Effects of pH on inhibitor-doped hybrid protective sol–gel coatings on the copper electrode surface

Abstract In this study, hybrid inhibitor-doped sol–gels were synthesized using 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT), 3-glycidoxypropyltrimethoxysilane (GPTMS), and tetraethoxysilane (TEOS) at different pH values (4, 7, and 11). The fabricated sol–gels were applied as coatings via a self-assembly method to obtain corrosion resistance for copper substrates in 3.5% NaCl. The AHMT-doped hybrid sol–gel coatings were characterized through different methods. Interactions between the hybrid AHMT-doped sol–gel and copper metal were demonstrated by quantum chemical calculations based on the density functional theory and molecular dynamics simulations. The results from electrochemical impedance spectroscopy and potentiodynamic polarization analysis of the hybrid AHMT-doped sol–gel coating at pH 4 demonstrated enhanced corrosion resistance compared to the data from the tests at pH values of 7 and 11. This can be explained by the formation of an effectively packed layer, which acted as a physical barrier against corrosive chloride ions that protected copper metal against corrosion.