Necessity of a palladium coating to ensure hydrogen oxidation during electrochemical permeation measurements on iron

Electrochemical permeation experiments have been carried out with iron samples, the detection side being coated or not with palladium. It is clearly seen that when the quantity of hydrogen which diffuses through the iron membrane is important, the imposition of a potential higher than the hydrogen equilibrium potential at the detection side is not a sufficient condition to ensure the complete oxidation of hydrogen atoms. A part of hydrogen atoms coming to the detection side combine and give molecular hydrogen; these atoms are not measured in the anodic oxidation current recorded at the detection side. Then this anodic current is not a reliable measurement of the hydrogen flux. On a palladium coated detection side, the oxidation of hydrogen atoms seems to be complete even in drastic charging conditions. The use of a palladium coating on the detection side of ferrous samples is necessary for a reliable exploitation of the results.