JPS5943559B2 - Electrolytic coloring method for aluminum or its alloy materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aluminum or its alloy material (hereinafter simply referred to as aluminum material).

) Regarding the electrolytic coloring method, in detail, when an aluminum material after anodizing treatment is electrolytically colored in an electrolytic bath containing a metal salt, the brightness of the anodic oxide film and its capacitive impedance during the coloring electrolysis are constant. In order to take advantage of this relationship, first find a certain relationship for a given aluminum material, then continuously measure the capacitive impedance of the aluminum material during electrolysis, and use this as a guide. It relates to an electrolytic coloring method that allows an anodized film of constant brightness to be obtained through electrolytic coloring. Various methods of electrolytic coloring of aluminum materials have been proposed and implemented in the past, but aluminum materials are anodized in advance and then subjected to direct current electrolysis or alternating current electrolysis in an electrolytic bath containing metal salts. It is a common practice to precipitate a metal in a porous layer of an oxide film, and then color the anodic oxide film in a color unique to the precipitated metal.

This electrolytic coloring method is generally referred to as a metal salt electrolytic coloring method, and the degree of coloring of the anodic oxide film is relatively stable, so this coloring method is a widely used electrolytic coloring method for aluminum materials. In addition, in this method, the metal in the electrolytic bath is precipitated into the anodic oxide film, which is colored by the metal, so the amount of metal deposited is proportional to the color concentration, producing an anodic oxide film with the same concentration. To achieve this, it is necessary to control the amount of precipitated metal. However, up to now, it has been difficult to control the amount of precipitated metal to a constant level in the metal salt electrolytic coloring method, and it is impossible to surface-treat aluminum materials to the same concentration depending on the electrolytic coloring of the aluminum material. However, after surface treatment, it is necessary to perform "color matching" with the naked eye. For example, after electrolytically coloring the aluminum material A to the degree A and surface treating it,
When coloring an aluminum material to the same concentration as this, the aluminum material is once colored and then pulled out from the electrolytic cell. Then, compare this aluminum material with an aluminum material colored to A grade or a color sample of A grade. For example, if the color is light, the aluminum material is immersed in the electrolytic bath again, electrolytically colored, and the aluminum material is pulled out again. It is necessary to perform color matching. On the other hand, if the degree of coloring of the aluminum material is darker than the color sample, it is necessary to perform the surface treatment of the aluminum material again from the first step. Also, although the color matching process is extremely complicated,
Since the color matching itself relies on the color sense, errors are likely to occur, which leads to high defective rates and increased costs, which is also a major problem. The present invention aims to solve the above-mentioned drawbacks, and in particular, when anodized aluminum material is electrolytically colored in an electrolytic bath containing a metal salt, the capacitance impedance of the anodic oxide film during electrolysis is controlled to maintain the same concentration. The purpose of this study is to propose a method for producing an anodic oxide film. The method of the present invention will be sequentially explained below.

First, the aluminum material is subjected to pretreatment such as degreasing, water washing, etching, etc. in a conventional manner, and then an anodized film is formed on the aluminum material by, for example, direct current electrolysis.

This pretreatment and anodic oxidation treatment may be carried out by any conventional method as long as the purpose can be achieved, and of course it is sufficient if the electrolytic conditions etc. are also carried out in a conventional manner. Next, after anodizing the aluminum material as described above, it is immersed in an electrolytic bath containing metal salts and electrolyzed there to color the anodic oxide film on its surface. The film is electrolytically colored, and the relationship shown in FIG. 2 between the capacitance impedance and brightness of the anodic oxide film is determined.

In addition, the electrolytic coloring treatment in this case generally refers to a treatment in which metal ions in an electrolytic bath are precipitated into the pores of a pre-generated anodic oxide film and colored. In normal cases, AC electrolysis is sufficient. However, in addition to this, coloring can also be achieved by direct current electrolysis, pulse electrolysis, or electrolysis using a combination of these waveforms and alternating current. Next, after preliminarily electrolyzing the aluminum material as described above, the aluminum material is then electrolytically colored industrially. At this time, the capacitive impedance of the anodic oxide film during electrolysis is continuously changed as described below. Electrolysis is continuously performed until the value reaches a value corresponding to a predetermined desired brightness based on the relationship previously determined for each aluminum material.

