JPS5855240B2 - Coloring method of anodized film using current reversal electrolysis and aluminum alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to coloring an anodic oxide film using current reversal electrolysis and an aluminum alloy. By periodically changing the polarity and applying a negative current to chemically form the film, allowing the film to contain and accumulate sulfur compounds, and immediately heating the film in an aqueous solution,
This relates to a method of coloring the anodic oxide film by reacting the metal in the film with a sulfur compound, and changing the alloying element and amount added to the aluminum alloy, current reversal conditions, etc. to color the anodic oxide film in various tones.

Generally, anodic oxide films on aluminum and its alloys are porous and can be easily colored using the pores. Taking advantage of this property, they are currently widely used in decorative items, equipment parts, kitchen items, building materials, etc. There is.

A commonly used method for coloring anodized films is to adsorb organic dyes into the fine pores of the film, but the colored films produced by this method have poor weather resistance and are susceptible to exposure to sunlight. It cannot be used for parts and materials that are exposed to sunlight, and it has the disadvantage that if it is lightly colored, it will fade even indoors.

The following methods are available to compensate for these shortcomings.

(1) Alloy method: This is a method in which an alloy element that is easily colored by anodization is added to the aluminum material used to form the film, and the anodic oxide film is chemically formed to produce natural color. It has the disadvantage that the amount of paint is limited and that it does not produce color unless it is a thick film.

(2) Method using electrolyte: This method uses an alloy that easily develops color as in (1), and also uses a special electrolyte that easily develops color during film formation.It has excellent light resistance, but the electrolyte Compared to sulfuric acid electrolytes, however, they are more complicated to manage and more expensive, require high voltages for film formation, and have drawbacks such as a limited variety of color tones.

(3) Secondary AC electrolysis: This method involves forming the anodic oxide film in an electrolytic solution such as sulfuric acid, and then performing secondary AC electrolysis in a solution containing heavy metal salts to color it. It is relatively abundant and is the most commonly used coloring method for building materials.

However, in this method, the composition of the secondary electrolyte is complex and the control range of electrolytic conditions is narrow, making operation and management difficult, and the color tone tends to vary.

Furthermore, in order to obtain products with many different color tones, an electrolytic cell and a power source are required for each color tone, resulting in high equipment costs.

(4) Method using current reversal electrolysis (% patent application number 1973-
051218): This method was developed to improve the drawbacks of the above methods.

In other words, aluminum and its alloys are placed in sulfuric acid or an electrolytic solution containing sulfuric acid, and the polarity is periodically changed to reverse the current, forming a film while accumulating sulfur compounds in the film, and then heating the metal salt. It is colored by immersing it in a solution.

This method can be easily colored by simply immersing the film in a metal salt solution after forming the film, and by changing the metal salt and current reversal conditions, various color tones can be obtained. It has the advantage of being able to be colored economically.

In the present invention, during anodic oxide film formation, the polarity is periodically changed, a negative current is passed at a reversal ratio of 50% or less, and the film formation is interrupted, thereby suppressing polarization and heat generation while achieving high speed. A method of obtaining a hard film using a method of forming a hard film using a new anodizing method proposed in Patent Application Publication No. 131932/1980, ``Anodic oxidation method of aluminum and its alloys by current reversal electrolysis'', A method of coloring an anodic oxide film in various tones by immersing it in a solution containing warm metal salts such as nickel, cobalt, copper, silver, and lead, i.e. Application No. 54-051
Using the new coloring method proposed in No. 218, ``A method for coloring anodic oxide films of aluminum and its alloys using current reversal electrolysis'', we investigated the coloring of anodic oxide films by alloying elements of aluminum materials. We have found that the cane can be colored more easily and more advantageously than before without immersing it in a metal salt solution after chemical formation.

In other words, the purpose of the present invention is to periodically change the polarity, reverse the current, flow a negative current, and interrupt the film formation, thereby suppressing the heat generation caused by polarization and electrolysis, and forming a thick film at high speed at high temperatures. A method to obtain an anodic oxide film with high sheath hardness and to color the film in various tones extremely easily by reacting the sulfur compounds accumulated in the film by reduction of sulfuric acid electrolyte with the metal ions present in the film. It provides:

The present invention reacts with sulfur compounds such as iron, copper, and cobalt,
Current reversal electrolysis involves periodically changing the polarity of an aluminum alloy containing alloying elements that easily stain in sulfuric acid or an electrolytic solution containing sulfuric acid. In other words, a positive current forms an anodic oxide film, and a negative current forms a sulfur compound in the film. After the film is chemically formed by repeatedly accumulating sulfur, it is immersed in a heated solution such as boiling water or a sealing solution and heated to cause the metal ions present in the film to react with the sulfur compound, forming an anode. It colors the oxide film in various colors.

The features of the present invention are (1) It is possible to color the aluminum alloy very easily and economically by forming an anodic oxide film on the aluminum alloy in sulfuric acid or an electrolytic solution containing sulfuric acid, and then heating it in boiling water or a sealing solution. It is true.

(2) It is possible to color the aluminum alloy in various tones by changing the type and content of additive elements, and since the metal involved in coloring is uniformly distributed throughout the film,
A uniform and stable color tone can be obtained.

(3) In addition to the escape of the aluminum alloy, the color tone can also be changed by changing the reversal ratio of changing the polarity and flowing a negative current, the formation time, etc., and adjusting the amount of sulfide.

