Multilayer Core–Shell Structured CIP@2-MI/MBI/EP with Synergistic Corrosion Resistance and Microwave Absorption Properties

Magnetic metal absorbers will inevitably suffer from corrosion and aging failure in actual application environments (air, salt spray, acid/alkali, etc.), resulting in serious deterioration of their performance. Using inert, densified materials to modify absorber surface is an effective and feasible solution. Herein, a core-shell structure carbonyl iron composite absorbent (CIP@2-MI/MBI/EP) was prepared by in-situ polymerization with 2-methylimidazole (2-MI), 2-mercaptobenzimidazole (MBI), epoxy resin (EP) as the precursor, and carbonyl iron powder (CIP) as the core. The core-shell structure has enhanced both of corrosion resistance and microwave absorbing performance due to the effect of alleviating the intrusion of corrosive media and low dielectric characteristics of the corrosion inhibitors MBI and EP. The results of electromagnetic parameter test exhibited the minimum reflection loss(RL) of the modified absorbent at 13.78   GHz is -69.57   dB, and the thickness is only 1.65   mm. Electrochemical tests revealed the corrosion potential (E corr )of the composite powder shifted positively from -0.680   V to -0.012   V compared to original CIP. The corrosion current (i corr ) decreased from 59.1 μA/cm 2 to 0.1562 μA/cm 2 , and the annual corrosion rate (CR) decreased by 2 orders of magnitude to 0.0223   mil/year. These results attest to the exceptional corrosion resistance of the composites. In addition, the results of salt spray experiments revealed that the morphology and composition of CIP@2-MI/MBI/EP absorbers remained largely unchanged after 720 H salt spray test. Meanwhile, the acid resistance test (PH=1) further demonstrated the outstanding anti-corrosion performance of the composites. The research offers a new option for the development and design of high-efficiency microwave absorbent with robust corrosion resistance.