Composition And Method For Inhibiting Acid Attack Of Metals

Abstract

A composition comprising a nitrogenous organic compound, a carboxylic acid and a sulfonium salt for use in an acidic aqueous composition for the purpose of inhibiting acid attack on metallic surfaces which are contacted with the acidic composition.

Description

This invention relates to reducing the attack of acid on metals which are contacted with an acidic aqueous composition. More particularly, this invention relates to a composition and its use in an acidic aqueous solution for the purpose of inhibiting or reducing the tendency of acid attack of metallic surfaces which are subjected to the acidic aqueous solution.

There are many applications in which a metallic surface is contacted with an acidic aqueous composition. For example, it is known to utilize acidic aqueous compositions for the purpose of cleaning or pickling metallic surfaces to remove therefrom unwanted oxide scales and other undesirable corrosion products or unwanted deposits. Another example of such an application is the use of metallic conduits to convey acidic compositions.

In such applications, it is known to add inhibitory compositions to the acid composition for the purpose of inhibiting acid attack on the metallic surfaces that are contacted with the acidic composition. The inhibitory composition functions to reduce or prevent the tendency of the acid to corrode or degrade the metallic surface without adversely affecting the desired properties of the acidic composition. Materials which so function generally are referred to as "acid inhibitors."

Examples of acid inhibitors are disclosed in the following U.S. Pat. Nos. 2,758,970; 2,807,585; 2,941,949 and 3,077,454. Acid inhibitors disclosed in the aforementioned patents include nitrogen-containing compounds, triphenyl sulfonium chloride, and acetylenic alcohols. These acid inhibitors are a few examples of the many that are known. Some examples of other known inhibitors are arsenic compounds, thioureas, heterocyclic compounds containing sulfur and nitrogen, such as mercapto benzothiazole, and aldehydes, such as formaldehyde and benzaldehyde.

Although many of the heretofore known acid inhibitors have been used effectively in relatively dilute acidic solutions under relatively mild temperature conditions, their use under relatively high temperature conditions or in relatively concentrated acidic solutions is accompanied by less inhibition of acid attack on the metal than might be desired. An example of an application where such a problem is encountered is in the acidizing of oil wells.

By way of background, it is noted that oil wells are acidized in order to stimulate or increase oil flow into the drill hole. Oil flow may be hindered due to the blockage of pores in the oil-bearing rock by carbonates and other rock components. This tends to prevent rapid seepage of oil to the drill hole from distant parts of the oil field. This problem can be alleviated by pumping an acidic composition into the well. The acid functions to enhance oil flow by cleaning and enlarging the rock pores.

In the acidizing process, the acidic composition, for example hydrochloric acid, is pumped into the hole through metallic tubing which is vulnerable to attack by the acid. Acid inhibitors have been utilized in the acidic composition to reduce the degradation of the metallic tubing by the acid. However, the trend in oil well acidizing is toward the utilization of more concentrated solutions of acid. For example, it is becoming more common to employ a 28 percent or 30 percent solution of hydrochloric acid rather than a 15 percent hydrochloric acid solution as used in the past. Heretofore known acid inhibitors do not protect adequately the metallic tubing when such concentrated acidic solutions are utilized.

Another trend that has intensified the problem is that of drilling oil wells deeper than has been done in the past. The deeper the oil well, the higher the temperature at the hole bottom. Acid attack on the metallic tubing is more severe at higher temperatures. Whereas maximum temperatures of 150.degree. F were encountered in the past, presently it is not unusual for oil wells to be drilled so deeply that temperatures well over 200.degree. F are encountered at the bottom hole.

In view of the above, it is an object of this invention to provide an improved acid inhibitor.

It is another object of this invention to provide acid inhibitors which are effective to inhibit acid attack of metallic surfaces which are exposed to acidic solutions of relatively high concentrations at relatively high temperatures.

It is still another object of this invention to provide an acidic composition comprised of an acid of the type that attacks metals and an improved acid inhibitor which inhibits the tendency of the acid to attack metals which are contacted with the composition.

An additional objective of this invention is to provide an improved process for reducing acid attack on metallic surfaces by acidic compositions which come into contact therewith.

Still another objective of this invention is to provide an improved oil well acidizing process.

In accordance with this invention, it has been found that a composition comprising: (A) nitrogenous organic compound, (B) carboxylic acid, and (C) sulfonium salt can be extremely effective when present in an acidic aqueous composition for inhibiting acid attack of metals which are contacted therewith.

Generally speaking, the acid inhibitor composition of this invention, which can contain optional ingredients and additives, can be used in any application in which it is desired to prevent acid attack of metals. This includes applications wherein an acidic cleaning solution is utilized to clean or rid metallic surfaces of oxide scales and other undesired deposits and corrosion products. It includes also applications wherein an acidic solution, which is utilized to acidize oil wells, comes into contact with a metallic conduit during use.

Each of the aforementioned ingredients, (A), (B), and (C) above, is an essential component of the acid inhibitor of this invention and is described more fully hereinafter. By way of introduction, the carboxylic acid and sulfonium salt components can be any one of these well known classes of compounds and the nitrogenous organic component can be any nitrogen-containing organic compound. In general, the nitrogen-containing component will be one which itself exhibits acid inhibiting properties when present in an acidic solution. Many kinds and types of nitrogen-containing organic compounds exhibit such properties. Many of them have been utilized previously as acid inhibitors and are well known and available commercially. Examples of such compounds, which also are referred to herein as "inhibitor base," include coal tar bases (pyridine and its derivatives) and their quaternary salts, alkyl amines, aryl amines, ethylene oxide condensates of amines, Mannich bases, piperidines, and derivatives of piperidines.

