THE ELECTROCHEMICAL PERMEATION OF HYDROGEN IN STEELS WITHOUT PALLADIUM COATING .1. INTERPRETATION DIFFICULTIES

There is no general agreement on the experimental conditions used in t he hydrogen electrochemical permeation method. Particulary, the necess ity of a palladium coating on steel is not yet recognized. To answer s ome questions concerning the boundary conditions, experiments were car ried out on pure iron and low alloyed steels without palladium coating . It is shown clearly that in this case surface phenomena are not cont rolled. Especially, the passivation layer on the exit side induces var iation of the hydrogen concentration on this side with time. Consequen tly no quantitative evaluation can be made for diffusion parameters, a s long as the mathematical model issued from the usual stationary boun dary conditions is used.