Electrode

An electrode assembly, having improved dimensional stability, for use in the electrolytic production of manganese dioxide and comprising a hanger bar member, at least one corrugated panel member having oppositely opposed upper and lower ends, said at least one panel member being fixedly attached to said hanger bar member at the upper end of said at least one panel member and a stiffening bar member fixedly attached to said lower end of said at least one corrugated panel member.

FIELD OF THE INVENTION 
This invention relates to electrode assemblies and particularly to 
electrode assemblies having improved dimensional stability for use in the 
electrolytic production of manganese dioxide. More particularly, the 
invention relates to electrode assemblies of titanium having improved 
dimensional stability. 
BACKGROUND OF THE INVENTION 
The use or desirability of using titanium electrodes in electrolytic 
processes for the extraction of metals and metal oxides is well known. 
See, for example, U.S. Pat. Nos. 4,319,977 and 4,460,450. This use or 
desirability of using electrodes constructed of titanium is based on a 
number of advantages offered by titanium over other materials that have 
been employed in such electrode structures in the past. Of the numerous 
advantages provided by the use of titanium electrodes, the most noteworthy 
are their durability, low corrosiveness and the improved quality of the 
metal or metal oxide deposits recovered therefrom on a long-term basis. 
However, according to U.S. Pat. No. 4,319,977, a major drawback to the use 
of such titanium electrodes is their cost, titanium being an expensive 
metal. Thus, in the above patent, it is disclosed that much effort has 
been expended in developing electrodes, based on titanium, of reduced cost 
but without sacrificing the advantages associated with the use of 
titanium. One such development disclosed in the above patent comprises an 
electrode of a sandwich-type construction in which a core metal having 
good electrical conductivity is coated with titanium on both sides. Such 
sandwich-type construction reduces the cost of the electrode while 
retaining all of the advantages afforded by titanium. 
Another development disclosed in the above patent comprises an electrode 
utilizing corrugated sheets of titanium. According to the above patent, 
the conventional thickness of titanium electrodes is on the order of about 
4 mm. The use of corrugated sheets of titanium as electrodes presumably 
allows the use of thinner sheets of the titanium metal thereby reducing 
the overall costs of the electrode while retaining the rigidity associated 
with titanium electrodes constructed of thicker sheets of the metal. 
However, the reduction in thickness afforded by corrugating sheets is said 
to be very small and hardly pays for the cost of corrugation. The 
disclosure in U.S. Pat. No. 4,319,977 concludes that, overall, simple 
(i.e., single) corrugated sheets of titanium have not proven to be 
economically viable and particularly in the thicknesses desired. 
The invention in the above referenced patent itself is directed to an 
improved electrode for use in the electrolytic production of manganese 
dioxide. the electrode disclosed in the referenced patent comprises two 
continuous sheets of a metal, e.g., titanium, joined in a face-to-face 
relationship. At least one of said sheets is corrugated so as to provide 
rigidity to the electrode. In turn, the two joined sheets are attached to 
a hanger bar by means of a series of straps machined into the sheets. 
Another patent disclosing the use of corrugated sheets of metals such as 
titanium in electrode assemblies is U.S. Pat. No. 4,460,450. In general, 
the disclosure in this patent relates to the providing of an electrode 
having current-carrying components which provide good electrically 
conductive connections between a core metal and the jacket metal of said 
current-carrying components. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided an electrode 
assembly having improved dimensional stability for use in the electrolytic 
manufacture of manganese dioxide. The improved electrode assembly 
comprises a hanger bar member, at least one corrugated panel member 
fixedly attached to said hanger bar member at one end of said at least one 
corrugated panel member and a stiffening bar member fixedly attached to 
said at least one corrugated panel member at the end thereof opposite said 
hanger bar member. 
The hanger bar member which has a longitudinal dimension and oppositely 
opposed ends is comprised of a solid core of an electrically conductive 
metal and a cladding thereon of a lesser electrically conductive and more 
corrosion resistant metal. The hanger bar member further is characterized 
as having a pair of engaging means. Each of said engaging means of said 
pair of engaging means is laterally disposed to the longitudinal dimension 
of said hanger bar member and spacially arranged inwardly from he 
oppositely opposed ends of said hanger bar member. At least one of said 
engaging means of said pair of engaging means provides for contact between 
the hanger bar member and an electric current-carrying bus bar. 
