Adsorption films based on indazole derivatives for application to protect Cu in sulfuric acid: Experimental and theoretical approaches

Abstract

BackgroundFinding more cost-effective, low-toxicity corrosion inhibitors to reduce copper corrosion in acidic environments is critical. MethodsThe anti-corrosion abilities and mechanisms of 5‑bromo-1H-indazole (5-BIA) and 7‑bromo-1H-indazole (7-BIA) on Cu in 0.5 M H2SO4 environment have been explored by a way of combining both experimental and theoretical approaches. Significant findingsElectrochemical experiments have shown that both 5-BIA and 7-BIA are capable of acting as highly effective corrosion inhibitors for copper, and 5-BIA has a more prominent protective ability than 7-BIA, which has also been proved by weight loss experiments, SEM and AFM. The corrosion inhibition efficiency (ηE) of 1.5 mM 5-BIA and 1.5 mM 7-BIA is as high as 97.1 % and 94.0 %, respectively. The adsorption of 5-BIA and 7-BIA on the metal surfaces conforms to the Langmuir monolayer adsorption model, and both chemosorption and physical adsorption exist. In addition, quantum chemical calculations reveal that 5-BIA has smaller energy gap (ΔE) and hardness (η) values, and larger dipole moment (μ), absolute electronegativity (χ), and chemical softness (σ) values, thus exhibiting better anti-corrosion ability. Molecular dynamics simulations display that both 5-BIA and 7-BIA can be adsorbed on the Cu (111) surface in an approximately parallel approach, which is conducive to achieving 5-BIA and 7-BIA to hinder the process of copper corrosion as much as possible.