JPH09241888A - Method for coloring aluminum material yellowish brown - Google Patents

Abstract

PROBLEM TO BE SOLVED: To color anodically oxidized coating electrolytically colored bronze and excellent in weather resistance and light resistance of an aluminum material in yellowish brown by an easy and inexpensive method. SOLUTION: Anodically oxidized coating of an aluminum or aluminum alloy material is colored bronze by electrolytic coloring treatment and is thereafter immersed in an aq. soln. of ferric ammonium oxalate, the spectral reflectance characteristics of colored coating by two coloring methods are synthesized, and the coating is colored yellowish brown having various lightness and saturation. Furthermore, in the above stage, it is preferable that the anodically oxidized coating is immersed in an aq. soln. of ferric ammonium oxalate and is colored yellow, and after that, bronze electrolytic coloring is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coloring an anodized film of aluminum or aluminum alloy material (hereinafter referred to as aluminum material).

[0002]

2. Description of the Related Art Aluminum materials are widely used for building materials such as sashes and interior panel materials, furniture, and vehicle parts because they are lightweight, have good workability, and have corrosion resistance. It is common to perform film treatment. This coating has excellent corrosion resistance, but as it is the white tint of the metal ingot, it is monotonous and lacks in hobby. Therefore, various colors are painted or colored depending on the application. Is increasing. Among them, the electrolytic coloring treatment is extremely stable against the environment because it is colored by adsorbing chemically stable metal salts in the fine pores of the oxide film formed by the anodic oxidation treatment, and for a long period of time. It does not discolor or fade even outdoors and is widely used.

As described above, the coloring of the anodized film by the electrolytic coloring method is widely used, but recently, with the widespread use of aluminum materials such as building materials and vehicle parts, the tint of coloring and the concentration thereof have been changed. Requests are coming in. For example, conventionally, dark colors such as bronze have been mainly used mainly for building materials, but in recent years, with the widespread use of these colored aluminum materials, various color shades and color tones depending on the environment of use have been produced. It is becoming more demanding. For example, in the living environment, it is becoming more and more desirable to use wood-based natural materials, but in view of functional requirements and costs, aluminum materials are used to manufacture interior panels and furniture for these building materials. Even when doing so, it is required to use a coloring material having a color harmonized with the natural material. Therefore, in order to meet the demands for these various colors, the aluminum materials having these anodic oxide coatings are colored with such various colors using various dyes and paints. However, depending on the method of coloring with a dye, since the dye itself is relatively instable, the weather resistance and light resistance of the colored film are not sufficient, and it is not preferable because it causes fading in an outdoor use environment. In the case of using paints as well, when it is necessary to use paints containing special pigments that cause cost increase, it is not possible to meet the specifications of important sealed products to satisfy the corrosion resistance and weather resistance of building material products. Met. For this reason, it has been attempted to color such various colors by a coloring method by electrolytic coloring, but to the representative of the coloring that is desired from the harmony with the wood-based natural material as described above. There is a yellowish brown electrolytic coloring method. Especially for interior panels and furniture of building materials, it is possible to feel the relaxed atmosphere of wood, or for items that are used in everyday life, the calm color feeling is preferred,
There is a strong demand for such brown colored products.

As these brown-based coloring methods, an aluminum or aluminum alloy material on which an anodized film is formed is electrolyzed in a sulfuric acid bath to which selenium salt and copper sulfate are added to give a yellowish brown coloration (JP-A-58-58). No. 117892) or an aluminum or aluminum alloy material having an anodized film formed thereon is subjected to AC electrolysis in a sulfuric acid bath, and then AC electrolysis is performed in a bath containing a substance that releases a tin salt and sulfur to obtain an ocher color. (Japanese Patent Laid-Open No. 59-67391). However, in the former coloring method, since selenium is a toxic substance, it is not preferable from the viewpoint of production and its use environment, and in the latter coloring method, the second sulfuric acid bath is followed by the second sulfuric acid bath after the anodization with the first sulfuric acid bath. It requires a two-step pretreatment for secondary anodic oxidation to form an anodized film with a double film structure, which complicates the process and causes a cost increase, and its color is reddish. It was a yellowish ocher color and could not be said to satisfy the above-mentioned demand for the yellowish brown color tone.

