US3329589A - Method of producing lead coated copper sheets - Google Patents

Method of producing lead coated copper sheets Download PDF

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Publication number
US3329589A
US3329589A US263029A US26302963A US3329589A US 3329589 A US3329589 A US 3329589A US 263029 A US263029 A US 263029A US 26302963 A US26302963 A US 26302963A US 3329589 A US3329589 A US 3329589A
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Prior art keywords
lead
copper
sheet
cathode
cell
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US263029A
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English (en)
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Lebrun Gaston
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Houilleres du Bassin du Nord et du Pas de Calais
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Houilleres du Bassin du Nord et du Pas de Calais
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/04—Wires; Strips; Foils

Definitions

  • Lead-coated copper sheet has many important uses in engineering, wherever it is desired to protect a copper surface from corrosion by atmospheric and other deleterious agents. Such uses include weatherproof roofing material in building construction to prevent attack of the copper by the sulfuric acid produced by oxidation and dissolution of the sulfur content in flue gases by atmospheric oxygen and humidity; corrosion-resisting lining material in tanks and other vessels in various chemical plants; lead-lined tubing for heat-exchangers and the like.
  • the lead plating of copper sheet has usually been effected by dripping the copper sheet in a bath of molten lead, sometimes also by spraying methods.
  • One common expedient has been to add a lead-tin alloy containing at least 1% tin.
  • a ternary alloy comprising lead, tin and copper is present and provides the requisite bond.
  • the presence of the tin (or other third constituent used) detracts from the purity of the overlying lead surface layer, and it is well-known that the presence of even minute proportions of impurities in the lead plating considerably lowers the impervious character of the plating, and the eifectiveness of the protection afforded by it to the underlying copper surface.
  • the particles of foreign material, such as tin, present at the lead surface are points of incipient corrosion from which the attack spreads rapidly to the surrounding areas. The same can be said of the small surface defects that are inevitably present in the lead coating when applied by the conventional methods, especially dip-coating.
  • Objects of this invention are to provide a composite, copper-lead sheet material or laminate having greatly improved characteristics over comparable materials currently produced, especially in the purity and freedom from defects of the lead surface layer, as well as in the high strength of the bond at the copper-lead interface; to provide practical and economical electrochemical methods for the production of such sheet materials or laminates, including both simple copper-lead laminates and lead-copper-lead laminates; to provide such composite sheet material wherein the depth of the lead coating can be conveniently and controllably varied over a wide range, as from one tenth of a millimeter (or less), to ten or more millimeters. Other objects will appear.
  • the process may comprise first electrodepositing a layer of copper and then using the deposited layer as a base for electrodepositing a layer of lead.
  • the process may comprise electrodepositing a layer of lead, using this as a base for electrodepositing a layer of copper, and using this in turn to electrodeposit further a layer of lead, thereby providing a copper sheet lead-coated on both sides.
  • Composite or laminate sheet materials including both copper-lead and lead-copper-lead laminates, when produced by the electrolytic methods of the invention, and characterized by a high purity of the lead layer and the absence of any third constituent, as well as by an intimate continuous bonds at the interface or interfaces of the lead and copper layers, constitute new articles of manufacture included within the scope of the present invention.
  • FIG. 1 is a view in simplified vertical cross section of a first type of electrolytic cell usable in the process of the invention
  • FIGS. 2 and 3 similarly illustrate two alternative types of electrolytic cells usable in further embodiments of the improved process.
  • the apparatus illustrated in FIG. 1 comprises a tank 1 which may be made of concrete internally lined with a suitable impervious plastic coating.
  • the tank is filled with a body of electrolyte 2 the nature of which will be later specified.
  • the tank further contains two anodes 3 and 4 having vertical upper portions extending along opposite sides of the tank and downwardly converging lower sections. Between the anodes is mounted a removable rotatable cathode structure 5 comprising a hollow cylinder or drum e.g. of cast iron secured on a shaft suitably journalled for rotation in the tank.
  • Revolving-cathode electrolytic cells of this general kind are known so that the details thereof need not be described.
  • the open V defined by the lower parts of the anodes 3 and 4 serves to reduce the variations in anode-cathode spacing to an acceptable value.
  • a groove 6 is formed in the periphery of the revolving cathode drum 5 along a generatrix thereof and may have its surfaces coated wit-h a suitable insulating varnish to provide a gap in the metal sheet that will be electrodeposited around the drum 6.
  • the drum is completely immersed in the electrolyte 2 and is supplied from a negative source at a terminal 7 connected with the shaft of the drum, while the anodes 3 and 4 are connected to the positive source at the terminal 8.
  • a doctor blade 9, made of glass or the like, may be provided as shown (especially in the first, copper-depositing step of the process presently described), and is provided with means for imparting to it a rapid reciprocatory motion parallel to the axis of the cathode drum 5 to improve the uniformity of the deposited metal (copper) and avoid the formation of trees or the like.
  • rotation of the cathode creates agitation in the electrolyte bath, promot ing smooth ion exchange reactions and enhancing the uniformity of the deposited layer.
  • the process being described includes two stages, the first of which electrodepositing a layer of copper around the periphery of the revolving cathode drum 6, and the second stage residing in electrodepositing a layer of lead over the copper sheet obtained in the first stage, while said sheet is positioned around the periphery of the same revolving cathode drum 6 transferred into an electrolytic cell similar to the one shown in FIG. 1, but arranged for the electrodeposition of lead.
  • the anodes 3 and 4 are made of copper which may be of a purity grade in the range e.g. from 98.5 to 99.0%.
  • the electrolyte 2 may have the following composition: 60 to 80 grams per liter H 30 and 120160 g./liter copper sulfate CuSO-SH O.
  • the bath temperature is in the range from 20 to 50 C.
  • the direct current used . is in the range 3000-4000 amps.
  • the cathode current density is about 4 amps/dm
  • the voltage drop across the cell is about 2-3 volts.
  • the electrical efficiency is about 96%.
  • the cathode drum 5 is rotated at a speed of about 40 r.p.m.
  • Electrolyte is circulated continuously over a flow circuit not shown, including suitable pumping and filtering means.
