lnlhe potentiostatic charging technique for measurement of permeation current, an anodic potential is
applied to the palladium coated side of the steel membrane, to ionise the permeated hydrogen. Different
authors have applied dierent potentials ranging from +200 mV to -560 mV with respect to
HgIHgO electrode. In the studies on the exact range of potentials, two regions of plateau, both in
the negative and positive regions were observed in the plotting of permeation current vs. apphied potential.
In situ cyclic voltammetric studies, carried out at palladium side of steel membrane, in 0.2 M NaOH
solution, gave rise to two reproducible humps at -200 mV and - 360 mV, indicating the exact range
of potentials for the ionisation of permeated hydrogen. This observation was substantiated by measuring
the actual quantum of ionisation at intetvals of 25 mV, both in the negative and positive plateau regions.
Cyclic voltammetric studies with pure palladium, steel and palladised steel in 0.2N NaOH solution are
also found to support the finding that the region of -200 mV to -360 mV with respect to HgIHgO
electrode is the most suitable to be adopted for the efficient ionisation of diffused hydrogen in the
permeation cell
