The electrochemical permeation method, and galvanostatic charging conditions, were used to measure H diffusion in annealed or cold-worked samples. The diffusivity in the annealed material was independent of cathodic current densities ranging from 2.5 to 250A/m2. In the case of cold-worked material, it was lower when the cathodic current density was lower. The temperature dependence of the diffusivity at 292 to 339K (at a cathodic current density of 10A/m2) could be described by:

D (m2/s) = 3.69 x 10-7 exp[-36.82(kJ/mol)/RT]

Cold-rolled material exhibited a lower diffusivity and a higher activation energy for diffusion (figure 1).

The Electrochemical Determination of Diffusivity and Solubility of Hydrogen in Copper. Y.Sakamoto, K.Takao: Journal of the Japan Institute of Metals, 1982, 46[3], 285-90