Comparative studies of two benzaldehyde thiosemicarbazone derivatives as corrosion inhibitors for mild steel in 1.0M HCl

Two benzaldehyde thiosemicarbazone derivatives namely 3-methoxy, 4-hydroxyl-benzaldehyde thiosemicarbazone (MHBT) and 2-hydroxyl, 3-methoxy-benzaldehyde thiosemicarbazone (HMBT) were synthesized and their inhibition behavior for mild steel in 1.0M HCl solution was investigated using gravimetric measurements and electrochemical tests. Weight loss measurements suggested that these two compounds acted as efficient inhibitors for mild steel in 1.0M HCl solution and the inhibition efficiency reached a maximum value of 96.1% and 95.7% for HMBT and MHBT, respectively. Potentiodynamic polarization results revealed that both of these two compounds were mixed-type inhibitors. Scanning electron microscopy and energy dispersive spectrum were performed to confirm the presence of benzaldehyde thiosemicarbazone derivatives on mild steel surface. The adsorption of these two inhibitors on mild steel surface in 1.0M HCl solution follows the Langmuir adsorption isotherm. Correlation between the molecular structure and inhibition property were also discussed using quantum chemical calculations.