CA2170332C - Cathodically protected concrete article, anode, and process for production thereof - Google Patents
Cathodically protected concrete article, anode, and process for production thereof Download PDFInfo
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- CA2170332C CA2170332C CA 2170332 CA2170332A CA2170332C CA 2170332 C CA2170332 C CA 2170332C CA 2170332 CA2170332 CA 2170332 CA 2170332 A CA2170332 A CA 2170332A CA 2170332 C CA2170332 C CA 2170332C
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- anode
- metal
- precursor compound
- catalyst precursor
- valve metal
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- 238000000034 method Methods 0.000 title claims description 10
- 238000004519 manufacturing process Methods 0.000 title description 2
- 229910052751 metal Inorganic materials 0.000 claims abstract description 56
- 239000002184 metal Substances 0.000 claims abstract description 55
- 238000000576 coating method Methods 0.000 claims abstract description 31
- 239000011248 coating agent Substances 0.000 claims abstract description 30
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract description 29
- 150000001875 compounds Chemical class 0.000 claims abstract description 28
- 239000000463 material Substances 0.000 claims abstract description 27
- 239000003054 catalyst Substances 0.000 claims abstract description 20
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 19
- 239000000956 alloy Substances 0.000 claims abstract description 19
- 239000012018 catalyst precursor Substances 0.000 claims abstract description 19
- 238000007751 thermal spraying Methods 0.000 claims abstract description 13
- 238000005507 spraying Methods 0.000 claims abstract description 12
- 239000002131 composite material Substances 0.000 claims abstract description 11
- 230000007797 corrosion Effects 0.000 claims abstract description 9
- 238000005260 corrosion Methods 0.000 claims abstract description 9
- 239000012779 reinforcing material Substances 0.000 claims abstract description 7
- 239000002243 precursor Substances 0.000 claims description 14
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 13
- 229910052719 titanium Inorganic materials 0.000 claims description 11
- 239000010936 titanium Substances 0.000 claims description 11
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 6
- 239000003960 organic solvent Substances 0.000 claims description 6
- 238000007750 plasma spraying Methods 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 3
- 230000002401 inhibitory effect Effects 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- -1 platinum group metal compound Chemical class 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 2
- 150000002504 iridium compounds Chemical class 0.000 claims description 2
- 239000006193 liquid solution Substances 0.000 claims description 2
- 238000010422 painting Methods 0.000 claims description 2
- 239000007921 spray Substances 0.000 claims description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims 6
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims 3
- 229910052759 nickel Inorganic materials 0.000 claims 3
- 239000011135 tin Substances 0.000 claims 3
- 229910052718 tin Inorganic materials 0.000 claims 3
- 229910017052 cobalt Inorganic materials 0.000 claims 2
- 239000010941 cobalt Substances 0.000 claims 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims 2
- 239000012685 metal catalyst precursor Substances 0.000 claims 2
- 229910052763 palladium Inorganic materials 0.000 claims 2
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 claims 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims 1
- 229910052797 bismuth Inorganic materials 0.000 claims 1
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims 1
- 239000011247 coating layer Substances 0.000 claims 1
- 150000001869 cobalt compounds Chemical class 0.000 claims 1
- IUYOGGFTLHZHEG-UHFFFAOYSA-N copper titanium Chemical compound [Ti].[Cu] IUYOGGFTLHZHEG-UHFFFAOYSA-N 0.000 claims 1
- 229910052741 iridium Inorganic materials 0.000 claims 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims 1
- IXQWNVPHFNLUGD-UHFFFAOYSA-N iron titanium Chemical compound [Ti].[Fe] IXQWNVPHFNLUGD-UHFFFAOYSA-N 0.000 claims 1
- 229910001092 metal group alloy Inorganic materials 0.000 claims 1
- 150000002739 metals Chemical class 0.000 claims 1
- 229910052758 niobium Inorganic materials 0.000 claims 1
- 239000010955 niobium Substances 0.000 claims 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 claims 1
- 229910052762 osmium Inorganic materials 0.000 claims 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 claims 1
- 229910052703 rhodium Inorganic materials 0.000 claims 1
- 239000010948 rhodium Substances 0.000 claims 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 claims 1
- 229910052707 ruthenium Inorganic materials 0.000 claims 1
- DPGAAOUOSQHIJH-UHFFFAOYSA-N ruthenium titanium Chemical compound [Ti].[Ru] DPGAAOUOSQHIJH-UHFFFAOYSA-N 0.000 claims 1