When an aluminum material is electrolytically colored in this manner, the aluminum material is always uniformly colored to a desired brightness, and there is no need for any color matching during or after electrolysis.
In other words, it is known that when an aluminum material on which an anodic oxide film has been formed is subjected to alternating current electrolysis in an aqueous solution containing a metal salt, as the electrolytic coloring progresses, the current waveform becomes distorted as shown by A in Figure 1. ing.

It is also known that the electrolytic current distorted in this way is made up of the sum of the reaction current (Falade current) (indicated by C in Fig. 1) and the capacitive current (indicated by C in Fig. 1). ing. However, this reaction current is related to the reduction reaction rate of metal ions and hydrogen ions in the electrolytic bath, and is a variable under these.On the other hand, as the electrolysis time elapses, the capacitive current changes, but this The reason why the capacitance current changes is that the amount of metal deposited in the pores of the anodic oxide film changes depending on the length of the electrolysis time. Therefore, the present inventor focused on the fact that the capacitance current is related to the amount of metal precipitation, and specifically determined the relationship between the change in the capacitance current and the degree of coloration of the anodic oxide film.

Recently, the degree of coloring of the anodic oxide film changed due to changes in capacitance current without being significantly influenced by other electrolytic conditions. Further, regarding this relationship, when we determined the relationship between control factors during electrolytic coloring and the degree of coloring, we found that the capacitive impedance (hereinafter simply referred to as capacitive impedance) of the anodic oxide film.

) was found to be proportional to the degree of coloration (particularly, brightness) of the film as shown in FIG. Therefore, in the method of the present invention, since the capacitive impedance during electrolytic coloring increases and the brightness of the anodic oxide film decreases (the lower the brightness, the darker the color), the degree of coloring of the anodic oxide film during electrolysis increases. is determined based on the value of the capacitive impedance, a desired capacitive impedance is determined in advance, and when the capacitive impedance reaches that value during electrolysis, the electrolysis is stopped.

When electrolyzed in this manner, an anodic oxide film with a constant capacitance impedance is always obtained, the degree of coloration is always constant, and no color matching is required after electrolysis.

Although there are still many unknown reasons for this,
The degree of coloring of the anodized film during electrolysis is determined by the amount of metal deposited at that time and its mode, rather than the degree of formation of the film, and these can be easily understood quantitatively as capacitive impedance. It seems to be from

In addition, when detecting the relationship between capacitive impedance and brightness during electrolysis as described above, and furthermore, when continuously detecting the capacitive impedance of the anodic oxide film, the apparatus having the configuration shown in Fig. 3 is usually used. Easy to implement.

That is, in FIG. 3, reference numeral 1 is a transformer, 2 is a potential detector, 3 is an electrolytic cell, 4 is a current detector, 5 is a tuning detector, and 6 is a capacitive impedance measuring device.

Therefore, in this device, for example, an aluminum material that has been anodized in advance is used as one or both poles, and an alternating current voltage is applied therebetween by the transformer 1 to perform alternating current electrolysis. During this electrolysis, the voltage between the two electrodes is measured by a potential detector 2, and the current during electrolysis is detected by a current detector 4. In addition, the current obtained in this way shows an AC waveform corresponding to A in Fig. 1, and therefore, only the capacitive current (corresponding to the opening in Fig. 1) is separated and measured in the synchronous detector 5. be done.

Further, as mentioned above, the voltage obtained by the potential detector 2 enters the capacitive impedance measuring device 6, and the separated capacitive current enters the measuring device 6, so that the capacitive impedance during electrolysis is determined by the numerical ratio. required. According to this, in addition to finding the trend relationship shown in FIG. 2, the capacitive impedance is also continuously measured with the measuring device 6 during subsequent electrolytic coloring, and when the value corresponds to the desired brightness, If electrolysis is completed at , coloring can be done to the same brightness. Furthermore, although the case of alternating current electrolysis has been described above, even electrolysis with a waveform other than this, for example, a pulse waveform, can be easily carried out using the apparatus shown in FIG.

Furthermore, if the relationship between capacitive impedance and brightness is determined for a given aluminum material using the device shown in FIG. 3, and the device shown in FIG. Can be colored.

In other words, in the device shown in Fig. 4, if the capacitive impedance is set to a desired value in advance, the capacitive impedance is continuously measured, and when the value reaches the desired value, the coloring process of the aluminum material is automatically performed. It is something that stops at.

