JPS5921393B2 - Sulfur additive for multilayer nickel plating bath - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for forming multilayer electroplating on metal substrates, and more particularly to a method for forming multilayer electroplating consisting of three adjacent nickel electroplating layers. This invention relates to a plating bath useful in improvements and methods thereof.

U.S. Pat. No. 3,090,733 also describes an improved multi-layer plating applied to a metal substrate and a method for performing the improved multi-layer plating, comprising three layers of nickel electroplating that are adjacent to each other. There is.

As described in the patent, this multilayer plating consists of three layers of nickel of a certain thickness bonded together, with the nickel intermediate layer having a higher sulfur content than the sandwiching nickel layers. The upper layer of nickel has a significantly higher sulfur content than the bottom layer of nickel. As disclosed in that patent, various inorganic and organic sulfur-containing compounds can be mixed into the bath in which the nickel intermediate and top layers are plated to achieve the desired sulfur content in each of these layers. can.

Examples of sulfur compounds that can be used include various thiodontates, sulfites, bisulfites, hyposulfites, hydrosulfides, sulfoxylates, sulfinates, thiocyanates, sulfoxides, sulfonic acids, Included are mercapto aromatic acids, thioureas, thiohydantoins, sulfonamides, sulfonimides, sulfonyl halides, sulfones, and the like. Although the method of this patent provides greatly improved corrosion protection even with much thinner nickel plating than conventional methods, there are some operational difficulties with this method.

For example, it has been found that the use of the sulfur-based additives shown in that patent makes the plating bath extremely sensitive to air agitation and high temperatures, thereby inhibiting the speed of the plating operation.

Furthermore, electrolytic removal of metal contaminants such as zinc, copper and lead produced in the plating bath cannot be performed until the sulfur-containing additive has been decomposed by oxidation. This therefore means that these impurities must be removed before replenishing the sulfur-containing additive before restarting the plating operation. This is of course time consuming and expensive. Therefore, the object of the present invention is to provide a three-layer nickel multilayer plating system that can increase the plating rate and remove metal impurities by electrolysis without decomposing the sulfur compound additive in the bath. The objective is to provide an improved method for forming.

Another object is to provide an improved electroplating bath for use in the present invention to apply three-layer composite electroplating.

Other objectives will become apparent by themselves from the detailed description provided below.

In order to accomplish the above objects, the present invention provides a method for applying a coating of approximately 0.15 to 1.5 mils (approximately 3.8 mils) to the surface of base metals susceptible to corrosion.
An improved method for forming a nickel-containing multilayer plating on the base metal by electrodepositing an adherent bottom layer of a nickel plating with a thickness of ~38 μ) and an average sulfur content of less than about 0.03%. wherein the bottom layer has a thickness of about 0.005 to about 0.2 mil (
(approximately 0.13 to approximately 5.0μ) with an average sulfur content of approximately 0.0
An adhesive interlayer of electroplating containing 5 to 0.3% nickel is electrodeposited, with a thickness of about 0.2 to 1.5% on top of this intermediate plating layer.
Mill (approximately 0.13-38μ), average sulfur content 0.0
An adhesive top layer consisting of electroplating containing 2 to 0.15% nickel is applied, the sulfur content of this adhesive top layer being lower than that of the intermediate layer, the improvement being that The sulfur source for the intermediate layer consists in the presence of at least one nitrile or amide thioether sulfonate in the electroplating bath.

That is, by using a nitrile or amide thioether sulfonate different from the sulfur-containing compounds as described in U.S. Pat. No. 3,090,733, by operating the plating bath under air agitation, and It can be carried out under high temperatures and therefore metal impurities such as zinc, copper and lead can be electrolytically removed without the need to first decompose their sulfur-containing compounds, while at the same time plating It has been discovered that the speed can be increased. More particularly, in the practice of the present invention, a nitrile or amide thioether sulfonate salt is incorporated into at least the electroplating bath used to form the intermediate nickel-containing layer as a sulfur source for the intermediate layer. However, it is preferable that it is also included in the electroplating bath for the middle and upper Nitsukel-containing layers as a sulfur source for both layers.

