RU2386731C1 - Electrolyte for deposition of silver-indium alloy - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to electrolytic metallurgy. Electrolyte contains the following, g/l: caustic silver 15-25, indium sulphate 5-15, trilon B 30-40, boric acid 20-30, sodium dodecyl sulfate 0.2-0.3.

EFFECT: obtaining uniform lustrous coatings with high corrosion resistance and micro-hardness.

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Description

The invention relates to the field of electroplating, in particular to the electrolytic deposition of a silver-indium alloy.

Known electrolyte for the deposition of a silver-indium alloy containing silver chloride, indium sulfate, potassium ferricyanide, ammonium sulfate, potassium carbonate, polyethylene polyamine [1]. However, precipitation can be obtained from this electrolyte only at low current densities (0.2-0.8 A / dm ² ), moreover, they are characterized by low hardness (600-670 MPa) and corrosion resistance (0.2-0.3 g / m ² · h).

The result of the invention is the extension of the range of operating current densities and improving the quality of coatings (increasing their hardness and corrosion resistance).

The proposed electrolyte differs from the known one in that, in addition to silver and indium salts, it contains trilon B (ethylenediaminetetraacetic acid disodium salt) and additional boric acid and sodium dodecyl sulfate are added to its composition in the following ratio of components, g / l:

- silver nitrate - 15-25;

- indium sulfate - 5-15

- Trilon B - 30-40

- boric acid - 20-30

- sodium dodecyl sulfate - 0.2-0.3.

Trilon B binds silver and indium ions into strong trilonate complexes (logβ _Ag-EDTA = 7.32 and logβ _In-EDTA = 24.95), which prevents the hydrolysis of salts and improves the stability of the electrolyte.

The additional introduction of boric acid helps to increase the buffer properties of the solution, its electrical conductivity, and also improves the uniformity of the distribution of metal on the cathode.

Surfactant sodium dodecyl sulfate, adsorbed on the cathode, inhibits the recovery of metal ions, while improving the wettability of the coatings.

The electrolyte is prepared by dissolving silver, indium and trilon B salts in separate portions of water. Part of the trilon B solution is added with stirring to the silver salt solution, and the second half of the complexon is added to the indium salt solution. Mixtures of the solutions are left for 10-15 minutes for complete complexation, and then, slowly (with vigorous stirring), an indium complexonate solution is added to the silver complexonate solution. Boric acid and sodium dodecyl sulfate are added to the resulting mixture and the electrolyte volume is adjusted to working water.

The electrodeposition of the coatings is carried out at a cathodic current density of 0.5-1.5 A / dm ² , at a temperature of 20-25 ° C, pH 7.0-8.0 with stirring using a silver anode.

Specific examples of the use of electrolyte and some properties of the resulting coatings are presented in the table.

As a result of the use of the proposed electrolyte, the range of working current densities expands 1.5-2 times in comparison with the known electrolyte.

The microhardness of the coatings obtained from the proposed electrolyte is 15-20% higher than deposited from the known electrolyte. The corrosion rate of coatings deposited from the proposed electrolyte is 2-3 times lower than that obtained from a known solution.

Using the proposed electrolyte allows you to precipitate light, shiny, strongly bonded to the base coat. Precipitation withstands bending at an angle of 90 ° without kink and does not exfoliate from the base after heating at 250 ° C for 1 hour and subsequent sharp cooling.

Literature

1. Zakirova E.A., Tumbinsky V.A., Zaitseva L.V. Protection of metals, 1979, Vol. 15, No. 2, pp. 241-242.

Table The electrolyte compositions and properties of the resulting coatings Electrolyte components (g / l) and research results The composition of the examples one 2 3 Silver nitrate fifteen twenty 25 Sulphate Indium 5 10 fifteen Trilon B thirty 35 40 Boric acid twenty 25 thirty Sodium dodecyl sulfate 0.2 0.25 0.3 The current density, A / DM ² 0.5 1,0 1,5 Temperature ° C 20,0 22.5 25.0 Stirring rpm 60 60 60 pH 7.0 7.5 8.0 Current output,% 92 94 96 The indium content in the alloy,% 4.7 6.5 9,4 Microhardness, MPa 760 724 710 The corrosion rate, g / (m ² · h) 0.09 0.12 0.15

Claims (1)

An electrolyte for the deposition of a silver-indium alloy containing silver nitrate and indium sulfate, characterized in that it additionally contains trilon B, boric acid and sodium dodecyl sulfate in the following ratio of components, g / l:
silver nitrate 15-25 indium sulfate 5-15 Trilon B 30-40 boric acid 20-30 sodium dodecyl sulfate 0.2-0.3