Abstract: The formation and aggravation of hydrogen damage in Fe-3 wt-% Si alloy during cathodic charging Were studied by means of Lange transmission X-ray topography.Results showed that hydrogen damage did not form in the specimens charged in 0.5 mol/L H_2S0_4 so- lution without poison,and occurred with addition of 250 mg/L As_2O_3 even at very low charge current density.As charging at a certain current density,the size of the damage may enlarge up to a limit yet no more by prolonged time.The damage size increased with increase of charging current density,but not so apparent at high current density. An external tensile stress could promote the formation of hydrogen damage obviously. It seems that for charging in H_2SO_4 solution containing poison,the drop of hydrogen permeation curve against time prolongation is due to the formation of hydrogen damages.

Key words: hydrogen embrittlement, X-ray topography, Fe-3 wt-%Si alloy