Microwave-assisted aqueous extract of lady's mantle roots: A green-sustainable inhibitor of mild steel corrosion in HCl acid

This study presents a novel and environmentally sustainable approach to mitigating mild steel corrosion in acidic environments through the use of an aqueous extract of Lady's Mantle roots (LMRAE). The extract was prepared via microwave-assisted extraction and evaluated as a corrosion inhibitor for mild steel in 1 M HCl acid solution. A comprehensive set of techniques, including weight loss, electrochemical tests, FT-IR, and surface analysis, was employed to evaluate LMRAE's inhibition performance under varying conditions. The extract demonstrated outstanding inhibition performance, achieving efficiencies of 93.78 % at 30 °C and 95.03 % at 50 °C at 15 % concentration. Electrochemical measurements confirmed that the extract functions as a mixed-type inhibitor with predominantly anodic action, significantly reducing both anodic dissolution and cathodic hydrogen evolution. Thermodynamic studies indicated that the adsorption process is spontaneous, endothermic, and governed by a combination of physisorption and chemisorption, with chemisorption being dominant at higher temperatures. Adsorption behavior followed both Langmuir and Temkin isotherms with high correlation. FT-IR spectra confirmed the interaction of active functional groups with the metal surface, while Monte Carlo simulations revealed strong planar adsorption of major LMRAE constituents on Fe (110), in agreement with experimental findings. Compared to other natural inhibitors, LMRAE exhibited superior corrosion resistance, eco-friendliness, cost-effectiveness, and industrial potential. These results demonstrate the viability of LMRAE as a high-performance green inhibitor and highlight the broader potential of microwave-assisted extraction for sustainable corrosion protection. • Lady's Mantle root extract inhibited mild steel corrosion up to 95.03 % in 1 M HCl at 50 °C. • The green inhibitor was extracted using microwave-assisted, water-based, sustainable methodology. • Electrochemical results confirmed a mixed-type inhibition mechanism with predominant anodic suppression. • Thermodynamic data showed spontaneous, endothermic inhibition mainly driven by chemisorption. • Lady's Mantle root extract outperformed other green inhibitors in efficiency, cost, safety, and sustainability.