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Sustainable zinc corrosion control in hydrochloric acid using Calotropis gigantea: a multi-approach investigation combining experiments, RSM, and quantum simulations

Department of Chemistry, , Shri J S Bhakta and Shri K M Bhakta Arts, Shri A N Shah Science and Shri N F Shah Commerce College, Surat, India

E-mail: 1212bhumi@gmail.com

Received: 20 August 2025 Accepted: 27 October 2025

Abstract:

The current investigation delved into the anti-corrosion properties of a novel ethanolic extract derived from Ankado leaves (Calotropis gigantea) (ALE), targeting the corrosion of zinc in a hydrochloric acid (HCl) solution ranging from 0.05 to 0.10 M, at temperatures between 303 to 333 K. To assess these properties, a combination of well-established techniques such as weight loss (WL), electrochemical measurements, density functional theory (DFT) modelling, molecular dynamics simulations (MD), response surface methodology (RSM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were utilized. At a temperature of 303 K and an inhibitor concentration of 2.0 g/L, the ethanolic extract demonstrated exceptional corrosion inhibition efficiency, resulting in a 99.69% reduction in weight loss (WL), 96.30% in EIS, and 98.80% in PDP. The results of both the PDP and EIS indicate that the corrosion inhibition process is regulated by charge transfer, with the ALE extract functioning as a mixed-type inhibitor. The ALE is a potent corrosion inhibitor, as evidenced by the experimental data, and its efficacy increases as the inhibitor concentration increases. The adsorption behaviour of the extract on the zinc surface was further elucidated through a more thorough examination of the effect of concentration and temperature. A corresponding adsorption isotherm was also identified. The Langmuir adsorption isotherm agrees with the adsorption of the ALE extract on the zinc surface. The extract’s negative adsorption free energy values, ranging from − 5.14 to − 40.95 kJ/mol, indicate that adsorption is spontaneous. The optimal corrosion inhibition efficiency of 99.51% was predicted by the optimisation outcome of the RSM model at a temperature of 303 K and an inhibitor concentration of 2.0 g/L. Furthermore, DFT calculations were implemented to establish a correlation between the inhibitory effects of the compounds and their molecular structures. The inhibitor molecules are aligned nearly parallel to the zinc surface, as demonstrated by MD simulations. The observed corrosion inhibition trends were consistent with the binding energy predicted by the simulations, supporting the reliability of the computational models used in the study.

Keywords: Calotropis gigantea; Corrosion; Density function theory; Molecular dynamics simulations; Zinc; Response surface methodology

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-025-04481-y

Chemical Papers 80 (2) 1665–1689 (2026)