JPS62287092A - Zinc-nickel alloy plating bath - Google Patents

Abstract

PURPOSE:To obtain a Zn-Ni alloy plating bath having superior stability, low corrosiveness and no toxicity and giving a film having a uniform alloying ratio, a uniform thickness and fine luster by adding an aliphatic amine or a polymer thereof to a Zn-Ni alloy plating bath and adjusting the bath to a proper pH. CONSTITUTION:At least one kind of aliphatic amine or a polymer thereof is added to a Zn-Ni alloy plating bath and the bath is adjusted to >=11pH to obtain an alkaline Zn-Ni alloy plating bath. At least one kind of aromatic aldehyde may be further added as a brightener as required. The plating bath as an electrolytic soln. contains a proper amount of an electrolyte such as NaOH, KOH, Na2CO3 or K2CO3, a Zn source such as ZnO and an Ni source such as NiSO4.6H2O. Monoethanolamine or polyethyleneimine may be used as the aliphatic amine or a polymer thereof and it is preferably added by such an amount that the molarity is made equal to or higher than the molarity of the Ni source.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) 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) Zinc is added to the surface of steel products to ensure excellent corrosion resistance.
It is known to apply nickel alloy plating.

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 performing zinc-nickel alloy plating using an acid bath. When such an acidic bath is used, the current efficiency is high and plating can be performed at a high current density, so there is an advantage that the plating can be performed quickly. The method of using an acid bath can effectively plate parts with simple shapes such as steel plates and wire rods, taking advantage of the advantages mentioned above.
For parts with complex shapes such as pressed parts, welded parts, pipe parts, etc., there is a problem in that it is not possible to obtain good uniformity in the alloy ratio and film thickness of the zinc-nickel alloy coating formed on the surface of steel products. There is.

Further, a technique for forming a zinc-nickel alloy using a neutral bath is disclosed in JP-A-59-185792. The method of using a neutral bath can improve the properties of the formed alloy film compared to the case of an acid bath when plating parts with complex shapes, but it requires a large amount of zinc and nickel to dissolve. a complexing agent must be used,
Therefore, special consideration must be taken for wastewater treatment, and there are also problems in terms of bath stability. Also,
In the case of neutral baths, it is common to add large amounts of chloride to increase the conductivity of the bath.

However, since chlorides are extremely corrosive, corrosion of plating equipment and the plating product itself becomes a problem.

Furthermore, a method of performing zinc-nickel alloy plating using alkaline external temperature is disclosed in Japanese Patent Application Laid-Open No. 51-28533. Since alkaline external temperature uses a less corrosive electrolyte, it is more advantageous than acid baths and neutral baths in terms of the cost of plating equipment.

(Problem to be solved) In the conventional alkaline external temperature as disclosed in JP-A-51-28533, it is required to contain cyanide, but cyanide is 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 uses an alkaline plating solution that has excellent bath stability, low corrosiveness, and does not contain toxic cyanide compounds. We have created a plating bath that can ensure excellent uniformity in the alloy ratio and film thickness of the alloy plating film formed on the surface of steel products, and can perform zinc-nickel alloy plating with good gloss. is intended to provide.

According to the research of the present inventors, when performing zinc-nickel alloy plating using alkaline external temperature, by adding at least one type of aliphatic amine or these polymers to the plating solution, cyanide compounds can be added to the plating solution. It has been found that the intended purpose can be achieved without any inconvenience.

The spacing bath of the present invention contains at least one type of aliphatic amine or a polymer thereof, and pl! It is characterized by an alkaline ectotherm of 11 or more.

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 Na as an electrolytic substance.
OHSK OH, Na2C03, K2CO2,
etc., in an appropriate amount in the range of 1 to 300 g/l. Furthermore, the electrolytic solution of the present invention contains Zn○, ZnS0417H20
, ZnCO3, Zn (CHs CO○)2 and other zinc component-containing compounds, and N i S O4 6H2ONiC
Contains nickel compounds such as O3, (N)(,)2・N1(SO4)2・6H20. In this case, these zinc component-containing compounds and nickel component-containing compounds have a zinc concentration of 1 to 70 g/l and a nickel concentration of 0.1 to 70 g/l in the electrolytic solution.
It is preferable to adjust the amount added so that it becomes 118 g/l.

Further, the aliphatic amine or polymer thereof in the plating solution is preferably added at a concentration equal to or higher than the molar concentration of the nickel component. When two or more types of amines are added, the amount to be added may be determined based on the total molar concentration.

