US2845328A

US2845328A - Method of inhibiting corrosion in tankers

Info

Publication number: US2845328A
Application number: US473158A
Authority: US
Inventors: Alan H Fleishhacker
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-12-06
Filing date: 1954-12-06
Publication date: 1958-07-29
Anticipated expiration: 1975-07-29

Description

July 29, 1958 A. H. FLEISHHACKER METHOD OF INHIBITING CORROSION IN TANKERS Filed Dec. 6, 1954 INVENTVOR. ALAN H FLE/SHHACKER A T TORNEVS United States Pateh t O METHOD or INHIBITING CORROSION IN ZTANKERS Ala H- El ishhask S l-Franc s C I ARn'iF- tivaP ee?" e flfifhsefla PIP-4 215 10 ct ims c1. 21 2,-s

1 ,This.iuvent onre t a vtnet sf nh bitin 't ,lcorrosion that occursvinthe interior, of tankers, and more ,particularly. to the use of afog ,ofa corrosion "inhibitor for suchpurpose. Corrosion that occurs in theinterior of tanker ships is a .nai .p. ob 'e in t s ipping st yan sth carry light oil products, such as gasoline and kerosene are flst bieqte tto pa i la y severe c rrosi 1 Th light Oil products dissolve any protective greasyfihnthat: may be -rep esen mst est d lkhea the a sq sfi sshari edt h t ghtwoil filmrem n Q t st sevapwo'rates leaving clean steel exposed; Inaccordancewith the usual practice in the industry, suflicientballast vvater s,t1,. n Pump n s o th t k o. render he p ssea rt y- Th e i va ab e. a t a Wa w h ene a v1,.err play df ballast, p d yrcorrodes h .unprqteqt sste :e Fur er p e he te in erio of the, ankeu hi is, not immersed in thesalt ,wa ter ballast is rusted by the m i tsa tm sph ----.Tan er arryi gheaWeiLrIM- -!-1. su s r deo t. kewi sufi e rtesion dama ,,la. .Q I5 .Q n. s ta k i sua y r s se e as in ships carrying the lighter, more volatile i l prqduets.

llhe extent of corrosion damage in tankers is so great m hat tankers carrying the h'ghtoil products generallyhave only iron; six v to ten years of operation beforernajor repairs are required in order to maintain thestructural ,strength and seaworthirress of the ships. H It is generally accepted inthe industry that the cost of repairing 'co 1 rosiQu dama e for a. flee t n m y avera e shi as aManytsql ti the ta k cer qs o Pr b em ha shee p opos ,.i e u in ..p ot c .ma n 9 ea .stect o c' eh t s fic on,..o v co os o gin ib prs, la theseawa l t rspra d dire t y a a st! urfaces of the, tanks. Incorporation of corrosion inhibisidir yr nto asoline r s 'a so 'be tp c as v r mate i lrd dva t a eub e flenequute .a lrmet edsheretqfo ugse tedwhi hh erpteren Widespread acceptance of such methodsjhy lthe industry. :1; Rmte t w s at g h e. b e nsatisf ete yi because of h nsho li p tan n hcond tionsr ease tered,i,and the difliculty, and XPenseof cleaning the i nter-r o s rfaqesof e. tanker s fi iently qproyi asprqp base for the, coating. ,Dehumidificationis expensive and Q nd syery fle s ,wh n. s s aters a l t s. claim L Cathqdi p t c a dwu u-so nble. nhibitors di Ql -;,l r, he eawa al as fe ttqo sa st e or in epa s l lt nker t n .cc ,,with t e se Wat al remain lmpr teetedbythesem i -nfilt t q i li, e.

