On the efficiency of barbituric acid and its thio derivatives as aluminium corrosion inhibitors: A computational study

Abstract

The corrosion inhibition efficiency of the barbituric acid and its thio derivatives were herein monitored by the execution of a variety of density functional theory (DFT) computations. The 1,3-diazinane-2,4,6-trione (BA); 6-sulfanylidene-1,3-diazinane-2,4-dione (1S); 2,6-bis(sulfanylidene)-1,3-diazinan-4-one (2S); and 1,3-diazinane-2,4,6-trithione (3S) compounds were devoted as aluminum corrosion inhibitors. Global and local quantum descriptors were determined for the neutral and protonated forms of the modelled inhibitors in gas and aqueous phases. As the global indices indicated, reverse and proportional correlations were noticed between the number of S atoms in the studied inhibitors and their ionization potential and electron affinity. Accordingly, the inhibition efficiency of the studied compounds generally increased in the order BA < 1S < 2S < 3S. In the same line, the obtained values of local nucleophilic and electrophilic Fukui function indices affirmed the further favorability of the 3S compound over other studied analogs. Utilizing molecular dynamics simulations, the most favorable configurations for inhibitor∙∙∙aluminium (Al)(111) complexes were characterized. Binding energy calculations revealed the efficiency of the corrosion inhibition increased in the order BA∙∙∙Al (−0.95 eV) < 1S∙∙∙Al (−1.71 eV) < 2S∙∙∙Al (−2.16 eV) < 3S∙∙∙Al (−2.49 eV). Upon the presented findings, the current work would be a sufficient linchpin for future research related to the aluminium corrosion inhibition process, particularly with the incorporation of acids and their thio derivatives.