JP3562123B2 - Achromatic gray coloring method for aluminum material - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for coloring an anodized film of aluminum or an aluminum alloy material (hereinafter, referred to as an aluminum material).
[0002]
[Prior art]
Aluminum materials are widely used for building materials such as sashes and interior panel materials or for vehicle parts because of their light weight, good workability, and corrosion resistance, but anodic oxide film treatment is generally performed to improve their corrosion resistance. It is. Although this film is excellent in corrosion resistance, since it has a white tint of metal intact as it is, it may not be suitable for a color environment in various uses, and is monotonous and lacks in taste. For this reason, depending on the application, painting and coloring treatment of various colors are often performed. Among them, the electrolytic coloring treatment is extremely stable to the environment because a chemically stable metal salt is precipitated in fine pores of an oxide film formed by the anodic oxidation treatment and colored, and is extremely stable for a long time. It does not discolor or fade even outdoors, and is widely used.
[0003]
In recent years, as the use of aluminum materials such as building materials and vehicle parts has become widespread, various demands have also been placed on the tint of coloring, the concentration thereof, and the like. For example, a dark color tone such as a bronze color has been mainly used for architectural applications in the past, but in recent years, a calm color tone of a so-called achromatic color system of a gray system has been favored. In response to this, it has been difficult to produce such a color tone by a conventional electrolytic coloring method.
[0004]
That is, as such a conventional gray coloring method, there is a method of electrolytic coloring in a Ni-Zn bath described in JP-A-61-143593. According to this coloring method, a masking agent for nickel ions, such as gluconic acid, and a supporting electrolyte, such as ammonium sulfate, are added to a coloring bath containing an aluminum material previously subjected to anodizing treatment as a main component containing nickel salts and zinc salts. The anodized film is colored in a simple gray color or a slightly colored gray color tone by electrolytic coloring with alternating current, direct current or rectangular wave current in an electrolytic coloring bath adjusted to pH 4.5 or higher. . Another feature of this electrolytic coloring method is that the degree of precipitation and dispersal of nickel salt in fine pores of the anodic oxide film is increased, thereby improving the corrosion resistance, abrasion resistance and throwing power of the conventional electrolytic coloring method. It is superior to a colored film, and it is difficult to obtain a further coloring effect by other methods.
However, even by a method of electrolytically coloring the anodic oxide film of the aluminum material in the Ni-Zn bath to obtain a gray color, since this coloring method is originally a bronze-based coloring method, it is adjusted by variously changing the electrolytic conditions and the like. However, the resulting gray still had a strong yellow tint, failing to satisfy the market demand for purer achromatic gray shades.
[0005]
[Problems to be solved by the invention]
The present invention has been devised in order to solve such a problem. An electrolytic colored film having excellent corrosion resistance and uniformity obtained by the Ni-Zn bath method can be obtained in an inexpensive achromatic gray color by a simple method. The purpose is to convert to.
[0006]
[Means for Solving the Problems]
According to the first aspect of the invention, in order to attain the object, after anodizing an aluminum oxide film by electrolytic coloring by a Ni-Zn bath method, a mixed valence complex composed of any of molybdenum, tungsten, and vanadium is adsorbed. It is colored in gray. Further, the second invention is characterized in that a mixed valence complex made of any of molybdenum, tungsten, and vanadium is adsorbed and colored on an anodic oxide film of an aluminum material, and then colored gray by electrolytic coloring by a Ni-Zn bath method. It is to let.
[0007]
[Action]
The electrolytic coloring method using a Ni-Zn bath in the first step on which the present invention is based is a method in which metallic Ni and Zn are reduced into fine pores of an anodized film and an alloy is deposited to color the film gray. It is. Looking at the spectral reflectance of the film colored by this method, a clear peak does not appear as shown in FIG. 1, and it tends to be slightly higher on the long wavelength side. For this reason, the color of this film reflects a little more light on the long wavelength side, and becomes yellowish gray.
