US20140251793A1 - Cathodic protection current distribution method and apparatus for corrosion control of reinforcing steel in concrete structures - Google Patents
Cathodic protection current distribution method and apparatus for corrosion control of reinforcing steel in concrete structures Download PDFInfo
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- US20140251793A1 US20140251793A1 US13/788,525 US201313788525A US2014251793A1 US 20140251793 A1 US20140251793 A1 US 20140251793A1 US 201313788525 A US201313788525 A US 201313788525A US 2014251793 A1 US2014251793 A1 US 2014251793A1
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- anodes
- tape
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- 239000004567 concrete Substances 0.000 title claims abstract description 49
- 238000004210 cathodic protection Methods 0.000 title claims description 16
- 229910001294 Reinforcing steel Inorganic materials 0.000 title claims description 10
- 230000007797 corrosion Effects 0.000 title claims description 7
- 238000005260 corrosion Methods 0.000 title claims description 7
- 238000000034 method Methods 0.000 title description 4
- 229910052751 metal Inorganic materials 0.000 claims abstract description 30
- 239000002184 metal Substances 0.000 claims abstract description 30
- 229910003455 mixed metal oxide Inorganic materials 0.000 claims abstract description 26
- 239000011248 coating agent Substances 0.000 claims abstract description 22
- 238000000576 coating method Methods 0.000 claims abstract description 22
- 239000000853 adhesive Substances 0.000 claims abstract description 14
- 230000001070 adhesive effect Effects 0.000 claims abstract description 14
- 239000010970 precious metal Substances 0.000 claims abstract description 10
- 238000003466 welding Methods 0.000 claims abstract description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 12
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- 239000010936 titanium Substances 0.000 claims description 11
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 claims description 6
- 239000000835 fiber Substances 0.000 claims description 6
- 229910052715 tantalum Inorganic materials 0.000 claims description 6
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 4
- 229910052758 niobium Inorganic materials 0.000 claims description 4
- 239000010955 niobium Substances 0.000 claims description 4
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims description 2
- 239000004917 carbon fiber Substances 0.000 claims description 2
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 2
- 229910052741 iridium Inorganic materials 0.000 claims description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 2
- 229910052763 palladium Inorganic materials 0.000 claims description 2
- 229910052707 ruthenium Inorganic materials 0.000 claims description 2
- 229910045601 alloy Inorganic materials 0.000 claims 2
- 239000000956 alloy Substances 0.000 claims 2
- 239000012811 non-conductive material Substances 0.000 claims 2
- 238000009434 installation Methods 0.000 abstract description 8
- 150000002739 metals Chemical class 0.000 abstract description 6
- 239000013256 coordination polymer Substances 0.000 abstract 1
- 239000000758 substrate Substances 0.000 description 7
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000011440 grout Substances 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000011150 reinforced concrete Substances 0.000 description 3
- 239000010959 steel Substances 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- 238000005536 corrosion prevention Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000003467 diminishing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 229960000443 hydrochloric acid Drugs 0.000 description 1
- 235000011167 hydrochloric acid Nutrition 0.000 description 1
- 230000007257 malfunction Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- -1 rebar chairs Chemical class 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F13/00—Inhibiting corrosion of metals by anodic or cathodic protection
- C23F13/02—Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
- C23F13/06—Constructional parts, or assemblies of cathodic-protection apparatus
- C23F13/08—Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
- C23F13/16—Electrodes characterised by the combination of the structure and the material
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/20—Resistance against chemical, physical or biological attack
- C04B2111/26—Corrosion of reinforcement resistance
- C04B2111/265—Cathodic protection of reinforced concrete structures
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F2201/00—Type of materials to be protected by cathodic protection
- C23F2201/02—Concrete, e.g. reinforced
Definitions
- This invention relates generally to corrosion control in reinforced-concrete structures and, in particular, to mixed-metal-oxide (MMO) coated precious-metal tape and mesh that may be installed directly on concrete surfaces without the need for slots, holes, cementitious grout or concrete.
- MMO mixed-metal-oxide
- Cathodic protection is a method for controlling corrosion of reinforcing steel, including steel structures in chloride contaminated concrete.
- CP Cathodic protection
- Various types of impressed current cathodic protection anodes for reinforced concrete structures have been developed in the past.
- the anode is one of the most critical components for a cathodic protection system, as it is used to distribute cathodic protection current to the reinforcing steel.
