U.S. patent application number 16/696382 was filed with the patent office on 2020-03-26 for cathodic corrosion protection.
The applicant listed for this patent is Vector Corrosion Technologies Ltd.. Invention is credited to Tejal Nikita Rathod, George Sergi, David Matthew Simpson, David William Whitmore.
Application Number | 20200095691 16/696382 |
Document ID | / |
Family ID | 58637304 |
Filed Date | 2020-03-26 |
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United States Patent
Application |
20200095691 |
Kind Code |
A1 |
Simpson; David Matthew ; et
al. |
March 26, 2020 |
Cathodic Corrosion Protection
Abstract
In a method for cathodically protecting and/or passivating a
metal section in an ionically conductive material such as steel
reinforcement in concrete or mortar, an impressed current or
sacrificial anode communicates electrical current to the metal
section and a storage component of electrical energy which can be a
cell, battery or capacitor is provided as a component of the anode.
The storage component can have replacement energy introduced by
re-charging or replacing the component from an outside supply.
Typically the cell or storage capacitor has an outer case which
carries an anode material as an integral outer component.
Inventors: |
Simpson; David Matthew;
(Halesowen, GB) ; Sergi; George; (Park Hall,
GB) ; Rathod; Tejal Nikita; (Hall Green, GB) ;
Whitmore; David William; (Winnipeg, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Vector Corrosion Technologies Ltd. |
Winnipeg |
|
CA |
|
|
Family ID: |
58637304 |
Appl. No.: |
16/696382 |
Filed: |
November 26, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15341532 |
Nov 2, 2016 |
|
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16696382 |
|
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62250153 |
Nov 3, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23F 13/20 20130101;
C23F 13/06 20130101; C23F 2201/02 20130101 |
International
Class: |
C23F 13/20 20060101
C23F013/20; C23F 13/06 20060101 C23F013/06 |
Claims
1. A method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising: providing
an anode for communication of an electrical current to the metal
section in the ionically conductive material; a storage component
of electrical energy with two poles for communicating electrical
current generated by release of the electrical energy; electrically
connecting one pole to the metal section, electrically connecting
the other pole to the anode and placing the anode in ionic contact
with the ionically conductive material such that the electrical
current can flow from the storage component through the electrical
connection to the metal section thus reducing a total amount of
electrical energy; wherein replacement electrical energy is
introduced into the storage component while in situ.
2. The method according to claim 1 wherein the anode and the
storage component are both at least partly contained in the
ionically conductive material.
3. The method according to claim 1 wherein the storage component is
connected as a single unit with the anode.
4. The method according to claim 1 wherein the storage component is
contained within a closed or sealed canister defining the anode on
an exterior surface.
5. The method according to claim 1 wherein the replacement
electrical energy is introduced by re-charging the storage
component.
6. The method according to claim 5 wherein the storage component is
subsequently re-charged by a solar cell.
7. The method according to claim 5 wherein the storage component is
subsequently re-charged by a piezo-electrical cell.
8. The method according to claim 5 wherein the storage component is
subsequently automatically repeatedly re-charged.
9. The method according to claim 5 wherein the storage component is
subsequently re-charged by a recharging power supply which is an
integral unit with the storage component.
10. The method according to claim 5 wherein the storage component
is subsequently re-charged by applying voltage between a first
connection to the other pole of the storage component and a second
connection to the metal section.
11. The method according to any claim 5 wherein there is an
electrical connection to allow charging of the storage component by
a recharging power supply without current from the recharging power
supply going to the metal section.
12. The method according to claim 5 wherein the storage component
is charged after installation while electrical connection to the
metal section is maintained which acts to pass extra current to the
metal section to passivate the metal section or reduce future
current requirement to maintain passivity or mitigate corrosion of
the metal section.
13. The method according to claim 1 wherein the replacement
electrical energy is introduced by replacing the storage
component.
14. The method according to claim 1 wherein the storage component
is a cell or battery of cells.
15. The method according to claim 1 wherein the storage component
is a capacitor.
16. The method according to claim 1 wherein the anode comprises a
material which is not less noble than the metal section.
17. The method according to claim 1 wherein the anode comprises
stainless steel.
18. The method according to claim 1 wherein the anode comprises a
material which is less noble than the metal section so that it is
sacrificial.
19. The method according to claim 18 wherein the anode and the
storage component is arranged such that, when the storage component
is discharged, the sacrificial anode operates such that electrons
can flow from the anode through the electrical connection to the
metal section.
20. The method according to claim 1 wherein said anode is collated
with or is in electrical contact with a body of sacrificial anode
material.
21. A method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising: providing
an anode for communication of an electrical current to the metal
section in the ionically conductive material; providing a capacitor
for storage of electrical energy with two poles for communicating
electrical current generated by release of the electrical energy;
and electrically connecting one pole to the metal section,
electrically connecting the other pole to the anode and placing the
anode in ionic contact with the ionically conductive material such
that the electrical current can flow from the capacitor through the
electrical connection to the metal section.
22. A method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising: providing
a stainless steel anode for communication of an electrical current
to the metal section in the ionically conductive material;
providing a storage component of electrical energy with two poles
for communicating electrical current generated by release of the
electrical energy; electrically connecting one pole to the metal
section and electrically connecting the other pole to the anode and
placing the stainless steel anode in ionic contact with the
ionically conductive material such that the electrical current can
flow from the storage component through the electrical connection
to the metal section.
23. A method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising: providing
an anode for communication of an electrical current to the metal
section in the ionically conductive material; providing a storage
component of electrical energy with two poles for communicating
electrical current generated by release of the electrical energy;
electrically connecting one pole to the metal section and
electrically connecting the other pole to the anode and placing the
anode in ionic contact with the ionically conductive material such
that the electrical current can flow from the storage component
through the electrical connection to the metal section; locating
the storage component in a container; and after a period of
operation, replacing the storage component in the container with a
replacement storage component to provide additional electrical
energy.
Description
[0001] This application is a continuation of application Ser. No.
15/341,532 filed Nov. 2, 2016.
[0002] This application claims the benefit under 35 USC 119 (e) of
Provisional application 62/250,153 filed Nov. 3, 2015.
[0003] This invention relates to a method and/or an anode assembly
for cathodically protecting and/or passivating a metal section in
an ionically conductive material using a cell or battery of cells
to provide a voltage.
BACKGROUND OF THE INVENTION
[0004] Impressed current systems using a battery are known. Such
impressed current systems can use other types of power supply
including common rectifiers which rectify an AC voltage from a
suitable source into a required DC voltage for the impressed
current between the anode and the steel. It is also known to
provide solar panels to be used in a system of this type.
[0005] In all cases such impressed current systems require regular
maintenance and checking of the status of the power supply to
ensure that the power supply does not fail leading to unexpected
and unacceptable corrosion or overprotection of the steel within
the structure to be protected. While such maintenance can be
carried out and the power supply thus ensured, this is a relatively
expensive process.
