Corrosion Resistance of Titanium, Zirconium, and Stainless Steel in Organic Compounds I. R. LANE, JR., L. B. GOLDEN, AND W. L. ACHERMAN U . S . Bureau of Mines, College Park, M d .
0
RGANIC compounds are not ordinarily thought of as being as destructive to metals as inorganic compounds such a s the trong mineral acids and the heavy metal chlorides. Most organic acids are classified as weak acids, and their corrosive attack on the various common metals and alloys used in chemical processing equipment might be expected to be rather mild. In general, this is true, but there are many exceptions and the choice of a material for use in the organic chemical industry must be carefully made. Performance demanded of metals and alloys is often very exacting. I n the food processing and pharmaceutical industries the materials of construction must be not merely corrosion resistant, but in most cases entirely free from any corrosion, since the introduction of even very small amounts of metal salts into the products may seriously affect their quality or even make them worthless. Thus, materials completely resistant t o corrosive attack are essential to a large proportion of the organic chemical industry. References concerning the corrosion resistance of titanium and zirconium in organic compounds have been, for the most part, confined t o one or two compounds a t one specific concentration and temperature. The most extensive data on titanium and its resistance to organic compounds compiled recently has been that of Hutchinson (10)in which the results of tests in a number of organic acids and several chlorinated hydrocarbons have been listed. These data have also been reproduced in descriptive literature published by several corporations engaged in the production of titanium ( 4 , 12). Dean (Q, Gillett ( 7 ) , Hoyt (9), and the Corrosion Handbook ( 2 ) each refer t o one or two tests in acetic, oxalic, or citric acids. This paper describes the results obtained with titanium, zirconium, and Carpent,er Yo. 20 stainless steel exposed to the corrosive action of various organic compounds, both anhydrous and in aqueous solution, a t several temperatures. METHODS AND MATERIALS
-
The apparatus used in these tests conforms to the recommendations of the American Society for Testing Materials as contained in the Tentative Method of Total Immersion Corrosion Tests of Nonferrous Metals ( I ) . A detailed description of the apparatus is contained in previously published papers (6, 8). Aeration was suppIied either by compressed air from the laboratory air line. or by cylinder nitrogen. The air was purified by passing i t through a solution of 3% sodium hydroxide t o remove carbon dioxide, then through a water wash bottle which served t o humidify the air and thus prevent the pores of the aerator from being clogged by salt crystallization. Finally, the air was passed through a tower packed loosely with glass wool in order t o remove any entrained droplets of water. From here, the air went to the aerators in the test flasks. When cylinder nitrogen was used, the gas was f i s t passed through a saturated solution of chromous sulfate (acidified with sulfuric acid) t o remove any oxygen present, then through the same scrubbing train as used for air. Unless otherwise indicated, test solutions were aerated with air a t the rate of 250 ml. per minute during a test period of 6 days. Tests a t the boiling point (nonaerated) were made in