V. Je i l l e o t .se ub nhibit d s lv d the the ,e tireq nt y. f bal st r requ fl cps stnp e t uth 'v u -.r laq n of co od d.s eellbe a eiot the large amounts of water soluble inhibitor required. A iIOIhel' proposed method of ,redueing tanker corrosion lnvolyes spraying a stream of a liquid colfroston 'nhibitor ,ctly onto the interior surfaces; o f th nke u e a. .a et s le maeat tr ass a 9 ice lzatented July 29, 1958 guired to co ver the interior of a tanker when the inhibitor ,oil product cargo. The same 'objection' 'also appl'es'ito ithe metho d in which the corrosion"inhibitoris'ftihrecftly incorporated in the oilproduct cargof In 'additi0n"it' is diificult to direct a sprayed streafn of corrosi'o irihibitor into all the nooks and crannies of the interior offa tanker since the drops of spray are sufficiently large to be strongly efie cted by gravitational force andffall dovvn'v'v'ards when I the initial momentum of the spray isspent. 'A's a s'ult, it is apparent that a simple economicalsolutionfto the tanker corrosion 'problem 'vvoul'd be of con derable vfalue arid importance. '17 f I 2 In summary, this invention comprises the creation of a ifog of a water insoluble 'corrosidninhibit'or jwhich p ref- ,era bly has a high aflinity-fer meat-amine directionjof 20 jsuch foginto the interior of a tankerto pro duce'a' fil m'of e orro sion inhibitor on all metal surfaces exposed to the Le T e {corrosion n h bit s P fe bl iis gw h a liquid carrier before it is converted into a fog'in'or'der to loidalgdispersion in which pmmesbr a" eoi'rdsion or s oluti on of corrosion inhibitor in fa car rierfaredisl pfii' vd i l I W t f The corrosion inhibitor fog is applied to the interior; of I the ta nkerafter the oil productveargo has been "Iiai'ged an before I the Water ballastv is; pumped into the tanker. QConsequently, the filmbf w'ater ihsolublecoriosion in- .Qhibitor' formed on the interior: offtheftanker: mains as I a protective coating in tanklcompartments containing 7 vva'te'riba llast when as in emptycoiripartmeiits the Water ballast is discharg'ed at the anaemia returri'voyage, 40 U etpargo; 1 j.

,Some of .the corrosion inhibitor fog introduced into 7 the tank compartmentsis deposited fithefre ii 1 liquid that is usually present at the bottom of'taiikers rn ser vice b"cause of the difliculty in pumping "the :thnkicoinpart- J the or'rosion inhibitor deposited; on the "b0 0f'the rises on the surface of ;the. ballast Watera H inhibitor is lighter than the balla'st vvater. A

Water level risesQand also when it isloshes around due the 'rollof the ship 'at sea, the corrosion on tssurface is likewiseplaced on the exposed metalin' the mpai trnent, thereby adding to the protectiveifiln irof c rrosioninhibitor. 7 5 f V 1, S'ricl'ethe fog ofcorrosion inhibitor is a colloidal type dispersionvwhich spreads to all ac'cessibl e" areas .and osits a of corrosion inhibitor iri-all nooks and n ies,v the fog' may be introduced i-into the tanker om the' outside of the tanker at almost any convenient location, 'such as a hatch... This advantagejobt ained by employing the method of this invention is Idue to the j falc at for all practical purposesfthe fog is :not effected I, particles of corrosion inhibitor in the s ray method,v

Jo" F thermore, a relatively small amount 'of corrosion i fog applied in accordance 'With this invention (1 protection for the e it'ire interiorgof a tanker.

'nts eornpletelydry. This'iiqu'id sloshes' around'duecompartment. Intanks that are filled vvithballastvva'ter,

s the co partment is. filled, because corrosion e ballast j y gravity in this method, as are the comparativelydarge.

Consequently, the cost of inhibiting corrosion in this manner is very low in comparison to other methods, such as the spray method, and substantial savings may be effected. Also, the small amount of corrosion inhibitor that is introduced into the interior of the tanker is not sufficient to produce a cargo contamination problem.

The single figure of the drawing is a schematic vertical sectional view taken across the width of a tanker illustrating the manner in which the nozzle of a fog producing apparatus may be inserted through a hatch of a tanker to fill the interior with a fog of a corrosion inhibitor. The interior of tanker 2 is subjected to a corrosion inhibitor fog 3 introduced through hatch 4 into center tank compartment 5. The fog is created by any conventional atomizing fog producing means 6. Wing tanks 7 may be subjected to a fog of a corrosion inhibitor in the same manner by introducing the fog from the outside of the tanker through any suitable hatch openings 8 provided in such wing tanks 7.

In greater detail, any of the well-known efficient corrosion inhibitors that are water insoluble, have a greater afiinity than water has for metal, and are substantially non-volatile at the usual temperatures encountered, may be employed for the purposes of this invention. The corrosion inhibitor must be substantially water insoluble so that it will not be dissolved when the water ballast is pumped into the tanker with resultant breaking of the protective film. Likewise, a high afiinity for metal is desirable so that the corrosion inhibitor will preferentially adhere to the metal and not be floated off and displaced by water when the ballast water is added to the tanks. Organic corrosion inhibitors that have low interfacial tension display the desired preferential wetting of metal which enables them to displace water on metal surfaces.

