JPH059765A - Acidic cleaning liquid for aluminum and cleaning method - Google Patents

Abstract

(57) [Summary] [Objective] An acidic cleaning solution for cleaning aluminum does not contain chromium ions and fluorine ions, and does not use ferric ions, or obtains excellent etching characteristics even when the amount used is small. [Structure] One or more selected from sulfuric acid or sulfuric acid and nitric acid, and oxidation ions of diphenylamine, oxidation ions of diphenylbenzidine, oxidation ions of diphenylamine sulfonate, and oxidation ions of diphenylbenzidine sulfonic acid. 0.5 to 5 of the oxidized ion of
g / l.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acid cleaning solution used for appropriately etching and cleaning the surfaces of aluminum, aluminum alloy (hereinafter, referred to as "aluminum") plates, cans, containers, etc. Regarding the cleaning method.

Drawing and
Since lubricating oil for processing is used when molding into a beverage container or the like by an ironing molding operation (hereinafter referred to as DI processing) or the like, lubricating oil or smut of aluminum fine powder adheres to the surface of aluminum. Cleaning liquids have been used to remove these and maintain a clean aluminum surface.

[0003]

2. Description of the Related Art Chromic acid-based or hydrofluoric acid-based cleaning agents have been widely used to remove lubricating oil and smut that adhere to the aluminum surface by DI processing. Since the chemical compounds are harmful, waste liquid treatment equipment is required to maintain a healthy social environment and working environment. Since the cost of this waste liquid treatment facility significantly increases the cost of the product, the development of a non-chrome / fluorine-free aluminum surface cleaner has been promoted.

Japanese Unexamined Patent Publication Nos. 61-106783 and 6
No. 1-231188 discloses that an acidic aqueous solution of pH 2 or less adjusted with sulfuric acid and / or nitric acid achieves sufficiently satisfactory surface cleaning with an aluminum surface cleaner containing ferric ion. ing. The effect of ferric ion is to promote the etching action of sulfuric acid and nitric acid on aluminum. That is, these acidic aqueous solutions do not contain or contain a small amount of fluorine ions, and the etching of aluminum by acidic aqueous solutions of pH 2 or less adjusted with sulfuric acid and / or nitric acid is promoted by ferric ion, which is satisfactory. Achieves surface cleaning. Further, in the above-mentioned publication, the concentration of ferric ion is 0.2 to 4 g / l, and the value is 1.25 g / l in the examples.

The effect of the ferric ion is related to the fluorine-containing aluminum surface cleaning liquid, but it is described in JP-B-52.
As described in No. 223230, the etching rate of aluminum is high in the presence of a large amount of fluorine ions when ferric ions are not present, but when ferric ions are present, the etching rate of fluorine ions is suppressed. Is
Satisfactory surface cleaning is achieved because of the effect of obtaining an appropriate etching rate with sulfuric acid or the like.

Further, in order to keep the cleaning effect constant during treatment, the above-mentioned aluminum surface cleaner needs to control the treatment bath, especially the concentration of ferric ion. Conventional treatment bath management methods have been performed by measuring electrical conductivity and redox potential. In the above-mentioned JP-A-61-231188, the concentration of ferric ion in the treatment bath is measured by the redox potential,
In order to maintain a proper aluminum surface cleaning effect, a treatment bath management method for oxidizing ferrous ions to ferric ions when ferric ions are reduced to ferrous ions by a predetermined amount or more is disclosed. There is.

[0007]

However, the measurement of the electric conductivity or the redox potential requires an electric conductivity meter or a potentiometer, respectively. Further, if the bath is continuously used, a recorder and the like must be attached to the measuring instrument, which causes a problem that the bath management cost becomes very high.

