JPS61127898A - Electrolytic pigmentation method of aluminum or aluminum alloy - Google Patents

Abstract

PURPOSE:To color uniformly an A4l material to a wide range of color tones in a flexible state in the stage of electrolytic pigmentation of said material by executing two stages of current conduction treatments at the successively increased current densities then dropping forcibly the current density. CONSTITUTION:The Al material on which an anodically oxidized film is formed is electrolytically colored in an aq. soln. contg. an inorg. salt. The material is first subjected to the current conduction treatment for 30 seconds - 10 minutes at approximately the constant current density within the range of 0.05-0.25A/dm<2> total current density or 0.03-0.14A/dm<2> negative current density. The material is then subjected to the current conduction treatment so that the peak current density attains 0.25-1.20A/dm<2> total current density or 0.14-0.70A/dm<2> negative current density. The current density is thereafter forcibly dropped at least once so as to be made about 10-95% of the current density at the point of this time. These treatments are executed in the same bath. The stability of the color tones and throwing power are improved by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrolytic coloring method for aluminum or aluminum alloy (hereinafter referred to as aluminum). Electrolysis that colors the aluminum by electrolyzing the film in an electrolytic solution in which a metal salt is dissolved using alternating current or a waveform that has an equivalent effect to precipitate the metal or metal oxide of the metal salt in the electrolytic solution into the oxide film. In the coloring method, it is possible to color a wide range of colors with one electrolytic solution, and it is possible to make the coloring uniform, and it is also effective when electrocoating a colored film when it is colored in a light color, for example, a pale bronze color (Stenco). Color removal relates to an improved method that suppresses changes in color tone due to staining, etc., and enables uniform coloring without unevenness.

Conventional technology Conventionally, aluminum is anodized to form an oxide film, which is then subjected to alternating current electrolysis in an electrolyte containing a metal salt such as a nickel salt, thereby producing an anodized film of a metal or metal oxide. The method of coloring by precipitation into the pores is already known as the electrolytic coloring method (% Publication No. 38-1715) and is widely used.

However, in this type of electrolytic coloring method, when trying to color a wide range of colors from pale bronze (stainless steel color) to black using an electrolytic solution of one composition, it is difficult to color the electrolytic solution with It is necessary to improve the colorability by increasing the amount of metal salt. However, if the coloring property is improved, the coloring time will inevitably be shortened when coloring in a light color, which makes color matching difficult and causes problems such as poor color stability and coverage. be. On the other hand, if the coloring property is suppressed, the adhesion property will improve, but if the coloring is done in a deep color, the coloring time will be longer.
This not only increases the electrolytic treatment cycle time but also causes problems such as film breakdown.

Therefore, in order to obtain colored films of various tones, it is necessary to prepare electrolytic solutions each having a composition corresponding to the desired color tone and to replace the electrolytic solution each time.

Problems to be Solved by the Invention As described above, according to the method of performing electrolytic coloring by replacing the electrolytic solution each time depending on the desired color tone, the work of replacing the electrolytic solution is troublesome, and Setting and operating the electrolytic conditions corresponding to the liquid composition is complicated, and there are various disadvantages such as having to prepare various electrolytic solutions in advance (this makes it difficult to manage the electrolytic solutions. When trying to color a wide range of colors using a liquid, for example, when trying to color a light color such as pale bronze (stainless steel) using a bronze-colored electrolyte, the coloring time is short, so the stability of the color and the adhesion may be affected. It has the disadvantage that it has poor spinability and is prone to color loss and color change during subsequent electrodeposition coating.Also, the coloring time for each color tone is not constant, and it is necessary to adjust the coloring density by the coloring time. For,
It is extremely difficult to match the colors, and there are various disadvantages such as uneven coloring occurring in the depressions and protrusions when processing shapes with complicated shapes. Preferably, simultaneous framing of different shapes is l'Fj! As mentioned above, it is extremely difficult to carry out treatment by bathing, and improving this situation has become a recent challenge.

