86 2
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
proportion of microorganisms contained in the massecuite leave the centrifugal in the wash. Therefore, when it is the practice t o separate the molasses and the wash, a less contaminated molasses is procured with undoubtedly improved keeping quality. I n this connection a digression may be permitted, which may be worthy of trial: namely, where molasses is not fermented and it is desired t o keep i t for some time, we would suggest the use of a thin layer of oil on the surface. This would prevent a mass infection a t t h a t vulnerable point and could be easily removed. The oil in this way need not affect either the quality, odor, or taste of the molasses. On the other hand, where mold growth already covers the surface i t might be advisable t o spray with toluene, which is cheap enough t o be economical, germicidal enough t o kill the molds, and volatile enough to be removed within a few days by exposure to the air. Since the pressure of time does not permit of the opportunity of developing these suggestions in the sugar mill, they are advanced for what they may be worth. Returning t o the latter half of Table I, i t will be seen that where the massecuite was heated t o 122' F. (jo" C.) the untreated sample contains only about one-eighth the number of bacteria and one-fifth the number of molds present in the massecuite heated t o 104' F. (40' C.). This means that a partial sterilization has already been effected. The treatment with superheated steam was interrupted and the final results show t h a t 93 per cent of t h e bacteria and 91 per cent of the molds were eliminated. It was t o be expected that these figures would be somewhat below those obtained in the first instance, since the partial sterilization referred to probably eliminated the least resistant organisms and left a flora relatively more resistant than the one originally present. The interruption of the steam treatment must have been responsible for some loss in efficiency. Finally, the difference may be ascribed t o the fact t h a t t h e layer of sugar in this instance was twice as thick as t h a t used i? the first instance. It is to be expected that four important factors would be operating in such an experiment, 'uiz., temperature of steam, duration of application, thickness of layer of massecuite, and speed of centrifugal. From the data set forth i t is evident t h a t the use of superheated steam under the conditions of the experiment was instrumental in almost entirely eliminating the microorganisms present, the important consideration being t h a t this was accomplished without increasing the moisture content of the sugar perceptibly, as in washing with water. As a matter of fact, under mill conditions it might be anticipated that even better results might be obtained where higher temperatures might be so readily available. The procedure has the merits of ( I ) Simplicity in construction and operation. ( 2 ) Economy in equipment, installation, and operation. (3) Efficiency under all conditions. (4) Yielding a cleaner wash.
Vol.
12,
No. 9
I n working out a chart for predicting the keeping quality of sugar it was shown t h a t two factors, moisture ratio and degree of infection,l operated simultaneously. It is obvious, therefore, t h a t such a striking reduction in mass infection can be effected by the use of superheated steam in the centrifugals that the keeping quality may be greatly enhanced even where t h e moisture is somewhat more $han i t should be. For example, a sugar having a moisture ratio of 0.08 will deteriorate when 10,000t o IOO,OOO mold spores per gram,are present. A reduction of 98 per cent, however, bringing the content down t o about 1,000 spores per gram would make this sugar safe even though t h e moisture ratio increased t o as much as 0.14 t o 0.16. Thus it may be said t h a t in the investigations on sugar deterioration carried forward in this laboratory, the study of the microorganisms and their activities, which made possible the prediction of the keeping quality of sugars, has found its logical completion in the development of an adequate means for eliminating the microorganisms and consequently preventing sugar deterioration. However, i t must be emphasized again that the sugar must be properly handled under sanitary conditions with a minimum possibility of absorbing moisture in order t o ensure its safe keeping, since, under optimum conditions, the microorganisms soon propagate rapidly enough t o become detrimental. SUMMARY
I-A
simple, economical, and efficient method has been developed for employing superheated steam in laboratory centrifugals. 2-By means of this treatment the bacterial content of sugar has been reduced 93 t o 99.5 per cent, and the number of mold spores has been reduced 92 t o 98 per cent. The microorganisms in molasses are reduced similarly to a lesser extent. 3-This elimination of microorganisms improves t h e keeping quality of the sugar as well as the molasses. 4-With superheated steam treatment, the practice of separating molasses and wash results in a considerable reduction of microorganisms in molasses, with consequent improvement in its keeping quality. THE CAUSE AND PREVENTION OF AFTER-CORROSION ON THE BORES OF FIREARMS',' By Wilbert J. Huff EXPLOSIVES CHEMICAL LABORATORY, PITTSBURGH EXPERIMENT STATION, BUREAUOF MINES,PITTSBURGH, PA.
