Petroleum43ase Protective Coatings
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WILL H. SHEARON, JR. Associate Editor
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in collaboration w i t h
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HE exprasslon “protective coatings” hae become so all. .’ embracmg m the last few years that, in any discussion of the subject, there must first be a careful delineation of the scope of the particular presentation, lest author and reader become entangled in the veritable maze of products called protective con& ings and the information which is available about them. One group of these products is built around petroleum-base coatings and is limited further to those, materials whicb are in no senae paints and which have no decorative a i m at all but are strictly pmrvatives and waterproofing agents. Certain typea of 8% phalt m t i c s and rusGpreventive compounds fall into this class; t h e materials and a specific plant installation for their manufacture are described here. Since the operations which led to the construction of this plant and constitute a major portion of its output rye based on the use of petroleum asphalt, it is interesting to consider just how hisbric and vereatile a material this complex substance is. A general definition (I) desoriheanative and pyrogenous asphalts as comparatively nonvolatile bitumens of dark color and variable brudnw; they are composed principally of hydrocarbons, substantially free from oxygenated bodies. Depending on origin and treatment, the compoeition will vary, and there maybe an oxygen content of from 2 to 8% in eome petroleum asphalts. The use of asphalt can be traced back to Babylonian times, and for thousmds of yesrs it was used as a building material.. The practice of caulking boat ~ e a m swith asphalts and pitches is as old a8 civilised man. It is a matter of history that during the Babylonian flood the entire inside and outside of a boat was smeared with saphalt, and this may have been the first instance in whicb it wa8 used to completely waterproof and protect in a manner similar to present-day use of undercoatings. There are numerow substanma gronped under the generic term, asphalt; among t h e are the natural asphalts, the 8%
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A. J. HOIBERG Lion Oil Company,E1 Dondo, Ark.
phaltites, asphaltic pyrohitumens, and the petroleum asphalts. Apparently the exploitation of the Seyssel asphalt in France at the beginning of the 19th century was the firat modern use of natursl asphalt. This was marketed under the name rook &g phalt mestic and was used for road surfacing and, to a limited extent, waterproofing. It was some years later before use of even natursl asphalt for surfacing and roofing took hold in the United Gtate. Today, however, both natural and petroleum asphalts find their use8 legion in pavements, as joint fillers, in m t i e flooring and roofing, pipe sealing compounds, impregnated papers, electrical insulation, paints, and dozens of other applications in addition to the undercoatings and N S t preventives discuased here. The reasons for the myriad applications of this substance arc well stated by Anderson (S), who e a y that ~ asphalt and coal tar pitches rank foremost among common organic coatings in low water-permeability. Water and oxygen slowly permeate the coating by molecular diflusion, but their concentrations remain 80 low 88 not to.cause corrosion. Electrolytes are etrectively excluded hy macroscopically intact coatings. Practical tests show that pipe lines may be adequately protected from the action of corrosive soils by bituminous coatings correctly formdated and applied. Abraham, whose treatise, “Asphalts and Allied Snbstanma,” (I) has grown from leas than 900 to more than 2wo pages in the last 20 years and is concrete evidence of the importance of 8% phalts and the work which has been and is being done with them, puts his h g e r on the technical attractivenw of petroleum B B ~ phalts when he says that the consistencics of native bitumens are predetermined, but that of most pymgenous bitumen@can he controlled by the treatment to which they are subjected in the course of prodbction. Since the asphaltic end products may vary almost endlesely, according to the type of crude oil and the relining steps through which it is put, the manufacturer of
I+ December 1949
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INDUSTRIAL AND ENGIrjEERING CHEMISTRY
asphaltic products Finds the problem mainly one of selecting the proper raw materials to fit the product which he desires. Rust preventives compounded on a lubricating oil.base are not quite as new in the sense of wide public usage as are asphalt undercoatings, but they are still in their infancy. Twenty years ago great progress was made with metals to handle higher temperatures and pressures and a wider range of fluids and gases, but progress in protective coatings for these metals was lagging considerably. A few were on the market, but practically all had limited uses and were difficult to apply, Consequently there was a need for additional coatings with a wider range of uses-coatings that could easily be made, handled, applied, and removed. The growth of the petroleum industry itself, with its demand for protective coatings for pipe lines, storage tanks, and refining units of all kinds, has been a great stimulant in this field, and military needs in the last World War provided the final impetus t o real action. Now, says Albin ( 2 ) , the emphasis has changed from development to application, and as the picture stands today, it is only necessary t o select and apply the correct rustproofing material for the protection required. LION OIL COMPANY
