JP2009127097A - Copper-zinc alloy electroplating bath, and plating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper-zinc alloy electroplating bath which can form a uniform and gloss alloy layer having the objective composition without using a cyanide even at higher current density than heretofore, and has excellent productivity. <P>SOLUTION: The copper-zinc alloy electroplating bath comprises: a copper salt; a zinc salt; an alkali metal pyrophosphate salt; and amino acid or its salt, and in which the concentration of the amino acid or the salt thereof is 0.08 to 0.22 mol/L. As the amino acid or the salt thereof, histidine or the salt thereof can be suitably used. The pH of the copper-zinc alloy electroplating bath suitably lies in the range of 10.5 to 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a copper-zinc alloy electroplating bath and a plating method using the same, and more specifically, a glossy uniform alloy layer can be formed without containing a cyanide compound even at a high current density. The present invention relates to a copper-zinc alloy electroplating bath and a plating method using the same.

  Currently, copper-zinc alloy plating is widely used industrially as decorative plating in order to give a metallic luster and color tone of brass color to metal products, plastic products, ceramic products and the like. However, since the conventional plating bath contains a large amount of cyanide, its toxicity is a big problem, and the treatment load of the cyanide-containing waste liquid is also large.

  As such a solution, a large number of copper-zinc alloy plating methods not using a cyanide have been reported today. For example, sequential plating is a practical method for applying brass plating to a product to be plated. In such a method, a copper plating layer and a zinc plating layer are sequentially plated on the surface of the product to be plated by electrodeposition, A thermal diffusion process is performed. In the case of sequential brass plating, a copper pyrophosphate plating solution and an acidic zinc sulfate plating solution are usually used (for example, Patent Document 1).

On the other hand, a copper-zinc plating bath not containing a cyanide compound has also been reported as a method for simultaneously plating copper-zinc, and a plating bath using a glucoheptonic acid bath or a potassium pyrophosphate bath with histidine added as a complexing agent has been reported. It has been proposed (for example, Patent Document 2).
JP-A-5-98496 Japanese Patent Publication No. 3-20478

However, in the sequential plating as described in Patent Document 1, there are a number of copper plating layer forming step, galvanizing layer forming step and thermal diffusion step, and processing steps. is there. Moreover, in the copper-zinc alloy electroplating bath described in Patent Document 2, there is no problem of toxicity as in the case of using a bath using a cyanide compound, but it is possible to form a glossy uniform alloy layer. The current density is 5 A / dm ² or less, which is a problem that it is smaller than the current density required for forming the alloy layer with high productivity. In any case, a copper-zinc alloy plating bath that does not use a cyanide compound is difficult to put into practical use at present.

  Accordingly, an object of the present invention is to form a uniform and glossy alloy layer having a target composition without using a cyanide compound even at a higher current density than in the prior art, and having excellent productivity. -To provide a zinc alloy electroplating bath and a plating method using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that in a copper-zinc alloy electroplating bath containing at least one selected from alkali metal pyrophosphate and amino acids or salts thereof, the copper -By making the concentration of the amino acid or salt thereof in the zinc alloy electroplating bath about 10 times as high as about 0.01 mol / L which has been conventionally presented, a glossy uniform alloy layer can be obtained from a low current density to a high level. It has been found that it can be obtained over a range of current densities, and the present invention has been completed.

  That is, the copper-zinc alloy electroplating bath of the present invention contains a copper salt, a zinc salt, an alkali metal pyrophosphate, and at least one selected from an amino acid or a salt thereof, and the amino acid or a salt thereof. The concentration of is 0.08 mol / L to 0.22 mol / L.

  The concentration of the amino acid or salt thereof in the copper-zinc alloy electroplating bath of the present invention is preferably 0.1 mol / L to 0.13 mol / L. Preferably, histidine or a salt thereof can be used as the amino acid or a salt thereof. Furthermore, the pH of the copper-zinc alloy electroplating bath of the present invention is preferably in the range of 10.5-12.

Moreover, the manufacturing method of the copper-zinc alloy plating film of this invention is the copper-zinc alloy electroplating method using the said copper-zinc alloy electroplating bath, The cathode current density in this plating bath is 5 A / dm < ² >. More than 13 A / dm ² or less.

  According to the present invention, with the above configuration, a uniform and glossy alloy layer having a target composition can be obtained in a wide current density range from a low density current to a high density current without using a cyanide compound. It is possible to form a copper-zinc alloy electroplating bath that can be formed and can utilize a higher current density than before, and productivity can be increased.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The copper-zinc alloy electroplating bath of the present invention contains a copper salt, a zinc salt, an alkali metal pyrophosphate, and at least one selected from an amino acid or a salt thereof, and the concentration of the amino acid or a salt thereof is adjusted. It is adjusted to 0.08 mol / L to 0.22 mol / L.

  Any copper salt may be used as long as it is known as a copper ion source for a plating bath. For example, copper pyrophosphate, copper sulfate, cupric chloride, copper sulfamate, cupric acetate, base Copper carbonate, cupric bromide, copper formate, copper hydroxide, cupric oxide, copper phosphate, copper silicofluoride, copper stearate, cupric citrate, etc. You may use only a seed | species and may use 2 or more types.

