CLEANING BY SURFACE DISPLACEMENT OF WATER AND OILS H. R. BAKER P. B. LEACH C. R. SINGLETERRY W. A. ZISMAN
Maintenance and renewal o f complex electrical and electronic equz$ment can be greatly simpliJied with the aid of basic surface chemistv.
The authors discuss the
theoretical aspects o f surface chemist?
appropriate to such maintenance and describe some proved methods for restoring damaged equipment to use
s a result of equipment damage in floods, hurricanes,
A tornadoes, heavy rains, and rapid thaws, millions of dollars of damage are done annually to homes, factories, and equipment of all kinds. Immersion in water is particularly serious for electrical power plants, motors, controls, radios, radars, and other electronic devices, switchboards, automobiles, machinery, tools, and instruments. Similar damage results from the accidental flooding of basements, pleasure boats, and ship compartments or from the aftermath of fighting a fire. Insurance company figures show that in the U. S. the total nonmilitary water and smoke damage annual losses amount to many millions of dollars. These losses can be greatly reduced by prompt application of the salvage procedures to be described below. The damage could be still further reduced if equipment in hazardous locations were properly conditioned before flooding conditions occurred. The principles and recommended procedures summarized in this report are the result of an extended post-World War I1 series of investigations by us (2-70, 72-74, 76, 77) of methods for cleaning and salvaging naval ship, ordnance, and aircraft equipment. However, the principles of surface-chemical oil and water displacement involved, and the methods of application will apply to routine maintenance and salvage of many other types of equipment in any location. Other investigators have reported on water-displacing compositions and emulsion-type cleaners between 1946 and 1955 (7, 79, 20, 23-25, 27-29, 32), but the materials and procedures presented here are very different in mode of action, effectiveness, and range of applicability. Success in preventing corrosion and deterioration in flooded equipment depends upon : ( u ) complete removal of all salts (or corrosion-promoting chemicals often present in the sea or in flood waters), ( b ) removal of all the water, and (c) proper application of an effective, thin-film, rust preventive. All of these steps should be taken as soon as possible after removal of the equipment from the fire-swept or flooded area. However, the flooded equipment is often left coated by oily materials, such as fuel oil, lubricants, or oily residues from the incomplete pyrolytic decomposition of rubber and plastics. Usually, it is difficult or impractical to remove all of these adherent, oily residues with organic solvents; they also act to prevent the effective action of the waterdisplacing compositions. This report will summarize our work in developing: (1) cleaning emulsions for rapidly and economically removing oily coatings from mechanical, electrical, or electronic equipment, (2) water-displacing compositions that rapidly displace water from surfaces of equipment, parts, and crevices accessible to a liquid spray VOL. 5 9
NO. 6 J U N E 1 9 6 7
29
0
I 7 0'
40
80
120
160
2W
240
280
I
320
1011116 Mllil rC1
Figurc 7. Initial rpraodiing cos&imt aliphatic waf-dirplm~ngc a n p o d
us. b0iIi.g p o d for Umiotu
and thus accelerate greatly the drying process, (3) aggressive chemical cleaners to remove corrosion products not otherwise removed, and (4) special techniques for facilitating the chemical salvaging process.
MECHANISM OF WATER DISPLACEMENT The effective displacement of a layer of one liquid coating a solid surface by another liquid is accomplished largely by specific surface-chemical action rather than by a simple solution or emulsification process. The mechanism has not been analyzed before, although the role of surface tension variations in producing localized flow of liquids has long been known as the Marangoni effect. In 1855 James Thomson (33) first reviewed the subject. Seriven and Sternliig (37) have summarized the present situation, and Bascorn, Cottington, and Singleterry (75) have related the effect to certain conditions for the spreading of organic liquids over solid surfaces. I n 1948 Baker and Zisman (73,74) discussed the many classes of polar liquids that they had found most effective in displacing thick films of water from solid surfaces and also reported extensively on their characteristic large initial spreading coefficients. The initial spreading coefficient, S , of liquid b on liquid u is well known to be related to the surface and interfacial tensions by:
-
+
= 70 (7b 7.3 Here a relates to the liquid being displaced and 6 to the liquiddisplacing agent. Nearly all of the values of , S were obtained by measurements of the initial spreading pressure, F,, at 25" C. using the piston monolayer method (27, 34). A condensation of their results will be found in Table I. Values of S, above 10 dynes/cm. at 25" C. were obtained only if the organic compound had a polar-nonpolar structure containing both hydrophilic and hydrophobic groups. They also found that in any homologous group of such compounds, the initial spreading coefficientincreased as the solubility in water increased and as the boiliig point decreased (Figure 1). 50
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE 1. CHARACTERISTIC INITIAL SPREADING COEFFICIENTS, Sh, FOR CERTAIN CLASSES OF ORGANIC LIQUIDS ON WATER Clan of Livid S,, Dytur/m. of 20'C.
Paraffins( C 6to Cl0) Ammatic hydmcarbons (bcnzme and pmpylbcnzcnc) Cyd0paraffiIU Ketones ( C . to CIO) Est- (various types) Alcohols ( C Sto C,,) Ethers ( C Sto CI.) Ether alcohols fmm glycols
* nafa w
~ obtained e =if 25-
3.5 to -3.0. 5.5 to 9.9a
zm or less. 26 to 46 30 to 43 15 to 50 18 to 31 36 to 42
c.
