Prototype materials based on aniline oligomers have been shown to inhibit corrosion. The electronic behavior of these aniline trimers parallels that of polyaniline (PAni), but the oligomers are a much more tractable system for analysis. The anti-corrosion process involves the acid/base chemistry of the oligomers, their electron donor/acceptor properties, and the interaction of the oligomers with the metal surface.
Thermodynamic parameters for several competing reaction sequences occurring during the interaction of an iron (or aluminum) surface and aniline trimers are determined by hybrid ab initio/density functional theory (DFT) calculations. These parameters are used to interpret the extent of electron transfer at the polymer-surface interface at equilibrium. The rate of electron transfer from the metal to trimer, and from one trimer to another, is estimated using Marcus-Hush theory. The relevance of these rates to the corrosion process is illustrated. The pH dependence of corrosion inhibition by oligoanilines is discussed, as well as the effect of the spin state of the oligomer.
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