JPH0711492A - Formation of colored coating film on aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To provide the formation of a colored coating film on an aluminum or aluminum alloy, with which the aluminum or aluminum alloy having im proved corrosion, weather and wear resistance can be obtained and the coating film is lightly colored by thickly forming the coating film on the surface of the aluminum or aluminum alloy. CONSTITUTION:In the formation of a colored coating film on an aluminum or aluminum alloy, the primary coating film is formed on the surface of the above aluminum or aluminum alloy by supplying AC current, the polarity reversion frequency of which is continuously changed at unit time intervals (20ms), in a liquid mixture of an organic acid and an inorganic acid to the aluminum or aluminum alloy dipped in the liquid mixture. Then the lightly colored secondary coating film is formed on the resulting surface of the above aluminum or aluminum alloy by supplying DC current in the above liquid mixture to the aluminum or aluminum alloy while applying a prescribed DC voltage. Thus the colored coating film having a thick film thickness and a light color can be formed on the surface of the aluminum or aluminum alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a colored film of aluminum or an aluminum alloy by forming a colored film on the surface of aluminum or an aluminum alloy by electrolytic coloring.

[0002]

2. Description of the Related Art As a conventional technique, for example, Japanese Examined Patent Publication No. 63-
Japanese Patent No. 38438 discloses a method for forming a colored coating film of aluminum. In this method for forming a colored film of aluminum, a colored film of aluminum is formed by superposing a direct current or an alternating current and performing anodizing treatment. In this case, as shown in FIG. 1, as the film thickness of the film formed on the surface of aluminum gradually increases,
The state in which the color tone of the coating changes from light to dark is shown.

On the other hand, a method for forming a colored coating film of aluminum capable of obtaining a desired coloring density by applying an alternating current to aluminum on which an anodized film is formed and selecting the number of pole conversion of the alternating current is disclosed in Japanese Patent Publication No. 49-316
No. 14 publication.

[0004]

By the way, in order to improve the corrosion resistance, weather resistance and wear resistance, it is necessary to increase the film thickness of the film formed on aluminum. In the case of the prior art disclosed in the publication, there is a disadvantage that the coating formed on the surface of aluminum inevitably has a dark color and cannot be lightly colored.

On the other hand, in the prior art disclosed in Japanese Patent Publication No. 49-31614, the aluminum film can be colored in a light color by controlling the number of times of alternating current conversion, but the film thickness of the film. However, there is an inconvenience in that

The present invention has been made in order to overcome the above-mentioned inconveniences, and improves the corrosion resistance, weather resistance and wear resistance by forming a thick coating film formed on the surface of aluminum. An object of the present invention is to provide a method for forming a colored coating film of aluminum or an aluminum alloy capable of coloring the coating film in a light color.

[0007]

In order to achieve the above-mentioned object, the present invention provides aluminum or aluminum alloy immersed in a mixed solution containing an organic acid and an inorganic acid with the number of times of pole conversion during electrolysis. A step of forming a primary coating by applying a changed alternating current, and a step of forming a secondary coating by applying a direct current to the aluminum or aluminum alloy on which the primary coating is formed. Characterize.

[0008]

In the method for forming a colored coating film of aluminum or aluminum alloy according to the present invention described above, first, the number of pole conversions during electrolysis is performed for aluminum or aluminum alloy immersed in a mixed solution of organic acid and inorganic acid. A primary coating is formed on the surface of the aluminum or aluminum alloy by passing the changed alternating current. Next, by applying a direct current at a predetermined voltage, a secondary coating formed on the surface of the aluminum or aluminum alloy is formed. In this case, it is possible to increase the thickness of the secondary coating and to form a light colored coating on the surface of aluminum or aluminum alloy.

[0009]

The preferred embodiments of the method for forming a colored coating film of aluminum or aluminum alloy according to the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a film forming apparatus for carrying out the method for forming a colored film of aluminum or aluminum alloy according to the present invention. This film forming apparatus 1
0 is an aluminum material 16 in the electrolytic solution 14 in the container 12.
an electrolysis section 18 in which a pair of electrodes consisting of a and 16b are immersed in a state of being separated by a predetermined distance; an amplifier 20 electrically connected to the electrodes and amplifying and outputting an input signal;
Connected to the amplifier 20 via a changeover switch SW,
An AC generator 22 for outputting a predetermined AC signal to the amplifier 20 side. The AC generator 22 stores data for creating the predetermined AC signal in the AC generator 22.
A signal input section 24 for inputting to the is connected. An oscilloscope 26 for checking the alternating current signal generated by the alternating current generator 22 is connected to the alternating current generator 22. Further, the amplifier 20 has a direct current generator 28 for outputting a direct current to the electrolysis section 18 via the changeover switch SW.
Are connected. The aluminum material 16a,
As 16b, a pre-treated material for removing oxides and fats and oils on the surface is used.

