JPS60110895A - Electrolytic coloring method of aluminum and aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain various color tones including neutral tints by forming the electrolytic or spontaneously colored film formed on the surface of an Al-base metallic blank material into electrolytically colorable structure then coloring electrolytically said film. CONSTITUTION:An Al or Al alloy blank material as one electrode is electrolyzed in a bath prepd. by adding metallic salt such as tin to an org. acid or sulfuric acid using Al, carbon, etc. as the other electrode. A colored film is thus formed by chemical conversion. A porous alumite layer 2 is thereby formed on the surface of the Al substrate 1, which layer 2 has many pores 3 opening on the front side having a barrier layer 4 formed thickly between the base part thereof and the substrate 1. Said layer is anodized to make the layer 4 thin so that the succeeding reanodization or electrolytic coloring is made possible. The material is thereafter immersed or reanodized in an acidic or alkaline bath. Then the pores 3, particularly the bottom parts thereof are expanded and the anion adsorbed on the pore wall in the previous stage is substd. with seed anion, by which the film structure and compsn. of the layer 2 are reformed to permit electrolytic coloring. When a metal 5 is then precipitated in the bottoms of the pores 3 in an electrolytic coloring bath, the layer 2 forms various colors according to the degree of the precipitation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an electrolytic coloring method for coloring aluminum rafts and their alloy materials.

(Prior art) As a method of electrolytically coloring an aluminum element to color it red, blue, etc., for example, a tertiary electrolytic method (#"\public 1'& 54-13860 fs special public trB 57-7
239 etc.) are known.

Generally, in the tertiary electrolysis method, an oxide film is chemically formed during the ↑+Y solution, which mainly uses sulfuric acid as the primary solution, and then anodized in an acidic bath as a secondary electrolysis to further chemically form the oxide film. ,3
As the next electrolysis, electrolytic coloring is performed in an electrolytic solution such as nickel sulfate. However, with conventional coloring methods, it is not only difficult to control the color tone, but also only monotonous colors can be obtained, making it difficult to meet the diverse demands of recent customers. - (Objective of the invention) To provide an electrolytic coloring method that can obtain various color tones including various intermediate colors that cannot be obtained by conventional electrolytic coloring methods.

(Structure of the Invention) The present invention C. A colored film formed on the surface of aluminum or aluminum alloy by electrolytic coloring or natural coloring,
This is an electrolytic coloring method for aluminum and aluminum alloys, which is characterized in that after forming a film structure that can be electrolytically colored, electrolysis and coloring are performed to obtain a film with a new color tone.

(Description of the Invention) (1) During electrolysis, aluminum or an aluminum alloy material is used as one electrode, and the other electrode is made of, for example, aluminum, carbon, or nutless.

(2) The colored film formed by electrolytic coloring can be formed, for example, in an organic acid bath such as malonic acid, maleic acid, oxalic acid, sulfosalicylic acid, or in sulfuric acid with Sn, Mn, Co, .
It is a colored film that is chemically formed in a bath containing gold II (salt) such as Cu. Note that organic acid baths usually have low electrical conductivity, so
Electricity LL of SOV or more for AC and about 50 to 70 V for DC
need to be applied. In this case, since the barrier layer of the aluminium (h") formed is thicker, an oxide film that is generally richer in corrosion resistance is obtained.

As shown in Figure 2i', a porous alumite layer 2 is formed on the surface of the aluminum base 1 in this process. H.72 has a large number of bores 3 that are open to the surface side, and a barrier layer 4 is formed between the bottom surface of the bores 3 and the substrate 1.

(3) The above-mentioned naturally colored film may be made of, for example, aluminum alloy, Al-Si type, An-Mn type,
This film is obtained by a method in which components in the alloy such as AI-Mg-S and i-thread are diffused into the film to develop color. In the case of this natural coloring, a colored film having a color density of 14%, as shown in FIG. 1, is formed.

(4) The method for obtaining the electrolytically colorable film structure is, for example, applying a direct current, alternating current, or pulsed current at a voltage of 20 V or less for 30 minutes.
This is a method of anodic oxidation by applying an electric current for 0 seconds or more.

This step is necessary as a pretreatment step for re-anodizing or electrolytic coloring to be performed later. For example, in the above-mentioned electrolytic coloring, a colored film is obtained by applying a voltage of 50 V or more AC.

