Nature-Derived corrosion inhibition of steel in HCl by Pančić spruce essential Oil: Insights from experimental and Computational Approaches

Abstract

This study examines the potential of essential oil extracted from the needles of Pančić spruce as an innovative, eco-friendly corrosion inhibitor for carbon steel in a 1 M HCl solution. Analysis by GC/MS and FTIR revealed that the essential oil is rich in active organic compounds. Impedance measurements showed a significant increase in charge transfer resistance values for steel samples treated with the oil, achieving a maximum inhibition efficiency of 93 % at a concentration of 200 ppm after 4 h. Polarization measurements indicated that the oil acts as a mixed-type inhibitor. SEM demonstrated that the oil significantly altered the surface morphology of carbon steel. Adsorption studies followed the Langmuir isotherm, while thermodynamic analysis suggested that the organic components of the oil adsorb onto the metal surface through a combination of physisorption and chemisorption. XPS confirmed the presence of a protective film consisting of Fe oxides/hydroxides and phytochemicals from the essential oil. Theoretical methods (DFTB-MD) supported the experimental data, predicting strong interactions between key phytochemicals and the Fe surface. This study opens the door for further exploration of conifer essential oils as sustainable corrosion inhibitors, contributing to the global shift towards green chemistry and reducing the environmental footprint in industrial applications.