Furthermore, when ferric ions are reduced to ferrous ions, in the conventional method of oxidizing ferrous ions to ferric ions in order to maintain an appropriate aluminum surface cleaning effect, an oxidizing agent is used. As an example, when hydrogen peroxide is added, the coexisting surfactant is oxidized due to the OH molecule generated by the reaction of hydrogen peroxide and ferrous ion shown in the formula below, and the surfactant is decomposed to reduce the weight. To do. ^{_{H 2 O 2 + Fe 2+ →}} Fe 3+ + OH - + OH

This reaction does not occur unless ferrous iron ions are present, and it is necessary to measure the redox potential or the like to detect the concentration of iron ions. Therefore, bath management methods other than this measuring method are possible. To find a redox agent that turns into iron ion. Therefore, the present inventors have found that the aluminum etching mechanism of ferric ion in an acidic aqueous solution adjusted to pH 2 or less with sulfuric acid and / or nitric acid is Fe ³⁺ + e
^- → Fe ²⁺ cathodic reaction occurs, focusing on the fact that aluminum etching is promoted as one anodic reaction, and based on the results of examination of elements and compounds other than ferric ion that can realize the same mechanism, It was found that metallic mercury fine particles similarly have an appropriate etching effect in an acidic aqueous solution of pH 2 or less prepared by sulfuric acid or sulfuric acid and dilute nitric acid. Further, as a result of examining the oxidized ion of diphenylamine, the oxidized ion of diphenylbenzine, the oxidized ion of diphenylamine sulfonate, or the oxidized ion of diphenylbenzidine sulfonic acid, similar effects were observed.

[0010]

The elements and compounds exhibiting a proper etching effect on aluminum have a standard redox potential of + 0.77 ± 0.09 volt at 25 ° C. It has been found that an element or compound having a potential has a proper etching effect for aluminum in sulfuric acid or an acidic aqueous solution adjusted to pH 2 or less with sulfuric acid and diluted nitric acid, and has completed the present invention. However, since mercury is a harmful substance, it cannot be used in practice, but organic oxidation-reduction agents for diphenylamine oxidized ion, diphenylbenzidine oxidized ion, diphenylamine sulfonate oxidized ion, or diphenylbenzidine sulfonic acid oxidized ion They can be used alone or as a mixture.

Since the standard redox potential of + 0.77 ± 0.09 volt is the same as that of Fe ³⁺ → Fe ²⁺ , ferric ion is used in combination with the above-mentioned diphenylamine oxidized ion. can do. However, the amount of ferric ion used can be made very small so as not to reduce the amount of the surfactant.

Further, control of the aluminum surface cleaning treatment bath is carried out by controlling the oxidation type ion of diphenylamine oxidation type ion,
Or, when the oxidation type ion of diphenylbenzidine is used, the color of the detergent bath changes from purple blue to colorless at the redox potential around +0.76 V. Therefore, the effectiveness of the detergent can be measured by the redox potential. It is characterized by observing the discoloration point without the need for management. However, in the case of containing dilute nitric acid, it exhibits a purple blue color while nitric acid coexists. Further, since the discoloration potential of diphenylamine sulfonate is +0.83 V, the oxidation type color is red purple and the reduction type color is colorless, the surface cleaning treatment bath can be controlled by observing the discoloration point.

Therefore, the present invention does not contain a chromate ion or a fluorine ion, but is an oxidation type ion of diphenylamine, an oxidation type ion of diphenylbenzidine, an oxidation type ion of diphenylamine sulfonate or an oxidation type ion of diphenylbenzidine sulfonic acid. Containing 0.5 to 5 g / l of an organic redox agent used alone or in combination,
The present invention relates to an aluminum surface cleaning agent, which is an acidic aqueous solution having a pH of 2 or less adjusted with sulfuric acid or a mixed acid of sulfuric acid and dilute nitric acid. Content of organic redox agent is 0.5 g /
If it is less than 1, the effect is reduced, while if it exceeds 5 g / l, there are problems in economic efficiency and solubility. Therefore, the amount of the organic reducing agent is limited to the above range.

Further, the aluminum surface cleaning agent may further contain 0.05 to 0.5 g / l ferric ion in addition to the above-mentioned components. The amount of ferric ion is 0.
If it is less than 05 g / l, there is no effect of promoting aluminum etching. On the other hand, if it exceeds 0.5 g / l, it causes inconveniences such as generation of sludge and reduction of the amount of surfactant. Preferably there is.

