Synthesis of hollow carbonyl iron microspheres via pitting corrosion method and their microwave absorption properties

► Hollow carbonyl iron microspheres were prepared via pitting corrosion of commercial carbonyl iron microspheres in ferric solution. ► Several other hollow metal particles such as Ni, Co and Cu can also be prepared through this pitting corrosion method. ► The hollow carbonyl iron microspheres show more excellent microwave absorption properties than the initial ones.