JPS58147592A - Method for pigmenting aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain a durable desired deep color in a short time, by forming an anodic oxide film on an Al material, subjecting the film to AC electrolytic treatment in an aqueous sulfuric acid soln. at low voltage, and pigmenting the film. CONSTITUTION:An anodic oxide film is formed on Al or an Al alloy, and the film is subjected to AC electrolytic treatment in an aqueous sulfuric acid soln. at about 3-20V anodic oxidation voltage which is below the electrolytic voltage during the formation of the anodic oxide film. After finishing the pretreatment, the film is washed, colored with a dye or an inorg. pigment, washed, and subjected to treatment for sealing the pores. By this method, even in case of a thin film having >=about 10mum thickness, a desired deep color with a superior hue and superior luster free from irregular color is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the coloring method, an anodic oxide film is formed on aluminum or an aluminum alloy, and then the anodic oxide film is subjected to AC electrolysis in an aqueous sulfuric acid solution at an electrolytic voltage lower than the primary electrolytic voltage of about 3 to 20 V. By processing and then coloring, it is possible to perform deep coloring, such as black dyeing, evenly, making it an extremely desirable product with excellent color tone. Moreover, aluminum can be washed with high productivity and at low cost. Another object of the present invention is to provide a method for coloring an aluminum alloy.

Conventionally, to color aluminum or aluminum alloy (hereinafter simply referred to as aluminum), in order to obtain a deep color in the general VC dyeing or coloring process with inorganic pigments, the following steps were taken: (1) increasing the solute concentration of the processing solution; (2) increasing the solute concentration of the processing solution; increase the liquid temperature,
(3) Measures such as lengthening the processing time can be considered, but these measures have various problems. That is, (1
) means that it is easy to obtain a deep color at the end of the bath build-up period, but slight differences in film thickness directly affect the color density;
Different colors appear, making it difficult to obtain a good desired product.

Furthermore, the degree of coloring is greatly affected by the temperature distribution and stirring condition of the processing liquid, making color unevenness extremely likely to occur. In addition, there are disadvantages such as the processing liquid is unstable, tends to form precipitates, and has a short lifespan.
Since the coloring speed is fast in the above method, it is difficult to control the coloring rate, and it is easy to cause smearing, color difference, and color unevenness.Also, a pore sealing effect occurs during the coloring process, which tends to result in non-uniform coloring. Furthermore, the method (3) has extremely low productivity and is not suitable for industrial implementation at all.

In addition, as a means to improve the colorability of aluminum, it has been proposed that, unlike the above-mentioned means, the characteristics of the aluminum surface layer where coloring is performed are modified.For example, (4) Increasing the electrolyte temperature during oxidation treatment, (5) lowering the current density, (
6) Increasing the concentration of the electrolyte, (7) Using a floating source or a DC power source with a lot of pulsating current, etc.) are possible, but it is possible to obtain good colored aluminum even with just one of these methods. I can't do it.

For example, in the methods (41, (6), and (7)), the aluminum surface film becomes extremely soft, and the surface film formation efficiency is low, resulting in low productivity.
The method 7) has the drawback that a phenomenon of film peeling occurs during electrolysis, resulting in a film with poor corrosion resistance, and furthermore, a yellowish tinge. Furthermore, the method (5) requires a long anodizing treatment time, resulting in extremely poor productivity and is not suitable for industrial implementation.

Moreover, instead of simple anodizing treatment as described above, for example, after forming an anodized film on aluminum, this aluminum is colored by electrolytic treatment at an electrolytic voltage of 0.5 to 2 V, and then paint is applied. A method such as drying (Japanese Unexamined Patent Application Publication No. 1983-I Z6i No. 1), or after forming an anodic oxide film on aluminum, electrolytically coloring the aluminum by electrolyzing it in alternating current in a metal salt water bath solution,
Next, a method of dyeing with Yukinzome Tsuge (Japanese Patent Application Laid-Open No. 1973-
28.136), a means of carrying out electrolytic treatment in two stages has been proposed as N+J treatment of coloring treatment with dyes or pigments. The inventor of the present invention has also conducted various studies on methods of performing electrolytic treatment in two stages when coloring with dyes, etc., and has found that the degree of coloring is greatly affected by the second stage of electrolytic treatment,
The color quality of the layer C was not good under the processing conditions described in the above publication.