In another step of the present invention, a mixed valence complex of molybdenum, tungsten, and vanadium is adsorbed on the anodic oxide film, and the mixed valence complex color is developed. Taking molybdic acid as an example, an aluminum anodic oxidizing material is immersed in an aqueous solution of an ammonium salt of molybdic acid to adsorb hexavalent molybdate ions to the anodic oxide film, and then to an aqueous solution of tin chloride, tin sulfate or the like. Reduction with valence tin causes the formation of a mixed valence complex of Mo (V) -O-Mo (VI) in the pore. The valence complex develops a blue color due to electron transfer between molybdenum atoms, and exhibits a color generally called molybdenum blue. As shown in FIG. 2, the spectral reflectance characteristic of the film colored by this method does not show a clear peak, but tends to decrease as the wavelength becomes longer.
[0008]
By performing a blue immersion coloring method on the electrolytic coloring film of the Ni-Zn bath, these two spectral reflectance characteristics can be superimposed. That is, after sequentially performing these two coloring methods on the anodic oxide film and looking at the spectral reflectance characteristics, as shown in FIG. 3, these two spectral reflectance characteristics overlap to form a flat reflection spectrum, Achromatic grey, which does not show the color of the wavelength. Further, the lightness of the achromatic gray of the colored film can be easily controlled by adjusting the coloring conditions of these two coloring steps, respectively, as apparent from the reflection intensity of each of the colored films. .
The colored film formed by the Ni-Zn bath electrolytic coloring method is excellent in weather resistance, light resistance and uniformity, and the colored film formed in the second step is itself excellent in weather resistance and light resistance. The colored film can easily and inexpensively obtain a colored film having these characteristics while utilizing a conventional excellent Ni-Zn bath electrolytic coloring method.
[0009]
Embodiment
In the coloring method of the present invention, a pretreatment such as a degreasing treatment, an alkali etching treatment, and a desmutting treatment of an aluminum material to be treated is performed as a first half step, and an anodizing treatment is performed in an acidic aqueous solution such as sulfuric acid. To form a porous anodic oxide film having a thickness of This is subjected to an electrolytic coloring treatment and a dip coloring treatment by a Ni-Zn bath method, and colored to a required achromatic color of gray to black, and finally a clear coating with an acrylic resin is performed and baked, or It is immersed in boiling water and immersed in water containing a sealing aid to perform a sealing treatment. Alternatively, in the above steps, the steps of the coloring treatment by the electrolytic coloring treatment and the immersion treatment are interchanged.
[0010]
The aluminum material used in the present invention may be any material as long as an anodic oxide film can be formed thereon. Pure aluminum materials such as JIS A1100 materials, Al-Mg-Fe-Si materials such as JIS A6063 materials, etc. Those used for building materials such as pipes and extruded profiles are preferred. For the anodic oxide film treatment, a normal anodic oxidation treatment bath such as sulfuric acid, oxalic acid or sulfonic acid can be used, but a commonly used sulfuric acid bath is preferred. In the case of the sulfuric acid bath method, a porous anodic oxide film having a thickness of 3 to 40 μm is formed at a bath temperature of -5 to 30 ° C. at a temperature of 10 to 300 g / l.
The electrolytic coloring is performed by a Ni-Zn bath method as described in JP-A-61-143593, that is, an AC method, a DC method, or an electrolytic method using a pulse waveform in an aqueous solution containing a sulfate of Ni and Zn. .
[0011]
The electrolytic coloring treatment using the Ni—Zn bath in the first step of the present invention will be specifically described. The composition of the electrolytic bath is 10 to 200 g / l of nickel sulfate, nickel ammonium sulfate, nickel acetate, and nickel sulfamate as nickel salts. 1 to 50 g / l of zinc sulfate, zinc chloride and zinc acetate as zinc salts (note that the concentration ratio of Ni: Zn = 1: 0.1 to 0.5), and a chelating agent (electrodeposition of Ni and Zn). 1-50 g / l of tartaric acid, citric acid, gluconic acid and boric acid, 1-200 g / l of magnesium sulfate and ammonium sulfate as supporting electrolytes (improving the electrical conductivity of the bath), and 1-200 g / l of aluminum sulfate as an aluminum ion concealing agent. , Tartaric acid, citric acid, 4 to 12 g / l (maintained at 500 ppm or less of Al ions to prevent induction of film defects due to precipitation of Al compounds). And integer, further, as a regulation component, monovalent cation (Na, K, NH ₄₎ to 20PPM below (spalling occurrence of induced prevention), preferably 5 to 9 (pH pH 4.5 or more baths If it is less than 4.5, precipitation of Ni and Zn is difficult). The aluminum material having the anodic oxide film formed thereon is electrolytically colored in the electrolytic bath at a bath temperature of 15 to 30 ° C., an AC frequency of 5 to 100 Hz, and an electrolytic voltage of 10 to 30 V for 10 seconds to 15 minutes.
