The electrochemical permeation method is often used to study hydrogen
diffusion and trapping in steels; unfortunately, there is great scatte
r in the experimental results. To identify the reason for this scatter
ing, experiments were carried out using pure iron and pure palladium s
pecimens. It is clearly shown that on the iron samples, surface phenom
ena are not controlled. In particular, the passive layer on the exit s
ide induces variation of the hydrogen concentration on this side with
time. On palladium samples, such phenomena can be controlled and stati
onary conditions as well as good reproducibility can be obtained. The
use of a palladium coating on the exit side of ferrous samples can hel
p to better control the surface phenomena during permeation experiment
s and so to obtain meaningful measurements.