Although higher or lower amounts can be used as will be explained more fully hereinafter, it generally will be expedient to utilize from about 5 to about 85 weight percent of the nitrogenous organic compound, about 5 to about 70 weight percent of the carboxylic acid, and about 0.1 to about 40 weight percent of the sulfonium salt based on the total weight of the inhibitor composition. Speaking generally, the acid inhibitor of this invention should comprise from about 0.05 to about 5 weight percent of the acidic aqueous composition based on the total weight of the composition.

Turning now to a more detailed description of the components comprising the acid inhibitor of this invention, the nitrogenous organic compound can be any of the nitrogen-containing organic compounds. The inhibitor bases can be organic nitrogen bases, such as those derived from coal tar; alkyl and aryl amines, as well as any of their many derivatives including, for example, ethylene oxide condensates of amines and Mannich bases; and cyclic amines such as piperidines and derivatives thereof. By way of example, alkylamines that can be utilized are propylamine, nonylamine, pentadecylamine, eicosylamine, isoamylamine, dihexylamine, dioctadecylamine, and diaminopentane. Other examples of the inhibitor base component are amides, ureas, and thioureas such as acetamide, formamide, urea and 1-phenyl-2-thiourea.

Of the numerous types of inhibitor bases that can be used, the preferred are the long chain alkyl amines, that is those having at least 10 carbon atoms, piperidine derivatives and Mannich bases and derivatives thereof. Mannich bases are particularly preferred, especially those made from rosin amines. The Mannich bases are a class of compounds that can be prepared by the reaction of an amine, a ketone and formaldehyde. Examples of various types of Mannich bases which can be used are defined by the three formulas set forth below: ##SPC1##

wherein R.sup.1 and R.sup.3 each represents hydrogen or a hydrocarbon radical such as, for example, alkyl, alkenyl, aralkyl, aryl and cyclic groups including polycyclic, cycloaklyl and heterocyclic groups; and wherein R.sup.2 represents a hydrocarbon radical such as, for example, alkyl, alkenyl, aralkyl, aryl and cyclic groups including polycylic, heterocyclic and cycloalkyl groups. Examples of these radicals include methyl, isopropyl, octadecyl, dodecyl, decenyl, octenyl, benzyl, phenyl, naphthyl, cyclopentyl, cyclohexyl and thiazolyl.

A preferred class of Mannich bases for use as the nitrogenous organic component in the acid inhibitor composition of this invention is disclosed in U.S. application Ser. No. 699,051, filed Jan. 19, 1968, of Dudlik and Gardner. This class of Mannich bases encompasses amine compounds which have acid inhibition properties. They are prepared by reacting, in the presence of acid, the following ingredients: formaldehyde, a ketone and an amine starting material of the formula

wherein n is an integer ranging from about 2 to about 20; R is selected from the group consisting of hydrogen and CH.sub.3 (CH.sub.2).sub.m.sub.-1 wherein m is an integer ranging from 1 to about 21; and Z is selected from the group consisting of hydrogen and the propylamine radical.

As pointed out in said application, the above reaction is a Mannich type reaction. Generally speaking, it consists of the condensation, in the presence of acid, of an amine with formaldehyde and a ketone having at least one reactive hydrogen atom. Examples of such ketones are: acetone, methylethyl ketone, isobutylmethyl ketone; diacetone alcohol; 2,4-pentanedione; acetonylacetone; phorone; mesityl oxide; cyclopentanone, propiophenone; acetonaphthone; acetophenone; p-methoxyacetophenone; p-cloroacetophenone; 2-heptanone; 2-undecanone; 2-acetylcyclohexanone; butyrophenone; naphthalenone; cyclohexanone; and tetrolophenone.

It is pointed out in said application Ser. No. 699,051 that although the Mannich reaction has been known and investigated for some time, there exists various uncertainties about the reaction which preclude in many cases a correct prediction of the specific amine compound or mixture of amine compounds that will be produced by the reaction. In this connection, it is noted that the mechanism of the Mannich reaction has not been established. A number of theories on the reaction mechanism have been advanced, but no one theory has been agreed upon as being a correct and full explanation of how the various and many kinds of amines and ketones known to react with formaldehyde do react.

Experience in synthesizing amine compounds by a Mannich reaction has shown that it is not unlikely that the reaction product will comprise in some cases a mixture of amine compounds rather than a specific amine.

It has been found that regardless of the particular amine compound or mixture of amine compounds produced by reacting the amine starting material of Formula IV with ketone and formaldehyde as set forth above, the reaction product exhibits excellent acid inhibition properties.

Despite the uncertainties of the specific product that will be produced in a Mannich reaction, it has also been found that by reacting amine starting materials of Formula IV above with formaldehyde and a ketone having at least one reactive hydrogen in the presence of sufficient acid to maintain the pH of the reaction below 7, there can be obtained amine compounds of the general formula

wherein n is an integer ranging from about 2 to about 20; R is selected from the group consisting of hydrogen and CH.sub.3 (CH.sub.2).sub.m.sub.-1 wherein m is an integer ranging from 1 to about 21; and X is selected from the group consisting of ##SPC2##

wherein R.sup.1 and R.sup.2 are each a hydrocarbon radical, and the group ##SPC3##

wherein R.sup.3, R.sup.4 and R.sup.5 are each a hydrocarbon radical.

