Eco-Compatible Protection of Mild Steel in 1 M HCl Using N-(ortho-anisyl)piperazine: A Synergistic Electrochemical and DFT Approach

Wael Alsaedi; Ahmed ahmedal-amiery

doi:10.62638/ZasMat1555

Authors

Wael. H. Alsaedi Department of Chemistry, College of Science, Taibah University, Madinah, Saudi Arabia Author https://orcid.org/0009-0009-2715-4468
Ahmed ahmedal-amiery Science and Technology Parks, Al-Ayen Iraqi University, AUIQ, An Nasiriyah, Thi Qar, Iraq; Energy and Renewable Energies Center, University of Technology, Baghdad, Iraq Author https://orcid.org/0000-0003-1033-4904

DOI:

https://doi.org/10.62638/ZasMat1555

Abstract

The corrosion behavior of mild steel in 1 M HCl was investigated in the presence of N-(ortho-anisyl)piperazine (NAP), a heterocyclic organic inhibitor, using electrochemical methods, surface analysis, and quantum chemical modeling. Potentiodynamic polarization (PDP) studies revealed that NAP acts as a mixed-type inhibitor, achieving up to 84% inhibition efficiency at 0.5 mM concentration. Adsorption of NAP on the steel surface followed Langmuir isotherm behavior, indicating monolayer coverage and spontaneous adsorption, supported by a negative Gibbs free energy of –30.03 kJ·mol⁻¹. Scanning electron microscopy (SEM) confirmed a significant reduction in surface corrosion features in the presence of NAP. Density functional theory (DFT) calculations showed favorable electronic descriptors, including a high HOMO (–7.927 eV), low LUMO (1.307 eV), and a positive electron transfer fraction (ΔN = 0.398), supporting strong donor–acceptor interactions with the mild steel surface. Molecular mechanics parameters indicated stable structural flexibility ideal for adsorption. A comprehensive inhibition mechanism involving both physisorption and chemisorption is proposed. The study highlights NAP as an eco-friendly and efficient corrosion inhibitor, offering a synergistic understanding of inhibition through experimental and theoretical approaches.

Keywords:

corrosion inhibitor, DFT, potentiodynamic polarization, SEM, piperazine

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