Title of Invention

"A PLATE FOR METAL DEPOSITION"

Abstract

A plate fabricated from metals which are different from the metal being refined, examples of such metals include aluminium and stainless steel for use as the cathode in an electrolytic cell in which refined metal is deposited onto the plate from an acidic solution of a metal salt, wherein the plate is arranged to be supported vertically and partially immersed in the solution, in which the tendency for the cathode plate to be attacked in the vicinity above the solution level up to welded hanger bar is eliminated or greatly reduced by coating of an electrically non-conductive material in a manner such that it extends and encapsulates on the width of each of its two un immersed faces from the level of the solution in the cell up to welds of the hanger bar and manual or mold coating of entire length of its side edges that remain immersed in electrolyte solution to ease the stripping of deposited metal between these coated edges. The coating may be of a materials of high surface energy that maximize the bond strength between coating material and metal substrate especially Aluminium to yield corrosion protection of long durations enhancing the service life of Cathode Plates by one & half to two times of their normal service life.

Full Text

A plate for metal deposition The present invention relates to a plate for metal deposition for use in the electrolytic cell, which is having two faces for the deposition of a metal. Further, it is hanged from a hanger bar so that it is partially submerged in the electrolytic solution of the cell and it is coated with an electrically nonconductive material. This invention relates to electrodes for use in the electrolytic system for deposition of purified metals at cathode. The final step in the production of metal, following roasting and leaching, is electrowinning, in which aqueous metal ions are electrolyzed to Zinc metal at cathode while oxygen is liberated at anode. The current flow between the electrodes transmitted by molten electrolytic salts or solution result into final purified metal deposition on cathode and oxygen being released at anode. This liberation of oxygen at the solution level of electrolytic medium cause corrosion and rusting of cathode. Various prior art methods and techniques have been reported which form an electrolytic system where the barrier between the electrodes at the level lower then the electrolytic solution is used for reducing the corrosion. The problems of solution line corrosion can be solved by attaching a film or coating of a protective material to the starting sheet prior to commencement of the electrolytic operation to effectively inhibit corrosion of the cathode at the solution line. DETAILED DESCRIPTION: Refining or winning of many non-ferrous metals can be achieved by electrolysis. For metals, which are more readily oxidized and reduced than water, one electro-refining technique comprises placing an anode fabricated from the crude metal and a cathode together in suitable acid bath. Application of a voltage between the anode and the cathode cause the crude metal to oxidize and pure metal ions to migrate electrolytically through the acid bath to the cathode. The metal ions are deposited on the cathode as a refined metal of high purity, leaving the majority of impurities on the floor of the acid bath. Alternatively, in the electro-winning process the anode is fabricated from a material other than the metal being refined, for example for the electro-winning of copper one anode used is fabricated from an alloy of Lead, Tin and Calcium (Pb, Sn and Ca). The metal to be refined, copper in this case, is delivered to the electrolytic bath in soluble form, primarily from a leaching and solvent extraction process. Application of a voltage across the anode and cathode causes the copper to migrate from the solution and deposit on the cathode in a refined metallic state. The cathodes are typically comprised of a flat, square or rectangular deposition plate attached along an upper edge to an electrically conductive hanger bar. The hanger bar, which straddles the tank which houses the acid bath during refining, is in turn in electrical contact with an external power source, conventionally by means of a pair of electrically conductive bus bars which run in parallel along opposite edges of the tank and upon which the ends of the hanger bar rest. The hanger bar therefore serves a dual purpose: providing the means for suspending the deposition plate within the acid bath and providing a path for the flow of electrical current between the deposition plate and the power source. After a suitable period of time when sufficient copper has migrated from the anode to the stainless steel cathode, or from soluble (solution) form to the cathode, the cathode is removed from the acid bath. Alternatively, other metals can be used for the fabrication cathodes. In the event one of these metals is used, the refined metal can be extracted by a variety of well known stripping techniques, including scraping, hammering, the use of compressed air, etc. This has the benefit that the cathode can be reused with little or no preparatory work being required other than the removal of previously refined metal Since the beginning of the commercial use of electrolysis to recover zinc from zinc sulfate solutions aluminum cathodes have been used. The zinc is deposited on the aluminum cathode from the zinc sulfate solution and stripped off periodically for melting. Aluminum cathodes have a high initial cost due to the fact that a specially refined metal must be employed in their manufacture. Ordinary commercial aluminum is not satisfactory