- MMO coated anodes are manufactured by coating a mixture of precious metal oxides on a specially treated precious metal. The coated substrate undergoes multiple thermal treatments at elevated temperatures to achieve good bonding properties between the substrate and the coating.
- titanium is widely used as substrate material due to its resistance to corrosion, resistance to chemical attacks and high mechanical strength, other anodes such as tantalum, niobium and zirconium anodes are also used for different applications.
- MMO-coated titanium anode Since the first MMO-coated titanium anode was developed in 1984, many concrete structures have been protected using this material. To install the anodes, however, they must be embedded in concrete or cementitious grout. For example, titanium mesh with a concrete overlay, titanium ribbon or ribbon mesh embedded in cemetitious grout in saw-cut slots, or discrete anodes embedded in grout in drilled holes. However, these types of installations add burden to the structure and lead to some durability concerns. A useful review of MMO-coated anodes and installation techniques may be found in “Cathodic Protection of Steel in Concrete” By Paul Chess, Taylor & Francis (1998), ISBN 0419230106, the entire content of which is incorporated herein by reference.
- the existing concrete must be cut or drilled to install the anodes.
- the concrete covers over the reinforcing steel are shallow or congested, such installation procedures are not feasible.
- the anodes are somehow installed in the slots or drilled holes, the vicinity of the reinforcing steel near the anodes may cause an electrical short circuit, resulting in malfunction of the cathodic protection system.
- This invention overcomes the shortcomings of prior art by allowing mixed-metal-oxide (MMO) coated precious-metal tape to be installed on dry concrete structures without the need for slots or holes.
- MMO mixed-metal-oxide
- a semi-electrically conductive and gas-permeable coating or overlay is used in combination with a MMO-coated precious-metal tape anode to improve current distribution at low voltages.
- the electrical resistivity of the semi-conductive coating is lower than that of typical concrete. However, when the semi-conductive coating is moist in a local area, the resistivity is still high enough to prevent the concentration of cathodic protection current discharging to the concrete substrate.
- MMO-coated tape anodes may be installed on the concrete surfaces using non-conductive adhesives without developing an electrical short circuit between the anode and the reinforcing steel. Interconnections between the tape anodes and bare metal distribution elements may be made with conductive adhesive or spot welding. Alternatively, MMO-coated mesh anodes may be embedded in the semi-conductive coating without contacting to the concrete substrate. Interconnections between the mesh anodes and bare metal distribution elements may be made with conductive adhesives or spot welding.
- the anodic can be operated at anode current densities higher than 110 mA/m 2 .
- the chlorine gas evolved on the anode diffuses away though the porous semi-conductive coating before it tunes to hydro-chloric acid.
- the semi-conductive media may include carbon, MMO coated metal(s) or any passive bare metal powder or fibers mixed with any electrolytic cementitious or plastic media.
- FIG. 1 illustrates tape anode installation on a concrete surface and covered with a semi-conductive coating.
- the tape anode is fixed on the concrete surface by non-conductive adhesive and the top of the tape discharge current;
- FIG. 2 illustrates a mesh anode installation within a semi-conductive coating
- FIG. 3 is an example of a possible installation method of tape anodes to a bare-metal element
- FIG. 4 illustrates chlorine gas generated on an anode diffusing away to atmosphere.
- This invention relates to protection and corrosion prevention of reinforced concrete structures using mixed-metal-oxide (MMO) coated precious-metal tape anodes.
- the anodes are attached to a concrete surface using a non-conductive adhesive and covered with a semi-conductive layer to provide cathodic protection or chloride removal.
- the bare metal surface of the tape is fixed on the concrete surface using a non-conductive adhesive, such that the MMO-coated metal surface of the tape is exposed.
- the substrate metal tape anode may be composed of titanium, tantalum, zirconium, or niobium. However, the most preferred metals are titanium or titanium alloys because of the corrosion resistance and availability.
- the tape anode width is preferably over 5 mm, and the thickness is in the range of 0.001 mm to 1 mm, preferably between 0.1 mm to 0.3 mm.
- FIG. 1 is a simplified cross-sectional diagram showing a metal tape anode 1 attached to concrete 4 through non-conductive adhesive 3 .
- thin coated semi-conductive media 2 is coated over the metal tapes.
