Iron-chromium ferritic alloy is a candidate for the interconnect of solid oxide fuel cells (SOFCs). Gastightness is one of the most important properties of the interconnect in a planar-type SOFC. Hydrogen permeation in an iron-chromium alloy was measured in an atmosphere simulating an SOFC at 1073 K. Hydrogen permeability of the oxide scale, which was mainly composed of Cr2O3, was estimated by comparison between experimental results and calculation. The result was approximately 1.3 x 10(-13) mol m(-1) s(-1) Pa-1/2 at 1073 K, which is about four orders of magnitude lower than that of iron. This study revealed quantitatively that the oxide layer, mainly consisting of Cr2O3, that formed on the alloy suppressed hydrogen permeation. (C) 2004 The Electrochemical Society.