for cathode use due to its high tendency to corrode in the presence of an electrolyte. High-grade aluminum is also corroded by electrolytes commonly employed, especially above the solution line. In addition, the deposited zinc has a tendency to stick to the aluminum cathode due to the presence of fluoride ion in the electrolyte, which etches the aluminum cathode. Furthermore, it is generally necessary to apply edge strips to facilitate stripping of the zinc deposits from the aluminum. The above-referred method for removal of zinc from the cathode plates involves removing the cathode plates or lifting them from the cell and returning the cathode plates to the cell after the zinc is removed. The cathode plates can be cleaned such as by brushing or washing, or both, prior to being returned to the cells. In some cases, the removal of the zinc from the cathode plates involves the use of crowbars and other prying devices which can be extremely harsh on the cathode plate which, in turn, requires a degree of robustness to withstand the repeated stripping or removal of the zinc product and the harshness involved in that operation. That harshness plus the harshness of the environment, especially the corrosive electrolyte fumes, at the electrolyte-air interface, requires a robust product both from the standpoint of chemical attack and physical attack. Corrosion at the electrolyte-air interface thins the cathode plate, reducing current carrying capability and plate strength and robustness, and accordingly shortening useful cathode plate life. If a cathode plate could sustain a 50% increase in useful life, it would be a substantial saving. Typical cathode life in present relatively high productive commercial cells is around 12 to 18 months for a plate 0.25 inch thick. Attaining for instance 18 to 24 months' life would be highly beneficial. Generally speaking, greater strength, hardness and corrosion resistance can cooperate to enhance cathode plate life. Corrosion removes metal in the electrolyte bath surface region and this metal removal weakens the plate at that site. If the metal has a low yield strength, that compounds the problem because the metal remaining after the corrosion effect has difficulty coping with the forces encountered in removing the zinc. Hence, a higher strength and better corrosion resistance cooperate to increase cathode plate life. Hardness also contributes to robustness in sustaining the day-to-day prying and gouging effects encountered in stripping zinc product off the plate. In electrowinning processes using conventional cathodes, for example Aluminium Cathodes with purity above 99.5% in the refining of Zinc there is corrosion & erosion of Aluminium metal on the major faces of the cathodes at the solution line, i.e. at the line where the electrolyte surface meets the exposed surface of the cathodes. Corrosion also occurs on the cathode surfaces in areas above the solution line due to acid vapors or splashing of or inadvent contact of the electrolyte with the exposed cathode surfaces. Such corrosion may be reduced or entirely eliminated if there is provided on the exposed surface of the cathode a strip of electrically non-conductive material, which is encapsulated across all of the cathode width. The cathode should be positioned in the electrolyte so that the surface of the electrolyte meets the conductive metal plate at a line where the surface of the conductive metal plate is protected by a coating of an electrically non-conductive material. While the plastic materials claimed in prior arts, as non-conductive could be used for coating, said to be resistant to the electrolyte at operative temperatures, the longevity of the bonding on the conductive cathode plate does not seems to have been fully measured or assessed. All the different claimed plastic materials during tests did not yield bond duration of more than three to six weeks. Our invention comprised of a method to identify composite plastic & ceramic materials that are not only highly chemical resistant in aggressive environments but also yield long duration chemical bonding by wetting & penetrating into the substrate before hardening at room temperature contributing to bond strength through mechanical interlocking in a manner such that the bonding of non-conductive material coated on the surface of the cathode plates especially Aluminium alloy above the solution level, remain adhered intimately without peeling off for more than 6 to 8 months or more. Aluminium surfaces are normally protected against corrosion by a passivating aluminium oxide film. However, further protection may be needed by employment of organic coatings. It is desirable that the coating contains certain functional groups, which enhance adhesion to the naturally formed or modified oxide present on the metal surface by promoting physical or chemical bonding between the coating and the substrate surface. Accordingly, there is provided a plate for metal deposition for use in the electrolytic cell wherein the plate is composed of an electrically conductive metal plate having two faces with a manual or mold coating of electrically non-conductive material for the deposition of metals and its position is such that it is arranged to be supported vertically and partially immersed in the electrolytic solution. One of the preferred embodiments is plate for metal deposition for use in the electrolytic cell wherein the electrically conductive plate is formed from stainless steel for deposition of Copper metal. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein electrically conductive plate is formed from aluminium alloy having a purity of above 99.50% by weight of aluminium for deposition of Zinc metal. