JPH0319312B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method of plating using an acidic galvanizing solution that is chlorine-free or contains a low concentration of chlorine, typically a zinc sulfate plating solution. Conventional technology and its problems Conventionally, peptone, dextrin, etc. have been used as brightener components in zinc sulfate plating solutions. The gloss and leveling properties of the coating are very inferior to those of the matte coatings obtained using other zinc sulfate plating solutions, especially zinc chloride plating solutions, and for this reason, its use is limited to gloss and leveling. In addition to insufficient strength, it also had poor throwing power, so it could only be used for galvanizing steel sheets, and was unsuitable for general decorative plating. For this reason, a galvanizing solution with good gloss, leveling properties, and throwing power has been strongly desired. SUMMARY OF THE INVENTION In view of the above circumstances, the present inventors have discovered that a zinc plating film that does not contain chlorine ions or has a low concentration can produce a galvanized film that does not cause poor plating and has particularly good gloss, leveling properties, and throwing power. As a result of extensive research into plating methods, we found that a protein hydrolyzate containing specific amino acid components, such as glycine, hydroxyproline, and proline, such as collagen, was added to an acidic zinc plating solution containing chlorine at a concentration of 0 to 50 g. When plating is performed using a plating solution containing a hydrolyzate of , a polyether nonionic activator, and a compound having a C=O group, the coverage is particularly good and the plating film is uniform. It was discovered that a good plating film with excellent gloss can be obtained, and this led to the present invention. That is, as mentioned above, it is known that peptone is used as a brightener component in the zinc sulfate plating method. A protein hydrolyzate containing preferably 20 to 80% by weight of glycine, hydroxyproline, and proline is added to a zinc sulfate plating solution, and a polyether nonionic activator and C= Surprisingly, when adding a compound containing an O group, excellent gloss, leveling, and
This is what we found out that it is possible to obtain more power. The present invention will be explained in more detail below. Structure of the Invention The acidic galvanizing method according to the present invention uses zinc ions, chloride ions at a concentration of 0 to 50 g/g, a protein decomposition product containing glycine, hydroxyproline, and proline as amino acids, and a polyether nonionic activator. and a compound having a C═O group. Here, zinc sulfate is preferably used as a source of zinc ions constituting the plating solution used in the present invention, but is not limited thereto.
The content of zinc ions is 8 g or more per plating solution, preferably 8 to 140 g, more preferably 20 to 140 g.
60g is preferred. In addition, in the present invention, chloride ions are not necessarily required, but 50g/or less, preferably 35g/
Chloride ions can be added at a concentration of up to 100 g/g/g/g. When zinc chloride is used, chloride ions can be supplied directly, but when they are insufficient or when zinc chloride is not used, they can be supplied using potassium chloride, sodium chloride, or the like. A protein hydrolyzate is further added to the plating solution of the present invention, and as a result, as described above, plating with good coverage, uniformity, and good gloss is achieved. In this case, among conventionally known protein hydrolysates, those with large molecular weights are called peptones, and those with small molecular weights are called polypeptides, and are distinguished from each other. Here, peptone is used as a brightening agent in zinc sulfate plating baths, and it is also known that it has a slight leveling effect, but this effect is insufficient and does not provide excellent gloss or shine.
A uniform plating film with leveling and throwing power cannot be obtained using this peptone. The protein hydrolyzate of the present invention contains various amino acids, including glycine, alanine, serine, threonine, proline,
Examples include hydroxyproline, valine, isoleucine, leucine, phenylalanine, tyrosine, methionine, aspartic acid, glutamic acid, arginine, histidine, lysine, hydroxylysine, and tryptophan. Among these amino acids, the protein hydrolyzate of the present invention must necessarily contain glycine, hydroxyproline, and proline. For example, if a protein hydrolyzate that does not contain hydroxyproline is used, The effect on the adhesion film is significantly inferior, and the effect is only as good as 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%. Specifically, a hydrolyzate such as collagen can be used as a protein hydrolyzate. Further, the protein hydrolyzate of the present invention preferably has a molecular weight of 250 to 50,000, particularly 800 to 10,000. Furthermore, the content of protein hydrolyzate is determined by plating solution 1.
The amount is 0.1 g or more, preferably 0.1 to 10 g. If the content is less than 0.1g, the gloss and leveling effect of the mating film may not be sufficiently effective. The plating solution used in the present invention contains a polyether nonionic activator and carbon dioxide along with the protein hydrolyzate.
A compound having a =O group (aldehyde, ketone) is added. In this case, it is also more effective to add at least one of aromatic carboxylic acid, sulfonic acid-based anionic activators, and carboxy-based and imidazoline-based amphoteric activators in addition to these additives. The gloss can be further improved. Here, as the polyether 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~
(80wt%) (5) Polyoxyethylene polyhydric alcohol aliphatic ester (EO addition amount 5-50mol), etc., and the amount added is 0.05-10g/,
In particular, it is 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 0.01 to 10 g/,
Especially 0.005-3g/, more preferably 0.005-0.2
It is preferable to set it as g/. Furthermore, the aromatic carboxylates include benzoate, salicylate, m,p-chlorobenzoate, 2,4-dichlorobenzoate, cinnamate, etc., and the amount added is 0 to 10g/, especially 0.05
The amount is preferably 10 g/, more preferably 0.5 to 2 g/. Furthermore, examples of 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.
~5g/, especially 0.05-5g/, more preferably 0.2-0.5g/, and the amount of the amphoteric active agent added is 0-5g/, particularly 0.05-5g/, more preferably 0.5-1.0g/. It is preferable. In the present invention, additives such as PH buffering agents such as sodium sulfate and boric acid, other brightening agents, and leveling agents may be added as other components. 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 acidic galvanizing method of the present invention includes adding a polyether nonionic activator and a protein hydrolyzate containing glycine, hydroxyproline, and proline as amino acids to a chlorine-free or low-concentration acidic galvanizing solution. Plating is carried out using a plating solution to which a compound having a C=O group (aldehyde, ketone) has been added, and the plating film obtained by the method of the present invention has particularly good throwing power, and is uniform and smooth. It has a glossy appearance and the adhesion of the chromate film is good. Therefore, it can also be used for decorative plating, which has been difficult in the past. Hereinafter, the present invention will be explained in more detail by referring to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited to the following Examples. The compositions (% by weight) of protein hydrolysates A and B used in the following examples 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 the plating film A degreased and pickled 10 cm x 7 cm polished steel plate was used as the 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 the table.

