CS270099B1 - Complexing and brightening ingredient - Google Patents

Abstract

When electroplating nickel-iron alloys, in addition to primary or secondary gloss-forming additives, other additives must be added to complex the Fe3 ions present, which have a negative effect on the quality of the coating. Compounds of general formula © X© (I), ch2ch2oh R - N - R t !H2CH2OH where R is a hydrocarbon residue with 5 to 12 C atoms, Rl is H, C* - C4 alkyl or HOCHgCHg-, X is chlorine, bromine or HOSO-j”, serve as high-quality gloss-forming additives in electroplating and it has been found that they have complexing effects on Pe3+ ions. With the help of these additives, highly glossy coatings with a defined Ni/Fe ratio can be obtained. The additives should be added in an amount of 2 to 500 mg/l of the electroplating bath.

Description

The invention relates to organic compounds which serve as gloss-forming additives, facilitating the precipitation of glossy coatings in the plating of nickel-iron alloys and at the same time complexing Fe 2+ ions well.

For many years, galvanic deposition of nickel has been used as an intermediate layer for subsequent chromium deposition to obtain corrosion-resistant metal coatings. In many cases, nickel coatings have been used for decorative purposes with high gloss, ductility and other necessary parameters * Various organic substances have been used to achieve these physical and mechanical properties of surfaces; To reduce costs, the possibilities of using alloys, especially nickel-iron, were sought, because the low price of iron and its alloys contrasts sharply with the price of nickel, thus favoring the prices of products.

The issue of precipitation of glossy coatings of nickel-iron and nickel-iron-cobalt alloys is the subject of a number of publications and patents. Of these sources, we list only the most important and those that are used industrially: Metal Finishing, December 1967, p. 67; British Pat, writings: G.B. 312 441) 942 144) 1 039 798) -1 105 189) 1 438 552} 1 438 551} 1 435 551; 1,435 26?) 1,522,272) U.S. Pat. documents 3,633,864) 3,151,971; 3,151,972; 3,151,973; 2,782,154; Ger. Offen 2,333,069) 2,431,332; 2,152,785; 3,001,879.

It was shown that of the two ionic forms of iron, the Fe ² Fe @ ^+, ferrous ion Fe ²⁺ is optimum for coating, whereby a low matter concentration of Fe ions ^ *. In the practical implementation of the deposition of ferrous alloys, the oxidation with aerated oxygen or the anodic oxidation of the Fe ion accumulates an excessive amount of Fe ions in the bath, which have a negative effect on the quality of the deposited coatings. With this excess, the basic salts of Fe 2+ precipitate in the bath, which results not only in an unpleasant load on the anode space and the filters, but also in their sedimentation, which provides undesired deposits. This causes spots on the coating or local mattes, especially in the edge areas. In the case of high concentrations of suspended Fe 2+ salts, they settle on the micro-surface of the precipitated alloy. This defect is called orangepeel.

These facts have led to an intensive search for suitable agents and additives that would mitigate these negative effects. The current state of the art solves the reduction or overcoming of the problem associated with the formation of Fe 2+ salt precipitates in essentially two ways:

The first recommends the addition of reducing agents, which ensure that only Fe ions are present in the bath. Although a wide variety of such agents are available, they are generally unstable under operating conditions and produce harmful reduction products or adversely affect the composition characteristics of the bath. Another disadvantage is the difficult inspection of the bath and the equipment (Handbuch der Galvanotechnik, Bd. II 19, p. 467; Ger. Offen 2,509,377, 2,830,572, 2,815,786).

The second method, widely used in practice, solves the above-mentioned problem by adding additives to galvanic baths which form Fe ^{2+ ions of the} soluble compound, either by complexation or by chelation. From a technological point of view, such additives must meet the following requirements:.

it must be stable during electrolysis, ie reduction (cathode), oxidation (anode), it must be compatible with other additives which are used either singly or in combination as grain refining additives and brighteners, ie they must not adversely affect equipment and other additives must be relatively cheap and available with little dependence on the concentration limit and jx · tolerance to the concentration of Fe ions, they must form stable complexes with Fp ⁺ ions in a wide range of operating conditions.

CS 270099 Bl

The prior art discloses a number of complexing (stabilizing) compounds which have some of the above characteristics. For example, hydroxy- and polyhydroxycarboxylic acids such as citric, tartaric, malic, ascorbic, gluconic, glucoheptanoic and others, including their alkali and ammonium salts (Metalloberflache 29.1 (1975); dtto 33,540 (1979); Powlaki ochronne 5.2 (1979)). U.S. Pat. No. 3,806,429; GB Pat. No. 1,438,553; 1,438,554 and the above-cited patents.

In many cases, these agents complex Fe ²⁺ ions well, but are not suitable 2+ for baths with a high concentration of Fe ions, or form glossy coatings only in a narrow range of current densities.