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein the metal plate is supported vertically and partially immersed in the electrolytic solution positioned by welding to a hanger bar. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein the metal plate is positioned in the electrolyte so that the surface of the electrolyte meets the conductive metal plate at a line where the surface of the conductive metal plate is protected by a coating of electrically non-conductive material. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein a manual or mold coating of electrically non-conductive material is provided on the entire length of its immersed edges to ease the stripping of deposited metal. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein the manual or mold coating of electrically non-conductive material comprises hot or cold cure plastic composites forming a system of covalent bonds across the interface. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein the manual or mold coating of electrically non-conductive material is strong and durable capable of providing minimum bonding longevity of 6 to 8 months or more duration depending upon effects of variations in the solution levels in electrolytic cells & the stripping techniques employed i.e. manual or mechanical. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the manual or mold coating of electrically non-conductive material comprises composites of modified epoxide resins and hardening components in ratio of 3: 1 to 10:. 1. Another preferred embodiment is plate for metal deposition for use in the electrolytic cell wherein the manual or mold coating of electrically non-conductive material comprises composite of modified epoxide resins XXXXXXXXXXXX and hardening component such as amines, anhydrides, peroxides, saturated polyesters, carboxyfunctional aerylies. amino and phenolic resins etc. Accordingly, the present invention is an improvement over the processes of the prior art in that it solves the problems inherent in the use of aluminum cathodes by substitution of zinc cathodes without encountering the problems that are caused by the application of paint or other coatings to the zinc cathodes. Also, provided an electrically conductive metal plate having two faces for the deposition of a purified metal such as copper. In the invention there is provided on the unimmersed surface of the cathode plates a coating of electrically nonconductive material which extends across all of the cathode width in a manner such that it extends and encapsulates on entire width & edges of each of its two faces from slightly below the level of the solution in the cell up to welds of the hanger bar. The cathode should be positioned in the electrolyte so that the surface of the electrolyte meets the conductive metal plate at a line where the surface of the conductive metal plate is protected by a coating of electrically non-conductive material. The barrier structure of the invention can be fabricated from any substance that is not attacked by the electrolyte and is suspended from the structure that holds the electrodes and extends into the solution of the electrolyte between cathode and anode. These barriers must be of sufficient vertical height to cover variations in the height of solution in the cell. The barrier can be of any thickness that can be handled conveniently. EXAMPLES: Example 1: - A plate is provided in a running factory for metal refining on the surface of the cathode plates by cold cure method strips of electrically non-conductive suitable plastic materials of different kinds, suggested in previous art, resistant at operative temperatures to the electrolyte capable of forming an intimately bonded coating on the conductive metal plate so as to form a liquid proof seal between the plate and the plastic material and sufficiently flexible or tough to withstand the fairly rough handling customary towards increased productivity without fracturing the layer and exposing the metal of the plate beneath the applied coating layer. The cathode plates were positioned in the electrolyte cells so that the surface of the electrolyte met the conductive metal plate at a line where the surface of the conductive metal plate was protected by strips of suggested electrically non-conductive materials and periodically inspected at a gap of two weeks. The bonding of the strip with the cathode plates showed signs of peeling after 4 weeks and completely got debonded prior of six weeks. Example 2: - A plate is provided in a running factory for metal refining on the surface of the cathode plates by hot cure method strips of electrically non-conductive suitable plastic materials of different kinds, suggested in previous art, resistant at operative temperatures to the electrolyte capable of forming an intimately bonded coating on the conductive metal plate so as to form a liquid proof seal between the plate and the plastic material and sufficiently flexible or tough to withstand the fairly rough handling customary towards increased productivity without fracturing the layer and exposing the metal of the plate beneath the applied coating layer. The cathode plates were positioned in the electrolyte cells so that the surface of the electrolyte met the conductive metal plate at a line where the surface of the conductive metal plate was protected by strips of suggested electrically non-conductive materials and periodically inspected at a gap of two weeks. The bonding of the strips with cathode plates showed signs of peeling after 4 weeks and completely got debonded prior of six weeks. Example 3: - A plate is provided in a running factory for metal refining on the