- the semi-conductive coating preferably comprises a cementitious or plastic material with suspended conductive or semi-conductive particles to adjust the electrical resistivity.
- the semi-conductive coating comprises a flowable, hardening cementitious or plastic medium, which may include a layer of carbon fibers or passive metal fibers, further including a distribution of oxides of titanium, tantalum, iridium, ruthenium, palladium, or cobalt.
- the electrical resistivity may range from 100 ohm-cm to 20,000 ohm-cm. These moderately high resistances prevent electrical short circuits if any metal exposed from the concrete. However, the electrical resistivity is low enough to distribute the current to the entire covering concrete surface.
- the thickness of the semi-conductive media 2 is in the range of 1 mm to 25 mm, preferably between 3 mm to 7 mm.
- the anode tapes are typically spaced on concrete surfaces according to the cathodic protection current requirement for the reinforcing steel in concrete. The spacing is also based on the current requirement of the reinforcing steel.
- the tape anodes 1 or 6 may be electrically interconnected at points 8 to bare metal tapes 7 by means of spot welding or conductive adhesive.
- the “bare” metal tape may be the same metal as the tape anode or different materials may be used.
- the semi-conductive coating is resistant to the acid which may develop on the anode surface.
- FIG. 4 illustrates how chlorine gas evolved on the metal tape surface and within the semi-conductive coating may diffuse away from the anode system though the porous coating 2 . Because the invention allows the anodes to operate at anodic current densities higher than 110 mA/m 2 without generating acid, this also allows using as chloride removal system using larger current densities. The negatively charged chlorides which are attractive to the positive charged anode, they turn to chlorine gas. The gas diffuses away to the surrounding atmosphere through the semi-conductive layer.
Abstract
Mixed-metal-oxide (MMO) coated precious-metal tape is installed directly on concrete surfaces using an electrically non-conductive adhesive with semi-conductive coating or overlay, thereby obviating the need for slots or holes to the concrete structures which are not subject to direct moisture. The tape anodes may be installed on the concrete surfaces exposing metals without developing an electrical short circuit between the anode and the metals due to the non-conductive adhesive. The semi-conductive layer over the metal tape can distribute the CP current uniformly to the entire concrete surface without developing electrical short circuit. Overall the invention provides for quick and low cost installation on many concrete structures. Interconnections between the tape anodes and bare metal distribution elements may be made with conductive adhesive or spot welding.
Description
- This invention relates generally to corrosion control in reinforced-concrete structures and, in particular, to mixed-metal-oxide (MMO) coated precious-metal tape and mesh that may be installed directly on concrete surfaces without the need for slots, holes, cementitious grout or concrete.
- Cathodic protection (CP) is a method for controlling corrosion of reinforcing steel, including steel structures in chloride contaminated concrete. Various types of impressed current cathodic protection anodes for reinforced concrete structures have been developed in the past. The anode is one of the most critical components for a cathodic protection system, as it is used to distribute cathodic protection current to the reinforcing steel.
- One of the most effective and durable anodes is made of a material which is resistance to corrosion, for example a mixed-metal-oxide (MMO) coated titanium substrate. MMO coated anodes are manufactured by coating a mixture of precious metal oxides on a specially treated precious metal. The coated substrate undergoes multiple thermal treatments at elevated temperatures to achieve good bonding properties between the substrate and the coating. Although titanium is widely used as substrate material due to its resistance to corrosion, resistance to chemical attacks and high mechanical strength, other anodes such as tantalum, niobium and zirconium anodes are also used for different applications.
- Since the first MMO-coated titanium anode was developed in 1984, many concrete structures have been protected using this material. To install the anodes, however, they must be embedded in concrete or cementitious grout. For example, titanium mesh with a concrete overlay, titanium ribbon or ribbon mesh embedded in cemetitious grout in saw-cut slots, or discrete anodes embedded in grout in drilled holes. However, these types of installations add burden to the structure and lead to some durability concerns. A useful review of MMO-coated anodes and installation techniques may be found in “Cathodic Protection of Steel in Concrete” By Paul Chess, Taylor & Francis (1998), ISBN 0419230106, the entire content of which is incorporated herein by reference.
- For the slotted or discrete types of installations, the existing concrete must be cut or drilled to install the anodes. However, when the concrete covers over the reinforcing steel are shallow or congested, such installation procedures are not feasible. Even if the anodes are somehow installed in the slots or drilled holes, the vicinity of the reinforcing steel near the anodes may cause an electrical short circuit, resulting in malfunction of the cathodic protection system.