- 229910052715 tantalum Inorganic materials 0.000 claims 1
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims 1
- 229910052721 tungsten Inorganic materials 0.000 claims 1
- 239000010937 tungsten Substances 0.000 claims 1
- 229910052726 zirconium Inorganic materials 0.000 claims 1
- 238000006243 chemical reaction Methods 0.000 abstract description 2
- 230000003014 reinforcing effect Effects 0.000 description 10
- 239000000243 solution Substances 0.000 description 7
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- 229910000831 Steel Inorganic materials 0.000 description 4
- 239000010959 steel Substances 0.000 description 4
- 230000008021 deposition Effects 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- 239000011149 active material Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004210 cathodic protection Methods 0.000 description 2
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 2
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 238000005488 sandblasting Methods 0.000 description 2
- 229910052725 zinc Inorganic materials 0.000 description 2
- 239000011701 zinc Substances 0.000 description 2
- 229910021638 Iridium(III) chloride Inorganic materials 0.000 description 1
- 229910001294 Reinforcing steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000001476 alcoholic effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000003125 aqueous solvent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000010285 flame spraying Methods 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 150000003304 ruthenium compounds Chemical class 0.000 description 1
- BIXNGBXQRRXPLM-UHFFFAOYSA-K ruthenium(3+);trichloride;hydrate Chemical compound O.Cl[Ru](Cl)Cl BIXNGBXQRRXPLM-UHFFFAOYSA-K 0.000 description 1
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 150000003609 titanium compounds Chemical class 0.000 description 1
- DANYXEHCMQHDNX-UHFFFAOYSA-K trichloroiridium Chemical compound Cl[Ir](Cl)Cl DANYXEHCMQHDNX-UHFFFAOYSA-K 0.000 description 1
Landscapes
- Prevention Of Electric Corrosion (AREA)
- Coating By Spraying Or Casting (AREA)
Abstract
A concrete article reinforced with a ferrous material in said concrete article can be cathodically protected from corrosion by the application of a coating composite which can be applied, for instance, by thermally spraying a valve metal or alloy thereof together with a catalyst precursor compound onto a surface of said concrete article. Alternatively, the concrete article may be previously or subsequently coated with a catalyst precursor compound to form a separately layered anode coating. Conversion of the catalyst precursor compound to an electrochemically active catalyst occurs during thermal spraying or by the application of the thermally sprayed valve metal or alloy thereof over the previously applied catalyst precursor compound. Connecting the anode coating and the ferrous reinforcing material in the concrete structure to an electrical circuit and impressing a current sufficient to cause the ferrous material to act as the cathode in said circuit provides protection of the ferrous material against corrosion.
Description
A CATHODICALLY PROTECTED CONCRETE ARTICLE.
ANODE. AND PROCESS FOR PRODUCTION THEREOF
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention is directed to cathodic protection of existing concrete structures having ferrous reinforcing elements.
ANODE. AND PROCESS FOR PRODUCTION THEREOF
BACKGROUND OF THE INVENTION
1. Field of the Invention This invention is directed to cathodic protection of existing concrete structures having ferrous reinforcing elements.
2. Description of Related Prior Art It is known that cathodic protection against corrosion of ferrous reinforcing elements in concrete structures can be provided by connecting in an electrical circuit an anode in contact with the structure which is used to impress a direct current on the ferrous reinforcing structures acting as cathodes.
Corrosion of reinforcing ferrous materials in concrete bridge decks, support structures, and parking garages can be provided by incorporating an anode as described in U.S. 4,880,517 in newly formed concrete structures.
In U.S. 4,506,485, a process is disclosed for inhibiting corrosion of reinforcing metal rods embedded in concrete subsequent to formation of the concrete structures by the application of a sacrificial metal coating to the concrete member subsequent to cleaning the surface by sandblasting. The anode coating is applied by flame-spraying. The metal is applied in the molten form and is often zinc although it is disclosed that the metal can be of some other conductive metal. Subsequent to application of the metal coating, the coating may be connected to a source of direct current which provides a flow of electrical current between the coated layer and the reinforcing metal elements within the concrete.
