JP3445154B2 - Manufacturing method of colored aluminum material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a colored aluminum material, and more specifically, to anodize an anodized film formed by anodizing an aluminum material in an electrolytic solution containing a high voltage type electrolyte. Related to coloring technology. In this specification, the aluminum material means
It is a general term for aluminum and aluminum alloys.

[0002]

2. Description of the Related Art With the recent diversification of consumer life and demand preference, it has been required to color aluminum products with various colors or patterns. Conventionally, as a method for coloring an anodized aluminum material, an electrolytic coloring method by AC electrolysis in a bath containing a metal salt is well known. In particular, an anodized film obtained by anodizing at a high voltage in an electrolytic solution containing a high voltage type electrolyte, for example, an anodized film obtained by anodizing at a high voltage using phosphoric acid or an organic acid, Since it has a dense barrier layer and is excellent in corrosion resistance, abrasion resistance, etc., it may be desired to electrolytically color such an anodized film.

However, the AC electrolytic coloring method has a drawback that it cannot be colored at a voltage considerably lower than an applied voltage (hereinafter referred to as an anodizing voltage) during anodizing treatment. This is because the (−) component of the alternating current is not affected by the anodizing voltage, but the (+) component begins to flow only after the peak voltage thereof reaches about 70 to 80% or more of the anodizing voltage. . Further, if the voltage during AC electrolytic coloring is too high, the anodic oxide film may peel off from the aluminum base metal. In particular, when electrolytically coloring an oxide film obtained by anodizing at a high voltage as described above, high-voltage alternating current is required, which is not desirable from the viewpoint of energy saving. There is a problem that it is easy to peel off from.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and its basic purpose is to perform anodic oxidation in an electrolytic solution containing a high voltage type electrolyte. An object of the present invention is to provide a method for producing a colored aluminum material, which can electrolytically color an anodized film of an aluminum material obtained by the treatment at a voltage lower than the anodizing voltage and can form a colored oxide film having excellent film performance. Further, the object of the present invention is to provide an aluminum material which has sufficient light resistance and durability even when it is used outdoors, has no discoloration or fading, is robust, and has a colored oxide film of a desired color that is bright and has a relatively low level. It is an object of the present invention to provide a method which can be produced in an electrolytic coloring solution containing a metal salt at a high concentration in a short time.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, an aluminum material is anodized at a high voltage of 30 V or more in an electrolytic solution containing a high voltage type electrolyte. After the treatment, in an electrolytic coloring solution containing a metal salt and having a conductivity (in the case of an acidic bath of pH 2 or less, the conductivity when a strong acid is removed) of 3.0 to 20 mS / cm, There is provided a method for producing a colored aluminum material, characterized in that an electrolytic coloring treatment is performed by applying an AC voltage having a peak voltage that is equal to or lower than the voltage used during anodizing treatment and that is 1/2 or more thereof. In a preferred embodiment, the metal salt content is 0.5 to
An electrolytic coloring liquid contained at a rate of 100 g / l is used.

According to the second aspect of the present invention, an aluminum material is subjected to anodizing treatment at a high voltage of 30 V or higher in an electrolytic solution containing a high voltage type electrolyte, and then an electrolytic coloring solution containing a metal salt. Where the peak voltage of the (+) component is an alternating voltage larger than the peak voltage of the (−) component , and
The peak voltage of the (+) component is less than or equal to the voltage during anodizing.
And a method of manufacturing a colored aluminum material, characterized in that electrolytic coloring treatment is performed by applying an AC voltage that is ½ or more of that. In a preferred embodiment, the upper Symbol AC voltage {(+) component of the peak voltage} / - ratio of {() component of the peak voltage} is in the range of 2-12. In the present specification, the peak voltage of the (-) component means a value represented by an absolute value.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The conventional AC electrolytic coloring method is mainly applied to an anodized film obtained by anodizing an aluminum material in an aqueous sulfuric acid solution (hereinafter referred to as anodized sulfuric acid when particularly mentioned). In this case, the AC electrolysis can be carried out at a relatively low voltage, and is generally carried out near the working voltage (about 13 to 16V) at the time of anodizing, that is, about 8 to 25V AC. When the voltage used during AC electrolysis is about 8 V or less, no current flows, so that coloring does not occur. On the other hand, when it exceeds about 25 V, too much current flows and the anodic oxide film peels off (film destruction). This is because the following phenomenon occurs as a coloring mechanism of the anodized film.