The corrosion inhibitor should also be relatively nonvolatile at the temperatures encountered so that it will remain a liquid fog at least until it has deposited on the tanker surfaces. If the corrosion inhibitor is converted into a gas when it is directed into the interior of the tanker and the gas subsequently condenses to a liquid, it does not form the desired continuous film on all interior surfaces of the tanker. The volatility of the corrosion inhibitor is a particular consideration when steam is used as the gaseous medium for dispersing the corrosion inhibitor.

Since the temperature of steam falls down rapidly to about 212 F. when ejected from the fog producing means 6, it is desirable to employ a corrosion inhibitor that does not have any substantial vapor pressure at that temperature. Corrosion inhibitors that have boiling points above 400 F. are usually substantially non-volatile at 212 F., and may be dispersed with steam without vaporizing to a gas. If a dispersing gas other than steam is employed at normal atmospheric temperature, the corrosion inhibitor need only be substantially non-volatile at the normal temperatures encountered.

An example of a suitable corrosion inhibitor is wool grease. Derivatives of wool grease that meet the foregoing requirements are also satisfactory. For example, Wool grease in which all or a part of its free acidity is combined with the oxide of a divalent metal to form the corresponding metal soap is particularly useful for the purposes of this invention. Divalent metal soaps of sulfonic acids derived from petroleum, which are known as mahogany sulfonates, are also most useful corrosion inhibitors for application to the interior of tankers in the form of a fog.

The well-known corrosion inhibitors composed of fatty acids of long chain aliphatic amines and diamines provide another class of inhibitor that may be employed advantageously. One type of such a compound which produces excellent results because of the effectiveness of small amounts in reducing corrosion is the oleic acid soap of a diamine which contains both a primary and a 4 secondary amino group. The oleate of an amine having the structure RNH-CH CH --CH NH in which R is a mixture of straight chain saturated and unsaturated hydrocarbon radicals of 16 to 18 carbon atoms in length, is a specific example of this useful type of corrosion inhibitor. This amine is sold by Armour Chemical Co. under the name Duomeen-T. Either the dioleate or the mono-oleate of such amine can be readily prepared by merely mixing the amine with oleic acid in proper proportions, either in equimolar ratios for the mono-oleate, or two moles of the oleic acid to one mole of the amine for the dioleate, which is preferred. Although the foregoing compositions are examples of suitable corrosion inhibitors, any of the well-known corrosion inhibitors having the physical properties specified herein may be employed for inhibiting tanker corrosion by means of the fog of this invention. In general, compounds that may broadly be classified as substantially water insoluble soaps are preferred as corrosion inhibitors since they are effective in inhibiting corrosion even when present in small amounts.

A liquid carrier is preferably mixed with the corrosion inhibitor before it is converted into a fog in order to reduce the viscosity of the corrosion inhibitor. This is generally desirable since suitable corrosion inhibitors usually are too viscous to be readily converted into a true fog by conventional atomizing equipment. However, when the corrosion inhibitor is of a sufficiently low viscosity to enable it to be atomized into a fog without the necessity of prior dilution by a carrier, the carrier may be omitted.

In addition to its function in aiding the formation of a fog, the carrier provides a less viscous corrosion inhibitor solution which results in the deposit of a thinner film on metal surfaces than would otherwise be obtained. Also, the carrier acts as an extender for the corrosion inhibitor, and it enables a small amount of corrosion inhibitor to provide a thin continuous protective film over a large surface area. Consequently, the use of a carrier renders the method of this invention more efficient and economical.

Any liquid carrier that is Water insoluble so that it will not dissolve in the water ballast, and which is a solvent for the corrosion inhibitor may be employed. Nontoxic carriers are preferred so that they will not be a health hazard. The viscosity of the carrier should preferably be in the range of from 35 to 200 Saybolt Universal at F. so that it Will provide a solution of inhibitor and carrier having a viscosity in that same approximate range when a major proportion of carrier is employed. A carrier that provides a viscosity of the solution of inhibitor and carrier of between about 100 and 200 Saybolt Universal at 100 F. is preferred, since this viscosity range has been found desirable for creation of a fog by conventional atomizing means. Also, optimum film coverage on the metal surfaces of the tanker is obtained with fogs created from solutions in such preferred viscosity range.

