Theoretical and electrochemical performance of Quinazoline Schiff-base hybrid as levelling agents for C-steel electropolishing in acidic medium

This study leverages an innovative knowledge of electrolytic polishing (EP) mechanisms by introducing a newly synthesized Quinazolin Schiff-base hybrid (N-(arylidene)-2-(4-oxoquinazoline-3(4H)-yl) acetohydrazide (QA)) as a levelling agent for C-steel surfaces in 8M H₃PO₄. Several spectroscopic methods, including FT-IR, ¹H NMR, and ¹³C NMR, were employed to verify the chemical structures of QA derivatives. EP with QA derivatives, particularly N'-(3-Methylbenzylidene)-2-(4-oxoquinazolin-3(4H)-yl) acetohydrazide (m-CH3-QA), reduced surface roughness by 83.24%, smoothing defects. QA adsorption on C-steel followed a physical adsorption mechanism, supported by kinetic and thermodynamic analyses. Scanning electron microscopy (SEM), water contact angle (WCA) measurements, and atomic force microscopy (AFM) confirmed improved hydrophilicity/hydrophobicity and a protective corrosion-resistant layer. Energy-dispersive X-ray (EDX) spectroscopy revealed changes in surface composition due to QA adsorption. Computational analyses, including Chemical Reactivity Descriptors, Molecular Electrostatic Potential (MEP), Fukui indices, and Local Dual Descriptors, identified strong interactions between QA molecules and Fe ions at specific atomic sites. These findings demonstrate how QA derivatives enhance surface quality through adsorption, resulting in fewer imperfections than untreated surfaces and a promising approach for improving C-steel surfaces. In addition to theoretical calculations, atomic absorption spectroscopy (AAS) was employed as an alternative to gravimetric techniques. The results from both approaches align well with each other and with those obtained through the electrochemical method.