Experimental and Theoretical Study on the Corrosion Inhibitive Potentials of Schiff Base of Aniline and Salicyaldehyde on mild steel in 0.5M HCl

Abstract

The need to control and ultimately eradicate the scourge of metal corrosion has become necessary given the high incidence of deaths and loss of property resulting from it. The choice of π-conjugated organic systems has been justified in that they are easier to produce and their modes and rates of adsorption are very superb, a consequence of the π-electrons. In this work, a Schiff base of the reaction of aniline and salicyaldehyde was applied as corrosion inhibitor on mild steel via weight loss techniques (at different inhibitor concentrations and at different temperatures) from which the corrosion rate (Cr), degree of surface coverage (θ) and the percentage inhibition efficiency (%IE) were calculated. The molecule was modelled and optimized using Density functional theory (DFT) with B3LYP correlation and 6-31G* and 6-31+G* basis sets to obtain the electronic properties like the frontier molecular orbitals energies (EHOMO and ELUMO), energy band gap (Eg), dipole moment (μ) and the reactivity descriptors like chemical hardness (η), softness (δ), global electrophilicity index (ω) and fraction of electrons transferred (ΔN). The Cr increased with increase in temperature and decreased as the inhibitor concentration increases while the %IE followed a reverse pattern. From the R2 values, the molecule’s adsorption obeyed the Freundlich adsorption isotherm. ΔG values which turned negative confirmed that the reactions are exothermic and spontaneous. The results obtained are consistent with available experimental data.