1-liter boiling flasks connected by ground-glass joints to reflux condensers. Titanium sheet was produced by powder consolidation, sintering, and hot rolling. A few incidental tests were also conducted with arc-melted titanium. I n each of these instances, the arcmelted metal and powder metallurgy processed metal were found to be identical in their corrosion resistance. T h e metal was finished by cold-rolling, 40% reduction t o size. Chemical analysis showed a carbon content of 0.03 to 0.04% and nitrogen not exceeding 0.05 t o 0.06%. The amount of oxygen present may range from 0.10 to 0.15%. Spectrographic examination revealed the following impurities: iron, 0.10%; magnesium, chromium, lead, manganese, and copper, 0.005 t o 0.05%. Zirconium sponge was melted in a graphite crucible and poured into a graphite mold. The "as cast" ingots were welded in a mild steel sheath, forged and rolled a t 850" C. The sheath was removed and the zirconium sheet rolled a t 650' C. and cleaned by sandblasting and pickling. The metal was subsequently cold-rolled t o 0.10 cm. (0.040 inch) in thickness. Chemical analysis showed a carbon content from 0.142 t o 0.207% and iron from 0.046 t o 0.052% for various lots of sheet. Additional impurities included magnesium, 0.02%; oxygen, 0.07%; nitrogen, 0.01%; aluminum, 0.02 to 0.05%; and hafnium, 0.5 to 1.5%. Spectrographic analysis showed traces of nickel, titanium, and silicon. Although the hafnium content varied over a range of 1%,i t did not appear to be a significant variable in these experiments. The stainless steel used was a highly alloyed material having the following nominal analysis: chromium, 20.00%; nickel, 29.00%; molybdenum, 2.00% minimum; copper, 3.0070 minimum; silicon, l.OOyo; carbon, 0.07% maximum; and manganese, 0.75%. In the following tests both titanium and zirconium were used in the form of the cold-rolled metal, whereas the stainless steel was in the annealed condition. Specimen configuration for all tests is shown a t the end of Table I. Information on the source and purity of the corrosive media used will be found in the tables. The metal samples were sheared roughly to size from sheet stock and then machined t o 0.008 to 0.013 cm. (0.003 to 0.005 inch) oversize, surfaced with 50-mesh abrasive cloth on a wet-belt grinder, and numbered with a Vibrotool. Final surfacing was made with 120-mesh abrasive cloth. The samples were then degreased by rubbing with a water paste of clean pumice powder and washed in distilled water. After a final washing in aceton?, they were dried and weighed to 0.1 mg. All tests were run in quadruplicate in conformity with A.S.T.M. recommendations. After testing, it was found t h a t corrosion products could be removed easily from the metal simply b y gentle scrubbing with a rubber stopper under running water. The samples then were washed in distilled water, rinsed in acetone, dried, and weighed. CORROSION RATES
Carboxylic Acids. FORMIC ACID. The corrosion rates for titanium, zirconium, and stainless steel in various concentrations of formic acid at 3 5 O , 60°, and 100" C . are shown in Table I. None of the titanium samples showed visible signs of corrosion 1061
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more resistant t o oxygen-frec formic acid solutions than to those which are air aerated. Specimen Configuration Titanium and zirconium, 2.54 X 2.54 X 0.1 cm. For example, in air aerated Stainless steel, 2.54 X 2.54 X 0.17 o m . Boiling tests, 1.27 X 5.08 cm. 90% acid at 100" C. the rate A r . Corrosion Rate, 6-Day Test, 3Iils/Tear for the steel was 34.7 mils per Concn., Titanium Stainless steel Zirconium Wt. year as compared to 0.05 mil 35O C. 60° C. 100O C. 35' C. 60' C. 100" C. 35' C. 60" C. 100' C. Akcida % per year for tit,anium. But in Formic 10 0 06 0 07 0 18 0 13 3 98 0 51 0 04 0 00 0 02 boiling, nonaerated 90% acid Formic 25 0 08 0 02 0 04 0 13 28 8 4 05 0 05 0 00 0 02 2 46 o 03 o 00 0 03 0 0: n n4 o 15 15 6 Formic 50 o 10 the rates were, respective]); 14 7 o 04 n 05 o 00 o 02 0 01 n 06 0 13 17 6 Formic 90 0 00 10 6 30 0 00 Formic 1.11 and 118 mils per year. 25 96 0 6 27 0 09 Formic ~n 1.90 - ~ C E T I C ACID. C o r r o s i o n ... . . , 300 ... 0 19 Formicb ~. 1.11 Formicb 90 ,.. 118 , . n 16 ra.t.eswere zero or negligible foi, 0.10 0 13 1.85 50 0 25 0.27 0 19 0.17 0 07 0 09 FormicC 12.4 0 00 0 87 n . 12 0 00 Formic 90 0.00 0 17 0 09 0 03 titanium, zirconium, and stainn.18 0.39 0.22 Formicd 10 0 03 less steel in all concentrations G4.7 2.20 Formicd 25 0 01 0 17 1-12 3.80 17.4 Formicd 50 0 0fi 0 02 of air aerated acetic acid a t 35", 0.12 2.00 0 00 . , . . . 