2020 年 84 巻 9 号 p. 285-294
Researches on appropriate hydrogen charging methods for simulating hydrogen absorption in low alloy steels, stainless steels and high Ni alloy, from actual environments were overviewed. Both absorbed hydrogen concentrations and hydrogen desorption profiles were compared between various hydrogen charging conditions using thermal desorption analysis (TDA) on hydrogen-charged samples. For low alloy steels, immersion or cathodic hydrogen charging in aqueous solutions were appropriate for simulating hydrogen absorption from atmospheric corrosion or high pressure gaseous hydrogen environments. Absorbed hydrogen concentration could be controlled by adding appropriate amount of hydrogen-promoter or adjusting cathodic current density and applied potential in aqueous solutions. Comparisons in TDA profiles showed that the ratio of strongly-trapped hydrogen and weakly-trapped hydrogen changed depending upon the total amount of absorbed hydrogen. This result means the state of hydrogen in steels can change according to the amount of absorbed hydrogen. For stainless steels or high Ni alloy, cathodic hydrogen charging in aqueous solutions was appropriate for simulating high pressure gaseous hydrogen environments or galvanic coupling conditions. TDA profiles apparently differed depending on hydrogen charging temperature or duration. However, numerical simulation indicated that these profiles were decided by initial hydrogen distribution in specimens, not by trapped hydrogen, contrary to low alloy steels.