Organic Inhibitors to Prevent Chloride-Induced Corrosion in Concrete: Atomistic Simulations of Triethylenetetramine-Based Inhibitor Film

Inhibitors are largely used to prevent chloride-induced corrosion in reinforced concrete structures thanks to both a barrier effect on chloride penetration and a competition with the adsorption of the inhibitor. The interaction mechanisms between passive film on carbon steel, the inhibitor molecule and chlorides still require deeper understanding. Theoretical studies based on Molecular Mechanics (MM) and Molecular Dynamics (MD) methods can be useful to better understand the passive film formation and its interaction with chlorides. In this work the interaction between a triethylenetetramine (TETA) inhibitor film on -FeOOH surface and chlorides was studied using MD methods. After MM optimization in the initial adsorption stage, some chlorides are close to protective TETA film. After MD run at room temperature effectively chlorides remain close to the protective film. In order to have an effective barrier on chloride attack the metal oxide must remain wholly covered by the protective film. The TETA film well covers the lepidocrocite surface but cannot kinetically efficiently prevent the chloride-induced corrosion compared to other organic films exposing COO- groups because it does not exert any repulsion to chlorides.