The detergent of the present invention contains nonionic, cationic, anionic and amphoteric ionic surfactants in a concentration range of 0.1 to 10 g / l, like the conventionally known detergents. be able to. The most frequently used concentration range is 0.5-2 g / l. The temperature of the processing liquid is room temperature to 80
C., usually in the range of 60 to 75.degree. In addition, the treatment time is 10 to 10 regardless of the dipping method or the spray method.
It is in the range of 120 seconds, and usually in the range of 50 to 60 seconds.

Further, the aluminum cleaning method according to the present invention is such that when the aluminum is cleaned with the acidic cleaning solution having the above composition, the cleaning solution becomes decolored or becomes a state close to that when the cleaning solution is peroxidized. It is characterized in that at least one kind of ion selected from hydrogen, nitrite ion, peroxosulfate ion, metavanadate ion and cerium ion is added to restore the colored state, and further washing is continued. To determine the color of the cleaning solution, prepare a standard solution in advance, extract the test solution from the bath, and visually compare the two solutions.
The determination method enables easy and reliable determination.

[0017]

In the etching method for cleaning aluminum with sulfuric acid or a mixed acid of sulfuric acid and nitric acid, the oxidation type ion of diphenylamine, the oxidation type ion of diphenylbenzidine, the oxidation type ion of diphenylamine sulfonate, and the oxidation type of diphenylbenzidine sulfonic acid Standard redox potential (V _C ) of ions is + 0.77 ± 0.0 at 25 ° C.
It is 9 volts. The standard oxidation-reduction potential (V _a ) of aluminum (Al → Al ³⁺ reaction) is −1.66 at 25 ° C.
Since V _a << V _c at _a pH of 2 or less at 2 V, the etching of aluminum is promoted by the cathode reaction of the redox agent such as the oxidized ion of diphenylamine.

During the treatment in the aluminum surface cleaning treatment bath of the present invention, the oxidation type ion of diphenylamine and the oxidation type ion of diphenylbenzidine are changed from purple blue to colorless in the case of a sulfuric acid bath and coexist with nitric acid. In the case of a bath, the color changes from purple-blue to colorless, and that of diphenylamine sulfonate changes from magenta to colorless. When this discoloration occurs or the color becomes almost colorless, the function of the organic reducing agent ceases, so hydrogen peroxide that can oxidize this,
At least one ion selected from nitrite ion, peroxosulfate ion, metavanadate ion and cerium ion is added to restore the colored state.

Next, the examples and the evaluation of the cleaning properties thereof will be specifically described.

EXAMPLES The cleaning characteristics of samples A to D shown in Table 1 were evaluated. Evaluation Test Sample A3004 An aluminum can body (a can container without a lid) obtained by performing DI processing on an aluminum alloy plate, to which lubricating oil and smut were adhered, was used for the test.

[0020]

[Table 1]

In the preparation of the above cleaning solution, sulfuric acid has a concentration of 94.0% (17.6 mol / l) and nitric acid has a concentration of 69.
0% (15.4 mol / l), hydrogen peroxide has a concentration of 35.
0% of each was used as a stock solution. The diphenylamine used was 5 g dissolved in 90 g sulfuric acid. Cleaning liquid sample No. In A and B, iron was adjusted to be 0.2 g / l by adding 3.6 ml of a 20% ferric sulfate aqueous solution.

Further, with respect to the samples of cleaning agents A, B, C and D in Table 1, nonionic surfactants were used in a concentration range of 1 g / l. Hydrocarbon derivatives, abietic acid derivatives, primary ethoxylated alcohols, modified polyethoxylated alcohols, etc. were used as the surfactants.

In samples C and D, hydrogen peroxide was added to make diphenylamine an oxidized form. Samples A and B are acid cleaning solutions of Comparative Examples that do not contain oxidized diphenylamine. In samples A and B, hydrogen peroxide, which is an oxidizing agent for ferrous iron, was used. The pH of these samples was 2.0.

Treatment conditions A can container of a test sample was treated at a treatment temperature of 60 with each of the above cleaning agents.
Spray spray cans at ~ 70 ° C for 60 seconds, then at room temperature for 1
It was spray-washed with tap water for 5 seconds and then with deionized water for 5 seconds, and dried with hot air at 95 ° C.

Detergency Evaluation The following items were tested, and the results are shown in Table 2.

