Mechanisms of metal dusting corrosion of iron

Metal dusting is a severe form of corrosive degradation that Fe, Co, and Ni base high-temperature alloys undergo when subjected to environments supersaturated with carbon (a c. 1). This corrosion process leads to the break-up of bulk metal into metal powder. The present study focuses on the fundamental understanding of the corrosion of Fe in carbon-supersaturated environments over the temperature range 350-1050degrees C. Building on earlier research, the role of deposited carbon in triggering corrosion is further clarified. The corrosion rate peaks at similar to575degrees C with a sharp decrease in rate on either side of the maximum. High-resolution electron microscopy reveals, in addition to metal particles, a mixture of graphitic carbon, amorphous carbon, and filamentous carbon in the corrosion product. While the presence of a surface layer of Fe3C is characteristic of corrosion up to 850degrees C, such a layer is absent at the higher temperatures. The focus of this research is to understand reaction mechanisms by characterizing interfacial processes at the nano level. (C) 2002 The Electrochemical Society.