- When a MMO-coated titanium anode is operated greater than 110 mA/m2 of anode current density in chloride contaminated concrete, acid is generated at the anode-concrete interface due to the chlorine gas evolution by the anodic reaction. As a result, cement paste of the concrete as the electrolyte which contact to the anode is dissolved by the acid. This leaves the non-conductive aggregates at the anode-concrete interface and causes the increases of the circuit resistance, diminishing the cathodic protection current.
- When MMO coated precious metal tape is installed with electrically conductive adhesive, or when any form of MMO coated precious metal anodes are embedded in the dry concrete structure which is not subject to direct moisture, rain or seawater splashes, the circuit resistance increases with time due to the electrochemical osmosis at the anode-concrete interface. Once the circuit resistance exceeds the maximum DC power supply, the current from the anodes decrease with time. The electrochemical osmosis condition increases with increasing the anode voltage. Eventually, the anodes cannot discharge any current at the maximum voltage of the power supply.
- When high conductive media is used as an anode to cover the concrete surface, an electrical short circuit is often developed by the exposed metals, such as rebar chairs, steel wire ties. When highly conductive media is used as an anode to cover the concrete surface, the concentration of cathodic protection current from the local portion of the anode system to shallow rebars develop acid generation, resulting in poor current distribution to a concrete structure.
- This invention overcomes the shortcomings of prior art by allowing mixed-metal-oxide (MMO) coated precious-metal tape to be installed on dry concrete structures without the need for slots or holes. In the preferred embodiments, a semi-electrically conductive and gas-permeable coating or overlay is used in combination with a MMO-coated precious-metal tape anode to improve current distribution at low voltages. The electrical resistivity of the semi-conductive coating is lower than that of typical concrete. However, when the semi-conductive coating is moist in a local area, the resistivity is still high enough to prevent the concentration of cathodic protection current discharging to the concrete substrate.
- According to the invention, MMO-coated tape anodes may be installed on the concrete surfaces using non-conductive adhesives without developing an electrical short circuit between the anode and the reinforcing steel. Interconnections between the tape anodes and bare metal distribution elements may be made with conductive adhesive or spot welding. Alternatively, MMO-coated mesh anodes may be embedded in the semi-conductive coating without contacting to the concrete substrate. Interconnections between the mesh anodes and bare metal distribution elements may be made with conductive adhesives or spot welding.
- Since MMO coated anodes are not embedded or contact to concrete, the anodic can be operated at anode current densities higher than 110 mA/m2. The chlorine gas evolved on the anode diffuses away though the porous semi-conductive coating before it tunes to hydro-chloric acid. By utilizing this high current discharge capability of the anode system with the semi-conductive coating, the system facilitates electro-chemical chloride extraction from the chloride contaminated concrete.
- Through the use of a semi-conductive layer covering over the anodes, electrical short circuits can be prevented even though the semi-conductive coating contacts with exposed metals from the concrete surface. The semi-conductive media may include carbon, MMO coated metal(s) or any passive bare metal powder or fibers mixed with any electrolytic cementitious or plastic media.
- When carbon powder or fibers are used as the electrical media to produce semi-conductive layer, the carbon is consumed by passing through the cathodic protection current with time. However, when a large current is required for a long time of period, MMO coated metal powder or fibers may be used to extend the life of the semi-conductive layer. When passive metal powder or fibers are used under their break-down potential, they can be used without consumption of the metals.
-
FIG. 1 illustrates tape anode installation on a concrete surface and covered with a semi-conductive coating. The tape anode is fixed on the concrete surface by non-conductive adhesive and the top of the tape discharge current; -
FIG. 2 illustrates a mesh anode installation within a semi-conductive coating; -
FIG. 3 is an example of a possible installation method of tape anodes to a bare-metal element; and -
FIG. 4 illustrates chlorine gas generated on an anode diffusing away to atmosphere. - This invention relates to protection and corrosion prevention of reinforced concrete structures using mixed-metal-oxide (MMO) coated precious-metal tape anodes. In the preferred embodiments, the anodes are attached to a concrete surface using a non-conductive adhesive and covered with a semi-conductive layer to provide cathodic protection or chloride removal. As such, the bare metal surface of the tape is fixed on the concrete surface using a non-conductive adhesive, such that the MMO-coated metal surface of the tape is exposed.
