US2070679A - Process for preparing nonmetallic articles for electro-plating - Google Patents

Description

Patented Feb. 16, 1937 UNITED STATES PROCESS FOR PREPARING NONMETALLIC ARTICLES FOR ELECTm-PLATING Rudolf Pebiick and Kurt mm, Berlin, Germany No Drawing. Application August 4. 1934, Serial No. 738,540. In Germany August 7, 1933 2 Claims.

The invention relates to a process for preparing for electro-plating solid non-metallic bodies, especially those made of compressed materials, such as artificial resin and similar substances, by

5 preliminary coppering in the cold.

It has been proposed to prepare in the cold non-metallic articles to be electro-plated by first applying to the article by means of a resin varnish a layer of metal which is electrically conduc- 10 tive and then immersing the article so treated in a non-galvanic copper bath (coppering by immersion), the actual electro-deposition (such as nickeling, silvering etc.) following.

This process has the disadvantage that the ar- 15 ticle rendered conductive by the layer of metal powder receives in the non-galvanic copper bath an extremely thin coat of copper which does not adhere to the base substance and which will not withstand the mechanical stresses imposed by 2:) polishing or grinding while at the same time this coating of copper does not form aneifective base for the subsequent treatment in alkali baths.

It has furthermore been proposed to produce non-metallic articles suitable for the actual elec- 25 tro-deposition treatment by rendering them electrically conductive by means of a solution of copper bronze and celluloid lacquer, and then immersing the articles into a galvanic acid copper bath. It has been found, however, that the ad 30 hesiveness of the coatings so produced is not perfect and particularly that it is not possible to polish these coatings without the coating dissolving, at least in part.

These disadvantages are avoided according to the inventionby effecting the preliminary coppering in the following manner. 1

An electrically conductive layer of metal powder which has a lower potential than copper is applied to a non-metallic article by means of a 40 suitable varnish such'as a copal or other resin varnish, the surface of the article being roughened or similarly treated in known manner. The article'so treated is immersed in an acid copper, bath which acts as a binding bath without the use 45 of an electric current acting from without, in order to coat it with a closely adhering thin copper skin which ensures a uniform distribution of the current in a subsequent electro-deposition operation for the formation of a second film of copper.

'fhisgalvaniccopperingproceedsinflmumal manner, that is to say the article leaving the binding bath is placed in a galvanic acid copper bath in the manner usual in the manufacture of electrotype plates. Following this electrotype coppering operation, which advantageously lasts for from one to two hours and by means of which a base, which can be mechanically treated, is applied to the article, there is carried out the usual improving operation, namely nickeling, silvering, etc. 10

In order to be certain that the copper skin completely covers the electrically conductive article it is advantageous to select as the electrically conductive layer a metallic powder the colour of which differs sufllciently from the colour of the copper such for example as an alloy of lead and zinc.

We claim:

1. The process for preparing moulded articles of artificial resin for electro-plating which consists in roughening the external surfaces of the articles, applying to the roughened surfaces by means of a varnish a thin electrically conductive layer of a metal alloy powder containing lead and a metal of a potential lower than copper g5 and of a color differing from that of copper, immerging the articles in a first acid copper bath, removing them from said first acid copper bath after the formation of a thin copper skin on their surfaces, placing them in a second acid copper 'bath, and applying an electric current for electrolytic deposition of a copper layer on the copper skin formed in the first acid copper bath.

2. The process for preparing non-metallic articles for electro-plating which consists in rough- 5 ening the external surfaces of the articles, applying to the roughened surfaces by means of a varnish a thin electrically conductive layer of a metal alloy powder containing lead and a metal of a potential lower than copper and of a color 40 differing from that of copper, immersing the articles in a first acid copper bath, removing them from said first acid copper bath after the formation of a thin copper skin on their surfaces,

placing them in a second acid copper bath, and

applying an electric current for electrolytic deposition of a copper layer on the copper skin formed in the first acid copper bath.

RUDOLF PEBOCK.

KURT