KR850001214B1 - Method for producing colored aluminum articles - Google Patents

Abstract

The surface of an Aluminum article is coated with an anodic oxidation film by a conventional method. The bottom of the pores of the anodic oxidation film are enlarged in order to obtain the coloring which changes according to the interference effect of light. After the reforming treatment, the Al articles receive a preliminary electrolytic treatment, and then, the anode Al articles are sent through the electrolytic coloring treatment via an electrolytic bath, which contains a metallic base and direct current.

Description

Manufacturing method of colored aluminum article using interference of light

1 is a schematic perspective view of a flexure plate used in the experiments of Example 1 and Comparative Example 1.

2 (a) and 2 (b) are diagrams showing patterns of pulse voltages applied during respective electrolytic coloring processes.

The present invention provides a method for producing an aluminum material having a primary color pigmented anodized film, in particular, anodization of the anodized film pores on aluminum which has been subjected to anodized film by a conventional method in advance. The present invention relates to a method for producing a colored aluminum material based on interference of light by performing electrolytic coloring.

In recent years, colored aluminum materials have been widely used in vehicles, shrinking agents, exterior materials, and the like, but the colored aluminum materials used for these applications are required to be weather resistant, that is, they do not fade or discolor even after long-term exposure to sunlight or wind and rain. As a coloring method excellent in weatherability, the aluminum material which previously gave an anodized film is made into one pole, and this is electrolyzed in the electrolytic bath containing soluble salts of metals, such as nickel, tin, and cobalt, or it is made into a cathode, A so-called metal salt electrolytic coloring method is performed in which electrolytic products of metal salts are sedimented and deposited in the pores of the anodized film by direct current electrolysis, and the coatings are colored with the color according to the type of metal salt.

By the way, in the conventional electrolytic coloring method, the color tone of the film obtained by electrolytic coloring is basically determined by the type of metal salt contained in the bath, and industrially gray because the color tone is rich and pale even if the electrolytic conditions are slightly changed. It was limited to monochromatic and dark color systems such as color system, bronze system, and black system, and various kinds of colored aluminum materials including light system could not be obtained. In addition, in order to obtain a colored aluminum material having a different color, there is also a complicated problem such as the need to change the type of metal salt contained in the electrolytic bath.

In recent years, as a supplement to the drawbacks of such conventional electrolytic coloring methods, as disclosed in U.S. Patent No. 4,066,816, Japanese Patent Application No. 54-13860, Japanese Patent Application No. 54-23658, A method of obtaining an aluminum material having an extremely broad color tone of a light color system has been developed by simply adjusting the electrolysis time.

This method basically performs an anodizing treatment on the aluminum material on which the anodized film has been subjected to electrolytic coloring, followed by reforming of the anodizing film, and at least the volume of the bottom portion of the coated work where the electrolytic precipitate of the metal salt precipitates. The thickness of the sedimentation-adhesion layer of the metal salt electrolytic precipitate at the time of electrolytic coloring is made thin, and the height from the base part of the barrier layer to the upper surface of the sedimentation-adhesion part is enlarged by visible light. It is intended to obtain coloring due to the interference of light by making it approximately equal to the wavelength of, and according to this method, the change of the length of the electrolytic treatment time, that is, the change of the thickness of the precipitate deposit layer of the precipitate Bright pigments of various primary colors based on light interference in the order of purple, indigo, blue, green, yellow, orange and red Since the colored aluminum material is messed up, it is much more economical than the conventional coloring method because it is not only rich in kinds of colors, but also an aluminum material having various desired color shades can be obtained by the same metal salt-containing electrolytic bath. On the other hand, the method is difficult to "color" in order to obtain a precisely desired color because the color change rate is so fast that the electrolysis time elapses, and in particular, the aluminum material having a complicated shape is subjected to the coloring based on the interference color. In the case of lowering, it is difficult to stably obtain an aluminum material of uniform color tone, such as uneven current decomposition due to a change in the counter electrode distance based on the shape of the aluminum material, causing partial color unevenness.

As a method of eliminating the unevenness and instability of the color tone in the colored aluminum material by such an interference color electrolytic coloring method, for example, Japanese Patent Application Laid-Open No. 53-128547 discloses an anodized film for electrochromic coloring and electrolytic coloring. As an intermediate treatment of the treatment, it is described that the barrier oxide coating treatment is performed, and then the alternating electrolytic coloring treatment using a metal salt-containing electrolytic bath is described.

