JP2577689B2 - Zincate type zinc alloy plating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zincate zinc alloy plating bath containing a nickel (II) salt in the presence of a complexing agent and adding a brightener. In particular, it is suitable for iron structures that also require impact resistance when secondary processing (usually plastic processing) is performed after plating, for example, cover parts (drawing processing) and pipe parts (bending processing) around the engine. About the plating bath.

[0002]

2. Description of the Related Art It is well known that the corrosion resistance of a zinc plating film is improved by codepositing nickel (Ni) into the zinc plating film. Therefore, various zinc-nickel alloy plating baths capable of eutecting nickel have been proposed.

As a typical plating bath capable of eutectoid zinc-nickel alloy, there is a zincate-type zinc alloy plating bath containing a nickel salt by using a complexing agent. For example, it is disclosed in the abstracts of the 70th Annual Meeting of the Academic Lecture Meeting (Metal Surface Technology Association), pp. 28-29, 1984.

[0004] In zinc-based plating, chromate treatment is often performed after plating for the purpose of improving corrosion resistance and the like. However, if the eutectoid content of nickel is too high, a good chromate film cannot be obtained. Conversely, if the eutectoid rate is too low, the function of improving corrosion resistance is not exhibited. Therefore, the width of the eutectoid rate of nickel needs to be limited to 2 to 20%.

[0005] Further, in terms of appearance, it is desirable that the plated surface has a gloss. This is because the quality of the plated surface after the post-treatment such as the chromate treatment is greatly affected by the glossiness of the plated surface before the treatment.

In the plating step, it is technically difficult to make the current density uniform over the entire surface of the object to be plated. For example, in an object to be plated having irregularities, the convex portions have a higher current density than the concave portions, but it is difficult to approximate the current densities of these portions. Therefore, important conditions required for a practical zinc alloy plating bath are that, in addition to obtaining a good bright plating film with a wide current density, an almost constant alloy ratio can be secured over a wide current density range. .

As a result of examining whether or not the above-mentioned conventional zinc-nickel alloy plating baths can withstand practical use, in these alloy plating baths, the current density range in which a bright plating film can be obtained is only narrow. It was also found that the eutectoid ratio of nickel to zinc fluctuated greatly depending on the current density.

Therefore, a zincate type zinc alloy plating bath capable of obtaining a bright plating film in a wide current density range and having a small variation in the eutectoid rate of nickel due to high and low current densities has been disclosed by the same applicant as the present applicant. (JP-A-62-23887, JP-A-2-23887).
No. 141596).

The zinc-nickel alloy plating bath comprises a zinc compound, an alkali hydroxide and a nickel (II) salt, a complexing agent for solubilizing the nickel (II) salt, and an alkylated highly polymerized polyalkylene polyamine. And a heterocyclic nitrogen-based compound.

[0010]

With the recent expansion of the application of zinc-nickel alloy plating to products requiring impact resistance during plastic working such as cover parts and pipe parts around the above-mentioned engines, plating There has been an increasing demand for higher impact resistance of the coating.

However, it has been found that it is difficult for the plating film formed by the zinc-nickel alloy plating bath having the above structure to satisfy the above requirements.

Further, since the main brightener is composed of two components, the consumption speed of each component is different, the component balance of the brightener is easily lost, and the replenishment of the brightener is troublesome.

In view of the above, it is an object of the present invention to provide a zincate zinc alloy plating bath which can provide a zinc-nickel alloy plating film having excellent impact resistance and in which the component balance of a brightener is not easily lost. I do.

[0014]

Means for Solving the Problems The present inventors have made intensive development efforts to solve the above-mentioned problems, and as a result, have arrived at a zincate zinc alloy plating bath having the following structure.

A zincate zinc alloy plating bath containing a zinc compound, an alkali hydroxide, a nickel (II) salt, a complexing agent for solubilizing the nickel (II) salt, and a main brightener. Wherein the complexing agent is a reaction product of an amine compound and monoglycidyl ether and / or polyglycidyl ether, and the primary brightening agent is a multifunctional compound obtained by adding a heterocyclic nitrogen compound to an alkylated highly polymerized polyalkylene polyamine. It is a synthetic brightener.

[0016]

[Detailed description of means]

A. The plating bath of the present invention comprises a zinc compound, a zinc compound,
An alkali hydroxide and a nickel (II) salt;
I) It is a prerequisite to contain an amine complexing agent for solubilizing a salt and a two-component main brightener of an alkylated highly polymerized polyalkylene polyamine and a heterocyclic nitrogen compound.

As a zincate type bath, usually,
Use the one with the following conditions.

Zincate bath conditions Zinc ion 4 to 30 g / L Nickel ion 0.5 to 6 g / L Alkali hydroxide (NaOH) 30 to 200 g / L Complexing agent 1 to 50 mol per mol of nickel Temperature 10 to 60 ° C Nickel Eutectoid rate 3 to 10% (preferably 4 to 8%) Cathode current efficiency 35 to 95% under strong alkaline condition of pH 13 or more In the above zincate bath, the zinc compound is usually Z.
nO can be used, and N 2
aOH, KOH and the like can be used.

