Efficiency of Various Corrosion Inhibitors to Resist Carbonation and Chloride Induced Corrosion

Abstract

Concrete is the second most used material by humans after water. Concrete may be considered as best construction material but its durability can adversely be effected by various means. Corrosion of steel present in reinforced concrete is most significant durability problem in the world of civil engineering. Concrete structures in coastal areas and aggressive environments are constantly exposed to these corrosive substances. Out of those substances, chlorides and CO2 are the most dominating. These can cause reduction in strength, spalling, expansion or mass loss in concrete. Hence, many methods have been developed to reduce or prevent corrosion of steel in concrete. From all the methods available for corrosion protection, corrosion inhibitors sound very promising. Inhibitors that are available in market usually have a tendency to protect against only one factor of corrosion i.e. either carbonation or chlorides along with the fact that commercially available corrosion inhibitors are very expensive and affect the total cost of structure. Due to which, there arises a need to find a cheaper replacement which can inhibit corrosion due to carbonation and presence chlorides. In this study of finding more effective inhibitors, effectiveness of some commonly available cheap chemicals is evaluated. Corrosion inhibition of Picolinic Acid, 4-Aminobenzoic acid, Salicylaldehyde and 2-Aminopyridine with 1% addition is assessed. Fe 500 HYSD steel bars of 12 mm diameter and 60 mm length are being prepared and then submerged partially in six different solutions for different time periods with a maximum of 480 hours. Corrosion monitoring of these steel bars is performed at 1 hour, 24 hours, 48 hours, 120 hours, 240 hours and 480 hours of immersion. The amount of resistance to corrosion provided by respective inhibitor is obtained by two tests i.e. Half-Cell Potential and Linear Polarization Resistance sweep tests. It has been observed that all of the chemicals used as corrosion inhibitors, have successfully inhibited corrosion, and were able to form a passive layer which protected the steel surface from further corrosion.