JPH0319313B2 - - 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. It is also attracting attention because there are no pollution problems caused by high concentrations of chlorine ions. However, conventionally, zinc sulfate plating solutions have used peptone, dextrin, etc. as brightener components, but the luster of the matte film obtained from zinc sulfate plating solutions containing these types of brightener components has decreased. The leveling properties are different from other acidic galvanizing solutions,
In particular, the gloss and leveling properties of the plating film obtained using zinc chloride plating solution are very inferior to those obtained using zinc chloride plating solution. It was only used for plating and was unsuitable for general decorative plating. In addition, this type of acidic zinc plating solution usually contains pH buffering agents such as sodium acetate and boric acid, so when the pH is increased during wastewater treatment, acetate ions in the plating solution form complex salts with zinc, etc. These ions also cause problems in wastewater treatment, such as increasing COD. In addition, boric acid similarly has problems in wastewater treatment. However, acidic zinc plating solutions that do not contain both acetate ion and boric acid at the same time,
It has no PH buffering effect, and causes plating defects such as roughening of the glare film and burning in high current density areas. For this reason, conventionally, at least one of acetate ions and boric acid was added to the acidic zinc plating solution.
The seeds are what is contained. Summary of the Invention In view of the above circumstances, the present inventor has discovered that an acidic zinc plating solution that does not contain chlorine ions or is used at a low concentration of 50 dl/lower has good properties even if it does not contain either acetate ions or boric acid. As a result of intensive research into an acid zinc electroplating method that has a PH buffering effect, does not cause plating defects, and provides an acid zinc plating film with good gloss, leveling properties, and coverage, we found that zinc ion 8dl / or more and does not contain chlorine ions or 50dl/
To an acidic galvanizing solution containing the following concentration, preferably 1 dl/or more of an aminocarboxylic acid or its salt and preferably 1 dl/or more of a protein hydrolyzate containing glycine, hydroxyproline, and proline as amino acids are added. Surprisingly, when plating is performed using a staining solution, excellent gloss, leveling and throwing power that cannot be obtained when peptone is added, and acetate ions and boric acid are removed. It's good even if it doesn't exist at all
It has been found that it has a PH buffering effect, and that the plating film is more uniform than when using boric acid or the like, and that burns are less likely to occur even in high current density areas, and a good plating film can be obtained, which led to the creation of the present invention. It is something. The present invention will be explained in more detail below. Structure of the Invention The acidic galvanizing method according to the present invention includes zinc ions of 8 dl/or more, chlorine ions of 0 to 50 dl/,
Electroplating of a plated object using an acidic zinc plating solution containing an aminocarboxylic acid or a salt thereof and a protein hydrolyzate containing glycine, hydroxyproline, and proline as amino acids and not containing acetate ions or boric acid. It is characterized by: 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. . The content thereof is 50 g or less per plating solution, preferably 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 of these aminocarboxylic acids and the like can be used. In the present invention, the aminocarboxylic acids and their salts may be used alone or in combination of two or more. The content of aminocarboxylic acid or its salt is preferably 1 g or more, more preferably 5 to 20 g per plating solution. According to the present invention, even if the blended amount of aminocarboxylic acids is at least as above, the PH buffering effect is good due to the combined effect with a protein hydrolyzate containing a specific amino acid, and the resulting plated film is not roughened. Therefore, a good plated film is obtained without causing burning in the high current density portion, and the object of the present invention is achieved. The plating solution used in the present invention is further added with a hydrolyzate containing a specific amino acid along with an aminocarboxylic acid and/or its salt, which improves the PH buffering effect of the plating solution of the present invention and the plating film. It is possible to improve the properties of the film, ensure that all parts from the high current density part to the low current density part are in a uniform and smooth deposition state, and significantly reduce the occurrence of burns in the high current density part. It can be prevented. The protein hydrolyzate of the present invention is slightly different from conventionally known protein hydrolysates. That is, among the conventionally known protein hydrolysates, those with large molecular weights are peptone,
Those with small molecular weight are called polypeptides.
Each is distinct. Here, peptone is used as a brightening agent in a zinc sulfate plating bath, and although it is known that it has a slight leveling effect, this effect is insufficient and it has excellent properties. A sticky coating cannot be obtained using this peptone. The protein hydrolyzate of the present invention contains various amino acids, and the amino acids include glycine, alanine, serine, threonine, proline, hydroxyproline, valine, isoleucine, leucine, phenylalanine, tyrosine, methionine, and asparagine. Among these amino acids, the protein hydrolyzate of the present invention must necessarily contain glycine, hydroxyproline, and proline. For example, when a protein hydrolyzate containing no hydroxyproline is used, the effect on the plated film is significantly inferior, and the effect is only comparable to that obtained using conventional peptone. At this time, the total content of glycine, hydroxyproline, and proline in the hydrolyzate is 20 to 80%.
(% by weight, the same applies hereinafter), and particularly preferably 40 to 60%. The protein hydrolyzate of the present invention contains amino acids as described above, but the molecular weight is
250 to 50,000, particularly preferably 800 to 10,000. In addition, the content of protein hydrolyzate is plating solution 1
The amount is preferably 0.1 g or more, more preferably 0.1 to 10 g. In the present invention, in addition to these additives, it is effective to further add one type, preferably all, of a polyether nonionic surfactant, an aromatic carboxylic acid, and a compound having a C═O group (aldehyde, ketone). It is also more effective to add at least one of a sulfonate-based anionic activator, a carboxy-based or imidazoline-based amphoteric activator, and this can further improve the precipitation state in the high current density area. can. Here, as the 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 20~
(80 wt%) (5) Polyoxyethylene polyhydric alcohol aliphatic ester (EO addition amount 5 to 50 mol), etc., and the amount added is 0 to 10 dl/, especially 0.05 to 10 dl/, more preferably 0.5 to 2 dl/
It is preferable that In addition, aromatic carboxylates include benzoate, salicylate, m,p-chlorobenzoate,
Examples include 2,4-dichlorobenzoate, cinnamate, etc., and the amount added is 0 to 10 dl/, especially 0.05 to 10
dl/, more preferably 0.5 to 2 dl/. 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 dl/, particularly 0.005 to 3 dl. /, more preferably 0.005 to 0.2
It is preferable to set it to dl/. Furthermore, sulfonate-based anionic activators, carboxy-based or imidazoline-based amphoteric activators include dialkyl sulfosuccinates, alkylnaphthalene sulfonates, naphthalene sulfonate formalin condensates, 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.
-5 dl/, especially 0.05-5 dl/, more preferably 0.2-0.5 dl/, and the amount of the amphoteric active agent added is 0-5 dl/, especially 0.05-5 dl/, more preferably 0.5-1.0 dl/. It is preferable. 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 dl/or more of zinc ions and no chlorine ions or 50 dl/
An acidic zinc plating solution containing an aminocarboxylic acid or a salt thereof and a protein hydrolyzate containing glycine, hydroxyproline and proline as amino acids, and containing no acetate ion or boric acid, It is characterized by electroplating a plated object, and the plating film obtained by the method of the present invention has a uniform and smooth appearance, and the adhesion of the chromate film is also good. The plating solution used in the invention does not contain acetate ions or boric acid, so wastewater treatment is easy. It is suitable for use in place of acidic zinc plating solution. Hereinafter, the present invention will be explained in more detail by showing comparative examples, working examples, and comparative examples, but the present invention is not limited to the following examples. The compositions (% by weight) of the protein hydrolysates A and B used are shown below. Protein (collagen) hydrolyzate A Glycine 20.9% Alanine 8.8 Proline 13.8 Hydroxyproline 12.2 Aspartic acid 5.8 Glutamic acid 10.0 Arginine 7.9 Lysine 3.9 Others Remaining 100.0% Protein (casein) hydrolyzate B Lysine 7.0% Arginine 2.8 Aspartic acid 6.6 Glutamine Acid 18.1 Proline 9.0 Glycine 1.8 Alanine 2.8 Others Remaining 100.0% [Reference example] The following composition Z _o SO ₄・7H ₂ O 300g / Na ₂ SO ₄ 30 Boric acid 30 Protein hydrolyzate A or B 2 Acidic zinc with pH 3.5 A plating solution was prepared, and the appearance of the plating film was examined using a Hull cell tester. 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, and at a liquid temperature of 25° C., and the appearance of the resulting plating film was evaluated. The results are shown in Table 1.

