US2840525A - Method of inhibiting corrosion of metal surfaces - Google Patents

Description

METHOD OF HNHIBITING CORROSION F METAL SURFACES Loyd W. Jones, Tulsa, fikla assignor to Pan American Petroleum Corporatiom'a corporation of Delaware No Drawing. Original application October 1, 1953, Se-

rial No. 383,689. Divided and this application August 2, 1956, Serial No. 609,334

7 Claims. (Cl. 2528.55)

This invention relates to inhibiting corrosion. More particularly it relates to inhibitors for most types of corrosion occurring in oil wells and associated equiprnent or combinations of the various types of corrosion discussed herein. The corrosion inhibitors also act as demulsifiers and parafiin removing agents. They may also be employed to clear water-blocked formations.

This application is a division of U. S. patent application Serial Number 383,689, filed October 1, 1953, which is a continuation-impart of my copending application U. S.

Serial Number 288,705 filed May 19, 1952, now U. S.

I amines are preferred. The acid portion is carboxylic in nature and contains at least or 6 carbon atoms. Preferably this portion is obtained from the liquid phase partial oxidation of normally liquid petroleum fractions. Other acids such as lauric or oleic are also satisfactory.

These salts are unique in that they inhibit corrosion by hydrogen sulfide, carbon dioxide, light organic acids, oxygen or combinations of these materials. They are also unique in that at least certain of the salts avoid the usual emulsion and gel problems encountered when salts of fatty acids are added to oil. Some of' the salts also prevent paraflin deposition on metallic surfaces. These salts may be employed in the form of oil solutions for systems in which the liquid is predominantly oil. For systems in which the liquid is predominantly water the inhibitor should be used in a water dispersible form. In the case of water having a low salt content, most of the non-ionic water-soluble emulsifiers of either the ester or ether type are suitable dispersing agents. If the water contains considerable salt, then a special class of non-ionic water-soluble dispersing agent should be em ployed. This class of dispersing agent is more particularly described and claimed in my copending application U. S. Serial Number 335,161 filed February 4, 1953. In general, this class of dispersing agent has the formula RXW, wherein R is an aliphatic hydrocarbon radical containing at least 12 carbon atoms, X is an ether type linkage selected from the group consisting of oxygen and sulfur and W is a water-soluble portion selected from the group consisting of polyglycols and polyglycerols containing at least 4 ether linkages.

If it is desired to introduce inhibitors through the tubing in a well, or to provide a slowly dispersible form in any application, they may be produced in stick form by use of oil-soluble waxes such as parafiin or of watersoluble binders such as gelatin, as more fully described and claimed in the copending application U. S. Serial Number 283,345 filed on May 16, 1952, by Jack P. Barrett, now abandoned.

The salts are employed in concentrations or" about 20 to 50 parts per million of corrosive liquids in mildly corrosive systems consisting predominantly of oil. As

2,840,525. Patented June 24, 19 58 corrosive liquids consisting predominantly of oil. If the corrosive liquid is predominantly water the concentration may vary from 10 to 20 parts per million in moden ately corrosive systems up to about 200 parts per milhon in highly corrosive systems. As little as 10 parts per million gives appreciable protection in both oil and water systems. The inhibitor may be applied continuously or intermittently. If applied intermittently the concentration should be calculated on the basis of the entire volume of corrosive liquids to which the metal surface will be exposed before the next treatment. 7

While the salts disclosed in U. S. Patent 2,756,211 constitute a considerable improvement over prior art inhibitors, they are still susceptible to improvement in certain respects. For example, while the use of oxidized petroleum acids to form thesalt gives a product which usually avoids emulsion formation between water and oil, in many areas positive demulsifying action is also desired. While prevention of paraflin deposition has been noted, a more positive para-flin-removing action would be desirable in many locations. Also, while amine salts of the oxidized petroleum acids taught in the parent application have been found to possess only limited gel forming ability in oil, the. concentration of the inhibitor which can be added to oil for purposes of storage in a convenient liquid form is limited by the high pour-point of the oil solutions. Some pour points are as high as around 40 F., making their use in colder areas difiicult. A salt With a decreased gel forming tendency and, conse quently, reduced pour point wouldtherefore be desirable.

also obviously be desirable even though the disclosed amine salts are highly superior compared to inhibitors previously taught in the prior art'.

With the above problems in mind, an object of the present invention is to provide an improved corrosion inhibitor for the typesof corrosion encountered in oil wells, and combinations of the various types. Amore particular object is to provide a corrosion inhibitor which does not cause emulsions between oil and water. A still more particular object is to provide a corrosion inhibitor which also possesses positive demulsifying ability. An additional object is to provide a corrosion inhibitorwhich also acts not only to prevent paraflin depositionbut removes paraflin which has already been deposited on metal surfaces. A further object of the invention is to provide a corrosioninhibitor with decreased tendency to gel hydrocarbons sothat high concentrations of inhibitors in oil can be handled without encountering excessively high pour points. A still further object is to provide a corrosion inhibitor which may also be used to remove water blocks from formations.

