CS254436B1 - Additive to weakly acidic zinc baths, which increases leveling and gloss levels - Google Patents

Abstract

The additive consists of compounds of the general formula 1, where R 1 , R 2 - H-, x-alkyl, where χ = 1 to 9, with a straight or branched chain, R 3 - y-alkyl, where y = 1 to 16 with a straight or branched chain, phenyl, 1-naphthyl, 2-naphthyl, mono-, di- or tri-alkylphenyl, mono-, di- or tri-alkoxyphenyl and n = 0 to 10, which may be contained alone or in mixtures. In combination with aromatic aldehydes and ketones, it increases the leveling and gloss level in areas of low current densities of less than 30 A per m 2 during galvanic zinc plating in weakly acidic baths. It acts only after processing by passing an electric current of 3 to 5 A . h per 1000 ml of bath. The optimal concentration ranges from 0.0001 to 0.05 g per 1000 ml. It is advisable to add it to gloss-forming additives, which, when regularly dosed, ensures its optimal concentration in the solution.

Description

(54) Additive to weakly acid galvanizing baths to increase leveling and gloss levels' (51) Int. Cl. ⁴

C 25 D 3/22

CS 254 436 B1 (57) The additive consists of compounds of the general formula 1 in which R ₁ , R ₂ - H-, x-alkyl, where χ = 1 to 9, both straight-chain and branched, R ₃ -y-alkyl, where y = 1 to 16 with both straight and branched chain, phenyl, 1-naphthyl,

2-naphthyl, mono-, di- or tri-alkylphenyl, mono-, di- or tri-alkoxiphenyl and n = 0 to 10, which may contain alone or in mixtures. Combined with aromatic aldehydes and ketones, the equalization r _x - n - (ch ₂ ) _d - ch = ch - o - Rj (i) and the gloss level in low current ¹ densities less than 30 A per m ² when galvanizing weakly acid baths. It only works after being processed by a current of up to 5 A. h per 1000 ml bath. The optimum concentration ranges from 0.0001 to 0.05 g per 1000 ml. It is advisable to add it to the brightening agents to ensure optimum concentration in the solution at regular dosing.

R 1 - N - (CH ₂ ) _n - CH = CH - O - R ₃ (1) ^R 2

The invention relates to an additive for weakly acidic zinc baths containing ammonium salts, i.e. based on zinc chloride or sulphate, ammonium chloride or acetate, or both or without ammonium salts, i.e. based on zinc chloride or sulphate, sodium or potassium chloride and acid borates in various proportions and containing brighteners based on aromatic ketones or aromatic aldehydes and ketones.

A number of woodcutting agents containing aromatic aldehydes and ketones have been proposed in the past, but the common drawback of all is that when applied in weakly acid galvanizing baths they have a relatively low leveling ability in the region of very low current densities, which is associated with low gloss levels of zinc coatings. in electrically shielded areas of plated objects. This feature is not a problem with plating on hinges, as it is usually operated at higher current densities and perfect shading is not required in shielded areas. However, in the case of mass plating in drums, there is often a situation where the capacity of the current sources used is not sufficient, in particular for the plating of small goods with a large total area, and the electrolysis proceeds at a very low current density. For goods with high demands on the appearance of coatings, the desired quality cannot be achieved even at high concentrations of brighteners. The described problem has been solved by designing other types of brightening agents, which however need to be prepared by complex syntheses, which disproportionately increases their cost.

This deficiency is eliminated by an additive according to the invention, the essence of the invention being that it consists of compounds of the general formula

R - N - (CH) - CH = CH - O - R ₃ ,

I ^R 2 where R is, ₍ R, - H-, CH ₃ (CH,) * -, where x = 0 to 8, both straight and branched,

R ₃ - CH ₃ (CH 2) -, wherein y = 0-15 with both straight and branched chain, phenyl, 1-naphthyl, 2-naphthyl, mono-, di- or tri-alkylphenyl, mono-, di- or tri -alkoxiphenyl and - 0 to 10, which may also be present alone or in mixtures.