0 06 Formicd 90 0.04 5 0.00 0 no 0.03 0 03 0 03 0 00 0.00 dcetic 0 02 60", and 100" C. I n boiling 25 0.01 0.07 0.00 0.00 o no 0.07 0 01 0 00 Acetic 0 00 ;... n glacial (99.5%) acetic acid the 0.08 0.01 0.00 0 05 0 01 0.08 0 00 0 03 0 00 Acetic 0.12 75 0.00 0 09 0 01 0.04 0 00 0 03 0.00 Acetic 0 00 rates were still very low, the 0.23 99 5 0.00 0 10 0 00 0 04 0 00 0 00 0.01 0 05 Acetic 0.04 0.67 99 6 0 00 Acetic steel having the highest corro0.46 8 30 0 03 99 3 Acetic anhydride sion rate (0.67 mil per year). 339 0.00 0 00 100 Chloroaceticb, ... 0.29 8 45 Dichloroacetic, b~ J 100 Tit,aniuni was only slightly 573 , . . 455 1on ... Trichloroacetic h J 0.14 0 12 1 88 0 08 0.00 o 00 0 03 10 0 10 0 03 Lade corroded by boiling 99.5y0 0.35 0 00 23 2.06 0 11 0.03 0.02 0 00 0 03 0 08 Lactic acetic anhydride (0.46 mil per 0.17 2.2'4 0 03 0 65 0.00 0 00 0 05 x 0 08 0 06 Lactic 0 19 0.33 0 00 0.11 0 07 83 0 00 0.00 0 00 0 00 Lactic year), but the stainless steel 0 . 5 5 9 35 . . . 0 0 1 10 Lactic" 1 09 8 40 25 ... 0 00 Lactic b vas appreciably attacked (8.30 0 . 7 9 11 6 . . . 3 0 . . . 0 07 Lactic 12.2 mils per year). Corrosion rates 0.40 ... ,.. 0 09 85 Lactic" 0.00 0 00 0 29 0.13 0.12 0 00 25 0'00 0 00 0 '00 Tannic for zirconium were negligible. C.P. (Baker's analyzed) unless otherwise noted. Serated with nitrogen, 100 ml./min. CHLORO.4CETIC .4C!I11. St,aiIle Reagent grade (Merck). Boiling and nonaerated. Sonaerated and static. f Practical (Eastman Xodak). leas steel showed little resistanct to att'ack by boiling chloroacetic acid, whereas both titanium and zirconium were in air aerated acid solutions and corrosion rates were negligible, completely resistant. Titanium was much more resistant t o the action of boiling dichloroacetic acid than zirconium which, in no case exceeding 0.18 mil per year. However, in boiling, nonaerated acid solutions results were different. In boiling in addition t o an appreciable corrosion rate (8.45 mils per year), 50y0 acid, for example, the rate for titanium as 300 mils per was susceptible to pitting attack. Although the pit.s were few in number they were rather large and extended in depth as year cornpared to 0.04 mils per year in air aerated acid of t,he much as half the thickness of the sample. Keither metal w:ts same concentration a t 100" C. Rates for titanium in nonaerated iesistant to boiling trichloroacetic acid, "an organic acid \+hic*h and static 50 and 90% acid did not exceed 0.27 mils per year. is nearly as strongly acidic as the mineral acids'' ( 6 ) . The important part played by oxygen in inhibiting corrosion LACTICACID. Titanium, zirconium, and stainless steel o ere was clearly demonstrated in the various formic acid solutions iesistant to all concentrations of air aerated lactic acid a t 35', using oxygen-free nitrogen as the aerating medium instead of air. BO", and 100' C. The most severe corrosion encountered was Rates in oxygen-free 50% acid solution a t both 60" and 100" C. for titanium in 50% acid a t 100' C., where the rate was only and in oxygen-free 25% solution a t 100" C. were many times 2.24 mils per year. Rates for stainless steel TTere all less than higher than in the corresponding air aerated solutions a t these 0.7 mil per year and for zirconium less than 0.1 mil per year. temperatures. These tests also demonstrated the phenomenon On the other hand, the stainless steel samples were not nearlv of "borderline passivity" shown by titanium. In certain solutions it has been found t,hat individual samples may or may not as resist,ant in boiling acid solutions as the titanium. The maximum rate for titanium was 1.09 mils per year in a boiIing 25y6 be actively corroded depending upon various factors, among which may be thickness and continuity of air-formed oxide films, lactic acid solution Thile the steel was corroded most severely smoothness of the surfaces, and variations in rate of aeration. in boiling 85% acid (12.2 mils per year). TANNIC ACID. The corrosion rates for titanium, zirconium, and In each set of four samples tested in nitrogen aerated 