JPH0676679B2 - Method for multicolor electrolytic coloring of aluminum or aluminum alloy - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor electrolytic coloring method for aluminum or an aluminum alloy, and in particular, has limited the field of use by coloring an oxide film such as aluminum or an aluminum alloy into a lightfast multicolor. This makes it possible to further expand the applications of the colored film.

[0002]

2. Description of the Related Art An anodized film formed on aluminum or the like is placed in a tank filled with a solution containing a metal salt, and an alternating voltage is applied between the other electrode in the same tank to color the anodized film. The inorganic coloring method used is Japanese Patent Publication No. 38-171.
No. 5 (Patent No. 310401) is well known.
However, it is difficult to obtain multicolored coloring by this method. Further, in Japanese Patent Publication No. 54-85137, an oxide film is further anodized with a solution containing phosphoric acid or the like to form a layer of an oxide film for optical interference having a structure different from that of the film initially formed. There is a third electrolytic coloring method for coloring, and in Japanese Patent Publication No. 53-64635 and the like, there is a method of depositing a metal on a fibrous oxide film formed by phosphoric acid or the like to obtain a multicolor film by utilizing light interference.

Further, a third electrolytic coloring method has been proposed,
The yield is low and is not suitable for practical use. The coloring control method called CLCC method previously proposed by the applicant improves the yield, but the secondary electrolysis process mainly containing phosphoric acid increases the coloring cost, There are many difficulties in handling metal complexes of aluminum and aluminum or coloring metals. In the method disclosed in JP-A-54-85137, there is a feature that the oxide film is thin and the light interference is strong and the color changes depending on the surface condition. However, when this feature is also used as a building material, stains and scratches are caused. However, there is a drawback that the hue is significantly changed when a transparent electrodeposition coating film is used for the purpose of protecting the film and improving the surface condition.

[0004]

The electrolytic coloring is characterized in that a colored film having strong light resistance can be obtained, and it is widely applied to building materials and the like. The color obtained by this is the bronze-based coloring, which is the easiest. Moreover, the color of this system is in great demand.
However, the color obtained by electrolytic coloring has a correlation with the color when the colored metal is made into ultrafine particles, and various colors cannot be obtained even if the type of metal salt is changed. Therefore, it is necessary to control the thickness of the interference portion with extremely high accuracy. Further, when a colored film is used for a building material or the like, there is a problem that unless an interference portion is formed in the lower layer of the oxide film, the hue changes depending on the surface condition and it cannot be used.

In the recent diversified times, there are many demands for coloring different systems, but there are many difficulties in multicoloring,
It was unable to meet the demand. The biggest difficulty is that management of the electrolytic cell and solution requires a huge amount of money, and there is a problem in profitability even if a new capital investment is made due to the relatively low demand for colors. It is difficult to use anodizing solutions and coloring solutions that have not been used as in the past, and even if multiple colors can be obtained by different processes. Therefore, it was a dream of this industry that conventional bronze-based equipment can be used as it is, and multicoloring can be performed without changing the electrolytic cell or solution. In order to realize this, an anodic oxide film made of pure sulfuric acid can be used as the anodic oxide film, which is the most widely used conventional bronze-based coloring, and is mainly composed of nickel salt or cobalt salt or a mixture thereof and boric acid. Coloring is also a condition for the coloring solution. However, the anodic oxide film formed by sulfuric acid is a film that has been considered difficult to be multicolored.

[0006]

In consideration of the above points, the present inventors have tried various experiments and trial productions, and as a result, have been aware of the current value for forming an oxide film while the oxide film is being formed. When it is reduced, the oxide film with a different structure can be formed in the lower layer of the oxide film that has been formed so far, and the degree of structural change of the oxide film can be adjusted by the decrease width of the current or voltage. It was found that the thickness can be adjusted by the time and level from the time when the current is reduced to the time when the current is cut off. Focusing on this, this method is used to obtain an oxide film for optical interference as the lower layer of the oxide film initially formed. I was able to.

However, the anodic oxide film thus obtained has a very low withstand voltage in the coloring solution as compared with an ordinary oxide film, and it is difficult to obtain stable coloring and covering. . Further, when the period for forming the initial film is set to zero and the current density for anodic oxidation is extremely reduced from the initial stage of anodic oxidation to obtain the interference film, it is the same as in Japanese Patent Publication No. 53-64635. It is thought that an interference film can be obtained for this reason, but the anodic oxide film of sulfuric acid does not cause any coloration. In order to eliminate this drawback, by applying an alternating current with a direct current component controlled so that anodic polarization occurs on the colored film side in the coloring solution and further anodic oxidation, stable coloring and covering can be obtained. However, it is possible to color, and not only it is possible to obtain a colored film with a relatively small change in hue due to the surface condition and parallax, but it is also possible to color aluminum that has not been anodized by completely reducing the anodizing time to zero. It turned out to be possible.

