Novel gemini cationic thiazole-based surfactants as carbon steel corrosion inhibitors in 1 M HCl using experimental and theoretical tools

This paper examines two novel Gemini cationic surfactants based on thiazole derivatives (TAC) as anticorrosion compounds for carbon steel in 1 M HCl. This task was achieved using a diversity of tools, comprising mass loss (ML), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), scanning electron (SEM) microscope, energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), and computational density functional (DFT) theory. The shift in corrosion potential revealed the compounds' efficacy as cathodic inhibitors. The impedance measurement confirmed that a shielding film had formed on the carbon steel. The inhibitory action was found to be increased with increasing the inhibitor concentration which reached 79% for TAC 6 and 87% for TAC 18 at 50 ppm, while it slightly decreased with raising the temperature from 303 to 323 K. The mechanism of adsorption minds the Langmuir adsorption isotherm. The mixed physical and chemical adsorption of the inhibitors on the steel surface was confirmed by thermodynamics and kinetic characteristics. Electrochemical techniques examined the synergism inhibition of both inhibitors in the presence of inorganic salts at 303 K which indicated to follow CuCl₂ > MnCl₂ > CoCl₂. The synergetic inhibition of both inhibitors in the presence of CuCl₂ reached 96% for TAC 6 and 97% for TAC 18. Both inhibitors in the presence of salts were changed to act as mixed-type inhibitors.