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

## TL;DR

This paper introduces a new Quinazoline Schiff-base compound that significantly improves the surface quality of C-steel during electropolishing in an acidic solution.

## Contribution

The study presents a novel Quinazoline Schiff-base hybrid as an effective levelling agent for C-steel electropolishing.

## Key findings

- The QA derivative m-CH3-QA reduced surface roughness by 83.24%.
- QA adsorption on C-steel followed a physical adsorption mechanism.
- Computational analyses confirmed strong interactions between QA and Fe ions.

## Abstract

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.

The online version contains supplementary material available at 10.1038/s41598-025-25001-8.