Novel electrodes are disclosed in U.S. 4,392,927 which are composite coatings on an electroconductive base applied thereto by thermal spraying. A
valve metal functions as a matrix material and the electrocatalytically active particles applied to the electroconductive base are embedded therein. The electrocatalytically active particles are selected from a metal consisting of platinum group metals and iron group metals and oxides thereof. The deposited electrocatalytically active particles have a particle size smaller by at least one order of magnitude than the matrix particles.
SUMMARY OF THE INVENTION
Anodes deposited on the surface of a concrete structure reinforced with a ferrous material are disclosed. The anodes are useful as a means for preventing corrosion of said ferrous reinforcing materials in the concrete structure when the reinforcing ferrous materials are connected in an electrical circuit with the composite anode.
The anodes of the invention comprise either a composite of a valve metal or alloy thereof and an electrically active catalyst or separate layers of an electrically active catalyst and a valve metal or alloy thereof. The application of precursor catalyst compounds to the concrete substrate can be by painting or spraying, etc. an aqueous or organic solvent solution of a soluble precursor compound on the surface of the concrete or on the coated surface of the concrete. Application can also be by thermal spraying of a precursor catalytic material together with a valve metal or alloy thereof onto the concrete surface. In either case, the precursor catalytic compound is converted by the application of heat to the electrocatalytically active material such as the oxide. Where the precursor catalyst compound is applied onto the concrete surface, the subsequent application of a thermally applied valve metal or alloy thereof can provide the requisite heat necessary to convert the catalyst precursor compound to the electrocatalytically active material such as the oxide.
Thermal spraying of a precursor catalytic material together with a valve metal or alloy thereof results in the conversion of the catalytic precursor material to the electrocatalytically active form.
In one broad aspect, there is provided an anode deposited on a surface of a concrete structure reinforced with a ferrous material said anode comprising a coating of a valve metal or alloy thereof and an electrically active metal catalyst, wherein said valve metal is applied to said surface as a continuous sheet or as a closely spaced particulate deposit by thermal spraying, arc-spraying, or plasma spraying (a) together with a catalyst precursor compound to said surface of a concrete structure or (b) said catalyst precursor compound is applied separately by thermal spraying, arc-spraying, or plasma spraying or (c) said catalyst precursor compound is applied separately utilizing a liquid solution and activated by the application of heat.
In another broad aspect, there is provided a concrete article having an anode deposited on the surface thereof and reinforced with a cathodically protected ferrous material comprising (a) an anode having separate coating .50455-4 layers or (b) a composite anode comprising a thermally sprayed valve metal or alloy thereof and an electrically active metal catalyst wherein said ferrous material and said anode are connected to an electrical circuit wherein said ferrous material acts as the cathode in said circuit; and wherein said anode is applied as a continuous sheet or as a closely spaced particulate deposit.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a novel anode formed in situ on the surface of a concrete structure reinforced with a ferrous material. A concrete article having separate catalytic and valve metal layers or a composite anode deposited thereon, a novel anode, and a process for inhibiting corrosion of a ferrous reinforcing material in a concrete structure is disclosed. The concrete surface is desirably cleaned prior to deposition of the composite or separate layer anode formed in situ thereon. The concrete surface can be treated to dislodge and displace weathered concrete or exposed concrete which has been mechanically abraded or loosened or has disintegrated by atmospheric effects or the like. Sandblasting is a suitable means of cleaning the surface to provide a roughened, pocked, or irregular surface which affords mechanical adhesion for the anode coating to be deposited thereon. Thereafter, prior to any further deterioration of the sandblasted surface a molten metal is deposited by thermal -3a-spraying. As disclosed in U.S. 4,506,485, a zinc or other conductive metal has been coated onto sandblasted concrete surfaces to provide a sacrificial coating which eventually degrades to the point where the sacrificial coating no longer provides protection against corrosion of a reinforced ferrous material within the concrete structure. Contrastingly, the process of the invention provides, in one embodiment, for the deposition of a molten valve metal or alloy thereof together with a molten precursor catalyst material. Alternatively, in another embodiment, a precursor catalytic compound which is water or organic solvent soluble can be painted or otherwise applied onto the concrete surface prior to thermal spraying of the concrete surface with a coating of a valve metal or alloy thereof or painted onto said valve metal coating. In either case, the precursor catalyst material is converted by the heat of the thermal spraying process or by subsequent exposure of the painted precursor catalyst compound to heat sufficient to convert the precursor material to the electrocatalytically active form such as the oxide.
