Research on Corrosion Inhibition Performance of 1,2 - Diphenyl - 1H - Imidazo [4,5 - f][1,10] Phenanthroline as a New - Type Inhibitor for Mild Steel

In order to improve the corrosion inhibition performance and the application scope of o - phenanthroline derivatives, a new type of 1,2 - diphenyl - 1H - imidazo [4,5 - f][1,10] phenanthroline (HIP) corrosion inhibitor was synthesized by molecular design method. The corrosion inhibition effect on mild steel in hydrochloric acid medium and the adsorption behavior on the surface of mild steel were studied through weightlessness method, electrochemical method and scanning electron microscope. In addition, the adsorption thermodynamics of corrosion inhibitor molecules were analyzed, and the relationship between the molecular structure of HIP and corrosion inhibition performance was further studied by quantum chemical method. Results showed that HIP had good corrosion inhibition performance for mild steel in 1.0 mol/L HCl solution, and the corrosion inhibition efficiency was 97.0% under the temperature of 40 ℃ with the inhibitor concentration of 1.0 mmol/L. Moreover, the adsorption of HIP on the surface of mild steel was an exothermic reaction process belonging to Langmuir isotherm adsorption. The standard Gibbs free energy = -40.5 kJ/mol) on the surface of mild steel indicated that the adsorption of HIP on such surface was chemical adsorption. Meanwhile, the potentiodynamic polarization curve showed that HIP was a mixed corrosion inhibitor restraining both the cathode and the anode, but the corrosion current density changed little when the anode polarization exceeded - 300 mV. Besides, the theoretical calculation results were consistent with the experimental results.