The effect of inhibiting Ferula Asafoetida L. extract used in anodized-conversion treatment to improve corrosion protection of aluminum alloy: Experimental and quantum chemical calculations

This study investigates the efficacy of a green inhibitor derived from Ferula Assafoetida L. (FAL) extract, incorporated into the post-anodizing sealing bath, to enhance the corrosion resistance of AA1050 aluminum alloy. The protective performance was evaluated relative to traditional hot-water sealing. Electrochemical measurements, including potentiodynamic polarization and electrochemical impedance spectroscopy, revealed a pronounced concentration-dependent effect. The sample sealed with 200 ppm FAL extract exhibited exceptional performance, with a corrosion current density of 0.89 µA/cm², an order of magnitude lower than that of the hot-water seal (15.56 µA/cm²), and a polarization resistance of 54.3 kΩcm². Complementary field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy provided structural and chemical insights. The 200 ppm sample showed a dense, composite morphology with isolated pores and a high carbon content (23.0 wt%), confirming the formation of a stable organic-inorganic barrier. Fourier-transform infrared spectroscopy indicated post-corrosion cross-linking of the FAL film at 200 ppm, forming a resilient polymeric network. X-ray diffraction confirmed the presence of boehmite in all sealed samples. Quantum chemical calculations identified ferulic acid as the primary active component in the FAL extract, possessing the highest HOMO energy and strongest electron-accepting ability, thereby facilitating stable adsorption on the aluminum surface.