CS253533B1 - Ingredient for electrolytic weak acid zinc bath - Google Patents

Abstract

The composition of a gloss-forming additive for an electrolytic weakly acidic zinc plating bath, with or without ammonium salts, for the deposition of semi-gloss and? high-gloss zinc coatings for the plating of small bulk goods in drums or bells is addressed. This additive contains at least one non-ionic surfactant, at least one weak acid without complexing effects, at least one aromatic ketone, alkaline salts of at least one aromatic sulfonic acid, optionally 1 simple aliphatic or aromatic aldehyde, at least one alkylene oxidized dihydric alcohol with at least one triple bond, all in the amounts indicated and up to 100% by weight solvent.

Description

The invention relates to a gloss-forming additive for an electrolytic weakly acidic zinc plating bath, with or without ammonium salts, for the deposition of semi-gloss to highly glossy zinc coatings for plating of piece goods on hangers or bulk plating of small bulk goods in drums or bells.

One of the most widespread methods of electrolytic galvanizing is plating in weakly acidic baths. The basis of these baths is a simple zinc salt - chloride or sulfate, ammonium chloride or alkaline chloride and additives, which are the main components of the baths.

Bright galvanizing in weakly acidic baths has a number of advantages, in addition to technical ones - semi-gloss to high-gloss coatings, excellent covering ability and leveling efficiency, minimal risk of hydrogenation of steel - and economic ones - low production costs - and ecological ones - the bath does not contain any poisons or corrosives, it is minimally dangerous during work.

The basic composition of the baths - zinc salts and chlorides - are practically the same concentration in all known types of baths. However, the baths known and used so far differ in their ingredients in terms of effects.

Many baths - despite their undeniable advantages - also have a number of disadvantages, for example, additives often contain various complexing agents, such as amines, ammonium salts, etc., which prevent the complete precipitation of heavy metals from wastewater and are then environmentally harmful, the deposited zinc coatings sometimes have unfavorable internal stress values, so that spontaneous cracking occurs, sometimes even its adhesion to the base material is impaired. The deposited coatings are less shiny, with larger or smaller grayish veils, in some cases the baths only work at relatively low current densities, at higher current densities, rough growths occur on the edges of the goods.

The above-mentioned shortcomings in plating in a weakly acidic galvanizing bath are eliminated by adding a gloss-forming additive to the electrolytic solution.

253,533 weakly acidic zinc plating baths according to the invention. The essence of the invention lies in the fact that the additive contains at least one nonionic surfactant, e.g. addition products of higher fatty alcohols and/or alkylphenols and alkylene oxide in an amount of 2 to 50 wt. %, polyethylene-polypropylene glycol copolymers in an amount of 0.01 to 30 wt. %, at least one weak acid without complexing effects, e.g. boric acid, acetic acid, in an amount of 0.1 to 10 wt. %, at least one aromatic ketone, e.g. benzalacetone, naphthylmethylketone, acetophenone in an amount of 0.01 to 10 wt. %, alkali salts of at least one aromatic sulfonic acid, e.g. benzenedisulfonic acid, naphtholsulfonic acid, naphthylaminedisulfonic acid in an amount of 0.001 to 2 wt. %, at least one alkylene-oxidized dihydric alcohol with at least one triple bond, e.g. the reaction product of 2-butyne 1,4-diol with at least one mole of ethylene oxide and/or propylene oxide in an amount of 0.001 to 10 wt. % and to ICO wt. % of a solvent, for example water, ethanol, acetone. To improve the physical and mechanical properties of the coatings, especially the internal stress values, it is advantageous if the gloss-forming additive according to the invention further contains a simple aliphatic or aromatic aldehyde, for example acetaldehyde, formaldehyde, benzaldehyde in an amount of 0.001 to 2 wt. %.

The additive does not contain any complexing agents and its production is simple. The bath with the additive according to the invention is suitable for plating piece goods on hangers while the goods move in the bath at an average speed of 2 to 6 m/min. at a cathode current density of

0.2 to 7 A/dm even for bulk plating of small bulk goods at an average cathode current density of 0.2 to 2.5 A/dm.

