Chemistry: electrical and wave energy – Apparatus – Electrolytic
Patent
1998-05-22
1999-07-27
Valentine, Donald R.
Chemistry: electrical and wave energy
Apparatus
Electrolytic
264252, 26427211, C25B 100, C25C 702
Patent
active
059284820
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for producing a mother plate for electrolytic cleaning and to a mother plate produced according to said method, so that the deposits accumulated on the mother plate surface during electrolytic cleaning are easily removable from the mother plate.
The refining of many metals, such as copper, zinc and nickel, includes electrolytic cleaning where harmful impurities are separated from the metal to be produced. The metal produced in electrolytic cleaning is gathered on the cathode by means of electric current. Usually electrolytic cleaning is carried out in tanks filled with an electrolyte containing sulphuric acid and, immersed therein, a number of plate-like anodes and cathodes made of some electro conductive material and placed in an alternating fashion. At the top edges, the anodes and cathodes are provided with lugs or bars for suspending them at the tank edges and for connecting them to the power circuit. The metal to be produced is brought into the electrolytic process either as soluble anodes, so-called active anodes, or as dissolved in the electrolyte at some preceding process stage, in which case the employed anodes are insoluble, so-called passive anodes.
The cathode used in electrolytic cleaning can be produced of the desired metal to be produced, in which case the deposit need not be stripped from the original cathode plate. Usually, however, the cathode, i.e. the mother plate, to be immersed in the electrolytic tank is made of some other metal than the one to be produced. Such materials of the mother plate can be for instance stainless steel, aluminum or titanium. In that case the metal to be produced is gathered on the surface of the mother plate in deposits, which are stripped from the mother plate at defined intervals.
Owing to electric current, the metal produced in electrolytic cleaning is accumulated in deposits on all electro conductive surfaces of the mother plate, i.e. if the mother plate is completely electro conductive, the metal to be produced covers in a uniform deposit the mother plate in all parts immersed in the electrolyte. Now the deposits of the metal to be produced, accumulated on two sides of the mother plate, are on three sides attached to each other over the narrow edges of the mother plate, and thus the deposits of the metal to be produced are extremely difficult to remove from the mother plate. In order to facilitate the removal of the deposits of the metal to be produced from the surfaces of the mother plate, it is necessary to prevent the metal to be produced from accumulating deposits over the narrow edges of the mother plate, i.e. the edges of the mother plate must be made non-conductive.
The best-known way to make the edges of the mother plate non-conductive is to cover the edges with edge strips made of some insulating material, such as plastic. Generally the insulating strips are plastic profiles with a groove-shaped cross-section and are pressed onto the edges of the mother plate and remain in place either owing to the pressure created by the transformation, by rivets inserted through the mother plate or due to a combination of these. Because of the structure of the edge strips, the edge strips become too thick with respect to the required insulation, and the seam between the strip and the mother plate is not compact, but both the electrolyte and the metal to be produced have access therein. When electrolyte enters in between the mother plate and the edge strip, this often leads to an intensive corrosion of the mother plate, which results in the detachment of the strip and in an essential shortening of the mother plate's life. On the other hand, when the metal to be produced begins to accumulate in between the mother plate and the edge strip, this causes both a detachment of the strip from the mother plate and essential difficulties in the removal of the metal to be produced, in which case the edge strip is rapidly destroyed, either when removing the metal to be produced or owing to the wedging effect thereof.
A mother plate
REFERENCES:
patent: 4207147 (1980-06-01), Babin
patent: 4406769 (1983-09-01), Berger
patent: 4776928 (1988-10-01), Perlich
patent: 5314600 (1994-05-01), Webb et al.
patent: 5785827 (1998-07-01), Dougherty
Outokumpu Wenmec OY
Valentine Donald R.
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