The first asphalt operations of the Lion Oil Company a t El Dorado, Ark., began, in 1929, in the paving field. These were extended t o roofing and finally t o specialties. Up t o mid-1949 these specialties were industrial applications concentrated in the airblown asphalt and cut back groups such as asphalt laminant for paper, waterproofing compounds, joint seals, and dipping blacks. One 50-barrel batch mixer sufficed for the entire production of fibrated roofing products and various protective coatings. With the completion of a new and modern protective coatings plant in May 1949, Lion has entered the field with a wide line of coatings, rust preventives, and preservatives. The manufacture of a representative number of these items will be described. Lion is considered to be one of the larger manufacturers in the asphalt field, with a production of more than 200,000 tons annually. Approximately 4% of this amount goes into the production of the special coatings handled in its protective coatings plant. I t s crudes are of three general types: the Smackover, containing 28% asphalt, the Urbana, also with a high asphalt content, and the Schuler, with about 14%. Average analyses of these crudes and the corresponding asphalts are shown in Table I. Since in selecting asphalts for further processing there are a number of points to be considered, including low and high temperature properties, stability, adhesion, and tendency to gel when cut back, it is important to have such steady high grade asphalt sources of known
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composition; the particular group mentioned above allows considerable versatility in operations. Petroleum asphalt either occurs as asphaltic bodies already present in the crude oil, or it may be produced during thermal cracking processes. According to the character of their high molecular weight constituents content, crude oils may be classified as asphaltic, containing a considerable amount of asphalts and only traces, if any, of the solid paraffins; semiasphaltic, containing a moderate quantity of asphalts; and nonasphaltic, asphaltic bodies nil or limited. The latter two classes usually carry appreciable quantities of solid paraffins. Petroleum asphalts are mainly of two types derived from asphaltic or semiasphaltic crudes and distinguished according t o the refining process as residual (straight-run), formed by distillation of crude oils under noncracking conditions, usually with steam and vacuum, and air-blown, produced by oxidation of heavy reduced crude oils. A limited quantity of petroleum asphalts (cracked asphalts) is refined from cracked residues by distillation and/or air blowing. Such cracked residues are derived by thermal cracking of stocks from any of the above crudes. In 1948 petroleum asphalt represented about 89% of all domestic asphalt sales, including native bituminous rock. A survey (10) of the history, source, and general nature of asphaltic bitumen adds two additional reasons for the wide acceptance of asphalts-their general nature and the refiner's ability to process them readily to give the qualities desired for specific applications. Some of their desirable inherent qualities are: solubility in common hydrocarbon solvents; fluidity on heating to moderate temperatures, thus allowing brush or spray application; ease of emulsification with soap or clay;. high imperviousness to water; and extreme resistance to deterioration on aging. Lion manufactures a number of asphalt coatings, including dry kiln mastic, plastic cement, sound deadeners, roof coatings, and undercoatings. The type asphalt used and the other materials added vary according to the coating, and the asphalt may be reduced or cut back with different solvents into various types of cuts. I n the paving field with kerosene, for instance, the cut is known as MC or medium curing; with naphtha, R C or rapid curing; and with lubricating or gas oils, SC or slow curing liquid asphaltic materials. In coating manufacture, to increase tensile strength and toughness, a filler may be added t o the cut back, asbestos fiber usually being the most satisfactory. Clay or limestone may also be added to effect further filling and toughen the coating and to provide additional abrasion resistance and sounddeadening characteristics (high limestone, sand, or clay content). Dry kiln mastic, which is used to prevent acid decomposition of mortar or insulation, has a high fiber content; plastic cement contains a tacky cut back, fiber, and additional mineral filler.
