Hydrogen permeation through membranes with cracks in protection layer

Three-dimensional calculations of permeation through membranes with a cracked protection layer have been performed. Analytical solution for the one-dimensional permeation problem has been considered for the case where the absorption influx is determined by the surface opened by the cracks. Good agreement between the two solutions has been found. Cracking of the protection barrier leads to smaller degradation of its properties if permeation through the bare membrane takes place in the surface limited regime. Even small cracking (0.001% of surface is open) can reduce the permeation reduction factor down to 10 if permeation through the bare membrane takes place in pure diffusion limited regime. Only severe cracking (10% of surface is open) can lead to the same reduction if permeation through the bare membrane takes place in pure surface limited regime.