As mentioned above, the amount of sulfur in the middle nickel-containing layer is preferably in the range of about 0.05-0.3%, while the amount of sulfur in the upper nickel-containing layer is about 0.05% to 0.3%.
It is desirable that the content be within the range of 0.02 to 0.15%. Therefore, the amount of nitrile or amide thioether sulfonate contained in the plating bath used to form these layers is within the range of about 0.01 to 0.4 y/l to form the intermediate layer. Approximately 0% of the electroplating bath used for
．． approximately 0.01 to 0.04 f/l in the electroplating used to constitute the top layer.
The exact amount of nitrile or amide thioether sulfonate included in the G'SO electroplating bath will, of course, be determined by the particular compound used. Therefore, as long as the specific amounts of these compounds used are sufficient to provide the desired amount of sulfur in the nickel-containing plating layer, amounts above or below the preferred ranges mentioned above may be used. In some cases, it is acceptable to use the amount as well. The novel nitrile or amide thioether sulfonates that can be used in the process of the invention have the following general formula: where M=Na, K, NH4 or H, . R1 alkylene group having 2 to 4 carbon atoms, R, = hydrogen or alkyl group having 1 to 4 carbon atoms, R2 = hydrogen, aryl group, or ÷CH2+RnYm-1-2, Y1X or aryl group, R3 , R4-hydrogen or 1 to 4 carbon atoms
an alkyl group, n=0 to 3].

Generally, these compounds are obtained by reacting a mercaptoalkylsulfonate with an unsaturated nitrile or amide so as to add a mercapto group to the double bond of the unsaturated nitrile or amide.

This reaction is preferably carried out in the presence of a copper catalyst, but
This reaction occurs even without the use of a copper catalyst. This reaction is also usually carried out in an aqueous system in a basic medium, preferably at 7.5
~100) carried out in an aqueous system with a pH of ~100). Examples of these reactants include the following compounds, but of course the exemplified compounds do not limit the scope of the compounds of the general formula used in the method of the invention: Among these compounds: Particularly good results are obtained when using reaction products of mercaptopropanesulfonate and dicyanobutene or acrylonitrile.

These substances which are preferably used in the process of the invention are therefore mentioned below, but of course this should not be construed as limiting the nitrile or amide thioether sulfonates that may be used, but is merely an example of these substances. It should be understood as indicating the following. The three-layer nickel multilayer coating obtained by the method of the present invention is composed of a matte nickel nickel as the bottom layer, a matte, semi-glossy or bright nickel layer as the top layer; As shown, the bottom layer has a higher sulfur content.

In the absence of a finishing chrome plating, this three-layer nickel-containing coating provides excellent corrosion protection, but in many cases this upper two-layer coating is replaced by a known finishing layer of glossy chrome or finely cracked chrome. It is preferable to coat with a microporous chromium plating, and in this case, the chromium plating preferably has a thickness in the range of about 0.005 to 0.2 mil (0.13 to 5.0μ). ) Generally, it is preferred that the bottom Niskel-containing layer be thicker than the top layer, with a ratio within the range of about 50:50 to 80:20 to provide the best ductility of the coating. However, when ductility is not a primary concern, the thickness of the bottom layer can be made thinner than the thickness of the top two-layer containing layer, in which case a typical ratio of both layers is about 40:60.
However, it still exhibits an excellent corrosion prevention effect on the base metal surface. It is worth noting that the nickel-containing layer constituting the multilayer coating according to the invention may also contain small amounts of other components besides sulfur. Examples of these components include carbon, selenium, tellurium, zinc, cadmium,
There is iron, etc. Furthermore, a significant amount of cobalt, for example up to at least 50%, may be included in the nickel-containing electroplated layer. However, on the other hand, it is often found that it is desirable for the bottom nickel-containing electroplated layer to be as pure as possible.
Therefore, the bottom layer nickel-containing electroplating may be a Watt-type nickel plating bath, a nickel plating bath containing fluoroborate, high chloride, sulfamate, or a substantially sulfur-free semi-bright nickel plating bath. This can be done using a plating bath. The electroplating bath used to deposit the middle nickel-containing plating layer may be similar to the bath for depositing the bottom layer nickel-containing plating, or it may be an alkaline nickel electroplating bath, or it may be a sodium, ammonium, lithium or A type of nickel plating bath with a high magnesium content may also be used. The bath for applying this interlayer nickel-containing electroplating will, of course, contain one or more nitrile or amide thioether sulfonates, the content of which will provide the required sulfur content of the interlayer as described above. It must be in sufficient quantity. Similarly, the electroplating bath used to deposit the Dobe Futsukeru plating layer may be the same as that used for plating the intermediate layer, except that sulfur compounds such as nitriles or amide thioether sulfonates may be used. The concentration must be lower than the concentration of sulfur compounds contained in the bath used for plating the interlayer. Furthermore, if it is desired to perform decorative plating, it is desirable to use a bright nickel plating bath using one or more organic sulfo-oxy compounds for plating the upper nickel-containing layer. These sulfo-oxy compounds are described in U.S. Pat. Nos. 2,512,280 and 2,800.
, No. 440, in order to impart smoothness and brightness to the plating, it is preferable to use an unsaturated compound or an amine in combination. Wetting agents to prevent pitting, buffering agents such as boric acid, formic acid, citric acid, acetic acid and fluoroboric acid may also be added to these plating baths.