Only a minor proportion of the liquids having high initial spreading coefficientswere found highly effective in displacing thick layers of water from solid surfaces. Effectiveness in water displacement was measured by using a method similar in principle to one described by Thomson (33). A drop of the water-displacing compound was placed gently on the surface of a clean water layer 1 or 2 mm. thick which rested on a clean horizontal steel plate (Figure 2). If the liquid drop was effective, a hole rapidly formed in the water layer and an approximately circular area of the bare dry metal plate was soon exposed; the maximum diameter attained was used as a measure of the agent's effectiveness in displacing water. The results of such measurements on representative members of various classes or organic liquids are presented in Table 11. Comparison of the data of Figure 1 and Table I1 shows that all of the notably effective waterdisplacing compounds were appreciably soluble in water. This observation provides the key to an understanding of the primary water-displacing mechanism, which is not surprising since it is a nonequilibrium dynamic effect. Several mechanisms participate in the displacement of water by such liquid organic agents, but their relative importance depends upon the experimental conditions. Of especial importance is the water solubility of the displacing agent. When a drop of a water-soluble spreading agent (such as butanol) is placed on the sur-
face of a laver of clean water 1 mm. thick. it dissolves as it spreads (Figure 3 4 . Since the surrounding area of the water has a higher surface tension than the butanol solution in the immediate vicinity of the spreading drop, a localized and large surface tension gradient develops which is equivalent to a large spreading pressure directed radially outward. The result is a flow of the surface layer of the water in the same direction. This radial pressure effect is an example of the Marangoni effect (37,33). Many years ago Bressler and Talmund ( B ) ,as well as Schulman and Teorell (30), described the viscous drag caused by a spreading, oriented, insoluble monolayer on the bulk water beneath. They recognized the cause was the hydrogen bonding between hydrophilic groups of the adsorbed molecules with the water molecules beneath. This viscous drag is accompanied by a radial outward movement of the water. A circular depression is created in the water surface, and in the center there remains a central mound of butanol (Figure 3b). The water depression persists and grows because the radial gradient in surface tension must be greatest at the periphery of the butanol drop and least at the center; the greater the rate of spreading of the agent, the deeper the circular depression. However, during this spreading process, the butanol continues to dissolve in the water immediately beneath the central mound. As the butanol diffuses downward it contacts the solid/water interface, and eventually is adsorbed as a hydrophobic monolayer. As long as the solution process continues beneath the central butanol mound, the radial spreading pressure also continues. Whenever the agent’s spreading movement is sufficiently rapid, inertial effects of the radially moving mass of water are manifested. Usually an annular water ridge quickly appears around the central spreading drop. Eventually a circular annulus forms which scan distorts and breaks up into a circular array of small water mounds (Figure 2). Such a break-up process is familiar evidence of the characteristic instability of a toroidal liquid mass which always strives to minimize its free surface energy. Analysis of the residual drops of liquid reveals that each consists of an aqueous solution of butanol. The rate at which the water annulus breaks up into discrete drops depends upon the molecular weight, viscosity, and volatility of the agent. Whenever the agent has a chemical structure such as to be strongly adsorbed on the steel surface to form an hydrophobic film, a completely dry surface area exhibiting a large and characteristic contact angle with a drop of water remains exposed after the spreading process ceases (Figure 3 4 . In the case of an agent such as butanol, the central mound is rapidly consumed during the water-displacing process; since any butanol which had adsorbed on the steel in stage d (Figure 3) will desorb into the air or into
NEW1
b
c
d
Figurc 3. Displacement mcchrmism by
watn soluble agmt
AUTHORS H. R. Baker, P. B. Leach, and C. R. SingrCtmy me on the staf and W.A . Zisman is S u p e r i n t d t of the
Chemistry Division, U. S.Naval Research Laboratory. V O L 5 9 NO. 6 J U N e 1 9 6 7
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TABLE II. WATER-DISPLACING ABILITY AND RELATED PROPERTIES OF VARIOUS LIQUID ORGANIC COMPOUNDS
(Data were obtained at 20' C.) Dimctn (Cm.) o/ Arm o/ Wotar Duplorrd by D 0.025-MI. Drop of Agrnt I-Mm. Tluck Lo)" Z--Mm. Thick L q n Moximum
Methanol
I-Butanol
0.7924O 0.7905. 0.7854' 20/4 0.8108.
2-Methyl-1-pmpanol 1-Pentanol
0.81 69') 0.8160'
2-Methyl-2-butanol
0.810
, Ethanol
2-Propanol
Complctcb
20.10
18'
... ...
1.9 1.9 2.5
Does not penetrate
48.5
5.0
3.8 Recovera immediately
49.3 39.5
4.4
43.6
6.3 4.4 3.8 1.3 Float3 3.1
Does not penetrate
1.9 Recovers immediately Does not penetrate 1.3 Recovcrs immediately 1.3
4.4
1.3 Recovera immediately 5.0 Recovcrs in 15 Sec.
7.20
1-Horanol 1-Hepfanol 2-MethyI-7-ethyl-4-undecanol 3,9-Diethyl-6-tridecanol Cellaolve (nlvcol monoethvl .~ . ether) Butyl Cellosolve (glycol monohutyl e t h n ) Methyl ethyl ketone Mbhyl-n-amyl-ketone
0.8475* 0.93110
2.iid 0.46d Complete=
36.9 37.3 22.0 19.6 40.2
0.9019*
complete
39.6
4.4
0.80610.8166.
1.5;
46.2 35.8
2.5 6.9
Cellosolve acetate (ethylene glycol monocthyl ether acetate) n-Octane
0.9748'
6.56
43.2
3.1
0.7036b
a,
n-Dcdecane
0.766, 20/9 0.8799 0.821
z
BWUm.Z Solvessa No. 1 (boilin range93'- 135'8.)
0.2
Dacs not penetrate
Does not penetrate
-6.0 9.9 11.9
Data fmm"Synthctic Om!aoie Chemicals,'' 1959 cd. Union Carbide ChemicalaCo. 6 Data fmm "Handbook of Chc&by,and Phy+,'' 44thcd.. Chemical Rub& Co. 1963. =Data fmm "Synthcfic Oganic C h e G F i 9 4 7 cd., Sharplea Chemic&, Inc. dData from "Syothctic Orgamc Chcmual4'. 12th cd. Carbldcnnd Carbod Chem*& Cap., 1946.