Subsequent to formation of the anode of the invention in situ on the surface of a concrete structure, the coated metal layer is connected to a source of direct current and the circuit is completed by connecting the reinforcing ferrous material within the concrete structure so as to provide the surface coating as the anode and the reinforced ferrous material as the cathode. The imposed or impressed current is opposite and equal to the naturally occurring current which results under normal circumstances and leads to the deterioration of the ferrous material which reinforces the concrete structure. The net result of imposing a direct current which is opposite and equal to the naturally occurring current is to prevent electrolytic action on the reinforcing ferrous material which, therefore, maintains its integrity over a long period of time.
In some instances it is not necessary to have an external source of direct current in the circuit between the anode coating of the invention and the ferrous material reinforcement of the concrete structure if the surface coating is composed of a valve metal such as aluminum which is higher in the electromotive series than the reinforcing ferrous metal.
The anode coating of the invention is, generally, deposited on the cleaned surface of the concrete in a thickness of about 0.001 inches to about 0.010 inches, preferably, about 0.003 inches to about 0.005 inches, and, most preferably, about 0.005 inches. The anode coating can be provided as a continuous sheet as a grid pattern, or as a closely spaced particulate deposit.
SPECIFIC EMBODIMENTS OF THE INVENTION
Where not otherwise specified in the specification and claims, temperatures are in degrees centigrade, and parts, percentages, and proportions are by weight.
The following Examples illustrate the present invention and should not be construed, by implication or otherwise, as limiting the scope of the appended claims.
EXAMPLE 1:
A concrete slab was fabricated having dimensions of 14 inches x 7 inches x 2 inches. Imbedded in the slab was a piece of steel mesh which simulated reinforcing steel bar typical in many concrete structures such as bridges and support pillars. The steel mesh protruded at one end of the concrete slab thus allowing electrical connection. Titanium was arc-sprayed onto the concrete block using a titanium wire having a diameter of 0.0625 inches. The spray distance was about 6 inches and the arc was formed at about 25 volts and 200 amps. The measured thickness of the coating was about 0.005 inches. Next a solution of cobalt nitrate, Co(N03)21 was prepared at a concentration of 1.5 mols per liter in water. Subsequent to arc-spraying of the titanium onto the concrete slab, this catalyst solution is brush coated onto the titanium surface which has been allowed to cool. The catalyst was activated after evaporating the water by heating with a propane torch to an estimated temperature of about 300 C to about 1200 C for several minutes on all parts of the titanium coating.
The concrete block was placed in an air atmosphere having a relative humidity of between 90 and 100 percent and the anode surface thus prepared is connected to the positive post of a regulated power supply and the steel reinforcing material is connected to the negative post. The power supply is adjusted to give a constant current of 1.16 milliamperes which is calculated to be equivalent to a current density of 2 milliamps per square foot on the catalyzed titanium surface. The initial voltage measured between the titanium surface and the steel reinforcing material was 1.36 volts. After 25 days of operation the voltage had risen to 1.344 volts.
EXAMPLE 2:
Example 1 is repeated substituting an alcoholic solution of chloroplatinic acid and iridium trichloride which is brush coated onto the titanium surface 2i70332 formed by arc-spraying. The concentration of the platinum and iridium compounds was 7.5 grams/liter and 3.5 grams/liter, each calculated as the metal.
Evaluation was conducted at a current density of 10 milliamps per square foot.
The initial voltage was 2.3 volts. After 31 days the voltage was 2.84 volts.
EXAMPLE 3:
Example 2 is repeated substituting a mixture of catalyst precursor compounds comprising a butanol soluble ruthenium compound and a butanol soluble titanium compound. The concentration of the ruthenium trichloride hydrate was 16.1 g/liter and the concentration of ortho-butyl titanate was 17.6 g/liter, each calculated as the metal. When tested as described in Example 2, the initial voltage was 2.37 volts. After 31 days the voltage was 3.26 volts.
