RU2365683C1 - Sulphosalicylate electrolyte for sedimentation of copper-nickel alloy - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to field of electrolytic metallurgy and can be applied for electrosedimentation of protective-decorative coatings with copper-nickel alloy. Electrolyte contains, g/l: copper sulfate five-water 7-20, nickel sulfate seven-water 30-70, sulphosalicylic acid two-water 60-90, ammonium sulfate 5-25, ammonium hydroxide (30% water solution of ammonium) 3-7, saccharine 0.5-1.5.

EFFECT: increase of productivity, increase of glitter, cohesion of coatings with base.

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Description

The invention relates to galvanic deposition of coatings with a copper-nickel alloy with a copper content of 15-80% and can be used to deposit protective-decorative, corrosion-resistant coatings and to reduce the transient electrical resistance of low-current contacts.

Known cyanide, thiosulfate, nitrate, pyrophosphate, tartrate-pyrophosphate, trilonate, sulfate and ammonia electrolytes for the deposition of copper-nickel alloy [1-4].

A disadvantage of the known methods is the difficulty of deposition of thick (over 5 μm) shiny coatings with decorative properties, high environmental hazard (cyanide), low current efficiency (thiosulfate), the need to mix the electrolyte during operation (pyrophosphate, trilonate), low productivity.

The closest to the characteristics of the deposited coating is a pyrophosphate electrolyte having the following electrolyte composition, g / l: nickel (in terms of metal) 100, copper (in terms of metal) 6-7, potassium pyrophosphate (free) 65-70, Rochelle salt 25-30 [2].

However, pyrophosphate electrolyte is notable for its complexity in preparation and high concentration of potassium pyrophosphate (450 g / l) for the complexation of metal ions, which significantly increases the cost of production and the environmental hazard of galvanic wastewater. The electrolyte is characterized by low productivity, the working current density is 0.5-1.0 A / sq. Dm, the current efficiency is 80%. When the bath is working, stirring is necessary.

The technical result of the proposed electrolyte is the deposition of shiny high-performance copper-nickel coatings that are well bonded to the base. So the working current density is 1.5-2.5 A / dm.sq., the current output is over 90%. The concentration of sulfosalicylic acid for the complexation of metal ions is 80 g / l.

Thus, the use of sulfosalicylate electrolyte can improve the performance of the electrodeposition process, as well as obtain well-adhered shiny coatings with a copper-nickel alloy over 10 microns.

This is achieved by the fact that sulfosalicylic electrolyte for the deposition of a copper-nickel alloy containing copper sulfate pentahydrate, nickel sulfate seven-water, according to the proposed invention additionally contains sulfosalicylic acid two-water, ammonium sulfate, ammonium hydroxide and saccharin, in the following ratio, g / l: sulfate copper pentahydrate 7-20, nickel sulfate heptahydrate 30-70, sulfosalicylic acid two-water 60-90, ammonium sulfate 5-25, ammonium hydroxide (30% aqueous ammonia solution) 3-7, saccharin 0.5-1.5.

The mechanism of action of sulfosalicylic acid is the formation of complex compounds with metal ions in the electrolyte, which leads to the convergence of the potentials of the restoration of metal ions at the cathode. For copper, logK ₁ = 9.52, logK ₂ = 16.45; for nickel, logK ₁ = 6.61, logK2 = 10.81 [5].

Solutions with signs of the claimed electrolyte are not identified.

To study the effect of the concentration of copper ions in the electrolyte on the composition of the deposited alloy, four aqueous electrolytes were prepared, the compositions of which are given in table 1.

The electrolyte was prepared as follows.

In separate containers, these components are dissolved, then the solutions of copper and nickel salts are mixed. Dissolved sulfosalicylic acid is poured into the resulting solution and mixed. The resulting mixture is neutralized by the gradual addition of a solution of ammonium hydroxide, producing continuous stirring, until a dark green solution is formed and the pH is adjusted to 7.2-7.5. At the end, a saccharin solution is introduced, and the electrolyte is brought to the required volume. The pH of the obtained electrolyte is checked and, if necessary, adjusted with a solution of ammonium hydroxide or sulfuric acid, using stirring, after which the prepared electrolyte is kept in a sealed container, opaque to light, or in a dark place for a week. Before use, adjust the pH as described above.

Table 1. The compositions of electrolytes. Components Electrolyte Electrolyte Electrolyte Electrolyte No. 1 Number 2 Number 3 Number 4 Copper sulfate pentahydrate 7 10 fifteen twenty Nickel Sulphate fifty fifty fifty fifty Sulfosalicylic acid 80 80 80 80 Ammonium sulfate 10 10 10 10 Ammonium hydroxide (30% aqueous ammonia) 4,5 4,5 4,5 4,5 Saccharin one one one one

The electrolysis was carried out in a bath of 0.5 l at an electrolyte temperature of 30-60 ° C, a cathodic current density of 0.5-3.0 A / dm ² , pH = 6.0-8.0 with a ratio of the working surface of the cathodes and anodes 1 :5.

As anode material, it is recommended to use a copper-nickel alloy or copper. The use of nickel anodes is undesirable, since their passivation has been identified.