(1) When electrolytically coloring, it is necessary to alternate time (instantaneous) and negative (instantaneous) anodized film by alternating current electrolysis. Oxygen generation (understood that the generated oxygen oxidizes and fixes metals and restores the anodized film) and attracts metal ions (electrophoretic deposition of metal ions into the anodized film pores). It is needed to occur. (2) When anodizing treatment is performed at about 15 V to generate sulfuric acid alumite, when the anodized film is an anode, current does not flow when the peak voltage of the (+) component of the AC voltage is about 12 V or less (when flowing). Oxygen essential for coloring is generated). On the contrary, when the anodized film is a cathode, current flows even if the peak voltage of the (-) component of the AC voltage is about 1 to 2 V, and hydrogen is generated. (3) Further, when the anodic oxide film is the cathode, there is no resistance, so that the current that flows increases linearly as the voltage increases. On the other hand, in the case of an anode, a barrier layer at the bottom of the holes of the anodic oxide film grows due to the generation of oxygen, and this becomes a resistance, so that the current gradually stops flowing. Therefore, when the AC voltage (peak voltage is 1.41 times that) is about 8 V or more (peak voltage is about 12 V or more), oxygen is generated and metal ions are attracted, the alumite sulfate is colored, and at about 25 V or more, hydrogen is generated. The number of occurrences increases, and film peeling easily occurs.

The above consideration on the alumite sulfate also applies to the case where the anodizing treatment is performed in the electrolytic solution containing the high voltage type electrolyte. However, in this case, since the AC electrolytic coloring needs to be performed at a higher voltage, the above-mentioned problem becomes more severe. In fact, 12
Aluminum material anodized at 0V is AC80V
When alternating current electrolysis is performed using a conventional electrolytic coloring solution, a large current flows, a large amount of gas (hydrogen) is generated from the anodized film side, and the anodized film peels off. In this case, if the consideration about the alumite sulfate is applied one step further, the AC electrolytic coloring is performed on the film formed by the anodic oxidation treatment at about 120 V under the condition that oxygen is appropriately generated and hydrogen is hardly generated. It will be good.
In order to achieve such a condition, two measures are proposed according to the present invention, and the first aspect thereof is to set an AC voltage such that oxygen is appropriately generated when the anodized film is an anode, and It is characterized in that the composition of the electrolytic coloring liquid is adjusted so that a current does not flow so much at the time of the cathode, that is, the conductivity of the electrolytic coloring liquid is regulated within a certain range, while the second aspect is that of the alternating voltage. Use a special waveform in which the peak voltage of the (+) component is larger than the peak voltage of the (-) component, and the peak voltage of the (+) component is
It is characterized in that the voltage is equal to or lower than the theoretical voltage and is 1/2 or higher .

That is, according to the method for producing a colored aluminum material of the first aspect of the present invention, after the aluminum material is anodized at a high voltage of 30 V or more in an electrolytic solution containing a high voltage type electrolyte, Conductivity (in the case of an acidic bath having a pH of 2 or less, the conductivity when a strong acid is removed) is 3.0 to
In an electrolytic coloring solution adjusted to be in the range of 20 mS / cm, an AC voltage having a peak voltage that is not higher than the voltage during anodization treatment and that is not lower than 1/2 of the voltage during anodic oxidation treatment so as not to cause film destruction is applied, For example, in the above example, electrolytic coloring treatment is performed using a sine wave having a peak voltage of about 80 to 120V. This method is characterized in that the concentration of the metal salt in the electrolytic coloring solution can be considerably lowered, and that the anodic oxide film can be colored dark in a short time. The conductivity of 3.0 to 20 mS / cm as used herein means that the pH of the electrolytic coloring liquid is about 3
In the case of a weak acid to neutral bath of ˜7, it means the conductivity of the electrolytic coloring solution, and in the case of an acidic bath where the pH of the electrolytic coloring solution is 2 or less, it means the conductivity of the electrolytic coloring solution excluding strong acid. This is because when an electrolytic coloring solution contains strong acids such as sulfuric acid, sulfamic acid, acetic acid, and oxalic acid, the anodized film is repaired during electrolytic coloring. ) (It does not mean that the current does not flow so much when the anodized film is the cathode)
Because. By adjusting the conductivity of the electrolytic coloring solution so as to be within the above range, even if the alternating voltage is set so that oxygen is appropriately generated when the anodized film is the anode, the current is not so much when it is the cathode. Since it does not flow, no film breakage occurs.

