Chemical forms of hydrogen desorbed by permeation through pure iron and oxide dispersion strengthened steels

To clarify factors controlling variation of chemical forms of hydrogen desorbed by permeation phenomena through the oxide dispersion strengthened ferritic (ODS) steels, permeation behaviors of hydrogen through pure alpha iron (Fe) and the ODS steel into a pure argon (Ar) gas atmosphere have been examined by hydrogen permeation experiments with a tritium tracer technique. Difference of chemical forms of hydrogen desorbed by permeation through pure Fe and the ODS steel was explained by oxygen potential at a downstream side which was determined by an amount of hydrogen supplied by permeation and a moisture content in the Ar gas atmosphere at a certain temperature. Due to very high stability of chromium oxides formed on the ODS steels, most of hydrogen desorbed as a hydrogen gas molecular form into the Ar gas atmosphere in the present experimental temperatures ranging from 303 K to 623 K.