JPS63247396A - Method for making anodic oxide film or aluminum opaque and white - Google Patents

Abstract

PURPOSE:To form an opaque white film which is not made transparent even by wetting with water, by treating an anodically oxidized Al material with an aq. soln. contg. F ions by one- or two-step treatment. CONSTITUTION:An anodically oxidized Al material is treated with an aq. soln. contg. F ions in the form of hydrofluoric acid, ammonium fluoride or the like or an aq. soln. contg. F ions and a metallic salt such as aluminum fluoride by immersion in the soln. or other method. The Al material may be treated with an aq. metallic salt soln. and an aq. soln. contg. F ions in no particular order. By the one- or two-step treatment, F ions are adsorbed on Helmholtz layers on the walls of pores in the anodic oxide film and the diffusion and penetration of the metallic salt into the pores are facilitated. Ions of the metal form hydroxide, opaque fluoride or opaque double salt in the pores, increase the opacity and whiteness of the anodic oxide film and toughen the film.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is an opaque aluminum anodic oxide film that can maintain an opaque white color without becoming transparent even when the white aluminum anodic oxide film is wet with water. This invention relates to a whitening method.

[Conventional technology]

Transparent colored coating materials for aluminum have been widely used for a long time, but in recent years, there has been a demand for opaque pastel colored coating materials.

For this purpose, a method was proposed in which the basic oxide film was whitened, and then dyed or electrolytically colored, and a method of forming a white film by electrolytic treatment in an acid bath or an alkaline bath was attempted, but two different methods were used. It has not been put into practical use for some reason.

It is said that an opaque white film is formed when aluminum material is anodized in a chromic acid bath or an ematal bath.
In the case of materials other than high-purity aluminum, a pure opaque white film with a grayish tinge cannot be obtained. Also, when a strongly etched aluminum material is anodized, a whitish oxide film is obtained, but its opacity is weak, and a whitish oxide film is also formed by anodic oxidation using the current recovery method, but this is also white. The taste and opacity are weak.

Furthermore, after forming an anodic oxide film, calcium salt,
A method of obtaining an opaque white film by immersion or electrolysis in an aqueous solution of barium salt, aluminum salt, etc. is known. However, increasing the opaque whiteness using this method has the problem of deteriorating the hardness and corrosion resistance of the oxide film, and it is known that if the whitening treatment is too strong, so-called "powdering" will occur on the aluminum. However, there were problems such as difficulty in controlling the bath in which the white product was produced and the fact that it became transparent when wet with water.

[Problem that the invention seeks to solve]

The present invention aims to solve the problems of the conventional methods, such as the deterioration of the hardness and corrosion resistance of the film, the difficulty of "dusting" or bath management, and the fact that it becomes transparent when wet with water. The object of the present invention is to obtain a means for forming an opaque film and a pastel colored opaque film.

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the above-mentioned object, the present inventor has conducted repeated research and found that when an aluminum oxide film is immersed or electrolyzed in an aqueous solution of calcium salt, barium salt, aluminum salt, etc. The opaque whitening film is
Recognizing that the opacity was weak because the metal ions could not sufficiently penetrate into the alumite pores, we immersed the aluminum material, on which an anodized film had been previously formed, in a fluorine ion-containing aqueous solution or a fluorine ion-containing aqueous solution containing metal salts. The present invention has been made based on the discovery that the object can be achieved by electrolytic treatment or by treatment with a fluorine ion-containing aqueous solution before or after the metal salt aqueous solution treatment.

In other words, the present invention provides a one-step treatment in which an aluminum material that has been anodized in advance is treated with an aqueous solution containing fluorine ions or an aqueous solution containing metal salts, or a treatment with an aqueous solution containing fluorine ions before or after treatment with an aqueous metal salt solution. This is a method for making an aluminum anodic oxide film opaque and white in a two-stage process.

Aluminum materials to which the present invention can be applied are not limited in type, and include building materials such as sash, curtain walls, interior and exterior materials, road materials,
Wheels for aircraft and vehicles.

