Thin films of FexO on chemically polished Fe were investigated by using sensitive electrochemical techniques. The oxide was formed on the exit side of the membrane sample. The H which arrived at the oxide/Fe interface was in an atomic or protonic state; thus assisting H-uptake by the oxide. The wustite films were formed by oxidation in a H2O+H atmosphere. The dependence of the H permeation current upon temperature, film thickness and degree of non-stoichiometry was studied. It was found that H permeation through the oxides was possible, but the permeation coefficients were only of the order of 10-21molH/cm bar½s at 25C. The H diffusion coefficient was deduced to be of the order of 4 x 10-10cm2/s. Measurements of the potential dependence of permeation across the film indicated that H migrated, in the oxide, as a charged particle (proton).

K.Schomberg, H.J.Grabke: Steel Research, 1996, 67[12], 565-72