JPH0319311B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method of plating using an acidic zinc plating solution that does not contain acetate ions or boric acid, and does not contain chlorine ions or has a low concentration. Prior art and its problems Recently, instead of the acidic zinc plating solution containing high concentration of chlorine ions, an acidic zinc plating solution that does not contain chlorine ions or has a low concentration and uses zinc sulfate as the zinc source has been introduced, which does not corrode the equipment. Also, it is attracting attention because it does not cause pollution problems due to high concentration of chlorine ions, but this type of acidic zinc plating solution usually contains sodium acetate,
Contains pH buffering agents such as boric acid, so when the pH is raised during wastewater treatment, acetate ions in the plating solution form complex salts with zinc, etc.
This causes wastewater treatment problems such as increased COD. In addition, boric acid similarly has problems in wastewater treatment. However, acidic galvanizing solutions that do not contain both acetate ions and boric acid at the same time do not have a pH buffering effect and may cause roughening of the glare film or cause burns in high current density areas. Causes poor eye contact. For this reason, conventionally, acidic zinc plating solutions contain at least one of acetate ions and boric acid. SUMMARY OF THE INVENTION In view of the above circumstances, the present inventor has discovered that an acidic galvanizing solution that does not contain chlorine ions or contains them at a low concentration of less than 50 g/ml has good properties even if it does not contain either acetate ions or boric acid. As a result of intensive research into an acidic zinc electroplating method that has a pH buffering effect, does not cause plating defects, and provides a good acidic zinc plating film, we found that zinc ion 8
Aminocarboxylic acids or their salts are added to acidic galvanizing solutions that contain chlorine ions or more and do not contain chlorine ions or contain less than 50 g/
Surprisingly, when plating is carried out using a plating solution containing 10 g or more, it has a good pH buffering effect even in the absence of acetate ions or boric acid, and is better than when boric acid is used. The present invention was based on the discovery that the plated coating becomes uniform, the high current density portions are less likely to be burnt, and a good plated coating can be obtained. In other words, aminocarboxylic acids and their salts have long been known as additives for acidic galvanizing solutions, but the amounts added are small, and as mentioned above, they are often used in combination with acetate ions and boric acid. That's what I was doing. On the other hand, aminocarboxylic acids or their salts are used in acidic zinc plating solutions that do not contain acetate ions or boric acid at all, have a relatively high concentration of 10 g or more, and do not contain chlorine ions or have low concentrations. It is a new finding of the present inventors that it is possible to obtain a taming film with good PH buffering effect and excellent physical properties. The present invention will be explained in more detail below. Structure of the Invention The acidic galvanizing method according to the present invention contains zinc ions at a concentration of 8 g/or more, and does not contain chlorine ions or contains chlorine ions at a concentration of less than 50 g/
The method is characterized in that the plated object is electroplated using an acidic zinc plating solution containing 10 g or more of an aminocarboxylic acid or a salt thereof and not containing acetate ions or boric acid. Here, as a source of zinc ions constituting the plating solution used in the present invention, zinc sulfate is preferably used, but the source is not limited thereto. In addition, since acetate ion is not used in the present invention, zinc acetate is not used. As mentioned above, the content of zinc ions is 8 g or more per plating solution, preferably 8 to 140 g, more preferably 20 g
~60g. Further, in the present invention, plating can be performed without adding any chlorine ions, but chlorine ions may be added at a low concentration. When containing chloride ions, when zinc chloride is used, it is supplied from this, but if it is insufficient or when zinc chloride is not used, it can be supplied with potassium chloride, sodium chloride, etc. . Its content is less than 50g per plating solution, but
Preferably it is 5 to 35 g, more preferably 10 to 25 g. The plating solution of the present invention further contains an aminocarboxylic acid or a salt thereof, and as a result, good plating can be achieved in a chloride-free or low-concentration system without acetate ions or boric acid, as described above. It is. In this case, examples of the aminocarboxylic acid include glycine, alanine, serine, cysteine, glutamic acid, lysine, tyrosine, tryptophan, β-alanine, and aminobenzoic acid, with alanine and glutamic acid being particularly preferred. Furthermore, as the aminocarboxylic acid salt, sodium salts of these aminocarboxylic acids and the like are used. In the present invention, the aminocarboxylic acids and their salts may be used alone or in combination of two or more. As described above, the content of the aminocarboxylic acid or its salt is 10 g or more per plating solution, preferably 10 to 50 g, more preferably 15 to 30 g.