According to this method, the coloring is adjusted by adjusting the initial film formation time and current value, the amount of current decrease, the time and level from the time when the current is decreased until the current is cut off, and various colors can be obtained. It was Also, the thicker the initial oxide film, the stronger the interference color and the easier it was to obtain a primary color. When the time from when the voltage drops to when the voltage cuts off further increases, colors of a system with a long wavelength appear and this is repeated. When the current for anodic oxidation is significantly reduced to 1/10 or less of the initial current, a very vivid color close to the primary color can be obtained, but the film formed in the initial stage and the film having structural change The mechanical strength of the boundary surface is lowered and peeling is likely to occur, and this tendency is strong particularly when a period in which the current is lowered is extended to produce a color having a long wavelength. To prevent this problem, the sharpness of the color is reduced, but the reduction rate of the current is reduced or reduced stepwise.

The anodizing power source used in the present invention achieves the same purpose with a direct current or a current obtained by superimposing an alternating current on the direct current. However, if a constant current power source is used, control is easy.
However, in this case, it is necessary to accurately grasp the area of the film. Power supplies for anodic oxidation in actual production lines often do not meet this accuracy requirement. In this case, prepare a small high-precision constant-current power supply, switch to a high-precision power supply when the current is low, or set the output of both power supplies to 0R with a diode, and shut off the power supply with a large capacity when the current drops. , Automatically switch to a high-precision, small-capacity power supply. Furthermore, in the coloring solution, the throwing power and the subtle color tone can be adjusted by the time of anodic polarization on the oxide film side and the direct current component flowing through this electrode. It can be adjusted and various hues and brightness can be controlled.

When the primary anodic oxidation is omitted, a longer wavelength is obtained as the anodic polarization period and its DC current component are larger, and the brightness is adjusted depending on the cathodic polarization period and its DC current component. Is possible. Furthermore, if the voltage drop period is set to zero, conventional bronze-based colors can be output as they are, and a universal electrolytic coloring system that can produce colored films with various colors from conventional colors with the same equipment. Easy to build. Increasing the anodic polarization described here means that the current flowing from the film side for coloring to the solution is positive, and the integral value of this current for one cycle is positive, and the cathode polarization is This means that the integrated value is negative.

As proposed by the applicant of the present invention, the electrodeposition of metal during coloring is performed when the cathode polarization on the coloring electrode side is strong. The amount of the deposited metal is almost proportional to the integrated value of the current for one cycle. When the anodic polarization is strong, the oxide film is further oxidized, and the metal electro-folded on the oxide film is stripped off. This action is all performed by the integrated value of the current for one cycle, and only the DC component at this time acts, and the control of this DC component is the most important for obtaining stable coloring. The AC component of the current has various actions within a short time within one cycle, but the positive and negative balance is zero, it has little effect on the brightness of coloring, and has the greatest effect on throwing power, so the DC component It does not require as much accuracy.

The coloring power supply for carrying out the present invention can be realized with a constant voltage or a constant current, and since the waveform does not need to be a sine wave, it can also be realized with a power supply that has already been announced. However, in coloring with a constant voltage of alternating current, the direct current component is determined by the non-linear characteristics of the colored film with respect to the positive and negative voltages, and it is impossible to control the direct current component accurately. Stable coloring cannot be obtained when there is a large change. The CLCC method already proposed by the present applicant is optimal because the intensity and polarity of polarization can be freely controlled, any variable elements due to the power source can be corrected, and the coloring state can be freely programmed. Further, in order to carry out the present invention, the solution for anodic oxidation can be a sulfuric acid solution which is most often used or a solution in which aluminum sulfate is intentionally mixed to control the dissolution of aluminum. Although the range of use is limited, the voltage of the non-linear characteristic is reduced with sulfuric acid, etc., and even if a solution of phosphoric acid, oxalic acid, an organic acid or a mixed acid thereof is added, multicoloring can be obtained and different hues can be obtained. Is possible.

