Crevice Corrosion Resistance of Alloy 22 in High-Nitrate, High-Temperature Dust Deliquescence Environments

Environmental Degradation of Engineered Barrier Materials in Nuclear Waste Repositories

“…The crevice corrosion susceptibility of alloy 22 is only promoted by the presence of chloride ions, and it can be fully inhibited by the presence of other anions in solution such as nitrate, bicarbonate, sulfate, fluoride, phosphate, and so on [71][72][73]. The best inhibitor of crevice corrosion in alloy 22 is nitrate [69,74,75]. The presence of inhibitor is generally stated using the ratio R ¼ [inhibitor]/[Cl À ].…”

Crevice corrosion of nickel-based alloys considered as engineering barriers of geological repositories

“…49 Nitrate stands out among groundwater inhibitors due to its high concentration in Yucca Mountain groundwater and its remarkable inhibiting efficiency. 28,29,34,44,52,58,59 Nitrate shows R CRIT values from 0.1 to 0.5 for alloy 22, in different testing conditions. Sulphate and carbonate, for instance, shows R CRIT values from 1 to 2 in similar testing conditions.…”

“…30,65 However, as discussed above for the case of TCP precipitation in thermally aged alloy 22, contradicting results are reported by different research groups. 28,35,44 There is limited information on the influence of bright and black annealing on crevice corrosion susceptibility of Ni-Cr-Mo alloys. 27,66,74 Black-annealing oxide from a solution heat treatment at 1121°C for 20 min followed by water quenching does not affect crevice corrosion resistance of alloy 22.…”

“…5 Deliquescence salts may exist even at temperatures significantly higher than the boiling temperature of water (~155°C). 7,27,28,44 Chloride, which is present in these brines, is the main deleterious species that causes crevice corrosion. Crevice corrosion occurs above the critical crevice temperature (CCT) and it is hard to initiate in Ni-Cr-Mo alloys if [Cl − ] is low.…”

“…The preferred specimen in crevice corrosion testing is a prism or multiple crevice assembly. 28,34,37,38,44 This specimen contains a hole through which a nut-and-bolt system adjusts a couple of ceramic crevice formers on the alloy surface. The crevice formers are previously wrapped with PTFE tape of 70 µm thickness.…”