In general, I accomplish the objects of my invention I In this formula R" is an aliphatic hydrocarbon radical containing from about 16 to 18 carbon atoms. Alox 425 is a trademark of the Alex Corporation for a mixture of acids derived from normally liquid hydrocarbons by liquid phase partial oxidation. This salt has several unique properties such as, for example: i

( 1) His highly solublein oil. i v

(2) Oil solutions of the salt have low pour points.

An improved corrosion inhibiting ability would (3} It' reduces the interfacial tension between oil and Water to nearly zero dynes per centimeter.

(4) It tends to remove water from many water-blocked formations.

, ('5) It does not act as an emulsifier of oil and water.

(6): It has apositive demulsifying action on emulsions of'water and oil.

(7) It is a highly effective corrosion inhibitor even compared to other amine salts.

(,8) It prevents deposition of parafiin from oil onto metallic surfaces, and there is evidence indicating that it exerts a positive paraffin-removing action on parafiin already deposited.

All these properties are attributable to the strongly polar nature of portions of both the amine and the acid. Since both the. amine and the acid have strongly polar. portions, the salt also is highly polar. Being. highly polar, the salt is not readily solvated by oil. Therefore, it has less tendencyto form gels in oils than less polar materials which are more highly solvated by'theoils- This. decreased gelforming tendency in turn presumably accounts for the increased oil solubility. It also apparently accounts for the lower pour point'of oil solutions. That is, it is necessary to cool oil solutions of thesalt to lower temperatures before ellan'on of the solution becomessufiicient to prevent. pouring.

Having a more polar portion than most salts, particularthose ofthe amines, the salt of. Duomeen-T and Alex "'35 is more surface active. This. accounts for the ability decrease the interfacial tension. between oil and water. direct application of this property is the removal of ater from water-block formations ofoilwells. When the salt, preferably in oil solution, is injected into such formations the inter-facial forces between. water and oil are reduced to such extent that they are insufiicient to hold the connate water against the force of the oil flowing through the formation to the well. Therefore, the water flows from the formation and the water block is removed. The demulsifying action is also undoubtedly related to the increased surface activity of the salt due to its highly polar portion.

A combination demulsifying action. between standard demulsifiers, such as various organic sulfonates, and the amine-acid salts has been noted. This is probably due to. the reduction. of. interfacial. tension between the water and oil phases by the salt, combined with the action of the standarddemul'sifier to counteract the etfects of emulsion stabilizers. such as. electric charges and. the like.

The highlypolar salt is probably adsorbed. on metallic surfaces to some. extent. It is much more likely, as pointed out in the parent application referred to above, that the amine-and. acid portions of theloosely-bound salt are separately adsorbed on different portions of the surface. The proposed amine and acid,,being more highly polar, become more strongly attached to the metallic surfaces to be protected than the less polar materials. The increased corrosion-inhibiting ability is due partly to this fact and. partlyto the decreased emulsion-forming tendency. The probable reason why emulsions decrease the corrosion-inhibiting abilities of most amine salts is that these salts, being surface. active, tend to become concentrated at the large. interfacial. surface between the liquids rather than. on the metal surface. When emulsion formation is decreased, more of the inhibitor becomes available for deposition onthe metal surfaces to be protected. The reduced interfacial tension between oil and water also probably facilitates displacement of'wat'er from the metal surface by a protective oil film.

The strongly-adsorbedhighly-polaramine and acid have been found to produce; an excellent lubricating'film which greatly reduces wear. 'In: one. pumping well, use of the salt has already extended'by'a factor of 5: or 6 the average period between pumping rod-pulling jobs. thecorrosion problems were minor, but perhaps just sufficient to roughen the rubbing surfaces slightly and accel- In the Well, I

4 1' erate wear. The reduced wear might also be due to the simple lubricating actions of the strongly adsorbed films on both rubbing surfaces.

The paraffin-removing ability of the salt may be due to several factors. One of these is an increased parafinsolubilizing power of the polyamine salt compared to salts of monoamines. The solubilizing power of the salts has been demonstrated in connection with the Alox 425 acids. These acids are not completely soluble in oil. The

il-insoluble materials are probably hydroxy acids. Whatever the nature of the materials, however, they are apparently drawn into oil solutions by a solubilizing action of the amine salt. It has been observed that the polyamines are more effective in solubilizing these oil-insoluhis constituents of Alox 425 acids. Therefore, they are undoubtedly also more effective in solubilizing materials such as parafiin. Another factor which may account for increased paratfin-removing ability is the presence of. alcohols, ketones,.esters and the like in Alox 425 acids. These materials are-fair parafiin solvents. Since twice as much acid. is required to neutralize Duomeen-T as. is required. to neutralize octadecyl amine, for example, more of the alcohols, ketones and esters which accompany the Alox 425 acids are present whenthe polyamine salt is. employed. These solvents probably contribute in some degree to the improved parafiin-removing ability of the polyamine salts of Alex 425 acids.

