JPH06240494A - Method for coloring anodically oxidized film of aluminum - Google Patents

Abstract

PURPOSE:To provide a method by which an anodically oxidized film of Al can be colored grayish and the grayish color tone immediately after the coloring can be prevented from changing by post-treatment such as drying. CONSTITUTION:When an anodically oxidized film of Al is colored through a 1st process in which AC electrolytic treatment is carried out in a bath contg. phosphoric acid and a 2nd process in which AC electrolytic treatment is carried out in an electrolytic coloring bath contg. only one or more of salts of Al, Ti, Mg, Ba and Ca and one or more of salts of Ni, Co, Zn, Fe, Sn, Cu and Ag, the anodically oxidized film is immersed in a soln. contg. at least one of salts of NH4, K and Li between the 1st and 2nd processes, during the 2nd process or after the 2nd process. The resulting color tone immediately after the coloring is surely prevented from changing.

Description

Detailed Description of the Invention

[0001]

The present invention relates to, for example, sashes, sliding doors,
The present invention relates to a method of coloring an anodized film of aluminum or its alloys used for building products such as entrances, showcases, daily necessities, castings, vehicle parts, etc. Is prevented from being changed by post-treatment such as drying.

[0002]

2. Description of the Related Art A method for forming an aluminum anodic oxide film by electrolytic treatment in a bath containing phosphoric acid and then performing electrolytic coloring treatment is disclosed in, for example, Japanese Patent Publication No. 54-13860. , Is known.

Meanwhile, when chemical conversion of the aluminum anodic oxide coating with phosphoric acid, coating is as rich in PO ₄ ^3-. Therefore, for example, when electrolytic coloring treatment using a Ni salt is performed, the precipitated nickel hydrate is combined with PO ₄ ³⁻ to become nickel phosphate hydrate. This nickel phosphate hydrate changes from colorless to blue depending on the state of hydration, so it is light gray immediately after coloring, but when hydration is reduced by hot water drying or hot air drying, it becomes blue. Changes to. That is, the color tone immediately after coloring is changed by post-treatment such as drying, and it is difficult to obtain a desired color tone.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of coloring an aluminum anodized film in a grayish color tone and preventing the color tone immediately after coloring from being changed by a post-treatment such as drying.

[0005]

The method for coloring an aluminum anodic oxide coating of the present invention comprises a first step of subjecting the aluminum anodic oxide coating to an alternating current electrolytic treatment in a bath containing phosphoric acid,
One or more kinds of Al salt, Ti salt, Mg salt, Ba salt, Ca salt, and Ni salt, Co salt, Zn salt, Fe salt,
A method for coloring through a second step of subjecting to an alternating current electrolytic treatment in an electrolytic coloring bath containing only one or more salts of Sn salt, Cu salt and Ag salt, which is a NH ₄ salt or K salt. , A Li salt is immersed in a solution containing at least one of the Li salt and the Li salt, which is performed either between the first step and the second step, during the second step, or after the second step. It is what

A usual anodic oxidation method is adopted for forming the aluminum anodic oxide film. That is, for example, sulfuric acid, phosphoric acid, inorganic acids such as chromic acid, or oxalic acid, sulfosalicylic acid, organic acids such as malonic acid, or sodium hydroxide, in an alkaline aqueous electrolytic bath such as trisodium phosphate, DC The method of electrolysis is adopted by AC, pulse, PR wave, or AC / DC superposition method.

In the first step, the bath may contain an organic acid such as oxalic acid, malonic acid or sulfamic acid.

The type and concentration of the salt used in the second step are appropriately selected depending on the color tone to be colored.

NH ₄ salt, K salt and Li salt are, for example, sulfuric acid,
Used as a salt with nitric acid.

When the dipping treatment is carried out in the second step, the salt to be used is added to the electrolytic coloring bath.

[0011]

The aluminum anodic oxide film is formed by the first step, and the entire pores of the film are enlarged.
PO ₄ will contain a lot of ^3.

[0012] For example, when the above-mentioned dipping treatment using K salt is performed in the second step using Al salt and Ni salt, a hydrate of nickel-potassium phosphate is obtained. Since the amount of water of crystallization is fixed by the action of the K salt, this hydrate has a property that the state of hydration is unlikely to change and therefore does not discolor. Therefore, the color tone immediately after coloring does not change due to post-treatment such as drying.