As the coloring solution, it is possible to use a general solution mainly composed of a metal salt of nickel, cobalt, tin, copper or the like, which is a conventional bronze-based coloring solution, or a mixture of these salts. However, other impractical metal salts or mixtures thereof are possible. In addition, when the primary electrolysis is not performed or in the coloring solution for the purpose of coloring the oxide film in a state where coloring is not easy, an inorganic acid or organic acid or its compound is added to the metal salt, and the pH optimum for coloring is maintained by a buffering agent. It is desirable to improve the coloring efficiency. In addition, when multicolored,
When the compound of aluminum and acid contained in the solution for electrolysis changes the transparency of the oxide film that is initially generated, or when an acid is added to the coloring solution, the concentration of the acid and the complex compound such as aluminum or the coloring metal Since the surface of the colored film changes subtly due to this, keeping these concentrations constant is the point of obtaining a reproducible colored film. The feature of the present invention lies in the method of applying an electric current in the anodic oxidation and the coloring solution, and it goes without saying that the material of the electrode, the solution for the anodic oxidation, the components and the composition of the coloring solution and the like may be different from those in the following examples.

[0014]

[Function] When the formation current is lowered during the formation of the anodic oxide film, an oxide film having a changed structure is formed below the initially formed oxide film. It is considered that the oxide film with this structural change has finer pores than the oxide film initially formed. The finer the pores, the lower the free energy for the solute in the solution to solidify, and the solutes preferentially precipitate in the micropores in which the structural change occurs. The substance crystallized in the fine pores forms a layer having a light absorption and reflection state different from that of the oxide film initially formed. Further, since light interference occurs due to the relationship between the film thickness of this layer and the wavelength of light, it is considered that various colors can be obtained by adjusting the thickness of this layer. In the case of directly coloring aluminum that has not been anodized or in a film that is difficult to color, when the aluminum is anodically polarized at the initial stage of coloring, it is anodized and finer pores are formed. It is considered that if the cathodic polarization is increased, various colors can be obtained for the same reason as above.

[0015]

EXAMPLES Next, examples of the present invention will be specifically described. An aluminum alloy A5052P material (magnesium 2.5%, chromium 0.25%) was used as the plate material.
The color difference meter used was CR200 manufactured by Minolta, and the name of the color was based on the Japanese traditional color second edition of Dainippon Ink and Chemicals.

[0016]

Example 1 A conventional bronze color. The aluminum plate was used as the anode and the other electrode was used as graphite in a 15% sulfuric acid solution at a direct current of 1.4 A% dm ²
Direct current electrolysis for 0 minutes, washing this with water, and using graphite as the other electrode in a coloring solution, AC component 50 Hz 250 mA%
dc ² and a DC component of 64 mA in the direction of anodic polarization
/ Min ² for 1 minute, and then the direct current component is 75 mA / dm ² in the direction of cathodic polarization with the same alternating current component of 50 Hz.
When it was run for a minute, the usual bronze-based coloring was obtained as described below. Coloring solution is already known nickel sulphate 6
Hydrosalt 93g / l, magnesium sulphate 7 hydrate 175
g / liter, boric acid 40 g / liter, tartaric acid 4 g /
1 (light metal Vo1, 37 No4 1987) was used after adjusting the pH to 4.5 with a buffer solution of ethylenediamine.

[Table 1]

In this case, the lightness can be changed substantially in inverse proportion to the direct current component and time when the electrode on the colored side is subjected to cathode polarization. However, when the direct current component exceeds a certain limit, the brightness rises conversely. Further, if the temperature of the coloring solution is increased, the limiting current also increases, so that the control range for the DC component and the brightness increases.

[0018]

Example 2 Multicoloring at normal film thickness. Aluminum plate as the anode and the other electrode as graphite in a 15% sulfuric acid solution at a direct current of 1.4 A / dm ²
Direct current electrolysis was carried out for 0 minutes, then the current value was reduced to 1/10 and this time was continued for T minutes to form an anodic oxide film, which was quickly washed with water so as not to dry, and in the same coloring solution as in Example 1. When colored under the same conditions, the coloring shown in Table 2 was obtained.