Various alloy materials can be used depending on the purpose of coloring materials such as cosmetic cases and audio equipment panels, but they can also be applied to so-called natural coloring materials in which a colored film is formed by anodizing. Even if the film is a colored film, it is possible to obtain a film with a whitish pastel color by the treatment of the present invention.

Therefore, the anodizing treatment performed on such aluminum materials in advance requires sulfuric acid, phosphoric acid, oxalic acid, chlorine 30% by weight, and bath temperature 20% to form a porous anodic oxide film.
This is done by anodic oxidation treatment for 15 to 60 minutes with a DC current density of 1 to 3 Vdm + electrolytic voltage of 15 to 18 V using a bath at ~30°C. As a result, the transparent film on ordinary materials becomes naturally colored. If it is a material, a transparent colored film will be formed depending on its characteristics, and this will be used in the treatment of the present invention.

For example, ammonium fluoride, sodium fluoride, aluminum fluoride, etc. are preferable, and other fluorides such as potassium fluoride, sodium silicofluoride, barium fluoride, and calcium fluoride may be used. Fluoride is mentioned, each of these alone or.

It is used as an aqueous solution in which two or more types are appropriately mixed.

1゛The metal salt-added fluorine ion-containing aqueous solution and the metal salt used for the metal salt aqueous solution are the same type of salts, and the metal salt-added fluorine ion-containing aqueous solution contains the hydrofluoric acid and/or fluoride. It is a mixed aqueous solution of and a metal salt, and the metal salt is, for example.

Aluminum sulfate, nickel sulfate, stannous sulfate.

Soluble metal salts such as sulfates such as magnesium sulfate, zinc sulfate, nitrates such as calcium nitrate, barium nitrate, oxalates such as barium oxalate, ammonium salts such as ammonium molybdate may be used; Each of these can be used alone or in a suitable combination of two or more. However, in the case where a metal salt is allowed to coexist in a fluorine ion-containing aqueous solution in these combined additions, a calcium salt that precipitates as CcLF2 is not preferable because it eliminates the effect of fluoride ions.

The one-stage treatment of the present invention is treatment with a fluorine ion-containing aqueous solution or a metal salt-added fluorine ion-containing aqueous solution, and in the case of hydrofluoric acid, 0. The metal salt is added in a range of 5 to saturated solubility, preferably 5 to 100 g/l. If the fluorine ion concentration is high, the immersion time or electrolysis time can be shortened, but if the bath is strongly acidic or alkaline, the anodic oxide film will dissolve.
It is desirable that the bath has a pH of 2 to 9. or.

The higher the solubility of fluoride, the easier it is to manage the bath; however, even if the solubility of calcium fluoride is below the lower limit of the preferred concentration range (5 g/13), it is still within the above range. Moreover, if the pH value is within the above range, it can be used and good results can be obtained.

Treatment methods using these aqueous solutions include the immersion method and the electrolytic method.
The immersion treatment is for 60 minutes, and if the concentration is high and the bath temperature is high, the immersion time is shortened to 30°C and the voltage is 3 to 10V.
The treatment is for ~10 minutes.

Further, the two-stage treatment is one in which treatment with a fluorine ion-containing aqueous solution is performed before or after treatment with a metal salt aqueous solution. The fluorine ion-containing aqueous solution used for this treatment is
Use a fluorine ion-containing aqueous solution with the same concentration as that used in the one-stage treatment.

This process is performed under the same conditions as the one-stage process. The metal salt aqueous solution has a concentration of 5 g/l to saturation concentration, preferably 5 to 1
o o g71, and the pH value is adjusted to be in the range of 2 to 9 before use. If this concentration is high, there is a risk that the anodic oxide film will be dissolved in the case of sulfate.

As the treatment methods using these aqueous solutions, there are the immersion method and the electrolytic method, as in the case of the one-stage treatment. In the immersion method, immersion is performed for 5 to 60 minutes at an aqueous solution temperature of 20 to 80°C. If the liquid temperature is low, the processing time will be longer, but if the temperature is too high, the film may dissolve, and the processing time may be shortened. The opacity of the coating is low, and the coating may dissolve over a long period of time, so treatment should be carried out within the above range.

or.