The carrier should also preferably be non-volatile at the temperatures to which the mixture is subjected, and be heat stable at such temperatures. In other words, the carrier should neither volatilize nor decompose during application of the material. Conversion of the carrier into a gas by either volatilization or chemical breakdown is undesirable, since as a gas it no longer serves as a carrier for the corrosion inhibitor. Generally, carriers that have average boiling points of at least 350 F. are suitable when steam is employed as the dispersing gas. If a gas at normal atmospheric temperatures is employed to atomize the corrosion inhibitor mixture, the carrier need only be stable and non-volatile at such normal atmospheric temperatures.

Liquid hydrocarbons having the properties specified are preferred as carriers since they are inexpensive, readilyavailable, and provide excellent results. Suitable hydrocarbons may range in specific gravity between 0.85 and i5 .1.05'.-.and .,have. anilinegpoints l between= .'F. .1and .200 ffhe; ,products --so1dy.'by sthe petroleum refiners, suchqras .petroleumspirits; aromatic typeldiluents,vkerosena min- ,eral seal, gastoil, :dieselfuel, neutraloil and transformer 1: oil are specific examples ..of satisfactory -liquid hydro- ,carbon carriers. -In addition .to thesecarriers,-substiptutedproductssuch as halogenated "hydrocarbon derivatives including chlorinated ,parafiins rand chlorinated-1di- -phenyls may be 2 employed :ifldesired when i the-y have xthe :specified-physical ,properties. ;However, substitutedhydrocarbons are more expensive than the regular petroleum products.

- The -;pr 0p0rti0nal amount 10f corrosion inhibitor. and carrier employed is not particularly :criticabas long.as lthe viscosity of .the-solution enablesit torbe atomized-and ..a.-fog created. -With .thenelficient corrosion inhibitors -.named herein, such as theoleate :of Duom'een-T sold1by .Annour-Chemical C0,, as little as -0.0l%.-by-we ight corrosion inhibitOr-f'andI99-.99 .by weightcarrier may .be employed. With less efficient corrosion inhibitors :;a larger". proportion of corrosion .inhibitor is usually. em- .ployed. Generally, itis-notcpractical to employ :more than 50% by weight corrosion inhibitor to 5.0% :by

weight of-the less viscous carrier, since many suitable corrosion inhibitors are viscous and difficult to atomize. .Also, .it is. usually preferable toemploy-.-a major spropor- .tion',of-;the carrier ;since,-as previously explained, .the .car-

..rier .acts as .an vextender, for the corrosion inhibitorland renders the process moregefiicient. :However, thencarrier may .be- ,omitted ,in.c-ases-1when- Ethe corrosion: rinhibitor -ean benatomizednor-dogged qwithout ptior dilution rbyria t-carrier. .Ilhe solution; of corrosion inhibitoriand carrier z may :be, prepared simplyeby thoroughly. mixing :the.;corro- ..sion:.inhibitor together with :the [carrier :in a ssuitable -rcontainer. 1 1

With rrespectwto, fogq producing :means: requiring aj gas under; pressure-tot create the: 59%, 2 anyggas "may .:be,: utilized as the -.-dispersing-. means-for atomizing ithe .corrosioniinhibitor.-solution. in. order to, create .the fog. Such; type: of

.ifog-,pr,oducing meansris preferred. @However, any it'ype' not} mechanical. fog producing imean's :not requiring .a 'gas maywbe: employed. whenragas -;-is' employed topproduee the fog, in order to reduce the possibility ofifirezbrrexgplosion in the: tanker .itvis -preferable -=to :use an .inert 1 gas rather-than -.-a; gas, =SI1Chw'aS Lair, which i contains wavailable aoxygen. V

.Steam-is ..extremely.desirable and;.is preferred for iatomi zing ;the :corrosion inhibit-orsolution. since it. iszinert. Eurthermore, substantially all tankerszhave anravailable s our,ce..of steam'- supply. riGonsequently, :steamyprovides scale atomization and; creation of ca.,fog-.:may"conveniently 1- -betca rried-out withafog generatorvheads such asrfinxathe gJIodd i-Insecticidal Fog. Applicator which E is :sold? :byatlie v GombustionEquipment Division of Todd Shipyards lCorp- ..oration. ".Other atomizing equipment such. as that shown .imUnited StatesPatent'No. 2,321,792;v may: be employed. .Snflicient corrosion i-inhibitorafog is directed into the in- .-terior of .the: tanker to producera-l. continuous film on-.-th'e ..meta1-.surfaces. 'I heintrQduction ofsadditional corrosion inhibitor fog after a film has beenw formed may be :con-