The principal explanation of the paraffinremoving ability probably lies inthe reduced interfacial tension between oil and water, and the consequent demulsifying action. It has been noted many times that the parafiin deposited in a well is generally associatedwith considerable quantities of water. Where little: water is present, paraffin deposition is' rarely a problem. Apparently it is an emulsion of paraflin and water which deposits. The amine-acid salt, by breakingthis' emulsion, causes its removal from wells where it is deposited.

When the term salt is employed with reference to a process, the term means either the: preferred. reaction product or the product formed in situ by use ofthe amine and acid separately. While the neutral salt is generally preferred, as much as twice the stoichiometric amount of either the amine or acid may be present and most of the advantages will still be retained.

The acids used in forming the salts of my invention are those produced by the process described. in U. S. Patents 1,690,768 and 1,690,769 issued to Burwell. The hydrocarbon feed to the oxidation process for producing the acids should be a. petroleum fraction which is normally liquid. Kerosene is the preferred raw material. This class of hydrocarbons is preferred since it produces acids in the desired molecular weight range containing from about 5' to about 20 carbon atoms per molecule; Hydrocarbons of a parafiinic nature are preferred as feed stock tothe oxidation processsince they produce aliphatic acids having straight chains which align themselves to give closely-packed protective films.

In general, it is preferred to oxidize the'hydrocarbo'n to such an extent that two phases separate. The lower phase has. a higher content of acids which are superior for purposes of my invention, probably because of the presence of hydroxyl groups whichmake these acids much more polar in nature. Due to their higher polarity they are less oil-soluble and less susceptible to removal by oil from surfaces on which they have been deposited. Furthermore, their salts with polyamines are more polar, and hence more'surface active and less strongly solvated by Although the highly oxidized acids are preferred, thosei produced by a light oxidation of a normally liquid petroleum: fraction produce unique non-emulsifying salts with p'olyamines. Salts of these lightly-oxidized acids also possess some of the same powers of reducing interfacial tension and removing paraffin possessed by salts of the highly oxidized acids, but to a lesser degree.

The preferred polyamine is Duomeen-T. Other satisfactory polyamines from Armour and Company are DuomeenS and Duomeen-C. In Duomeen-T the longhydrocarbon chain is derived from tallow acids and, hence, most of these chains are saturated. In Duomeen-S, on the other hand, most of the hydrocarbon chains are unsaturated since they are derived from soy bean oil acids. With DuomeenC, the acids are derived from coconut oil and constitute a mixture of saturated and unsaturated acids. Most of the hydrocarbon chains in Duomeen-T and Duomeen-S contain from 16 to 18 carbon atoms. Since coconut oil is made up of acids having a wide range of molecular weights, the resulting amines have a correspondingly varied range of chain lengths, for example from about 8 to 18 carbon atoms. As indicated in U. S. Patent 2,756,211, a hydrocarbon radical of at least carbon atoms should be present. Such radicals insure the formation of a film of suflicient thickness on the metal to resist penetration even by combinations of corrosive materials such as oxygen and hydrogen sulfide. The straight chain aliphatic hydrocarbon radicals are very much preferred to insure closer packing of the molecules forming the film. However, other hydrocarbon radicals having at least about 10 carbon atoms are also effective to a smaller degree.

The polar portion of the amine should contain at least two amino groups separated by from 2 to 4 carbon atoms. This portion may be heterocyclic in nature but preferably should be aliphatic since the salts of the non-cyclic aliphatic polyamines have surprisingly superior corrosion inhibiting abilities compared to salts of the. cyclic polyamines.

So far as I have been able to determine, the aliphatic polyamines preferred in my invention may best be represented by the formula:

hydrogen atom and Y is a radicalselected from the groupconsisting of H and R. The Duomeens are members of this class, having the simplified formula: 1

RNHRNH The preferred amine is Duomeen-T having the formula: RNH(CH NH As previously noted, R" in this formula is an aliphatic hydrocarbon radical containing from about 16 to 18 carbon atoms.

The principal application of the disclosed salts is as inhibitors for corrosion by oxygen, hydrogen sulfide, carbon dioxide, carboxylic acids containing from 2 to 4 carbon atoms per molecule, or combinations of these individual corrosive materials. One or more of these materials, or combinations thereof, occur in various types of oil wells. In treating such wells it is recommended that at least about 5 parts of the corrosion inhibitor be added per million parts of Well liquids, including both water and oil. This concentration should beused whether the inhibitor is added in slugs, for example once a day or so, or is added continuously. Preferably, a preliminary period of treatment at higher concentrations up to 50 times the suggested steady rate should be employed for a week or so at the beginning of the treatment. If the oil Well produces predominantly oil, an oil solution of the inhibitor should be added. If the well produces more than about 50 percent water, then a water-dispersible form of the inhibitor may be added. Such a form is 'described more fully and claimed in my copending application U. S. Serial Number 335,161, previously noted. Although a treatment of 5 parts per million produces apare required for systems consisting predominantly of oil than for systems whichare substantially oil-free. The

concentrations for preventing wear should be the same as those for inhibiting corrosion since the problem in both cases is to establish a protective film.

