JPS6286195A - Electrolytic coloring method for aluminum and aluminum alloy - Google Patents

Abstract

PURPOSE:To efficiently form a uniform and beautiful colored layer on the surface Al by immersing an Al material subjected to an anodic oxidation treatment in an electrolytic coloring liquid and impressing a specific AC voltage thereto. CONSTITUTION:The Al or Al alloy material is anodized by an ordinary method using an acidic soln. such as sulfuric acid, oxalic acid or sulfamic acid to form an anodized film on the surface. The material is then immersed into the electrolytic coloring liquid which dissolves the sulfate, nitrate, phosphate, hydrochloride, oxalate, tartarate, etc. of metals such as Ni, Co, Cu, Mg, Fe, Mo, and Sn. The AC voltage of such a waveform as shown in the 1st time in which the AC voltage by the phase control of a thyristor as shown in the 3rd time is superposed on both the positive and negative voltages of a sinusoidal AC voltage (2nd time) is impressed to the Al material to electrolytically color said material. The control of the electrolytic voltage is executed with high accuracy and the beautiful and uniform electrolytic coloring is made possible.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for electrolytically coloring aluminum or aluminum alloy (hereinafter simply referred to as "aluminum").
More specifically, the present invention relates to a method for electrolytically coloring anodic oxidized aluminum by applying an alternating voltage with a specific waveform to efficiently color the aluminum surface uniformly and beautifully.

[Prior art and problems to be solved by the invention] Generally, in the technology of alternating current electrolytic coloring of aluminum, control of the applied alternating current voltage is very important. In particular, the method of increasing the voltage applied during electrolytic coloring has a large effect on the coverage of the coloring.
45798, etc., various ideas for boosting the voltage have been made.

However, all of these methods have the disadvantage that, although the operations are complicated, the color coverage is not sufficiently improved and the coloring speed is slow.

In addition, in order to obtain deep coloring by electrolytic coloring method,
Application of high voltage is required, but if high voltage is applied from the beginning of electrolysis, an excessive current will flow, and hydrogen gas will be generated more than metal deposition, which may cause problems such as making it difficult to color the product as a whole. Therefore, it is common practice to first apply a low voltage and then apply a high voltage.

There are two main ways to control this voltage: 1) sliding a brush on the winding to control the voltage to the required level, and 2) changing the conduction angle of the silicon-controlled rectifier (S, C, R,). There are two ways to control the voltage by increasing the voltage.

Among these methods, the latter method (■) uses an AC voltage with a waveform in which the initial part of the phase angle of each positive wave and negative wave of the sine wave is canted, as shown in Figure 3. The drawback is that the voltage is high and it has a negative effect on coloring.

Therefore, voltage control has usually been performed using the former method (2). This method (■) is suitable for small-scale
, V, R, (Slide Voltage R
egulator.

(Sliduc) method, and in large-scale cases I
, V, R, (Induction Voltag
Both control methods involve mechanical movement. Therefore, it is extremely difficult to control small movements on the order of 0 and IV with high precision, and as a result, this is a factor that significantly delays the possibility of automation through computer control. In addition, devices that use motors to slide on windings are large-scale devices that require a large space to install, are heavy, and have various drawbacks, such as a high risk of failure due to abrasion or contamination of the sliding surfaces. There is.

The present inventors have developed a method that can overcome the drawbacks of the above-mentioned conventional techniques, adjust the electrolytic voltage with high precision, eliminate the problem of coloring, and apply beautiful and uniform electrolytic coloring to the aluminum surface. I researched as much as possible.

[Failure to solve the problem]

As a result, they discovered that the objective could be achieved by electrolytically coloring aluminum that had been subjected to anodizing treatment using a specific superimposed alternating current voltage, thereby completing the present invention.

That is, in electrolytically coloring aluminum that has been subjected to anodizing treatment in an electrolytic coloring solution containing a metal salt, the present invention uses a superimposed AC voltage obtained by superimposing an AC voltage by phase control of a thyristor on a sine wave AC voltage. Along with using
The present invention provides a method for electrolytically coloring aluminum, characterized in that the superimposed AC voltage is controlled by the thyristor described above.

The aluminum used in the method of the present invention has its surface subjected to anodic oxidation treatment. The anodic oxidation treatment carried out here may be carried out by a conventionally widely used method. Usually, the surface of aluminum is degreased and cleaned, and this is used as an anode, and aluminum, graphite, etc. are used as a cathode, and sulfuric acid,
This is carried out by applying direct current in an acidic electrolyte such as oxalic acid or sulfamic acid.

In the method of the present invention, aluminum that has been anodized as described above is electrolytically colored using a specific superimposed AC voltage. The superimposed AC voltage used here has a waveform as shown in Figure 1; It is formed by superimposing voltages.

The sine wave alternating current voltage as shown in FIG. 2 may of course be one drawn from a predetermined tap of the transformer, or may be one drawn through the entire conduction angle of the thyristor. On the other hand, the AC voltage whose conduction angle is adjusted by the phase control of the thyristor usually has a waveform in which initial portions of the phase angles of the positive and negative waves of the sine wave are cut, as shown in FIG.

In such a superimposed AC voltage, the inrush current is softened because the voltage change when the thyristor conducts is small compared to the phase-controlled AC voltage (that is, the conduction angle is controlled) as shown in FIG. Adverse effects on electrolytic coloring can be reduced.

The method of the present invention uses the above-mentioned superimposed AC voltage during electrolytic coloring treatment, and controls this voltage by controlling the conduction angle of a thyristor.

