RU1770458C - Electrolyte for bright galvanizing - Google Patents

Abstract

Usage: protection against corrosion of parts of the automotive, radio engineering, electronic industries. The composition of the galvanizing electrolyte, g / l: zinc salt 30-200, sodium chloride 100-200, boric acid 10-40, nonionic surfactant 5-25, carboxyl compound 1-10. Carbonyl compound 0.05-1.0. aminoacetic acid 0.5-10.0. glutamic acid or its derivative or a mixture thereof. 2 tab.

Description

The invention relates to the field of electroplating, in particular to the deposition of zinc coatings, and can be used in the automotive, radio engineering, electronic industries.

Various electrolytes are used for the deposition of zinc coatings, among which, in the USSR and in industrialized countries, weakly acidic electrolytes of brilliant galvanizing are widely used. The advantage of these electrolytes is a high deposition rate, good hiding and scattering abilities of the electrolyte, exceptional gloss and micro-uniformity of zinc coatings deposited from this electrolyte. These properties of electrolytes are largely determined by the brightening composition, which includes several components, usually a nonionic surfactant, carboxylic, carbonyl compound, etc. A characteristic feature of these electrolytes is that the concentration of the brightening composition is 10-15 g / l. which is significantly higher than that of cyanide and alkaline non-cyanide electrolytes. Another feature of weakly acidic electrolytes of brilliant galvanizing is that the deposited zinc coating contains a large number of ingredients, in particular carbon, the amount of which is 0.95% 1. A high concentration of carbon in the coating, as well as other impurities, is malignant in electroplating, unless the coating is alloyed to impart any specific properties to the deposit.

So. increasing the carbon concentration in the coating increases the hardness of the coating.

It should also be noted that the majority of electrolytes of weakly acid galvanized in the Soviet Union are used as. for example DKhTI-102 (Dnepropetrovsk Chemical-Technological Institute) VSHI-1 (Voroshilovgrad Agricultural Institute). Likonda ZnSR Limeda SC, Limeda OC (Institute of Chemistry and Chemical Technology, Vilnius) and others have ammonium chloride and res.co potassium chloride (Limeda NC electrolyte). This is from VJ VJ

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also applies to the processes of foreign firms - Excellux (Schering, Germany), Kenvel P (firm ZM, USA), etc. Moreover, there, according to 2, where 20 processes of brilliant galvanizing are described - in all formulations, ammonium or potassium chloride is used as the conductive salt. Taking into account the scarcity of these salts, the development of a brilliant galvanizing electrolyte based on sodium chloride, a cheap non-deficient material, is very urgent.

The objective of the proposed technical solution is the development of a sodium chloride-based brilliant galvanizing electrolyte, which makes it possible to deposit shiny soft zinc coatings in a wide range of current densities.

The galvanizing electrolyte was developed jointly with the electrochemists of the Republic of Romania, who were given a similar task and therefore the work was carried out in the framework of bilateral cooperation between countries on the topic U.3.1.4. concentration of potassium salts. As for ammonium salts, their use is currently problematic, because the maximum permissible concentration in water bodies (MAC) for ammonium ion (NH is 2 mg / L, for C 300 mg / L, K 50 mg / L and Na + 120 mg / L 3.

The use of sodium chloride in traditional galvanizing electrolytes instead of ammonium or potassium chloride leads to a narrowing of the range of current densities at which brilliant coatings are deposited 4. Therefore, the technical solution proposed jointly with the Republic of Romania was the development of a slightly acid brilliant galvanized electrolyte to precipitate coatings in a wide range of current densities.

A brilliant galvanizing electrolyte 5 is known which contains zinc salt, ammonium chloride, nonionic surfactant. carboxyl and carbonyl compounds, as well as M-picolin oxide 5. Glossy zinc coatings are deposited from this electrolyte in a wide range of current densities, but the electrolyte contains ammonium ions and a large amount of carbon 0.8-0 is included in the zinc coating. 9%, and the coatings are relatively hard, reaching 100 kg / cm or more.

The closest to the proposed invention in terms of technical nature and the achieved effect is a galvanizing electrolyte 6 containing a zinc salt.

alkali metal salt, boric acid, nonionic surfactant, carboxylic and carbonyl compounds, as well as amino acid and its salt. Precipitated from this electrolyte.

shiny zinc coatings at current densities from 0 to 18 A / dm (in a Hull cell with a volume of 267 ml),

The disadvantage of this electrolyte is that the zinc coating deposited

of this solution is relatively solid, reaching at 2 A / dm2 116 kg / cm2. The purpose of the invention is the deposition of brilliant zinc coatings in a wide range of current densities.

hardness.

