Experimental and theoretical studies of benzaldehyde thiosemicarbazone derivatives as corrosion inhibitors for mild steel in acid media

The inhibition behavior of three benzaldehyde thiosemicarbazone derivatives namely p-methoxybenzaldehyde thiosemicarbazone (MOBT), p-carboxybenzaldehyde thiosemicarbazone (COBT) and p-ethylbenzaldehyde thiosemicarbazone (EBT) for mild steel in 1.0 M HCl solution was studied systematically using gravimetric measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy and energy dispersive spectrum. Gravimetric measurements revealed that the corrosion rate decreased with the increase of inhibitor concentration and COBT inhibitor exhibited the highest inhibition efficiency of 96.4% at 300 mu M. Potentiodynamic polarization results suggested that these three compounds acted as mixed-type inhibitors. Adsorption of these three inhibitors on mild steel surface in 1.0 M HCl solution conforms to Langmuir adsorption isotherm. Theoretical calculations were also performed and the results agreed well with the experimental measurements. (C) 2018 Elsevier B.V. All rights reserved.