Unveiling the Corrosion Inhibition Mechanism of Thiazole and Benzo[d]thiazole Gemini Surfactants Using Experimental and Theoretical Approaches

This study investigates the corrosion inhibition performance of two cationic Gemini surfactants related to thiazole and benzo[d]thiazole on AISI 1015 carbon steel in HCl solution using gravimetric weight loss electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and quantum chemical calculations. The adsorption behavior was analyzed and found to follow the Langmuir adsorption isotherm model. The thermodynamic and kinetic parameters for both corrosion and adsorption reactions suggest mixed physical and chemical adsorption. Electrochemical results indicate that both inhibitors TAC 12 and TBC 12 significantly reduce corrosion rate by forming a protective adsorbed film on the steel surface, with inhibition efficiency reaching 87-89% at 50 ppm, where TBC 12 provides a more stable and insulating film over time compared to TAC 12. Potentiodynamic polarization studies confirm that inhibits both cathodic and anodic reactions with a dominant cathodic inhibition mechanism. Additionally, quantum chemical calculations and molecular dynamics simulations reveal strong interactions between the inhibitor molecules and the steel surface, validating the experimental findings. Furthermore, the addition of inorganic salts such as MnCl2, CuCl2, and CoCl2 enhanced the inhibition efficiency through a synergistic effect. Electrochemical studies indicate that salts facilitate cooperative adsorption, improving surface coverage and stabilizing the protective film. Among the tested salts, CuCl2 exhibited the most significant enhancement due to its strong interaction with the inhibitor and metal surface. Overall, the results demonstrate that TAC 12 and TBC 12 are efficient corrosion inhibitors for steel, providing insights into its adsorption mechanism and potential industrial applications.