HYDROGEN EVOLUTION AND ABSORPTION WITHIN GRAIN-BOUNDARY GROOVES IN SENSITIZED STAINLESS-STEEL UNDER CONDITIONS OF ANODIC POLARIZATION

This paper presents evidence for the electrolytic generation of hydrogen within the grain boundary grooves of a sensitized 430 stainless steel membrane while both of the sample's outer surfaces are anodically polarized with respect to the hydrogen evolution reaction (HER). The grooves are formed by the anodic dissolution of the chromium depleted zone adjacent to the precipitated chromium carbides. Hydrogen absorption is shown to occur from within the steel using the Devanathan-Stachurski hydrogen permeation cell. This result is consistent with earlier observations of gas evolution from within grain boundary grooves. It follows that the local electrode potentials inside the grooves are considerably less noble than those applied at the outer surfaces. An IR potential shift mechanism explains the results.