P
543
s
$ 4
5
E Y
30
k
8
2 c
10
E
0 0.01
0.I
1.0
,oo
IO
IOLUIILIW IN WNU AT 20°C IWEISWT f€R
CWTI
Figure 4. Relation of w a f n mIubility to initial speuding coc&ic114 and wofn displacing abilify of simple mmhydric alcohols. The wrticnl lines through points in fhr rcp'on of strong displacmmi me p r o p a t i d in langfh (0 fhr meas O/ (I 2-mm. wafnfiim displocrd by fhr respecfiw &O/IU~S 32
INDUSTRIAL AND ENGINEERING CHEMISTRY
the adjacent water soon afterward, the water layer finally spreads back over the bare metal surface. However, if the butanol drop contains a s m a l l concentration of an essentially insoluble and nonvolatile surface-active cnmpound able to adsorb quickly from the solution to coat the bare steel surface with an hydrophobic monolayer, the resulting adsorbed film will prevent the water from respreading long after the butanol has disappeared. I n . this way the bulk water layer is permanently displaced fmm the steel surface in that area; thus the displaced water can be removed easily and completely by gravity flow, evaporation with or without an air jet, or by mechanical disturbance. For example, a 1% weight concentration of glyceryl monooleate in butanol is highly effective. A higher liquid alcohol, such as decanol, adsorbs on the steel to produce an effective water repellent film of adequately low volatility; hence no hydrophobic solute needs to be added for "permanent" water displacement. &ring the later stages of the displacement ofwater by a butanol solution of a hydrophobic rust inhibitor, the meding edge Of the water layer develops a well-defined contact angle with the steel surface. This suggests that
adsorption of the rust inhibitor carried by the spreading butanol film takes place through the thin edge of the retreating water layer; thus it creates a hydrophobic film from which the water retracts spontaneously. I n this way a supplementary mechanism of water displacement is provided which operates after the p’rimary sweeping action of the spreading butanol drop has brought it within adsorption range of the steel surface. The importance of the water solubility in the displacement mechanism is made more evident by plotting &, against the solubility in water of each of the n-alkanols (Figure 4). The orders of magnitude of these solubilities are indicated by the vertical dotted lines in the figure. In the extreme right-hand zone, the vertical bar through each point is proportional to the maximum area of water that one drop of the alcohol will displace in a 2-mm. film. We see that displacement of a 2-mm. water film occurs only when the most powerful displacing agents are used. Furthermore, the largest areas displaced are observed with alcohols whose solubilities in water are less than about 25y0by weight but greater than aboui 2y0.Alcohols with solubilities between about 2Oj, and 0.1% cause mild or weak displacements of the 1-mm. layer of water, but they cannot displace the 2-mm. layer. Alcohols having solubilities below 0.1% are unable to displace even a 1-mm. layer. The mechanism by which the water solubility of an aliphatic alcohol is able to contribute to the final total water displacement effect is evident from the observations described earlier in connection with Figure 3. As increasing water solubility is always associated with decreasing interfacial tension, as stated in Pound’s rule (22, Z S ) , we see that in dealing with substances of high water solubility (like butanol), the initial spreading coefficient will be approximately the difference between the surface tension of water and of the alcohol.
MECHANISM OF O I L DISPLACEMENT Bernett and Zisman (16) have recently demonstrated theoretically and experimentally that the mechanism just outlined for water displacement from solid surfaces can be generalized so that an essentially similar surface-chemical displacement can occur to a wide variety of organic liquids. The same process can be applied to displacing all of the physically adsorbed liquid from any solid surface. A spreading drop of the appropriate liquid agent will surround itself with an annular area of bare metal outside of which there will be seen a ridge and later an annulus of the displaced organic liquid or “oil.” The essential conditions are the same as were found for water. The liquid-displacing agent must have a n appreciably lower surface tension (Y~)than the surface tension (Y~)of the “oil” to be displaced. I n addition, the agent must be sufficiently soluble in the “oil” or be sufficiently volatile so that the spreading agent will evap-
orate completely after spreading a short distance. Widely applicable and most generally effective agents for such purposes include various classes of perfluorocarbon and dimethylsilicone derivatives. However, an aliphatic hydrocarbon (or a derivative) can be effective at 25’ C. in displacing an organic liquid if its surface tension (Y~)is higher than the surface tension of the organic liquid (va) at that temperature; the displacing effect is greater the larger the difference in Y, - Yb. Ample experimental evidence has been obtained for the correctness of the preceding conclusions. For example, experiments on the displacement from steel of a layer of Navy Special fuel oil, 1-mm. thick, by various organic liquid agents are summarized in Table 111.
WATER- D ISPLAC I NG COM POSIT ION S
A water-displacing composition suitable for cleaning and equipment salvaging must displace water efficiently and resist rewetting, must not do significant permanent damage to electrical insulation, and must protect ferrous TABLE 1 1 1 . SURFACETENSIONSAND RELATIVE FUEL O I L DISPLACING ABILITY OF SELECTED ORGANIC SOLVENTS AT 25’ C. Solvent Relative Surface OilTension Disf lacing ”Yb? Y a - ”Yb,a Action Solvent or “Oil” Dynes/Cm. DyneslCm. on Steel 1-Chloroper15.1 15.8 Vigorous fluorononane Perfluor0 kero14.0 Vigorous 16.9 sine n-Hexane Vigorous 18.4 12.5 n-Decane 23.9 7.0 Strong 140’ C . flash ali25.0 Strong 5.9 phatic naphtha Methyl chloro25.7 5.2 Strong form Diesel fuel Weak 27.6 3.3 Xylene 28.5 Very 2.4 weak a-MethylnaphNone 38.5 -7.6 thalene a Note:
T h e fuel oil used had a surface tension y a
3
30.9 dynes/cm. at 2 5 O C .
metal surfaces from rusting. It is also desirable that the composition should not create intolerable fire or health hazards; it should be stable when stored for a long time before use ; and for most common applications it must be inexpensive enough to permit commercial production, stocking to be ready for application, and widespread use. For most applications such compositions should comprise : (a) the displacing liquid, ( b ) the surface-active rust inhibitor, and (c) a suitable oxidation inhibitor. Each ingredient must satisfy all of the preceding requirements. A list of effective water displacers should include the aliphatic alcohols from propyl to hexyl, methyl amyl VOL. 5 9
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JUNE 1967
33
