Corrosion behavior and microwave absorption properties of FeSiCr magnetic alloys in acidic saline environments

Magnetic alloy powders combining corrosion resistance and microwave absorption capability are highly desirable for harsh-environment applications; however, the coupling between corrosion evolution and electromagnetic performance remains poorly understood. Herein, the corrosion behavior, microstructural evolution, and microwave absorption performance of FeSiCr powders were systematically investigated during a 30-day exposure in an acidic saline (5 wt% NaCl, pH = 3). The results reveal a three-stage corrosion process driven by selective oxidation. In Stage 1, preferential oxidation of Cr and Si forms a protective oxide layer that suppresses Fe corrosion and improves impedance matching, enabling D12-FeSiCr to achieve an optimal RL min of −51.75 dB and a maximum RCS reduction of 28.1 dB m 2 , outperforming the pristine D0-FeSiCr sample (−48.82 dB). In Stage 2, depletion of surface Cr and Si accelerates Fe oxidation and corrosion kinetics, while the porous iron oxides weaken magnetic properties but introduce additional dielectric polarization loss, leading to only slight deterioration in microwave absorption performance. In Stage 3, a stable corrosion layer slows further corrosion; however, reduced magnetic loss and degraded impedance matching ultimately results in inferior absorption performance. This work reveals the intrinsic coupling between corrosion behavior and electromagnetic properties, providing fundamental insights for environmentally robust microwave absorber design.