Regulation of phosphate coating growth on iron powders via interfacial reaction and ion diffusion for enhanced corrosion resistance and microwave absorption

Purpose The purpose of this study is to address the high susceptibility of magnetic metal powder absorbers to corrosion and failure in marine environments by developing a strategy for depositing phosphate coatings on their surfaces via controlled dissolution reactions and ion diffusion, thereby enhancing the absorbers’ durability. Design/methodology/approach By controlling temperature and stirring speed to adjust interfacial reaction kinetics and mass-transfer conditions, a dense phosphate coating with a certain thickness was deposited on the iron powder surface. Findings Results show that the iron@phosphate composite synthesized at 60 °C–800 rpm for 30 min achieves both excellent corrosion resistance and electromagnetic absorption performance. The dense phosphate coating served as an effective barrier against the penetration of NaCl solution, decreasing the corrosion current density (Icorr) from 30.27 µA/cm2 before the phosphate coating to 0.04 µA/cm2 after coating, significantly enhancing corrosion resistance. Meanwhile, the minimum reflection loss (RLmin) was −49.8 dB, with an effective bandwidth (EAB) of 6.1 GHz. Originality/value This strategy simultaneously enhances corrosion resistance while maintaining strong interfacial polarization loss and impedance matching, thereby realizing excellent electromagnetic absorption performance.