If wells have been treated, auxiliary field equipment such as flow lines, separators and the liquid space of tanks will also be protected by the inhibitor in the oil from the wells. If at least some wells have not been treated, then introduction of inhibitor into the auxiliary equipment in the previously-suggested concentrations and forms may be advisable.

Animportant application of my invention is in preventing corrosion of metal parts in water-flooding or wa tar-disposal systems. In such systems the inhibitor should be maintained in all parts of the system intermittently or continuously, preferably in a water-dispersible form.

For protecting metal surfaces exposed to corrosive vapors such as the inside of casing and outside of tubing near the tops of wells, the vapor space of tanks or gas pipe lines, the inhibitor may be applied by brush or spray, preferably as an oil solution. The inhibitor may be applied more effectively, as Well as more simply, by introducing it into the vapors in the form of a fog. For such applications it is suggested that the inhibitor, in a solution containing about 50 percent by weight each of the inhibitor and an oil such as kerosene, be sprayed into the vapor space in an amount equal to about 1 gallon of solution per thousand square feet of metal surface to be protected. The film which is formed in this manner can then be maintained by injecting smaller amounts of from /6 to the volume of the original treatment at intervals of from about one week to one month, depending upon the severity of corrosion and erosion by flowing gases. 7

Another field application of the inhibitor is in drilling fluids to inhibit oxygen corrosion of drilling equipment, particularly the drill pipe. Concentrations of inhibitors should be approximately the same as for oil well treatments. Since the drilling fluid is recycled continuously, addition of inhibitor is necessary only to make up for the amount lost into the formations or on bit cuttings r separated from the drilling fluid. A similar application tested with considerable success was concerned with prevention of corrosion of the ballast tanks on submersible drilling barges. This also suggests the application to any marine vessel into 'which air-containing water is occasionally introduced.

Excellent slushing compounds can be prepared by adding the inhibitor to the greases or gels normally employed for this purpose.

The inhibitor may also be employed in refinery operations, particularly those which handle sour oils. Refinery corrosion generally occurs in equipment such as fractionating columns, strippers, heat exchangers, and condensers where liquid Wateris present together with cor- I rosive agents such as oxygen, hydrogen sulfide, carbon If the inhibitor is to be introduced into columns such as fractionators or strippers, it should be injected above the highest point at which liquid water occurs. The inhibitor, being non-volatile, will then run down the column, protecting the portions exposed to the corrosive agents in the presence of Water.

7 If the inhibitor is to be employed to prevent corrosion of exchangers, condensers or the like, it is simply injected into the inlet to the equipment-preferably in 'oil solution if the system is predominantly oil, and in a waterdispersible form if the system is predominantly aqueous. If the inlet material is a vapor, spraying of the inhibitor into the stream asa fog is the preferred method of injection. As in other applications, introduction of the inpreciable protection which is, in many cases, quite adhibitor may be either continuous or intermittent.

The concentration of inhibitor employed at the beginning of treatment of refinery equipment-should be from" about 50 to 260 parts perrnillion by weight'of' liquid and vapors treated. After a prclimiharytreatment at= these-concentrations, to establish inhibiting films,- the concentration can usually be reduced over a period of" time toa value as low-as about 5 parts-per'million, or even lower in exceptional cases; It willbe' understood that-whenreference is-made to'refineries, the'termis' employed broadly to include all petroleum processing equipment such as natural gasoline plants, sulfur removing installations or dehydrating apparatus.

If theamine-acid salt is employed" as a demul'sifier, it should preferably be introduced into the we'llproducing" the emulsion. In this way it can act'on'thewater and oil at the bottom of the well, thus-preventing formation of the emulsion. t' the same-time, the amine-acid salt acts'to'prevent corrosion and paraffin. deposition; It" is possible, however, to add the, salt to. the' emulsion after it is formed by injecting it into flow lines, separators, 2f tanksor the like; The amount of salt'usedas adernulsifier depends on the severity of" emulsion. in such" case.

