Transactions

CLARKE, W HITE, UPTHEGROVE—CONDENSER TUBES AND T H E IR CORROSION 523
the condenser test, but vary widely in the impingement test
probably as a result of surface conditions.
Cold-drawn aluminum brasses of three different producers are
represented by photomicrographs 1, 2, and 3, Fig. 7, showing
microstructures for the original 14, 1, and 2 tubes, respectively.
No apparent relation exists between the microstructure for these
three tubes and their corrosion resistance.
Similar variations or lack of any direct relation between microstructure
and the corrosion resistance were also found for the
Admiralty metal which was represented in the tests by seven
tubes. All admiralty tubes were furnished in an annealed condition
and varied from the small uniform grain size of photomicrograph
6 of Fig. 9 to the medium grain size of photomicrograph
7, Fig. 9. The small uniform microstructure of photomicrograph
6 was found in tubes 21 and 11, or the tubes making the best and
poorest showing in the impingement test for the tubes of this
type. Tubes 21 and 11 were not made by the same producer.
The maximum grain size for the admiralty tubes is shown in
photomicrograph 7, Fig. 9, representative of tubes 20 and 25.
Owing to the small number of cupronickel tubes in the test
and their generally unsatisfactory performance, no photomicrographs
of these tubes are included in this paper. The same also
holds for the bronze tube.
C onclu sio n s
On the basis of the particular conditions pertaining to this
specific investigation, the following conclusions may be drawn:
1 Aluminum brass, for the specific water conditions under consideration,
is superior in its corrosion resistance to cupronickel,
admiralty metal, and bronze.
2 Microstructure, as such, does not appear to be a controlling
factor. A hard-drawn or an annealed material may show equally
good corrosion-resistance properties.
3 Cupronickel, admiralty, or bronze tubes are not suitable
for use under the proposed water conditions.
4 Internal stresses of an order to produce cracking, under the
conditions of the standard A.S.T.M. mercurous-nitrate test, do
not necessarily decrease the corrosion resistance of the tubes, nor
does their absence necessarily increase the corrosion resistance.
It should not be inferred from this conclusion, however, that tubes
should be furnished under such conditions of internal stress that
they will crack in the mercurous-nitrate test. It is realized that
expanding tubes in the tube sheets produce local stresses at these
points but it is felt to be the lesser of two evils.
5 Arsenic, while present in some degree in all aluminumbrass
tubes, does not appear to be, in itself, a controlling factor.
A content of 0.01 and one of 0.07 per cent, when properly associated
with other factors, gives equally good results.
6 Phosphorus in traces was found in all of the top-rating
aluminum tubes. Its presence or absence does not appear to be a
controlling factor.
7 Proper manufacturing procedure is, beyond any question
of a doubt, an important factor in the production of highly corrosion-resistant
aluminum-brass tubes.
A c k n o w led gm en t
The authors wish to acknowledge the valuable assistance and
cooperation of the operating department of The Narragansett
Electric Company in collecting the basic data of this paper.
Discussion
F. L. LaQue* and C . A. C r a w fo r d.* It is always a problem to
choose the proper material for condenser tubes which are to oper-
4 Development and Research Division, The International Nickel
Company, Inc., New York, N. Y.
ate with a cooling water with which there has been no previous
experience. The authors describe an interesting attack on this
problem which presumably resulted in the choice of a satisfactory
tube material for the particular installation in which they were
interested.
Since a similar technique might be applied in other cases, it
would seem to be desirable to make a critical appraisal of the test
methods in the light of available data from other sources and
practical experience with the materials under consideration.
The most surprising feature of the test results was the relatively
small difference in ratings between the 70-30 copper-nickel-alloy
tubes and the admiralty tubes installed in the exerimental condensers.
There have been fewer opportunities to compare the
copper-nickel alloy with aluminum brass, but it may be said that
test results and practical installations have shown that the copper-nickel
alloy should not regularly be rated below aluminum
brass.
The failure of these test results to coincide with such general
experience may have been due to such causes as the following:
1 Some peculiar characteristic of the water. In this connection,
it would increase the usefulness of the test results if the authors
could supply a typical analysis of the water.
2 Effects of minor constituents in the tubes. Research
abroad, and more recently in this country, has shown that the
performance of the 70-30 copper-nickel alloy may be influenced
to an important extent by such minor constituents as manganese,
iron, zinc, and carbon. It is not suggested that this was an important
factor in the present tests, nevertheless, in order to correlate
these test results with other studies along the same line, we
would be pleased if the complete analysis of the copper-nickel
tubes could be reported. If such analyses are not available, we
would appreciate the opportunity to have analyses made, using
any portions of the test tubes which may still be available.
Through the kindness of the authors of the paper, an opportunity
was provided to make chemical analyses of sections taken
from the copper-nickel alloy tubes which were included in the
tests. These analyses yielded the following results:
Composition
Tube no. Cu Nia Fe Si Mn C Zn Sn
16 69.30 29.8 0.22