JP2000273695A - Formation of gray colored aluminum or aluminum alloy material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To color aluminum or aluminum alloy material formed with an anodically oxidized film on the surface to dark gray of a low lightness value by subjecting the aluminum or aluminum alloy material to an electrolysis with impressed voltage lower than that of an anodic oxidation treatment to give rise to a current restoration phenomenon, then electrolyzing the material in an acidic electrolytic coloring liquid of a specific pH. SOLUTION: The aluminum or aluminum alloy material formed by extrusion molding according to the conventional method is subjected to a surface preparation by mechanical manipulation, such as a blasting method and is then subjected to the anodic oxidation treatment at about 5 to 100 V in the electrolyte, such as sulfuric acid or oxalic acid. The anodically oxidized film is thereafter formed on this surface and is subjected to current restoration by DC energization with voltage of about 0.5 to 80 V lower than the impressed voltage of the anodic oxidation treatment. The anodically oxidized film is electrolytically colored in the acidic electrolyte coloring liquid which contains 1 to 30 g/l sulfuric acid, 0.1 to 3.0 g/l stannous sulfate, 10 go 100 g/l nickel sulfate and 20 to 100 g/l ammonium sulfate and has the pH <=3.0. As a result, the gray colored aluminum material having the dark color of about 40 to 50 in lightness index L value is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a gray coloring of aluminum or an aluminum alloy material widely used in the field of construction such as sashes and entrance doors.

[0002]

2. Description of the Related Art Aluminum materials formed with an anodized film are widely used in the field of building materials such as sashes and entrance doors. However, the color tone of the conventionally obtained anodic oxide film is mainly from bronze to black due to electrolytic coloring, and in recent years, demand for gray color tone has been increasing in accordance with diversification of user needs.

[0003] As an alloy which develops a gray color by anodizing treatment, Al-Fe alloys, Al-Si alloys, and Al-Mg alloys which have been added to Mg to form age-hardened alloys have been known.
-Si alloys are known. Furthermore, Si-Mg-F
Also known is an e-Al alloy extruded material, which is a dark gray color in which 85% or more of the total number of precipitates having a size of 0.1 to 2 μm among the metallic Si precipitates are uniformly distributed. (See Japanese Patent Application Laid-Open No. 8-109427).

[0004] Further, the Al alloy surface after the extrusion molding is subjected to a mechanical strain by applying a mechanical operation to cause an aging treatment, followed by DC electrolysis to form an anodic oxide film. It is also known that DC electrolysis is performed at a voltage lower than the applied voltage to cause a current recovery phenomenon to form a gray-colored oxide film (Japanese Patent Publication No. Hei 5-
No. 2751).

Further, an aluminum or aluminum alloy material having an anodized film formed on its surface is anodized using an acidic electrolytic coloring solution containing sulfuric acid, stannous sulfate, nickel sulfate and ammonium sulfate as an electrolytic coloring solution. It is also known that the anodic oxide film is colored gray by secondary electrolytic coloring (see JP-A-10-147889).

[0006]

However, in the above-mentioned conventional gray coloring methods, the limit of the lightness index L value is about 60 in any case. Further, when an attempt is made to obtain a dark gray color, a method using tertiary electrolytic coloring or electrodeposition coating has an L value of 40 to 40.
50 is possible, but in tertiary electrolytic coloring, there is a problem that the color change due to electrolytic coloring is severe, and in electrodeposition coating, scratches are easily noticeable. It is assumed that the scratches are not noticeable because they are not colored by color painting. In the present invention, not only the conventional L value of about 60 but also L
It is an object of the present invention to provide a dark gray colored aluminum or aluminum alloy material having a value of about 40 to 50. That is, an object of the present invention is to provide a wider range of dark gray aluminum or aluminum alloy material.

