Evaluation of Greener Corrosion-Inhibiting Admixtures for Steel Reinforcements in Concrete

In this study, corrosion of thermo-mechanically treated (TMT) rebars with and without 3.5% NaCl for various concentrations (0.1%, 0.2%, 0.3% and 0.4%) of green corrosion inhibitors, namely glucosamine and stevioside, was systematically studied in simulated concrete pore solution (SCPS). Open-circuit potential measurements revealed that inhibited system showed passive behaviour compared with control system in SCPS. Potentiodynamic polarization studies revealed that inhibitor stevioside offers more than 88% inhibition efficiency at 0.3% concentration in SCPS containing 3.5% NaCl. Similarly, linear polarization resistance and impedance measurements showed higher polarization resistance and charge transfer resistance values, respectively, at 0.3% concentration for inhibited systems when compared with control (without inhibitor). In the second part, the optimized concentration of glucosamine and stevioside showed better performance against corrosion of rebar in the solution study admixed into concrete. The corrosion of TMT rebar embedded in concrete with and without inhibitors is subjected to simulated marine exposure for a period of 180 days and evaluated the corrosion inhibition. Gravimetric weight loss and electrochemical techniques were employed to study the efficacy of inhibitors in SCPS and concrete medium. It is found that the time taken for corrosion-induced cracking in concrete admixed with stevioside inhibitor is approximately 20 times that of control concrete and that stevioside inhibitor is relatively better corrosion inhibitor than other inhibitor reported.