GB2598800A - Conductive coating anode for impressed current cathodic protection of reinforced concrete structures - Google Patents

Abstract

A conductive coating anode is detailed for an Impressed Current Cathodic Protection (ICCP) system for protection of reinforced concrete structures from corrosion. The anode system comprises an anode having a conductive coating (204) forming a matrix with a concrete surface of the reinforced concrete structure (202) The conductive coating (204) comprises zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight which is applied directly to the concrete surface. The anode may be attached to the reinforced concrete structure and may comprise platinum clad wire and covered with a textile material such as a carbon fibre mat (208). The conductive coating (204) may be overcoated with one or more layers.

Description

CONDUCTIVE COATING ANODE FOR IMPRESSED CURRENT CATHODIC

PROTECTION OF REINFORCED CONCRETE STRUCTURES

TECHNICAL FIELD

[0001] The present invention relates to systems and methods for impressed current cathodic protection of reinforced concrete structures from corrosion, and more specifically to a conductive coating anode for impressed current cathodic protection of the reinforced concrete structures for corrosion protection.

BACKGROUND OF THE INVENTION

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] "Corrosion" is a natural process that converts a refined metal into a more chemically-stable form such as oxide, hydroxide, or sulphide. The corrosion of steel reinforcement in concrete structures is the biggest durability issue and leads to rust formation, cracking, delamination and degradation of structures. The global economic cost of corrosion losses is estimated to be 3.4% of the world's GDP.

100041 To deal with corrosion and deterioration issues, cathodic protection (CP) has proven to be the most effective for reducing the rate of corrosion in reinforced concrete structures regardless of extent of salt contamination. It is estimated that more than 2 million m= of reinforced concrete have been protected by CP world-wide, the United Kingdom's share being in excess of 200,000 m2.

[0005] Cathodic protection is the most successful technique to protect chloride contaminated concrete structures from corrosion. The basic principle of cathodic protection systems is to provide an external electric potential to the steel reinforcement and prevent electron flow from anode to the cathode area. This favours cathodic reaction and slows anodic (corrosion) reaction. This is done by making the entire area of metal in a concrete structure to be protected cathodic relative to a sacrificial or driven anode.

[0006] There are two basic kinds of cathodic protection systems -sacrificial (SACP) and impressed current cathodic protection (ICCP). In SACP less noble metals than steel like zinc or aluminium are connected with the steel bar and the dissolution of this anode metal provides current instead of an external power supply.

[0007] An impressed current cathodic protection (ICCP) system avoids the recurring cost and downtime penalties of the sacrificial anode system. The principle of ICCP systems is to negatively shift the steel/concrete/reference electrode potential of the protected structure by delivering sufficient polarization current, such that initiation and propagation of corrosion is suppressed, corrosion induced failure is prevented during lifetime of the structure and pitting is prevented. Anodes for ICCP need to be good electrical conductors, have low corrosion rate and be able to tolerate high currents without forming a resistive oxide layer.

[0008] The most critical component of any cathodic protection system is to design an effective anode system to distribute protection current efficiently and economically to reinforced concrete structures which are to be protected. In addition, the anode system must be easy to install and possess long term durability. Various anode systems for ICCP applications have been developed for reinforced concrete structures such as thermal sprayed zinc, titanium anodes, conductive anodes and conductive cementitious anodes.

100091 One of the most effective and easily applicable anodes are conductive coating anodes which include organic and mineral coatings containing a variety of formulations of carbon pigmented solvent or water dispersed coatings and metallic coatings such as thermal sprayed zinc. Zinc based anodes are mostly preferred for their application in reinforced concrete. However, use of such zinc based anodes is limited mainly as galvanic anodes. Also, use of zinc as galvanic or sacrificial anode cathodic protection does not show a uniform distribution of current and is unable to deliver the required current unless the galvanic zinc is periodically wetted.

[00010] Various forms of zinc (Zn) anodes have been developed such as thermally or arc sprayed coating of Zn, Zn-Al or Al-Zn-In and rolled zinc sheets. Thermally sprayed zinc (TSZ) anodes are found to be more effective to be used as an ICCP anode, however, such TSZ based anodes are used for both galvanic and ICCP systems. However, use of TSZ as ICCP systems engenders loss of bond between anode and concrete substrate or high voltage demand that is greater than operating limits. Further, for long term performance of TSZ anode, it is essential to maintain moisture at Zn-concrete interface. This lowers the voltage required for effective operation of the ICCP system, increases performance of the galvanic system, and redistribute anode dissolution products into the concrete pore structure.

[00011] There is therefore a need to develop technologies, which are capable of catering to the deficiencies associated with the conventional anode systems for ICCP applications to protect reinforced concrete structures from corrosion. The present invention has been made in view of the need for overcoming such deficiencies.

SUMMARY OF THE INVENTION

[00012] An aspect of the present invention pertains to a conductive coating anode for impressed current cathodic protection of a reinforced concrete structure, including zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight, wherein the conductive coating anode is applied to a concrete surface of the reinforced concrete structure to form a durable matrix with the concrete surface and supports flow of a protective current to the concrete surface.

[00013] According to an embodiment of the present invention, the conductive coating anode further contains aromatic hydrocarbons and binders.

[00014] According to an embodiment of the present invention, the conductive coating has a service life of 40-45 years, i.e., higher than any available traditional carbon based conductive coating or thermally sprayed zinc anodes.

[00015] Another aspect of the present invention relates to an anode system for impressed current cathodic protection of a reinforced concrete structure, the anode system including an anode having a conductive coating forming a durable matrix with a concrete surface of the reinforced concrete structure, wherein the conductive coating contains zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight, and supports flow of a protective current from the anode to one or more metallic members of the reinforced concrete structure.

1000161 According to an embodiment of the present invention, the conductive coating is applied to the concrete surface without thermal treatment.

[00017] According to an embodiment of the present invention, the conductive coating is applied to the concrete surface by any of a roller, brush or a spray gun.

[00018] According to an embodiment of the present invention, the carbon base material is graphite powder having a particle size of less than 53 pm.

[00019] According to an embodiment of the present invention, the conductive coating is over-coated with a thin layer of paint for decorative finish, if required.

[00020] According to an embodiment of the present invention, the anode includes platinum clad wire installed as a primary anode conductor and covered with a suitable robust fabric material such as carbon fibre mat.

