JPH09143795A - Method for electrolytically coloring aluminum material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a colored film excellent in uniformity of color tone and corrosion resistance on the surface of an aluminum material. SOLUTION: The aluminum material on which a porous anodically oxidized film is previously formed is immersed into an electrolytic coloring liq. containing one or >=2 kinds metal salts selected among phosphoric acid, chromic acid, boric acid, sulfamic acid, oxalic acid and citric acid and containing no sulfate to form a barrier layer having 50-150nm thickness and containing no sulfate ion by a direct current anodic electrolysis of 50-150V, then the aluminum material is subjected to a direct current cathodic electrolysis or an alternate current electrolysis in the same soln. The second anodically oxidizing treatment for extending the bottom part of fine pore by executing the secondary anodically oxidizing treatment in an acid or alkali soln., moreover, the third anodically oxidizing treatment for enlarging the fine pore size may be applied before to the 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 electrolytically coloring an aluminum material which forms a colored film having excellent coloring uniformity and corrosion resistance.

[0002]

2. Description of the Related Art In a secondary electrolysis method for electrolytically coloring an aluminum material, the aluminum material is anodized in a solution such as sulfuric acid and electrolyzed in a solution containing a metal salt such as Ni or Sn to form an anodized film. The colored film in which the metal is deposited is formed in the micropores. A third electrolytic coloring method is also known, in which the aluminum material after anodization is electrolyzed in an acidic solution to change the shape of the fine pores and then electrolytically colored in a solution containing a metal salt. Since the products that have been subjected to the electrolytic coloring method are given various colors and have excellent light resistance,
It is used in a wide range of fields including building materials such as building sashes and outer walls. The commercial value of a colored product varies greatly depending on whether or not the coloring is uniform. Therefore, in order to improve the coloring uniformity, various methods have been proposed in the past (Japanese Patent Publication No. 59-48960, JP-A-6-27).
No. 2082, etc.). Corrosion resistance has also become a problem with the deterioration of the atmospheric environment such as acid rain, but it is difficult to cope with these problems by the conventional electrolytic coloring method.

[0003]

However, the demand for uniform coloring is becoming stricter and the conventional method still tends to cause color unevenness on the surface after coloring. Particularly in applications such as the outer wall of a building, it is necessary to finish one panel and the entire building to a uniform color tone, and it is difficult to form a colored film that meets such requirements. The non-uniformity of coloring is mainly in the electrolytic coloring process. In the electrolytic coloring process, aluminum materials of various complicated shapes are placed between two counter electrodes in the electrolytic cell to be electrolyzed, but the potential distribution is non-uniform in the electrolytic cell, and as a result, the current density is at the center of the aluminum material. And edge, concave surface and convex surface are different. Different current densities cause differences in the amount of metal deposited in the micropores of the anodized film. The amount of deposited metal has a correlation with the lightness, and the lightness decreases as the amount of deposition increases. Therefore, the lightness differs depending on the installation position in the electrolytic cell, the central portion and the end of the material to be treated, the concave surface and the convex surface, etc., and if it is remarkable, it becomes a defective product.

When a liquid having a low pH such as acid rain adheres to the anodized film, the film is chemically dissolved. When the melting reaches the base aluminum, corrosion progresses,
The appearance is significantly impaired. The present invention has been devised to solve such a problem, and by increasing the thickness of the barrier layer to reduce the influence of solution resistance to a relatively negligible level, an electrolytic solution having a non-uniform potential distribution can be obtained. Even in a tank
The purpose of the present invention is to obtain a colored aluminum material excellent in color tone uniformity and corrosion resistance by allowing a current having a substantially uniform density to flow in any part of the aluminum material to be electrolyzed. Further, the present invention proposes a method for suppressing coloring non-uniformity due to the manufacturing history of materials and the like, and a method for enabling various colored states to be obtained using the same coloring bath.

