CNDO study of the tautomeric structure of uracil and its effect on the electrochemical corrosion behaviour of mild steel in acid media

The effect of uracil compound on the electrochemical corrosion behaviour of mild steel in 1 M sulphuric and hydrochloric acid solutions, as corrosive media, has been studied. Weight loss measurements and potentiostatic polarization scanning were included. The anodic and cathodic parameters (e.g., Tafel slopes, charge transfer coefficients, corrosion currents and corrosion potentials), values of activation energies and the cathodic protective current in the absence and presence of different uracil concentrations revealed that this compound has an anticorrosive character. The corrosion potential E(corr.) of steel was affected by increasing uracil concentration. The slight shift in E(corr.) and the increase in activation energies due to addition of the investigated compound, together with the shift of the potentiostatic anodic polarization curves to slightly higher potential regions denoted a mixed-type inhibitor. The electronic energies and charge densities for the different tautomeric forms of uracil were calculated by the CNDO/SCF method. The obtained results together with the polarization studies indicate that the inhibition occurs by simple blocking of both cathodic and anodic sites on the steel electrode surface through the adsorption process.