[0006] Alternatively galvanic systems can be used which avoid
necessity for any power supply since the voltage between the steel
and the anode is provided by selecting a suitable material for the
anode which is sufficiently electro-negative to ensure that a
current is generated to provide corrosion protection. These systems
have obtained considerable success and are widely used.
[0007] There are two primary limitations of ordinary galvanic
anodes as used in steel reinforced concrete. The first relates to
the mass of zinc per anode which, depending on the required current
output, limits the useful life of the anode. The second is the
actual current output of the anode which may or may not be
sufficient to halt corrosion of the steel. The current output is
limited by the driving voltage, which is essentially a fixed
property and varies with exposure conditions, age of the anode, and
build-up of corrosion products over time.
[0008] Reference is also made to U.S. Pat. No. 8,961,746 (Sergi)
issued Feb. 24, 2015, U.S. Pat. No. 8,968,549 Mar. 3, 2015 (Sergi)
and U.S. Pat. No. 7,264,708 (Whitmore) issued Sep. 4, 2007 all
issued to the present assignees the disclosures of which are
incorporated herein by reference or may be referenced for more
relevant information.
SUMMARY OF THE INVENTION
[0009] According to one aspect of the invention there is provided a
method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising:
[0010] providing a cell or battery of cells with two poles;
[0011] providing an anode of a material which is not sacrificial to
the metal section;
[0012] electrically connecting one pole to the metal section,
electrically connecting the other pole to the anode and placing the
anode in contact with the ionically conductive material such that
electrons can flow from the cell or battery of cells through the
electrical connection to the metal section;
[0013] the cell or battery of cells being connected as a single
unit with the anode.
[0014] According to a second aspect of the invention which is
usable independently of the first aspect, there is provided a
method for cathodically protecting and/or passivating a metal
section in an ionically conductive material, comprising:
[0015] providing an anode for communication of an electrical
current to the metal section in the ionically conductive
material;
[0016] providing a storage component of electrical energy with two
poles for communicating electrical current generated by release of
the electrical energy;
[0017] electrically connecting one pole to the metal section,
electrically connecting the other pole to the anode and placing the
anode in ionic contact with the ionically conductive material such
that the electrical current can flow from the storage component
through the electrical connection to the metal section;
[0018] wherein replacement electrical energy is introduced into the
storage component while in situ.
[0019] According to a third aspect of the invention which is usable
independently of the other aspects defined herein, there is
provided a method for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0020] providing an anode for communication of an electrical
current to the metal section in the ionically conductive material
where the anode is of a material which is not sacrificial to the
metal section;
[0021] providing a storage component of electrical energy with two
poles for communicating electrical current generated by release of
the electrical energy;
[0022] electrically connecting one pole to the metal section,
electrically connecting the other pole to the anode and placing the
anode in ionic contact with the ionically conductive material such
that the electrical current can flow from the storage component
through the electrical connection to the metal section thus
reducing a total amount of electrical energy contained in the
container;
[0023] wherein the storage component is connected as a single unit
with the anode.
[0024] According to a fourth aspect of the invention which is
usable independently of the other aspects defined herein, there is
provided a method for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0025] providing an anode for communication of an electrical
current to the metal section in the ionically conductive
material;
[0026] providing a capacitor for storage of electrical energy with
two poles for communicating electrical current generated by release
of the electrical energy;
[0027] and electrically connecting one pole to the metal section,
electrically connecting the other pole to the anode and placing the
anode in ionic contact with the ionically conductive material such
that the electrical current can flow from the capacitor through the
electrical connection to the metal section.
[0028] According to a fifth aspect of the invention which is usable
independently of the other aspects defined herein, there is
provided a method for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0029] providing a stainless steel anode for communication of an
electrical current to the metal section in the ionically conductive
material;
[0030] providing a storage component of electrical energy with two
poles for communicating electrical current generated by release of
the electrical energy;
[0031] electrically connecting one pole to the metal section and
electrically connecting the other pole to the anode and placing the
stainless steel anode in ionic contact with the ionically
conductive material such that the electrical current can flow from
the storage component through the electrical connection to the
metal section.
[0032] According to a sixth aspect of the invention which is usable
independently of the other aspects defined herein, there is
provided a method for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0033] providing an anode for communication of an electrical
current to the metal section in the ionically conductive
material;
[0034] providing a storage component of electrical energy with two
poles for communicating electrical current generated by release of
the electrical energy;
[0035] electrically connecting one pole to the metal section and
electrically connecting the other pole to the anode and placing the
stainless steel anode in ionic contact with the ionically
conductive material such that the electrical current can flow from
the storage component through the electrical connection to the
metal section;
[0036] locating the storage component in a container;
[0037] and after a period of operation, replacing the storage
component in the container with a replacement storage component to
provide additional electrical energy.
[0038] Where, as stated above the anode is not sacrificial to the
metal section, typically the material is therefore electropositive
relative to the metal section. However some part of the anode may
be sacrificial or the anode may be partially sacrificial.
[0039] The arrangement herein can be used where the anode is in the
form of a plurality of associated anodes all connected to the cell
or battery of cells.
[0040] The storage component as defined above can be a cell or
battery or battery of cells/batteries or it can be a capacitor or a
supercapacitor or ultracapacitor which provides a system for
storing charge different from conventional electrolytic cells or
batteries. A supercapacitor is a high-capacity electrochemical
capacitor with capacitance values much higher than other
capacitors. These capacitors typically have lower voltage limits
than standard or conventional capacitors. They typically store 10
to 100 times more energy per unit volume or mass than standard
capacitors, can accept and deliver charge much faster than
batteries, and tolerate many more charge and discharge cycles than
rechargeable batteries. Supercapacitors do not use the conventional
solid dielectric of standard capacitors. They use electrostatic
double-layer capacitance or electrochemical pseudo-capacitance or a
combination of both instead. Electrostatic double-layer capacitors
use carbon electrodes or derivatives with much higher electrostatic
double-layer capacitance than electrochemical pseudo-capacitance,
achieving separation of charge in a Helmholtz double layer at the
interface between the surface of a conductive electrode and an
electrolyte. The separation of charge is of the order of a few
angstroms (0.3-0.8 nm), much smaller than in a conventional
capacitor.
[0041] Supercapacitors are a great advancement on normal capacitors
being capable of storing a high charge once fully charged. The
capacity of a 2.7V 200 F supercapacitor is capable of holding a
charge of the order of over 500 C (A.times.seconds). Typical
cathodic protection systems require around 170 to 400 C/m2 of steel
per day so such a capacitor is able to provide, when fully charged,
enough charge to protect 1 m2 or more of steel for a day. This
represents 2-5 mA/m2 current density. In order for example to
double this figure then we need to double the capacitance to around
400 F. If the capacitor is recharged on a daily basis, then
logistically a system utilising supercapacitors of this size spaced
at intervals to provide current for 1 m2 or more of steel can be an
effective cathodic protection system. Daily recharging can easily
be provided by solar panels, for example, but other means of
producing reasonably regular bursts of current could be used as
charging components for the supercapacitors. An example of such
could be piezoelectric materials which can be incorporated in
roads, parking garages, bridges, runways etc. enabling current to
be generated by loading and/or movement of the structure or
vehicles passing over them.
