GB2026031A

GB2026031A - A circuit arrangement to increase the life of electrodes used as anodes

Info

Publication number: GB2026031A
Application number: GB7916381A
Authority: GB
Original assignee: Orszagos Koeolaj es Gazipari Troeszt
Current assignee: Orszagos Koeolaj es Gazipari Troeszt
Priority date: 1978-05-15
Filing date: 1979-05-11
Publication date: 1980-01-30
Also published as: SU1034611A3; DE2919113C2; FR2426094A1; DD143835A5; SE7904136L; DE2919113A1; GB2026031B

Abstract

A circuit arrangement for increasing the life of electrochemical electrodes comprises a source of DC (1), a switching device (2), three electrodes (3, 4, 5) of which one is always a cathode (3) and another is always an anode (5) while the potential of the third (4) is controlledly varied by control unit (6) so that it functions alternatively as a cathode and as an anode. <IMAGE>

Description

SPECIFICATION A circuit arrangement to increase the life of electrodes used as anodes The invention relates to a circuit arrangement for increasing the life of electrodes in electrolytic media.

It is known that the current-emitting electrode i.e. the anode, in an electrolytic medium suffers a loss of weight as a result of current flowing through it, in accordance with Faraday's law. Thus, the mass of the anode to be used is essentially determined by the weightloss factor which is functionally related to the composition of its constituent materials, by the expected lifetime and by the current load.

Especially in electro-chemical anti-corrosion systems, materials with a low weight-loss factor, such as graphite, silicon-steel, platinumcoated titanium, are not used widely due to their costliness. Also, in order to reduce the energy losses, the geometric dimensions which ensure resistance do not allow a significant decrease in the mass of the anode, and therefore the use of such anodes is not economic.

There are several conventional ways of producing electrodes, especially foil electrodes.

But in these cases the primary aim is the formation of a metallic layer on the surface of the foil, and the lifetime of the electrode is only a secondary consideration. Thus, e.g.

U.S. patent specification No. 3,420,760 relates to a method in which the surface of the electrode is formed electrolytically. The method is characterised especially by the particular manner of removing harmful oxide layers, but this disclosure does not deal with ways of increasing the lifetime of electrodes.

The same applies to German patent specification Nos. 1,564,501 and 1,564,486 on the same subject.

U.S. Patent Specification Nos. 2,146,488 and 3,082,164 also allude to an electrolytic treatment of electrodes but they do not seen to produce electrodes with an increased lifetime.

An aim of the present invention is to provide an anode electrode system which enhances the lifetime of anodes made of materials with a high weight-loss factor by rationally combining an auxiliary electrode made from materials of a low weight-loss factor and a mechanical or electronic switching element.

This aim is sought to be achieved by using a circuit arrangement which contains a direct current source (rectifier), a so-called anode electrode, a cathode electrode, a so-called auxiliary electrode which is made preferably of materials of low weight-loss factor, a mechanical or electronic switching element, and a control unit. These constructional parts are connected with each other in such a way that the anode electrode will be polarized alternatively anodically and cathodically. The magnitude and/or duration of anodic or cathodic polarity can be altered by manual control, or by an automatic controlling device.

The invention will now be described in connection with a preferred embodiment shown schematically in the enclosed drawing which is a circuit diagram of that embodiment.

As can be seen in the drawing, a direct current source (rectifier 1) is connected to a cathode electrode 3, an electrode 4 and to an auxiliary electrode 5, throuhg an electronic or mechanical switching device 2.The switching device 2 is also connected to a control unit 6.

The polarity of the electrode 4 is variable, so that it may function as an anode or cathode, as determined by the control unit 6. The time duration of its anodic or cathodic polarity must be set in such a way that the electrode 4 is always negative in potential relative to its environment.

Narurally, the extent of anodic and cathodic polarity is also influenced by the mutual positions of the cathode electrode 3, the anode electrode 4 and the auxiliary electrode 5, and by the ratio of their surface areas.

The above-described device may in essence be broken down into two pairs of electrodes wherein the cathode electrode 3 always functions as a cathode, the auxiliary electrode 5 always functions as an anode, while the electrode 4 alternatively functions as anode and cathode.

