US2434731A - Platinum sheet electrode - Google Patents

Description

Jan. 20, 1948. A. E. zu ELTi 2,434,731

PLATINUM SHEET ELECTRODE Filed Nov. 16, 19,45'

3nventor zzzZ/zz Patented Jan. 20, 1948 PLATmUMasHEE'nELEemcnE Alexander E'. zu Elti, New'Yliirk, If, assignor' to Baker '82 (30: Inc, Newark; N. J1, aicorporation" of New Jersey Application November 16, 1943;-.Serial No.*51 0, 466- 2 Claims; (01. 211L486) The presentlinvention relates. to an electrode for usein electrochemical processeshmore particularly to an-improved type of platinum sheet electrode and to a method of forming same.

Platinum sheet electrodes are employed. in manyelectrochemical processes, such as thee-lectrolytic production of hypochlorites; chlorates, perchlorates, and persulphates; Platinum and its alloys with other metals, such as gold or iridium,.are preferably used for such electrodes in spite of their very high initial cost andilow electrical conductivity, because thesemetals' produceresults which cannot beob tained with other metals" and becausethey are able to withstand the highly corrosive efiects of the liquids and vapors with which the electrodes come in con? tact. These electrodes consist in substance of a thin sheet or foil of platinum orits alloys which is submerged in the electrolytic bath and-to which the current is supplied by means of oneor more current terminals that may, for example, have the'form of feeding rods. The sheet form of 'the electrodes is dictated by the desire to providea maximum of surface with a minimum Weight of massive metal while maintaining. sufficient. elec trical conductivity.

The high cost of platinum and its alloys makes it desirable to employ high current densities.- In order to use such high current densitiespit is necessary to provide for sufiicient electrical .conductivity to overcome excessive heating of'the electrode, particularly of'thosepartswh-i-ch are not submerbed'in the electrolyte and'therefore do not benefit from the cooling. efiect of the elec trolytic. bath. Suflicientconductivity can be obtained by increasing the volume of the metal in relation to its surface area; This, however, will result in raising the cost of the electrode to a prohibitive level.

It has been attempted to-solvetheproblem of overheating, particularly at the'current terminals, by constructing these of a. highly conductive metal, such as copper, bronze or silver. 'Ihu's; for'example, the-current hasb'een led in 'atithe top of the vertical sheet by means of a'number of feedingrodsof copper, it being desirable'to place such feeding rods at frequent intervals along the upper-edge in order'to assure even distribution ofcurrent overthesheet and .to'avoid excessive heating at the contact points of the feeding rods and the sheet: Inasmuch as copper is readily corroded, itis necessary to cover the copper feeding rods with a corrosion'resistant layer. They may, for example, be clad with platinum, but the labor involved in manufacturing'a reliable, platinum clad feeding rod'is excessive and theamou-nt of platinum required remains considerable.

The object of the present invention is to.-construct a'platinum sheet electrode whichw-illhave I satisfactorl'ly'supplied to a platinum sheet by meansfofa. feeding bar which is constructed and attached"alongftheupper edge of the sheet in the" following. novel manner. The feeding. bar is madefromia tube of a metal of high electrical. condtictivi'ty,1such' as copper, bronze or silver; Said tube'is platinum clad on the outside for. whichpurpose. one of several methods maybe..employedfdepending on the size required (cf.", for example, the British Patent No. 447,827). This tube. is carefully collapsed. and flattened app ying; controlled) pressure, which results in. ajlstri'pI of conductive metal that is platinum cladfon all sides except at the ends. This strip is then foldediover along its longitudinalaxis forming... a channel shaped clamp or vise into which the upper edge of a-platinum sheet is inserted. To insure a better grip. the sheet may be folded along its upper edge. Pressure is then appliedto. close. the clampor vise over the upper edge. of the sheet thus firmly fixing the sheet therein'i, 'If'he originaltube has now become a solid composittbar similar to a bus bar and constitutes. a good; conductor distributing the currentevenlyto the. sheet along its upper edge. Itmigh't seem easier to. simply weld or solder the sheetto asolid, platinum clad, base metal rod, but this. is: not practicable, because the thin platinumij layer on-the rod'will blister or break during the welding or soldering. operation due tothe much lower meltingpoint of -the base metal-f.

Itfisfobvi'ousI that my novel arrangement for supplying current to the sheet possesses a numher off important. advantages over those previously, employed... In the first place the conduotivem'etalincluded in the composite feeding her supplies the required electrical conductivitytofassure' against overheating that portion ortheelectrodewhicl'ris'not immersed in the elect-rolyticbath. All parts of 'the feeding bar that can possibly come into contact' with the corrosive-vapors from the electrolytic bath are platinum clad; so that there'isn'o danger whateversof the conductive metal becoming corroded. A minimumiiamountof platinum is required, becausertheiprot'ective layer can be. kept quite thin. At theesame time; the barprovides a rigid supportnforqthei-rupper edge of thethin platinum 'sheem which reduces-the {danger of its becoming bentaor otherwise: deformed; Theends of. 1. the novel feeding, bar-1 should, project beyond either wall of the electrolytic tank or cell and can there be supplied with current by any suitable means at points removed from the corrosive effect of the vapors or splash from the electrolytic bath.

