One-pot synthesis of Schiff base as an excellent corrosion inhibition for Inconel 800 alloy in sulfuric acid medium: Experimental, DFT calculation and spectroscopic inspections

Abstract

A new heterocyclic Schiff base was synthesized and characterized, namely: N¹,N³-Bis(1-(pyridin-2-yl)ethylidene)malonohydrazide (H₂L). The molecular chemical structure of H₂L was characterized using proton nuclear magnetic resonance (¹HNMR), Infrared spectroscopy (IR), and elemental analysis. The inhibition effect of compound H₂L against the corrosion of Inconel 800 in 1 M H₂SO₄ was studied by chemical (weight loss) and electrochemical techniques (Tafel polarization and electrochemical impedance spectroscopy, EIS). Electrochemical and gravimetric measurements showed that% IE increases with increasing concentration and exhibited a maximum efficiency of 91 % at 18 × 10⁻⁶ M by the WL method. Inhibition efficiency increases with higher concentration and decreases as the temperature increases. The polarization technique indicates that this compound behaves as a mixed-type inhibitor. The adsorption of this compound was found to obey the Langmuir adsorption isotherm. The surface examination of the Inconel 800 surface with H₂L was tested using scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), and atomic force microscope (AFM) to confirm that H₂L was adsorbed on Inconel 800 forming a film. The kinetic and thermodynamic parameters were calculated and discussed. The results of the theoretical study using DFT confirm the experimental results.