Data on the effect of the concentration of copper ions in the electrolyte and the cathode current density on the composition of the deposited alloy are shown in table 2.

table 2 The effect of the concentration of copper in the electrolyte on the composition of the deposited alloy. The current density, A / DM ² The copper content in the deposited alloy,% The concentration of Cu ²⁺ in the electrolyte, M 0,028 0.04 0.06 0.08 0.5 63 85.7 90 94.3 1,0 35,4 52,2 68.3 83 1,5 26.5 43 34 thirty 2.0 19 34 45.7 53 2.5 16.5 thirty 42 46.7 3.0 16 25.6 37.8 43.0

As can be seen from table 2, with increasing concentration of copper salt in the electrolyte increases the proportion of copper in the deposited alloy in the entire range of working current densities. The general pattern of a change in the proportion of copper in the deposited alloy with a change in the cathode current density at different contents of copper salt in the electrolyte is traced. With increasing current density, a decrease in copper in the deposited alloy is observed, which is associated with a shift in the cathode potential towards negative values.

Table 3 presents data on the effect of electrolyte temperature on the composition of the deposited alloy.

As can be seen from the data in Table 3, an increase in the temperature of the electrolyte leads to an increase in the fraction of copper in the deposited alloy, which is associated with a shift in the cathode potential toward positive values. The temperature also affects the appearance of the coating, shiny alloy coatings are deposited at a temperature of 45-50 ° C and a current density of 1-2 A / dm. Electrodeposition is recommended at a temperature of 50 ° C, providing a brilliant appearance of the coating.

Table 3 The effect of electrolyte temperature on the composition of the precipitated alloy. Current density A / dm ² The copper content in the deposited alloy,% Electrolyte temperature, ° С thirty 40 fifty 60 0.5 50,2 56 85.7 99 1,0 34.7 37.8 52,2 71.7 1,5 27 28.5 43 48.6 2.0 22.2 23.7 34 40 2.5 21.1 24.7 thirty 34.2 3.0 19 twenty 25.6 thirty

Data on the effect of pH of the electrolyte on the composition of the deposited alloy are presented in table 4.

Table 4 The effect of electrolyte pH on the composition of the precipitated alloy. The current density, A / DM ² The copper content in the alloy,% electrolyte pH 6.0 6.5 7.0 7.50 8.0 0.5 87 86 85.7 87 86.6 1,0 58.8 53.9 52,2 54 64,4 1,5 46 45.7 43 45.7 50.1 2.0 35 34.6 34 37.7 41.3 2.5 32,5 28.9 thirty 32,7 34.6 3.0 28,2 27.3 25.6 29.5 31.6

As can be seen from table 4, a change in the pH of the electrolyte practically does not affect the composition of the deposited alloy. Shiny coatings with a copper-nickel alloy precipitate at pH 6.5-7.5.

Sulfosalicylic electrolyte is characterized by a current efficiency of 90-95%, depending on the composition of the deposited alloy. With increasing concentration of copper salt in the electrolyte, the current efficiency increases.

The scattering capacity of the sulfosalicylic electrolyte, measured in the Moler cell, was 43% for the metal.

The internal stresses measured by the flexible cathode method strongly depend on the composition of the deposited alloy and vary on internal compression stresses, when the copper content in the alloy is above 60% to tensile stresses, when the copper content is below 60% in the alloy. However, they remain relatively low and amount to 100-200 MPa, which is relatively lower than for pure nickel. The deposited copper-nickel alloy in the region of zero internal stresses has a shiny glossy appearance of light color.

The values of transient electrical resistance of the coatings with the alloy at a current of 10 mA range from 0.008-0.034 Ohms with a contact load of 2.0 to 0.2 N, respectively. With an increase in the nickel content, it decreases, but with a load of 1 N or higher, the electrical resistance is almost equal for alloys with a composition of 35-80% copper.

Thus, the use of sulfosalicylic acid allows the deposition of thick, well-bonded shiny coatings with a copper-nickel alloy without mechanical mixing of the electrolyte.

Information sources

1. Fedotiev N.P., Bibikov N.N., Vyacheslavov P.M., Griliches S.Ya. Electrolytic alloys. M., Mechanical Engineering, 1962.312 p.

2. Vyacheslavov P.M. Electrolytic deposition of alloys. Ed. 5th, rev. and add. - L .: Engineering, Lehning. Separation, 1986. - 112 p., Ill. - (B-galvanic engineering; Issue 5).

3. V.V. Bondar, V.V. Grinina, V.N. Pavlov. Electrodeposition of double alloys. (Results of science and technology), 1979, 16, 329 pp., Bibl. 1106.

4. Patent RU 2106436 C1.

5. Lurie Y. Yu. Handbook of analytical chemistry. 5th ed., Revised. and add. - M .: Chemistry. 1979.- 480 p., Ill.

Claims (1)

Sulfosalicylate electrolyte for the deposition of a copper-nickel alloy containing copper sulfate pentahydrate, nickel sulfate heptahydrate, characterized in that it additionally contains sulfosalicylic acid two-water, ammonium sulfate, ammonium hydroxide, saccharin in the following ratio of components, g / l:
Copper sulfate pentahydrate 7-20 Nickel Sulphate 30-70 Sulfosalicylic acid, two-water 60-90 Ammonium sulfate 5-25 Ammonium hydroxide (30% aqueous ammonia) 3-7 Saccharin 0.5-1.5