INDUSTRIAL AND ENGINEERING CHEMISTRY
These curves represent measurements of the deepest pits found after 19- and 24-month exposure. The steep slopes indicate the rapidity of the attack. I n some cases the experimental results were too minute to be entirely indicative, but in several other cases actual penetration of the samples occurred during exposure, and the lives of these samples were definitely measurable. The dotted lines indicate the extrapolated data for the metals of series A. The data of Table X were calculated from the results of the corrosion tests after 19 and 24 months of exposure, respectively. These results show that the life expectancies of these alloys can be estimated with a fair general agreement even from corrosion data which are quite minute (see also Table V). TABLEx. MAXIMEMLIFE O F 20-GAGE STAINLESS CONDENSIXG FLUEGASVAPORS Sample No.
Max. Life, Years ,-
19-mo. test 24-mo. test
b b b
b b b
2” 12 2 25 2a 13 3 3 4 5 Test strip penetrated during exposure. b Corrosion very light, no calculation possible with d a t a available..
Metal or Alloy Iron Copper Zinc Aluminum Lead Steels Chrome Chrome Stainless Stainless Stainless Stainless Stainless Stainless
LIFE OF ‘2o-G.4GE
hpprox. Compn. Commercial steel And a few of its alloys Commercial S n d some of its alloys Commercial
17 27 18-8 18-8-Ti 18-8-Cb 18-8- M 0 26-12 25-20
FLUEGASES” Life. Yeara l b
7 8 8 15
3 3-4 4-8 2-5 b 2-5 b c
5-9 2-3 b
The combustible gas wa6 manufactured city gas.
Corrosion very light. no calculation possible with available d a t a .
b Strips were penetrated during exposure tests.
STEEL I N
Max. Life, Years Sample No. 19-mo. test 24-mo. test
Vol. 34, No. 12
The increase of nickel in similar alloys from 12 to 20 resulted in a marked and serious increase in the rate of attack. The actual corrosion of the alloy steels was preceded by staining. This was followed b y localized pitting action, which continued t o be so severe during the subsequent spreading of the general corrosion that actual penetration of some of the strips occurred during the test exposure. As a result of series A and B, i t was estimated that 20-gage (0.032-inch or 0.81-mm.) metal would fail b y corrosion and eventual perforation due t o pitting, when exposed on one side only in an atmosphere of condensing flue gas vapors resulting from the combustion of manufactured city gas, within the approximate time limits given in Table XI.
Summary As a result of the series A tests, in which a number of different metals and alloys were exposed to the action of flue gas vapors, it was found that corrosion began upon exposure and continued more or less rapidly throughout the test period, depending upon the resistance of the individual metal or alloy. Practically no corrosion occurred during these tests in the case of a sample strip of 18-8 stainless steel. As a result of the series B tests, however, in which a number of the so-called stainless steels were continuously exposed to a similar flue gas atmosphere for 2 years, serious attack did occur, which revealed several developments. It was found that none of the chrome-nickel steels were appreciably attacked for a year. Then only a few were affected in several months more of continued exposure. B u t after about a year and a half, all but three of the twentytwo original samples had succumbed to the effects of the vapors. The attack was so suddenly severe that, within a few months from the time of the first signs, perforation of some of the strips had occurred. As might have been expected from series A, the sample containing 17 per cent chromium and no nickel was attacked first. The increase in the chromium content to 27 per cent delayed the initial attack, but did not prevent subsequent and severe corrosion. The initial attack upon the ordinary 18-8 chrome-nickel steels indicated a wide range in the susceptibility of these alloys depending upon their source and previous treatment. The low carbon content of the special 18-8-S samples did not appear to have influenced the eventual rate of corrosion once i t had begun. Of the 18-8 steels made up with fractions of titanium, columbium, and molybdenum, only those containing molybdenum withstood the attack of the flue gases after two years. The samples made up with a 25-12 chrome-nickel content showed relatively low susceptibility to the effects of flue gas.
(1) Barkley, J. F., U. S.Bur. Mines, Tech. Paper 436 (1928). (2) Bosbyshell, J. H., and Yeaw, J. S., Am. Gas Assoo. Proc., 1939, 518-42. (3) Johnstone, H.F., Univ. Ill. Eng. Expt. Sta., Bull. 228 (1931). (4) Maoonaohie, J. E., “Deterioration of Domestio Chimneys”, Toronto, Consumers’ Gas Co., 1932. ( 5 ) Mueller, F. P., Am. Gas Assoc. MonthZg, 18,35 (1936). (6) Murphy, E. J., Am. Gas Assoc. Proc., 1939,553-6. (7) Shnidman, Louis, Ibid., 1935,706-25. (8) Shnidman, Louis, and Yeaw, J. S., Ibid., 1937,697-715. (9) Ibid., 1939,542-52. (IO) Speller, F. N., “Corrosion Causes and Prevention”, 2nd ed., p. 214, New York, MoGraw-Hill Book Co., 1935. (11) Wood, J. W., Parrish, E., and others, “Corrosion from Products of Combustion of Gas”, Parts I, 11,111,and IV, Repts. 33, 34, 36, and 38 of Joint Researoh Comm. of Inst. of Gas Engrs. and Leeds Univ., 1933, 1934, 1935, 1936. PREEENTED before t h e Division of Gas and Fuel Chemistry a t the 104th Meeting of the AMERICAN CHEMICAL SOCIETY.Buffalo, N. Y.
Sulfur Dioxide-Correction On page 1019 of my article in the September issue, the ammonium sulfite-bisulfite process used for the recovery of sulfur dioxide at the Trail smelter was erroneously described as being developed by the American Smelting and Refining Company. The process used was developed by the Consolidated iMining and Smelting Company of Canada, Ltd. [Lee, Lepsoe, and Chapman (to Consolidated Mining and Smelting Company of Canada, Ltd.), U. S. Patent 2,021,558 (Nov. 19, 1935)]. On page 1020 it is stated that the cyclic process has supplanted the one in which sulfur dioxide was recovered as an intermediate step in the production of ammonium sulfate. I am informed by Robert Lepsoe that the ammonium bisulfite acidification with sulfuric acid is still the main process used there for the production of 100 per cent sulfur dioxide. H. F. JOHNSTOND