In situ observations of silver-decoration evolution under hydrogen permeation: Effects of grain boundary misorientation on hydrogen flux in pure iron

An in situ silver decoration technique using a light microscope was developed. Hydrogen was introduced from the bottom surface of an annealed pure iron specimen, and its top surface was covered with a chemical solution containing silver ions. Samples were exposed for sufficient time for hydrogen permeation to occur from the back to the top surface. The resultant in situ silver decoration visualized that the hydrogen flux through low-angle grain boundaries is lower than that observed at high-angle grain boundaries. The in situ silver decoration technique can be used for kinetic analysis of solute hydrogen in ferritic iron and steels. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved: