JPH01129979A - Surface treatment of aluminum - Google Patents

Abstract

PURPOSE:To form a protective coating film having superior light reflective property and corrosion resistance on the smooth surface of an Al plate by bringing the Al plate into contact with a treating soln. contg. a specified small amt. of 8-hydroxyquinoline. CONSTITUTION:The surface of a pure Al plate is smoothened by electropolishing, washed and dried. The Al plate is then immersed in a treating soln. of 2-12 pH contg. >=0.001wt.% 8-hydroxyquinoline to form a coating film of an Al-oxine chelate on the surface of the Al plate. By forming this coating film, a surface protective coating film having >=80% light reflecfance and superior corrosion resistance is surely formed on the surface of the Al plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of aluminum, and more particularly, to a method for surface treatment of aluminum suitable for forming a surface protective film having excellent corrosion resistance and light reflectivity.

[Conventional technology]

Although aluminum is covered with an oxide film that is stable in the atmosphere, it is easily corroded in acidic and alkaline environments, and even under normal conditions, it cannot maintain sufficient corrosion resistance when used for a long period of time. therefore,
Regarding the use of aluminum, some surface treatment is required.

Methods of surface treatment of aluminum for the purpose of corrosion prevention include a method of treating with an inorganic solution and a method of treating with an organic solution.

Typical inorganic solutions include anodizing treatment in which aluminum is electrolyzed in an electrolyte solution as an anode, and chemical conversion treatment in which it is immersed in a chromate, phosphoric acid-chromate solution, etc. to form a chemical conversion film. etc.

On the other hand, examples of organic solution treatment include painting and immersion treatment with an organic solution. For example, as described in JP-A-50-44945 and JP-A-50-44946, each has 1 to 20 carbon atoms and 1 to 1 boxy group in the molecule.
There is a method in which a compound containing a substituted dinando acid and an aliphatic amine represented by the general formula % (which has 20 atoms is different and is an atomic group containing a μ-bonyl group) is brought into contact with metals.

Furthermore, as described in Japanese Patent Application Laid-Open No. 55-113548, there is a method of applying an aluminum chelate compound to the surface of at least one of the semiconductor element and the lead frame.

Furthermore, as described in JP-A No. 61-287155, there is a method of forming a protective layer made of a reaction product of a metal and an organic substance of triazoles on the surface of a part of a semiconductor element and an electrical connection member thereto. be.

[Problem that the invention seeks to solve]

Among the conventional techniques mentioned above, anodic oxidation treatment and chemical conversion treatment, which are inorganic solution treatments, have the advantage of being able to form a strong film on the aluminum surface, but on the other hand, they contain harmful substances such as chromium ions and fluoride ions in the treatment bath. Therefore, problems such as environmental pollution, toxicity to the human body, and wastewater treatment are associated. Therefore, it requires a large amount of equipment, consumes a lot of power, and is economically disadvantageous.

On the other hand, an immersion treatment method using an organic solution, which is an organic solution treatment, is known as a surface treatment method that is relatively simple and has low toxicity. The suppressing mechanism is due to physical adsorption in which cationic organic substances are adsorbed to negatively charged parts of the metal surface, and chemical adsorption between the electron donating group and the metal. However, it exhibits a suppressive effect in solution due to adsorption to the surface of simple metals.

It does not show sufficient corrosion resistance in other environments, such as in large swords.

Furthermore, the method of applying an aluminum chelate compound is aimed at forming an aluminum oxide film on the aluminum surface by performing a baking treatment after applying the aluminum chelate compound. However, since the baking process is performed at high temperatures, the aluminum chelate compound is destroyed and the reverse Kr#
May reduce eating habits.

Furthermore, a method of forming a protective layer of metal and an organic substance such as rear seals on a metal surface is a method of obtaining a metal surface with high corrosion resistance by focusing on a strong chemical bond between the metal and the organic substance.

However, regarding aluminum, it was confirmed that although triazoles exhibit high corrosion resistance in an acidic environment, they are ineffective in an alkaline environment.

Furthermore, in surface treatment methods aimed at improving corrosion resistance, some kind of film is generally attached to the base metal to protect it. Therefore, the light reflectance after treatment is significantly reduced. Conventional anodic oxidation treatment, immersion treatment with organic substances, etc. pose a problem in that the light reflectance of the aluminum surface after treatment is significantly lower than that of the aluminum surface.

The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to significantly improve the corrosion resistance reliability of aluminum by forming a stable kA chelate compound skin with high corrosion resistance and reflectivity through chelate bonding on the aluminum surface. There is a need to provide a surface treatment method that improves the light reflectance of the aluminum surface and does not reduce the light reflectance of the aluminum surface.

[Means for solving problems]

To summarize the present invention, the present invention relates to a method for surface treatment of aluminum, and in the surface treatment of aluminum, aluminum is brought into contact with a treatment solution containing 8-hydroxyquinoline (hereinafter abbreviated as oxine). It is characterized by

The present inventors investigated back-loaded oxine, which has an inhibitory effect in a wide range of acidic to alkaline conditions, and found that oxine shows high corrosion resistance. It has been found that high aluminum surfaces can be obtained.

The above object is achieved by bringing the aluminum surface into contact with oxine, which is another agent, to form a kA-oxine chelate compound film having excellent corrosion resistance and reflectivity.

In the present invention, in a relatively simple treatment with an organic solution, a poorly soluble complex is formed on the aluminum surface by bonding which has a much stronger bonding force than the adsorption bond of aluminum. That is, the aluminum key V-)
Focusing on the stability constant of At-oxine, corrosion resistance reliability is improved by bringing oxine, which has a significantly large stability constant, into contact with aluminum to form a dense chelate film of At-oxine. Furthermore, by controlling the oxine concentration and pH, a method for surface treatment of aluminum with excellent light reflectivity is provided.

Effects such as oxine concentration give aluminum high corrosion resistance and high light reflectivity.

That is, in an acidic solution, oxine depletes the phenol type, interacts with aluminum, replaces HO- with
A five-membered ring kA-oxine chelate (1) coordinately bonded with
form. On the other hand, in an alkaline solution, oxyy takes the quinone form, acts with aluminum, bonds with N, and coordinates with 0 to form At-oxine chelate (11).

(1) (n) The stability of the At-oxine chelate formed as described above is very high, so it is stable even in a corrosive environment, and has a strong protective effect on the aluminum base, so it exhibits high corrosion resistance.

Furthermore, when an organic solvent such as alcohol is used in place of the aqueous solution of oxine, the corrosion resistance of the sheath layer is further improved by the following effects. That is, since water is desired to exist in the processing liquid, the influence of residual water after processing is extremely small. Furthermore, since organic substances are easily soluble in organic solvents, using a solution dissolved in a volatile solvent has advantages in step 1, such as the ability to save labor in the cleaning step after treatment.

The pH of oxine is adjusted to 2 to 12.0 to form the most stable At-oxin in the solution.

That is, the chelate compound film formed on the aluminum surface in the treatment bath having the above pH range is hardly soluble, has high protective power, and has significantly improved corrosion resistance.

Furthermore, if oxine is contained in an amount of at least 1001% by weight, a kA-oxine chelate compound film with high corrosion resistance is formed. Since oxine is difficult to dissolve in water, heating the treatment liquid will dissolve an appropriate amount of oxine, making it easier to obtain kA-oxine chelate.

In addition, aluminum is almost constant from ultraviolet to infrared, and 9
Shows a large light reflectance close to 0x. Normally, when aluminum is surface-treated, a protective layer is formed on the aluminum surface, so that the light reflectance is significantly reduced to 50% or less. However, when the oxine concentration is set to IIL01 to 105 weight X and treated in an acidic solution, it is possible to obtain a reflectance as high as that before treatment.

