Steady-state concentration profiles of hydrogen in tubular metallic membranes

Abstract

This article analyzes the stress-induced diffusion (SID) model for hydrogen transport in thin cylindrical membranes when the planar approximation, usually adopted in the literature, is relaxed. The SID model, explicitly formulated for a cylindrical membrane predicts a non-linear steady-state concentration profile, characterized by a concentration gradient at the inner surface which can be significantly lower than the macroscopic concentration gradient imposed, depending on the initial hydrogen content of the membrane. We provide analytical arguments to show that this effect is due to the fact that concentration-induced stresses do not relax at steady state, and this is a peculiar feature of thin hollow cylinders, not occurring in thin plates.