US2051928A

US2051928A - Electrodeposition

Info

Publication number: US2051928A
Application number: US755371A
Authority: US
Inventors: Charles E Yates
Original assignee: Anaconda Copper Mining Co
Current assignee: Anaconda Copper Mining Co
Priority date: 1934-11-30
Filing date: 1934-11-30
Publication date: 1936-08-25
Anticipated expiration: 1953-08-25

Description

Aug. 25, 1936. -cz. E. YATEs ELEcTRoDPosITIoN Filed Nov. 50, 1954 wmv] Patented ug. 25, i936 yELECTRODEPOSI'IION Charles E. Yates, Perth Amboy, N. J., assignor to Anaconda Copper Mining Company, New York, N. Y., a corporation of Montana Application November so, 1934, serial No. '155,371

16 Claims.

This invention relates to the eiectrolytic deposition of thin metallic sheets and foils and is concerned more particularly with a novel apparatus by which the production of thin sheets and foils 5 of uniform thickness and without pinholes can be carried on without interruption for long periods of time at a high output rate. The new apparatus may be used to special advantage in the manufacture of products of copper and an l embodiment of the invention suitable for that purpose will accordingly be described in detail for purposes of explanation. It is to be understood, however, that the utility of the invention is not limited to the deposition of that particular metal l and it will be apparent that the new apparatus may be employed for the production of sheets and foils of various other metals which can be deposited with facility.

The new apparatus includes a rotating drum' cathode on which metal is continuously deposited and from which the deposit is continuously stripped as the drum rotates. It also includes means by which thickening of the edges of the deposit and plating of metal on those portions of the drum where a deposit is not desired are prevented. In these particulars, the new apparatus involves the principles disclosed in my co-pending application, Serial No. 622,171, filed July 13, 1932, but it is superior to the apparatus of I that application in that higher current densities may be employed and a greater output thus obtained, without any impairment of the quality of the product.

In the prior apparatus, the cathode drum is mounted so that a portion of its cylindrical deposit surface is continuously immersed in the electrolyte in a lead-lined tank and this drum is provided with circumferential channels at its ends. Ports are formed through the bottoms of i the channels leading to the spaces at the ends of the drum, and the drum is provided with partition means for isolating the minor bodies of electrolyte at the ends of the drum from the main body of electrolyte in the tank. In order to prevent thickening of the edges of the deposit sheet and also to complete the isolation of the minor bodies of electrolyte, endless belts are provided at the ends of the drum, each belt having a portion which closes the open end of that portion of 50 its channel lying below the electrolyte level and also overlies the edge of the deposit surface adjacent the channel. In each conned body of electrolyte at the end of the drum, there is a sub-cathode maintained at a potential lower than i that of the drum itself, and with this arrange.

ment, any current which flows from the anode and passes into the confined bodies of electrolyte does not cause a deposition of metal on the inner surfaces of the channels or on the ends of the drum but flows at once to the sub-cathodes.

The use of the novel features referred to makes it possible to carry on the production of sheets and foils in the prior apparatus over long periods of time without interruption, and the deposit strips easily from the drum and is of substantially uniform thickness from edge to edge. But it has been found that when a cell of the prior construction is operated at a voltage in excess of a particular value, current flows from the anode to the tank lining and thence to the cathode and sub-cathodes. This results in a change in the electrical relations between `the cathode and the sub-cathodes with the result that copper is deposited upon the lining and 'also upon the inner surfaces of the channels, the ends of thedrum, o

and the sub-cathodes. In such a cell which has a lead lining and contains a lead anode, the voltage at which the lining enters the circuit is about 3.4 volts, and the apparatus must therefore be operated at a. voltage below 3.4 volts alg5 though considerably higher voltages are desirable and could be us'ed butfor the flow of current to and from thelining. In that apparatus, therefore, the advantages of employing a lead lining,-

instead of a non-conductive lining of mastic, for

example, have been obtained at some sacrifice in the output rate.

