object to be treated is used as an anode, and is immersed in the electrolytic solution. Electrolysis is caused between the cathode immersed in the same electrolytic solution and the anode, and an anodic oxide film made of aluminum oxide or hydroxide is grown on the surface of the object to be treated.

  The anodic oxide film thus formed has a thickness of several μm to several tens of μm. Generally, the film has a porous structure in which innumerable pores of several tens of nm are formed in the depth direction from the surface. It has become. The thickness of the oxide film on the bottom of the hole (bottom wall of the hole) is several tens of nm, and this thin oxide film determines the corrosion resistance of the entire anodic oxide film.

  In order to improve the corrosion resistance of the anodic oxide film, a sealing treatment for filling the holes is necessary. As the sealing treatment, there are known a method in which an object to be treated on which an anodized film has been formed is immersed in boiling water, and a method in which the object to be exposed to high-temperature steam at 100 ° C. or higher in a steam kettle.

According to this method, it is known that a dense layer is formed on the porous structure of the anodic oxide film. This layer is generally called a boehmite layer, and it has been said that a dense boehmite layer improves corrosion resistance. However, even if the sealing treatment is performed by this method, a boehmite layer exhibiting high corrosion resistance is not formed with good reproducibility, and the corrosion resistance may be insufficient.
Japanese Patent No. 3803353

When the present inventors performed sealing treatment in which the anodic oxide film was brought into contact with boiling water at 100 ° C. or higher, no dense layer was formed even if anodic oxidation treatment and sealing treatment were performed under exactly the same conditions. Some have a thick film of 1 μm or more, and it has been found that the thickness of the dense layer varies.
Even when the sealing treatment was carried out with water vapor of 100 ° C. or higher instead of boiling water, variation was similarly caused.

  In order to further improve the sealing performance, even if the sealing time is extended to 2 hours, usually 30 minutes, the problem of variation in the thickness of the dense layer has not been solved. Further, in consideration of the influence of contamination before the sealing treatment, even if the processing object is sufficiently cleaned before the sealing treatment and the sealing treatment is performed, the variation in the film thickness of the dense layer is not improved.

  Also, considering the influence of the film structure of the anodic oxide film, the applied voltage was changed during film formation of the anodic oxide film, and the sealing process was performed by changing the film structure, but the variation in the thickness of the dense layer was improved. There wasn't.

In order to solve the above-mentioned problems, the present invention provides a method for producing a protective film, comprising densifying the anodic oxide film of a treatment target having an anodic oxide film formed on the surface thereof, and producing a protective film, Densification of the anodic oxide film is higher than the first temperature after contacting pure water having a first temperature of 70 ° C. or higher and 90 ° C. or lower with the anodic oxide film for 15 minutes or longer. The hot water brought to a second temperature of 100 ° C. or higher is brought into contact with the anodic oxide coating, or the water vapor made to the second temperature of 100 ° C. or higher, which is higher than the first temperature , In the method for producing a protective film , the surface of the anodic oxide film is brought into contact with the anodic oxide film in a pressure-treated treatment tank so that the surface of the anodic oxide film is a dense layer having a thickness of 1.0 μm or more .
The present invention is a method for producing a protective film, wherein the warm water is an alkaline aqueous solution obtained by adding any one alkali selected from the group consisting of ammonia, triethanolamine, and hydrazine to the pure water. It is a protective film manufacturing method to be used .

  Since the dense layer (protective film) of the anodic oxide film is made thick and the film thickness becomes uniform, the corrosion resistance is improved.

Reference numeral 2 in FIG. 1 indicates an anodizing apparatus. In order to form a film, it is put as an electrolytic solution 26 in the electrolytic cell 21 of the anodizing device 2.
The object to be treated 11 is attached in close contact with the attachment 23 connected to the plus terminal of the power supply 25. The treatment object 11 was immersed in the electrolytic solution 26 while being attached to the attachment device 23, and the cathode plate 22 connected to the negative terminal of the power supply 25 was immersed in the electrolytic solution 26.

While maintaining the electrolytic solution 26 at a predetermined oxidation temperature, the power supply 25 is operated, a predetermined oxidation voltage is applied between the object to be processed 11 and the cathode plate 22, and a direct current voltage with a predetermined current density is applied to a predetermined voltage. Oxidation time treatment object 11
An aluminum material made of one or both of aluminum and an aluminum alloy is exposed on at least the surface portion of the processing object 11, and the current density is the current flowing through the processing object 11 by the aluminum of the processing object 11. It is a value divided by the area of the portion where the material is exposed.

When a current flows through the object 11 to be processed, aluminum melts as ions from the surface portion. The aluminum ions are bonded to oxygen generated by electrolysis of water or hydroxyl groups, and either one of aluminum oxide (Al ₂ O ₃ ) and aluminum hydroxide (AlH ₃ O ₃ ) is formed on the surface of the object 11 to be processed. Or both are produced and an anodic oxide film of aluminum is formed.