The plating bath is typically operated at room temperature, i.e., within the temperature range of about 20<0>C to at least about 85<0>C, and under acidic bath conditions having a pH within the range of about 1-6. It is noteworthy that the electroplating bath of the present invention can be operated similarly to the method disclosed in U.S. Pat. No. 3,090,733 to provide multilayer nickel-containing trilayer plating. . However, in the present invention, by using a specific sulfur-containing compound as described above instead of the sulfur compound disclosed in the patent, the plating speed can be further increased, and air agitation and high temperature can be used. In addition, it is not necessary to decompose the organic sulfur compound first,
It has been clearly shown that metal impurities such as zinc, copper and lead can be removed from plating baths by electrolysis.

Therefore, the method of the present invention (Maru U.S. Pat. No. 3,090,
Although operations similar to those disclosed in '733 can be used to apply three layers of nickel plating over steel, aluminum, zinc, magnesium, brass and similar base metals susceptible to corrosion, It has been shown that the method is improved over the method described in the patent by using a specific and special sulfur-containing compound that has a unique action compared to the typically disclosed compounds. ing.

To assist those skilled in the art to better understand the spirit of the invention and the manner in which it may be carried out, some examples are set forth below, unless otherwise specified. , parts and percentages are all expressed by weight, and temperatures are in °C. Example 1 Preparation of the composition: 1 mole of mercaptopropanesulfonic acid was added to 1 liter of water and the pH was adjusted to 8.5 using aqueous sodium hydroxide solution.

When 5V copper acetate and 1.1 mol of acrylonitrile are added to this solution and heated to 45°C, an exothermic reaction occurs and the temperature of the solution rises to 80°C. After about 2 hours, the reaction will be completed,
The remaining unreacted acrylonitrile is removed by distillation under reduced pressure. In the same manner, 1 mercaptopropanesulfonic acid was added.
, 4-dicyanobutene, acrylamide and N-Ter
It can be reacted with t-butylacrylamide.
Example 2 A steel panel was plated with three layers of nickel as follows: a substantially sulfur-free semi-bright nickel plate with a thickness of 15μ (0.6 mil) and a sulfur content of 0.003%;
1,4-dicyano-2-[(3'-sulfopropyl)thio]-butane sodium salt (compound #1), which is a reaction product of R-mercaptopropanesulfonic acid and dicyanobutene, was added at a concentration of 0.05 f/l. nickel solution containing 6
High sulfur content nickel plating with a sulfur content of 0.143% and a thickness of 1.5 μm (0.06 min(c)) obtained from an air-stirred plating bath at 2.8°C, saccharin and sodium allylsulfonate. 10μ (0.4 mil) thickness obtained from a nickel plating bath containing 0.05% sulfur content.
Glossy nickel plating.

A thickness of 0.25μ (0.01 min) is applied on top of this plating deposit.
After plating with chromium (c), a Corrod coat accelerated corrosion test was conducted.

After 16 hours, there was only one failing score.
A similar panel without the high sulfur interlayer produced more than 25 failure points.

Example 3 A plating was prepared in the same manner as described in Example 2, except that the concentration of the reaction product of mercaptopropanesulfonic acid and dicyanobutene was increased to 0.1 t/l.

The sulfur content of the intermediate precipitate layer was increased to 0.22%. The three-layer nickel-chrome plating thus obtained was also substantially superior to a plating of the same thickness without the thin high sulfur-containing intermediate plating layer. Example 4 A steel panel was plated with three layers of nickel as follows: A, thickness 10μ (0.4 min(C), sulfur content 0.003
% substantially sulfur-free semi-gloss nickel plating, from a bath of air-stirred nickel solution at a temperature of 60°C containing sodium nitrilo-propane mercaptopropanesulfonate (compound #2) at a concentration of 0.09/l. The resulting high sulfur content nickel plating had a sulfur content of 0.16% and a thickness of 1.75 microns (0.07 mils); 0.4 mil), sulfur content 0.
05% glossy nickel plating.

This nickel deposit layer has a thickness of 0.25μ (0.01 mil).
Chromium plating was applied and a CASS test was conducted.

After 20 hours, the base metal showed no erosion points, whereas a similar panel without the high sulfur interlayer had 14 or more failure points.

