Imidazole-core-based polybenzoxazine-silica (poly(IMP-aptes)-silica) hybrid composites were developed via an in-situ sol-gel process to enhance thermal stability, flame retardancy, and corrosion resistance. The benzoxazine monomer (IMP-aptes) was synthesized through a Mannich reaction involving imidazole bisphenol (IMP), 3-aminopropyl triethoxysilane (aptes), and paraformaldehyde. Structural confirmation was achieved using FT-IR and 1H NMR spectroscopy, while DSC analysis assessed curing behavior. Poly(IMP-aptes)-silica hybrids were formulated using varying loadings of tetraethyl orthosilicate (TEOS) and/or hexadecyltrimethoxysilane (HDTMS). TGA results revealed improved thermal stability, with silica-reinforced hybrids exhibiting a char yield of 65 %, compared to 57 % for the neat matrix. UL-94 flammability testing confirmed V-0 ratings, demonstrating enhanced flame retardancy. SEM analysis of surface morphology, and post-burn char confirmed uniform silica dispersion and compact char formation. Corrosion resistance was systematically evaluated for neat poly(IMP-aptes) and hybrids containing 0, 10, 20, 30, and 40 wt% of TEOS and HDTMS, applied as coatings on mild steel substrates. Based on initial performance, extended 28-day immersion studies (with 7-day intervals) were conducted for 40 wt% TEOS- and HDTMS-reinforced systems. The 40 wt% HDTMS-reinforced hybrid demonstrated superior performance, maintaining 95 % inhibition efficiency up to 21 days and peaking at 98 % in the initial phase. Additionally, coatings applied to cellulose substrates achieved oil-water separation efficiencies exceeding 98 % with flux value of 10185 L m−2 h−1. Overall, the developed poly(IMP-aptes)-silica hybrids exhibited enhanced thermal stability, flame resistance, hydrophobicity (water contact angle ∼140°), and long-term corrosion protection.