The electrochemical behavior of 304L stainless steel sheets was studied by cyclic voltammetry in 0.1M NaOH. The hydrogen produced by electrolysis at values more negative than -1.6 V diffuses into the electrode; at more positive potentials, it diffuses back towards the surface, where it is reoxidized. Application of a potential step from -1.6 to -0.3 V produces a current which obeys the semi-infinite diffusion equations. Sheets contaminated by tritium were studied on the basis of the above results. At -0.3 V, the oxide layer is not destroyed; the tritium which it contains is oxidized and passes rapidly into the solution, smaller amounts, due to the tritium diffusing from the bulk of the metal, are subsequently oxidized. At -1.3 V, essentially the same phenomenon is observed, except that the oxide layer is destroyed. At -1.6 V, penetration of hydrogen occurs concomitantly to the oxidation of tritium. Applications to the decontamination of tritium containing steel are discussed.