Tests have proved that in the circuit system according to the invention the weight loss of the electrode 4 can be largely or completely transferred to the auxiliary electrode 5 which is made of materials of preferably, low weight loss factor. Consequently, the mass of the auxiliary electrode 5 can be essentially much smaller in a suitable construction than that of the electrode 4, therefore the lifetime of this anode system is determined exclusively by the auxiliary electrode 5.

The control unit 6 may be automatically or manually operable; it may be programmed.

As the broken lines show, the DC source 1, the switch 2 and the control unit 6 may form an integrated structural unit of "black box".

CLAIMS (11 May 1 97c) 1. A circuit arrangement for extending the lifetime of electrodes used as anodes comprising a direct current source, a switching device, a first cathode electrode, a second electrode and a third anode electrode, wherein a first input of the switching device is connected to a control unit, a second input of the switching device is coupled to the direct current source and the outputs of the switching device are coupled to the cathode electrode and to the second and third electrodes respectively, the control unit being effective to vary the potential of the second electrode with

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A circuit arrangement to increase the life of electrodes used as anodes The invention relates to a circuit arrangement for increasing the life of electrodes in electrolytic media. It is known that the current-emitting electrode i.e. the anode, in an electrolytic medium suffers a loss of weight as a result of current flowing through it, in accordance with Faraday's law. Thus, the mass of the anode to be used is essentially determined by the weightloss factor which is functionally related to the composition of its constituent materials, by the expected lifetime and by the current load. Especially in electro-chemical anti-corrosion systems, materials with a low weight-loss factor, such as graphite, silicon-steel, platinumcoated titanium, are not used widely due to their costliness. Also, in order to reduce the energy losses, the geometric dimensions which ensure resistance do not allow a significant decrease in the mass of the anode, and therefore the use of such anodes is not economic. There are several conventional ways of producing electrodes, especially foil electrodes. But in these cases the primary aim is the formation of a metallic layer on the surface of the foil, and the lifetime of the electrode is only a secondary consideration. Thus, e.g. U.S. patent specification No. 3,420,760 relates to a method in which the surface of the electrode is formed electrolytically. The method is characterised especially by the particular manner of removing harmful oxide layers, but this disclosure does not deal with ways of increasing the lifetime of electrodes. The same applies to German patent specification Nos. 1,564,501 and 1,564,486 on the same subject. U.S. Patent Specification Nos. 2,146,488 and 3,082,164 also allude to an electrolytic treatment of electrodes but they do not seen to produce electrodes with an increased lifetime. An aim of the present invention is to provide an anode electrode system which enhances the lifetime of anodes made of materials with a high weight-loss factor by rationally combining an auxiliary electrode made from materials of a low weight-loss factor and a mechanical or electronic switching element. This aim is sought to be achieved by using a circuit arrangement which contains a direct current source (rectifier), a so-called anode electrode, a cathode electrode, a so-called auxiliary electrode which is made preferably of materials of low weight-loss factor, a mechanical or electronic switching element, and a control unit. These constructional parts are connected with each other in such a way that the anode electrode will be polarized alternatively anodically and cathodically. The magnitude and/or duration of anodic or cathodic polarity can be altered by manual control, or by an automatic controlling device. The invention will now be described in connection with a preferred embodiment shown schematically in the enclosed drawing which is a circuit diagram of that embodiment. As can be seen in the drawing, a direct current source (rectifier 1) is connected to a cathode electrode 3, an electrode 4 and to an auxiliary electrode 5, throuhg an electronic or mechanical switching device 2.The switching device 2 is also connected to a control unit 6. The polarity of the electrode 4 is variable, so that it may function as an anode or cathode, as determined by the control unit 6. The time duration of its anodic or cathodic polarity must be set in such a way that the electrode 4 is always negative in potential relative to its environment. Narurally, the extent of anodic and cathodic polarity is also influenced by the mutual positions of the cathode electrode 3, the anode electrode 4 and the auxiliary electrode 5, and by the ratio of their surface areas. The above-described device may in essence be broken down into two pairs of electrodes wherein the cathode electrode 3 always functions as a cathode, the auxiliary electrode 5 always functions as an anode, while the electrode 4 alternatively functions as anode and cathode. Tests have proved that in the circuit system according to the invention the weight loss of the electrode 4 can be largely or completely transferred to the auxiliary electrode 5 which is made of materials of preferably, low weight loss factor. Consequently, the mass of the auxiliary electrode 5 can be essentially much smaller in a suitable construction than that of the electrode 4, therefore the lifetime of this anode system is determined exclusively by the auxiliary electrode 5. The control unit 6 may be automatically or manually operable; it may be programmed. As the broken lines show, the DC source 1, the switch 2 and the control unit 6 may form an integrated structural unit of "black box". CLAIMS (11 May 1 97c) 1. A circuit arrangement for extending the lifetime of electrodes used as anodes comprising a direct current source, a switching device, a first cathode electrode, a second electrode and a third anode electrode, wherein a first input of the switching device is connected to a control unit, a second input of the switching device is coupled to the direct current source and the outputs of the switching device are coupled to the cathode electrode and to the second and third electrodes respectively, the control unit being effective to vary the potential of the second electrode with respect to the third electrode in such a way that the second electrode functions alternatively as a cathode or as an anode. 2. The circuit arrangement as claimed in claim 1 wherein the control unit is operated either automatically or manually and is designed to adjust the magnitude and/or duration of anodic or cathodic polarisation of the second electrode. 3. The circuit arrangement as claimed in claim 1 or 2, wherein the direct current source (rectifier) the switching device and the control unit form an integral structural unit. 4. A circuit arrangement according to any preceding claim wherein the third electrode is made from material(s) of relatively low weightloss factor. 5. A circuit arrangement substantially as herein described with reference to and as shown in the accompanying drawing. CLAIMS (20 Sep 1979)

