CATHODE AND A METHOD OF FORMING A CATHODE
A cathode for receiving electro deposition of metal, the cathode comprising a planar conductive sheet and raised portions disposed on at least one surface of the planar conductive sheet, wherein the planar conductive sheet and the raised portions are integrally formed.
The invention relates to a cathode for use in the electrolysis of metal ions and a method of forming said cathode. In particular, although not exclusively, the invention relates to a cathode that is particularly useful for the electrolysis of cobalt ions or nickel ions from a solution.
BACKGROUND TO THE INVENTIONThe electrolysis of metal ions contained in a solution to give a solid metal product is a well known technique for isolating relatively pure metals. A solid cathode is placed into a metal ion solution and an electric current is applied to the cathode. Electro deposition of the metal onto the cathode then occurs. Periodically, the cathode and the attached metal product are removed from the solution. The solid metal product is then stripped from the cathode and, ideally, the cathode is then reused. The material for a cathode is suitably conductive to allow the metal product to deposit. Additionally, the cathode material allows easy removal of the metal product from the cathode, yet the metal product does not separate prematurely. A cathode that is robust such that it may be subjected to repeated deposition and stripping cycles with minimal treatment of the cathode between each cycle is preferred.
The electro deposition of cobalt metal presents additional difficulties, as cobalt metal electro deposits contain inherently high internal stresses. The electro deposition of cobalt onto standard flat stainless steel blanks, edged by non-conductive edge strips, results in a sheet of cobalt metal which has a tendency to prematurely separate from the cathode. If the non-conductive edge strips are eliminated, the cobalt metal grows around the edges of the cathode, which solves the problem of premature separation of the metal from the cathode. However, the cobalt metal is much more difficult to remove from the cathode and attempts to remove it may easily result in damage to the cathode. Damage to the cathodes may require each cathode be repaired on a frequent basis, which leads to higher plant operating costs.
The electro deposition of cobalt as a multiplicity of pieces is advantageous, as these are more easily handled in downstream processing.
Previous attempts at resolving the difficulties involved in the electro deposition of cobalt have resulted in the manufacture of cathodes by the application of a non-conductive mask to a stainless steel blank sheet such that a pattern of isolated conductive metal portions are exposed to an electrolysis solution.
CA 1,078,324 discloses such a cathode, in which the mask is an epoxy-based paint. The conductive portions are recessed in relation to the masking layer. One problem with this cathode is that the masking film is exposed to a harsh environment both in the electrolytic solution and in the stripping procedures. The masking film easily becomes cracked and damaged, particularly at the edge of the conductive portions. Breakdown of the masking film leads to metal deposits forming on the damaged areas, which in turn leads to further damage of the masking film. Thus, the cathode becomes unusable and at regular intervals the cathode must be stripped of the masking film, cleaned and new masking film re-applied.
CA 1,066,657 discloses a cathode wherein metal discs are attached to a plate or a wire grid. A non-conductive resin is filled into the interstitial area surrounding the discs. Alternatively, heavy gauge corrugated wires are attached to an assembly and resin is filled into the interstitial area leaving the bends in the wire uncovered. In these cathodes the conductive portions are either flush with or stand proud of the surrounding non-conductive resin.
OBJECT OF THE INVENTIONIt is an object of the invention to overcome or at least alleviate one or more of the above problems and provide the consumer with a useful or commercial choice.
DISCLOSURE OF THE INVENTIONIn one form, although it need not be the only or indeed the broadest form, the invention resides in a cathode for receiving electro deposition of metal, the cathode comprising:
a planar conductive sheet; and
raised portions disposed on at least one surface of the planar conductive sheet, wherein the planar conductive sheet and the raised portions are integrally formed.
The cathode may further comprise:
a non-conductive material which surrounds the raised portions, wherein a surface of the raised portions remains exposed.
Preferably, each of the raised portions have a planar top surface, wherein the planar top surface has a shape selected from a substantially circular shape, a substantially square shape, a substantially diamond shape or a substantially lozenge shape.
In one preferred embodiment, the raised portions form a front surface array located on a front surface of the planar conductive sheet and a rear surface array located on a rear surface of the planar conductive sheet. Preferably, the front surface array has a substantially similar configuration as the rear surface array. Alternatively, the front surface array has a substantially different configuration to the rear surface array.
In another form, the invention resides in a method of forming a cathode for receiving electro deposition of metal, the method comprising:
masking areas of a planar conductive sheet with a masking material to form a masked conductive sheet;
applying a chemical to the masked conductive sheet to chemically etch unmasked areas to form a planar conductive sheet having integrally formed raised portions formed in masked areas, and etched areas.
