RU2346088C1 - Electrolyte for indium deposition - Google Patents

Abstract

FIELD: metallurgy, electrolysis.

SUBSTANCE: invention concerns field of galvanostegy and can be used at plating made of indium. Electrolyte contains, g/l: sulfuric indium 20-40, acetous ammonium 30-40, trilon B 40-50, sodium dodecyl sulfate 0.1-0.3, thiourea 0.3-0.5.

EFFECT: hardening and increasing of corrosion stability of coatings.

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Description

The invention relates to the field of electroplating, in particular, to electrolytic deposition of indium.

Known electrolyte for precipitation of indium containing indium sulfate and ammonium, Trilon B (ethylenediaminetetraacetic acid) [1]. However, rough matte dark gray coatings with a coarse-grained structure with a microhardness of up to 120 MPa and a corrosion rate of 0.1 N are deposited from the indicated electrolyte. a solution of sulfuric acid 0.30-0.36 g / (m ² · h).

The objective of the invention is the development of an index electrolyte for coatings with increased values of hardness and corrosion resistance.

The proposed electrolyte differs from the known one in that, in addition to indium, ammonium and trilon B salts, it additionally contains surface-active additives — sodium dodecyl sulfate and thiourea, as it contains ammonium acetate in the following ratio, g / l:

- indium sulphate 20-40;

- Trilon B 40-50;

- ammonium acetate 30-40;

- sodium dodecyl sulfate 0.1-0.3;

- thiourea 0.3-0.5.

The introduction of ammonium acetate instead of sulfate improves the stability of the electrolyte, increasing its conductivity and buffering properties. A surfactant, sodium dodecyl sulfate, adsorbed on the cathode inhibits the recovery of metal ions, while improving the wettability of the precipitates, which leads to an increase in the uniformity of the distribution of metal on the surface of the cathode and to improve the quality of the coatings. The addition of thiourea to the electrolyte increases the polarization of the cathode, grinds the structure of sediments and reduces their porosity.

The electrolyte is prepared by dissolving the indium salt and trilon B in separate portions of water. The trilon B solution is introduced with stirring into the resulting metal salt solution, left for 10-15 minutes until complete formation of the complexes. Ammonium acetate, sodium dodecyl sulfate and thiourea are added to the resulting mixture, and then the volume of the electrolyte is adjusted to the working medium with distilled water.

The electrodeposition of coatings (thickness) is carried out at a cathodic current density of 1-3 A / dm ² , a temperature of 20-25 ° C, pH 8-10 using a lead anode.

Specific examples of the use of electrolyte and some properties of the resulting coatings are presented in table 1.

Due to the introduction of surface-active additives in the electrolyte, the quality of the coatings sharply improves: they become light, fine-crystalline, dense and shiny. The microhardness of coatings obtained from the proposed electrolyte is 25-35% higher than coatings deposited from a known electrolyte. The corrosion rate is 15-20% less than that of coatings deposited from a known electrolyte.

Using the proposed electrolyte allows you to get bright, shiny, firmly adhered to the steel base coatings that withstand bending at an angle of 45 ° without kink and do not exfoliate from the base after heating to 250 ° C for 1 hour and subsequent sudden cooling.

LITERATURE

1. Azhogin F.F., Belenky M.A. and others. Electroplating. Reference Edition. - M.: Metallurgy, 1987.736 p.

Electrolyte components and their composition Electrolyte components (g / l) and research results The composition of the examples one 2 3 Sulphate Indium twenty thirty 40 Trilon B 40 45 fifty Ammonium Acetate thirty 35 40 Sodium dodecyl sulfate 0.1 0.2 0.3 Thiourea 0.3 0.4 0.5 The current density, A / DM ² one 3 5 Temperature ° C 20,0 22.5 25.0 Stirring rpm 60 60 60 pH 8 9 10 Current output,% 98 97 96 Microhardness, MPa 150 165 175 The corrosion rate, g / (m ² · h) 0.28 0.24 0.25 Appearance of coatings Light, dense Bright, shiny Light gray, semi-shiny

Claims (1)

An electrolyte for precipitation of indium, including indium and ammonium salts, trilon B and water, characterized in that it additionally contains sodium dodecyl sulfate and thiourea, and as indium and ammonium salts, sulfuric acid indium and acetic acid ammonium in the following ratio of components, g / l:
sulfuric acid indium 20-40 acetic acid ammonium 30-40 Trilon B 40-50 sodium dodecyl sulfate 0.1-0.3 thiourea 0.3-0.5