In general, however, it is suggested that concentrations in the range of 2 to 4-or 5 times those suggested for inhibiting corrosion should be" employeda;

The amine-acicl' salt may be used to remove paraifin from two locations in a well; One locationisthe' inside wall of the tubing through which' the oil flows to" the surface. The other is the pore. space of formations as kerosene since the cost'i's much less' and the eifectiveness is substantially the same:

My invention-will be better understood from consideratiorr of the following" examples:

I EXAMPLE. I

Todetermi'ne the elfectiveness as a corrosion inhibitorof the proposed salt of Duomeen-T and A'l'ox 425" acids,

comparcd -to-sal'ts of-other aminesand acids, thefollow-- Into l liter glass-bottles, 800

insertion ihto-tlie rubber stoppers employed to close thestream of corrosive gases-wasbub'bled continuousl'y tl'lwllgll the liquids in the bottles at a rate of bottles.

about 2- cubic foot per hour, while thetemperaturewvas maintained? at 100F. The corrosive gases consisted of 2 percent. hydrogensulfide and 98 percent air. The

bottles were shaken vigorously tor -15 consecutive minutes- At the end of 7 days, the panels" were"- every two hours. dipped in dilute inhibited hydrochloric acid solution,

rubbed liglitlyto remove adhering scale; rinsed in distilled water; dried and weighed. Theresults are-presented in- Tabl'e-Ii Table! Weight Loss; 7 Cone. of Grams Percent Amine.- Acid; Salt; 7 aligning}; Remarks- .m. p p Control Inhibited . Y S11 ht rnul ion, uniform )rotco- 2 1g em on e-- 0.7550 0.0431: 2 ing. Duomeen-T do 300 99.5. Noemulsion, uniform protection.

. 0. 8181 0. 0078- 00 10o 3 99.0 Do.

0. 109 j Do Olejc 100 0.6607 Q0877 92.1 Thick emulsion, panels ctchtd.

through which oil flows to the Well. For removing parafiin from inside tubing, the salt may be added in the same ways as suggested for inhibiting, corrosion. It has been foundhlat the concentrations. oflsalt suggested for inhibiting corrosion are suitable for removing parafi'ih where parahin problems are not too serious. Higher concentrations, in the range of 2 to 4 or 5 times as great, are suggested for more serious cases of'parafiin deposition. in tubing,

For removing parafiin from pore spaces, a solution, preferably in a petroleum fractionsuch as kerosene, containing from about 0.001 to about 1.0 percent or more of the amine-acid salt should be pumped into the formation and then be allowed tofibw back out. A volume of solution sufficient to fill, the pore volume out to a distance of at least about 4 or 5' feet sliouldQbe injected. The treating cycle may be repeated one or. more times with either fresh or previously-used. solution. Parafiin solvents such as carbon tetrachloride,.carbon disulfide, benzene or the like may be employed as. a. solvent for the salt, but since petroleum fractions are so. effective, use of the more expensive solvents is rarely justified.

When a water blockis to be removed from, a formation, the procedure, concentrations and volumes should be substantially the same as when paraflinisremoved from the pore space. The solvent for the salt may be a Water solvent such as ethanol, acetone or thelike. In generaL. however, I prefer to employ a petroleum. fractionsuch;

ArmeemI-L'I is. a. trademark of Armour and Company for a mixture of about 70' percent octadecyl amine and about 30 percent hexadecyl' amine. Duomeen-T and Alox. 425. have been. previously identified chemically.

The greatly decreased emulsifyingtendcncy of. the Alex. 425 acid salts is to be noted. The salt of Alex 425. acids with Duomeen-T is. particularly outstanding in thatv it caused noemulsionat all, even. athigher. concentrations. This. particular. salt is. also outstanding in that its: inhibiting, power at. 100 p. p.111. is. superior. to 300 p.. p. mof the salt of. monoamines such as Armeen-HT.

EXAMPLE II.

To. compare the efiectiveness of Alox 425 salts of' aliphatic polyaminesto saltsof cyclic polyamines, static bottle tests were. conducted as follows:

One-liter Florence. flasks were flushed free of. air. by streams. of. nitrogen. Into. each flask approximately 1 liter. oflair-free. 5. percentv sodiumchloride brine containing, known amounts of hydrogen. sulfide was introduced. Thecorrosioninhihitor. to be tested'was then introduced; dissolvedin. 501mlof. kerosene. Atared polishedImildT steel. test. panel, 1; inchby 1 inchby ,5 inch, was then loweredinto. each.flask,, supported. by a glass hook which. was. in. turnhelchhy the. rubber. stopper. used. to. seal. the flask. Eachpanelwasheld infthe oil layer 5 seconds. at the;start1ofl the test and. then exposed to the brine phase fortheremainder. of. the. 7-day test.. Resultsare. reported inTIlable-IL Table II Weight Loss, Salt H s Grams Percent Amine 00110., Cone, Inhibi- Remarks p. p. m. p. p m. tion, Av

Control Inhibited - 0267 0.0007 Uniform protection. Dmmeen-T 0 0343 I 0.0007 No emulsion.