The nickel (II) salt may be NiSO
_{4 · 6H 2 O, NiCl 2} · 6H 2 O ,, Ni (OH) 2
Etc. can be used.

B. A first feature of the present invention is that in the above basic bath, the complexing agent (chelating agent) for solubilizing the nickel salt is a reaction product of an amine compound and monoglycidyl ether and / or polyglycidyl ether. This is the first feature.

(1) Examples of the amine compound include polyamines such as ethylenediamine, diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine (PEHA), 1,3-diaminopropane, and hydroxyethylethylenediamine. Examples thereof include amino alcohols such as monoethanolamine, ditanolamine, and triethanolamine. In particular, polyamines such as DETA and PEHA are preferable because an optimum nickel eutectoid rate can be stably obtained at a relatively low nickel concentration.

(2) The monoglycidyl ether and polyglycidyl ether include methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, glycidol, bis- (2,3-
Epoxy propyl) ether and the like can be used.

(3) The compounding amount of the amine compound derivative as a complexing agent is 1 to 50 mol, preferably 8 to 24 mol, per 1 mol of nickel ions. In the case of a reaction product of PEHA and methyl glycidyl ether, 45 to 130 g is preferable for 1 g of nickel ion.

If the amount of the complexing agent is too small, Ni ions are destabilized in the bath, and the suppression of nickel is insufficient, so that the nickel eutectoid rate tends to increase. If the complexing agent becomes excessive,
Organic matter adsorption to the film increases, and black chromate hardly reacts to the high current density portion.

C. A second feature of the present invention resides in using a single synthetic compound obtained by adding a heterocyclic nitrogen compound to an alkylated highly polymerized polyalkylene polyamine as a main brightener.

(1) The above-mentioned alkylated highly polymerized polyalkylene polyamine is obtained by partially alkylating a basic nitrogen atom of a highly polymerized polyalkylene polyamine with an alkylating agent having a C1 to C3 alkyl group.

Here, a highly polymerized polyalkylene polyamine
As the average degree of polymerization of 10 to 260 (average molecular weight of 500 to
11200), such as polyethyleneimine, poly
Use propylene imine, polybutylene imine, etc.
And the alkylating agent is a compound of C1 to C3.
Object, eg CH_Three Cl, CH_Three Br, CH_Three I, C_Two H
_Five Br, C_Two H_Five I, (CH_Three )_Two SO_Four , (C_Two H
_Five )_Two SO_Four , C_Three H₇ I, C_Three H₇ Cl, C_Three H₇ B
r or the like can be used.

(2) Examples of the above heterocyclic nitrogen compound include an imidazole compound, a pyrazole compound and a pyrrole compound.

As the imidazole compound, in addition to imidazole, 1-methylimidazole, 1-ethylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1-vinyl Examples thereof include imidazole, 2-methyl-1-vinylimidazole, 1- (2′-hydroxyethyl) imidazole, and 1- (2′-hydroxyethyl) 2-methylimidazole.

(3) The reaction for adding a heterocyclic nitrogen compound to the alkylated highly polymerized polyalkylene polyamine is usually carried out using epihalohydrin.

As the epihalohydrin, epichlorohydrin, epibromohydrin and the like can be used.

The amount of the multifunctional brightener which is a single compound is 0.5 to 50 g / L (preferably 1 to 15 g / L).
L). And, by unifying the main brightener component by synthesis, the replenishment response to the depletion of the brightener is simplified, and the component of the main brightener in the bath is compared with the system in which two components were conventionally added. It is difficult to lose balance.

If the amount of the multifunctional brightener is too small, it is difficult to perform both functions of the following components.

The alkylated highly polymerized polyalkylene polyamine has a function of expanding the allowable current density range to a lower current density side and stabilizing the eutectoid ratio of nickel to zinc.

The heterocyclic nitrogen compound prevents abnormal deposition of kogation and the like on the high current density side, expands the current density range in which a good plating film can be obtained to the high current density side, and stabilizes the eutectoid rate of nickel. It has the function of

Conversely, if the amount of the multifunctional brightener is excessive, the adsorption of organic substances to the film increases, and the black chromate does not react to the high current density portion. Nickel eutectoid rate becomes too high.

D. Further, in the plating bath of the present invention, in order to further improve the glossiness, a gloss auxiliary may be used as necessary in addition to the above two types of brighteners. As the gloss auxiliary, polyvinyl alcohol (PVA),
Water-soluble polymers such as gelatin, sulfur compounds such as thiourea,
Those selected from the group consisting of aromatic aldehydes such as anisaldehyde, heliotripin, vanillin and the like and mixtures thereof can be used. And the additive of this gloss auxiliary is 0.01 to 30 g / L (preferably 0.1 to 30 g / L).
05 to 10 g / L).

[0038]

EXAMPLES Next, examples performed to confirm the effects of the present invention will be described together with comparative examples.