[0007]

According to the present invention, a current recovery phenomenon is caused by electrolyzing an aluminum or aluminum alloy material having an anodized film formed on its surface at a voltage lower than the voltage applied in the anodizing treatment. Then pH 3.0
This is a method for forming a gray-colored aluminum or aluminum alloy material, characterized by electrolytic coloring in the following acidic electrolytic coloring solution. In the present invention, the aluminum or aluminum alloy material is first subjected to anodic oxidation treatment, but prior to that, if a surface adjustment treatment is performed, a current recovery treatment in a later step may be performed in a short time. It does not have to be applied.

The surface is adjusted by mechanical operation on a material extruded according to a conventional method. As a method of this surface adjustment, there are a glast method in which abrasive grains such as glass particles, sand, iron powder, and alumina particles are sprayed, a high-pressure injection method in which a liquid such as water is injected at a high pressure, a brush method in which a material surface is damaged by a brush or the like. There are various mechanical means such as a roller method using an embossing plate roll and a press method of embossing by a mold press.

In the anodic oxidation treatment, the aluminum material is subjected to a process such as degreasing, washing with water and, if necessary, smut removal by a usual method, and then the aluminum material is connected to the anode and subjected to DC electrolysis according to a conventional method. To form an anodic oxide film.

That is, a well-known electrolyte solution of an inorganic acid and / or an organic acid, for example, sulfuric acid, chromic acid, phosphoric acid or the like, or a mixed acid thereof, oxalic acid, malonic acid, or a mixed acid thereof or an inorganic acid In an electrolyte containing
The aluminum alloy is anodized using a direct current or similar current waveform. The application voltage, application time, etc. of the anodic oxidation treatment are sufficient as usual, but usually,
Depending on the type of treatment liquid, the treatment is performed in the range of 5 to 100V. If it is less than 5 V, it takes a long time to obtain a desired film thickness, and productivity is poor. On the other hand, if it exceeds 100 V, there is large variation in the film thickness, and there is no waste in energy for processing at a high voltage. Undesirably large.

After the anodizing treatment, a current is recovered by applying a direct current at a voltage lower than the applied voltage using the aluminum alloy as an anode. The conditions for this current recovery depend on the type of the treatment liquid, but are lower than the applied voltage of the anodic oxidation treatment in the range of 0.5 to 80.0 V for 1 to 100 minutes, preferably 1.0 to 50.0 V. Perform for 1-50 minutes in range. 0.5
If it is less than V, it takes a long time to develop color, and productivity and film performance deteriorate, which is not preferable. On the other hand, if it is more than 80 V, it is not preferable because it causes uneven coloring. Similarly, if it is less than 1 minute, uneven coloring occurs, while if it exceeds 100 minutes, the coloring time is too long and productivity and film performance deteriorate, which is not preferable.

Incidentally, the current recovery treatment liquid may be the same as or different from the anodization treatment liquid. If different, it is desirable to use, for example, oxalic acid, phosphoric acid, malonic acid, or the like as the current recovery treatment liquid, or a voltage higher than the anodization treatment voltage may be applied depending on the conductivity of the liquid. .
If the same processing solution is used, the current density of the anodizing process is slightly increased, an anodic oxide film is formed in a short time, and a part of the color forming process is performed in the processing tank within the remaining time. It is more preferable to adjust the degree of coloring in the coloring step. For the current recovery, any method can be adopted, such as switching the applied voltage of the anodic oxidation treatment to a low voltage, or temporarily stopping the energization and reducing the voltage to zero before applying the voltage. In addition, the current recovery phenomenon may be caused to appear only once, but after reaching a steady state, the applied voltage is increased within a short time to a voltage higher than the applied voltage but lower than the applied voltage of the anodizing treatment, and the applied voltage is reduced again. The operation may be performed a plurality of times to increase the degree of coloring.

In the film coloring treatment by the current recovery method, the time required for coloring is significantly shorter when the surface adjustment treatment is performed than when no surface adjustment is performed. In addition, since the rotation and the like are considerably uniform, it is very easy to control the degree of color development. According to the method of the present invention, the interaction between the surface adjustment by mechanical operation, the aging treatment, and the coloring treatment by the current recovery method, in an extremely short time as compared with the ordinary coloring method by current recovery, and with good turnability, An achromatic gray-black colored film can be obtained.