As the factors that affect the conductivity of the electrolytic coloring solution, metal salts and acids contained in the electrolytic solution are considered, but various ammonium salts are the most influential components and the most influential components. Is ammonium sulfate. Therefore, as the most suitable method for adjusting the conductivity of the electrolytic coloring liquid to the above range by the method of the present invention,
Addition of ammonium sulphate can be mentioned. When ammonium sulfate is added, the content of ammonium sulfate in the electrolytic coloring solution is appropriately about 30 g / l or less, preferably 0 to
It is about 15 g / l, more preferably about 3 to 10 g / l. Further, in order to adjust the conductivity of the electrolytic coloring liquid to the above range, the concentration of the metal salt in the liquid is set low, for example, 0.5 to 1
It is also effective to adjust the amount to about 100 g / l or to replace a part of the acid group of the strong acid in the electrolytic coloring solution with the acid group of the weak acid. Generally, the electrolytic coloring liquid contains a metal salt of a strong acid, such as nickel sulfate, but the electrolytic coloring liquid containing a sulfuric acid group is
The electric conductivity is inevitably high. Therefore, it is preferable to add a weak acid such as boric acid to the electrolytic coloring solution to adjust the electric conductivity to a low level.

On the other hand, in the method for producing a colored aluminum material according to the second aspect of the present invention, the aluminum material is anodized at a high voltage of 30 V or higher in an electrolytic solution containing a high voltage type electrolyte, and then a metal salt is added. In an electrolytic coloring solution containing (+)
The peak voltage of the component is greater than the peak voltage of the (-) component, preferably {peak voltage of the ((+) component} / {(-)
The component is subjected to electrolytic coloring treatment by applying an AC voltage having a ratio of component peak voltage} within the range of 2 to 12. For example, in the example described above, the peak voltage of the (+) component is about 80 to 120 V (about 50 to 90 V at the nominal value of normal AC).
V) and (−) components are subjected to electrolytic coloring treatment using a waveform set so that the peak voltage is about 10 to 35V. This method can be carried out using an electrolytic coloring solution having a relatively high metal salt concentration for electrolytically coloring conventional alumite sulfate as it is, and is characterized in that the anodized film can be colored dark in a short time. Have. Even in the method of the second aspect, the peak voltage of the (+) component of the AC voltage during the electrolytic coloring treatment is less than or equal to the voltage during the anodizing treatment and 1 /
Set to be 2 or more, and that to adjust the conductivity of the electrolytic coloring solution to be within the range described above.

As described above, according to the method of the present invention, even an anodized film formed by anodizing treatment at a high voltage of 30 V or higher in an electrolytic solution containing a high voltage type electrolyte,
By appropriately selecting the composition of the electrolytic coloring solution (conductivity) and the voltage of the AC electrolytic treatment according to the anodizing conditions, electrolytic coloring can be carried out in a short time without causing film destruction. According to the method of the present invention, colored aluminum materials of various tones can be produced by changing the type and concentration of the metal salt in the electrolytic coloring solution, and it can be combined with other suitable methods such as a masking method. By doing so, it is also possible to color a multicolored pattern. Therefore, the colored aluminum material obtained by the method of the present invention is a building material for buildings and houses, a sash,
It can be used in various fields such as architectural wall materials such as curtain walls, panels, gates, etc., as well as electrical product frames such as audio equipment, landscape materials such as signboards.