ketone, acetylacetone, amyl acetate, Cellosolve acetate, ethyl acetoacetate, butyl or propyl lactate, ethyl or methyl carbonate, and the Cellosolves (73,74). Of the many other compounds that exhibited good waterdisplacing ability, some have been omitted here because their vapor pressures were so low that too much time would be required for complete evaporation from salvaged equipment; other compounds having lower molecular weights were not considered widely useful because of their high evaporation rates and the resulting unacceptable fire or toxicity hazards; and certain promising compounds were ruled out because they caused excessive soflening or disintegration of common types of electrical insulation ( 2 4 8 ) . In view of the requirements outlined above, the butyl and pentyl alcohols were considered especially well suited for our applications (73, 74); however, there are many other liquids in the same boiling point range that may well be useful for a narrower range of applications. A N Sinhibitor ~ in a water-displacing composition must play a dual role; during the water-displacing action it must adsorb on ferrous metals to form an hydrophobic barrier film which will prevent respreading by the displaced water; and during subsequent service or storage of the salvaged equipment, it must prevent rusting. The mechanism of the inhibiting action and the other characteristics of such polar-nonpolar rust inhibiting compounds have been discussed fully in various reports and publications of this laboratory; a condensed technical discussion has been published by Zisman and Murphy (35). Basic barium dinonylnaphthalene sulfonate was chosen as most suitable compound for use in waterdisplacing fluids because, in addition to being soluble in butanol and pentanol, it is compatible with the usual hindered phenolic oxidation inhibitors, it adsorbs on metals as an excellent hydrophobic film which is an effective rust inhibitor, it carries a basic reserve which is essential for corrosion inhibitors that must operate in the presence of acid vapors or corrosive fingerprints (77,35), and it is commercially available as a well-defined and reproducible product. Stability against oxidation and deterioration during storage is most desirable in water-displacing liquids because long shelf-storage times under adverse conditions can often be expected. The oxidation stabilities of several waterdisplacing fluids and compositions were examined using the standard ASTM (D525-46) bomb test for the oxidation stability of gasoline. The usual 50-ml. sample was held at 100 p.8.i. and 100° C. The fact that butanol-1 has an induction period of 8 hours is indicative of fair storage stability. However, butanol-1 containing 0.1 weight % of such well-known gasoline and oil antioxidants as 2,6di-tnt-butyl-4-methylphenol,or the same concentration of 2,4diethyl-6-tnt-butylphenol,raised the induction period to over 216 hours. After the addi34
INDUSTRIAL A N D ENGINEERING CHEMISTRY
WElDHl CONCEl(R*ION ff SIODDUD IMMIII
I-
Figure 5. Efcct of dtlurion with ly&ocarbonr (St&d solvcnt, 704' C. parh naphtha) on initid sprcoding c.c@& and on mater-displacing wtimty of butanol-7
tion of 3.0 weight % ' of glyceryl mono- and dioleate, or the same concentration of basic barium dinonylnaphthalene sulfonate, no deterioration was found in waterdisplacing ability of the rust-inhibited composition even after storage at ambient temperatures for 10 and 6 yearn, respectively. For reasons of economy, the use of a nonpolar hydrocarbon solvent as a diluent in a polar water-displacing compound was investigated. The effect of such a hydrocarbon diluent on the initial spreading coefficient and on the water-displacing effectiveness of butanol-1 is graphed in Figure 5. It can be seen in the upper graph that the pryence of small concentrations of Stoddard solvent (104' F. flash naphtha) in butanol-1 caused only a minor decrease in the initial spreading coefficientuntil the proportion of hydrocarbon in the solution exceeded 75%. In the lower graph it is seen that only 20% hydrocarbon caused a large drop in the maximum area of water displaced. A hydrocarbon of higher vapor pressure might improve the water-displacement efficiency, but it would also increase the fire hazard. Dilution of the alcohol agent with mineral spirits in sufficient concentration to be an important economy does not appear promising because there results such a large decrease in water-displacing ability, but it might be an acceptable economy for some specialized applications.
01L-DISPLACING COMPOSITIONS Any useful oil-removing composition for cleaning and salvaging use must have the following characteristics:
(a) I t should remove oil residues rapidly and gently and not require mechanical treatment or brushing of the surface. (6) I t should not cause significant damage during cleaning and salvaging treatment to the common electrical insulating materials found in electrical, electronic, and other equipment. (c) I t should be no more flammable than the oil it removes. ( d ) I t should be noncorrosive to the metals present and should retard the rusting of any ferrous metal surfaces to which it is applied. ( e ) I t should be nontoxic and nonirritating to the human skin. (f) It should be commercially available and cheap. I t was thought that an emulsion-type cleaner would be especially effective in meeting these requirements since the dispersed hydrocarbon component of the emulsion would dilute and dissolve the fuel oil, while the water portion would serve to flush away the contaminants. Furthermore, the continuous water phase would reduce the flammability and health hazard of the cleaner formulation as well as lower the overall cost of manufacture or shipment of the composition. After having been used, the emulsion spray and contaminants could then be flushed away with fresh water or seawater depending on the availability. Past experience had indicated that some form of surfactant would be needed to hold the hydrocarbon and water in a useful emulsion. Therefore, the relative efficiencies of different surfactants were compared by using, for the organic liquid phase, a standard mixture of a chlorinated solvent and a hydrocarbon diluent. The composition of the mixture was arrived at by determining the volume ratio of the chlorinated solvent and aliphatic hydrocarbon solvent which would have a specific gravity very close to that of water. A solvent mixture with such a density would yield an emulsion with water to resist stratification and gross separation of the organic and aqueous phases. The least toxic chlorinated solvent available, methyl chloroform ( 4 ) , when mixed with Stoddard solvent (flash point 104” F.) in the ratio of two parts by volume Stoddard solvent to one part methyl chloroform, gave a mixture with a specific gravity near that of water. By use of this solvent mixture without surfactant, the maximum quantity that could be included in a moderately stable oil-in-water emulsion was about 35’% by volume. The solvent mixture was next standardized to make various aqueous test emulsions. In the search for a suitable emulsifying agent, 1.O% by weight of the surfaceactive agent was dissolved in the standard solvent comprising a 2 to 1 volume ratio of hydrocarbon to methyl chloroform ; this solution was then emulsified with about 65 volume yowater. T o estimate the effectiveness of the
TABLE IV. EFFECTIVENESS OF EMULSIONS CONTAINING VARIOUS SURFACTANTS I N T H E DISPLACEMENT O F NAVY SPECIAL FUEL O I L FROM STEEL (0.0625 M1. of an emulsion of 35 vol. yGsolvent, 65 vol. yGwater containing 1.0 wt. yo emulsifier. Solvent was a 2-to-1 b y vol. mixture of Stoddard solvent and methyl chloroform) Area of Oil Disjkzced, EmulsiJer Used After Chemical Type Trade Namea 5Min.,Sq.Cm. Emulsion without an 1.6 Above organic solvent emulsifier water emulsion Pluronic L-63 3.7 A condensate of ethylene oxide with a hydrophobic base formed by condensing propylene oxide with propylene glycol Polyethylene glycol 3.5 Polyethylene glycol 400 monooleate monooleate S1006 3.3 A polyethylene glycol Nonisol 100 ester of lauric acid Triton X-155 3.2 An alkyl aryl polyether alcohol Pluronic L-43 3.1 A condensate of ethylene oxide with a hydrophobic base formed by condensing propylene oxide with propylene glycol Tergitol nonionic NPX 2.9 Nonylphenyl ether of polyethylene glycol 2.9 Sorbitan trioleate Span 85 2.8 A condensate of ethylPluronic L-62 ene oxide with a hydrophobic base formed by condensing propylene oxide with propylene glycol 2.5 Igepal CO-630 Nonylp henoxypolyethyleneethanol 2.4 Alkaterge C A substituted oxazaline 2.0 Igepal CO-530 Nonylp henoxypolyethyleneethanol a “Detergents and Emulsifiers,” published by John W. McCutcheon, Inc., Morristown, N. J. (1964 Annual).
