WO2008118589A1 - Composite anode for cathodic protection - Google Patents

Composite anode for cathodic protection Download PDF

Info

Publication number
WO2008118589A1
WO2008118589A1 PCT/US2008/054839 US2008054839W WO2008118589A1 WO 2008118589 A1 WO2008118589 A1 WO 2008118589A1 US 2008054839 W US2008054839 W US 2008054839W WO 2008118589 A1 WO2008118589 A1 WO 2008118589A1
Authority
WO
WIPO (PCT)
Prior art keywords
ionically
conductive material
anode
composite
mineral
Prior art date
Application number
PCT/US2008/054839
Other languages
French (fr)
Inventor
John E. Bennett
Original Assignee
Bennett John E
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from PCT/US2007/007317 external-priority patent/WO2007126715A2/en
Application filed by Bennett John E filed Critical Bennett John E
Priority to US12/531,779 priority Critical patent/US8157983B2/en
Priority to EP08730606A priority patent/EP2132360A1/en
Priority to CA002681232A priority patent/CA2681232A1/en
Publication of WO2008118589A1 publication Critical patent/WO2008118589A1/en

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23FNON-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
    • C23F13/00Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • C23F13/06Constructional parts, or assemblies of cathodic-protection apparatus
    • C23F13/08Electrodes specially adapted for inhibiting corrosion by cathodic protection; Manufacture thereof; Conducting electric current thereto
    • C23F13/10Electrodes characterised by the structure
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B26/00Compositions of mortars, concrete or artificial stone, containing only organic binders, e.g. polymer or resin concrete
    • C04B26/02Macromolecular compounds
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/005Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing gelatineous or gel forming binders, e.g. gelatineous Al(OH)3, sol-gel binders
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B28/00Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
    • C04B28/02Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23FNON-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
    • C23F13/00Inhibiting corrosion of metals by anodic or cathodic protection
    • C23F13/02Inhibiting corrosion of metals by anodic or cathodic protection cathodic; Selection of conditions, parameters or procedures for cathodic protection, e.g. of electrical conditions
    • EFIXED CONSTRUCTIONS
    • E04BUILDING
    • E04CSTRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/01Reinforcing elements of metal, e.g. with non-structural coatings
    • E04C5/015Anti-corrosion coatings or treating compositions, e.g. containing waterglass or based on another metal
    • EFIXED CONSTRUCTIONS
    • E04BUILDING
    • E04CSTRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/01Reinforcing elements of metal, e.g. with non-structural coatings
    • E04C5/015Anti-corrosion coatings or treating compositions, e.g. containing waterglass or based on another metal
    • E04C5/017Anti-corrosion coatings or treating compositions containing cement
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00482Coating or impregnation materials
    • C04B2111/00525Coating or impregnation materials for metallic surfaces
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/00474Uses not provided for elsewhere in C04B2111/00
    • C04B2111/00853Uses not provided for elsewhere in C04B2111/00 in electrochemical cells or batteries, e.g. fuel cells
    • CCHEMISTRY; METALLURGY
    • C04CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04BLIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2111/00Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
    • C04B2111/20Resistance against chemical, physical or biological attack
    • C04B2111/26Corrosion of reinforcement resistance
    • C04B2111/265Cathodic protection of reinforced concrete structures
    • CCHEMISTRY; METALLURGY
    • C23COATING 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
    • C23FNON-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
    • C23F2201/00Type of materials to be protected by cathodic protection
    • C23F2201/02Concrete, e.g. reinforced

