GB2060699A - Electroplating apparatus - Google Patents

Abstract

The apparatus comprises an electrically insulating hollow vessel 1 which contains a reservoir 3 for electrolyte in electrical contact with the positive terminal of a direct current supply, and a length of fibrous material 7 which extends from the reservoir to the exterior of the vessel. In operation the reservoir is charged with electrolyte and the fibrous material absorbs water by capillary action and becomes moist throughout its length as a result contacting the moist fibrous material with an article 8 to be plated and applying a sufficiently large potential difference leads to deposition of positive ions onto the surface of the article. <IMAGE>

Description

SPECIFICATION Improvements in electroplating This invention relates to an apparatus for and a method of electrodeposition of metallurgical surfaces.

Electropiating has conventionally been performed by immersing an inert anode and a cathode comprising the article to be plated in a bath containing a solution of the metal ions to be deposited and applying a potential difference across the electrodes. During the electrolysis, positively charged metal ions migrate to the cathode where they become deposited as a metal surface.

This bath method of electroplating presents difficulties in certain circumstances, particularly when selected small areas of large assemblies are required to be plated. Pieces too large for bath plating have to be dismantled, often at considerable expense and inconvenience and, in addition, large volumes of electrolyte may be required.

A recent development of the electroplating technique provides a method by which sound metallurgical surfaces can be laid down from electrolytes held in absorbant materials attached to portable electrodes, so removing the need for large immersion tanks. The use of portable equipment provides a useful system for selective plating of components that are impractical to plate in other ways.

Large assemblies which require selective plating in small areas can be treated in situ, thereby eliminating the need for costly dismantling and transport and also the large capital investment associated with bath plating shops.

The electrolytes used with the portable anode are specially formulated and generally are of high metal ion concentrations. The voltages used are usually in the range 4-25V, however deposition takes place at high current densities compared with those used in bath techniques, therefore relative movement of the anode and cathode is of great importance. Using too slow an anode movement may result in a "burnt" deposit whereas too fast a movement may result in a reduction of efficiency and in some cases no deposition. The use of specially formulated electrolytes permits increased rate of deposition and as they are contained in the absorbant material that surrounds the anode items of almost any size can be plated without the restriction of bath size.

However, the portable anodes used in this technique are relatively cumbersome so small or complicated assemblies may be difficult to plate and unacceptable results may be obtained.

Another feature of convential portable anodes is that the electrolyte solution entrained in the absorbant material attached to the anode requires intermittent replenishing by immersion in a vessel containing stock electrolyte, although some anodes are available with continuous feed from an external reservoir.

According to the present invention there is provided an apparatus for electrodeposition'of metallurgical surfaces comprising an electrically insulated hollow vessel which contains a reservoir for electrolyte in electrical contact with the positive terminal of a direct current supply, and a length of fibrous material which extends from the reservoir to the exterior of the vessel.

The portable anode so described can be constructed to give a small compact unit capable, by means of a specially shaped fibrous anode, of electroplating small and complicated objects.

A preferred form of the invention is illustrated by way of example by the accompanying drawing in which Figure 1 is a sectional elevation of the apparatus.

Referring to the drawing, the apparatus comprises a tubular metal vessel 1, preferably of stainless steel and generally cylindrical, which is enclosed in an insulating plastic covering 2, in order to protect the operator against electric shock.

As it is desired that the apparatus should be held in a manner similar to that by which a pen is held, the tube may be of the same diameter throughout its length, although it may be somewhat constricted at the ends as illustrated.

The plastic covered metal tube is provided with a reservoir 3 for electrolyte defined, in the illustrated example by the inner wall of the tube and two metal inserts 4 and 5. In addition to defining a boundary of the reservoir for electrolyte, insert 4 also extends to an aperture at the end of the tube and is shaped to accept a tampon plug 6, which provides an electrical connection between the electrolyte and the positive terminal of a direct current source, usually a mains powered rectifier.

Insert 5 is shaped to accept a length of fibrous material 7 for example Nylon or Carbon impregnated Nylon, and comprises a cylindrical tube which extends from a circular disc provided with an aperture to an opening in the plastic covered tube.

In operation the reservoir 3 is charged with the necessary plating electrolyte by injection from a syringe from the anode insert end. The fibrous anode, which extends through insert 5 from the reservoir to the exterior of the tube, absorbs electrolyte by capillary action and becomes moist throughout its length as a result. A tampon plug 6 is fitted into the insert 4 to provide a connection with the positive terminal of the direct current source, and a metal article 8 to be plated is connected to the negative terminal.

Contacting the moist fibrous anode 7 with the article 8 and application of a potential difference of sufficient magnitude to cause electrolysis of the electrolyte results in deposition of positive ions onto the surface of article 8. The voltages employed are generally dependent on the electrolyte from which electrodeposition is to occur and usually lie in the range 4 to 25V.

Examples of the solutions most commonly used include a gold plating solution, an alkaline nickel plating solution and a neutral copper plating solution.

In another embodiment of the invention the tubular vessel may be of plastic or some other non-porous material.

Claims (4)

1. An apparatus for electrodeposition of metallurgical surfaces comprising an electrically insulated hollow vessel which contains a reservoir for electrolyte provided with a means for connection to the positive terminal of a direct current supply, and a length of fibrous material extends from the interior of the reservoir to the exterior of the vessel.

2. An apparatus as claimed in claim 1 wherein the vessel is a metal tube covered in an insulating material.

3. An apparatus as claimed in claim 1 or 2 wherein the vessel contains a reservoir for electrolyte in electrical contact with inserts in the vessel, one insert providing a means for connection to the positive terminal of a direct current supply, the other insert being shaped to accept a length of fibrous material extending from reservoir to exterior of vessel.

4. A method of electrodeposition of metallurgical surfaces using the apparatus claimed in any of the preceding claims comprising contacting the fibrous anode extending from the reservoir of electrolyte with the article to be plated which has been connected to the negative terminal of a direct current supply, and appiying a potential difference.