Adsorption Behavior of Organic Corrosion Inhibitors on Metal Surfaces—Some New Insights from Molecular Simulations

Some recent efforts toward studying adsorption, aggregation, and self-assembly of corrosion inhibitor molecules near metal/water interfaces via classical molecular simulations are reported. Two different approaches have been used. In the first approach, a coarse-grained model of corrosion inhibitor molecules is studied, and the following key findings are found: (a) hydrophobic interactions between the alkyl tails of corrosion inhibitor molecules are important for the formation of adsorbed self-assembled layers on the metal surface, (b) the morphology of the adsorbed layers are strongly influenced by molecular geometry, and (c) the relative strength of interactions between polar head and metal and between alkyl tail and metal are important determinants of adsorbed conformations. In the second approach, fully atomistic simulations are performed for a bulk aqueous phase and near metal/water interfaces of two kinds of model inhibitor molecules—imidazolinium-type and quaternary ammonium-type surfactants. From these simulations, the following are concluded: (a) these inhibitor molecules aggregate in the bulk phase as spherical micelles, (b) the unaggregated inhibitor molecules have a strong tendency to adsorb onto metal surfaces while inhibitor micelles show only a weak tendency to adsorb, and experience a long-range repulsion from the surface. Finally, it is discussed how the coarse-grained and fully atomistic simulations present a unified molecular picture of adsorption and self-assembly of corrosion inhibitor molecules on metal surface.