Noz-zleswof *this 1 type create a fog '5:

ris noti so ;;great.- that=a cargo contamination problem will beencountered. The =filr'n. can be: of. any; thickness :as long -as it remains unbroken. with film thicknesses of between-0.001- inch.aridw0.002 .-Einch;of thecorro'siontinhibitorsolution :as suchithickness Good results-have beentobtained s provides-adequate protection for extended-periods. 1How- .metalsurfacewith a film thicknessof-about 0.002' in"ch of corrosion inhibitorxsolution. ':-However,:thisxamountiis :not; particularly critical since efiicient corrosioniinhibito'rs are effective inrfilm thicknesses even less than: 0:001 inch. The amount of gas required to atomize l2,pounds;of:soluventing corrosion when applied ;to; metal surfaces .in-Lthe :tion varies with the :type. ofatomizing equipmentizand'ihe gas pressure. Approximately 200 cubic. feetofigasratis60 pounds .per square-inchupressure .mayLrbe employed ito create a fog from '12; pounds of. corrosion inhibitorusolutioni that will adequately cover'.1000 squarefeet-ofasurface.

.Typical examples of solutions of corrosion inhibitor and carrier thatihave :produced :excellentiresults impreform'of a fogzaresas follows:

Example 1 'P j m a iby weight 'Raw wool grease (corrosion inhibitor) f20 vPetroleum distillate (specific gravity 0.88, viscosity .Calcium soap .of mahogany sulf onic acids (corrosionninhibitor -0 Transformer'zoil (specific gravity 3-90, viscosity? Saybolt Universal at F;, and aniline point (carrier) vino Example III "Previously mentioned --oleic 'acidsoap cfa diamin'e sold 'by Armour Chemical "Co; "under the -na me'i'.

The following. is an :example of: the -ma nner in which -the center tank compartment 5 of a. typical ymediumgsize ,gasoline tanker of modern-de'sign-having a- .capacityv:of

about -v 8,700 .barrels (42 gallons per barrel) :of gasoline and. a vtotal surface area of approximately -1-7,-600-. squa-r e feet .of ,metal may-.bestreated in -accordance--With-2th-is invention. The v17,6003squaresfeet surfacewarearof ithe center tank is composed .of.':about 9,600 -s quarei,-feet of structural supporting members and about 8,000-sguarerfeet of..plating. The rusualatanker :ofthis typen-cont-ains eight wseparate center .tank compartments and .-a-- total ,of six- 1 teenv .wing rtanks 7. Each -wingtankscontains .a. total: of

-.ab,out.1'2,800 square feet of surface areaofrWhich about 7,850 square feet .is -.on structural supporting-:mem-bers 2 and about 4,950 squareifeetis' metalplating. Thesside wing ztanks.;have -a capacity of .-about :3,900 barrels of gasoline.

After .thecargo of gasoline is :discharged introduceia .fog :of .sthencorrosion inhibitor-solution specifiednin .the foregoingExampleII fromthe outsideofwthe'ship through a'hat'ch-v into thewinterior of the-tankcompartmeng whioh -.is :acenter-tank compartment 5'in this example. Create the fog by atomizing the solutionvof:oorrosion=-inhibitor .and .carrier,--which solution :hasi a viscosityeof about7150 :SayboltzUniversalrat 100 F *with anmconVenient-iatrima ti-nued as a safety.factoraif:tdesiredias :long as .the excess :75 izing means, .-suchy:as:=a Binksspray gun usinggrstea ncas the operation is completed. About 25 gallons of the corrosion inhibitor-carrier solution covers the metal surface of a center tank compartment of the 17,600 square feet surface area specified including the bottom regardless of whether or not it has some residual liquid thereon, which amounts to about 1.5 gallons of corrosion inhibitor solution of every 1,000 square feet of surface to be protected. However, to insure complete coverage it is desirable to employ an excess of corrosion inhibitor solution to take care of voids and unusual conditions that may be encountered inside the compartment, Usually an excess of about up to 15% will be sufficient. As previously mentioned the amount of corrosion inhibitor-carrier solution specified provides a coating of about 0.002 inch thick, and lesser amounts may be employed since corrosion inhibitor solution coatings of less than 0.001 inch in thickness have been satisfactory for inhibiting corrosion. About 3,500 cubic feet of steam at 60 pounds per square inch pressure atomizes 25 gallons of corrosion inhibitorcarrier solution with the specified type of atomizing apparatus.