Definitions

  • This invention generally relates to the field of galvanic cathodic protection of steel embedded in concrete structures, and is particularly concerned with the performance of embedded sacrificial anodes, such as zinc, aluminum, and alloys thereof.
  • cathodic protection is capable of controlling corrosion of reinforcing steel over an extended period of time without complete removal of the salt-contaminated concrete.
  • Cathodic protection reduces or eliminates corrosion of the steel by making it the cathode of an electrochemical cell. This results in cathodic polarization of the steel, which tends to suppress oxidation reactions (such as corrosion) in favor of reduction reactions (such as oxygen reduction).
  • Cathodic protection was first applied to a reinforced concrete bridge deck in 1973. Since then, understanding and techniques have improved, and today cathodic protection has been applied to over one million square meters of concrete structure worldwide. Anodes, in particular, have been the subject of much attention, and several different types of anodes have evolved for specific circumstances and different types of structures.
  • ICCP impressed current cathodic protection
  • inert anodes such as carbon, titanium suboxide, and most commonly, catalyzed titanium.
  • ICCP also requires the use of an auxiliary power supply to cause protective current to flow through the circuit, along with attendant wiring and electrical conduit.
  • This type of cathodic protection has been generally successful, but problems have been reported with reliability and maintenance of the power supply. Problems have also been reported related to the durability of the anode itself, as well as the concrete immediately adjacent to the anode, since one of the products of reaction at an inert anode is acid (H + ). Acid attacks the integrity of the cement paste phase within concrete.
  • GCP galvanic cathodic protection
  • Bartholomew et al discloses a method of patching an eroded area of concrete comprising the use of a metal anode having an ionically conductive hydrogel attached to at least a portion of the anode.
  • the anode and the hydrogel are flexible and are conformed within the eroded area, the anode being in elongated foil form.
  • Whitmore discloses the use of a deliquescent material bound into a porous anode body, which acts to maintain the anode electrochemically active, while providing room for the expansive products of corrosion.
  • the same patent discloses several mechanical means of making electrical connection to the reinforcing steel within a hole drilled into the concrete covering material. Many of these means involve driven pins, impact tools, and other specialized techniques. These techniques are all relatively complex and difficult to perform.
  • the anodes described above and the means of connection disclosed have become the basis for commercial products designed to extend the life of patch repair and to cathodically protect reinforced concrete structures from corrosion. But some embodiments, such as the use of high pH to maintain the anode in an electrochemically active state as described by Page, result in protective current that is small and often inadequate to mitigate corrosion. Use of the chemicals such as lithium nitrate and lithium bromide, result in a higher current, but even this current is sometimes inadequate in cases of high chloride contamination and the presence of strong corrosion of the reinforcing steel. Also, some of the chemicals used to maintain the zinc anode in an electrochemically active state render the corrosion products of zinc largely insoluble.
  • the present invention relates to an apparatus and a composite anode for cathodic protection of reinforced concrete, and more particularly, to a method and apparatus for improving the performance and service life of embedded anodes prepared from sacrificial metals such as zinc, aluminum, and alloys thereof.
  • the present invention more specifically relates to an apparatus and a composite anode for cathodic protection wherein the performance of the sacrificial anode is enhanced by the use of a combination of chemicals and a compressible, water retaining phyllosilicate such as vermiculite in an ionically conductive material such as a cementitious grout, thereby forming an activating matrix surrounding the sacrificial anode.
  • 'surrounding' is meant at least partial encapsulation of the anode. This combination is particularly effective absorbing the expansive corrosion products of the zinc anode.
  • the chemical component of the activating matrix may be any one, or a combination of, the chemicals previously disclosed in the prior art. These include chemicals that are deliquescent or hygroscopic, also sometimes known as humectants. Such chemicals maintain the region near the anode moist and highly conductive. Particularly advantageous are lithium nitrate, lithium bromide, or other deliquescent or hygroscopic chemicals. Other chemicals intended to raise the pH of the matrix to a value greater than about 13.5 are also known to be effective. A water-retaining phyllosilicate mineral resembling mica has been found to be a particularly useful component of the present invention. A specific form of this mineral is vermiculite.
  • Vermiculite particles in the matrix appear to serve both functions of increasing the protective current delivered by the anode, and effectively absorbing the expansive products of corrosion.
  • the anode itself may be in a variety of forms, but is preferably in an elongated foil, or ribbon form.
  • the anode is composed of zinc, magnesium, aluminum or their alloys, or combinations of these metals.
  • the ionically conductive material that binds the phyllosilicate particles together, and to the zinc anode, may be either of a cementitious nature, or may be a hydrogel, as taught by the aforementioned prior art.
  • the composite anode for cathodic protection also incorporates an elongated metallic conductor that serves to electrically connect the sacrificial anode to the reinforcing steel, or other metal to be protected, thereby providing an electrical path for the flow of protective current.
  • the elongated metallic conductor may be attached to the reinforcing steel by one of several methods, such as wrapping, twisting, resistance welding, tig welding, mechanical compression and the like.
  • the present invention also relates to a method of cathodic protection of reinforced concrete, and more particularly, to a method of improving the performance and service life of embedded anodes intended to apply cathodic protection to reinforcing steel and other metals embedded in concrete.
  • Figure 1 illustrates one method of utilizing the anode assembly of the present invention
  • Figure 2 illustrates the anode assembly of Figure 1 in cross section
  • FIG. 3 illustrates the results of the tests described in Example 1 to follow.
  • the drawings are not necessarily to scale but are merely schematic representations, not intended to portray specific parameters of the invention.
  • the drawings are intended to depict only typical embodiments of the invention and, therefore, should not be considered as limiting the scope of the invention
  • Figure 1 shows the surface of a reinforced concrete structure 1 in plan view with an excavation 2, where loose and delaminated concrete has been removed. Reinforcing bars 3, running both horizontally and vertically, are shown exposed in the excavation 2.
  • a flexible, elongated anode assembly 4 is shown placed near the edge of the excavation 2.
  • the anode assembly 4 is fastened to reinforcing bars 3 with metallic wire conductors 5 for the purpose of making contact and allowing protective current to flow.
  • This anode assembly has a thickness of between about 0.01 inch and about 0.2 inch and a width between about 0.2 inch and about 2 inches. However, it is understood that the dimensions of the anode assembly are dictated by such parameters as the size of the excavation, and the flexibility, bend ability, and conductivity of the anode assembly, and ease of installation,
  • FIG 2 illustrates a cross sectional view of the structure of Figure 1.
  • the anode 6 is shown in a central configuration.
  • the metal anode 6 is enclosed on both sides by an activating matrix 7 to form the anode assembly 4.
  • the activating matrix 7 comprises an ionically conductive material, a phyllosilicate such as vermiculite, and at least one activating chemical designed to keep the anode metal in an electrochemically active state.