From the above, the surface treatment method using oxine, which is a chelating agent, forms a highly corrosion-resistant and highly reflective protective film on the aluminum surface by adjusting the nH% concentration in the treatment bath. It also solves the pollution problem and has advantages such as being relatively simple and low cost.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 A 99% aluminum plate (area: 10512) was electrolytically polished in an acetic acid-perchloric acid bath, washed with water, and dried to obtain a test piece. This test piece was immersed in a 101% by weight oxine aqueous solution adjusted to pH 9 for 10 minutes at room temperature and 80°C, washed with water, and dried. This test piece was heated 3X at 80℃.
It was immersed in salt water and subjected to a corrosion test for 200 hours. The results are shown in Table 1. As a comparative example, Table 1 also shows the results of one meal of tricarballylic acid-N-methimide subjected to the same surface treatment and aluminum without surface treatment in the conventional method.

Table 1 As is clear from Table 1, aluminum treated with oxine according to the present invention has a much smaller amount of corrosion than aluminum that is not treated, and a chelate film with high corrosion resistance is formed. On the other hand, it can be seen that the treatment with tricarballylic acid-N-methyimide according to the conventional method causes a larger amount of corrosion than the oxine treatment according to the present invention, and does not exhibit sufficient corrosion resistance.

Example 2 An aluminum test piece similar to Example 1 was treated with oxine C [
Figure 1 shows the results of a 200-hour corrosion test in 3% saline at 80° C. with different treatment pH. As a comparative example, the amount of corrosion without surface treatment is shown by a broken line. In other words, Figure 1 shows the amount of corrosion after oxine treatment with different pI (t+H (horizontal l1III)) and corrosion! (μm, vertical axis).
This is a graph showing the relationship between

As is clear from FIG. 1, in the oxine treatment according to the present invention, the amount of corrosion is significantly small in the range of T)H55 to 1α0, indicating sufficient corrosion resistance.

Example 3 An aluminum test piece similar to Example 1 was treated with oxine (D
H9) Change the treatment concentration and use 3% saline at 80℃ for 200
Figure 2 shows the results of the time corrosion test. As a comparative example,
The amount of corrosion without surface treatment is shown by the broken line. That is, FIG. 2 is a graph showing the amount of corrosion after treatment with varying oxine weight X in relation to oxine weight % (horizontal axis) and corrosion amount (μm, vertical axis). As is clear from FIG. 2, the oxine treatment according to the present invention exhibits sufficient corrosion resistance when containing Q,001% by weight or more, and forms a stable chelate film.

Example 4 An aluminum test piece similar to Example 1 was treated with 1 oxine.
015% modification, T)HA, O, and was immersed in this treatment bath at 80° C. for 20 minutes. Table 2 shows the reflectance after treatment and after the corrosion test, assuming that the reflectance before treatment is 1.

As a comparative example, the light reflectance without surface treatment and with conventional surface treatment are also shown.

Table 2 As is clear from Table 2, the oxine treatment according to the present invention shows a high reflectance of 19 or more before treatment, and the light reflectance after treatment and after the corrosion test is compared to aluminum before treatment. There was almost no change in the reflectance, indicating that the decrease in reflectance was extremely small.

On the other hand, the conventional method of anodic oxidation using sulfuric acid as an electrolyte and benzotriacy treatment has a significantly lower light reflectance after treatment and corrosion test than the oxine treatment of the present invention, and is effective for surface treatment. It can be seen that the reflectance decreases significantly.

〔Effect of the invention〕

According to the present invention, it is possible to solve the pollution problem and provide a simple aluminum surface treatment method with excellent corrosion resistance and light reflectivity.
#Eating reliability and light reflectivity can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the amount of corrosion after treatment with oxine with varying pH, and FIG. 2 is a graph showing the amount of corrosion after treatment with varying oxine weight percent. Patent applicant: Hitachi, Ltd.

Claims (1)

[Claims] 1. A method for surface treatment of aluminum, which comprises bringing aluminum into contact with a treatment solution containing 8-hydroxyquinoline. 2. The method for surface treatment of aluminum according to claim 1, wherein the treatment solution contains at least 0.001% by weight of 8-hydroxyquinoline and has a pH in the range of 2 to 12.0. 3. The method for surface treatment of aluminum according to claim 1, wherein the concentration and pH of 8-hydroxyquinoline in the treatment solution are controlled so that the reflectance of aluminum after the treatment is 80% or more.