RU2487967C1 - Oxalate electrolyte for depositing copper-tin alloy - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: electrolyte for depositing a copper-tin alloy contains components in the following ratio, g/l: copper sulphate pentahydrate 20-25, tin sulphate 3-10, ammonium oxalate 45-55, sodium acetate 10-20, gelatine 0.1-0.5, vanilin 0.1-0.5, methylene blue 5·10^-5-1·10^-3 mol/l, water - up to 1 l.

EFFECT: high lustre, improved environmental properties and high stability of the electrolyte.

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Description

The invention relates to galvanic deposition of coatings with a copper-tin alloy with a tin content of 5-35% and can be used to deposit protective, decorative, corrosion-resistant coatings, and also as a sublayer.

Known cyanide, sulfate, stannate-cyanide, pyrophosphate, oxalic acid electrolytes for the deposition of copper-tin alloy [1-4].

The disadvantages of the known methods are: high environmental hazard, high concentration of components, operation at elevated temperatures, low stability.

The closest in characteristics of the deposited coating is an oxalic acid electrolyte having the following electrolyte composition, g / l: copper sulfate 20-25, tin sulfate 3-10, ammonium oxalate 45-55, boric acid 15-25, gelatin 0.1-0, 2, triethanolamine 0.3-0.5, water up to 1 l [3].

However, oxalic acid electrolyte is characterized by low coating quality, high content of substances difficult to decompose in wastewater (boric acid) and the need for frequent adjustments as a result of partial tin oxidation.

The technical result of the proposed electrolyte is the deposition of protective and decorative, wear-resistant with a low value of transient electrical resistance of mirror-shiny coatings with a copper-tin alloy. The need for frequent adjustment of the electrolyte disappears, the environmental safety of the electrolyte increases.

This is achieved by the fact that an oxalic acid electrolyte for the deposition of a copper-tin alloy containing copper sulfate pentahydrate, tin sulfate, gelatin and water according to the invention, additionally contains methylene blue, vanillin, sodium acetate in the following ratio, g / l: copper sulfate pentahydrate 20-25; tin sulfate 3-10; ammonium oxalate 45-55; sodium acetate 10-20; gelatin 0.1-0.5, vanillin 0.1-0.5; methylene blue 5 · 10 ^-5 -1 · 10 ^-3 mol / l; water up to 1 liter

Comparative analysis with the prototype allows us to conclude that the inventive electrolyte differs from the known introduction of new components, namely sodium acetate, vanillin, methylene blue.

Table 1 shows the dependence of the change in the concentration of Sn (IV) on the concentration of methylene blue.

Table 1 The dependence of changes in the concentration of Sn (IV) on the concentration of methylene blue The concentration of additives, mol / l Q, A · h / l 0 one 5 10 fourteen 0 (no supplementation) C _{Sn (IV)} , mol / L 0.02 0.02 0.06 0.09 0.1 5 · 10 ^-5 C _{Sn (IV)} mol / L 0 0.012 0,035 0,038 0,038 2.5 · 10 ^-4 C _{Sn (IV)} mol / L 0 0.005 0.0076 0.0076 0.0075 5 · 10 ^-4 C _{Sn (IV)} mol / L 0 0.002 0 0 0.002 1 · 10 ^-3 C _{Sn (IV)} mol / L 0 0 0 0 0

It is important to note that methylene blue is not consumed during the deposition of the alloy, since the additive is regenerated at the cathode. From table 1 it is seen that with an increase in the additive, the oxidation rate of Sn (II) decreases and at C _add = 10 ^-4 mol / L, the process of oxidation of divalent tin does not occur. Therefore, the optimal concentration of the additive With _add = 10 ^-4 mol / L. Another feature of the additive is that when it is present in the electrolyte, the coatings are more shiny than in the prototype electrolyte.

The use of vanillin as a brightener provides a specular gloss at a current density of 0.5 A / dm ² .

Thus, the use of electrolyte can increase the stability of the electrolyte, improve the decorative properties of the coating, and also improve its environmental properties.

The electrolyte is prepared as follows.

In a container, 55 g of oxalic ammonium ammonium are dissolved in water at a temperature of 60 ° C, 0.2 g of gelatin in the form of a solution in warm water, 20 g of copper sulfate and 15 g of sodium acetate are added with vigorous stirring. Then enter 5 · 10 ^-4 mol / l of methylene blue, 0.1 g of vanillin. Tin sulfate is introduced in an amount of 6 g and is intensively mixed. Then the volume of the resulting solution was adjusted to 1 liter and cooled to room temperature. The desired pH = 5 is adjusted using oxalic acid or ammonia solution.

The prepared electrolyte has the following composition, g / l:

copper sulfate pentahydrate twenty tin sulfate 6 oxalic ammonium 55 sodium acetate fifteen vanillin 0.1 methylene blue, mol / l 5 · 10 ^-4 water up to 1 l temperature, 20 ° C cathodic current density, A / dm ³ 0.2-0.7

Examples with different concentrations of the inventive electrolyte are shown in table 2.

table 2 Examples of the composition of an oxalic acid electrolyte of a copper-tin alloy Electrolyte composition Electrolyte number one 2 3 4 (prototype) five-water copper sulfate twenty twenty twenty 23 tin sulfate 3 6 10 5 oxalic ammonium 55 55 55 fifty boric acid - - - twenty sodium acetate fifteen fifteen fifteen - gelatin 0.2 0.2 0.2 0.15 vanillin 0.1 0.1 0.1 - methylene blue, mol / l 5 · 10 ^-4 5 · 10 ^-4 5 · 10 ^-4 - triethanolamine - - - 0.4

A copper-tin alloy was applied to copper or copper alloys. The quality of the coatings obtained by the copper-tin alloy was evaluated in appearance in accordance with the requirements of GOST 9.301-86. To determine the stability of the electrolyte, a series of electrolyte generation cycles were performed. It turned out that if methylene blue is introduced into the oxalic acid electrolyte, it becomes more stable compared to the prototype. With the passage of 30 Ah in the electrolyte, no changes in the appearance of the coating were observed. The electrolyte does not contain substances that create an increased environmental hazard.

Thus, the proposed electrolyte allows to obtain coatings with a copper-tin alloy, the quality of which meets the requirements of the above standards and during the operation of the electrolyte does not undergo irreversible changes that violate its stability. An additional advantage of the electrolyte compared with the prototype is higher environmental safety, better appearance of coatings, includes a lower concentration of components, which reduces its cost.

Information sources:

1. Electroplating coatings in mechanical engineering. Directory. In 2 volumes / Ed. M.A.Shluger. - M .; Engineering, 1985.

2. V.V. Bondar, V.V. Grinitsa, V.N. Pavlov. Electrodeposition of double alloys. (Results of science and technology), 1979, 16, 329 p.

3. RF patent, 09/17/1997 05/20/1999, Lukomsky Yu.Ya., Kunina OL, Electrolyte bronzing, Russian patent No. 2130513 97115437/02.

4. Electrolytic deposition of alloys / Ed. V.A. Averikin. - M .: Mashgiz, 1961.

Claims (1)

An oxalic acid electrolyte for the deposition of a copper-tin alloy containing copper sulfate pentahydrate, tin sulfate, ammonium oxalate, gelatin and water, characterized in that it additionally contains sodium acetate, vanillin, methylene blue in the following ratio, g / l:
copper sulfate pentahydrate 20-25 tin sulfate 3-10 oxalic ammonium 45-55 sodium acetate 10-20 gelatin 0.1-0.5 vanillin 0.1-0.5 methylene blue, mol / l 5 · 10 ^-5 -1 · 10 ^-3