Hydrogen Analyses of FSW Cu-OFP Tested Under Creep Conditions in Sulphide Containing Environment

Friction stir welded oxygen-free phosphorus-doped copper (FSW Cu-OFP) is a candidate material for nuclear waste canisters, where long-term performance in corrosive environments is critical. This study investigates the effect of sulphide-containing aqueous environments on the creep behaviour of FSW Cu-OFP and the possible role of hydrogen. Creep tests were conducted in sulphide-containing buffer solutions, and hydrogen concentrations were measured before and after exposure. The results show that FSW Cu-OFP exhibits substantially higher creep rates in sulphide-containing water than in air, with creep rates increasing with sulphide concentration. The accelerated creep response may be associated with corrosion-related processes, including vacancy injection arising from general corrosion. Although the as-received FSW material contained approximately ten times more hydrogen than the base material, sulphide exposure did not increase hydrogen content. The results indicate that environmental hydrogen uptake is unlikely to be responsible for the observed creep acceleration.