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INVENTION
Patent of the Russian Federation RU2231580
A METHOD FOR OBTAINING A PROTECTIVE COATING ON THE SURFACE OF THE PRODUCTS
FROM THE ALLOY ON THE BASIS OF COPPER
Applicant's name: OAO Ekaterinburg Non-Ferrous Metals Processing Plant (RU)
The name of the inventor: Timofeev NI (RU); Saltykova N.A. (RU); Studenok ES (RU); Grokhovskaya L.G. (RU); Ermakov A.V. (RU); Sivkov M.N. (RU)
The name of the patent holder: JSC "Ekaterinburg Non-Ferrous Metals Processing Plant" (RU)
Address for correspondence: 620014, Yekaterinburg, Lenin Avenue, 8, JSC "Ez OTSM"
Date of commencement of the patent: 2003.01.05
The invention relates to the field of electrochemistry, in particular to methods for applying protective coatings to the surface of articles made of copper-based alloys, predominantly made of nickel silver, and can be used in the manufacture of memorable souvenirs, jewelry, cutlery, etc. The method includes an anodic treatment of products made of nickel silver in an aqueous solution containing 100-200 g / l of potassium hydroxide with an anodic current density of 2-20 A / dm 2 for 6-10 minutes at 5-70 ° C with a cathode made of nickel silver. The invention makes it possible to realize the method at a sufficiently high current density over a wide temperature range and to obtain colorless protective coatings on the products of nickel silver that retain their original appearance for a long period of storage.
DESCRIPTION OF THE INVENTION
The invention relates to the field of electrochemistry, in particular to the electrochemical methods of applying protective coatings to the surface of articles made of copper-based alloy, in particular from cupronickel, and can be used in the manufacture of souvenirs, jewelry, etc.
An electrolytic method for oxidizing copper or copper-plated steel parts is known. As electrolyte for oxidation, a solution of sodium hydroxide with a concentration of 80-120 g / l is used. The temperature of the electrolyte is 80-90 ° C, the anode current density is not less than 0.5 A / dm 2 with an exposure of 20-30 minutes with the possibility of shortening the duration of the process as the temperature of the electrolyte increases. The steel sheets serve as cathodes. Before oxidation, the surface of the parts is degreased and activated (AM Yampolsky, Galvanic coatings, L .: Mechanical Engineering, 1978, p. 144) .
The known method is intended for obtaining on the surface of copper and copper parts of protective coatings having a deep velvety black color changing the appearance of the products.
For products made of nickel silver, such as souvenirs, jewelry, cutlery, etc., it is preferable to obtain a colorless protective coating that does not alter the original color of the product. In addition, the known method is technologically complex due to the need to select the optimum mode of several variable process parameters and maintain a sufficiently high temperature of the electrolyte.
Common to the known and claimed methods is the anodic surface treatment of articles made from a copper-based alloy in an alkaline electrolyte to form a protective coating.
The method of anodic oxidation of copper and its alloys is closest in technical essence to the claimed method, which is conducted in an electrolyte containing 150-200 g / l sodium hydroxide at a temperature of 80-100 ° C, anodic current density of 0.8-2.0 A / Dm 2 and the duration of the process is 10-30 minutes. At the end of the process of oxidation indicates the appearance of gas bubbles in the processed parts or a sharp increase in the voltage of the process. The steel or nickel can be used as the cathode (S.Ya. Grihiles, Oxide and phosphate coatings of metals., Librarian galvanotechnics., L .: Mechanical Engineering, 1978, p.77-77) .
The method is intended for obtaining a protective coating on articles made of copper and such alloys as bronze and brass, but the method is not effective enough when coating the products with nickel silver. The known method is complicated in implementation and is characterized by low efficiency.
General for the known and claimed methods of obtaining protective coatings on the surface of articles made of copper-based alloy is the anodic treatment of the surface of articles in an alkaline solution.
The invention is directed to providing a process that is simple to carry out, providing a colorless protective coating on products made of a copper-based alloy, in particular a cupronickel.
This is achieved by the fact that in the method for obtaining a protective coating on the surface of articles made from a copper-based alloy by anodizing them with an alkaline solution, the anodic treatment of the pre-degreased products from the cupronickel is carried out in an aqueous solution containing 100-200 g / l potassium hydroxide with an anodic density Current 2-20 A / dm 2 for 6-10 minutes. The cathode is made of nickel silver. The temperature of the electrolyte can be from 5 to 70 ° C.
THE METHOD IS PROVIDED AS FOLLOWS:
Products made of nickel silver (souvenirs, jewelry, etc.) are degreased, washed with water, then subjected to an anode treatment in an alkaline electrolyte containing potassium hydroxide in an amount of 100-200 g / l. The cathode is a plate made of nickel silver, and the anode is a product made of nickel silver, on the surface of which it is necessary to obtain a protective coating. The anode current density is 2-20 A / dm 2 . The duration of the process is 6-10 minutes. At lower current densities and holding time, the process becomes inefficient, at large - the protective coating becomes visible. The anodic treatment is carried out at temperatures of 5-70 ° C. After the treatment, the products are washed with running water and dried (in air, in a warm air stream or by wiping with a soft cloth).
Example 1. Anodic treatment of defatted and washed products of nickel-silver grade MH-19 in the amount of 12 pieces with a diameter of 60 mm, with a total area of 260 cm 2, was carried out in an alkaline electrolyte containing 150 g / l potassium hydroxide. The products served as an anode. The nickel plate was used as the cathode. The anodic treatment was carried out at an electrolyte temperature of 25 ° C, an anode current density of 2 A / dm 2 for 6 minutes, followed by washing the products from the electrolyte with running water and drying. The surface of the products had a light appearance and did not differ visually from the original products. When stored in a sealed container above 1% by weight solution of sodium sulfide (Na 2 S) for 7 days, the surface of the products did not darken. Non-coated coins from the same batch darkened within 1 hour.
Example 2. Pre-degreased and washed products of MH-M-Mts-10-1-1.5 grade nickel in the form of discs with a diameter of 36.7 mm in an amount of 7 pieces with a total area of 155 cm 2 were subjected to anodic treatment. The anode used the products themselves, and as the cathode - a plate made of nickel silver grade MN-19. Electrolysis was carried out at a temperature of 60 ° C, an anodic current density of 17 A / dm 2 for 10 minutes without adjusting the process regime. The products were then washed with running water and dried. The color of the surface of the nickel products after the treatment did not change. With the subsequent exposure of products having a protective coating, in the air for three months, it was noted that they did not darken, unlike similar products that do not have a protective coating.
Thus, the claimed method, realized at a high current density over a wide range of temperatures, is technologically simple, sufficiently intense, and provides colorless protective coatings on products of copper-based alloys, in particular, nickel, retaining their original appearance during long-term storage.
CLAIM
A method for obtaining a protective coating on the surface of articles of a copper-based alloy by anodizing them in an alkaline solution, characterized in that the anodic treatment of the products from the cupronickel is carried out at a temperature of 5-70 ° C in an aqueous solution containing 100-200 g / l potassium hydroxide , With an anode current density of 2-20 A / dm 2 for 6-10 min and with a cathode made of nickel silver.
print version
Date of publication 09.12.2006гг
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