Corrosion inhibition efficiency and adsorption behavior of azomethine compounds at mild steel/hydrochloric acid interface

•Azomethine compounds are good inhibitors for mild steel in 1M HCl.•The inhibition efficiency follows the order: SB1>SB2>SB3>SB4>SB5.•The adsorption process followed Langmuir adsorption isotherm. The adsorption and inhibition effect of azomethine compounds: PhN=NAC (COCH3)=NC6H4Y {Y=OCH3 (SB1), CH3 (SB2), H (SB3), Br (SB4) and Y=Cl (SB5)} on mild steel in 1M HCl at 25°C were studied using gravimetric measurements, cyclic voltammetry, UV–visible Spectrophotométrique and scanning electron microscope (SEM) methods. Inhibition efficiency was found to increase with the increase in azomethine SB1-SB5 concentration. The adsorption of each inhibitor on mild steel surface obeys Langmuir adsorption isotherm. The results of cyclic voltammetry showed that the presence of azomethine compound decreases the charge density in the transpassive region. The UV–visible absorption spectra of the solution containing the inhibitor after the immersion of mild steel specimen indicate the formation of a (SB1-SB5)-Fe complex. SEM and EDX observations confirmed the existence of protective inhibitor film on a metal surface.