On the other hand, in the conventional bronze color electrolytic coloring method, a porous anodic oxide film is formed on an aluminum material by anodizing treatment, and then Ni, Co, Sn are used.
In a bath containing a water-soluble salt of a metal such as
This is a method of precipitating a metal salt such as Co or Sn to color the anodized film to a brownish color called bronze color. However, the colored film has excellent weather resistance and light resistance, and can be exposed to sunlight for a long time outdoors. It is widely used because it does not corrode or fade even when exposed to wind and rain. In addition, among them, when a specific method is used, the characteristics of the colored film are excellent in throwing power and coloring uniformity, and it is easy to control the lightness of coloring in the process of electrolytic coloring, and the shade can be freely adjusted. Some have advantages. However, even though the shade is brown, it is a brown from a light shade to a dark shade, rather it is a reddish color, so it does not meet the recent preference for brownish colors as described above. Although various attempts have been made to examine the coloring conditions by paying attention to these excellent controllability of coloring and film characteristics, it has been impossible to produce the desired yellowish brown color.

The present invention has been devised to solve such a problem, and enables an anodized aluminum material to be colored in a yellowish brown color which meets the above market requirements, and is harmful. It is possible to easily and accurately control the tint and lightness of the coloring without the use of special substances and without the need for special complicated steps in the processing operation. Also provides an excellent coloring method. Further, the present invention provides a method for coloring an anodic oxide film, which can meet the specifications of both sealing treatment and clear electrodeposition coating in a later step depending on the destination.

[0007]

In order to achieve the object, the first aspect of the present invention is a step of coloring aluminum aluminum or an aluminum alloy material on which an anodized film is formed in advance to a bronze color by electrolytic coloring treatment, and iron oxalate. The method is characterized in that the anodic oxide coating is colored yellowish brown by sequentially performing a step of dyeing the anodic oxide coating with yellow by immersing in an aqueous ammonium solution. In the second invention, the order of these steps is reversed, the anodized film is dyed yellow by immersion in an aqueous solution of iron ammonium oxalate in the first step, and the anodized film is electrolytically colored in the second step. By coloring in bronze by
The anodized film is colored in yellowish brown.

[0008]

In the present invention, the bronze color electrolytic coloring method is used for forming Ni, Co,
It deposits a metal such as Sn and colors the film in a brownish color called bronze. Looking at the spectral reflectance characteristics of the film colored by this method, no clear peak appears in a specific wavelength region as shown in FIG. 1, and the longer the wavelength, the higher the tendency. Therefore, a larger amount of long-wavelength light is reflected to give a reddish brown tint. On the other hand, the coloring method of immersing in an ammonium iron oxalate aqueous solution is a method of adsorbing yellow ammonium iron oxalate onto the anodic oxide film for coloring. As shown in FIG. 2, the spectral reflectance characteristics of the yellow film colored by this method do not show a clear peak, but the reflectance increases toward the long wavelength region and has a wide and flat reflectance characteristic from around 600 nm. , Has a strong yellow color.
When the coloring method of immersing in the aqueous solution of ammonium iron oxalate is applied to the bronze color electrolytically colored film, the spectral reflectance characteristic as shown in FIG. 3 is exhibited. That is, the two spectral reflectance characteristics are overlapped, the reflectance in the long wavelength region of the bronze-colored electrolytically colored film is increased as a whole, and a yellowish brown color can be obtained.

In this method, the tint and lightness of the brown color to be colored can be adjusted by selecting the respective coloring conditions for the two coloring methods. That is, the bronze color electrolysis method can easily control the brightness of coloring by changing the electrolysis time of coloring, and thereby,
The lightness of the brown film can be adjusted. Further, in the ammonium iron oxalate dip coloring method, the color can be easily controlled by the concentration of the dyeing solution, the temperature, the time and the thickness of the anodized film. In this way, in each of the two coloring methods, by separately controlling the coloring conditions of the lightness, the shade of the color, and the saturation, it is possible to easily and accurately determine the shade and the lightness of the brown color. Can be controlled.