Next, electrolytic coloring is performed in an acidic electrolytic coloring solution having a pH of 3.0 or less. As the acidic electrolytic coloring solution, 1 to 30 g / l of sulfuric acid and 0.1 to 3.0 g of stannous sulfate are used. 0g
/ L, a solution containing nickel sulfate in a concentration range of 10 to 100 g / l and ammonium sulfate in a concentration range of 20 to 100 g / l are preferable.

The electrolytic coloring liquid must be strongly acidic as described above, and has a pH of 3 or less, preferably 0.5 to 2.0.
5, more preferably in the range of 0.5 to 2.0. For this reason, the content of sulfuric acid is preferably in the range of 1 to 30 g / l. When the content of sulfuric acid is less than 1 g / l, the pH of the electrolytic coloring solution shifts to a slightly acidic side, and the color tone of the obtained colored oxide film becomes undesirably bronze. In addition, the concentration of stannous sulfate is preferably 0.1%.
1 to 3.0 g / l, more preferably 0.2 to 1.5 g
/ L, and the concentration of nickel sulfate is 10 to 100
A range of g / l is preferred. In particular, when the concentration of stannous sulfate increases, the color tone of the obtained colored oxide film tends to be colored and becomes a bronze color.

Ammonium sulfate is added to improve the conductivity of the solution especially when the concentration of sulfuric acid is low. However, in the electrolytic coloring solution of the composition system of the present invention, the color tone of the obtained colored oxide film is reduced. Has the function of shifting to a gray system. However, if the concentration of ammonium sulfate is too high,
It is not preferable to add a large amount of ammonium sulfate because it tends to lighten the color tone of the colored oxide film, and tends to produce nickel ammonium sulfate that is hardly soluble in an aqueous solution by acting on Ni ions. Therefore, the concentration of ammonium sulfate is preferably in the range of 20 to 100 g / l,
A more preferred range is 30 to 75 g / l.

Other electrolytic coloring conditions, such as current waveform,
The current density, energizing time, bath temperature and the like are appropriately selected from the range used in the usual electrolytic coloring of aluminum materials. For example, a working voltage of about 5 to 30 V is sufficient, and a suitable energizing time is usually about 0.5 to 10 minutes. As the current waveform, AC, AC / DC superimposed current, etc. can be applied, but it is convenient to use a normal AC power supply as it is. Further, as the counter electrode, a carbon, tin, nickel plate or the like can be used as in the conventional electrolytic coloring method.
It is also possible to darken the gray color tone of the obtained colored oxide film by using a current waveform in which the + component of the sine wave is increased, or by changing the current application method. Sn ²⁺ is oxidized and precipitated as Sn ⁴⁺ ,
Deterioration of the liquid may occur. In such a case,
It is desirable to add a weakly reducing substance in order to prevent this.

A colored oxide film is obtained by each of the above-mentioned steps. After that, if necessary, a process such as sealing or semi-sealing is performed, followed by electrodeposition coating and baking according to a known method.

According to the above-described color development method by current recovery, the barrier layer present at the bottom of the porous film is formed into a finely branched structure, and an achromatic gray-black color is obtained by refraction of light applied thereto. By adding an electrodeposition coating film on the surface, the refraction of light is further complicated, and as a result, an achromatic opaque gray black (pastel tone) having a strong fill feeling without the transparency of aluminum is obtained. be able to. In addition, the adhesion of the coating film is also improved by the unevenness of the oxide film surface, and a coating film having excellent properties such as corrosion resistance and weather resistance is obtained.

As a material, an aluminum alloy containing Mg and Si as main addition elements, for example, JIS6063
S alloy is preferably used, and the alloy composition is changed to
If the Si content is increased so as to increase the precipitation of g ₂ Si, a greater effect can be obtained.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described specifically with reference to examples.

