US2848411A

US2848411A - Electrode

Info

Publication number: US2848411A
Application number: US500730A
Authority: US
Inventors: Forest H Hartzell
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-04-12
Filing date: 1955-04-12
Publication date: 1958-08-19
Anticipated expiration: 1975-08-19

Description

United States Patent fine 2,848,41 l Patented Aug. 19, 1958 ELECTRODE Forest H. Hartzell, Dayton, Ohio Application April 12, 1955, Serial No. 500,730

3 Claims. (Cl. 204-290) This invention relates to electrodes and more particularly to a composite electrode for use in electrolytic cells for electroplating and the like.

In electroplating operations in which it is desired to effect the electrodeposition on an article to be plated of such metals as silver, nickel, copper, etc., an anode of such metal may be suspended in an electrolyte in which the article to be plated is also suspended and connected to a source of current to be the cathode of an electrolytic cell. In such case, the metal to be deposited is displaced electrolytically from the anode, goes into solution in the electrolyte, and is redeposited as a plating on the surface of the article to be plated as the cathode. When the electrodeposition of other metals, such as chromium, is desired, however, the metal to be deposited is introduced into the electrolytic cell as a solution of a metallic salt. In such cases, an anode of a dissimilar metal is used, such anode including the property of being resistant to electrolytic decomposition in the cell.

Since the quantity of metal electrolytically deposited on the .article :to be plated in a given time is proportional to the current passed through the anode and the electrolyte, the anode should be of high electroconductivity.

Since metals of high electroconductivity, Such as copper, are electrolytically decomposed if used as the anode even when chromium salt solutions are used as the electrolyte for the purpose of plating an article with chromium, such high conductivity anodes may not give satisfactory results in a chromium plating operation because copper from the anode will be deposited onto the article to be plated along with chromium from the electrolyte solution. Metals which are resistant to electrolytic decomposition in such a chromium plating cell, however, generally possess substantially less electroconductivity. For example, an anode .comprising lead or an alloy -of lead with tin or antimony is not subject to electrolytic decomposition.

Such an .anode, however, .has a vhigh resistance and a conductivity of (as little .as 6% or 7% .of that of, for example, copper. Such higher resistance vmay require a sufliciently high current density as to cause heating of the anode .actually to the point of vaporization of the electrolyte. Also, the current, seeking the path of least resistance may leave the anode in the .area of the surface of the electrolyte \to a much greater extent than at the lower levels of :the anode thereby producing uneven plating on the article to be plated and actual burning or corrosion of the anode at'the area of the electrolyte surface.

I-f it .is attempted to combat these several disadvantages by, for example, providing an electrode of a material with suitable resistance to electrolytic (decomposisionand encasing in the electrode a conducting core of highly conductive metal such as copper for the purpose of conducting the currentflsubstantially throughout the electrode --for more even distribution therefrom .in the plating bath, :it :has been found that the core portion itself may be subject to undesired electrolytic action in the bath upon erosion and/or chemical action of the bath on the lead and/or as a result of pin holes, eroded pitting, or similar imperfections in the encasing lead electrode in manufacture or use.

According to this invention, however, an electrode is provided for such electroplating operations having a main body portion of suitable metal substantially resistant to electrolytic decomposition in the electroplating cell, a core portion of a metal of high conductivity for conducting the current substantially uniformly to the electrode, and a protective sheath resistant to chemical attack and surrounding the core portion to protect it from contact with any portions of the electrolyte which may erode or otherwise penetrate the main body portion of the electrode. An electrode according to this invention also includes an air gap or insulating space between the core portion and the electrode at the por tion thereof generally in the area of the liquid level of electrolyte in the electroplating cell to combat the natural tendency of the current to be discharged adjacent the surface of the electrolyte to a greater extent than the lower levels in the electroplating bath.

It is, accordingly, a principal object of this invention to provide an electrode for use in electroplating operations of the character described and having a'main -body portion of a metal resistant to electrolytic decomposit-ion in "the electroplating bath, a highly conductive core portion, and a protective sheath to protect said core portion from attack by elements of the electrolytic bath which may penetrate the main body portion.

Another object of this invention is to provide an electrode of the character described having an insulated space F between. the core portion and the main body portion in the area of the liquid level in the electroplating bath.

A further object of this invention is to provide an electrode of the character described having ,a main body portion, a core portion of higher electroconductivity than said main body portion and encased thereby, and .a protective sheath for said core portion, with means for integrating and directly connecting said core portion with said main body portion at a plurality of points .along the lengths thereof.