emulsion formed, a film of Navy Special fuel oil 1.5 mm. thick was applied to the surface of a steel coupon placed horizontally on a leveling device. Onto this film a volume of 0.0625 ml. of the emulsion was dropped from a height of 1 cm. The area of steel from which the fuel oil was entirely cleared away by the cleaning composition was taken as the measure of oil-displacing power. The results on the area of oil film displaced are given in Table IV. Ten of the most effective surfactants of Table I V were subsequently tested under conditions simulating salvage operations by spraying the emulsion under standard conditions onto a steel plate uniformly coated with Navy Special fuel oil and inclined at 45’ from the vertical. VOL 59
NO. 6 J U N E 1 9 6 7
35
Corroded relay before (above) and after (below) cleaning
The coating had first been applied by dipping the steel plate in the oil and allowing it to drain for 5 minutes. The spray gun, Model 825, made by the Lincoln Engineering Co., Detroit, Mich., was operated a t 80-p.s.i. air pressure and directed at the plate from a distance of 2 feet. Each surfactant was tested in 1.0, 0.5, 0.25, and 0.1 weight % concentrations, based on the finished emulsion. This test revealed that emulsions of maximum stability did not remove the fuel oil film most effectively. I n all cases the composition containing the 0.25 weight concentration of surfactant provided the most efficient removal of the fuel oil. Emulsions containing the 0.1 weight yo concentration of surfactant broke so rapidly that handling was difficult. The most complete removal of the fuel oil occurred when the emulsion broke as it contacted the surface of the oil coating so that the solvent was released to spread on, dissolve, and displace the fuel oil film. Without the eroding action of the spray due to the momentum at impact, the cleaning emulsion would not penetrate and displace all of the fuel oil film. More effective fuel oil removal by the drops of emulsion obviously required a component in the organic solvent phase of the emulsion which would promote solubility and aid in the displacement of the fuel oil. An effective, cheap, and available component for this purpose was the fuel oil itself. A formulation resulted consisting of 90.0 volume % of the chlorinated hydrocarbon-aliphatic hydrocarbon solvent mixture and 10 volume ye fuel oil (Navy Special). T o this was added 0.4 weight yoemulsifier. When this organic solution was emulsified with 65% by volume of water, an emulsion resulted which removed fuel oil coatings much more completely and rapidly than the preceding materials. Instead of using a chlorinated hydrocarbon solvent to reduce the fire hazard of the 104" F. flash point aliphatic hydrocarbon component, we decided to formulate a halogen-free cleaning composition possessing a minimum flash point of 140" F. This value is slightly higher than 36
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
that of the fuel oil contaminant likely to be present. After some experimentation we adopted a formulation made up of an organic solvent phase consisting of 90.0 volume yo of 140" F. flash point aliphatic hydrocarbon solvent and 10 volume ye Navy Special fuel oil. T o this was added 0.5 weight 70 emulsifier. The increased amount of emulsifier in these formulations was required because of changes in composition and density of the organic phase. The above organic solution was emulsified with an equal volume of water at the time of use. This emulsion was as effective in the spray test for removal of fuel oil as the previous emulsion containing the methyl chloroform. However, omission of the Navy Special fuel oil from this emulsion resulted in an ineffective material. The emulsion containing the Navy Special fuel oil was not any more detrimental to the insulating materials of electrical equipment than the fuel oil itself. It was also noncorrosive to metals and it appeared not to irritate hun an skin. The 10 most effective emulsifiers of Table I V were evaluated in this new emulsion utilizing the spray cleaning method previously described ; the results were essentially the same as those already given in Table IV, polyethylene glycol 400 monooleate Sl006 was again the most suitable emulsifier because of its effectiveness with sea water as well as fresh water and its superior rust inhibition. Addition of the hTavySpecial fuel oil imparts a brown color to the oil emulsion. Since such a composition would not be acceptable for use on equipment not contaminated with fuel oil, a search was made for some other inexpensive and readily available liquid hydrocarbon which would also perform well. Of the many liquids studied, the following four deserve mention here : 1. Naphthenic-base turbojet engine oil MIL-O6081B, Grade 1005 2. Fuel oil, Diesel Marine MIL-F-l6884F, Type 1 3. Kerosine, MIL-K-3128 4. Jet fuel, MIL-J-5624D, Grade JP-5
The first liquid possessed the greatest fuel oil penetrating ability, and the second liquid followed closely. The kerosine penetrated the fuel oil coating better than the jet fuel but not nearly as rapidly as the first liquid. The penetrating property of the jet fuel was very much like that of the 140" F. flash point aliphatic solvent. From these and other experiments, it was concluded that almost any oily contaminant could be removed by the emulsion if a mutual solvent was included in the emulsion formulation. This result recalls certain aspects of the "diphase cleaners'' developed and reported by others (19, 20, 24, 25, 27-29, 32) ; however, we did not find any of the formulations developed by them to be suitable for the complete removal of fuel oil from metal surfaces. Nevertheless, these investigators also reported
that stable emulsions were less satisfactory than unstable ones for the removal of soil from metal surfaces. When the oil-cleaning emulsion containing fuel oil was used to salvage equipment covered with heavy grade (Bunker C) burner fuel oil, ease of displacement and removal was greatly increased by warming the formulation to about 100' F. before spraying the equipment. The higher temperature also hastened the removal of the Navy Special burner fuel oil, but in this case it was not essential. However, the removal of either fuel oil from equipment at temperatures below 40' F. would be difficult. The efficiency of these emulsion formulations was tested at emulsion spraying pressures ranging from 20 to 80 p.s.i. I n general, it was found that cleaning could be effected at the lower pressures, but larger quantities of the cleaning emulsion were needed. A fine spray ejected at a higher pressure cleaned better and used less emulsion. Other tests have also shown that even the most delicate insulation in use on electrical motors was not damaged by being sprayed with a fine spray at 80 p.s.i. even at a nozzle-to-surface distance of only a few inches.
EFFECT ON ELECTRICAL INSULATION Obviously the compositions employed to salvage electrical or electronic equipment from immersion in seawater should not materially affect insulating tapes, fabrics, plastics, or varnish under salvaging conditions. Experience has shown that for a solvent of a given type, the greater the volatility the less will be the effect of solvent on electrical insulation. For solvents of the same volatility, the rate of attack depends on the molecular structure. As would be expected, aliphatic hydrocarbon solvents in these emulsions were less harmful to electrical insulation than were the aromatic or chlorinated hydro-. carbons. I n the water-displacing compositions, aliphatic alcohols appeared to be the least harmful, with the Cellosolves, acetates, lactates, and ketones following in that order of increasing tendency to damage insulation. Exposure to the salvaging procedure of a wide variety of the common insulating materials approved for military equipment revealed that none were affected significantly by either the emulsion or water-displacing compositions (2, 4, 8). However, a few of the fiber-reinforced materials were softened by the water or they permitted fuel oil to penetrate between the layers of insulating materials so that it was necessary to use the cleaning emulsion in an ultrasonic field to remove the last traces of the fuel oil. This effect was eliminated when the cut edges of the fiber-reinforced insulation were treated with Specification MIL-V-1137 Varnish, Grade CA. I n actual applications the entire assembly, including the edges of these materials, would be treated during the impregnating process, thus reducing the tendency toward fuel oil penetration.