[00021] According to an embodiment of the present invention, the platinum clad wire is mounted in 2-3 mm wide and 1 mm deep rills grooved into the concrete surface.

[00022] According to an embodiment of the present invention, the suitable robust fabric material having a width of 50 mm covers a top surface of the platinum clad wire [00023] According to an embodiment of the present invention, the platinum clad wire is installed after application of a first layer of the conductive coaling and is embedded into a second layer of the conductive coating.

[00024] According to an embodiment of the present invention, the platinum clad wire of the anode system is connected to a direct current (DC) power supply.

[00025] According to an embodiment of the present invention, the conductive coating is anodically polarized and the one or more rebars (metallic members) of the reinforced concrete structure are cathodically polarized.

[00026] According to an embodiment of the present invention, the anode system is applied with a current density ranging from 0 to 50 mA;m2.

1000271 According to an embodiment of the present invention, the conductive coating has an electrical resistivity in the range of 1-15 kohm-cm.

1000281 According to an embodiment of the present invention, water vapour transmission rate of the conductive coating is 1.26 g/m2/hr with an equivalent layer thickness (sn) of 0.68 m.

[00029] Another aspect of the present invention relates to an Impressed Current Cathodic Protection (ICCP) system for a reinforced concrete structure, the ICCP system including an anode attached to the reinforced concrete structure, and a DC power supply connected to the anode to deliver a voltage thereto, wherein the anode has a conductive coating forming a durable matrix with the reinforced concrete structure, wherein the conductive coating contains zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight, and supports flow of a protective current to one or more metallic members of the reinforced concrete structure.

[00030] According to an embodiment of the present invention, the conductive coating contains 80-95% by weight zinc, 5-10% by weight graphite and 5-10% by weight solvent.

[00031] According to an embodiment of the present invention, the conductive coating includes at least two layers of coating having dry film thickness ranging from 200 pm to 350 pm.

[00032] According to an embodiment of the present invention, water transmissibility of the conductive coating is less than 0.1 kg/m2.h°-5. According to another embodiment of the present invention, water transmissibility of the conductive coating is 0.0016 kg/m2.1V-5.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

[00033] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[00034] In the figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. Dimensions provided in Figs. I to 4 as below are in millimetre (mm).

[00035] Fig. 1 illustrates an exemplary representation of a setup for conductivity test of anode system, in accordance with an embodiment of the present invention; [00036] Fig. 2 illustrates an exemplary schematic representation of the anode system in accordance with an embodiment of the present invention; [00037] Fig. 3 illustrates an exemplary representation of a setup for polarization test of a beam specimen, in accordance with an embodiment of the present invention; [00038] Fig. 4 illustrates an exemplary schematic representation of a slab specimen in accordance with an embodiment of the present invention; [00039] Fig. 5 illustrates an exemplary schematic representation of a slab specimen for durability testing in accordance with an embodiment of the present invention; [00040] Figs. 6A and 6B illustrate exemplary charts showing electrical resistivity of different conductive coatings in accordance with an embodiment of the present invention; [00041] Fig. 7 illustrates an exemplary chart showing the effect of graphite percentage content on conductivity of the conductive coating of the anode system in accordance with an embodiment of the present invention; [00042] Fig. 8 illustrates exemplary representations of scanning electron microscopy (SEM) micrographs of different conductive coatings in accordance with an embodiment of the present invention; [00043] Figs. 9A and 9B illustrate exemplary charts showing polarization and depolarization behaviour of slab specimens at two different current densities w.r.t AglAgC1/0.5MKC1 reference electrode at atmospherically exposed condition in accordance 20 with an embodiment of the present invention; 1000441 Fig. 10 illustrates exemplary charts showing potential shift and potential decay of a top bar and a bottom bar of 3 m beam specimens at different current densities with respect to MMO reference electrode at the atmospherically exposed condition in accordance with an embodiment of the present invention; [00045] Figs. I I A and I I B illustrate exemplary charts showing potential shift and potential decay of beam specimens at different current densities with respect to MMO reference electrode at partially submerged condition in accordance with an embodiment of the present invention; [00046] Figs. 12A and 12B illustrate exemplary charts showing potential shift and potential decay of slab specimens at different current densities with respect to MMO reference electrode at atmospherically exposed condition in accordance with an embodiment of the present invention; [00047] Fig. 13 illustrates an exemplary chart showing polarization of specimens with respect to MMO reference electrode during exposure cycles in accordance with an embodiment of the present invention; 1000481 Fig. 14 illustrates an exemplary chart showing as-found voltage across sample specimens during a period of 30 days, in accordance with an embodiment of the present invention; and 1000491 Fig. 15 illustrates an exemplary chart showing depolarization of specimens with respect to MMO reference electrode during exposure cycles in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

1000501 As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[00051] If the specification states a component or feature may", "can", "could", or might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[00052] Exemplary embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. This disclosure may however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those of ordinary skill in the art. Moreover, all statements herein reciting embodiments of the disclosure, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future (i.e., any elements developed that perform the same function, regardless of structure).

[00053] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[00054] In some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[00055] The present invention relates to a conductive coating anode for protection of a reinforced concrete structure from corrosion. The conductive coating anode acts as an anode which is applied to a concrete structure of the reinforced concrete structure. The conductive coating anode is connected to a direct current (DC) power supply. The conductive coating anode is anodically polarized and one or more rebars (metallic members) of the reinforced concrete structure are cathodical ly polarized in order to protect the concrete structure from corrosion and improve service life of the concrete structure.

[00056] Another aspect of the present invention relates to an anode system of an Impressed Current Cathodic Protection (ICCP) system for reinforced concrete structures. The anode system includes an anode having a conductive coating (also referred to as "coating layer", "Concrete Conductive Anode Paint" or "Concrete CAP" hereinafter) forming a durable matrix with a concrete surface of the reinforced concrete structure, wherein the conductive coating contains zinc and an electrically conductive carbon base material, i.e., graphite in the ratio of 9.6:1 by weight, and supports flow of a protective current from the anode to one or more metallic members, i.e., rebars, of the reinforced concrete structure. According to an embodiment of the present invention, the conductive coating may contain 80-95% by weight zinc, 5-10% by weight graphite and 5-10% by weight solvent. The Concrete CAP anode system is formed by applying the conductive coating on the concrete surface without thermal treatment. The Concrete CAP may be easily applied by roller or brush and can be over-coated by conventional paints for decorative finish to the structure, if required.