The amines of Formula V above, as well as their acid salts, exhibit excellent acid inhibition properties in acidic cleaning solution. With respect to the acid salts of the amines, it is noted that because the reaction is carried out in an acidic medium and maintained at a pH below 7, the product produced by the reaction will contain the acid salt of the amines represented by Formula V. As the acid salt has acid inhibition properties, it can be used without further treatment as the nitrogenous organic component in the acid inhibitor composition of this invention. On the other hand, if it is desired, the amine itself can be recovered from the acid salt of the amine.

In preparing the Mannich bases disclosed in said application Ser. No. 699,051, mixtures of ketones may be utilized in the reaction. When a mixture of ketones is utilized, there can be obtained compounds wherein R.sup.1 and R.sup.2 of the formula V (A) above and R.sup.3, R.sup.4 and R.sup.5 of the formula V (B) above are different hydrocarbon radicals.

When a mixture of ketones is utilized, the less or least reactive ketone or ketones should be added to the reaction mixture and allowed to react to some extent with the amine starting material and formaldehyde components prior to the addition to the reaction medium of the ketone having greatest reactivity. This procedure gives the ketones of lesser activity an opportunity to react with the amine and formaldehyde components.

On the other hand, when a single ketone is utilized, R.sup.1 and R.sup.2 of formula V (A) above will be the same hydrocarbon radical and similarly R.sup.3, R.sup.4 and R.sup.5 of the formula V (B) above will be the same hydrocarbon radical.

Preferably, the reaction is carried out using an excess of ketone. On the basis of one mole of amine starting material, there is preferably utilized one mole of ketone for each hydrogen atom attached to a nitrogen atom in the amine starting material, plus an excess of about one to two moles of ketone.

The formaldehyde component utilized in the reaction is preferably added to the reaction mixture in the form of an aqueous solution, such as for example the conventional 37 weight percent aqueous solution of commerce, or in the form of an organic solution, such as the readily available alcoholic solution known as "Formcel."

According to standard techniques, any material that readily breaks down to yield formaldehyde under the conditions of the Mannich reaction can be utilized instead of the aqueous and alcoholic solutions of formaldehyde referred to above. An example of such material as a source of formaldehyde is paraformaldehyde.

For each mole of amine starting material utilized, there is preferably utilized one mole of formaldehyde for each hydrogen atom attached to a nitrogen atom in the amine starting material, plus about 10 to 20 molar percent excess of formaldehyde.

As mentioned above, the reaction must be carried out in the presence of sufficient acid to maintain the pH of the reaction medium below 7. An inorganic or organic acid can be utilized. The preferred acid is hydrochloric acid. Hydrobromic, sulfuric and acetic acids are illustrative of other types of acids that can be utilized.

In a preferred sequence of steps to prepare the amine compounds disclosed in said application Ser. No. 699,051, acid is added to a mixture of the amine starting material (a compound of Formula IV above) and the ketone in amounts sufficient to impart to and maintain the reaction mixture at a pH below 7. Then formaldehyde is added slowly over a period of hours (for example, 2 to 3 hours) to the reaction mixture as it is continuously stirred. It is preferred that the reaction mixture be cooled to prevent overheating during the addition of the acid and the formaldehyde. The mixture can be then refluxed for a period of hours (for example, 20 to 24 hours) to maximize yield. The excess ketone may then be distilled off leaving behind amine product produced by the reaction.

Another preferred class of Mannich bases for use as the nitrogenous organic component in the acid inhibitor composition of this invention are those derived from rosin amines. This class of compounds, as well as their preparation, are disclosed in U.S. Pat. No. 2,758,970 to Saukaitis and Gardner, the disclosure of which is incorporated herein by reference. By way of summary, there is disclosed in said patent compounds of the formula

wherein R is a radical selected from the group consisting of abietyl, hydroabietyl and dehydroabietyl; Y is the group --CH.sub.2 R.sup.1 ; X is a radical selected from the group consisting of hydrogen and --CH.sub.2 R.sup.1 ; and R.sup.1 represents an alpha ketonyl group. When the phrase "Mannich base derived from rosin amine" is used herein, it means a compound of Formula VI above.

As disclosed fully in said U.S. Pat. No. 2,785,970, compounds of Formula VI above are prepared by reacting rosin amines, formaldehyde and ketone in the presence of acid. The term "rosin amine" refers to those primary amines which are made from rosins or rosin amines, and they may be considered as broadly including compounds containing the abietyl, hydroabietyl and dehydroabietyl radicals. In addition, the term includes primary amines derived from rosin and rosin acids, whether or not modified by hydrogenation or dehydrogenation. Examples of ketones which can be used in the preparation of Mannich bases derived from rosin amines are: acetone, methylethyl ketone; diacetone alcohol; 2,4-pentanedione; acetonyl acetone; isophorone, mesityl oxide; cyclopentanone; cyclohexanone; and acetophenone.

Compounds of Formula VI above can be prepared by reacting a rosin amine, ketone and formaldehyde in the presence of an acid, such as for example hydrochloric acid, acetic acid and sulfuric acid. Excess molar quantities of the ketone and formaldehyde should be used and the acid should be present in an amount sufficient to maintain the reaction medium acidic.

Another of the organic nitrogen-containing compounds that can be utilized in the inhibitor composition of this invention is a compound which can be considered a derative of piperidine or a substituted piperidine, such as for example, those represented by the two structural formulas set forth below: ##SPC4##

Wherein r.sup.1 and R.sup.2 each represents a hydrocarbon radical such as, for example, alkyl, alkenyl, aralkyl, aryl and cyclic groups including polycylic, heterocyclic and cycloalkyl groups. Compounds of Formulas VII and VIII above can be prepared by the reaction of an amine hydrochloride, a ketone and formaldehyde.

