Abstract: Inorganic salts produced in combustion of pyrotechnically generating aerosol (PGA) fire extinguishing agent are strongly hygroscopic and potentially corrosive to metal surfaces in humid circumstances. To reduce the potential corrosion of the aerosol particles, vaporized octadecyl amine was used to in-situ coat the solid aerosol particulates. XPS and SEM were used to characterize surface structures of the aerosol particles. The results show that surfaces of the solid aerosol particulates were coated effectively. It was obtained that the in-situ coated aerosol particulates decrease their hygroscopicity and corrosion to copper.