In the prior apparatus, the isolation of the bodies of electrolyte at the ends of the drum' has required the use yof two separate means,

namely, partition members mounted on the drum and contacting with the tank lining and belts which close the entrances to the circumferential channels. The partition means used in practice are strips of sheet rubber mounted on the ends 40 of the drum to form short cylinders with the v free edge of each cylindrical partition member engaging the tank lining. While these expedients accomplish the desired purpose, I have found that two separate means are not necessary,

and in the apparatus of the present application,

I have devised an end construction on the drum which makes it possible to use a single means both for preventing thickening at the edges of the deposit and for isolating the bodies of electrolyte .at the ends of the drum. This means includes a belt at each end of the drum which contacts with the deposit surface and also with 'a plate mounted in the tank between the end QI the drum and the lining. By making this i plate of insulating material and of the proper size and shape, I have found that it may be used for performing the further function of preventing ow of current from the anode through the lining to the cathode. Accordingly, the new apparatus is not only simpler than that of the prior application but it permits the use of higher voltages in a tank having a conductive lining. The novel features of construction of the apparatus, therefore, make available the advantages of a lead lining without sacrifice in output rate.

For a better understanding of the invention, reference may be had to the accompanying drawing, in which Figure 1 is a View in transverse vertical section through the apparatus with the cathode shown in elevation;

Figure 2 is a longitudinal vertical section through the apparatus with the cathode shown in elevation; l

Figure 3 is a sectional view through a portion of the drum and associated parts; and

Figure 4 is a fragmentary end view of the drum illustrating a modication.

Referring now to the drawing, the apparatus is shown as including a tank I0 of any suitable material, the tank having a lead Ilining II. Mounted on suitable supports I2 in the bottom Vof the tank are anodes I3, these. anodes being' of curved form and having lugs I4 at their upper ends which extend to the side Walls of the tank, with one lug of each anode making contact with a bus bar by which current is supplied to the anode. At their lower ends, the anodes are spaced apart to permit circulation of electrolyte, such circulation being promoted, if desired, by the use of air jets in accordance with standard practice.

The cathode I5 employed in the apparatus has the form of a drum mounted on a shaft I6 journaled in bearings I1 supported on the side Walls of the tank. The drum may be of any suitable construction, but preferably it includes end plates I8 of copper and a cylindrical copper member I9 providing the, curved surface. 'Ihe deposit surface is'formed by a continuous layer 20 of lead mounted on the cylindrical member I9 and projecting beyond the ends of -that member. 'I'he end plates ofthe drum are provided with a lead sheathing 2I, and at each end-of the drum and lying inward from the projecting edges of the cylindrical deposit member, there is a ring 22 of lead which has a radially projecting flange 23. This flange is separated from the end of the deposit member 2U by'a circumferential channel 24 and the outer end of the flange provides an inclined supporting surface 25, the outer edge of which lies inward from the cylindrical surface of the deposit member 20. At short intervals, ports 26 are formed through the ange lto lead from the bottom of the channel. Instead of employing a continuous circumferential ange with ports at each end of the drum as described, spaced lugs 21 may be used, as shown in Figure 4, each lug having an inclined supporting surface at its outer end similar to that designated 25 in Figure 3.

The cathode drum is provided with any suitable means for making electrical connection therewith as, for example, it may have a disc 28 on the end of shaft I6 which dips into mercury 29 in a cup 30 mounted on the tank wall, the cup being connected in the electrical system in the desired manner.

At each end of the drum is mounted a belt 3| which is trained about pulleys 32, suitably supported at' the top of the tank, and pulleys 33 mounted within the tank below the level of the electrolyte. Each belt is preferably a hollow rubber tube and it has a portion which lies in contact with the edge of the deposit surface of the drum and also withthe inclined surface 25 of the supporting means. The supporting means tend to force the belt toward the deposit surface so that the belt will overlie the edge of the latter to a substantial extent andthe amount' of the overhang of the belt may be varied by varying the tension on the belt. This can be accomlplished in any suitable manner as, for example,

by varying the positions of the pulleys 32, the mounting wherefor being adjustable for that purpose.