[0005]

In order to achieve the object, the electrolytic coloring method of the present invention comprises: phosphoric acid, chromic acid, boric acid,
An aluminum material having a porous anodic oxide film formed in advance is immersed in a coloring electrolyte solution containing one or more kinds of metal salts selected from sulfamic acid, oxalic acid, and citric acid, and containing no sulfate, and 50 to 150 V is applied. DC direct electrolysis of 50 ~
It is characterized in that a barrier layer containing no sulfate ion having a thickness of 150 nm is formed, and then the aluminum material is subjected to DC cathodic electrolysis or AC electrolysis in the same solution. The porous anodic oxide film is sulfuric acid with a concentration of 100 to 300 g / l,
An inorganic acid bath of phosphoric acid or the like, an oxalic acid concentration of 20 to 100 g / l, an organic acid bath of tartaric acid or the like, or an alkaline bath of sodium hydroxide or sodium carbonate concentration of 5 to 50 g / l is used. As electrolysis conditions, direct current density 1 to 2 A
/ Dm ² , electrolysis voltage 15 to 20 V, and bath temperature 15 to 25 ° C. are adopted. With this anodizing treatment, the thickness is 1 to 50 μm.
A porous anodic oxide film having a thickness of m, preferably 5 to 40 μm is formed. The anodized film has a large number of fine holes extending in the thickness direction as shown in the upper part of FIG. When a sulfuric acid bath is used for the anodizing treatment, it is preferable that the sulfuric acid components entrained in the fine pores be removed by sufficiently washing with water for several steps so that sulfate ions are not brought into the next step.

After the anodizing treatment, the aluminum material is electrolyzed in a coloring solution containing a metal salt. The method of passing through the two steps of this anodic oxidation → electrolytic coloring is usually called secondary electrolytic coloring, and Ni, Sn, Cu, Zn, Co, Fe, Se,
A coloring solution containing a metal salt such as Pb, Mo, V, Ti, Mn, Au, Ag, and Pd and containing no sulfate is used. For example, a coloring liquid containing an inorganic salt such as cobalt phosphate, molybdenum phosphate, manganese phosphate, silver chromate, and lead borate,
Nickel sulfamate, copper citrate, manganese oxalate,
The concentration of the coloring liquid containing an organic salt such as iron oxalate or the coloring liquid containing both metal salts is adjusted to a concentration of 20 to 200 g / l. Boric acid, tartaric acid, citric acid, malonic acid, oxalic acid, gluconic acid and salts thereof (for example, ammonium salt) can be added to the coloring liquid at a concentration of 5 to 50 g / l as a barrier layer formation promoter. When the concentration of the barrier layer formation accelerator is less than 5 g / l, the effect of thickening the barrier layer is small and a non-uniform pattern is generated as a colored state. The upper limit concentration of the barrier layer formation promoter is determined depending on the solubility of each drug used. The coloring liquid is adjusted to pH 3 to 7 with magnesium oxide, magnesium hydroxide or the like in order to suppress bath aging. When the pH is less than 3, the anodic oxide film is dissolved and is not colored, and when the pH is more than 7, a precipitate is easily generated in the bath.

Since the coloring liquid forms a thick barrier layer, if a carry-on from the previous step is carried out, the sulfate ion is added to 10%.
It is preferable to suppress it to 00 ppm or less. In addition, in order to suppress the generation of spalling due to the incorporation of ions such as Na and K into the barrier layer during electrolytic coloring, it is preferable to control the total concentration of Na ions and K ions to 10 ppm or less. . First in electrolytic coloring
In the process, DC anode electrolysis is performed to grow the barrier layer to a thickness of 50 to 150 nm. As a result, the electrolysis voltage rises and the solution resistance during coloring becomes relatively small to a negligible level, the color variation due to the solution resistance is concealed, and the throwing power (uniformity) on the object having a complicated shape is uniform. (Coloring) is improved. Further, by thickening the barrier layer, color variation due to manufacturing history of the material to be treated is prevented, and corrosion resistance is also improved. Barrier layer thickness is 50 nm
If the amount is less than the above, the adjusting effect by the direct current anode electrolysis is not sufficient, and the amount of the deposited metal due to electrolytic coloring becomes nonuniform depending on the site, and it becomes difficult to obtain uniform coloring and the corrosion resistance becomes low. However, when the thickness of the barrier layer exceeds 150 nm, spark discharge is likely to occur during electrolytic coloring, current is concentrated in a part of the film and burning occurs, and hydrogen gas is generated at the film / aluminum interface. This is not preferable because a spalling phenomenon occurs in which the film peels off.