b
TABLE I. TYPICAL PROPERTIES OF CRUDEOILS AND ASPHAUFS
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CRUDEOILS Smackover A.P.I. 21 Visoosity a t loOD F., sec. 250 Carbon residue ?& 6.2 Sulfur content '% 2.5 Total gasoline And naphtha % 10 28 Asphalt content, 100 penetiation, %
Urbana 18 1080 7.5 1.5 2.0 34
Schuler 33.2 58 2.3 1.4 30 14
STEAMAND VACUUM RE:DUCED ASPHALTS Smackover Urbana Schuler Softening point (Rand B), F. 114 111 101 Penetration at 77O F,,. 100 -a . / 5 880.. mm./lO 100 100 250 Penetration at 3 Z 0 F., 200 gJ60 sec., mm./lO 37 Flash point C 0 . C a ' F. 625 Ductility a t 7 i 0 F.,'$cm./min., cm. loo+ Loss on heating at 326' F., % ' 0.01 Oliensis spot test 'e Negative Specific gravity a t 77'/77' F. 1.010 Ductility at 39.2' F., 5 cm./min., cmI. 25 4'% Solubility in CClr, 3 99.9 a Cleveland open cup method.
ASPHALT COATING MANUFACTURE
Today most roofing and base asphalts for coatings are made by a combination of steam and vacuum reduction and air blowing, rather than a process of straight reduction alone. This is done to combine the characteristics of flexibility a t low temperatures with those of high softening point and low flow a t high temperatures, and has also been carried over into the manufacture of undercoatings. Kastens (12)discusses both processes from the standpoint of current practice. Air blowing asphalt changes the physical characteristics so that it becomes harder, heavier in gravity, lower in ductility, and higher in softening point (14). The extent to which these physical and chemical changes take place, of course, depends on the nature and proportions of constituents in the original asphalt and on the processing and oxidation t o which it is subjected. From an economic standpoint this air blowing is important because it extends the possibilities of making useful asphalts from petroleum residues not suitable for processing by the usual methods.
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I N D U S T R I A L A N D E N.G I N E E R I N G C H E M I S T R Y
Mixing floor with bag storage in background
Bottom v i e w o f mixing line
vo1. 41, No. 12
Filling drums
Figure 1. Undercoating Mixing Operations The first complete disclosure of the piocess for oxidizing bituminous materials was in 1881 b> DeSmedt; Byerley, further developing the DeSmedt process, patented a method (9) of oxidizing petrolcum asphalt by bloving air through asphaltic oils maintained a t 600' F. Bycrley was the first to manufacture blown asphalt on a commercial scale. The general theory is that hydrogen is removed in the form of water, the hydrocarbons polymerize, and the asphalt is converted into a tough, rubberlike product having a higher fusing point than unblown asphalt from the same crude, and, because of improved physical properties, it is much more resistant to temperature changes. Present practice ( I O , 1 2 ) is to reduce the crude oil in pipe stills to a consistency depending on the properties required in the bloivn product, and then to charge the residue to a blowing still. Here from 20 to 50 cubic feet of air per minute per ton of residue are introduced, for a period of from 5 to 10 hours, with temperatures maintained in the range 440 to 550 F. Undercoatings must be easy to apply, either by spray or brush, and the solvent must be selected carefully. It is necessary to decide whether a low flash point solvent, with rapid drying but accompanying fire hazard, is desired or a high flash point type with less hazard but longer drying time. The more or less general trend appears to be toward a 300" to 400" F. boiling-range naphtha. A compatible asphalt which will provide other properties desired is then selected, and manufacturing can begin. Raw Materials. Both the naphtha for cutting and the asphalt residue or flux come from the refinery. After the asphalt is air blown at the refinery's asphalt plant, solvent is added t o make the vehicle or base cut back, and this is stored in a steam heated tank prior to being used in the further