The electrolytic solution 26 includes an acid such as oxalic acid or sulfuric acid, and the anodic oxide film has a porous structure in the electrolytic solution 26.
The processing object 11 on which the anodic oxide film 12 is formed is pulled up from the electrolytic solution 26, removed from the fixture 23, and washed with pure water.

  The code | symbol 4 of FIG. 2 has shown the 1st sealing processing apparatus. Hot water 46 having a first temperature (70 ° C. or more and 90 ° C. or less) is placed in the first heat treatment tank 41 of the first sealing treatment device 4. While maintaining the temperature of the hot water 46 at the first temperature, the processing object 11 on which the anodic oxide film 12 is formed is immersed in the hot water 46 for a predetermined first processing time (5 minutes to 60 minutes).

When the anodic oxide film 12 comes into contact with the hot water 46 at the first temperature, a discontinuous surface is formed on the surface and the voids in the anodic oxide film 12 are exposed (first heat treatment step).
After the first heat treatment step, hot water having a second temperature higher than the first temperature or water vapor having the second temperature is applied to the anodic oxide film 12 for a predetermined second treatment time (5 minutes to 60 minutes). ) Make contact.

  As described above, since the voids in the anodic oxide film 12 are exposed by the first heat treatment step, the hot water or water vapor not only contacts the surface of the anodic oxide film 12 but also enters the voids.

When the constituent material (aluminum oxide or aluminum hydroxide) of the anodic oxide film 12 comes into contact with hot water or water vapor, it absorbs water and boehmite (Al ₂ O ₃ .H ₂ O) or bayerite (Al ₂ O ₃ .3H). ₂ O) and the like, and the volume expands, the voids of the anodic oxide film 12 are sealed, and a dense protective film is formed on the surface portion of the anodic oxide film 12 (second heat treatment step). ).

  When hot water is used in the second heat treatment step, for example, the hot water 46 is heated while the processing object 11 is immersed in the hot water 46 in the same tank as the first heat treatment step. After the temperature of the hot water becomes, the state in which the processing object 11 is immersed in the hot water is maintained for the second processing time. Alternatively, the object to be treated 11 is pulled up from the hot water 46, soaked in hot water having a second temperature arranged in a separate tank from the first heat treatment step, and the hot water is maintained in the second temperature while being maintained at the second temperature. The state in which the processing object 11 is immersed is maintained for the second processing time.

When water vapor is used in the second heat treatment step, after the processing object 11 is pulled up from the hot water 46, the pot (processing tank) of the steam sealing device (second sealing processing device 5) as shown in FIG. 51) Arrange the processing object 11 within. A state in which the treatment tank 11 is exposed to the steam while the treatment tank 51 is filled with the steam at the second temperature by the steam generator 55 and the temperature of the steam is maintained at the second temperature. Maintain the second processing time.
When using water vapor in the second heat treatment step, the internal pressure of the treatment tank 51 may be normal pressure (1 atm) or may exceed normal pressure.

  An aluminum alloy plate (A5052P, see JIS H4000) having a width of 30 mm, a length of 45 mm, and a thickness of 2 mm is used as a substrate, and the substrate is immersed in a 10% sodium hydroxide aqueous solution at 40 ° C. for 1 minute as a pretreatment for forming an anodic oxide film. After degreasing, it was washed with water and immersed in a 35% sulfuric acid aqueous solution at room temperature to remove smut (black deposit).

  The substrate after the pretreatment is treated, an electrolytic solution in which 30 g of oxalic acid is dissolved in 1 liter of pure water is used, the oxidation temperature is 15 ° C. or higher and 25 ° C. or lower, the oxidation voltage is 60 V or higher and 100 V or lower. The anodic oxide film 12 was formed under the conditions shown in Table 1 below for the density, oxidation time, and film thickness of the anodic oxide film 12.

Using the processing object 11 on which the anodic oxide film 12 was formed, the first heat treatment step was performed under the conditions shown in Table 1 above, and five samples of Reference Examples 1 to 4 were prepared.
When the fracture surface of each sample was observed with a scanning electron microscope (SEM), when the first temperature was 60 ° C., nothing was formed on the anodic oxide film 12 (pore layer), and the first heat treatment was performed. The surface condition did not change before and after the operation.

  On the other hand, when the first temperature is 70 ° C., 80 ° C., and 90 ° C., a discontinuous surface appears from the surface of the anodic oxide film 12 to a depth of 1 μm, and the voids in the anodic oxide film 12 are exposed. did. SEM photographs when the first temperature is 60 ° C., 80 ° C., and 90 ° C. are shown in FIGS.