The method may further comprise:
applying a non-conductive material to the etched areas of the planar conductive sheet.
Further features of the present invention will become apparent from the following detailed description.
To assist in understanding the invention and to enable a person skilled in the art to put the invention into practical effect, preferred embodiments of the invention will be described by way of example only with reference to the accompanying drawings, wherein:
With reference to
The size and shape of the raised portions 110 may vary. Suitably, each of the raised portions 110 has a planar top surface 113. In one embodiment, the shape of the planar top surface 113 of each raised portion 110 is circular as shown in
The edges of the cathodes 100 may be covered by non-conductive edge strips 130, 131, 132 to prevent electro deposited metal from growing around the edge of the cathode 100. Conventional edge strips, as are well known in the art, may be used.
The cathode 100 is attached to a hanger bar 150 to facilitate the introduction and removal of the cathode 100 from an electrolytic bath and to provide an electrical connection to the cathode. Conventional hanger bars, as are well known in the art, may be used.
As shown in
The raised portions 110 of the cathode 100 are preferably formed by chemically etching the surface of the planar conductive sheet of metal 105.
In the second step (
In the third step (
Suitably, raised portions 110 are formed by the chemical etching process on both a front surface and a rear surface of the planar conductive sheet 105 of the cathode 100.
The cathode 100 with raised portions 110 formed by chemical etching of a sheet of metal 105 is quick and easy to manufacture. As the raised portions 110 are level with or proud of the surrounding non-conductive material 120, removal of electro deposited metal is less likely to cause damage to the non-conductive material 120.
Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention. For example, the size and shape of the cathode may vary, as may the size, number and shape of the raised portions. Additionally, more than one type of shape of raised portion may be used on a cathode.
It will be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit and scope of the invention.
Claims
1. A cathode for receiving electro deposition of metal, the cathode comprising:
- a planar conductive sheet; and
- raised portions disposed on at least one surface of the planar conductive sheet, wherein the planar conductive sheet and the raised portions are integrally formed.
2. The cathode of claim 1 further comprising:
- a non-conductive material which surrounds the raised portions, wherein a surface of the raised portions remains exposed.
3. The cathode of claim 1, wherein the planar top surface of each of the raised portions has a substantially circular shape.
4. The cathode of claim 1, wherein the planar top surface of each of the raised portions has a substantially lozenge shape.
5. The cathode of claim 1, wherein the planar top surface of each of the raised portions has a substantially diamond shape.
6. The cathode of claim 1, wherein the raised portions form a front surface array located on a front surface of the planar conductive sheet and a rear surface array located on a rear surface of the planar conductive sheet.
7. The cathode of claim 6, wherein the front surface array has a substantially similar configuration as the rear surface array.
8. The cathode of claim 6, wherein the front surface array has a substantially different configuration to the rear surface array.
9. The cathode of claim 1, further comprising a hanger bar attached to the top of the planar conductive sheet.
10. The cathode of claim 1, further comprising non-conductive edge strips covering at least one edge of the planar conductive sheet.
11. A method of forming a cathode for receiving electro deposition of metal, the method including the steps of:
- masking areas of a planar conductive sheet with a masking material to form a masked conductive sheet;
- applying a chemical to the masked conductive sheet to chemically etch unmasked areas to form a planar conductive sheet having integrally formed raised portions formed in the masked areas, and etched areas.
12. The method of claim 11, wherein areas on both a front surface and a rear surface of a planar conductive sheet are masked with the masking material to form a masked conductive sheet; and the chemical to chemically etch the unmasked areas is applied to both a front surface and a rear surface of the masked conductive sheet to form a planar conductive sheet having a front surface array of integrally formed raised portions located on a front surface of the planar conductive sheet and a rear surface array of integrally formed raised portions located on a rear surface of the planar conductive sheet.
13. The method of claim 11, further including the step of applying a non-conductive material to the etched areas of the planar conductive sheet.
14. The method of claim 11, further including the step of attaching non-conductive edge strips to at least one edge of the planar conductive sheet.
Type: Application
Filed: Sep 8, 2009
Publication Date: Sep 29, 2011
Applicant: STEELMORE HOLDINGD PTY LTD (Slacks Creek, Queensland)
Inventor: Jason Robert Cerezo (Slacks Creek)
Application Number: 13/062,150
International Classification: C25B 11/02 (20060101); C23F 1/02 (20060101);