Probing the inhibition superiority of a novel vanillin derivative tri-cationic surfactant for mild steel corrosion in 1 M HCl

In this research, two novel tri-cationic surfactant derivatives were synthesized, stemming from vanillin – a compound employed as a sweetener in the food and beverage industry, a flavoring agent in perfumery, and an odor masking substance in cleaning products and animal feed. The structural characteristics of these synthesized compounds were unequivocally confirmed by FT-IR, 1 H NMR, and 13 C NMR spectroscopic analyses. Furthermore, their efficacy in inhibiting the corrosion of St37 steel was systematically evaluated by integrating gravimetric (weight-loss) measurements with complementary electrochemical techniques. For the corrosion experiments, 1 M HCl was selected as the corrosive medium, and solutions were prepared with inhibitor concentrations set at 1, 5, 10, 50, and 100 ppm. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements were conducted during the electrochemical tests to ascertain the performance of the prepared inhibitors. High inhibition efficiency values, reaching up to 98.7 %, were obtained at the optimum inhibitor concentration of 100 ppm. The adsorption behavior was observed to be consistent with the Langmuir isotherm model. Additionally, theoretical calculations (DFT) were utilized to explore the correlation between the molecular structure of the inhibitors and their corrosion inhibition effectiveness. The results unequivocally demonstrate that these two newly synthesized vanillin derivative tri-cationic surfactants function as highly effective corrosion inhibitors for St37 steel within a 1 M HCl solution.