[Table 2]

Criteria Note 1. The case where the degreasing and the desmutting are completed and the aluminum plate has a sufficiently etched white appearance is regarded as good, and the following 5 grades are evaluated according to the degree of whitening. ◎: All white; ◯: Partly light gray △: Partly light gray; ×: Partly gray XX: All gray Note 2. Immediately after washing with spray water, the container is shaken three times to drain water, the container is left standing upward, and the water-wetted area% of the outer surface of the container after 30 seconds is measured and displayed.

Note 3. A transparent adhesive tape is adhered to the inner surface of the container after drying, which is peeled off and attached to a white backing paper, and the whiteness of the tape pasting surface is compared with other backing paper parts. The case where the smut is completely removed from the aluminum plate and the surface of the aluminum plate is not contaminated is regarded as good, and the evaluation is made on a scale of 5 according to the degree of contamination. ◎: No pollution; ○: Trace pollution △: Slight pollution; ×: Medium pollution XX: Large pollution

Control of cleaning liquid When 60 DI can bodies were spray-cleaned under the above processing conditions using the cleaning liquids of Samples C and D, the initial purple-blue color faded, so that the total volume was 5 liters. 1 for liquid
When 20 ml of a molar hydrogen peroxide solution was added, the initial blue color was restored. After that, the same washing treatment was continued.

[0029]

According to the present invention having the above-mentioned constitution, the lubricating oil and the aluminum smut adhering to the aluminum surface are removed by the chemical conversion treatment without containing harmful chromium ions and fluorine ions which pollute the pollution and the working environment. It is possible to achieve the cleaning so that the painting work can be smoothly processed. Furthermore, even if iron ions, which decompose the surfactant when hydrogen peroxide coexists, do not exist as ferric ions in the aluminum surface cleaning solution, the aluminum surface can be sufficiently cleaned. There is. Further, since the acid cleaning solution is easily managed, the accuracy of acid cleaning management is improved.

Claims (6)

[Claims] 1. Sulfuric acid or sulfuric acid and nitric acid, and an oxidized ion of diphenylamine, an oxidized ion of diphenylbenzidine, an oxidized ion of diphenylamine sulfonate,
And 0.5 to 1 or more types of oxidation type ions selected from the oxidation type ions of diphenylbenzidine sulfonic acid.
An acidic cleaning solution for aluminum or aluminum alloy having a pH of 2.0 or less containing 5 g / l and containing neither chromium ion nor fluorine ion. 2. One or two selected from sulfuric acid or sulfuric acid and nitric acid, and an oxidation ion of diphenylamine, an oxidation ion of diphenylbenzidine, an oxidation ion of diphenylamine sulfonate, and an oxidation ion of diphenylbenzidine sulfonic acid. 0.5-5 of more than one type of oxidized ion
pH containing g / l and 0.05 to 0.5 g / l of ferric ion and not containing chromium ion and fluorine ion
Acid cleaning solution for aluminum or aluminum alloy of 2.0 or less. 3. The acidic cleaning liquid for aluminum or aluminum alloy according to claim 1, which contains 0.05 to 5 g / surfactant. 4. Aluminum or aluminum alloy,
Sulfuric acid or sulfuric acid and nitric acid, and one or more kinds of oxidation selected from diphenylbenzidine oxidation ion, diphenylbenzidine oxidation ion, diphenylamine sulfonate oxidation ion, and diphenylbenzidine sulfonic acid oxidation ion. In the case of washing with an acidic cleaning liquid having a pH of 2.0 or less containing 0.5 to 5 g / type of type ions, when the color development due to the oxidized type ions in the cleaning liquid becomes decolored or close to it, Characteristically, one or more ions selected from hydrogen peroxide, nitrite ion, peroxosulfate ion, metavanadate ion and cerium ion are added to the cleaning liquid to restore the colored state, and then further cleaning is performed. A method for cleaning aluminum or an aluminum alloy. 5. The acidic cleaning liquid contains a surfactant in an amount of 0.05 to 5
The method for cleaning aluminum or aluminum alloy according to claim 4, wherein g / content is included. 6. The acidic cleaning liquid contains ferric ion in an amount of 0.05 to
The method for cleaning aluminum or aluminum alloy according to claim 4, characterized in that the content is 0.5 g / l.