Therefore, an object of the present invention is to solve the above-mentioned problems, to increase the versatility of the production line so that coloring can be done in a wide range of colors using one standard electrolyte, and to be able to color in a flexible state. The object of the present invention is to provide an electrolytic coloring method.

One direct object of the present invention is to provide an electrolytic coloring method that allows uniform coloring in a wide range of colors using one reference electrolytic solution and that has excellent color stability and spreadability.

Another direct object of the present invention, in relation to the above object, is that the coloring time for each color tone is relatively constant, and there is almost no coloring unevenness due to individual differences in color matching. The object of the present invention is to provide an electrolytic coloring method that can be colored into various desired colors with relatively simple operations.

Means for Solving the Problems The present invention achieves the above object by regulating the current density during electrolytic coloring.

In other words, the electrolytic coloring method for aluminum according to the present invention involves electrolyzing an anodic oxide film formed on the surface of aluminum in an aqueous solution containing an inorganic metal salt using an alternating current or a waveform having an equivalent effect. '[When coloring, the aluminum is heated at a total current density of 0.05 to 0.
25 [A/dn? ] or purchase current density g 0.03~0.
3 at approximately constant current density within the range of 14 (A/a, 7:)
Electricity is applied for 0 seconds to 10 minutes, and then in the same bath, the peak current density or total current density is 0.25 to 1.20 (A/dm), or the negative current density is 0.14 to 0.7OCA'. /di], and then the current density is forcibly lowered at least once.

Effects and Modes of the Invention The present inventors have conducted intensive research to explore an electrolytic coloring method that can be colored in a wide range of colors using one electrolytic solution, and have determined the relationship between coloring time and current density (current It has been found that the above-mentioned problems can be solved by determining a current density pattern) and controlling the current density pattern according to the current density pattern corresponding to each color tone.

There are two types of current density patterns: a perfusion density pattern that focuses on stabilizing the color tone of light colors, and a current density pattern that focuses on shortening the coloring time of dark colors such as dark bronze and black.

In the case of light coloring (lightening), a current density pattern is used that suppresses coloration while improving rootability.

On the other hand, in the case of deep coloring (deepening), the current density pattern is designed to improve coverage and color progression and shorten the coloring time.

The present invention relates to an electrolytic coloring method using a current density pattern for the former case of light coloring.

The present invention will be explained in detail below.

Conventionally, when coloring in a light color, the coloring time is generally short,
As mentioned above, color matching is difficult, and color stability and coverage are poor. In addition, since anodic electrolysis is performed in the subsequent electrodeposition coating, color loss and color tone changes are likely to occur due to the outflow of the Kinpei compound adsorbed to the bottom of the alumite pores to the pore surface layer (1°). According to research, the current density pattern during electrolytic coloring after anodizing treatment has a total positive and negative current density of 0.
25~I, 20 CA/dm) or negative current density 0
．． 14 to 0.70 (A/d higher than the final current density of , then at least 1
By lowering the current density, preferably 10 to 95 times lower than the current density at the time of fluctuation, stabilization of light color tone, improvement of coverage, and uniform coloring when framing different types of shapes at the same time. It has been found that the effect of suppressing color tone changes caused by color removal during electrodeposition coating, etc. can be obtained.

The electrolytic coloring method according to the present invention is based on a first method using a constant current density.
It consists of a step energization process, a second step energization process that applies a higher current density than the first step energization process, and a third step energization process that reduces the current density.

In the first step energization process, a voltage (current density) of 8 degrees is applied where the current does not attenuate or hardly attenuates during the energization time, and the film quality is adjusted to improve coverage and color tone stability.
This is achieved by stabilizing the initial current density before the second step energization process. The current density is the total current density 0.
05-0.25 [A/dm] or negative current density 0.03
~0.141: A/d♂] and the current application time is 30 seconds or more, preferably 60 seconds or more, so that the anodic oxide film is sufficiently modified.

The second step energization treatment is performed to improve the degree of coloring and coverage, and the total current density is 0.25~
1.20 (A/d) or negative current density 0.14 to 0
．． The current density is increased so that the peak current density falls within the range of 70 CA/d). The current density may be varied so that a smaller peak occurs before reaching this peak current density, that is, the current density may be increased gradually.

