A Model for Decreasing Hydrogen Absorption in Metals Applicable to Ion Implanted Membranes

摘要

A model is presented for decreasing hydrogen absorption by catalyzing the hydrogen evolution reaction (h.e.r.). Its salient features are the presence of a metal on the substrate surface with a higher exchange current density for the h.e.r. than that of the substrate, and a mechanism of hydrogen evolution for which the coverage of the surface is a function of the overpotential. Pt-implanted Fe membranes are evaluated with regard to their catalytic character for the h.e.r. using a Devanathan-Stachurski permeation cell. These data are in full accord with, and illustrate, the above model for decreasing H absorption. Factors affecting the choice of implants for decreasing hydrogen absorption (via modification of the overpotential and the hydrogen coverage) include the nature of the implanted species for catalyzing the h.e.r.; the concentration profile of the implanted species, in particular its concentration in the surface atomic layer(s); and the tendency for enrichment of the surface in the implanted species, as occurs during open circuit corrosion. These factors are illustrated in the data. (Author)