JP2008179843A - Whitening-treatment liquid composition for aluminum or aluminum alloy, and whitening treatment method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment liquid for changing the surface of aluminum or an aluminum alloy into a decorative white surface through simple and easy chemical treatment without using a fluorine compound which is very toxic and stimulative, and without needing a special apparatus, and to provide a treatment method therefor. <P>SOLUTION: The whitening treatment liquid includes a base liquid of 1 kg, which is prepared by mixing phosphoric acid with sulfuric acid, and additionally a bismuth compound of 0.001 to 0.020 moles in terms of a bismuth element; and preferably further includes additionally a nitrogen-containing polycarboxylic acid. The whitening treatment method includes treating aluminum or the aluminum alloy in the liquid heated to 90 to 110°C for 60 to 120 seconds to whiten the surface. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a white processing liquid for forming a white surface on the surface of aluminum or an aluminum alloy (hereinafter simply referred to as an aluminum alloy), and a processing method therefor.

Aluminum alloys are light, durable, and easy to process, so they are used in various applications, and surface treatment is widely performed to improve design and durability. As design diversifies, white treatment is performed as one of surface treatments for light, thin and small articles having complicated shapes such as exteriors of mobile phones and digital cameras.

As described in Non-Patent Document 1, the surface treatment of the aluminum alloy includes a method of chemical treatment using etching, boehmite method, chemical conversion film, etc., and an anodic oxidation method using a special aluminum alloy or a special bath. There are paintings. As a chemical treatment method, treatment with a liquid containing a fluorine compound as proposed in Patent Documents 1 to 3 has been used for a long time because of its simplicity of work and high whiteness of the surface obtained. Yes. However, it is necessary to use an expensive material that is resistant to hydrofluoric acid for a chemical tank or a hanger that supports a product, and waste liquid treatment is also troublesome. In addition, it is highly irritating and deteriorates the working environment, so it is a method that is avoided at the moment when the environment is regarded as important. As a chemical treatment method that does not use a fluorine compound, as disclosed in Patent Documents 4 to 5, an alkali bath having a characteristic liquid composition has been proposed, but an excellent white surface like a fluorine compound currently used. Cannot be obtained. As another method, as disclosed in Patent Documents 6 to 7, a method of making white after anodization by changing the alloy component of the aluminum alloy has been proposed, but it is not a general-purpose material, but price and availability. It is necessary to consider strength and the like, and is complicated. On the other hand, in the anodic oxidation method using a special bath, the finished surface becomes non-uniform depending on the shape of the article to be treated, or a dedicated bath for whitening is required. In addition, etching with chemicals after mechanical processing such as blasting and further anodizing are also carried out, but the cost is high, and mechanical processing is complicated and thin articles are deformed by impact of shots. May cause defective products. In the case of painting, there may be a disadvantage that the white processed product is partially peeled off during long use. In these mechanical or electrolytic methods, the equipment may be complicated, the processing surface may be easily influenced by the shape of the article to be processed, or may be peeled off during use. Therefore, although it is not environmentally preferable, white treatment with a fluorine compound is still mainstream from the viewpoint of simple workability and high whiteness.

Japanese Patent Publication No. 41-16363 Japanese Patent Publication 48-43016 Japanese Patent Publication No.49-19506 Japanese Patent Publication No.41-10490 JP 48-36038 A JP-A-3-47937 JP 10-17965 A “Aluminum Surface Technology Handbook”, Light Metal Publishing, (1980), p. 519-521

The present invention is a chemical treatment method that is excellent in terms of equipment and cost, and has excellent durability during use, and without using a fluorine compound that is highly harmful or irritating. It is an object of the present invention to provide a white processing liquid that forms a high white surface and a processing method thereof.

As a result of diligent research to solve the above problems, it was discovered that the surface of the aluminum alloy becomes an excellent white surface by chemical treatment with a phosphoric acid-sulfuric acid mixed solution containing a specific amount of a bismuth compound. It has been completed.

That is, a white treatment liquid for aluminum or aluminum alloy (0.001 to 0.020 mol of a bismuth compound as a bismuth element is added to 1 kg of a basic liquid obtained by mixing phosphoric acid and sulfuric acid ( The basic solution contains 80.8 to 42.5% by weight of phosphoric acid and 4.9 to 49.0% by weight of sulfuric acid (claim 2), based on 1 kg of the basic solution. 0.001 to 0.020 mol of nitrogen-containing polycarboxylic acid is added (Claim 3), and the nitrogen-containing polycarboxylic acid is composed of iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, and salts thereof It is characterized by being 1 type or 2 types or more selected from the group (Claim 4). Furthermore, the white treatment method of the surface of aluminum or aluminum alloy which treats with the liquid which adds 0.001-0.020 mol of bismuth compounds as a bismuth element with respect to 1 kg of the basic liquid obtained by mixing phosphoric acid and sulfuric acid ( A fifth aspect of the present invention is also summarized in that a liquid obtained by adding 0.001 to 0.020 mole of nitrogen-containing polycarboxylic acid to 1 kg of the basic liquid is used (claim 6).