Each step of the method for producing a colored aluminum material of the present invention will be described in detail below. First, if necessary, the aluminum material surface is subjected to pretreatment such as degreasing, etching, and neutralization. Then, by connecting the aluminum material pretreated as described above to the anode, in an acidic electrolyte solution containing a high-voltage type electrolyte, using a direct current or a similar current waveform or alternating current waveform, alternating-current superposition waveform The aluminum material is electrolytically oxidized to form an anodized film. As the electrolytic solution, oxalic acid, maleic acid, malonic acid, sulfamic acid, tartaric acid, high-voltage organic acids such as sulfosalicylic acid,
High-voltage inorganic acids such as phosphoric acid, boric acid, and ammonium borate,
And an electrolytic solution containing a mixture thereof can be used. These are all high-voltage type electrolytes, and the anodizing voltage varies depending on the electrolyte used, but the voltage is 30 to 2
00V, preferably about 30 to 150V. The high voltage type electrolyte itself as described above is well known and is described in, for example, Japanese Patent Publication No. 55-24510. The concentration of the high-voltage electrolyte in the electrolytic solution is 0.05 to 20 W / V
% Is appropriate.

The aluminum material anodized as described above is then colored by an electrolytic coloring method. As the metal salt used in the electrolytic coloring method, for example, nickel, cobalt, chromium, copper, tin, cadmium, titanium, manganese,
Molybdenum, calcium, magnesium, vanadium,
Sulfates, nitrates, hydrochlorides of iron, gold, silver, lead, zinc, etc.
Oxalate, acetate, tartrate, chromate, phosphate and the like can be mentioned. Electrolytic coloring is carried out by using these metal salts, mineral acids or organic acids (for example, boric acid, sulfuric acid, oxalic acid, phosphoric acid, chromic acid, sulfamic acid, acetic acid), preferably weak acids, their ammonium salts, amino salts, imino acids. The anodized aluminum material is subjected to a suitable electrolytic treatment such as AC electrolysis or AC / DC electrolysis in a coloring bath containing salt or the like. As a result, the anodized film is bronze, amber, black,
It is colored in various colors such as gray, green, blue, and brown.

As the conditions for electrolytic coloring, as described above, in the method of the first aspect of the present invention, the film is not broken in the electrolytic coloring liquid whose conductivity is adjusted within the predetermined range. It is performed by applying an AC voltage having a peak voltage that is equal to or lower than the voltage during the anodic oxidation treatment and that is ½ or more thereof. The concentration of the metal salt in the electrolytic coloring solution is about 0.5 to 100 g / l, preferably 1.0 to 70 g as described above.
/ L is suitable. On the other hand, in the method of the second aspect of the present invention, the peak voltage of the (+) component is larger than the peak voltage of the (-) component, preferably {peak voltage of the ((+) component) / {(-) component). Peak voltage ratio is 2 to 12
The electrolytic coloring treatment is performed using an AC voltage within the range.
In the case of this method, the conventional electrolytic coloring solution having a relatively high metal salt concentration for electrolytically coloring alumite sulfate can be used as it is, but preferably the metal salt concentration is 0.5 as described above. Approximately 100 g / l is desirable. In the method of the second aspect as well, the peak voltage of the (+) component of the AC voltage during the electrolytic coloring treatment is set so as to be equal to or lower than the voltage during the anodizing treatment and equal to or higher than 1/2 thereof. It is preferable to add various ammonium salts such as ammonium sulfate and weak acids such as boric acid so that the conductivity of the coloring liquid is within the above range. The colored coating of the aluminum material thus obtained can be subjected to sealing treatment or clear coating, if necessary.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to the following Examples.

Example 1 An aluminum material A1050P which had been degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added at 30 g / g.
1, an anodized film having a film thickness of about 9 μm was formed by performing anodization at 120 V DC for 50 minutes in an electrolytic solution containing 30 g / l of maleic acid at 30 ° C. For reference, the aluminum material A1050P that has been degreased, etched, and neutralized by a conventional method is used as an anode, and sulfuric acid is added to 180
Anodization was performed for 35 minutes under conditions of DC 15V (current density 1.0 A / dm ² ) in an electrolytic solution containing g / l at 20 ° C. to form an anodized film having a film thickness of about 10 μm.
Thereafter, each of the obtained anodized aluminum materials contained nickel sulfate (6 hydrate) 20 g / l, boric acid 7 g / l, magnesium sulfate (7 hydrate) 4 g / l, ammonium sulfate 9 g / l, and contained ammonia water. AC electrolysis was performed at various voltages shown in Table 1 for 3 minutes at room temperature in an electrolytic coloring bath (conductivity = 18 mS / cm) adjusted to pH 5.5 by adding
The anodized film was colored. The results are shown in Table 1.