[0042] That is, piezoelectric materials could be used to generate
electricity to power an impressed current system directly, or to
charge/recharge batteries or capacitors/supercapacitors.
[0043] In some embodiments the anode is a sacrificial anode formed
of a material which is less noble than the metal section to be
protected. However in other cases the anode is not less noble than
the metal sections to be protected so that it is the same as the
metal, typically steel or is more noble than the steel; so that it
is partially or fully inert during the process. If the anode is
formed of a sufficiently inert material anode it does not corrode
significantly during the flow of the electrons.
[0044] High current output is required from the storage component
such as a battery. As described above, one pole is connected to the
metal section to be protected. Electrons flow from the storage
component to the metal section such that corrosion of the metal
section is reduced. The other pole is connected to an anode or if
suitable, the casing of the storage component itself can be used as
the anode. In the case of a zinc-alkaline battery the polarity of
the battery is such that the case of the battery, if it is made of
a suitable material will act as the anode and will be able to
distribute the necessary current through the ionically conductive
material such as mortar or concrete. Other batteries, such as most
lithium batteries, typically have only a small pole which has the
proper polarity which may not be large enough to deliver the
required current into the ionically conductive material. A separate
anode can be provided for connection to the appropriate pole. The
anode may encase or coat the whole storage component such as a
battery or capacitor. Anodes can be made of any inert conductive
material such as MMO coated titanium or other noble metal or
sub-metal, conductive coating, conductive ceramic material etc. and
can be embedded in an alkaline mortar or an inert material such as
sand which may be dosed with an alkali solution. Stainless steel
can also be a suitable current carrier when embedded in mortar or
compacted sand dosed with alkali such as a saturated solution of
lithium hydroxide. Anodes may also comprise sacrificial materials
such as zinc which are less noble than the metal section to be
protected.
[0045] Preferably in some embodiments the storage component is
initially charged or is subsequently re-charged while in situ that
is while in contact with the ionically conductive material. The
arrangement may include or preferably includes automatic switching
systems to effect the periodic charging process. For example the
storage component can be charged by a solar cell or by an outside
power source such as a second battery or a power supply. Also in
some cases there may be provided a system which operates to
subsequently automatically and repeatedly or periodically carry out
the re-charge.
[0046] In another case, the storage component is subsequently
re-charged by a recharging power supply which is an integral unit
with the anode and the storage component. However the system also
may operate as a periodic maintenance programme where a power
supply is brought into operation periodically as required to effect
the re-charging of an anode assembly or a set of anode assemblies
in a structure.
[0047] Preferably the storage component is subsequently re-charged
by applying voltage directly between both terminals or between a
first connection to a terminal of the storage component and a
second connection to the metal section. In one arrangement the
anode comprises sacrificial anode material, or the anode, which is
sacrificial to the metal section, is collated with or in electrical
contact with a body of sacrificial anode material which gives a
boost of current until the sacrificial anode material is consumed,
following which the current discharge is through the anode.
[0048] In one arrangement storage component is connected to the
metal section and is charged, in an initial charging step or in a
subsequent re-charging, after installation by a connection to the
one terminal and a second connection to the metal section. This
method of connection acts to pass extra current to the metal
section during the charging or re-charging step to passivate the
metal section or reduce future current requirement to maintain
passivity or mitigate corrosion of the metal section.
[0049] Typically the single unit comprising the storage component
and the anode or anodes is at least partly buried in the ionically
conductive material. However application to the surface or other
modes of mounting where the anode is in ionic contact with the
material can be used.
[0050] In one particularly preferred arrangement the storage
component comprises a cell with an outer case wherein the case is
fully or partially formed of the anode material so that the anode
is formed by the outer case either by an outer surface of the same
material or as a coating or layer on the exterior of the case. In
this case the outer case or at least the outer layer can be formed
of a material which is more noble than steel. In this arrangement
the anode forms directly the outer case of the cell where the case
contains and houses the cathode material of the cell the
electrolyte, the anode material and other components of the cell.
That is, in this embodiment, the anode is defined by a layer or
coating on the outer surface of the storage component itself or
actually as the outer surface of the storage component and not as
an additional element which is separate from the storage component.
Where the storage component is a cell, the outer case of the cell
can directly carry the material of the anode or even the outer case
of the cell is the anode. The anode material may cover the whole
surface or may be a partial covering leaving other areas
exposed.
[0051] In another case the case and the anode are formed
independently and the anode forms a separate body which conforms in
shape to the outer case of the cell. Typically such cells are
cylindrical but other shapes can be used. This arrangement is
particularly applicable where the cell is replaceable rather than
rechargeable to introduce the additional energy after the original
cell is sufficiently depleted to be no longer effective.
[0052] In another case the anode is a separate body which is
electrically connected to one terminal of the storage
component.
[0053] The above features can be preferably used for protection of
steel reinforcing or structural members in concrete or mortar
material where it is well known that corrosion can cause breakdown
of the concrete due to the expansive forces of the corrosion
products and due to the reduction to the steel strength. However
uses in other situations can arise.
[0054] The term impressed current anode used herein is intended to
distinguish from the sacrificial anode where the sacrificial anode
is formed of a material, typically of zinc, which is less noble
than the metal section so that it preferentially corrodes relative
to the metal section to be protected. The impressed current anode
is one which is used in conjunction with an external power supply
and does not need to be less noble than the metal section.
Typically such impressed current anodes are formed of titanium,
platinum, niobium, carbon and other noble metals and oxides which
do not corrode readily, or they can be formed of iron or less noble
materials such as zinc.
[0055] For use during a sacrificial or galvanic phase of operation
of the above method, the ionically conductive filler material
preferably contains at least one activator to ensure continued
corrosion of the sacrificial anode. However the activator can also
be located at other positions in the system. Suitable filler
materials can be in the form of solids, gels or liquids.
[0056] Gels can include carbomethyl cellulose, starches and their
derivatives, fumed silica or polymer gel electrolytes, e.g. acrylic
acid in a potassium hydroxide solution or polyvinyl
chloride/acetate-KOH composites with additions of bentonite,
propylene carbonate and or alumina. The alkali hydroxide in these
gels acts as a suitable activator.
[0057] Suitable activators include alkali hydroxides, humectants,
catalytic materials and other materials which are corrosive to the
sacrificial anode metal. Activators may be used alone or in
combination.
[0058] For use during a sacrificial or galvanic phase of operation
of the above method, the ionically conductive filler material
preferably has a pH sufficiently high for corrosion of the
sacrificial anode to occur and for passive film formation on the
sacrificial anode to be avoided. Alternatively, the filler may have
a lower pH and/or contain other activators for corrosion of the
sacrificial anode to occur and for passive film formation on the
sacrificial anode to be avoided.
[0059] The anode and methods herein are preferably designed for use
where the metal section is steel and the ionically conductive
material is concrete or mortar.