Although the electrolytic method requires equipment costs, it is technically preferable because it promotes the diffusion of fluorine ions into the pores of the film and the removal of hydrogen ions from the pores of the film, and uses a bath temperature of 10 to 30°C and a carbon counter electrode. However, the current may be alternating current or direct current, and the voltage may be 3
Electrolyze for 5-60 minutes at ~10v.

In this way, whether it is a one-stage treatment or a two-stage treatment, treatment is performed with an aqueous solution containing fluorine ions.

Fluorine ions are adsorbed to the Helmholt layer inside the pore walls of the film, and this neutralizes the positive charge in the pores of the anodic oxide film, making it easier for metal salts to diffuse and enter into the pores, causing metal ions to In the pores of the anodic oxide film, hydroxides, insoluble fluorides, and insoluble double salts are formed, increasing the opacity and whiteness, and also making the anodic oxide film durable.

Furthermore, by treatment with an aqueous metal salt solution, it is possible to improve the whiteness or obtain a pastel color. In other words, by filling the pores of the anodic oxide film with metal salts, the whiteness of the resulting film is increased. Therefore, even in the case of electrolytic treatment, strong electrolysis that causes metal to precipitate in the pores is not possible. There is no need to carry out any treatment, and the metal salts can be adsorbed into the pores by mild electrolysis.
This may be done to the extent that it promotes filling. However, even if a certain degree of electrolytic coloring occurs, whitening will still occur and a pastel-colored film will be obtained. It is also possible to process.

The film obtained by making the anodic oxide film opaque and white has a smooth appearance similar to chinaware, does not become transparent even when wet with water, and has excellent hardness and corrosion resistance.

After the treatment according to the method of the present invention, sealing treatment is carried out by a conventional method or transparent resin such as acrylic resin, '7
The product is manufactured by applying a rear paint finish process similar to electro-deposition of resin.

〔Effect of the invention〕

The present invention is to treat an aluminum material that has been subjected to a normal anodizing treatment with an aqueous solution containing fluorine ions through a membrane treatment or a two-stage treatment, so that even when wet with water, it does not become transparent and maintains its white color. If the anodic oxide film is colored, it can be made into a pastel tone.
By simply adding a fluorine ion-containing aqueous solution tank to a conventional surface treatment line, existing electrolytic coloring baths can be used as is, and the system has been recognized for its excellent effects, such as being able to easily achieve the objective while minimizing modifications to the existing process. It will be done.

〔Example〕

Next, nine embodiments of the present invention will be described.

Example 1 Aluminum material with purity 99.5q6 was mixed with 15% by weight H2S
After anodizing for 60 minutes at a DC voltage of 18 V in an O4 bath (20°C) to form a film with a thickness of 20 μm, 5 g/11 ammonium fluoride was added.

It was immersed for 20 minutes at 20°C using an aqueous solution of sodium fluoride and potassium fluoride. As a result.

No matter which aqueous solution was used, the anodic oxide film was opaque and white and had excellent corrosion resistance.

Example 2 An aluminum material with a purity of 99.5% was prepared in the same manner as in Example 1.
After anodic oxidation treatment for 0 minutes to form a film with a thickness of 20 μm, it was immersed in a 50 g/l aluminum fluoride aqueous solution at 60°C for 0 minutes. As a result.

A corrosion-resistant opaque whitening film was obtained in the same manner as in Example 1. Example 3 Example 1 using 6063 alloy as the aluminum material
After performing anodization treatment in the same manner as in Example 1, immersion treatment in a fluorine ion-containing aqueous solution was performed in the same manner as in Example 1. As a result, as in Example 1, a corrosion-resistant, opaque, whitened film was obtained.

