A facile strategy for constructing dual magnetic/pH-responsive TA@Fe3O4 nanocontainers enabling efficient inhibitor delivery and enhanced corrosion protection

The incorporation of functional fillers into epoxy coatings is an effective approach to impart specific properties; however, the random distribution of fillers within polymer matrices often limits their utilization efficiency. Herein, a magnetic core–shell nanocontainer (TA@Fe 3 O 4 ) was rationally designed and fabricated by encapsulating Fe–tannic acid (Fe–TA) complexes within hollow mesoporous Fe 3 O 4 nanospheres. In this architecture, Fe 3 O 4 serves dually as a magnetically responsive core for field-directed enrichment and as an intrinsic carrier for tannic acid (TA), thereby eliminating the need for additional carrier engineering. The surface Fe–TA complexes undergo pH-responsive coordination transformation under acidic conditions, enabling the controlled release of TA molecules. The released TA subsequently chelates with the metal substrate to form a compact passivation layer, providing active corrosion inhibition. Magnetic-field guidance significantly shortens the diffusion path of TA, thereby enhancing its delivery efficiency to corrosion-prone regions. Electrochemical impedance spectroscopy revealed a substantial improvement in corrosion resistance: the |Z| 0.01Hz value of the magnetically modulated coating (M-TF/EP) reached 1.41 × 10 10  Ω·cm 2 , approximately one order of magnitude higher than that of non-modulated coating (TF/EP). This work presents a straightforward yet highly effective strategy that integrates magnetic targeting and pH- triggered inhibitor release within a single nanostructure by directly coating the inhibitor onto a magnetic carrier, thereby enabling active and intelligent corrosion protection without complex synthesis procedures.