JPS5937357B2 - Method for producing aluminum plate with colored alumite film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aluminum plate having a beautiful colored alumite film.

Conventionally, the method of forming a colored alumite film on the surface of an aluminum plate is to anodize the aluminum plate with sulfuric acid, chromic acid, oxalic acid, etc., and then electrolyze it in an electrolytic solution containing an inorganic substance. Electrolytic coloring method, or electrolyzing the aluminum plate in a sulfuric acid bath and then electrolyzing in an acidic bath containing D phosphoric acid, modifying only the deep layer of the film to D phosphoric acid, and then applying nickel, cobalt or stannous tin. A tertiary electrolytic coloring method in which electrolysis is performed in a bath containing one or two salts is known.

However, the coating formed by the secondary electrolytic coloring method lacks D gloss unless it is polished in advance, and the color development is mainly based on the absorption and emission of light by the metal or metal compound in the coating. Colors were also limited to a single color.

In addition, the film obtained by the tertiary electrolytic coloring method has a variety of colors due to the effect of light interference, but it is an iridescent color that appears to be a mixture of red and green that changes depending on the viewing direction. I couldn't get it. The object of the present invention is to quickly produce an aluminum plate having a beautiful and shiny colored alumite film.
Our goal is to provide reliable manufacturing methods.

The principle of the conventional electrolytic coloring method can be summarized as follows.

That is, in the first electrolytic step, electrolysis is performed using direct current, pulsating current, etc. that does not contain negative current as the anode current to form a porous alumite film on the surface of the aluminum substrate, and the second
In the electrolytic process, colloids of metals or metal compounds are deposited in the pores of this alumite film. The coloring produced by the secondary electrolytic coloring method is mainly based on the absorption and emission of light by the metal or metal compound contained in the colloid, and the coloring produced by the 13th electrolytic coloring method is accompanied by a light interference effect.

In the first electrolytic step of the conventional electrolytic coloring method, the present invention forms a glossy alumite film without a single pit by using a current containing a part of negative current in the electrolytic current, and furthermore, it has a beautiful iridescent color. It was confirmed through numerous experimental results that a film could also be obtained, and the process was completed based on this.

That is, the present invention provides a colored aluminum plate including a first electrolytic step of forming an alumite film on the surface of an aluminum plate, and a second electrolytic step of coloring the aluminum plate having the alumite film obtained from the first electrolytic step. In the method for manufacturing an aluminum plate having an alumite film, the anode current in the first electrolytic step is {total amount of current on the (+) side}/{
(-) side current amount} is 1/1 or more.

Here, {total amount of current on the (+) side}/{total amount of current on the (1) side} is as follows in Fig. 1, which shows an example of the change over time of the anode current.
It refers to the ratio S,/S of the total area S of the positive current region 1 and the total area S2 of the negative current region 2. According to the method of the present invention, in the first electrolytic step, the rate of dissolution and oxidation of aluminum changes compared to the conventional method because the anode current contains a moderate amount of negative current, and the aluminum substrate is heated. An alumite film with pores larger than those obtained by conventional electrolytic methods is formed on the surface, and the soluble aluminum turns into complex salts and becomes glossy, sometimes depositing on the surface of the film outside the pores when inside the pores. reach.

During the second electrolytic process, a large amount of metal or metal compound colloid is precipitated into these pores, giving them various colors. Beautiful iridescent colors can also be obtained due to the strong light interference effect brought about by both colloidal particle groups. In addition, because the pores are large, not only thick films but also thin films of 1 μm or less, which have been considered difficult in the past, are quickly colored, eventually turning black. {Total amount of current on the (+) side} / {Total amount of current on the (-) side}
There is an appropriate range of It is undesirable because it creates stains and spoils the bright colors.

{Total amount of current on the (+) side}/{Total amount of current on the (-) side} is 1/1
In this case, the aluminum salt is deposited only in the pores and exhibits some primary coloring, and a bright color is obtained in the second coloring step. In particular, it is preferable that the ratio {total amount of current on the (+) side}/{total amount of current on the (1) side} is 2/1 to 10/1, since more vivid colors can be obtained without staining. The anode current used in the first electrolytic step according to the present invention may have a ratio of {total amount of current on the (+) side}/{total amount of current on the (-) side} of 1/1 or more, and the anode current shown in FIG. In addition, alternating current having various waveforms such as the pulse type shown in FIGS. 2 to 4, the SCR type, or a mixed wave thereof can be used.

Particularly, with the waveform shown in FIG. 4, it is also possible to ascertain the electrical characteristic value of the formed film from the current value at constant voltage alternating current to ensure coloring. Further, the electrolytic pressure in the first electrolytic step is not particularly limited, but if the voltage is too high, coloring in the second step will be difficult.

Therefore, a voltage of 25V or less is usually used. Especially 8
If it is around V, the gloss will increase and more vivid colors will be obtained, which is preferable. The current and voltage used in the second electrolytic step may be those used in conventional electrolytic coloring methods.

The electrolytic bath according to the present invention uses an acidic or alkaline bath that makes the pore size relatively large even in conventional electrolytic methods.

