Interfacial Properties of Electron-Donating and Electron-Withdrawing Group-Substituted Chiral Schiff Bases on Mild Steel Corrosion in 1 M Hydrochloric Acid Solution

Abstract

Interfacial properties of chiral Schiff bases derived from electron-donating and electron-withdrawing group-substituted salicylaldehyde, respectively, with l-tryptophan, 2-((2-hydroxy-5-methoxybenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid (SB1) and 2-((2-hydroxy-5-nitrobenzylidene)amino)-3-(1H-indol-3-yl)propanoic acid (SB2) on mild steel corrosion in 1 M hydrochloric acid (HCl) solution, were investigated using different techniques like weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy–energy dispersive X-ray spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, UV–visible spectroscopy and X-ray diffraction. All the listed experimental results proved that the corrosion inhibition efficiency of inhibitors mainly depends on its electron-donating ability, as electron-donating group-substituted inhibitor (SB1) has excellent inhibition efficiency on corrosion of mild steel in 1 M HCl compared to electron-withdrawing group-substituted inhibitor (SB2). Density functional theory was further employed to provide insights into the mechanism of interaction between the inhibitor and the mild steel surface. Calculated quantum chemical parameters (EHOMO, ELUMO , ΔE, etc.) were act as evident to state that SB1 was better in inhibiting corrosion of mild steel in 1 M HCl compared to SB2.