Corrosion resistance of hydrangea-like nano-Ni/amino N-doped rGO epoxy composite coatings constructed via magnetic field-oriented alignment

Abstract

Two-dimensional nanofillers can mitigate the widespread issue of steel corrosion by enhancing the barrier performance of conventional organic coatings. However, their dispersion, interfacial compatibility, as well as alignment and orientation within the coating matrix significantly influence the final protective performance. Nitrogen-doped reduced graphene oxide (rGO) with a high content of amino nitrogen (NH₂-N-rGO) was synthesized via a pyrolysis method. The introduction of amino functional groups enabled chemical bonding with epoxy resin, thereby enhancing the interfacial compatibility of rGO within the coating matrix. Subsequently, hydrangea-like nickel nanoparticles were uniformly grown on the surface of NH₂-N-rGO (Ni@NH₂-N-rGO), endowing the rGO with magnetic properties. The resulting magnetic filler was incorporated into an epoxy resin (EP) matrix and subjected to magnetic alignment (MA) treatment to fabricate the Ni@NH₂-N-rGO/EP(MA) composite coating. Under the influence of a uniform magnetic field, the hydrangea-like Ni nanoparticles induced a reorientation of the rGO sheets, aligning them parallel and orderly along the direction of the substrate. This alignment fully exploited the impermeability of rGO, significantly increasing the diffusion resistance and the tortuosity of the penetration path for corrosive species, thereby markedly enhancing the corrosion resistance of the epoxy composite coating. Our results provide new insights into fully harnessing the functional potential of two-dimensional nanomaterials within conventional protective coatings.