[0060] The anode apparatus including the impressed current and
sacrificial components is typically buried in the concrete or other
solid material so that it is fully encased by the concrete or a
filler material, but this is not essential and the anode may be
only partially buried or in direct or indirect physical or ionic
contact with the concrete.
[0061] The anode apparatus including the impressed current and
sacrificial components may be surrounded by an encapsulating
material or ionically conducting filler material which may be a
porous material or porous mortar material. Suitable encapsulating
materials can be inorganic or organic and may be any ionically
conductive cementitious, polymer or non-cementitious material or
mortar including geopolymers or modified Portland cements. The
encapsulating material may be solid, gel or liquid and may be
deformable.
[0062] The power supply may include a solar panel which drives the
impressed current anode and rechargeable galvanic anode so as to
provide long term protection when the solar power is on and
off.
[0063] The construction and methods proposed herein are designed
particularly where the metal section is steel and the ionically
conductive material is concrete or mortar. However the same
arrangements may be used in other corrosion protection systems such
as for pipes or other constructions in soil, and in many other
systems where such anodes can be used.
[0064] Preferably the assembly includes a reinforcing layer, such
as disclosed in U.S. Pat. No. 7,226,532 issued Jun. 5, 2007 to
Whitmore, the disclosure of which is incorporated by reference or
to which reference may be made for further details not disclosed
herein, to restrain and resist forces such as expansion,
contraction and deformation forces which may be caused by corrosion
of the anodes, deposition of sacrificial anode ions and other
physical/environmental forces such as freezing, thawing, wetting,
drying and thermal expansion/contraction.
[0065] The invention as defined and described herein can also be
provided as an assembly, as opposed to a method for cathodically
protecting and/or passivating a metal section in an ionically
conductive material. Thus the following definitions of the
invention presented herein are included herein. Each of these
independent definitions can be used in conjunction with any one of
or all of the subsidiary features as defined above.
[0066] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0067] an anode of a material which is not sacrificial to the metal
section;
[0068] a storage component of electrical energy with two poles for
communicating electrical current generated by release of the
electrical energy;
[0069] an arrangement for electrically connecting one pole to the
metal section;
[0070] an arrangement for electrically connecting the other pole to
the anode;
[0071] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the storage component through the electrical
connection to the metal section;
[0072] the storage component being connected as a single unit with
the anode.
[0073] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0074] an anode;
[0075] a storage component of electrical energy with two poles for
communicating electrical current generated by release of the
electrical energy;
[0076] an arrangement for connection of one pole to the metal
section;
[0077] an arrangement for electrically connecting the other pole to
the anode;
[0078] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the cell or battery of cells through the electrical
connection to the metal section;
[0079] wherein the anode comprises at least part of an outer
surface of the storage component.
[0080] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0081] an anode for communication of an electrical current to the
metal section in the ionically conductive material;
[0082] a container including a storage component of electrical
energy with two poles for communicating electrical current
generated by release of the electrical energy;
[0083] an arrangement for connection of one pole to the metal
section;
[0084] an arrangement for electrically connecting the other pole to
the anode;
[0085] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the cell or battery of cells through the electrical
connection to the metal section;
[0086] wherein the storage component is rechargeable.
[0087] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0088] an anode for communication of an electrical current to the
metal section in the ionically conductive material;
[0089] a container including a storage component of electrical
energy with two poles for communicating electrical current
generated by release of the electrical energy;
[0090] an arrangement for connection of one pole to the metal
section;
[0091] an arrangement for electrically connecting the other pole to
the anode;
[0092] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the cell or battery of cells through the electrical
connection to the metal section;
[0093] wherein the storage component is replaceable.
[0094] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0095] an anode for communication of an electrical current to the
metal section in the ionically conductive material;
[0096] a container including a storage component of electrical
energy with two poles for communicating electrical current
generated by release of the electrical energy;
[0097] an arrangement for connection of one pole to the metal
section;
[0098] an arrangement for electrically connecting the other pole to
the anode;
[0099] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the cell or battery of cells through the electrical
connection to the metal section;
[0100] wherein the storage component is a capacitor.
[0101] An assembly for cathodically protecting and/or passivating a
metal section in an ionically conductive material, comprising:
[0102] an anode for communication of an electrical current to the
metal section in the ionically conductive material;
[0103] a container including a storage component of electrical
energy with two poles for communicating electrical current
generated by release of the electrical energy;
[0104] an arrangement for connection of one pole to the metal
section;
[0105] an arrangement for electrically connecting the other pole to
the anode;
[0106] the assembly being arranged for placing the anode in ionic
contact with the ionically conductive material such that electrons
can flow from the cell or battery of cells through the electrical
connection to the metal section;
[0107] wherein the storage component has an outer surface at least
partly of stainless steel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0108] Embodiments of the invention will now be described in
conjunction with the accompanying drawings in which:
[0109] FIG. 1 is a schematic illustration of a corrosion protection
method according to the present invention using a first arrangement
of anode apparatus.
[0110] FIG. 2 is the schematic illustration of FIG. 1 showing the
connection of the components for operation in the impressed current
sacrificial protection mode.
[0111] FIG. 3 is a schematic illustration of a corrosion protection
method according to the present invention using a second
arrangement of anode apparatus.
[0112] FIG. 4 is a schematic illustration of a corrosion protection
method according to the present invention using a third arrangement
of anode apparatus.
[0113] FIG. 5 is a schematic illustration of a corrosion protection
method according to the present invention using a fourth
arrangement of anode apparatus, showing a connection of the
components for re-charging.
[0114] FIG. 6 is the schematic illustration of another arrangement
of FIG. 1 which can be used showing an alternative connection of
the components for re-charging.
[0115] FIG. 7 is a schematic illustration of a corrosion protection
method according to the present invention using a further
arrangement of anode apparatus.
[0116] FIG. 8 is a schematic illustration of a further arrangement
of the anode apparatus.
[0117] FIG. 9 is a schematic illustration of a further embodiment
of corrosion protection method according to the present invention
using another arrangement of anode apparatus.
[0118] FIG. 10 is a schematic illustration of a further embodiment
of corrosion protection method according to the present invention
using another arrangement of anode apparatus in which the apparatus
uses a supercapacitor which is recharged using a piezo-electric
charging system.
[0119] FIGS. 11 and 12 are battery anode progress graphs of voltage
and current vs time for the battery casing directly inserted in the
hole in the concrete slab with FIG. 10 showing a graph relating to
a second battery connected in series to the first battery as
described in the first set of examples.
[0120] FIG. 13 shows a graph of results for an assembly as
described herein with a battery and a MMO coated titanium anode
showing current before (as received) and after recharging where the
results are set out in Tables 1 and 2 hereinafter.
[0121] FIG. 14 shows a graph of results for an assembly as
described herein with a battery and a Zn anode showing current
before (as received) and after recharging where the results are set
out in Tables 3 and 4 hereinafter.
[0122] In the drawings like characters of reference indicate
corresponding parts in the different figures.
