JPS63206494A - Bright copper-zinc-tin alloy electroplating bath containing no cyanide compound - Google Patents

Abstract

PURPOSE:To provide the titled electroplating bath with which copper-zinc-tin alloy plating of a golden color having a high ornamental value is obtd. by incorporating an alkali metal salt of pyrrophosphoric acid, etc., as a complexing agent as well as amino acid (salt) together with copper salt, zinc salt and tin salt into said bath and providing extremely good brightness thereto. CONSTITUTION:The bright copper-zinc-tin alloy electroplating bath contg. no cyanide compd. is obtd. by making combination use of three kinds of the compds.; the alkali metal salt of the pyrrophosphoric acid as the complexing agent and the oxycarboxylic acid (salt) as well as the amino acid (salt) together with the copper salt, zinc salt and tin salt. All of ordinary electroplating methods are applicable to execute the bright copper-zinc-tin alloy plating by using the bath of this invention. Namely, the electroplating of, for example, an object to be plated can be executed simply by executing the plating under the plating conditions of about 10-50 deg.C bath temp., about 10.0-14.0pH of the bath and about 0.1-5A/dm<2> cathode current density. Since the bath of this invention does not contain the cyanide compd., the bath is the harmless and stable electroplating bath which does not generate toxic gases, etc., and is free from precipitate formation, etc.

Description

[Detailed Description of the Invention] Good 1" Hisashi B Yatatsu The present invention provides a bright copper-zinc-tin alloy electroplating bath (hereinafter "electroplating bath" is simply referred to as "plating bath") that does not contain cyanide compounds. Regarding.

Conventional technology and its problems Copper-zinc-tin alloy metal plating, also called substitute gold plating, is a decoration method used to impart a golden metallic luster and color tone to metal products, plastic products, ceramic products, etc. Widely used as plating. Copper-zinc alloy plating is also used for the same purpose, but often results in a so-called brass-colored plating with a yellow-green tint. Therefore, when a color tone similar to that of No. 24 gold plating is desired, a copper-zinc-tin alloy plating bath in which tin is added to a copper-zinc alloy plating bath is used. However, copper, which is currently widely used industrially,
All zinc-tin alloy plating baths are made by adding sodium stannate, potassium stannate, etc. to a copper-zinc alloy plating bath containing a large amount of cyanide, and their toxicity is a major problem.

Although many reports have been made regarding copper-zinc alloy plating baths or copper-zinc monotin plating baths that do not contain cyanide compounds, none of them have been put to practical use.

For example, T. L. Ramachar's research on plating foil using potassium pyrophosphate as a complexing agent [Electroplating and Metal Finishing, 12,
326 (1959)), but this potassium pyrophosphate bath has drawbacks such as a narrow golden luster range of the resulting copper-zinc alloy plating and easy passivation of the anode. Koshiura et al. solved the above drawbacks by adding a mixture of alkanol polyamine and epihalohydrin to a potassium pyrophosphate bath, and further added stannate to prepare a cyanide-free copper-zinc-tin solution. Developed an alloy plating bath (Japanese Patent Application Laid-Open No. 59-215492). However, in this method, the metal ratio of the precipitated alloy is Cu.
:Zn=7-8:3-2, whereas the metal concentration ratio in the plating bath is Cu:Zn=approximately 1:9, making it difficult to select an anode for stable continuous operation. It has the disadvantage of being

A method for solving the problems The inventor of the present invention has conducted intensive research in view of the problems of the above-mentioned prior art, and as a result, has found that copper salt! II! Alkali metal salts of pyrophosphoric acid or alkali metal salts of polyphosphoric acid and oxycarboxylic acids or salts thereof as complexing agents, together with lead salts and tin salts;
By using a non-toxic bath that contains amino acids or their salts and does not contain cyanide compounds, a golden copper-zinc-tin alloy plating film with extremely high gloss and high decorative value can be coated with a wide range of electrical currents. The present invention has been completed with the discovery that a range of densities can be obtained.

That is, the present invention provides at least one selected from a) copper salts, zinc salts and tin salts, b) alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid, and c) oxycarboxylic acids and their salts. The present invention relates to a bright copper-zinc-tin alloy electroplating bath that does not contain cyanide compounds and is characterized by containing at least one selected from d) amino acids and salts thereof.

