JPH0637708B2 - Chemical polishing method for aluminum or its alloy - Google Patents

Description

The present invention relates to a chemical polishing method for aluminum or its alloys, and more particularly to a chemical polishing method that does not require desmutting treatment.

[Prior Art] In recent years, reduction of phosphorus and nitrogen contents in factory wastewater has been a subject of technical improvement, and the chemical polishing industry for aluminum also needs to remove phosphorus and nitrogen in wastewater.

Phosphorus in wastewater is relatively easy to remove, but biological treatment of nitrogen is common, the scale of treatment equipment is large, and there are many control items in operation, so the cost for removing nitrogen is large. Is a problem. Therefore, there is a need for a chemical polishing process that does not require wastewater treatment of nitrogen, that is, does not use nitric acid as a nitrogen source.

As a chemical polishing liquid for aluminum or its alloys, phosphoric acid-nitric acid system and phosphoric acid-sulfuric acid-nitric acid system have been widely used industrially. Since these chemical polishing liquids contain nitric acid, it is necessary to denitrify the waste liquid, which is unsuitable from this viewpoint. In addition to these, there is phosphoric acid-sulfuric acid system as a chemical polishing liquid for industrially widely used aluminum or its alloys. Quantity 40-50%
It was necessary to perform desmutting treatment with the above solution, and it was unavoidable to remove the nitrogen content in the wastewater. In particular, desmutting treatment performed before the chemical polishing step is indispensable, and if it is desired to omit it, phosphoric acid-sulfuric acid-based chemical polishing liquid will cause pits on the surface to be polished due to the effect of smut that has already adhered due to caustic degreasing treatment. However, there is a drawback that the appearance of the treated surface remarkably deteriorates due to the occurrence of excessive etching.

[Problems to be Solved by the Invention] In order to solve the above problems of the prior art, the present invention aims to provide a chemical polishing method for aluminum or its alloys that does not require desmutting treatment.

For example, the conventional method followed by an anodizing step shows that the steps of caustic degreasing-water washing-desmutting (40 to 50% nitric acid) -water washing-chemical polishing-water washing-anodizing step are performed. According to the method of (1), the steps are caustic degreasing-water washing-chemical polishing-water washing-anodizing step, which makes it possible to omit two steps from the steps after caustic degreasing in the conventional method.

[Means for Solving the Problems] In order to solve the above problems, the present invention relates to a method in which aluminum or an alloy thereof is subjected to caustic degreasing treatment, washed with water, and then treated with a thiophene derivative having a carboxyl group and a sulfide or disulfide compound having a carboxyl group. 0.001 each
~ 0.5 wt%, 0.001 ~ 1.0 wt% copper or nickel ion
% Of a phosphoric acid-sulfuric acid-based chemical polishing liquid for chemical treatment of aluminum or its alloy.

The phosphoric acid-sulfuric acid type chemical polishing liquid is composed of 85% phosphoric acid 50-80 wt% 98% sulfuric acid 20-50 wt%.

After the caustic degreasing treatment by adding the thiophene derivative having a carboxyl group and the sulfide or disulfide compound having a carboxyl group to the chemical polishing bath,
Even without desmutting treatment, the number of pits generated on the surface to be polished was significantly reduced. This has made it possible to chemically polish aluminum or its alloys without the need for desmutting. However, when these two kinds of additives are individually added to the chemical polishing liquid, the above effect is obtained but it is weak. A synergistic effect was obtained by using these two additives together.

In the method of the present invention, a detailed description of the action mechanism of the thiophene derivative and the sulfide or disulfide in the chemical polishing liquid is not yet clear, but for the smut immediately precipitated by caustic degreasing treatment, the thiophene derivative and The carboxyl group in the sulfide or disulfide molecule interacts with the thiophene derivative and sulfur in the sulfide or disulfide molecule, and adverse effects due to this smut, such as pit generation,
It is presumed that it acts to prevent excessive etching.

In addition, trace metal components eluted from aluminum or its alloys into the chemical polishing liquid are captured by the carboxyl group in the molecule of the sulfide or disulfide compound,
Reprecipitation on the surface to be polished is prevented.

In the present invention, thiophene alone or a thiophene derivative having a functional group other than a carboxyl group does not have such an effect, while compounds having a carboxyl group other than a sulfide or disulfide compound do not have such an effect. Further, a sulfide or disulfide compound having a functional group other than a carboxyl group has no effect,
Even if two or more kinds of these compounds are arbitrarily used in combination, there is no effect.

Therefore, in the present invention, the combined use of a thiophene derivative having a carboxyl group and a sulfide or disulfide having a carboxyl group is essential.

The thiophene derivative used in the present invention has a carboxyl group in its molecule, It is represented by. R ₁ is an aliphatic group having 0 to 3 carbon atoms.

Here, thiophene or thiophene having a functional group other than a carboxyl group attached thereto, such as 2-aminothiophene, has a low boiling point and is therefore unsuitable as an additive for a chemical polishing liquid having a bath temperature of 90 to 110 ° C.

Specific examples of the thiophene derivative having a carboxyl group used in the present invention include the following compounds. However, it is not limited to these examples.

Thiophenecarboxylic acid Or Thiophene acetic acid 2-thiophenebutyric acid Is mentioned.

On the other hand, the sulfide or disulfide has a carboxyl group in the molecule, but a functional group other than the carboxyl group, such as a hydroxyl group or an amino group, may be present. However, in the case where there is no carboxyl group and only the above functional group, for example, thiodiethylene glycol or cystamine, the above effect is not exhibited.