  • the activating matrix 7 on each side of the anode is bound on one side by a protective plastic sheet 8, such as polyethylene, designed to protect the activating matrix 7 during shipping and handling.
  • the protective plastic sheet 8 is removed prior to placing the patch material into the excavation.
  • the present invention relates broadly to all reinforced concrete structures with which cathodic protection systems are useful.
  • the reinforcing metal in a reinforced concrete structure is carbon steel.
  • other ferrous-based metals can also be used.
  • the anode assembly of the present invention relates to galvanic cathodic protection (GCP), that is, cathodic protection utilizing anodes consisting of sacrificial metals such as zinc, aluminum, magnesium, or alloys thereof. Of these materials, zinc or zinc alloys are preferred for reasons of efficiency, longevity, driving potential and cost. Sacrificial metals are capable of providing protective current without the use of ancillary power supplies, since the reactions that take place during their use are thermodynamically favored.
  • the sacrificial metal anodes may be of various geometric configurations, such as flat plate, expanded or perforated sheet, or cast shapes of various designs.
  • a preferred configuration of the anode, and anode assembly of the present invention is a flexible elongated foil, or ribbon configuration.
  • the composite anode is elongated and flexible, in which case it is easily conformed to be placed around the edge of the excavated patch, thereby mitigating the anode ring effect of corrosion. It may also be useful to fix the elongated composite anode around the edge of the excavated patch with non-conductive ties.
  • the ties may incorporate a non-conductive shield to prevent an excessive amount of current to pass to the reinforcing bar adjacent to the composite anode.
  • the anode metal is surrounded, on at least one side, by an ionically conductive material.
  • the ionically conductive material may be one of several known conductive cementitious grouts, or may be a material known as a hydrogel.
  • the word "hydrogel” as used herein is meant to include any ionically conductive adhesive gel which is a coagulated colloid that typically is a viscous and tacky, jellylike product. In broad terms, water can be present in the hydrogel from about 5% to 95% by weight, and is usually present in major amount, e.g. 70-90 weight percent.
  • Preferred hydrogels for the present invention are organic, polymeric structures that have a molecular weight sufficiently high for the hydrogels to be self-supporting.
  • inorganic, polymeric structured hydrogels may also be used, e.g. those based on polysilicates or polyphosphates.
  • the use of mixtures of organic and inorganic hydrogels is also contemplated.
  • the self-supporting hydrogels are form stable under normal conditions, and have good ionic conductivity, as well as good adhesiveness or tackiness. This adhesiveness as well of the flexibility of the hydrogel allows it to securely adhere to the anode metal even when the metal is bent or twisted.
  • Hydrogels useful for this invention are further specified in U.S. Patent 5,292,411, the teachings of which are incorporated herein by reference.
  • the vermiculite used in the present invention is a phyllosilicate mineral resembling mica.
  • Vermiculite mined in the US is a hydrated phlogopite or biotite mica that expands or delaminates to many times its volume when heated, a process called exfoliation.
  • Vermiculite used in the present invention is in exfoliated form, and is incorporated essentially within the ionically conductive material.
  • the particle size for the vermiculite used may range from about 0.01 to 0.1 centimeter.
  • Vermiculite may be used in the present invention by incorporating into the activating matrix in the amount of between about 2% and about 15% of total weight, more particularly, between about 5% and about 12%.
  • sacrificial metal anodes tend to passivate in the alkaline environment of concrete, it is necessary to provide an activating agent within the ionically conductive material to maintain the anode in an electrochemically active and conductive state.
  • the use of deliquescent or hygroscopic chemicals serves to maintain a galvanic sprayed zinc anode in an active state, thereby continuing to deliver protective current.
  • Two of the most effective chemicals for this purpose namely lithium nitrate and lithium bromide (LiNO 3 and LiBr), enhance the performance of sprayed zinc anodes.
  • LiNO 3 and LiBr serve to improve the performance of embedded discrete anodes. It has been found that a mixture of lithium nitrate and lithium bromide in an amount of between about 1% and about 15% is particularly effective for this purpose.
  • a steel reinforced 12 x 12 x 4-inch (30.5 x 30.5 x 10.2 cm) concrete test block was constructed using concrete with the following mix proportions:
  • Airmix air entrainer (0.95% oz/CWT) - about 6.5% air
  • the test block contained about 24 inches (60 cm) of #4 (12 mm dia.) reinforcing bar, or about 0.25 square feet (240 square centimeters) of steel surface area.
  • Each test block was cast with two blockouts for two test cells, each blockout forming a circular test cavity about 4 inches (10 cm) in diameter x 2.75 inches (7 cm) deep.
  • a 'blockout' is a block or form that is placed in wet concrete when formed. When the blockout is removed from the concrete at a later time, it leaves a cavity or void.
  • An anode was first constructed by soldering 40 grams of pure zinc to galvanized tie wires. The zinc was then cast into a mixture containing 65% sand, 15.2% Type III cement, and 19.8% lithium liquid mixture, prepared by combining 40% by volume saturated lithium bromide solution and 60% by volume saturated lithium nitrate solution. The mixture surrounding the anode was allowed to cure, and the anode was then placed into a cavity in the test block and mortared in place with Eucopatch, a one-part cementitious repair material produced by The Euclid Chemical Company. The anode was connected to the reinforcing bars in the test block with a 10 ohm resistor, which facilitated measurement of the flow of protective current.
  • This anode was subjected to 5 mA of impressed current in constant current mode of operation. In this way, a total charge equivalent to several years of service life can be impressed on the anode in a period of about 60 days.
  • the effectiveness of the anode can be determined by observation of the cell operating voltage. Lower operating voltage indicates that an anode will deliver a higher level of protective current when operated in galvanic mode.
  • Control The operating voltage of the control anode is shown by the line labeled "Control" on Figure 3. Operating voltage began at about 1.0 volt, and increased to about 5.0 volts after 60 days.
  • a second anode was prepared in a similar manner, except that the matrix surrounding the anode contained 8.6% vermiculite by weight. After curing of the mortar surrounding the anode, the anode was placed into a test cavity and mortared in place with Eucopatch. This anode was connected to the reinforcing bars in the same manner as the Control.
  • the operating voltage of the anode surrounded with the vermiculite mixture is shown by the line labeled "8.6% Vermiculite" on Figure 3. In this case, operating voltage began at about 0.5 volts, and increased to only about 1.5 volts after 60 days. This improvement is again expected to result in a higher polarization of the steel surrounding the anode, a greater level of cathodic protection, and a longer effective service life of the anode.
  • Figure 3 illustrates the results of the tests described hereinabove.
  • This figure shows cell voltage of test blocks operated in accelerated mode using an impressed current of 5 milliamps as a function of time.
  • the data labeled "Control” was obtained by a standard control test block as described in Example 1, and is again considered good performance.
  • the data labeled "8.6% Vermiculite” was obtained from a test block in which 8.6% by weight of the matrix surrounding the anode consisted of vermiculite, a phyllosilicate mineral resembling mica.
  • cracks had developed on the surface of the control block, with cracks measuring up to 0.047-inch wide after 51 days on line. Cracks were barely discernable on the surface of the block containing vermiculite, and measured no more than 0.002-inch wide after 57 days on line.
  • the present invention is useful for providing an enhanced level of corrosion protection for steel reinforcement that is used in concrete structures such as bridges, buildings, parking structures, piers, and wharves.

