| Quick-solidified radar absorbing coatings (RAC) was prepared by carbonyl iron powder (CIP) absorbent and polyurethane (PU) adhesive for the requirement of battlefield repair in this paper. And the interface between RAC and substrate was primary researched. The primary batch formula of Quick-solidified RAC was gained through investigation on PU kinds, the modified multi-hydroxide, the ratio of the multi-isocyanate and the multi-hydroxide, catalyst and CIP contents. The effects of CIP, SCA, wetting agent and surface treatment process on the interface behavior (wettability) of Quick-solidified RAC and the interface structure between coatings and substrate were studied to enhance the adhesion of coatings. Surface defects of Quick-solidified RAC were solved by various additives. And the primary batch formula of Quick-solidified RAC was optimized further. Manual mechanical damage dimension and models (flat and dihedral) were repaired with Quick-solidified RAC, and the absorption properties of repairing coatings could reach about 80% of the original coating, which matches the requirement of battlefield quick repairThe primary batch formula of Quick-solidified RAC was studied. Hexamethylene diisocyanate (HDI) biuret was chosen as the multi-isocyanate, the mixture of 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA) and Hydroxyl Polyacrylic Resin (HPAR) with the molar ratio was 2:5 as the multi-hydroxide. The index of isocyanate (R) was 1.15, the optimal proportion of adhesive and absorbent was 4:1(weight), and the content of dibutyltin dilaurate (DBTDL) was 0.03% of the system. The properties of Quick-solidified RAC were shown as follows: the cured on the common temperature, the surface solidified time of 30min, the entire solidified time of 3 hours, the adhesion of 4.6MPa, the impact strength of 50 kg·cm. The least reflectivity of Quick-solidified RAC was -9.4dB and the band below -8dB was 6.0GHz (12～18GHz).The interface behavior (wettability) of Quick-solidified RAC was studied, and the interface structure between RAC and substrate was primary researched by FT-IR, RA-IR, SEM and EDXA. And the results indicated that, with the content of CIP increasing, surface tension and contact angle of coatings decreased gradually, work of adhesive and the adhesion of coatings increased. Surface tension and contact angle of coatings were decreased by adding wetting agent (0.1wt% BYK-306), but work of adhesive increased, and the adhesion of coatings was 5.0MPa. The adhesive strength between CIP and PU was enhanced by adding SCA, surface tension and contact angle of coatings were decreased by adding SCA (1.0wt% KH-506), work of adhesive increased, and the adhesion of coatings was increased as 21.7% (5.6MPa). Because the surface energy and roughness of substrates was increased by surface treatment with abrading and chemical corrosion, which enhanced the course of adhesion and permeation, adhesion of coatings was improved. The films of KH-550 was formed after surface treatment with KH-550 hydrolysis solution, surface energy reduced, silanes reacted with the group of hydroxyl of the steel surface. The film of KH-550 integrated with RAC, because the amino-group reacted with the group of carbimide. Substrate was treated by 5.0wt% KH-550 hydrolysis solution, adhesion of coatings was improved as 58.7% (7.3MPa).Moreover, the surface defects of the coating film, such as lower dispersivity, air bubble and sinkhole, were decreased by adding dispersant (1.0~1.5wt% of CIP, BYK-W980), antibubbling agent (0.2~0.3wt% Deform5400) and levelling agent (0.3~0.4wt% Levelov 837). The batch formula of Quick-solidified RAC was optimized by adding kinds of additive agents, the adhesion of coatings was improved as 7.8MPa and the other performance of coatings was steady.After optimization, quick-solidified RAC and the right surface treatment process were used for repairing kinds of mechanical damage dimension with flat and dihedral coatings. And the result showed that, quick-repair flat coatings made the reflectivity recovered better, the reflectivity of repairing coatings could reach 85% of that of original coatings in the range of 8～18GHz. In the range of 8～12GHz reflectivity of flat repairing coatings was better than that in the range of 12~18GHz. The absorption properties of dihedral repaired coatings could reach about 80% of that of original coatings in the range of 8～18GHz, which was not better than that of flat repaired coatings. In conclusion, the absorption properties of damage coatings could matches the requirement of battlefield quick repair after repaired.
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