ORNL-1816 - the Molten Salt Energy Technologies Web Site

tests in order to establish the effect of added
nickel fluoride. In the absence of added chromium
metal, the plot of the chromium concentration after
test vs the nickel fluoride added followed a linear
relationship, although the amount found in the
case of very large additions of NiF, was smaller
than stoichiometric. Metallographic tests showed
a heavy subsurface void formation to a depth of
21 mils at the hot end (8OOOC) and 5 mils at the
cold end (65OoC), while the corresponding blank
capsules (no NiF,) showed only light attack to a
depth of 1 to 2 mils.
A series of lnconel capsules containing the
same two fluoride melts and NiF with chromium
pellets added were subjected to t l e same type of
testing. The after-test chromium values were
above stoichiometric, and metallographic exami-
nation of the capsule walls indicated that the
NiF, additions had little effect on the amount
of attack. The heaviest attack was to a depth of
3 mils, with the average being 1 to 2 mils. The
cold ends had thin metal deposits and a slight
void formation.
PERIOD ENDING DECEMBER 70,1954
Effect of Chromium Valence State on Corrosion of
I nc onel
H. J. Buttram I?. E. Meadows
Materials Chemistry Division
Additions of chromous and chromic fluorides
were made to NaZrF, and NaF-ZrF,-UF,4 (53.5-
40.0-6.5 mole %) in lnconel capsules to determine
the effect of chromium valence state. iMetallo-
graphic examination showed that chromous fluoride
additions had essentially no effect even in the
case of large additions (18,000 ppm Cr’”). The
depth of attack was about 1 mil. As would be
expected, when chromic fluoride was added, the
lnconel showed attack to a depth of 4 mils and
some evidence of intergranular penetration. The
chromous ion has been demonstrated as the stable
state in the NaF-ZrF,-UF, systems; therefore,
it is reasonable to assume that, when chromic
fluoride is the additive, chromium metal will be
removed from the lnconel to enable the chromium
to be reduced to the chromous state. Chemical
analyses made after these tests were inconclusive
and difficult to interpret.