Eco-friendly multi-component corrosion inhibitors from natural sources: Theoretical and experimental insights for carbon steel protection in acidic environments

This study investigates the use of rubber seed extract (RSE) as an environmentally friendly, bio-based corrosion inhibitor for carbon steel in acidic environments (3.0 M H₃PO₄). RSE, derived from an agro-industrial byproduct, contains a range of bioactive compounds, such as peptides, thioureas, and alkaloids, identified through LC-MS analysis, which suggest a multifunctional adsorption mechanism. Theoretical simulations, including density functional theory (DFT) and molecular dynamics (MD), demonstrate stable adsorption of RSE on iron surfaces, characterized by strong electron-donating interactions. High adsorption energies (≤ –800 kJ mol⁻¹) and stable dipole moments further confirm the robust interfacial interactions. Electrochemical measurements reveal that RSE can inhibit corrosion by up to 89.4 %, indicating mixed-type inhibition behavior. Surface analyses show that RSE forms a protective organic-inorganic film on the metal surface through coordination with polar groups. These results present a comprehensive inhibition mechanism involving electronic shielding, physical barrier formation, and chemical bonding, positioning RSE as a promising, sustainable inhibitor for corrosion control in acidic conditions. This study provides valuable insights into the structure-property-function relationships of plant-derived inhibitors and offers guidance for the design of future eco-friendly corrosion control agents. • RSE inhibits carbon steel corrosion through multi-functional adsorption and electronic shielding. • Molecular dynamics simulations show RSE molecules adapt to different iron crystal facets. • Electrochemical analysis confirms mixed-type inhibition with significantly reduced corrosion current. • Surface film formation and antibacterial properties highlight multifunctional potential.