JPH0581680B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention is directed to Zn compounds, alkali hydroxides and Fe
The present invention relates to a zincate type zinc alloy plating bath containing metal salts of (,) or Ni () together with their chelating agents, and further mixed with a brightness additive. <Conventional technology> Zinc alloy plating such as Zn-Fe and Zn-Ni has superior corrosion resistance compared to zinc plating.
Various plating baths have been reported. In order to further improve corrosion resistance, this zinc alloy plating is often subjected to chromate treatment after plating, similar to zinc plating. In this case, the eutectoid ratio of different metals such as Fe and Ni needs to be within a range where the corrosion resistance of the plating film is good and a chromate film is well formed. These eutectoid rates are Zn−
In Fe alloy plating, the Fe eutectoid rate is 0.1 to 5.
It is known that in Zn-Ni alloy plating, the Ni eutectoid rate is 2 to 20%. In order to obtain these alloy platings, zincate type zinc alloy plating baths in which dissimilar metals are solubilized using a complexing agent are known from publications. for example,
Regarding Zn-Fe alloy plating, see "Practical surface technology,
Volume 29, No. 8 (1982), pp. 383-387 (Published by Metal Surface Technology Association), and JP-A-60-
181293, etc., and Zn-Ni alloy plating is described in "Metal Surface Technology Association, 70th Academic Conference Abstracts (1982)", pages 28-29, etc. <Problems to be Solved by the Invention> However, when the present inventors performed plating with the zincate type zinc alloy plating bath described in the above publication, they found that in a wide range of current densities, It was found that it was difficult to obtain a uniform glossy appearance and a uniform eutectoid ratio of dissimilar metals. <Means for solving the problems> In order to solve the above problems, the present inventors
As a result of intensive development efforts, we came up with a zincate type zinc alloy plating bath with the following configuration. In a zincate type zinc alloy plating bath containing a Zn compound, an alkali hydroxide, and a metal salt of Fe(,) or Ni() together with a complexing agent thereof, and further mixed with a brightness additive, the brightness additive is
The basic nitrogen atom of polyalkylene polyamine
It is characterized by being a C ₁ to C ₃ alkylated polyalkylene polyamine or a product containing this as a main component. <Detailed Description of Means> Each configuration of the present invention will be described in detail below. (1) Zn compounds, which are the basic composition of zincate baths,
For example ZnO and alkali hydroxides such as NaOH,
The content of KOH is usually 5 to 40 g/Zn concentration for the former, and 30 to 200 g/NaOH for the latter.
Let it be g/. (2) The concentration of metal salts of Fe (,) or Ni (), which are dissimilar metals, is usually the former as the concentration of each metal.
0.02-5g/, the latter 0.02-5g/.
As each metal salt, for example, the former Fe ₂
( _SO4 ) ₃・_7H2O , _FeSO4・_7H2O , Fe(OH) ₃ ,
FeCl ₃・6H ₂ O, FeCl ₂・4H ₂ O, etc., the latter
NiSO ₄ .6H ₂ O, NiCl ₂ .6H ₂ O, Ni(OH) ₂ , etc. are used. In order to stabilize (solubilize) these in the bath, a complexing agent (chelating agent) is used.
In the case of the latter, the following items listed on pages 2 and 3 of the publication are replaced with the following items listed on page 28 of the aforementioned "Metal Surface Technology Association, 70th Academic Lecture Abstracts". I can give an example. The amount of the complexing agent used is 1 to 100 mol per 1 mol of different metal ions. Oxycarboxylic acid salts such as citrate, tartrate, and gluconate; Amino alcohols such as monoethanolamine, diethanolamine, and triethanolamine; Ethylenediamine (EDA), diethylenetriamine,
One or two of polyamines such as triethylenetetramine; aminocarboxylic acid salts such as ethylenediaminetetraacetate and nidrotriacetate; polyhydric alcohols such as sorbitol and pentaerythritol; thioureas, etc.