The energization time of this second step energization process is preferably 20 seconds or more, preferably 30 seconds or more.

In the third step energization treatment, the current density is forcibly lowered, which has the effect of improving coverage, adjusting color tone, and preventing color stripping, resulting in a colored film with a stable finish. During this period, the starvation density is forcibly lowered at least once, and the current density is lowered to 10 to 95 times the current density at the time of fluctuation. If the current density decreases by a factor of 10 or less, the time required to obtain the desired coloring becomes longer, making it impractical. Moreover, if it is 95 inches or more, the effect of forcibly lowering it, that is, the improvement in turning performance cannot be obtained, which is not preferable. The energization time after the second step energization process, that is, after the forced current density drop, is preferably 30 seconds or more, preferably 60 seconds or more.

The above-mentioned current density pattern may be controlled by a voltage variation method, but since the desired current density must be set by adjusting the voltage for each number of meters processed, the operation is complicated, and it also has problems in terms of accuracy. It is extremely bad and has the drawback of not being able to produce sufficient effects. Therefore, in the present invention, electrolytic coloring is carried out using alternating current or a waveform having an effect equivalent to alternating current, but the current density pattern is controlled by either positive or negative total current density or negative current density. The negative current density is approximately 55% of the total positive and negative current density, although it varies slightly depending on changes over time in the energization process, conditions of the anodizing process, electrolytic coloring process, etc.

Next, an example of a method of controlling the current density pattern will be described below. In the case of control using negative current density, do as shown in Figure 1.The standard negative current density pattern to be controlled is memorized, and each time the next product is processed, a current corresponding to the area to be processed is applied. Automatically adjusts the power supply so that the current flows according to the standard negative current density pattern. The total current density pattern is controlled in the same manner as the negative current density pattern, and the schematic configuration of the control device is shown in FIG.

Although the control of any of the above current density patterns is basically the same, an example of the control method will be described in detail with reference to FIG. 2, taking the total current density pattern as an example.

(1) Input the standard current density pattern (memory pattern) to be set into the memory circuit 6. For example, a current is actually applied to the product and input from the rectifier circuit 10h) to the memory circuit 6.

(11) Next, at the same time as passing current through the product 3 to be controlled, a memory pattern is simultaneously output from the memory circuit 6 to the calculation command circuit 5, and a current tK converted to the area of the product to be controlled is calculated;
Compare with the amount of current flowing through product 3 to be controlled.

(Tsukuda) If the amount of current flowing through the product to be controlled after seconds of energization time is Act, and the amount of current calculated from the memory pattern after seconds is Lpt, then in the comparison in (11) above, if Apt) Lct. A command is issued from the arithmetic command circuit 5 to increase the voltage of the AC power source 4 and to decrease the voltage of the AC power source 4 if Apt (Act).
The calculation command is repeated until the energization ends so that t=Act.

In this way, changes over time in the current density of the product to be controlled and the current density of the memory pattern are controlled in a similar manner. 1st
In the case of negative current density control shown in the figure, a positive/negative current separation circuit 8 is provided in front of the negative current rectifying circuit 7 to rectify only the negative current, and the operations (1) to It) described above are performed.

FIG. 3 shows the composition of an example of the total current density pattern controlled as described above.

By the above operations, it is possible to pattern the change in current density over time during the current application process, and thereby, even if the number of processed products is different, electrolytic coloring can be applied according to the set current density pattern. Note that this operation may be performed manually to control the voltage so that the current flows according to a set current density pattern.