In the direct current anode electrolysis, stainless steel, carbon, etc. are used as a counter electrode, and the voltage is 50 to 150 in the constant voltage method.
V (preferably 50 to 120 V), electrolysis time 10 seconds to 5
Min, bath temperature of 20 to 30 ° C. is adopted, and the current density is 0.05 to 1 A / dm ² (preferably 0.
1 to 0.5 A / dm ² ), electrolysis time is 10 seconds to 5 minutes, and bath temperature is 20 to 30 ° C. 5 barrier layers
Whether or not it has grown to a thickness of 0 to 150 nm is determined by the fact that the electrolysis voltage reaches 50 to 150 V when electrolysis is performed with the bath composition described above. The thickness of the barrier layer is 50 to 15
After adjusting to 0 nm, electrolytic coloring treatment (cathodic electrolysis) for depositing a metal in the fine pores of the porous anodized film is performed as shown in the upper part of FIG. The height h of the deposited metal adjusts the shade of the color tone, and the higher the height h, the darker the surface of the color tone. The color tone that appears in this structure changes from brown to black depending on the color of the precipitate itself and the reflection / absorption of light.

When this electrolytic coloring is carried out in the same electrolytic bath as the anode electrolysis, handling is easy and the potential distribution in the bath is the same in two steps, so that it is suspended in an electrolytic bath in which the potential distribution is non-uniform. Uniform coloring is possible regardless of the lowered position. When direct current electrolysis is performed, the effective current density is 0.
The electrolysis conditions are 1 to 0.5 A / dm ² , electrolysis voltage of 50 to 150 V, bath temperature of 20 to 30 ° C., and electrolysis time of 20 seconds to 3 minutes. In AC electrolysis, AC having a waveform such as a sine wave, a triangular wave, a trapezoidal wave, and a rectangular wave is appropriately used, and an AC having a frequency of 1 to 100 Hz is used, and an effective current density is 0.1 to 0.5 A / dm.
² , electrolysis conditions of peak voltage 50 to 150 V, bath temperature 20 to 30 ° C., electrolysis time 30 seconds to 5 minutes are adopted. The AC waveform has different effects on the film formation depending on whether it is positive or negative, and a waveform with many negative portions is preferable. As the aluminum material to be electrolytically colored, use the one in which the bottoms of the micropores are enlarged as shown in the middle part of FIG. 3 by the third electrolytic coloring in which the anodizing treatment is followed by reanodizing treatment in an acid or alkaline solution. You can For example, in the case of fine pores having a pore diameter of 10 nm in an anodized film having a thickness of 20 μm, a cylindrical bottom portion having a diameter of 30 nm and a height of about 70 nm is formed by reanodizing treatment. Since the metal is deposited in the expanded fine pores, variations in the height of the metal deposit due to the metallographic nonuniformity of the matrix of the material to be treated, the nonuniformity of the potential distribution of the electrolytic cell, etc. are reduced. , One semi-transmissive surface is formed. The reflected light at the semi-transmissive surface and the reflected light at the aluminum / barrier layer interface interfere with each other to obtain a blue to green color tone. The re-anodizing treatment also has a function of substituting the sulfate ions stored in the fine pores in the anodized film when the anodizing treatment is previously performed using a sulfuric acid bath.

In the re-anodizing treatment, when immersed in phosphoric acid, a phosphoric acid-oxalic acid mixed solution, etc., the concentration is 100 g / l, and the bath temperature is 4
A condition of 0 ° C. and a soaking time of 5 minutes and a condition of a concentration of 10 g / l, a temperature of 20 ° C. and a soaking time of 1 minute are adopted when soaking in an alkaline bath. Further, in anodic electrolysis using phosphoric acid having a concentration of 100 g / l and a bath temperature of 20 ° C., a current density of 0.5 A / d
m ² , electrolysis voltage of 50 to 150 V, electrolysis time of 1 minute are adopted. Further, it is also possible to use an aluminum material in which fine pores are elongated below the enlarged bottom pores as shown in the lower part of FIG. 3 by the fourth electrolytic coloring which is again anodized. The fourth electrolytic coloring strengthens the film structure and
Any color tone can be obtained. At this time, a bath of phosphoric acid, sulfuric acid, oxalic acid, sulfamic acid or the like which gives a porous film is used as an electrolytic bath. In the case of a sulfuric acid bath, a direct current density is 0.1 to 1 A / dm ² , and an electrolysis voltage is 10 Electrolysis conditions of -20V and bath temperature 15-25 ° C are adopted. At this time, the anodic oxide film is adjusted to a thickness of 0.1 to 1 μm according to the color tone to be obtained again by the anodic oxidation treatment. When the sulfuric acid bath is used for the re-anodizing treatment again, it is preferable to perform sufficient water washing treatment thereafter. The aluminum material colored in this way is made into a product by a sealing treatment, a clear coating treatment or the like. In the sealing treatment, the aluminum material after the coloring treatment is immersed in a sealing treatment material bath containing high temperature water, a nickel salt-based compound or the like to improve the corrosion resistance. In the clear coating treatment, a clear coating film is formed by electrodeposition coating of acrylic-melamine resin, spray coating of acrylic resin or fluororesin coating, and the like.