In this method, the barrier layer is applied to the aluminum material in an intermediate manner, thereby reinforcing the barrier layer over the entire anodized film and performing a portion of the aluminum material, ie, metal salt electrolytic deposition, which is easily passed through the current. By forming a barrier film of a thick film preferentially in a portion where the coloring speed is faster than that of other parts and where color shifts tend to be darker, the current distribution during the next electrolytic treatment is made uniform, and the color tone is uniform. In order to reduce the coloring speed as a whole, in the above-described method, since the alternating current is used in carrying out electrolytic coloring by metal salts, the relative change in voltage value and current value is severe, so that the relationship between the electrolysis time and the color tone change of the aluminum material is appropriate. Capture and stabilize the aluminum material of the desired color tone In order to obtain it must have been subjected to is extremely complex set of electrolysis conditions.

The inventors pay attention to the method of coloring the positive electrode by the direct current, which is relatively easy to control the current value, by using the aluminum material after the adjustment of the barrier layer as the cathode, and performing constant current direct current electrolysis at low current density in the metal salt-containing electrolytic bath. It succeeded in coloring the aluminum material of uniform color tone with controllability by comparatively gentle color change. This method is different from the alternating current electrolytic method, which must be controlled by voltage control. Therefore, it is easy to manage the amount of electricity contributing to electrolysis. In the present invention, an aluminum material having a desired color tone can be easily and stably reproduced, but a so-called spalling occurs in which the film is extremely destroyed during the king's electrolysis. I could see the turbidity of the unknown color.

As a result of their studies, the inventors have found that the uniformity of the coloring and the stability of the color tone in the aluminum material are not impaired when the pulse current in the positive direction is intermittently added to the above-described cathode DC current during electrolytic coloring. It has been found that it is possible to prevent the occurrence of sporling and the turbidity of the color.

That is, according to the present invention, the pores of the anodized film are reformed so that coloring based on the interference effect of light is obtained by electrolytic coloring on the aluminum material which has been subjected to the anodized film by a conventional method in advance. In carrying out, firstly, the aluminum material after the reforming treatment is used as the anode, and preliminary electrolytic treatment for the adjustment of the barrier layer is performed for a while, and then, as the cathode, a positive pulse current in the electrolytic bath containing the metal salt. Electrolytic coloring by the addition of a direct current is a method for producing a colored aluminum material using the interference of light.

According to the present invention, in performing electrolytic coloring of an aluminum material based on conventional interference of light, it is very difficult to improve the nonuniformity of the color tone based on the shape of the aluminum material, and The difficulty of "coloring" due to transition can be improved and overcome by a simple method, and a colored aluminum material of uniform color tone can be obtained.

Hereinafter, the method of the present invention will be described in detail again.

In the present invention, first, the anodizing film is modified so that the aluminum anodized film material obtained according to a conventional method is subjected to electrochromic treatment to perform coloring based on the interference of light. For example, it is performed by electrolytic treatment of the aluminum material which gave the gold oxide film in the aqueous solution mainly containing phosphoric acid or chromic acid.

By performing such a film-forming treatment, the bottom volume of the coating work in which the metal salt electrolytic precipitate precipitates and precipitates at least in the metal salt electrolytic coloring process is enlarged or branched into shape, and the metal salt is electrolyzed by subsequent electrolytic coloring treatment. By sedimentation and deposition of the precipitate as a thinly diffused layer on the bottom of the pores, color development is obtained based on the indirect action of light in spectral order from purple to red with the passage of the electrolysis time.

In the present invention, when electrolytic coloring treatment is performed on the aluminum material subjected to the film-forming reforming treatment as described above, the electrolytic bath used for the adjustment of the barrier layer using this as an anode is used. You may use the metal salt containing electrolytic bath similar to the electrolytic coloring process performed next. However, it is not necessary to necessarily use the same electrolytic bath, and an electrolytic bath having a capability of generating a barrier layer may be used.

As an example of such an electrolytic bath, a dilute aqueous solution such as boric acid, borax, ammonium borate, ammonium stannate, ammonium phosphate, citric acid or a bath in which a suitable metal salt is dissolved in these aqueous solutions is used.

In the pretreatment process, the anode current density in the treatment is allowed up to about 3 A / dm ² , but in general, it is appropriate to carry out at about 0.05-0.5 A / dm ² .

Although the electrolysis time varies depending on the current density, this treatment is intended to achieve a uniform current distribution in each part of the aluminum material during the next electrochromic treatment. As short as possible, energization for a short time is preferred, and the width is sufficiently achieved by performing at most 2 minutes or less, generally at about 10-60 seconds at a current density of 0.05-0.5 A / dm ² .

After preliminary electrolytic treatment, the aluminum material is electrolytically colored in a metal salt electrolytic bath using the cathode as an anode, and as the electrolytic bath, nickel, cobalt, etc. are used as an aqueous solution of metal salts conventionally used for electrolytic coloring by this type of metal salt. Can be used. Although it depends also on the kind of metal salt containing a bath, it is preferable to remain weakly acidic by inorganic acids, such as sulfuric acid and boric acid, or organic acids, such as tartaric acid and citric acid.

