The behavior of two indazole derivatives on the copper/sulfuric acid interface in terms of adsorption and corrosion inhibition

• Fluoroindazole (5-FIA) and chloroindazole (5-CIA) were selected as excellent corrosion inhibitors for copper in sulfuric acid media. • Both 5-FIA and 5-CIA were shown to be adsorbed on the surface of copper in parallel. • The corrosion inhibition capability of the 5-CIA was more prominent than that of the 5-FIA. • The results of experiments and theories coincided with each other. To reduce the degree of copper corrosion by the pickling solution, the introduction of organic inhibitors into the pickling solution is a reasonably effective measure.5-fluoro-1H-indazole (5-FIA) and 5‑chloro-1H-indazole (5-CIA) may act as exceptional inhibitors. Based on experimental and theoretical methods, the antiseptic ability of two indazole derivatives on copper in sulfuric acid was researched. The results of electrochemical experiments show that in the test solution containing 1 mM inhibitors, the corrosion inhibition efficiency ( η ) of 5-FIA and 5-CIA was 90.4% and 94.3%, respectively, indicating that 5-FIA and 5-CIA have outstanding corrosion inhibition capabilities and their antiseptic effects are in the order of 5-FIA < 5-CIA, which is also confirmed by observations of Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Furthermore, both 5-FIA and 5-CIA are mixed-type inhibitors and their adsorption behavior follows Langmuir isothermal adsorption model. The results of X-ray Photoelectron Spectroscopy (XPS), theoretical calculations, and molecular dynamics simulations further reveal the mechanism that 5-CIA has stronger adsorption capacity than 5-FIA.