[Table] Protein hydrolyzate A contains three types of amino acids: glycine, hydroxyproline, and proline, but protein hydrolyzate B does not contain hydroxyproline. Therefore, as can be seen from Table 1, the appearance of plating is good when protein hydrolyzate A is used, but is poor when protein hydrolyzate B is used. Example 1, Comparative Example The following composition Z _o SO ₄・7H ₂ O 300g/ Na ₂ SO ₄ 50 〃 Aminocarboxylic acid/salt Amount shown in Table 2 Protein hydrolyzate A Amount shown in Table 2 Acidic pH 3.5 A galvanizing solution was prepared and the appearance of the galvanized film was examined using a Hull cell tester. The appearance of the plating film was evaluated in the same manner as in the reference example. The results are shown in Table 2.

[Table] Example 2 Z _o SO ₄ 200g/ KCl 60 〃 Aspartic acid 10 〃 Protein hydrolyzate A 2 〃 PH 3.5 Plating temperature 25℃ D _k 2A Plating time 10 minutes 1 dm ² vent with the above composition and conditions When the cathode was plated, a galvanized film with a good appearance was obtained, with little pH fluctuation and uniform throughout from the high current density area to the low current density area. Example 3

【table】

[Table] When a bent cathode of 1 dm ² was plated under the above composition and conditions, a galvanized film with good appearance was obtained, with little pH fluctuation and uniform throughout from the high current density area to the low current density area. It was done.

Claims (1)

[Claims] 1. 8 dl/or more of zinc ions and 0 chlorine ions
~50dl/, and an aminocarboxylic acid or its salt,
Contains a protein hydrolyzate containing glycine, hydroxyproline and proline as amino acids,
An acidic zinc plating method characterized by electroplating a plated object using an acidic zinc plating solution that does not contain acetate ions or boric acid. 2 The acidic galvanizing solution contains 1 dl/or more of aminocarboxylic acid or its salt and 0.1 dl/ml of protein hydrolyzate.
An acidic zinc plating method according to claim 1, which comprises the above. 3. The acidic zinc plating method according to claim 1 or 2, wherein the content of glycine, hydroxyproline, and proline in the protein hydrolyzate is 20 to 80% by weight.