BIPOLAR CONCRETE PENETRATING CORROSION INHIBITORSEPCO®KP-200 Bipolar Concrete penetrating corrosion inhibiting admixture USES For protection of reinforcement against chlorides. As an admixture to concrete for protecting reinforcement steel in structure exposed to aggressive corrosion like marine structures, foundations, jetties, docks, mooring berths, bridges, sewerage systems, chlorinating plants, chimneys, cooling towers, power plants, refineries & buildings. PROPERTIES EPCO-KP-200 is a hi-tech corrosion inhibitor system that works on the Bipolar Inhibition Mechanism (B.I.M) which inhibits corrosion of steel in concrete at both the poles. Safe to concrete, safe to environment. Conforms to RDSO Specifications. EPCO®KP-100 Surface applied bipolar concrete penetrating corrosion inhibitor USES In repairs and rehabilitation of concrete structures, to protect the embedded reinforcement against chlorides. Also for structures and foundations exposed to salinity. PROPERTIES When surface applied it diffuses through the concrete by virtue of its affinity for steel Corrosion Control: From the literature survey and case studies it has been reported that 40% of failure of structures is on account of corrosion of embedded steel reinforcement in concrete. Therefore corrosion control of steel reinforcement is a subject of paramount importance. First and foremost for corrosion control is the good quality of concrete through good construction practices. It is a very vast subject touches the fundamentals of choosing constituents material and good rules to be followed during various stages or production of concrete, in particular the use of lowest possible water/cement ratio having regard to workability. In view of the general availability of superplasticizers, it should be used to cut down the W/C ratio to make dense concrete. Proper mix design, use of right quality and quantity of cement for different exposure conditions is to be adopted. Recently it has been realized that lower W/C ratio which has been always associated with lower permeability is not enough to make impermeable concrete contributing to high durability. Use of supplementary cementitious materials such as fly ash, ground granulated blast furnace slag (ggbs), silica fume etc. are required to be used as admixtures or in the form of blended cement in addition to lowest possible W/C ratio to make concrete dense. These materials improve more than one properties of concrete, which will eventually reduce corrosion of reinforcement. Tests on mortar containing ggbs have shown that water permeability is reduced 1. It is also reported that 60 per cent ggbs educed the diffusion of chloride ions into the concrete by as much as 10 times. the most widely used admixture is based on calcium nitrite but have proved to be deleterious at high chloride concentrations. which are responsible for reducing corrosion of steel reinforcement. This demands certain other measures to control the corrosion of steel reinforcement. They are widely used in many industries to effectively reduce the corrosion rate of steel and other metals. Chloride removal 6. Commercial products for the control of corrosion of steel reinforcement in atmospherically exposed concrete were first produced in the 1970's. Metallurgical methods 2. particularly. Of the available materials. Different methods such as rapid quenching of the hog bars by series of water jets. It is added to the concrete during mixing of concrete.2 Corrosion inhibitors: Corrosion inhibitors. which come in powder.2.by a factor up to 100. phosphates. It is always not possible to make such ideal concrete. They are listed and briefly explained. which retard the corrosion reaction at the anode: Corrosion can be prevented or delayed by chemical method by using certain corrosion inhibiting chemicals such as nitrites. The typical dosage is of the order of 10-30 litres per m3 of concrete depending on chloride levels in concrete. retard the rate of the corrosion reaction. 3. They can be introduced into the concrete mix at the time of construction/ repair or (in a suitable formulation) applied to the surface of an existing concrete structure. Coatings to concrete 3. Coatings to reinforcement 4.1 Metallurgical Methods: Steel can made more corrosion resistant by altering its structure through metallurgical processes. Cathodic protection 7. Silica fume contributes to the all-round improvements in the quality of concrete. the problems become more serious. The improvement in the microstructure of hydrated cement paste is ultimately responsible for protecting the steel reinforcement from corrosion. There are three main types of inhibitors: 3. There are many situations where stainless steel reinforcements are used for long term durability of concrete structures. it will be durable by itself and also it can take care of the reinforcement contained in it o a great extent. in view of the complex environmental and exposure conditions.1 Anodic inhibitors. Further the inherent long term drying shrinkage and micro cracks in concrete. and by such other process the mechanical properties and corrosion resistance property of steel can be improved. They increase the time to the onset of corrosion and then act to reduce the rate of corrosion. In short it can be said that if we make good concrete with low permeability and improved microstructure. Corrosion inhibitors 3. . Re-alkalization 5. benzoates etc. or by keeping the hot steel bars for a short time in a water bath. At low dosage there is concern that they will suppress generalized corrosion but may fail to eliminate all anodic sites. gel and liquid form. They protect the steel at both the anodic and the cathodic sites. in the high pH of concrete. cracking and spalling to become apparent and several more years before deterioration occurs. the steel is protected by a passivating layer of ferric oxide on the surface of steel.7-kg/ m3 of chloride is present in the concrete at the rebar. it may take several years for staining. the passivating layer also contains