Still another object of this invention is .to provide in av composite electrode of the character described means for assuring the uniform electric contact between the highly conductive core and the encased main body port-ion of the electrode notwithstanding the encasement of the core portion in a protective sheath therefor. Y

A still further object of this invention is to provide a method for assembling an electrode of the character described having a sheathed highly conductive core portion-embedded in a main body portion of dissimilar metal.

Still another object of this invention vis to provide a method for manufacturing .a composite electrode of the character described in which a core portion is embedded in a main body portion and electrically united therewith substantially throughout the lengths thereof notwithstanding the provision of a protective sheath substantially encasing said core portion as embedded in said :main

body portion.-

Still a further object of this invention is to provide 131.1 electrode of the character described having a main body portion comprising lead, a highly conductive core .comprising copper, a protective sheath of chemically resistant steel substantially encasing said core portion Within said main body portion, andapluralityofdirect contact points integral with said main body portion :and penetrating said sheath in fused direct contact relation with said copper core portion.

Other objects and advantages of this invention will be apparent from the following description, the attached drawing and the appended claims.

In the drawing,

Fig. 1 is a perspective view of an electrode embodying this invention;

Fig. 2 is a plan view partly broken away showing a partly assembled electrode embodying this invention;

Fig. 3 is a partial longitudinal section of an electrode embodying this invention with some parts being broken away;

Fig. 4 is a cross section of an electrode embodying this invention along the lines 44 of Fig. 2;

Fig. 5 is a cross section of an electrode embodying this invention along the line 55 of Fig. 2;

Fig. 6 is a cross section of an electrode embodying this invention along the line 6-6 of Fig. 2;

Fig. 7 is a cross section of an electrode embodying this invention along the line 7-7 of Fig. 2; and

Fig. 8 is a perspective view of one sheath member of an electrode embodying this invention.

Referring to the drawing, in which like parts are indicated by like reference numerals throughout the several views, Fig. 1 shows an electrode embodying this invention having a main body portion 10 and a core portion 11 embedded in the main body portion 10. A hook 12 is provided at one end of the core portion for suspending the electrode in the electroplating bath and for providing .a contact member for the connection of the electrode to a source of electric current in known manner, the hook ,12 being encased in the metal of the body portion 10 except for a contact gap 14 to leave a portion of the core 11 exposed.

Considering an electroplating operation in which the electrolyte or plating bath includes a solution of chromium salts for the electrodeposition of a chromium plating on an article to be plated, the main body portion 10 preferably comprises a metal resistant to electrolytic attack in said bath, such as lead or an alloy of lead with tin or antimony, while the core portion 11 preferably comprises a highly conductive material such as copper. While longitudinally of substantially uniform thickness, the main body portion 10 preferably has an irregular cross section including a plurality of points, ridges, or edges 13 from which the electric current will more readily flow into the plating solution.

As indicated in Fig. 2, the core 11 extends substantially throughout the length of the electrode and includes a plurality of holes 15. As shown in Figs. 3 and 6-7, the core 11 is encased in a sheath comprising a U-shaped channel member 20 and a fiat member 21 each of which extends throughout the greater portion of the length of the core 11 from the bottom thereof up to approximately the point indicated at 22. Thereabove the core 11 is encased in an inverted U-shaped sheath member 25 (Fig. 8) the width of which is substantially greater than the core 11 so that the sides 26 of member 25 are laterally spaced apart from the core member leaving an insulating air space 27 therebetween. Member 25 and the air gaps 27 are positioned longitudinally within the main body portion 10 of the electrode so as to extend from just above the normal liquid level in the electroplating bath to just below that level eifecting insulation between the core 11 and the main body portion 10 adjacent the liquid level in the area where current has the greatest tendency to flow nonuniformly from the electrode at the liquid level in the bath.

The uppermost portion of the core 11 above the air gaps 27, is also encased in a sheath comprising U-shaped member 30 and the flat extension 31 on member 25. As indicated in Figs. 3 and 7, the sheath member 20 is provided with a plurality of holes 32 substantially coincident with the holes in the core 11, which holes 32 are preferably chamfered as indicated at 33 and of somewhat larger diameter than the holes 15. The

various sheath members

20, 21, 25, and 30 comprise material 4 such as steel resistant to chemical attack by elements in the electroplating bath.