As a result of detailed experiments on what kind of pretreatment should be applied to aluminum in order to dye aluminum with a desired color tone or color it with inorganic pigments, the inventors found that: In the electrolytic treatment in step ['', an aqueous sulfuric acid solution is used as the treatment liquid, and the electrolytic voltage is lower than the electrolytic voltage in the first stage, and AC electrolysis is carried out at a voltage of about 3 to 20 μm. It was discovered that coloring using inorganic pigments is good for dyeing.

Ie, pre-treatment on aluminum, ie? After carrying out conventional pretreatment such as degreasing, water washing, etching, water washing, neutralization, and water washing, the pretreated aluminum is subjected to a conventional anodizing treatment for about 3 to 30 minutes. 15μm
After forming a thick anodic oxide film, the aluminum on which this anodic oxide film has been formed is then heated to a concentration of about 50 to 300 g.
/11 sulfuric acid aqueous solution, temperature is about 10 to 4σG, frequency is about 10 to 100Hz, current density is about 05 to 4A.
This pretreatment can be carried out by performing a pretreatment in which the electrolysis voltage is lower than the electrolysis voltage in the previous step, and AC electrolysis treatment is performed for about 1 to 10 minutes at a voltage of about 3 to 20 V. According to the aluminum coloring method in which the aluminum is washed with water, then colored with a dye or inorganic pigment, and then washed with water and sealed, the desired coloration with extremely excellent color tone can be achieved with high productivity. It is something.

Similarly, in the above-mentioned electrolytic treatment step, if a sulfuric acid aqueous solution is used as the next electroshear treatment solution, it is only necessary to switch the power supply in the same treatment tank, and the process can be carried out extremely efficiently.

In the above step, if the voltage during the secondary %M treatment is too low, that is, in 3. However, if the voltage is higher than about 20V, the anodic oxide film formed by the first electrolytic treatment will be destroyed, and if the voltage is higher than the next electrolytic treatment, The anodic oxide film will also be destroyed, so the particularly desirable electrolytic voltage is -
Below the next remission voltage and about 10-20V, the father,
- If the current density during the next electrolytic treatment is too small, that is, below 05 A/di, the effect of this electrolytic treatment will be 1
1A/dm is not observed, and the coloring with dyes or inorganic pigments in the next process is not as desired.
If the current density is about 1 to 35 cm, the anodic oxide film will be destroyed and coloring with dyes or inorganic pigments in the next process will not be desirable.
A/CW, and the processing time of this secondary AC electrolysis is preferably about 2 minutes or more. On the other hand, if the sulfuric acid concentration exceeds 3009/l, it is not only difficult to control the voltage and current, but also the properties of the film deteriorate, making the next electrolytic treatment difficult. The coloring caused by dyes or inorganic pigments in the process is not desirable, and the concentration of the nitrous sulfuric acid aqueous solution is about 100 to 200 g/l, and the liquid temperature during the secondary AC electrolysis is particularly low. 15
It has been found that carrying out the process within the range of ~25°C is preferable for coloring with dyes or inorganic pigments in the next step.

The coloring of the anodic oxide film of aluminum with dyes or inorganic pigments is based on the physical and chemical properties of the anodic oxide film, such as the surface activity of the anodic oxide film, physical or chemical attraction, and the structure of the micropores. However, it is greatly influenced by

These factors are greatly influenced by the conditions of secondary electrolysis, and when an anodic oxide film is treated under the conditions of the present invention, the interaction between the treated anodic oxide film and dyes or inorganic pigments is reduced. This is preferred and appears to result in superior coloration with dyes or inorganic pigments.

The same shows a photograph taken with a scanning electron microscope of a cross section of aluminum subjected to the treatment process of the present invention, that is, the anodic oxide film was subjected to AC electrolysis under the secondary electrolytic treatment conditions described above.

Hereinafter, specific examples of the method for coloring aluminum or aluminum associations according to the present invention will be described.

Example 1 An aluminum plate (A 1050P-H24) was first
Pretreatment is carried out by two culms, including degreasing, etching, and neutralization according to the 6' method.