EXAMPLE 4:
A concrete slab similar to that described in Example 2 was coated with an aqueous solution of cobalt nitrate at a concentration of 1.5 molar. The water was evaporated and the concrete surface was heated with a propane torch so as to provide an estimated temperature of about 300 C to about 1200 C for several minutes. Thereafter, a titanium layer approximately 0.005 inches thick was arc-sprayed over the catalyst layer which had been activated by heating.
The prepared concrete block was then tested as indicated in Example 2. The initial voltage was 2.95 volts and after 28 days of operation had risen to 2.8 volts.
EXAMPLE 5:
Example 4 was repeated except that the catalyst precursor compound applied to the concrete surface was not heated prior to deposition of a titanium layer 0.005 inches thick by arc-spraying. When this sample was tested under similar test conditions as described in Example 1, the initial voltage was 2.99 volts and this voltage rose to 2.74 volts after 28 days.
EXAMPLE 6:
A concrete slab similar to that described in Example 2 was arc-sprayed with a titanium wire coated with a solution of ruthenium chloride and ortho-butyl titanate. The coating was applied from a solution of these compounds in butanol. After coating the wire with this solution, the organic solvent was evaporated and the coated wire was baked in an oven at 525 C for thirty minutes. The concrete slab was coated with a coating of approximately 0.005 inches. The concrete slab was tested in the same manner as described in Example 1 and found to have an initial voltage of 3.07 volts which, after 28 days, had risen to 2.93 volts.
While this invention has been described with reference to certain specific embodiments, it will be recognized by those skilled in the art that many variations are possible without departing from the scope and state of the invention, and it will be understood that it is intended to cover all changes and modifications of the invention disclosed herein for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.
Corrosion of reinforcing ferrous materials in concrete bridge decks, support structures, and parking garages can be provided by incorporating an anode as described in U.S. 4,880,517 in newly formed concrete structures.
In U.S. 4,506,485, a process is disclosed for inhibiting corrosion of reinforcing metal rods embedded in concrete subsequent to formation of the concrete structures by the application of a sacrificial metal coating to the concrete member subsequent to cleaning the surface by sandblasting. The anode coating is applied by flame-spraying. The metal is applied in the molten form and is often zinc although it is disclosed that the metal can be of some other conductive metal. Subsequent to application of the metal coating, the coating may be connected to a source of direct current which provides a flow of electrical current between the coated layer and the reinforcing metal elements within the concrete.
Novel electrodes are disclosed in U.S. 4,392,927 which are composite coatings on an electroconductive base applied thereto by thermal spraying. A
valve metal functions as a matrix material and the electrocatalytically active particles applied to the electroconductive base are embedded therein. The electrocatalytically active particles are selected from a metal consisting of platinum group metals and iron group metals and oxides thereof. The deposited electrocatalytically active particles have a particle size smaller by at least one order of magnitude than the matrix particles.
SUMMARY OF THE INVENTION
Anodes deposited on the surface of a concrete structure reinforced with a ferrous material are disclosed. The anodes are useful as a means for preventing corrosion of said ferrous reinforcing materials in the concrete structure when the reinforcing ferrous materials are connected in an electrical circuit with the composite anode.
The anodes of the invention comprise either a composite of a valve metal or alloy thereof and an electrically active catalyst or separate layers of an electrically active catalyst and a valve metal or alloy thereof. The application of precursor catalyst compounds to the concrete substrate can be by painting or spraying, etc. an aqueous or organic solvent solution of a soluble precursor compound on the surface of the concrete or on the coated surface of the concrete. Application can also be by thermal spraying of a precursor catalytic material together with a valve metal or alloy thereof onto the concrete surface. In either case, the precursor catalytic compound is converted by the application of heat to the electrocatalytically active material such as the oxide. Where the precursor catalyst compound is applied onto the concrete surface, the subsequent application of a thermally applied valve metal or alloy thereof can provide the requisite heat necessary to convert the catalyst precursor compound to the electrocatalytically active material such as the oxide.
Thermal spraying of a precursor catalytic material together with a valve metal or alloy thereof results in the conversion of the catalytic precursor material to the electrocatalytically active form.