[Table 2]

The coloring obtained by this method is a color with a calm quality, in which the brightness is lower than that in the state in which the current drop time is zero, the influence of the surface is relatively small, and the product is calm. This example is the simplest example, and although this condition is not the best and does not guarantee the strength of the film, color appears periodically with the time of current decrease, and the color becomes clear with the increase of time. It is an example showing that. Since the experiment was performed by creating data at random intervals for one week for convenience, the temperature of the solution varies from 20 ° C to 25 ° C and the coating area varies by about 5%. During this time, about 7 CC per square centimeter
Was carried out unchanged. Also, the order of experiments is random, unlike the current value. Furthermore, with the same colored solution as the oxide film under the same conditions as above, it was possible to stably obtain a variety of gray colors, which had previously been difficult, without lowering the film strength simply by changing the conditions of secondary electrolysis. . Further, by changing the anodizing current and time conditions, another color can be obtained, and it is also possible to produce a dark blue color (dark purplish blue) which is hardly affected by the surface. Also, it is not compatible with normal coatings, but if possible, change the acid concentration,
Further different coloring can be obtained by a method such as using mixed acid.

[0020]

Example 3 Gray-based coloring at a normal film thickness. Under the same conditions as in Example 2, only the direct current component in the direction of cathodic polarization was reduced to 43 mA / dm ^2, and various gray-based coloring was obtained.

[Table 3]

[0021]

Example 4 Multicoloring with a thin anodic oxide film. The aluminum plate was used as an anode, and the other electrode was used as graphite in a 15% sulfuric acid solution for direct current electrolysis for T minutes at a DC of 350 mA / dm ² , and this was quickly washed with water so as not to dry, and the same conditions were applied in the coloring solution of Example 1. When colored with
A vivid gold color was obtained in 2 minutes, and a color with a long wavelength was obtained as the time increased. The color obtained by this method is more influenced by the surface condition than those obtained in Examples 2 and 3.
With such a large current, the gold color is bright, but the other colors are lighter. However, if the current density is further reduced and the time is increased, a clear color is obtained. This method is also susceptible to the material.

[0022]

Fifth Embodiment A multi-color nickel bath without anodizing process. In this method, the color can be freely changed depending on the time and current value during which the electrode on the side to be colored is subjected to anodic polarization.

INDUSTRIAL APPLICABILITY According to the present invention, an anodizing solution similar to the case of obtaining a conventional bronze-based coloring, and a coloring solution can be used as it is to obtain a multicolored colored film, which is an enormous costly electrolytic cell. It is possible to easily obtain a multi-colored film by simply changing the method of applying the current without changing the equipment such as, and the thickness of the anodizing film can be arbitrarily selected. Even if the thickness of the oxide film is set to the film thickness specified by the conventional JIS, it is possible to easily obtain multiple colors. The color film obtained in this case has little change in color due to the influence of the surface,
Even if transparent electrodeposition coating is performed, there is little discoloration, and it is possible to compensate for the decrease in mechanical strength at the interface between the oxide film with a structural change and a normal oxide film. Further, although it is out of the regulation of JIS, multicoloring is possible even when anodization is not carried out or an oxide film with extremely thin film of sulfuric acid can be applied, and it can be applied to applications other than building materials.

Claims (2)

[Claims] 1. A current value or a voltage value for forming an anodic oxide film is lowered during the formation of a normal or high-speed anodic oxide film of aluminum or an aluminum alloy with a direct current or a current obtained by superimposing an alternating current on a direct current. , Control the anodic oxidation current or voltage and time until the current or voltage drops, and further control the time and current value or voltage value from the width of the drop or the state of the drop to the cutoff. Between the first means for forming an anodized film having an arbitrary thickness and a different structure on the lower layer of the obtained oxide film, and putting the thus obtained anodized film in a coloring solution containing a metal salt or the like, and between the other electrode. An alternating current containing a controlled direct current component is applied to the electrode, and during the initial period of coloring, the electrode on the side to be colored is strengthened by anodic polarization to further promote anodic oxidation, and then an alternating current with a controlled direct current component is applied. Sinking cathode with strong polarization Second means and, aluminum or aluminum multicolor electrolytic coloring method of the alloy, characterized in that to obtain a multi-color film by performing the electrodeposition. 2. An anodized film obtained by producing aluminum or an aluminum alloy with a direct current or a current in which an alternating current is superimposed on a direct current is put as it is in a coloring solution containing a metal salt or the like, and controlled between the other electrode. An alternating current containing a direct current component is applied, and in the initial period of coloring, the electrode on the side to be colored is made to have stronger anodic polarization, and further anodic oxidation is promoted. A multicolor electrolytic coloring method for aluminum or an aluminum alloy, which comprises forming a multicolor film by increasing the flow cathode polarization and performing electrodeposition of a metal.