The permeation and diffusion of H and D through the alloys were measured by using a membrane technique. At temperatures ranging from 180 to 550C, the H permeation results for Rodar could be summarised by:

P (/s cm atm½) = 4.9 x 10-3 exp[-13500/RT]

while the D permeation results could be summarised by:

Rodar:     P (/s cm atm½) = 4.8 x 10-3 exp[-13900/RT]

Niromet-42:     P (/s cm atm½) = 3.4 x 10-3 exp[-13600/RT]

The diffusivity results for Rodar were described by:

H:     D (cm2/s) = 6.3 x 10-3 exp[-11100/RT]

D:     D (cm2/s) = 2.6 x 10-3 exp[-10300/RT]

The D permeation measurements indicated that coatings of Sn or Sn-Pb alloy were very effective permeation barriers. At temperatures below 170C, these coatings exhibited a permeability which was some 5 orders of magnitude lower than an equivalent thickness of Rodar.

D.R.Begeal: Journal of Vacuum Science and Technology, 1975, 12[1], 405-9