JPS6319600B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a plating bath for zinc-nickel alloy plating, and particularly to a plating bath for zinc-nickel alloy using an alkaline plating solution containing no cyanide. (Prior Art) It is known that zinc-nickel alloy plating is applied to the surface of steel products in order to ensure excellent corrosion resistance. In conventional zinc-nickel alloy plating techniques, plating is generally performed using an acidic electrolytic bath such as a sulfuric acid bath, a hydrochloric acid bath, or a sulfamic acid bath. For example, Japanese Patent Publication No. 58-39236 discloses a method of plating zinc-nickel alloy using an acid bath. When such an acidic bath is used, the current efficiency is high and the plating process can be performed at a high current density, so there is an advantage that the plating process can be performed quickly. The method of using an acid bath has the above-mentioned advantages and can effectively perform plating treatment on simply formed parts such as steel plates and wire rods, but it is not suitable for press parts, welded parts, etc. For parts with complex shapes such as parts and pipe parts, there is a problem that a good uniformity in the alloy ratio and film thickness of the zinc-nickel alloy film formed on the surface of the steel product cannot be obtained. Further, a technique for plating zinc-nickel alloy using a neutral bath is disclosed in Japanese Patent Application Laid-Open No. 185792/1983. The method of using a neutral bath can improve the properties of the formed alloy film compared to the case of an acid bath for plating parts with complex shapes, but it requires a large amount of zinc and nickel to dissolve. complexing agents have to be used, which requires special consideration for wastewater treatment and also poses problems in terms of bath stability. Further, in the case of a neutral bath, it is common to add a large amount of chloride to increase the conductivity of the bath. However, since chloride is extremely corrosive, corrosion of the plating equipment and the plating product itself becomes a problem. Further, JP-A-51-28533 discloses a method of plating zinc-nickel alloy using alkalinity. Since an alkaline bath uses a less corrosive electrolyte, it is more advantageous than acidic baths and neutral baths in terms of the cost of plating equipment. (Problem to be solved) Conventional alkaline baths such as those disclosed in JP-A-51-28533 are required to contain cyanide compounds, which are extremely toxic. , there is a problem that it becomes necessary to carry out special wastewater treatment and the working environment deteriorates. (Means for solving the problem) The present invention was constructed in view of the above circumstances, and
Excellent alloy ratio and film thickness of the alloy plating film formed on the surface of steel products using an alkaline plating solution that has excellent bath stability, low corrosivity, and does not contain toxic cyanide compounds. It is an object of the present invention to provide a plating bath that can ensure uniformity and perform zinc-nickel alloy plating with good gloss. According to research conducted by the present inventors, when performing zinc-nickel alloy plating using an alkaline bath, the plating solution contains at least one type of hydroxy aliphatic carboxylic acid or a salt thereof and at least one type of fat. It has been found that by adding a group amine, the desired objective can be achieved without containing a cyanide compound. The plating bath of the present invention contains at least one type of hydroxy aliphatic carboxylic acid or a salt thereof, and at least one type of aliphatic amine or a polymer thereof, and is an alkaline bath with a pH of 11 or higher. Features. In a preferred embodiment of the invention, the plating bath further contains at least one aromatic aldehyde. The electrolytic solution used in the present invention contains NaOH, KOH, Na ₂ CO ₃ , K ₂ CO ₃ , etc. as an electrolyte.
It contains an appropriate amount in the range of ~300g/. moreover,
The electrolyte of the present invention includes ZnO, ZnSO ₄ 7H ₂ O,
Compounds containing zinc components such as ZnCO ₃ and Zn(CH ₃ COO) ₂ and NiSO ₄ 6 ₂ ONiCO ₃ , (NH ₄ ) ₂ Ni(SO ₄ ) ₂
Contains nickel component compounds such as 6H ₂ O. In this case, these zinc component-containing compounds and nickel component-containing compounds have zinc concentrations in the electrolyte of 1 to 70 g/
