SU413213A1 - - Google Patents

Description

one

The invention relates to the field of electrochemical deposition of coatings with alloys of non-ferrous and noble metals and can be used to coat electrocontacts with a rhodium-tungsten alloy.

An electrolyte is known for precipitating a rhodium-based alloy containing rhodium salt, sulfuric, boric and hydrofluoric acids. At a cathode current density of 0.5-0.1 a / dm and 20-25 ° C, a coating of rhodium precipitates are precipitated.

The proposed electrolyte differs from the known one in that sodium tungstate is introduced into it in the following ratio of components, g / l:

give birth to salt (metal) 8-10

sulfuric acid25-30

boric acid30-35

hydrofluoric acid 0.8-1.0

sodium tungsten 2.0-4.0 This contributes to the production of high-quality solid crystalline precipitates of the alloy of rhodium-tungsten.

The initial product for the preparation of the electrolyte is rhodium chloride with a content of 32% metallic rhodium. The electrolyte is prepared with distilled water. Rhodium chloride in an amount of 30 g / l is dissolved in a small amount of water heated to 60-80 ° C. To the resulting solution with vigorous stirring poured 40%

potassium hydroxide solution. A yellow precipitate of rhodium hydroxide precipitates out and the solution becomes colorless. Completeness of precipitation is checked by pouring in a solution of 1% phenolphthalein alcohol solution. The appearance of a light pink color indicates a complete precipitation of the hydroxide. The precipitate is filtered off and washed with 5% hot potassium sulphate solution until the ions disappear.

chlorine (qualitative reaction with a 1% solution of silver nitrate).

The precipitate is then washed in distilled water until the sulfate ions are removed (qualitative reaction with a 10% barium chloride solution). After complete washing of the precipitate, the rhodium hydroxide is transferred to a solution of sulfuric acid at a rate of 30 g / l and heated until the precipitate dissolves. A solution of sulphate of rhodium is formed.

In a separate dish, solutions of boric acid are prepared at a rate of 35 g / l and sodium tungstate at a rate of 4 g / l.

To prevent the formation of tungstic acid precipitate in the electrolyte

Sodium tungstate is placed with a solution of boric acid and then poured into a solution of rhodium sulphate. Hydrofluoric acid (60%) is added thereto in an amount of 1.0 g / l. The finished electrolyte is being worked out.

current, pass 1.0 a / h per 1 liter of solution. 3 When conducting electrochemical deposition at room temperature, current densities of 0.5-1.0 a / dm with insoluble platinum anodes were obtained using tungsten-rhodium alloy with microhardness of 2200-2380 kg / mm. The tungsten content in the alloy is 4.3-4.7%, the alloy deposition rate is 3-5 µm / hour. rm Subject of the Invention An electrolyte for precipitating a rlavium-based melt containing rhodium salt, sulfuric acid, 4 boric acid and hydrofluoric acid, which is due to the fact that, in order to obtain high-quality solid crystalline precipitates of the rhodium-wolfram alloy, inject sodium tungstate with the following ratio of components, g / l: salt of rhodium (per metal) 8-10 sulfuric acid 25-30 boric acid 30-35 nlavic acid 0.8-1.0 sodium tungstate 2.0--4.0