Quantum Electrochemical Approaches to Corrosion Inhibition Problems: Aniline Corrosion Inhibitors in Different Media

Ahhough the effectiveness of corrosion inhibitors are normally investigated experimentally. the approach is often time consuming, wearisome and expensive. Moreover, the fundamental investigations often need some sophisticated in struments capable of working in-situ on metal-solution interface. Thus, theoretical approaches have attracted many attentions in the last few years. In this work, molecular behavior of some aniline derivative as corrosion inhibitors of iron and copper in different corrosive media (HCI and H2S04) were investigated quantum electrochemically by some of our 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 the molecules inside electrical double layer and then correlated to their inhibitory POWCI'S. Some reasonably good correlations with opposite trends were observed for these media and discussed via ion-pair hypothesis and deprotonation phenomena. Comparing aniline adsorptions on iron and copper, the first was found more in chemical nature. Moreover, in both cases, the adsorptions were almost parallel (with corroding surfaces) and taken place through sp3 nitrogen lone pair ofamino group. Finally, for the inhibition phenomena, a mechanism was proposed.

Keywords:

Corrosion inhibition mechanism , Clu.ster/polarized continuum model , Anion effect , Copper and iron clusters , Ion pair hypothesis