Effects of para-substituted sodium benzoate derivatives on aluminum corrosion inhibition

The corrosion of aluminum radiators in high-voltage direct current transmission systems severely affects the working state of the converter valve. The inhibition of aluminum corrosion in sodium benzoate (SB) solutions was investigated via potentiodynamic polarization and electrochemical impedance spectroscopy, and the optimal concentration for maximum efficiency was determined. To improve the inhibition performance, −CH 3 , −NH 2 , and −NO 2 groups were introduced at the para-position to systematically evaluate the inhibition effects of para-substituted derivatives, including para-methyl (PMSB), para-amino (PASB), and para-nitro (PNSB) sodium benzoate. The surface was characterized by scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and theoretical calculations were performed to analyze the molecular orbital distribution, HOMO LUMO energy gaps, Fukui functions, and adsorption energies. The adsorption mechanism and corrosion inhibition mechanism of corrosion inhibitor molecules were identified, and the corrosion inhibition performance from high to low is as follows: PNSB (74.68%), PASB (72.72%), PMSB (68.90%), and SB (64.59%). PNSB has the best adsorption capacity and corrosion inhibition performance, which is attributed to the electron-withdrawing effect of the −NO 2 group, enhancing binding with the aluminum surface and reducing aluminum dissolution. • The electrochemical corrosion inhibition laws of sodium benzoate (SB), and para-methyl (PMSB), para-amino (PASB), and para-nitro (PNSB) sodium benzoate on aluminum have been clarified. • The −CH 3 , −NH 2 , and −NO 2 groups were introduced at the para-position of SB to systematically evaluate the inhibition mechanism of para-substituted derivatives • PNSB with the best adsorption capacity and corrosion inhibition performance, is attributed to its electron-withdrawing −NO 2 group enhancing binding with the aluminum surface and reducing aluminum dissolution.