  Next, after forming the anodic oxide film 12 under the conditions shown in the following Table 2 using the substrate after the pretreatment, the substrate is dipped in pure water and washed, and then the first and second conditions under the conditions shown in the following Table 2 are used. Two heat treatments were performed to prepare a plurality of samples of Examples 1 to 5 and Comparative Examples 1 to 3.

Note that pure water was used for all hot water (including boiling water and steam) in the second heat treatment step. In Examples 1 to 4 and Comparative Examples 1 and 2, the film formation conditions of the anodic oxide film 12 were the same as those in Reference Examples 1 to 4 described above. For Example 5 and Comparative Example 3, the same electrolyte solution as in Reference Examples 1 to 4 was used, but for the first 15 minutes, the current density was 5 A / dm ² , the oxidation voltage was 60 V to 70 V, and the oxidation temperature was 15 ° C. The current density is 10 A / dm ² for the next 15 minutes, the oxidation voltage is 70 to 130 V, the oxidation temperature is 17 to 30 ° C., and the anodic oxide film 12 is formed for a total of 30 minutes. went.

<SEM photo>
SEM photographs of fracture surfaces were taken for 10 samples of Example 1, 6 samples of Comparative Example 1, and 6 samples of Comparative Example 2. FIG. 7 shows an SEM photograph of Example 1, FIG. 8 shows an SEM photograph of Comparative Example 1, and FIG. 9 shows an SEM photograph of Comparative Example 2.

  As shown in FIG. 7, in Example 1, a dense layer having a film thickness of about 1 μm was confirmed on all ten samples. On the other hand, when looking at FIGS. 8 and 9, some samples have a dense layer formed, but like Samples 1 and 2 in Comparative Example 1 and Samples 1, 2 and 6 in Comparative Example 2, In some cases, it was unclear whether a dense layer was formed.

From the above, it was found that a dense layer was reliably formed by contacting the anodic oxide film 12 with hot water 46 instead of water vapor before exposing it to hot water or water vapor.
The samples of Example 1 and Comparative Example 1 were further subjected to the following corrosion resistance test.

<Corrosion resistance test>
After each sample was immersed in a 35% aqueous hydrochloric acid solution at room temperature, the time until a large amount of bubbles started to appear from the sample was measured. The measurement results are shown in Table 3 below together with the thickness of the dense layer measured from the SEM photograph.

As can be seen from Table 3 above, as the thickness of the dense layer increases, the time until bubbles start to appear tends to increase.
When the film thickness of the dense layer was about 1 μm, the time until a large amount of bubbles was generated was 350 minutes to 400 minutes, whereas the sample without the dense layer was around 200 minutes. If the dense layer is formed, it can be seen that the corrosion resistance is high.

  When Example 1 and Comparative Example 1 are compared, each sample of Example 1 has a thicker layer than Comparative Example 1, and the variation in thickness between samples is small. From the above, it can be seen that the protective film (dense layer) formed by the present invention is thick and has little variation in film thickness.

In Example 3, the thickness of the protective film was measured in the same manner as in Example 1. As a result, the film thickness and variations thereof were similar to those in Example 1. From the above, it was confirmed that even when the second heat treatment was performed by heating the hot water 46 as it was during the first heat treatment, there was no difference in effect from the case where it was performed in a separate tank.
For the samples of Examples 2, 4, 5 and Comparative Example 3, the thickness of the dense layer was measured in the same manner as in Example 1. The measurement results are shown in Tables 4 to 7 below.

  There is no significant difference between the results of Table 4 and Table 2 above, and the dense layer is thick at the second temperature regardless of whether it is hot water or water vapor that is contacted with the anodic oxide coating 12 in the second heat treatment. It can be seen that the variation in the film thickness is small.

  The weakly alkaline aqueous solution (ammonia water) used in Example 4 is generally known for promoting the sealing treatment. As seen from Table 5, since the dense layer is thicker in Example 4 than in other examples using pure water (neutral), in the present invention, making the warm water 46 alkaline is the formation of the dense layer. It can be seen that it does not adversely affect, but rather promotes the formation of a dense layer.

  In Example 5 and Comparative Example 3, as described in Table 2 above, when the anodic oxide coating 12 was formed, the first half was set to a low current density, and the second half was set to a high current density. In the latter half, the pore (hole) size of the anodic oxide film was increased, the film thickness of the wall portion that was not a pore was also increased, and the structure of the anodic oxide film was changed in the film thickness direction.

  However, comparing Tables 6 and 7 with Table 2 above, even if the structure of the anodic oxide film is changed, there is no significant difference in the thickness of the dense layer after the first and second heat treatments. Therefore, it can be seen that the present invention can form a dense layer regardless of the conditions during the formation of the anodic oxide coating and the structure of the anodic oxide coating.