In order vto accomplish its purpose of isolating a body of electrolyte at the end of the drum from r the main body of electrolyte, that portion of each belt which contacts with the drum must also bear against a stationary surface. Where high current densities are not desired, the belt may engage the tank lining or an extension therefrom, but I prefer to mount a plate 34 at each end of the drum to provide the surface with which the belt makes contact. The plates 34 are of insulating material and preferably of glass, and they are spaced sumciently close to the ends of the drum so that each belt is flattened throughout its contact with the adjacent plate and leakage between the belt and plate is prevented. With this arrangement, each belt and plate serve to prevent free circulation of electrolyte in contact with one end of the drum, and by overlying the edge of the deposit surface, the belt reduces edge thickening. The-'supporting means 23 prevent the belt from entering the space between the plate and the end of the cylindrical deposit member 20 and also force the belt toward the deposit surface so as to make good contact With, and overlie the edge thereof.

The plates 34 are mounted on supports at the bottom of the tank and they extend up above the electrolyte level and are of such a shape and size as to constitute ashield which masks the entire immersed portions of the ends of the drum and the anodes from the tank lining. The supporting means for the plates include blocks 35, which may be of lead or other suitable material and reston the tank bottom, and on top of each block is a cylindrical member 36 which may be a short length of lead pipe secured rigidly to the block. Resting freely on each cylindrical member 36 is a semi-cylindrical member 31 secured to the lower end of a plate 38 which extends upwardly and has a slot i'n its upper edge in which the lower edge of the plate 34 is received. The supporting plate 38 may swing about the cylindrical member 36 to a slight degree and thus adjust itself but it is heldin a generally vertical position by a strap member 39 secured tothe tank wall and loosely enclosing the plate 38. Two supports o'. the construction described areprovided for each glass plate 34 and the upper' end of the plate is held in proper relation'to the drum by means of rubber blocks 40 insertedv between the plate and tank lining. v

In each confined body of electrolyte between a plate 34 andv one end of the drum are mounteda pair of sub-cathode elements 4I, these subcathodes being plates of metal attached to metal straps 42 which extend over the top of the glass plate and are held in position in any suitable manner. The sub-cathodes are connected in the electrical system so that they are continuously maintained at a potential lower than that of the main cathode, and as a consequence, any current which passes from the anode and enters the confined body of electrolyte at either end of the 5 drum, by reason of. leakage of electrolyte past the belt, flows at once to a sub-cathode and does not cause a deposit of metal on the end of the drum.

With the apparatus described, a single means l at each end ofthe drum prevents thickening of the deposit along its edge and also prevents free circulation in contact with the endof the drum, and by using rubber belts and glass plates with which the belts contact, a highly eiective isolal tion of the minor bodies of electrolyte at the ends of the drum is obtained. At the same time, the contact of a rubber belt with its glass plate develops little friction and wear on the belt since the surface of the plate is smooth and con- 20 tinually wet by electrolyte, The glass plates not only serve to cooperate with the belts for the purpose mentioned, but they also shield the ends of the drum so that iiowv of current from the anodes through the tank lining to the drum is 25 prevented. The use of the plates, accordingly,

permits voltages much higher than those heretofore permissible in a lead-lined tank, and greater current densities can be .obtained than are possible without the plates. The new apparatus is 30- accordingly more eillcient than my prior apparatus because of the increased output of deposited metal that can be obtained. The new apparatus, therefore, affords all of the advantages of the old construction plus the additional ad- 35l vantages above pointed out.

I claim:

l. Apparatus for electrodeposition which comprises a tank containing an electrolyte, a portion at least of the inner surface of the tank in con- 40 tact with the electrolyte being of electroconductive material, an anode in the tank supplying current to the electrolyte, a cathode mounted to have a portion immersed in the electrolyte and withdrawing current therefrom, means 'in the 45 tank for preventing current from flowing from the anode through said electroconductive material to said cathode, means for preventing .free circulation of the electrolyte in contact with the ends of the cathode, and a sub-cathode at each 50 end of said cathode immersed in the electrolyte which contacts with said end, said sub-cathode being maintained ata lowerk potential than said cathode. l

2.,Apparatusfor electrodeposition which com- 55 prises atank containing an electrolyte,a portion at least of the inner surface of the tank in contact with the electrolyte being of electroconductive material, an anode in the tank supplying current to the electrolyte, a rotatingkdrum cathoo ode mounted to have a portion continuously immersed in the electrolyte and withdrawing current therefrom, plates in the tank'at the ends of the cathode for preventing flow of current from the anode through said electroconductlve 65 material to the cathode, means cooperating with the plates to prevent free circulation of the electrolyte in contact with the ends of the cathode, and' a sub-cathode at each end of said drum between said end and the adjacent plate and im- 70 mersed in the electrolyte which contacts: with said end, said sub-cathode being maintained at a potential lower than that of said drum.