[00057] The anode system and conductive coating have higher bond strength and high durability. The anode system is capable of being easily applied in cathodic protection systems and has longer service life and lower low carbon footprint compared to conventional carbon based conductive coating anodes. Also, the anode system is capable of being implemented and/or retrofitted in existing technologies pertaining to cathodic protection systems.

[00058] According to an embodiment of the present invention, minimum surface preparation is required by wire brushing, high pressure water jetting or light grit blasting the concrete surface and exposing little or no aggregates to remove laitance layer before application of the Concrete CAP on the concrete surface. The Concrete CAP anode system is highly sustainable with no or minimum concrete damage, and minimum energy requirement for surface preparation. In an embodiment, before coating, a platinum clad wire, for instance, Anomet platinum clad wire, may be installed as a primary anode conductor and may be covered with a suitable robust fabric material such as carbon fibre mat to protect the primary anode conductor from any physical damage. The conductive coating may then be applied in two layers having dry film thickness of minimum 250 Tim.

1000591 The anode system offers advantage of higher bond strength, longer service life, high durability, ease of application and low carbon footprint compared to conventional carbon based conductive coating anodes. In an embodiment, at the end of service life or in case of any damage, the conductive coating may be easily reapplied by jet washing the concrete surface before re-application of the conductive coating without removal of the old layer of coating.

This may reduce cost associated with maintenance of the reinforced concrete structures, and further helps in elimination of waste generated thereof.

[00060] Another aspect of the present invention relates to an Impressed Current Cathodic Protection (ICCP) system for reinforced concrete structures, the ICCP system including an anode attached to the reinforced concrete structure, and a DC power supply connected to the anode to deliver a voltage thereto, wherein the anode has a conductive coating forming a durable matrix with a concrete surface of the reinforced concrete structure, wherein the conductive coating contains zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight, and supports flow of a protective current from the anode to one or more metallic members of the reinforced concrete structure.

[00061] As shown in Fig. 2, a reinforced concrete structure (202) is coated with a coating layer (acting as an anode) (204) containing zinc and graphite an in the ratio of 9.6:1 by weight.

The coating layer (204) is applied over a concrete surface of the reinforced concrete structure (202) in two passes, i.e. the coating layer (204) includes two layers of coating having dry film thickness ranging from 200 pm to 350 pm. A platinum clad wire (206) acting as a primary anode conductor is mounted in 2-3 mm wide and 1 mm deep rills grooved into the concrete structure (202) and covered with a carbon fibre mat (208) for protection. The primary anode conductor (206) is embedded between the two layers of coating. The coating layer (204) is anodically polarized and a plurality of metallic members (rebars) of the concrete structure (202) are cathodically polarized. At least one miniaturized mixed metal oxide/titanium (MMO/Ti) decay probe (212) and at least one Ag/AgC1/0.5M KC1 reference electrode (210) are provided in the concrete structure (202) to monitor potential of steel/concrete/reference electrode.

[00062] According loan embodiment of the present invention, the coating layer/conductive anode paint is applied to the concrete surface without thermal treatment with the help of any of a roller, brush or a spray gun.

1000631 According to an embodiment of the present invention, the carbon base material is graphite powder having a particle size of less than 53 pm.

1000641 According to an embodiment of the present invention, the anode system is applied with a current density ranging from 0 to 50 mAim2. According to an embodiment of the present invention, the conductive coating has an electrical resistivity of 1-15 kohm-cm. Water vapour transmission rate of the conductive coating is 1.26 g/m2/hr with an equivalent layer thickness (s0) of 0.68 m.

[00065] According to an embodiment of the present invention, the conductive coating applied to the reinforced concrete structure for impressed current cathodic protection has a service life of 30-45 years.

EXAMPLES

SPECIMEN PREPARATION

1000661 All the concrete specimens of C32/40 grade were cast during the study with a water-cement ratio of 0.5 which is a similar grade for existing aged structures. The mix proportioning is finalized after successful trial mixing as per BS 1881-125:2013. The details of mix proportions of specimens are shown in Table 1 provided below. 3% NaC1 solution by weight of cement was deliberately added to the mixing water during casting as specified in the NACE Standard TM0294-2007 to accelerate corrosion of steel in concrete. Specimens were demouldcd after 24 hours and cured in salt (sodium chloride) solution at 20±1°C for a total period of 28 days. Three specimens were tested for each test.

Mix w/c Ratio Binder Sodium Chloride kg/m3 kg/m3 Water Cement Sand Gravel 3% salt 0.3 180 360 640.5 1189.3 10.8 Table 1: Mix prof calming, of concrete specimens

CONCRETE CAP FORMULATION

[00067] The Concrete CAP is a conductive anode coating. It mainly includes of zinc and highly conductive materials such as carbon base materials in the ratio of 9.6:1 by weight. Graphite was used as highly conductive material for present formulation. Zinc has purity of 99.995% and graphite powder has 98.6% carbon. The particle size of graphite powder used is 300 mesh i.e. 95 t%tc< 53 pm. The other components of the Concrete CAP include aromatic hydrocarbons, binder and solvent. The coaling is thoroughly mixed using high shear mixer before application. For case of application, the coating is diluted with 10% of solvent by weight of the coating.

SURFACE PREPARATION

[00068] The concrete surface was freed of loose and sandy parts. Surface contaminations were thoroughly removed, especially of oil, fats and wax. Optimum adhesion of the coating was obtained by wire brushing the concrete surface for 15-20 minutes exposing a finer proportion of aggregates and removing the laitance layer. After surface preparation, specimen surface was cleaned for any dust using non-contaminated compressed air before coating.

PRIMARY ANODE INSTALLATION

[00069] Current distribution into the Concrete CAP is affected by primary anodes embedded into the Concrete CAP composite coating. Platinum clad wire was selected as primary anode conductor and mounted in 2-3 mm wide and 1mm deep rills grooved into the concrete structure. A 50 mm wide carbon fibre mat is glued on top of the primary anode conductor to protect the anode from mechanical damages. Primary anode conductor was installed after application of the first layer of the composite Concrete CAP and then embedded into the second layer of the composite Concrete CAP.

MIXING AND APPLICATION OF COATING

1000701 The conductive coating anode was thoroughly mixed with high speed mechanical stirrers for 10-15 minutes for homogenization before application to the specimen. The Concrete CAP composite paint was then applied on the specimen surface like a conventional paint either with rollers or with a brush. The Concrete CAP was applied in two layers. The subsequent coating was applied on dry paint, preferentially on the next day but not later than 24 hours after application of previous layer. The total dry film thickness of paint is maintained in the range of 200-350 pm.