0 0263 0 0018 3 7 {Slighdt ilieteial agtaek H d lImida oline 200 600 0.0266 9 an p ng. ome 2 6pm ecy z 0 0280 0016 emulsion. 2Heptsdecyll-Hydroxyethyllm- 200 600 88322 Q0019 94.1 Do.

idazoline. 0 0280 M012 Although the concentration of the Duomeen-T salt of Alox 425 acids was only one-half those of the corresponding salts of the cyclic imidazoline derivatives, the degree of protection was superior. It will also be noted that the protection was uniform, whereas the salts of the cyclic amines permitted some local attack. The tendency of the cyclic amine salts to form slight emulsions at 200 p. p. m. concentration should be compared to the absence of emulsifying tendency of 300 p. p. m. of the Duomeen-T salt noted in Example I. It is apparent that while the cyclic polyamine salts of Alex 425 acids are very good inhibitors, the aliphatic polyamine salts of the same acids are even better in several respects.

EXAMPLE III To determine the effectiveness of the Duomeen-T salt of Alox 425 acids as an inhibitor'for'corrosion due to low molecular weight carboxylic acids and carbon dioxide, the following test was made:

About 1100 ml. of an aqueous 5 percent sodium chloride brine soiutionwas placed in each of several 2-liter round-bottomed flasks together with about 900 ml. of kerosene. A reflux condenser was placed over each flask and the systems were freed of air by boiling the water while bubbling a stream of oxygen-free carbon dioxide through the liquids for a period of 2 hours. The rate of carbon dioxide introduction was about 1 cubic foot per hour. To the air-free liquids, 500 milligrams of glacial acetic acid were added (about 500 p. p. m. by weight based on the water phase). Then 100 milligrams of the salt of Duomeen-T and Alox 425 acids were added to each of two of the flasks. None of the amine-acid salt was added to another flask used as a control. A polished, tared, mild steel panel was then suspended in the water phase in each flask on a glass rod passing through a seal in the flask. A reflux condenser was placed on the flask and the flask heater adjusted to hold the temperature just at the boiling point of water. For consecutive seconds out of each minute the panel was raised into the oil phase. After 24 hours, the panels were cleaned, dried and weighed as described in Example I. The control panel lost 0.1500 gram. One of the panels in the flasks containing inhibitor lost 0.0082 gram; the other lost 0.0020 gram. Thus, the average inhibition was 96.6 percent complete.

EXAMPLE IV The effectiveness of the Duomeen-T salt of Alex 425 acids was tested as an inhibitor of corrosion of surface equipment of a brine-disposal system in the East Texas,

substituted for the first set and injection of the amineacid inhibitor was started. The inhibitor was added as a kerosene solution containing 4- pounds of salt per gallon of solution. It was injected continuously into' the pump suction through a small controlvalve. Attempted rates of injection were as follows:

First 3 days-1 quart of solution per120 barrelsbrine. Next 2 weeks1 quart of solution per 240 barrels brine. Remainder of 32-day test1 quart of solution per 300 barrels brine.

These concentrations should have varied from about 22 p. p. m. by weight down to about 9 p. p. m. However, totreat the 81,000 barrels of brine according to this schedule should have required about gallons of the solution. Actually, only 68 gallons were injected because of d'ficulty in adjusting the control valve. Therefore, the concentrations were somewhat smaller than those suggested, the average being only about 8.5 p. p. m.

After 32 days, the second set of test nipples was re- Nipples 1 and 2 contained sulfide scale and were pitted. Nipples 10 and 20 were cleanof sulfide scale and were not pitted. It will be apparent that the air-sulfide corrosion, which cannot be prevented by most inhibitors now on the market, was effectively inhibited by the proposed amine-acid salt. Examination. of the nipples indicated most of the inhibitor was deposited near the pump, only traces of the oily material being carried through the line to the nipple near the Well. Much more effective inhibition near the well would undoubtedly have been obtained by use of the water-dispersible form described and claimed in my copending application U. S. Serial Number 335,161.

EXAMPLE V Pour points of oil solutions of amine-acid salts were de- 23 mols of ethylene oxide per molecule of lauryl alcohol,

about 0.4 pound of methyl alcohol and about 0.15 pound of water. The pour points are indicated inTable IV iii Table IV Concen- Form of Inhibitor Salt Constituents tration, ASTMPour lbs/gal. Point, F; SOIution Oil Solution Armeen HT and 4 45.-

A102: 425. Do Duomeen-T and 4 -155. Alex 425. Do "do 3 Below --20. Water Dispersiblc 'Armeen HT and 4 40.

102: 425. Do Duomeen-T and 4 15.

The melting point of Armeen HT averages about 135 F. That of Duomeen-T is about 105 F. The lower melting point of the Duorneen-Tundoubtedly accounts in part for some of the decrease in pour point of solutions of its salts. However; a decrease of about 30 F. in themelting point of one constituent of the salt in the solution could hardly be expected to produce a drop inpour point of 60 F. in straight oil solutions and 25F. in the complex \a ater-dispersible composition. The pour pointreduction is particularly important in northern areas where the temperature frequently remains at or below about F. for considerable lengths of time. In such areas more dilute solutions of the-water-dispersible form should be employed. The pour point of this form can also be reduced further by increasing the alcohol content'of' the preparation.

