Abstract: Soft magnetic composites (SMCs), coated with ultrahydrophobic insulating layer, are greatly desired to enhance corrosion resistance in practical applications. However, it still lacks scheme on simultaneously achieving in-situ insulating layer with ultrahydrophobicity. In this work, we design an ultrahydrophobic insulation approach through surface modification of FeSiAl by polyvinylpyrrolidone, achieving uniform Al₂O₃/CeO₂ layers on FeSiAl. The ultrahydrophobic CeO₂ layer significantly improves corrosion resistance of FeSiAl SMC in NaCl solution, exhibiting a high charge transfer resistance of 823 Ω cm² even after immersion in a 5 wt.% NaCl solution for 48 h. Meanwhile, the in-situ Al₂O₃/CeO₂ structure formed by solid-state reaction ensures effective permeability of 59 and power loss of 92 mW/cm³ (50 mT/100 kHz) with cut-off frequency of 88 MHz. This study not only presents a novel solution for enhancing corrosion resistance but also offers valuable insights into the development of high-frequency FeSiAl SMCs.

Key words: Soft magnetic composites, Surface modification, Corrosion resistance, Wettability, CeO₂ layer