Electrolytic coloring is performed by energizing the DC current which added the pulse current as shown in FIG. 2 to the aluminum material as a cathode. 2A and 2B show waveforms of a direct current for adding a pulse current used in the electrolytic coloring treatment method of the present invention, with the horizontal axis representing the electrolysis time and the vertical axis representing the current value. Of course, the waveform is not limited to that shown in the drawings, and other forms may be used. In addition, in order to facilitate the management of the amount of energization, it is preferable to conduct the energization by the constant current control. It is preferable to hold the wire at a relatively low current density, and the negative current density at the time of the cathode of the aluminum material is preferably about 1 A / dm ² or less, preferably about 0.05-0.5 A / dm ² .

The pulse current is added so that the positive current flows intermittently in the positive direction from the aluminum material as the cathode toward the counter electrode, but the magnitude of the pulse current in this case is about the same as the current value of the DC current flowing at the cathode of the aluminum material. Just do it.

The addition frequency of the pulse current, that is, the number of additions per unit time and the government time ratio, i.e., the addition of the pulse current, causes the aluminum material to become an anode momentarily and the time ta in which the current flows in the positive direction, and the aluminum material becomes the cathode. It is important to appropriately control each of the ratio ta / tc of the flowing time tc to suppress spoiling and color tone, and to maintain uniformity and stability of coloring of the aluminum material.

According to the experiment, the frequency of addition of the plural current is in the range of 200-2600 times / minute, preferably in the range of 300-1800 times / minute, and the government time ratio ta / tc is 0.3 or less, preferably in the range of 0.01-0.15. You may select appropriately.

When the addition frequency and the government time ratio of the pulse current are significantly smaller than the above ranges, the improvement effect of spoiling and color tone cannot be obtained, and when the addition frequency and the government time ratio are significantly larger than the above range. The progress of electrolytic coloring is extremely low, and uniform coloring may not be obtained at all.

As the electrolytic coloring progresses, the aluminum material is sequentially changed in color to purple, indigo blue, blue, green, yellow, orange, and red, so that electrolysis may be stopped at a desired color tone.

In addition, the aluminum material which finished electrolytic coloring is surface-sealed by the sealing process by high temperature steam or high temperature immersion paper, or electrodeposition coating lacquer etc. after washing with water as needed.

As described above, according to the method of the present invention, when the aluminum material subjected to the modification treatment of the anodized pores for the color development of the interference color is subjected to electrolytic coloring treatment with a metal salt to obtain a colored aluminum material based on the interference color. After carrying out preliminary electrolytic treatment for the adjustment of the barrier layer of the aluminum material, afterwards, the sputtering and color tone become turbid by energizing a DC current by current control with the aluminum material as a cathode and a positive pulse current added thereto. Since the primary color system coloring aluminum material of a uniform and stable color tone can be obtained without producing | generating, the industrial value is large.

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described.

Example 1

As an aluminum material, a bending plate as shown in FIG. 1 of JISA-1100 (length l; 200 mm, width W: 300 mm, surface A width 100 mm, surface B width 100 mm, surface A 'width 100 mm, surface A and Using a difference of depth of B of 100 mm), this was anodized by a DC current having a current density of 1 A / dm ^{2 in} a 15% sulfuric acid bath to form an average of 15 탆 anodized film on the surface.

Next, the aluminum material subjected to the anodization described above was used as one pole, and the carbonaceous electrode was used as the counter electrode, and electrolytic treatment was performed for 10 minutes with an alternating current of 10 V in a 100 g / l phosphoric acid bath. After the anodic oxidation coating was reformed, the aluminum material was used as the anode, and the carbon electrode was used as the counter electrode. In a nickel salt electrolytic bath having the following composition, a direct current was applied for 30 seconds at an anode current density of 0.2 A / dm ² . Pretreatment was performed with an electric current.

Bathtub

Nickel Sulfate NiSO ₂ 6H ₂ O 30 g / l

Magnesium Sulphate MgSO _{4 7} H ₂ O 10 g / l

Boric acid H ₃ BO ₃ 30 g / l

Tartaric acid 10g / l

Glass of water

Subsequently, electrolytic coloring by DC current in which a pulse current was added in a nickel salt electrolytic bath of the same composition in the preliminary electrolytic treatment using the aluminum material subjected to the preliminary electrolytic treatment as a cathode and a carbon electrode as a counter electrode. Was performed.

The electrolytic conditions in electrolytic coloring were as follows.

