Methyl 3-((2-mercaptophenyl) imino) butanoate (MMPB) was designed and synthesized as a corrosion inhibitor, which is functionalized with adjacent azole and thiol groups and a carboxylate tail. The inhibition efficiency of this compound has been investigated in different concentrations of HCl solutions. Then, the effect of temperature and inhibitor concentration was studied for further discussion about inhibition mechanism. In addition to potentiodynamic and electrochemical impedance spectroscopy, galvanic measurements were also realized for better explanation of interaction between inhibitor and metal surface. For this purpose, identical steel electrodes were immersed in separate test solutions with and without inhibitor, and then coupled to each other. The assessment of corrosion rate was realized with quantitative analysis of iron content in immersion test solutions. The corrosion current densities (i (corr)) were 20.40 and 200.30 mu A cm(-2), in the presence of 10 mM inhibitor and inhibitor-free test solutions, respectively. The energy barrier values against corrosion were also calculated in the presence and absence of inhibitor, with the help of surface coverage ratio and i (corr) values for different temperatures.