DETAILED DESCRIPTION
[0123] As shown in FIG. 1, a typical alkaline manganese
dioxide-zinc rechargeable cell comprises the following main units:
a steel can 12 defining a cylindrical inner space, a manganese
dioxide cathode 14 formed by a plurality of hollow cylindrical
pellets 16 pressed in the can, a zinc anode 18 made of an anode gel
and arranged in the hollow interior of the cathode 14, and a
cylindrical separator 20 separating the anode 18 from the cathode
14. The ionic conductivity (electrolyte) between the anode and the
cathode is provided by the presence of potassium hydroxide, KOH,
electrolyte added into the cell in a predetermined quantity. Other
types of rechargeable cells comprise similar main components (can,
cathode, anode, separator and electrolyte) but the composition of
the components may differ. Some of the types of cell may however be
of a different construction such as lead/acid cells or lithium
cells.
[0124] The can 12 is closed at the bottom, and it has a central
circular pip 22 serving as the positive terminal. The upper end of
the can 12 is hermetically sealed by a cell closure assembly which
comprises a negative cap 24 formed by a thin metal sheet, a current
collector nail 26 attached to the negative cap 24 and penetrating
deeply into the anode gel to provide electrical contact with the
anode, and a plastic top 28 electrically insulating the negative
cap 24 from the can 12 and separating gas spaces formed beyond the
cathode and anode structures, respectively.
[0125] The material of separator 20 consists of two different
materials, i.e.: a first material 30 made of fibrous sheet material
wettable by the electrolyte, and a second material 32 being
impermeable to small particles but retaining ionic permeability. An
expedient material for the first layer is a sheet material of
non-woven polyamide fiber, which is absorbent and serves as a
reservoir for electrolyte. The macro-porous structure of the
absorbent layer cannot prevent internal shorting by zinc dendrites
or deposits during discharge/charge cycling.
[0126] Shorting is prevented by the second 32 material which may be
a layer or layers of micro-porous or non-porous material which may
be laminated to or coated onto the fibrous sheet material. One
suitable material is one or more cellophane membranes laminated to
the non-woven polyamide sheet. Another is one or more coatings of
regenerated cellulose or viscose coated onto and partially
impregnating the non-woven polyamide sheet, resulting in a
composite material.
[0127] Other types of rechargeable cells may be used. In the
present arrangement, the type described above is used in a method
for cathodically protecting and/or passivating a metal section such
as steel reinforcing bar 40 in an ionically conductive material
such as concrete 41. The cell therefore includes a first terminal
42 and a second terminal 43 defined by the outer casing 12. The
first terminal 42 is connected to the pin or nail 26 which is
engaged into the anode material 18. The terminal 42 connects to a
connecting wire 42A which extends from the anode material 18 for
connection to the steel reinforcing bar 40 as shown in FIG. 2. In
practice the pin 26 and the wire 42A together with the terminal 42
may all form an integral structure where the wire extends into the
anode material in the form of the pin 26 or is sufficiently welded,
soldered, clamped or otherwise electrically connected. This is to
ensure an effective connection between the wire 42A and the anode
material 18.
[0128] In FIG. 1, anode 44 is applied as a coating onto the casing
12 of the cell. In this embodiment the anode 44 is of an inert
material so that it is more noble than steel. Examples of such
materials are well known. Thus the anode material 44 does not
corrode or significantly corrode during the cathodic protection
process.
[0129] The terminal 42 is connected to the steel reinforcement 40
by the wire 42A. Other electrical connection methods and materials
may be used. The wire may comprise steel, copper, brass or
titanium. The wire may comprise a layer of a second metal or alloy
or a layer of insulation. The second terminal defined by the casing
is connected to the anode by the contiguous surface therebetween.
As shown in FIG. 2, the anode 44 is placed in contact with the
ionically conductive material or concrete 41 so that electrons can
flow from the cell through the electrical connector 43 to the metal
section 40.
[0130] In this arrangement the application of the anode 44 onto the
outside surface of the casing 12 provides the structure as a common
single unit where the anode is directly connected to the cell and
forms an integral element with the cell. Anode 44 may comprise one
or more layers and may include a mixed metal oxide (MMO), catalytic
or sub-oxide layer.
[0131] In this embodiment, as the anode is formed of an inert
material which does not corrode in the protection process, the
anode and the cell contained therein can be directly incorporated
or buried in to the concrete or other ionically conductive material
without the necessity for an intervening encapsulating material
such as a porous mortar matrix. As there are no corrosion products
there is no requirement to absorb such products or the expansive
forces generated thereby. As the process does not depend upon,
continued corrosion of a sacrificial anode, there is no necessity
for activators at the surface of the anode. As the chemical
reaction at the surface of any inert anode during operation
generates acid (or consumes alkali) it is beneficial for the anode
to be buried in an alkaline material such as concrete or high
alkalinity mortar to prevent material near the anode from becoming
acidic. If desired, additional alkali may be added to the concrete
or other material the anode is in contact with.
[0132] Turning now to FIG. 3 there is shown an alternative
arrangement where the same cell is connected to and uses an anode
46 formed of a sacrificial material such as zinc. Again therefore
the anode is applied as a coating onto the outside surface of the
casing. Around the sacrificial anode 46 is provided a porous or
reinforced matrix 47 which is arranged to absorb any expansive
forces caused by the corrosion of the sacrificial anode 46 and
which may contain activators of a conventional construction for
ensuring continued corrosion of the sacrificial material. In
another embodiment the casing 12 is formed of a suitable inert
material more noble than steel and the sacrificial material of the
anode 46 is formed as a thin coating or a separate body which
corrodes away after a relatively short period of time leaving the
inert anode defined by the casing to continue further cathodic
protection. In this way the inert anode defined by the casing is
collated with or in electrical contact with the body of the
sacrificial anode material 46 and the anode material acts to
provide an initial boost of current until the sacrificial anode
material is consumed, following which the further cathodic
protection is obtained by the current discharge through the inert
anode defined by the casing 12.
[0133] In FIG. 4 is shown a further embodiment which uses the inert
anode 44 but provides an interior supply 48 of solid zinc within
the cell so as to ensure longevity of operation due to the presence
of sufficient zinc and cathode material within the system to
maintain the current flow from the cell through the anode 44 and
through the terminal 42 to ensure the cathodic protection of the
steel 40. The zinc may be cast rolled, pressed or otherwise
formed.
[0134] Turning now to FIG. 5 there is shown a system for recharging
the batteries or cells of the type shown in FIG. 1. It will be
appreciated that the combination forming the anode assembly can be
formed by a single cell where the casing of the cell directly
surrounds the cell and is directly attached to the anode. In other
arrangements schematically shown in FIG. 5 the current is supplied
by a battery 49 defined by separate cells 49A, 49B and 49C. The
cells can be constructed in any suitable arrangement and the
assembly into a battery is shown only schematically in FIG. 5. The
construction includes the anode 44 which is located on an exterior
casing of the battery 49. The battery includes the first terminal
42 and the second terminal 43.
[0135] A recharging system 50 is provided which can be used to
recharge each of the batteries 49. The recharging system 50 can
comprise a conventional rectifier type power source generating a
suitable voltage output for connection across the batteries.