Abstract

The galvanic cathodic protection of steel embedded in concrete structures is enhanced by the utilization of a flexible composite anode assembly containing a sacrificial anode member. The anode member is at least partially covered by a matrix comprising an ionically-conductive material. The conductive material includes at least one electrochemical activating agent such as a mixture of lithium bromide and lithium nitrate and a compressible water-retaining mineral such as a phyllosilicate mineral. The presence of this mineral in the matrix increases the current delivered by the anode, thereby resulting in a greater level of cathodic protection, and a longer effective service life of the anode. Exfoliataed vermiculite is a preferred phyllosilicate mineral and is present in an amount of between about 2% and about 15% by weight, based on the total weight of the matrix.

Description

COMPOSITE ANODE FOR CATHODIC PROTECTION
BACKGROUND OF THE INVENTION Technical Field.
This invention generally relates to the field of galvanic cathodic protection of steel embedded in concrete structures, and is particularly concerned with the performance of embedded sacrificial anodes, such as zinc, aluminum, and alloys thereof. Background Art
The problems associated with corrosion-induced deterioration of reinforced concrete structures are now well understood. Steel reinforcement has generally performed well over the years in concrete structures such as bridges, buildings, parking structures, piers, and wharves, since the alkaline environment of concrete causes the surface of the steel to "passivate" such that it does not corrode. Unfortunately, since concrete is inherently somewhat porous, exposure to salt over a number of years results in the concrete becoming contaminated with chloride ions. Salt is commonly introduced in the form of seawater, set accelerators, or deicing salt.
When the chloride reaches the level of the reinforcing steel, and exceeds a certain threshold level for contamination, it destroys the ability of the concrete to keep the steel in a passive, non-corrosive state. It has been determined that a chloride concentration of 0.6 Kg per cubic meter of concrete is a critical value above which corrosion of the steel can occur. The products of corrosion of the steel occupy 2.5 to 4 times the volume of the original steel, and this expansion exerts a tremendous tensile force on the surrounding concrete. When this tensile force exceeds the tensile strength of the concrete, cracking and delaminations develop. With continued corrosion, freezing and thawing, and traffic pounding, the utility or integrity of the structure is finally compromised and repair or replacement becomes necessary. Reinforced concrete structures continue to deteriorate at an alarming rate. In a recent report to Congress, the Federal Highway Administration reported that of the nation's 577,000 bridges, 266,000 (39% of the total) were classified as deficient, and that 134,000 (23% of the total) were classified as structurally deficient. Structurally deficient bridges are those that are closed, restricted to light vehicles only, or that require immediate rehabilitation to remain open. The damage on most of these bridges is caused by corrosion. The United States Department of Transportation has estimated that $90.9 billion will be needed to replace or repair the damage on these existing bridges.
Many solutions to this problem have been proposed, including higher quality concrete, improved construction practices, increased concrete cover over the reinforcing steel, specialty concretes, corrosion inhibiting admixtures, surface sealers, and electrochemical techniques, such as cathodic protection and chloride removal. Of these techniques, only cathodic protection is capable of controlling corrosion of reinforcing steel over an extended period of time without complete removal of the salt-contaminated concrete.
Cathodic protection reduces or eliminates corrosion of the steel by making it the cathode of an electrochemical cell. This results in cathodic polarization of the steel, which tends to suppress oxidation reactions (such as corrosion) in favor of reduction reactions (such as oxygen reduction). Cathodic protection was first applied to a reinforced concrete bridge deck in 1973. Since then, understanding and techniques have improved, and today cathodic protection has been applied to over one million square meters of concrete structure worldwide. Anodes, in particular, have been the subject of much attention, and several different types of anodes have evolved for specific circumstances and different types of structures.
The most commonly used type of cathodic protection system is impressed current cathodic protection (ICCP), which is characterized by the use of inert anodes, such as carbon, titanium suboxide, and most commonly, catalyzed titanium. ICCP also requires the use of an auxiliary power supply to cause protective current to flow through the circuit, along with attendant wiring and electrical conduit. This type of cathodic protection has been generally successful, but problems have been reported with reliability and maintenance of the power supply. Problems have also been reported related to the durability of the anode itself, as well as the concrete immediately adjacent to the anode, since one of the products of reaction at an inert anode is acid (H+). Acid attacks the integrity of the cement paste phase within concrete. Finally, the complexity of ICCP systems requires additional monitoring and maintenance, which results in additional operating costs. A second type of cathodic protection, known as galvanic cathodic protection (GCP), offers certain important advantages over ICCP. GCP uses sacrificial anodes, such as zinc and aluminum, and alloys thereof, which have inherently negative electrochemical potentials. When such anodes are used, protective current flows in the circuit without need for an external power supply since the reactions that occur are thermodynamically favored. GCP therefore requires no rectifier, external wiring or conduit. This simplicity increases reliability and reduces initial cost, as well as costs associated with long term monitoring and maintenance. Also, the use of GCP to protect high-strength prestressed steel from corrosion is considered inherently safe from the standpoint of hydrogen embrittlement. Recognizing these advantages, the Federal Highway Administration issued a Broad Agency Announcement (BAA) in 1992 for the study and development of sacrificial anode technology applied to reinforced and prestressed bridge components. As a result of this announcement and the technology that was developed because of this BAA, interest in GCP has greatly increased over the past few years.
In US Patent 6,022,469 by Page a method of galvanic cathodic protection is disclosed wherein a zinc or zinc alloy anode is surrounded by a mortar containing an agent to maintain a high pH in the mortar surrounding the anode. This agent, preferably lithium hydroxide (LiOH), serves to prevent passivation of the zinc anode and maintain the anode in an electrochemically active state. In this method, the zinc anode is electrically attached to the reinforcing steel causing protective current to flow and mitigating subsequent corrosion of the steel.
In US Patent 5,292,411 Bartholomew et al discloses a method of patching an eroded area of concrete comprising the use of a metal anode having an ionically conductive hydrogel attached to at least a portion of the anode. In this patent it is taught that the anode and the hydrogel are flexible and are conformed within the eroded area, the anode being in elongated foil form.
In US Patent 6,471,851 issued to Bennett on October 29, 2002 the use of deliquescent or hygroscopic chemicals, collectively called "humectants" is disclosed to maintain a galvanic sprayed zinc anode in an active state and delivering protective current. In US Patent 6,033,553, two of the most effective such chemicals, namely lithium nitrate and lithium bromide (LiNO3 and LiBr), are disclosed to enhance the performance of sprayed zinc anodes. And in US Patent 6,217,742 Bl, issued April 17, 2001, Bennett discloses the use OfLiNO3 and LiBr to enhance the performance of embedded discrete anodes. And finally, in US Patent 6,165,346, issued December 26, 2000, Whitmore broadly claims the use of deliquescent chemicals to enhance the performance of the apparatus disclosed by Page in US Patent 6,022,469.
