Transfer function analysis of hydrogen permeation through a metallic membrane in a Devanathan cell - Part II: Experimental investigation on iron membrane

The input impedance Z(1)(omega) = Delta V-1/Delta I-1 and the permeation transfer function (PTF) H(omega) = Delta I-2/Delta I-1 were simultaneously measured during hydrogen permeation through an iron membrane in a conventional electrochemical Devanathan double cell. Various experimental parameters, such as the thickness of the membrane or the polarization potential applied at the input side, were investigated, and their influence were discussed in the light of the model derived in the first part of this paper. In most cases an alkaline electrolyte was used in the input cell. The effect of a thin palladium layer deposited on the output side was also investigated. In acidic medium it was shown that the spontaneous corrosion at rest potential is sufficient to feed hydrogen permeation. At last, thiourea which is known to be a promoter of hydrogen penetration into iron materials, was added to the input solution. The effect of this additive on the evolution/permeation process was investigated by impedance/PTF analysis. (c) 2006 Elsevier B.V. All rights reserved.