Investigation of inhibition effect of some amino acids against steel corrosion in chloride-containing alkaline solution

The corrosion inhibitory effect against reinforced steel corrosion of four amino acids was evaluated comparing with sodium nitrite which is a widely used commercial inhibitor. The experiments were carried out in simulated pore solutions using electrochemical methods as well as optical microscopy. Electrochemical impedance spectroscopy (EIS) was mainly used to screen the resistance of different inhibitor systems to compare the efficiency of their inhibition against chloride-induced corrosion. Moreover, corrosion current density and corrosion rates were also calculated for each inhibitor at different chloride concentrations. Cyclic voltammetry (CVA) was conducted to analyze the corrosion process on the steel surface. Pitting potentials as well as repassivation potentials were recorded and the difference between them was compared. Optical microscopy was used for observing corrosion spots on steel surface at different time during the measurements. From the images and spectra, information can be interpreted as how chloride concentration influenced corrosion rate and to what extent can the four amino acids inhibit corrosion process. In general, pAB had the best inhibition effectiveness among the amino acids, followed by 11AUA. 6ACA and Gly showed similar performance during the experiments, both of whose corrosion inhibiting ability were not satisfactory. The difference of corrosion inhibition in amino acids may be owing to their carbon chain length and the existence of functional group. In total, the corrosion inhibitive effect of amino acids was not as good as that of sodium nitrite.Materials Science & EngineeringMaterials Science & EngineeringMechanical, Maritime and Materials Engineerin