The deposited zinc coatings - depending on the quantitative composition of the additive and its amount in the bath - can be slightly shiny to mirror-like and can be easily chromated in the usual types of chromating preparations. The coatings also exhibit good adhesion to the base material and physical and mechanical properties.

The invention is further explained in more detail by examples of its specific embodiment.

- 3 Example 1

To an electrolytic zinc plating bath containing 50 g/l zinc chloride, 150 g/l sodium chloride and 15 g/l boric acid, 50 cm of the additive according to the invention with the following composition was added:

- nonionic surfactants - reaction product of nonylphenol

with ethylene oxide 40 % wt. - polyethylene glycol polypropylene glycol copolymer 14 % wt. - salicylic acid 2 - a mixture of benzalacetone and naphthylmethylketone *0.8 _ tt _ - diethoxylated 2-butyne-1,4 diol 4 _ ’1 __ - sodium salt of naphthalenesulfonic acid 0.2 — ⁿ — - water, alcohol and acetone to 100

Bath pH 4.4 to 5

The deposited zinc coatings were very shiny with excellent covering ability during both curtain and bulk plating.

Example 2

To the galvanizing bath containing 60 g/l zinc chloride, 170 g/l potassium chloride and 20 g/l boric acid, 3 cm of the additive according to the invention with the following composition was added:

- nonionic surfactant - reaction product of nonylphenol with ethylene oxide

- polyethylene glycol polypropylene glycol copolymer

- boric acid

- acetic acid

- naphthyl methyl ketone

- benzalacetone

- acetaldehyde

- alkaline salt of 2-naphthyl, 3-6 disulfonic acid

- dipropoxylated 2-butyne-1,4 diol

- solvents: alcohol and water

The bath produced le% by weight under laboratory conditions

- J 6 - 0.02 - 0.6 - ”

- 0.04 - 0.001 up to 100 glass zinc coatings on goods during curtain plating with moving samples at 2 2

0.5 to 6 A/dm , preferably 3 to 4 A/dm . The coatings also showed very good internal stress values.

- 4 Example 3 253 533

To a galvanic bath containing 70 g/l zinc sulfate and 180 g/l ammonium chloride, 25 cm^ of the additive according to the invention with the composition:

- nonionic surfactant - addition product of higher fatty alcohols with ethylene oxide

- polyethylene glycol polypropylene glycol copolymer

- benzoic acid

- a mixture of benzalacetone and acetophenone

- ethyl vanillin

- formaldehyde

- sodium salt of naphtholdisulfonic acid

- diethoxylated 3-hexine-2,5 diol

- water, alcohol and acetone

- pH of the bath 4.5 to 4.8% by weight.

- ” 4 - 1.2 - 0.08 - 8 - 0.004 - 0.012 - up to 100 - Shiny zinc coatings of good quality were obtained during mass plating of small goods in drums at an average cathodic current density of 1 A/dm.

The invention can be used in electrolytic galvanizing of various products in the fields of mechanical engineering, electrical engineering and production cooperatives.

Claims (2)

Glossing agent for an electrolytic weakly acidic zinc bath, characterized in that it contains at least one non-ionic surfactant, for example adducts of higher fatty alcohols and / or alkylphenols and alkylene oxide in an amount of 2 to 50% by weight, polyethylene polypropylene glycol copolymers in an amount of 0.01 up to 30% by weight, at least one weak acid without complexing effects, for example boric acid, acetic acid, in an amount of 0.1 to 10% by weight, at least one aromatic ketone, for example benzalacetone, naphthylmethylketone, acetophenone in an amount of 0.01 to 10% , alkali salts of at least one aromatic sulfonic acid, e.g. at least one alkylene oxidized divalent alcohol with at least one triple bond, for example the reaction product of 2-butyne 1,4-diol with at least one mole of ethylene oxide and / or propylene-p oxide in an amount of 0.001 to 10 wt. to 100 wt. solvents such as water, ethanol, acetone. 2. The wood-forming additive according to claim 1, further comprising a simple aliphatic or aromatic aldehyde, for example acetaldehyde, formaldehyde, benzaldehyde in an amount of 0.001 to 2% by weight.