Computational simulation and statistical analysis on the relationship between corrosion inhibition efficiency and molecular structure of some hydrazine derivatives in phosphoric acid on mild steel surface

In this work, global reactivity descriptors (GRDs) are calculated in order to examine the link between corrosion inhibition efficiency and electronic properties of four Azines namely: 1,2-bis(pyrrol-2-ylidenemethyl) hydrazine (HZ(1)), 1,2-bis(thiophen-2-ylidenemethyl) hydrazine (HZ(2)), 1,2-bis(furyl-2-ylidenmethyl) hydrazine (HZ(3)) and 1,2-bis(pyridin-2-ylidenemethyl) hydrazine (HZ(4)). Apart from the neutral molecules, possible protonation at respective likely sites/heteroatoms was examined in order to predict the behavior of the compounds under experimental conditions of (2.0 M) H3PO4. The GRDs most pertinent to the potential actions of the studied compounds as corrosion inhibitors were investigated in both un-protonated and mono-protonated forms for adequate comparison. The proton affinities, Fukui functions on the active centers of both forms are also calculated at the DFT/B3LYP/6 - 311 + + G * * level of theory in the gas phase. The protonated sites showed slightest tendency of chemical adsorption to metallic surface. The type of interactions for Air-inhibitor/H3PO4/Fe-face system is determined by thermodynamic parameters of adsorption. QSAR results show good linearity between some GRDs (E-HOMO, E-LUMO & mu) and literature experimental inhibition efficiency (R-2 approximate to 1). Furthermore, molecular dynamics (MDs) simulation studies were applied to search for the final and lowest energy configurational spaces for HZ(i)/50H(2)O/3H(3)O(+)/PO43-/Fe{111} systems. The combination of GRDs with MDs parameters provides an effective means of understanding the physico-chemistry of these Azines.