Three corrosion inhibitors for coppers -- 3-amino-1,2,4-triazole (ATA), benzotriazole (BTAH), and 1-hydroxy-benzotriazole (BTAOH) -- were investigated by corrosion experiments and atomistic computer simulations. The trend of corrosion inhibition effectiveness of the three inhibitors on copper in near-neutral chloride solution is determined experimentally as BTAH ) ATA )) BTAOH. A careful analysis of the results of computer simulations based on density functional theory allowed to pinpoint the superior inhibiting action of BTAH and ATA as a result of their ability to form strong N-Cu chemical bonds in deprotonated form. While these bonds are not as strong as the Cl-Cu bonds, the presence of solvent favors the adsorption of inhibitor molecules onto the surface due to stronger solvation of the chloride anions. Moreover, benzotriazole displays the largest affinity among the three inhibitors to form intermolecular aggregates, such as [BTA-Cu]n polymeric complex. This is another factor contributing to the stability of the protective inhibitor film on the surface, thus making benzotriazole an outstanding corrosion inhibitor for copper. These findings cannot be anticipated on the basis of inhibitors’ molecular electronic properties alone, thus emphasizing the importance of a rigorous modeling of the interactions between the components of the corrosion system in corrosion inhibition studies.
Benzotriazole (BTAH) has been known for more than sixty years to be a very effective inhibitor of corrosion for copper and its alloys. In spite of numerous studies devoted to the investigation of BTAH action, the mechanism of its action is still not completely understood. The aim of this review is to summarize important work in the field of BTAH as a copper corrosion inhibitor, from the early discoveries to the present time. Special attention is given to the BTAH surface structure. The disagreement between findings and proposed mechanisms is discussed.
By means of a detailed mathematical reconstruction of X-ray-induced Auger Cu L3M4,5M4,5 spectra of Cu sample immersed into BTAH inhibited and non-inhibited 3% NaCl solution we were able to estimate the thickness of the Cu2O oxide layer. The results show that the presence of BTAH inhibitor substantially reduces the thickness of the Cu2O oxide layer formed on Cu in chloride media. The average thickness of the Cu2O layer below the inhibitor layer is estimated to be 1.3 nm, whereas the Cu2O thickness of the noninhibited sample is 2.2 nm.
Azoles and their derivatives are among the often used organic corrosion inhibitors for copper. For this reason, the adsorption of four azole molecules — imidazole, triazole, tetrazole, and pentazole — on Cu(111) and Al(111) surfaces has been studied and characterized using density functional theory calculations. We find that the molecules weakly adsorb in an upright geometry through nitrogen atom(s). Molecular electronic structure is only weakly perturbed upon adsorption and the molecule–surface interaction involves the hybridization between molecular sigma-orbitals and metal states, yet the main contribution to bonding comes from the electrostatic dipole interactions due to a large dipole moment of azole molecules. With increasing the number of nitrogen atoms in azole ring the molecular electronegativity and chemical hardness linearly increase. The harder the molecule the more difficult the hybridization with metal states, which can explain why with the increasing number of nitrogen atoms in azole ring the molecule–surface bond strength decreases thus following the imidazole ) triazole ) tetrazole ) pentazole trend.
In this paper the adsorption of imidazole corrosion inhibitor on clean Fe(100) was addressed by detailed density-functional-theory calculations. The adsorption of molecules in their protonated, neutral, and deprotonated forms was considered. The polymerization of adsorbed imidazole molecules on the surface was also considered and many potential intermolecular structures were evaluated. It is shown that even though the imidazole in protonated form binds stronger to the surface than the neutral form, it is prone to deprotonation (dehydrogenation) resulting in neutral form, which further dehydrogenates due to the breaking of the C2–H bond. Thermodynamically the stablest identified structures thus consist of strongly bound and densely packed C2 dehydrogenated imidazole molecules, which may act as a thin protective film. On the other hand, the polymerization of imidazole molecules upon adsorption has been found improbable.