Inhibitive properties, thermodynamic characterization and quantum chemical studies of secnidazole on mild steel corrosion in acidic medium

The inhibition of secnidazole (SEC) on the corrosion of mild steel in 0.01-0.04 M H₂SO₄ at 303-323 K was studied by gravimetric method. Results obtained show that SEC acts as inhibitor for mild steel in H₂SO₄ solution. The inhibition efficiency was found to increase with increase in SEC concentration but decreased with acid concentration and temperature, which is suggestive of physical adsorption mechanism although chemisorption may play a part. The adsorption of SEC onto the mild steel surface was found to follow the Langmuir adsorption isotherm. Both kinetic parameters (activation energy, pre-exponential factor, enthalpy of activation and entropy of activation) and thermodynamics of adsorption (enthalpy of adsorption, entropy of adsorption and Gibbs free energy) were calculated and discussed. Quantum chemical calculations using DFT at the B3LYP/6-31G* level of theory was further used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of secnidazole.