In one broad aspect, there is provided an anode deposited on a surface of a concrete structure reinforced with a ferrous material said anode comprising a coating of a valve metal or alloy thereof and an electrically active metal catalyst, wherein said valve metal is applied to said surface as a continuous sheet or as a closely spaced particulate deposit by thermal spraying, arc-spraying, or plasma spraying (a) together with a catalyst precursor compound to said surface of a concrete structure or (b) said catalyst precursor compound is applied separately by thermal spraying, arc-spraying, or plasma spraying or (c) said catalyst precursor compound is applied separately utilizing a liquid solution and activated by the application of heat.
In another broad aspect, there is provided a concrete article having an anode deposited on the surface thereof and reinforced with a cathodically protected ferrous material comprising (a) an anode having separate coating .50455-4 layers or (b) a composite anode comprising a thermally sprayed valve metal or alloy thereof and an electrically active metal catalyst wherein said ferrous material and said anode are connected to an electrical circuit wherein said ferrous material acts as the cathode in said circuit; and wherein said anode is applied as a continuous sheet or as a closely spaced particulate deposit.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a novel anode formed in situ on the surface of a concrete structure reinforced with a ferrous material. A concrete article having separate catalytic and valve metal layers or a composite anode deposited thereon, a novel anode, and a process for inhibiting corrosion of a ferrous reinforcing material in a concrete structure is disclosed. The concrete surface is desirably cleaned prior to deposition of the composite or separate layer anode formed in situ thereon. The concrete surface can be treated to dislodge and displace weathered concrete or exposed concrete which has been mechanically abraded or loosened or has disintegrated by atmospheric effects or the like. Sandblasting is a suitable means of cleaning the surface to provide a roughened, pocked, or irregular surface which affords mechanical adhesion for the anode coating to be deposited thereon. Thereafter, prior to any further deterioration of the sandblasted surface a molten metal is deposited by thermal -3a-spraying. As disclosed in U.S. 4,506,485, a zinc or other conductive metal has been coated onto sandblasted concrete surfaces to provide a sacrificial coating which eventually degrades to the point where the sacrificial coating no longer provides protection against corrosion of a reinforced ferrous material within the concrete structure. Contrastingly, the process of the invention provides, in one embodiment, for the deposition of a molten valve metal or alloy thereof together with a molten precursor catalyst material. Alternatively, in another embodiment, a precursor catalytic compound which is water or organic solvent soluble can be painted or otherwise applied onto the concrete surface prior to thermal spraying of the concrete surface with a coating of a valve metal or alloy thereof or painted onto said valve metal coating. In either case, the precursor catalyst material is converted by the heat of the thermal spraying process or by subsequent exposure of the painted precursor catalyst compound to heat sufficient to convert the precursor material to the electrocatalytically active form such as the oxide.
Subsequent to formation of the anode of the invention in situ on the surface of a concrete structure, the coated metal layer is connected to a source of direct current and the circuit is completed by connecting the reinforcing ferrous material within the concrete structure so as to provide the surface coating as the anode and the reinforced ferrous material as the cathode. The imposed or impressed current is opposite and equal to the naturally occurring current which results under normal circumstances and leads to the deterioration of the ferrous material which reinforces the concrete structure. The net result of imposing a direct current which is opposite and equal to the naturally occurring current is to prevent electrolytic action on the reinforcing ferrous material which, therefore, maintains its integrity over a long period of time.
In some instances it is not necessary to have an external source of direct current in the circuit between the anode coating of the invention and the ferrous material reinforcement of the concrete structure if the surface coating is composed of a valve metal such as aluminum which is higher in the electromotive series than the reinforcing ferrous metal.
The anode coating of the invention is, generally, deposited on the cleaned surface of the concrete in a thickness of about 0.001 inches to about 0.010 inches, preferably, about 0.003 inches to about 0.005 inches, and, most preferably, about 0.005 inches. The anode coating can be provided as a continuous sheet as a grid pattern, or as a closely spaced particulate deposit.
SPECIFIC EMBODIMENTS OF THE INVENTION
Where not otherwise specified in the specification and claims, temperatures are in degrees centigrade, and parts, percentages, and proportions are by weight.
The following Examples illustrate the present invention and should not be construed, by implication or otherwise, as limiting the scope of the appended claims.
