JPS639592B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of plating using an acidic zinc plating solution that does not contain ammonium ions, acetate ions, or boric acid. Conventionally, acidic zinc plating solutions using zinc chloride or zinc sulfate as the zinc source have been widely used, but these types of acidic zinc plating solutions usually contain PH buffers such as ammonium chloride, sodium acetate, or boric acid. include. However, with conventional plating solutions of this type, when the pH is raised during wastewater treatment, ammonium ions and acetate ions in the plating solution form complex salts with zinc, etc., and these ions also raise COD. , unfavorable in terms of wastewater treatment. In addition, boric acid similarly has problems in wastewater treatment. However, acidic zinc plating solutions that do not contain ammonium ions, acetate ions, and boric acid at the same time do not have a pH buffering effect and may cause the matte coating to become rough.
It causes plating defects such as burning in high current density areas. For this reason, conventionally, acidic zinc plating solutions contain at least one of ammonium ions, acetate ions, and boric acid. In view of the above circumstances, the present inventors have discovered that it is possible to obtain a good acidic zinc plating film that has a good PH buffering effect without containing any of ammonium ions, acetate ions, and boric acid, and does not cause poor plating. As a result of intensive study on the acid zinc electroplating method, we found that zinc ions of 10 g/or more and chlorine ions of 50 g/
When plating is carried out using a tamping solution containing aminocarboxylic acid or its salt at least 10 g/g/g/g/ or more, ammonium ions, acetate ions, and boric acid are surprisingly not present at all. We discovered that it has a good PH buffering effect even if it is not used, and that the plating film is more uniform than when using boric acid, and that even high current density areas are less likely to burn, and that a good plating film can be obtained. This led to the invention. That is, aminocarboxylic acids and their salts have been known as additives for acidic galvanizing solutions, but the amounts added are small, and as mentioned above, ammonium ions, acetate ions,
It was used in combination with boric acid. On the other hand, aminocarboxylic acids or their salts are not used together with ammonium ions, acetate ions, or boric acid, and 10
It is a new finding of the present inventors that it is possible to obtain a plated film having a good PH buffering effect and a good plating film by using it at a relatively high concentration of 1 g/g/g or more. The present invention will be explained in more detail below. The acidic zinc plating method according to the present invention includes 10 g/or more of zinc ions, 50 g/or more of chlorine ions,
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 ammonium ions, acetate ions, or boric acid. Here, examples of the supply source of zinc ions constituting the plating solution used in the present invention include zinc chloride, zinc sulfate, and the like. 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 10 g or more per plating solution, but preferably 10 g or more per plating solution.
~80g, more preferably 20-50g. Further, when zinc chloride is used, chloride ions are supplied from this, but when they are insufficient or when zinc chloride is not used, they can be supplied using potassium chloride, sodium chloride, etc. The content is 50g or more per plating solution, preferably 50 to 300g, more preferably
It is 100-200g. The plating solution of the present invention further contains an aminocarboxylic acid or a salt thereof, and as a result, as described above, good plating can be achieved even without containing ammonium ions, acetate ions, or boric acid. 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, the above-mentioned purpose of the present invention can be achieved reliably, but if it is less than 10 g//, the PH buffering effect will decrease and the resulting plated film will be rough. The object of the present invention cannot be achieved because the high current density portions are likely to be burnt or burnt. 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═O group (aldehyde, ketone),
It is preferable to add all of them, and thereby the properties of the plated film from the plating solution of the present invention that does not contain ammonium ions, acetate ions, and boric acid can be further reliably improved. All parts from the current density part 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 anionic 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/
, particularly preferably from 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)

[Formula] (R is H or an alkyl group having 1 to 20 carbon atoms, n=
5-60) (3)

[Formula] (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 Next, the aromatic carboxylates include benzoate, salicylate, m,p-chlorobenzoate,
Examples include 2,4-dichlorobenzoate, cinnamate, etc., and the amount added is 0 to 10 g/, especially 0.05 to 10
g/, more preferably 0.5 to 2 g/. Furthermore, compounds having a C=O 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 desirable to set it to g/. In addition, as sulfonate-based anionic activators, carboxy-based or imidazoline-based amphoteric activators,
Dialkyl sulfosuccinate, alkylnaphthalene sulfonate, naphthalene sulfonic acid formalin condensate, N,N-dimethyl-N-alkyl-N
-carboxyalkylene ammonium betaine,
2-alkyl-1-hydroxyethyl-1-carboxymethylimidazolinium salts and the like,
The amount of sulfonate anion activator added is 0 to 5.
g/, especially 0.05 to 5 g/, more preferably
The amount of the amphoteric active agent added is preferably 0-5 g/, particularly 0.05-5 g/, more preferably 0.5-1.0 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 or air may be used. 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. The plating film obtained by the present invention 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 ammonium ions, acetate ions, or boric acid. Therefore, wastewater treatment can be easily carried out, and it is suitably adopted in place of the conventional acidic zinc plating method containing ammonium ions, acetate ions, and boric acid. EXAMPLES Hereinafter, the present invention will be explained in more detail by showing Examples and Comparative Examples. Example 1, Comparative Example An acidic zinc plating solution with the following composition of 70 g of ZnCl ₂ / 220 g of KCl / 2 g of peptone / aminocarboxylic acid/salt with a pH of 5.0 was prepared as shown in Table 1, and its PH buffer was tested using a Hull cell tester. The effectiveness and appearance of the plating film were investigated. For comparison, a solution using 30g of sodium acetate instead of aminocarboxylic acid/salt, a solution using 30g of boric acid, and a solution with the following composition: 70g of ZnCl ₂ / 200g of NH ₄ Cl / 2g of peptone / PH 5.0 were used. Similar experiments were conducted using each. 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 Table 1.

【table】

[Table] Example 2 ZnCl ₂ 100g/ KCl 220g/ Alanine 15g/ Polyethyleneimine (molecular weight 5000) 2g/ C ₁₂ H ₂₅ -O-(CH ₂ CH ₂ O) ₁₅ H 6g/ Sodium benzoate 2g/, benzylidene acetone 0.38g / PH 5.2g / Plating temperature 25℃ Dk 2A Plating time 10 minutes When a ^1dm2 bent cathode was plated with the above composition and conditions, a galvanized film with little pH fluctuation and good appearance was obtained. Obtained.

Claims (1)

[Claims] 1 More than 10g of zinc ions and 50g of chlorine ions
g/ or more and aminocarboxylic acid or its salt 10
An acidic zinc plating method comprising electroplating an object to be plated using an acidic zinc plating solution which contains at least 100 g/g/g/g/g/g/g/g/g/ or more and does not contain ammonium ions, acetate ions, or boric acid.