The colored film thus obtained is excellent in weather resistance and light resistance because the bronze color is an electrolytically colored film, and ammonium iron oxalate is an inorganic compound and is chemically stable. It has excellent weather resistance and light resistance, and does not cause corrosion or fading even in outdoor environments. Moreover, since the first step is based on the bronze color electrolytic coloring method, existing methods and equipment can be used, and the coloring step using the ammonium iron oxalate of the second step does not require any special complicated treatment step and is easy. It can be colored at low cost.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the coloring method of the present invention, pretreatment such as degreasing treatment, alkali etching treatment, desmutting treatment, etc. is performed on an aluminum material to be treated in the preceding step, and anodization is performed in an acidic aqueous solution such as sulfuric acid. The treatment is performed to form an anodized film having a predetermined film thickness, for example, 3 to 40 μm. Bronze color electrolytic coloring treatment, and iron ammonium oxalate dip coloring treatment are used to color the product to the required lightness and dark brown color, and finally, it is finished by clear coating and baking treatment, or immersion in boiling water and sealing aid. A sealing treatment is performed by immersing in water containing an agent. Alternatively, in the above-mentioned main step, the steps of the electrolytic coloring treatment and the coloring treatment by the dipping treatment are performed before and after.

The aluminum material used in the present invention is not particularly limited as long as it can form an anodized film.
Pure aluminum alloy such as IS A1100 material, JIS A6063
Materials such as Al-Mg-Fe-Si based materials such as plates, tubes,
Those used for building materials such as extruded shapes are preferable. For the anodized film treatment, an ordinary anodizing bath such as a sulfuric acid, oxalic acid or sulfonic acid bath can be used, but a sulfuric acid bath is preferred. When using the sulfuric acid bath method: 10 to 300 g / l, bath temperature: -5 to 30
A porous anodic oxide film having a film thickness of 3 to 40 μm is obtained at a temperature of ° C.
In the bronze color electrolytic coloring, there is no particular limitation on the treating bath and treating conditions such as an alternating current method, a direct current method or an electrolytic method using a pulse waveform in an aqueous solution of a metal salt such as Ni, Co or Sn. For example, it may be carried out according to a known method such as the so-called Asada method (described in Japanese Patent Publication No. 38-1715) or the electrolytic coloring method described in Japanese Patent Publication No. 57-321119. In order to improve the coloring uniformity, a so-called unicol method is used in which a rectangular wave alternating current is used after the barrier layer is made uniform.
It is preferable to use an electrolytic coloring method according to (Japanese Patent Application Laid-Open No. 52037).

For example, (1) nickel sulfate (NiSO ₄
・ 6HO ₂ ) 25 g / l, ammonium sulfate ((NH
₄ ) ₂ SO ₄ ) A coloring method in which a 12g / l bath is used for 5 minutes at a constant voltage of an electrolysis voltage of 13V using a commercial alternating current, (2)
Boric acid (H ₃ BO ₃ ) 25 g / l, nickel sulfate (NiS
O ₄ · 6H ₂ O) 20 g / l, ammonium sulfate ((N
H ₄ ) ₂ SO ₄ ) A coloring method of treating with a constant voltage of 20 V for 2 minutes using a commercial alternating current in a bath of 15 g / l, or (3) nickel sulfate (NiSO ₄ .6HO ₂ ) 50
g / l, cobalt sulfate (CoSO ₄ 7H ₂ O) 50 g /
l, boric acid (H ₃ BO ₃ ) 40 g / l, sulfosalicylate 10 g / l in a bath with commercial alternating current and electrolysis voltage 10 V
The coloring method of treating with a constant voltage for 7 minutes can be applied.