Examples 1 to 3 An aluminum material A6063 which had been subjected to degreasing, etching and neutralization by a conventional method using a normal aluminum material A6063 alloy whose surface had not been adjusted was used as a material.
C. in a sulfuric acid bath at a current density of 1.56 A / dm ²
For 17 minutes and then at 15 V for 3 minutes. Thereafter, the current supply was stopped and the voltage was reduced to zero, and then a current recovery process was performed in the anodizing tank. Specific conditions are as shown in Table 1.

Next, the aluminum material subjected to the current recovery treatment is immersed in an electrolytic coloring liquid having a composition shown in Table 2 at 28 ° C. and a pH of 2 (provided that a weakly reducing substance is added), and the carbon is treated as a counter electrode. The electrolytic coloring was performed according to the conditions shown in Table 1.

After that, an electrodeposition coating treatment was carried out at 21 ° C. and 150 V for 2 minutes using an acrylic clear paint in a usual manner, followed by drying and baking.

The coloring state of the obtained colored aluminum material and the colored aluminum material after each step were measured using a color difference meter (CR-300, manufactured by Minolta Co., Ltd.). The results are shown in Table 3. In the table, L indicates the lightness index, a and b indicate the chromaticness index, and the smaller the L value, the deeper the color, and the smaller the a and b values, the closer to the achromatic color system. Note that a = b = 0 is an ideal achromatic color, but when the L value is lighter than 60, the b value is preferably less than 2.5, but when the L value is deeper about 40 or 50, , The b value may be 2.5 or more,
It is preferable to be about 5.0 or less.

As is evident from the results shown in Table 3, after the current recovery processing, all the L values are achromatic colors having an L value of 60 or more or a gray color close thereto. , The L value is a deep gray color close to an achromatic color of 38 to 52. In addition, even when the electrodeposition coating process is performed thereafter, the L value is slightly increased, but it can be seen that the colored state of a dark gray color close to achromatic is maintained.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

[0030]

According to the present invention, it is possible to obtain not only a conventional L value of about 60 but also a dark gray-colored aluminum or aluminum alloy material having an L value of about 40 to 50. That is, it is possible to obtain a gray aluminum or aluminum alloy material having a wider concentration.

[Procedure amendment]

[Submission date] April 1, 1999 (1999.4.1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

However, in the above-mentioned conventional gray coloring methods, the limit of the lightness index L value is about 60 in any case. Further, when an attempt is made to obtain a dark gray color, a method using tertiary electrolytic coloring or electrodeposition coating has an L value of 40 to 40.
While 50 is also possible, the three in order electrolytic coloring, severe changes in I <br/> Ru color electrodeposition coating, there are problems easily, such as noticeable scratches in electrodeposition coating, the color according to the present invention is an electrodeposition coating It is assumed that scratches are hardly noticeable because there is little change in color and it is not colored by electrodeposition coating. In the present invention, not only the conventional L value of about 60 but also L
It is an object of the present invention to provide a dark gray colored aluminum or aluminum alloy material having a value of about 40 to 50. That is, an object of the present invention is to provide a wider range of dark gray aluminum or aluminum alloy material.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

[0027]

[Table 1]

Claims (2)

[Claims] 1. A current recovery phenomenon is caused by electrolyzing an aluminum or aluminum alloy material having an anodized film formed on its surface at a voltage lower than an applied voltage of anodizing treatment, and thereafter, an acid having a pH of 3.0 or less is produced. A method for forming a gray-colored aluminum or aluminum alloy material, comprising performing electrolytic coloring in an electrolytic coloring liquid. 2. The acidic electrolysis coloring liquid contains 1 to 30 g of sulfuric acid.
l, stannous sulfate 0.1 to 3.0 g / l, nickel sulfate 10 to 100 g / l, ammonium sulfate 20 to 1
The method for forming a gray-colored aluminum or aluminum alloy material according to claim 1, which is contained in a concentration range of 00 g / l.