Experimental and theoretical evaluation of Aspirin as a green corrosion inhibitor for mild steel in acidic medium
Alexander I. Ikeuba, Omang B. John, Victoria M. Bassey, Hitler Louis, Augustine U. Agobi, Joseph E. Ntibi, Fredrick C. Asogwa
Abstract
A combined experimental and theoretical approach has been used to evaluate the corrosion inhibition potential of an ecofriendly, cost effective and benign compound (Aspirin) on mild steel in acidic media using hydrogen evolution technique within a temperature range 303 K – 333 K in sulphuric acid solution. The results show that Aspirin inhibits the corrosion of mild steel in acidic media. The inhibition efficiency of Aspirin was found to increase with inhibitor concentration and decreased with rise in temperature. The maximum inhibition efficiency was 79.2 % with 800 mg/L of Aspirin at 333 K. The corrosion reaction kinetics in the presence of Aspirin shows a transition from first order to second order kinetics on going on elevating the temperature of the system. The trend in activation energy, Ea and the enthalpy of activation, ΔH indicate that the corrosion process is endothermic, the entropy of activation, ΔS shows that the process is spontaneous. The experimental results were in consonance with Langmuir isotherm and a physical adsorption mechanism is proposed for the adsorption of inhibitor on the mild steel surface. Complementary information was obtained from theoretical computations which show that the EHOMO and ELUMO for Aspirin are -7.33 eV and -2.06 eV, respectively. Molecular dynamics simulation reveals a strong binding affinity between inhibitor and the steel surface with a binding energy of -117.2 kcal/mol at the most stable adsorption configuration.