Synthesis and Performance of a New and Simple Schiff Base Structure for Corrosion Inhibition of C38 steel in 1 M HCl Solution: Experimental Studies and DFT Investigation

Abstract

In order to investigate the corrosion of carbon steel (C38) in acidic media, experimental studies (weight loss measurements, electrochemical methods, thermodynamic adsorption isotherms and field emission scanning electron microscopy coupled with energy dispersive X-ray) and computational approach were adopted to study the newly synthesized and simple Schiff base structure, namely 4-((phenylimino)methyl) phenol (PIMP) as a corrosion inhibitor for C38 steel in 1M HCl. Characterization techniques (Fourier Transform Infrared spectroscopy, mass spectrometry, proton nuclear magnetic resonance) showed that PIMP was successfully synthesized with a yield of 63%. Experimental methods (weight loss, open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP)) showed that PIMP is a mixed-type inhibitor with an inhibition percentage of 91.1% under optimal conditions (7.5 mM PIMP at 30°C). These experimental results were supported by surface analysis (Field Emission Scanning Electron Microscopy (FESEM) coupled with Energy Dispersive X-Ray (EDX)), where PIMP molecules are adsorbed on the steel surface and form a protective barrier against aggressive ions, thereby limiting steel oxidation. The adsorption of PIMP on the carbon steel surface followed the Langmuir adsorption isotherm along with a mixture of physical and chemical adsorption, forming a complete and dense protective film on the C38 steel surface. Theoretical results using density functional theory (DFT) calculations showed that PIMP contains highly reactive centers and confirmed the experimental results obtained.