[0019]

[Table 1] As shown in Table 1, even in the case of a high-voltage type anodic oxide coating, if an electrolytic coloring liquid whose conductivity is adjusted to fall within a predetermined range is used and the alternating electrolysis voltage is set within an appropriate range,
It can be seen that various colors can be electrolytically colored according to the AC electrolysis conditions without causing destruction of the anodized film.

Comparative Example 1 Aluminum material A1050P degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added in an amount of 30 g /
1, an anodized film having a film thickness of about 9 μm was formed by performing anodization at 120 V DC for 50 minutes in an electrolytic solution containing 30 g / l of maleic acid at 30 ° C. For reference, the aluminum material A1050P that has been degreased, etched, and neutralized by a conventional method is used as an anode, and sulfuric acid is added to 180
Anodization was performed for 35 minutes under conditions of DC 15V (current density 1.0 A / dm ² ) in an electrolytic solution containing g / l at 20 ° C. to form an anodized film having a film thickness of about 10 μm.
Thereafter, each of the obtained anodized aluminum materials was treated with nickel sulfate (6 hydrate) 55 g / l, boric acid 44 g / l, magnesium sulfate (7 hydrate) 25 g / l, ammonium sulfate 55 g / l and a pH of about 5 AC electrolysis was carried out for 3 minutes at room temperature in the electrolytic coloring bath of 0.5 (conductivity = 59 mS / cm) at various voltages shown in Table 2 to color the anodized film. The results are shown in Table 2.

[0021]

[Table 2] As shown in Table 2, in the case of a high-voltage type anodic oxide film, a conventional electrolytic coloring solution for electrolytic coloring of alumite sulfate was not adjusted so that the conductivity was within the predetermined range specified in the present invention. When used, the anodic oxide coating could not be colored when the AC electrolysis voltage was low, while the anodic oxide coating was destroyed when the AC electrolysis voltage was high.

Example 2 Aluminum material A1050P degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added at 30 g /
1, an anodized film having a film thickness of about 9 μm was formed by performing anodization at 120 V DC for 50 minutes in an electrolytic solution containing 30 g / l of maleic acid at 30 ° C. Thereafter, the obtained anodized aluminum material was treated with an electrolytic coloring bath containing sulfuric acid 40 g / l, stannous sulfate 3 g / l, ammonium sulfate 30 g / l, and sodium thiosulfate 0.6 g / l (hereinafter,
It is called an acidic tin bath. Conductivity excluding sulfuric acid = 36 mS
/ Cm), a 5 times dilution thereof (only stannous sulfate was adjusted to the same concentration. PH = 1 or less, conductivity without sulfuric acid =
9.5 mS / cm) or a 10-fold diluted solution (only stannous sulfate was adjusted to the same concentration. PH = 1, conductivity excluding sulfuric acid = 6.5 mS / cm) and various values shown in Table 3 were obtained. AC electrolysis was performed at a voltage to color the anodized film. The results are shown in Table 3.

[Table 3]

Example 3 Aluminum material A1050P degreased, etched, and neutralized according to a conventional method was used as an anode, and oxalic acid was added at 10 g /
In an electrolyte solution containing 1 l, anodic oxidation was performed at DC 120V for 25 minutes to form an anodic oxide film. Next, this aluminum material was mixed with nickel sulfate (hexahydrate) 15 g / l,
Boric acid 4 g / l, magnesium sulfate (7 hydrate) 4 g /
1, pH containing 1.0 g / l ammonium thiosulfate
In an electrolytic coloring bath of 5.6 (conductivity = 7.3 mS / cm),
When AC electrolysis was performed at 75 V AC for 3 minutes, the anodized film was colored in grayish brown.

Example 4 Aluminum material A1050P degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added at 40 g / l.
Anodization was performed at 140V DC for 40 minutes in the contained electrolytic solution to form an anodized film. Next, this aluminum material was mixed with nickel sulfate (6 hydrate) 15 g / l, boric acid 4 g / l, magnesium sulfate (7 hydrate) 4 g / l.
1, pH containing 1.0 g / l ammonium thiosulfate
In an electrolytic coloring bath of 5.6 (conductivity = 7.3 mS / cm),
When AC electrolysis was performed at 75 V AC for 1 minute, the anodized film was colored brown. On the other hand, when AC electrolysis was performed at 80 V AC for 3 minutes, the anodized film was colored in gray black.

