Quantum chemical and electrochemical studies on the corrosion inhibition of aluminium in 1 N HNO3 using 1,2,4-triazine



The present study describes the inhibition of aluminium in 1 N HNO3 with different concentrations of 1, 2, 4-triazine precursors 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (AMTDT) and 4-amino-6-benzyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one (ABTDT) using electrochemical impedance spectroscopy adsorption studies and quantum chemical calculations at 298 K. As the electron density around the inhibitor molecule increases due to substitution, the inhibition efficiency also increases correspondingly. Quantum chemical approach was used to calculate some electronic properties of the molecule to ascertain the correlation between inhibitive effect and molecular structure of the inhibitor. The corrosion inhibition efficiencies of these molecules and the global chemical reactivity relate to some parameters, such as EHOMO, ELUMO, gap energy (ΔE), electronegativity (χ), global hardness (η), and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (ΔN). In addition, the local reactivity has been analyzed through the Fukui function and condensed softness indices.