SU1675396A1 - Electrolyte for cadmium plating - Google Patents

Abstract

The invention relates to the field of electroplating, in particular to electrolytic cadmium plating, and can be used in mechanical engineering, instrument-making and electronics industries. The purpose of the invention is to expand the range of operating current densities, increase the current output and scattering power. The cadmium electrolyte contains, g / l: cadmium oxide 25 40; Trilon B 100-140; sodium pyrophosphate 25-30. sodium tetrabornic acid sodium chloride 18-23. The introduction of ndtree tetraborate, sodium pyrophosphate and sodium chloride into the electrolyte allows us to expand the range of operating current densities (from 0.5 to 8 A / dm), increase the current efficiency (to) and the scattering ability (to 85,%). 2 tab.

Description

with

with

The invention relates to electroplating, in particular to electrolytic cadmium plating, and can be used in machine-building, instrument-making and electronics industries.

The purpose of the invention is to expand the range of operating current densities, increase the current efficiency and the scattering ability of the electrolyte.

Cadmium electrodeposition is carried out in an electrolyte containing, g / l: cadmium oxide 25-40

Trilon B100-140

Sodium Pyrophosphate25-30

Sodium tetraborate25-30

Sodium Chloride18-23

rn 10-12

The mode of electrodeposition is a temperature of 18–40 ° C, DK 0.5–8 A / dm2.

The introduction of the electrolyte composition of tetraborate and sodium pyrophosphate provides for the presence in the solution of ethylene diamine tetra acetate complex of cadmium complexes of pyrophosphate and tetraborate at the same time. In the process of electrolysis, this leads to an increase in cathodic polarization at low current densities (on the order of 0.5-1 A / dm) and its decrease with an increase in DK above 6 A / dm, which contributes to the expansion of the current density range and an increase in scattering power. In addition, tetraborate and sodium pyrophosphate are simultaneously buffer additives, which is important for maintaining a pH of 10–12, since a stable cadmium trilonate complex exists at pH 10, and

With VJ

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CJ

yoo o

pH 12 increases cathodic polarization and decreases deposition rate.

The addition of sodium chloride shifts the cathode potential towards less electronegative values by 25–30 mV, facilitating the discharge of cadmium ions at the cathode, which was established when removing polarization curves by the compensation method

The electrolyte is prepared as follows.

In half of the calculated amount of water heated to 30–40 ° C, trilon B is dissolved in which cadmium oxide is poured into the solution in small portions, intensively mixed after each addition until complete dissolution. Sodium tetraborate, sodium pyrophosphate and sodium chloride are dissolved in the remainder of the water. The resulting solutions are poured into the electrolyzer and the pH is adjusted to the desired value with hydrochloric acid or sodium hydroxide.

The compositions of the proposed electrolyte are presented in table. one.

Bonding quality is checked by applying a scratch mesh. The scattering ability is measured by the angular cathode method. The porosity of the coatings is determined by applying a filter paper.

Conducted corrosion resistance test.

The current output is measured by the coulometric method.

The results are summarized in table. 2

From the proposed electrolyte, dense, light, crystalline precipitates are obtained, at O 1-8 A / dm2, non-porous at a thickness of 3 µm and higher, which makes it possible to reduce the thickness of the coating and significantly save the extremely deficient cadmium.

The coatings obtained from the proposed electrolyte, due to their low porosity, have an increased corrosion resistance, which makes it possible to apply them in the conditions of the marine and tropical climate, as well as in the conditions of the industrial atmosphere containing aggressive gases and dust.

The dispersing ability of the electrolyte is 76-85% at a current efficiency of 98.2-100%.

Claims (1)

Invention Formula The cadmium electrolyte containing cadmium oxide and trilon B, is used in this case. in order to expand the range of operating current densities, increase current efficiency and scattering power, it additionally contains sodium pyrophosphoric acid, sodium tetraborate and sodium chloride in the following ratio of components, g / l: cadmium oxide 25-40 Trilon B100-140 Sodium Pyrophosphate25-30 Sodium tetraborate25-30 Sodium Chloride18-23 Table 1 T a 6 l and c j 7