Synthesis and evaluation of benzo[1,2,3]selenadiazole-isoxazoles as corrosion inhibitors for copper in NaCl: An integrated experimental and theoretical approach

In this study, we investigate the protective capabilities of two synthetic compounds, 5-methyl-5-(4-methylbenzo[d][1,2,3]selenadiazol-7-yl)-3-phenyl-4,5-dihydro-isoxazole (BHP) and 5-methyl-5-(4-methylbenzo[d][1,2,3]selenadiazol-7-yl)-3-(4-nitrophenyl)-4,5-dihydro-isoxazole (BNP), as corrosion inhibitors for copper in a 3.5 wt% NaCl solution. The chemical structure of these benzo[1,2,3]selenadiazolyl-isoxazole derivatives combines a benzo[1,2,3]selenadiazole core, which to our knowledge has not been previously studied for its anticorrosive activity on copper, with an isoxazole nucleus known in the literature as one of the most effective azoles in preventing copper corrosion. The efficiency and mechanism of copper corrosion inhibition were evaluated through electrochemical, theoretical, and morphological studies. Potentiodynamic polarization (PDP) showed that both BHP and BNP were effective in inhibiting copper corrosion. At 10(-3) M, BHP showed a maximum inhibition efficiency of 80.24 %, while BNP achieved an even higher efficiency of 89.83 %. Adsorption behavior analysis indicated that both compounds followed the Langmuir isotherm. In addition, the high value of K-ads (10(3) M-1) indicates a strong adsorption capacity of our molecules on the copper surface. The negative adsorption free energy (Delta G degrees(ads)=-34.14kJ/mol for BHP and Delta G degrees(ads)=-34.00kJ/mol for BNP) indicates a spontaneous adsorption process. Electrochemical impedance spectroscopy (EIS) showed that both compounds formed a thin protective layer on the copper surface, a finding further supported by surface morphology studies using scanning electron microscopy (SEM-EDX) and ATR-FTIR analysis.