In the present embodiment, the aluminum material 16a,
As 16b, an aluminum alloy of JIS A1080P-H24 was used. As the electrolytic solution 14, 10% by weight of sulfosalicylic acid, which is an organic acid, and 0.
A mixture of 5 wt% sulfuric acid was used and the temperature of the mixture was set to 20 ° ± 1 ° C.

Therefore, based on the above configuration, data for forming a predetermined AC signal is input to the AC generator 22 using the signal input section 24. The AC generator 22
As shown in FIG. 2, the AC signal output from the changeover switch SW and the amplifier 20 continuously changes its frequency from 100 Hz to 1000 Hz within a unit time of 20 ms. ,
The electrodes made of 16b were energized for a predetermined time shown in Table 1.
The amplitude of the AC signal was set to ± 56.15V. The AC signal output from the AC generator 22 was confirmed via the oscilloscope 26.

As described above, the aluminum material 16
A primary coating was formed on the surfaces of the aluminum materials 16a and 16b by continuously applying an alternating current to a and 16b for a predetermined time. Next, after forming the primary coating,
The aluminum material 16 is selected by switching the changeover switch SW.
A colored secondary film was formed by applying a direct current to a and 16b through a direct current generator 28. that time,
An aluminum electrode was used as the counter electrode. That is, the aluminum material 16a, 16b on which the primary coating is formed is connected to the anode in the electrolysis section 18, and a normal aluminum plate on which the primary coating is not formed is connected to the other cathode side to generate a direct current. Shed In this case, between the electrodes,
As shown in Table 1, a DC voltage of 50 V was applied for 30 minutes.

[0014]

[Table 1]

As a result, as shown in Table 1, when an alternating current is applied for 20 minutes and then a direct current is applied for 30 minutes, the thickness of the coating film formed on the surfaces of the aluminum materials 16a and 16b is about 36. The thickness is about 43.3 μm when the direct current is applied for 30 minutes after the alternating current is applied for 30 minutes, and the thickness is about 43.3 μm when the alternating current is applied for 40 minutes and the direct current is applied for 30 minutes. 50.0 μm
Thus, it was confirmed that the coating film gradually thickened as the energizing time was longer in the range of 20 to 40 minutes of energizing the alternating current.

FIG. 3 shows the relationship between the coloring density of the secondary coating formed on the surfaces of the aluminum materials 16a and 16b and the energizing time of the alternating current and the direct current. The effect of changing the color tone from a dark brown dark color to a light brown light color was obtained as the AC current was applied for a longer time. Further, FIG. 4 shows the relationship between the hardness and the coloring density of the aluminum materials 16a and 16b on which the secondary coating is formed. When an alternating current was applied for 20 minutes in the electrolytic solution and then a direct current was applied for 30 minutes, an aluminum material having a hardness of 240 HV could be obtained. In addition, when an alternating current is applied for 30 minutes and then a direct current is applied for 30 minutes, approximately 241 HV
It was possible to obtain an aluminum material having a hardness of. Similarly, after passing an alternating current in the electrolytic solution for 40 minutes and then applying a direct current for 30 minutes, an aluminum material having a hardness of about 246 HV could be obtained. From this, it is possible to obtain the effect that the hardness becomes higher as the time for which the alternating current is passed becomes longer.

In this experiment, the frequency of the alternating current was set to 1
Although it is changed so as to continuously increase in a unit time in the range of 00 Hz to 1000 Hz, the range of the frequency is not limited to this, and may be changed in the range of frequencies other than the range. . Further, it is not always necessary to change the frequency so as to increase or decrease, and an irregular alternating current may be used. Furthermore, the irregular change of the alternating current does not need to be periodically repeated, and does not have to be continuously energized.

[0018]

According to the method for forming a colored coating film of aluminum or aluminum alloy according to the present invention, the following effects can be obtained.

That is, by increasing the thickness of the film formed on the surface of aluminum or aluminum alloy,
Improves corrosion resistance, weather resistance and wear resistance,
The coloring density can be a light color.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a film forming apparatus for carrying out a method for forming a colored film of aluminum or an aluminum alloy according to the present invention.

FIG. 2 is an explanatory diagram showing a signal waveform of an alternating current for forming a primary coating.

FIG. 3 is an explanatory diagram showing a relationship between a film thickness of a colored film formed on the surface of aluminum or an aluminum alloy and a coloring density.

FIG. 4 is an explanatory diagram showing the relationship between the hardness and the coloring density of a colored coating formed on the surface of aluminum or an aluminum alloy.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Coating film forming apparatus 12 ... Container 14 ... Electrolyte 16a, 16b ...
Aluminum material 18 ... Electrolysis part 20 ... Amplifier 22 ... AC generator 24 ... Signal input part 26 ... Oscilloscope 28 ... DC generator

Claims (1)

[Claims] 1. A process of forming a primary coating by passing an alternating current, which is changed in the number of pole conversions during electrolysis, through aluminum or an aluminum alloy immersed in a mixed solution containing an organic acid and an inorganic acid, And a step of applying a direct current to the aluminum or aluminum alloy on which the primary coating has been formed to form a secondary coating.