Experimental and Theoretical Investigations on the Corrosion Inhibition of Lumazine over Mild Steel in 1M HCl

The corrosion inhibition efficiencies and adsorption characteristics of Lumazine over mild steel in 1 M HCl were investigated using electrochemical and theoretical methods. The Gravimetric and electrochemical methods used in the present investigation includes weight loss, Tafel polarisation and Electrochemical Impedance Spectroscopy methods respectively. The adsorption studies carried out using this inhibitor adhere to Langmuir adsorption isotherm. In addition, the equilibrium constant and free energy of adsorption were calculated for the inhibitors on mild steel in 1 M HCl. Density Functional Theory using B3LYP functional was utilised to calculate the quantum chemical parameters of the inhibitors which were used to determine their contribution to inhibition of corrosion. HOMO LUMO, mulliken atomic charge, condensed fukui functions, local softness, relative nucleophilicity and relative electrophilicity were analysed to study the possible site of the inhibitor molecule at the metal surface. The quantitative structure-activity relationship (QSAR) has been established to correlate the experimental inhibition efficiencies and the quantum chemical parameters to model mathematical equations describing theoretical inhibition efficiencies.