JPH06136598A - Method for coloring aluminum anodic oxide film - Google Patents

Abstract

PURPOSE:To obtain various color tones which have not been attained by previously DC-anodizing an anodic oxide film at a specified voltage. CONSTITUTION:An aluminum anodic oxide film is formed by anodization. The film is electrolytically colored in an electrolytic bath contg. plural kinds of metals having a different voltage at which the essential deposition reaction occurs as their salts. In this case, the anodic oxide film is previously DC- anodized at an optional voltage higher than the anodization voltage and lower than 30V. Ni and Zn are used as the plural kinds of metals. Consequently, the color tone is optionally controlled and changed within the range determined by the metal to be used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method of electrolytically coloring an aluminum anodic oxide coating by using a plurality of kinds of metals having different voltages at which a main precipitation reaction occurs. It is related to the method of making it possible to control. The aluminum anodic oxide film is an anodic oxide film formed on aluminum or an aluminum alloy.

[0002]

2. Description of the Related Art With the diversification of demand and taste in recent years, it has been required to color aluminum anodic oxide coatings in various color tones. Therefore, in the conventional electrolytic coloring treatment, a plurality of kinds of metals are used to diversify the obtained color tone. Since a plurality of kinds of metals differ in the voltage at which the main precipitation reaction occurs, the voltage of the above electrolytic coloring treatment is usually adjusted to the metal having the highest voltage at which the main precipitation reaction occurs. In this case, a metal having a low voltage causing the main precipitation reaction was also deposited, the amount thereof was almost fixed, and the obtained color tone was also almost fixed.

However, if various color tones that have not yet been obtained can be obtained even though the same electrolytic coloring treatment is carried out, it is considered that it is possible to cope with the diversification of demand preference more.

[0004]

An object of the present invention is to provide a method for coloring an aluminum anodic oxide film which can be obtained by controlling various color tones including those which have not been obtained yet, while performing the same electrolytic color treatment as in the prior art. The purpose is to do.

[0005]

The present invention is characterized in that an aluminum anodic oxide film formed by anodizing is electrolyzed in an electrolytic bath containing a plurality of kinds of metals, each having a different voltage at which a main precipitation reaction occurs, as a salt. A method of coloring by performing a coloring treatment, characterized in that the anodized film is previously subjected to DC anodic electrolysis at an arbitrary voltage within a range of 30 V or less, which is higher than the voltage of the anodizing treatment. is there.

The anodizing treatment is performed by a conventional method.

Examples of salts of plural kinds of metals include, for example,
(i) Ni and Zn, (ii) Ag and Cu, (iii) Ni, C
o, Cu, and the like. Not limited to two types, three or more types may be used.

[0008]

When the direct current anodic electrolysis is applied, the thickness of the barrier layer of the aluminum anodic oxide film is increased. Therefore, during the electrolytic coloring treatment, it becomes difficult for the current to flow at a low voltage, the deposition reaction of the metal having a low voltage where the main deposition reaction occurs is suppressed and the deposition amount becomes small, and when direct current anodic electrolysis is not performed. In contrast, the color tone will be different. The thickness of the barrier layer increases as the voltage of DC anode electrolysis increases.
The deposition reaction of a metal having a low voltage causing the main deposition reaction is suppressed as the thickness of the barrier layer is increased, and thus the obtained color tone changes depending on the voltage of the DC anode electrolysis.

For example, when (i) Ni and Zn are used, the precipitation of Ni is suppressed, the color tone is controlled in the range from yellowish gray to achromatic gray, and (ii) Ag and Cu are used.
When Ag is used, the precipitation of Ag is suppressed, and the color tone is controlled in the range from persimmon to reddish brown. (Iii) When Ni, Co, and Cu are used, the precipitation of Ni and Co is suppressed. , The color tone is controlled in the range from reddish light gray to reddish dark gray.

If the voltage of the DC anodic electrolysis is not more than the voltage of the anodic oxidation treatment, the thickness of the barrier layer does not increase, so that the above-mentioned action by the DC anodic electrolysis cannot be exhibited, and therefore the color tone does not change. When the DC anode electrolysis voltage is higher than 30 V, the barrier layer becomes too thick, and almost no current flows in the electrolytic coloring treatment, which makes it difficult for metal deposition to occur, and thus does not cause coloring.

