Glutamate- and Tartrate-Based Inhibitor Films to Prevent Chloride-Induced Corrosion in Reinforced Concrete: Efficiency of Dry or Hydrated Films via Molecular Dynamics Simulations

Due to their barrier effect against chloride penetration, corrosion inhibitors are widely used to prevent chloride-induced corrosion in reinforced concrete structures. The mechanisms of interaction between the protective film on carbon steel and chloride ions represent a crucial aspect of the design of new inhibitors. Theoretical studies based on molecular mechanic (MM) and molecular dynamic (MD) methods have proven useful in research on the formation of passive films and their intermolecular interactions with chloride ions, both under dry and hydrated conditions, allowing for further comparison with experimental data. In this study, glutamate- and tartrate-based inhibitor films are investigated. After MM/MD simulations, chloride ions are found to be kept away from the dry protective films via electrostatic repulsion, hence remaining distant from the lepidocrocite γ-FeO(OH) surface. These coatings are able to efficiently prevent chloride adsorption and film penetration due to the presence of COO− groups, which electrostatically and dynamically repel chlorides over time. Even on hydrated coatings, when complete coverage of the solid surface occurs, these OCIs are good potential candidates for preventing chloride-induced corrosion; however, in the presence of water, the penetration of chloride ions across the protective films can occur, thus rendering them relatively less effective.