US2331320A - Electrode for electrometallurgical purposes - Google Patents

Description

F. H. HARTZELL Original Filed Jan. 18, 1936 Oct. 12, 1943.

ELECTRODE FOR ELECTRO-METALLURGICAL PURPOSE \AAA/ 4 Patented Oct. 12, 1943 ELECTRODE FOR ELECTROIVIETALLUR- GICAL PURPOSES Forest H. Hartzell, Dayton, Ohio Application January 18, 1936, Serial No. 59,702 Renewed March 21, 1940 18 Claims.

Thi invention relates to electrometallurgy and more particularly to an improved electrode of composite construction and the herein described method of electroplating and maintenance of the plating bath made possible by use of such electrode.

Briefly stated electroplating consists in the deposit of an adherent film of metal upon articles, known as the work, by the electrolytic action of an electric current passed through a bath which may be either acid or alkaline containing a solution of the metal, from an anode suspended therein and connected with the positive sideof a source of electrical energy, to the work also suspended in the bath, which becomes the oathode and is connected with the negative side of the source of electrical energy.

When certain metals such as silver, nickel, copper, etc., are to be deposited, an anode of such metal is suspended in an electrolytic bath and connected to the positive side of the source of electrical energy in which event the material of the anode is decomposed and passes into the solution from which it is redeposited upon the work. However for electrodeposition of other materials such as chromium, the metal to be deposited is introduced intothe electrolytic bath in solution as a metallic salt, and an anode of dissimilar metal which will not be subject to electrolysis and hence insoluble in the bath under influence of the passing current is suspended therein to supply the necessary electric current for inducing the metallic deposit.

The quantity of electrolytic'deposit in a given time being proportional to the strength of the current passed through the bath it is desirable thatthe anode be of high electroconductivity.

Unfortunately however material of high electroconductivity of which copper is commercially preferable, if employed as the anode will be decomposed or dissolved in the plating olution and redeposited upon the work along with the chromium or other metals to the detriment and injury of the finished product. It has therefore been customary under such circumstances to employ as an anode an eleotronegative material insoluble in the plating bath such as lead or an alloy of lead with tin or antimony which while not subject to decomposition and insoluble in the plating solution, possess the disadvantage of high resistance to current flow. Such anode decreases the current flow therethrough to approximately only seven percent of that through copper. The resistance of such lead or lead alloy anode being so great the current, seeking the path of least resistance, tends to leave the anode in the upper stratum of the plating solution. The resistance of such lead or lead alloy anode material increases downwardly. 7 There is progressively less current discharged through the lower level of the plating bath where frequently the current supply is insufiicient for plating purposes. Due to such ununiform distribution of plating current at different levels of the plating bath it is difficult to induce sufiicient deposit of metal on those parts of the work adjacent to the bottom of the bath and especially within cavities and recesses of articles being plated.

To assure an ample current flow at lower levels of the bath and increase the rapidity of the metallic deposit, it is customary to build up a high current density which, however, further proportionately increases the current flow through the upper level of the bath and generates heat therein. The generated heat gradually burns the anode at the solution line and may eventually burn entirely through and separate the anode. Such burning and reduction of the cross area of the anode further decreases the conductivity thereof. The generation of heat causes gasification of the plating solution, the vapors of which are dangerous to workmen and result in further losses. Furthermore such con-' v and which will be more efficient in use, uniform in action, and of increased conductivity.

A further object of the invention is to provide an improved method of operation whereby plating deposits may be more eifectively and uniformly distributed upon the work.

A further object of the invention is to provide an anode of relatively high electroconductivity which will be insoluble in the ordinary plating bath. v v

A further object of the invention is to provide means and a mode of operation whereby ametallic deposit may be more rapidly effected.

A further object ofthe invention is to effect a more uniform deposit-of metal on all parts of the work.

A further object of the invention is to minimize the emanation of fumes from the plating bath.

A further, but highly important object of the invention is to effect electrodeposit of metal and particularly chromium and like material within recesses and cavities of the work.

A further object of the invention'is to minimize burning or bluing of the work and to provide an initial increased luster, whereby subsequent buffing will be minimized and both labor and material saved.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention consists of the features of construction, the parts and combinations thereof or their equivalent as hereinafter described and set forth in the claims.

Referring to the accompanying drawing wherein is shown the preferred but obviously not necessarily the only form of embodiment of the invention,

Fig. l is a perspective view of an electroplating anode forming the subject matter hereof.

Fig. 2 is a longitudinal sectional view thereof.

Fig. 3 is a transverse sectional view thereof on line 3--3 of Fig. 2.

Fig. 4 is a transverse sectional view on line 4-4 of Fig. 2.

Fig. 5 is a transverse sectional view of a modifled form of the anode.

Fig. 6 is a sectional side elevation of a further modification of the-anode. w

Fig. 7 illustrates a different form of anode.

Like parts are indicated by similar characters of .reference throughout the several views.