AGGRESSIVE CLEANERS FOR CORRODED AREAS OF SALVAGED EQUIPMENT
If the salvage procedure is used shortly after the equipment has been damaged by a flood or fire, corrosion of the equipment usually will be at a low level, and removal of the products by our salvaging procedure will be rapid and routine. However, days and weeks may elapse after the equipment has been damaged before the salvaging treatment can be started. During that delay some components may corrode extensively. Under such circumstances, it is often necessary to add another step in the salvaging procedure to renovate satisfactorily all parts of the equipment. T h e mild cleaning treatment already recommended here for the removal of oily contaminants and seawater from sensitive electrical and electronic gear may not remove all of the corrosion products encountered; then more active chemical cleaners should be used. For such purposes there are commercially available high alkalinity cleaning compounds, based on sodium polyphosphates and silicates; one of these in a solution of 2 ounces per gallon (maintained a t about 60' C.) has been found to provide a good generalpurpose pretreatment. Such solutions were not found to damage insulation or electronic components during dip exposures of two minutes or less while using ultrasonic agitation. Sulfamic acid ( 2 ounces per gallon), with a suitable inhibitor to reduce direct attack on metals, has been found effective for removing green corrosion stains from brass parts. The corroded unit had to be dipped for about one minute under ultrasonic agitation, then was rinsed in a neutralizing bath kept mildly alkaline with ammonium hydroxide prior to subjecting the entire assembly to the regular salvaging procedure. More aggressive chemical cleaners consisting of thickened paint-stripping solutions brushed on appropriate surfaces and flushed off with water are also useful; however, care is needed to protect electrical insulation from the paint-stripping compositions. A commercial preparation, which utilizes methyl chloride and rnethanol and contains a thickener to enable the solution to cling to vertical surfaces of equipment, has been effective. After a few minutes of application, the paint and excess chemicals should be washed from the equipment with an alkaline aggressive cleaner solution. The equipment should then be rinsed thoroughly with fresh water and subjected to the regular salvaging procedure. We have developed ( 9 ) a variety of improved aggressive cleaners of the brush-on type and have reported on their composition and behavior and results obtained with them in salvaging operations. TANK IMMERSION W I T H ULTRASONIC I t was difficult and time-consuming to get the last traces of fuel oil contaminant from deep crevices and inaccessible places in or near small or complex components VOL. 5 9
NO. 6
JUNE 1967
37
in electronic and mechanical equipment by the spray method (4, 5, 8, 9). However, we found that such equipment could be cleaned completely and quickly by an immersion in an ultrasonic cleaning tank containing our cleaning composition. Direct current electric motors and motor generators, time-consuming to salvage properly by simple spraying procedures, were also quickly and successfully salvaged when the ultrasonic equipment was used in conjunction with the spraying method for the primary removal of the fuel oil and seawater. For best results in such cleaning operations, the ultrasonic tanks needed to have at least 8 watts of power per square inch over the entire bottom or side of the tank, and for continuous salvaging use the magneto-striciivetype transducers were found preferable. Immersible transducers rather than bottom-mounted ones proved the more versatile, particularly in large installations. T o speed up the operation, the maximum transmission of ultrasonic power should be communicated to the cleaning emulsion with maximum cavitation at the surfaces to be cleaned; it was helpful to degas the emulsion briefly by raising its temperature to 85' to 'TOo C. with the ultrasonic tank in operation. The temperature of the liquid could then be reduced to that suitable b r the equipment to be cleaned. A 5- to 10-minute immersion in the ultrasonic tank usually was sufficient, depending upon the equipment and the nature of the contaminant. Complex items needed to be rotated occasionally during cleaning so that the ultrasonic agitation could reach all sides. This was particularly important for assemblies containing plastics, as these materials did not transmit the ultrasonic waves as well as metals. In tanks with bottom-mounted transducers, the equipment had to be suspended so that it did not contact the bottom of the tank. Where tightly adherent contamination was encountered, a presoak in a polyphosphate, inhibited sulfamic acid, or other aggressive cleaner before ultrasonic cleaning was helpful. Following the ultrasonic cleaning treatment, ultrasonic rinsing in degassed fresh water was required to flush the cleaning solution or emulsion out of the crevices into which it had been driven during the cleaning process. Finally, the cleaned and rinsed equipment had to be treated with a waterdisplacing fluid, followed by drying in a warm, ventilated oven, or with a dehumidifier. RECOMMENDED PROCEDURE FOR CLEANING AND SALVAGING The cleaning and waterdisplacing methods and compositions already described have been utilized in cleaning and salvaging a wide variety of electrical and electronic units. As the result of much experience, an integrated naval system of physical reconditioning or salvage has been established. Briefly, the salvage procedure involves the following steps:
OUNCES OF IOFIENB M I W MUONS W A l U Figure 6. Intmpolnfion chart f o r csiimoting thc m o m i of tetrasodium tthyimdimiwle&metute dihydrate required to soften wutcr of
known hardness
1. Mobile fuel oil or grease contaminant is removed by subjecting the equipment to ultrasonic radiation while immersed in the emulsion. This procedure is essential for electronic assembliesor for components bearing adherent contamination or corrosion products. Nondetachable equipment can often be cleaned by spraying with the cleaning emulsion, but spray cleaning is less efficient than ultrasonic cleaning. 2. The equipment is thoroughly flushed with fresh water to remove cleaning emulsion and traces of salt, using spray application or ultrasonic treatment as may be appropriate. 3. Bulk water is blown from the equipment with oilfree compressed air and all parts of the equipment are sprayed with the water-displacing composition, which causes most of the film-forming water to drain away. 4. The remaining water and water-alcohol azeotrope are then evaporated by blowing with warm air or by placing in a moderately warm oven for several hours. The recommended salvage procedures will be found in a later section. This system has been successfully applied to a great variety of flooded equipment. SOME NAVAL APPLICATIONS