The at least one corrugated panel member of the electrode assembly 
comprises a single corrugated sheet having oppositely opposed upper and 
lower ends and, in general, will be constructed of the same lesser 
electrically conductive and more corrosion resistant metal as the metal 
cladding of the hanger bar member. This at least one corrugated panel 
member will be fixedly attached, at the upper end thereof, to the hanger 
bar members. The attachment of the corrugated panel member to the hanger 
bar member will be such that the corrugated panel member is located in a 
position perpendicular to the longitudinal dimension of said hanger bar 
member and between each of the engaging means of the pair of engaging 
means of said hanger bar member. 
In general, attachment of the corrugated panel member to said hanger bar 
member will be effected by the use of penetrating welds. These penetrating 
welds will be applied on both sides of the corrugated panel member and 
along the exposed junctures or lines formed at the point of direct contact 
between the corrugated panel member and the hanger bar member along the 
longitudinal dimension of said hanger bar member. 
The stiffening bar member is fixedly attached to the oppositely opposed 
lower end of said corrugated panel member in a manner to provide direct 
contact between said stiffening bar member and said corrugated panel 
member. Preferably, the means employed for effecting this direct 
attachment will be the same as that employed for fixedly attaching the 
corrugated panel member, at its upper, oppositely opposed end, to the 
hanger bar member. Thus, the stiffening bar member is attached to the 
corrugated panel member through the use of penetrating welds along both 
sides of the corrugated panel member. Again, such penetrating welds will 
be located along the exposed junctures or lines formed at the point of 
direct contact between the panel member and the stiffening bar member 
along the longitudinal dimension thereof.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, therein is illustrated an electrode assembly 10 in 
accordance with the present invention comprising a hanger bar member 20 
having a longitudinal dimension, four corrugated panel members 30, 31, 32 
and 33 and a stiffening bar member 40. As shown in FIG. 4, which is a 
section view of hanger bar member 20 taken along line I--I, hanger bar 
member 20 is comprised of a core 15 of an electrically conductive metal 
and a cladding 16 of a lesser electrically conductive and more corrosion 
resistant metal. Although, in FIG. 4, the cladding 16 of lesser 
electrically conductive and more corrosion resistant metal is illustrated 
as extending to and over one of the oppositely opposed ends of hanger bar 
member 20, said cladding 16 can terminate at said end leaving the core 15 
of electrically conductive metal exposed. In a similar manner, the 
oppositely opposed end of hanger bar member 20 may comprise exposed metal 
core 15 of hanger bar member 20 only along the longitudinal dimension of 
said hanger bar member 20. 
The metal comprising core 15 can be any metal suitable for the conductivity 
of an electrical current, including, for example, such metals as copper, 
aluminum and the like. The cladding 16, as illustrated in the sectional 
view of FIG. 4, is a lesser electrically conductive and more corrosion 
resistant metal and, in general, is a valve metal such as, for example, a 
metal selected from the group consisting of titanium, tantalum, niobium 
and the like, and alloys thereof. When an alloy is employed as the 
cladding 16, said alloy will contain as the predominant material therein 
one of the aforementioned valve metals. 
Again referring to FIG. 1, said hanger bar member 20 is further 
characterized by a pair of engaging means comprising engaging means 12 and 
14. Each of said engaging means 12 and 14 of said pair of engaging means 
is laterally disposed to the longitudinal dimension of said hanger bar 
member 20. Furthermore, each of said engaging means 12 and 14 of said pair 
of engaging means is spacially arranged inwardly from the opposite ends of 
said hanger bar 20. 
