TWI421380B - Corrosion resistance of aluminum or aluminum alloys - Google Patents

Description

Corrosion resistant treatment method for aluminum or aluminum alloy

The present invention relates to a method of corrosion resistance treatment of aluminum or aluminum alloy.

Conventionally, as a method of performing corrosion-resistant treatment on aluminum or an aluminum alloy, for example, Patent Document 1 discloses a method in which a surface of an aluminum alloy is subjected to a barrier anodizing treatment and heated to perform a degassing treatment.

However, as disclosed in Patent Document 1, in each of the A1050 alloy, the A5052 alloy, and the A6061 alloy, the degreasing treatment is performed through a weakly alkaline degreasing liquid, and then a desmutation treatment is performed in an aqueous nitric acid solution to carry out a desmut treatment. The barrier anodic oxidation treatment of ammonium amide forms the morphology of the formed barrier anodized film. When observed by a scanning electron microscope, the A1050 alloy forms a comparative continuous film, but the film formed by the A5052 alloy and the A6061 alloy has There are many disadvantages, corrosion resistance and gas release characteristics in a vacuum environment.

Patent Document 1: Patent No. 3506827

Therefore, the present invention is to provide a barrier type anodized film which imparts corrosion resistance to aluminum or an aluminum alloy, and is provided by aluminum or aluminum which is excellent in gas release characteristics and which is excellent in gas release characteristics. The alloy corrosion resistant treatment method serves as an object.

To solve this problem, the inventors have found a solution as described below.

That is, the corrosion-resistant treatment method of the aluminum or aluminum alloy of the present invention, as described in the first item of the patent application, is characterized in that a dense oxide layer having a thickness of 5 to 20 nm is formed on the surface of the aluminum or aluminum alloy, and then, Block anodizing treatment.

The invention of claim 2 is the corrosion-resistant treatment method of aluminum or aluminum alloy according to item 1 of the application specification, wherein the oxide layer is formed by an oxidation treatment of an acidic solution.

The invention of claim 3 is the corrosion-resistant treatment method of aluminum or aluminum alloy according to the second item of the application scope, wherein the acidic solution contains 50 to 80% by weight of phosphoric acid and 1 to 5% by weight of nitric acid. And the acidic solution is heated to 80 to 100 ° C, and the aluminum or aluminum alloy is immersed for 1 to 10 minutes.

The fourth aspect of the patent application is the corrosion-resistant treatment method of aluminum or aluminum alloy according to any one of claims 1 to 3, wherein the aluminum or aluminum alloy formed by the oxide layer is in a vacuum, atmosphere or nitrogen. In the environment, the aluminum or aluminum alloy is heat-treated at 150 ° C to 300 ° C, and then the barrier anodizing treatment is performed.

According to the present invention, before the formation of the barrier anodizing film which imparts corrosion resistance to aluminum or an aluminum alloy, the barrier anodic oxide film can be made dense by forming a dense oxide layer, and can be excellent in corrosion resistance and gas release characteristics. Barrier anodic oxide film.

The best form for carrying out the invention

Aluminum or an aluminum alloy which can be used in the present invention is not particularly limited. For example, a pure aluminum-based 1000-based alloy, an Al-Cu-based, an A-Cu-Mg-based 2000-based alloy, an Al-Mn-based 3000-based alloy, an Al-Si-based 4000-based alloy, and an Al-Mg system can be used. 5000 alloy, Al-Mg-Si 6000 alloy, Al-Zn-Mg-Cu system, Al-Zn-Mg system 7000 alloy, 7N01 alloy, etc., but especially pure aluminum, 2000 series, 30,000 The aluminum alloys of the 5000, 6000, and 6000 series are effective for the present invention. The 4000 series aluminum alloy is in the alloy structure, and is dispersed in a certain number of μm. In the aluminum portion, a dense oxide film cannot be grown, so part of the treatment.

The dense oxide layer formed by the aluminum or aluminum alloy is 5-20 nm.

Further, in the present invention, the dense oxide film refers to a film which removes defects caused by the presence of non-metallic inclusions and the like, and has no continuous film of pores having a nanometer or higher, and the oxide layer is formed, although in the atmosphere. Oxidation or the like promotes oxidation, and the oxide layer does not become a thicker layer.

