Application of ascorbic acid as green corrosion inhibitor of reinforced steel in concrete pore solutions contaminated with chlorides

Abstract

The present work aims to investigate the inhibitive and preventive effects of ascorbic acid as an organic inhibitor against the corrosion of reinforcements immersed in simulated concrete pore solution, and also in mortars exposed to chlorides. The study was carried out using different electrochemical methods such as the open circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy to determine the inhibition efficiency of ascorbic acid. The prepared mortars were tested in order to investigate the corrosion potential and polarization resistance. The obtained results indicated that the optimum concentration of ascorbic acid was determined at 0.1 g/L, with an inhibition efficiency estimated at 88.96%. It is worth noting that ascorbic acid exhibits an anodic-type inhibition; its adsorption on the steel surface occurs by chemisorption, according to the Langmuir adsorption isotherm by the formation of chelated compounds with the Fe2+ ion. In addition, its preventive effect against corrosion is guaranteed up to a concentration of 0.1 mol/L NaCl. It should be noted that adding the optimum concentration of ascorbic acid to the mixing water of mortar can delay the onset of corrosion for up to 28 days in comparison with an uninhibited mortar containing 0.5 mol/L NaCl. Furthermore, it was found that ascorbic acid allowed obtaining a mortar with lower water accessible porosity and greater compressive strength than those of the reference mortar. It should also be known that ascorbic acid does not affect the capillary absorption coefficient of mortar.