A preferred class of piperidine derivatives for use as the nitrogeneous organic component in the acid inhibitor of this invention is disclosed in U.S. Pat. No. 2,807,585, the disclosure of which is incorporated herein by reference. The compounds disclosed in this patent have acid inhibiting properties and can be represented by the following structural formula: ##SPC5##

wherein R is alkyl, arylalkyl, cycloalkyl, hydrogen or the group

wherein R.sub.1 is alkyl, aryl or arylaklyl. Examples of "R" are methyl, ethyl, isopropyl, n-propyl, n-butyl, n-hexyl, n-octyl, benzyl, alpha naphthyl methyl, cyclohexyl and cyclopentyl. Examples of R.sub.1 are methyl, ethyl, n-propyl, n-amyl, isobutyl, phenyl, naphthyl, benzyl, and alpha naphthyl methyl.

Generally speaking and as disclosed in the U.S. Pat. No. 2,807,585, compounds defined by Formula IX can be prepared by a reaction of a ketone, formaldehyde, and an amine hydrochloride.

U.S. Pat. No. 2,807,585 discloses also the conversion of compounds represented by Formula IX above to materials which also have acid inhibiting properties. These materials may also be utilized as the nitrogeneous organic component in the composition of this invention. As noted in the patent, the conversion can be accomplished by heating compounds of Formula IX above at temperatures within the range of about 60.degree. C to about 150.degree. C for a period of time varying from about 5 minutes to about 24 hours, or the conversion can be accomplished by treating a compound represented by Formula IX with a solution of alkali which is preferably hot and most preferably boiling.

The acid component of the inhibiting composition of this invention is a carboxylic acid, that is an organic acid containing one or more carboxyl groups (--COOH). The carboxyl group is the functional group of this component and thus the carboxylic acid, in addition to being a mono- or poly-basic acid can be substituted or unsubstituted or it can be saturated or unsaturated. Examples of acids that can be utilized are hexanoic, octanoic, azelaic, isodecanoic, lauric, myristic, 12-hydroxy stearic, oleic, abietic, benzoic, palmitic, phthalic, salicylic, and suberic.

Preferably, the carboxylic acid is a fatty acid and most preferably one which contains more than five carbon atoms. Under relatively mild acidizing conditions, an inhibiting composition which contains a carboxylic acid having six or more carbon atoms performs better than one which contains a carboxylic acid having less than six carbon atoms. Under relatively severe acidizing conditions, it is much preferred to utilize in the inhibiting composition a carboxylic acid that has more than five carbons. In some applications involving relatively severe acidizing conditions, the presence of a carboxylic acid having less than six carbon atoms had an adverse effect on the inhibiting properties of the composition.

Of the numerous carboxylic acids which have been tested and found to be effective, oleic acid has been found to be exceptionally effective. It has given excellent results under a variety of acidizing conditions.

The third essential component of the inhibiting composition of this invention is a sulfonium salt of the formula

wherein R.sup.1, R.sup.2, and R.sup.3 are each hydrocarbon radicals, such as for example, those selected from the group consisting of alkyl, aryl and aralkyl and wherein X is an acid anion, preferably an anion of a strong mineral acid. Formula X above includes within its scope compounds wherein said R.sup.1, R.sup.2 and R.sup.3 radicals are the same radicals or are different radicals.

Formula X above includes also compounds wherein one or more of the said R.sup.1, R.sup.2 and R.sup.3 radicals contain one or more of the same or different substituents, examples of which include hydroxy, halo and alkyl groups.

Examples of the radicals R.sup.1, R.sup.2 and R.sup.3 of Formula X above are propyl, nonyl, dodecyl, isobutyl, phenyl, hydroxy-phenyl, dodecyl phenyl, benzyl and 4-hydroxy-3,5-dimethylphenyl. It is preferred that at least one of the aforesaid R.sup.1, R.sup.2 and R.sup.3 radicals be aryl or aralkyl and most preferably, each of said radicals is aryl, such as for example phenyl or p-chlorophenyl.

Examples of X, the acid anion, in Formula X above, are chloride, bromide, iodide and sulfate, the first mentioned being preferred.

Sulfonium salts and methods for their preparation are known. For example, they can be prepared by the reaction of an aromatic hydrocarbon with a sulfur monohalide in the presence of anhydrous aluminum chloride and a halogen.

The amounts of nitrogenous organic compound, carboxylic acid and sulfonium salt utilized in formulating the acid inhibitor of this invention can vary over a wide range. Although higher or lower amounts can be utilized, acid inhibitors comprising the following amounts of ingredients are recommended:

Approximate amounts- Component % by Weight __________________________________________________________________________ nitrogenous organic compound 5 to 85 carboxylic acid 5 to 70 sulfonium salt 0.1 to 40 __________________________________________________________________________

It is preferred that the nitrogenous organic compound and the carboxylic acid each comprise at least about 10 percent of the composition and that the sulfonium salt comprise at least about 0.5 percent of the composition. It should be appreciated that the acid inhibitor can be used in a variety of applications under a variety of conditions and consequently, it may be found expedient for a particular application to use the above components in amounts outside the above ranges. Suffice it to say that the components should be present in amounts such that upon addition of the acid inhibitor to an acidic solution, the solution will have less of a tendency to corrode or attack metals which come into contact with it.