  When the anodic oxide film 12 was formed by changing the electrolytic solution from the oxalic acid aqueous solution to the sulfuric acid aqueous solution, the porous anodic oxide film 12 was obtained in the same manner as in the case of using the oxalic acid aqueous solution. When this anodic oxide film 12 was used and the first and second heat treatment steps were performed under the same conditions as in Examples 1 to 5, a dense protective film was formed as in the case of using an oxalic acid aqueous solution. It was. From the above, it can be seen that the present invention can form a dense protective film even if the type of the electrolytic solution is changed.

  Although the above demonstrated the case where the process target object 11 was immersed in the warm water 46 at the 1st heat treatment process, this invention is not limited to this, Since the process target object 11 and the warm water 46 contact. If there is, the hot water 46 may flow over the surface of the processing object 11, or the hot water 46 may be sprayed on the surface of the processing object 11.

Further, in the second heat treatment step, as long as the hot water comes into contact with the object to be treated 11, the hot water may flow over the surface of the object to be treated 11, or the hot water is sprayed on the surface of the object to be treated 11. May be.
The second temperature may be equal to or higher than the first temperature, but is preferably 100 ° C. or higher in order to sufficiently hydrate aluminum oxide and aluminum hydroxide.

  The electrolytic solution is not particularly limited as long as the porous anodic oxide film 12 is formed. As an electrolytic solution in which the porous anodic oxide film 12 is formed, any one or more acids selected from the group consisting of oxalic acid, sulfuric acid, malic acid, and malonic acid are dissolved in water. There is an aqueous solution.

  The hot water 46 used for the first heat treatment is not limited to pure water or ammonia water. For example, an alkaline aqueous solution in which any one kind of alkali selected from the group consisting of ammonia, triethanolamine, and hydrazine is added to pure water can be used.

Also, hot water and water vapor used for the second heat treatment are not limited to pure water. For example, an alkaline aqueous solution in which any one kind of alkali selected from the group consisting of ammonia, triethanolamine, and hydrazine is added to pure water can be used.
The alkali added to the hot water 46, hot water, and water vapor is not particularly limited, but a volatile one is desirable in order to simplify the cleaning step after the first and second heat treatment steps.

The thickness of the dense layer formed by the sealing treatment according to the present invention is 0.5 μm or more and 2 μm or less.
The object to be treated is not particularly limited as long as an anodic oxide film is formed on the surface. For example, an all-aluminum material may be used, or a core material made of a material other than an aluminum material may be used in which a thin film of an aluminum material is formed.

  The aluminum material is not particularly limited as long as it is mainly composed of aluminum. In this case, the main component only needs to contain 50 atomic% or more of aluminum, and the form of aluminum may be an aluminum simple substance or an alloy.

  Used for surface treatment to increase the corrosion resistance of members made of aluminum materials. For members that are exposed to the inside of the vacuum chamber, such as the inner wall member constituting the inner wall of the vacuum chamber, such as a CVD device or an etching device, or an antenna member, and that may come into contact with the reaction gas, plasma of the reactive gas, or radicals Especially suitable.

Sectional drawing explaining the process of forming an anodic oxide film Sectional drawing for demonstrating a 1st heat treatment process Sectional drawing for demonstrating a 2nd heat treatment process SEM photograph of fracture surface of Reference Example 1 (60 ° C) SEM photograph of fracture surface of Reference Example 3 (80 ° C) SEM photograph of fracture surface of Reference Example 4 (90 ° C) SEM photograph of fracture surface of Example 1 SEM photograph of fracture surface of Comparative Example 1 SEM photograph of fracture surface of Comparative Example 2

Explanation of symbols

  11 …… Treatment object 12 …… Anodic oxide film 46 …… Warm water

Claims (2)

A method for producing a protective film, comprising densifying the anodic oxide film of a treatment target having an anodic oxide film of aluminum formed on a surface thereof, and producing a protective film,
The densification of the anodic oxide film is performed by bringing warm water of pure water brought to a first temperature of 70 ° C. or higher and 90 ° C. or lower into contact with the anodic oxide film for 15 minutes or more ,
Said first hot water that is high in 100 ° C. over a second temperature higher than the temperature in contact with the anode oxide film, or the first temperature the second temperature of 100 ° C. or higher have higher than A method for producing a protective film, wherein the water vapor is brought into contact with the anodic oxide film in a treatment tank having a pressure equal to or higher than normal pressure, and the surface of the anodic oxide film is formed into a dense layer having a thickness of 1.0 μm or more. The protective film manufacturing method according to claim 1 , wherein the warm water is an alkaline aqueous solution in which any one kind of alkali selected from the group consisting of ammonia, triethanolamine, and hydrazine is added to the pure water .