The case of using a method according to the Unicol method as the electrolytic coloring for bronze coloring in each of the first and second coloring steps of the present invention will be specifically described below.
In the bronze electrolytic coloring of the first step, nickel sulfate (NiSO ₄ .6HO ₂ ) 50 to 200 g / l, boric acid (H ₃ BO ₃ ) 20 to 40 g / l, tartaric acid 4 to 12 g / l
1, magnesium sulfate (MgSO ₄ 7H ₂ O) 0.5 to
The aluminum material was used as an anode in a 150 g / l bath at a current density of 0.05 to 3 A / dm ^{2 for} 20 seconds to 2 minutes to perform a direct current electrolytic treatment to make the barrier layer uniform, and then the aluminum material in the same bath. Is used as a cathode to apply an alternating current of a rectangular wave to perform electrolytic coloring treatment. The frequency of the rectangular wave alternating current applied to the aluminum material is 5 to 25 Hz, preferably 10 to 20 Hz. If the frequency is less than 5 Hz, the surface of the material to be treated becomes rough, and if it exceeds 25 Hz, the coloring speed is remarkably reduced, which is not suitable.
Further, the ratio of the positive current conduction time ta in the aluminum material of the rectangular wave alternating current applied to the material to be treated and the negative current conduction time tc in the aluminum material, the current ratio ta / tc is 0.0.
The treatment is performed in the range of 05 to 0.30, preferably 0.01 to 0.25. If the amount is less than 0.005 out of these ranges, the coloring property becomes non-uniform, and if it exceeds 0.03, the coloring speed becomes slow and the productivity is lowered. The waveform of the rectangular wave alternating current may be applied in the form of a uniform pulse as shown in FIG. 4, and as shown in FIG. 5, a period of T _{2 in which} a pulse is repeated for a period of T _{1 in} which a constant current flows is repeated. It may be provided. The energization time may be adjusted within a range of 2 to 6 minutes according to the target coloring state.

The metal salt of the bath composition is changed to Ni and Co, Sn
Sulfates such as are also applicable. Further, ammonium borate and ammonium tartrate may be applied instead of boric acid, and citric acid may be applied instead of tartaric acid. From the viewpoint of bath management, monovalent cations (Na, K, NH ₄ ) induce spalling, so it should be 20 PPM or less, and Al ions should be 500 PPM or less because they precipitate and cause film defects. Is preferred. In this electrolytic coloring treatment method, the barrier layer is made uniform by arranging a dense alumina layer formed between the aluminum substrate and the porous layer of the anodized film, a so-called barrier layer, in the electrolytic cell of the material to be treated. To make the thickness imbalance caused by the difference in position uniform, prevent film destruction due to deterioration of the anodic oxide film, prevent the occurrence of spalling phenomenon, and improve the throwing power in the electrolytic coloring process. Although this is an anodizing treatment, this homogenizing treatment can be carried out by anodizing treatment in an independent bath of boric acid, ammonium borate, ammonium tartrate or the like, if desired, as a bath separate from the electrolytic coloring bath.

In the second step, which is a coloring treatment for yellow dyeing by adsorption of ammonium iron oxalate, the bronze-color electrolytically colored aluminum material is 0.1 to 50 g / ammonium iron oxalate.
1. Immersing in an aqueous solution having a bath temperature of 5 to 70 ° C. for 1 to 15 minutes. After the coloring treatment, a required treatment such as a sealing treatment or a clear coating is performed according to the purpose.

Example 1 An aluminum material manufactured according to JIS A1100 was placed in a sulfuric acid bath for 1.
After electrolysis was performed at 5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, nickel sulfate 20 g / l, boric acid 2
In an aqueous solution of 5 g / l and 15 g / l of ammonium sulfate,
AC electrolytic coloring is performed for 2 minutes at a commercial AC voltage of 20V. It was colored bronze. The colorimetric value at this point is L ^* = 50.
4, a ^* = 3.62, b ^* = 14.3. Then, an aqueous solution of ammonium iron oxalate 10 g / l (bath temperature 60
(° C) for 5 minutes to give a dark brown coloration treatment and then a sealing treatment. Colorimetric values are L ^* = 53.0, a ^* = 5.35, b ^* =
It was 23.2. Here, L ^* , a ^* , and b ^* are L ^* a ^* b ^* color system display according to Japanese Industrial Standards (JIS Z8729), and the bronze color is L ^* value of 25 to 73, a ^*.
= 0 to 10, b ^* = 0 to 20. However, within this range, a ^* +
b ^* > 3. In addition, yellowish brown has an L ^* value of 27 to 7
5, a ^* = 0 to 10 and b ^* = 20 to 40.
However, it is large is more of b ^* than a ^*. It should be noted that in these, as a ^* increases, the redness increases, while on the other hand, b
^The larger the ^* , the more yellowish it tends to be.