With respect to the particular electrode assembly 10 illustrated in FIG. 1, 
each of said engaging means 12 and 14 of said pair of engaging means is a 
trough of semi-circular cross-section cut through said hanger bar member 
20. During the forming of said trough type engaging means 12 and 14, the 
electrically conductive metal core 15 of said hanger bar member 20 is 
exposed. For at least one of engaging means 12 and 14 this metal core 15 
is left exposed to permit intimate contact between said metal core 15 of 
hanger bar member 20 and a conventional current-carrying bus bar (not 
shown). Preferably, the lesser electrically conductive and more corrosion 
resistant metal cladding 16 on said hanger bar member 20 will be relieved 
around the edges of at least the engaging means of said pair of engaging 
means 12 and 14 intended for contact with the current-carrying bus bar. 
Such relief of the lesser electrically conductive and more corrosion 
resistant metal cladding 16 will further ensure the intimate contact 
between said metal core 15 of hanger bar member 20 and the 
current-carrying bus bar. 
As disclosed herein, the electrode assembly of the present invention 
further comprises at least one corrugated panel member having oppositely 
opposed ends. In a preferred embodiment, the electrode assembly of the 
present invention will comprise two or more of these corrugated panel 
members, the electrode assembly 10 illustrated in FIG. 1, for example, 
comprising four of such corrugated panel members identified by the numbers 
30, 31, 32 and 33, respectively. Each of said corrugated panel members 30, 
31, 32 and 33 is formed from a single sheet of a lesser electrically 
conductive more corrosion resistant material such as, for example, 
titanium. These single sheets, generally, will have a thickness of less 
than about 0.16 inch (4.0 mm) and preferably less than about 0.08 inch 
(2.0 mm) or less. In addition to the preferred use of titanium sheet, the 
corrugated panel members 30, 31, 32 and 33 also can be formed from single 
sheets of other lesser electrically conductive and more corrosion 
resistant metals such as the valve metals tantalum, niobium and the like. 
Single sheets of alloys of titanium as well as the alloys of the other 
valve metals listed immediately above also can be used in producing the 
corrugated panel members 30, 31, 32 and 33 of the electrode assembly 10. 
For example, single sheets of titanium/manganese alloys containing 8%, 12% 
and 16% by weight of manganese, have been found useful in forming the 
corrugated panel members 30, 31, 32 and 33, respectively. Generally, 
however, the preferred valve metal for use in forming the corrugated panel 
members in electrode assembly 10 is titanium, and particularly preferred 
titanium metals are those corresponding to ASTM Grades 1-4, 7, 11 and 12. 
The corrugated panel members 30, 31, 32 and 33 of electrode assembly 10 of 
this invention generally will be of a sinusoidal, trapezoidal or 
triangular shape or design. In addition to contributing to the overall 
stiffness of electrode assembly 10, such shapes or designs contribute to 
an increase in the effective surface area of these panel members 30, 31, 
32 and 33. Although each of these shapes or designs work well for the use 
to which the electrode assembly 10 is intended, the triangular design 
illustrated in FIGS. 1, 2 and 3 for the corrugated panel members 30, 31, 
32 and 33 provides the maximum effective surface area at the minimum cost. 
Irrespective of the particular shape or design of the corrugation utilized 
for said corrugated panel members 30, 31, 32 and 33, it has been found 
that the effective surface area of said corrugated panel members as well 
as the overall stiffness of electrode assembly 10 are affected by certain 
dimensional relationships associated with said corrugations. In this 
regard, both the effective surface area of said corrugated panel members 
and said overall stiffness of the electrode assembly are affected by the 
dimensional ratio of the distance between the peaks or midpoints of 
adjacent corrugated sections to the amplitude of the peaks or midpoints of 
said corrugated sections. Thus, it has been found that as the above 
defined ratio approaches a value of about 2:1, said effective surface area 
and overall stiffness increases. Although the effective surface area of 
corrugated panel members 30, 31, 32 and 33 can be further improved by 
means disclosed hereinbelow, the overall stiffness of electrode assembly 
10 appears to reach a maximum when the above ratio is established at a 
value of about 2:1. 