If the blending amount of aminocarboxylic acids is 10 g/or more, it is possible to reliably achieve the above-mentioned object of the present invention, but if it is less than 10 g//, the PH buffering effect will decrease and the resulting plated film will become coarse. Otherwise, the high current density portion is likely to be burnt, making it impossible to achieve the object of the present invention. In addition to the above-mentioned components, additives such as brighteners and leveling agents can be added to the plating solution used in the present invention, if necessary. As additives such as brighteners and leveling agents, those used in conventional acidic galvanizing solutions can be used without restriction, but in particular polyamine compounds, polyether-based nonionic activators, aromatic carboxylic acid salts, etc. , at least one compound having a C=0 group (aldehyde, ketone),
Preferably, it is preferable to add all of the components, thereby ensuring better properties of the plating film from the plating solution of the present invention that does not contain acetate ions or boric acid, and adding the entire amount to the high current density portion. All parts from the to the low current density part can be more reliably brought into a uniform and smooth deposition state, and the occurrence of burns in the high current density part can be significantly prevented. In addition to these additives, it is also effective to add at least one of a sulfonate-based anion activator, a carboxy-based or imidazoline-based amphoteric activator, and this can further improve the precipitation state in high current density areas. can do. Examples of polyamine compounds include polyethyleneimine, polyethyleneimine derivatives, polymers of aliphatic amines and epichlorohydrin, ethoxylated polyamine compounds, ethylene oxide adducts of aliphatic amines, etc.
-17980, JP-A-53-80334, JP-A-56-169789,
JP 56-102589, U.S. Patent No. 4100040, No.
4146441), but polyethyleneimine, especially one with a molecular weight of 500 to 3000, is preferably used, and the amount added is 0.05 to 10 g/
In particular, it is preferably 0.5 to 3 g/. In addition, as a polyether-based nonionic activator, (1) R-O-(CH ₂ CH ₂ O) _o H (R is H or an alkyl group having 1 to 20 carbon atoms, n=
5-60) (2) (R is H or an alkyl group having 1 to 20 carbon atoms, n
=5~60) (3) (n=10~70) (4) Polyoxyethylene polypropylene glycol block polymer (PPG: molecular weight 500~3000, EO content 30~
(80 wt%) (5) Polyoxyethylene polyhydric alcohol aliphatic ester (EO addition amount 5-50 mol), etc., and the amount added is 0-20 g/, particularly 0.5-20 g/, more preferably 2-8 g/
It is preferable that Aromatic carboxylates include benzoate, salicylate, m,p-chlorobenzoate, 2,4-
Examples include dichlorobenzoate, cinnamate, etc., and the amount added is 0 to 10 g/, especially 0.05 to 10 g/,
More preferably, the amount is 0.5 to 2 g/. Furthermore, compounds having a C=0 group (aldehydes,
Examples of ketones include benzylidene acetone,
Examples include aromatic carbonyl compounds such as cinnamic aldehyde, chlorobenzaldehyde, dichlorobenzaldehyde, and furfural acetone, and aliphatic ketones such as isobutyl methyl ketone and methyl vinyl ketone, and the amount added is 0 to 3 g, especially 0.005 to 3 g. /, more preferably 0.005 to 0.2
It is preferable to set it as g/. In addition, as sulfonate-based anionic activators, carboxy-based or imidazoline-based amphoteric activators,
Dialkyl sulfosuccinate, alkylnaphthalene sulfonate, naphthalene sulfonate formalin condensate, N,N-dimethyl-N-alkyl-
N-carboxyalkylene ammonium betaine, 2-alkyl-1-hydroxyethyl-1-
Examples include carboxymethylimidazolinium salts, and the amount of sulfonate anion activator added is 0.