Example 5 (1) 115'F (46
．． 10C) of Watts type nickel solution without air stirring and (2
) F of 145 (62.
Panels were deposited with a three-layer nickel plating as described in Example 1, except that the high sulfur content nickel plating layer was deposited from an air-stirred Watts-type nickel solution at 8°C), followed by chromium plating. Plated.

A 32 hour Corrod coat accelerated corrosion test was conducted on this panel.

Panels plated with high sulfur content Nickel Strike plating using benzene sulfinate have 1 rust point.
However, panels treated with a high sulfur strike plate using the reaction product of mercaptopropanesulfonic acid and dicyanobutene had only about 25 failure points. Example 6 A comparative test of the stability of the additives described in Examples 1, 4, and 5 was conducted, and the following results were obtained.

(1) PH is 1.5, temperature is 135'F (57.2℃)
When the sample was kept in a nickel solution for 16 hours, 47% of the benzene sulfinate contained therein was oxidized.

However, when (2) sodium nitrilo-propane mercaptopropane sulfonate was kept under the same conditions for 24 hours, no change was observed in the sulfonate.

Example 7 To test the plating performance of the compound of the present invention, pH 2.2
An air-stirred Wattnickel bath was prepared.

To this bath was added the reaction product of mercaptopropanesulfonic acid and N-Tert-butylacrylamide (compound #7) at a concentration of 40TI9/2. To a similar bath was added the reaction product of mercaptopropanesulfonic acid and acrylamide (compound #3) at the same concentration. As a result of plating using this plating bath, the plating when the reaction product with N-tert-butylacrylamide was added had better ductility than the plating when the acrylamide reaction product was added, but the gloss was inferior. It was on. Plating was carried out after adding 0.25 t/l of saccharin to each plating bath to increase the sulfur concentration to 0.082%, and the plating performance of each bath showed the same results. Example 8 Mercaptopropanesulfonic acid and 1,4- as a sulfur source
Reaction product with diamidobutene (compound #5) at 0.1
A concentration of 2 f/l was used to produce a mineral gold film similar to that described in Example 2.

The sulfur content of the intermediate layer was 0.20%. The corrosion resistance of this three-layer nickel-chromium coating was far superior to that exhibited by ore of the same thickness without the high sulfur content intermediate layer. Example 9 The same corrosion resistance test as in Example 8 was repeated using the reaction product of β-cyanostyrene and mercaptopropanesulfonic acid (compound #6) as the sulfur source, but the same results were obtained. Ta.

At a bath concentration of the compound of 0.12 y/l, the sulfur content of the intermediate layer was 0.18%. Although some specific examples of the present invention have been shown above, the above-described specific compositions and plating methods thereof are merely examples and do not limit the scope of the present invention.

Claims (1)

[Claims] 1 The following general formula▲ Numerical formulas, chemical formulas, tables, etc.▼ [In the formula, M=Na, K, NH_4 or H, R=alkylene group having 2 to 4 carbon atoms, R_1=H or 1 carbon atom
~4 alkyl group, R_2=H, aryl group or ▲ there is a mathematical formula, chemical formula, table, etc. ▼, m = 1 to 2, Y = X or an aryl group, X = -CN or ▲ mathematical formula, chemical formula, table, etc. Yes▼、R
_3, R_4=H or an alkyl group having 1 to 4 carbon atoms,
A sulfur additive for multilayer Watt nickel plating baths selected from the group consisting of thioether sulfonates with n=0 to 3. 2. The sulfur additive for a multilayer Watt nickel plating bath according to claim 1, wherein R is an alkylene group having 3 carbon atoms. 3. The sulfur additive for a multilayer Watt nickel plating bath according to claim 1, wherein R_3 and R_4 are hydrogen. 4 The thioether sulfonate has the following structural formula▲mathematical formula,
The sulfur additive for multilayer Watt nickel plating baths according to claim 1, characterized in that it has a chemical formula, table, etc. ▼. 5 The thioether sulfonate has the following structural formula NC-C
H_2-CH_2-S-(CH_2)_3-SO_3N
The sulfur additive for multilayer Watt nickel plating baths according to claim 1, characterized in that it has a. 6 Thioether sulfonate has the following structural formula ▲ mathematical formula,
The sulfur additive for multilayer Watt nickel plating baths according to claim 1, characterized in that it has a chemical formula, table, etc. ▼. 7 Thioether sulfonate has the following structural formula▲mathematical formula,
The sulfur additive for multilayer Watt nickel plating baths according to claim 1, characterized in that it has a chemical formula, table, etc. ▼.