Unexpectedly and for reasons unknown, the above described ratio also has 
been found to exert an effect on the quality of the deposit of desired 
product formed on said corrugated panel members 30, 31, 32 and 33 of 
electrode assembly 10. Thus, as this ratio approached the value of about 
2:1 or was established at said value, it was found that the deposit formed 
on said corrugated panel members exhibited improved physical 
characteristics, including improved smoothness, uniformity of thickness, 
density and the like. Furthermore, it was found that dry cell batteries 
produced from these deposits exhibited electrochemical activities which 
increased in proportion with these improvements in the physical 
characteristics of the deposits. 
The effective surface area of corrugated panel members 30, 31, 32 and 33 of 
electrode assembly 10 further can be increased and the passivation 
resistance thereof improved by providing the surfaces of said corrugated 
panel members with a multiplicity of minute indentations, i.e., hollows or 
pits. Such hollowing or pitting, i.e., roughening, of the surfaces of 
these corrugated panel members can be accomplished by known means such as, 
for example, by either chemical or mechanical treatment as disclosed in 
U.S. Pat. No. 3,436,323. Thus, the surfaces of the corrugated panel 
members 30, 31, 32 and 33 of electrode assembly 10 of the present 
invention can be roughened by either etching with a suitable etchant such 
as, for example, hydrochloric acid or by blasting with an abrasive 
material. Roughening of the surfaces of these corrugated panel members 
must be carefully controlled since the extent of the passivation 
resistance of said corrugated panel members is related to the regularity 
of the shape and size of the hollows and pits produced therein. In this 
regard, it was found that the passivation resistance of said corrugated 
panel members was particularly enhanced when the multitude of hollows or 
pits formed in the surfaces of the corrugated panel members were within a 
root mean square size of about 410.+-.50 microinches. To achieve such 
regularity of the hollows and pits in the surface of corrugated panel 
members 30, 31, 32 and 33, the use of blasting techniques is preferred 
over chemical etching techniques. When employing blasting techniques to 
roughen the surfaces of said corrugated panel members, it also is 
preferred to employ an abrasive material which possesses a hardness and 
toughness sufficient to withstand the forces brought to bear upon it when 
in use. Representative, but nonlimiting, examples of abrasive materials 
having the requisite hardness and toughness and capable of providing a 
roughened surface of hollows and pits having root mean square sizes of 
410.+-.50 microinches include fused aluminum oxide, metal shot including 
angular grit, sintered bauxite and the like. 
The passivation resistance of corrugated panel members 30, 31, 32 and 33 of 
electrode assembly 10 further can be enhanced by applying to the surfaces 
of said corrugated panel members an electrically conductive, electrolyte 
resistant film of a platinum group metal or metal oxide. Mixtures of said 
platinum group metals or metal oxides also can be applied to the surfaces 
of said corrugated panel members. Representative examples of said platinum 
group metals and metal oxides include platinum, ruthenium, palladium and 
the like and their corresponding oxides such as platinum oxide, ruthenium 
dioxide, palladium dioxide and the like. A particularly desirable 
passivation resistant film is that of ruthenium dioxide. A film of 
ruthenium dioxide readily can be applied to the surfaces of said 
corrugated panel members 30, 31, 32 and 33 by exposing said corrugated 
panal members to ruthenium hydroxychloride at temperatures of about 
450.degree. C. At such temperature, the ruthenium hydroxychloride 
decomposes to ruthenium dioxide which in turn is deposited on the surface 
of the corrugated panel members. 
Corrugated panel members 30. 31, 32 and 33 are fixedly attached at their 
upper ends directly to hanger bar member 20 and along the longitudinal 
dimension of hanger bar member 20 and between said engaging means 12 and 
14 by means of penetration welds. Such welds will be applied to both sides 
of said corrugated panel members 30, 31, 32 and 33 and along the exposed 
junctures or lines formed on both sides of said corrugated panel members 
where said corrugated panel members contact the surface of hanger bar 
member 20. Said penetration welds may constitute a series of continuous 
welds, i.e., welds of one-quarter inch length or greater, such as those 
illustrated in FIG. 2 as represented by weld 22, or may constitute a 
series of spot welds. 
Referring once again to FIG. 1, electrode assembly 10 further comprises a 
stiffening bar member 40 having a longitudinal dimension. This stiffening 
bar member 40 is fixedly attached along its longitudinal dimension 
directly to the lower ends of corrugated panel members 30, 31, 32 and 33. 