[0011]

Many aluminum materials to be electrolytically colored have a complicated shape, such as a building sash, depending on the application. When this aluminum material is placed in the electrolytic coloring tank 1 for electrolytic coloring, as shown in FIG. 1, a current easily flows through the aluminum material 2 in the portion A near the counter electrode 3 as compared with the portion B far from the counter electrode 3, The current density has a relation of I ₁ > I ₂ . This will be described along the electrical equivalent circuit of FIG. 2. Factors that influence electrolytic coloring include the total resistance of the solution resistances R ₀ and R ₁ and the impedance of the barrier layer. Regarding the portion A close to the counter electrode 3, the solution resistance R ₀ and the barrier layer impedance Z =
(R ² + X ² ) ^1/2 . Regarding the portion B far from the counter electrode 3, the solution resistance R ₀ + R ₁ and the impedance Z
It is. Comparing the resistances involved in both parts A and B,
R ₀ + Z <R ₀ + R ₁ + Z, and the part A near the counter electrode 3
The amount of resistance related to the aluminum material 2 is small, so that the current flows more easily in this portion A. As a result, there is a difference in the amount of precipitates that is proportional to the amount of electricity, and the portion A near the counter electrode 3 is dark and the portion B far from the counter electrode 3 is light, resulting in a difference in color tone of the colored film.

In the present invention, by thickening the barrier layer, it is possible to make the influence of the solution resistance due to the difference in distance from the counter electrode 3 to the aluminum material 2 relatively small to a negligible extent. There is. That is,
By increasing the thickness of the barrier layer, the resistance R of the barrier layer is increased.
Is made large, that is, the impedance Z is adjusted to a value as large as possible. As a result, when Z >> R ₀ + R ₁ > R ₁ , the resistance component relating to the near portion A and the far portion B of the aluminum material 2 becomes R ₀ + Z≈R ₀ + R ₁ + Z, and both portions A and B
The current density at is I ₁ ≈I ₂ . As a result, the surface after electrolytic coloring has a uniform color tone. In order to make the solution resistance in the usual bath composition range relatively small so that it can be ignored, it is necessary to grow the barrier layer to a thickness of 50 nm or more. However, in the conventional electrolytic bath composition, film destruction such as spalling occurs and coloring becomes impossible. Therefore, the thickness of the barrier layer was about 15 nm. The limitation on the thickness of the barrier layer is due to the use of an electrolytic bath containing sulfate ions. That is, the barrier layer is
It has a structure in which the anions of the electrolytic solution are partially unevenly distributed in the amorphous alumina, and when the sulfuric acid electrolytic solution is used, the outer layer portion of the porous film has many sulfate ions, and the aluminum side is pure alumina. And in the case of sulfuric acid electrolyte,
Since the thickness of the anion-mixed layer was thicker than that of the other electrolytes and had a high solubility in alumina, electrolysis at a high voltage was not possible and the barrier layer could not be grown thicker than 15 nm.

On the other hand, in the present invention, it was found that electrolysis can be performed even at a high voltage by using an electrolytic bath having a composition containing no sulfate ion. This is because the generated film is difficult to dissolve because it does not contain sulfuric acid. For example, a sulfamic acid-based electrolytic bath has a large molecule of sulfamic acid as compared with sulfuric acid, and thus is difficult to enter the barrier layer, and also has a very weak acidity and a small ability to dissolve a film. Further, since the barrier layer is grown thick, the barrier layer does not dissolve early in acid rain or the like, and corrosion of the aluminum substrate is suppressed. However, when the barrier layer has a thickness of more than 150 nm, the color tone after coloring tends to be uneven due to spalling. Further, by expanding the bottom of the micropores by re-anodizing film treatment, it is possible to better suppress the occurrence of coloring non-uniformity due to changes in materials and electrolysis conditions, and to form further micropores under the expanded bottom. As a result, it becomes possible to obtain various colored states due to the difference in the amount of deposited metal while using the same bath.

