High-temperature corrosion resistance

Ferritic stainless steels depend on chromium for high temperature corrosion resistance. A Cr202 scale may form on an alloy above 600°C when the chromium content is ca 13 wt % (36,37). This scale has excellent protective properties and occurs iu the form of a very thin layer containing up to 2 wt % iron. At chromium contents above 19 wt % the metal loss owiag to oxidation at 950°C is quite small. Such alloys also are quite resistant to attack by water vapor at 600°C (38). Isothermal oxidation resistance for some ferritic stainless steels has been reported after 10,000 h at 815°C (39). Grades 410 and 430, with 11.5—13.5 wt % Cr and 14—18 wt % Cr, respectively, behaved significandy better than type 409 which has a chromium content of 11 wt %. 

An excellent reference book for the high-temperature corrosion resistance of materials of construction is George Y. Lai, High-Temperature Corrosion of Engineering Alloys, ASM International, Metals Park, Ohio, 1990. 

Preoxidation treatment of the metal surfaces of the TRBPs and the GPCR reactors is strongly recommended to significantly enhance the high-temperature corrosion resistance. 

Nuclear thermochemical and high temperature electrolysis High temperature corrosion-resistant materials Advanced catalysts and membrane materials Durable electrode and seal materials for high temperature electrolysis... 

Turbine blades of jet engines are coated with a protective layer of platinum aluminide to impart high temperature corrosion resistance. Platinum is electroplated onto the blade using P-salt or Q-salt electroplating solutions (28,29). The platinum is then diffusion-treated with aluminum vapor to form platinum aluminide. Standards for the inspection and maintenance of turbine blades have become more stringent. Blades are therefore being recoated several times during their lifetime. 

Chromium-containing cobalt alloys have been developed for use requiring wear resistance and high temperature corrosion resistance. The nominal composition of some wear-resistant cobalt alloys is given in Table 4.49. 

Nonporous spinel oxide ceramics of MgAl204 are notable for their very good high temperature corrosion resistance to alkaline media. Sintered yttrium oxide exhibits still better corrosion resistance at high temperatures (Y2O3 melting point ca. 2400°C), but its utilization possibilities are limited by its high price. 

In diffusion coating, the substrate surface is enriched in an element that will provide high-temperature corrosion resistance. Typical elements are chromium (chromizing), aluminium (aluminizing), or silicon (siliconizing). The substrate is involved... 

In designing alloys for use at elevated temperatures, the alloys must not only be as resistant as possible to the effects produced by reaction with oxygen, but resistance to attack by other oxidants in the environment is also necessary. In addihon, the environment is not always only a gas since, in practice, the deposihon of ash on the alloys is not uncommon. It is, therefore, more realishc in these cases to speak of the high-temperature corrosion resistance of materials rather than their oxidation resistance. 

M. Fukumoto, C. Tachikawame, Y. Matsuzaka, M. Hara, Formation of Si diffusion layer on stainless steels and their high temperature corrosion resistance in molten salt, Corros. Sci. 56 (2012) 105—113. 

Structural material selection. The AHTR requires high-temperature corrosion resistant materials. Materials are the greatest challenge for all high-temperature reactors, including the AHTR. Materials have been identified that allow operation with molten salts to 750°C (Hastelloy-N). 

A1 Novel approaches to the improvement of high temperature corrosion resistance... 

High-temperature, corrosion-resistant components or skin material for the space craft... 

Because of the high temperature corrosion resistance and thermal stability exhibited by magnesium-chromium oxide refractories in copper smelting, converting and fire refining furnaces, little research has been conducted on other refractory families. However, the concern for hexavalent chromium (Cr ) as a potentially hazardous waste in spent refractories from copper production furnaces has prompted the recognition that a more environmentally acceptable material is needed for the copper industry. 

The presence of alumina is expected to provide enhanced high temperature corrosion resistance. Also, the introduction of Si02 into alumina based coatings has been found to form mullite and reduce the cracking within the coating (Marple et al., 2001). Mullite is known for its excellent creep resistance (Dokko et al., 1977 Lessing et al., 1975). 

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