Select and use more than one species. Among these, triethanolamine is particularly desirable. Sodium tartrate, sodium gluconate, NaCN triethanolamine, ethylenediamine, pentaethylenehexamine, quadrol,
1 from EDTA, 2Na, N-hydroxyethylethylenediamine (HEEDA), etc.
Select and use one species or two or more species. Particularly preferred among these are HEEDA and ethylenediamine. (3) The alkylated polyalkylene polyamine, which becomes the gloss additive or its main component, is obtained as follows, and the amount mixed in the plating bath is
The amount is 0.1 to 50 g/, preferably 1 to 10 g/. A polyalkylene polyamine with an average molecular weight of 600 to 5000 has C ₁ per equivalent of its basic nitrogen atom.
~ React with 0.1-2.1 mol of _C3 alkylating agent in an aqueous solution at 40-100 °C. Here, the above molecular weight is
If it is less than 600, it is difficult to suppress burnt at high current density, and if it exceeds 5000, it becomes difficult to dissolve in the plating bath. Further, as the polyalkylene polyamine, polyethyleneimine, polypropyleneimine, polybutyleneimine, etc. can be used, but polyethyleneimine is particularly desirable. As the alkylating agent, conventional alkylating agents such as CH ₃ Cl, CH ₃ Br, CH ₃ I,
C ₂ H ₅ Br, C ₂ H ₅ I, (CH ₃ ) ₂ SO ₄ , (C ₂ H ₅ ) ₂ SO ₄ ,
C ₃ H ₇ I, C ₃ H ₇ Cl, C ₃ H ₇ Br, etc. can be used. In the case of gloss additives based on alkylated polyalkylene polyamines, other ingredients include heterocyclic nitrogen compounds such as imidazole-epichlorohydrin reactants, dimethylamine-epichlorohydrin reactants, etc., which are commonly used as gloss additives. polyamines, polyvinyl alcohol (PVA), water-soluble polymers such as gelatin, anisaldehyde, heliotropin,
One type or a combination of two or more types of aromatic aldehydes such as vanillin and sulfur compounds such as thiourea are used. These other components are used by being mixed with the alkylated polyalkylene polyamine in an amount such that the total amount of the gloss additive is 0.01 to 30 g/g/. (4) The zinc alloy plating bath having the above structure can be used to plate objects by the rack method, barrel method, etc. in the same manner as normal zinc plating. <Actions and Effects of the Invention> The zincate type zinc alloy plating bath of the present invention contains an alkylated polyalkylene polyamine in which basic nitrogen atoms of a polyalkylene polyamine are partially alkylated from C ₁ to _{C 3} as a gloss additive. By using or having it as a main component, the following effects are achieved. Zn compounds, such as NnO, supply zinc ions,
Alkali hydroxide, such as NaOH, stabilizes zinc ions in the bath and improves conductivity, while metal salts use Fe.
(,) or Ni (), and the complexing agent stabilizes (solubilizes) these ions in the bath.
(Up to this point, it is the same as a conventional zincate-type alloy plating bath). The brightness additive is a dissimilar metal (Fe) precipitated in the plating film.