Alternatively a solar source 51 can be used to generate electrical
power which is controlled by the charger 50 to be applied to the
batteries 50.
[0136] Each of the cells is constructed in a manner which allows
the cell to be recharged. Such rechargeable cells are of course
well-known and their construction is available from many different
prior disclosures.
[0137] In the arrangement shown in FIG. 5 each of the batteries is
embedded within the concrete in a manner which leaves the terminals
42 and 43 or electrical connections to these terminals exposed for
connection to the battery charger 50. The terminals may comprise
simply contact points or wires and it is not intended that the
terminals require any particular construction or require any
connection component for connection to the output leads or
connectors on the charger. It is simply required that there be a
connection when required between the charger and the battery.
[0138] With the batteries in place in the concrete the charger can
be used to recharge each of the batteries while those batteries
remain in place. The charger 50 can be arranged for connection to
the plurality of batteries within a structure and can be arranged
to provide repeated automatic recharging of those batteries at set
periods to ensure that the voltage of the batteries remains at a
required level. Alternatively the system may be managed as part of
a maintenance system so that the batteries are recharged manually
by manual connection when required, for example after a known
period during which it is expected that discharge to an
unacceptably low capacity will occur.
[0139] As indicated at 62 is provided a switch or disconnect
mechanism which is used to disconnect the cell from the metal
section 40 in the event that it is required that no additional
current is supplied to the metal section during the charging
process.
[0140] In FIG. 5 is shown that the recharging process is carried
out by applying a voltage between the terminal 42 and the terminal
43 of the battery. However it will be appreciated that it is also
possible to carry out the recharging by providing a connection to
the battery at the casing or at the anode 44 and a further
connection to the terminal 42 or to the wire which connects to the
steel 40 or directly to the steel 40. If the steel within the
structure is electrically interconnected, multiple batteries may be
charged by using a single connection to the steel 40 in combination
with connection to terminal 43 of multiple batteries.
[0141] In FIG. 6 is shown another arrangement where the charger 50
is connected to charge the batteries 49 using only two wires 64 and
65 so that a single wire 64 is connected to the steel at one of the
steel bars in a case where there is an electrical interconnection
between all of the steel bars.
[0142] It will further be appreciated that the recharging after
installation by an electrical connection of the charger to
terminals 42 and 43 while terminal 42 is electrically connected to
the metal section 40 will act to pass extra current to the metal
section during charging. This will cause passivation of the metal
section or reduce future current requirements after the recharging
process is complete to maintain passivity or to mitigate corrosion
of the metal section.
[0143] In FIG. 7 is shown an alternative arrangement 58 where there
is provided a cell 59 which is connected to an anode 60 and to the
steel 43 and is also connected to a recharging system 61 so as to
form an integral construction of these components. Therefore it is
not necessary for the anode 60 to surround the cell 59 but the
anode can lie alongside or adjacent or otherwise be connected to
the cell. The recharging system 61 forms an integral part of the
system but does not need to be connected in any particular way to
the cell. The recharging system 61 is shown as also contained
within or at least in contact with the concrete 41 but of course
this is not necessary. The recharging system may include solar
panels, batteries, and transformer rectifiers to convert AC to DC
power, DC power supplies or other battery chargers.
[0144] In FIG. 8 there is shown a further alternative arrangement
in which the sacrificial anode and battery or cell are not a
combined unit and are mounted separately in the concrete and
connected by an electrical connection. One pole of the cell is
therefore connected to the steel 40 and the other pole is connected
to the sacrificial anode as shown. In this case the battery is
re-charged by the charger 50 which is connected at the terminals 66
and 67. An electrical switching mechanism 68 such as a field effect
transistor (FET) is provided connected between the terminals 66 and
67 which switches to be a closed circuit and allows the sacrificial
anode to operate in galvanic mode in the event that the battery
voltage drops below a threshold and until the battery is re-charged
periodically by the charger 50 being brought into the connection
for re-charging as shown. The FET 68 operates to reopen the circuit
from the closed circuit condition when the charging voltage is
applied.
[0145] The system therefore can use rechargeable batteries of the
type developed by Josef Daniel-Ivad. It has been found that the
magnitude of the current that can be delivered to steel in concrete
is sufficient to provide an effective protection even when using
the above inert anode materials rather than the sacrificial zinc
anode. The battery has been found also to provide a reasonable
length of operation while delivering a realistic amount of current.
In general the battery can provide a significant current using an
AA size battery for a period of one to two years. The mean
published power capacity an AA battery is around 2.35 Ah and that
of a D battery is 15 Ah. A standard D battery would thus be
expected to last approximately 6 to 12 years depending on the level
of current output. It is realistic that a specially designed
battery can be manufactured to last a minimum of 10 years. The D
size battery is of realistic size and zinc mass to function to
provide the current for the anode.
[0146] In FIG. 9 is shown a schematic illustration of a further
embodiment of corrosion protection method according to the present
invention using a further arrangement of anode apparatus where the
battery or other storage component for the charge is replaceable.
This is shown as a casing or enclosure 100 with outer surface 101
forming the anode in the manner previously described. Thus the
casing 100 can be formed entirely of anode material or may be
covered by a layer of the anode material. Inside the casing is
provided a cell 102 with one terminal 103 connected to the casing
so as to electrically communicate therewith. The casing includes a
top cover 104 which is arranged to be sealed onto a top opening 105
of the casing. The top cover 14 includes a centre terminal 106
insulated from the casing itself by suitable insulation 107. The
terminal 106 includes a portion 108 connecting to the other
terminal of the battery and a portion 109 connected to the wire 110
communicating with the steel 40. In this arrangement, instead of
charging the battery 102, the battery can be replaced by removing
the top cover and inserting a new battery into engagement with the
casing at one terminal and with the cover at the other terminal of
the battery. This replacement can be carried out while the casing
remains in place within the concrete material 41 simply by
providing the top cover in an exposed position. The casing 100 has
its outer surface remaining in contact with the concrete.
[0147] The anode formed by the casing may have a noble or
non-sacrificial material positioned outside or otherwise separate
from a portion or layer of sacrificial anode material so that
cathodic protection provided by the noble anode is not interfered
with by buildup of corrosion products from the sacrificial anode
material. Thus in FIG. 9 an additional layer or portions (not
shown) of an inert or non-sacrificial anode material is applied
outside layer 101.
[0148] The assembly may be used with a non-conductive stand off or
spacer 111 to prevent the anode from electrically contacting the
steel resulting in a short circuit. The non-conductive standoff may
be an integral part of the anode assembly and may be attached to
the anode assembly for example by the attachment member 112.
Attachment may be made at any suitable location on the anode
assembly. The nonconductive standoff may be used to hold the anode
in place during concrete placement. Nonconductive standoff may form
a non-perforated layer between the anode and the steel to allow the
anode to be installed close to the steel and maintain reasonably
uniform ionic current distribution to the steel section. This
arrangement is particularly important in patch repair where a
section of the concrete is removed adjacent to the steel and the
anode assembly is inserted into the opening or hole generated by
the concrete removal. This arrangement is also important in new
construction applications where the steel is exposed and it is
desired to prevent contact between the anode assembly and the steel
and provide more uniform current distribution to the steel. In
these situations the location of the anode assembly should be
controlled by the provision of a suitable standoff member 111 shown
above.