The foregoing description of the nitrogenous organic compounds, carboxylic acids and sulfonium salts has been concerned with those ingredients which are essential components of the composition of this invention. A composition containing said ingredients is effective as an acid inhibitor. However, it is preferred that additives be combined with the aforementioned essential ingredients in order to increase the overall effectiveness of the inhibiting composition. Such additives include materials which increase acid stability and oil miscibility of the composition. In general, these additives are surface active agents and solvents for the other components comprising the composition. Any surface active agent compatible with the other components of the composition can be used including anionic, cationic and nonionic surface active agents with the last mentioned being preferred. Examples of such additives are nonionic surface active agents, such as ethoxylated secondary alcohols and ethoxylated nonyl phenols and related compounds, such as thiols, and polar solvents such as alcohols, for example the lower alcohols, such as methanol and isopropanol.

In addition to the additives described above, other materials can also be added for the purpose of improving inhibiting and antipitting characteristics. Examples of such additives are acetylenic alcohols and mercapto alkanoic acids, such as for example, tolyl mercapto acetic acid (see U.S. Pat. No. 3,094,490).

Additives, such as those described above, have been used previously with acid inhibitors and the amounts employed in the composition of this invention can be determined readily from past experience. In general, however, the composition of this invention should comprise at least about 80 percent of the three essential ingredients, or, to state it another way, the total amount of additives present in the composition should be no more than about 20%.

In utilizing the composition of this invention to inhibit acid attack on metal, the composition is added to the particular acidic composition utilized in an amount effective to inhibit the attack of the acid on the metal which is exposed to the acid. The amount of inhibiting composition that will be effective to the extent desired will vary depending on a number of conditions. Such conditions include the particular components and amounts comprising the inhibiting composition, the particular acidic composition (including concentration) that is utilized, the type of metal cleaning operation or acidizing operation that is being performed and also the particular metal which is being subjected to said operations. As exemplary of the variety of conditions to which the inhibiting composition of this invention can be exposed or used, it is pointed out that in acidizing an oil well, the acidizing conditions can involve acidizing with an acidic solution containing 15 percent hydrochloric acid by weight at a temperature in the range of about 150.degree. F. or acidizing with an acidic solution containing about 28 to 30 percent by weight of hydrochloric acid at a temperature in the range of about 250.degree. F. Metal cleaning applications can be conducted under much less severe conditions.

In view of the various applications and conditions under which the inhibiting composition of this invention can be used, it will be appreciated that the most effective amount should be determined from experience gained in using the composition in a particular application. For guidance purposes, it is noted that it has been observed that generally good results can be obtained by adding the inhibiting composition to an acidic composition in an amount such that the inhibiting composition comprises from about 0.05 percent to about 5 percent of the total weight of the inhibitor-containing acid composition and preferably from about 0.5 percent to about 2 percent by weight.

If less than about 0.05 percent inhibitor is employed then the desired inhibiting effect, particularly when it is used with the more concentrated acids, is not as apparent. If more than about 5 percent of the inhibiting composition is employed, the inhibiting properties seem to increase very slightly over that observable when the inhibiting composition comprises about 4.5 percent to about 5 percent. Indeed, it has been observed that about 2 percent of the inhibiting composition gives maximum inhibition in any applications.

The inhibitor composition of this invention can be employed in any application where, for example, it is desired to inhibit the attack of an acid on metals, including metal cleaning operations and oil well acidizing. Presently, the most popular acid utilized in oil well acidizing is hydrochloric acid, which is utilized also to a relatively great extent in metal cleaning operations. In addition to being used with hydrochloric acid, the inhibiting composition of this invention can, of course, be utilized with other of the metal cleaning or pickling acids--the so-called nonoxidizing acids. Included in this category are inorganic acids such as phosphoric, sulfamic and sulfuric and organic acids such as acetic, citric, formic, glycolic and oxalic.

Of the various types of metal that can be protected from acid attack by utilizing the acid inhibitor of this invention, particularly effective results have been obtained for iron and steel. However, the acid inhibitor can also be utilized to protect from acid attack other metals such as for example, copper, brass, bronze and other alloys such as stainless steel.

As will become evident from the examples presented hereinafter, the acid inhibiting properties of compositions included within the scope of this invention tend to vary. Some of the inhibiting compositions are much more effective than others. All of the acid inhibitors included within the scope of this invention can be utilized to excellent advantage in applications where acid attack is a problem. Those inhibitors which have the more effective inhibiting properties can be utilized in applications where metallic surfaces are subjected to very severe corrosive environment, such as for example that encountered in acidizing oil wells with a relatively high concentrated solution of hydrochloric acid at relatively high temperatures. The excellent extent of protection afforded by the acid inhibitor under such conditions has heretofore been unattainable.

TEST PROCEDURES AND EXAMPLES

The following examples include illustrations of compositions within the scope of the invention. The examples include also evaluations of the acid inhibiting properties of compositions within the scope of the invention and of other compositions for the purpose of comparison. The outstanding acid inhibiting properties of the composition of this invention are strikingly pointed out in the examples.

In evaluating the acid inhibiting properties of the compositions of the examples, the following test equipment was utilized:

a. an electrically heated oil bath and a thermostat for controlling the temperature of the bath, and

b. a corrosion resistant bomb made from a nickel-molybdenum-iron alloy (Hastelloy B of Haynes-Stellite Co.) containing a removable glass liner.

