Inorganic/organic bilayer of silica/acrylic polyurethane decorating FeSiAl for enhanced anti-corrosive microwave absorption

Corrosive ions with immense penetrating ability often invalidate the traditional microwave absorber as well as cause severe corrosion. Herein, an inorganic/organic bilayer structure of silicon dioxide/polyurethane-acrylic (SiO2@PUA) is developed layer by layer on FeSiAl surface for addressing the dual-function of microwave absorption and anti-corrosion properties. The bilayer structure possesses the inorganic SiO2 layer with physical barrier function and organic outer layer (PUA) of hydrophobic nature. The as-prepared FeSiAl@SiO2@PUA composite structure filled with 20 wt% of paraffin wax displays a maximum reflection loss of −49 dB at 5.8 GHz, and a broad effective absorption bandwidth reaches 7.8 GHz (10.2–18 GHz) at 2.5 mm thickness. Besides, the corrosion behavior of FeSiAl, FeSiAl@SiO2, and FeSiAl@SiO2@PUA is investigated by immersing in a corrosive environment and electrochemical testing. Due to the multi-level protection of SiO2/PUA bilayer, the FeSiAl@SiO2@PUA is immersed in an alkaline salty environment (pH = 12) for 3930 h and the corresponding corrosion potential significantly increases from −0.166 to −0.047 V, indicating the enhanced anti-corrosion with relatively low corrosion current 2.16 × 10-6 A/cm2 and corrosion rate (6.94 × 10-13 m/s). The designing inorganic/organic hybrid structure provides an effective strategy to enhance the dual-function of microwave absorption and anti-corrosion and its application at the commercial level.