An experimental and theoretical investigation of adsorption characteristics of a Schiff base compound as corrosion inhibitor at mild steel/hydrochloric acid interface

This study investigates the effect of a Schiff base namely 2-[2-(2-(3-phenylallylidene)hydrazine carbonothioyl)hydrazinecarbonyl]benzoic acid (SB), on corrosion inhibition of mild steel in 1 M HCl. Electrochemical impedance measurement, potentiodynamic polarization and weight loss methods were applied to study adsorption of SB at metal/solution interface. Results revealed that SB is an excellent inhibitor for mild steel corrosion in 1 M HCl; showing a maximum efficiency 99.5% at concentration of 1.36 × 10 −6 M. Fourier transform infrared spectroscopy (FTIR) observations of the mild steel surface confirmed the formation of protective film on the metal surface by studied compound. Polarization studies showed that SB is a mixed-type inhibitor. Adsorption process obeyed Langmuir’s model with a standard free energy of adsorption (∆ G ° ads ) of −46.7 kJ mol −1 . Energy gaps for interactions between mild steel surface and inhibitor were found to be close to each other showing that SB possess capacity to behave as both electron donor and acceptor.