50% formic stainless steel in air aerated 25% tannic acid a t 35", 60", a n d acid a t 60' and 100" C. there was one titanium sample which showed no visible signs of corrosion and m-hose rate was less than 100" C. were either zero or very low. 0.2 mil per gear. Theee samples retained their passivity, whereas Di- and Tricarboxylic Acids. OXALIC ACID. ResultP. in various concentrations of air aerated oxalic acid at 35', 60°, their replicates did not. Two of the four samples exposed t o nitrogen aerated 25% acid a t 100" C. gave rates of leas than 0.3 and 100" C. are shown in Table 11. Titanium exhibited poor mil per year; rates for the other two were 227 and 32.2 mils per corrosion resistance to even very dilute solutions of acid a t year. Although examples of borderline passivity were not elevated temperatures. Even a 0.5% solution a t 60" C. gave a observed in boiling 507, formic acid as reported by Hutchinson rate of 94.5 mils per year and higher percentages and temperature gave correspondingly grpater corrosion rates. I n contrast, (IO), it is very likely that additional tests under these conditions zirconium gave very low rates, in no case exceeding 0.51 mil per would result in individual samples showing this phenomenon. year. In every concentration of acid tested the stainless steel From the data recorded in Table I i t appears that under oxygenwas far more corrosion resistant than titanium. For example, free conditions formic acid attacks titanium most vigorously in in 25% acid a t 100" C. the rate for titanium was 1945 mils per a concentration of 50%. year while that for the steel was only 12.5 mils per year. Zirconium showed no visible signs of corrosion and corrosion T A R T A R I C ACID. Air areated solutions of tartaric acid a t 35", rates were negligible, in no instance exceeding 0.19 mil per year. BO", and 100' C. had little effect upon titanium, zirconium, and Carpenter No. 20 stainless steel, in contrast to titanium, is
TABLEI. TITASIUM, ZIRCONIULI,ASD
STAISLESSSTEEL IN CARBOXYLIC ACIDS
C
1 .
L1
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May 1953
ZIRCONIUM,AND STAINLESSSTEEL IN DITABLE 11. TITANIUM,
ACIDS A N D ANILINE HYDROCHLORIDE
AND
TRICARBOXYLIC
Av. Corrosion Rate, &Day Test, Mils/Year Concn., Wt. Solutiona
%
35' C. 0.55 5.96 4.94 0.58
0.5 Oxalic 1.0 Oxalic 5.0 Oxalic O XR.li0 10 Oxalic . 25 ... Oxalic 10 0.00 Tartaric 25 0.00 Tartaric 0.08 50 Tartaric 0.00 10 Citric 25 0.00 Citric 0.00 50 Citric 50 ... Citric b 5 0.03 Aniline hydroclrloride 20 0.00 Aniline hydrochloride a All chemicals O.P. (Baker's analyzed). Boiling and nonaerated. 6 Samples pitted.
Titaninm 60' C. 94.5 177 368 450 470 0.10 0.10 0.02 0.06 0.04
looo C. 82.0 828 1200 1240 1945 0.13 0.00
0.01
...
0.00 0.00
stainless steel. Although the steel was the least resistant of the three materials, its maximum corrosion rate (in 50% acid a t 100" C.) was only 2.08 mils per year. CITRICACID. Data in Table I1 show that titanium, zirconium, and stainless steel are resistant to air aerated solutions of citric acid. However, in boiling 50% acid the rates for titanium and stainless steel were appreciable, 14.1 and 5.55 mils per year, respectively, while those for zirconium were negligible. Aniline Hydrochloride. Titanium and zirconium gave zero or negligible corrosion rates in air aerated 5 and 20% aniline hydrochloride solutions a t 35", 60', and 100" C. Rates for the stainless steel in these two solutions were appreciable a t all three temperatures. Corrosion of the steel was in the form of long, narrow, deep pits on the surfaces of the samples and on the edges as deep pin holes. Chlorinated Hydrocarbons. Titanium, zirconium, and stainless steel were tested in six different chlorinated hydrocarbonwater mixtures boiling under reflux for 6 days. For each material a pair of samples was exposed with half of the areas in the hydrocarbon layer and the other half in the water layer, while another pair was suspended above the water layer and exposed t o the mixed vapors. A blank was run at the same time.