In the present invention, three types of compounds, namely, an alkali metal salt of pyrophosphoric acid or polyphosphoric acid as a complexing agent, an oxycarboxylic acid or a salt thereof, and an amino acid or a salt thereof, are used together with a copper salt, a zinc salt, and a tin salt. Only then can the desired effects of the present invention be achieved.

If a bath consisting only of copper salts, zinc salts, tin salts, and alkali metal salts of pyrophosphoric acid or alkali metal salts of polyphosphoric acid is used, the resulting plating film will have a red copper color due to preferential precipitation of copper at low current density. At a current density of 8, discoloration occurs. In a very narrow range of current density between that range, that is, the maximum current density determined by the bath composition, a golden yellow plating film is obtained, but the gas traces are intense and the luster is poor. It is sufficient. In a bath consisting of copper salt, zinc salt, tin salt, and oxycarboxylic acid or its salt, the plating film becomes dark green and a golden plating film cannot be obtained. Copper salt, subsalt, tin The plating bath containing the salt and the above two types of compounds eliminates the preferential precipitation of copper at low current vIi degrees, making it possible to obtain a bright copper-zinc-tin alloy plating over a fairly wide current density range. However, as the current density increases, the color tone changes from yellow-green to golden yellow, causing color unevenness, making it insufficient for practical use as a decorative plating.On the other hand, copper J-1 zinc Addition of the two compounds as complexing agents and amino acids or their salts together with salts and tin salts produces a bright copper-zinc-tin alloy with a completely homogeneous 24-degree golden hue over a very wide current density. A plating film can be obtained.In the present invention, by appropriately changing the bath composition, a plating film of 0.05 to
A copper-zinc-tin alloy plating film with a homogeneous color tone and a golden yellow color can be obtained in an extremely wide current density range of about 5Δ/dm2.

Any known copper salt can be used, for example,
Pyrroline Mti4, Fti copper sulfate, cupric chloride, copper sulfamate, sulfur resistance, cupric acetate, i! Examples include dibasic copper carbonate, cupric bromide, copper formate, copper hydroxide, cupric oxide, phosphorus-resistant, copper fluorosilicate, copper stearate, cupric citrate, and the like.

Any known zinc salt can be used, for example,
Zinc pyrophosphate, i-resistant zinc, zinc chloride, zinc sulfamine, zinc oxide, zinc acetate, zinc bromide, FA male zinc carbonate, zinc oxalate, zinc phosphate, zinc silicofluoride, zinc stearate, zinc lactate etc. can be mentioned.

As the 'gj salt, any known salt can be used, such as sodium stannate, potassium stannate, and the like. In the present invention, two or more of the copper salts, zinc salts, and tin salts may be used in combination.

Any known alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid can be used, and examples thereof include sodium salts and potassium salts thereof.

Any known oxycarboxylic acid can be used, and examples thereof include glycolic acid, lactic acid, malic acid, citric acid, tartaric acid, gluconic acid, and glucoheptonic acid. Also, the salt and lithium salt,
Examples include sodium salts, potassium salts, calcium salts, and the like. Furthermore, as the tartarite W1 salt, in addition to the above-mentioned salts, tartarite (andemonyl potassium tartrate), Usutushi I
Salt (sodium potassium tartrate), etc. can also be used.

In addition, as the amino acid, any known amino acid can be used,
For example, α-amino acids or their [f
Examples include salts, sodium salts, and the like. In the present invention, two or more of the alkali metal salts of pyrophosphoric acid, alkali metal salts of polyphosphoric acid, oxycarboxylic acids and salts thereof, and amino acids and salts thereof may be used in combination.