The assembly and fabrication of a composite electrode embodying this invention may be described as follows: The main body portion 10 is cast or extruded in a manner to obtain maximum density and freedom from pin holes and/ or other imperfections which may in use provide a point of erosion, chemical attack, o other failure which would admit of penetration by the electrolyte into the main body portion 10. A longitudinal groove 35 is provided in the main body portion 10 in the side thereof opposite to the points or ridges 13. This groove is dimcnsioned to accommodate the core 11 and its surrounding

sheath members

20, 21, etc. That portion of groove 35 coincident with the air gaps 27 is made wider, as indicated in Figs. 2 and 5, to accommodate the member 25 and to provide space for the air spaces 27 surrounding the core 11.

The U-shaped

sheath members

20 and 30 are inserted into the groove 35 with the holes 32 in member 20 against the bottom of the groove. The core member 11 is then inserted into the groove and into the

upturned channel members

20 and 30 with the holes 15 in member 11 substantially coincident with the holes 32 in member 20. The

holes

15 and 32 are then filled with molten lead or lead alloy of which main body member 10 is composed. This molten metal flows through the

holes

15 and 32 to provide a fused unifying contact with the main body portion 10 as indicated in Figs. 3 and 7, the chamfered edges 33 and larger diameter of the holes 32 aiding in this unification. Preferably both the copper core 11 and the sheath member 20 are tinned before assembly to aid in producing the completely fused unifying contact upon the addition of the molten lead or lead alloy. Additionally, prior to filling the

holes

15 and 32 with molten metal, the tinned sheath 20 and core 11 are burned with a torch in position to produce a soldered or fused connection throughout.

With the

holes

15 and 32 substantially filled with molten lead or lead alloy, the

sheath members

21 and 25 are inserted into the groove 35 to overlie the core 11 and complete the sheathing thereof. The soldering and/or addition of molten lead or lead alloy over the core 11 to fill the

holes

15 and 32 may leave a residual layer 34 7 of lead between the core 11 and sheath member 21, which is positioned to overlie the upturned sides of sheath member 20. As indicated by a comparison of Figs. 5 and 6, the

sheath members

20 and 21 encase and contact the core 11 whereas the sides 26 of sheath member 25 are spaced from the core 11 to provide the air spaces 27 therearound. Thereafter additional molten lead or lead alloy is poured into the groove 35 above the

sheath members

21 and 25 and beyond the bottom end 36 of the core 11 to complete the encasing of the core member 11 and its protective sheath in the main body portion 10.

It will accordingly be seen that, in use, an electrode embodying this invention presents a number of advantages. The current is conducted through the highly conductive core 11 substantially throughout the longitudinal extent of the main body portion 10. Because the thickness of the main body portion 10 surrounding the highly conductive core 11 is substantially uniform throughout the length of the electrode, the resistance to current flow from the electrode is substantially uniform at all depths in the plating bath thereby providing for substantially uniform deposition of the plating metal on the article to be plated. The principal exception to the foregoing is in the area of the air spaces 27 where the insulating effect of the air spaces is provided to increase the resistance of current flow from the core portion 11 to the main body portion 10 to combat the natural tendency of the current more readily to leave the electrode adjacent the liquid level of the electroplating bath.

The core portion 11 is substantially completely encased in a chemically resistant sheath to protect it from electrolytic or chemical action by elements of the electroplating bath which may inevitably penetrate the main body portion due to erosion, chemical action, pin holes, and/or imperfections therein. Notwithstanding this, however, direct electric contact is maintained between the core portion and the main body portion sub: stantially throughout the lengths thereof by the plurality of direct contact points east through the holes and 32, as well as by direct electric contact through the

steel sheath

20, 21, etc. In this connection, it should be noted that, whereas the lead or lead alloy main body portion 10 has a conductivity approximately 6% or 7% of the copper core portion 11, the chemical resistant steel of the

sheath members

20, 21, etc., may have a conductivity approximately twice that of the main body portion 10, thus assuring reduced uniform resistance to current flow between the highly conductive core 11 and the electrolysis resistant main body portion 10 substantially throughout the lengths thereof.

Although the cross sectional contour of an electrode embodying this invention has been illustrated as embodying the ridges or protrusions 13, it will be understood that other contours may be provided in known manner. The size of the electrode, also, may be varied according to principles well understood in the art. Satisfactory results have been achieved, however, with a main body portion 10 of approximately 3 inches in Width at its point of greatest width, 1% inch in thickness at its point of greatest thickness, and inches long, and with the core member 11 being approximately inch wide and A inch thick.