Attachment of stiffening bar member 40 is effected in the same manner as 
attachment of the corrugated panel members 30, 31, 32 and 33 to hanger bar 
member 20, i.e., by the use of a series of continuous or spot penetration 
welds. The former illustrated in FIG. 3 and specifically represented by 
weld 42. 
The stiffening bar member 40 generally will be a solid member constructed 
from the same lesser electrically conductive metal as corrugated panel 
member 30, 31, 32 and 33 and the coating 16 on hanger bar member 20. Thus, 
film-forming metals such as titanium. tantalum, niobium and alloys of 
these film-forming metals with other materials will be employed to 
construct stiffening bar member 40. Typical of the film-forming alloys 
that can be used in construction of stiffening bar member 40 are the 
various titanium-manganese alloys described hereinabove in which the 
manganese constitutes 8%, 12% and 16% by weight of the total weight of the 
alloy. 
The electrode assemblies of the present invention, as exemplified by 
electrode assembly 10 illustrated in FIG. 1, have particular utility as 
anodes in electrolytic processes for the manufacture of battery grade 
manganese dioxide. In such processes, battery grade manganese dioxide is 
prepared by the electrolytic oxidation of acidic manganous sulfate 
electolyte solutions in a cell equipped, generally, with multiple cathodes 
and anodes. The passage of an electric current through this electrolyte 
and between the cathodes and anodes causes oxidation of the manganous 
sulfate at the anode and the deposition of a plate or coating of the 
desired manganese dioxide product on the anode. When this plate or coating 
has built up to the desired thickness, the anode bearing said plate or 
coating of manganese dioxide product then is removed from the cell and the 
plate or coating harvested therefrom. In general, such harvesting is 
accomplished by mechanical means such as, for example, flexing the anode 
to cause the manganese dioxide plate or coating to separate from the 
anode. 
The electrode assemblies of the present invention provide a number of 
significant advantages over those currently being employed or proposed for 
use in electrolytic processes for the manufacture of battery grade 
manganese dioxide. For example, the herein described electrode assemblies 
permit the use of significantly thinner, single sheet, corrugated panel 
members on which the desired manganese dioxide can be deposited, i.e., 
corrugated panel members formed from sheet stocks having thicknesses of 
about 4 mm and and less. In general, the corrugated panel members forming 
a part of the electrode assemblies of the present invention can be formed 
from sheet stocks ranging in thickness from about 0.5 mm to about 4.0 mm. 
In a preferred embodiment, said corrugated panel members will be formed 
from sheet stocks ranging in thickness from about 1.0 to about 3.0 mm and 
most preferably from sheet stocks ranging from about 1.0 mm to about 2.0 
mm in thickness. Furthermore, the ability to use single sheet corrugated 
panel members in these electrode assemblies avoids the problem of 
entrainment of cell electrolyte such as is encountered with electrode 
assemblies having panel members formed from flattened tubes or using 
corrugated panel members designed and constructed of two sheets fastened 
together (U.S. Pat. No. 4,319,977). Electrode assemblies having panel 
members formed from such flattened tubes or constructed of two sheets 
fastened together are characterized by open channels throughout the length 
of said panel members and in which channels cell electrolyte can be 
entrained as the oxide plate or coating builds up. Furthermore, the 
electrode assemblies of this invention exhibit improved deflection 
resistance (i.e., stiffness) which reduced the tendency of the electrode 
assembly to roll in the electrolytic cell, thereby reducing the 
possibility of contact between the electrode assembly and adjacent 
cathodes and the short circuits which can result from said contact. In 
addition, the improved deflection resistant characteristics of the 
electrode assemblies of this invention allow for easier removal of these 
electrode assemblies from the cell. Other advantages can be realized 
through the use of the electrode assemblies as described herein and 
defined in the appended claims. 
While the invention herein has been described and illustrated in terms of 
what at present are believed to be the preferred embodiments, it is to be 
understood that this invention is not to be limited to the specific 
embodiments and that changes may be made thereto without departing from 
the spirit and scope thereof except as provided in the following claims.