3. Apparatus for electrodeposition which comprises a tank containing electrolyte, an anode 'f5 inthe tank. for supplying current to the electrolyte, a rotating drum cathode mounted to have a portion of itsdeposit surface continuously immersed in said electrolyte and withdrawing from said electrolyte, means at each end of the cathode for preventing free circulation of electrolyte in 5 contact 4with said end, each means including a member traveling with the cathode in contact with a deposit surface thereof, and a fiat surface spaced from the end of the cathode and engaged by said member and lying at an angle to the axis of rotation of the cathode, and a subcathode immersed in the electrolyte at each end of said drum in space between said end and the adjacent at surface, said sub-cathode being immersed in the electrolyte and maintained ata potential lower than that of said drum.

4. Apparatus for electrodeposition which comprises a tank containing electrolyte, an anode in the tank for supplying current to the electrolyte, a rotating drum cathode mounted to have a portion of its deposit surface continuously immersed in said electrolyte and withdrawing current. from said electrolyte, means at each end of the cathode for preventing free circulation of electrolyte in contact with said end, each means including a member traveling with the cathode in contact with the deposit surface thereof, and a plate spaced from the end of the cathode and engaged by said member, and a sub-cathode at each end of said drum between said end and the adjacent plate, said sub-cathode being immersed in the electrolyte and maintained at a potential lower than that of said drum.

5. Apparatus vfor electrodeposition which comprises a tank containing electrolyte, an anode in 35 the tank for supplying current to the electrolyte, a rotating drum cathode mounted to have a portion of its deposit surface continuously immersed in said electrolyte and withdrawing current from said electrolyte, means at each end of the cathode 40 for preventing free circulation of electrolyte in contact with said end,'each means including an '.endless member having at least a portion in contact with the deposit surface of the cathode and traveling therewithand a platev spaced from the end of the cathode and engaged by said portion of the member, and a sub-cathode at each end of said drum between saidend andthe adjacent plate, said sub-cathode being immersed inthe electrolyte and maintained at a potential lower than that of said drum. i'

6. Apparatus for electrodeposition which comprises a tank containing electrolyte, k,an anode in the tank for supplying current, to the electrolyte, a rotating drum cathode mounted to have a portion of its deposit surface continuously immersed in said electrolyte and withdrawing current from said electrolyte, means at each end of the cathode for .preventing .free circulation of -electrolyte in contact with said end, each means including a rubber belt having at least a portion in contact with the deposit surface `oi' the cathode immersed in the electrolyte and traveling therewith, and a plate mounted inthe tank at the end of the cathode and having one face engaged by the belt, and a sub-cathode at each end of the drum between said end and the adjacent plate, said sub-cathode being immersed in the electrolyte and maintained at a potential .lower than that ofsaid drum. 70

il. In vapparatus for electrodeposition, the combination of a tank containing electrolyte, an anode in -the tank supplying current to the electrolyte, a rotating drum cathode mounted to have a portion of its cylindrical deposit surface continuously immersed in the electrolyte and withdrawing current therefrom, an endless member at each end of the drum and having at least a portion in contact with the deposit surface of the -drum and traveling therewith, and means on the drum for supporting the member, saidl means having surfaces engaging said member and lying inward from the deposit surface.

8. Apparatus for electrodeposition which comprises a tank containing electrolyte. an anode in the tank supplying current to the electrolyte, a rotating drum cathode mounted to have a-portion of its cylindrical deposit surface continuously immersed in the electrolyte and withdrawing current therefrom, a belt at each end of the drum having at least a portion in contact with the deposit surface of the drum and traveling therewith, means at the ends of the drum for supporting the belts, said means engaging portions of the belts inward from the deposit surface, and flat surfaces in the tank spaced from each end of the drum and lying at an angle to the axis of rotation of the drum, each surface being engaged by one of said belts.

