JPH06287792A - Gold-zinc alloy electroplating bath and its electroplating method - Google Patents

Abstract

PURPOSE:To impart a strength withstanding practical use without using Ni or Co and to control the luster and color tone of a deposit by incorporating carboxylic acids and a chelating agent into a gold-zinc alloy electroplating bath. CONSTITUTION:One or more kinds selected from monocarboxylic acids, dicarboxylic acids, hydroxycarboxylic acids and their carboxylates and a chelating agent are incorporated into a gold-zinc alloy electro-plating bath contg. gold as its cyanide complex salt and zinc sulfate as the zinc compd. The content of the gold cyanide complex salt in the bath is controlled to 1-50g/l based on the metal concn., that of the carboxylic acid (salt) to 10-300g/l, that of the chelating agent to a concn. necessary to adjust the zinc ion concn. in the bath to 10<-10>-10<-2>mol/l and that of, zinc sulfate to about 1-1/5g/l. The bath is used at about 3-7pH and about 30-90 deg.C and about 0.5-1.5A/dm<2> current density. The color tone of the plating appearance is controlled by adjusting the zinc ion concn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acidic cyan-based gold-zinc alloy electrolytic plating bath and its electrolytic plating method.

[0002]

2. Description of the Related Art Gold alloy plating is used in many fields because of its excellent physical properties as well as the economy of saving expensive gold. Among them, gold alloy plating such as gold-cobalt or gold-nickel is very excellent especially in hardness and wear resistance as compared with the case of using only gold,
Moreover, it is not inferior to gold in terms of its luster, aesthetics, corrosion resistance, excellent electrical characteristics, etc., and is widely used as practical products such as ornaments and accessories and industrial materials such as electrical contacts.

As described above, the demand for gold alloy plating such as gold-cobalt or gold-nickel is indispensable for daily life, and its demand is increasing more and more. Has been done.
For example, an acidic cyan gold plating bath is known. This acidic cyan gold plating bath has a lower current efficiency than the neutral plating solution and the alkaline plating solution, but is excellent in bath stability, and also has less pinholes in the precipitate. The composition is based on the bath of an organic acid such as citric acid and an organic acid salt such as sodium citrate, and potassium gold cyanide as a gold compound, nickel sulfamate, zinc as a compound such as cobalt or nickel. The compound contains, for example, zinc acetate. Cobalt, nickel, etc. impart gloss, hardness, and abrasion resistance to the precipitate by a small amount of eutectoid.

[0004]

However, in such a conventional gold alloy plating of gold-cobalt or gold-nickel, the nickel, cobalt, etc. contained therein have an effect on the human body. It has been pointed out from all sides that there is a risk of giving. For example, in the field of dermatology, nickel-plated necklaces, earrings,
It has been reported that contact with jewelry such as piercings, watch bands, coins, etc. may cause itching, rashes, etc. depending on the conditions (for example, Jiji Medical Journal 95, 1
034-1049 (1980) "About patch test, intradermal test, leukocyte vagus test in chromium, nickel and cobalt dermatitis"]. That is, the possibility that nickel ions are melted by sweat from the gold-nickel alloy plating in contact with the skin and the nickel ions become metal allergens and cause allergic contact dermatitis or the like is being studied by some people. As described above, research on the effects of nickel, cobalt and the like on the human body is currently underway, and in parallel with this, environmental regulations for compounds such as nickel and cobalt and development of alternative technologies are also desired.

The present invention has been made by paying attention to such a conventional technique, and gold-zinc suitable for gold-zinc alloy plating, which is attracting attention as a technique replacing gold-cobalt or gold-nickel alloy plating. An object of the present invention is to provide an alloy electrolytic plating bath and an electrolytic plating method thereof.