Example 4 A 6063 alloy material was anodized for 30 minutes in the same manner as in Example 1 to form an anodic oxide film with a thickness of 10 μm, and then treated with 5 g/l aqueous aluminum fluoride solution at 50% each.
9/l aluminum sulfate, zinc sulfate, nickel sulfate,
Cobalt sulfate, magnesium sulfate, stannous sulfate, aluminum nitrate, barium nitrate, barium oxalate, sodium stannate.

A 20 minute immersion treatment was carried out at 60° C. using separate aqueous solutions to which ammonium molybdate and other aqueous solutions were added. As a result, as in Example 1, a corrosion-resistant, opaque, whitened film was obtained.

Example 5 Instead of the immersion treatment with the metal salt-added fluorine ion aqueous solution in Example 4, each aqueous solution described in Example 4 with a bath temperature of 40°C was used, and an AC voltage of 10 V was used.

Alternatively, electrolytic treatment was performed at a DC voltage of -5V. In all of these results, similar to Example 1, a corrosion-resistant, opaque, whitened film was obtained.

Example 6 After forming an anodic oxide film with a thickness of 20 μm on an aluminum material with a purity of 99.5% in the same manner as in Example 2,
g/l aluminum fluoride,! = 509/la A mixed solution with aluminum acid was used for immersion treatment at 60'C for 20 minutes. As a result, as in Example 1, a corrosion-resistant, opaque, whitened film was obtained.

Example 7 An aluminum material with a purity of 99.5% was anodized in the same manner as in Example 4 to form an anodic oxide film with a thickness of 10 μm, and then 10 g/l of each was added to a 509/l aluminum sulfate aqueous solution. Separate aqueous solutions were prepared by adding barium fluoride, sodium fluoride, and sodium fluorosilicate aqueous solutions, respectively, and immersion treatment was performed at a liquid temperature of 50° C. for 20 minutes. This result shows that a corrosion-resistant opaque whitening film was obtained in the same manner as in Example 1.
After processing to form a 20 μm thick anodic oxide film.

2. - 5 g/l each as the first treatment of the Danizoni stage treatment.
Aqueous solutions of sodium fluoride, ammonium fluoride, potassium fluoride, and sodium silicofluoride were used separately and immersed at 20°C for 10 minutes.
As a subsequent treatment, 50 g/l each of aluminum sulfate, zinc sulfate and nickel sulfate.

Magnesium sulfate, cobalt sulfate, stannous sulfate.

Aluminum nitrate, barium nitrate, barium oxalate,
The anodized film that had been subjected to the first treatment using either an aqueous solution of sodium stannate or sodium molybdate was subjected to a second immersion treatment at a solution temperature of 60° C. for 10 minutes. As a result of testing by arbitrarily selecting and combining the aqueous solution used in the primary treatment and the aqueous solution used in the secondary treatment, both were tested in Example 1.
A corrosion-resistant, opaque, whitened film was obtained in the same manner.

Example 9 The order of use of the aqueous solutions used in Example 8 was reversed, and the metal salt aqueous solution used for the secondary treatment in Example 8 was used as the aqueous solution for the first treatment, and the first treatment was carried out at 60°C for 10 minutes. Then, as in Example 8, a test was carried out in which the fluorine ion-containing aqueous solution used for the first treatment in Example 8 was used as a second aqueous solution and a second treatment was performed at 60°C for 910 minutes using any combination as in Example 8. I did it. In all of these results, similar to Example 1, a corrosion-resistant, opaque, whitened film was obtained.

Example 10 Regarding the anodic oxide film formed using an oxalic acid bath,
The same treatments as in Examples 1 to 9 were performed, but in all cases, a yellowish opaque white coating (pastel-like coating) was obtained.
was observed to be formed.

Claims (1)

[Claims] 1) One-stage treatment in which pre-anodized aluminum material is treated with a fluorine ion-containing aqueous solution or a metal salt-added fluorine ion-containing aqueous solution, or a two-stage treatment in which an anodic oxidized aluminum material is treated with a fluorine ion-containing aqueous solution before or after treatment with a metal salt aqueous solution. A method for making an aluminum anodic oxide film opaque and white, characterized by making it opaque and white through treatment.