Example 2 An aluminum material manufactured according to JIS A1100 was subjected to 1.
After electrolysis was carried out at 5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, it was immersed in an aqueous solution of 10 g / l ammonium iron oxalate (bath temperature 60 ° C.) for 5 minutes to obtain a yellow colored film. At this point, the colorimetric value is L ^* = 79.04, a ^*
= -0.17 and b ^* = 22.09. Then, in an aqueous solution of 20 g / l of nickel sulfate, 25 g / l of boric acid, and 15 g / l of ammonium sulfate, AC electrolytic coloring was performed for 2 minutes at a commercial AC voltage of 20 V to give a yellowish brown coloring treatment and a sealing treatment. Colorimetric values are L ^* = 54.83, a ^* = 5.25, b ^*
= 23.21.

Example 3 An aluminum material manufactured according to JIS A1100 was subjected to 1.
After electrolyzing at 5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, a constant current rectangular wave (ta / t c = 0.5 A / dm ^{2 in} an aqueous solution of nickel sulfate 100 g / l).
(1/5, 10 Hz) was used for AC electrolytic coloring for 2.5 minutes to give a bronze color. The colorimetric values at this point were L ^* = 50.1, a ^* = 3.52, and b ^* = 13.26. Then, it was immersed in an aqueous solution of ammonium iron oxalate 10 g / l (bath temperature 60 ° C.) for 5 minutes to give it a yellowish brown coloring treatment and a sealing treatment. Colorimetric value is L ^* = 52.68, a ^* =
5.25 and b ^* = 22.1.

Example 4 Except that an aluminum material made according to JIS A6063 was used,
Coloring treatment was carried out in the same manner as in Example 1 to obtain a yellowish brown coloring material. Colorimetric values are L ^* = 49.85, a ^* = 3.52, b ^* = 2
2.2.

Results of weather resistance test The sample prepared in Example 1 was measured with a sunshine weather meter under the conditions described in JIS H8602 to obtain 300
It was tested for 0 hours. The color difference before and after the test was ΔE = 0.5, and no fading was observed. As a comparison, a yellow organic dye was used instead of the second step of Example 1, and a sample having the same color was tested in the same manner. As a result, the sample faded and became a bronze color.

[0022]

As described above, according to the present invention, various aluminum anodic oxide materials can be colored yellowish brown with arbitrary brightness and saturation. The brightness and the saturation can be easily and accurately controlled by adjusting each of the two coloring steps, and the production can be performed without increasing the cost. The colored product has excellent light resistance and weather resistance, and can meet both specifications of the sealed product and the electrodeposition coated product.

[Brief description of drawings]

FIG. 1 Spectral reflectance of a bronze electrolytically colored film.

FIG. 2 Spectral reflectance of a film colored by an ammonium iron oxalate dip coloring method.

FIG. 3 is the spectral reflectance of the colored film according to the present invention.

FIG. 4 is a current waveform applied to an aluminum material by an electrolytic coloring method using a rectangular wave alternating current.

FIG. 5 shows another current waveform applied to an aluminum material in an electrolytic coloring method using a rectangular wave alternating current.

Claims (2)

[Claims] 1. A yellow aluminum material, characterized in that an aluminum or aluminum alloy material on which an anodized film has been formed in advance is colored bronze by an electrolytic coloring treatment and then subjected to yellow dyeing which is immersed in an aqueous solution of ammonium iron oxalate. Brown coloring method. 2. An aluminum or aluminum alloy material on which an anodized film has been formed in advance is immersed in an aqueous solution of iron ammonium oxalate for yellow dyeing, and then colored bronze by an electrolytic coloring method. Yellow-brown coloring method.