[0006]

In order to achieve the above object, the present invention contains gold as a gold cyanide complex salt and zinc sulfate as a zinc compound in addition to monocarboxylic acid, dicarboxylic acid, Gold containing one or more carboxylic acids selected from the group consisting of hydroxycarboxylic acids and / or their carboxylic acid salts and a chelating agent
The zinc alloy electrolytic plating bath was used. The metal cyanide complex salt is contained in an amount of 1 to 50 g / l, and the carboxylic acid or carboxylic acid salt thereof is contained in an amount of 10 to 300 g / l.
^The amount contained was ^-10 to 10 ^-2 mol / l, and zinc sulfate was contained in an amount of 1 to 15 g / l. And again, such a plating bath, pH 3 ~ 7,
Liquid temperature 30-90 ° C, current density 0.5-1.5A / dm ²
The gold-zinc alloy electrolytic plating method used under the above operating conditions.

[0007]

In the plating bath of the present invention, the gold cyanide complex salt in the bath composition is contained in a metal concentration of 1 to 50 g / l, preferably 2-1.
It can be present at 5 g / l. Further, this plating bath uses a carboxylic acid or a carboxylic acid salt (preferably a carboxylic acid salt) as a buffering agent for stabilizing the bath, and the content thereof is 10 to 300 g / l. When the concentration is less than 10 g / l or more than 300 g / l, it is difficult to stabilize the pH of the liquid and impart conductivity to the liquid. Further, in the present invention, a predetermined amount of a chelating agent is added so that the zinc ion concentration in the bath can be adjusted to 10 ^-10 to 10 ^-2 mol / l. However, when the zinc ion concentration is less than 10 ^-10 mol / l, zinc is added. This is because the amount of gold-zinc alloy precipitates becomes extremely small when the eutectoid does not occur and the amount exceeds 10 ^-2 mol / l. As the zinc ion concentration in the bath increases, the total amount of the deposits decreases, but the amount of zinc in the deposits remains almost constant, so that the deposits exhibit a reddish color tone. . That is, the color tone of the plating appearance can be controlled by adjusting the zinc ion concentration in the bath. Zinc sulfate is used as a metal curing agent, and its content is 1
The reason for setting -15 g / l is that if it is less than 1 g / l, the eutectoid ratio and hardness of zinc will be reduced and the appearance will be dull, and if it is more than 15 g / l, a precipitate will form.

The gold-zinc alloy electrolytic plating bath of the present invention has p
H3-7, liquid temperature 30-90 ° C, current density 0.5-1.5
Used under operating conditions of A / dm ² . The pH is adjusted with sulfuric acid or potassium hydroxide. When the pH is low, preferably pH 4, a glossy surface of the deposited film is obtained regardless of the current density, and the deposited film changes from a glossy surface to a semi-glossy surface or a matte surface as the pH increases. That is, the gloss of the precipitate surface can be selected by adjusting the pH. The pH of 3 to 7 means that the pH is 3
This is because if it is lower, the deposition efficiency is extremely lowered, and if the pH is higher than 7, the deposited film becomes brown instead of gold. When the liquid temperature is lower than 30 ° C, the deposited film does not show a good appearance, and when the liquid temperature is higher than 90 ° C, the bath becomes unstable. If the current density is lower than 0.5 A / dm ^2, it is difficult to obtain a precipitate having a sufficient film thickness,
If it is higher than A / dm ^2, the precipitation amount of the gold-zinc alloy will be extremely reduced.

[0009]

The present invention will be described in more detail with reference to the following examples. Example 1 Potassium gold cyanide 15 g / l Potassium propionate 30 g / l Ethylenediamine 50 g / l Zinc sulfate 10 g / l pH 4 Liquid temperature 60 ° C. Current density 1 A / dm ² Nickel plating was applied in advance and gold strike plating was applied thereon. The test piece was subjected to gold-zinc alloy electroplating under the above conditions, and a deposit having a glossy and golden appearance was obtained. When this precipitate was examined by X-ray diffraction, it was found that the relative strength to pure gold was significantly increased, and it was confirmed that it has practically sufficient characteristics for gold alloy plating, such as adhesion and heat resistance. did it. In addition, in the same composition and conditions as the above, when plating was performed by replacing potassium propionate with propionic acid as the "monocarboxylic acid", the same effect was obtained.