According to the present invention, a white surface having a high use value can be formed on an aluminum alloy by a simple chemical treatment without using a harmful and irritating fluorine compound and without requiring special equipment. Can do.

The components and effective component amounts of the white treatment liquid for aluminum or aluminum alloy of the present invention will be described.

The white treatment liquid of the present invention uses a mixed liquid of phosphoric acid and sulfuric acid as a basic liquid, and the basic liquid contains phosphoric acid in an amount of 80.8 to 42.5% by weight and sulfuric acid in an amount of 4.9 to 49.0% by weight. . Phosphoric acid forms a thick, high-viscosity phosphoric acid liquid film on the surface of the aluminum base material and works to smoothen the surface. Sulfuric acid promotes acid corrosion and works to roughen the surface. Need to be. When the amount of sulfuric acid is 4.9% by weight or more, whitening occurs, and when the amount is less than this, roughening is less and smoothing with phosphoric acid is too strong, and glossing is performed, so that a sufficient white surface cannot be obtained. When the sulfuric acid concentration increases, the surface becomes rough, and when the sulfuric acid concentration exceeds 49.0% by weight, the smoothing by phosphoric acid is not sufficiently exhibited, and unevenness such as rolling traces becomes conspicuous. The concentration of phosphoric acid used is preferably 85% or 75%, but is not particularly limited in terms of availability, handling properties, and whitening effect. If 85% phosphoric acid and 98% sulfuric acid are used, the weight ratio of 85% phosphoric acid: 98% sulfuric acid is preferably in the range of 95: 5 to 50:50. The white surface obtained in the present invention is considered to be an irregular reflection surface based on fine roughening with phosphoric acid and sulfuric acid, and by changing the composition of phosphoric acid and sulfuric acid within this range, the desired roughness can be obtained. A composition having a large amount of phosphoric acid has a shallow depth and is fine, and when the amount of sulfuric acid is increased, the composition changes in a rough direction.

The bismuth compound is added in an amount of 0.001 to 0.020 mol as bismuth metal with respect to 1 kg of the base solution. If it is less than 0.001 mol, it becomes a semi-glossy surface and a white surface cannot be obtained, and if it is increased more than necessary, it is not economical. The mechanism of action of bismuth in the present invention is not clear, but it is considered that fine irregularities are formed on the aluminum surface, causing irregular reflection and whitening. The bismuth compound to be used is not particularly limited, and bismuth trioxide, bismuth nitrate, sodium bismuth, bismuth chloride, and the like can be used. Even if a compound such as iron, cobalt, nickel, copper, or molybdenum is added in place of the bismuth compound, the white surface is not obtained. Bismuth compounds and other metal compounds may be used in combination. However, the action of the metal varies depending on the type, and depending on the metal type, the unevenness of the surface becomes coarse, and an uneven surface with a uniform and shallow depth cannot be obtained, so that irregular reflection hardly occurs and the white surface may not be obtained. Select the metal species to be used in combination according to the desired white surface.

The white treatment liquid of the present invention preferably further contains nitrogen-containing polycarboxylic acids such as iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and their salts, and eliminates rolling traces and unevenness in whiteness. There is an effect to. The addition amount is preferably 0.001 to 0.020 mol with respect to 1 kg of the base solution. If it is less than 0.001 mol, there is no effect of eliminating unevenness, and even if it is increased more than necessary, it is not economically good, and adverse effects due to insoluble substances can also occur. Instead of the nitrogen-containing polycarboxylic acid, a chelating agent having a corrosion promoting effect on aluminum, such as oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, may be added, and an o-hydroxyazo compound, The same effect can be obtained by adding a compound in which a sulfonic acid group is introduced to an alizarin derivative, a tropolone compound, or the like, ethylenethiourea, sodium glycolate, p-hydroxybenzaldehyde, or the like.

In addition, surfactants usually used in chemical polishing can be used as appropriate. The addition of the surfactant produces effects such as prevention of pit generation and facilitating water washing.