A. Example (1) Synthesis of Complexing Agent 200 g of PEHA sufficiently stirred and homogenized in 830 g of pure water was reacted with 76 g of methyl glycidyl ether (“Epiol M”: manufactured by NOF CORPORATION) at 50 ° C. or lower to obtain 90 The solution was refluxed at 2 ° C. for 2 hours for synthesis.

(2) Synthesis of multifunctional brightener 500 g of polyethyleneimine having an average molecular weight of 10,000
("Epomin SP200" manufactured by Nippon Shokubai Chemical Industry Co., Ltd.) was dissolved in 920 g of pure water, and 420 g of dimethyl sulfuric acid was added at 50 ° C or less, and the mixture was heated at 80 ° C for 2 hours under reflux to obtain a high alkylation level. A polymerized polyalkylene polyamine was synthesized.

After 5970 g of pure water and 454 g of imidazole were added to the synthesized product and sufficiently stirred and homogenized, 924 g of epichlorohydrin was added at 50 ° C. or less, and imidazole was indirectly added to polyalkylenepolyamine to cause an addition reaction. A multifunctional brightener was synthesized.

(3) Preparation of zinc-nickel alloy plating bath Using the complexing agent and the synthetic brightener synthesized as described above, a zinc plating bath having the following composition was prepared.

Zincate bath composition Zinc ion 10 g / L Nickel ion 1 g / L NaOH 120 g / L Synthetic complexing agent 65.4 g / L Synthetic main brightener 2.74 g / L Auxiliary brightener Vanillin 0.05 g / L Thiourea 0 B. 0.5 g / L PVA 0.2 g / L Comparative Example (1) Synthesis of Main Brightener 1 420 g of dimethyl sulfuric acid was reacted at 50 ° C. or lower with 40 g of polyethyleneimine having an average molecular weight of 1200 (“Epomin SP012” manufactured by Nippon Shokubai Chemical Co., Ltd.) dissolved in 100 g of water. The mixture was heated and refluxed at 80 ° C. for 2 hours to synthesize an alkylated highly polymerized polyalkylene polyamine.

(2) Synthesis of main brightener 2 11 g of triethylamine and 20 g of imidazole were added to water 10
To the solution dissolved in 0 g, 41 g of epichlorohydrin is added over 30 minutes at 50 ° C. or lower while stirring. Furthermore, it heats to 95 degreeC with stirring, and after holding for 2 hours,
After cooling, the main brightener 2 is obtained.

(3) A zincate plating bath having the following composition was prepared using the complexing agent and the main brighteners 1 and 2 synthesized as described above.

The zincate plating bath of the comparative example used had the following composition.

Zinc ion 10 g / L Nickel ion 1 g / L NaOH 120 g / L Diethylenetriamine (complexing agent) 5.6 g / L Main brightener 14 ml / L Main brightener 2 3 ml / L Auxiliary brightener Vanillin 0.05 g / L L thiourea 0.5 g / L PVA 0.2 g / L C.I. Zinc nickel alloy plating Using each of the zincate plating baths of the examples and the comparative examples prepared above, bath temperature: 25 ° C., current density: 2 A / dm.
^2. Energizing time: Polished steel plate under the condition of 35 minutes (JISG 3141
Each test piece was prepared by performing plating on the described SPCC-B: 70 × 150 × 0.6 mmt).

D. Test Method and Results For the plating film obtained as a result, 200 g of steel balls were dropped from a height of 50 cm in order to check the adhesion of the plating film, and the presence or absence of peeling of the plating film was visually observed. In the example, the film did not peel off, whereas in the comparative example, the film peeled.

The appearance was uniform throughout the surface of both the examples and the comparative examples.

[0050]

In the zincate zinc alloy plating bath of the present invention, the complexing agent is a reaction product of an amine compound and an amine compound with monoglycidyl ether and / or polyglycidyl ether, and the main brightener is By using a multifunctional synthetic brightener in which a heterocyclic nitrogen compound is added to an alkylated highly polymerized polyalkylene polyamine, the adhesion of the plating film is lower than that of a conventional zincate bath having the same structure as in the above-described embodiment. And greatly improve. In addition, the conventional two types of main brighteners, alkylated polyalkylene polyamines and heterocyclic nitrogen compounds, have the function of extending the allowable current density range to the lower current density side and stabilizing the eutectoid ratio of nickel to zinc. And a function to prevent abnormal deposition of kogation and the like on the high current density side, expand the current density range where a good plating film can be obtained to the high current density side, and stabilize the eutectoid rate of nickel. However, since these compounds are synthesized to have multiple functions by a single compound, the difference between the consumption rates of the two components can be eliminated, and the plating process can be easily managed.

Claims (1)

(57) [Claims] 1. A zincate plating bath containing a zinc compound, an alkali hydroxide, a nickel (II) salt, a complexing agent for solubilizing the nickel (II) salt, and a main brightener. The complexing agent is a reaction product of an amine compound and a monoglycidyl ether and / or a polyglycidyl ether; and the main brightener is an alkylated highly polymerized polyalkylene polyamine to which a heterocyclic nitrogen compound is added. A zincate zinc alloy plating bath, which is a functional brightener.