These drawbacks are overcome by the complexing and gloss-forming additive according to the invention, which consists in that it contains a compound of the general formula I

CH 2 CH 2 OH

R - N - R ¹ (I) where

R denotes a hydrocarbon radical and 5 to 12 carbon atoms, denotes hydrogen, alkyl containing 1 to 4 carbon atoms or a HOCH ₂ CH ₂ group,

X represents a chlorine, bromine or HOSO 2 group in an amount of 2 to 500 mg / l of the galvanic bath. The aqueous acid galvanic bath for the deposition of glossy nickel-iron alloy coatings on corrosion-sensitive substrates contains nickel and iron ions, soluble primary, secondary, auxiliary secondary organic additives and reagents, and boric acid. The ratio of Ni: Fe ions in the bath is 50 to 2: 1. The ratio of the gloss-forming additive according to the invention to iron ions is 1: 3 to 2: 1. The pH of the bath is 2.5 to 5.5. The plating solution may contain one or more of the following compounds: nickel sulfate, nickel chloride, ferrous sulfate, nickel sulfonate, ferrous chloride, or more additives selected from the group of primary brighteners such as 1,4-di- (2-hydroxyethoxy) -2- butine, N- (1,2-dichloropropenyl) pyridinium chloride, 2,6,6-trimethyl-N-propargylpyridinium chloride, N-allylpyridinium chloride, 2-butyne-1,4-diol, thiourea derivatives, bis- (2-cyanoethyl) sulphide and other secondary brightening agents, for example saccharin, benzene- and toluenesulphonic acid amides and naphthalene 1,3,6-trisulphonic acid, sodium benzenesulphonic acid salts and the like, secondary luminous auxiliaries from the group of alkaline salts of allylsulphonic acid, styrenesulphonic acid, propargylsulphonic acid, diallylsulphonamide and others that minimize pitting corrosion.

The advantage of the complexing and gloss-forming additive according to the invention is that it forms high-gloss coatings with a defined Ni / Fe ratio, with advantageous and controllable internal stresses with fewer pores, while providing considerable savings in imported nickel, and thus also very economically advantageous. Another advantage is the use of cheap reagents based on domestic raw materials. ·

In the following examples, the additives according to the invention are mentioned in a mixture with other known primary or secondary additives, which, however, do not limit the scope of the invention.

Example 1

Sodium benzyl bis- (2-hydroxyethyl) ammonium chloride Triethylene glycol Saccharin Sodium allylsulfonate (or vinylsulfonate)

0.08 g / l 0.02 g / l 2.0 g / l 2.0 g / l

CS 270099 Bl

Example 2

Benzyl-tri8- (hydroxyethyl) ammonium chloride 0.010 g / l 0.020 g / l Triethylene glycol Saccharin. Allylsulfonate (or vinylsulfonate) »* sodium 2.0 2.0 g / i g / 1 Example 3 Bis- (2-hydroxyethyl) -p-toluenesulfonamide 0,0 0.050 g / 1 Pentaethylene glycol 0.080 g / 1 Saccharin 2.0 g / 1 ' Allylsulfonate (or vinylsulfonate) sodium . 2.0 g / 1 Example 4 Decyl-tris- (2-hydroxyethyl) ammonium chloride 0.03 g / 1 Diethylene glycol diethyl ether 0.02 g / 1. Saccharin • 2.0 g / 1 Allylsulfonate (or vinylsulfonate) sodium 2.0 g / 1

The comparison showed that the gloss of the coatings is comparable to foreign equivalents. The additives according to the invention have a positive effect on the mechanical properties of the coating. The stress was measured with an S / meter and applies to 20 mm tests.

Type of ingredients

Inner tension

Example 1

Example 2

Example 3

Example 4

Foreign ingredients

54.2

57.5

52.4

69.5 to 115.4

The additives according to the invention therefore have the stated mechanical properties better.

Claims (3)

OBJECT OF THE INVENTION A complexing and brightening additive for electroplating with a nickel-iron alloy, characterized in that it contains a compound of the general formula I ’CEjCHgOH R - N - R ¹ I. . ch ₂ ch ₂ oh wherein R is a hydrocarbon radical having 5 to 12 carbon atoms, R ¹ is hydrogen, alkyl having 1 to 4 carbon atoms or the group HOCH ₂ CH ₂ X denotes a chlorine or bromine atom or a HOSO 2 - group, in an amount of 2 up to 500 mg / l bath. (AND) CS 270099 Bl 2. A complexing and gloss-forming additive as claimed in claim 1, wherein the compound of the formula I is benzyl bis (2-hydroxyethyl) ammonium chloride in an amount of 20 to 200 mg / l of bath. 3. A complexing and gloss-forming additive as claimed in claim 1, wherein the compound of the formula I is benzyl tris (2-hydroxyethyl) ammonium chloride in an amount of 5 to 150 mg / l of bath. '