Unless otherwise indicated, the test procedure for evaluating the acid inhibiting properties of the composition of the examples was as follows:

There was placed into the glass liner of the bomb 100 ml. of either 15 weight percent or 28 weight percent hydrochloric acid solution. To the acid solution, a predetermined amount of a composition of the examples was added by means of a hypodermic syringe with stirring. A descaled, weighed metallic test specimen was then placed in the composition contained in the glass liner. The specimen was descaled previously by immersing it in 1:1 hydrochloric acid for 10 minutes, after which it was withdrawn, rinsed thoroughly with water and then acetone, dried in an oven at 120.degree. F. for 20 minutes and then cooled and weighed. The weight of the metal test specimens used was in the range of 25 to 45 grams and the area thereof was in the range of 3 to 4.5 square inches. The glass liner containing the hydrochloric acid, a composition of the examples and the metallic test specimen was then placed in the bomb. The bomb was closed and then immersed in the heated oil bath. At the end of a predetermined test time, the bomb was removed from the bath, opened, and the metallic test specimen withdrawn. The specimen was cleaned with water and acetone, then dried and weighed. Each specimen subjected to the test lost weight due to the corrosive effects of the hydrochloric acid. The extent to which the compositions of the examples were effective in reducing the weight loss of the specimens is a measure of the acid inhibiting properties of the composition--the lower the loss of weight, the better the inhibiting properties.

Set forth in Table I below are examples of various types of nitrogenous organic compounds or inhibitor bases which can be utilized as a component in the acid inhibitor of this invention. In addition to the nitrogenous organic compound identified in the table, the inhibitor composition contained oleic acid, triphenylsulfonium chloride, and a surface active agent in the following amounts:

nitrogenous organic compound 35% by weight oleic acid 40% by weight (Blend A) triphenyl sulfonium chloride (50% aqueous solution) 10% by weight surface active agent 1 15% by weight

Each of the compositions was evaluated in a 15 weight percent aqueous solution of hydrochloric acid and also a 28 weight percent solution of hydrochloric acid under different conditions. The amount of inhibitor present in the hydrochloric acid solution is expressed in volume per cent in the table and the temperature under which the evaluation was conducted is also set forth therein.

The metal specimens used in the test evaluations conducted at 250.degree. F. were N-80 oil well tubing. The test specimens used in the test evaluation conducted at 150.degree. F. were J&L J-55 tubing.

It is noted that in Example 17, the test composition comprised oleic acid, triphenylsulfonium chloride and a surface active agent but no nitrogenous organic compound, for which there was substituted isopropyl alcohol. This example is set forth for comparative purposes.

In Table I and other tables set forth hereinafter, various components of the acid inhibitor are identified by reference to the formulas set forth hereinabove. It is noted also that in the series of tests reported in Table I, as well as those reported in subsequent tables, the metal test specimens were subjected to the acid composition for either 2 or 6 hours after which its loss of weight was determined. However, the loss of weight reported in the tables is that which theoretically would have been obtained had the specimen been exposed to the acid composition for 24 hours, based on the loss of weight experienced in the actual time it was exposed which time is set forth in the tables. ##SPC6##

With respect to Table I above, it is first noted that Examples 1-10 are illustrative of the use of nitrogenous organic compounds which can be classified as Mannich bases and that those of Examples 11-16 are illustrative of the use of compounds which can be classified as derivatives of piperidine. The extent to which the compositions of Examples 1-16 were effective in inhibiting acid attack on the metallic specimens can be appreciated when it is considered that the same type of metallic specimens used in the test evaluations conducted at 250.degree. F. were almost destroyed when they were subjected at this temperature to 15 percent and 28 percent aqueous solutions of HCl which contained no acid inhibitor. In this same vein, a metallic specimen (N-80 tubing) when subjected to a 15% HCl solution at 150.degree. F, which contained no acid inhibitor loss weight at the rate of 1.91 lbs/sq. ft./24 hrs. A comparison of the test results of Example 17 with those of the other examples shows the important influence the presence of the inhibitor base has on reducing the loss of weight of the metallic specimen.

To further illustrate the variety of types of nitrogenous organic compounds that can be utilized as components in the acid inhibitor, there is set forth in Table 2 below additional examples. The compositions set forth in Table 2 correspond to those of Blend A above, that is the blend utilized in formulating the compositions of Table 1. For convenience, comparative Example 26 is also set forth in Table 2. The composition of this example corresponds to that of Example 17 in Table 1. ##SPC7##

Following the same scheme utilized to illustrate the various types of nitrogenous organic compounds that can be utilized in the acid inhibitor, there is set forth in Table 3 below examples which illustrate various types of carboxylic acids that can be used. The inhibitor composition contained the carboxylic acid identified in the table in the amount set forth below and also:

Carboxylic Acid 40% by weight Triphenyl sulphonium chloride (50% aqueous solution) 10% by weight (Blend B) Mannich base derived from rosin amine 1 35% by weight Tergitol 15-S-40 15% by weight

The metal specimens used in the test evaluations were N-80 oil well tubing. The other test conditions are set forth in the table, as is the amount of acid inhibitor (volume percent) added to the hydrochloric acid solutions. In comparative Example 40, isopropyl alcohol was substituted for the carboxylic acid component. ##SPC8##

As mentioned hereinabove, the preferred carboxylic acid is one which contains more than five carbon atoms. The test results reported in Table 3 above show that the acid inhibitors containing carboxylic acids having six or more carbon atoms (Examples 30-39) were much more effective in protecting the metallic specimens from acid attack than those acid inhibitors which contained carboxylic acids having less than five carbon atoms (Examples 27-29). However, it is noted that the acid inhibitors of Examples 27-29 were more effective than the inhibitor of Examples 40 (which contained no carboxylic acid) in the test evaluation in which 15% HCl was used. The acid inhibitors of Examples 30-39 containing the preferred acid components were for the most part extremely effective in both test evaluations.