[0011]

【Example】

(Comparative Example 1) An aluminum material (A6063S) on which an anodized film having a thickness of 9 μm was formed by anodizing by a conventional method using a sulfuric acid bath was placed in an electrolytic bath under the conditions (composition, bath, counter electrode) shown in Table 1. And was electrolyzed at 30 V for 3 minutes by a constant voltage AC electrolysis with a hard start. The color tone of the colored anodized film was a grayish yellow.

[0012]

[Table 1]

(Example 1) An aluminum anodic oxide film formed by the same anodic oxidation treatment as in Comparative Example 1 was dipped in an electrolytic bath under the conditions shown in Table 1 and preliminarily kept at 20 V for 1 minute and 2 minutes.
DC anodic electrolysis by soft start for 0 seconds, then,
The same AC constant voltage electrolysis as in Comparative Example 1 was performed to perform electrolytic coloring treatment. The color tone of the colored anodized film was an achromatic gray.

The difference in color tone obtained between Example 1 and Comparative Example 1 is based on direct current anodic electrolysis. This will be described below. When the same aluminum anodized film as in Example 1 was subjected to AC voltage scanning in an electrolytic bath under the conditions shown in Table 1, the result shown by the broken line A in FIG. 1 was obtained. The scanning voltage is boosted at 0.1 V / sec. In FIG. 1, the peak A ₁ near 15 V is due to the Ni precipitation reaction, and the peak A ₂ near 26 V is due to the Zn precipitation reaction. By the way, when the same aluminum anodic oxide coating as described above was subjected to AC constant voltage electrolysis by hard start for 3 minutes at 15 V and 26 V, respectively, a bronze color was obtained at 15 V and a yellowish gray was obtained at 26 V. A yellowish gray color was obtained at 26 V because the precipitation of Ni occurred first and the precipitation of Zn subsequently occurred.

On the other hand, the same aluminum anodic oxide film as described above was previously subjected to the same direct current anodic electrolysis as in Example 1,
When AC voltage scanning is performed under the same conditions as above, the result shown by the alternate long and short dash line B in FIG. 1 is obtained. Peak B ₂ due to Zn precipitation reaction
Has almost the same voltage and current density as the peak A ₂ of the broken line A, but the peak B ₁ due to the Ni precipitation reaction is the broken line A 2.
The current density is lower than the peak A ₁ of the above. That is, when direct current anodic electrolysis is performed in advance, the precipitation reaction of Ni is reduced. By the way, the aluminum anodic oxide film, which had been subjected to the same direct current anodic electrolysis as in Example 1, was applied at a voltage of peak B ₁ and a peak B ₂ for 3 hours.
Min, when AC constant voltage electrolysis by hard start,
A light bronze color was obtained at the voltage of peak B ₁ and an achromatic gray color was obtained at the voltage of peak B ₂ .

Further, the same aluminum anodic oxide film as described above was subjected in advance to the same DC anodic electrolysis as in Example 1 except that the voltage was 30 V and the other conditions were the same. The result is shown in C. The peak C ₁ due to the precipitation reaction of Ni and the peak C ₂ due to the precipitation reaction of Zn have lower current densities than the peaks B ₁ and B ₂ of the chain line B. That is, the higher the voltage of the DC anode electrolysis, the less the precipitation reaction of Ni and Zn. By the way, an aluminum anodized film having a voltage of 30 V and the same DC anodic electrolysis as in Example 1 was applied in advance for 3 minutes at a voltage of peak C ₁ and a peak C ₂ respectively, and an AC constant was determined by a hard start. When voltage electrolysis was performed, a light bronze color was obtained at the voltage of peak C ₁ , and a light achromatic gray was obtained at the voltage of peak C ₂ .

