Synthesis, Characterization and DFT Studies of New Azo-Schiff Base and Evaluation as Corrosion Inhibitor

Abstract

A new Azo-Schiff base namly 6,6'-((1E,1'E)-(1,2-  phenylenebis (azanylylidene)) bis (methanylylidene))  bis(3-(o-tolyldiazenyl)phenol) (A₁) have been synthesized and characterized by elemental analysis, FT-IR,¹H-NMR and Mass spectra. The new compound was evaluated as corrosion inhibitor for brass alloy in 0.5 M HCl, using weight loss . Weight loss  measurements was studied at different temperatures and concentration and  results show that the inhibition efficiency increases with decreasing temperature and increasing concentration of inhibitors and the highest inhibition efficiency was obtained at an optimum concentration of (1×10^-3 M) for inhibitor at      298 K . Thermodynamic parameters enthalpy of activation (Δ𝐻_𝑎^∗) , entropy of activation (Δ𝑆^∗_𝑎 ), and the activation energy (Ea) and for brass alloy corrosion and inhibitor adsorption, respectively, were determined and discussed. It has been determined that the adsorption for the studied inhibitors on brass complies with the Langmuir adsorption isotherm at 298 K, the calculated ΔG_ads values were found to be around -35 kJ mol^-1, which indicates that  inhibitor (Azo-Schiff base) is adsorbed on the brass surface by chemical and physical interactions. For further investigations DFT studies were employed to study the electrostatic potential  and explain the nature of interaction between the inhibitor molecules  and metal surface.