Benzoate-Based Inhibitor Film to Prevent Chloride-Induced Corrosion: Simulation Study of Efficiency of Dry or Hydrated Film

In the last 30 years, many synthetic organic substances have been proposed as promising inhibitors to prevent chloride-induced corrosion in reinforced concrete structures. Using molecular mechanics (MM) and molecular dynamics (MD) methods the formation of protective film on steel have been investigated at atomistic level considering different organic inhibitors, comparing the theoretical results with experimental data. In previous work, the interaction between chlorides and both dry and hydrated triethylenetetramine (TETA) film on hydroxylated gamma-FeOOH surface is studied. Using the same simulation protocol, the aim of this work is to investigate the interaction between the Cl- ions and the benzoate inhibitor film to understand how the corrosion process can be avoided. The dry benzoate film efficiently prevents the adsorption of chlorides on lepidocrocite (gamma-FeOOH) surface. At the same time the MD simulations show the hydrated benzoate film have a lower efficiency because some chlorides come into contact with the gamma-FeOOH surface, and moreover, at longer time they cause a depletion of organic inhibitors close to them, then an inhomogeneity in the exposed film. Not only the number of chlorides that penetrate through the protective film must be considered but also the stability of dry or hydrated protective film during the time.