During the past war the Bureau of Mines was requested to investigate the causes of the after-corrosion which sometimes appears on the oiled bore surfaces of firearms subsequent t o the use of high-pressure smokeless powder^.^ Experimentation had hardly begun when the armistice was signed, but because of the importance of the problem and the wide general in1
L O C . cit.
2
Published by permission of the Director, U. S. Bureau of Mines.
a Read before the Section of Physical Chemistry a t the 59th Meeting
of the American Chemical Society, St. Louis, Mo., April 12 t o 16, 1920. 4 Although this study was undertaken primarily in an advisory capacity, this Bureau is interested in the problems of corrosion as a part of its work lor the preservation and proper utilization of our mineral resources.
)
Sept,.,
1920
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
terest attached to i t , both in war and peace, it was deemed advisable t o continue the study. The Ordnance Department states t h a t more rifles are ruined by improper preparation for storage t h a n from any other cause,’ and t h e problem, though primarily military, touches t h e interest of every owner of a firearm. THEORIES O F CORROSION
Generally, this corrosion under oil has been attributed t o acid explosion products, such as acid nitrocellulose residues, or acids from t h e primer, or t o diffusing acid gases. P 0 WD E R R E SID U E S- Pr 0 b a bl y C 0 R R 0 S I VE those theories which entail t h e presence of nitric residues on the bore surface preponderate. Thus Guttmann2states: Most smokeless powders do not leave any residue worth speaking of and the barrels are perfectly clean after a shot, but after using they must be carefully cleaned, because traces of nitric compounds always remain which, combined with the action of the moisture in the air, will attack the barrel and rifling.
Such opinions have led t o t h e compounding of a large number of special and patented preparations seeking t o neutralize t h e residue with alkali or t o dissolve it by special organic preparation^.^.^ Substantially, the Ordnance Department advances such a theory as t h e justification for t h e use of t h e concentrated sodium carbonate so1ution.j Black powder is considered advantageous because i t does not leave such a corrosive residue.6 P O W D E R G A S OCCLUSION THEORY---Corrosion effects are sometimes observed for weeks or months after use in spite of repeated swabbing and oiling. This phenomenon suggests a “leaking or sweating-out” process and has inspired a theory which attributes aftercorrosion t o acid gases from t h e decomposition of nitrocellulose and nitroglycerin powders. These gases are supposed t o be driven by t h e pressure of explosion into the pores of the metal while i t is heated by t h e exotherm of explosion and t h e friction of t h e bullet; upon cooling, they slowly diffuse t o the surface and there cause corrosion.I I n a book upon rifles and ammunition, Ommundsen and Robinson8 hold that some acid products are forced into t h e steel beneath the surface and t h a t violent rusting begins immediately after t h e discharge of the 1 Ordnance Department, “Descriptions and Rules for the Management of U. S. Rifle Caliber 0.30 Model of 1917,” p. 45. Government Printing Office, 1918 * “The Manufacture of Explosives,” Vol. 11, p. 274. London, 1895. 3 The Beck patents: U. S. Patent 719,074, Jan. 27, 1903; Brit. Patent 15,078 (1901); Austrian Patent 9,766; Wild, U. S. Patent 768,835, Aug. 30, 1904; Klever, U. S. Patent 919,884, April 27, 1909; Brit. Patent 27,254 (1905); Ger. Patents 174,906 and 204,906; Fr. Patent 360,960 (1906); Brauu and the Saponia-Werke Ferdinand Boehm, U. S. Patent 862,305, Aug. 6, 1907; Austrian Patent 32,643; Brit. Patent 25,976 (1905). 4 A large number of “nitro-solvents” are used in the United States. In connection with this investigation a number of such solvents and gun oils have been analyzed by the Petroleum Section of this Bureau. The results will be given in another communication. 6 Ordnance Manual, LOG. cit., p. 43. 8 Marshall, “Explosives, Their Manufacture, Properties, Tests, and Uses,” 191s Ed., p , 61. 7 Pasdach, Kriegstechnische Z., 9, 1906 (from a translation by H. E. Fleischner) ; Pauling, Fr. Patent 409,569. “Rifles and Ammunition and Rifle Shooting,” Funk and Wagnalls Co., 1915, p. 282.
