In this work, hydrogen permeation tests were performed on pure iron membrane in 1 M sodium hydroxide at 298K, subjected to hydrogen charging under "quasi-potentiostatic" polarization conditions, i.e. constant cell voltage applied between the cathode (membrane entry side) and the anode (counter electrode), which is a typical situation during metal electrodeposition or cathodic degreasing on steel in metal finishing industry. Two consecutive charging-discharging runs were carried out. Prolonged hydrogen charging under quasi-potentiostatic polarization was investigated and the change of cathodic current density (i(in))(chg) and electrode potential (E-in)(chg) as well as permeation current density (i(out))(chg) were analysed. Three singularities were underlined for each experiment: (i) the curve (i(in))(chg) = f((E-in)(chg)), illustrating the inverse of hydrogen charge resistance R-HC(-1) evolution which was negative, equal to zero and then became positive; (ii) quasi-periodic instabilities during the R-HC(-1) zero period, probably induced by atomic reorganizing due to subsurface hydrogen insertion in the input-side; (iii) the same ratio (i(out))(chg)/(i(in))(chg) = -6 x 10(-5). During discharge runs, both sides of the membrane were polarized at the same potential (E-in)(dischg) = (E-out)(dischg) = -0.285 V/Hg/HgO/NaOH 1 M and the current densities, (i(in))(dischg) and (i(out))(dischg) which corresponded to the desorption rates of hydrogen, were measured. The following correlation (i(out))(dischg) vs. (i(in))(dischg) = -6 x 10(-5) was confirmed leading us to introduce the R-HC(-1) mirror con cept to observe the input-side subsurface reorganization by the survey of its potential vs. outside current density during the hydrogen charge. Thus, this R-HC(-1) mirror concept showed: (i) a non-stop and irreversible progress in the subsurface reorganization during the two permeations; (ii) a probable structural evolution to a stable subsurface structure, the only condition of a real steady-state charge when (E-in)(chg) and (i(in))(chg) were stable together, either under potentiostatic or galvanostatic conditions. (C) 2009 Elsevier B.V. All rights reserved.