It is preferable to adjust the amount added so that the nickel concentration is 0.6 to 118 g/. Further, the amount of the hydroxy aliphatic carboxylic acid or salt thereof in the plating solution is preferably in the range of about 1/4 to 10 times the molar concentration of the nickel component, that is, in the range of 0.01 to 2.0 mol/. It is determined. As the hydroxy aliphatic carboxylic acid or salt thereof to be added to this plating solution, any one such as tartaric acid, sodium tartrate, citric acid, sodium citrate, disodium citrate, glycolic acid, sodium glycolate, etc. can be used. can. In addition, the aliphatic amines added to the electrolyte include monoethanolamine, diethanolamine,
triethanolamine, ethylenediamine, diethylenetriamine, iminobispropylamine,
Triethylenetetramine, tetraethylenepentaminehexamethylenediamine, N,N'-bis-
(3-aminopropyl)ethylenediamine, etc. Examples of aliphatic amine polymers include "Polyethyleneimine G-35" provided by Vadeitsch Co., Ltd., "Epomin SP" and "Epomin P" manufactured by Nippon Shokubai Chemical Co., Ltd. -1000'', etc., or 3 to 4 represented by the structural formula below
Examples include grade amine polymers. _R1 to _R2 : H _{, CH3} , _{C2H5 , C3H7 R3} : (1) _CH2 - _CH2 - _CH2 (2) (3) CH ₂ CH ₂ ―O―CH ₂ CH ₂ (4) CH ₂ ―O―CH ₂ (5) (6) (7) (8) X ₁ , X ₂ : Inorganic anion n: 10 to 200 Further, the aromatic aldehyde as a brightening component added to the plating bath of the present invention includes vanillin, anisaldehyde, piperonal, veratraldehyde, salicylaldehyde, benzaldehyde. , P
- Contains tolualdehyde, etc., and it is desirable to add one or more of these aldehydes. In addition, the above aliphatic amine is contained in the plating solution at 0.03
It is desirable to contain it in an amount of mol/mole or more. According to the present invention, first, NaOH, KOH,
Electrolytes such as Na ₂ CO ₃ , K ₂ CO ₃ and ZnO,
A zincate solution is prepared by dissolving zinc component-containing compounds such as ZnSO ₄ .7H ₂ O, ZnCO ₃ and Zn(CH ₃ COO) ₂ . On the other hand, at least one hydroxy aliphatic carboxylate and NiSO ₄ 6H ₂ ONiCO ₃ ,
A nickel component compound such as ( _NH4 ) _2.Ni ( _SO4 ) _2.6H2O is dissolved to prepare _an aqueous solution, and this aqueous solution and the zincate solution are mixed to prepare a plating solution. In this case, the nickel concentration and the hydroxyaliphatic carboxylate concentration are determined depending on the required alloy ratio. (Effects of the invention) When zinc-nickel alloy plating is performed using the plating solution of the present invention, the uniformity of the alloy ratio in the zinc-nickel alloy plating film formed on the surface of steel products is extremely good. It is. Therefore, even when plating a complicated part, it is possible to form a plating film having a substantially uniform alloy ratio over the entire plating part. Further, the plating film formed using the plating bath according to the present invention has excellent uniform electrodeposition properties, and therefore has a substantially uniform film thickness over the entire plated area and has high gloss. A good plating film can be formed. Therefore, by using the plating bath of the present invention, it is possible to improve the quality of plated products, especially products with complex shapes such as pressed products, welded parts, pipe parts, etc. Furthermore, since the plating bath of the present invention does not contain toxic cyanide, problems such as deterioration of the working environment do not occur. Furthermore, since the plating bath of the present invention is an alkaline bath, it is less corrosive than acidic baths or neutral baths, and is advantageous in terms of costs for plating equipment and wastewater treatment equipment. (Example) Examples of the present invention will be described below. (Example 1) Bath composition ZnO = 15.6 g / NiSO ₄ 6H ₂ O = 12 g / NaOH = 120 g / Sodium tartrate = 10 g / Tertiary to quaternary amine polymer of structural formula (1) = 1 g /
Gloss component = 0.03 g / Zn / Ni = 83 / 17 PH > 14.0 Bath temperature = 30°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had good gloss, uniform film thickness, and alloy ratio. Table 1 shows the measurement results of the alloy ratio of current density and film thickness.