It has the effect of stabilizing the eutectoid rate of (or Ni) over a wide current density range and making the precipitated grains of the plating film finer. Therefore, it is possible to obtain a uniformly glossy plating film, and when it is chromate-treated, it not only has an excellent appearance but also has improved corrosion resistance compared to the conventional method. <Examples> In order to better understand the present invention, examples will be described below along with comparative examples. Note that the technical scope of the present invention is not limited to the embodiments, but extends to various embodiments without departing from the scope of the claims. In each example, the alkylated polyethyleneimine (abbreviated as "APEI") was
While cooling with water and stirring, 88 g of (CH ₃ ) ₂ SO ₄ was added over 30 minutes, and then the temperature was raised to 80°C while stirring and held for 2 hours, after which stirring was stopped and the mixture was allowed to cool. . In addition, Hull Cell (267c.c.) was used as a plating tank. This is because the Hull Cell allows plating results over a wide range of current densities to be obtained with a single plating. Then, the appearance of the matted film obtained by Hull Cell plating was visually observed, and the plated plate (Hull Cell plate: cathode) was cut into five equal parts (quarters) within a 10 cm range from the high current side, and each piece was The eutectoid rate of different metals in the plated film was measured by dissolving each piece in an acid and using atomic absorption spectrometry. The results are shown in Table 1. The plating films of each example had a uniform glossy or semi-glossy appearance, and the variation in the eutectoid rate was small (stable and stable) over a wide current density range. It is clear that there are The relationship between the position number on the Hull Cell cathode plate and the current density in Table 1 is as follows. In addition, the range indicating the position is indicated by the distance to the low current side, with the high current side being 0 cm. 0 to 2 cm...3.5 to 6 A/dm ² or more 2 to 4 cm...2 to 3.5 A/dm ² 4 to 6 cm...1 to 2 A/dm ² 6 to 8 cm...0.37 to 1 A/dm ² 8 to 10 cm...0 to 0.37 A /dm ² Example 1 (Zn-Fe plating): Current: 1A, plating time: 10 minutes, bath temperature: 25℃,
The test was conducted under the following conditions: anode: mild steel plate, cathode: copper plate. Here, the mild steel plate is hardly dissolved even as an anode in a strong alkaline plating bath such as a zincate bath, and acts as an insoluble anode. Further, the reason why a copper plate was used as the cathode was because if the material was iron, the iron component of the plated plate would be mixed in during the analysis of the eutectoid rate, which would greatly deviate the analytical value.

[Table] Example 2 Plating was carried out under the same conditions as in Example 1 except that only APEI was used as the gloss additive. Example 3 In Example 1, 3 g of dimethylamine-epichlorohydrin (molar ratio 1:1) reactant was added/
Plating was carried out under the same conditions except for the addition of . Comparative Example 1 Plating was carried out under the same conditions as in Example 1 except that APEI in the gloss additive was changed to 1.5 g/non-alkylated polyethyleneimine (molecular weight 1200). Comparative Example 2 Plating was carried out under the same conditions as in Example 1 except that 6 ml of a commercially available zincate brightener for galvanizing was used as the brightness additive. Comparative Example 3 In Example 1, ethylenediamine-epichlorohydrin (molar ratio 1:1) was used as the gloss additive.
Plating was carried out under the same conditions except that 5 ml of the reactant was used. Example 4 (Zn-Ni plating) Using a plating bath with the following composition, current: 1A, plating time: 10 minutes, bath temperature: 25℃, anode: zinc plate, cathode: bright steel plate. I performed a ceremonial ceremony.

[Table] Example 5 Plating was carried out under the same conditions as in Example 3 using a plating bath having the following composition. ZnO 10g / NaOH 120g / NiSO ₄ 6H ₂ O 3.6g / HEEDA 5.7g / APEI 3g / Example 6 In Example 3, vanillin 0.1g /
Plating was carried out under the same conditions except for the addition of . Comparative Example 4 Plating was carried out under the same conditions as in Example 3, except that APEI in the gloss additive was changed to 1.5 g/non-alkylated polyethyleneimine (molecular weight 1200). Comparative Example 5 Plating was carried out under the same conditions as in Example 3, except that 6 ml of a commercially available zincate brightener for galvanizing was used as the brightness additive.

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Claims (1)

[Claims] 1 Fe eutectoid rate is 0.1 to 5%, or Ni eutectoid rate is 2 to 5%.
An alloy plating bath for producing a 20% zinc alloy plating film, which contains a Zn compound, an alkali hydroxide, and a metal salt of Fe (,) or Ni () together with a complexing agent thereof, and further improves gloss. In the zincate-type Zn alloy plating bath in which an additive is mixed, the brightness additive is a polyalkylated polyalkylene polyamine in which the basic nitrogen atoms of the polyalkylene polyamine are partially alkylated from C ₁ to C ₃ or this. A zincate type zinc alloy plating bath characterized by having as a main component.