[0014]

Embodiment

Example 1: As an aluminum test material to be colored, an aluminum alloy A6063T ₆ having irregularities as shown in FIG. 4 was used.
The extruded profile was used. Width 300 mm, length 500 m
A sulfuric acid solution having a concentration of 160 g / l was put into an electrolytic cell having a depth of 300 mm and a depth of 300 mm and kept at 20 ° C. The aluminum material is used as the anode in this sulfuric acid bath, and the current density is 30 A at a current density of 1.5 A / dm ² .
Electrolyzed for 10 minutes and has micropores with a diameter of 10 nm and a thickness of 13 μm
An anodic oxide film was formed. After washing with water, nickel sulfamate 100 g / l, boric acid 50 g / l, tartaric acid 2 g / l
In a coloring bath having a bath temperature of 20 ° C., the aluminum material was used as an anode in the first step, and electrolysis was performed at a DC constant current of 0.3 A / dm ² until the voltage reached 70 V. This gives a thickness of 7
A 0 nm barrier layer was formed. Subsequently, in the same bath, electrolysis was carried out for 2 minutes with a rectangular wave alternating current (10 Hz, effective current density 0.3 A / dm ² , peak voltage 70 V) as the second step. When the color of the colored aluminum material was examined at points A and B in FIG. 4, L ^* = 45.
1, a ^* = 4.3, b ^* = 9.5, L ^* = 4 at point B
It was 5.7, a ^* = 4.6, b ^* = 9.8. Color _{^{difference, ΔE * ab = [(L}} A * -L B *) 2] + [(a A * -
^{_{a B *) 2] + [}} (b A * -b B *) 2] was ^1/2 = 0.7. That is, it was confirmed that the color tone of the aluminum material was smaller than the limit value of 1 to 3, which is the visually determinable limit value, and that the color tone of the aluminum material was finished uniformly.

Example 2 The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then, in the same coloring bath at 20 ° C. as in Example 1, the first step was to use an aluminum material as an anode and a DC constant current of 0.3 A.
Electrolysis was performed at a voltage of / dm ² to a voltage of 60 V to form a barrier layer having a thickness of 60 nm. Continue in the same bath, second
As a step, DC cathode electrolysis was performed at a current density of 0.15 A / dm ² for 3 minutes. When the color of the colored aluminum material was examined at points A and B in FIG. 4,
At point A, L ^* = 61.3, a ^* = 2.9, b ^* = 4.
At point 9 and B, L ^* = 62.0, a ^* = 3.2, b ^* =
It was 4.9, and both had a light brown color tone. The color difference was ΔE ^* _ab = 0.8, which was smaller than the visually permissible limit values 1 to 3, and it was confirmed that the color tone of the aluminum material was finished uniformly.

Example 3: The same electrolytic cell and aluminum material as in Example 1 were used, and similarly anodized.
Next, cobalt phosphate 50 g / l, boric acid 30 g / l,
2 including tartaric acid 2g / l and magnesium hydroxide 1g / l
In a coloring bath at 0 ° C., as a first step, an aluminum material was used as an anode and electrolysis was performed at a DC constant current of 0.2 A / dm ² until the voltage reached 90 V, to form a barrier layer having a thickness of 90 nm. Subsequently, in the same bath, electrolysis was performed as a second step with a sinusoidal alternating current (5 Hz, effective current density 0.2 A / dm ² , peak voltage 90 V) for 4 minutes. When the color of the colored aluminum material was examined at points A and B in FIG. 4, L ^* = 30.4, a ^* = 5.2, b at point A
^* = 10.3, L ^* = 30.6 at point B, a ^* = 5.
1, b ^* = 10.1, and both had a dark brown color tone. The color difference was ΔE ^* _ab = 0.3, which was smaller than the visually discriminable limit values 1 to 3, and it was confirmed that the color tone of the aluminum material was finished uniformly.