When the oxide layer is less than 5 nm, continuous layered growth is not easy, and it is a non-uniform oxide film. If it exceeds 20 nm, a dense oxide layer is not formed and becomes a porous structure. Thereafter, when the barrier anodic oxide film grows, the gas is released. many.

The method for forming the oxide layer is not particularly limited, and it is preferably carried out via an acidic solution. Further, the acidic solution contains 50 to 80% by weight of phosphoric acid and 1 to 5% by weight of nitric acid, and the acidic solution is heated to 80 to 100 ° C. It is better to immerse aluminum or aluminum alloy for 1~10 minutes.

Thus, a dense surface oxide layer having a thickness of 5 to 20 nm is formed on the surface of the aluminum or aluminum alloy to be easily composed.

Further, after the oxide layer is formed, it is preferred to heat the aluminum or aluminum alloy at 150 to 300 ° C in a vacuum, atmosphere or nitrogen atmosphere. Because of this, oxidation can be promoted.

The barrier anodizing treatment of aluminum or aluminum alloy formed by the oxide layer can be performed by electrolysis through an electrolyte solution.

As the electrolyte solution, for example, an adipate such as ammonium adipate or a borate such as a mixture of boric acid and ammonium borate, or a phosphate such as ammonium dihydrogen phosphate, tartrate, citrate or potassium hydrogen phthalate can be used. Any one of a solution of a carbonate such as phthalic acid salt or sodium carbonate, a citrate salt, sodium chromate or the like, or a mixed solution of these may be used.

In the aqueous electrolyte solution, the aluminum alloy or the aluminum alloy material is an anode, and the power source is used for electrolysis, and the cathode system can use an insoluble conductive material.

The electrolysis current is not particularly limited, and the DC current may be a DC density of about 0.2 to 5 A/cm ² , and the electrolysis time may be appropriately selected via electrolysis conditions such as the thickness of the formed film. Moreover, the applied voltage is not particularly limited and may be 20 to 500V.

Example

Hereinafter, an embodiment of the present invention will be described.

(Example 1)

The surface was cut by a lathe, and a round plate made of A5052 alloy having a diameter of 45 nm and a thickness of 3 mm was prepared as a workpiece. The material to be treated was immersed and stirred in a 85 ° C solution containing 80% by weight of phosphoric acid and 3% by weight of nitric acid, and oxidized for 2 minutes. The material to be treated was immersed in pure water and washed again with pure water.

Then, the object to be treated was immersed in a 10% by weight ammonium adipate solution at 40 ° C, and a barrier anodic oxide film was formed at a direct current voltage of 200 V for 1 hour.

(Example 2)

The same processed object as in Example 1 was prepared.

The material to be treated was immersed and stirred in a 85 ° C solution containing 80% by weight of phosphoric acid and 3% by weight of nitric acid, and oxidized for 2 minutes.

Then, the object to be treated was immersed in pure water, and then washed with pure water at 50 ° C, and then washed again with pure water.

The washed object is heated in a vacuum apparatus to a range of 10 ^{- 4} Pa, and heated at 300 ° C for 30 minutes, and then cooled to room temperature (about 10 ° C to 40 ° C, the same below) The solution was taken out from the atmosphere, immersed in a solution containing 10% by weight of ammonium adipate at 40 ° C, and a barrier anodic oxide film was formed at a direct current voltage of 200 V for 1 hour.

(Comparative Example 1)

The same processed object as in Example 1 was prepared.

The material to be treated was immersed in a solution containing 15% by weight of phosphoric acid and 1% by weight of hydrofluoric acid at room temperature for 3 minutes, immersed in pure water, and washed again with pure water at 50 ° C by immersion in pure water.

The washed material was immersed in a 3 wt% nitric acid solution for 1 minute, and washed with pure water.

Therefore, a barrier type anodic oxide film was formed under the same conditions as in Example 1.

(Comparative Example 2)

The same processed object as in Example 1 was prepared.

The material to be treated was degreased by acetone.

