Conventional weight loss, electrochemical measurements, quantum chemical calculations and scanning electron microscopy techniques were employed to investigate the inhibitive effects of two novel quinoline derivatives, 2-mercaptoquinoline-3-carbaldehyde and (Z)-3-((4-chlorophenylimino)methyl)quinoline-2-thiol on the corrosion of mild steel in I M HCl solutions. The decrease in the weight losses of mild steel samples has proved that both the additives were efficient inhibitors. The mixed mode of inhibition was confirmed by electrochemical polarizations. Both the inhibitors followed the Langmuir adsorption isotherm. In addition to this, the quantum chemical calculations were performed at B3LYP/6-31G(d,p) level to complement the experimental results. (C) 2013 Elsevier B.V. All rights reserved.