U.S. patent application number 09/765888 was filed with the patent office on 2002-07-25 for method and apparatus for cathodically protecting reinforced concrete structures.
Invention is credited to Giorgini, Roberto.
Application Number | 20020096438 09/765888 |
Document ID | / |
Family ID | 25074800 |
Filed Date | 2002-07-25 |
United States Patent
Application |
20020096438 |
Kind Code |
A1 |
Giorgini, Roberto |
July 25, 2002 |
Method and apparatus for cathodically protecting reinforced
concrete structures
Abstract
Galvanic protection of a reinforced concrete structure or a
metallic structure immersed or partially immersed in water or
seawater utilizes a sacrificial anode having a more negative
electrode potential than that of the metal to be protected but
connected to the reinforcement or metallic structure, and the anode
immersed in electrolyte solution creating an corrosive environment
for the anode. The electrolyte solution must exist for internal
charge transfer by ionic conductance, and to complete the electric
circuit of the galvanic cell therefore both the metal or reinforced
structure and the sacrificial anode have to be immersed in an
electrolyte solution. The anode will provide in that way sufficient
current to protect the reinforcement or metal structure against
corrosion. The present invention resides in a method where the
sacrificial anode immersed in an electrolyte solution can be
positioned on a remote location e.g. in a small container away from
the reinforced concrete or metal structure. This is done in a
manner that both electrolyte solutions in which one electrolyte
solution the metal or reinforced structure is immersed and second
electrolyte solution the anode is immersed are connected through
two metallic non-corrosive current distributors providing an
electrical bridge between both electrolytes. The current density
can be adjusted by increasing or decreasing the surface area of the
current distributor immersed in the electrolyte solution in which
the anode is immersed.
Inventors: |
Giorgini, Roberto; (Capelle
a.d. Ijssel, NL) |
Correspondence
Address: |
CONCORDE BV
HOOFDWEG 40
CAPELLE a.d. IJSSEL
2908 LC
NL
|
Family ID: |
25074800 |
Appl. No.: |
09/765888 |
Filed: |
January 22, 2001 |
Current U.S.
Class: |
205/734 ;
205/740 |
Current CPC
Class: |
C23F 2201/02 20130101;
C23F 13/06 20130101; C23F 2213/31 20130101 |
Class at
Publication: |
205/734 ;
205/740 |
International
Class: |
C23F 013/00 |
Claims
What I claim as my invention is:
1) A method of galvanically protecting a reinforced concrete
structure comprising the steps of: (a) electrically connecting a
sacrificial anode to the steel reinforcement of the concrete
structure, the anode having a more negative electrode potential
than that of the steel reinforcement; (b) the sacrificial anode to
be immersed in an electrolyte solution creating a corrosive
environment for the anode, and providing in that way sufficient
current to protect the reinforcement against corrosion; (c) the
sacrificial anode immersed in an electrolyte solution being
positioned on a remote location e.g. in a small container away from
the reinforced concrete; (d) providing an electrical bridge between
both the electrolyte solutions by electrically connecting the
current distributor which is immersed in the electrolyte solution
in which the anode is immersed and a current distributor applied on
the surface of the reinforced concrete.
2) A method of galvanically protecting a steel or metal structure
immersed or partially immersed in water or seawater or any other
electrolyte solutions comprising the steps of: (a) electrically
connecting a sacrificial anode to the steel or metal structure
immersed or partially immersed in water or seawater or any other
electrolyte solutions, the anode having a more negative electrode
potential than that of the steel or metal structure; (b) the
sacrificial anode to be immersed in an electrolyte solution
creating a corrosive environment for the anode, and providing in
that way sufficient current to protect the steel or metal structure
immersed or partially immersed in water or seawater or any other
electrolyte solutions against corrosion; (c) the sacrificial anode
immersed in an electrolyte solution being positioned on a remote
location e.g. in a small container away from the steel or metal
structure immersed or partially immersed in water or seawater or
any other electrolyte solutions; (d) providing an electrical bridge
between both the electrolyte solutions by electrically connecting
the current distributor which is immersed in the electrolyte
solution in which the anode is immersed and a current distributor
which is immersed in the water or seawater or any other electrolyte
solutions in which the steel or metal structure is immersed.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Method and Apparatus for Cathodically Protecting Reinforced
Concrete Structures.
