The dependence, upon the cathodic charging current density, of the apparent H diffusivity in pure Fe was measured by using an electropermeation cell. The results could be described by the relationship:

D (cm2/s) = -3.48 x 10-9 + (1.25 x 10-9) [I (μA/cm2)]½

This cathodic current-dependence was explained in terms of trapping theory and a basic electrochemical model. This explanation was rather different to the usual concept of a concentration dependence of the diffusivity. A double plateau in the permeation curve was detected at low charging-current densities.

Effect of Cathodic Charging Current Density on the Apparent Hydrogen Diffusivity through Pure Iron. W.Y.Choo: Journal of Materials Science, 1984, 19[8], 2633-8