Corrosion inhibition of mild steel by two new S-heterocyclic compounds in 1 M HCl: Experimental and computational study

•SB and DBTDA are effective mixed type (cathodic/anodic) inhibitors in 1 M HCl.•Inhibition efficiency of compounds increases with increasing concentration.•Adsorption of compounds on mild steel surface obeys Langmuir’s isotherm.•SEM method shows the existence of protective film of SB and DBTDA on metal surface.•Theoretical calculations provide good support to experimental results.

The inhibition ability of a new S-heterocyclic Schiff base (SB) and the corresponding amine (DBTDA) towards mild steel corrosion in HCl solution was studied at various concentrations and temperatures using weight loss, polarization curves, electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM) methods. The experimental results reveal that SB and DBTDA are efficient mixed type corrosion inhibitors, and their inhibition efficiencies increase with increasing concentration. The adsorption of these inhibitors on mild steel surface obeys Langmuir isotherm. Quantum chemical parameters are calculated using the Density Functional Theory method (DFT). Correlation between theoretical and experimental results is discussed.