1. Alternating current motors in a variety of sizes up to 5 hp. were salvaged after having been immersed in seawater covered with Navy Special fuel oil. The recommended salvage procedure was rapid and inex-
pensive, and the salvaged equipment has performed entirely satisfactorily ever since. T o salvage d.c. motors, motor generators, and controllers it was necessary to use : ( a ) the ultrasonic tank agitation method to promote action of the emulsion cleaner, and ( 6 ) a fresh water rinse. Alternating current motors up to 40 hp. have been successfully salvaged by other naval activities using this system with ultrasonic cleaning and rinsing. 2. Various radio transmitters (Type COL-52245), radio receivers (Type CKP-46159A), a i d rectifier power units (Type COL-20218), all of which had been similarly submerged and exposed, were salvaged by our techniques and put back into normal use (8). Here also the ultrasonic tank agitation method had to be used to promote action of the emulsion cleaner as well as of a fresh water rinse. Finally, this equipment was dried in an oven. 3. A large variety of new radio communication and radar equipment on board the aircraft carrier U.S.S. Constellation was damaged in the much publicized fire in December 1960 while the ship was under construction at the New York Naval Shipyard. Circumstances prevented the immediate application of the salvaging treatment. Because of the soaking of the equipment by water used to put out the fire, marked corrosion occurred everywhere. Nevertheless, by judicious use of selected metal cleaning compounds followed by the oil- and water-displacement treatments described here, it was possible to clean and restore the equipment and return much of it to the service for which it was intended (7). Several million dollars worth of equipment was salvaged which otherwise would have been scrapped, and a long delay was avoided in returning the ship to active duty. 4. When an HH52A heliocopter accidentally sank and another crashed into the ocean during U. S. Coast Guard operations, the valuable communication equipment was reclaimed with the ultrasonic cleaning tank method and the recommended oil- and water-displacement materials. Even the wiring and the fuselage were restored to use by spraying with the emulsion cleaner ( 5 ) . 5. After 7 years of active service at Patrick Air Force Base near Cape Kennedy, Fla., the accumulation of seawater, salt residues, dust, and soluble corrosion products had rendered the equipment comprising an AN/FPS16(XN-1) missile- and satellite-tracking radar impractical to maintain and unreliable. The entire installation, including the antennas and all of the complex equipment in the trailer, was restored to full and reliable operation by application of the salvaging system recommended here (6). 6. Corrosion products from a variety of badly corroded electrical relays and switches were removed effectively by the applications of our newly developed, thickened, paint-on-type aggressivecleaners. After that, the components were cleaned with the recommended emulsion using the ultrasonic tank method; also, a fresh water rinse was given in an ultrasonic tank. After
spraying each piece with the water-displacing fluid and drying it in an oven, the equipment was returned to normal service (9).
PROCEDURE AND FACILITIES FOR RECOVERY OF EQUIPMENT AFTER WATER IMMERSION AND/OR OILCONTAMINATION On-Site Treatment. (1) Immediately after removing equipment from the water, it should be flushed thoroughly with fresh water to remove mud, salts, and so forth. (2) The above treatment should be followed at once with a spray of water-displacing, rust-inhibiting composition (Type I). (This protects equipment during necessary inspection or inquiry and during transport to repair station.) Final Reconditioning Procedure. (1) The equipment should be disassembled enough to allow access of cleaning solutions and to reduce electronic equipment to units of a size permitting immersion in the ultrasonic cleaning tanks. (2) The oily contamination, seawater, and salt should be removed with the emulsion cleaning composition in an ultrasonic bath. (Pressure spray application or immersion in air-agitated tank may be substituted if circum.stancesrequire, but the treatment will be less efficient.) (3) The equipment should be flushed with fresh-water spray or dipped to remove the emulsion cleaner, and then rinsed in the ultrasonic bath of fresh water (if possible). (4) The rinse water should be blown off the equipment with clean compressed air and the equipment should be sprayed with water-displacing composition (Type 11). ( 5 ) The equipment should be dried in an oven at 50' to 70' C. (depending on the temperature tolerance of the equipment) for several hours or overnight. When an oven cannot be used, a portable hot air blower or a dehumidifier may be substituted, or the equipment may be allowed to dry at room temperature for a longer time. (6) Electrical or electronic equipment should be checked for proper operation, any defective components located and replaced, and necessary adjustments should be made before returning it to service. EQUIPMENT AND CHEMICALS REQUIRED FOR SALVAGE PROCEDURES Spray Equipment. (1) Pressurized tap water or an auxiliary tank with a pump and spray equipment to spray fresh water. (2) A paint-spray gun or other spraying equipment for applying displacing liquid in a fine mist. Ultrasonic Cleaning Bath. An ultrasonic cleaning apparatus with a power rating of at least 8 watts/in? with cleaning and rinsing tanks both large enough to accommodate the equipment to be cleaned. Clean Compressed Air Supply. Clean compressed air supply or high-velocity cold air blower for removal of rinse water. VOL. 5 9
NO. 6 J U N E 1 9 6 7
39
Drying Equipment. Drying oven with temperature control and/or portable hot air blower or dehumidifier for final drying of salvaged equipment. Chemicals
1. Water - displacing, rust - inhibiting composition (Type I). This is a well-inhibited, general-purpose, water-displacing fluid formulated as follows : Wt. % 93.75
n-Butyl alcohol (I-butanol) 2,6-Di-tert-butyl, 4-methylphenol Basic b a r i u m dinonylnaphthalene sulfonate (50% inhibitor concentrate i n n a p h t h a )
