Transactions

520 TRANSACTIONS OF THE A.S.M.E. AUGUST, 1941
same tube, aluminum brass. Section 14 showed no measurable
wall reduction, while section 27 showed roughly a 25 per cent decrease
at the point of maximum corrosion.
Aluminum brass was found to have performed about equally
well in the impingement test, whether it was in the hard-drawn or
in the annealed condition. Of the aluminum brasses in groups
1 and 2 , good corrosion resistance, three are annealed and two
are hard-drawn. In group 5, showing roughly a 25 per cent reduction
in wall thickness by pitting, two of the aluminum brasses
were hard-drawn and one was annealed. In the same way, the
tube materials of the individual manufacturers showed no definite
tendencies consistently favoring annealed or hard-drawn aluminum
brass.
Conclusions that may be drawn from the results of the impingement
tests are:
1 Under the conditions set up in the test procedure, aluminum
brass, from a general average standpoint, is superior to all other
materials.
2 The resistance of the aluminum brass to impingement corrosion
is of the same order, whether in the hard-drawn or the
annealed condition.
3 Admiralty metal, from a general average standpoint, is
inferior to all of the other materials.
4 The black-skin treatment of the admiralty metal is not effective
in increasing the resistance of the metal to impingement
corrosion.
5 Maximum resistance to impingement corrosion is not dependent
upon any single factor, but embodies the combined effects
of composition and manufacturing procedure.
C o n d e n s e s T ests
The condenser-corrosion tests were made on a miniature condenser
which is shown diagrammatically in Fig. 1. Four different
grades of tubes were placed in the condenser, namely, tubes of
the type known as aluminum brass, cupronickel, admiralty, and
one bronze tube consisting of 8 8 per cent copper, 4 per cent zinc,
4 per cent tin, and 4 per cent lead. The water velocity was 7
fps. The tubes were heated from the blowdown system of a 400-
pound boiler. The temperature of the condensing water taken
from the river, ranged from 35 F to 80 F. The test was of approximately
2 2 months’ duration with but one serious interruption
which was for a period of about one month.
On the completion of the test run, the tubes were removed from
the condenser and examined for the purpose of determining the
extent to which corrosion had taken place.
As it appeared desirable to run certain tests on the tubes from
the condenser for comparison with the tube material which had
not been subjected to the experimental run, it was not feasible
to split the tubes longitudinally. In consequence, sections of
each tube approximately one inch in length and from five different
positions were obtained. This procedure not only made it possible
to obtain a reasonable accurate survey of the extent of the
corrosion, but also made it possible for material to be secured for
the mercurous-nitrate and the various physical tests. The locations
of these various sections are shown in the upper diagram in
Fig. 2.
Corrosum-Besistance Condenser Test. The one-inch sections
were examined under a low-power binocular to determine the
nature and extent of the corrosion. Using the arbitrary arrangement
scheme followed for the impingement-test rating, a comparison
was made, first of the sections within any tube, and then
on the basis of sections from corresponding positions in all tubes.
As before, minimum corrosion was rated as 1 and maximum as 9.
Depth of penetration of attack, rather than extent to which attack
was general, was used as a basis for the ratings. Thus, a
single pit of appreciable depth would rate the corrosion resistance
lower than a general attack of little penetration. Micrometer
readings of wall thickness, and also metallographic measurements,
were made where any question existed as to the extent of a general
corrosion attack. Examination was also made of the ends of the
adjoining sections in checking final ratings. Inasmuch as the
end sections A and F always showed lower degrees of corrosion
than the sections from any of the other positions, they were eliminated
in the final ratings and do not appear in any of the tabulations.
Table 8 and the upper-rating diagram in Fig. 2 give the results.
Loss-irtr-Weight Condenser Test. An analysis of the extent of
the corrosion was also made on six-inch center sections from each
of the tubes in question. The results are given in Table 9 and
in Fig. 2.
C o rrosion-R e sista n c e C o m b in ed R a tin g
As a means of correlating the various ratings made on the
basis of the results of the impingement test and the experimental
condenser test, a combined rating was set up. The ratings determined
by the impingement test have been given a rating of 1 ;
the ratings from the loss of weight on the six-inch sections, a rating
of 1 ; and the ratings from the corrosion-resistance condenser
TABLE 8 EXPERIMENTAL CONDENSER TEST—RATED ON
BASIS MAXIMUM CORROSION SHOWN AT ANY SECTION
Rating Tube Material Condition
1
8 A1 brass Annealed
6 A1 brass Hard-drawn
2
2 A1 brass Hard-drawn; end annealed
5 A1 brass Annealed
12 A1 brass Hard-drawn; relief anneal
3
7 A1 brass Hard-drawn
10 A1 brass Annealed; Snead E
1 A1 brass Hard-drawn
14 A1 brass Hard-drawn
27 A1 brass Hard-drawn
4
15 A\ brass Annealed
4 Al brass Annealed
9 Al brass Hard-drawn
19 Cupronickel Hard-drawn; end annealed
5
13 Al brass Annealed
6
(23 Admiralty Annealed; black skin
\26 Cuproniokel Annealed
i20 Admiralty Annealed
7
21 Admiralty Annealed
22 Admiralty Annealed
8
25 Admiralty Relief annealed; end annealed
(18 Cupronickel Annealed
9
\25 Admiralty Annealed
11 Al brass Annealed
(
17 Cupronickel Annealed
30 Bronze Hard-drawn
TABLE 9 WEIGHT LOSS IN PER CENT IN EXPERIMENTAL
CONDENSER-TUBE TEST
MIDDLE
BASED
OF
ON
TUBE
6-INCH SECTION FROM
Loss,
Rating per cent Tube Material Condition
i
fl.O 18 Cupronickel
.1.2 8 Aluminum brass Annealed
/1.5
2 7 Aluminum brass Hard-drawn
,1.6 1 Aluminum brass Hard-drawn
2.2 6 Aluminum brass Hard-drawn
2.2
3 14 Aluminum brass Hard-drawn
2.3 15 Aluminum brass Annealed
2.3 27 Aluminnm brass Hard-drawn
2.6 2 Aluminum brass Hard-drawn; end annealed
4 2.6 10 Aluminum brass Annealed
2.9 5 Aluminum brass Annealed
2.9 12' Aluminum brass Relief and end annealed
3.0 13 Aluminum brass Annealed
5 3.4 4 Aluminum brass Annealed
4.2 9 Aluminum brass Hard-drawn
5.9 19 Cupronickel Hard-drawn; end annealed
6 7.3 24 Admiralty Relief annealed; end annealed*.
7.5 21 Admiralty Annealed
8.1 17 Cupronickel Annealed; Snead A
7 9.2 20 Admiralty Annealed
9.7 26 Cupronickel Annealed
J10.6 22 Admiralty Annealed
8
\11.5 23 Admiralty Annealed; blaek skin
[12.8 11 Admiralty Annealed
9 415.3 25 Admiralty Annealed
16.7 30 Bronze Hard-drawn