Previous corrosion studies identified carbon steels as promising materials for the manufacture of long-lived high-level waste containers that could act as an engineered barrier in a rock-salt repository. In the present work, the effect of electron beam (EB) and tungsten-inert-gas (TIG) welding (potential container closure techniques) on the corrosion behaviour of the preselected fine-grained structural steel TStE355 (DIN No. 1.0566) was investigated. The steel was examined in three
material conditions such as unwelded, only-welded, and welded plus stress-relief thermal treated in a disposal relevant MgC12-rich brine at 150°C and a ganmm radiation field of 10 Gy/h. The results indicate that the unwelded steel is resistant to pitting corrosion in the sense of an active-passive corrosion element and its general corrosion implies corrosion allowances acceptable for thick-walled containers. The EB- and TIG- welding decrease significantly the corrosion resistance of the steel. The only-welded specimens suffer from severe local corrosion attacks in the welds and in the heat-affected zone (HAZ). On the contrary., the thermal treated steel is resistant to local corrosion in the brine, as the unwelded material. In view of these results, tile TStE355 carbon steel continues to be considered a promising material for long-lived
containers. To avoid local corrosion problems in the region of the welded container cover, a stress-relief thermal treatment of the welds is recommended. Keywords: corrosion, HLW container material, carbon steel, disposal, salt brines