JPS5927398B2 - Surface treatment method of copper or copper alloy or plated products with these metals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for plated products made of copper or copper alloys.

Conventionally, surface treatment methods for copper, copper alloys, or plated products made of these metals, specifically coloring treatments using cuprous oxide, involve chemical conversion in a solution containing a strong oxidizing agent or alkali. Well-known methods include anodic oxidation treatment or anodization treatment performed in an alkaline solution. However, in these methods, the processing solution generally deteriorates rapidly and bath management is extremely difficult.
Processing at a high temperature of 00°C reduces workability.
In addition, such work depends largely on the skill of the worker, and the progress of the work and the quality of the finished product are determined by the worker's good judgment, which not only makes it difficult to maintain uniform quality but also makes mass production difficult. However, due to the use of oxidizing agents and alkalis, there were many drawbacks such as corrosion resistance and discoloration.

In particular, the high concentration of the treatment liquid is likely to exacerbate the recent waste liquid pollution problems. In order to solve the above-mentioned problems, the inventors have conducted repeated research and experiments on methods for oxidation coloring of copper, copper alloys, or plated products using these metals. The present inventors have discovered that a colored chemical conversion film is formed on the surface of copper, copper alloys, or plated products made of these metals by PR electrolytic treatment in a concentrated electrolyte solution, leading to the completion of this invention. .

That is, the present invention is a surface treatment method in which a metal suboxide film is formed on the surface of copper, copper alloy, or a plated product made of these metals by performing PR electrolytic treatment in an aqueous solution.

The metal in this invention includes iron, zinc, tin, silver, or an alloy thereof in addition to the above-mentioned copper.

The above-mentioned PR electrolysis is a method of electrolyzing by alternately and periodically passing a direct current and a reverse current, and the article becomes an anode in the case of a direct current and a cathode in the case of a reverse current. In addition, in this invention, the electrolyte has an electrolyte concentration of about 0.05% and a pH of 6, as shown in the examples below.
A low concentration of ~11 is used.

Specifically, when copper, copper alloys, or plated products of these metals are subjected to PR electrolysis in an aqueous solution, the copper first dissolves at the anode to expose the active surface, and at the same time generates nascent oxygen.

Next, when the polarity is transferred to the cathode, the copper remains unchanged and produces hydrogen. Therefore, when the switching period between direct current and reverse current is long, only dissolution occurs and no oxidation occurs, as in the case of electrolytic degreasing.On the other hand, when the switching period between direct current and reverse current is shortened, the amount of dissolution at the anode becomes very large. The amount of oxidation caused by oxygen during the nascent stage increases with time.

In other words, the anode is constantly oxidized in an activated state, and as this oxidation progresses, the color tone changes from brown to blue to golden to red to dark blue.The switching period of direct current and reverse current, current density, This color tone can be freely selected by appropriately selecting the electrolysis time, etc. In this case, the liquid composition used has little to do with the above-mentioned oxidation conditions.

The present invention will be specifically explained below using examples. PR electrolysis (switching cycle: 2 seconds) was carried out in an aqueous solution at a liquid temperature of 25° C. and a current density of 0.1 A/Dnl2, and after 10 minutes, a dark blue colored copper plate was obtained.

Example 2 A copper plate was pickled with 10% sulfuric acid, washed with water, and then subjected to PR electrolysis treatment (switching cycle: 2 seconds) in an aqueous solution at a temperature of 25°C and 0.03A/Dm2, and after 30 minutes. A copper plate colored dark blue was obtained.

Example 3 The same procedure as in Example 2 was repeated except that the current density was changed to 0.01 A/Dm2, and a copper plate colored blue was obtained after 10 minutes.

As is clear from the above explanation, the present invention is a colored film treatment by PR electrolysis using the above-mentioned low concentration electrolyte,
Since the oxidation depends on the oxygen generated by electrolysis, it can be treated with industrial water at ℃, and it has good adhesion to the substrate and excellent corrosion resistance, making it suitable for surface treatment before painting. This method solves the problems of conventional methods, such as almost no change in the processing solution and the difficulty in managing the solution due to aging of the solution.
Furthermore, by selecting the switching period, current density, electrolysis time, etc., color tone can be easily controlled and quality can be made uniform.In particular, it is easy to treat waste liquid, and the risk of pollution problems is drastically reduced, making it easier for the industry. The utility value of the above is extremely large.

Claims (1)

[Claims] 1. A metal suboxide film is formed on the surface of copper, copper alloy, or plated products made of these metals by performing PR electrolysis in a low-concentration electrolyte with an electrolyte concentration of 0.05% or less and a pH of 6 to 11. 1. A method for surface treatment of copper or copper alloys or plated products made of these metals, characterized by forming.