It was noted that, during the hydrogenation of metals under high-fugacity conditions (such as electrolytic charging), non steady-state diffusion produced concentration versus distance profiles which could not be calculated by assuming a simple diffusion behavior. Such profiles were calculated by using finite-difference methods, and considering specific models for the concentration-perturbation of the appropriate jump activation barriers. The results showed that much higher H concentrations were produced, for a given penetration distance, than would be expected by assuming Fickian diffusion.

Concentration-Distance Profiles Resulting from the Hydrogen-Charging of Metal Lattices under High-Fugacity Conditions. D.Zang, R.B.McLellan: Acta Materialia, 1999, 47[7], 2225-42