STUDY OF HYDROGEN PERMEATION IN METALS BY ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

The transport of hydrogen in Fe was studied by means of the electroche mical permeation technique combined with the electrochemical impedance spectroscopy technique. The result of such measurements is a transfer function relating the output to the input hydrogen fluxes: H-ls,H-le (omega) = Delta l(s)(omega)/Delta l(e) (omega). It is shown that the p resence of surface films, that lags hydrogen permeation and diminishes hydrogen electrochemical detection, modifies significantly the transf er function H-ls,H-le (omega). Results obtained for Fe specimens with and without Pd coatings are presented and discussed.