The blending amount of each of the above components in the bath of the present invention is not particularly limited and may be selected as appropriate, but considering the ease of industrial handling, the copper salt should be about 2 to 40 g/Q in terms of copper content. , zinc salt 0.5 to 30 g/Q P in terms of zinc content
i! 0.1 to 5 g/QWia of tin salt, 150 to 400 g/q of alkali metal salt of pyrophosphoric acid and/or alkali metal salt of polyphosphoric acid, and oxycarboxylic acid and/or its salt. About 50-400g/Q and amino acid and/or its salt 0.5-50'J/Q
It is sufficient to mix them to a certain extent. The concentration ratio of Cu and Zn (Cu:Zn) in the plating bath is not particularly limited and can be selected as appropriate, but it is usually about 9 to 1:1, and this will produce a golden yellow plating film. be able to. However, taking into consideration stable continuous operation, the copper salt should be used at a copper conversion rate of 5 to 15 g/Q, and the zinc salt should be used at a zinc conversion rate of 1
It is preferable to add about 109/Q to make the concentration ratio about 5 to 1,5:1.

1lFA is mr of zinc salt! The addition of 1 or less has the effect of making the color tone of the plating film uniform and making it closer to a golden yellow color. Further, when a pyrophosphate is used as the copper salt or zinc salt, the total pyrroline M salinity including this pyrophosphate may be within the above range.

When applying bright copper-zinc-tin alloy plating using the bath of the present invention, any ordinary electroplating method can be used. p
H10, about 0-14.0, cathode current density 0.1-5A
Electroplating may be carried out under plating conditions of approximately /dm2 without stirring, mechanical stirring, or air stirring. In this case, as the anode, any one used in ordinary electroplating of copper-zinc-tin alloy can be used. Before electroplating, the body to be plated is coated with puff Ffl, sharp grease, etc. in accordance with the conventional method.
Pretreatment such as dipping in dilute acid may be performed, or base plating such as bright nickel plating may be performed.

Further, after plating, usual operations such as water washing, hot water washing, drying, etc. may be performed, and if necessary, immersion in a dilute dichromic acid solution, clear coating, etc. may be performed.

In the present invention, the object to be plated is not particularly limited, and any object to which a copper-zinc-tin alloy plating film is normally applied can be used, such as metal products, plastic products, ceramic products, etc. , It is preferable to apply an undercoating to these according to a conventional method before plating with the bath of the present invention.

Effects of the Invention According to the bath of the present invention, it has extremely excellent gloss and has 8114
A valuable golden copper-zinc-tin alloy plating film can be obtained over a wide current density range.

Furthermore, since the bath of the present invention does not contain cyanide, it does not generate toxic gases or the like, and is harmless and stable without the formation of precipitates. When a copper-zinc alloy is used for the anode, the dissolution is uniform and the plating bath composition can be kept stable simply by replenishing the tin salt. Furthermore, Cu in the pottery bath:
Zr11 degree ratio is 2 to 1.5, which is almost the composition of the plating film
: About 1 [lr/
Therefore, even when using an insoluble anode such as carbon or platinum-plated titanium, stable continuous operation is possible only by replenishing a mixture of copper salt, zinc salt, and tin salt with a constant composition.

EXAMPLES Below, Examples and Comparative Examples will be given to further clarify the characteristics of the present invention.

Examples 1 to 5 and Comparative Examples 1 to 3 Mock bath compositions listed in Table 1 (Examples 1 to 5) and Table 2 (Comparative Examples 1 to 3) (addition m of each component is all 9/Q )
Electroplating was performed under the same plating conditions, and the appearance and color tone of the resulting plated film was observed.

The results are shown in Table 3. In addition, in Tables 1 and 2, copper salts,
In the terms of zinc salt and tin salt, the values shown in parentheses are the respective metal content equivalent values ('J/Q).

Table 2 Table 3 From Table 3, in the bright copper-zinc to tin alloy plating bath of the present invention, 1) an alkali metal salt of pyrophosphoric acid and/or an alkali metal salt of polyphosphoric acid, 2) an oxycarboxylic acid and/or or a salt thereof, and 3) an amino acid and/or a salt thereof. Through the synergistic action of the three components, a golden copper-zinc-tin alloy plating film with high poultry value and an extremely excellent luster is produced.
It can be seen that the current density can be obtained over a wide range of current densities.

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Claims (1)

[Claims] (1) At least one selected from a) copper salts, zinc salts, and tin salts, b) alkali metal salts of pyrophosphoric acid and alkali metal salts of polyphosphoric acid, and c) oxycarboxylic acids and their salts. A cyanide-free bright copper-zinc-tin alloy electroplating bath characterized by containing at least one kind and at least one kind selected from d) amino acids and their salts.