*
863
piece. They recommend t h e use of abrasive and alkaline greases. CORROSION PROM THE PRIMER. NON-CORROSIVE PRIMING coiwosIrIoNs-Since 1900 the patent literature records a number of attempts t o diminish or prevent after-corrosion by the use of various priming mixtures.’ The theories involved have been various and conflicting. Some compositions were designed t o produce an alkaline residue which would take up the acids assumed t o be formed. One employed chromates2 t o give a protective coating on the gun barrel. Another3 composition contained no oxygen. Halogens were thought t o produce acid and so were eliminated14although some retained potassium chlorate in certain of their noncorrosive priming composition^.^ iMarshalla states t h a t potassium chlorate forms chloride which causes the barrel t o rust. He does not state whether other ingredients produce corrosive or acid residues or not. Whelen’ held t h a t the primer produces corrosive acid. He thought nitrocellulose residues were in themselves harmless but t h a t they mechanically interfered with t h e cleaning process. He recommended several cleaning agents, among which was a mixture of amyl acetate, acetone, and oil-all non-solvents for potassium chloride. E M P I R I C A L O B S E R V A T I O N S O F P R A C T I C A L R I F L E MEN-
A compilation of the observations of a number of practical riflemen only added t o the confusion of these conflicting opinions. Some had never encountered after-corrosion under oil. Others invariably encountered i t save when cupro-nickel was removed. Some thought after-corrosion could be eliminated by rubbing t h e nose of the bullet with a heavy lubricant. Many testified t o t h e “leaking” effects subsequent t o cleaning. EXPERIMENTAL
RIFLES,
AMMUNITION,
OIL, A K D
EQUIPMENT-Four
U. S. infantry rifles, two of t h e model of 1903, and two of‘the model of 1917,were employed. To duplicate service conditions they were used as received, without special treatment. The ammunition was t h e standard service cartridges primed with typical fulminate, sulfocyanide, and sulfur compositions from various .sources. N o qualitative differences were ever noted in t h e corrosive effects of ammunition from these I sources. 1 H. Zeigler, Ger. Patent 122,389 (1900); Brit. Patent 14,583 (1900); Austrian Patent 7,074 (1901). (From “Initial-explosivestoff” Escales and Stettbacher, Leipzig, Veit and Co., 1917, pp. 369-370, also pp. 7 and 331333.) Westfalische-Anhaltische Sprengstoff-aktien Gesellschaft, Ger. Patent 176,719; Fr. Patent 348,721; Lang, Ger. Patent 209,812; Ernest Goodwin and Eley Bros., Brit. Patent 2,682 (1911); U. S. Patent 1,029,287 (1912); Meyer, Brit. Patents 21,337 (19111, 23,493 (1911), 25,550 (1912); Claessen and the Rheinisch-Westfalisch Sprengstoff-akt. Ges., Ger. Patent 277,566 (1915); F r . Patent 455,369; Buell, U. S. Patent 1,308,393. 2 ivestfalische-AnhaltischeSprengstoff-akt.-G-s., Ger. Patent 176,7 19; Fr. Patent, 348,721. 3 Lang, Ger. Patent 209,812. 4 0. Mertens, 2. ges. S c h i e s s - S p r e n g s t o ~ ~9. ,(1914), 70. 5 Westfalische-Anhaltische Sprengstoff-akt.-Ges., Ger. Patent 176,7 19; Fr. Patent 348,721 ; Claessen and the Rheinisch-Westfalisch Sprengstoffakt-Ges., Fr. Patent 455,369. 8 LOC. cit., pp. 61, 426. 7 “The American Rifle,” Century Co., 1918, p. 599
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
864
The oil employed was st widely known brand of light oil having the following composition:‘ Per cent Animal oil (possibly prime lard oil). 52.50 Mineral oil (34’ Be. neutral oil, frequently used as a spindle oil) 47.50 Free acid (probably oleic acid in the animal oil). 1.32
.........................
..............
This will hereafter be denominated “Oil A,” As this oil gave excellent protection against atmospheric corrosion and practically none against after-corrosion, these properties rendered i t very useful for the purpose of the study. To control the humidities to which the fired rifles were exposed, two wooden cases lined with galvanized iron and supplied with snugly fitting covers were designed as humidors. Each could hold comfortably four fully assembled rifles, placed so t h a t the barrels lay horizontal. The bottom of each case was covered with glass photographic trays which served as containers for the salt or solutions used t o control the humidity. PRELIMINARY EXPERIMENTS-A number of preliminary firing tests were made, using many hundred rounds of service ammunition. The rifles were then carefully swabbed out with cloth and Oil A. Upon exposure t o a n indoor atmosphere during several winter months no after-corrosion appeared. TABLE I
DATE RIFLE HUMIDITY REMARKS May 14 A Forty rounds were expended in each rifle, the bores were then swabbed with Oil A, and exposed over calcium chloride May 28 A Zero N o corrosion B June 5 A No corrosion B Rifles used without change in the next firing test (Table I V )
Vol.