After a film of the solution of corrosion inhibitor and carrier has been deposited on the interior surfaces of the tanker compartment by a fog in the manner described, pump sea water ballast into the compartment in the customary manner in order to render the ship seaworthy. The corrosion that usually occurs in the compartment during the return voyage is inhibited by this method at a low cost, since the film of corrosion inhibitor protects the metal from the corrosive action of the sea water.

The sea water ballast is pumped out of the tank compartments after the return voyage, and the tanker is filled with its oil product cargo. The amount of corrosion inhibitor solution applied in accordance with this invention is not suflicient to cause a contamination problem even for example with the strict requirements applied to a cargo of aviation gasoline. With 25 gallons of corrosion inhibitor solution applied to the center tank compartment of 8,700 barrels (365,000 gallons), even if all of the corrosion inhibitor solution is dissolved in the cargo, the amount of corrosion inhibitor in the cargo will be only about 1 part in 15,000, or about 0.007%, which is well within the permissible contamination limits. Furthermore, the major proportion of the corrosion inhibitor solution is desirably a liquid hydrocarbon carrier which does not interfere with the combustion characteristics of the cargo. Consequently, the fog of this invention provides protection against corrosion without causing a cargo contamination problem.

I claim:

1. The method of inhibiting corrosion in the interior of an oil tanker or the like adapted to contain an oil cargo on one trip and water ballast on another trip whereby the water ballast would otherwise cause said corrosion, which comprises introducing into said interior a fog of a water insoluble corrosion inhibitor and a water insoluble carrier before said water ballast is added to said interior, filling said interior with said fog to form a protective film of said corrosion inhibitor on all the exposed surfaces of said interior, said corrosion inhibitor and said carrier being substantially nonvolatile at the temperatures to which they are subjected while in said interior, and subsequently introducing water ballast into said interior.

-ca1go on one trip and water ballast on another trip 8 whereby the water ballast would otherwise cause said corrosion, which comprises introducing into said interior before said water ballast is added thereto a fog of a composition comprising a water insoluble corrosion inhibitor present in an amount up to 50% by weight and dissolved in a water insoluble carrier, said carrier having a viscosity of from 35 to 200 Saybolt Universal at F., filling said interior with said fog to form a protective film of said corrosion inhibitor on all the exposed surfaces of said interior, said composition of said corrosion inhibitor and said carrier being substantially non-volatile at the temperatures to which they are subjected while in said interior, and subsequently introducing water ballast into said interior.

3. The method of inhibiting corrosion in the interior of a tanker during the period in which the tanker contains water ballast, which comprises providing a water insoluble corrosion inhibitor having a viscosity enabling it to be atomized into a fog and which has a greater affinity than water has for metal, atomizing said corrosion inhibitor with a dispersing gas to form a fog, introducing said fog into the interior of said tanker while said interior is empty before addition of the water ballast, filling said interior with said fog to form a protective film of said corrosion inhibitor on all the exposed surfaces of said interior, said inhibitor being substantially non-volatile at the temperatures to which it is subjected while in said interior, and subsequently introducing water ballast into said interior.

4. The method of inhibiting corrosion in the interior of a tanker during the period in which the tanker contains water ballast, which comprises providing a liquid solution of a water insoluble corrosion inhibitor dissolved in a water insoluble liquid carrier, atomizing said solution with an inert dispersing gas to form a fog, introducing said fog into the interior of said tanker while said interior is empty and before addition of the water ballast, filling said interior with said fog to provide a protective film of said solution deposited on the metal surfaces of said interior, said solution being substantially non-volatile at the temperatures to which it is subjected while in said interior, and subsequently introducing water ballast into said interior.

5. The method of inhibiting corrosion in the interior of a tanker during the period in which the tanker contains water ballast, which comprises providing a solution of a water insoluble corrosion inhibitor having a boiling point of at least 400 F. dissolved in a water insoluble liquid carrier which has a boiling point of at least 350 F., atomizing said solution with steam to form a fog, introducing said fog into the interior of said tanker while said interior is empty and before addition of the water ballast, filling said interior with said fog to provide a protective film of said solution deposited on the metal surfaces of said interior, said solution being substantially non-volatile at the temperatures of said atomizing steam in said interior, and subsequently introducing water ballast into said interior.

