JPH0237437B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic coloring method for aluminum or an aluminum alloy, and particularly to an electrolytic coloring method that can stably obtain a pale gray colored film.

The electrolytic coloring method for aluminum and aluminum alloys, known as the Asada method, involves electrolyzing in an electrolytic solution containing metal salts to precipitate metal into the pores of the anodic oxide film and coloring it. It is thought that the appearance of color is due to light absorption or even light interference.

In the past, various electrolytic coloring solutions have been proposed for use in such electrolytic coloring methods for aluminum and aluminum alloys, and electrolytic coloring methods using various waveforms, including alternating current, have been proposed, but these methods can produce deep colors in a short time. The main purpose of this method is to improve the throwing properties and to improve the throwing properties, but it is not sufficient in terms of stably obtaining a light colored film. In fact, in on-site production, even when attempting to obtain a light-colored electrolytically colored film, there is insufficient reproducibility, and the instability of coloring in light colors has been pointed out as a major problem with the electrolytic coloring method.

Furthermore, until now, there has been no known method for reliably obtaining a light gray colored film.

The present inventors solved the above problems and conducted extensive research on a method for stably obtaining a pale gray electrolytically colored film of aluminum or aluminum alloy. When electrolytic coloring is performed using an electrolytic coloring solution containing nickel salt with a waveform in which a positive current that is 50 to 500 times that of a negative current is applied, a pale gray electrolytically colored film can be obtained stably and with good reproducibility. It has been discovered that gray electrolytic coloring management has become extremely easy on-site, and it has become possible to create pale gray, a color that has rarely been seen in the past.

That is, according to the results of the studies conducted by the present inventors, for example, when electrolytically coloring an anodic oxide film of aluminum or aluminum alloy obtained by sulfuric acid electrolysis, the barrier layer formed by this sulfuric acid electrolysis is Due to the dissolving action, variations in the resistance of the barrier layer occur, but when an anodic oxide film with a barrier layer with such variations is electrolytically colored using the normal AC electrolysis method, the barrier layer can be repaired by the positive current. However, since the negative current is also large, the repair cannot be completed in time, and as a result, as shown in Figure 1, variations in the height of the deposited metal 2 occur depending on the variations in the barrier layer 1. , 4 is the pore wall, and 5 is the pore).

Therefore, in electrolytic coloring using a normal AC electrolytic method, variations occur in the height of the deposited metal, which reduces the interference effect of light, which poses a major problem in realizing lightening of electrolytic coloring. On the other hand, in one cycle, the negative current is 10 to 50 msec,
When electrolytic coloring is performed using a waveform in which the positive current is 50 to 500 times the positive current, the barrier layer is sufficiently repaired because the positive current is large. There is no variation,
It has been found that since the resistance becomes almost constant and the height of the deposited metal 2 also becomes constant, the light interference effect becomes high. Therefore, in lightening an electrolytically colored film due to the interference effect using the height of the deposited metal as an interference film, by making the positive current larger than the negative current in this way, the height of the deposited metal becomes constant, Since the interference effect is enhanced, it is possible to reliably and stably obtain a light-colored electrolytically colored film, and in this case, if an electrolytic coloring solution containing nickel salt is used, a golden color can be obtained using conventional methods. The inventors discovered that a light gray colored film, which had not been obtained in the past, could be obtained due to increased light interference, leading to the present invention.

The present invention will be explained in more detail below.

The electrolytic coloring method for aluminum or aluminum alloys of the present invention involves electrolytically coloring an anodic oxide film obtained using an electrolytic solution such as sulfuric acid or oxalic acid by further electrolyzing it with an electrolytic coloring solution containing nickel salt. , the object to be treated is electrolyzed in an electrolytic coloring solution using a waveform in which a negative current of 10 to 50 msec and a positive current of 50 to 500 times the negative current are applied in one cycle.

In this case, the anodic oxide film used for this electrolytic coloring is not particularly limited, and for example, a film obtained by electrolyzing aluminum or aluminum alloy using a normal electrolyte such as sulfuric acid or oxalic acid may be used. Can be done. According to the present invention, even if an anodic oxide film is used in which the resistance of the barrier layer varies, as is the case with films produced by sulfuric acid electrolysis, the barrier layer can be repaired to make its resistance constant, and thereby the deposited metal can be fixed. By keeping the height constant, a stable light-colored electrolytically colored film can be obtained.
An anodic oxide film with variable resistance of the barrier layer can also be used without any problem.

In the present invention, the type of aluminum or aluminum alloy used is not particularly limited.

In the electrolytic coloring method of the present invention, a conventionally known electrolytic coloring liquid containing a nickel salt can be used as the electrolytic coloring liquid.

When performing electrolytic coloring, as mentioned above, a waveform in which the negative current is 10 to 100 msec and the positive current is 50 to 500 times the negative current is used in one cycle, which ensures more stable and pale coloring. A gray electrolytically colored film is obtained. Note that any power source may be used as long as the above waveform can be obtained.

