USE OF PURE METALS TO ANALYZE HYDROGEN ELECTROCHEMICAL PERMEATION IN STEELS

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.