DE688814C - free nickel deposits - Google Patents

Description

For a long time there has been the problem of pore or crater formation in galvanic deposits passed, and it was generally assumed that this was caused by iron, especially in the ferrous state. Another view was that suspended dirt was responsible may be. If there are also noteworthy reasons from experts in this regard existed, they have never found general recognition. In practical use of Plating baths it was then common practice to consider the said evil as one combat chemical problem by chemical means, d. H. it became the bath depolarizing or oxidizing agent added.

The practical use of chemical depolarizing agents, such as hydrogen peroxide ' in galvanic baths is known per se. The use of oxidizing agents, such as soluble metal nitrates, has in the Considerable practice has taken place.

According to the invention, however, the purpose is to produce pore-free nickel deposits Electrolytic way to generate, can be achieved by the fact that the surface tension reduced to an amount that does not exceed 50 dynes / cm. This will cause gas bubbles to build up on the work surface avoided.

Namely, it has been found that the pore formation phenomenon is not caused by the presence of iron or suspended dirt or the chemical action of hydrogen, but by physical conditions by means of which a gas bubble that forms on a plating surface is caused The high surface tension of the electrolyte stubbornly ¹ remains there and mechanically prevents a metal deposit at the point where the bubble is located. When the surface tension of the liquid solutions forming the plating baths was measured, it was found to be generally 60 to 70 dynes / cm, while pure water was 80 grams per centimeter. These measurements

genes have been made with the Du Nouy tension meter.

If the surface tension is kept suitably low, the gas escapes mechanically without there being any possibility of adhering to the work surface, regardless of the p _{E of} the solution.

The plating bath can be prepared in a conventional manner and if desired ίο with the addition of a gloss agent, which on it tends to change the crystal shape so that a dense glossy surface is created will. A number of such additives of greater or lesser effectiveness stand for this »5 at command.

The setting of a surface tension of Proven to be 40 dynes / cm and less. It is of course possible to use both the discounted Surface tension as well as chemical depolarizers such as hydrogen peroxide etc., to be used when the surface tension is only reduced to 50 to 40 dynes / cm will. The entire benefit of depolarizers disappears though when there is surface tension is decreased to 40 dynes / cm or less. The surface tension determination is expediently carried out using the Du Nouy tension meter, such as in the journal "Experimental Physical Chemistry" by Daniels, Matthews & Williams (published by the McGraw-Hill Book Company, New York 1934) on pages 22 to 25.

However, an even better instrument for this purpose is the voltmeter from De Jaeger (ζ. B. described in the magazine for inorganic chemistry 101, 1 to 214 or in the work "Advanced Practical Physics for Students" by B. L. Warnop & H. T. Flint, pp. 140 to 143, published by Methuen, London, 1927). The D Jaeger's instrument adapts particularly closely to the actual working conditions since it is based on measuring with formed bubbles, and it is accordingly after all Directions much more precise.

Among the means which are expediently used, the bath surface tension to reduce, come for example higher alcohols and especially sulphurized higher alcohols, e.g. B. alcohols with more than 3 carbon atoms, etc., into consideration. Heretofore, brighteners or means for influencing the shape of the crystalline were sometimes used Precipitation is used, i.e. types of gum such as tragacanth gum, gum arabic, also gluconates and sulfurized hydrocarbons. When using this However, up to now the quantities have not been so large that they reduce the surface tension could affect or prevent pore formation, and the result was real many times that the pore formation was increased, probably as a result of the the plating adsorbed organic molecules that act as nuclei to collect gas bubbles act on the surface, whereby the surface tension is not low enough, to allow them to escape, and so it is so far using these agents necessary and usual, oxidizing or depolarizing agents, such as hydrogen peroxide, to use.

It has also been found that when considering the plating bath which has such Amount of aromatic sulphonate or other brightening agent contains sufficient quantities of substances which bring the surface tension down so far that it does not exceed 50 dynes / cm, advantageously down to below 40, the new result is that the bath can be used can without resorting to hydrogen peroxide. The plated Surfaces are then not only shiny, but also completely free from pore formation. Up to a certain amount, soap bark or saponin is already in galvanic Baths have been used as additives. But here, too, one has to rely on the surface tension conditions of the bath no consideration has been given and insufficient amounts have been added, an effective reduction of the surface tension and the corresponding elimination to achieve pore formation. This earlier use of soap bark actually only referred to such operations, in which it is immaterial whether pore formation occurs or not.

The present invention thus includes a monitoring of the galvanic precipitation solution from a previously unknown Aspects from and a monitoring in particular in terms of reducing the Surface tension to amounts that have never been considered before, and thus means that have never been used before can be used. Furthermore, an agent, even if it has heretofore been known as a brightener, can suffice more can be added to lower the surface tension to the amount which has been indicated above as necessary, and thereby to achieve the new result of avoiding pore formation, without an additional oxidizing or depolarizing agent for the Bad to take help. This principle applies to any nickel bath

Concentration or p _H within the ordinary practical use applicable.

As a practical example to illustrate the invention, like the following Plating baths are given:

I. NiSO ₄ -OH ₂ 0 452.8 to 1415 g each 4.5 1

NiCl ₂ · 6 H ₂ 0 84.9 to 198.1 g each 4.5 1

H ₃ BO ₃ 84.9 to 141.5 g each 4.5 1

Sulfurized higher alcohols 5.66 g per 4.5 1

II. NiSO ₄ -6 H ₂ 0 452.8 "to 1415 g each 4.5 1

NiCl ₂ · 6 H ₂ O 84.9 to 198.1 g each 4.5 l

H ₃ BO ₃ 84.9 to 141.5 g each 4.5 1

As a gloss agent:

Sulfuric acid reaction product of resin oil 28.3 to 113.2 g per 4.5 l

Sulfurized higher alcohol 5.66 g per 4.5 1

III. NiSO ₄ · 6 H ₂ 0 452.8 to 1415 g each 4.5 1

NiCl ₂ · 6 H ₂ O 84.9 to 198.1 g each 4.5 l

H ₃ BO ₃ 84.9 to 141.5 g each 4.5 1

As a gloss agent:

Naphthalene sulfonate 28.3 to 113.2 g per 4.5 1

Sulfurized higher alcohols 5.66 g per 4.5 1

The current tightness can be 5 to 75 amps per 929 square cm and the temperature 43.5 ° C.

Claims (4)

Patent claims: 1. Process for the electrolytic generation of pore-free nickel deposits, characterized in that the surface tension of the bath is reduced to an amount equal to 50 dynes / cm does not exceed. 2. The method according to claim 1, characterized in that the surface tension is set to below 40 dynes / cm. 3. The method according to claims 1 or 2, characterized in that a gloss agent is used as an additive to the agent for reducing the surface tension in the plating bath. 4. Process according to Claims 1 to 3, characterized in that the brightening agent is a sulfonated naphthalene compound. S-method according to claims 1 to 4, characterized in that the agent is a sulfurized alcohol having more than 3 carbon atoms to reduce surface tension.