EXAMPLE 1:
A concrete slab was fabricated having dimensions of 14 inches x 7 inches x 2 inches. Imbedded in the slab was a piece of steel mesh which simulated reinforcing steel bar typical in many concrete structures such as bridges and support pillars. The steel mesh protruded at one end of the concrete slab thus allowing electrical connection. Titanium was arc-sprayed onto the concrete block using a titanium wire having a diameter of 0.0625 inches. The spray distance was about 6 inches and the arc was formed at about 25 volts and 200 amps. The measured thickness of the coating was about 0.005 inches. Next a solution of cobalt nitrate, Co(N03)21 was prepared at a concentration of 1.5 mols per liter in water. Subsequent to arc-spraying of the titanium onto the concrete slab, this catalyst solution is brush coated onto the titanium surface which has been allowed to cool. The catalyst was activated after evaporating the water by heating with a propane torch to an estimated temperature of about 300 C to about 1200 C for several minutes on all parts of the titanium coating.
The concrete block was placed in an air atmosphere having a relative humidity of between 90 and 100 percent and the anode surface thus prepared is connected to the positive post of a regulated power supply and the steel reinforcing material is connected to the negative post. The power supply is adjusted to give a constant current of 1.16 milliamperes which is calculated to be equivalent to a current density of 2 milliamps per square foot on the catalyzed titanium surface. The initial voltage measured between the titanium surface and the steel reinforcing material was 1.36 volts. After 25 days of operation the voltage had risen to 1.344 volts.
EXAMPLE 2:
Example 1 is repeated substituting an alcoholic solution of chloroplatinic acid and iridium trichloride which is brush coated onto the titanium surface 2i70332 formed by arc-spraying. The concentration of the platinum and iridium compounds was 7.5 grams/liter and 3.5 grams/liter, each calculated as the metal.
Evaluation was conducted at a current density of 10 milliamps per square foot.
The initial voltage was 2.3 volts. After 31 days the voltage was 2.84 volts.
EXAMPLE 3:
Example 2 is repeated substituting a mixture of catalyst precursor compounds comprising a butanol soluble ruthenium compound and a butanol soluble titanium compound. The concentration of the ruthenium trichloride hydrate was 16.1 g/liter and the concentration of ortho-butyl titanate was 17.6 g/liter, each calculated as the metal. When tested as described in Example 2, the initial voltage was 2.37 volts. After 31 days the voltage was 3.26 volts.
EXAMPLE 4:
A concrete slab similar to that described in Example 2 was coated with an aqueous solution of cobalt nitrate at a concentration of 1.5 molar. The water was evaporated and the concrete surface was heated with a propane torch so as to provide an estimated temperature of about 300 C to about 1200 C for several minutes. Thereafter, a titanium layer approximately 0.005 inches thick was arc-sprayed over the catalyst layer which had been activated by heating.
The prepared concrete block was then tested as indicated in Example 2. The initial voltage was 2.95 volts and after 28 days of operation had risen to 2.8 volts.
EXAMPLE 5:
Example 4 was repeated except that the catalyst precursor compound applied to the concrete surface was not heated prior to deposition of a titanium layer 0.005 inches thick by arc-spraying. When this sample was tested under similar test conditions as described in Example 1, the initial voltage was 2.99 volts and this voltage rose to 2.74 volts after 28 days.
EXAMPLE 6:
A concrete slab similar to that described in Example 2 was arc-sprayed with a titanium wire coated with a solution of ruthenium chloride and ortho-butyl titanate. The coating was applied from a solution of these compounds in butanol. After coating the wire with this solution, the organic solvent was evaporated and the coated wire was baked in an oven at 525 C for thirty minutes. The concrete slab was coated with a coating of approximately 0.005 inches. The concrete slab was tested in the same manner as described in Example 1 and found to have an initial voltage of 3.07 volts which, after 28 days, had risen to 2.93 volts.
While this invention has been described with reference to certain specific embodiments, it will be recognized by those skilled in the art that many variations are possible without departing from the scope and state of the invention, and it will be understood that it is intended to cover all changes and modifications of the invention disclosed herein for the purpose of illustration which do not constitute departures from the spirit and scope of the invention.
Claims (15)
1. An anode deposited on a surface of a concrete structure reinforced with a ferrous material said anode comprising a coating of a valve metal or alloy thereof and an electrically active metal catalyst, wherein said valve metal is applied to said surface as a continuous sheet or as a closely spaced particulate deposit by thermal spraying, arc-spraying, or plasma spraying (a) together with a catalyst precursor compound to said surface of a concrete structure or (b) said catalyst precursor compound is applied separately by thermal spraying, arc-spraying, or plasma spraying or (c) said catalyst precursor compound is applied separately utilizing a liquid solution and activated by the application of heat.