manufacturing or fibrating steps, Different types of cut backs are made, varying the flux or the solvcnt, or both, depending on the &ade (heavy, medium, and light) of pipe-, t a n k - , or undercoating desired. Asbestos is received from Canada, in different grades classified according to fiber length. A highly absorptive type limestone is not desired, and a size to pass a 200-mesh sieve is obtained from northern Arkansas. Both limestone and asbestos are stored and handled in paper bags, as shown in Figure 1. Since the operating level is on the second floor, the bags are delivered t o that floor by means of a rubber belt conveyer ( 5 A ) . In designing the plant (Figure 2) a number of types of asbestos handling equipment were considered, and certain manufacturers' recommendations were for bulk bins, rather than bag storage. This recommendation was finally abandoned, homTever, because some of the asbestos as received is less than 200-mesh and, during storage, would have a tendency t o separate into a nonuniform mix. The clay, which is used as a filler, is not used directly as brought into the refinery but as spent clay after it has been through the O
O
contact process treaters in the lubricating oil plant,. The prirrcipal advantage of using this spent clay is that since i t is already impregnated with oil, it will not, absorb oil from the asphalt (as fresh clay might) and thus render the asphalt coating brittlc in time. The clay is picked up from the lube oil plant and brought to the protective coatings plant in 55-gallon open head drums as needed. Manufacturing Steps. The cut-back asphalt is charged by pumping a t 90" to 100" F. from the steam heated storage tank into one of three 2300-gallon insulated misers (1-4).Tempcratures in this range are considered sufficient, since they- allow easy flow without being high enough to result in poor mixing or to cause excessive loss. $1~0temperatures must be maintained low in drumming, othcrwise settlement of filler might, occur. Each individual mixer is gaged by weight, using a calibrated gagc stick t o determine t.he pounds of c u t h a c k asphalt actually pumped into the mixer. The correct number of pounds of filler is then determined from this figure. The mixers, with rotary-type stirrers, are welded mild steel and cast iron construction, but differ in the design of tmhestirrer eniployed. The stirrer shaft,s are motor-driven ( I A , 6 A ) ; tiTo 01t h e mixers have two 6Binch horizontal arms passing between fixed horizontal arms. An additional top arni, slightly less in diameter than the mixer, is equipped with scraper blades, and a bottom arm follows the contour of the mixer bot,tom. A 20-hp. motor rotat'es the stirrer shaft a t 27 r.p.m. The shaft of the third mixer is drivcn by a 25-hp. motor a t 84 r.p.m., and the stirring mechanism consists of a three-blade screw propeller and a centricone with inner vanes. It is planned to change from the centricone type of agitator to paddle type in this mixer, hoir-ever, because the centricone is satisfact,ory only fur light coatings and will not handlo heavy mixes in the desired time. Each of the t,hree mixers is equipped with a screening tce (3'1) containing a Type 302 stainlcss steel screen with 0.0625-inch perforations, a screw-type variablc speed pump ( 6 A ) with a capacity of 50 to 75 gallons per minute, and a homogenizer. All the mixers are interconnected, so that, the mix can be circulated constantly in and out of a single mixer during the blending process or can be pumped to, or through, the other mixers. The piping is SO arranged that the homogenizer can be bypassed if desired, but no drumming can be carried out n-ithout the mixture passing through the screen. __--
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Figure 2. Process Flow Sheets for Production of Undercoatings and Rust Preventives at El Dorado, h l c . , Plant o f Lion Oil Company
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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> TANK ......
