In the present work, a new organic inhibitor, namely (2(-4(chloro phenyl-1H-benzo[d]imidazol)-1-yl)phenyl) methanone (CBIPM), that has an inhibitive effect on the ordinary steel corrosion in 5.0 M HCl has been studied using electrochemical measurements (potentiodynamic polarization and electrochemical impedance spectroscopy). The obtained results showed that the inhibition efficiency increased with concentration and reached 98.6% at 10−3 M. In addition, the CBIPM takes its performance at the temperature range of 298–328 K. The adsorption of the inhibitor on the ordinary steel was well described by the Langmuir isotherm. On the other hand, the establishing of correlation between the molecular structures of quantum chemistry indices was carried out using the density functional theory.