It has been found that this additive, in combination with aromatic ketones or aromatic aldehydes and ketones, has the ability to increase the balance

254 436 and a gloss level in areas of low current densities of less than 30 A per m " and its effect in mass metallization of appearance-intensive goods is very positive. It does not act immediately after dosing into the galvanic bath, but only after elaboration by passing an electric current of 3 to 5 A.h per 1000 ml bath. The optimum concentration in the bath is in the range of 0.0001 to 0.05 g per 1000 ml, when the upper limit is exceeded, the internal stresses of the coatings are increased. During bath operation, it decomposes under the influence of electric current, so it is advisable to add it in a proportional amount to brightening agents containing aromatic aldehydes and ketones, which ensures its optimal concentration in solution at regular dosing.

A detailed explanation is given in the following examples.

Example 1

0.02 g of an additive according to the invention, wherein R and R 1 = ethyl, R ₃ = 3-methylbulyl, η - 1, was metered into a weakly acid galvanizing bath containing 70 g of zinc chloride, 30 g of boric acid, 150 g * chloride sodium, 3 g potassium 4-methoxybenzoate, 10 g nonionic surfactant (8 ethoxy groups per molecule), 5 g ethylene-propylene oxide copolymer (MW 2500), 0.03 g vanillin, 0.2 g benzylideneacetone in a 1000 ml bath. The bath was worked up by passing an electric current of 5 Ah per 1000 ml.

The level of gloss and leveling was evaluated on panels in a Hull cell test plating at a current of 0.1 A and a plating time of 15, 30, 45 and 60 minutes.

The same test was carried out with an additive-free bath according to the invention.

A visual comparison of the panels plated in both baths shows that in the bath without additive a satisfactory leveling and hint of gloss was achieved after 45 to 60 minutes. In the additive bath, a hint of gloss was achieved after only 15 minutes, after 45 to 60 minutes the panel surface was well aligned and a mirror gloss was achieved.

Example 2

0.015 g of an additive according to the invention, wherein R and R 1 = 4-methylpentyl, R ₃ = phenyl, n = 4, was metered into the bath of Example 1. The elaboration and test metallization were also carried out as in Example 1. The luster has already been achieved after 30 to 45 minutes.

Example 3

0.025 g of an additive according to the invention, wherein R and R 1 = methyl, R ₃ = 7-ethylnonyl, n = 3, was metered into the bath of Example 1. Work-up and metallization were carried out as in Example One. Good alignment and mirror shine were achieved after 30 to 45 minutes.

Example 4

0.005 g additive of the invention wherein R and R = 4-methylpentyl, R ₃ = phenyl, n = 7 and 0.005 g additive

254 436 wherein R 1 and R 1 = methyl, R ₃ = 7-ethylnonyl, n = 5, was metered into the bath of Example 1.

The elaboration and test plating was carried out as in Example 1. Quality alignment and mirror shine were achieved after 30 to 45 minutes.

The invention can be used in the galvanizing of products in the field of engineering and electrotechnical companies and production cooperatives.

Claims (1)

SUBJECT OF THE INVENTION Addition to weakly acidic galvanizing baths, which increases the leveling and gloss level of low current densities less than 30 A per m ', applicable in baths based on zinc chloride or zinc sulphate and ammonium chloride or acetate, both or without ammonium salts, ie based on zinc chloride or sulphate, sodium or potassium chloride and boric acid in various proportions and containing brightening agents based on aromatic ketones or aromatic aldehydes and ketones, characterized in that it consists of compounds of the general formula R ₃ - N - (CH ₂ ) _n - CH = CH - O - R ₃ , ^R 2 where R is ₍ , R 1, - H-, CH ₃ (CH ₃ ) -, where x = 0 to 8, - s both unbranched and branched, R ₃ - CH ₃ (CH ₃ ) wherein y = t) to 15 with straight and branched chain, phenyl, 1-naphthyl, 2-naphthyl, mono-, di- or tri-alkylenenyl, mono-, di- or tri-alkoxiphenyl; 10, which may contain alone or in mixtures.