Set forth in Table 4 below are examples which illustrate various types of sulfonium salts that can be utilized in the acid inhibitor of this invention. The inhibitor composition contained the sulfonium salt identified in the table in the amount set forth below and also:

Sulfonium salt 20% by weight Mannich base of Blend B above 36% by weight (Blend C) Oleic acid 36% by weight Tergitol 15-S-40 8% by weight

The metallic specimens used in the test evaluation were N-80 oil well tubing. The other test conditions are set forth in the table as is the amount of acid inhibitor (volume percent) that was added to the hydrochloric acid solutions. In comparative Example 48, isopropyl alcohol was substituted for the sulfonium salt component. ##SPC9##

The Examples set forth in Table 4 illustrate the advantages of utilizing as the sulfonium salt component one which contains aryl or aralkyl groups (Examples 42-45) over those salts which contain all alkyl groups. A preferred sulfonium salt is triphenyl sulfonium chloride, the effectiveness of which is shown strikingly in the reported test results.

As mentioned hereinabove, the components comprising the acid inhibitor can be used in a wide range of amounts. The examples set forth in Tables 5 and 6 below are illustrative of this. The metallic test specimens used in the test evaluations reported in the tables were N-80 oil well tubing. The other test conditions are set forth in the tables, as is the amount of acid inhibitor (volume percent) that was used in the hydrochloric acid solution. Examples 49 and 58 of Table 5 and Examples 59 and 68 of Table 6 are set forth for comparative purposes. ##SPC10## ##SPC11##

The examples set forth in Table 7 below compare the properties of an inhibiting composition within the scope of this invention with those of compositions comprised of one or two of the essential components of the composition of this invention. The metallic specimens used in the test evaluations were API-N-80 tubing. The other test conditions are set forth in the table as is the amount of acid inhibitor (volume percent) present in the hydrochloric acid solution. ##SPC12##

As mentioned previously, other materials may be added to the inhibiting composition to improve its overall effectiveness. The examples which follow are illustrative of compositions within the scope of this invention which contain one or more additives, including solvent, antipitting ingredients, and other acid inhibitors which can be added to the inhibiting composition of this invention. The nitrogenous organic compound in each of the examples is referred to as "Mannich base." It is the Mannich base identified in Blend B above.

% by weight Example 73 Tolyl mercapto acetic acid 5.0 Tergitol 15-S-40 10.0 Mannich Base 35.0 Oleic acid 40.0 Triphenyl sulfonium chloride (50% aqueous solution) 10.0 Example 74 Tergitol 15-S-40 10.0 Mannich base 40.0 Mixture of oleic and linoleic acids (Pamak Number1--Hercules) 40.0 Triphenyl sulfonium chloride (50% aqueous solution) 10.0 Example 75 Tolyl mercapto acetic acid 5.0 Tergitol 15-S-40 10.0 Mannich base 35.0 Mixture of oleic and linoleic acids 40.0 (Pamak Number 1--Hercules) Triphenyl sulfonium chloride (50% aqueous solution) 10.0 Example 76 Tolyl mercapto acetic acid 6.7 Tergitol 15-S-40 6.7 Mannich base 26.6 Acetylenic alcohol OW-1 (OW-1, Air Reduction Co.) 5.0 Oleic acid 50.0 Triphenyl sulfonium chloride (50% aqueous solution) 5.0 Example 77 Tolyl mercapto acetic acid 6.7 Tergitol 15-S-40 6.7 Mannich base 26.6 Oleic acid 50.0 Acetylenic alcohol (AP-1, Air Reduction Co.) 5.0 Triphenyl sulfonium chloride (50% aqueous solution) 5.0 Example 78 Tergitol 15-S-40 6.7 Isopropanol 10.0 Acetylenic alcohol (OW-1, Air Reduction Co.) 5.0 Mannich base 33.3 Oleic acid 40.0 Triphenyl sulfonium chloride (50% aqueous solution) 5.0

Claims

1. An acid inhibiting composition for use in an acidic aqueous composition of the kind which tends to attack metallic surfaces which are contacted therewith consisting essentially of in weight percent:

A. about 5 percent to about 85 percent of a nitrogenous organic compound which itself exhibits acid inhibiting properties when present in said acidic aqueous composition, said compound selected from the class consisting of: (1) mixtures of pyridine and alkyl derivatives thereof; (2) alkyl amines; (3) piperidine; (4) a Mannich base prepared by the Mannich reaction, in the presence of acid, of formaldehyde with a ketone having at least 1 reactive hydrogen and an amine starting material of the formula

wherein n is an integer ranging from 2 to about 20; R is selected from the group consisting of hydrogen and CH.sub.3 (CH.sub.2).sub.m.sub.-1 wherein m is an integer ranging from 1 to about 21; and Z is selected from the group consisting of hydrogen and the propylamine radical, said acid being present in an amount sufficient to maintain the pH of the reaction below 7, and wherein for each mole of said amine starting material there is utilized at least 1 mole of formaldehyde and 1 mole of ketone for each hydrogen atom attached to a nitrogen atom in the amine starting material; and (5) a rosin amine derivative of the formula:

wherein R is a radical selected from the group consisting of abietyl, hydroabietyl and dehydroabietyl; Y is --CH.sub.2 R.sup.1 ; X is selected from the group consisting of hydrogen and --CH.sub.2 R.sup.1 ; and R.sup.1 represents an alpha ketonyl group;