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IPLAMT PROCESS SERIES
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
The mixem were wt into the wcond Boor in such a manner (Figure1) that the pumps could be mounted on the 6181 Boor with their suctions directly under the mixers. In this way asphalt 80 cumulation in the pump lines is eliminated. Fillers are fed to the mixem thmugh a gymcentric screen vibrator (la) attached to each mixer. With the top of the mixer just a short distance above the Boor level, it was possible to wt the gymcentric srreens at w& level, making the feeding of the asbatoa or other filler by haod a relatively easy operation.
t OW
The spent clay is added by hand through thc vibrator, aud virculatingis startrd (with the homogeuizer by-passed) just as BOOR 88 the 6rat clay is added. Since this spent clay contains some resinous ma'terials and sulfonic mi& from the lube oil plant, a small amount of Caustic soda is added by hand, ae the next stcp, in order to neutralize theee materials to their sodium salts. This treatment actually results in a material improvement of the a s phallic properlies, berawe the sodium salts art as water-displac-
IS). Asbestos is then added by hand through the vibrator, aird the
ing agenta (11,
homogeniaer is cut into the line during the addition of the last five or S k each. The entire charging and blending proces has thus consumed approximately 2 hours. The blend w circulated through the hwnogenizer for 30 i o 60 minutes after the last of the asbestos is put into the mixer. This step is absolutely mandatory if a completely uniform run1 hmmgenmue mixture is to be obtained, and in order to produre a good underwating, it is necwary that the fiber bc neither torn nor lumped. The construction of thr homogenierr, which was d e signed and built especially for this particular use and which is aimply based on a piece of %inch pipe housing placed in the eird a t i n g Line, ia shoan in Figure 3. Following the charging and blending procms and the h o m o p n i s i g , a period of 30 to 45 minutes is takrn for teating. During this time the undercoating is not circulated; stirrinK of the mixture is accomplihed only through w e of the mixrr agitator. Top and botwm eamples are taken for uniformity, and a small laboratory adjacent to the filling Boor mrawres pease penetration, Stormer viscosity, and Bash point ( I ) . The consistenry t a t s are very importsot as they measure uniformity of the coating in the mirerandalaodetennineiftheproductisin thecorrect rangesfor application by the consumer. Penetration and viscosity tesb on the asphalt bbse iwlf are also made by various laboratories before and after the asphalt is blown, and by the pnitwtivc coatings laboratory afler cut hack and as a check on individual hatches as the mixea are started. When an individual hatch is ready for drumming it is pumped into 55gallon d-. A drum h placed on males immediately under the outlet, and an automatic cut06 tled in with the scales closa, the 6Uog valve aeearh drum ia filled. The hlliogoperation is shown in Figure 1. To produre 88 h m e , the approximate equivalent of one mixer hatch, requires about from 4 to 4.25 hours f r o m m a r i t o h n i . Oneday'soperation willresult in twobatrhes
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Vol. 41, No. 12
per mixer, or an average total for all mixers of 200 to 230 drums (475 pounds each) per %hour day. Cork mastics are ala0 made by adding a small amount of ashesto8 fiber to the cut hack and then using virgin cork ae the main filler. This results in a light coating with ineulating properties; it can be used on Pullman c m and the like. There are also certab asphaltics made up in the same manner as mt preventives, hut these are actually undercoatings and are used for crate-ooab ing compounds and for special shipping conditions. Properties. The h i s h e d asphalt undercoating h d s its principal use in automobilea as an underbody sealer and silencer and dries rapidly to a flexible, tough, waterproof and corroeionpmf costing which givw good performance over a wide range of temperatures. It doea not dry to touch mxm after application, hut a coating 0.0625 inch thick will he fum within 12 hours. This characteristic is valuable Since, in addition to a d e c r e e in inflammability of the coating, a h e r bond to the metal is developed and a denser film with improved shock and abraaion resistance is obtained over that of a coating which loses a considerable quantity of solvent in spray application. Weighing 8.6 pounda, 1gallon will cover an area of 25 square feet if applied 0.0625 inch thick (meaeured in wet thicheae). It will not flake or separate fmm metal even at subzero t e m p tures, and at tsmperatures as high as 400' F., it will not flow on a metal surface at an angle of 75". At ordinary or wing oven temperatures, around 175" F., it will not corrode steel, copper, or aluminum, and it shows excellent resistance to the action of acids and alkalies. No chipping, flaking, or appreciable wear is evident after 40 minutea exposure to the action of steel shot. A continuous coating is completely waterproof and shows excellent 6re resistance. RUST PREVENTIVES There me two broad clag4es of mat preventives-the nondrying types, or slushing compounds, and the types which dry to a hard film. Although they may be called paints, theee products do far more to inhibit corrofflouthan do paints, which merely protect surfaces. Those of the firatc h , at least, afford temporary protection only. This protection may be entirely mechanical in nature, accomplished by use of a thick film, or it may be positive in action, using only a thin coating (1 to 10 mils) with chemicals added 88 corrosion inhibitors. Classified according to type, petroleum-base r u s t preventives fall into three groups: preservative oils, which usually form a continuous wating from 0.0005 to 0.001 inch thick by draining; .solvent cut hacks, which are also generally thin-film in type and can be either soft base or hard base; and semisolid and solid, generally waxes. Some of the advantages and didvrtntages of each of these various types are outlined in Table 11.
