Theoretical prediction and experimental study of 2-phenyl-1,4-dihydroquinoxaline as a novel corrosion inhibitor for carbon steel in 1.0 HCl

Corrosion inhibition by 2-phenyl-1,4-dihydroquinoxaline (phq) on carbon steel in 1.0 m hcl is investigated using electrochemical techniques (eis and potentiodynamic polarization),sem and quantum chemical calculation. inhibition efficiency of 89% is reached with 5×10-3 m of phq at 303 k. potentiodynamic polarization showed that the phq behaves as mixed-type inhibitor. the nyquist plots showed that increasing phq concentration,charge-transfer resistance increased and double-layer capacitance decreased,involving increased inhibition efficiency. adsorption of the inhibitor molecules corresponds to langmuir adsorption isotherm. also,the activation thermodynamic parameters of dissolution were calculated and discussed. theoretical calculations have been used to make the correlation between the effectiveness of inhibition of our studied inhibitor and their molecular structure.