The effects of thiourea and benzotriazole on the H permeation into Fe were studied using a Devanathan–Stachurski electrochemical double cell equipped with a thin Fe membrane. Hydrogen was cathodically generated on the entry side and fully oxidized on the exit side. The spectral analysis of both the electrochemical impedance on the entry side and the permeation transfer function between the ac current signals on the 2 faces of the membrane were recorded. The modifications of the impedance diagrams and the transfer function diagrams induced by the presence of the organic additives were interpreted at the light of the mechanistic model of the transfer function which was recently derived. It was concluded that both additives inhibit the H evolution reaction, but thiourea promoted H penetration by inhibiting the recombination reaction, whereas benzotriazole adsorption inhibited the formation of the Hads and therefore their penetration into the metal matrix.

Effect of Organic Additives on Hydrogen Permeation into an Iron Membrane Studied by Frequency Analysis Techniques. N.Amokrane, C.Gabrielli, G.Maurin, L.Mirkova: Electrochimica Acta, 2007, 53[4], 1962-71