[0149] Where a cylindrical anode assembly is used with a drilled
hole, the drilled hole can be arranged to approximately match the
shape of the anode assembly so that the provision of the spacer 111
is not required. A filler material can be inserted into the hole to
provide ionic connection and maintain the anode assembly in
position.
[0150] In one embodiment, the case of the cell is formed of a
sacrificial anode material and this material corrodes and is
consumed during operation of the assembly. When the sacrificial
anode material is consumed in at least one location, the cell will
be perforated and they will therefore be ionic contact between the
electrolyte within the cell and the ionically conductive material
or concrete. The remaining portion of the case which is formed of
the sacrificial material will continue to corrode relative to the
cathode of the cell, as these two components are now in ionic
contact with each other. This reaction will consume sacrificial and
material from the casing and reduce the ability of the casing to
function as an effective anode. If the anode of the cell is formed
of zinc or some other material which is less noble than steel, the
anode of the cell will begin to function as a sacrificial anode
relative to the steel as there is now an ionic connection between
the anode of the cell and the steel. In this manner the assembly
typically will continue to provide corrosion protection to the
steel as a simple galvanic anode, after the sacrificial anode
material of the casing of the cell is consumed.
[0151] This arrangement allows the assembly to provide two-stage
corrosion protection for the steel. The first stage provides a
higher driving voltage and thus a higher current to the steel cell
voltage and the potential between the sacrificial anode material
casing and the steel are additive. The second stage provides a
lower driving voltage and thus a lower current to the steel. When
the cell becomes fully ineffective, the driving voltage is the
difference in potential between the anode of the cell and the
steel. This anode arrangement can transition from the first stage
to the second stage automatically without any intervention.
[0152] In some arrangements as described herein the storage
component is associated with a sacrificial anode. The storage
component may be rechargeable or replaceable so as to extend the
life of the anode assembly well beyond the life of a single charge
of the storage component. At the same time however if the amount or
positioning of sacrificial anode material generates sufficient
corrosion products to reduce or halt the protection process, the
recharging or replacement of the cell may no longer become
effective. It is necessary therefore to choose an amount of
sacrificial anode material which matches the ability of the
assembly to continue to operate. This can be overcome in some cases
by providing also an inert anode material as part of the anode body
which may be provided as a layer inside the sacrificial material.
Thus when the sacrificial material is depleted before the operation
of the system is degraded by the presence of corrosion products,
the assembly continues to operate using the inert anode which has
become exposed. In FIG. 10 is shown a further arrangement using a
casing or enclosure 100 with outer surface 101 forming the anode in
the manner previously described. In this arrangement a storage
component is provided by a supercapacitor 120 and is connected by
the terminals 103 and 108 to the terminal 109 and the case 100 as
previously described. In this embodiment the control circuit 50
receives charging current from a piezo-electric charging system 121
which is actuated by loading or movement of the concrete structure
to which it is attached for example by the movement of vehicles.
Such piezo-electric changing systems have previously been known and
are available to persons skilled in this art for generating an
ongoing current which can be applied to the supercapacitor for
storage to replace current depleted to carry out the impressed
current cathodic protection. The capacitor 120 is contained within
the container 100 which provides the anode on the outer surface as
an integral component therewith. Such capacitors typically have an
outer container wall of a plastics material so as to protect and
insulate the operating components and this can be inserted into the
container 100 as a separate component, or the container and anode
can be formed onto the outer surface of the housing of the
capacitor. The capacitor can be replaced if necessary by insertion
of a new capacitor into the container.
[0153] Daily recharging can easily be provided by solar panels, for
example, but other means of producing reasonably regular bursts of
current could be used as charging components for the storage
component such as the supercapacitor in this example. An example of
such could be piezoelectric materials which can be incorporated in
roads, parking garages, bridges, runways etc. enabling current to
be generated by loading or movement of the structure or vehicles
passing over them.
[0154] That is, piezoelectric materials could be used to generate
electricity to power an impressed current system directly, or to
charge/recharge batteries or capacitors/supercapacitors.
EXAMPLES
[0155] In one example a Duracell D size battery was stripped of its
label and was directly inserted into a hole in a reinforced
concrete slab of dimension 28.times.19.times.10.5 cm high. The bare
metal casing of the battery was partially inserted into a 42 mm
diameter hole which was 38 mm deep. The space between the battery
and the inner surface of the hole was filled with ionically
conductive gel comprised of lithium hydroxide, water and
carboxymethylcellulose. The other terminal of the battery was is
connected to all of the steel bars in the concrete slab (four
transverse and two longitudinal bars, each 2 cm in diameter) such
that electrons flowed to the steel and the steel would be
protected. An arrangement of this type when tested gave an initial
current of around 3 mA and maintained a current of over 1 mA for
145 days. The barrel itself is nickel coated steel which is not
totally inert. Once there is a break in the nickel coating,
corrosion of the steel will occur under the conditions that prevail
at the surface of the metal. This may be overcome by providing a
coating which may be thicker or a coating which is a more effective
inert anode material such as MMO coated titanium, titanium
sub-oxide, platinum, niobium or any other such material. The steel
barrel may also be replaced with a barrel which is wholly made of
more effective inert anode material as listed above.
[0156] If the steel barrel is allowed to corrode, it will
eventually perforate such that the battery is no longer a closed
cell. If this happens, some or all of the ionic current from the
anode of the battery may flow directly to the reinforcing steel
instead of flowing to the cathode of the battery. This would
compromise the added voltage of the battery but it would allow the
anode of the battery to continue to protect the reinforcing steel
as a simple galvanic system.
[0157] A two battery setup can be used. In a second example, a
sample as described above was prepared and a second battery was
connected in series with the first battery. The casing of the first
battery was directly inserted and used as the anode. This
arrangement increased the driving voltage by a factor of two and
surprisingly, the current to the steel reinforcement increased by a
factor of three to four. Initial current was 9.5 mA and a current
of 3 to 4 mA was maintained for over 110 days. Further batteries
(#3 and #4) were added in series to further increase the driving
voltage. The increase in current to the steel reinforcement was
roughly proportional to the increase in voltage.
[0158] In a further example, a D size battery was connected to
various noble and sacrificial anode materials including MMO coated
titanium, titanium sub-oxide tube, brass and zinc. Testing was
completed on reinforced concrete blocks of the same dimensions as
described above. The anodes were embedded in the concrete hole
using ionically conductive gel. Batteries were electrically
connected to the anode materials and to the reinforcing steel. The
non-inert anodes especially zinc delivered higher initial current
than the inert anodes. Nonetheless a current of at least 1 mA was
achieved by all anodes.