- The substrate metal tape anode may be composed of titanium, tantalum, zirconium, or niobium. However, the most preferred metals are titanium or titanium alloys because of the corrosion resistance and availability. The tape anode width is preferably over 5 mm, and the thickness is in the range of 0.001 mm to 1 mm, preferably between 0.1 mm to 0.3 mm.
-
FIG. 1 is a simplified cross-sectional diagram showing ametal tape anode 1 attached toconcrete 4 throughnon-conductive adhesive 3. To distribute cathodic protection current to the entire concrete surface before traveling into the concrete and reinforcing steel bars, thin coatedsemi-conductive media 2 is coated over the metal tapes. - The semi-conductive coating preferably comprises a cementitious or plastic material with suspended conductive or semi-conductive particles to adjust the electrical resistivity. In accordance with one preferred embodiment, the semi-conductive coating comprises a flowable, hardening cementitious or plastic medium, which may include a layer of carbon fibers or passive metal fibers, further including a distribution of oxides of titanium, tantalum, iridium, ruthenium, palladium, or cobalt. By adjusting the composition of the
semi-conductive media 2, the electrical resistivity may range from 100 ohm-cm to 20,000 ohm-cm. These moderately high resistances prevent electrical short circuits if any metal exposed from the concrete. However, the electrical resistivity is low enough to distribute the current to the entire covering concrete surface. The thickness of thesemi-conductive media 2 is in the range of 1 mm to 25 mm, preferably between 3 mm to 7 mm. - Furthermore, as shown in
FIG. 2 , the anode tapes are typically spaced on concrete surfaces according to the cathodic protection current requirement for the reinforcing steel in concrete. The spacing is also based on the current requirement of the reinforcing steel. As shown inFIG. 3 , thetape anodes points 8 tobare metal tapes 7 by means of spot welding or conductive adhesive. The “bare” metal tape may be the same metal as the tape anode or different materials may be used. - The semi-conductive coating is resistant to the acid which may develop on the anode surface.
FIG. 4 illustrates how chlorine gas evolved on the metal tape surface and within the semi-conductive coating may diffuse away from the anode system though theporous coating 2. Because the invention allows the anodes to operate at anodic current densities higher than 110 mA/m2 without generating acid, this also allows using as chloride removal system using larger current densities. The negatively charged chlorides which are attractive to the positive charged anode, they turn to chlorine gas. The gas diffuses away to the surrounding atmosphere through the semi-conductive layer.
Claims (14)
1. A system for controlling the corrosion of reinforcing steel in a concrete body having a surface, comprising:
a mixed-metal-oxide (MMO) coated precious-metal anode indirectly bonded to the surface of the concrete body through an electrically non-conductive material; and
a semi-conductive coating covering the anode and at least portions of the surface of the concrete body to distribute cathodic protection current from the concrete surface to the anode without the anode making a direct electrical connection to the concrete body.
2. The system of claim 1 , wherein the electrically non-conductive material is a non-conductive adhesive.
3. The anode of claim 1 , wherein the anode is composed of carbon, titanium, tantalum, zirconium, niobium, or alloys thereof, or MMO coated titanium, tantalum, zirconium, niobium, or alloys thereof.
4. The anode of claim 1 , wherein the coating is composed of oxides of titanium, tantalum, iridium, ruthenium, palladium, or cobalt.
5. The system of claim 1 , wherein the anode is in the form of an elongate tape.
6. The system of claim 1 , wherein the anode is in the form of an elongate tape having a width of 5 mm or greater and the thickness in the range of 0.001 mm to 1 mm.
7. The system of claim 1 , including a plurality of anodes interconnected with a bare metal tape.
8. The system of claim 1 , including a plurality of interconnected anodes spaced-apart on the surface of the concrete.
9. The system of claim 1 , including a plurality of anodes interconnected with a bare metal tape using an electrically conductive adhesive.
10. The system of claim 1 , including a plurality of anodes interconnected to a bare metal tape using spot-welding.
11. The system of claim 1 , wherein the semi-conductive coating includes a layer of carbon fibers or passive metal fibers.
12. The system of claim 1 , wherein the electrical resistivity of the semi-conductive coating is in the range of 100 ohm-cm to 20,000 ohm-cm.