0.25
6.00
100.00
2. Water-displacing composition (Type 11). This composition differs from Type I above by containing less rust inhibitor. It is intended for final water displacement on cleaned electronic equipment and is formulated as follows :
wt*% 98,75
n-Butyl alcohol (1-butanol) 2,6-Di-tert-butyl, 4-methylphenol Basic b a r i u m dinonylnaphthalene sulfonate (SOYo inhibitor concentrate i n n a p h t h a )
0.25
1 .oo
~
100,00
The rust inhibitor concentration in this composition is reduced to avoid difficulties with switch contacts. Type I1 should not be used when maximum rust inhibition is required. I n preparing either water-displacing fluid, first the oxidation inhibitor and then the rust inhibitor concentrate is dissolved in the butyl alcohol and stirred well. 3. Concentrate for preparation of emulsion cleaner. This material has the composition given below : Vol. D r y cleaning solvent, T y p e 11, Fed. Spec. P-D680 formerly P-S-661, N a v y Stock KO., 55-gal. drums, W6850-285-8011, 5-gal. cans, \V 6850274-5421 F u e l oil, diesel marine, T y p e I, mil. spec. Mil-F16884F, Ships, N a v y Stock KO.,5-gal. cans, WF9140-255-7764 Surfactant, nonionic
70
94.00
5.00
1 00 100.00
Polyethylene glycol 400 mono-oleate, S1006, a product of Glyco Products Co., Inc., Empire State Building, New York, is the surfactant recommended. However, detergent, general-purpose, mil. spec. Mil-D-16791 C-AK1Type 11, Navy Stock No., 5-gal. cans, 7930-531-9716, can be used if the surfactant suggested is not available. The cleaner concentrate is prepared by dissolving the surfactant and the diesel fuel oil in the dry cleaning solvent. Immediately prior to use, this concentrate is emulsified with water in proportions of from 15 to 50 vol. 70 depending upon the degree of oily contamination to be removed. 40
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
4. Water Softener. The water used for preparing the emulsion cleaner should not have a hardness greater than 10 pap.m. If it is harder than that, it is beneficial to add a water softener to counteract the hardness. Tetrasodium ethylenediaminetetraacetate dihydrate is recommended. The dosage of this chelating-type softener may be determined graphically from Figure 6 . This compound is available commercially from Geigy Industrial Chemicals, Saw Mill River Road, Ardsley, N. Y., or from Antara Chemicals, 435 Hudson St., New York. 5. Brass Brightener. About 1.0 vol. yG of household ammonia can also be added to the cleaning emulsion used for cleaning electronic components to help brighten the brass parts of the equipment if desired. REFERENCES (1) Anon., “Metal Finishing,” 48, 61 (1950). (2) Baker, H. R., U. S. Patent 3,078,189 (1963). (3) Ibid., 3,167,514 (1965). (4) Baker, H. R., Leach, P. B., “Salvage of Flooded Electrical Equipment,” N.R.L. Rent. 5316. June 16.1959. (5) Baker, H. R., Leach, P. B., “Surface Chemical Methods of Displacing Water and/or Oils and Salvaging Flooded Equipment. Part 3. Field Experience in Recoveriq E quii;ment and Fuselage of HHS2A Helicopter after Submersion ept. 6158, Oct. 19, 1964. at Sea,” A .R.L (6) Ibid Part 5. Field Experience in Removing Sea-Water Salt Residues Sand Dust,”and Soluble Corrosive Products from AN/FPS-16 (XN-I) Miseiie- and Satellite-Tracking Radar,” N.R.L. Rept. 6334, Oct. 15, 1965. (7) Baker, H. R., Leach, P. B., Singleterry, C. R., “Surface Chemical Methods of Displacing Water and/or Oils and Salvaging Flooded Equipment. Part 2. Field Experience in Recovering Equipment Damaged by Fire Aboard U.S.S. Consfellation and Equipment Subjected to Salt-Spray Acceptance Test,” N.R.L. Rept. 5680, Sept. 1 9 , 1961. (8) Baker H. R Leach P. B Singleterry, C. R., Zisman W. A “Surface Chemical hdthods ‘Af Dispfacing’Water and/or Oils and Salvaqing Flooded Equipment. Part 1. Practical Applications,” N.R.L. Rept. 5606, Feb. 23, 1961. (9) Ibid., Part 4--.4ggressive Cleaner Formulations for Use on Corroded Equipment,” TU-.R.L. Rept. 6291, June 15, 1965. (10) Baker, H. R., Singleterry, C. R., U. S . Patent 3,138,558 (1964). (11) Baker H. R., Singleterry, C. R., Solomon, E. M., I N n , ENC. CHEM.46, 1035 (1454). (12) Baker, H. R., Singleterry, C . R., Zisman, W. A , , “Factors Affecting the Surface-Chemical Displacement of Bulk Water from Solid Surfaces,” N.R.L. Rept. 6368, Feb. 24, 1966. (13) Baker, H. R., Zisman, W.A,, U. S. Patent 2,647,839 (1953). (14) Baker, H. R., Zisman, U’. A., “Water-Displacing Fluids and Their Application to Reconditioning and Protecting Equipment,” N.R.L. Rept. C-3364, Oct. 4, 1948. (15) Bascom, W. D.. Cottington, R. L., Singleterry, C. R., “Dynamic Surface Phenomena in the Spontaneous Spreadinp of Oils on Solids,” Advan. Chem. Ser., No. 43, p. 355, 1964. (16) Bcrnett, M. K., Zisman, W. A , , J. Phys. Ckem. 70, 1064 (1966). (17) Bernett, M. K., Zisman, W. A., “Solution Systems for the Displacing of Organic Liquids from Solid Surfaces,” h-.R.L. Rept. 6402, May 25, 1966. (18) Bressler, S. E., Talmund, D. C., Physik. Z.Sooiel Union 4, 864 (1933). (19) Campbell, C. A,, U. S . Patent 2,399,205(1946). (20) Zbid., 2,583,165 (1952). (21) Clinton, W. C., Pomerantz, P., Zisman, W. A., “Spreading Pressure, Snterfacial Tension, and Adhesional Energy of the Lower Alkanes, Alkenes, and Alkyl Benzenes on Water,’’ N.R.L. Rept. 6495, Jan. 19, 1967 (to appear in J . Colloid Interface Sci.). (22) Donahue, D. S., Bartell, F. E., J . Phw. Chem. 56,480 (1952). (23) Galven, G. D., McAuley, A. E., U. S. Patent 2,615,815 (1952). (24) Osipow, L., Pine, H., Snell, C. T., Snell, F. D., IND. ENC. CHF.M. 47, 845 (1955). (25) Osipow, L., Segura, G., Jr., Snell, C. T., Snell, F. D., Zbid., 45, 2779 (1953). (26) Pound, J . R., J . Phys. Chem. 30, 719 (1926). (27) Reich, I., Snell, F. D., Ind. Eng. Chem. 40, 1233 (1948). (28) Ibid., p. 2333. (29) Samuel, D. L., “Water Displacing Fluids,” Sci. Lubrication (London) 1, 2 (January 1949). (30) Schulman, J., Teorell, T., Trans. Faraday Soc., 34, 1337 (1938). (31) Scriven, L. E., Sternling, G.V., 12’ature 187, 186 (1960). (32) Syatyn, B. J., U. S. Patent 2,399,267 (1946). (33) Thomson, James, Phil. M a g . , Ser. 4, IO, 330 (1855). (34) Timmons, C. O., Zisman, U. A., “Spreading Pressure, Interfacial and Adhesional Energy of Normal Alcohols and Halocarbons on Water’’ (N.R.L. Rept. in preparation). (35) Zisman, W. A,, Murphy, C. M., “Polar Organic Rust Inhibitors,” in “Advances in Perroleum Chemistry and Refining,” Vol. SI, pp. 94-103, Edited by K. A . Kobe and J. J. McKetta, Interscience, New York (1959).
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