Also, the alkyl portion of the sulfide or disulfide is an aliphatic group. Specifically, the following compounds are exemplified, but the compounds used in the present invention are not limited to these exemplified compounds, and salts such as sodium and potassium of this carboxyl group are also included.

(1) A sulfide or disulfide having a bilaterally symmetrical structure with S (sulfur atom) in between, and has the general formula (HOOC
-R ₂₎ represented by the ₂ S or _{(HOOC-R 3 -S) 2} , R 2, R 3 is an aliphatic group, or _R 2 having 1 to 4 carbon atoms, R
Sulfide or disulfide in which H of ₃ is a substituted group, for example, thiodiglycolic acid S (—CH ₂ —COOH) ₂ 3,3′-thiodipropionic acid S (—CH ₂ —CH ₂ —COOH) ₂ dithioglycolic acid _{(-S-CH 2 -COOH)} 2 dithiodipropionic acid _{(-S-CH 2 -CH 2 -COOH} ) 2 α, α'- dithiodipropionic acid Thiodisuccinic acid Cystine (2) It is an asymmetric sulfide and has a general formula of R ₄ -S-R.
_A sulfide represented by _5- COOH, wherein R ₄ and R ₅ are an aliphatic group having 1 to 3 carbon atoms or a group in which H of R ₄ and R ₅ is substituted, for example, carboxymethylmercaptosuccinic acid Methionine Is mentioned.

The amounts of the above thiophene derivative and sulfide or disulfide added to the phosphoric acid-sulfuric acid chemical polishing bath are respectively
It is 0.001 to 0.5 wt%. If it is less than 0.001 wt%, it has no effect, and because of the smut generated by caustic degreasing, many pits are generated on the treated surface after chemical polishing, and the appearance deteriorates. Moreover, the effect is not improved even if added in an amount exceeding 0.5 wt%, which is economically wasteful.

Copper or nickel ions added together with the above two kinds of additives have an effect as a brightening agent, and specific compounds are added as oxides, inorganic acid salts and organic acid salts. For example, copper oxide, nickel oxide, copper sulfate, nickel sulfate, copper nitrate, nickel nitrate, copper acetate, nickel acetate, etc. are used.

As in the conventional example, the amount added is 0.001 to 1.0 wt% as copper or nickel ions. If it is less than 0.001 wt%, there is no effect. Occasionally, the treated metal surface may become satin.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples. In addition, the amounts of the respective components described in the examples are all% by weight.

Example 1 Composition of Polishing Solution 85% Phosphoric Acid 60% 98% Sulfuric Acid 39.5% Nickel Sulfate 0.1% Water 0.4% Metallic aluminum 1% was dissolved in the above solution, and various thiophene derivatives were added to a basic bath having a specific gravity of 1.700 at 100 ° C. And 0.05% each of sulfide and disulfide. In Comparative Examples, 0.1% was added when one kind of additive was used, and 0.05% was added when two kinds of additives were used.

The chemical polishing was carried out at a bath temperature of 100 ° C. for an immersion time of 30 seconds, and the results of chemical polishing of AA1100 aluminum or 5052 aluminum without desmutting treatment after caustic degreasing are shown in Table 1.

From the above results, the thiophene derivative of the present invention containing a carboxyl group and a sulfide or disulfide are added to a phosphoric acid-sulfuric acid-based chemical polishing bath to obtain a surface equivalent to or more than the state of the surface for chemical polishing which requires general desmutting treatment. It turns out that Further, a thiophene derivative having a carboxyl group, the addition of only one of the sulfide or disulfide having a carboxyl group, only a small effect is observed, thiophene derivative having a carboxyl group and a sulfide having a functional group other than the carboxyl group or It can be seen that there is no synergistic effect even when disulfide is used together.

Example 2 In order to determine an appropriate addition amount of a thiophene derivative and a sulfide or a disulfide, the same treatment conditions as in Example 1 were used except that the addition amounts of thiophene acetic acid and thiodipropionic acid were changed to the basic bath shown in Example 1 above. The AA1100 aluminum is chemically polished by the above, and the state of the treated surface is shown in the following Table 2 by the notation method of Table 1.

As is clear from the above results, the addition amount of 0.001% has some effect, but when one of the two types of additives is 0.05%, the effect is obtained even if one of the additives exceeds 0.005%. It turns out that the improvement of the can not be expected.

Example 3 The same chemical polishing bath of the present invention prepared by adding 0.05% of 2-thiophenecarboxylic acid and thiodiglycolic acid to the basic bath of Example 1 and the conventional chemical polishing bath using AA1100 aluminum as the sample were the same as those of Example 1. Chemical polishing was performed under the conditions and comparison was made.

The results are shown in Table 3.

As is clear from the above results, it can be seen that the chemical polishing liquid of the present invention can obtain a treated surface that is as excellent as that obtained by the desmutting treatment, even without the desmutting treatment.

[Effects of the Invention] As described above, according to the method of the present invention, in chemically polishing aluminum or its alloy, after performing caustic degreasing treatment, an excellent chemically polished surface can be obtained without desmutting treatment. it can.

Claims (1)

[Claims] 1. Aluminum or its alloy is subjected to caustic degreasing treatment and washed with water, and then 0.001 to 0.5 wt% of a thiophene derivative having a carboxyl group and a sulfide or disulfide compound having a carboxyl group, and 0.001 to 1.0 wt% of a copper or nickel ion. A method of chemically polishing aluminum or an alloy thereof, which comprises treating with a phosphoric acid-sulfuric acid-based chemical polishing liquid contained.