In the electrolytic coloring method of the present invention, there are changes in the film quality of the aluminum anodic oxide film as before, including barrier layer adjustment operations in the anodizing process, intermittent electrolysis, current recovery electrolysis,
It is also possible to fully understand and utilize changes in color tone, coverage, and layer chromaticity due to electrolytic control such as immersion in a liquid after the completion of electrolysis. There are various types of salts - examples include salts of metals such as nickel, cobalt, chromium, copper, magnesium, iron, cadmium, titanium, manganese, molybdenum, calcium, vanadium, tin, lead, zinc, etc. There are inorganic acid salts such as nitrates, sulfates, phosphates, hydrochlorides, and chromates, and organic acid salts such as nitrates, acetates, and tartrates, and these are used selectively. Preferably, two or more of these metal salts, more preferably three or more, are used in combination to significantly improve the degree of coloring progress and coverage. It may be added for the purpose of improving the rolling ability. Such strong reducing compounds include, for example, dithionite salts such as sodium dithionite, zinc dithionite, and ammonium dithionite, thiosulfates such as ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, and iron thiosulfate. salts, thioglycolates such as thioglycolic acid, ammonium thioglycolate, and sodium thioglycolate.

Aluminum or aluminum alloy to be colored by the method of the present invention refers to pure aluminum or pure aluminum mixed with one metal such as silicon, magnesium, copper, nickel, zinc, chromium, lead, bismuth, iron, titanium, or manganese. Or it is an alloy containing two or more types. After degreasing and cleaning the surfaces using a conventional method, these are used as anodes, and -
10,000, sulfuric acid, oxalic acid,
It is anodized by applying electricity in a normal acidic electrolyte such as sulfamic acid.

The film electrolytically colored by the method described above is sealed, if necessary, by known means such as boiling water, chemical sealing, or pressurized steam. Further, after performing this pore sealing treatment, or without performing the pore sealing treatment, the surface may be further protected by spray coating, dipping coating, or electrodeposition coating with a resin paint, if necessary.

EXAMPLES Next, the method of the present invention will be explained in more detail with reference to Examples.

Example 1 An extruded aluminum profile A-60638 that was degreased, etched, and smut removed by a conventional method was heated to 17.5 W/V.
% sulfuric acid aqueous solution to serve as an anode, and an aluminum cathode provided as a counter electrode, a 15V DC current was applied for 35 minutes at a current density of 1.2A/dm to anodize the surface by approximately 12 microns. A film was formed. This was washed with water. Next, the length is 300 kan, the width is 100 kan, and the height is 150 kan.
A container was used as a device for coloring electrolysis, a counter electrode was placed in one place, and the material to be treated was placed in the container with a length of 150 mm, a width of 70 mm, and a thickness of 1.3 mm, and the distance between the electrodes was 250 mm. AC electrolysis was performed according to the total current density pattern shown in FIG. In other words, the current density hardly attenuates in 5 seconds.
, l A/dm', and after electrolysis for 115 seconds, the current density was increased to a peak current density of 0-6 A/dm' in 5 seconds, and when that voltage was held for 3 minutes, the current density attenuated to 0.35 A/dm'. . 0.25A/d (71A/d before fluctuation)
%) K drop and after 30 seconds, 0.2 A/d
Ty? K decayed. Then add O, 15A/d (
When AC electrolysis was carried out using a current density pattern of 75° (before fluctuation) and electrolysis for 90 seconds, an even and uniform light bronze colored film was obtained on both the counter and non-counter electrode surfaces of the extruded aluminum profile. It was done.

Electrolyte: Nickel sulfate (hexahydrate) 251/ to magnesium sulfate (7 hydrate) IOy/ to cobalt sulfate ('
)' 21/l ammonium thiosulfate
11/ ammonium sulfate 30 f
/l boric acid 10 liters/lpH5,
6 After washing the colored film with water, it was washed with pure water at 70°C for 4 minutes. This was immersed in a 10% solution of self-dispersing thermosetting acrylic resin electrodeposition paint, and then applied with a stainless steel plate as a counter electrode for 3 minutes at +60V, and after washing with water, heated at 180℃ for 4 minutes.
It was baked and dried for 0 minutes to form a coating film of 8 μm. The color tone was almost the same as the color tone before electrolayer coating. Further, when an accelerated weather resistance test was conducted for 3000 hours using a weather meter, no abnormalities were observed, and no abnormalities were observed after 72 hours in a Cath test, confirming that the material had sufficient performance as an exterior material.

