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

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... ance 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. CONCLUSIONS 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.