ELECTRICAL CONDUCTIVITY TEST

[00071] Conductance of the composite Concrete CAP was measured according to NACE TM0105. This test was performed to decide the percentage of graphite to be mixed with zinc paint. Graphite percentage was varied from 2-20% by weight of zinc paint and electrical conductivity was determined. The solvent percentage was also varied in the mix to achieve the desired consistency.

[00072] A total of three 200x100x20 mm plastic board specimens (102) were used for each mixing ratio. Four strips of dual conductive copper tape (106) (10 mm wide) was fixed on each plastic board after coating it with Concrete CAP (104) each acting as an electrode. Strips (106) were placed 20 mm apart and 35 mm from the edge of the board. All specimens (102) were coated with two layers of Concrete CAP coating (104). Conductivity is inversely proportional to resistivity. Thus, the resistance (R) was measured by applying a DC power supply (denoted as "DC" in Fig. 1) between the two outer strips (106) and measuring the voltage generated between the two inner strips (106) using a voltmeter and calculating the resistance in accordance with Ohm's law, as shown in Fig. 1. Bulk resistivity was then calculated from resistance values. The conductivity of sample is inversely proportional to resistivity, i.e. lower the resistivity, higher the conductivity.

BOND STRENGTH

[00073] The objective of the bond strength test was to obtain bond strength between Concrete CAP composite coating and the concrete surface initially, immediately after curing of coating and then after exposure to extreme environmental condition. The bond strength test was carried out using Elcometer 106/6 Adhesion equipment. Concrete cubes of size 100x100x100 mm were cast for the test. The substrate was cured in potable water for 28 days then, allowed to air dry for at least a month prior to coating and pull-off tested as recommended by ASTM D7234 -12. After the completion of the coating, a metallic disc of 20 mm diameter was attached to the specimens by using epoxy. The bond strength test was performed after full curing of the epoxy resin i.e. after 24 hours. The bond strength was evaluated using the pullout test method, in which the anode overlay was pulled to determine its bond with the substrate. The pull-off force was manually applied on the disc until the failure of the bond was achieved.

Both failure load and failure mode were recorded and analysed.

PERMEABILITY PROPERTIES OF COATING

[00074] Permeability property of coating was measured in terms of water absorption and water vapour transmission as per BS 1062-3 and BS EN ISO 7783 standards, respectively. For water absorption, concrete specimens of 100 mm diameter and 50 mm thickness were cured for 28 days, coated on one side only and then initial conditioned as per BS 1062-3 standard.

Before conditioning, edges and reverse sides of the specimen were sealed against water by two-component epoxy resin. Specimens were subjected to three cycles comprising of 24h storage in potable water at 23 ± 2°C, followed by 24 hr drying at 50 -± 2°C. Specimens were then stored at 50 ± 2°C for 24h after last cycle and finally conditioned in atmosphere for another 24h at 23 ± 2°C and 50 ± 5% relative humidity. The specimens were then placed in water with the coated surface facing the water side and weight gain was measured for 24h at frequent intervals after placing the specimen in water. The water absorption rate was then computed.

[00075] The conductive coating being a non-self-supporting coating, was applied on the porous substrate and tested for water vapour transmission using cup method. The cup was filled 30 with water and the amount of moisture lost through the coating covering the mouth of the cup was measured by subsequent weighing as per BS EN ISO 7783-2 standard.

POLARIZATION TEST

[00076] The principle of this test was to assess the performance of the anode for ICCP system installed on reinforced concrete elements.

[00077] Tests were carried out on various reinforced concrete geometries with different steel and concrete ratios. The conductive coating was applied on a top face of each specimen after surface preparation. Specimens were tested for different exposed conditions i.e. atmospherically exposed at 50 ± 5% relative humidity and partially submerged condition for varied constant current densities. For initiating cathodic protection current in the specimen, negative terminal of the power supply was connected to the steel bars and positive terminal to the primary anode conductor. The polarization and depolarization behaviour of steel in concrete specimens were recorded every minute using a computerized data logger. The polarization recorded was 'ON' potentials when the system was energised. The constant current density was supplied for 5-7 days for each current level, and the polarization characteristics were recorded. Specimens were polarized until steel/concrete/reference electrode potential becomes nearly constant and then, the system was powered off and "Instant-OFF" potentials were recorded for a 24-hour period, at 1-minute interval. The final depolarization was then analysed to determine whether protection criterion has been met in accordance with BS EN ISO 12696:2016 standard i.e. 'Instantaneous OFF' potential more negative than -720 mV (vs Ag/AgC1/0.5M KU) or 100 mV decay criterion over a maximum of 24 hours.

[00078] Different concrete geometries on which Concrete CAP performance was assessed are described below: [00079] Fig. 2 illustrates an exemplary schematic representation of the anode system in accordance with an embodiment of the present invention. The first test was carried on 200x200x70 mm slab with steel and concrete ratio and steel and anode ratio of 0.28:1. Two ribbed steel bar of 10 mm diameter with allowance for 50 mm cover were embedded in the slab. The exposed length of the steel bar in contact with concrete inside the specimen was IOU mm. The exposed end of each rcbar outside the mould has been covered with a heat-shrink sleeve to protect it from corrosion when the specimens were placed in water and/or salt solution. Each specimen contains one miniaturized mixed metal oxide/titanium (MMO/T 0 and one Ag/AgC1/0.5M KCI reference electrode to monitor steel/concrete/reference electrode potential, as shown in Fig. 2. Tests were carried out in atmospherically exposed conditions at ± 5% RH at two different constant current densities, i.e., Sand 20 mAlm2 of steel surface area.

[00080] The second set of experiment was carried out on 120 x 330 x 3000 mm long beam with steel and concrete ratio of 0.28:1 and steel and anode ratio of 1.05:1. Beam geometries are shown in Fig. 3.

[00081] Four ribbed steel bars of 10 mm diameter were embedded in concrete with 25mm cover. The exposed length of the steel bar in contact with concrete inside the specimen was 2950 mm. The exposed end of each rebar outside the mould has been covered with a heat-shrink sleeve to protect it from corrosion when the specimens were placed in water and /or salt solution. Each specimen contains thirteen miniaturized mixed metal oxide/titanium (MMO/Ti) and two Ag/A8C1/0.5M KC1 reference electrode, placed at different locations along the reinforcements to monitor steel/concrete/reference electrode potentials. MMO/Ti reference electrode was placed at every 500 mm near both top and bottom steel bars along beam length.