[0002] U.S. Pat. No. 5,292,411; Bartholomew, John J. ; Mar. 8,
1994; discloses a method for cathodically protecting a reinforced
concrete structure by adhering a metal anode such as a zinc anode
sheet to a surface of the concrete structure. A pressure sensitive
coating of an ionically conductive hydrogel is on a surface between
the anode and the concrete surface.
[0003] Relating to the Cathodic Protection of Structures
[0004] U.S. Pat. No. 4,078,510 ; Morgan, John Harold; Mar. 14,
1978; discloses a method of surveying a cathodically protected
metallic structure at least partly immersed in a liquid, such as an
undersea pipeline which has sacrificial anodes attached at regular
intervals along its length. The potential differences in the water
between a point adjacent an anode, and test points adjacent the
pipeline are measured, and the varying level of protection along
the pipe is determined from the variations between the measured
potential differences.
[0005] Method for Preventing Corrosion of a Reinforced Concrete
Structure
[0006] U.S. Pat. No. 5,341,562 ; Furuya, Akio ; Aug. 30, 1994;
discloses a method for preventing corrosion of a reinforced
concrete structure having a reinforcing steel embedded therein,
which comprises coating an aggregate-containing primer on the
surface of the reinforced concrete structure, to form a primer
layer having a rough surface, metal-spraying a metal having an
ionization tendency larger than iron on the primer layer to form a
metal spray coating layer, and connecting the metal spray coating
layer and the reinforcing steel by an electrically conductive
material.
[0007] Galvanic Protection of Rebar by Zinc Wire
[0008] U.S. Pat. No. 5,449,563 ; Zhang, Xiaoge G. ; Sep. 12, 1995:
discloses a method for preventing corrosion of a reinforced
concrete structure by attaching a zinc wire, such as by welding,
soldering or co-extrusion, along the length of the rebar. Zinc wire
attached to the rebar provides galvanic protection to the steel to
prevent iron corrosion and subsequent deterioration of the
reinforced concrete.
[0009] Cathodic Protection System for Reinforced Concrete
[0010] U.S. Pat. No. 5,968,339 ; Clear, Kenneth C.; Oct. 19, 1999;
resides also in a cathodic protection system of reinforced concrete
which comprises a conductive corrodible metal anode positioned at a
point remote from the surface of the concrete structure. An
electric circuit connects the anode and the reinforcement of the
concrete structure. A current distributor positioned on a surface
of the concrete structure is connected to the anode by a salt
bridge. The salt bridge preferably is a capillary tube that is
filled with an ionically conductive fluid and/or solid material.
The salt bridge extends into the container with the electrolyte
solution in contact with the anode and connects the anode with the
current distributor.
BACKGROUND OF THE INVENTION
[0011] The present invention relates to a method and apparatus for
galvanically protecting reinforced concrete structures, such as the
decks or substructures of bridges, wharfs and parking garages and
steel or metal structures immersed or partially immersed in water
or seawater or any other electrolyte solution, such as off-shore
platforms and structures or seagoing vessels.
[0012] Anodes for use in applications as mentioned in the
introduction are used to prevent corrosion on the surface of the
reinforcement of concrete structures and other various steel or
metal structures, exposed to an ionically conducting medium. They
comprise an active current transferring surface, which is in
electric contact with the medium and which transfers a direct
current between that surface and the surface of the structure,
through the medium. The current influencing the corrosion processes
is transferred between the electrode and the structure via the
ionically conducting medium.