Referring to the drawing, l is an electrode embodying the present invention of which 2 is the core of preferably bar copper but which may comprise other highly electroconductive material. At its upper end the core is provided with an enlarged head having exposed faces for direct contact with the conductor bus bars 4. For convenience of manufacture this headis formed by attaching heavy copper collars 3 to opposite sides of the core 2 by riveting, welding or otherwise. The head of the core has a transverse hole through the collars 3 and interposed portions of the core bar 2 for reception of a hanger bolt 5.

The core 2 is encased in a jacket 6 of dissimilar metal which is insoluble in the particular electrolytic bath in which that electrode is to be employed as an anode. For use in a chromium plating bath the jacket 6 or encasing material is preferably lead or a lead alloy containing antimony or tin. Before applying the jacket or encasement the conductive core 2 after being acid treated is tinned by being dipped into a hot solder 0r tinning bath in order that the encasement material may form a perfect union with the core.

Before being encased the core is insulated throughout a portion of its length by a wrapping I l of mica or other electro-insulating material, affording an insulated zone coincident with the upper level of the plating bath in which the anode is to be suspended and extending a short distance above and below the liquid level. Such zone is ordinarily eight to ten inches deep, but may be more or less. The encasement or jacket 6 is preferably of substantially uniform depth throughout the length of the anode leaving the side faces of the head or collars 3 exposed for direct contact with the bus bars 4. While longitudinally of uniform thickness the encasement is of irregular or angular cross sectional contour to afford a series of high points or edges from which the electric current will more readily flow into the plating solution. The resistance afforded by the jacket or encasement material is thus equalized throughout the length of the anode. The current is conducted uniformly throughout the length of the highly conductive core and the resistance afforded by the encasement material is merely that of the thickness of such jacket which is substantially the same at all levels. Therefore the current supply is equally as great at the lower levels as in the higher zones, and greater than that at the top of the plating bath where the current flow is diminished by the insulation of the anode within such zone. This restriction of current flow at the top of the bath reduces the deposit upon the work hangers and minimizes metal losses and also prevents burning of the anode at the liquid level.

Instead of a lead or lead alloy encasement, for plating other metals utilizing a different bath, iron or steel or other protective encasement may be used. The invention is not restricted to the particular material of either the core or the encasement. The dominant idea is that of increasing the conductivity or reducing the resistance of an electrode of a material which would otherwise offer high resistance to the flow of electrical current by providing a highly conductive core by which the current will be conducted to the lower levels of the plating bath and the resistance of the electrode more nearly equalized throughout its length, or conversely providing a highly conductive electrode which is protected by a surface covering insoluble in the electrolyte in which the electrode is to be used.

While for ordinary usage straight bar type of electrode will be found quite efficient, it is sometimes desirable to form an anode to correspond with the shape of the work to be plated. In Fig. 6 there is shown a special electrode having a J- shaped form of core of which the stem 7 is insulated and only the upturned arm 8 thereof encased in the protective material supplies electric current. The arm 8 terminates below the level of the plating bath and the maximum discharge therefrom is through the lower levels of the bath. Merely as illustrative of the wide range of forms in which the electrode may be embodied, there is shown in Fig. 7 a substantially inverted T-shaped element having an insulated stem 1 and a transverse conductive head 9 from which extend a plurality of upturned conductive arms 8 which terminate below the liquid level of the bath. These special forms of electrodes like the straight form before described comprise a highly electroconductive core encased in a protective jacket of material insoluble in the particular bath in which it is to be employed.

The use of the present electrode further facilitates the recharging and maintenance of the charged condition of the plating bath by enabling a more uniform circulation of the charging current at difierent levels of the bath. It is usually the practice to recharge the plating bath at night or during other intervals between active periods of plating operation. Heretofore this has been effected by continuing the flow of plating current from the regular plating anode to a dummy" cathode of less size than the ordinary quantity of work thereby accumulating an excess of electric charge in the bath which is gradually dissipated during the succeeding plating operation. The dummy cathode receives a plating deposit which becomes waste metal. By the use of the present method and electrode it is possible to continue the charging of the bath during theplating operation thereby keeping the bath at a constant potential. While the bath may be re harged from the same source of electrical energy from which plating current is supplied, aseparate source of electrical energy for charging purposes is preferable. The current supplied may be of either direct or alternating character. I

From the above description it will be apparent that there'is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute, the invention has been described in language more or less specific as to structural features, it is to tions within the legitimate and. valid scope of.

the appended claims. I

Having thus described my invention, I claim:

1. A composite electrode for electrometallurgical use including a core and an encasement therefor of metals of dissimilar solubility in the particular electrolytic bath in which it is to be employed, and an insulator disposed between the core and encasement and extending therealong from above to below the level of a normal electrolytic bath.

2. A electrode for electrometallurgical use including an electroconductor, an electroconductive protective coating thereon resistant to electrolytic action of the particular bath in which the electrode is to be used, and an insulator disposed .between the electroconductor and coating and I the electrode a substantial distance below the surface of a normal electrolytic bath in which the electrode is disposed.

