Steels continued high-temperature corrosion

The extent to which low alloy steels react to high temperature corrosive environments is the subject of this chapter. In view of the commercial importance of these steels, the published literature on this topic is extensive and is being continually enlarged. The reader is encouraged to refer to the many excellent papers and current issues of the journals, referenced at the end of the chapter, for more detailed and contemporary information on the topic. 

A dense and electronically insulating layer of L1A102 is not suitable for providing corrosion resistance to the cell current collectors because these components must remain electrically conductive. The typical materials used for this application are 316 stainless steel and Ni plated stainless steels. However, materials with better corrosion resistance are required for long-term operation of MCFCs. Research is continuing to understand the corrosion processes of high-temperature alloys in molten carbonate salts under both fuel gas and oxidizing gas environments (29, 28) and to identify improved alloys (30) for MCFCs. Stainless steels such as Type 310 and 446 have demonstrated better corrosion resistance than Type 316 in corrosion tests (30). 

The most critical parts, the contact parts of the rotating assembly, are most frequently made in one of the many stainless steels. Nevertheless some manufacturers continue to supply howls in carbon steel. The 316-type stainless steel is a common material for the smaller decanters, but for the larger machines at higher g-forces, materials with higher strength, such as the duplex stainless steels, must be used. Where high temperatures, or extra high speeds, or corrosive materials are in use, special corrosion-resistant or temperature-resistant materials may be used. 

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