【table】

[Table] (Example 2) Bath composition ZnO = 6.5g / NiSO ₄ 6H ₂ O = 47 5g / NaOH = 100g / Sodium tartrate = 32g / Tetraethylenepentamine = 2g / Gloss component = 0.05g / Zn / Ni = 33/67 PH > 14.0 Bath temperature = 30°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had a uniform thickness and alloy ratio, and had good gloss at a current density of 0.2 to 5 A/dm ² . The measurement results of alloy ratio and film thickness for each current density are
Shown in the table.

[Table] (Example 3) Bath composition ZnSO ₄ 7H ₂ O = 56 g / NiSO ₄ 6H ₂ O = 12 g / NaOH = 40 g / Disodium citrate = 11 g / Polyethyleneimine G-35 = 0.3 g / Gloss component =0.03g/Zn/Ni=83/17 PH≈13.0 Bath temperature = 40°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had good gloss, uniform film thickness, and alloy ratio. Table 3 shows the measurement results of alloy ratio and film thickness for each current density.

[Table] (Example 4) Bath composition Zn=6.5g/ (NH ₄ ) ₂・Ni(SO ₄ ) ₂・6H ₂ O=47.5g/ KOH=90g/ Sodium glycolate=20g/ Tetraethylenepentamine= 5g / Gloss component = 0.05g / Zn / Ni = 50 / 50 PH > 14.0 Bath temperature = 30℃ Current application time = 10 minutes Change the current density under the above conditions to form a zinc-nickel alloy plating film on the Fe surface did. This plating film had a uniform thickness and alloy ratio, as well as good gloss. The measurement results of alloy ratio and film thickness for each current density are shown in the fourth column.
Shown in the table.

[Table] (Example 5) Bath composition ZnO = 6.5g / NiSO ₄ 6H ₂ O = 47.5g / NaOH = 20g / Sodium gluconate = 46g / Polyethyleneimine SP003 = 0.2g / Gloss component = 0.1g / Zn / Ni=83/17 PH≒12.5 Bath temperature=25°C Current application time=10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had good gloss, uniform film thickness, and alloy ratio. Table 5 shows the measurement results of alloy ratio and film thickness for each current density.

【table】

[Table] (Example 6) Bath composition ZnO = 6.5g / NiSO _{4.6H 2} O = 47.5g / NaOH = 150g / Sodium citrate = 10g / Sodium tartrate = 30g / Polyethyleneimine SP003 = 0.2g / Gloss component =0.1g/Zn/Ni=33/67 PH>14 Bath temperature = 30°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had a uniform thickness and alloy ratio. Table 6 shows the measurement results of alloy ratio and film thickness for each current density.

[Table] (Example 7) Bath composition ZnO = 18.8g / NiSO ₄ / 6H ₂ O = 22.4g / NaOH = 150g / Tartaric acid = 12.8g / Triethanolamine = 12.8g / 3 ~ of structural formula (1) Quaternary amine polymer = 1g/
Gloss component = 0.05 g / Zn / Ni = 33 / 67 PH > 14 Bath temperature = 30°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. This plating film had a uniform thickness and alloy ratio. Table 7 shows the measurement results of alloy ratio and film thickness for each current density.

[Table] (Comparative Example 1) Bath composition ZnCl ₂ = 100g / NiCl ₂ 6H ₂ O = 120g / NH ₄ Cl = 220g / Brightener (commercially available) = 50g / Zn/Ni = 61/39 PH = 5.8 Bath Temperature = 35°C Current application time = 10 minutes A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density under the above conditions. The alloy ratio of this plating film changes significantly when the current density is changed. Table 8 shows the measurement results of alloy ratio and film thickness for each current density.

[Table] (Comparative Example 2) Bath composition Zinc cyanide = 100g / Potassium nickel cyanide = 35g / NaOH = 40g / Zn/Ni = 37/63 PH>14 Bath temperature = 60℃ Current application time = 10 minutes Under the above conditions A zinc-nickel alloy plating film was formed on the Fe surface by varying the current density. The alloy ratio of this plating film changes significantly when the current density is changed. Also, the current density
When it becomes 0.5A/dm ² or less, the film thickness decreases rapidly. Table 9 shows the measurement results of alloy ratio and film thickness for each current density.

[Table] Figure 1 plots the changes in the nickel component in the coatings by varying the current density for the frosted coatings formed in Example 6, Comparative Example 1, and Comparative Example 2 of the present invention. Results are shown. According to this, in the case of the tamped coating using the bath of the comparative example, when the current density decreases, the amount of nickel component in the alloy coating increases rapidly. On the other hand, in the plating film of Example 6, the ratio of the nickel component hardly changes even if the current density decreases. Further, FIG. 2 shows the relationship between the film thickness and the current density for the example shown in FIG. 1. According to this, the thickness of the alloy coating formed using the plating bath according to the present invention decreases continuously as the current density decreases, whereas that of Comparative Example 1 has a high current density and a low thickness. The difference in film thickness at current density is large, and in Comparative Example 2, the film thickness decreases rapidly at low current density. Therefore, the plating bath of the present invention provides good gloss and film thickness even when plating is performed on complex-shaped plating parts where the current density varies depending on the location. Since the uniformity of the alloy ratio can be ensured, it can be effectively used for such plated parts.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the nickel component in the alloy coating and current density, and FIG. 2 is a graph showing the relationship between the thickness of the alloy coating and current density.

Claims (1)

[Scope of Claims] 1 Contains at least one type of hydroxy aliphatic carboxylic acid or a salt thereof and at least one type of aliphatic amine or a polymer thereof, and has a PH
A plating bath for zinc-nickel alloy, characterized by a plating bath of 11 or more. 2. The plating bath for zinc-nickel alloy according to claim 1, wherein the electrolytic solution further contains at least one type of aromatic aldehyde.