CS230998B1 - Additive for galvanic zinc bath with low cyanide and zinc content - Google Patents

Abstract

The invention addresses the formulation of an additive to a galvanic bath for the deposition of semi-gloss zinc coatings, namely a bath with a low zinc and cyanide content, enabling the deposition of high-quality coatings. The additive is formed by a solution containing from 2 to 22 wt. % alkali silicates, from 0.2 to 18 wt. % polyetheralkylene alcohol, for example polyethylene glycol, from 0.3 to 12 wt. % ethyl vanillin, gel-forming additives, for example from 0.02 to 3 wt. % disodium salt of ethylenediaminetetraacetic acid, from 0.005 to 0.1 wt. % heterocyclic diazone, for example pyrimidine, from 0.001 to 0.5 wt. % heterocyclic diazone, for example pyrimidine, from 0.001 to 0.5 wt. % polyvinyl alcohol and up to 100 wt. % solvents, such as ethanol and water.

Description

Author of the invention ŠULC _{J1R1 ing>} , p _SAHA>

Happy marcela, bald over the lab

Addition to galvanic bath with low content of cyanides and zinc

The invention solves the formulation additives to the electroplating bath for the deposition of semi-zinc coating bath and _the low zinc cyanide and allowing secretion of high quality coatings. The additive comprises a solution containing from 2 to 22 wt. % alkali silicates, from 0.2 to 18 wt. % polyethylene glycol, for example polyethylene glycol, from 0.3 to 12 wt. from 0.02 to 3% by weight of ethylvanillin;

% disodium salt. % of ethylenediaminotetraacetic acid, from 0.005 to 0.1 wt. % heterocyclic diazone, for example pyrimidine, from 0.001 to 0.5 wt. % heterocyclic diazone, for example pyrimidine, from 0.001 to 0.5 wt. % polyvinyl alcohol and up to 100 wt. % solvents such as ethanol and water.

23Ο 998

230 998

BACKGROUND OF THE INVENTION The present invention relates to a low cyanide and zinc galvanizing bath additive for the deposition of semi-gloss zinc coatings.

Galvanizing baths with a high content of cyanides and zinc are known and widely used. Because of their cyanide content, these baths are ecologically unsuitable, waste water from operations where they are used, endangers the environment and their disposal is technically and economically demanding. Therefore, low-cyanide and zinc-containing zinc baths have been developed which, while having less buffering capacity and lower zinc current yield, substantially reduce the ecological hazards of the zinc process and bring savings in chemical consumption even in wastewater disposal. As additives to this type of galvanizing bath, in particular, substances formed by condensation between nitrogen heterocycles and epichlorohydrin or other compounds which are economically demanding are used. So far, this has made it difficult to use environmentally friendly galvanizing baths. Further, an additive containing available compounds is known; however, the bath with this additive is not suitable for universal use - both for bulk and pendant plating - and has a low elimination current density range.

The known additives for low-cyanide-zinc galvanizing baths are further improved by the additive according to the invention, which consists in that the additive consists of alkali metal silicates, for example sodium silicate,

230 998 in an amount of 2 to 22 wt. % of a polyetheralkylene alcohol, for example polyethylene glycol, in an amount of from 0.2 to 18 wt. % of a brightening agent, for example, disodium ethylenediaminotetraacetic acid, in an amount of 0.02 to 3 wt. %, with ethylvanillin in an amount of from 0.3 to 12 wt. %, heterocyclic diazone, for example pyrimidine, in an amount of from 0.005 to 0.1 wt. % and polyvinyl alcohol in an amount of from 0.001 to 0.5 wt. % based on the total weight of the additive; residue up to 100 wt. % are solvents such as ethanol and water.

The production of the additive is simple, does not require complicated synthesis, and thus brings energy savings during bath operation. The bath with the additive according to the invention has universal use for bulk and hinged metallization and has a wider range of coating deposition and / or coating over the known baths of this type. it operates at a wider range of current densities, from 0.5 to 7 A / dm. The polishes are semi-glossy when the dark film is clarified in both pendant and bulk plating. The bath is economical because it is composed of available raw materials and operates at temperatures from 20 to 35 ° C.

The invention is explained in more detail below with reference to specific embodiments thereof:

Example 1

To the galvanizing bath containing 6.8 g / l of zinc, 11 g / l of sodium cyanide and 52 g / l of sodium hydroxide, an additive according to the invention was added in an amount such that the silicate content was 1 g / l, polyethylene glycol 0.2 g / 1, disodium salts of ethylenediaminotetraacetic acid 0.01 g / l, ethylvanillin 0.2 g / l, pyrimidine 0.005 g / l and polyvinyl alcohol 0.002 g / l. The bath was tested and showed good excretion efficiency and hiding power.

Example 2 ²³⁰ 998

In the galvanizing bath containing 8.7 g / l of zinc, g / l of sodium cyanide and 67 g / l of sodium hydroxide, the additive according to the invention was applied so as to have a silicate content of 4.3 g / l, polyethylene glycol 3.5 g / l, disodium ethylenediaminotetraacetic acid 0.4 g / l, ethylvanillin 5.2 g / l, pyrimidine 0.041 g / l and polyvinyl alcohol 0.1 g / l. In laboratory testing, the bath showed good excretion efficiency and hiding power.

Example 3

To the galvanizing bath containing 8 g / l of zinc, g / l of sodium cyanide and 60 g / l of sodium hydroxide, the additive according to the invention was added in an amount such that the silicate content was 2.6 g / l, polyethylene glycol 1.7 g / 1, disodium

- salts of ethylenediaminotetraacetic acid 0.2 g / l, ethylvanillin 2.7 g / l, pyrimidine 0.23 g / l and polyvinyl alcohol 0.05 g / l. Laboratory tests have shown good performance and quality of coatings over a working temperature range of 20 to 35 ° C and a current density of 0.5 to 7 A / dm ² .

and

The bath with the additive according to the invention has universal use for bulk and hinged plating. It can be used in all galvanizing shops to make semi-gloss zinc coatings on various metal products.

SUBJECT OF THE INVENTION

Claims (1)

230 998 Addition to the low-cyanide-zinc galvanizing bath, characterized in that it consists of alkali metal silicates, for example sodium silicate, in an amount of from 2 to 22% by weight. % of a polyetheralkylene alcohol, for example polyethylene glycol, in an amount of from 0.2 to 18 wt. % of a brightening agent, for example disodium ethylenediaminotetraacetic acid in an amount of 0.02 to 3 wt. %, with ethylvanillin in an amount of from 0.3 to 12 wt. % heterocyclic diazone, for example pyrimidine, in an amount of 0.005 to 0.1 wt. % and polyvinyl alcohol shaved in an amount of from 0.001 to 0.5 wt% * based on the total weight of the additive; the remainder to 100 wt. they are solvents such as ethanol and water.