9. Apparatus for electrodeposition which comprises a tank containing electrolyte, an anode in the tank supplying current to the electrolyte, `a rotating drum cathode mounted to have a portion of its cylindrical deposit surface continuously immersed in the electrolyte and withdrawing current therefrom, a belt at each end of the drum having at least a portion in contact with the deposit surface of the drum and traveling vtherewith, a circumferential supporting member at each end of the drum for supporting a belt, a plate in the tank at each end of the drum, each plate being engaged by a belt, and a sub-cathode at each end of the drum immersed in the electrolyte between -said end and the adjacent plate, said sub-I cathode being'maintained at a potential lower than that of said drum.

10. Apparatus for electrodeposition which comprises a tank containing electrolyte, an anode in the tank supplying current to the electrolyte, a rotating drum cathode mounted to have a portion of its cylindrical deposit surface continuously immersed in the electrolyte and withdrawing current therefrom, a belt at each end of the drum having at least a portion in contact with the deposit surface of the drum and traveling therewith, a plurality of lugs arranged circumferentially at each end of the drum for supporting a belt, a plate in the tank at each end of the drum, each plate being engaged by a belt, anda subcathode at each end of the drum immersed in the electrolyte between said end and the adjacent plate, said sub-cathode being maintained at a potential lower than that of said drum.

11. Apparatus for electrodeposition which comprises a lead-lined tank containing electrolyte,

I an anode in the tank supplying, current to the electrolyte, a rotating cathode drum having a cylindrical deposit surface, a portion of which is continuously immersed in the electrolyte andl lining to the drum, a pair of belts, one at'each means for the belts mounted on the drum and spaced from the deposit surface.

12. In an electrolytic tank, the combination of a rotating drum cathode having a cylindrical deposit surface, circumferentially disposed supporting means at the ends of the drum having inclined supporting surfaces lying inward from the deposit surface, and a pair of belts one at each end of the drum, said belts having portions supported by said supporting means and in contact with said supporting surfaces.

13. In apparatus for electrodeposition, the combination of an electrolytic tank, a rotating drum cathode having a cylindrical deposit surface a portion of which is continuously immersed in the electrolyte in the tank, a pair of plates supported from beneath in the tanky adjacent the ends of the drum, a pair of members one at each end of the drum each member having a portion engaging the deposit surface of the drum and traveling therewith and also engaging the adjacent plate, and a sub-cathode immersed lin the electrolyte at each end of said drum and lying between said end and the adjacent plate, said sub-cathode being maintained at a potentiallower than that of said drum.

14. In apparatus for electrodeposition, the combination of an electrolytic tank, a rotating drum cathode having a cylindrical deposit surface, a portion of which is continuously immersed in the electrolyte in the tank, circumferential supportv ing means at the ends of the drum, a smoothsurfaced plate at each end of the drum, said plate being supported from beneath in the tank and extending from below the lowest part of said drum toabove the level of the electrolyte', an endless rubber belt at each end of the drum, said beltengaging the immersed portion of the deposit surface and traveling therewith and also bearing against the .surface of the adjacent plate, said belt being in part supported by one of said circumferential `supporting means, and. a subcathode immersed in the electrolyte at each end of the drum between said end and the adjacent plate, said sub-cathode being maintained at a potential lower than that of said drum.

15. In apparatusfor electrodeposition, a drum cathode having a cylindrical deposit surface, supporting members at the ends of the`drum, each member having a working surfaceflying inward and spaced from the deposit surface`and inclined inward and toward said deposit surface, and a pair of endless belts one at each end of the drum,

each belt having a portion supported by the worki current to the electrolyte,a rotating drum cathode mounted to have a portion continuously immersed in the electrolyte and withdrawing current therefrom, a sub-cathode mounted in the tank at each end of the drum and maintained at a potential lower than that of the drum, plates in the tank at the ends of the drum for preventing iiow of current from the anode through said electroconductive material to the drum and subcathodes, and means cooperating with the plates to confine minor bodies of electrolyte at the ends of the drum, said minor bodies of electrolyte being in contact with the ends of the drum, the subcathodes, and thinner surface of the tank.

CHARLES E. YATES.