Composition and protective ability of rust layer formed on weathering steel exposed to various environments |
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Authors: | T Kamimura S Hara M Yamashita |
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Affiliation: | a Corporate Research and Development Laboratories, Sumitomo Metal Industries, Ltd., 1-8 Fuso-cho Amagasaki, Hyogo 660-0891, Japan b Investigation and Research Division, Sumitomo Metal Technology Inc., 1-8 Fuso-cho Amagasaki, Hyogo 660-0891, Japan c Department of Mechanical and System Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2201, Japan |
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Abstract: | The compositional change of rust (corrosion products) layer formed on weathering steel exposed to atmosphere with different amount of air-borne sea salt particles in Japan have been investigated by the X-ray diffraction method. The mass ratio (α/γ) of crystalline α-FeOOH to γ-FeOOH, in the rust layer formed on the weathering steel exposed in an industrial environment, increases with an increase in exposure duration. The α/γ is closely related to the corrosion rate in environments when the amount of air-borne salt is less than 0.2 mg NaCl/dm2/day (2.31 × 10−7 g NaCl/m2/s). However this is not the case in seaside environments with a higher amount of air-borne salts. The mass ratio (α/γ∗) of crystalline α-FeOOH to the total mass of γ-FeOOH, β-FeOOH and Fe3O4, in the rust layer formed on the weathering steel is related to the corrosion rate even in seaside environments certainly more than 0.2 mg/dm2/day (2.31 × 10−7 g/m2/s) of air-borne salt particles. When the α/γ∗ is more than 1, a higher corrosion rate more than 0.01 mm/year (3.17 × 10−13 m/s) is not observed. The α/γ∗ is a protective ability index of rust formed on weathering steel. |
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Keywords: | Low alloy steel Weathering steel X-ray diffraction Atmospheric corrosion Rust |
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