Electrochromic condition

Pulse frequency 300 times / min

ta / tc ratio 0.10

Cathode Current Density 0.1A / dm ²

Anode Current Density Pulse 0.1A / dm ²

Bath temperature 25 ℃

Electrolysis is performed without accompanying the sporling phenomenon. The relationship between the energization time and the color tone of the film is shown in the first table.

[Table 1]

Comparative Example 1

In the same manner as in Example 1, the same aluminum material as in Example 1 was subjected to the anodizing film treatment and the coating pore reforming treatment, and then to preliminary electrolytic treatment in a metal salt electrolytic bath having the same composition as in Example 1. Alternating current was carried out with a 15V pole voltage, but at 4 minutes of energization, the surface A (A ') became deep reddish purple and the surface B became pale bronze, and the color of the surface A (A') and surface B was not different at all. .

Example 2

JISA-1100 plate material (150 mm x 150 mm) was used as the aluminum material, and the same color electrolytic treatment bath as used in Example 1 was used after anodizing and modifying the coating work under the same conditions as in Example 1. Using a aluminum material as the anode, a direct current was conducted at a cathode current density of 0.15 A / dm ² for 45 seconds, and preliminary electrolytic treatment was performed. Subsequently, electrolytic coloring was performed by switching a power supply, making an aluminum material the cathode, and energizing the direct current which added the pulse current on the following conditions.

Electrolytic Coloring Condition

Pulse frequency 600 times / min

ta / tc ratio 0.10

Cathode Current Density 0.1A / dm ²

Anode Current Density Pulse 0.1A / dm ²

Bath temperature 25 ℃

The relationship between energization time and color tone is shown in the 2nd table | surface.

[Table 2]

As can be seen from Table 2, Comparative Example 2, that is, electrolytic coloring using a conventional interference color, had little uniformity in coloration and a rapid change in color tone, making it difficult to "color" to obtain a desired color tone.

Example 3

An extrusion material of JISA-6063 (outer dimension 50 mm x 100 mm x 12 mm cross-section H type) was used as the aluminum material, which was anodized by a DC current having a current density of 1 A / dm ^{2 in} a 15% sulfuric acid bath, An average of 20 µ anodized film was formed.

Next, this electrode was made into one pole, and 10 V for 2 minutes in alternating electrolysis in a 120 g / l phosphoric acid bath using a counter electrode, followed by an anode DC current for 20 minutes for 1 minute to be used as a positive electrode to reform the coating pores. Was performed.

Next, this aluminum material is used as the anode. Using as a counter electrode, preliminary electrolytic treatment was performed by energizing a DC current for 32 seconds at a cathode current density of 0.15 A / dm ² in a mixed electrolyte bath of nickel salt and cobalt salt of the following composition.

Bathtub

Nickel Sulfate NiSO ₄ / 6H ₂ O 30 g / l

Ammonium Sulfate (NH ₄ ) ₂ SO ₄ 50g / l

Boric acid H ₃ BO ₃ 40 g / l

Glass of water

Subsequently, electrolytic coloring by direct current with the addition of a positive pulse current was performed in an electrolytic bath of the same composition in the preliminary electrolytic treatment, using the aluminum material subjected to the preliminary electrolysis as a cathode, and using a carbon electrode as the counter electrode.

Electrochromic condition

Pulse frequency 420 times / min

ta / tc ratio 0.12

Cathode Current Density 0.15A / dm ²

Anode Current Density Pulse 0.12A / dm ²

Bath temperature 25 ℃

Electrolysis was carried out without being accompanied by a spalling phenomenon. The relationship between the duration of the current supply and the coloration is shown in Table 3. At all stages of the color change, the aluminum material was able to obtain clean and clean coloration.

Comparative Example 3

The same aluminum material as used in Example 3 was subjected to electrolytic treatment, and the modification and pre-electrolytic treatment of the pores of the film were the same as those in Example 3. In subsequent processing for electrolytic coloring, the aluminum material was electrolyzed in the same manner as the electrolytic conditions used in Example 3 without adding a pulse current.

During electrolysis, sporadic and coarse electrodeposition of metals was found.

Because of this, the delivery could not continue anymore.

[Table 3]

Claims (1)

An electrolytic coloring treatment of an aluminum material subjected to anodization in accordance with a conventional method is carried out to enlarge the pore bottom portion of the anodized coating in order to obtain coloring based on the interference of light, and then to perform inhibition coloring treatment. At this time, the aluminum material after the reforming treatment is first used as an anode, and preliminary electrolytic treatment is performed for the adjustment of the barrier layer for a while, and then, as a cathode, a direct current applied by applying a positive pulse voltage in an electrolytic bath containing a metal salt. A method for producing a colored aluminum material using the interference of light, characterized in that the electrolytic coloring.

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