  Any zinc salt may be used as long as it is a known zinc ion source for a plating bath. For example, zinc pyrophosphate, zinc sulfate, zinc chloride, zinc sulfamate, zinc oxide, zinc acetate, bromide. Zinc, basic zinc carbonate, zinc oxalate, zinc phosphate, zinc silicofluoride, zinc stearate, zinc lactate, etc. can be mentioned, and only one of these may be used, or two or more may be used May be.

  Any alkali metal pyrophosphate can be used as long as it is known, and examples thereof include a sodium salt and a potassium salt thereof.

  The concentration of the amino acid or salt thereof in the copper-zinc alloy electroplating bath of the present invention is 0.08 mol / L to 0.22 mol / L, preferably 0.1 mol / L to 0.13 mol / L. When the concentration of amino acid or salt thereof is less than 0.08 mol / L, a uniform alloy layer cannot be obtained when the current density is high, whereas when the concentration of amino acid or salt thereof exceeds 0.22 mol / L. The copper composition of the alloy layer becomes high, and an alloy layer having a uniform composition cannot be obtained.

  Any known amino acid can be used, for example, glycine, alanine, glutamic acid, aspartic acid, threonine, serine, proline, tryptophan, histidine, etc. α-amino acid or its hydrochloride, sodium salt, etc. Among them, histidine is preferable. In addition, only 1 type may be used among these and 2 or more types may be used.

  The pH of the copper-zinc alloy electroplating bath of the present invention is not particularly limited as long as it is usually used, but the pH is preferably in the range of 10.5 to 12. When the pH is within this range, a uniform alloy layer can be easily obtained even when the current density is high. For adjusting the pH of the copper-zinc alloy electroplating bath of the present invention, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide and alkaline earth metal hydroxides such as calcium hydroxide are preferably used. Potassium hydroxide is preferred.

  The compounding amount of each component in the present invention is not particularly limited and can be appropriately selected. However, in consideration of industrial handling, the copper salt is 2 to 40 g / L in terms of copper and the zinc salt is 0 in terms of zinc. 0.5-30 g / L, pyrophosphoric acid alkali metal salt 150-400 g / L, amino acid or a salt thereof is preferably about 0.2-50 g / L.

The plating method using the copper-zinc alloy electroplating bath of the present invention uses the copper-zinc alloy electroplating bath of the present invention, and performs plating at a high current density of more than 5 A / dm ² and not more than 13 A / dm ^2. Is to do. When performing copper-zinc alloy electroplating using the copper-zinc alloy electroplating bath of this invention, a normal electroplating method is employable. For example, electroplating may be performed at a bath temperature of about 30 to 40 ° C. with no stirring, mechanical stirring, or air stirring. At this time, any anode can be used as long as it is used for electroplating of a normal copper-zinc alloy. By using the copper-zinc alloy electroplating bath of the present invention, it becomes possible to perform plating at a high current density of more than 5 A / dm ² and not more than 13 A / dm ² , which is more productive and glossy than before. A uniform copper-zinc alloy layer can be formed.

  Prior to the electroplating, the object to be plated can be subjected to usual pretreatments such as buffing, degreasing and dilute acid immersion according to conventional methods, or it can be subjected to base plating such as bright nickel plating. It is. In addition, after plating, usual operations such as washing with water, washing with water, and drying may be performed, and if necessary, immersion in dilute dichromate solution, clear coating, and the like may be performed.

  In the present invention, the material to be plated is not particularly limited, and any one that is usually coated with a copper-zinc alloy electroplating film can be used. For example, steel filaments used for steel cords for reinforcing rubber articles are used. Metal products, plastic products, ceramic products, etc. can be mentioned.

Hereinafter, the present invention will be described in more detail with reference to examples.
In accordance with the composition of the copper-zinc alloy electroplating bath shown in Table 1 below, copper-zinc alloy electroplating baths of each example and comparative example were prepared, and according to the plating conditions in the following table, the copper-zinc alloy electroplating bath was prepared. Plating treatment was performed. The plating bath was evaluated by obtaining a current density range in which a glossy uniform alloy layer can be obtained. The obtained results are also shown in the table below.

  Comparing the results of Examples 1 to 3 and Comparative Example in the above table, the glossy uniform alloy layer is obtained by adjusting the concentration of the amino acid or its salt to the range of 0.08 mol / L to 0.22 mol / L. It was confirmed that the range of current density that can be formed extends to the high current density side.

Claims (5)

  A copper salt, a zinc salt, an alkali metal pyrophosphate, and at least one selected from an amino acid or a salt thereof, and a concentration of the amino acid or a salt thereof is 0.08 mol / L to 0.22 mol / L. A copper-zinc alloy electroplating bath.   The copper-zinc alloy electroplating bath according to claim 1, wherein the concentration of the amino acid or a salt thereof is 0.1 mol / L to 0.13 mol / L.   The copper-zinc alloy electroplating bath according to claim 1 or 2, wherein the amino acid or a salt thereof is histidine or a salt thereof.   The copper-zinc alloy electroplating bath according to any one of claims 1 to 3, wherein the pH is 10.5 to 12. Copper as claimed in any one of claims 1 to 4 - zinc alloy electroplating bath of copper was used - in zinc alloy electroplating method, a cathode current density in the plating bath exceeds the 5A / dm ² 13A / The manufacturing method of the copper-zinc alloy plating film characterized by setting it as dm < ² > or less.