Therefore, the barrier layer 4 is formed thicker, and the electrical resistance of the film is increased. Therefore, if you directly perform re-anodization or electrolytic coloring, it is necessary to apply a voltage higher than the voltage used in the electrolytic coloring process, and in that case, no effective current will flow, making it impossible to form a film or electrolytically color. It is. On the other hand, if this pretreatment step is carried out in advance, the barrier layer 4 becomes thinner and its electrical resistance decreases, so that re-anodization or electrolytic coloring can be carried out at a lower voltage.

(5) The method for obtaining the electrolytically colorable film structure is, for example, immersion in an acidic bath such as phosphoric acid, chromic acid, sulfuric acid, oxalic acid, nitric acid, etc., or an alkaline bath such as sodium hydroxide, phosphoric acid\sodium, etc. is a method of re-anodizing.

According to this step, the film in the alumite layer 2 is dissolved, resulting in the pore diameter ('4,'?) as shown in FIG.
The pore diameter at the bottom of pore-3 is expanded. Also, electrolysis f
It may get mixed into the oxide film in the previous process such as the fly process, or it may get mixed in with the oxide film in the pre-processing process such as the fly process, or the hole 11 of the bore 3. Oxalate ions and the like adsorbed by the octopus are substituted for anionic species (for example, phosphate ions, nitrate ions, etc.) in the bath in this step. This conclusion 4 (47/L/The film structure and film composition of Mite layer 2 are changed by 1 tVl,
next? 1 to enable effective coloring in the lj decoloring process.
Konaro.

(6) 1-Note '117. Decolorizing baths include, for example, Sn,
Nj, , Cv-.

(It is a bath containing a metal salt containing a metal such as 2o or Ii'q, and a pH buffer such as boric acid, tartaric acid, sulfosalicylic acid, or cresol sulfonic acid, or a chelating agent.

Note that metal, metal oxide, metal hydrate, or a mixture thereof is precipitated in the bore 3 of the oxide film generated on the surface of the aluminum or aluminum alloy of one electrode during electrolysis. It is colored in multiple colors. For example, the alumite layer 2- develops various colors depending on the state shown in FIG.

The pH buffer has the effect of adjusting the TJH of the electrolytic solution to W1M and preventing gas generation during electrolysis, and the effect of adjusting the pI of the electrolytic solution near the electrode surface during 711 solution. In addition, the chelating agent has the effect of adjusting the behavior of metal ions in the electrolytic solution during main electrolysis, and improves the coloring effect by promoting the metal electrodeposition reaction.

(7) The above-mentioned electrolytic coloring method includes, for example, alternating current, direct current,
This is a method of energizing by alternating alternating current and direct current or by pulse.

Fourthly, for example, the following method can be used. That is, in the electrolytic coloring bath, a positive DC or pulsed voltage is first applied, and then a negative DC or pulsed voltage or an AC voltage is applied. The voltage when applying a positive voltage is preferably 3V to 30V, and the current density is preferably 0.01A/dm to 1. The current application time is preferably 2 seconds to 60 seconds. The subsequently applied DC or pulsed negative voltage or AC voltage is preferably 10
V~30V, current density is preferably 0.1 A,/d-
m~i,o A/佽, and various colors can be obtained by varying the negative voltage or alternating current voltage and energization time while taking into account the positive voltage and energization time.

Of course, the positive voltage that is initially applied can also be omitted.

(8) After completing the 18-color electrolytic process, the film is preferably subjected to a sealing treatment using boiled water or steam, or painted if necessary.

(Example) First Example: A hanging tool 1o as shown in FIG. 4 is used. In Figure 4, 1
1 is an electrolytic frame, 12 is an electrolytic frame, and 13 is an extruded type.

The sample 10 was immersed in an organic acid bath with an oxalic acid solution, and a mixture of 1+E 7 (1V x 7) was applied for 30 minutes.

This rises to the state shown in FIG. 1, and the film takes on a golden color. Next, apply a direct current of 15 V for 2 minutes in the same bath. This makes the barrier layer 4 thinner. A direct current of 10 V x 5 minutes was applied in a phosphoric acid bath to obtain a part as shown in FIG.

