DE1106140B - Acid bath for galvanic deposition of nickel coatings - Google Patents

Description

The invention relates to electroplating baths from which very shiny nickel coatings can be produced; the coatings produced should be very smooth and free from internal stresses.

It is already known to use coumarin and some of its derivatives, namely its alkyl and acyl derivatives, as To be used in addition to galvanic nickel baths. Of these additives, however, only the coumarin was used used by itself, and it is actually the only compound that gives satisfactory results.

Nonetheless, the use of coumarin also has considerable disadvantages, since this is caused by evaporation, by chemical or electrochemical decomposition into unknown compounds and possibly is lost from the bath by mixing with the deposited nickel. The decomposition products that accumulate in the galvanic bath after a certain period of time, reduce the quality of what is deposited therefrom Nickel plating and must therefore be removed by applying the whole bath with activated charcoal and optionally treated with hydrogen peroxide. Do not avoid the whole bathroom must be taken out of service.

It is also known to use coumarin-6-sulfonic acid in galvanic nickel baths, but It is stated in several references that coumarinsulfonic acids as such correspond to the unsubstituted coumarin are inferior to each other and that other suitable compounds are therefore also used must in order to obtain satisfactory nickel coatings.

It has now been found that galvanic nickel baths are obtained by means of some special coumarin derivatives, the nickel coatings result in the nickel coatings obtained by means of the known coumarin derivatives in their Properties are superior.

The bath according to the invention for the electrodeposition of smooth and shiny nickel coatings with a content of coumarin derivatives is characterized in that it contains 6-sulfamidocoumarin, hydrocoumarin sulfonate or contains a salt of this compound and / or 6-acetamidocoumarin. The nickel electrolyte can preferably from a salt commonly used for nickel plating, e.g. B. the sulfate or chloride. Advantageously, a Watts solution is used for the bath, i. H. a solution that contains both nickel sulfate and also contains nickel chloride.

Compared to coumarin, the new bath additives are more economical because they have about the same manufacturing costs can be used in a much smaller amount. So from z. B. 6-acetamido or 6-sulfamidocoumarin to achieve the same effect only fifth part of the amount of coumarin required second hand.

Furthermore, the resulting decomposition products practice

Acid bath for the galvanic deposition of nickel coatings

Applicant:

Wilmot-Breeden Limited,
Birmingham (Great Britain)

Representative: Dr. W. Schalk, Dipl.-Ing. P. Wirth,

Dipl.-Ing. G. E. M. Dannenberg

and Dr. V. Schmied-Kowarzik, patent attorneys,

Frankfurt / M., Große Eschenheimer Str. 39

Claimed priority:
Great Britain 21 February 1957

Ulrich Francis Marx, Birmingham (Great Britain),
has been named as the inventor

has a much less adverse effect on the properties of the deposited coating than that Decomposition products of coumarin. These decomposition products can also be removed by that the solution is pumped through a filter bed filled with only a small amount of charcoal, which the has the particular advantage that this can be done by circulating the bath without the entire bath except Operation must be set.

5 All of the coumarin derivatives proposed according to the invention lead to good smoothing. Hydrocoumarinsulfonate results in a pliable deposit, while 6-sulfamidocoumarin and 6-acetamidocoumarin are both shiny as well as flexible deposits and are therefore to be preferred. When using the 6-sulfamido- and 6-acetamido derivatives are approximately equally pliable, the latter having Connection a better smoothing and the former connection a broader area in which glossy coatings can be obtained.

The following examples serve to illustrate the nickel baths according to the invention for production galvanic coatings, the bath in each case being a Watts solution of the following composition:

NiSO ₄ -OH ₂ O 250 g per liter

NiCl ₂ -OH ₂ O 45 g per liter

H ₃ BO ₃ 30 g per liter

Water to 1000 ecm

109 579/372

example 1

In this example, 6-sulfamidocoumarin was used in a concentration between 0.01 g / l and the saturation at the deposition temperature, preferably between 0.05 and 2.5 g / l and particularly advantageously between 0.25 and 0.5 g / l, used. The deposition can be carried out at a pn value of 2 to 6, preferably from 4 to 5, and at a temperature between 45 and 65.degree. C., preferably about 55.degree. The current density can be about 0.001 to 0.01 A / cm ² , preferably about 0.004 to 0.008 A / cm ^a . Shiny deposits were achieved here.

Example 2

The coumarin bisulfate compound (hydrocoumarinsulfonate), the preparation of which was described by Dodge, JACS, 1916, 38, p. 446, was used as an additive. The concentration of the sodium or potassium salt in the bath was 0.01 to 2.5 g / l, preferably between 0.25 and 0.5 g / l. The deposition can be carried out at a pa value of 4, a temperature of 55 ° C. and a current density of about 0.0044 A / cm ² , with semi-glossy deposits being achieved.

Example 3

As an additive, 6-acetamidocoumarin was used in a concentration of 0.01 g / l to saturation, preferably 0.10 to 0.30 g / l, and the deposition was carried out at 55 ° C., a pn value of 4 and a current density of about 0.0044 A / cm ^a .

Claims (2)

Patent claims: 1. Acid bath for the galvanic deposition of smooth and shiny nickel coatings with a Coumarin derivative content, characterized in that it contains 6-sulfamidocoumarin, hydrocoumarin sulfonate or contains a salt of this compound and / or 6-acetamidocoumarin. 2. Bath according to claim 1, characterized in that it is the coumarin derivative in an amount of 0.01 g / l contains up to the saturation concentration in the bath. Considered publications:
French Patent No. 1 103 555;
U.S. Patent No. 2,694,041. © 109579/372 Φ.61