Experimental and Computational Insights into the Effects of -NH₂ and -Cl Functional Groups on the Copper Corrosion Inhibition by Benzotriazole

The influences of -NH 2 and -Cl groups on the copper corrosion inhibition in 0.5 M H 2 SO 4 solution by benzotriazole were studied using experimental methods and density functional theory calculations. Mass loss tests, potentiodynamic polarization, and surface morphology analyses revealed notable differences: while unmodified benzotriazole showed an inhibition efficiency of 76.6%, the -Cl derivative increased this to 87.6%, whereas the -NH 2 derivative dropped it to 61.0% at the concentration of 5 × 10 −4 M. Density functional theory calculations indicated these differences are not due to electronic properties or inhibitor-copper interaction energies but rather to the inhibitor’s influence on the oxygen reduction reaction, especially O 2 and H 2 O adsorption. The -NH 2 group formed strong hydrogen bonds with O 2 and H 2 O, reducing oxygen reduction inhibition, while the -Cl group repelled O 2 , resulting in enhanced inhibition. Free energy analysis of the oxygen reduction reaction supported these findings. These new insights into benzotriazole derivatives’ copper corrosion inhibition mechanisms offer valuable guidance for developing next-generation corrosion inhibitors.