[00082] Primary anode conductor was placed along the length of the beam. Tests were carried in atmospherically exposed conditions at 50 ± 5% RH at two different constant current densities, i.e., 10 and 20 mA/m2 of steel surface area and in partially submerged conditions at 20 and 30 mA/M2 current density per steel surface area.

[00083] The last set of experiment was canied out on 750 x 750 x 70 mm slab with steel and concrete and steel and anode ratio of 0.75:1. Slab geometry is shown in Fig. 4. Welded wire mesh grid of 710 x 710 mm with an aperture size of 1 lmm and diameter of 1.6 mm was embedded near the top of the slab on one side of 750 x 750 mm side to act as a cathode. Side cover was 20 mm and spacing between anode and wire mesh grid was 32 mm. Each specimen contains twelve miniaturized mixed metal oxide/titanium (MMO/Ti) and three AglAgC1/0.5M KC1 reference electrode, placed at a distance of 180mm along both the directions to monitor steel/concrete/reference electrode potentials. Primary anode conductors were placed at three locations i.e. 50 mm, 375 mm and 700 mm.

[00084] Tests were carried in atmospherically exposed conditions at 50 ± 5% RH with one, two and three primary anode conductors connected to the power supply at a time during testing. Tests were caried out for two different constant current densities, i.e. 10 and 20 mA/m2 of steel surface area.

DURABILITY TEST

1000851 The main aim of this part of the experimentation was to assess the performance and durability of the Concrete CAP conductive coating as an anode for the ICCP system under simulated extreme environmental conditions, particularly the effect of changing temperature and relative humidity.

[00086] Three concrete cubes of 100x100 x100 mm were cast with one steel bar of 10 mm diameter and exposed reinforcement (612) having a length of 80 mm. Each specimen (602) also contains one miniaturized mixed metal oxide/titanium (MMO/Ti) reference electrode (604) to measure steel/concrete/reference electrolyte potential during the test. All the connections were insulated with heat-shrink sleeves (606). Two adjacent surfaces of the specimen (602) were coated with the Concrete CAP coating (608). One surface was used for testing bond strength before the exposure to severe environmental conditions and the other face after the exposure. Primary anode conductor (610), i.e., platinum clad wire, was placed on the second face for cathodically polarizing the steel during exposure, as shown in Fig. 5. Specimens were then exposed to cyclic wet, dry and humidity conditions with frequent salt sprays in between cycle in laboratory environmental chambers in order to simulate aggressive outdoor conditions such as the marine environment. The exposure cycle was chosen as per BS EN ISO 11997-1 7i.c. 60°C and 0% RH for 3hrs and then 50°C and 95% RH for next 5hrs. Test cycle was repeated for total of 90 cycles i.e. 720 hours.

1000871 The specimens were polarized at a constant current density of 20 mA /m2 throughout the exposure cycles and both polarization and depolarization behaviour were monitored. The bond strength between coating and concrete was then tested after the exposure to check an effect of extreme environmental conditions on the bond strength between coating and concrete surface, which is the main reason of failure for conductive coating anodes currently available in the market.

SERVICE LIFE TEST

[00088] The principle of this test is to get an indication of anodes ability to perform satisfactorily for a specific number of years. The test was performed in accordance with NACE TM0294 standard. The accelerated test requires passing high current from anode to steel, which 30 may lead to its premature failure, thus test was performed in an aqueous solution. A 20x20x20 mm Concrete CAP block with Anomet platinum clad wire at the centre of the block for electrical connection was cast by filling the mould with paint and then oven-dried at 40°C and used as an anode. The anode area was approximately 20 cm= after drying. For the cathode, 12.7 mm diameter titanium rod was used. Test cell used was a beaker fitted with a rubber stopper at the top to hold the electrodes and reduce air contact. Ag/AgC1/0.5M KC1 was used as a reference electrode and a 3% NaCl solution was used as an electrolyte. Two additional holes were located on the stopper, one to vent gases away from the electrical connection and another to measure the pH of the test solution.

[00089] The anode was polarized at a constant current of 17.8 mA as per standard.

Parameters such as cell voltage, cell current, anode potential vs AglAgC110.5M KC1 reference electrode and pH of the electrolyte were recorded until anode failure which is marked by a rapid escalation in both cell voltage and anode potential. The time of failure is recorded when the anode potential increased by 4.0 V above its initial value.

M1CROSTRUCTURAL STUDY [00090] The field-emission scanning electron microscope (FE-SEM) analysis was performed to study the distribution of two components in the Concrete CAP at an accelerating voltage of 15-20kV. Samples were taken from polarization specimens after the test, grinded, cold mounted and polished before the test. The microstructures of the prepared samples were examined using secondary electron (SE) in a Zeiss Gemini Sigma 500VP scanning electron microscope (SEM).

EXPERIMENTAL RESULTS

SELECTION OF HIGHLY CONDUCTIVE MATERIAL

[00091] To improve zinc rich paint property, a variety of highly conductive carbon based materials were tested for their incorporation with zinc. The selection was made based on its electrical conductivity and bond strength properties. The materials tested include carbon black, coke breeze and graphite powder. The comparison of various formulation is shown in Table 2 below. It was observed that graphite powder performed best among the tested materials and was further tested in detail.

Conductive Material Electrical Resistivity (kohm-cm) Bond Strength (MiPa) Zinc 5377 2.7 Zinc + Carbon Black 26 2.7 Zinc + Coke Breeze 21 2.9 Zinc + Graphite Powder 14 3.0 Table 2: Comparison of addition of different conductive materials on zinc rich paint properties

ELECTRICAL CONDUCTIVITY

[00092] Figs. 6A and 63 illustrate exemplary charts showing electrical resistivity of different conductive coating anodes in accordance with an embodiment of the present invention. Electrical conductivity was selected as the primary analysing parameter to decide the percentage of graphite to be mixed with the zinc paint. Various combination of graphite content was mixed with zinc paint along with solvent to achieve maximum conductivity. It was observed that the electrical conductivity of the Concrete CAP is highly dependent on graphite content.