TABLE 11. COMPA~USON OF Rum PREVE~VES BY TYPES Type compound heaervative O i l s
Bsmiaolid and adid
Soft or hard bsao ao1vent type
Advaotaaea
Disadvantages
December 1949
There is some feeling (2) that there is a strong tendency, but not generally accepted practice, on the part of manufacturers and suppliers to distinguish their products according to the service for which they are intended. Such a distinction generally results in four groupings : 1.
9.
3. 4.
, I
I.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Corrosion preventive Bearing compounds Greases Oils Metal conditioning compounds Solvent-type rust preventives (outdoor) Solvent-type rust preventives (indoor)
Bnother guide for classifying and selecting rust preventives is found in the specifications issued by government agencies, and particularly the armed services, although they may be somewhat confusing owing t o general absence of standardization. Some of these are being revised a t the present time in the interests of uniformity. The source just quoted regarding usage groupings feels that with these government specifications as guides, the most satisfactory groupings will be based on physical characteristics rather than usage and confirms the three-group classification already discussed. Because of the multiplicity of uses to which these compounds may be put, and the fact t h a t there is no general type which is a panacea for all conditions, the compounding must be done very carefully with the particular application in mind. Two important reasons for using solvent cut backs are that it makes cold application possible and allows reduction of film thickness to within the range 2 t o 4 mils. Particularly in the case of the oils and other thin-film materials removability is a prime consideration, and the preventive should be easy to remove by wiping with a cloth saturated with kerosene or Stoddard solvent. Many of the compounds combine the functions of a rust preventive and a lubricating oil, and one of the main problems has been ( 2 ) to produce an oil which retains the advantages of high refinement and a t the same time has sufficient metal-wetting properties to protect the metal part. Further, an ordinary lubricating oil wopld allow rusting to start probably within an hour after application due to displacement of the oil by moisture. Particularly in the case of thicker films is it important to emphasize the necessity for film continuity. Beckman (8) has concluded that electro-osmosis and diffusion of electrolytes are less important factors than supposed in the mechanisms effecting corrosion of metal surfaces protected with bituminous coatings and that even the direct diffusion of water vapor is not too significant. Apparently the dominant cause of occasional failure may be laid to small fissures or imperfections in the coating. These problems have been solved to a great extent by the use of additives and/or inhibitors, both in the compounding of the preventive and, in oil bases, in the manufacture of the oil itself. There are hundreds of these compounds, which can be chromates, nitrates, phosphates, soaps of polyvalent metals, petroleum sulfonates, or organic condensation products (4, 5, 13). An additional problem, however, beyond the high cost of these additives and inhibitors, has been the fact that up until recently so many of the materials which were satisfactory rust inhibitors had the disadvantages of promoting oxidation of the protective fiIm itself or of causing foaming or the formation of oil-water emulsions. Most of these were unsaturated compounds or metal compounds with known oxidizing properties. Polar compounds play an important part in rust inhibition today and a number of discussions have been published (4-6)relative t o the theory, properties, and action of oils containing these compounds. Whether inhibitive or additive, the major objectives ( 7 ) in treating a lubricating oil are to: (1) increase the wetting speed; (2) inhibit oxidation of the film; (3) increase the film strength; (4) increase adhesion characteristics; and (5) enhance lubricating qualities when required, Metal conditioning compounds are primarily for application to metal surfaces to loosen or disintegrate the rust and put the surface in a condition t o satisfactorily receive a priming coat, or with finished metal parts to rcmove corrosive fingerprints and other contaminants and to provide a thin coating t o prevent rust-
