The inhibitory effect of thiourea-based compounds was evaluated using carbon steel body specimens in hydrochloric acid media. Thiourea derivatives, N-(pyrimidin-2-ylcarbamothioyl)benzamide and N-(6-methylpyridin-2-ylcarbamothioyl)benzamide, were synthesized using a simple route with good yields of approximately 70%. The inhibitory efficiencies were obtained by means of weight-loss experiments and electrochemical techniques (e.g. polarization curves and electrochemical impedance spectroscopy). The presence of a methyl functional group showed a better inhibitory efficiency compared with the derivate inhibitor without such modification. Analyzing Langmuir isotherms, G 0 ads values indicate the chemical Downloaded by [University of Sherbrooke] at 15:32 12 April 2015 ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT 2 adsorption of thiourea-based compounds. The E Corr values obtained for the thiourea derivative with the methyl functionality was cathodically shifted by approximately −0.08 V, with an inhibition efficiency of 81%.