[00093] Fig. 7 illustrates an exemplary chart showing the effect of graphite percentage content on conductivity of the conductive coating/conductive anode paint of the anode system. Observation of the logarithmic plot from Fig. 7 shows a steep increase in conductivity within the range 5-10% graphite.

[00094] When the graphite content was increased from 10-12% the conductivity of the paint only increases slightly. The minimum electrical resistivity was achieved with Zinc paint + 12% graphite + 5% solvent. However, the consistency of the paint was thick, making it difficult for application. Considering ease of application and minimum resistivity, zinc paint with 10% graphite and 10% solvent was selected as the final mix proportion for the Concrete CAP. The resistivity at this mix was about 99.7% lower compared to zinc paint without any graphite. This low resistivity was achieved with two coats of paint.

1000951 Zinc paint with no or low level of graphite showed almost similar resistivities. Zinc particles in zinc paint are isolated from each other. As graphite content is increased beyond 5%, graphite particles improve electrical contact between zinc showing a sharp increase in the conductivity at a certain critical concentration called as the percolation limit. Here this can be observed in the region 5-10% graphite, where a relatively small increase in the graphite shows a large increase in conductivity. The relative distance between the conductive particles reduce drastically, some even have direct contact, which facilitates electron transfer, giving rise to high conduction. This can be observed from SEM micrographs, as illustrated in Fig. 8. For Zinc paint with 10% graphite, needle-shaped graphite fibres could be observed connecting the zinc particles making it highly conductive. As observed, the average size of zinc particles varies from 3-7 frtm.

[00096] Beyond the critical concentration, rate of increase in the conductivity with increasing graphite content occurs at a much slower rate, because in this region, the increase in graphite concentration simply signifies an increase in the number of networks formed.

PERMEABILITY PROPERTIES OF THE COATING

[00097] Table 3 shows water absorption rate of the Concrete CAP coating. The water transmissibility of coating was found to be 0.0016 kg/m2.h", which was 14% lower as compared to concrete without coating and classed as W3 i.e. low permeable coating as per BS EN 1062-1:2004 standard. The water transmissibility of coating was found less than 0.1 kg/m2.11", hence as per BS EN 1504-2:2004 standard, coating restricts diffusion of chloride ions and capillary water absorption.

Sample Water Absorption Water Vapour Transmission (WVT) Rate (kg/ire/ski) VVVT Rate g/m2/11 Equivalent air layer thickness, so (m) T_Incoated sample 2.1/10-4 Coated sample 1.6/10 1.26 0.68 Table 3: Water absorption rate for Concrete CAP coated and uncoated sample 1000981 Performance of coating is also affected by its capability of aiding or restricting the passage of water vapour. For Concrete CAP coating, water vapour transmission rate was found to be 1.26 g/m2./hr with an equ i val cnt layer thickness (s0) of 0.68m. Hence coating comes under class 1 (sip< 5m) coaling and is permeable to water vapour as per BS EN 1504-2:2004 standard. Thus, Concrete CAP coating allows moisture to evaporate and thus prevents long term disbondment and premature failures.

POLARIZATION TEST

[00099] Figs. 9A and 9B show polarization and depolarization behaviour evaluation of the Concrete CAP coating with two different applied current densities, i.e. 5 and 20 mA/m2 per steel surface area.

[000100] As observed, steel/concrete/reference electrode potential rise increases with increase in applied current density. Furthermore, from Fig. 11B, it may be observed that the average 4-hour and 24-hour decay increases as polarization current density increases. All the specimens met the BS EN ISO 12696:2016 standard and 100mV decay polarization criterion when polarized with 20 mA/m2 of current density per steel surface area. About 150 my (vs AglAgC1/0.5 M KC1 steel/concrete/reference electrode) potential decay was observed in 24 hours. Moreover, the as-found voltage was approximately 2V. The as-found voltage also increases with increase in applied current density. After depolarizing samples with 5 mA/m2, passivation was not reached, thus not affecting the interpretation of 20 mA/m2 current density. The required current density for Concrete CAP anode was found to be within the permissible limit of ICCP system for old structures as prescribed in BS EN ISO 12696:2016 standard.

[000101] To assess the performance of Concrete CAP on the actual size of beams used on sites, polarization test was performed on life size concrete samples, i.e. beam samples sized (120 x 330 x 3000 mm). Two cases were studied based on exposure conditions i.e. atmospherically exposed and partially submerged conditions.

[000102] For atmospherically exposed conditions two constant current densities were applied i.e. 10 and 20 mA/m2. Tests were carried out with one end and two ends of primary anode conductor (at two extreme beam ends) connected to the power supply to determine number of connections required to primary anode conductor. Polarization and depolarization behaviour are shown in Fig. 10. Pre-energization potentials showed all the bars were in active corrosive state.

10001031 As observed, for top bars to satisfy BS EN ISO 12696:2016 standard protection criterion, both ends of the primary anode conductor were required to be connected with the power supply. Moreover, 20 mAltn2 of current density per steel surface area was required to provide full protect to the steel bars. When specimens were polarized for 20 mA/m2 current density with just one end of the primary anode conductor connected to the power supply, steel/concrete/reference electrode potential decays vary from 80-150 mV along top reinforcement at different points. Bottom bars did not meet the decay criterion. However, when the conductor is connected at two extreme ends, for the same applied current density, all monitoring points on the top reinforcement met the decay criterion. No change in steel/concrete/reference electrode potential decays was observed for the bottom reinforcement potentials. As-found voltage dropped to by from 15V. Due to higher depth of the beam specimens, bottom bars did not satisfy the polarization criterion, as expected and required anode to be applied at more faces.

[000104] Specimen were also tested in partially submerged condition with the bottom two bars completely submerged in salt solution and top two bars exposed to the atmosphere. The constant current density of 20mA/m2 per steel area was applied first and then increased to 30 mA/m2 with both ends of conductor connected to positive terminal of power supply.

Polarization and depolarization data are plotted in Figs. 11A and 11B.

[000105] It was observed that, on submerging the specimen in water, pre-energization potentials increased, moving steel to more active corrosive state. When specimens were polarized for 20 m Alm2 current density steel/concrete/reference electrode potential decays vary from 50-120 mV along top reinforcement at different points and 20-40 my for bottom bars.

No bar satisfied the decay criterion. Thus, specimens were polarized for higher current density.

As observed from the graph, when constant current density of 30mA/m2 was applied, all reference electrodes on the top bar satisfied 100 mV decay criterion, however, no major change in steel/concrete/reference electrode potential was observed for bottom bars. This may be due to the submerged condition of the bottom bars, creating conditions for limiting oxygen state.

