Sample records for alloy-ti99

  1. In-situ corrosion testing of selected HLW container materials under the conditions of the HLW test disposal in the Asse salt mine

    The materials investigated were: The corrosion resistant (passively corroding) materials Ti 99.8-Pd, Hastelloy C4, Nickel and Cr-Nr steel 1.4833, and the corrosion allowance (actively corroding) TStE 355 carbon steel. Specimens of the above-mentioned materials were stored for about five years in an electrically heated cased borehole at temperatures between 170 C and 190 C. The casing consisted of steel with corrosion protection of Ti 99.8-Pd. During the test duration, the specimens were exposed to water/brine and gases (mainly CO2, CH4 and H2) released from the rock salt or generated by corrosion (H2). The corrosion results indicate that the alloy Ti 99.8-Pd is highly resistant to pitting and crevice corrosion, and its general corrosion rate is negligible low (<0.1 μm/a). Nickel is subjected to non-uniform general corrosion, and its corrosion rate (13 μm/a) is clearly higher than that of Ti 99.8-Pd. The Cr-Ni steel 1.4833 investigated suffers from severe pitting corrosion and stress corrosion cracking. Therefore, the Cr-Ni steels must be excluded as material for long-lived containers. The Cr-Ni-Mo alloy Hastelloy C4 shows a high resistance to general corrosion, but the formation of some small pits on the specimen surface was observed. For this reason there is some doubt about the suitability of Hastelloy C4 as container material. The corrosion allowance (actively corroded) material carbon steel TStE 355 shows a good resistance to pitting and crevice corrosion, and its general corrosion rates (13-37 μ/a) imply corrosion allowance acceptable for thick-walled containers. In view of these results, the alloy Ti 99.8-Pd and the carbon steels continue to be considered as the most promising materials for the realization of the corrosion resistant and corrosion allowance container concept, respectively. Further indepth corrosion studies on these materials are in progress. (orig./MM)