Inhibition and adsorption behavior of thiophenol derivatives on copper corrosion in saline medium

Three thiophenol derivatives with different substituent groups, 2-Naphthalenethiol (2-NT), 4-Chlorothiophenol (4-Cl) and p-Toluenethiol (4-MT) were selected to study the corrosion inhibition performance for copper in saline medium. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements, and weight loss tests were performed to compare the effect of different concentrations and various types of thiophenol derivatives on corrosion inhibition performances. Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and Surface-enhanced Raman spectroscopy (SERS) were utilized to characterize surface morphology and molecular structures of copper samples after corrosion in saline medium or electrochemical tests. Quantum chemical calculations were applied to further investigate the microscopic mechanism of the interaction between thiophenol derivative inhibitor molecules and copper surface. XPS, SERS, and theoretical calculations results indicate that thiophenol derivative inhibitors were adsorbed on Cu surface by Cu–S chemical bond. It was also found that these thiophenol derivative inhibitors could effectively inhibit the corrosion of copper by chemisorption and the efficiency follows the order of 2-NT >4-Cl >4-MT. The larger conjugated aromatic structure in 2-NT may be responsible for the measured higher inhibition efficiency of 2-NT.