The as-found voltage varies from 3-4 V and dropped compared to atmospherically exposed conditions. This may be due to reduced resistivity of concrete in submerged conditions, allowing easy passage for ionic mobility.

[000106] Thus, the Concrete CAP anode performed well in both atmospheric and partially submerged conditions, satisfying BS EN 12696:2016 standard polarization criterion within the prescribed application of constant current density. However, higher current density is required for submerged conditions, as a result of higher initial corrosion rate. Moreover, as-found voltage remains within the limits.

[000107] The Concrete CAP anode performed satisfactorily when applied to life size corroded reinforced concrete beams. The applied current density remains within the limit as prescribed in BS EN ISO 12696:2016 standard.

[000108] To test anode performance for concrete structures having higher steel to concrete ratio, anode test was performed on a large slab having a dimension of 750 x 750 x 70 mm. Primary anode conductor was placed at different location to monitor current throwability. All the tests were performed in atmospherically exposed condition with one, two and three conductors connected to the power supply at a time. Initially, the test was performed with one conductor at two different current densities i.e. 10 and 20 mAlm2. Followed by connecting two and three conductors. Polarization and depolarization behaviour is shown in Figs. 12A and 12B. Pre-energization potentials show wire mesh was in corrosive state before application of current density.

[000109] It was observed that for all the cases 100mV decay criterion was satisfied. All the reference electrodes placed at different locations satisfied the criterion. Even only 10 mAlm2 of applied current density satisfied the polarization criterion. However, the major difference was observed in terms of as-found voltage. When two extreme end conductors were connected, as-found voltage was found to be optimum i.e. 9V, compared to 13V when one conductor was connected. However, no major difference was observed when three conductors were connected. Thus, to maintain the as-found voltage low, primary anode conductor should be placed after every 0.75-1.0m when the Concrete CAP anode is applied.

[000110] Finally, the test was repeated after applying the top coating, to monitor the effect of application of topcoat over the Concrete CAP. Results are shown in Figs. 12A and 12B. As observed, specimens still satisfy depolarization criterion, and no major difference was observed in the depolarization values. However, as-found voltage increased by 4.0V but still remains lower than the recommended values.

[000111] Thus, the Concrete CAP anode perfoimed well even for reinforced concrete with high steel to concrete ratios. The applied current density remains within the limit as prescribed in BS EN ISO 12696:2016 standard. Moreover, the as-found voltage remains low.

Furthermore, primary anode conductor needs to be placed at every 0.75-1.0m.

DURABILITY TEST

[000112] Fig. 13 shows potential values of the anode as a function of experimental time 1.e. 30 days respectively. It may be observed that humidity plays a strong influence on anode performance. The constant current was maintained for 25 days, and then starts to shift till end of the exposure cycle.

[000113] From the polarization graph, it is evident from pre-energization steel/concrete/electrode potential that steel embedded in concrete presented active corrosion behaviour (>-250 mV vs AgrAgCl). Once the constant current is switched on steel/concrete/electrode potential continues to move in negative direction, reaching -400 mV ("ON" potential) in 30 days i.e. at the end of 90 cycles a potential rise of 170 mV was observed.

This shows effectiveness of the Concrete CAP anode for protecting corroded steel bar in the impressed current mode.

[000114] In accordance with exposure cycles, it can be clearly observed that sled/concrete potential changes as environment changes from dry to wet. During dry stages (high temperature and no humidity), lhe steel/concrete potential drops by 20-30 mV during initial days of exposure. This drop continued to increase with time, and 100-120 mV drop was observed during end of exposure cycles. The steel/concrete potential reached as high as -280 mV at last dry cycle. In contrast, during wet stages (low temperature and 95% humidity), steel/concrete potential reverted back to its initial potential before dry stage and increased with time reaching as low as -400 mV at last wet stage. This may be due to reduced concrete or anode resistivity during welling cycle, making it more electrically conductive and increased ionic mobility. Hence, this behaviour shows anode performance is dependent on environmental conditions, making it more effective during wetting.

[000115] Fig. 14 shows as-found voltage during polarization of the corroded reinforced concrete samples. The voltage drops during the wet stage and rises during the dry stage of exposure cycle. At the end of polarization period, voltage rises as high as by 5V. The voltage difference between dry and wet stages increases from IV at early exposure cycle to by 2V at end of exposure period. This shows increased resistance of anode/concrete. Also, some white products were observed at the anode surface, which is believed to be zinc oxidation products, also formed at zinc-concrete interface. Formation of these products increases the required as-found voltage with time and current requirement by anode. However, il can be seen thal this has not affected anode performance even after 90 cycles of exposure and sufficient polarization was achieved to protect corroded steel, as observed in depolarization graph, as shown in Fig. 15).

[000116] Evaluating the rebar depolarization and measuring "OFF" potential after 24 hours, potential decay of 290 mV was achieved (100 mV), thus, satisfying BS EN ISO 12696:2016 standard criterion of ICCP anode. Thus, anode performed satisfactorily when operated at 20 mA/m2 of constant current density to protect corroded reinforced concrete exposed to accelerated environmental conditions.

[000117] The bond test was carried out at the end of durability testing to determine anode-failure after exposure to aggressive environment. This is because de-bonding is one of the main reasons for failure of existing commercially available conductive anode paints.

[000118] Both failure load and failure mode were recorded in this test. The average pull-off failure stress obtained after durability testing i.e. passing about 50 kCilm2 of charge in extreme environmental conditions, the pull-off strength increased by 20% reaching 3.0 MPa.). This may be due to the formation of zinc oxidation products at anode-concrete interface. However, for both cases, the observed bond strength is greater than the required value of 1.5 MPa (for flexible systems with trafficking) and 2.0 MPa (for rigid systems with trafficking) recommended by BS EN 1504-2:2004 standard. Thus, the anode paint used satisfies the bond strength requirement.

The pull-off strength of Concrete CAP anode was 17% and 50% higher than thermally sprayed zinc before and after exposure (after 50kC/m2).

[000119] The detailed failure mechanism is given in Table 4. As observed, the main failure was within the substrate for both cases giving high bond strength.

