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Recently, the researches of hydrogen energy have been developed. However, the
hydrogen penetrates into the metal and it causes hydrogen embrittlement.
Concerning the investigation of hydrogen embrittlement, in spite of the fact that
stile studies have been conducted for many years, the mechanism of hydrogen
embrittlement has not yet been clarified. For example, hydrogen embrittlement is
typical for steels used for a petroleum-refining reactor. This will be due to the
following reason. Hydrogen penetrates from a container wall surface when a
petroleum-refining reactor operates under high temperature and pressurized
hydrogen environmental conditions. Major part of the hydrogen remain in the
wall for a long time during cooling process when the reactor is out of operation,
which results in the delayed fracture [1,2]. Therefore, clarification of the
hydrogen diffusion behavior in the metal is important for prevention of hydrogen
embrittlement fracture.
To clarify the behavior