Mechanistic understanding and performance assessment of Urospermum dalechampii-based green inhibitors for enhanced corrosion resistance of carbon steel in acidic media

Abstract

The increasing demand for environmentally responsible corrosion protection solutions highlights the need for innovative, sustainable inhibitor materials. In response, this research uniquely explores the corrosion inhibitory potential of solvent extracts derived from Urospermum dalechampii, methylene dichloride (MUDE), Ethyl acetate (EUDE), and n-butanol (BUDE), targeting the corrosion resistance enhancement of 25Cr2Ni4WA steel when immersed in acidic conditions (1.0 M hydrochloric acid). The experimental methodology integrates diverse investigative techniques, including gravimetric assessments, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), complemented by advanced microscopic analyses employing scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) and atomic force microscopy (AFM). Results demonstrated substantial corrosion reduction, with maximum inhibitory efficiencies of 78 %, 83 %, and 76 % for MUDE, EUDE, and BUDE, respectively, at optimal extract concentrations and ambient conditions. Elevated temperature testing indicated reduced inhibitor effectiveness, suggesting physisorption as the dominant mechanism. Surface morphology analyses confirmed the formation of dense protective films, significantly lowering surface roughness from 43.7 nm (uninhibited) to 15.3 nm (EUDE-treated samples). Quantum chemical analyses identified active electron-donor and acceptor groups within key phytoconstituents, promoting robust adsorption on steel surfaces, a conclusion supported by molecular dynamics simulations that highlighted energetically favourable interactions. Collectively, these findings affirm Urospermum dalechampii extracts as potent, environmentally friendly corrosion inhibitors, providing a viable sustainable solution for corrosion management in aggressive acidic conditions, and paving the way for future studies focused on scaling up extract production, optimizing formulation stability, and evaluating performance under real industrial conditions.