  • a conventional amp-hour counter is preferably provided to measure the current flow through the cathode. This measurement may be indicated in units thickness deposited copper and can serve to control the deposited depth.
  • the cathode drum 5 with the copper sheet obtained in the first stage is bodily removed from the electrolysis cell in which the copper sheet was formed, is rinsed free of electrolyte and is transferred to another cell, essentially similar to the one first described.
  • the anodes 3 and 4 are made of substantially pure lead, and the electrolyte 2 comprises a suitable lead salt solution, e.g. an acidic lead fiuoroborate solution.
  • a suitable lead salt solution e.g. an acidic lead fiuoroborate solution.
  • One composition for the lead-plating electrolyte that has been successfully used comprises from 70 to 120 g./liter of an aqueous solution containing 50% lead fluoroborate,
  • the bath temperature may be from to 40 C.
  • the current characteristics may be the same as in the first stage.
  • the rate of cathode rotation can also be the same.
  • Lead is then found to deposit at a rate of about 0.15 millimeter per hour, and is chemically pure.
  • the depth of deposited lead can be controlled in a manner similar to that used in the first stage, i.e. by measuring the amount of current that has flowed through the cathode. This provides an extremely convenient and accurate method of monitoring the depth of the deposited lead layer, which may be varied widely as from less than 0.1 to 10 mm. or more depending on requirement.
  • the product is a copper-lead laminated sheet.
  • the process may be carried out in three stages rather than two; in the first stage, using an electrolytic cell with lead anodes and lead salt electrolyte, a layer of lead is deposited on the periphery of the removable cathode drum; this drum with the sheet of lead thereon is rinsed and transferred into another electrolysis cell having copper anodes and copper salt electrolyte; the cathode drum carrying the resulting copper-lead laminate can then be returned to the first cell, or placed in a similar cell, for depositing a further lead layer on the opposite side of the copper sheet.
  • sequence just indicated is advantageous in that it permits the laminate to be retained on a single cathode drum throughout the process, thereby greatly facilitating handling operations.
  • the surface of the cathode drum is preferably polished and slightly greased prior to the initial electroplating step to facilitate the subsequent removal of the final laminate sheet.
  • the final sheet, after removal from the drum surface, may be passed through conventional straightening means and cut to size.
  • the copper-lead and lead-copper-lead laminates obtained in the manner described have a beautiful smooth, absolutely uniform aspect, with the cathode side being bright and the electrolyte side matte. No structural defects whatever can be detected in the lead surface. Microscopic examination of test-fractured sheets indicates a continuous, gradual transition between the lead and copper layers rather than a sharp interface there between, and the bond between the layers is extremely strong.
  • laminate sheets according to the invention can, in use, be subjected to various treatments, including soldering and welding operations for assembly, without any risk of delamination or tendency for the different-metal layers to separate. Soldering may be effected using pure lead, or lead-tin along containing not more than about 10% tin.
  • an electrolysis tank 10 made of concrete with an impervious plastic lining contains a body of electrolyte 11.
  • Electrolyte circulating means 12 are provided including filter means 13, a circulating pump 14 and a valve 15.
  • a substantial rate of electrolyte circulation should be used in order to promote agitation in the bath and ion exchange reactions, in the absence of the revolving cathode of FIG. 1.
  • a suitable range of flow rates with the apparatus described by way of example is approximately from 2 to 3 m. per hour and per in. of cathode surface.
  • lead anodes 16 Dipping into the electrolyte in the tank are lead anodes 16 (three shown) and intervening copper sheets 18 (two shown), that are to be lead-plated.
  • the lead anodes are connected to positive terminal 17, and the copper cathodes are connected to negative terminal 19.
  • the copper sheets 18 are assumed to have been produced separately by a method capable of yielding copper with the degree of purity required for practicing the lead-plating method of the invention, as by electrolysis.
  • the current characteristics and electrolyte composition used may be substantially the same as indicated for the lead-plating stage in Example 1.
  • the end product in this case is fiat copper sheeting lead plated on both sides.
  • An electrolysis tank 20 contains a body of electrolyte 21 which may be similar in composition to that indicated for the lead plating stage in Example 1.
  • a suitable stand within the electrolyte is a set of spaced lead anodes 23, which are of the generally triangular prismatic form shown in order to minimize variations in anode-cathode spacing as described for the V-shaped anodes 3-4 in FIG. 1.
  • Electrolyte circulating means include the conduit 22 with filter, pump and valve means therein as in FIG. 2.
  • the rate of flow of electrolyte through the system can be made substantially lower than in Example 2, a rate of about 1 m. per hour and per m? cathode surface being suitable.
  • the composite copper-lead tubes produced by electrodeposition have an extremely strong copper-lead bond.
  • the high-purity -lead plating is perfectly smooth and uniform imparting a remarkably high degree of chemical protection to the underlying copper surface.
  • a method of producing lead-plated copper sheet comprising electrodepositing copper to a substantial thickness over the peripheral surface of a removable cathode having a polished, non-adherent peripheral surface and which is disposed in a first electrolysis cell having a copper anode and a copper-salt electrolyte, bodily transferring said removable cathode With the copper sheet on the periphery thereof into a second electrolysis cell having a lead anode and a lead-salt electrolyte, electrodepositing lead over the exposed periphery of said sheet in said second cell, and removing the resulting lead-plated copper sheet from said non-adherent peripheral surface of the cathode.
  • a method of producing copper sheet lead-plated on both sides thereof comprising electrodepositing lead over a polished, non-adherent peripheral surface of a removable cathode in a first electrolysis cell having a lead anode and a lead-salt electrolyte, bodily transferring said cathode with the lead sheet thereon into another electrolysis cell having a copper anode and copper-salt electrolyte and electrodepositing copper to a substantial thickness over the exposed periphery of said lead sheet in said second cell, then bodily transferring said cathode with the copperplated lead sheet thereon into another electrolysis cell having a lead anode and a lead-salt electrolyte and electrodepositing lead over the exposed periphery of the copper plating of said sheet in said last mentioned cell, and removing the resulting copper sheet lead-plated on both sides from said non-adherent surface of the cathode.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electroplating Methods And Accessories (AREA)
US263029A 1962-03-07 1963-03-05 Method of producing lead coated copper sheets Expired - Lifetime US3329589A (en)

