DE542413C - Facility for electroplating - Google Patents

Description

Facility for electroplating During the electroplating of the Inner surfaces of hollow bodies are often forced through a relatively small opening to introduce the anode. There is a risk of being touched the anode supply with the cathodically connected hollow body short circuit occurs or that by excessive crossing of streamlines between the anode and the Edge of the insertion opening as well as the neighboring surface parts of the galvanic Excessive coating in these places at the expense of places deeper inside becomes strong. This becomes all the more apparent, the higher the level in the electroplating process required voltage. In such cases one is therefore forced to use the anodic Isolate feed. The insulation material is high enough except for one Insulation value still sufficient resistance to the electrolyte and resistance against mechanical stress. That is why one usually uses the various types of rubber and celluloid on wood, while glass and ceramic material show insufficient resistance. For: electrolytes with a very strong oxidizing ability, how they z. B. found in chrome plating use, but also keep the different Rubber types did not stand sufficiently against this attack, and one is therefore forced to to replace the insulating protection device very often.

According to the invention, this drawback can be avoided in that the metal parts which are in conductive connection with the anode and which are connected to the Bath come into contact, made from tantalum, whose oxide also protects against such acids is resistant to the other oxides, e.g. B. that of aluminum attack.

It is well known that aluminum and also iron and other metals against strongly oxidizing agents, such as. B. concentrated nitric acid, chromic acid etc., becoming passive and persistent, and this well-known fact was also in industry already evaluated on a large scale (evaporation dishes made of aluminum in the chemical industry, iron containers and fittings in the chromic acid industry etc.). In all of these areas of application, however, the resistant material is important no voltage or at most a cathodic voltage has been applied should counteract any dissolution through electrochemical action.

In contrast to this, the new method becomes just the fact exploited that tantalum with anodic polarization with a protective barrier layer covers. This barrier does not rely on one rem unstable Passivation, as it occurs in the de-energized state, but on training a dense, completely blocking oxide layer, which is also stronger against attack Acids is resistant. The tantalum then works inside like a normal one metallic conductor and externally, apart from its mechanical properties, like an insulator made of rubber or glass.

One already has anodically connected parts in electrolytes to the same Purpose made of aluminum or provided with protective coatings made of aluminum. It has been shown, however, that the aluminum does indeed have safe-acting barrier layers forms; when the effect of the electrolyte is essentially oxidizing. But when the electrolyte significant amounts of strongly corrosive acids, such as. B. sulfuric acid, Contains phosphoric acid, boric acid, etc., the barrier layer on the aluminum will be destroyed under the influence of these acids. Tantalum is far superior to aluminum, because there are safe barrier layers even when using the above-mentioned electrolytes forms.

In carrying out this inventive concept, it goes without saying it is not necessary to choose the entire anode feed from tantalum, you can also, in order to increase the conductivity for a given line cross-section, select a core Cover copper or another suitable metal tightly with tantalum, where = at it does not matter whether this is done mechanically by rolling, pressing, Spraying on or by painting or electrolytic application.

To ensure that the tantalum has a blocking effect from the very first moment and to anticipate the passivation period, even if it is only very short, can also use the tantalum outside the actual bathroom with one of the known ones suitable solutions (chromic acid, phosphate, etc.) anodis.ch using any high voltage are coated with the barrier layer.

In further pursuit of the inventive concept, in addition to the supply lines also other parts of the anode surface are covered with tantalum to these parts of the To make anode electrolytically ineffective.

Claims (1)

PATL.NTANSPRUCII: device for electroplating, -in particular for Internal surface chrome plating, with only partially effective anode surfaces in use of electrolytes with a content of metal oxide-dissolving acid, e.g. B. sulfuric acid, Boric acid o. The like., Characterized in that those with the anode in conductive Connected parts that come into contact with the electrolyte and their electrolytic work is to be suppressed, consist of tantalum or with are provided with a coating of tantalum.