[Table] Protein hydrolyzate A contains three types of amino acids: glycine, hydroxyproline, and proline, but protein hydrolyzate B does not contain hydroxyproline. Therefore, as seen from the table,
The appearance of plating is good when protein hydrolyzate A is used, but is poor when protein hydrolyzate B is used. Example 1

Using a plating solution with the composition shown in [Table], a Hull cell test was conducted at a solution temperature of 25°C in the same manner as in the reference example. Tests were conducted under the conditions of a current of 0.5 A for 10 minutes and a current of 2 A for 10 minutes, and the appearance of the resulting frosted coating was evaluated.
In the Hull cell test at 0.5A for 10 minutes, the gloss remained even at low current densities, and in the test at 2A for 10 minutes, the entire surface was uniformly glossy. Example 2

【table】

A Hull cell test was conducted in the same manner as in Example 1 using a plating solution having the composition shown in [Table]. In the 0.5A-1 minute test, the gloss remained even at low current densities, and at 2A-10
In the minute test, the entire surface was uniformly glossy. [Comparative Example] A Hull cell test was carried out in the same manner as in Example 1 using a plating solution having the following composition: Z _o SO ₄ .7H ₂ O 300 g/Na ₂ SO ₄ 30 boric acid 30 g/peptone 2 PH 3.5. In the 0.5A - 10 minute test, the luster did not persist even at low current densities, and at 2A -
The entire surface was matte during the 10 minute test.

Claims (1)

[Claims] 1. A protein hydrolyzate containing zinc ions, chloride ions at a concentration of 0 to 50 g/amino acids, glycine, hydroxyproline, and proline;
An acidic zinc plating method comprising electroplating an object to be plated using an acidic zinc plating solution containing a polyether nonionic activator and a compound having a C═O group. 2. The acidic zinc plating method according to claim 1, wherein the zinc salt supplying zinc ions is zinc sulfate. 3. The acidic galvanizing solution contains 8 g/or more of zinc ions, 0.1 to 10 g/of protein hydrolyzate, 0.05 to 10 g/of polyether nonionic activator, and C=
The acidic zinc plating method according to claim 1 or 2, which contains 0.01 to 10 g of a compound having an O group. 4. The acidic zinc plating method according to any one of claims 1 to 3, wherein the content of glycine, hydroxyproline, and proline in the protein hydrolyzate is 20 to 80% by weight. 5. Claims 1 to 4 in which at least one of aromatic carboxylic acid, sulfonic acid anionic activator, and carboxylic and imidazoline amphoteric activator are added to the acidic galvanizing solution. acid galvanizing method.