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FR890247A FR1325682A (fr) 1962-03-07 1962-03-07 Procédé de préparation électrolytique d'un matériau complexe cuivre-plomb

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100012501A1 (en) * 2006-09-27 2010-01-21 Outotec Oyj Method for coating a cooling element

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US428087A (en) * 1890-05-20 Davis gaerett
US527110A (en) * 1894-10-09 Charles r
US1543861A (en) * 1924-05-16 1925-06-30 Mccord Radiator & Mfg Co Method of and apparatus for producing copper sheets electrolytically
US2422902A (en) * 1942-02-24 1947-06-24 Western Electric Co Method of electrolytically cleaning and plating conductors consisting principally of copper
US2485258A (en) * 1944-01-03 1949-10-18 Standard Oil Dev Co Electrodepositing lead on copper from a nitrate bath
US2569367A (en) * 1946-01-08 1951-09-25 Champion Paper & Fibre Co Endless metal belt and method of making the same
US2894885A (en) * 1945-01-06 1959-07-14 Allen G Gray Method of applying copper coatings to uranium

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US428087A (en) * 1890-05-20 Davis gaerett
US527110A (en) * 1894-10-09 Charles r
US1543861A (en) * 1924-05-16 1925-06-30 Mccord Radiator & Mfg Co Method of and apparatus for producing copper sheets electrolytically
US2422902A (en) * 1942-02-24 1947-06-24 Western Electric Co Method of electrolytically cleaning and plating conductors consisting principally of copper
US2485258A (en) * 1944-01-03 1949-10-18 Standard Oil Dev Co Electrodepositing lead on copper from a nitrate bath
US2894885A (en) * 1945-01-06 1959-07-14 Allen G Gray Method of applying copper coatings to uranium
US2569367A (en) * 1946-01-08 1951-09-25 Champion Paper & Fibre Co Endless metal belt and method of making the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100012501A1 (en) * 2006-09-27 2010-01-21 Outotec Oyj Method for coating a cooling element
US8377513B2 (en) * 2006-09-27 2013-02-19 Outotec Oyj Method for coating a cooling element

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BE628910A (fi)

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