Migratory Type Corrosion Inhibitor for Preventing Corrosion in Reinforced Concrete

Abstract

In general, reinforced concrete has proved to be successful in terms of both structural performance and durability. However, there are instances of premature failure of reinforced concrete components due to corrosion of the reinforcement. The two factors provoking corrosion are the ingress of chloride ions from deicing salts or sea water or the reaction of the alkaline pore solution with carbon dioxide from the atmosphere, a process known as carbonation. A number of techniques are available for the prevention of corrosion. Despite of the huge demand, a simple, cheap, and reliable technique which either protects the steel from corrosion or at least lowers its corrosion rate is still lacking. Over the past decade, however, concrete repair industry has developed novel techniques that are claimed to prevent or at least reduce corrosion of steel in concrete. The use of the “corrosion inhibitors” is of increasing interest as they can be used in reinforced concrete either as preventive measure for new structures (addition to the mixing water) or as surface applied inhibitors for preventive and restorative purpose. Addition to the mixing water does not require any additional working steps and allows a simple handling of the inhibitor, unless it affects the properties of the cement paste adversely. Application from the concrete surface could be a promising technique to protect already existing structures from corrosion or increase the lifetime of structures that already show corrosion attack. The application of inhibitors on the concrete surface requires the transport of the substance to the rebar where it has to reach a sufficiently high concentration to protect steel against corrosion or reduce the rate of the ongoing corrosion. This thesis investigates the effectiveness of migrating type corrosion inhibitors on the concrete slabs made with different water-cement ratios. Therefore effectiveness of corrosion inhibitor, when applied on concrete surface, will depend upon the factors like quality of concrete etc because the inhibitor have to pass through concrete cover to reach the rebar. The effect of Corrosion Inhibitor on the half cell potential measurements and corrosion current has been studied. From the experiments, it has been observed that i.e. corrosion current obtained is similar for all water-cement ratios indicating that corrosion inhibitor protect all types of concrete by the same proportion. It is also concluded that only two coats of corrosion inhibitor are sufficient in reducing corrosion rate.