EXAMPLE VI The ability of the salt to break emulsions and prevent. their formation was recently demonstrated in-connection, with a Well in the Chocolate Bayou field of Texas. The operator was using the salt of Armeen HT and Alox'42-5. acids as an inhibitor. The salt was added as a kerosene solution containing about 4 pounds of salt per gallon of solution. This inhibitor solution was added at a rate of about 2 quarts per day. The well production averaged about 6 to 10million cubic feet of gas per day, together with about 50 to 100 barrels, of condensate and about 1 to 2 barrelsof Water. Corrosion control was good, as indicated by a low iron content of the water. However, the amount of inhibitor employed caused the formation of a slight emulsion. When this emulsion was treated in the laboratory with about 200 to 400 parts per million of the Duomeen-T salt of Alex 425 acids, the emulsion broke immediately, thus demonstrating the ability of this particular salt to break even those emulsions caused by other amine salts. On the basis of this observation, the. Ducmeen-T salt of Alex 425 was employed in subsequent treatment of the Well. No further emulsion troubles have been noted, thus demonstrating the emulsion-preventing ability of this salt.

EXAMPLE VII The water-block removing ability of an oil solution. of the salt of Duomeen-T and Alex 425 acids was determined in the laboratory by use of a core of Springer sand obtained from a well in the Velma field of Oklahoma. The core was drilled with oil, shipped in oil and stored in oil until used in the test. The core tested was drilled from the large core received, using oil as a lubricant during the drilling. The resulting test core was a cylinder having a circular cross-section of 2.78 square centimeters and a length of 2.71 centimeters. This core was mounted in a rubber stopper through which a hole had been. bored slightly smaller than the core. The stopper was; in turn, mounted in a tapered Lucite holder to which inlet and outlet connections were made. Various liquids were forced through the core under a differential pressure of approximately one atmosphere and at a room temperature of about 75 to 80 F. Permeability values were obtained by measuring the volume of liquid flowing out of the core over a short period of time, such as a minute or two, and calculating the permeability which would account for this rate of flow. In every case Where brine wasforced through the core, the brine was one prepared by dissolving in fresh waten96 O0 p. p. m. by Weight of sodium chloride, 9.,000- p.- p; m. calcium chloride and 3,990 p. p. m. magnesium chloride. The hydrocarbon employed. for flushing and as a solvent for interfaciah tensionsreducing agents was a narrow-boiling petroleum raction containing hydrocarbons predominantly in the range having from to. 12 carbon atoms. permoleculei The procedure and results were as follows:

l) The permeability. of thecore. to flow. of; thopetme leum fraction was firstdetermined to be 185 millid'arcibs:

(2) One liter of the brine wasforced' through the core: The permeability of the core to the flow of brine at the end of this operationiwas. 1.6/Lmillidarcies.

('3) The petroleum fraction was again. introduced and after. 6.16 ml. had been forced through the core, the, per.- meability to the. flow of, the hydrocarbon was only 52 millidarcies, showing the core tobewater-blocked- (4) A solution of a polyoxyethylene sorbitol tetraoleate obtained from. the Atlas Powder Company under the trademark G2854 was then. forced through thecore. to

remove. the water; block. This material is known. to re duce the interfacialtension between water and oil. A- solution; of 015- percent by. Weight iuthe petroleum fraction. wasemployed. After 173 ml. oil thesolution had been forced through the core, the permeability tofiow of the solution was found to be 179 millidarcies.

(5) The pure petroleum iractionwas next pumped through the core to determine if the improved permeability was. permanent. This flushing operation was-continued. until the; interfacial tension betweenwater and the effiuent; hydrocarbon returned to its normal value. The permeability to fiow of the petroleum fraction atthibiilno was. 15.3. millidarcies. l

(6) The blockingand cleaning steps were repeated; us-

mg a second; Atlas interfacialtension reducer with ap-- proximately the same results.

(7) The core was again water-blocked lay-introducing the brine. Permeability to the flow of the petroleum-trac tion. after the blocking operation was 52.4 millidarcies- (8) A. solution containing 0130 1 percent of the Duoineen-T salt of Alox '425 acids in-t-he petroleum fractron was thenforced through the core.

was 53.7 millidarcies;

(9) The concentration: of the saltwas increased to- Introduction: of 194 1121. of this solution Volume Through, m1. Permeability,

hilllidarcles (12) Upon flushing the; core with the. pure petroleum fraction, the permeability increased. to 189:.5'mil1idarcies instead. of decreasing, as had been. characteristic offiiishr ing after treatment with the Atlas compounds.

(13) The interfacial tension between the brine and the prctroleum fraction containing various concentrations of the amine-acid salt. were determined. The, results are presented in Table V.

After96 ml. had beennntroduced, the permeability to fibw -ofitliesolution It will be apparent that the amine-acid salt is somewhat more efiective than the non-ionic material for removing water block from formations. The reason for the greater eliect is probably a stronger tendency to be adsorbed on the sand grains, resulting in a greater ability to displace the water. Obviously, the concentration of the amine-acid salt in oil used for removing water blocks should be about 0.05 percent or more since a sharp increase in permeability occurred when the concentration was increased to this value from the 0.01 percent previously used.