In US patent 7,160,433 B2 issued January 9, 2007 , a method of cathodic protection of reinforcing steel is disclosed comprising a sacrificial anode embedded in an ionically conductive compressible matrix designed to absorb the expansive products of corrosion of the sacrificial anode metal.
In US Patent No. 6,572,760 B2, issued June 3, 2003, Whitmore discloses the use of a deliquescent material bound into a porous anode body, which acts to maintain the anode electrochemically active, while providing room for the expansive products of corrosion. The same patent discloses several mechanical means of making electrical connection to the reinforcing steel within a hole drilled into the concrete covering material. Many of these means involve driven pins, impact tools, and other specialized techniques. These techniques are all relatively complex and difficult to perform.
Finally, in US Patent 6,193,857, issued February 27, 2001, Davison, et al describes an anode assembly comprising a block of anode material cast around an elongated electrical connector (wire). Other claims disclose making contact between the elongated connector and the reinforcing steel by winding the connector around the reinforcing steel and twisting the ends of the connector together using a twisting tool.
The anodes described above and the means of connection disclosed have become the basis for commercial products designed to extend the life of patch repair and to cathodically protect reinforced concrete structures from corrosion. But some embodiments, such as the use of high pH to maintain the anode in an electrochemically active state as described by Page, result in protective current that is small and often inadequate to mitigate corrosion. Use of the chemicals such as lithium nitrate and lithium bromide, result in a higher current, but even this current is sometimes inadequate in cases of high chloride contamination and the presence of strong corrosion of the reinforcing steel. Also, some of the chemicals used to maintain the zinc anode in an electrochemically active state render the corrosion products of zinc largely insoluble. In this case the expansive corrosion products apply stress to the surrounding concrete, and when this stress exceeds the tensile strength of the concrete, cracking of the concrete can occur. Although several potential solutions have been proposed, including the ionically compressible conductive matrix described in US 7,160,433 B2, cracking remains a problem in some cases.
It would be of great benefit to increase the protective current higher than was previously possible using the prior art as described in the patent literature above. It would also be of benefit to overcome the problem of potential cracking of the overlaying concrete due to expansive corrosion products.
DISCLOSURE OF THE INVENTION
The present invention relates to an apparatus and a composite anode for cathodic protection of reinforced concrete, and more particularly, to a method and apparatus for improving the performance and service life of embedded anodes prepared from sacrificial metals such as zinc, aluminum, and alloys thereof. The present invention more specifically relates to an apparatus and a composite anode for cathodic protection wherein the performance of the sacrificial anode is enhanced by the use of a combination of chemicals and a compressible, water retaining phyllosilicate such as vermiculite in an ionically conductive material such as a cementitious grout, thereby forming an activating matrix surrounding the sacrificial anode. By 'surrounding' is meant at least partial encapsulation of the anode. This combination is particularly effective absorbing the expansive corrosion products of the zinc anode.
The chemical component of the activating matrix may be any one, or a combination of, the chemicals previously disclosed in the prior art. These include chemicals that are deliquescent or hygroscopic, also sometimes known as humectants. Such chemicals maintain the region near the anode moist and highly conductive. Particularly advantageous are lithium nitrate, lithium bromide, or other deliquescent or hygroscopic chemicals. Other chemicals intended to raise the pH of the matrix to a value greater than about 13.5 are also known to be effective. A water-retaining phyllosilicate mineral resembling mica has been found to be a particularly useful component of the present invention. A specific form of this mineral is vermiculite. Vermiculite particles in the matrix appear to serve both functions of increasing the protective current delivered by the anode, and effectively absorbing the expansive products of corrosion. The anode itself may be in a variety of forms, but is preferably in an elongated foil, or ribbon form. The anode is composed of zinc, magnesium, aluminum or their alloys, or combinations of these metals. The ionically conductive material that binds the phyllosilicate particles together, and to the zinc anode, may be either of a cementitious nature, or may be a hydrogel, as taught by the aforementioned prior art.
The composite anode for cathodic protection also incorporates an elongated metallic conductor that serves to electrically connect the sacrificial anode to the reinforcing steel, or other metal to be protected, thereby providing an electrical path for the flow of protective current. The elongated metallic conductor may be attached to the reinforcing steel by one of several methods, such as wrapping, twisting, resistance welding, tig welding, mechanical compression and the like.
The present invention also relates to a method of cathodic protection of reinforced concrete, and more particularly, to a method of improving the performance and service life of embedded anodes intended to apply cathodic protection to reinforcing steel and other metals embedded in concrete.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following specification with references to the accompanying drawings, in which:
Figure 1 illustrates one method of utilizing the anode assembly of the present invention;
Figure 2 illustrates the anode assembly of Figure 1 in cross section; and
Figure 3 illustrates the results of the tests described in Example 1 to follow. The drawings are not necessarily to scale but are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention and, therefore, should not be considered as limiting the scope of the invention
MODES FOR CARRYING OUT THE INVENTION
Turning now to the drawings, Figure 1 shows the surface of a reinforced concrete structure 1 in plan view with an excavation 2, where loose and delaminated concrete has been removed. Reinforcing bars 3, running both horizontally and vertically, are shown exposed in the excavation 2. A flexible, elongated anode assembly 4 is shown placed near the edge of the excavation 2. The anode assembly 4 is fastened to reinforcing bars 3 with metallic wire conductors 5 for the purpose of making contact and allowing protective current to flow. . This anode assembly has a thickness of between about 0.01 inch and about 0.2 inch and a width between about 0.2 inch and about 2 inches. However, it is understood that the dimensions of the anode assembly are dictated by such parameters as the size of the excavation, and the flexibility, bend ability, and conductivity of the anode assembly, and ease of installation,
Figure 2 illustrates a cross sectional view of the structure of Figure 1. In this Figure, the anode 6 is shown in a central configuration. The metal anode 6 is enclosed on both sides by an activating matrix 7 to form the anode assembly 4. Although not shown, the activating matrix 7 comprises an ionically conductive material, a phyllosilicate such as vermiculite, and at least one activating chemical designed to keep the anode metal in an electrochemically active state. The activating matrix 7 on each side of the anode is bound on one side by a protective plastic sheet 8, such as polyethylene, designed to protect the activating matrix 7 during shipping and handling. The protective plastic sheet 8 is removed prior to placing the patch material into the excavation.
The present invention relates broadly to all reinforced concrete structures with which cathodic protection systems are useful. Generally, the reinforcing metal in a reinforced concrete structure is carbon steel. However, other ferrous-based metals can also be used.