The hydroxy aliphatic carboxylic acids or their salts added to this plating solution include tartaric acid, sodium tartrate, citric acid, sodium citrate, disodium citrate,
Any one such as glycolic acid or sodium glycolate can be used.

Aliphatic amines added to the electrolyte include monoethanolamine, jetanolamine, triethanolamine, ethylenediamine, diethylenetriamine, iminobispropylamine, triethylenetetramine, tetraethylenepencumine, hexamethylenediamine, N, N'
-bis-(3aminopropyl)ethylenediamine, 1,
Examples of the aliphatic amine polymer include 18-diamino-4,8,11,15,-tetraasooctadecane, etc. Also, examples of the aliphatic amine polymer include polyethyleneimine G-35J, a trade name provided by Badish Co., Ltd., Nippon Shokubai Kagaku Kogyo Co., Ltd. Manufactured by
Examples include polyethyleneimine such as Epomin SP and Epomin P-1000j, and tertiary to quaternary amine polymers represented by the following structural formulas.

R1-R2' 8% CHs, C2H5, C3+-(
7R3: (1) CH2CH2CH2 (2) CH2-CH-CH2 H (3) CH2CH2-○-CH2CH2 (4) CH
2-○-CH2 (5) CH2-CH-CH2 CH3 (6) CH2CH-CH I3 0H0H (7) CH2CH2-C-CH H (8) CH2-CH-CH CH20H X= , X2: Inorganic anion n: 10 to 200 In addition, the aromatic aldehyde as a gloss component added to the plating bath of the present invention includes niline, anisaltehyde,
Hyheronal, veratraldehyde, salicylaldehyde, benzaldehyde, P-)raldehyde, etc. are included, and it is desirable to add one or more of these aldehydes.

Further, it is desirable that the aliphatic amine is contained in the plating solution at 0.03 mol/1 or more.

According to the present invention, first, NaOH, KOH.

Electrolytes such as N a 2 CO 3 and K 2 Co 3 and Z
n○, ZnSo4・7H20, ZnCO3, Zn(Ct
A zincate solution is prepared by dissolving a zinc component-containing compound such as (3c○0)2. On the other hand, at least one kind of aliphatic amine or these polymers is added with N, So, ・
6H20, NiCO3, (NH4)2・N1(So4)
A nickel component compound such as 2.6820 is dissolved to prepare an aqueous solution, and this aqueous solution and the above zincate solution are mixed,
Prepare the plating solution. In this case, the nickel concentration and the concentration of aliphatic amines or their polymers are determined depending on the required alloy proportions.

(Effects of the Invention) When zinc-nickel alloy plating is performed using the plating bath of the present invention, the uniformity of the alloy ratio in the zinc-nickel alloy plating film formed on the surface of a steel product is extremely good. Therefore, even when plating a complicated part, a plating film having a substantially uniform alloy ratio can be formed over the entire plating part.

Furthermore, 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 a plating film with good gloss. can be formed. therefore,
By using the plating bath of the present invention, plated products,
In particular, the quality of products with complex shapes such as pressed products, welded parts, pipe parts, etc. can be improved.

Furthermore, since the plating bath of the present invention does not contain toxic cyanide compounds, problems such as deterioration of the working environment do not occur.

Further, since the plating bath of the present invention has an alkaline external temperature, it is less corrosive than an acid bath or a neutral bath, 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 Zn0 = 9.5 g/l (7.5 g/1 as Zn)
NiSO4・6H20 = 12g/1 (1.
5g/1) NaOH = 120g/l Triethylenetetramine - 75g/l (molecular weight = gloss component = 0.01g/I Zn/Ni = 83/17 ptl>14.0 Bath temperature = 30°C Current application time = 10 minutes above A zinc-nickel alloy plating film was formed on the Fe surface by changing the current density under different conditions.
It had good gloss, uniform film thickness and alloy ratio.

Table 1 shows the measurement results of alloy ratio and film thickness for each current density.

Table 1 (Example 2) Bath composition Zn0=1 1.3g/I (9.0g/I as Zn
l) NIS Oa・5H20=4.1g/1(Nt
1.0g/l) Na OH = 120g/l Polyethyleneimine SP 103 = 5.1g/l (
Molecular weight = 300) 1 Zn/Ni = 90/10 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 is
It had a uniform film thickness and alloy ratio, and especially good gloss at a current density of 0.2 to 5 A/dm2.

Table 2 shows the measurement results of alloy ratio and film thickness for each current density.

