In this work, hydrogen permeation tests were performed on pure iron membrane in 1 M sodium hydroxide at 298K. Prolonged consecutive hydrogen charging under galvanostatic polarization were investigated in alkaline (1 M NaOH) and NaCN-containing (1 M NaOH + 0.25 M NaCN) electrolytes. Both cathodic potential membrane ((E-in)(chg)) and permeation current density (i(in))(chg) were analysed. The analysis of the permeation transients underlined several singularities: (i) no plateau for the permeation transients - corresponding to a steady-state - under a long-lasting negative polarization, in alkaline media, (ii) quasi-periodic instabilities probably induced by atomic reorganizing due to sub-surface hydrogen insertion in the input side and (iii) the effects of successive galvanostatic steps. (C) 2010 Elsevier B.V. All rights reserved.