Investigation of 3-(phenylsulfinyl)indoles self-assembled monolayer for the inhibition of iron corrosion in acidic media

3-(phenylsulfinyl)indoles have been synthesized by the direct sulfoxide reaction of 1H-indoles with benzenesulfenamide in water as a green reaction medium. The corrosion inhibition effects and the hydrophobicity of the self-assembled films were explored by electrochemical methods and surface analysis methods. The results show that the self-assembled film mainly inhibits the cathodic process of the iron electrode. After the iron electrode was assembled in 5 mM 3-(p-tolylsulfinyl)-1H-indole/3-((4-fluorophenyl)sulfinyl)-1H-indole ethanol solutions for 9 h, the corrosion inhibition efficiencies in 1.0 M HCl solution reached 91.50% and 94.24%, respectively. The surface morphology of the self-assembled film on iron exposed to the test solution was examined using scanning electron microscopy and the chemical composition of the corrosion inhibition surface was analyzed by X-ray photoelectron spectroscopy. In the quantum chemical calculation part of this study, the active adsorption sites on the metal surface are located in the indole-sulfoxide framework, forming feedback bonds and coordination bonds with an iron atom.