A potentiostatic electrochemical technique was used in order to assess the hydrogen permeation performance in relation to the microstructural characteristics of two microalloyed steels with similar strength produced by different manufacturing processes, taking into account the fact that one of the steels is considered to be in the developmental stage (steel 13). The tests were carried out at steels' rest potentials in an aqueous sour environment at 25 and 50 degrees C. The results indicate that steel B is better than steel A at 25 degrees C to resist any embrittlement effect related to hydrogen. This behavior could be explained in terms of reversible and irreversible sites for hydrogen trapping. At 50 degrees C, both steels have a dramatically better hydrogen permeability performance. Moreover, hydrogen diffusion activation energies, effective diffusive coefficients and sub-surface hydrogen concentration values are in accordance with the observed behavior of the steels. (c) 2005 Published by Elsevier Ltd on behalf of the International Association for Hydrogen Energy.