[0012]
In the second step, the adsorption of the mixed valence complex of molybdenum, tungsten, vanadium or the like to the anodic oxide film is performed by removing the aluminum material having the anodic oxide film formed thereon using an ammonium salt, a sodium salt of molybdic acid, tungstic acid, or vanadic acid. After being immersed in a first bath composed of an aqueous solution of a potassium salt and adsorbed in pores, it is immersed in a second bath composed of an aqueous solution of a chloride such as tin or iron or a sulfate as an inorganic acid salt reducing agent. The mixed valence complex is formed and adsorbed by partial reduction treatment in a pore.
The relationship between the bath components of the adsorption treatment bath with the mixed valence complex and the color it exhibits is as follows.
Mo: (5-6 valent mixed system) oxoacid ion of molybdic acid, for example, (NH ₄ ) ₂ MoO ₄ : molybdenum blue, Mo can take a divalent to hexavalent state. Polyacid ions are formed.
W: (5-6 mixed system) oxoacid ion of tungstic acid, for example, Na ₂ WO ₄ , tungsten blue V: (4-5 valent mixed system) ... oxoacid ion of vanadic acid, For example, the concentration of the Na ₃ VO ₄ and vanadium blue baths may be any concentration up to the saturation concentration. For example, the concentration and immersion time of the first bath and the second bath are respectively 0.1 to 400 g / l of ammonium molybdate, 0.5 to 15 minutes of immersion time at a bath temperature of 0 to 60 ° C., and tin sulfate. (II) Coloring treatment is performed by adjusting the immersion time according to each concentration within a range of 0.1 to 150 g / l, bath temperature of 0 to 60 ° C, and immersion time of 0.5 to 15 minutes.
[0013]
The reaction occurring here is a reaction between the ammonium molybdate adsorbed in the fine pores of the anodized film and the tin sulfate in the bath, and the mixed valence complex of blue Mo (V) and Mo (IV) (molybdenum blue). ) Is generated, but it is not clear at this time how much pentavalent is present.
The mixed valence complex may be formed by any method as long as it can be adsorbed on the anodic oxide film. However, since the mixed valence complex does not exist stably in an aqueous solution and easily precipitates, a two-bath system is used. A method of producing a mixed valence complex and adsorbing it at the same time in the immersion step is preferable.
By this adsorption step, the anodic oxide film colored by the electrolytic coloring changes from its yellowish gray to achromatic gray. According to this method, the lightness of gray to black can be easily controlled by selecting appropriate conditions for the two steps of electrolytic coloring and coloring by adsorption of the mixed valence complex.
After the coloring treatment, a necessary treatment such as a sealing treatment or an electrodeposition coating is performed according to the purpose.
[0014]
Example 1
JIS A6063 aluminum material is electrolyzed in a sulfuric acid bath at a current density of 1.5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, and then 30 g / l of boric acid, 20 g / l of nickel sulfate and 6 g / zinc sulfate. In an electrolytic coloring bath (pH 6.5) consisting of 25 g / l of magnesium sulfate and 40 g / l of ammonium sulfate, electrolysis was carried out at a constant voltage of 17 V for commercial alternating current for 2 minutes to give a yellowish gray color.
Then, it is immersed in an aqueous solution of 20 g / l of ammonium molybdate for 5 minutes, and subsequently, immersed in an aqueous solution of 8 g / l of tin (II) sulfate for 5 minutes to form molybdenum blue, subjected to sealing treatment, and subjected to achromatic coloration. Gray material was obtained. The colorimetric values were L ^* = 74.52, a ^* = 0.05, and b ^* = 0.06.
Here, L ^* , a ^* , and b ^* are represented by L ^* a ^* b ^* color system according to Japanese Industrial Standards (JIS Z8729), and a gray colored film formed by a Ni-Zn bath has an L ^* value of 24 to 80. , A ^* are -1 to 1 and b ^* are 1 to 10 levels. The achromatic gray in the present invention has an L ^* value of 24 to 80, and a ^* has -1 to 1, b ^* Is in the range of -1 to 1.