12,
No. 9
TABLE I11 Days after Washing with Sodium Carbonate HUMIDITY Solution DATE RIFLS Per cent REMARKS June 6 C Atmospheric 100 rounds were expended in D each rifle, and the bores were then swabbed with Oil A June 7 C 100 Rifles placed in the humidor D containing pure water June 9 C 100 Bores of both rifles were heavily D corroded, although all other metal parts were bright and unattacked. Cold saturated sodium carbonate solution was pumped up and down through each a Sew times followed by water and d r i patches. Finally rifles were oiled with Oil A and reexposed First June 10 C 100 A trace of corrosion was found D in each bore. This was wiped off with a cloth swab and Oil A. The r#Ees were then reexposed Second June 11 C 100 N o corrosion D Seventh June 16 C 100 No corrosion D Ninth June 18 C 100 No corrosion ~
,
D
Eleventh
June 2 0
Fourteenth
June 23
1
C
D _C
u
100 100
No corrosion
No corrosion On Tune 23. both rifles were treated with m e t a l - fouling solution.1 This gave a deep blue, showing the presence of cupro-nickel 102.)
................... ................ .................................
:3” f :
Ammonium persulfate.. Ammonium carbonate., [200 9.) Ammonium hydroxide (28 per cent). . . . . . . . 177 cc. 6 oz ) Water. 118 cc. l4 02:) (Ordnance Manual, LOG.cit., p. 45)
clearly. The swabs photographed are those of June 9, Tables 111, IV, and V. Fig. 2 shows the successive first swabs from one of the rifles of Table 111. The
TABLEI1
DATE RIFLE HUMIDITY RSMARKS May 14 C u Forty rounds were expended in each rifle, the bores were then swabbed with Oil A , and exD posed over 44 per cent sulfuric acld May 23 C ga No corrosion D June 5 C No corrosion
d
D
3;
Rifles used without change in the next firing test (Table 111)
F I R I N G TESTS AT K N O W N HUMIDITIES-The first tests (Tables I and 11) were carried out as follows: The rifles, without previous treatment, were fired until forty rounds had been expended in each. Each bore was then swabbed with cloth and Oil A until i t appeared bright and the swabs were no longer discolored. A generous coating of oil was allowed t o remain on the bore. Over the trays in one humidor was spread anhydrous calcium chloride t o give a humidity of approximately zero, while into the trays of the other was poured a 44 per cent solution of sulfuric acid t o give a humidity of approximately 50 per cent. The rifles were hung in place, two in each humidor. No after-corrosion appeared, although they were allowed t o remain under these conditions for 2 2 days. The rifles were then employed in the tests of Tables I11 and IV. To obtain the humidity of approximately I O O per cent pure water was substituted for the calcium chloride. Table V shows t h a t the corrosion was after-corrosion, which evidently requires a humidity greater than approximately s o per cent. Fig. I also shows this 1 The above analysis was made by Mr. N. A. C. Smith, of the Petroleum Section of the Pittsburgh Station of the Bureau of Mines.
Fro. I
legends “First Day,” etc., designate the day on which the swab was obtained, reckoned from the date dn which the sodium carbonate was used. The oorresponding swabs from the other rifles were similar in appearance with those shown. Fig. 3 shows the appearance of the swabs from one of the rifles of Table IV. The legends “Third Day-so per cent . .Humidity,”
Sept.,
T H E J O U R N A L O F I N D V S T R I A L A N D E,VGINEERING C H E M I S T R Y
1920
FIG.
2-sWABS
FROM THE
TESTSOF TABLE 111
etc., show the relations between humidity and the length of exposure. Days after Exposure
Second Third Ninth
TABLEI V HUMIDITY DATE RIFLE Per cent REMARKS June 6 A Atmospheric 100 rounds were expended in each, and the bores were then swabbed B with Oil A June 7 A 50 The rifles were placed in the humidor containing 44 per cent B sulfuric acid June 9 A 50 No corrosion B June 10 A ‘50 No corrosion B June 16 A 50 No corrosion. Both rifles were B transferred t o humidor containing water
Days after Transfer t o 100 Per c+nt Humidity Second June 18
A B
100
June 20
A B
100
Seventh June 23
A B
100
Fourth
TABLE V-NEW DATE June 7 June June June June June June
9 10 16 18 20 23
HUMIDITY 100per cent
Heavy corrosion in the bores of both. All other parts bright. Bores were swabbed clean wtth cloth and oil and re-exposed Continued corrosion in the bores of both rifles, less than t h a t noted on June 18 No corrosion. On June 23 both rifles were cleaned using the metal fouling solution. In both the colorless-solution turned t o a very dark blue, showing the presence of cupro-nickel fouling
BARRELS,NEVERFIRED REMARKS Bothbarrels were coated with Oil A and exposed No corrosion No corrosion No corrosion N o corrosion No corrosion No corrosion
CUPRO-NICKEL F O U L I N G N O T C A U S E O F A F T E R coRRosIox-In these plates i t will be noted t h a t the fired rifles gave some color t o all of the patches. When marked “no corrosion” this color was a light green. Tested with potassium ferrocyanide and acetic acid, this green gave t h e mahogany-brown of copper ferrocyanide. The detached corner of the swab marked “Ninth Day,” Fig. 2 , was tested in this manner. The metal-fouling solution used on June 23 likewise showed t h a t cupro-nickel fouling was present throughout the tests. As rifles C and D, Table 111, had ceased t o corrode after June I O , there is no apparent connection between the cupro-nickel fouling and -after-corrosion.