(4) Since there is no need to use a metal salt solution for coloring, wastewater treatment is easy and there is no need for coloring equipment after film formation.

etc. are mentioned. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Electrolyte Sulfuric acid 20 weight φ Current reversal conditions Repetition period 13.3Hz Reversal ratio 15
Positive current density 4A/dm Power heat treatment Boiling water Under the above conditions, a carbon plate was used as a counter electrode to form a film for 20 to 40 minutes, and the color tone of the film after being immersed in boiling water for 20 minutes and power heat was as shown in Table 1. It became.

The coating is changed by periodically passing a negative current using a current reversal method, and when heated in boiling water, the anodized coating becomes colored.

The color tone varies depending on the type of element added to the aluminum alloy.

For example, the A 1-Cu alloy is pale yellow when it is coated as it is, but it becomes pale moss color after 20 minutes of coating (24 μm), and light gray after 40 minutes of coating (48 μm).

The coloring of the film is progressed by a strong heat treatment using boiling water.
The color tone becomes darker as the coating thickness increases and as the copper content in the alloy increases.

The Al-Fe alloy is light gray in color when it is coated, but it becomes dark gray (24 μm) after mechanical heat treatment with boiling water.
The color becomes pale black (48 μm), and the higher the iron content, the darker the color tone.

The Al-Co alloy has a color ranging from gray to gray-yellow, and various color tones can be obtained by changing the type of caloric element added in the alloy, the amount of caloric added, and the thickness of the coating.

Example 2 Electrolyte current reversal conditions Sulfuric acid 20 weight type Repetition cycle 18Hz Reversal ratio 15% Positive current density 4A/dm2 Heat treatment Sealing solution Under the above conditions, the chemically converted film was sealed containing nickel salt for 20 minutes. As a result of heating to zero in a treatment solution, the color tones shown in Table 2 were obtained.

The color tone of the Al--Cu alloy was almost the same as when heated with boiling water, and the Al--Fe alloy and Al--Co alloy became darker than when heated with boiling water, and a blackish tone was obtained.

For these reasons, after forming a film by current reversal electrolysis, it can be colored by heating with boiling water, a sealing solution, etc., and sealing can be performed at the same time.

Example 3 Electrolyte 20% sulfuric acid type Flow reversal conditions Repetition period 13.3Hz Positive current density
4 A/d m2 Formation time 20 ruts Under the above conditions, the film was formed by changing the reversal ratio of periodically passing a negative current, and as a result of heating in boiling water and sealing solution, the results shown in Table 3 were obtained. The color tone was obtained.

In film formation by current reversal electrolysis, when the reversal ratio is changed, the color tone of any alloy film changes.

In other words, if the reversal ratio is small, the color tone will be light; if the reversal ratio is large, the negative current will increase, and the amount of sulfur compounds that will be accumulated in the film and react with the metal in the film will increase, resulting in a dark color tone of the film. .

From these facts, by changing the current reversal ratio, it is possible to adjust the negative current during film formation and easily change the color tone.

Example 4 Electrolyte Sulfuric acid 20 weight φ Bath temperature 20°C Current reversal conditions Reversal ratio 15% Positive current density 4 A/d Creation time 20 waves n Under the above conditions, the current for Al-Fe (1.4%) alloy was Table 4 shows the color tone and properties of the film when the film formed by changing the repetition cycle of inversion was heated for 20 minutes in a sealing solution kept at 95°C.

When the repetition period is from 20 Hz to 100 Hz, there is almost no change in color tone, and a blackish dark gray coloring is obtained.

When the repetition rate is 200 Hz or more, the film thickness becomes thinner and the coloring becomes lighter.

In the repetition period O1, that is, in direct current electrolysis without current reversal, the color develops naturally and becomes a light gray tone, but it does not become colored in the heat treatment after film formation.

Regarding the thickness and hardness of the film, the strength of the film produced by the current reversal method is superior to that produced by the direct current method, and by using the illegal method, a high-quality anodic oxide film can be obtained, and the film can be easily colored in various tones. .

Example 5 Electrolyte bath temperature current reversal conditions Sulfuric acid 35% by weight + 10 g/l oxalic acid 15°C Repetition period 13.3Hz Reversal ratio 15 factor 4 A/dm2 Positive current density Under the above conditions, the chemically converted film was heated in boiling water. As a result of the Calo heat treatment for 20 minutes, the color tones shown in Table 5 were obtained.

Films chemically formed in a sulfuric acid-oxalic acid mixed bath can also be colored to the same color tone as films formed in a sulfuric acid bath. can be colored.

[Brief explanation of drawings]

FIG. 1 shows an example of an inverted current waveform caused by a converter, and FIG. 2 shows an example of an inverted current waveform caused by a power supply device.

Claims (1)

[Claims] 1. An aluminum alloy containing an alloying element that reacts with sulfur compounds and becomes colored is placed in sulfuric acid or an electrolytic solution containing sulfuric acid, by converting the polarity and reversing the current. By chemically forming the film while passing a negative current, sulfur is added to the film. It is characterized by accumulating compounds, immersing the alloying elements and sulfur compounds present in the film in a solution at room temperature such as boiling water or sealing solution, and causing them to react and color by being heated. A coloring method for anodic oxide films using current reversal electrolysis and aluminum alloys.