Example 2 Potassium gold cyanide 15 g / l Dipotassium maleate 150 g / l Nitrilotrimesmethylenephosphonic acid 57 g / l Zinc sulfate 4 g / l pH 4 Liquid temperature 50 ° C. Current density 1 A / dm ² Nickel plating was carried out in advance, and When the gold-zinc alloy electrolytic plating was performed on the test piece having the gold strike plating thereon under the above-mentioned conditions, a deposit having a glossy and golden appearance was obtained. When this precipitate was examined by X-ray diffraction, it was found that the relative strength to pure gold was significantly increased, and it was confirmed that it has practically sufficient characteristics for gold alloy plating, such as adhesion and heat resistance. did it. In addition, plating was performed under the same composition and conditions as described above, except that dipotassium maleate was replaced with maleic acid as the "dicarboxylic acid", and the same effect was obtained.

Example 3 Potassium gold cyanide 15 g / l Tripotassium citrate 75 g / l Citric acid 75 g / l Zinc sulfate 5 g / l pH 3.8 Liquid temperature 45 ° C. Current density 1 A / dm ² Nickel plating was performed in advance. When the gold-zinc alloy electrolytic plating was performed on the test piece having the gold strike plating thereon under the above-mentioned conditions, a deposit having a glossy and golden appearance was obtained. When this precipitate was examined by X-ray diffraction, it was found that the relative strength to pure gold was significantly increased, and it was confirmed that it has practically sufficient characteristics for gold alloy plating, such as adhesion and heat resistance. did it.

Example 4 Potassium gold cyanide 15 g / l Dipotassium malate 30 g / l Ethylenediamine 50 g / l Zinc sulfate 10 g / l pH 4 Liquid temperature 60 ° C. Current density 1 A / dm ² Nickel plating was applied in advance and gold strike was applied thereon. When the plated test piece was subjected to gold-zinc alloy electrolytic plating under the above conditions, a deposit having a glossy and golden appearance was obtained. When this precipitate was examined by X-ray diffraction, it was found that the relative strength to pure gold was significantly increased, and it was confirmed that it has practically sufficient characteristics for gold alloy plating, such as adhesion and heat resistance. did it. It should be noted that when plating was performed under the same composition and conditions as described above, replacing dipotassium malate with malic acid as the “hydroxycarboxylic acid”, the same effect was obtained.

[0013]

INDUSTRIAL APPLICABILITY The gold-zinc alloy electrolytic plating bath and the electrolytic plating method according to the present invention do not use nickel or cobalt, which may affect the human body, and are therefore advantageous in terms of safety and hygiene in the plating workplace and living environment. is there. Further, the gold-zinc alloy plating bath and the electrolytic plating method thereof according to the present invention can obtain a plated product having sufficient strength to withstand practical use, while using no nickel or cobalt at all. P
Since the gloss and color tone of the deposit can be controlled by adjusting the H and zinc ion concentrations, the plated product has the effect of being highly versatile for decoration and industry.

Claims (6)

[Claims] 1. Containing gold as a gold cyanide complex salt, zinc sulfate as a zinc compound, and one or more carboxylic acids selected from the group consisting of monocarboxylic acids, dicarboxylic acids and hydroxycarboxylic acids. And / or one or more carboxylates selected from the group consisting of monocarboxylates, dicarboxylates, and hydroxycarboxylates,
A gold-zinc alloy electrolytic plating bath containing a chelating agent. 2. A gold cyanide complex salt is used in a metal concentration of 1-5.
The gold-zinc alloy electrolytic plating bath according to claim 1, containing 0 g / l. 3. A carboxylic acid or a carboxylic acid salt is added in an amount of 10 to 3.
The gold-zinc alloy electrolytic plating bath according to claim 1 or 2, containing 100 g / l. 4. The gold-zinc alloy electrolytic plating bath according to claim 1, wherein the chelating agent is contained in an amount such that the zinc ion concentration in the bath can be adjusted to 10 ⁻¹⁰ to 10 ⁻² mol / l. . 5. The gold-zinc alloy electrolytic plating bath according to claim 1, which contains 1 to 15 g / l of zinc sulfate. 6. The gold-zinc alloy electrolytic plating bath according to claim 1, which has a pH of 3 to 7 and a liquid temperature of 30 to 90.
A gold-zinc alloy electrolytic plating method used under operating conditions of a temperature of 0.5 to 1.5 A / dm ² .