Bulletin of Faculty of Education, Nagasaki University : Natural Science

The permeation behavior of hydrogen through pure aluminum has been investigated in the temperature range of 625 K to 778 K by a gas permeation technique. The permeation rate of hydrogen was strongly affected by the conditions of the surface where the hydrogen was introduced into the sample. They varied characteristically by repeating the permeation run, which was bounded in the temperature range of 690K to 700K. At a higher temperature than 700K, the surface oxide layer was reduced by hydrogen during the permeation run, which resulted in the larger permeation rate of hydrogen in the subsequent permeation runs. At the sensitized surface by the reduction, the temporary poisoning took place and the permeation rate of hydrogen was decreased. The poisoned surface, however, was cleaned by keeping the sample under high vacuum at a higher temperature than 700K. The poisoning was closely related to the presence of carbon and its compounds on the top surface where the hydrogen was introduced into the sample