Example 4 The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then, in a coloring bath containing nickel sulfamate 50 g / l, cobalt phosphate 20 g / l, boric acid 50 g / l and tartaric acid 2 g / l at 20 ° C., the first step was to use an aluminum material as an anode and a DC constant current of 0.3 A. / Dm ² and voltage is 9
Electrolysis was carried out to 0 V to form a barrier layer having a thickness of 90 nm. Subsequently, in the same bath, as a second step, electrolysis was performed for 2 minutes with a rectangular wave alternating current (10 Hz, constant voltage, peak voltage 90 V). Regarding the aluminum material after coloring, FIG.
When the color was examined at points A and B, L ^* = 7 at point A
4.4, a ^* = 3.6, b ^* = 5.4, L ^* = B point
74.0, a ^* = 3.5, b ^* = 5.2, both of which had a light brown color tone. The color difference is ΔE ^* _ab = 0.
It was 5 which is smaller than the limit value 1 to 3 that can be visually judged, and it was confirmed that the color tone of the aluminum material was finished uniformly.

Example 5: The same electrolytic cell and aluminum material as in Example 1 were used, and similarly anodized.
Then, in a solution at 20 ° C. containing 100 g / l phosphoric acid,
The aluminum material was used as an anode and subjected to anodic electrolysis at a direct current of 20 V for 2 minutes to expand the portion of the bottom of the micropores having a length of 50 nm to a diameter of 30 nm. The re-anodized film,
In the same coloring bath at 20 ° C. as in Example 1, the first step was to use an aluminum material as an anode and a constant DC current of 0.3 A / dm 2.
Electrolysis was performed at ² until the voltage reached 80 V to form a barrier layer having a thickness of 80 nm. Subsequently, in the same bath, as a second step, a rectangular wave alternating current (10 Hz, effective current density 0.3 A / d
Electrolysis was carried out for 2 minutes at m ² and peak voltage of 80V. The color of the colored aluminum material was examined at points A and B in FIG. 4, and L ^* = 61.7, a ^* = − at point A.
1.4, b ^* =-4.6, L ^* = 62.0 at point B, a
^* =-1.4 and b ^* =-5.1, and both had a gray-blue color tone. The color difference was ΔE ^* _ab = 0.6, which was smaller than the visual judgment limit values 1 to 3, and it was confirmed that the color tone of the aluminum material was finished uniformly.

Example 6 The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then, in a solution of tartaric acid (50 g / l) at 35 ° C., anodic electrolysis was carried out at a direct current of 20 V for 4 minutes to expand a portion of the bottom of the micropores having a length of 100 nm to a diameter of 30 nm. The re-anodized film was anodized with an aluminum material as the first step in the same coloring bath at 20 ° C. as in Example 1,
Electrolysis was performed at a DC constant current of 0.3 A / dm ² until the voltage reached 110 V to form a barrier layer having a thickness of 110 nm. Then, in the same bath, square wave alternating current (10H
Electrolysis was performed for 3 minutes at z and peak voltage of 110 V). The color of the colored aluminum material was examined at points A and B in FIG. 4, and at the point A, L ^* = 53.2, a ^* =
0.6, b ^* =-18.5, L ^* = 53.5 at point B,
a ^* = 0.7 and b ^* =-18.0, both of which had a blue color tone. The color difference was ΔE ^* _ab = 0.6, which was smaller than the visual determination limit values 1 to 3, and it was confirmed that the color tone of the aluminum material was finished uniformly.

Example 7: The same electrolytic cell and aluminum as in Example 1
A minium material was used and similarly anodized.
Then, a solution containing 5 g / l of sodium hydroxide at 15 ° C.
Anode electrolysis at DC 15V for 1 minute in
Expand the bottom of the pores with a length of 30 nm to a diameter of 30 nm.
Was. The same film as in Example 1 was used after the re-anodizing treatment.
The aluminum material is exposed to the first step in a coloring bath at ℃.
DC pole constant current 0.3A / dm ^Two And the voltage is 120V
To form a barrier layer with a thickness of 120 nm
did. Square wave alternating current as the second step in the same bath
Electrolysis was performed at (10 Hz, peak voltage 120 V) for 3 minutes.
Regarding the aluminum material after coloring, points A and B in FIG.
When the color was examined at point A, L at point A^* = 65.8,
a^* = -5.9, b^* = 9.3, L at point B^*= 66.
3, a^* = -6.0, b^* = 9.5 and both are yellow
It had a green hue. Color difference is ΔE^* _ab = 0.5
Is less than the visual judgment limit values 1 to 3, and aluminum
It was confirmed that the color tone of the material was finished uniformly.

