Theoretical confirmation of benzothiazole derivatives as corrosion inhibitors for carbon steel in hydrochloric acid

This study presents an in-depth theoretical approach based on density functional theory (DFT) to elucidate the mechanisms of corrosion inhibition of benzothiazole derivatives 2-mercaptobenzothiazole (MBT) and 2-aminobenzothiazole (ABT) on carbon steel in a 1 M HCl solution. Quantum chemistry parameters, including Frontier molecular orbitals energies, electrostatic potential maps (MEP), and Fukui indices were calculated in order to evaluate the inhibition mechanisms of these two drifts. The results indicate that MBT has a higher HOMO energy and greater electron donor capacity than ABT, thus promoting stronger chemisorption on the steel surface. In addition, MBT's tendency to protonate enhances its physisorption due to electrostatic forces acting on the metal surface in an acidic environment. These theoretical results are consistent with experimental observations from electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM), confirming the superior inhibitory performance of MBT compared to ABT, especially after prolonged immersion time. This study highlights the essential role of molecular electronic properties in determining inhibitor efficacy and supports the rational design of high-performance benzothiazole-based corrosion inhibitors.