<i>Ephedra fragilis</i> plant extract: A groundbreaking corrosion inhibitor for mild steel in acidic environments – electrochemical, EDX, DFT, and Monte Carlo studies

The present study introduces an innovative approach to sustainable corrosion inhibition by utilizing the aerial parts of <i>Ephedra fragilis</i> (EF) as a natural inhibitor for steel in hydrochloric acid solutions. Unlike conventional synthetic inhibitors, EF extracts offer an eco-friendly and renewable alternative, emphasizing their potential for industrial applications. Both water and ethanolic extracts were evaluated, and their bioactive compounds were identified using high-performance liquid chromatography. The ethanolic extract was rich in <i>p-coumaric acid</i>, <i>sinapic acid</i>, and <i>hydrated catechin</i>, while the aqueous extract predominantly contained <i>catechin</i>, <i>gallic acid</i>, and <i>3-hydroxybenzoic acid</i>. Electrochemical techniques, including open circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, demonstrated remarkable corrosion inhibition efficiency, reaching up to 97%. The extracts exhibited mixed-type inhibition behavior, with efficiency improving as the concentration increased. Specifically, inhibition efficiencies of 96.13 and 96.84% were achieved using the Tafel method, highlighting the superior performance of EF extracts compared to many synthetic counterparts. Furthermore, scanning electron microscopy revealed the formation of a dense, protective organic layer on the steel surface, which underpins the high inhibition efficiency. This study not only validates the use of EF as an efficient, sustainable corrosion inhibitor but also opens new avenues for the integration of plant-based inhibitors into industrial practices, providing a long-term, eco-friendly solution to steel corrosion challenges.