The anode assembly of the present invention relates to galvanic cathodic protection (GCP), that is, cathodic protection utilizing anodes consisting of sacrificial metals such as zinc, aluminum, magnesium, or alloys thereof. Of these materials, zinc or zinc alloys are preferred for reasons of efficiency, longevity, driving potential and cost. Sacrificial metals are capable of providing protective current without the use of ancillary power supplies, since the reactions that take place during their use are thermodynamically favored. The sacrificial metal anodes may be of various geometric configurations, such as flat plate, expanded or perforated sheet, or cast shapes of various designs. A preferred configuration of the anode, and anode assembly of the present invention is a flexible elongated foil, or ribbon configuration. In one embodiment of the present invention, the composite anode is elongated and flexible, in which case it is easily conformed to be placed around the edge of the excavated patch, thereby mitigating the anode ring effect of corrosion. It may also be useful to fix the elongated composite anode around the edge of the excavated patch with non-conductive ties. The ties may incorporate a non-conductive shield to prevent an excessive amount of current to pass to the reinforcing bar adjacent to the composite anode.
The anode metal is surrounded, on at least one side, by an ionically conductive material. The ionically conductive material may be one of several known conductive cementitious grouts, or may be a material known as a hydrogel. The word "hydrogel" as used herein is meant to include any ionically conductive adhesive gel which is a coagulated colloid that typically is a viscous and tacky, jellylike product. In broad terms, water can be present in the hydrogel from about 5% to 95% by weight, and is usually present in major amount, e.g. 70-90 weight percent. Preferred hydrogels for the present invention are organic, polymeric structures that have a molecular weight sufficiently high for the hydrogels to be self-supporting. It is to be understood, however, that inorganic, polymeric structured hydrogels may also be used, e.g. those based on polysilicates or polyphosphates. Moreover, the use of mixtures of organic and inorganic hydrogels is also contemplated. The self-supporting hydrogels are form stable under normal conditions, and have good ionic conductivity, as well as good adhesiveness or tackiness. This adhesiveness as well of the flexibility of the hydrogel allows it to securely adhere to the anode metal even when the metal is bent or twisted. Hydrogels useful for this invention are further specified in U.S. Patent 5,292,411, the teachings of which are incorporated herein by reference. The vermiculite used in the present invention is a phyllosilicate mineral resembling mica. Vermiculite mined in the US is a hydrated phlogopite or biotite mica that expands or delaminates to many times its volume when heated, a process called exfoliation. Vermiculite used in the present invention is in exfoliated form, and is incorporated essentially within the ionically conductive material. The particle size for the vermiculite used may range from about 0.01 to 0.1 centimeter. Vermiculite may be used in the present invention by incorporating into the activating matrix in the amount of between about 2% and about 15% of total weight, more particularly, between about 5% and about 12%.
Since sacrificial metal anodes tend to passivate in the alkaline environment of concrete, it is necessary to provide an activating agent within the ionically conductive material to maintain the anode in an electrochemically active and conductive state. As previously mentioned, the use of deliquescent or hygroscopic chemicals, collectively called "humectants" serves to maintain a galvanic sprayed zinc anode in an active state, thereby continuing to deliver protective current. Two of the most effective chemicals for this purpose, namely lithium nitrate and lithium bromide (LiNO3 and LiBr), enhance the performance of sprayed zinc anodes. These two chemicals LiNO3 and LiBr serve to improve the performance of embedded discrete anodes. It has been found that a mixture of lithium nitrate and lithium bromide in an amount of between about 1% and about 15% is particularly effective for this purpose.
EXAMPLE 1
A steel reinforced 12 x 12 x 4-inch (30.5 x 30.5 x 10.2 cm) concrete test block was constructed using concrete with the following mix proportions:
Type IA Portland cement - 715 lb/yd3
Lake sand fine aggregate - 1010 1b/yd3
No. 8 Marblehead limestone - 1830 lb/yd3
Water - 285 lb/yd3
Chloride (added as NaCl) - 5 lb/yd3
Airmix air entrainer (0.95% oz/CWT) - about 6.5% air The test block contained about 24 inches (60 cm) of #4 (12 mm dia.) reinforcing bar, or about 0.25 square feet (240 square centimeters) of steel surface area. Each test block was cast with two blockouts for two test cells, each blockout forming a circular test cavity about 4 inches (10 cm) in diameter x 2.75 inches (7 cm) deep. For purposes of this invention, a 'blockout' is a block or form that is placed in wet concrete when formed. When the blockout is removed from the concrete at a later time, it leaves a cavity or void.
An anode was first constructed by soldering 40 grams of pure zinc to galvanized tie wires. The zinc was then cast into a mixture containing 65% sand, 15.2% Type III cement, and 19.8% lithium liquid mixture, prepared by combining 40% by volume saturated lithium bromide solution and 60% by volume saturated lithium nitrate solution. The mixture surrounding the anode was allowed to cure, and the anode was then placed into a cavity in the test block and mortared in place with Eucopatch, a one-part cementitious repair material produced by The Euclid Chemical Company. The anode was connected to the reinforcing bars in the test block with a 10 ohm resistor, which facilitated measurement of the flow of protective current.
This anode was subjected to 5 mA of impressed current in constant current mode of operation. In this way, a total charge equivalent to several years of service life can be impressed on the anode in a period of about 60 days. The effectiveness of the anode can be determined by observation of the cell operating voltage. Lower operating voltage indicates that an anode will deliver a higher level of protective current when operated in galvanic mode.
The operating voltage of the control anode is shown by the line labeled "Control" on Figure 3. Operating voltage began at about 1.0 volt, and increased to about 5.0 volts after 60 days.
A second anode was prepared in a similar manner, except that the matrix surrounding the anode contained 8.6% vermiculite by weight. After curing of the mortar surrounding the anode, the anode was placed into a test cavity and mortared in place with Eucopatch. This anode was connected to the reinforcing bars in the same manner as the Control. The operating voltage of the anode surrounded with the vermiculite mixture is shown by the line labeled "8.6% Vermiculite" on Figure 3. In this case, operating voltage began at about 0.5 volts, and increased to only about 1.5 volts after 60 days. This improvement is again expected to result in a higher polarization of the steel surrounding the anode, a greater level of cathodic protection, and a longer effective service life of the anode.
Figure 3 illustrates the results of the tests described hereinabove.. This figure shows cell voltage of test blocks operated in accelerated mode using an impressed current of 5 milliamps as a function of time. The data labeled "Control" was obtained by a standard control test block as described in Example 1, and is again considered good performance. The data labeled "8.6% Vermiculite" was obtained from a test block in which 8.6% by weight of the matrix surrounding the anode consisted of vermiculite, a phyllosilicate mineral resembling mica. Following completion of the test, cracks had developed on the surface of the control block, with cracks measuring up to 0.047-inch wide after 51 days on line. Cracks were barely discernable on the surface of the block containing vermiculite, and measured no more than 0.002-inch wide after 57 days on line.
INDUSTRIAL APPLICABILITY
The present invention is useful for providing an enhanced level of corrosion protection for steel reinforcement that is used in concrete structures such as bridges, buildings, parking structures, piers, and wharves.
The foregoing description of various aspects of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed and, obviously, many modifications and variations are possible. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of the invention as defined by the accompanying claims.

