Analysis of the Corrosion Products Formed on Ti and a Ti-Pd Alloy During Exposure in Hot Water
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SCIITIFIC BASIS F0RRADICICTVE 1WST>'NAGPICCTV Werner. Ditze, editor
ANALYSIS OF THE CORROSION PRODUCTS FORMED ON Ti AND A Ti-Pd ALLOY DURING EXPOSURE IN HOT WATER
INGEMAR OLEFJORD AND HAKAN MATTSSON Department of Engineering Metals, S-412 96 GCteborg, Sweden
Chalmers University of Technology,
ABSTRACT This is
a preliminary report dealing with the surface analysis of reaction
products formed on Ti and a Ti-Pd alloy during their exposure in hot water. The compositions of the aqueous media were varied with respect to the dissolved oxygen and the content of chloride ions. sure times were 10 min.
and 6 months.
exposed at 800C and 950C in
The temperature was 60 C and the expo-
Work is
in progress
the aqueous solutions.
in which samples are
Surface analysis was also
performed on a sample which had been exposed in water-saturated bentonite. It
appears from the ESCA spectra that the oxide products formed on the sur-
face consist of TiO
The results also indicate that the thickness of the film
formed at 60 C in water is
in
the range 50 A to 100 A. This is
somewhat more
than that obtained after exposure in water at room temperature. 6 months increases
Exposure for
the thickness of the oxide two to three times compared to 0
that obtained during the short exposure at 60 C. The analyses of the samples that had been embedded in bentonite indicate that the surface reaction products are thinner than those found on the surface after exposure in
an open vessel.
INTRODUCTION This investigation is
one part in
a research program dealing with the
possibility of using Ti or a Ti0.2weight %Pd alloy as a material for the encapsulation of radioactive waste.
The canister will be placed in deposition
holes in bedrock at approximately 500 m depth. with a sand-bentonite mixture.
These holes will then be refilled
The design of the capsule system, details of
the refilling and the composition of the environments
are described elsewhere
(). The aim of this project is
to study by surface sensitive techniques
(ESCA)
the reaction products formed on the surfaces of Ti and a Ti-Pd alloy during exposure in an environment similar to that existing in bedrock at a depth of 500 m.
The oxygen content at this depth is
very low and the reducing components
in the bentonite will consume oxygen so that the capsule environment will be
670
almost oxygen free. The temperature is during the first
0
assumed to attain a maximum of 95 C
period after the waste is
deposited. The real situation is
simulated on the laboratory scale. The metals are exposed to water-saturated bentonite clay at a realistic pressure. Exposure times of up to a maximum of three years are planned. In parallel with the water-saturated bentonite exposure, mental series has been set up.
The aim of this work is
a second experi-
to make more fundamental
studies of the reactivity of the metals with hot water containing various amounts of oxygen and sodium chloride. is
In this case the maximum exposure time
planned to be about half a year.
THE EQUIP
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