Example 2 In the method of Example 1, the total current density pattern was changed to the pattern shown in FIG. 5, that is, after electrolysis at 0.2 A/dm for 115 seconds, where the current density hardly attenuated in 5 seconds,
The current density was increased to a peak of 0-55 A/dm' in 10 seconds and then decayed to a current density of 0.4 A/da in 55 seconds. The same treatment as in Example I was carried out, except that AC electrolysis was carried out to lower the temperature to 0.18 A/dm' (45 cm before fluctuation) and attenuate it to O-l 5 A7'dm after 120 seconds. , the same results as in Example 1 were obtained.

Example 3 The same method as in Example 1 was carried out except that an electrolytic solution having the following composition was used, and the same results as in Example 1 were obtained.

↑Isolate solution: Nickel sulfate (hexahydrate) 25y/ is magnesium sulfate (7hydrate) 201/ is cobalt sulfate (7 hydrate)
hydrate) for/ammonium sulfate
30 f/l boric acid 20 y/
1 pH 5,0 Comparative Example Instead of the total current density pattern yts of Example 2, AC electrolysis was performed for 60 seconds at a constant voltage of 12 V, and the degree of coloring was adjusted to the same as Example 2. The color tone was reddish.
The counter electrode surface was colored slightly lighter than the non-counter electrode surface. That is,
The coverage was inferior to that of Example 2. this,
Electrodeposition coating was carried out in the same manner as in Example 1, and after washing with water, baking and drying at 180° C. for 40 minutes resulted in a pale bronze color with a stronger reddish tinge.

Effects of the Invention As described above, according to the electrolytic coloring method of the present invention, after energization treatment at a constant current density, the current density is increased so that the peak current density falls within a higher current density range, and then the current density is forcibly applied. Because alternating current electrolysis is performed by lowering the current density, we can stabilize the color tone of light colors, improve coverage, uniform coloring when framing different types of shapes at the same time, suppress color change due to color removal during electrodeposition coating, etc. A unique effect was obtained.

Furthermore, according to the method of the present invention, by changing the current density pattern, it is possible to color a wide range of colors from basic colors to light colors using one electrolytic solution, and it is possible to color in a flexible state. , the versatility of the production line becomes even higher. For example, when electrolytically coloring using a bronze-colored electrolyte as the basic color, by changing the current density pattern, electrolysis can produce a wide range of colors from this bronze color to light colors such as medium stain color and light stain color. Can be colored,
Also, if you use a dark bronze electrolyte as the basic color,
Electrolytic coloring is possible in a wide range of colors from this deep bronze color to bronze color or relatively light bronze color.

Moreover, the coloring time for each color tone is relatively constant, and the light density pattern is controlled according to a preset total current density pattern or negative current density pattern, so the operation is relatively simple. It also has the advantage of being highly accurate, with almost no unevenness in coloring due to individual differences among color-matchers, and allowing uniform coloring to a desired tone.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a control device for a negative current density pattern in the electrolytic coloring method of the present invention, Fig. 2 is a schematic diagram of a control device for a total current density pattern, and Fig. 3 is a controlled total current density pattern. 4 is a graph showing the change in total current density over time in Example 1.
The figure shows a glass showing the change in total current density over time in Example 2.

Claims (1)

[Claims] 1. When electrolytically coloring an anodic oxide film formed on the surface of aluminum or an aluminum alloy in an aqueous solution containing an inorganic metal salt using alternating current or a waveform having an equivalent effect, Aluminum or aluminum alloy is heated at a total current density of 0.05 to 0.25 [A/d
m^2] or negative current density 0.03 to 0.14 [A/d
m^2] at a constant current density for 30 seconds to 10 minutes, and then in the same bath, the total current density was 0.25 to 1.20 [A/dm^ 2] or aluminum or aluminum alloy, which is characterized by being energized to a negative current density of 0.14 to 0.70 [A/dm^2], and then forcibly lowering the current density at least once. electrolytic coloring method. 2. The electrolytic coloring method according to claim 1, characterized in that the current density is forcibly lowered to 10 to 95% of the current density at the time of variation.