[0159] In a further example, a stainless steel anode was used and
was embedded in compacted sand dosed with a saturated solution of
lithium hydroxide. The stainless steel anode was used to pass 30 to
50 mA current for a period of 14 days. Minimal corrosion was
evident on the stainless steel anode surface after passing a total
charge of 12.5 A-hrs of charge.
[0160] In yet a further series of examples, zinc alkaline
rechargeable AA size batteries were connected to mixed metal oxide
(MMO) coated titanium and zinc anodes which were partially embedded
in ionically conductive gel in a hole in a reinforced concrete
block as described above. In each case the anode was connected to
the terminal marked+ and the steel was connected to the terminal
marked--on an as received rechargeable battery. Current flowing to
the steel was recorded. The battery was then disconnected and
discharged. After discharging the battery the voltage of the
battery was measured to confirm it was discharged. The battery was
then recharged and reconnected. The current was recorded after the
battery was recharged. These steps were taken with both the inert
MMO titanium anode and the sacrificial zinc anode.
[0161] The current produced when the battery was connected to the
sacrificial anode was greater than the current produced when the
battery was connected to the inert MMO coated titanium anode. In
both cases the current from the recharged battery exceeded the
current from the original battery.
[0162] The concept of using a battery or a rechargeable battery of
the type described herein is an improvement over the conventional
galvanic anode available in the market. A current output of more
than 1 mA can be maintained for many weeks without a significant
drop in the battery voltage indicating that cathodic protection can
be maintained for several years. An inert anode such as MMO coated
titanium can be wrapped around, coated onto or otherwise
electrically connected to the casing of the battery. Alternatively
the barrel of the battery may partially or fully comprise titanium
and can be coated with MMO or titanium sub-oxide. A portion of
sacrificial anode material such as zinc can be provided in
combination with an inert anode to provide additional current until
the sacrificial portion is consumed. The outer barrel of the
battery can also be used as an impressed current anode in cases
where an additional power supply is used to provide an initial
charge to passivate the steel. Specially designed batteries can be
modified to provide the desired parameters for this application
such as low current, long life operation and to be more suitable
for direct embedment into the concrete.
[0163] FIGS. 11 and 12 are battery anode progress graphs of voltage
and current vs time for the battery casing directly inserted in the
hole in the concrete slab with FIG. 10 showing a graph relating to
a second battery connected in series to the first battery as
described in the first set of examples.
[0164] FIG. 13 shows a graph of results for an assembly as
described herein with a battery and a MMO coated titanium anode
showing current before (as received) and after recharging, based on
the results set out hereinafter in Tables 1 and 2.
[0165] FIG. 14 shows tables and a graph of results for an assembly
as described herein with a battery and a Zn anode showing current
before (as received) and after recharging, based on the results set
out hereinafter in Tables 3 and 4.
TABLE-US-00001 TABLE 1 Ti MMO Area of Ti MMO exposed 6 cm2 Battery
Igo Green 1.5 V Negative terminal of the battery is connected to 6
bars of steel, positive terminal of the battery connected to the
MMO titanium ribbon anode MMO titanium ribbon is placed in a
conductive gel in the concrete sample. Initial voltage of battery
1.571 V for the Original Battery in as received condition. Date
Time Current mA Voltage V 24 Sep. 2015 10:48 3.8 24 Sep. 2015 10:49
1.27 24 Sep. 2015 10:50 1.5 24 Sep. 2015 10:51 1.29 24 Sep. 2015
10:52 1.277 1.542 24 Sep. 2015 10:53 1.273 24 Sep. 2015 10:55 1.24
24 Sep. 2015 10:59 1.183 24 Sep. 2015 11:08 1.166 24 Sep. 2015
11:17 1.241 24 Sep. 2015 11:42 1.243 24 Sep. 2015 12:04 1.258 24
Sep. 2015 12:08 1.256 24 Sep. 2015 12:10 1.258 24 Sep. 2015 12:11
1.259 24 Sep. 2015 12:21 1.262 24 Sep. 2015 12:57 1.268
TABLE-US-00002 TABLE 2 Recharged Igo battery connected back to the
Ti MMO Initial Voltage 1.569 V Date Time Current mA 25 Sep. 2015
9:02 2.731 25 Sep. 2015 9:03 1.95 25 Sep. 2015 9:04 1.821 25 Sep.
2015 9:05 1.762 25 Sep. 2015 9:06 1.725 25 Sep. 2015 9:07 1.697 25
Sep. 2015 9:10 1.64 25 Sep. 2015 9:16 1.575 25 Sep. 2015 9:25 1.519
25 Sep. 2015 9:39 1.449 25 Sep. 2015 9:55 1.385 25 Sep. 2015 10:17
1.351 25 Sep. 2015 10:32 1.339 25 Sep. 2015 10:56 1.324 25 Sep.
2015 11:03 1.321
TABLE-US-00003 TABLE 3 Zinc rod anode Area of Zinc exposed 6 cm2
Battery Igo Green 1.5 V AA size Negative terminal as marked on the
battery is connected to 6 bars of steel, positive terminal of the
battery connected to the zinc rod anode. Zinc rod is placed in a
conductive gel (lithium hydroxide, carboxymethylcellulose and
water) in the concrete reservoir. Original Battery: Initial voltage
of battery 1.5694 V (as received) Date Time Current mA Voltage V 22
Sep. 2015 9:27 7.505 22 Sep. 2015 9:29 6.737 22 Sep. 2015 9:30
6.678 22 Sep. 2015 9:31 6.642 22 Sep. 2015 9:32 6.613 1.542 22 Sep.
2015 9:33 6.58 22 Sep. 2015 9:34 6.561 22 Sep. 2015 9:38 6.518 22
Sep. 2015 9:40 6.498 22 Sep. 2015 9:47 6.38 22 Sep. 2015 10:01
6.377 22 Sep. 2015 10:01 6.332 22 Sep. 2015 10:15 6.294 22 Sep.
2015 10:26 6.273 22 Sep. 2015 10:34 6.245 22 Sep. 2015 11:29 6.191
22 Sep. 2015 11:46 6.176 22 Sep. 2015 11:48 6.174 1.523 22 Sep.
2015 11:52 6.172
TABLE-US-00004 TABLE 4 Recharged Igo battery connected back to the
zinc rod anode Initial Voltage 1.644 V Date Time Current mA Voltage
V 25 Sep. 2015 11:48 9.222 25 Sep. 2015 11:49 8.268 25 Sep. 2015
11:50 8.07 25 Sep. 2015 11:51 7.975 25 Sep. 2015 11:53 7.864 25
Sep. 2015 11:55 7.795 25 Sep. 2015 12:09 7.522 25 Sep. 2015 12:22
7.308 25 Sep. 2015 12:51 7.219 25 Sep. 2015 13:24 7.107 1.576 25
Sep. 2015 13:48 7.041 25 Sep. 2015 14:07 7.015
[0166] Since various modifications can be made in my invention as
herein above described, and many apparently widely different
embodiments of same made within the spirit and scope of the claims
without department from such spirit and scope, it is intended that
all matter contained in the accompanying specification shall be
interpreted as illustrative only and not in a limiting sense.
* * * * *