Influence of the Cr content on the permeation of hydrogen in Fe alloys

In this work, the permeability of hydrogen through samples of pure Fe metal and through two different FeCr alloys was experimentally analyzed in order to determine the influence of the Cr content on hydrogen transport properties. The gas evolution permeation technique was used to measure the hydrogen transport parameter of permeability in three alloys: pure Fe metal, Fe5%Cr alloy and Fe10%Cr alloy. The experimental measurements were carried out with temperatures ranging from 423 K to 823 K and for high purity hydrogen loading pressures ranging from 1.0 x 10(3) Pa to 1.5 x 10(5) Pa. We observed that the permeability obtained for the three materials considered in this temperature range follows an Arrhenius law. The resultant diffusive permeability for pure Fe metal, Fe5%Cr alloy and Fe10%Cr alloy were found to be, Phi(Fe) = 3.11 x 10 (8) exp(-35.1 (kJ mol (1))/RT), Phi(Fe5%Cr) = 4.34 x 10 (8) exp(-39.1 (kJ mol (1))/RT) and Phi(Fe10%Cr) = 3.46 x 10 (8) exp(-39.7 (kJ mol (1))/RT), respectively. The resulting activation energies turn to be slightly larger for the alloys containing Cr, in comparison to pure Fe, but do not seem to be significantly influenced by a large variation of the Cr content. In general terms, the increase in the content of Cr in the alloy, leads to smaller values of the permeability for the studied Cr contents. (C) 2012 Elsevier B. V. All rights reserved.