The same applies to the case where the salt used in the second step and the above-mentioned dipping treatment is other, and also when the dipping treatment is carried out before or after the second step.

In the first step, when an organic acid is added to the bath, a nickel phosphate / organic acid hydrate having the same properties as the nickel / potassium phosphate hydrate is obtained. The discoloration is surely prevented.

[0015]

EFFECTS OF THE INVENTION According to the method for coloring an aluminum anodic oxide film of the present invention, a hydrate of a phosphoric acid compound having a property that the hydration state is unlikely to change can be deposited during electrolytic coloring. The color tone immediately after coloring can be prevented from being changed by post-treatment such as drying. Also, a grayish tone can be obtained. In particular, when an organic acid is added to the bath in the first step, it is possible to reliably prevent the color tone immediately after coloring from changing.

[0016]

【Example】

(Examples 1 to 13) Aluminum material (A6063S-T)
The plate of 5) (size: 50 × 100 mm, thickness 1 mm) is anodized in a 17 wt% sulfuric acid bath to have a thickness of 10 μm.
Of an aluminum anodic oxide film was formed.

This film is subjected to a first step of alternating current electrolytic treatment in a bath containing phosphoric acid, and then NH ₄ salt, K salt, L
It is subjected to a treatment of immersing it in a solution containing at least one of i salts, and then Al salt, Ti salt, Mg salt, Ba salt, C
one or more of a salts, and Ni salts, Co salts,
It was subjected to a second step of performing an alternating current electrolytic treatment in an electrolytic coloring bath containing only one or more of Zn salt, Fe salt, Sn salt, Cu salt and Ag salt.

Table 1 shows specific conditions of the first step and the second step, and the obtained color tone. The conditions of the above-mentioned dipping treatment were to dip in a 50 g / l ammonium sulfate solution at room temperature for 10 minutes. Also, in both processes,
Carbon was used as the counter electrode.

[0019]

[Table 1]

After the second step, the film colored in the color tone shown in Table 1 was post-treated as follows. That is, after rinsing with water for 10 minutes, rinsing with hot water at 85 ° C. for 10 minutes, and then 1
It was dried with hot air at 120 ° C. for 5 minutes. Then, a room-temperature-drying acrylic silicone resin-based clear coating, "Bertite Clear No. 2000" (manufactured by NOF CORPORATION) was spray-coated to form a coating film having a thickness of 10 µm.

Even after such post-treatment and coating, the color tone obtained through the second step in Examples 2 to 13 did not change at all. Moreover, in Example 1, although it was slightly bluish, it was slight and almost unchanged. It is understood that the difference between Example 1 and Examples 2 to 13 is due to whether or not the bath of the first step contains an organic acid.

(Other Examples) In Examples 1 to 13, the dipping treatment is performed between the first step and the second step, but the dipping treatment is performed during the second step or the second step. It may be carried out after the step, and the same effect is obtained. In addition,
When it is carried out during the second step, it is carried out by adding the salt used in the above dipping treatment to the electrolytic coloring bath.

Further, the following immersion treatment may be performed. For example, (1) 5 g / l lithium sulfate solution is added to the electrolytic coloring bath of the second step, (2) 10% after the second step.
Immerse in a g / l potassium sulfate solution at 80 ° C. for 10 minutes.

Claims (2)

[Claims] 1. A first step of subjecting an aluminum anodic oxide film to an alternating current electrolytic treatment in a bath containing phosphoric acid, and an Al salt and Ti.
One or more of salts, Mg salts, Ba salts, Ca salts, and Ni salts, Co salts, Zn salts, Fe salts, Sn salts, C
A method of coloring through a second step of performing an alternating current electrolytic treatment in an electrolytic coloring bath containing only one or a plurality of u salts and Ag salts, which is an NH ₄ salt, K salt or Li salt. Aluminum which is characterized in that the treatment of immersing in a solution containing at least one of the above is carried out either between the first step and the second step, during the second step, or after the second step. Method for coloring anodized film. 2. The method for coloring an anodized aluminum film according to claim 1, wherein the bath in the first step also contains an organic acid.