Claims

What I claim is:
1. A composite anode for cathodic protection of a reinforced concrete structure, comprising: at least one sacrificial anode member; an ionically-conductive material at least partly covering said at least one sacrificial anode member; at least one electrochemical activating agent incorporated within the ionically- conductive material; and at least one elongated metallic conductor bonded to the at least one sacrificial anode member; characterized in that a compressible water-retaining mineral in exfoliated form is incorporated within the ionically conductive material.
2. The composite anode of claim 1 wherein said at least one sacrificial anode member is zinc or a zinc alloy.
3. The composite anode of claim 1 wherein the ionically-conductive material is a cementitious-based material.
4. The composite anode of claim 1 wherein the ionically-conductive material is a hydrogel.
5. The composite anode of claim 1 wherein the electrochemical activating agent is an alkaline hydroxide present in sufficient amount to maintain the pH of the ionically- conductive material above about pH 13.3.
6. The composite anode of claim 1 wherein the electrochemical activating agent is a deliquescent or hygroscopic material.
7. The composite anode of claim 6 wherein the electrochemical activating agent is lithium nitrate, lithium bromide, or combinations thereof.
8. The composite according to claim 1 wherein the compressible water-retaining mineral is incorporated into the composite in exfoliated form in an amount of between about 2% and about 15% by weight.
9. The composite according to claim 8 wherein the water-retaining mineral is a phyllosilicate mineral.
10. The composite according to claim 9 wherein the phyllosilicate mineral is exfoliated vermiculite.
11. A method for the cathodic protection of a reinforced concrete structure, comprising: providing at least one sacrificial anode member; at least partly covering said at least one sacrificial anode member with an ionically-conductive material; incorporating at least one electrochemical activating agent within the ionically- conductive material; characterized by incorporating a compressible water-retaining mineral in exfoliated form within the ionically conductive material, bonding at least one elongated metallic conductor to the at least one sacrificial anode member, and connecting the elongated metallic conductor to the reinforcing steel of the reinforced concrete structure, thus causing protective current to flow.
12. The method of claim 11 wherein the sacrificial anode member is zinc or a zinc alloy.
13. The method of claim 11 wherein the ionically-conductive material is a cementitious-based material.
14. The method of claim 11 wherein the ionically-conductive material is a hydrogel.
15. The method of claim 11 wherein the electrochemical activating agent is an alkaline hydroxide present in sufficient amount to raise the pH of the covering material above about pH 13.3.
16. The method of claim 11 wherein the electrochemical activating agent is a deliquescent of hygroscopic material.
17. The method of claim 16 wherein the electrochemical activating agent is lithium nitrate, lithium bromide, or combinations thereof.
18. The method according to claim 11 wherein the compressible water-retaining mineral is incorporated into the composite in particulate form in an amount of between about 2% and about 15% by weight.
19. The composite according to claim 18 wherein the water-retaining mineral is a phyllosilicate mineral.
20. The composite according to claim 19 wherein the phyllosilicate mineral is exfoliated vermiculite.
21. A reinforced concrete structure cathodically protected by a composite anode comprising: at least one sacrificial anode member comprising an ionically-conductive material at least partly covering said at least one sacrificial anode; at least one electrochemical activating agent incorporated within the ionically- conductive material; characterized by a phyllosilicate mineral, in exfoliated form incorporated within the ionically conductive material; and said at least one sacrificial anode member including at least one elongated metallic conductor bonded to the ionically conductive material.
22. The reinforced concrete structure of claim 21 wherein the at least one sacrificial anode member is zinc or a zinc alloy.
23. The reinforced concrete structure of claim 21 wherein the ionically-conductive covering material is a cementitious-based material or a hydrogel.
24. The reinforced concrete structure of claim 21 wherein the electrochemical activating agent is a deliquescent or hygroscopic material comprising lithium nitrate, lithium bromide, or combinations thereof.
25. The reinforced concrete structure according to claim 21 wherein the phyllosilicate mineral is exfoliated vermiculite.
26. The reinforced structure of claim 25 wherein the vermiculite is present in the ionically conductive material in particulate form in an amount of between about 2% and about 15% by weight.
PCT/US2008/054839 2006-04-06 2008-02-25 Composite anode for cathodic protection WO2008118589A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US12/531,779 US8157983B2 (en) 2007-03-24 2008-02-25 Composite anode for cathodic protection
EP08730606A EP2132360A1 (en) 2006-04-06 2008-02-25 Composite anode for cathodic protection background of the invention
CA002681232A CA2681232A1 (en) 2006-04-06 2008-02-25 Composite anode for cathodic protection