The platinum clad tube from which my feeding bar is constructed should not have too great a wall thickness, otherwise the platinum layer will crack during the folding operations. One may, for example, employ a tube one inch in diameter with a wall one-sixteenth of an inch thick. If more conductive metal is desired to insure ample conductivity and strength, one may loosely insert a smaller conductive metal tube inside the platinum clad one and thus increase the thickness of the resultant feeding bar. In this manner one also reduces the danger of cracking the platinum layer at the folds. The platinum layer need only be a few thousandths of an inch thick. I have found that layers from about 0.004 to about 0.008 inch thick are satisfactory. The platinum sheets are generally rectangular in shape, although this is not necessary. They should, of course, possess a straight upper edge to fit into the feeding bar. Later, if desired, the bar and sheet can be bent. The sheets vary in thickness from about 0.0005 to 0.01 inch depending on their size. Obviously the dimensions here given are merely illustrative and my invention is not limited thereto.

I shall now more. particularly describe my novel electrode by reference to the accompanying drawings forming a part hereof:

Fig. 1 illustrates the platinum clad, conductive metal tube from which my novel feeding bar is constructed. The ends, which will not require protection from corrosion, are shown exposed. A conductive metal tube has been loosely inserted in the platinum clad one to insure ample conductivity and strength.

Fig. 2 shows the flattened tubes after the collapsing operation.

Fig. 3 illustrates the manner in which the composite strip is folded along its longitudinal axis to form a clamp or vise for holding the sheet electrode and this drawing shows the sheet electrode which is folded along its upper edge in order to insure a firmer grip by the feeding bar after the final pressing step.

Fig. 4 represents the final electrode according to my invention. Portions'of the feeding bar and sheet are shown cut away to better illustrate the manner of attachment.

It will be noted that all parts of the electrode coming into contact with the liquid or vapors of the electrolytic bath either consist of solid platinum or are wholly clad therewith in such a Way as to absolutely protect the conductive metal from corrosion. The ends of the feeding bar which, when the electrode is placed in the bath, project beyond the walls of the electrolytic cell, need not be platinum clad and the drawings, therefore, show the conductive metal exposed at these ends.

It is apparent that my invention is susceptible of many further modifications without departing from the spirit thereof. While the drawings show a plain platinum sheet, one may also use sheets that are perforated, protruded, corrugated or otherwise bent. Various types of gauze, strips or the like may likewise be employed. All that is necessary is that the active portion of the electrode possess a substantially two dimensional form. Furthermore, one might clamp several 4 sheets in the feeding bar and provide suitable means for holding them apart in the bath.

It is obvious that in place of pure platinum or its alloys with iridium or gold, one might employ for my electrodes any other highly corrosion resistant metal or alloy. Naturally, the chief benefits of my invention will be attained in the case of the very costly platinum and its alloys where a saving in the amount of metal employed is of paramount importance.

In the following claims the expressions platinum and sheet should be given their broadest possible interpretations in the light of the foregoing.

I claim:

1. A sheet electrode for electrochemical processes, comprising an electrode plate of electrically conductive corrosion resistant platinum metal, and a channel shaped electrical feeding bar having a core of electrically highly conductive metal, said core being subject to corrosion in an unprotected state, said electrical feeder bar, including its involute surfaces, and including all surfaces in contact with the electrode plate, being clad externally with a covering of corrosion resistant platinum metal, the ends of the feeder bar remaining unclad from such points which are safe from corrosion, said electrode plate bein mechanically sealed to said feeder bar within the channel of said feeder bar along the full width of the upper portion of the electrode plate and in electrically conducting contact along both sides of said upper portion.

2. A sheet electrode for electrochemical processes, comprising an electrode plate of electrically conductive corrosion resistant platinum metal, and a channel shaped feeder bar having a core of electrically highly conductive copper, said copper core, including its involute surfaces, and including all surfaces in contact with the electrode plate, being clad externally with a covering of corrosion resistant platinum metal, the ends 'of the feeder bar remain unclad from such points which are safe from corrosion, said electrical plate being mechanically secured to said feeder bar within the channel of said feeder bar along the full width of the upper portion of the electrode plate and in electrically conducting contact along both sides of said upper portion.

ALEXANDER E. ZU ELTZ.

REFERENCES CllTEE) The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,002,462 Sibley Sept. 5, 1911 1,179,872 Stromquist Apr. 18, 1916 1,863,362 Wurdack June 14, 1932 2,012,536 l-lonig Aug. 27, 1935 1,077,894 Stevens Nov. 4, 1913 1,477,099 Baum Dec. 11, 1923 1,977,499 Tetrault Oct. 16, 1934 2,011,885 Young Aug. 20, 1935 1,760,046 Dixon May 27, 1930 2,117,454 Sandler May 17, 1938 2,041,004 Levan May 19, 1936 2,068,564 Murphy Jan. 19, 1937 2,125,037 Sykes July 26, 1938 578,070 Woolf Mar. 2, 1897 FOREIGN PATENTS Number Country Date 132,588 Germany July 22, 1902

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