Next, this pretreated aluminum plate was heated to a concentration of about 150. ! ? /l of sulfuric acid aqueous solution, the bath temperature is about 20"
Anodic oxidation treatment is carried out for about 25 minutes using a lead plate as a cathode under conditions of a current density of 1.3 A/2 and a voltage of about 18 V to form an anodic oxide film with a thickness of about 10 μm on the surface of the aluminum plate.

Subsequently, in the same bath solution, the electrolytic voltage is about 18 V or higher,
AC electrolytic treatment was carried out for about 3 minutes under conditions of a current density of about 4h7ch, z or less, and a bath temperature of about 20°C.

After washing the aluminum plate treated as described above with water, use a black dyeing solution (1" ACC manufactured by Jitsukei Pharmaceutical Co., Ltd.
12 (concentration 10 Vl) for about 10 minutes, and then sealed in deionized boiling water for about 20 minutes.

Example 2 An aluminum plate was pretreated in the same manner as in Example 1 up to the step of AC electrolytic treatment, and after washing the aluminum plate subjected to AC electrolytic treatment with water, a 6σC/ferric ammonium oxalate solution (concentration Approximately 10 Vl) The instep is immersed for approximately 5 minutes to give it a golden color, and then soaked in deionized boiling water for approximately 20 Vl.
Seal the hole for a minute.

An aluminum plate similar to that of Example 1 was pretreated in the same manner as in Example 1, and then anodized for approximately 55 minutes under the same conditions as in Example 1. After forming the anodic oxide film of 1, om Ijj, the AC electrolytic treatment in the previous example was not carried out, but it was colored using the same black dyeing solution or ferric ammonium oxalate bath solution as in the previous example, and then desorbed. The hole was sealed in ionized boiling water for 20 minutes.

Observing the degree of coloring of the colored aluminum-lamb plates obtained in the above Examples and Comparative Examples, it was found that those according to the above Examples had a more constant coloring density than those of the Comparative Examples, and had no reeds or uneven coloring. It was beautiful, had an excellent color tone, and was extremely desirable. In addition, the products according to the above examples are superior in gloss compared to those according to comparative examples, and can be used, for example, in applications requiring brightness, and can be used before buffing, chemical polishing, etc. Likelihood θ obtained by processing
It was also something that did not reduce the number of people.

Further, the time required for the blue coloring performed as in the above embodiment is half of the time required for coloring as performed in the comparative example, resulting in significantly higher productivity.

Furthermore, regarding the durability of the coloring of aluminum plates, 6JI
I For example, Taber abrasion loss, alkali resistance,
In terms of properties such as the CAST test and accelerated weather resistance, the products according to the present invention are comparable despite having a thin colored film layer, and for example, properties such as Taber abrasion loss are about three times better, which is extremely It is also highly durable.

As mentioned above, the method for coloring aluminum or aluminum alloy according to the present invention is to form an anodic oxide film on aluminum or aluminum alloy, and then use the electrolytic voltage lower than that at the time of forming the anodic oxide film in a sulfuric acid water bath solution to
Since alternating current electrolysis treatment is performed at an anodizing voltage of ~20V and then coloring treatment is applied, even if the thickness of the anodic oxide film is thin, it is not as thick as the conventional method, for example, about 20 μm thick. Even with a thin film of approximately 10 μm or less in thickness, it is now possible to color the desired deep color, with excellent tone and gloss, and with no uneven coloring, and the durability of the coloring obtained in this way is extremely good. Furthermore, since the desired deep coloration can be achieved even with a thin film, the time required for the coloring treatment is extremely short, and it has the advantage of being highly productive and low cost.

[Brief explanation of the drawing]

The drawing shows the structure of aluminum that has been subjected to AC electrolytic treatment carried out in the method for coloring aluminum or aluminum alloy according to the present invention. This is an electron micrograph. Patent applicant: Mitsubishi Aluminum Co., Ltd. +1 Agent: Katsumi Utaka☆-2

Claims (1)

[Claims] After forming an anode and an oxide film g on aluminum or an aluminum alloy, galvanic debris treatment is performed again in an aqueous sulfuric acid solution at an anodizing voltage of about 3 to 20 V, which is lower than the electrolytic voltage at the time of forming the anodic oxide film, and then colored. A method for coloring aluminum or aluminum alloy, characterized by applying a treatment.