ORNL-1771 - Oak Ridge National Laboratory

The static and seesaw corrosion testing faciiiiies
were used for further studies of brazing alloys,
special Stell ite heats, Hostel loy R, Inconel, graph-
ife, and various ceramics in sodium, fluoride fue!
mixtures, and other mediums. For the fabrication
of many reactor components it may be well to have
a brazing alloy that is compatible both with sodium
and with the fluoride fuels. Therefore several cor-
rosion tests were performed on Inconel joints brazed
with high-temperature btazing allays. From this
work it was found that the brazing alloy 67% Ni-13%
Ge-ll% Cr--6% Si-2% Fe-1% Mn has goad cor-
rosion resistance in fluoride fuels and fair corrosion
resistance in sodium. Two special heats of Stellite
were tested that had a lower carbon content than
those tested previously, and it was found that the
lower carbon content increased the corrosion
resistance in the fluoride fuels.
High-density graphite was tested in sodium and
in fluoride mixtures; It has very poor resistance to
sodium attack but seems to have fair resistance to
the fluoride fuels. Various hard-facing materials,
ceramics and cermets, have been investigated froin
the corrosion standpoint for use as bearings, seals,
and valve seats; AI,O, MgA1,0,, ZrO,, and Sic
were tested in sodium, a fluoride fuel, lithium, and
lead. In these tests, Sic showed the best corrosion
resistance.
In the thermal-convection loop corrosion studies,
emphasis has shifted to fuels with the uranium
present as UF, and to loops of Hasteltoy B. Hot-
leg attack is not found in lnconel loops in which
ZrF,-base fluoride mixtures with the uranium as
UF, are circulated. A deposit is, however, found
on the hot-leg surface. Only preliminary information
is available, but it appears that neither attack nor
a hot-leg layer is found with alkali-metal-base fluo-
ride mixtures containing UF,. Mixtures of UF, and
UF, will result in a reduction in attack from that
found with only UF, but some attack is present
and in high-uranium-content systems it may be
s i gn i f i cant.
The addition of zirconium hydride to the ZrF,-
base fuel mixtures containing UF, was found to
6. CORROSION RESEARCH
W. D. Manly G. M. Adamson
Metal lurgy Division
W. R. Grimes F. Kertesr
Materia I s Chemistry D ivi s ion
PERlOD ENDlNG SEPTEMBER IO, 1954
result in the formation of F, and in a reduction
in corrosion. However, to obtain a complete ab-
sence of corrosion, sufficient hydride must be
added to cause a loss of wanium.
Several Hastelloy i3 loops have now been SUC-
cessfully operated in both the as-received ond the
over-aged conditions. In both cases, a considerable
increase in hardness occurs during operation. With
ZrF,-bose mixtures containing UF,, very I ittle
attack is found, even after Io00 hr.
The mass transfer characteristics OC type 316
stainless steel in molten lithium were studied by
using thermal-convection loops. After 1000 hr of
loop operation, there was no sign of plug formation,
and only a small amount of mass transfer was found
in one ot the loops. The investigation of the car-
rosion and mass transfer characteristics of materials
in contact with liquid lead has shown that certain
alloys possess a much greater resistance to mass
transfer than the pure components of those alloys.
The probable reason for this resistance to mass
transfer can be related to the formation of inter-
metallic compounds in these alloys. This has been
proved in the case of alloys; of 45% Cr-55% Co,
Ni-Mo alloys, and the Fe-Cr-base stainless steels.
The flammability of liquid sodium alloys has
been studied, and it has been found that only bis-
muth and mercury have an effect on the fiammabi I ity
of sodium. It was found that the degree of reaction
of No-Bi and No-Hg alloys with air was not signifi-
cantly changed when the pressure was varied froin
0.25 to 1 atm. An investigation has been staried to
determine the amount of hydrogen I iberated when
NaOH is heated to 900°C in an inert environment,
The container problem has been solved by using a
large single crystal of magnesium oxide. A thermo-
dynamic study of the alkali-metal hydroxides has
shown that hydrogen is important in stabilizing
NaQH at temperatures above 600°C. This is the
temperature range at which mass transfer becomes
significant in Ni-NaOH systems. These computa-
tions link the formation of hydrogen with the forma-
tion of unsaturated oxygen ions, which may be
necessary for mass transfer to occur.
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