Electrochemical and quantum chemical studies of some azomethine compounds as corrosion inhibitors for mild steel in 1 M hydrochloric acid

•Azomethine compounds inhibit the corrosion of mild steel in 1 M HCl solution.•Inhibition efficiency increased in the order of compounds SB1 > SB2 > SB3 > SB4 > SB5.•Polarization method indicated that the inhibitors act as mixed type inhibitors.•Adsorption of azomethine compounds on mild steel surface obeys Langmuir’s isotherm.•Quantum chemical parameters were correlated with experimental results.

The corrosion inhibition effect of new azomethine compounds: PhNNC (COCH3)NC6H4Y {Y = OCH3 (SB1), CH3 (SB2), H (SB3), Br (SB4) and Y = Cl (SB5)} on mild steel in 1 M HCl, was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and quantum chemistry analysis. It has been found that the inhibition efficiency increased with increasing inhibitor concentration. The polarization curves showed that these Schiff bases function as mixed inhibitors. The adsorption of studied compounds on mild steel surface was found to follow the Langmuir isotherm. Molecular modeling was used to correlate corrosion inhibition properties and calculated quantum chemical parameters.