ZIRCONIUM, AND STAINLESS STEEL I N TABLE111. TITANIUM, CHLORINATED HYDROCARBON-WATER MIXTURE
0.18 2.08 Carbon tetrachloridea 0.01 0.04 Chloroformb 0.12 Ethvlene dichloride C 0.18 Trichloroethylened 0.04 0.01 Tetrachloroethylenee 0.02 0.02 Tetrachloroethanef 0.02 0.05 a Analytical reagent (Mallinckrodt). C.P. (Baker's analvaed). " , C (Dol;). (Eastman Kodak). Stabilized with ethyl alcohol (Eastman Kodak). f Technical grade (Eastman Kodak).
0.18 0.03 0.11 0.03 0.02 0.01
I n the carbon tetrachloride-water mixture (250 ml. of each) average corrosion rates for titanium and zirconium were very low while those for the stainless steel were much higher (Table 111). Corrosion rates in the vapor zone were less for titanium and zirconium than in the liquid zone, while the opposite was true for the steel samples. Their rate immersed was only 0.66 mil per year, in contrast to 3.53 mils per year in the vapor zone. In addition, the stainless steel samples showed staining where the carbon tetrachloride-water interface was in contact with the sample surfaces. The titanium and zirconium samples showed no visible signs of corrosion. Furthermore, these two metals had no catalytic effect upon the
0.49
0.36 0.03 0.05 14.1 0.00 0.00
Stainless steel 35' C. 60° C. 100" C. 0 11 0 58 0.06 1.30 3 20 0.08 5 60 0.25 2.67 3.20 16 8 0.19 12 5 ... 4.01 0.43 0 22 0.00 0.24 0 13 0.07 2 08 0.08 0.36 0.03 0 17 0.00 0.00 0 09 0.00 0 02 0.29 0.00 ... 5 55 1.74c 1 57c 5 200 13.66~
35' C. 0.08 0.13 0.29 0.48
...
0.00 0.00 0 05
0.00
0.00 0.23
...
Zirconium 60'C. 100' C. 0.14 0.17 0.20 0.25 0.30 0.28 0.51 0.46 0.29 0.24 0.04 0.00 0.00 0.05 0.00 0.01 0.04 0.00 0,OO 0.09 0.06 0.00
...
0.06
0.01
0.00
0.00
0.00
0.00
0.00
decomposition of carbon tetrachloride since the acidity developed in the water layer during the test was no greater than that. developed in the blank. The stainless steel did catalyze t h e decomposition of this compound t o a slight extent, as was shown by the development of appreciable acidity in the water layer. However, the catalytic effect was no greater than that caused by nickel or Monel metal which are considered to be highly satisfactory materials for handling chlorinated hydrocarbon solSents. Comparison with data on carbon tetrachloride presented by the International Nickel Co. (11) indicates that this steel is the equal of nickel and somewhat superior to Bfonel. The average corrosion rates for the stainless steel, nickel, and Blonel were, respectively, 2.08, 2.00, and 4.00 mils per year. It follows from this that both titanium and zirconium are superior to nickel and Monel for uses involving chlorinated hydrocarbons. Tests using chloroform, ethylene dichloride, trichloroethylene, tetrachloroethylene, and tetrachloroethane gave very low average corrosion rates for all three materials and there was no appreciable difference between rates in the vapor zone and the liquid zone. There was little or no catalytic effect upon the decomposition of these compounds. SUMMARY