Therefore, the area surrounded by broken line A in Fig. 4 is
It has the same configuration as shown in Fig. 3, and a comparator 7 is connected to the output side of the tuning detector 5, and the comparator 7 compares it with a preselected value, and the difference becomes zero. At times, the sweet switch element 9 is configured to be turned off.

With this structure, when the aluminum material is colored to a desired concentration in the electrolytic bath 3, the switch element 9 is turned off by the zero signal from the comparator 7, and the electrolytic coloring is stopped. In FIG. 4, reference numeral 8 denotes a current measuring device, which allows the capacitive current at the capacitive impedance of a desired color to be set in advance. Next, examples will be described.

Example 1 A plate made of A1100 aluminum material was degreased and cleaned by a conventional method, and an anodized film was applied on the plate by a conventional method in an electrolytic bath of 15% sulfuric acid.

Next, this plate material was subjected to alternating current electrolytic coloring at 12 in the apparatus shown in Fig. 3 in an electrolytic bath consisting of an aqueous solution containing 3% nickel sulfate, 3% boric acid, and 2.5% ammonium sulfate, with a carbon material as a counter electrode. I did this. As a result, a deep bronze-colored anodic oxide film was obtained on the plate material by coloring electrolysis for about 5 minutes. Further, at this time, the capacitive impedance was measured with the measuring device 6, and the capacitive impedance was 135 Ω/d in 50 cycles. Next, using the plate material made of the AllOO aluminum material mentioned above, this plate material was also degreased, cleaned and anodized in the same manner as above, and then AC electrolyzed in a colored electrolytic bath having the same composition. In this case, the measuring device 6 of FIG.
Coloring electrolysis was performed while observing the capacitance impedance in the 0th cycle, and when the value reached 135Ω/d, the current supply was stopped and the electrolysis was completed.

When a colored anodic oxide film was produced on the board in this way, the color was exactly the same as the color of the board previously obtained,
Furthermore, when I measured the brightness with a colorimeter, the brightness was 26.
．． 5, and the concentrations were also completely consistent. Example 2 Under the same conditions as Example 1, AllOO aluminum. An alternating current voltage was applied to the aluminum plate in the apparatus shown in FIG. 4 to electrolytically color the plate.

In this case, the capacitive current of a capacitive impedance corresponding to the desired color density was set in the current measuring device 8 in advance. Under these conditions, perform alternating current electrolysis and coloring, while similarly detecting the capacitance current with detector 5, compare this value with the set current in comparator 7, and when the difference becomes zero, switch A signal was sent to element 9 to automatically cut off the current and complete electrolytic coloring. When electrolysis was repeated five times in this manner, the color obtained was the same all five times. As explained in detail above, the method of the present invention, when carrying out colored electrolysis in an electrolytic bath containing a metal salt, considers the coloring or concentration factor at that time as capacitive impedance,
Since the coloring process uses this as a guide, there is no need for color matching, and the electrolytic coloring process itself can be controlled outside the electrolytic bath, making it possible to automate the process. Furthermore, since the degree of coloring can be accurately controlled in this way, it is possible to prevent product defects, and furthermore, it is possible to save labor during electrolytic coloring and improve productivity.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the analysis aspect of the current waveform during electrolysis in the method of the present invention, Figure 2 is a graph showing an example of the relationship between capacitive impedance and brightness in the method of the present invention, Figures 3 and 4 are respectively 1 is a circuit diagram of an example of a device implementing the method of the present invention; FIG. Code, 1...Transformer, 2...Potential detector, 3...Electrolytic cell, 4...Current detector, 5... Tuning detector, 6... Capacitive impedance measuring device, 7... Comparator, 8...
...Current measuring device, 9...Switch element.

Claims (1)

[Claims] 1. When subjecting pre-anodized aluminum or its alloy material to electrolytic coloring in an electrolytic bath containing a metal salt, first the aluminum or its alloy material is preliminarily electrolytically colored; After determining the relationship between the capacitive impedance of the anodic oxide film and the brightness of the anodic oxide film, the aluminum or its alloy material is continuously electrolytically colored, and the capacitive impedance of the anodic oxide film during that time is continuously determined. An electrolytic coloring method for aluminum or its alloy material, characterized in that the electrolytic coloring process is terminated when the impedance reaches a capacitance impedance corresponding to a desired brightness in the above relationship.