~5g/, especially 0.05-5g/, more preferably 0.2-0.5g/, and the amount of amphoteric active agent added is 0-5g/, especially 0.05-5g/, more preferably 0.5-1.0g/. is preferred. Furthermore, a hydrolyzate of a protein containing glycine, hydroxyproline, and proline as amino acids, such as a hydrolyzate of collagen, can be added as a brightener at a concentration of 0 to 10 g/, particularly 0.1 to 10 g/. The pH of the plating solution used in the present invention is 2.5 to 2.5.
6.5, particularly preferably 4.5 to 5.5. When plating is carried out using the above-mentioned plating liquid, there are no restrictions on the type of object to be plated, and zinc plating is performed after appropriate pretreatment. In this case, the plating conditions can be changed in various ways, but usually the plating temperature is 15 to 40°C, especially 20 to 35°C, and the cathode current density is 0.1 to 5 A/ ^dm2 , especially 0.5 to ³ A/dm2. will be adopted. Stirring of the plating solution is not necessarily required, but stirring using a cathode rocker, air, etc. may be employed. Further, it is preferable to use zinc for the anode plate. Note that the plating time is appropriately selected depending on the desired plating film thickness. Furthermore, the plating method of the present invention can also be carried out by employing a barrel plating method. After plating, chromate treatment and other post-treatments can be performed if necessary. Effects of the invention The method of the present invention contains 8 g/or more of zinc ions and does not contain chlorine ions or contains 50 g/
A galvanized object is electroplated using an acidic zinc plating solution containing at least 10 g of aminocarboxylic acid or its salt at a lower concentration and containing neither acetate ion nor boric acid, and the present invention The plating film obtained by this method has a uniform and smooth appearance, and the adhesion of the chromate film is good, and the plating solution used in the present invention does not contain acetate ions or boric acid, so wastewater treatment is easy. It is easy to carry out and can be suitably employed in place of acidic zinc plating methods that do not contain chlorine ions or have a low concentration, such as conventional zinc sulfate plating methods that contain acetate ions and boric acid. EXAMPLES Hereinafter, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited to the following examples. Example 1, Comparative Example The following composition Z _o SO ₄・7H ₂ O 300g/Na ₂ SO ₄ 30 Peptone 2 Aminocarboxylic acid/salt An acidic zinc plating solution with pH 3.5 in the amount shown in the table was prepared and Hull Cell test was conducted. The PH buffering effect and the appearance of the plating film were investigated using a test tube. For comparison, a solution containing no aminocarboxylic acid/salt and a solution containing boric acid instead of aminocarboxylic acid/salt were used.
Using a liquid with a composition of 30g/ each,
A similar experiment was conducted. PH buffering effect A Hull cell test was conducted using a degreased and pickled 10 cm x 7 cm polished steel plate as a cathode at a current of 2 A for 30 minutes, and the PH fluctuation during this period was investigated. Appearance of plating film A degreased and pickled 10 cm x 7 cm polished steel plate was used as a cathode, and a Hull cell test was conducted at a current of 2 A for 10 minutes to evaluate the appearance of the resulting plating film. The results are shown in the table.

[Table] Example 2 Z _o SO ₄・7H ₂ O 200g/ KCl 60 〃 Alanine 15 〃 Polyethyleneimine (molecular weight 5000) 2 〃 C ₁₂ H ₂₅ -O-(CH ₂ CH ₂ O) ₁₅ H 6 〃 Benzoic acid Soda 2 〃 Benzylidene acetone 0.38 〃 PH 3.5 Plating temperature 25℃ D _k 2A Plating time 10 minutes When a 1 dm ² bent cathode was plated with the above composition and conditions, the zinc plating had little pH fluctuation and a good appearance. A deposited film was obtained.

Claims (1)

[Claims] 1 Contains 8g/or more of zinc ions, and
Contains no chloride ions or a concentration of less than 50g/aminocarboxylic acid or its salts
An acidic zinc plating method characterized by electroplating a plated object using an acidic zinc plating solution containing 10 g or more and containing neither acetate ion nor boric acid.