Titanium is resistant to attack by all concentrations of air aerated formic acid, but is attacked severely by boiling 50% acid. It is only slightly resistant to this solution a t 100' C. under oxygen-free conditions. This metal exhibits the phenomenon of "borderline passivity" in certain concentrations of nitrogen aerated 25 and 50% formic acid solutions a t 60' and 100" C. Corrosion rates for zirconium are negligible. The 20-29 chromium-nickel type stainless steel, in contrast t o titanium, is more resistant to ouygen-free formic acid solutions than t o those which are air aerated. The three materials show excellent resistance t o all concentrations of acetic acid. Stainless steel is appreciably attacked by boiling acetic anhydride and is severely attacked by boiling chloroacetic acid. Both titanium and zirconium are completely resistant to the latter. Titanium is much more resistant than zirconium to the action of boiling dichloroacetic acid. Neither metal is resistant to boiling trichloroacetic arid, Titanium, zirconium, and stainless steel are fully resistant t o all concentrations of air aerated lactic, tannic, tartaric, and citric acids. Stainless steel shows appreciable corrosion in all concentrations of boiling lactic acid, whereas the other two metals are fully resistant. Corrosion rates for titanium and stainless steel in boiling 5oY0 citric acid are appreciable, while those for zirconium are negligible. Titanium exhibits poor corrosion resistance to even very dilute solutions of oxalic acid a t elevated temperatures. In contrast, zirconium corrodes at very low rates. Stainless steel, while not comparable to zirconium, is far more corrosion resistant than titanium in these solutions.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Titanium and zirconium give zero or negligible corrosion rates in air aerated aniline hydrochloride solutions. Stainless steel ie unsatisfactory because of a tendency to form deep pits. The three materials are resistant t o boiling chlorinated hydrocarbonwater mixtures. With the exception of stainless steel in carbon tetrachloride, these materials also have little or no catalytic effect on the decomposition of the hydrocarbon under such conditions. LITERATURE C I T E D
(1) Am. Yoc. Testing Materials, Standards, Pt. I-B,793-802 (1946). (2) Coriosion Handbook (H. H. Uhlig, ed.), p. 347, New York,
John Wley & Sons, 1948. (3) Dean, R. S., Long, J. R., Wai tman, F. S., and Anderson, E. L., Met& Technol., 13, No. 2, 12-13 (1946); T e c h . Publ. 1961.
Vol. 45, No. 5
(4) E. I. Du Pont de Nemours and Go., Wilmington, Del., “Du Pont Titanium hfetal,” (Tech. Bull., 3rd ed.), pp. 9-10 (1951). (8) Fieser, L. F., and Fieser, M., “Organic Chemistry,” abridged ed., p. 154, Boston, D. C. Heath and Co., 1944. (6) Gee, E. A., Golden, L. B., and Lusby, I?’. E., Jr., IND.ENG. CHEM.,41, 1668-73 (1949). (7) Gillett, H. IT.,Foote Prints, 13, 5-7 (1940). (8) Golden, L. B., Lane, I. R., Jr.,and Acherman, W. L., IND. ENG.CHEM.,44, 1930-9 (1952). (9) Hoyt, S. L., “Metals and Slloys Data Book,” p. 286, New York, Reinhold Publishing Corp., 1943. (10) Hutchinson, G. E., and Permar, P. H.. C o r ~ o s i o n ,5, 322-3 (1949). (11) International Kickel Co., New York, Tech. Bull. T-23,pp. 3-4 (1942). (12) Titanium Metals Corp., New York, “Handbook on Titanium Metal,” 4th ed., p. 33, 1981. RECEIVED for review September 24, 1952.
ACCEPTED January 26, 1933.