1 Table 2 (Example 3) Bath composition Zn5Q44HzO=60g/1 (13.5 as Zn
g/1) NiSOa・6 H20=6.7g/1(Ni
1.5g/l) NaOH = 150g/1 1.18-diamino-4,8,11,15-tetraazooctadecane = 7°5g/l (molecular weight = 288°5
) Gloss component - 0.01g/I Zn/Ni = 90/10 pH > 14.0 Bath temperature = 25°C Current application time - 10 minutes The current density was varied under the above conditions to form a zinc-nickel alloy plating film on the Fe surface. was formed. This plating film is
It had a uniform film thickness and alloy ratio with good gloss.

Table 3 shows the measurement results of alloy ratio and film thickness for each current density.

Table 3 (Example 4) Bath composition Zn0=11. '3g/] (Zn Toshite 9.0g
/l)(NH,>2・N1(SO2)2-6H20
=6.7g/1 (1.0g/l as Ni) KOH=90g/l Triethanolamine-5.1g/I (molecular weight-149
,2) Polyethyleneimine 5Poo3-2.5g/l
(Molecular weight = 300) Gloss component - 0.02 g/I Zn/N i = 90/ 10 pH > 14.0 Bath temperature - 30°C Current application time - 10 minutes By changing the current density under the above conditions, zinc was deposited on the Fe surface. -A nickel alloy plating film was formed. This plating film is
It had a uniform film thickness and alloy ratio, as well as good gloss.

Table 4 shows the measurement results of alloy ratio and film thickness for each current density.

Table 4 (Example 5) Bath composition Zn0 = 19.0 g/l (15.0 g as Zn
/1) NiCC・6 H20=lO, Og/1 (2.5 g/l as Ni) NaO) (= 150 g/l Tetraethylenepentamine - 16.0 g/l (molecular weight =
189.3) Tertiary to quaternary amine polymer of structural formula (1) = 20g/1b (molecular weight -800) Zn/Nl -86/14 pH>14.0 Bath temperature = -25°C Current application time - 10 minutes Above conditions A zinc-nickel alloy plating film was formed on the Fe surface by changing the current density. This plating film is
It 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 5 (Comparative Example 1) Bath composition ZnCA2 = 100 g/l N+Cj22.6 ) (20 = 120 g/l NH4C
1 = 220 g/l Brightener (commercially available) = 50 g/I Zn/Ni = 61/39 pl (= 5.8 Bath temperature - 35°C Current application time - 10 minutes The current density was varied under the above conditions to coat the Re surface. A zinc-nickel alloy plating film was formed on the
When changing the current density, the alloy ratio changes significantly. Table 6 shows the measurement results of alloy ratio and film thickness for each current density.

Table 6 (Comparative Example 2) Bath composition Zinc cyanide - 100g/l Nickel potassium cyanide = 35g/l NaOH = 40
g/I Zn/Ni = 37/63 p) I>14 Bath temperature -60°C 1! J Current density was varied for 10 minutes under the above conditions to form a zinc-nickel alloy plating film on the Fe surface. This plating film is
When changing the current density, the alloy ratio changes significantly. Furthermore, when the current density becomes less than (), 5 A/dn+2, the film thickness decreases rapidly. Table 7 shows the measurement results of alloy ratio and film thickness for each current density. □ Table 7, Figure 1 shows the results of plotting the changes in the nickel component in the coatings by varying the current density for the plating coatings formed in Example 2, Comparative Example 1, and Comparative Example 2 of the present invention. It is shown.

According to this, in the plating film using the bath of the comparative example,
As the current density decreases, the amount of nickel component in the alloy coating increases rapidly. On the other hand, the plating film of Example 2 was
Even if the current density decreases, the ratio of the nickel component hardly changes.

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 alloy film formed using the plating bath according to the present invention has a film thickness that continuously decreases as the current density decreases, whereas that of Comparative Example 1 has a high current density and a low current density. The difference in film thickness with respect to density is large, and in Comparative Example 2, the film thickness decreases rapidly on the low current density side.

Therefore, the plating bath of the present invention provides good gloss and film thickness, even when plating parts with complex shapes 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 drawings]

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 not showing the relationship between the thickness of the alloy coating and current density.

Claims (2)

[Claims] (1) A plating bath for zinc-nickel alloy containing at least one type of aliphatic amine or a polymer thereof and having a pH of 11 or more. (2) The plating bath for a zinc-nickel alloy according to claim (1), wherein the electrolytic solution further contains at least one type of aromatic aldehyde.