4. An electrode for electrometallurgical use,

- 5. An electrode for electrometallurgical use including an electroconductive member and an en-r closure of insulating material defining a nonconductive zone coincident with the upper level of a bath in which the electrode is to be employed and extending a limited distance below the liquid level of the bath whereby ,the electrical potency of said electrode will be confined to lower levels 7 of; such bath, and an encasement for the core? and insulating material of metal of different electroconductivity than the core.

6. An electrode for electrometallurgical use, including a core of highly electroconductive material, an encasement therefor of metal insoluble in the bath in which the electrode is to be used, and an enclosure of insulating material within the easement and surrounding the core from a point" above the liquid level of the bath to a point therebelow by which a zone of minimum electrical activity is created in the top level of the bath and zones of increased electrical activity are created at lower levels thereof.

7. As an article of manufacture an electrode for metallurgical use including a core of highly electroconductive material and a protective coating therefor the electroconductive material insoluble in the particular electrolyte in which the electrode is to be used, an insulator /disposed between the core and the encasement and extending from the unsubmerged end of the electrode a substantial'distance below the level of a normal electrolytic bath, the encasement being of irregular cross sectional contour to afford ribs terminating in sharp edges and extending longitudinally of the electrode.

8. A composite electrode for electrometallurgical use, including a core of highly electroconductive material and a casement therefor including longitudinally succeeding portion of dissimilar electroconductive material, and a series of continuous longitudinal relatively sharp angular ribs formed on the casement aifording uninterrupted current flow jetties intersecting successive levels of the electrolytic bath in which the electrode is immersed.

9. As an article of manufacture, a compo ite electrode for metallurgical use, including a core of electroconductive electrolysable material, and

a continuous unitary casement of electroconductive non-electrolysable material of irregular cross electro-conductive and electro-conductive materials respectively so arranged that the flow of electric current relative to the electrode is greater through a lower level of an electrolytic bath in which the electrode is immersed than such flow through an upper level thereof.

11. A composite electrode for electrometallurgical use, including a copper core, a lead bearing covering therefor, enclosing and protecting the copper core against action of an electrolytic bath in which it may be immersed, and a body of electrical insulating material also enclosing a portion of the core and producing a zone of nonelectroconductivity, said enclosures being so arranged as to minimize the flow of current relative to the electrode through the upper levels of the bath and to afford increased current flow through lower levels thereof.

12. A composite electrode for electrometallurgical use, including an elongated copper core and a continuous unitary lead bearing encasement for the copper core including succeeding longitudinal sections of electrical insulating and of electroconductive character respectively enclosing and protecting the copper core against action of an electrolytic bath in which it may be immersed, said encasement being of irregular cross section including a plurality of longitudinal lineal projecting angular jetties vertically intersecting difierent levels of the electrolytic bath for concentration of the current flow therethrough relative to the electrode.

13. An electrode for electrometallurgical use comprising an electroconductive core including a vertical portion and a laterally extending continuation of the lower end of the vertical portion of the core, a protective insulating covering for the vertical portion of the core prohibiting flow of current therefrom, and an electroconductive protective covering resistant to electrolytic action of the particular bath in which the electrode is to be used, enclosing the insulating covering and the laterally extending continuation of the lower end of the core.

14. An electrode for, electrometallurgical use comprising an electroconductive core, a non-electroconductive protective cover for an initial portion of the core prohibiting flow of electric cur;--

rent therefrom and an electroconductive protective covering, resistant to the electrolytic action of the particular bath in which the electrode is to be used, enclosing the non-electro-conductive protective cover and remaining terminal portion of the core.

15. An electrode for electrometallurgical use comprising an electroconductive core, a non-electroconductive protective cover enclosing a portion of the core prohibiting flow of electric current therefrom and an electroconductive protective covering resistant to the electrolytic action of the particular bath in which the electrode is to be used enclosing the non-electroconductive protective cover and remainder of the core and transmitting current therefrom.

16. An electrode for electrometallurgical use comprising an electroconductive core, including a vertical portion and a laterally oifset continuation thereof, an electroconductive protective enclosure, resistant to the electrolytic action of the particular bath in which the electrode is to be used, enclosing the vertical portion of the core and the laterally offset continuation thereof, and a non-electroconductive protective enclosure for the vertical portion intermediate the electro-conductive protective enclosure and the core for minimizing flow of electric current relative thereto.

17. An electrode for metallurgical use, including an electroconductive core, a continuous one piece protective encasement of electroconductive material resistant to the electrolytic action of the particular bath in which the electrode is to be used enclosing at least a portion of the core to be submerged in the bath, a non-electroconductive body enclosing a portion only of the core and positioned to extend partially above and partially below the liquid level of said bath, and a plurality of parallel continuous longitudinal surface corrugations on said protective encasement.

18. An electrode for metallurgical use, including an electroconductive core, a continuous one piece protective encasement of electroconductive material resistant to the electrolytic action of the particular bath in which the electrode is to be used enclosing at least a portion of the core to be submerged in the bath and a body of nonelectroconductive material surrounding the core coincident with the liquid level of the bath, and continuous longitudinal uninterrupted angular edges on said encasement for uniform vertical distribution of electric current flow therefrom. FOREST H. HARTZELL.

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