Quantum electrochemical approaches to corrosion inhibition properties of some aniline derivatives in acidic media

The molecular behavior of some aniline derivatives as corrosion inhibitors of iron and copper in acidic media (HCl and H2SO4) were investigated quantum-electrochemically by some recently developed models based on density functional theory and cluster/polarized continuum approaches. In this regard, electrical dipole moment, charges on hetero atoms and acidic hydrogen, electronic chemical potential, and extent of charge transfer were determined for both neutral and protonated forms of molecules inside an electrical double layer and correlated to their inhibitory powers. Good correlations were observed for both acidic media. The results were discussed via ion-pair hypothesis and deprotonation phenomena. The adsorption of aniline molecules on iron seems to have chemical properties, while that on copper has a more physical nature. Moreover, in both cases, adsorptions are almost parallel with the corroding surfaces and take place through an sp(3) nitrogen lone pair. Finally, a mechanism is proposed for the inhibition phenomena. (c) 2007 The Electrochemical Society.