From consideration of the above description and exam ples, it will be apparent that I have accomplished the objeots of my invention. A considerably superior corro sion inhibitor has been provided in that lower concentrations produce the same or greater uniformity and degree of inhibition produced by higher concentrations of other inhibitors. In addition, the inhibitor exerts a positive demulsifying action, as well as avoiding the emulsion problems often caused by other inhibitors. The gelforming tendency of the inhibitor is so low that high concentrations in oil can be handled without danger of solidifying in cold weather. The material also acts to prevent paraflin deposition and to remove parafiin which has already been deposited. The ability of the salt to remove water blocks has also been demonstrated.

I claim: 7

1. A method of inhibiting corrosion of metal surfaces by fluids containing water and a member of the group of corrosive materials consisting of oxygen, hydrogen sulfide, carbon dioxide, carboxylic acids containing from 2 to 4 carbon atoms per molecule, and combinations of these individual corrosive materials, comprising adding to said fluids at least about 5 parts per million by weight of a polyamine salt of a carboxylic acid, said acid being derived by liquid phase partial oxidation of a normallyliquid petroleum fraction, and said polyamine having the formula RNHR'NH wherein R is a hydrocarbon radical 14 containing at least about carbon atoms, N is a nitrogen atom, H is a hydrogen atom, and R is a hydrocarbon radical containing from 2 to 4 cerbonatoms.

2. The method of claim 1 in which said polyamine has the formula R"NH(CH NH wherein, R" is an aliphatic hydrocarbon radical containing from 16 to 18 carbon atoms.

3. The method of claim 2 in which said acid is derived by liquid phase partial oxidation of kerosene.

4. A method for inhibiting corrosion of ferrous metals by fluids containing water and hydrogen sulfide comprising adding to said fluids at least about 5 parts per million by weight of a polyamine salt of a carboxylic acid, said acid being derived by liquid phase partial oxidation of a normally-liquid petroleum fraction, and said polyamine having the formula RNHR'NH wherein R is a hydrocarbon radical containing at least about 10 carbon atoms, N is a nitrogen atom, H is a hydrogen atom, and R is a hydrocarbon radical containing from 2 to 4 carbon atoms.

5. The method of claim 4 in which said polyamine has the formula R"NH(CH NH wherein R" is an aliphatic hydrocarbon radical containing from 16 to 18 carbon atoms.

6. The method of claim 5 in which said acid is derived by liquid phase partial oxidation of kerosene.

7. A method of inhibiting corrosion of metal surfaces by fluids containing water and a member of the group of corrosive materials consisting of oxygen, hydrogen sulfide,

carbon dioxide, carboxylic acids containing from 2 to 4 carbon atoms per molecule, and combinations of these individual corrosive materials, comprising adding to said fluids at least about 5 parts per million 'by Weight of a polyamine salt of a carboxylic acid, said acid being derived by liquid phase partial oxidation of a normallyliquid petroleum fraction, and said polyamine having the formula RNHRNH- wherein R is an aliphatic hydro carbon radical containing at least about 10 carbon atoms, N is a nitrogen atom, H is a hydrogen atom, and R is a hydrocarbon radical containing from 2 to '4 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS 2,587,546 Matuszak Feb. 26, 1952 2,675,355 Lytle Apr. 13, 1954 2,723,233 Lytle Nov. 8, 1 955 2,736,658 Pfohl Feb. 28, 1956 2,756,211 Jones July 24, 1956

Claims (1)

1. A METHOD OF INHIBITING CORROSION OF METAL SURFACES BY FLUIDS CONTAINING WATER AND A MEMBER OF THE GROUP OF CORROSIVE MATERIALS CONSISTING OF OXYGEN, HYDROGEN SULFIDE, CARBON DIOXIDE, CARBOXYLIC ACID CONTAINING FROM 2 TO 4 CARBON ATOMS PER MOLECULE, AND COMBINATIONS OF THESE INDIVIDUAL CORROSIVE MATERIALS, COMPRISING ADDING TO SAID FLUIDS AT LEAST ABOUT 5 PARTS PER MILLION BY WEIGHT OF A POLYAMINE SALT OF A CARBOXYLIC ACID, SAID ACID BEING DERIVED BY LIQUID PHASE PARTIAL OXIDATION OF A NORMALLYLIQUID PETROLEUM FRACTION, AND SAID POLYAMINE HAVING THE FORMULA RNHR''NH2, WHEREIN R IS A HYDROCARBON RADICAL CONTAINING AT LEAST ABOUT 10 CARBON ATOMS, N IS A NITROGEN ATOM, H IS A HYDROGEN ATOM, AND R'' IS A HYDROCARBON RADICAL CONTAINING FROM 2 TO 4 CARBON ATOMS.