The migration of H in annealed and hardened AISI420 was studied electrochemically (constant-current) at between 283 and 343K. The permeation rate, effective diffusivity and solubility were deduced from the data. The diffusion data were described by:

D (m2/s) = 1.80 x 10-5 exp[-33.9(kJ/mol)/RT]

while the permeation data were described by:

P (mol/ms) = 1.32 x 10-5 exp[-22.8(kJ/mol)/RT]

The solubility values which were calculated from the permeation data were in good agreement with those that were obtained by using an electrochemical H solubility measurement technique.

C.H.Tseng, W.Y.Wei, J.K.Wu: Materials Science and Technology, 1989, 5[12], 1236-9