The treated object to be washed was subjected to the same conditions as in Example 1 to form a barrier type anodic oxide film.

(Comparative evaluation 1)

The gas release characteristics of the samples of the barrier anodic oxide film forming the ammonium adipate of Examples 1, 2 and Comparative Examples 1, 2 were evaluated. The gas release characteristics were evaluated by using a temperature rise and fall measurement device (ALBACKTECNICAL JOUNOL No. 58 P. 30), and the gas release amount per unit area between the temperatures up to 300 ° C was measured. The results are shown in Table 1.

The gas release amount of Examples 1 and 2 in which a dense oxide layer of about 10 nm was formed before the barrier anodizing treatment was compared with the samples of Comparative Examples 1 and 2 in which the oxide layer could not be formed, and the amount of release was small.

(Comparative evaluation 2)

The surface of the barrier anodized layer of the samples of Example 1 and Comparative Example 1 was observed by a scanning electron microscope (SEM), and the surface SEM image was as shown in FIG. Fig. 1(a) is a surface SEM image of Example 1, and (b) is a surface SEM image of Comparative Example 1. As compared with Example 1, it can be understood that Comparative Example 1 has many disadvantages and the oxide film is thick. The reason why the amount of release in Comparative Example 1 is large can be estimated from this structure.

(Comparative evaluation 3)

The samples before the formation of the barrier anodic oxide film by the adipic acid of Examples 1 and 2 and Comparative Examples 1 and 2 were subjected to spectroscopic analysis in the deep direction, and the thickness of the surface oxide layer was determined for each sample. In the manner of position, 8 points were taken out, and the deviation of the thickness of the oxide layer was obtained. The results are shown in Table 2. Further, the thickness of the surface oxide layer is a half value of the maximum value of oxygen.

From Table 2, it was found that the samples of Comparative Examples 1 and 2 in which the oxide layer was not formed by the pretreatment were used, and the samples of Examples 1 and 2 had little variation between the measurement points, and a homogeneous oxide layer was formed.

In the above embodiment, an aluminum alloy of the A5052 type was used, but an aluminum alloy of pure aluminum, 2000 series, 3000 series, 5000 series, and 6000 series was confirmed to be effective for the present invention.

Further, in the barrier anodizing treatment, ammonium adipate has been used, but it is confirmed that ammonium borate or ammonium phosphate can also be used.

Industrial use possibility

The corrosion resistance method of the aluminum or aluminum alloy of the present invention can impart corrosion resistance to a component placed in a vacuum environment such as a semiconductor manufacturing apparatus and a thin film forming apparatus.

[Fig. 1] (a) SEM image of Example 1 (b) SEM image of Comparative Example 1

Claims (2)

An anti-corrosion treatment method for aluminum or aluminum alloy, characterized in that an acidic solution containing 50 to 80% by weight of phosphoric acid and 1 to 5% by weight of nitric acid is heated to 80 to 100 ° C, and then the aluminum or aluminum alloy is impregnated 1 ~10 minutes, after forming a dense oxide layer having a thickness of 5 to 20 nm on the surface of the aluminum or aluminum alloy, a barrier type anodizing treatment is performed, and the dense oxide film is removed by the presence of non-metallic inclusions or the like. Disadvantages, there is no continuous film of pores above the nanometer level. After the oxide layer is formed, the oxide layer does not become a thicker layer even though oxidation is promoted in the atmosphere, and the barrier type anodizing treatment is used. Any one of a solution of a diacid salt, a borate, a phosphate, a tartrate, a citrate, a phthalate, a carbonate, a citrate, a sodium chromate or the like or a mixed solution thereof The electrolyte solution is such that the current density of the direct current is 0.2 to 5 A/cm ² and the applied voltage is 20 to 500 V. An anti-corrosion treatment method for aluminum or aluminum alloy according to claim 1 is characterized in that the aluminum or aluminum alloy forming the oxide layer is in a vacuum, atmosphere or nitrogen atmosphere, and the aluminum or aluminum alloy is at 150 ° C. After the heat treatment at ~300 ° C, the above-described barrier anodizing treatment is performed.