While the methods and forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise methods. and forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a method for constructing a composite electrode having a core portion and a main body portion of dissimilar metals for use in an electrolytic cell having a fluid electrolyte, the steps comprising forming a main body portion for said electrode including a-metal resistant to electrolysis in said cell, forming in said main body portion a longitudinal groove substantially throughout the length thereof, the width and depth of said groove being larger than the dimensions of said core portion, forming a generally U-shaped sheath for said core portion of a metal difierent from said core portion and said main body portion and resistant to chemical attack in said electrolytic cell, forming a plurality of coincident holes through said core portion and said U-shaped sheath, assembling said sheath and said core portion in said groove, uniting said sheath and core portion with said main body portion by introducing molten metal through said holes, covering the exposed upper surface of said core portion with an additional sheath member, and substantially filling said groove above said additional sheath member with molten metal to form said composite electrode.

2. In a method for constructing a composite electrode having a core portion and a main body portion of dissimilar metals for use in an electrolytic cell having a fluid electrolyte, the steps comprising forming said main body portion for said electrode including a metal resistant to electrolysis in said cell, forming in said main body portion a longitudinal groove substantially throughout the length thereof, the width and depth of said groove being larger than the dimensions of said core portion, forming a generally U-shaped sheath for said core portion of a metal diiferent from said core portion and said main body portion and resistant to chemical attack in said electrolytic cell, tinning said sheath and said core portion for fused unification thereof, forming a plurality of coincident holes through said core portion and said U-shaped sheath, assembling said sheath and said core portion in said groove with said core portion within said sheath and separated thereby from said main body portion, heating said assembled elements effecting fused integration of said core portion, said sheath portion and said main body portion at their respective adjacent surfaces, introducing molten metal into said groove over said core portion and through said holes uniting said sheath and core portion with said main body portion, covering said core portion with an additional sheath member for encasing said core portion substantially completely, and substantially filling said groove above said additional sheath member with molten metal to form said composite electrode.

3. A composite electrode for use in an electrolytic cell having a liquid electrolyte in which said electrode is suspended and at least partially immersed, comprising in combination an elonagted main body portion including a metal resistant to electrolytic attack by said electrolyte, a core within said main body portion and extending substantially throughout the length thereof, said core including a metal of greater conductivity than said main body portion for conducting electrical current substantially throuhgout said main body portion, a protective steel sheath encasing said core for protection thereof against chemical attack by substances in said electrolyte which penetrate said main body portion, and means spacing said core from said main body portion adjacent one end thereof and generally positioned to extend from above to below the level of said liquid electrolyte, and a plurality of direct contact points penetrating said steel sheath. and integrally uniting said main body portion with said core through said sheath.

References Cited in the file of this patent UNITED STATES PATENTS

Claims

3. A COMPOSITE ELECTRODE FOR USE IN AN ELECTROLYTIC CELL HAVING A LIQUID ELECTRLYTE IN WHICH ELECTRODE IS SUSPENDED AND AT LEAST PARTIALLY IMMERSED, COMPRISING IN COMBINATION AN ELONGATED MAIN BODY PORTION INCLUDING A METAL RESISTANT TO ELECTRLYTIC ATTACK BY SAID ELECTROLYTE, A CORE WITHIN SAID MAIN BODY PORTION AND EXTENDING SUBSTANTIALLY THROUGHOUT THE LENGTH THEREOF, SAID CORE INCLUDING A METAL OF GREATER CONDUCTIVITY THAN SAID MAIN BODY PORTION FOR CONDUCTING ELECTRICAL CURRENT SUBSTANTIALLY THROUGHOUT SAID MAIN BODY PORTION, A PROTECTIVE STEEL SHEATH ENCASING SAID CORE FOR PROTECTION THEREOF AGAINST CHEMICAL ATTACK BY SUBSTANCES IN SAID ELECTROLYTE WHICH PENETRATE SAID MAIN BODY PORTION, AND MEANS SPACING SAID CORE FROM SAID MAIN BODY PORTION ADJACENT ONE END THEREOF AND GENERALLY POSITIONED TO EXTEND FROM ABOVE TO BELOW THE LEVEL OF SAID LIQUID ELECTROLYTE, AND A PLURALITY OF DIRECT CONTACT POINTS PENETRATING SAID STEEL SHEATH AND INTEGRALLY UNITING SAID MAIN BODY PORTION WITH SAID CORE THROUGH SAID SHEATH.