Evaluating Sources of Air Pollution GORDON P. LARSON, GEORGE I. FISCHER, AND “ALTER J. H-4JIJIIXG A i r Pollution Control District, C o u n t y
s
TUDIES of air pollution have been confined largely to the development of atmospheric sampling methods and the measurement of the contaminants in the air. The data on air samplin’g for any locality must be related to the activities in that localitr which produce the pollution, if the information is to be of full value in a program for air pollution control. The purpose of this paper is to present methods for determining the quantities of the various pollutants created within a n area and t o show how these emissions can be related t o air sampling data. Methods shown in this study have been invaluable in promoting intelligent direction of control and research programs, and if applied periodically, they should reveal t h e benefits of a program for control of air pollution. The important pollutants of t h e Los Angeles atmosphere and their concentrations listed in Table I are representative of air sampling data obtained during clear and smog periods (10). Investigations covering these contaminants have led t o a number of conclusions regarding the causes of the characteristic haze that often reduces visibility t o less than 1 mile (11, 11),the causes of gas damage t o vegetation (d,S, 8),the nature of the eye-irritating materials ( 6 ) ,and t h e high rate of rubber cracking (6, 7). A complete discussion of these experimental studies is beyond the scope of this paper. A brief picture of the part each pollutant plays in causing t h e effects observed during periods of smog is shown in Figure 1. It can be seen that the essential materials for smog formation are hydrocarbons, ozone, nitrogen dioxide, sulfur dioxide, and visible pollutants such as smoke, dusts, fumes, and mists.
of Los Angeles,
Los Angeles, Calif.
M E T H O D S APPLIED TO SOURCES
Two major problems are involved in a n estimate of pollution discharged t o the atmosphere. Production or consumption rates must be determined for each type of operation, and a correlation of the amount of a pollutant emitted to the amount of material processed or consumed must be established for each type of operation. This correlation is developed by analyses of the sources for the quantities and types of pollutants discharged. More than 350 tests on sources of pollution in the Los Angeles area a e r e made. The collected samples were analyzed for materials that previously had been found in the air. Extreme care was taken to ensure that the chemical and physical methods used on the source tests were equivalent to those used in the identification work on atmospheric samples. While testing procedures have not attained complete standardization. stack sampling follows procedures in use by others and provides reproducible results. All test information was related to the quantities of material processed or consumed during the sampling periods. The correlations developed are listed in Tables I1 and 111. Pollution sources were surveyed t o determine production and consumption rates for various operations. Some results of this survey are listed in Table 1 1 7 . All hydrocarbon sources were not tested, because of the difficulties involved in quantitative determinations of this type. A literature survey indicated t h a t refinery hydrocarbon losses are equivalent to from 1 to 2% of the refinery crude oil throughput (4,6, I S ) . It is considered that the bulk of this loss is t o the atmosphere, since many of the hydrocarbons involved are relatively volatile and extensive precautions are taken t o TABLE I. CONCENTRATIONS OF POLLUTANTS IK LOSANGELESATMOSPHERE restrict losses through effluent water sys(Average values as measured over downtown Los Angeles on various days, 1951) tems and ground seepage. One per cent Concentrations, P.P.M. b y Volume Concentrations, Mg. per Cubic Meter of the 550,000-barrel daily crude oil Periods of Periods of Periods of Periods of throughput of Los Angeles County reGases good visibilitya intense smog Aerosols good visibilitya inteme s m o g b fineries corresponds to a daily hydrocarAcrolein e Present Aluminumd 0 003 0 008 Calciumd Lower aldehydes 0.07 0.4 0 006 0 007 bon loss to the atmosphere of 830 tons. Carbond Carbon monoxide 3.5 23.0 0 035 0 132 Based on calculations, extrapolation of Formaldehyde 0.04 0.09 Irond 0 003 0 010 Hydrocarbons 0.2 1.1 Leadd 0 002 0 042 limited test data, and operating informaOxidants‘ 0.1 0.5 Ether-soluble Oxides of nitrogen 0.08 0.4 aerosols 0.012 0,120 tion from refiners, 80% of this over-all Ozonef 0.06 0.3 Silicond 0.007 0.028 loss can be accounted for (Table V). Bulfur dioxide 0.05 0.3 Sulfuric acid 0.00 0.110 The difference betwen the over-all losses a Visibility approximately 7 miles. Visibility approximately 1 mile or less. and the losses that can be accounted for No quantitative method known for measuring low concentrations of atcrolein. d As determined b y flame spectrophotometric an alysis. is attributed to leaks from pumps and e As determined by liberated iodine method a n d reported as ozone. fittings, storage losses for materials f As determined b y rubber cracking. other than crude oil and gasoline, ~~
