Hydration of Triethylenetetramine Based Inhibitor Film Accelerate the Chloride‐Induced Corrosion in Concrete: A Molecular Dynamics Study

Organic corrosion inhibitors can be used to prevent chloride-induced corrosion in reinforced concrete structures by improving the performance of the reinforcement. In this theoretical study Molecular Mechanics (MM) and Molecular Dynamics (MD) simulations are performed in order to better understand the interaction mechanisms with the passive film present on steel, in particular considering an iron oxide hydroxide gamma-FeOOH surface, which can be subjected to chloride-induced corrosion when covered by a hydrated triethylenetetramine (TETA, molecular structure NH2-CH2CH2-(NHCH2CH2)(2)-NH2) inhibitor film. MD simulations are a very useful tool because they describe at the atomistic level both the specific solid surface and the organic inhibitors molecules in the passive film in presence of chloride ions as studied in previous work and the role of water molecules explicitly considered in this new investigation. Hydration of organic TETA inhibitor film in presence of chloride ions always accelerates the corrosion process, as is known experimentally. In this theoretical work water molecules effectively induce chloride ions to adsorb more quickly on the gamma-FeOOH surface and in greater numbers than in the same simulations studied without water molecules. This TETA film cannot efficiently prevent the chloride-induced corrosion process because it cannot exhibit a significant repulsion to chloride ions and the hydrated film accelerates the penetration of chloride into the protective film. This theoretical work is important for understanding the organic inhibitor able to form a stable hydrated film by preventing the chloride-induced corrosion or mitigating corrosion damage of reinforced concrete.