[0013] As can be understood from the patents mentioned in the
references cited, where a galvanic cell is used it is important
that the electrolyte contacting the anode is such that sustained
active corrosion of the anode can occur and that the electrolyte
must also be in contact with the surrounding concrete for internal
charge transfer by ionic conductance, and to complete the electric
circuit. Salt bridges as ionically conductive fluids and/or solid
materials as described in the above mentioned patents are known for
decades within the field of electrochemistry and used in several
applications.
[0014] However, a disadvantage of salt bridges as an ionically
conductive material applied in galvanic cells is the increasing
electric resistivity by increasing the distance of the anode and
the metal structure being protected. The use of salt bridges will
therefore limit the distance between the anode and the structure
being protected.
[0015] The present invention will overcome this limitation by
replacing the salt bridge by two current distributors, and both
connected to each other with an electric or metal conductor or
circuit such as cupper wire.
BRIEF SUMMARY OF THE INVENTION
[0016] The present invention resides in a method for galvanically
protecting of a reinforced concrete structure or steel or metal
structure immersed or partially immersed in water or seawater or
any other electrolyte solution of which the sacrificial anode
immersed in an electrolyte solution can be positioned on a remote
location e.g. in a small container away from the reinforced
concrete or steel or metal structure. This is done in a manner that
both electrolyte solutions in which the electrolyte solution the
metal or reinforced structure is immersed and the other electrolyte
solution the anode is immersed are connected through two metallic
non-corrosive current distributors providing an electrical bridge
between both electrolytes.
[0017] The sacrificial anode is immersed in an electrolyte solution
having a pH which is maintained sufficiently high for corrosion of
the anode to occur and for passive film formation on the anode to
be avoided. The anode material selected will determine the
electrolyte pH required to maintain active corrosion.
[0018] The anode is preferably zinc or a zinc alloy but the anode
may be aluminium, an aluminium alloy, cadmium, a cadmium alloy,
magnesium or a magnesium alloy or another material which has a more
negative standard electrode potential than the reinforcement of
concrete or steel or metal structure immersed or partially immersed
in water or seawater or any other electrolyte solution under the
prevalent conditions.
[0019] The electrical connection which is replacing the salt bridge
used in galvanic cells to seperate the electrolyte solution
consists of two metallic non-corrosive current distributors and
both connected to each other with an electric or metal conductor or
circuit such as cupper wire.
[0020] The current distributors are preferably non or low corrosive
electric conductive materials such as Platinum, Carbon, Stainless
Steel or activated Titanium.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0021] FIG. 1 is a perspective view of the basic invention of which
the following numbers represent:
[0022] 1 electrolyte solution
[0023] 2 sacrificial anode
[0024] 3 current distributor
[0025] 4 electric lead
[0026] 5 electric lead
[0027] 6 current distributor
[0028] 7 electrolyte solution
[0029] 8 steel or metal structure
[0030] FIG. 2 is a perspective view of reinforced concrete
protected in a manner of the present invention of which the
following numbers represent:
[0031] 1 reinforced concrete stucture
[0032] 2 reinforcement
[0033] 3 current distributor
[0034] 4 electric lead
[0035] 5 electric lead
[0036] 6 container
[0037] 7 electrolyte solution
[0038] 8 sacrificial anode
[0039] 9 current distributor
[0040] FIG. 3 is a perspective view of a steel or metal structure
immersed or partially immersed in water or seawater or any other
electrolyte solution protected in a manner of the present invention
in which the following numbers represent:
[0041] 1 electric lead
[0042] 2 steel or metal structure
[0043] 3 water or seawater or any other electrolyte solution
[0044] 4 electric lead
[0045] 5 container
[0046] 6 electrolyte solution
[0047] 7 sacrificial anode
[0048] 8 current distributor
[0049] 9 electric insulator
[0050] 10 current distributor
DETAILLED DESCRIPTION OF THE INVENTION
[0051] In the embodiment of FIG. 1, the galvanic cell comprises 2
containers with both an electrolyte solution 1 en 7. The first
container comprises an anode 2 and a current distributor 3. The
current distributor 3 is connected by a lead 5 with a similar metal
current distributor 6 which extends into the electrolyte solution
of the second container. A preferred lead 5 is a metallic conductor
such as cupper wire which connects both current distributors 3 en
6. A preferred current distributor 3 is a non or low corrosive
conductive material such as Platinum, Carbon, Stainless Steel or
activated Titanium. An electric lead 4 connects the anode 2
directly with a metal structure 8 to be galvanically protected. A
preferred lead 4 is a metal conductor such as cupper wire.