2. The anode of claim 1 wherein said catalyst precursor compound comprises a water or organic solvent soluble platinum group metal, cobalt, tin, or nickel precursor compound which is applied by painting said surface of said concrete structure or the surface of said valve metal coating or alloy coating thereof.
3. The anode of claim 2 wherein said metal catalyst precursor is converted to the electrically active metal or oxide during spray application or converted to the electrically active metal catalyst by subsequent application by thermal spraying, arc-spraying, or plasma spraying of said valve metal or alloy thereof.
4. The anode of claim 3 wherein said valve metal is selected from the group consisting of titanium, tantalum, aluminum, zirconium, bismuth, tungsten, niobium, and alloys thereof.
5. The anode of claim 4 wherein said anode is a composite comprising said platinum group metal and said platinum group metal is selected from the metals of the group consisting of platinum, palladium, ruthenium, rhodium, osmium, iridium, and mixtures thereof; and said valve metal or alloy thereof.
6. The anode of claim 4 wherein said anode is a composite comprising the valve metal alloy selected from the group consisting of titanium-palladium, titanium-ruthenium, titanium-iron, and titanium-copper.
7. The anode of claim 4 wherein said anode is a composite comprising a cobalt, nickel, tin, or their oxides as said metal catalyst.
8. A concrete article having an anode deposited on the surface thereof and reinforced with a cathodically protected ferrous material comprising (a) an anode having separate coating layers or (b) a composite anode comprising a thermally sprayed valve metal or alloy thereof and an electrically active metal catalyst wherein said ferrous material and said anode are connected to an electrical circuit wherein said ferrous material acts as the cathode in said circuit; and wherein said anode is applied as a continuous sheet or as a closely spaced particulate deposit.
9. The concrete article of claim 8 wherein said electrically active metal catalyst is applied to said surface by thermal spraying from a metal catalyst precursor composition.
10. The concrete article of claim 8 wherein said electrically active metal catalyst is applied as a catalyst precursor compound to the surface of said concrete article with a water or organic solvent soluble catalyst precursor compound which is activated by heat or not activated prior to thermal spraying of said valve metal or alloy thereof.
11. The concrete article of claim 10 wherein said coated surface has an anode thickness of about 0.001 inch to about 0.010 inch.
12. A process for inhibiting corrosion of a ferrous reinforcing material in a concrete structure comprising:
A) cleaning a surface of said structure, B) applying as a continuous sheet or as a closely spaced particulate deposit a catalyst precursor compound to said surface alone or in combination with a thermally sprayed coating of a valve metal or alloy thereof, and C) connecting said coating and said reinforcing material to an electrical circuit wherein said coating acts as the anode in said circuit.
A) cleaning a surface of said structure, B) applying as a continuous sheet or as a closely spaced particulate deposit a catalyst precursor compound to said surface alone or in combination with a thermally sprayed coating of a valve metal or alloy thereof, and C) connecting said coating and said reinforcing material to an electrical circuit wherein said coating acts as the anode in said circuit.
13. The process of claim 12 wherein said catalyst is applied as a water or organic solvent solution of a precursor compound comprising a nickel, tin, or cobalt compound or a platinum group metal compound or mixtures thereof.
14. The process of claim 12 wherein said catalyst precursor compound and said valve metal or mixture thereof are applied simultaneously to a surface of said concrete structure by arc-spraying.
15. The process of claim 14 wherein said valve metal is titanium and said catalyst precursor compound is a mixture of platinum and iridium compounds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US39480495A | 1995-02-27 | 1995-02-27 | |
| US08/394,804 | 1995-02-27 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2170332A1 CA2170332A1 (en) | 1996-08-28 |
| CA2170332C true CA2170332C (en) | 2008-01-29 |
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ID=23560492
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2170332 Expired - Fee Related CA2170332C (en) | 1995-02-27 | 1996-02-26 | Cathodically protected concrete article, anode, and process for production thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2170332C (en) |
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1996
- 1996-02-26 CA CA 2170332 patent/CA2170332C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2170332A1 (en) | 1996-08-28 |
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