A Study on Rust Layer Formed on Weathering Steel: Characterization and Evaluation of Corrosion Resistance

摘要

The rust layer formed on weathering steel and plain carbon steel exposed to coastal environment was characterized by means of polarized microscope, Raman spectroscopy and Moessbauer spectroscopy. Electrochemical impedance spectroscopy (EIS) was also applied to evaluate the stability of rust layer. Polarized microscope and Raman spectroscopy provide information on the distribution of various oxide phases with color difference; black inner layer which was composed of α/γ-FeOOH with a small amount of Fe_3O_4 and γ-Fe_2O_3. Nano-sized α-FeOOH, which was not detected by XRD, was analyzed by Mossbauer spectroscopy at room temperature. EIS results suggest that the rust resistance represents the corrosion resistance of weathering steel indicating a measure of resistance against penetration of corrosive media. Because of relatively dense inner layer and large amount of nano-sized α-FeOOH, 0.3 wt% Mo added weathering steel showed good corrosion resistance.