Example 8: The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then in a solution containing 100 g / l phosphoric acid at 15 ° C.,
Anodic electrolysis was carried out for 2 minutes at a direct current of 20 V, and a portion having a length of 50 nm at the bottom of the micropores in the coating was expanded to a diameter of 30 nm. Successively, anodic electrolysis was carried out for 50 seconds in a constant current of 0.5 A / dm ² in a bath of sulfuric acid 150 g / l at a bath temperature of 20 ° C., and further 10 nm in diameter and 120 n in depth under the expanded bottom pore.
Then, a re-anodized film of m was formed again and washed thoroughly with water.
Then, in the same coloring bath as in Example 1 at 20 ° C., the aluminum material was used as an anode in the first step, and a DC constant current of 0.3 was used.
Electrolyze until the voltage reaches 120 V at A / dm ² , then 120
A barrier layer having a thickness of nm was formed. Subsequently, in the same bath, electrolysis was performed for 3 minutes with a rectangular wave alternating current (10 Hz, peak voltage 120 V) as the second step. When the color of the colored aluminum material was examined at points A and B in FIG. 4, L ^* = 63.6, a ^* =-0.5, b ^* = at point A
17.7, L ^* = 63.1, a ^* =-0.4 at point B,
b ^* = 17.2, and both had a yellow color tone. The color difference is ΔE ^* _ab = 0.7, which is the limit value 1 of visual judgment.
It was confirmed that the color tone of the aluminum material was smaller than 3 and the color tone of the aluminum material was finished uniformly.

Comparative Example 1: The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Next, nickel sulfate 100 g / l, boric acid 50 g / l,
In a coloring bath containing 20 g of tartaric acid at 20 ° C., the first step is to use an aluminum material as an anode and a constant DC current of 0.3 A /
When electrolysis was attempted until the voltage reached 70 V at dm ² , the film was broken by pitting and the electrolysis voltage could only be increased to 45 V. Therefore, the colored electrolysis in the second stage had to be stopped in the same bath, and a colored film could not be obtained.

Comparative Example 2: The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then, in the same nickel sulfate coloring bath at 20 ° C. as in Comparative Example 1, as a first step, an aluminum material was used as an anode and electrolysis was performed at a DC constant current of 0.3 A / dm ² until the voltage reached 40 V, and a barrier layer having a thickness of 40 nm was used. Was formed. Subsequently, in the same bath, as a second step, electrolysis was performed for 2 minutes with a rectangular wave alternating current (10 Hz, effective current density 0.3 A / dm ² , peak voltage 40 V). FIG. 4 shows the colored aluminum material.
When the color was examined at points A and B, L point L ^*
= 35.1, a ^* = 4.8, b ^* = 10.3 dark brown,
At point B, L ^* = 40.1, a ^* = 3.3, b ^* = 9.8.
It was brown. The color difference was ΔE ^* _ab = 5.2, and obvious color unevenness occurred.

Comparative Example 3: The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
Then, in a bath at 20 ° C. containing 100 g / l phosphoric acid, 20
Anodic electrolysis was performed for 2 minutes for V. Cobalt sulfate 30g / l, magnesium sulfate 15
In a coloring bath containing 20 g / l of boric acid and 15 g / l of boric acid, the first step was to use an aluminum material as an anode and electrolysis at a DC constant current of 0.3 A / dm ² until the voltage reached 80 V. Coating damage due to coating,
The electrolysis voltage could only be increased up to 45V. Therefore, the colored electrolysis in the second stage had to be stopped in the same bath, and a colored film could not be obtained.