6. The method of inhibiting corrosion in the interior of a tanker during the period in which the tanker contains water ballast, which comprises providing a solution of a water insoluble corrosion inhibitor .present in an amount up to 50% by weight and dissolved in a water insoluble liquid carrier having a viscosity of between 35 to 200 Saybolt Universal at 100 F., atomizing said solution with a dispersing gas to form a fog, introducing said fob into the interior of said tanker while said interior is empty and before addition of the water ballast, filling said interior with said fog to provide a protective film of said solution deposited on the metal surfaces of said interior, said solution being substantially non-volatile at the temperatures to which it is subjected while in said interior, and subsequently introducing water ballast into said interior.

7. The method of inhibiting corrosion in the interior of a tanker during the period in which the tanker contains water ballast, which comprises providing a solution of a Water insoluble soap dissolved in a mineral oil, atomizing said solution with an inert dispersing gas to form a fog, introducing said 'fog into the interior of said tanker while said interior is empty and before addition of the water ballast, filling said interior with said fog to provide a protective film of said solution deposited on the metal surfaces of said interior, said solution being substantially non-volatile at the temperatures to which it is subjected While in said interior, and subsequently introducing water ballast into said interior.

8. The method of inhibiting corrosion in the interior of an oil tanker ship or the like during the period in Q which the tanker contains sea water ballast, which comprises providing a solution of a water insoluble soap corrosion inhibitor present in an amount up to 50% by weight and dissolved in a water insoluble mineral oil,

. said solution having a viscosity of between 100 and 200 Saybolt Universal at 100 F., and being substantially nonvolatile at 212 'F.; atomizing said solution with steam to form a fog; introducing said fog into theinterior of said tanker while said interior is empty and before addition of the Water ballast, filling said interior with said fog to provide a protective film of said solution deposited on the metal surfaces of said interior, and subsequently vintroducing water ballast into said interior.

9. The method of inhibiting corrosion in an interior compartment of a ship during the period in .which the ship contains water ballast, the ship having an opening in saidcompartment and a source of steam supply on said ship, which comprises providing a water insoluble liquid composition that has the property of inhibiting corrosion of metal, utilizing said steam to atomize said composition and create a fog, before the addition of the water ballast, introducing said fog from the outside of said compartment through said opening into said compartment until the interior of said compartment is filled with said fog to provide a thin protective film of said which comprises inhibiting corrosion of the metal in said compartment which would otherwise be caused by said water ballast by forming a fog of a solution of a water insoluble corrosion inhibitor dissolved in awater in;

soluble carrier, directing the fog into the interior of said.

compartment before said water ballast is added to the compartment, filling said compartment With said fog to form a protective film of said corrosion inhibitor on the all exposed interior surfaces of said compartment, said corrosion inhibit-or and said carrier being substantially non-volatile at the temperatures to Whichthey are subjected while in said compartment, and then introducing water ballast into said compartment.

References Cited in the file of this patent UNITED STATES PATENTS 2,126,430 Unger Aug. 9, 1938 2,297,230 Langen Sept. 29, 1942 2,307,343 Whippel Jan. 5, 1946 2,634,223 Clendenin Apr. 7, 1953 2,673,817 Burns Mar. 30, 1954

Claims

10. THE METHOD OF PROTECTING THE INTERIOR METAL COMPARTMENT OF A TANKER SHIP AFTER AN OIL CARGO HAS BEEN DISCHARGED FROM SAID COMPARTMENT AND WHICH COMPARTMENT IS ADAPTED TO CARRY WATER BALLAST ON A RETURN TRIP, WHICH COMPRISES INHIBITING CORROSION OF THE METAL IN SAID COMPARTMENT WHICH WOULD OTHERWISE BE CAUSED BY SAID WATER BALLAST BY FORMING A FOG OF A SOLUTION OF A WATER INSOLUBLE CORROSION INHIBITOR DISSOLVED IN A WATER INSOLUBLE CARRIER, DIRECTING THE FOG INTO THE INTERIOR OF SAID COMPARTMENT BEFORE SAID WATER BALLAST IS ADDED TO THE COMPARTMENT, FILLING SAID COMPARTMENT WITH SAID FOG TO FORM A PROTECTIVE FILM OF SAID CORROSION INHIBITOR ON THE ALL EXPOSED INTERIOR SURFACES OF SAID COMPARTMENT, SAID