Corrosion behavior of SUS-304L SS, which is used as a typical material for reactor structures has been studied under the steam containing CsOH at temperatures of 450-750°C. The steam was supplied by heating the aqueous solution of CsOH with concentrations 0-320 mM at 110°C. The mass gain by oxygen uptake increases parabolically with reaction time. Since the activation energy of reaction rate constant is consistent with that of self diffusion of Fe in Fe304, it can be considered that the corrosion reaction is determined by the diffusion rate of Fe atoms in the outer oxide layer. The effect of CsOH on the corrosion reaction under the steam is large in the initial stage of the reaction, but small in the final stage. The mechanism of corrosion reaction has been discussed on the basis of microstructure and composition of the reaction layers.
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