The Effect of Fe-anion Interactions on Corrosion of Ferrous Surfaces by Phosphonium Ionic Liquids

Experiments and simulations were used to investigate interactions between ferrous surfaces and trihexyltetradecylphosphonium benzoate or salicylate. Differences between the ionic liquids were observed in open circuit potential, potentiodynamic polarization, cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, and long-duration corrosion tests. While both ionic liquids were far less corrosive than water, salicylate exhibited slower charge transfer and lower surface protection potential than benzoate. These observations were analyzed using simulations of chemical reactions between ions and an ideal Fe(100) surface. Simulation results showed that salicylate and benzoate differed in their bonding configurations and orientations, suggesting distinct adsorption mechanisms for these similar ionic liquids.