[0015]
Example 2
JIS A6063 aluminum material was electrolyzed in a sulfuric acid bath at a current density of 1.5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, and then immersed in an aqueous solution of 20 g / l ammonium molybdate for 5 minutes. It was immersed in an aqueous solution of tin (II) sulfate 8 g / l for 5 minutes to develop molybdenum blue.
Then, in an electrolytic coloring bath (pH 6.5) consisting of boric acid 30 g / l, nickel sulfate 20 g / l, zinc sulfate 6 g / l, magnesium sulfate 25 g / l, and ammonium sulfate 40 g / l, at a constant voltage of 17 V commercial AC for 2 minutes. The cells were electrolyzed and sealed to obtain an achromatic gray film material. The colorimetric values were L ^* = 75.32, a ^* = 0.06, and b ^* =-0.1.
[0016]
Example 3
Coloring was carried out under the same conditions as in Example 1 except that JIS A1100 aluminum material was used, and an achromatic gray coloring material was obtained. The colorimetric values were L ^* = 68.42, a ^* = 0.00, and b ^* = 0.12.
[0017]
Example 4
Coloring was performed under the same conditions as in Example 1 except that the electrolytic coloring treatment was performed for 4 minutes to obtain a dark gray material. The colorimetric values were L ^* = 52.22, a ^* = 0.05, and b ^* = 0.18.
[0018]
Example 5
Coloring was performed under the same conditions as in Example 1 except that 20 g / l of sodium tungstate was used as the mixed valence complex, to obtain a gray coloring material. The colorimetric values were L ^* = 73.62, a ^* = 0.02, and b ^* =-0.06.
[0019]
Example 6
Coloring was performed under the same conditions as in Example 1 except that 5 g / l of ammonium vanadate was used as the mixed valence complex, to obtain a gray colored material. The colorimetric values were L ^* = 72.62, a ^* = 0.02, and b ^* = 0.12.
[0020]
Comparative Example JIS A6063 aluminum material was electrolyzed in a sulfuric acid bath at a current density of 1.5 A / dm ² for 23 minutes to form a 10 μm anodic oxide film, and then boric acid 30 g / l, nickel sulfate 20 g / l, and zinc sulfate. In an electrolytic coloring bath (pH 6.5) composed of 6 g / l, magnesium sulfate 25 g / l, and ammonium sulfate 40 g / l, electrolysis was performed at a constant voltage of 17 V commercial AC for 2 minutes. The colorimetric values of the obtained sample were L ^* = 76.68, a ^* = 0.38, b ^* = 3.25, and were yellowish gray.
In the Ni-Zn bath electrolytic coloring method, b ^* was generally 3 or more, although it varied depending on the lightness. When L ^* = 75, b ^* = 3, and as L ^* decreases, b ^* increases, so that the color changes to yellowish even when the brightness changes. Therefore, in the Ni-Zn bath electrolytic coloring method, an achromatic gray cannot be obtained at any brightness.
[0021]
【The invention's effect】
As described above, according to the present invention, a colored film excellent in weather resistance, light resistance and uniformity obtained by coloring an anodic oxide film of an aluminum material by a Ni—Zn bath electrolytic coloring method is easy and inexpensive. Can be converted to a neutral gray.
[Brief description of the drawings]
FIG. 1 is a spectral reflectance of an anodic oxide film of an aluminum material colored by a Ni—Zn bath electrolytic coloring method. FIG. 2 is a spectral reflectance of an anodic oxide film of an aluminum material colored by an ammonium molybdate immersion coloring method. The spectral reflectance of the colored film of the present invention

Claims (2)

Aluminum, which is obtained by electrolytically coloring an anodic oxide film of aluminum or an aluminum alloy material with a Ni-Zn bath, and then adsorbing a mixed valence complex made of any of molybdenum, tungsten, and vanadium to obtain a gray color. Achromatic gray coloring method for materials. After adsorbing a mixed valence complex made of any of molybdenum, tungsten, and vanadium on an anodic oxide film of aluminum or an aluminum alloy material, it is colored gray by electrolytic coloring with a Ni-Zn bath. Achromatic gray coloring method for aluminum material.

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