ing in storage. It is necessary that they be homogeneous liquids over a wide temperature range (at least 10" t o 90"F.), that their viscosity be such that they can be applied easily by spraying or brushing, and that they be noncorrosive, rust-inhibitive, harmless to personnel, and noninjurious to wood or painted surfaces. Manufacturing Steps. Five units of equipment are available for rust preventive manufacture-three mixers and two soap kettles. The mixers are all straight-side mixing tanks with dished bottoms ( 1 A ) and have 30-inch motor-driven ( 4 A ) turbine screw propellers, with straps for antiswirl baffles. Two of these 7 X 7 foot mixers are 2200-gallon capacity; one is steam jacketed and the other unjacketed. The third is 5 X 5 feet, jacketed, and of 800-gallon capacity.
Figure 4.
Saponifiers
The saponification equipment, Figure 4, consists of two straight-side soap mixers ( 1 A ) ; one is a 250-gallon pressure vessel, 3 feet 6 inches X 3 feet 2 inches, steam jacketed for a maximum temperature of 355' F. and pressure of 125 pounds per square inch. Agitation is with a %foot, 3-inch stirrer with scrapers, maximum speed 31 r.p.m., and two 2-foot, 4-inch paddles operating in opposite directions a t 31 r.p.m.; the assembly is driven by a 5-hp. double parallel gearhead motor. The low pressure kettle is 5 X 5 feet, 800-gallon capacity, and steam-jacketed, but made for use at only 15 pounds per square inch pressure. It also is provided with a double-motion stirrer operated by a 15-hp. double parallel gearhead motor, and consisting of two 3.5-foot horizontal paddles rotating a t 23 r.p.m. and a 4.78-foot stirrer with scraper blades rotating in the opposite direction a t 23 r.p.m. Pumps for discharging all of the rust-preventive kettles are 7.5-hp. motor-driven rotary type pumps. OIL-TYPE RUSTPREVENTIVE. Although oil-type rust preventives are by no means all lubricant types, steps in manufacturing a lubricant type may be given as a typical example in this plant. The base oil in this preventive consists of an additive-type lubricating oil containing a detergent and an antioxidant. To this base oil is added a sulfonate as a corrosion inhibitor, a metallic hydroxide, oxidized paraffin wax, and a water-displacing agent. The mechanism of action of various additive compounds is not entirely understood. A simple question of improving protection against rusting might be most likely explained by adsorption a t the metal compound interface (6). However, for the most serviceable compound, various different requirements must be met. Combinations of additives are necessary and usually a synergistic combination with respect to more than one property provides the most satisfactory solution. As the cost of additives is an impor-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLE 111. TYPICAL PHYSICAL PROPERTIES OF LIONRUSTPREVENTIVES
Viscositya, SUS Pour point F Flash point C 0 C., F. Fire point, b.O.C.,a F. Gravity, OA.P.1. Lb./gallon
Volatiles, % Solids Film characteristics Drying time, minutes
Oil-Type (Lubricating) SAE 10 SAE 30 244 588 - 25 - 10 375 435 415 470 19.7 19.1 7.8 7.8 0.4 I
.
Oily, nondrying
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Soft 135
0.2
Oil-Type Preservative, Medium 600 0 400
460 19.4 7.8
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0.2
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Oily. nondrying
Oily, nondrying
Special Preservative, Lube Oil 69 - 70 310 340 22.7 7.6
SolventType Hard Bhse 350 (77' F.)
Oily, nondrying
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Oil-Base,
100i
280
105 b
Wax-Film Solvent Diluent 160 (77' P.)