B. about 5 percent to about 70 percent of a carboxylic acid having at least six carbon atoms and selected from the group consisting of fatty acids and saturated dicarboxylic acids; and

C. about 0.1 percent to about 40 percent of sulfonium salt having the formula

wherein R.sup.1, R.sup.2, and R.sup.3 are hydrocarbon radicals selected from the group consisting of alkyl having one to 12 carbon atoms, aryl and aralkyl, wherein at least one of said R.sup.1, R.sup.2, and R.sup.3 is

2. A composition according to claim 1 wherein said carboxylic acid is a

3. A composition according to claim 1 wherein said carboxylic acid is a

4. A composition according to claim 3 wherein said fatty acid is oleic

5. A composition according to claim 1 wherein in said sulfonium salt each

7. A composition according to claim 1 wherein said sulfonium salt is

8. A composition according to claim 1 including also another acid

9. A composition consisting essentially of water, an acid of the type that tends to attack metallic surfaces and, in an amount at least sufficient to reduce said acid attack of said metallic surface, the acid inhibiting composition of claim 1. and wherein said acid which tends to attack said metallic surfaces is different from said fatty acid and said saturated

10. A composition according to claim 9 wherein said acid inhibiting composition comprises about 0.05 weight percent to about 5 weight percent

11. A composition according to claim 10 wherein said acid inhibiting composition comprises about 0.5 weight percent to about 2 weight percent

12. A method for inhibiting acid attack of metallic surfaces comprising contacting a metallic surface with an acidic aqueous composition consisting essentially of an acid of the type that tends to attack metals which are contacted therewith and, in acid inhibiting amounts, the acid inhibiting composition of claim 2, wherein said acid which tends to attack said metals is different from said fatty acid and said saturated

13. A method according to claim 12 wherein the nitrogenous organic compound

14. A method according to claim 12 wherein the carboxylic acid of said acid

15. A method according to claim 12 wherein each of said R.sup.1, R.sup.2, and R.sup.3 in the sulfonium salt of said acid inhibiting composition is

16. An acid inhibiting composition for use in an acidic aqueous composition of the kind which tends to attack metallic surfaces which are contacted therewith consisting essentially of in weight percent:

A. about 10 percent to about 85 percent of a nitrogenous organic compound which itself exhibits acid inhibiting properties when present in said type of acidic aqueous composition, said compound selected from the class consisting of: (1) a long chain alkyl amine having at least 10 carbon atoms; (2) a Mannich base prepared by the Mannich reaction, in the presence of acid, of formaldehyde with a ketone having at least 1 reactive hydrogen and an amine starting material of the formula

wherein n is an integer ranging from 2 to about 20; R is selected from the group consisting of hydrogen and CH.sub.3 (CH.sub.2).sub.m.sub.-1 wherein m is an integer ranging from 1 to about 21; and Z is selected from the group consisting of hydrogen and the propylamine radical, said acid being present in an amount sufficient to maintain the pH of the reaction below 7, and wherein for each mole of said amine starting material there is utilized at least 1 mole of formaldehyde and 1 mole of ketone for each hydrogen atom attached to a nitrogen atom in the amine starting material; and (3) a rosin amine derivative of the formula:

wherein R is a radical selected from the group consisting of abietyl, hydroabietyl and dehydroabietyl; Y is --CH.sub.2 R.sup.1 ; X is selected from the group consisting of hydrogen and --CH.sub.2 R.sup.1 ; and R.sup.1 represents an alpha ketonyl group;

B. about 10 percent to about 70 percent of a fatty acid having at least six carbon atoms; and

C. about 0.5 percent to about 40 percent of a sulfonium salt having the formula

wherein R.sup.1, R.sup.2, and R.sup.3 are hydrocarbon radicals selected from the group consisting of alkyl having 1 to 12 carbon atoms, aryl and aralkyl, wherein at least one of said R.sup.1, R.sup.2, and R.sup.3 is

17. A composition according to claim 16 wherein said fatty acid is oleic

18. A composition according to claim 16 wherein said nitrogenous organic

19. A composition according to claim 16 wherein said sulfonium salt has

20. A composition according to claim 19 wherein said sulfonium salt is

21. A composition according to claim 16 including also an antipitting

22. A composition according to claim 16 including also a nonionic surface active agent selected from the group consisting of ethoxylated secondary

23. A composition according to claim 16 wherein said nitrogenous organic

24. A composition according to claim 16 wherein said nitrogenous organic

25. In the process wherein acid attack on a metallic surface by an acidic aqueous composition is reduced by incorporating in the composition an acid inhibitor, the improvement comprising utilizing as the acid inhibitor the acid inhibiting composition of claim 23, wherein said acid which tends to attack said metallic surface is different from said fatty acid and said

26. A process according to claim 25 wherein said acid comprises

27. A process according to claim 25 wherein said metallic surface is a pipe utilized to convey said acidic aqueous composition in the acidizing of an

28. In the process wherein acid attack on a metallic surface by an acidic aqueous composition is reduced by incorporating in the composition an acid inhibitor, the improvement comprising utilizing as the acid inhibitor the acid inhibiting composition of claim 16, wherein said acid which tends to attack said metallic surface is different from said fatty acid of said

29. A process according to claim 28 wherein said acid comprises

30. A process according to claim 29 wherein said metallic surface is a pipe utilized to convey said acidic aqueous composition in the acidizing of an oil well.