In this oral presentation at the EUROCORR 2011 conference, we presented our study aimed at more detailed insight of BTAH inhibiting mechanism against corrosion of copper. The study utilizes corrosion experiments and extensive atomistic computer simulations based on density functional theory . Three azole based inhibitors were investigated: BTAH, 3-amino-1,2,4-triazole (ATA) and 1-hydroxybenzotriazole (BTAOH). The trend of corrosion inhibition effectiveness in near neutral chloride solution was first determined experimentally as BTAH ≥ ATA )) BTAOH. To disentangle the factors involved in the inhibition mechanism, we then carefully analyzed the results of computer simulations, according to which the inhibitor molecules in neutral form interact rather weakly with the copper surface . On the other hand, the interaction between deprotonated molecules (resulting from, e.g., BTAH → BTA– + H+) and the surface is far stronger. A remarkable inhibiting property of benzotriazole is attributed to its ability to form strong N–Cu chemical bonds in deprotonated form. Although these bonds are not as strong as the Cl–Cu bonds, the presence of solvent favors the adsorption of BTA– molecules onto the surface due to stronger solvation of Cl– anions compared to BTA–. Our findings therefore affirm the competitive adsorption scenario as a plausible mechanism for inhibiting the corrosion of copper in near-neutral chloride solutions. Additionally, benzotriazole displays the most pronounced tendency to form stable intermolecular aggregates—e.g., [BTA-Cu]n polymeric complexes—which further contribute to the stability of the protective inhibitor film on the surface. Moreover, such organometallic complexes also allow a very dense packing of the inhibitor on the surface resulting in an effective diffusion barrier. Our study emphasizes the importance of a rigorous modeling of the interaction between the components of the corrosion system in the corrosion inhibition studies employing quantum chemical calculations.
B.03 Paper at an international scientific conferenceCOBISS.SI-ID: 25020711
This is the second out of three oral presentations presented by members of project team at the EUROCORR 2011 conference, where we focused on the bonding between corrosion inhibitor molecules and transition metal surfaces by means of atomistic density functional computer simulations. Namely, adsorption of inhibitor molecules onto the surface is regarded as an important step in the formation of inhibitive film on the surface. An important question is related to the effect of the metal reactivity on the participation of metal d-states in the molecule-surface interaction. As a model system a benzimidazole molecule and two transition metals—a less reactive Cu and a more reactive Fe—were chosen. We demonstrate that the role of metal d-states in the molecule-surface bonding is far more important for reactive metals. In particular, on Fe surfaces the benzimidazole molecule is strongly adsorbed parallel to the surface with a pronounced pi-d hybridization. On the other hand, the molecule interacts weakly with copper surface through sigma-molecular orbitals and the main contribution to bonding comes from electrostatic dipole interactions.
B.03 Paper at an international scientific conferenceCOBISS.SI-ID: 25020967