Adsorption of L-Tryptophan-derived chiral Schiff bases on stainless steel surface for the prevention of corrosion in acidic environment: Experimental, theoretical and surface studies

Abstract

The effect of Schiff bases derived from L-Tryptophan, methyl 2-((2-hydroxybenzylidene)amino-3-(1H-indol-3-yl)propanoate (S1) and 2-(((1-hydroxy-3-(1H-indol-3-yl)-1,1-diphenylpropan-2-yl)imino)methyl)phenol (S2), on the corrosion inhibition of stainless steel (SS) in 1 M hydrochloric acid (HCl) solution was investigated. Electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were used to understand the inhibition efficiency of the inhibitors. We found that the inhibitors S1 and S2 have good inhibition efficiency on corrosion of stainless steel in 1 M HCl. Polarization measurements confirmed mixed mode of inhibition of S1 and S2 with predominant control of cathodic reaction. SEM-EDX, FT-IR, UV–visible and X-Ray Diffraction (XRD) results revealed that the inhibitor molecules were adsorbed on SS surface and their adsorption on SS obeyed Langmuir's adsorption isotherm. Density functional theory (DFT) was employed to find out quantum chemical parameters (EHOMO, ELUMO and ΔE). The obtained theoretical results have been compared with the experimental results.