To elucidate the role of alloying metals such as Ni, Cu and Cr in weathering steels on the formation of alpha-FeOOH rust by atmospheric corrosion of the steels in industrial and urban districts, influence of alloying metal ions on the formation, morphology and adsorption properties of alpha-FeOOH particles synthesized by aerial oxidation of neutral FeSO4 solution was examined. The addition of Cu(II) and Cr(III) dramatically suppresses the crystal growth of alpha-FeOOH and turns the rod-shaped alpha-FeOOH particles into nano-sized irregular ones. Besides, increase of amount of added Cr(III) forms the iron oxyhydroxysulfate named as Schwertmannite (Fe8O8(SO4)(OH)(6)). Whereas, the Ni(II) addition shows no noticeable influence on the growth of alpha-FeOOH crystal and particles. These results imply that the inhibitory effect of crystal and particle growth of alpha-FeOOH is in order of Cr(III) > Cu(II) >> Ni(II). The adsorption of CO2 gas on the alpha-FeOOH particles is impeded by adding Cu(II) and Cr(III). Whereas, the formation of Schwertmannite by adding Cr (III) enhances the CO2 and SO2 adsorption. These results suggest that alloying Cu and Cr in weathering steels inhibit the crystal and particle growth of alpha-FeOOH to accelerate the formation of protective rust layer composed of fine alpha-FeOOH and/or Schwertmannite rust particles on the steels in urban and industrial atmosphere. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.