Specimen Temee) RHeu, tubstrate DM' rt,,, Failure Area of Fracture (%) No. (%) (°C) (pm) 0413M Type I 20.0±1.0 60.0+2.0 24.0+0.25 319 2.5 A, WC A = 90,131C = 10 2 24.0+0.25 314 3.0 A, WC A= 98,131C = 02 * Te",. ('C) = environmental temperature RI-L", (%) = enviromnentkl relative humidity, Tyabs,.., CC) = substrate temperature, DPI' (i.tm) -dry film thicla ess, Gay (MPa) -average pull-off stress, A -failure occurring within concrete substrate, AiLi= failure between concrete substrate and coating, BIC = inter-coat failure, -IY = failure between adhesive and coating Table 4: Bond strength and failure type of specimens before and after exposure to aggressive environment

SERVICE LIFE

[000120] Anode was polarized at a constant current of 17.8 mA until anode failure, which is marked by an increase of anode potential by 4.0 V above its initial value. Total time of polarization before failure was 32 days. After 32 days, a sudden jump in anode potential was observed, which marked failure of the anode. Moreover, the pH of the test solution changed from 8.5 to 11.8 during the polarization period, indicating formation of oxides or hydroxides. Also, after end of 32 days, about lOg of anode was consumed.

[000121] Using the obtained data and equation Q=it, where Q is the total amount of charge passed, i is applied current density and is time, it can be estimated that when the anode is operated at 20 mA/M2 current density, it performs satisfactorily up to approximately 40-45 years. The typical service life of paint anode system is 15-20 years. Hence, Concrete CAP has service life more than any currently available waling anode systems in the market.

[000122] In operation, permeability results shows zinc-rich paint coating to be water vapour permeable, thus preventing long term disbondment and premature failure. The polarization results illustrate the satisfactory performance of the anode system for the specimens with different steel to concrete ratios. The experimental results satisfy 100 mV depolarization criterion i.e. criterion (b) of BS EN 12696 standard.

10001231 The proposed anode system is highly durable in extreme aggressive conditions and is capable of maintaining its higher bond strength with a substrate compared to conventional carbon based conductive coating anodes. The service life of the anode system was estimated from the accelerated service life test to be 40-45 years, i.e. higher than any available traditional carbon based conductive coating or thermally sprayed zinc anodes operated at 20 mA/m2 current density. The claimed conductive coating of the anode system for ICCP applications has lower carbon footprint than conventional carbon based conductive coating anodes and thermally sprayed zinc anodes.

10001241 While embodiments of the present disclosure have been illustrated and described, it will be clear that the disclosure is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the disclosure, as described in the claims.

Claims (25)

1. We Claim: I. A conductive coating anode for impressed current cathodic protection of a reinforced concrete structure, comprising zinc and an electrically conductive carbon base material in the ratio of 9.6:1 by weight, wherein said conductive coating anode is applied to a concrete surface of the reinforced concrete structure to form a durable matrix with the concrete surface and supports flow of a protective current to the concrete surface.
2. 2. The conductive coating anode as claimed in claim 1, wherein the carbon base material is graphite.
3. 3. The conductive coating anode as claimed in claim 1, wherein the conductive coating anode contains 80-95% zinc by weight.
4. 4. The conductive coating anode as claimed in claim 1, wherein the conductive coating anode contains 5-10% graphite by weight.
5. 5. The conductive coating anode as claimed in claim 1, wherein the conductive coating anode contains 5-10% solvent by weight.
6. 6. The conductive coating anode as claimed in claim 1, wherein the conductive coating anode is applied to the concrete surface by any of a roller, brush or a spray gun.
7. 7. The conductive coating anode as claimed in claim 1, further comprising aromatic hydrocarbons and binders.
8. 8. An Impressed Current Cathodic Protection (ICCP) system for protection of a reinforced concrete structure (102, 202, 602) from corrosion, the ICCP system comprising: an anode attached to the reinforced concrete structure; and a direct current (DC) power supply connected to the anode to deliver a voltage thereto, wherein the anode has a conductive coating (104, 204, 608) forming a durable matrix with a concrete surface of the reinforced concrete structure (102, 202, 602), wherein the conductive coating (104, 204, 608) comprises zinc and an electrically conductive carbon base material in the ratio of 9.6:! by weight, and supports flow of a protective current from the anode to one or more metallic members of the reinforced concrete structure (102, 202, 602).
9. 9. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) is applied to the concrete surface without thermal treatment.
10. 10. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) is applied to the concrete surface by any of a roller, brush or a spray gun.
11. 11. The ICCP system as claimed in claim 8, wherein the carbon base material is graphite powder having a particle size of less than 53 pm.
12. 12. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) contains 80-95% by weight zinc.
13. 13. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) contains 5-10% by weight graphite.
14. 14. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) contains 5-10% by weight solvent.
15. 15. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) of the anode is over-coated with a thin layer of paint for decorative finish.
16. 16. The ICCP system as claimed in claim 8, wherein the anode includes platinum clad wire (206) installed as a primary anode conductor and covered with a suitable robust fabric material such as carbon fibre mat (208).
17. 17. The ICCP system as claimed in claim 16, wherein the platinum clad wire (206) is mounted in 2-3 mm wide and 1 mm deep rills grooved into the reinforced concrete structure (102, 202, 602).
18. 18. The ICCP system as claimed in claim 8, wherein the conductive coating (104, 204, 608) includes at least two layers of coating having dry film thickness ranging from 200 pm to 350 25 pm.
19. 19. The ICCP system as claimed in claim 8, wherein the platinum clad wire (206) is connected to a direct current (DC) power supply.
20. 20. The ICCP system as claimed in claim 8, wherein the conductive coaling (104, 204, 608) is anodically polarized and the one or more metallic members the reinforced concrete structure (102, 202, 602) are cathodically polarized.
21. 21. The ICCP system as claimed in claim 8, wherein the anode system is applied with a current density ranging from 0 to 50 mAlm2.
22. 22. The ICCP system as claimed in claim 8, wherein the conductive coating (104, 204, 608) has an electrical resistivity in the range of 1-15 kohm-cm.
23. 73. The ICCP system as claimed in claim 8, wherein water vapour transmission rate of the conductive coating (104, 204, 608) is 1.26 g/m2/hr with an equivalent layer thickness (sD) of 0.68 m.
24. 24. The ICCP system as claimed in claim 8, wherein water transmissibility of the conductive coating is less than 0.1 kg/m2.h".
25. 25. The ICCP system as claimed in claim 8, wherein water transmissibility of the conductive coating is 0.0016 kg/m2.h".