In preparing the white processing liquid according to the present invention, a predetermined amount of each of the components listed above is added and stirred and mixed, whereby a white processing liquid can be obtained.

Next, the white processing method of the present invention will be described. The white processing liquid of the present invention can be used for general aluminum alloys that are frequently used for ordinary decoration applications such as JIS 1050, 1100, 5052, 5056, 6063 and the like. In order to obtain higher whiteness, it is preferable to use a pure aluminum system of 1050 or 1100.

The white treatment method of the present invention is performed by heating the white treatment liquid to 90 to 110 ° C., immersing the article to be treated for 60 to 120 seconds, and then washing and drying. If the liquid temperature is less than 90 ° C., the dissolution of aluminum does not proceed and whitening becomes difficult. If the temperature exceeds 110 ° C., the surface of the treated surface becomes too rough and the whiteness decreases. Dissolution causes thinning, resulting in economic and strength disadvantages. In addition, the treatment time immersed in the white treatment liquid is appropriately set according to the type, size, liquid temperature, aluminum concentration in the liquid, etc. of the aluminum alloy. If the length is too long, it becomes thin due to excessive dissolution of aluminum, which is not economical and the strength decreases. When the aluminum concentration in the liquid is low, the etching action is intense and the rolling marks may be conspicuous. In the new liquid, a stable treated surface can be obtained by dissolving aluminum so as to be about 0.3%. Further, when the white treatment liquid is repeatedly used and the aluminum concentration is excessively increased, the dissolution of aluminum does not proceed and the whitening of the treated surface may be reduced. In such a case, whiteness can be obtained again by adding a new solution to reduce the aluminum concentration to, for example, 1% or less.

Next, examples of the present invention will be specifically described in comparison with comparative examples.
<Examples 1-11 and Comparative Examples 1-5>
An aluminum alloy plate (1 × 50 × 100 mm) with a rolling trace was degreased and washed, treated with a liquid having the composition shown in Tables 1 to 3 and treatment conditions, then washed with water and dried, and the surface condition was visually observed. . Moreover, L value which is an index of whiteness was measured by Minolta color difference meter CR-200. The results are also shown in Tables 1-3.

In Examples 1-4, the surface of the brightness whose L value is nearly 90 similar to the comparative example 1 processed with the fluorine compound was obtained. In Comparative Example 2, which is a known example of a phosphate-sulfuric acid satin solution, a white surface was not obtained. Even when the aluminum concentration of the treatment liquid was relatively high at 1%, in Examples 2 to 4 in which the nitrogen-containing polycarboxylic acid or a salt thereof coexisted, there was no white density unevenness and a sufficient white surface was obtained. In Examples 5 to 7 in which bismuth was 0.001 mol or more with respect to the base solution, a white surface was obtained, but in Comparative Example 3 where the amount of bismuth was 0.0004 mol, a white surface was not obtained. Further, in Comparative Examples 4 and 5 in which a nickel compound or a copper compound was added instead of the bismuth compound, a white surface was not obtained. In addition, a white surface was obtained in Examples 8, 6, and 9 to 11 in which the basic solution contained 5 to 50% by weight of 98% sulfuric acid.

INDUSTRIAL APPLICABILITY The present invention can be used for whitening of aluminum or aluminum alloy used in a portion where decoration is important.

Claims (6)

A white treatment liquid for aluminum or aluminum alloy, wherein 0.001 to 0.020 mol of a bismuth compound is added as a bismuth element to 1 kg of a basic liquid obtained by mixing phosphoric acid and sulfuric acid. 2. The white treatment solution for aluminum or aluminum alloy according to claim 1, wherein the basic solution contains 80.8 to 42.5 wt% of phosphoric acid and 4.9 to 49.0 wt% of sulfuric acid. The white treatment liquid for aluminum or aluminum alloy according to claim 1, wherein 0.001 to 0.020 mol of nitrogen-containing polycarboxylic acid is added to 1 kg of the basic liquid. 4. The aluminum according to claim 3, wherein the nitrogen-containing polycarboxylic acids are one or more selected from the group consisting of iminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, and salts thereof. Or a white processing solution for aluminum alloys. Aluminum or aluminum alloy, characterized by being treated with a white treatment liquid obtained by adding 0.001 to 0.020 mol of a bismuth compound as a bismuth element to 1 kg of a basic liquid obtained by mixing phosphoric acid and sulfuric acid White processing method. 6. The white treatment method for aluminum or aluminum alloy according to claim 5, wherein the white treatment liquid is formed by adding 0.001 to 0.020 mol of nitrogen-containing polycarboxylic acid to 1 kg of the basic liquid.