FIG 3 - s N A B S
86 5
FROM THE TESTSOF TABLEIv
This was tested further as follows: Two new barrels, freed from grease, were fouled by driving through each, by mechanical means, five bullets removed from service cartridges. With each succeeding bullet, t h e driving grew m&e difficult. I n one barrel, the jacket of the fifth bullet struck; further driving carried out most of the lead core, leaving the cupronickel jacket about half-way down the bore. Since i t undoubtedly made metallic contact with the steel i t was allowed t o remain. To increase the amount of cupro-nickel present, filings from jackets were thrown into the bores. The whole was coated with Oil A and exposed t o I O O per cent humidity. No corrosion developed in either barrel. N O EVIDENCE OF G A S DImusIoN-The observations recorded in Tables I11 and IV contradict Pasdach’s theory of diffusing acid gases. Corrosion once initiated proceeded rapidly for a few days only, then ceased. Moreover, while rifles A, B, C, and D were fired on the same date (June 6), two of them (C and D) had ceased t o corrode by June 1 1 . According t o the gas diffusion theory, all the corrosive gas had therefore passed out from the steel. Rifles A and B were maintained a t the same temperature, and i t is therefore proper t o expect t h a t such gas in their barrels had disappeared, and t h a t in consequence no aftercorrosion would appear. However, when exposed t o approximately I O O per cent humidity on June 16, both rifles corroded heavily. Furthermore, the prevention of after-corrosion by the use of certain aqueous solutions, such as the sodium carbonate solution recommended by the Ordnance Department, does not accord with the gas diffusion theory, for i t is difficult t o conceive how such a solution could penetrate beneath the surface of the steel and remove gases previously dissolved or occluded there. Again, this gas theory fails t o explain the pitting action of the after-corrosion. If the steel acts as a solvent, one may expect the attack of the diffusing acid gases t o take place over the entire surface. Examination of corroded bore sections, however, shows
866
T I I B JOLIKA?J.ILOI? I N I j L T S T K I A L
renters of corrosion completely surrounded by bright
metal.
This i s illustrated hv Fir,
4.
P’l
CHLORIDE
a coating of potassium chloride fails to explain the Lorroszon following repeated cleanings over long inter vals of time, that it fails t o explain the light sweating the sodium cart o explain the in each. The bores were then treated with ammonia, ntinuance under or with dilute potassium hydroxide. surfaces do not obtained were examined for nitrat ther it may be hydrogen peroxide and the ph suggested that the wide use and many endorsements A. Noble, Phil. Tvarir., 206 !190S), 207; s nitro-solvents and gun oils controvert Powders and Their Action in Closed Chambers n, or that the after-corrosion experienced irom the Russian by.flernadou, Washington, G 1904, p. 46; Sarrau aiid Vielie. .%rem. 9oadr. .SdO., 1 (1884-5). 126. 337 ions of Arizona and the Sahara does not from Brunswig (Bnr. Ed. of Munioc and Kibler), P. 164-5. accord with the experimental findings reported above P Cushman and Gardner, “The Corrosion and Preservation of Iron It may be shown, however, that all of these confusand Steel,” New York, 1910, p. 38; Dunstan, Jowett and Gaulding. . I . Chem. Soc., 81 !1905), 1548. nts are in no way at variance with the conconditions is known to furnish very corros
j
I According to the Ordnance Department, the mesa temperature of tbe gases throughout the bore during the explo3ion oi the present service cartridge ia about 2150’ C. (3900“ I?): 6. Noble, Lor. cil.
I ~ L Chcm Soc,38!i911),382. *Ordnance Manual, Loc iii , P. 44
Sept.,
io20
T H E J O I ' R N A L OF INI>GS1'I
