COSE/Cu hybrid films constructed by Cu2+ mediation with camellia oleifera shell extracts for Q235 steel anti-corrosion

An organic-inorganic hybrid film on the Q235 steel surface has been in situ constructed through the unique synergy of camellia oleifera shell extracts (COSE) and Cu²⁺, displaying excellent and stable corrosion inhibition performances in 1.0 M HCl solution. The inhibition performances and the underlying synergistic mechanisms of the COSE/Cu hybrid film are deeply investigated by combining experimental and theoretical approaches as well as comprehensive characterizations. It clarifies that the COSE/Cu hybrid film is primarily composed of adsorbed COSE organics and the in situ generated Cu nanoparticles. The COSE/Cu hybrid film can significantly enhance the hydrophobicity of the steel surface and improve the inhibition efficiency (96.30%) for Q235 steel in 1.0 M HCl solution. Electrochemical tests show that COSE/Cu significantly inhibits cathodic corrosion reactions, increases R_ct to 741.0 Ω cm², and has the lowest unified interface reaction coefficient (0.9×10⁻⁵ s⁻¹). Quantum chemistry, molecular dynamics simulations, and density functional theory calculations results show that the synergy between Cu²⁺ and the active components of COSE promoted both charge transfer between COSE/Cu and Fe and adsorption on the steel surface. This research firstly represents the systematic exploration of the active components of COSE for corrosion inhibition and simultaneously reveals the unique synergistic mechanism between COSE and Cu²⁺ in detail.