Comparative Example 4: The same electrolytic cell and aluminum material as in Example 1 were used, and anodizing treatment was similarly performed.
The anodic oxide film was subjected to anodic electrolysis for 2 minutes at a direct current of 20 V in a solution containing phosphoric acid of 100 g / l at 15 ° C., and the bottom portion of the micropores having a length of 50 nm was enlarged to a diameter of 30 nm. Then a direct current of 0.
Anode electrolysis was performed at 5 A / dm ² for 50 seconds and the diameter was 10
nm and a length of 120 nm were formed. Then, using a coloring bath containing nickel sulfate 50 g / l and boric acid 50 g / l at 20 ° C., the first step is to use an aluminum material as an anode and electrolyze at a constant DC current of 0.3 A / dm ² until the voltage reaches 30 V. , A 30 nm thick barrier layer was formed.
Then, in the same bath, a rectangular wave alternating current (10
Electrolysis was performed for 3 minutes at 30 Hz and a peak voltage of 30 V). When the color of the colored aluminum material was examined at points A and B in FIG. 4, L ^* = 41.3, a ^* = − at point A
7.4, b ^* = 0.3 dark green, and L ^* = 40.
The dark blue color was 8, a ^* = 0.3 and b ^* =-6.9.
The color difference was ΔE ^* _ab = 10.6, clearly different colors were mixed, and the coloring was uneven.

The corrosion resistance of the aluminum material treated in each of the above examples was investigated by the Cass corrosion resistance test according to JIS H8681 and JIS H8601. The survey results are shown in Table 1 as rating numbers. The rating number is represented by a numerical value corresponding to the corrosion area ratio, and a high numerical value indicates that the corrosion resistance is excellent. As is clear from Table 1, the test pieces colored according to the present invention are superior in corrosion resistance to the test materials of Comparative Examples.

[0027]

Further, the aluminum materials colored in Examples 4 and 8 and Comparative Examples 2 and 4 were immersed in pure water at 95 ° C. for 30 minutes to seal the fine pores of the anodic oxide film. With respect to each sample after the sealing treatment, the insulation breakdown voltage was measured in a room at a temperature of 25 ° C. and a relative humidity of 60% using an insulation voltage measuring device. The dielectric breakdown voltage was obtained by applying an alternating voltage to the film gradually and causing a current to flow rapidly. Table 2 shows the survey results. Example 4 and Comparative Example 2 and Example 8 and Comparative Example 4 were all treated under the same conditions except for the coloring treatment. However, as seen in Table 2, Examples 4 and 8 show higher dielectric breakdown voltage than Comparative Examples 2 and 4. From this, it is also understood that the aluminum material colored according to the present invention can be used as an electric part or the like requiring a withstand voltage.

[0029]

[0030]

As described above, in the present invention, a coloring liquid containing no sulfate is used, and a barrier layer of 5 is used.
By coloring and electrolyzing a film grown to a thickness of 0 to 150 nm, a stable color tone without color unevenness is developed and corrosion resistance is improved. The aluminum material having a colored film having a uniform color tone thus obtained is
Used in various fields such as building materials. Further, since it has excellent withstand voltage characteristics, it is also used as a material for electric parts and the like. Further, by changing the structure of the fine pores in which the metal is deposited and filled by the electrolytic coloring treatment, it is possible to improve the level of coloring uniformity and achieve diversification of coloring states.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating that the current density varies depending on the distance between the aluminum material and the counter electrode during electrolytic coloring.

FIG. 2 is a diagram for explaining a difference in current density with an electrical equivalent circuit.

FIG. 3 is a chart for explaining the shape change of fine pores in an anodized film and the state of metal deposition for coloring for each electrolytic coloring method.

FIG. 4 is a perspective view showing an aluminum test material used in Examples.

Claims (3)

[Claims] 1. A colored anolyte film containing a sulphate-free colored electrolyte containing one or more kinds of metal salts selected from phosphoric acid, chromic acid, boric acid, sulfamic acid, oxalic acid and citric acid and containing no sulfate. The aluminum material on which the
Electrolytic coloring of an aluminum material, characterized in that a barrier layer containing no sulfate ion having a thickness of 50 to 150 nm is formed by direct current anode electrolysis of 0 to 150 V, and then the aluminum material is subjected to direct cathodic electrolysis or alternating current electrolysis in the same solution. Method. 2. An aluminum material on which a porous anodic oxide film is formed is re-anodized in an acid or alkali solution to enlarge the bottom of the fine pores, and then the aluminum material to be electrolytically colored according to claim 1. Electrolytic coloring method. 3. An aluminum material on which a porous anodic oxide film is formed is reanodized in an acid or alkali solution to enlarge the bottom of the micropores, and then re-anodizing treatment to further lengthen the micropores. A method for electrolytically coloring an aluminum material, wherein the electrolytic coloring is performed according to claim 1.