[0052] In the operation of this embodiment, the anode 2 is consumed
by the electrolyte solution 1. This causes a current flow between
the metal structure 8 and anode 2, via lead 4, which protects the
metal structure 8.
[0053] In the embodiment of FIG. 2, the galvanic protection system
comprises an anode 8 which is remote from the reinforced concrete
structure 1. A current distributor 3 is positioned on the surface
of the reinforced concerte structure 1. The current distributor 3
can be in the form of a metal mesh or conductive coating. The
current distributor 3 is connected to a lead 4 which extends into a
container 6. The lead 4 is connected with a metal current
distributor which extends into the electrolyte solution. Anode 8 is
positioned inside the container 6. The container 6 is filled with
an electrolyte solution 7. A preferred lead 4 is a metallic
conductor such as cupper wire which connects the current
distributor 9 with the current distributor 3. A preferred current
distributor 3 is a non-corrosive metal such as Platinum or
activated Titanium An electric lead 5 connects the anode 8 directly
with the reinforcement 2.
[0054] In the operation of this embodiment, the anode 8 is consumed
by the electrolyte solution 7. This causes a current flow between
the reinforcement 2 and anode 8, via lead 5, which protects the
reinforcement.
[0055] An advantage of this embodiment of the present invention is
that the anode 8 can be serviced and replaced without accessing
that portion of the galvanic protection system physically attached
to the concrete structure and can be positioned on a remote
location in a container 6 on a great distance away from the
reinforced concrete. Unlike a salt bridge the metallic conductor
will have no distance limitations due to increasing
resistivity.
[0056] In the embodiment of FIG. 3, the galvanic protection system
comprises an anode 7 which is remote from a steel or metal
structure 2 immersed or partially immersed in water or seawater or
any other electrolyte solution. A current distributor 10 is
positioned on a specific part of the surface of the steel or metal
structure 2 which specific part of the surface is immersed in the
water or seawater or any other electrolyte solution but isolated
from the structure by an electric insulator 9. The current
distributor 10 can be in the form of a non or low corrosive
material such as Platinum, Carbon, Stainless Steel or activated
Titanium. The current distributor 10 is connected to a lead 4 which
extends into a container 5. The lead 4 is connected with a metal
current distributor which extends into the electrolyte solution.
Anode 7 is positioned inside the container 5. The container 5 is
filled with an electrolyte solution 6.
[0057] A preferred lead 4 is a metal conductor such as cupper wire
which connects the current distributor 10 with the current
distributor 8. A preferred current distributor 8 is a non or low
corrosive meterial such as Platinum, Carbon, Stainless Steel or
activated Titanium. An electric lead 1 connects the anode 7
directly with the steel or metal structure 2.
[0058] In the operation of this embodiment, the anode 7 is consumed
by the electrolyte solution 6. This causes a current flow between
the steel or metal structure 2 and anode 7, via lead 1, which
protects the steel or metal structure.
[0059] An advantage of this embodiment of the present invention is
that the anode 7 can be serviced and replaced without accessing
that portion of the galvanic protection system which is normally
physically attached under water or seawater or any other
electrolyte solution to the steel or metal structure, and can be
positioned on a remote dry location in a container 6 on top or
inside the steel or metal structure. A salt bridge can not operate
in such an embodiment as the water or seawater will go easily
through a capillary tube filled with an ionically conductive fluid
due to the static pressure.
* * * * *