This goal is achieved by the fact that in the known brilliant galvanizing electrolyte containing zinc salt, sodium chloride, boric acid, nonionic surfactant,

carboxylic and carbonyl compounds, aminoacetic acid, utlutamic acid or its derivative of the general formula is introduced:

° i hsoon soon-s-sn2-sn

R, - H2

where RI is H. -HE; R2 — H, —CH3, with the following content of components (g / l):

Zinc Salt30-200

Sodium Chloride 100-200

Boric acid 10-40

Nonionic surfactant 5-25

Carboxyl compound 1-10 5 Carbonyl compound 0.05-1.0

Aminoacetic acid 0.5-10.0 y-Glutamic acid or its derivative of the general formula 0.05-0.5

sooL-sngsnSO ° N

0

R.

 NH

or a mixture thereof

, - Zinc chloride and / or zinc sulfate are used as the zinc salt. Nonionic surfactants can be: a copolymer of ethylene oxide and propylene, for example laprol 2402C; an ethoxylated higher alcohol, for example ALM-10 syntanol, and / or an ethoxylated higher phenol, for example, OP-10 excipient. As carbonyl compounds, benzoic, salicylic or

5 phenylacetic acid, and from carbonyl derivatives - benzylideneacetone. furfurilideneacetone or p-methoxybenzylideneacetone.

As an additional additive use: y-glutamic acid

 soon nsoo-s-sn2-sn

y-hydroxyglutamic acid / nocoo-c-sn2-sn

,

12

y-hydroxy-y-methyl-glutamic acid

n / soon nsoo-s-sn, -sn

CH3 NH2

or y-methylglutamic acid

N

nsoo-s-sno-sn

soon

sn.

 NH

or a mixture thereof. The electrolyte is prepared in series

dissolving sodium chloride, boric acid and zinc salt in a separate container. Then, a surfactant prepared previously as a 20% solution is added. After that, aminoacetic acid, a carboxylic compound and an amino derivative are sequentially introduced. The carbonyl compound is dissolved in ethanol (10% solution) and added to the electrolyte with continuous stirring. From the electrolyte thus prepared at pH 5.0-6.2, completely shiny zinc coatings are deposited at current densities of 0.1-5.0 A / dm2 (cathode rod movement). Zinc coatings have a high degree of gloss - 80-90% relative to the silver mirror, relative to soft 65-80 kg / mm. The current efficiency is 94-99% at current densities of 5.0-0.1 A / dm. Correction is made according to analysis - for basic salts and for additives by the amount of transmitted electricity. Correction is carried out after passing 3-4 A / L of electrolyte through the solution. On the basis of the studies, the Soviet-Romanian additive Limeda L RC was developed, consisting of two brighteners Limeda LRTS-1 and Limed LRTs-2 (TU 88 LitSSR 67-88),

the production of which has been mastered at the Institute's Experimental and Experimental Base. The electrolyte was introduced at the Novopolotsk plant Meter.

The table shows the composition of various

electrolytes, solution parameters and some physical and mechanical properties of coatings,

As can be seen from the table, amino derivatives introduced into the electrolyte allow

obtain brilliant zinc coatings in a wide range, characterized by reduced hardness.

An advantage of the electrolyte is that. that all additives are produced by industry of the USSR and Romania, which made it possible to jointly produce a bright-forming composition and introduce electrolyte into production.

Claims (1)

The claims Brilliant galvanizing electrolyte containing zinc salt, sodium chloride, boric acid, nonionic surfactant. a carboxyl compound, a carbonyl compound, aminoacetic acid, and the like. that, in order to reduce the hardness of zinc coatings, it additionally contains y-glutamic acid or its derivative of the general formula , nsso s sngsn where RI —H, —OH: R2 —H, —CH3. or a mixture thereof at the following combination of components, g / l: zinc salt -30-200: Sodium Chloride -100-200: boric acid - 10-40 non-inogenous surfactant -5-25: carboxylic compound 1-10: carbonyl compound 0.05-1.0; aminoacetic acid - 0.05-10.0: y-glutamic acid. or a derivative of the formula. or a mixture thereof -0.05-0 5. .soon Table continuation