13. The system of claim 1 , wherein the semi-conductive coating is sufficient porous for chlorine gas escape therethrough to atmosphere.
14. The system of claim 1 , wherein the anode is in the form of a mesh.
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US13/788,525 US20140251793A1 (en) | 2013-03-07 | 2013-03-07 | Cathodic protection current distribution method and apparatus for corrosion control of reinforcing steel in concrete structures |
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US13/788,525 US20140251793A1 (en) | 2013-03-07 | 2013-03-07 | Cathodic protection current distribution method and apparatus for corrosion control of reinforcing steel in concrete structures |
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Cited By (9)
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US20140262824A1 (en) * | 2013-03-15 | 2014-09-18 | Physical Sciences, Inc. | Corrosion protection system for non-immersed equipment |
US20140305807A1 (en) * | 2013-04-16 | 2014-10-16 | Shenzhen University | Cathode Protection Method for Reinforced Concrete Structure and Apparatus Therefor |
WO2017042387A1 (en) * | 2015-09-10 | 2017-03-16 | Koch GmbH | Method for laying an anode system for cathodic corrosion protection |
US10262773B2 (en) * | 2013-08-16 | 2019-04-16 | Shore Acres Enterprises Inc. | Corrosion protection of buried metallic conductors |
US10333234B2 (en) | 2017-08-14 | 2019-06-25 | Shore Acres Enterprises Inc. | Corrosion-protective jacket for electrode |
JP2019167611A (en) * | 2018-03-26 | 2019-10-03 | 株式会社ケミカル工事 | Electric protection structure of concrete structural body, and electric protection method |
US11121482B2 (en) | 2017-10-04 | 2021-09-14 | Shore Acres Enterprises Inc. | Electrically-conductive corrosion-protective covering |
US11421392B2 (en) | 2019-12-18 | 2022-08-23 | Shore Acres Enterprises Inc. | Metallic structure with water impermeable and electrically conductive cementitous surround |
US11725289B2 (en) | 2017-05-22 | 2023-08-15 | E-Chem Technologies Ltd. | Expandable anode assembly |
Citations (4)
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Cited By (14)
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US20140262824A1 (en) * | 2013-03-15 | 2014-09-18 | Physical Sciences, Inc. | Corrosion protection system for non-immersed equipment |
US20140305807A1 (en) * | 2013-04-16 | 2014-10-16 | Shenzhen University | Cathode Protection Method for Reinforced Concrete Structure and Apparatus Therefor |
US10665364B2 (en) | 2013-08-16 | 2020-05-26 | Shore Acres Enterprises Inc. | Corrosion protection of buried metallic conductors |
US10262773B2 (en) * | 2013-08-16 | 2019-04-16 | Shore Acres Enterprises Inc. | Corrosion protection of buried metallic conductors |
WO2017042387A1 (en) * | 2015-09-10 | 2017-03-16 | Koch GmbH | Method for laying an anode system for cathodic corrosion protection |
US11725289B2 (en) | 2017-05-22 | 2023-08-15 | E-Chem Technologies Ltd. | Expandable anode assembly |
US10333234B2 (en) | 2017-08-14 | 2019-06-25 | Shore Acres Enterprises Inc. | Corrosion-protective jacket for electrode |
US11349228B2 (en) | 2017-08-14 | 2022-05-31 | Shore Acres Enterprises Inc. | Corrosion-protective jacket for electrode |
US11757211B2 (en) | 2017-08-14 | 2023-09-12 | Shore Acres Enterprises Inc. | Electrical grounding assembly |
US11121482B2 (en) | 2017-10-04 | 2021-09-14 | Shore Acres Enterprises Inc. | Electrically-conductive corrosion-protective covering |
US11894647B2 (en) | 2017-10-04 | 2024-02-06 | Shore Acres Enterprises Inc. | Electrically-conductive corrosion-protective covering |
JP2019167611A (en) * | 2018-03-26 | 2019-10-03 | 株式会社ケミカル工事 | Electric protection structure of concrete structural body, and electric protection method |
JP7270918B2 (en) | 2018-03-26 | 2023-05-11 | 株式会社ケミカル工事 | Cathodic protection structure and cathodic protection method for concrete structures |
US11421392B2 (en) | 2019-12-18 | 2022-08-23 | Shore Acres Enterprises Inc. | Metallic structure with water impermeable and electrically conductive cementitous surround |
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