| Abstract |
| The objective of this study is to understand the effect of Si, on the corrosion property of the Ca-modified weathering steel and to determine the proper range of such alloying elements to maximize the effect of Ca on the corrosion resistance of the steel. The pH of a thin water film covering the steel was measured to evaluate the effect Ca addition on pH value. The electrochemical impedance spectroscopy (EIS) was employed to evaluate the corrosion resistance of the Ca-modified weathering steel. The characteristics of rust formed on the weathering steels having different alloy chemistry were examined. Analysis on the inclusion morphology and composition showed that the Ca-containing inclusions were mainly composed of Ca-Al-Mn-O-S,and Si was not founded in them except the specimen containing 0.6%Si. In distilled water, the Ca-modified specimens with or without Si showed higher pH values as Ca content was increased. The effect of Ca addition was not greatly affected by the addition of Si when the steel contained a proper Ca content of 50-70 ppm. In the impedance test, the specimens containing higher amounts of Ca showed higher polarization resistance, meaning better corrosion resistance. The analysis on the rust layers formed on the Ca-modified steel surface showed that the dense inner layer was mainly composed of a-FeOOH and y-FeOOH, whereas the loose outer layer was composed of ν-FeOOH and β-FeOOH. Fe₃O_(4) was distributed randomly throughout the rust layer. The specimens containing a high amount of Ca showed a dense and compact morphology, and the specimens containing Si also showed a dense and compact one. The result of Mossbauer analysis showed that more α-FeOOH was formed as Ca content was increased. (Received May 24, 2004) |
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| Key Words |
| Weathering steel, Ca addition, Corrosion resistance, α-FeOOH |
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