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Alloy 22 (UNS N06022), a Ni-Cr-Mo-W based alloy, is a candidate material for the outer wall of nuclear waste package (NWP) containers. Even though the alloy is highly stable at low temperatures, it could undergo microstructural changes during processing such as welding and stress relieving. Formation of topologically close-packed (TCP) phases such as , P, , etc. and Cr-rich carbides could make the material susceptible to localized corrosion. Hence, it is important to correlate the microstructural changes with the corrosion resistance of the alloy by nondestructive and rapid electrochemical tests. In this investigation, different electrochemical test solutions were used to quantify the microstructural changes associated with aging and welding of the wrought alloy 22. The results of double-loop (DL) electrochemical potentiodynamic reactivation (EPR) tests in 1 M H 2 SO 4 ϩ 0.5 M NaCl ϩ 0.01 M KSCN solution indicated Cr depletion during initial stages of aging of wrought alloy 22. Results of EPR tests in 2 M HCl ϩ 0.01 M KSCN solution at 60 °C correlated well with the Mo depletion that occurred near TCP phases formed during aging of both weld and wrought alloy 22 materials. The EPR test results were compared with standard chemical weight loss measurements specified by ASTM standard G-28 methods A and B.

Rupture of passive film is considered as an essential step in the stress corrosion cracking (SCC) process. At constant load, accumulation of creep strain is often associated with the strain to passive film rupture. Therefore, low-temperature creep behavior of a material is important from an SCC point of view. Constant load creep studies carried out on alloy 22 (a Ni-22Cr-13Mo-4W alloy) in acidified chloride environments at 80 °C showed a logarithmic creep behavior. The creep strain decayed logarithmically and reached values less than 4 ϫ 10 Ϫ9 /s, which is lower than the detectable limit of laboratory scale SCC tests. 304 SS showed SCC failure in acidified chloride solutions in simulated open circuit conditions. A steady-state creep strain rate could be observed during SCC failures, of the order of 10 Ϫ5 to 10 Ϫ6 /s. The high creep strain rate of 304 SS can be correlated to the observed higher corrosion currents, which were more than 40 times that observed in alloy 22. When the dissolution rate of alloy 22 was increased by impressing about 1 mA/cm 2 anodic current, a steady-state creep strain rate of 6.5 ϫ 10 Ϫ8 /s was observed. The results indicated that anodic dissolution increased the localized plasticity of the material, resulting in creep strain. However, alloy 22 did not show SCC.

A quick and dependable technique has been developed that allows us to selectively produce anodized TiO2 in the form of nanotubes. The process employs mild chemical conditions and ambient temperature. The method can consistently produce nearly 100% surface coverage of nanotubes within 10 min of anodizing. Anodizing in relatively high pH electrolytes for 1 hour permitted us to produce nanotubes of 2μm length. We attribute the repeatability of our results to a brief pre-anodizing etching step that consistently leads to excellent anodizing results. Without this etching step, we experienced very poor consistency in that only small patches of titania nanotubes were formed.

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