some ferrous oxide. Migratory Bipolar Corrosion inhibitors are organic inhibitors. When you add 20-litres/ m3. Further more the inhibitor within the concrete matrix reduces the rate of chloride ion migration towards steel.7 kg/ m3. Calcium nitrite corrosion inhibitor comes in a liquid from containing about 30 per cent calcium nitrite solids by weight.3 Bipolar inhibitors They retard the corrosion process both at the anode and the cathode.2 Cathodic inhibitors Which retard the reaction at the cathode and seek to prevent oxygen reaching the reinforcing steel. By virtue of its high vapour pressure. At low dosages. which can initiate corrosion when the chloride ions reach the steel. Fig. the longer the onset of corrosion will be delayed. This is true even in dense concrete. The basic advantage of the product lies in the ease of use.2. However. Studies have proved that addition of these types of corrosion inhibitors has no deleterious effect on the properties of concrete. In this category organic Migratory bipolar corrosion inhibitors are the most widely used. Although the corrosion process starts when the threshold level is reacted. These combine the benefits of both anodic and cathodic inhibitors at relatively low dosages.2.Fig 10 Corrosion inhibiting effects of calcium nitrite As mentioned earlier. corrosion will not begin until over 7. 3. Concrete penetrating corrosion inhibiting admixture upon addition into the concrete matrix plays . thus stabilizing the passivating layer even in the presence of chlorides. The Bipolar corrosion inhibitor chemistry involves migration of its molecules by electron density distribution to both the anodic and 11 cathodic sites of the steel. The concentration of nitrite must by sufficient to cope up with the continuing ingress of chloride ions. The nitrite ions present in the corrosion-inhibiting admixture will oxidize the ferrous oxide to ferric oxide. 10 shows that without an inhibitor the reinforcing steel starts to corrode when the chloride content at the rebar reaches a threshold level of 0. It also dislodges previously absorbed chloride ions and water molecules on the steel surface. 3. use of less than 18 litres/ m3 of calcium nitrite solution is not recommended. Since most structures in a chloride environment reach a level of about 7 kg of chloride iron per m3 during their service life. This barrier coating then raises the chloride threshold concentration for corrosion. very high affinity and virtue of diffusion these inhibitors migrate towards the steel in concrete and get deposited in a monomolecular layer. Adding calcium nitrite increases this corrosion threshold. The more corrosion inhibitor is added. they are effective at reducing corrosion rates but are generally less efficient than the anodic type. 05 – 1. even with generic classifications.I.0 Dosage 3 kgs per cubic meter of concrete. ENV 1504-9 recommends application of Concrete penetrating corrosion inhibitors as a proven corrosion control strategy. pH Minimum 9. Effective even at higher temperatures. both as surface applied inhibitors and as admixed inhibitors.a major role in inhibiting the corrosion process. Concrete penetrating type.01 – 1. Eco-friendly. However it is Essential to carry out trial mix with desired admixtures along with Migratory Corrosion Inhibitor. Admixed inhibitors are used in the fresh mortar/concrete being placed for strengthening the structure.6205 standard Specification for Admixed corrosion inhibitor Base Bipolar Organic inhibitor. The principle of most inhibitors is to develop a very thin chemical layer on the surface of the reinforcement. Tropical Compatibility: Material shall have evaluated test reports indicating significant reduction in corrosion rate after minimum of 90 thermal cycles at 60oC followed by 8 weeks of accelerated corrosion. The European Committee for standardization (CEN) pr. pH Minimum 9. Surface applied inhibitors are used by spraying on the complete surface of the structure being repaired so that protection to the unexposed reinforcement is taken care of. Specification for surface applied Corrosion inhibitor Base Bipolar Water based Organic inhibitor.6205 from reputed laboratories like CSIR & I. (Linear polarization method) The inhibitor shall be non-toxic & safe to plant and human life. However. Effect on concrete No adverse effect on physical properties in fresh & hardened concrete in properties the absence of any other admixtures. They are available.6205 Should pass tropical climate test (thermal cycles) Acceptance Criteria: Migratory Bipolar Corrosion Inhibitor should be tested as per ASTM-G-109/ JIS . Colour Brownish Specific Gravity 1.T. Two codes available internationally for testing these types of inhibitors are ASTM G 109 & JIS A 6205. SHRP-S-666 (Strategic Highway Research Programme) has recommended these types of corrosion inhibitors for concrete structures subjected to chlorideinduced corrosion. There is a very wide range of corrosion protection performance from different inhibitor formulations. Eco-friendly.08 at 25o C Viscosity at 250C 11-12 sec by Ford B4 Cup. As the true effect of an inhibitor can only be evaluated from corrosion rate measurements before and after application and by reference to a control area. such systematic evaluations are lengthy processes and are in their early stages.02 at 25o C Viscosity at 250C 11-12 sec by Ford B4 Cup. Cycles Evaluation Should pass ASTM-G-109 standard & JIS . Evaluation Should pass JIS . such evaluations need to be representative of field concretes and conditions. Compatibility for Compatible for higher thermal cycles No deleterious effects Higher Thermal even at high temperature. Independent evaluation and certification of performance is desirable.5 Dosage To be sprayed at the rate of 4m2 / ltr Toxicity Non-toxic . Concrete penetrating type. . Toxicity Non-toxic. General Building Corporation of Japan has evaluated this product in concrete extensively and has reported rebar life extension by six times. Colour Colorless Hazy liquid Specific Gravity 1.