This report was prepared as an account of work sponsore d by an agency of the United States Governm~nt . Ne ith e r th~ United States Governmen t nor any agency thereof, or any of their employees , ma kes an y w.'lrr:m t y, expres s ed or implied, or assumes any legal liabil i ty of respons i bilit y for any third'par ty's use , or the results of such use , of any informatio n, apparatus , product or process disclosed in this report, or represent s that its use by such third party would not infringe privately owned rights.

No abstract

A technique was developed to monitor crevice corrosion of Grade-12 titanium In a high magnesium synthetic brine under hydrothermal conditions. The current between the cathode and anode, and the potential of the whole crevice assembly, provide information on th-ious stages of corrosion. Occasionally, the decoupled poten «,f the cathode and anode are measured to give supporting information about the crevice conditions. A parallel test is run on a specimen which has small wells to collect crevice solution whose pH is determined at room temperature. The current/potential results show that the crevice corrosion incubation period for a Grade-12 titanium crevice formed between two Teflon plates is approximately two days at 150°C. Optical and SEM observations show that the corrosion starts as isolated pitting which spreads along the surface as shallow pits. The corrosion conditions change significantly as the T102 corrosion product fills the crevice, and the rate of corrosion may be greatly reduced after several days. The rate of crevice corrosion of commercial purity (Grade-2) titanium under similar conditions is approximately three orders of magnitude higher. In this case, active dissolution of metal starts during the initial heating of the autoclave and the incubation period is negligible.

No abstract

The corrosion behavior of TiCode-12 (Ti-0.3 Mo-0.8 Ni) high level nuclear waste container alloy has been studied for a simulated WIPP brine at a temperature of 150°C or below. Crevice corrosion was identified as a potentially important failure mode for this material. Within a mechanical crevice, a thick oxide film was found and shown to be the rutile form of TiO2, with a trace of lower oxide also present. Acidic conditions were found to cause a breakdown of the passive oxide layer. Solution aeration and increased acidity accelerate the corrosion rate. In hydrogen embrittlement studies, it was found that hydrogen causes a significant decrease in the apparent stress intensity level in fracture mechanics samples. Hydride formation is thought to be responsible for crack initiation. Stress corrosion cracking under static loads was not observed. Attention has also been given to methods for extrapolating short term uniform corrosion rate data to extended times.