The aluminum anodic oxide film, which had been subjected to the same DC anodic electrolysis as in Example 1 in advance, was subjected to 18 V (peak B
₁ )), 22V, 26V (equivalent to peak B ₂ ), 30
When constant voltage AC electrolysis was performed in an electrolytic bath under the conditions shown in Table 1 at V, and the amounts of Ni and Zn deposited in the obtained colored film were measured, the results are shown in FIG. That is, as the voltage increases, the amount of Ni decreases and the amount of Zn increases. Even at 30V, Ni was precipitated. Therefore, at the voltage of peak A ₂ and peak B ₂ ,
It is considered that not only Zn was deposited, but Ni and Zn and their intermetallic compounds were deposited. Table 2 shows the color measurement results (Hunter color system) of the colored film obtained by each of the above voltages with a color difference meter. Table 2 shows the aluminum anodic oxide film having a voltage of 30 V and the same DC anodic electrolysis as in Example 1 except that
In case of alternating voltage electrolysis at 18V and 30V respectively,
The case where AC constant voltage electrolysis at 30 V is performed without performing DC anodic electrolysis is also shown.

[0018]

[Table 2]

As described above, when direct current anodic electrolysis is performed on the aluminum anodic oxide film, the barrier layer is modified, that is, the thickness of the barrier layer increases, and it becomes difficult for current to flow at a low voltage. The precipitation reaction of Ni, which is the main precipitation reaction at a low voltage, is suppressed, that is, the amount of Ni precipitation is reduced, and the color tone changes from a yellowish gray to an achromatic gray. In Example 1, the voltage of DC anodic electrolysis is set to 20V and 30V, but the voltage of DC anodic electrolysis is 20V if the voltage is higher than the voltage of anodic oxidation treatment for forming an anodic oxide film and is 30V or less, Three
It is not limited to 0V. By arbitrarily setting the voltage of DC anode electrolysis within the above range, the thickness of the barrier layer can be arbitrarily increased, the Ni precipitation reaction can be arbitrarily suppressed, and the color tone can be changed from yellowish gray to achromatic gray. It can be arbitrarily changed within the range.

Comparative Example 2 An aluminum material (A1050P) on which an anodized film having a thickness of 9 μm was formed by anodizing by a conventional method using a sulfuric acid bath was used under the conditions (composition, bath, counter electrode) shown in Table 3. It was immersed in an electrolytic bath and subjected to AC constant voltage electrolysis by hard start at 25V for 3 minutes to perform electrolytic coloring treatment. The color tone of the colored anodized film was persimmon.

[0021]

[Table 3]

(Example 2) An aluminum anodic oxide film formed by the same anodic oxidation treatment as in Comparative Example 2 was immersed in an electrolytic bath under the conditions shown in Table 3 and preliminarily kept at 22 V for 1 minute for 2 minutes.
DC anode electrolysis with 2 seconds soft start, followed by:
The same AC constant voltage electrolysis as in Comparative Example 2 was performed to carry out electrolytic coloring treatment. The color tone of the colored anodized film was reddish brown.

The difference in color tone obtained between Example 2 and Comparative Example 2 is based on DC anodic electrolysis. This will be described below. When the same aluminum anodized film as in Example 2 was subjected to AC voltage scanning in an electrolytic bath under the conditions shown in Table 3, the result shown by the broken line D in FIG. 3 was obtained. The scanning voltage is boosted at 0.1 V / sec. In FIG. 3, the peak D ₁ near 18 V is due to the precipitation reaction of Ag, and the peak D ₂ near 25 V is due to the precipitation reaction of Cu. By the way, when the same aluminum anodic oxide film as described above was subjected to AC constant voltage electrolysis by a hard start at 25 V for an energization time of 3 minutes, a persimmon color was obtained as indicated by * in Table 4. This is because the precipitation of Ag occurred first, and the precipitation of Cu subsequently occurred.

On the other hand, the same aluminum anodic oxide film as described above was previously subjected to the same DC anodic electrolysis as in Example 2,
When the AC voltage is scanned under the same conditions as above, the result shown by the solid line E in FIG. 3 is obtained. The peak E ₂ due to the Cu precipitation reaction has almost the same voltage and current density as the peak D _{2 of the} broken line C, but the peak E ₁ due to the precipitation reaction of Ag has a current density lower than that of the peak D _{1 of the} broken line D. It's getting low. That is, when direct current anodic electrolysis is performed in advance, the precipitation reaction of Ag is reduced. By the way, an aluminum anodic oxide film that had been subjected to the same direct current anodic electrolysis as in Example 2 in advance was set to 18 V.
(Equivalent to peak E ₁ ) and 25V (corresponding to peak E ₂ ) were subjected to AC constant voltage electrolysis by hard start for 3 minutes respectively, as shown in Table 4, and as shown in Table 4, gold was colored at 18V and red at 25V. A brown color was obtained.