After that, 100 g/I of nickel sulfate was used as an electrolytic coloring bath.
I.

Negative DC -16VXa using a bath of 30 g/l boric acid
Minutes were applied. As a result, the state shown in FIG. 3 is obtained, in which one layer of golden yellow and one layer of blue are superimposed, and a green color having a unique tone is uniformly obtained over the entire surface.

If the negative direct current is applied for 1 minute, the original golden yellow and red will be superimposed and a persimmon color with a unique tone will be obtained uniformly over the entire surface. Further, if the application time is extended to 3 minutes or more, the color becomes black after passing through a characteristic bronze color.

Furthermore, when electrolytic coloring was carried out by re-anodizing in a phosphoric acid bath, the color was pink under the same conditions;
When 0 V was applied for 5 minutes, a reddish-purple color was uniformly obtained over the entire surface.

Second Example: The mold material 13 shown in FIG. 4 is made of Δi-SQL alloy, and is naturally colored by applying a direct current of 20 V×30 minutes in a sulfuric acid bath.

As a result, the state shown in FIG. 1 is obtained, and the film exhibits a gray color. The thickness of the film is about 12 μm. lKt sulfuric acid 1
0 g/(!) and phosphoric acid 50 g,/l (5 minutes a1 in D mixed acid bath) to make the film into the state shown in Figure 2. Then, as an electrolytic coloring bath, nickel sulfate/L' 100 g, 7 g
, using a bath of 30 g/l of boric acid, AC 18 V
Apply for 5 minutes.

As a result, the state shown in FIG. 3 is obtained, and by superimposing the original gray and red, a reddish-gray having a unique tone is obtained. If you extend the AC energization time, it will turn blue-gray and then about 1
It turns black in 0 minutes.

(Effects of the Invention) Various color tones including various intermediate colors that cannot be obtained by conventional electrolytic coloring methods can be obtained. Moreover, the process is simple and can be easily adopted industrially.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are schematic vertical cross-sectional views of the film, and FIG. 4 is a front view of the hanging device used in the example. Patent applicant: Nippon Aluminum Industry Co., Ltd.
:Ka Agent Patent Attorney Takashi Mori 1;-□苧゛-P 31st Sea

Claims (1)

[Scope of Claims] (1) A colored film formed on the base surface of aluminum or aluminum alloy by electrolytic coloring or natural coloring,
Vlj: f'l'i' After forming a colorable film structure,
Aluminum and aluminum alloys characterized by performing electrolytic coloring and superimposing the colors to form a film with a new color tone. i1: i'+' (iR5 method. (2) The colored film formed by the electrolytic coloring described above is formed by adding Sn, Mn, Co, Cu to sulfuric acid in an organic acid bath such as malonic acid, maleic acid, oxalic acid, or sulfosalicylic acid. etc. metal'
A method for electrolytically coloring aluminum and alumina J alloy according to claim 1. A method for electrolytically coloring aluminum and aluminum alloys according to claim 1, which is a film obtained by a method of coloring by: Claim 1 is a method of anodic oxidation by applying direct current, alternating current, or pulsed current at a voltage of 20 V or less for 30 seconds or more in the same bath r4 as used for obtaining the anodizing method.
The method for electrolytic coloring of aluminum and aluminum alloys described in . (5) Method for obtaining the above-mentioned electrolytically colorable film structure;
Acidic baths such as phosphoric acid, chromic acid, sulfuric acid, oxalic acid, nitric acid,
Or immerse or re-anodize in an alkaline bath such as sodium hydroxide or sodium phosphate? The method for electrolytically coloring aluminum and aluminum alloys according to claim 1, which is a method for coloring aluminum and aluminum alloys. (6) The electrolytic coloring bath is; Sn, Nj-, Cu,
Metal salts containing metals such as Co and Fe, and pH of boric acid, tartaric acid, sulfosa'If acid, cresol sulfonic acid, etc.
The method for electrolytic coloring of aluminum and aluminum alloys according to claim 1, wherein the bath contains a mild 9R agent or a chelating agent. (7) The electrolytic coloring method for aluminum and aluminum alloys according to claim 1, wherein the electrolytic coloring method is an alternating current, direct current, alternating current and alternating current, or pulsed current.