For example, in the first electrolysis step, a bath containing one or more of oxalic acid, sulfamic acid, phosphoric acid, caustic soda, etc. is used. However, among these, especially solutions containing 2 to 10 W/V% of oxalic acid or sulfamic acid have a phosphoric acid concentration of 1.
In an electrolytic bath made of phosphoric acid added to give a concentration of ~5W/VIf6, preferably 2~3W/V%, aluminum ions eluted during electrolysis form stable soluble phosphates and the solution becomes stable. D is preferred. Phosphoric acid concentration is 1W/V
% or less, this effect is small, while if it exceeds 5W/V (F6), the alumite film becomes soft.Also, a solution of caustic soda may be used in the bath.In this case, the one electrolyzed in the caustic soda bath, 2-5 in an acidic bath such as sulfuric acid
If electrolysis is continued for about a minute, a film with a brighter color can be obtained in the second electrolysis step. In addition, in the second electrolysis step,
Although the same baths as those used in conventional electrolytic coloring methods are used, baths containing metal salts of nickel, tin, and copper are preferred in order to obtain deep and black colors.

Furthermore, the temperature of the bath is not particularly limited, and the bath can be carried out at room temperature. The electrolysis time for both the first and second electrolysis steps is not particularly limited and may be within the conventionally used range.

If this electrolysis time is short, the color tone of the obtained film will be pale.D
1 On the contrary, the longer it is, the darker it will be. Since the color tone of the film differs depending on the length of the electrolysis time, it is also possible to create a pattern on the colored film itself by making a difference in the length of the electrolysis time between a specific part of the aluminum plate and other parts. can. In addition to this, when patterning is performed, if a difference in electrolytic voltage is generated locally in the first electrolytic step, a difference occurs in the barrier thickness of the alumite film, which appears as a difference in color tone. In addition, by masking a part of the surface of the aluminum plate on which the film is to be formed so that it does not participate in the electrolytic reaction, it is also possible to form an iridescent film only on a specific part of the surface of the aluminum plate. It is possible.

On the other hand, it is also possible to first color the entire surface and then partially decolorize it. The purity of the aluminum plate used is not particularly limited, and it can be used for practical purposes as long as it has a purity that allows the formation of an alumite film.

The present invention can also be applied to pre-anodized plates and cast products of specific compositions.

By covering the formed iridescent film with a coating film or the like, it is possible to obtain a film with a different taste.

The film thus formed exhibits a beautiful, glossy iridescent color or black color that cannot be obtained by conventional electrolytic coloring methods.

In addition, it is more robust than painted products, and has the advantage of not burning, peeling, discoloring, or fading even when heated or exposed to sunlight for a long period of time. Furthermore, in the present invention, unlike conventional AC electrolysis, the b anode current includes a moderately small negative current.
The (-) side current can be reduced to a fraction of a fraction, and the aluminum complex salt causes a polishing phenomenon, and furthermore, the resistance value of the so-called barrier layer deep in the film is made uniform, and local current concentration can be avoided.

Therefore, it has the great effect of suppressing the roughening of the surface during normal electrolysis and the occurrence of electrolytic scratches made up of micropores called pits. 1. Saving electricity, omitting preliminary polishing, improving product yield, and reducing the need for tap water into the bath. The economic advantages such as ease of use are enormous. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Examples 1 to 6, Comparative Example 1 Aluminum plates with a purity of 98.5% to 99.5% were treated in the first electrolysis step and the second electrolysis step under the conditions shown in Table 1.

The results are shown in the results column of Table 1. In the results column, ◎ and ○ indicate that a shiny and beautiful iridescent or black film was obtained, and ◎ in particular indicates that it was extremely beautiful. × is
It means that something beautiful could not be obtained. From Table 1, {total amount of current on the (+) side}/{total amount of current on the (-) side} is 1/
If it is 1 or more, an iridescent film can be obtained, especially 2/1 to 1.
It can be seen that when the ratio is 0/1, an extremely beautiful iridescent film can be obtained.

Further, the aluminum plate having the obtained iridescent film was heated with a city gas combustion burner, but no discoloration or fading occurred.

As described above, according to the present invention, it is possible to obtain an aluminum plate having a strong, glossy, and beautiful iridescent or black alumite film that could not be obtained by conventional methods.

[Brief explanation of drawings]

FIGS. 1 to 4 are drawings showing examples of current waveforms used in the first electrolytic step. 1...Positive current region, 2...Negative current region.

Claims (1)

[Claims] 1. A first electrolytic process for forming an alumite film on the surface of an aluminum plate, and a second electrolytic process for coloring an alumite plate having an alumite film obtained from the first electrolytic process. In the method for manufacturing an aluminum plate having a colored alumite film, an alternating current with a ratio of {total amount of current on the (+) side}/{total amount of current on the (-) side} is 1/1 or more is used as the anode current in the first electrolytic step. A method for producing an aluminum plate having a colored alumite film, characterized in that: 2. The method for producing an aluminum plate having a colored alumite film according to claim 1, wherein the colored alumite film has gloss. 3 A patent claim characterized in that an alternating current in which {(+) side current total})/{(-) side current total} is 2/1 to 10/1 is used as the anode current in the first electrolytic step. Range 1
A method for producing an aluminum plate having a colored alumite film according to item 1 or 2. 4 As the electrolytic bath in the first electrolytic step, 1 selected from the group consisting of caustic soda, phosphoric acid, oxalic acid, and sulfamic acid.
4. A method for manufacturing an aluminum plate having a colored alumite film according to any one of claims 1 to 3, characterized in that a bath containing a species or two or more components is used. 5. Claim No. 5, characterized in that an acidic bath containing one or more salts selected from the group consisting of nickel salts, tin salts, and copper salts is used as the electrolytic bath in the second electrolytic step. A method for producing an aluminum plate having a black alumite film according to any one of items 1 to 4.