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
USPCT/US/07/7317 2007-03-24
PCT/US2007/007317 WO2007126715A2 (en) 2006-04-06 2007-03-24 Activating matrix for cathodic protection

Publications (1)

Publication Number Publication Date
WO2008118589A1 true WO2008118589A1 (en) 2008-10-02

Family

ID=39877037

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2008/054839 WO2008118589A1 (en) 2006-04-06 2008-02-25 Composite anode for cathodic protection

Country Status (1)

Country Link
WO (1) WO2008118589A1 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2829638A4 (en) * 2012-03-22 2015-10-28 Sekisui Plastics Adhesive hydrogel and method for electrolytic protection of concrete structure
EP2875171A4 (en) * 2012-07-19 2016-07-06 Vector Corrosion Technologies Ltd Corrosion protection using a sacrificial anode
AU2015200284B2 (en) * 2012-07-19 2017-10-05 Vector Corrosion Technologies Ltd Corrosion protection using a sacrifical anode

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5292411A (en) * 1990-09-07 1994-03-08 Eltech Systems Corporation Method and apparatus for cathodically protecting reinforced concrete structures
US6572760B2 (en) * 1999-02-05 2003-06-03 David Whitmore Cathodic protection
US20040048129A1 (en) * 2002-08-13 2004-03-11 Taft Karl Milton Composite polymer electrolytes for proton exchange membrane fuel cells
US20040238347A1 (en) * 2001-09-26 2004-12-02 Bennett John E. Cathodic protection system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5292411A (en) * 1990-09-07 1994-03-08 Eltech Systems Corporation Method and apparatus for cathodically protecting reinforced concrete structures
US6572760B2 (en) * 1999-02-05 2003-06-03 David Whitmore Cathodic protection
US20040238347A1 (en) * 2001-09-26 2004-12-02 Bennett John E. Cathodic protection system
US20040048129A1 (en) * 2002-08-13 2004-03-11 Taft Karl Milton Composite polymer electrolytes for proton exchange membrane fuel cells

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2829638A4 (en) * 2012-03-22 2015-10-28 Sekisui Plastics Adhesive hydrogel and method for electrolytic protection of concrete structure
US9803115B2 (en) 2012-03-22 2017-10-31 Sekisui Plastics Co., Ltd. Adhesive hydrogel and method for electrolytic protection of concrete structure
EP2875171A4 (en) * 2012-07-19 2016-07-06 Vector Corrosion Technologies Ltd Corrosion protection using a sacrificial anode
AU2015200284B2 (en) * 2012-07-19 2017-10-05 Vector Corrosion Technologies Ltd Corrosion protection using a sacrifical anode

Similar Documents

Publication Publication Date Title
US8157983B2 (en) Composite anode for cathodic protection
US7160433B2 (en) Cathodic protection system
US7488410B2 (en) Anode assembly for cathodic protection
US11519077B2 (en) Galvanic anode and method of corrosion protection
CA2880235C (en) Galvanic anode and method of corrosion protection
EP0738337B1 (en) Ionically conductive agent, system for cathodic protection of galvanically active metals, and method and apparatus for using same
CA2392818C (en) Improvement in cathodic protection system
US20140202879A1 (en) Anode assembly for cathodic protection
US6958116B1 (en) Cathodic protection system
WO2008118589A1 (en) Composite anode for cathodic protection
EP2132360A1 (en) Composite anode for cathodic protection background of the invention
WO2005080637A1 (en) Anode assembly and means of attachment
WO2018169495A1 (en) Sacrificial anode for steel reinforcement in concrete
Bennett et al. Galvanic Anodes For Use In Reinforced Concrete–Recent Test Results

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 08730606

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2681232

Country of ref document: CA

WWE Wipo information: entry into national phase

Ref document number: 12531779

Country of ref document: US

NENP Non-entry into the national phase

Ref country code: DE

WWE Wipo information: entry into national phase

Ref document number: 2008730606

Country of ref document: EP