1. A circuit arrangement for extending the life of an electrode in an electrolytic medium, comprising a direct current source, a first cathode electrode, a second electrode, the life of which is to be extended, a third auxiliary anode electrode, the second electrode being of material(s) having a relatively higher weight loss factor than the material(s) of the third electrode, switching means connecting the DC source to the electrodes, and control means operative to control the switching means to maintain the first electrode at a negative potential with respect to the third electrode and to vary the potential of the second electrode with respect to the third electrode in such a way that the second electrode functions alternatively as a cathode and as an anode.

2. A circuit arrangement as claimed in Claim 1, wherein the control means is operative to vary the magnitude and/or duration of the anodic and cathodic polarisation of the second electrode.

3. A circuit arrangement as claimed in Claim 1 or Claim 2, wherein the control means is operative automatically to vary the potential of the second electrode.

4. A circuit arrangement as claimed in Claims 1, 2 or 3 wherein the direct current source, the switching means and the control means form an integral structural unit.

5. A circuit arrangement as claimed in any preceding Claim, wherein the mass of the third electrode is substantially smaller than that of the second electrode.

6. A circuit arrangement as claimed in any preceding Claim, wherein the time duration of the respective anodic and cathodic polarisations of the second electrode are such as to maintain the second electrode at a negative polarity with respect to its environment in the electrolytic medium.

7. A circuit arrangement substantially as herein described with reference to and as shown in the accompanying drawings.

8. An electrolytic process wherein a first cathode electrode a second electrode and a third auxiliary anode electrode are immersed in an electrolytic medium, the second electrode being of material(s) having a relatively higher weight loss factor than the material(s) of the third electrode, and wherein the potential of the third auxiliary anode electrode is maintained positive with respect to the first cathode electrode, and the potential of the second electrode is varied with respect to that of the third electrode, in such a way that it functions alternatively as an anode and as a cathode whereby the rate of weight loss of the second electrode is substantially reduced.

9. A process as claimed in Claim 8, wherein the magnitude and/or duration of the anodic and cathodic polarisations of the second electrode are varied.

1 0. A process as claimed in claim 8 or Claim 9, wherein the second electrode is maintained at a negative polarity with respect to its environment in the electrolytic medium.

11. A process as claimed in any one of Claims 8 to 10, wherein the mass of the third electrode is substantially less than that of the second electrode.

1 2. A process as claimed in any one of Claims 8 to 11, wherein the potential applied to the second electrode is varied automatically in accordance with a predetermined programme.

1 3. An electrolytic process substantially as herein described with reference to and as shown in the accompanying drawing.