Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1998-05-27
2000-01-25
Bell, Bruce F.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
204286, 204288, 204280, 26417717, 264230, 264231, 264239, 264248, 264252, 264299, 264325, 2643281, 26433113, C25D 100
Patent
active
060174293
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improved cathode element for the production of electrolytic copper, and more particularly to an improved reusable type of cathode element. The invention also relates to a method of manufacturing the cathode element.
In recent times, more and more electrolytic copper production plants have switched from the use of copper cathode plates intended for one-time use only to the use of reusable cathode elements made of stainless, acid-proof steel plate, for instance. Because copper coatings that precipitate onto a steel cathode plate do not adhere particularly firmly to the plate, the coating can be removed quite easily from the plate as copper plate and the cathode element can be returned to the electrolytic bath and reused.
However, in order for the copper coating to be easily removed from the cathode element it is necessary for the coating to be deposited solely onto the main surfaces of the cathode element and not on its edge surfaces. If the copper coating is permitted to extend around the edge surfaces of the cathode and therewith join the coatings deposited on the front and the rear sides of the cathode element, there is formed a sleeve-like coating which is difficult to remove. In order to avoid deposits in the proximity of the edge surfaces of the plate, the surfaces are insulated against electrical conductivity.
This electrical insulation is at present achieved by fitting insulating clamping strips, normally plastic strips, over the edge surfaces of the cathode plates. These electrically insulating strips have a U-shaped cross-section and are normally dimensioned so that the U-profile will seat against the plate and therewith hold the strip in position.
It is worthy of note in this respect that the cathode elements are located in an extremely difficult environment as the copper builds up on the cathode plate. This environment is both acid and warm (e.g. 16% sulphuric acid at +60.degree. C.) and the cathode elements remain in the electrolytic bath for long periods of time with no interruption (e.g. 7-10 days).
However, the clamping strips provided around the edge surfaces of the cathode element tend to loosen, e.g. as a result of direct contact with some other object or some other cathode element--hits, impacts, wear--or when the precipitated copper coatings are stripped from the main surfaces of the cathode elements. Stripping of the copper plates from the cathode elements is also liable to affect the edge strips mechanically, causing the strips to loosen or inflicting damage thereon.
The environment in which the strips are located also has an affect on their useful life span. Long stay times in high temperatures and in acid environments accelerates relaxation of the material from which the clamping strips are made therewith reducing the strip clamping forces, among other things.
In certain cases, these plastic strips are supplemented internally with a seal, e.g. a sealing strip which lies against the surface of the cathode plate. This seal is intended to reduce the penetration of electrolyte and therewith reduce undesirable copper formations inwardly of the clamping strip. The formation of copper layers is liable to urge the strips away from the cathode plate, causing the strips to fall into the electrolyte bath and unavoidably resulting in the formation of copper around the edge surfaces of the cathode plate and therewith joining the copper coatings on the main surfaces of the plate and rendering stripping of the plate difficult to achieve.
Another problem with known techniques resides in he undercuts that occur at the junction of the strips with the cathode plate. These undercuts cause the copper coating nearest the strip to press the strip outwards; in other words, the known techniques provide no release angle for the copper plates deposited on the electrode plates.
The plastic strips normally seat solely along the vertical side edges of the cathode plate, and the bottom edge which is most likely to be damaged when the plate is stripped is insulating with a layer
REFERENCES:
patent: 3523873 (1970-08-01), Elkin
patent: 4207147 (1980-06-01), Babin
patent: 4670124 (1987-06-01), Bartsch et al.
patent: 4749464 (1988-06-01), Dufresne et al.
Bell Bruce F.
Svedala Skega AB
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