In other words, the sine wave AC voltage is first held at a constant voltage, and then an AC voltage whose conduction angle has been adjusted by the phase control of the thyristor is superimposed thereon to control the voltage of the entire superimposed AC voltage.

Note that in order to significantly vary this superimposed AC voltage, first adjust the sine wave AC voltage as appropriate according to the desired value and fix it.
Thereafter, phase control is performed using a thyristor to control slight voltage fluctuations in the entire superimposed AC voltage.

As described above, in the method of the present invention, since the voltage used for electrolytic coloring treatment is controlled by a thyristor, control within a small range of about 0.1 V is easy and can be performed with high precision.

Examples of circuit diagrams of a power supply that generates a superimposed AC voltage used in the method of the present invention are shown in FIGS. 4 and 5. The transformer shown in FIG. 4 may have two or more stages of taps. Further, the number of thyristors in FIG. 5 may be two or more, and the greater the number, the greater the effect of softening the rush current. The method of controlling the superimposed AC voltage will be explained based on FIG. 5. First, the bidirectional thyristor 1 is controlled by sequentially turning on the conduction angle up to 10 cm.

Thyristor 1 is fully turned on to boost the voltage to IOV, then bidirectional thyristor 2 is used to control the voltage to 20V, and after two thyristors 1 and 2 are fully turned on, bidirectional thyristor 3 is used to increase the voltage to 30V.
It will be controlled up to.

The electrolytic coloring solution used in the method of the present invention contains various metal salts depending on the purpose. Specific examples of these metal salts are nickel and cobalt.

Examples include sulfates, nitrates, phosphates, hydrochlorides, oxalates, and tartrates of metals such as copper dimagnesium, iron, molybdenum, and tin.

Also, the conditions for electrolytic coloring, such as voltage 9 energization time,
The liquid temperature, etc. may be selected appropriately as in the normal case.

〔Effect of the invention〕

According to the method of the present invention, since a thyristor is used, voltage control can be performed easily and with high precision.Also, since a superimposed AC voltage is used, an adverse effect on coloring due to inrush current can be avoided, and the aluminum surface can be uniformly and darkly colored. Coloring is applied. Furthermore, a relatively simple power supply device as shown in FIGS. 4 and 5 can be used (also, commercially available alternating current can be used, so it is extremely economical).

It should be noted that the method of the present invention is of course applicable to ordinary AC electrolytic coloring of aluminum, but is even more effective for those in which the barrier is further modified before performing AC electrolytic coloring. This is because by changing the degree of modification of the barrier layer, the alternating current voltage fE can be selected at will, that is, the alternating current voltage that causes the least inrush current.

〔Example〕

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

Example 1 Nickel sulfate hexahydrate 30 g/I! , 25 g/ff of magnesium sulfate heptahydrate, 20 g/l of boric acid, and 15 g/β of ammonium sulfate, and an electrolytic coloring solution with a pH of 5.5.
Place the anodized aluminum test piece (8-6063-T,...2
n +
Electrolytic coloring treatment was performed at a voltage of 15 V for 4 minutes. As a result, the test piece was uniformly colored in a deep bronze color.

Comparative Example 1 Electrolytic coloring was carried out under the same conditions as in Example 1, except that the three bidirectional thyristors shown in Figure 5 were used as the power source, and the bidirectional thyristor was used as a power source that could control up to 30 V. processed.

As a result, although the test piece was slightly colored, spalling occurred in the portion of the test piece that came into contact with the liquid surface.

Example 2 10g/β of stannous sulfate, Log/l sulfuric acid, and 3g of antioxidant (trade name: Stanaskive, manufactured by Yuki Shoji)
/l of electrolytic coloring solution was placed in a beaker of 11,
Anodized aluminum test piece (A-6063'rs, 2m5X18
0 x 70 dragon) was processed as follows.

First, using a DC voltage and using the test piece as an anode, raise it to 30V at 0.33V/sec, hold it at 30V for 3 minutes, and then power the circuit shown in Figure 4 (20V from the tap of the transformer).
The electrolytic coloring process was carried out at 23 V for 5 minutes using a power source in which a voltage of 10 V was superimposed on the phase-controlled voltage of a thyristor.

As a result, the test piece had a uniform bronze color on both sides.

Comparative Example 2 In Example 2, the operation was carried out under the same conditions as in Example 2 up to the treatment with direct current, and then 2
Electrolytic coloring treatment was performed at 3V for 5 minutes.

As a result, only a slight coloring was obtained on the test piece, and the coloring was also non-uniform.

[Brief explanation of drawings]

FIG. 1 shows an example of the waveform of a superimposed AC voltage used in the method of the present invention, FIG. 2 shows a waveform of a sinusoidal AC voltage, and FIG. 3 shows a waveform of an AC voltage obtained by controlling the phase of a thyristor. Fourth
5 and 5 are circuit diagrams of a power supply used in the method of the present invention.゛Figure 1 Figure 2 Figure 3 Figure 4 Procedure Kugisha official document (spontaneous) November 20, 1985 Director General of the License Agency Michibu Uga Indication of the case Patent application 1986-224888 Name of the invention Aluminum or Relationship with aluminum alloy incident
Patent applicant Fujisasoshi Co., Ltd. Kyushu Fujisash Co., Ltd.

Claims (1)

[Claims] (1) When anodized aluminum or aluminum alloy is electrolytically colored in an electrolytic coloring solution containing a metal salt, a superimposed AC voltage is obtained by superimposing an AC voltage based on thyristor phase control on a sine wave AC voltage. 1. A method for electrolytically coloring aluminum or an aluminum alloy, characterized in that the superimposed AC voltage is controlled by the thyristor.