SU1068547A1 - Electrolyte for depositing coating of silver-copper alloy - Google Patents

Abstract

ELECTROLYTE TO DECLARE COATINGS WITH SILVER-COPPER ALLOY containing silver and copper nitrates, thiourea, which also contains acetone and methanol yellow and / or gelatin to increase the copper content in the alloy, increase the gloss of coatings and improve their adhesion. in the following ratio of components, g / l: Silver nitrate (. in terms of silver) 3.6-6 Copper nitrate (in terms of copper) 7-9, .6 16-23 Thiourea 250-500 mi g Acetone .. Methanilic CO 0.02-0.08 yellow 0.2-0.5 and / or gelatin

Description

00 SP

4 Nl

The invention relates to electroplating, in particular to electrolytic deposition of silver-copper alloy coatings, and can be used as coatings for electrical contacts, as well as for decorative purposes.

A pyrophosphate electrolyte is known for the deposition of silver-copper alloy coatings. This electrolyte allows you to get at room temperature and current density of 0.5-0.7 A / dm silver-copper alloy with a copper content of 4-70% L13.

However, the composition of the alloy strongly depends on the stability of the pH maintenance. The coatings are dense; wear resistant, hard but not shiny.

A monoethanolamine electrolyte is also known for the deposition of silver-copper C23 alloy coatings.

However, this electrolyte allows the alloy to be deposited only on copper and brass, which have previously been amalgamated and coated with a thin layer of silver from cyanide or ferro elec- tron electrolyte. The content of copper in the alloy reaches only 1-7%, depending on the current density of 0.2 O, 8 L / dm. This reduces the possibilities of using electrolyte.

Closest to the invention is a urea electrolyte containing silver and copper nitrates and thioureas. ,

The known electrolyte makes it possible to obtain, at current densities of 0.4 O, 5 A / dm of silver alloy coating with copper content of 2-63.6% 131

However, the obtained precipitates of the alloy, although fine-crystalline, are non-shiny and weakly coupled with the main one.

The aim of the invention is to increase the copper content in the alloy, increase the gloss of the coatings and improve their adhesion.

The goal is achieved by the fact that the electrolyte for the deposition of silver-copper alloy coatings containing silver and copper nitrates, thiourea, additionally contains acetone and methanilic yellow and / or gelatin in the following ratio of components, g / l:

Silver nitrate

{in terms of

on silver) 3.6-6

Copper nitrate

(in terms of

for copper) 7-9,6

Thiourea16-23

Acetone 250-500 4

Methanil

yellow -0.02-0.08

And / or gelatin 0.2-0.5

The deposition process is recommended to be carried out at room temperature (18-25 s) and current densities of 0.1-0.4 with copper or silver anodes.

5 The electrolyte is prepared as follows. 250-350 ml of distilled water without heating dissolve the required amount of thiourea and dilute with acetone (250-500 ml) (1st solution).

0 Separately, the required amounts of silver and copper nitrates (2nd solution) are dissolved in 100–200 ml of distilled water, and the second solution is slowly poured into the first solution while stirring.

5 solution. If necessary, add distilled water to a volume of one liter.

It is possible to prepare a general solution from concentrated solutions (0.5 Q 1 M / l) of silver and copper nitrates and a .1 M / l solution of thiourea and acetone with the same sequence. Gelatin is added in the form of a freshly prepared 1% solution, and

5 methanil yellow in solid form. The amount of silver and copper salts is chosen so as to obtain a silver-copper alloy with a copper content of up to 20% at current densities of no more

Q 0.2 A / dm2.

The amount of thiourea is taken in such a way that the sugar concentration of marmar of silver and copper (mol / l) is approximately two times less than the concentration of thiourea. With this ratio of components get more stable (electrolyte.

The presence of acetone increases the stability of the electrolyte, improves adhesion of coatings to the base and

0 dissolving anodes. The amount of aceto; Additions of the yellow iron or gelatin are based on the desired alloy composition, as they are increased. the number of all these components.

5 tons increases the copper content in the alloy and extends the range of current densities in which it is possible to obtain shiny coatings.

Acetone roughly halves

surface tension of the electrolyte, improves the wettability of the electrodes and the quality of coatings. Cathodic polarized curves showed that acetone depolarizes the release of copper and

increases the polarization of silver release. The presence of methanilic yellow or gelatin in electrolyte complicates the release of silver and cawbiM contributes to an increase in the copper content in the alloy.

The joint introduction of acetone and methanilic yellow and / or gelatin into the electrolyte provides for obtaining qualitative coatings with an alloy at room temperature, in particular, increases gloss and adhesion to the substrate.

Brilliant coatings can be obtained in the range of current densities of 0.1 O, 4 A / dm. At high current densities, a decrease in the deposition rate and a decrease in the copper content in the alloy, a decrease in the brightness of the coatings occur.

Specific examples of the electrolyte composition, deposition conditions, and the phyi co-chemical properties of silver-copper alloy coatings are given in Table 1.

The hardness of the coatings was determined by the standard method using the PMT-3 instrument. Internal voltages were determined by the flexible cathode method. To determine adhesion, silver-copper alloy was deposited on 90-μm thick brass plates. Ddgesy was determined by the method of multiple bending at 180.

As can be seen from Table. 1, the proposed electrolyte ensures high adhesion of coatings to the substrate, high.

What microhardness (190-200 kg / cm) compared with the known electrolyte

In tab. 2 shows the gloss data of the coatings.

The flash was measured with a universal photometer 1) M-5b with respect to a polished sieve plate.

As can be seen from the table. 2 of the proposed electrolyte receive bright precipitates in a wide range of current densities. Electrolyte coatings without the addition of organic substances (acetone, methanil yellow and gelatin) are obtained only matte.

Thus, the proposed electrolyte makes it possible to obtain, at low current densities, the silver copper with a copper content of up to 20% well adhered to the base coating. The coatings have a better physical and mechanical properties (gloss, microhardness).

The proposed electrolyte can be used to obtain coatings for electrical contacts and for decorative purposes, thus avoiding a deficit of pure silver.

table 2

Silver nitrate (for metal) 6 Nitrate m-for metal) 7.3 38.0 26.0 20.0 15.0 10.0

thiourea 23

Acetone, ml / l 333

Methanil. Yellow 0.02

26.0 10.0 7.0 6.0

31.0 20.0 12.0 8.0 5.0

Pshpublyaschie

Excellent 10.0 10.0 7.5 5.0

Claims (1)

from-agues solution, Trans Electroch. Soc. 1938, v. 74, p. 229-253. : ELECTROLYTE FOR DEPOSITING COATINGS WITH SILVER-COPPER ALLOY, containing silver and copper nitrates, thiourea, characterized by the fact that, in order to increase the copper content in the alloy, increase the gloss of coatings and improve their adhesion, it additionally contains acetone, and methanyl yellow and / or gelatin in the following ratio of components, g / l: Silver nitrate (. in terms of silver) Copper nitrate £ in terms of copper) Thiourea Acetone.. Methanil yellow And / or gelatin 3.6-6 7-9.6 16-23 _Q 250-560 ml §