surface of the cathode plates by hot or cold cure method coating of electrically non-conductive plastic & ceramic composite materials forming a system of covalent bonds across the interface such that it was strong and durable, which extended across all of the cathode width in a manner such that it encapsulated on entire width of each of its two faces from slightly below the level of the solution in the cell up to welds of the hanger bar. The cathode plates were positioned in the electrolyte cells so that the surface of the electrolyte met the conductive metal plate at a line where the surface of the conductive metal plate was protected by a coating of suggested electrically non-conductive materials and periodically inspected at a gap of two weeks. The bonding of the coating with the cathode plates showed no signs of peeling after 2, 4, 6, 8, 12, 16 weeks and remained intimately bonded beyond 16 weeks. Example 4: - A plate is provided in a running factory for metal refining on the immersed edges of the cathode plates by hot or cold cure mold use method coating of electrically non-conductive plastic & ceramic composite materials forming a system of covalent bonds across the interface such that it was strong and durable, which extended across all of the immersed edges of cathode in a manner such that it encapsulated on entire length of each of its two side edges. The cathode plates were positioned in the electrolyte cells so that the surface of the electrolyte met the conductive metal plate at a line where the surface of the conductive metal plate was protected by a coating of suggested electrically non-conductive materials and periodically inspected at a gap of two weeks. The bonding of the coating with the cathode plates showed no signs of peeling at coated edges length after 2, 4, 6, 8, 12, 16 weeks and remained intimately bonded beyond 16 weeks. Example 5: - A plate is provided wherein the bonding with the cathode plate remained intimately bonded beyond period of 16 weeks, on removal of coating by hammering showed the protected surfaces & the edges of cathode plate intact without any signs of corrosion attack, pitting or thinning of any kind whatsoever. I Claim: - 1) A plate for metal deposition for use in the electrolytic cell wherein the plate is composed of an electrically conductive metal plate having two unimmersed faces with a manual or mold coating of electrically non-conductive material and its position is such that it is arranged to be supported vertically and partially immersed in the electrolytic solution for the deposition of metals 2) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the electrically conductive plate is formed from stainless steel for deposition of Copper metal. 3) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein electrically conductive plate is formed from aluminium alloy having a purity of above 99.50% by weight of aluminium for deposition of Zinc metal. 4) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the metal plate is supported vertically and partially immersed in the electrolytic solution positioned by welding to a hanger bar. 5) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the metal plate is positioned in the electrolyte so that the surface of the electrolyte meets the conductive metal plate at a line where the unimmersed surface of the conductive metal plate is protected by a coating of electrically non-conductive material. 6) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein a manual or mold coating of electrically non-conductive material is provided on the entire length of its immersed edges to ease the stripping of deposited metal. 7) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the manual or mold coating of electrically non-conductive material comprises hot or cold cure plastic composites forming a system of covalent bonds across the interface. 8) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the manual or mold coating of electrically non-conductive material is strong and durable capable of providing minimum bonding longevity of 6 to 8 months or more duration depending upon effects of variations in the solution levels in electrolytic cells & the stripping techniques employed i.e. manual or mechanical. 9) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the manual or mold coating of electrically non-conductive material comprises composites of modified epoxide resins and hardening components in ratio of 3: 1 to 10: .1. 10) A plate for metal deposition for use in the electrolytic cell as claimed in claim 1 wherein the manual or mold coating of electrically non-conductive material comprises composites of modified epoxide resins of the kind such as herein described and hardening component such as amines, anhydrides, peroxides, saturated polyesters, carboxyfunctional acrylics, amino and phenolic resins etc. 11) A plate for metal deposition for use in the electrolytic cell substantially as herein described and illustrated with reference to the examples.

Documents:

2976-DEL-2008-Abstract (5-1-2010).pdf

2976-del-2008-abstract.pdf

2976-DEL-2008-Claims (5-1-2010).pdf

2976-del-2008-claims.pdf

2976-del-2008-Correspondence-Others-(12-03-2014).pdf

2976-DEL-2008-Correspondence-Others-(5-1-2010).pdf

2976-del-2008-correspondence-others.pdf

2976-del-2008-correspondence-po-(21-04-2009).pdf

2976-DEL-2008-Description (Complete) (5-1-2010).pdf

2976-del-2008-Description (Complete)-(12-03-2014).pdf

2976-del-2008-description (complete).pdf

2976-del-2008-form-1.pdf

2976-del-2008-form-18.pdf

2976-del-2008-Form-2-(12-03-2014).pdf

2976-del-2008-form-2.pdf

2976-del-2008-form-3.pdf

2976-del-2008-form-5.pdf

2976-DEL-2008-Form-9-(21-04-2009).pdf