Other electrolysis conditions are not particularly limited, but the voltage is usually 20V or higher, particularly 20 to 100V, and the electrolysis time is preferably 1 to 10 minutes, particularly 3 to 7 minutes. In this case, in the conventional electrolytic coloring method using AC electrolysis, treatment at high voltage generates a large amount of hydrogen gas, and the film is likely to be destroyed due to the influence of impurity chlorine ions in the electrolytic coloring solution. Coloring is performed with a voltage of about 15 V (peak value of about 14 to 21 V), and high voltage is difficult to use, but according to the present invention, there is no problem even if electrolysis is performed at high voltage, and positive voltage (barrier High voltage can be obtained for both layer repair potential) and negative potential (metal negative potential).
Furthermore, in the case of conventional AC electrolysis, coloring is done in a short time of about 30 seconds, but in this case, a difference of 1 second can greatly affect the amount of metal deposited. On the other hand, in the present invention, the electrolysis time can be extended, and since there is more positive current than negative current, the barrier layer can be repaired sufficiently and reliably, and the electrolysis management is also easier. be. Therefore, according to the present invention, as described above, a high voltage can be applied and the coloring time can be lengthened, so that stable coloring can be performed under stable and easily manageable electrolytic conditions. For example, the barrier layer produced by sulfuric acid electrolysis is about 15V x 10Å, but when repairing this barrier layer, the present invention can use a higher voltage than conventional AC electrolysis. Since it can be repaired thicker and the repair time is longer, it is possible to more reliably reduce the influence of the barrier layer of sulfuric acid electrolysis, which has many variations, and to perform metal deposition at a stable deposition potential with a constant resistance, metal deposition in each hole. This makes it possible to more reliably equalize the amount and stabilize the coloring.

Note that the temperature of electrolytic coloring is not particularly limited, but
Usually carried out at room temperature.

As detailed above, according to the present invention, for a negative current of 10 to 50 msec in one cycle, the 50 msec
By electrolytically coloring using an electrolytic coloring solution containing nickel salt with a waveform in which a positive current of ~500 times is applied, the height of the precipitated metal in each pore of the anodic oxide film can be made as uniform as possible, This enhances the light interference effect, making it possible to reliably obtain a light gray colored film with good reproducibility.In addition, the negative current is small compared to the positive current, allowing high voltage to be obtained, and also making it possible to extend the coloring time. This makes it easier to manage light gray coloring, and enables light gray coloring, which is rarely seen in the past.

EXAMPLES Hereinafter, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited to the following examples.

Example A-6063-T ₅ material was used as the aluminum material, and after degreasing, etching, and neutralization according to conventional methods, it was subjected to direct current electrolysis using a sulfuric acid bath to form a colorless anodic oxide film. did.

Next, electrolytic coloring was carried out under the following conditions using an electrolytic coloring solution having the following composition.

Liquid composition NiSO ₄・6H ₂ O 25g/ (NH ₄ ) ₂ SO ₄ 15 〃 H ₃ BO ₃ 15 〃 PH 4.5 Electrolysis conditions 1 cycle Negative current 30msec Positive current 3sec Voltage 35V Temperature 30℃ Electrolysis time 7min Obtained The electrolytically colored film is light gray, and the results of observing this electrolytically colored film with an electron microscope are as follows.
As shown in FIG. 2, the height of the deposited metal in each pore was almost the same.

Here, all 10 samples were electrolytically colored under the above conditions, and all of them had the same light gray color, with no variation in hue, and it was possible to obtain light-colored electrolytically colored films with good reproducibility. did it.

Comparative Example After forming an anodized film by sulfuric acid electrolysis in the same manner as in the example, electrolytic coloring was performed using the same electrolytic coloring solution under the following conditions.

Electrolysis conditions AC electrolysis 50Hz Voltage 13V Temperature 30°C Electrolysis time 30sec The electrolytically colored film obtained was golden yellow and no light color was obtained. Further, as shown in FIG. 1, the electrolytically colored film was observed with an electron microscope, and the height of the deposited metal in each pore varied.

Here, the results of electrolytic coloring of 10 samples showed that the colored films had a yellowish or black tinge, and had different shading, and the colored films had variations in hue.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the state of metal deposition in the pores of the anodic oxide film when the conventional electrolytic coloring method using AC electrolysis is adopted, and Figure 2 is an explanatory diagram showing the state of metal precipitation in the pores of the anodic oxide film when the method of the present invention is adopted. It is an explanatory view showing the state of metal precipitation in

Claims (1)

[Claims] 1. When electrolytically coloring aluminum or aluminum alloy, after anodizing the aluminum or aluminum alloy, in one cycle in an electrolytic coloring solution containing nickel salt, a positive current of 50 to 500 times the negative current of 10 to 50 milliseconds is applied. An electrolytic coloring method for aluminum or aluminum alloy, characterized in that a pale gray colored film is obtained by electrolysis using a waveform of applied current.