Example 5 Aluminum material A1050P degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added at 40 g / l.
Anodization was performed at 140V DC for 40 minutes in the contained electrolytic solution to form an anodized film. Next, this aluminum material was mixed with nickel sulfate (6 hydrate) 15 g / l, boric acid 4 g / l, magnesium sulfate (7 hydrate) 4 g / l.
AC electrolysis was carried out for 1 minute at 80V AC in an electrolytic coloring bath (conductivity = 18 mS / cm) of pH 5.6 containing 1 g, ammonium sulfate 9 g / l, and ammonium thiosulfate 1.0 g / l. The film was colored black.

Example 6 An aluminum material A1050P that had been degreased, etched and neutralized according to a conventional method was used as an anode, and phosphoric acid was added at 30 g /
1, and 30 g of maleic acid in an electrolytic solution containing 50 g / l at 30 ° C. were anodized for 30 minutes under the conditions of DC140V (current density 1.0 A / dm ² ) to form an anodized film. Then, this aluminum material was mixed with nickel sulfate (6
Hydrate) 30 g / l, boric acid 20 g / l, magnesium sulfate (7 hydrate) 20 g / l, ammonium sulfate 30 g
In an electrolytic coloring bath (conductivity = 42 mS / cm) containing 1 / l and adjusted to pH 6 with ammonia water, as shown in FIG. 1, the power supply voltage has a peak voltage of (+) component of 75 V and a peak of (−) component. When AC electrolysis was performed for 3 minutes using a sine wave (60 Hz) with a voltage of 15 V, the anodic oxide film was colored a deep bronze color. When a high-conductivity electrolytic coloring solution is used as described above, film breakage occurs in normal AC electrolysis, but in the present example, good coloring was achieved by using the special power supply waveform as described above. .

[0027]

As described above, according to the method of the present invention,
Electrolysis of an anodized film of an aluminum material obtained by anodizing at a high voltage of 30 V or more in an electrolytic solution containing a high voltage type electrolyte at a voltage lower than the anodizing voltage in a short time without causing film destruction. Can be colored. Further, according to the method of the first aspect, an electrolytic coloring solution containing a relatively low concentration of metal salt can be used, which is advantageous in terms of cost. The colored aluminum material obtained by any of the methods has excellent film performance, exhibits sufficient light resistance and durability even when used outdoors, and has no discoloration or fading and is robust and vivid. Since it has a colored colored oxide film, it can be suitably used in various fields.

[Brief description of drawings]

FIG. 1 is a graph showing a waveform of an AC voltage used for electrolytic coloring in Example 6.

Claims (4)

(57) [Claims] 1. An aluminum material is anodized in an electrolytic solution containing a high-voltage type electrolyte at a high voltage of 30 V or more, and then contains a metal salt and has an electrical conductivity (in the case of an acidic bath having a pH of 2 or less). Is the electrical conductivity excluding strong acid) is 3.0
A colored aluminum material, characterized in that electrolytic coloring treatment is performed by applying an AC voltage having a peak voltage that is not more than a voltage during anodizing treatment and is not less than ½ of that in an electrolytic coloring solution of 20 mS / cm. Production method. 2. The electrolytic coloring solution contains 0.5 to 1 of a metal salt.
A content of 100 g / l.
The method described in. 3. An aluminum material is anodized in an electrolytic solution containing a high voltage type electrolyte at a high voltage of 30 V or higher, and then in an electrolytic coloring solution containing a metal salt, the peak of the (+) component. voltage (-) greater exchange than the peak voltage of the component
Current voltage, and the peak voltage of the (+) component is positive
A method for producing a colored aluminum material, characterized in that an electrolytic coloring treatment is carried out by applying an alternating voltage that is equal to or lower than the voltage during the polar oxidation treatment and is 1/2 or more of the voltage. Wherein said AC voltage {(+) component of the peak voltage} / - according to claim 3 in which the ratio of {() component of the peak voltage} is characterized to be within the scope of 2 to 12 Method.