[0025]

[Table 4]

As described above, when direct current anodic electrolysis is performed on the aluminum anodic oxide film, the thickness of the barrier layer increases, and it becomes difficult for the current to flow at a low voltage, and the main deposition reaction at a voltage lower than Cu occurs. The precipitation reaction of Ag that occurs is suppressed, that is, the amount of Ag precipitation is reduced, and the color tone changes in the range from persimmon to reddish brown. In Example 2, the voltage of the DC anodic electrolysis is set to 22V, but the voltage of the DC anodic electrolysis is limited to 22V as long as it is in the range of 30V or less higher than the voltage of the anodizing treatment for forming the anodized film. is not. By arbitrarily setting the voltage of the DC anode electrolysis within the above range, the thickness of the barrier layer can be arbitrarily increased, the precipitation reaction of Ag can be arbitrarily suppressed, and the color tone can be arbitrarily changed within the range from persimmon to reddish brown. be able to.

Comparative Example 3 An aluminum material (A1100P) on which an anodized film having a thickness of 9 μm was formed by anodizing by a conventional method using a sulfuric acid bath was prepared under the conditions (composition, bath, counter electrode) shown in Table 5. It was immersed in an electrolytic bath and subjected to an AC constant voltage electrolysis by a hard start at 28 V for 3 minutes to carry out an electrolytic coloring treatment. The color tone of the colored anodized film was reddish light gray.

[0028]

[Table 5]

(Example 3) An aluminum anodic oxide film formed by the same anodic oxidation treatment as in Comparative Example 3 was immersed in an electrolytic bath under the conditions shown in Table 5 and preliminarily kept at 20 V for 1 minute for 2 minutes.
DC anodic electrolysis by soft start for 0 seconds, then,
The same AC constant voltage electrolysis as in Comparative Example 3 was performed to perform electrolytic coloring treatment. The color tone of the colored anodized film was reddish dark gray.

The difference in color tone obtained between Example 3 and Comparative Example 3 is based on DC anodic electrolysis. This will be described below. When the same aluminum anodized film as in Example 3 was subjected to AC voltage scanning in an electrolytic bath under the conditions shown in Table 5, the result shown by the broken line F in FIG. 4 was obtained. The scanning voltage is boosted at 0.1 V / sec. In FIG. 4, the peak F ₁ near 14 V is due to the Ni precipitation reaction, the peak F ₂ near 18 V is due to the Co precipitation reaction, and the peak F ₃ near 28 V is due to the Cu precipitation reaction. is there. By the way, the same aluminum anodic oxide coating as above was electrolyzed by constant-voltage AC at 28 V for 3 minutes with a current-carrying time of 3 minutes.
As shown in, a reddish light gray was obtained. This is because the precipitation of Ni first occurs, then the precipitation of Co occurs,
This is because the precipitation of Cu subsequently occurred.

On the other hand, the same aluminum anodic oxide film as described above was previously subjected to the same DC anodic electrolysis as in Example 3,
When AC voltage scanning is performed under the same conditions as above, the result shown by the solid line G in FIG. 4 is obtained. The peak G ₃ due to the Cu precipitation reaction has almost the same voltage and current density as the peak F _{3 of the} broken line E, but the peak G ₁ due to the Ni precipitation reaction and the peak G ₂ due to the Co precipitation reaction are the peaks of the broken line E. The current density is lower than that of F ₁ and peak F ₂ . That is, when direct current anodic electrolysis is performed in advance, the precipitation reactions of Ni and Co are reduced. By the way, the aluminum anodic oxide film previously subjected to the same DC anodic electrolysis as in Example 3
V (corresponding to peak G ₂ ) and 28V (corresponding to peak G ₃ )
When a constant-current AC electrolysis was carried out by a hard start for 3 minutes each with an energizing time, a bronze color was obtained at 18V and a reddish dark gray was obtained at 28V, as shown in Table 6.

