Synthesis, Identification, Theoretical and Experimental Studies for Carbon Steel Corrosion Inhibition in Sea Water by Some New Schiff base Derivatives linkage to 5-Nitro Isatin Moiety

Abstract

This research includes synthesis of new 5-Nitro isatin derivatives started from 5-Nitro-3-(Ethyl imino acetate)-2-oxo indol, namely 5-Nitro-3-(imino acetohydrazide)-2-oxo indole (1); 5-Nitro-3-[(iminoacetyl) phenylsemi carbazide]-2-oxo indole (2); 5-Nitro-3-[(imino acetyl) phenylthiosemicarbazide]-2-oxo indole (3); and 5-Nitro-3-[(imino aceto) N,N-di methyl urea]-2-oxo indole (4). The derivatives were characterized by using FTIR, ¹H-NMR, ¹³C-NMR and C.H.N.S analysis with the measurement of some physical properties. Quantum mechanical method of the Density Functional Theory (DFT) of B3LYP with a level of 6-311++G (2d, 2p) were used for calculating the geometrical structure, physical properties and inhibition efficiency parameters, all were studied at the equilibrium geometry in four media (vacuum, DMSO, ETOH and H₂O). The theoretical results showed that compound (2) is the best corrosion inhibitor among the others. Finally, the corrosion protectiveness, kinetics, and thermodynamics of the prepared compound (2) effect on C-steel in 3.5% NaCl solutions had been studied using the potentiodynamic polarization, SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy) measurements.

Keywords: 5- nitro isatin, Schiff bases, Corrosion inhibitors, Quantum chemical calculations, electrochemical measurements.