[0032]

[Table 6]

As described above, when direct current anodic electrolysis is performed on the aluminum anodic oxide film, the thickness of the barrier layer increases, and it becomes difficult for the current to flow at a low voltage, and the main deposition reaction at a voltage lower than Cu occurs. The precipitation reaction of Ni and Co that occurs occurs is suppressed, that is, the precipitation amount of Ni and Co is reduced, and the color tone changes from a reddish light gray to a reddish dark gray. In Example 3, the voltage of DC anodic electrolysis is set to 20V, but the voltage of DC anodic electrolysis is limited to 20V as long as it is within the range of 30V or less higher than the voltage of the anodic oxidation treatment for forming the anodic oxide film. is not. By arbitrarily setting the voltage of the DC anode electrolysis within the above range, the thickness of the barrier layer can be arbitrarily increased, the precipitation reaction of Ni and Co can be arbitrarily suppressed, and the color tone from reddish light gray to red. It can be changed as desired within the range of tasteful dark gray.

(Example 4) In Examples 1 to 3, the DC anode electrolysis and the subsequent electrolytic coloring treatment are carried out in the same electrolytic bath, but they may be carried out in different electrolytic baths. Play. For example, when the DC anode electrolysis in Example 3 and the electrolytic coloring treatment are performed in different baths, Table 5
Among the bath compositions shown in (1), a bath containing pH 3.8 and a bath temperature of 20 ° C. and containing only H ₃ BO ₃ as a component was used as a DC anode electrolysis bath. A bath containing a metal salt may be used as a bath for electrolytic coloring treatment. The same applies to the cases of Examples 1 and 2, and among the bath compositions shown in Tables 1 and 2, NH ₄ C ₇ H ₅ O ₃ as a component for the DC anodic electrolysis bath (in the case of Example 1) , H ₂ SO ₄ (in the case of Example 2) only, and a bath containing the remaining metal salt as a component may be used as the electrolytic coloring treatment bath.

[0035]

As described above, according to the coloring method of the present invention, the aluminum anodic oxide film formed by the anodic oxidation treatment is an electrolytic bath containing as a salt a plurality of kinds of metals having different voltages at which the main precipitation reactions occur. In this method, the anodic oxide film is subjected to direct current anodic electrolysis at an arbitrary voltage in the range of 30 V or less, which is higher than the voltage of the anodic oxidation treatment. By increasing the thickness of the barrier layer of the oxide film to an arbitrary thickness, it is possible to suppress the deposition amount of the metal having a low voltage causing the main deposition reaction in the electrolytic coloring treatment. That is, by arbitrarily changing the voltage of the DC anode electrolysis within the above range, the deposition amount of the metal having a low voltage in which the main deposition reaction occurs is arbitrarily suppressed, and the color tone is arbitrarily set within the range determined by the metal used. It can be controlled and changed. Therefore, it is possible to obtain various color tones that have not yet been obtained, even though the electrolytic coloring treatment is performed using the same metal as in the past, and it is possible to cope with the diversification of demand tastes.

For example, if Ni and Zn are used as the metal, a very strongly desired achromatic gray can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the action of DC anode electrolysis in Example 1.

FIG. 2 is a diagram for explaining the action of direct current anode electrolysis in Example 1.

FIG. 3 is a diagram for explaining the action of DC anode electrolysis in Example 2.

FIG. 4 is a view for explaining the action of direct current anode electrolysis in Example 3;

Claims (2)

[Claims] 1. A method for coloring an aluminum anodic oxide film formed by anodizing treatment by electrolytic coloring treatment in an electrolytic bath containing a plurality of kinds of metals, each of which has a different voltage at which a main precipitation reaction occurs, as a salt. In advance, the voltage applied to the anodized film should be greater than the voltage applied in the anodizing treatment.
A method for coloring an aluminum anodic oxide film, which comprises subjecting a DC anodic electrolysis to an arbitrary voltage within a range of 0 V or less. 2. The method for coloring an aluminum anodic oxide film according to claim 1, wherein the plurality of kinds of metals are Ni and Zn.