US3647690A - Corrosion-inhibiting compositions - Google Patents

Abstract

THIS INVENTION CONCERNS OIL-SOLUBLE CORROSION INHIBITING COMPOSITIONS COMPRISING AT LEAST ONE ANTI-CORROSIVE METAL SALT OF NAPHTHENIC OR AROMATIC TYPE ACIDS COMBINED WITH AT LEAST ONE OIL-SOLUBLE SURFACTANT HAVING AN HLB VALUE BETWEEN 1 AND 6. THESE COMPOSITIONS HAVE SUBSTANTIALLY GREATER CORROSION-INHIBITION PROPERTIES THAN DO THE ANTICORROSIVE SALTS THEMSELVES.

Description

United States Patent 3,647,690 CORROSION-INHIBITING COMPOSITIONS Edward A. Cross, Beaumont, Tex., assignor to Texaco Inc., New York, N.Y.

N0 Drawing. Filed Mar. 25, 1969, Ser. No. 810,345 Int. Cl. Cltlm 5/22 US. Cl. 252-333 5 Claims ABSTRACT OF THE DISCLOSURE This invention concerns oil-soluble corrosion inhibiting compositions comprising at least one anti-corrosive metal salt of naphthenic or aromatic type acids combined with at least one oil-soluble surfactant having an HLB value between 1 and 6. These compositions have substantially greater corrosion-inhibition properties than do the anticorrosive salts themselves.

This invention concerns corrosion-inhibiting compositions and their formulation in petroleum products.

More particularly, this invention relates to combinations of oil-soluble metal salts of naphthenic or aromatic type acids and oil-soluble surfactants which impart substantially improved corrosion inhibition to petroleum products than do the salts or surfactants used singly.

Metallic surfaces, particularly those containing ferrous metals require protection against corrosion. Not only does corrosion have an adverse effect on the appearance and performance of metal surfaces but it reduces the operational life of the metal and necessitates expensive and unplanned repair or replacement. In addition, as in the case of automotive parts and many types of industrial machinery, vibration can cause the finely divided metal oxides to fall off and lodge themselves between moving parts where they can function as abrasives. Further, inasmuch as automobiles and industrial mechanisms are frequently exposed to moisture and acidic products, it is well established to add corrosion inhibitors to lubricating formulations including greases and oils.

Corrosion inhibitors may be of the oil-soluble or watersoluble type. The water-soluble type is generally preferred for the protection of metal under static conditions whereas the oil-soluble inhibitors are utilized more frequently for moving parts such as bearings where the grease film is continually sheared and displaced.

Among the more Widely used anti-corrosives employed in lubricating oils and greases are the oil-soluble metal salts of naphthenic and aromatic acids. Not only do these salts readily dissolve in the oleoginous lubricating stock, but they are relatively stable even at both relatively elevated and depressed temperatures. In addition these metal salts are widely available in commercial quantities. Unfortunately, some metal salts of naphthenic or aromatic type acids such as the alkaline earth metal sulfonates and heavy metal naphthenates are not highly elfective when used alone even at relatively high concentrations. There is, therefore, a definite need for enhancing the effectiveness of the rust and corrosion inhibiting properties of these salts by the use of small quantities of additives.

Recently, during the course of exploratory work on increasing the effectiveness of the metal salts of naphthenic and aromatic type acids, it was unexpectedly found that the addition of small quantities of certain oil-soluble surfactants to the metal salts of naphthenic or aromatic acid type inhibitors greatly enhances their efiicacy as corrosion inhibitors and in some cases improves the water resistance of the grease or oil without any adverse effects. This is particularly true in greases of the lithium soap type. While the mechanism of how this enhancement takes place is not fully understood at this time and no mechanism or "ice,

theory is relied upon for patentability, perhaps the following facts may be useful.

While the structure of the useful surfactants vary, all show in common a low hydrophile-lipophile balance (HLB). HLB is the relatively simultaneous attraction that the surfactant demonstrates for water and oil. Substances having a low HLB, from 0 to 12, are lipophilic and consequently poorly hydrophilic. Thus the surfactants that enhance the corrosion inhibiting properties of the metal salts of the aromatic type acids, are strongly lipophilic and have little or no dispersability in water. The HLB values of these surfactants can be calculated according to methods disclosed in various publications of the technical literature. See for example, Becher, Paul Emulsions: Theory and Practice, A.C.S. Monograph No. 162, p. 231, Reinhold Publishing Corporation, NY. (1965). However, for the purpose of classifying the useful group of surfactants which potentiate the aforementioned classes of corrosion inhibitors, the following simplified classification system, based upon visual observation of the dispersibility of the surfactant in water is employed.

Appearance: Visual 1 HLB value No dispcrsibility in Water 1-4 Poor dispersion 3-6 Milky dispersion 6-8 Stable milky dispersion 10-13 Clear solution 13+ 1 Based upon shaking about one part by weight of surfactant in ten parts by Weight of water for a period of five minutes.

Using the above visual scale, the favored surfactants have an HLB value between 1 and 6, particularly when incorporated into lithium soap greases.

To recapitulate, it is an object of this invention among others to enhance the effectiveness of metal salts of naphthenic or aromatic acids as corrosion inhibitors in lubricating oils and greases.

It is a more specific object of this invention to provide novel lithium soap greases formulations with improved corrosion-resistance properties.

Another object of this invention is to improve the Water resistance of greases treated with the above described corrosion inhibitors without adversely affecting their other properties.

Other objects will suggest themselves to those skilled in the art after a further reading of this application.

In practice, the above objects are achieved by incorporating into the grease or lubricating oil to be protected, a corrosion inhibiting amount of a composition comprising:

1) At least one oil-soluble metal salt of naphthenic or aromatic type acid selected from the group consisting of alkali metal salts, alkaline earth metal salts, heavy metal salts and their mixtures, and

(2) At least one oil-soluble surfactant having an HLB value between about 1 and 6, then blending until a homogenous mixture is obtained.

In the preferred practice each parts by weight of the lubricating oil base to be protected, containing 3 to 25 parts by weight of the lithium salt of fatty acid or acids as the thickener, is admixed with from about 2 to 5 parts by weight of a corrosion inhibiting composition comprising the following components in the indicated proportions:

1) From two to ten parts by weight of at least one oil soluble metal salt selected from the group consisting of lead naphthenate and alkaline earth metal dialkyl naphthalene sulfonates, and

(2) One part by weight of at least one oil-soluble surfactant having an HLB value between 1 and 6, then the admixture is heated with stirring to about 200-230 F. for 15 minutes to 60 minutes or more, and milled to the desired consistency.

In order to more clearly disclose the inventive concept, the following additional information is submitted:

(A) Oil-soluble metal salt of naphthenic or aromatic type acids-This term as used throughout this application includes the oil-soluble, alkali metal, alkaline earth metal and heavy metal salts of substituted cyclic or monoand diaromatic rings containing at least one acid group such as -COH or -\SO H. Illustrative oil-soluble metal salts of the above type include the lead, antimony, sodium, barium and calcium salts, among others. Specific compounds include lead naphthenate, antimony naphthenate, sodium dinonyl naphthalene sulfonate, barium dinonyl naphthalene sulfonate, calcium octadecyl benzene sulfonate and calcium dinonyl naphthalene sulfonate, among others.

(B) Oil-soluble surfactant having a low HLB-These are oil-soluble surfactants derived from aliphatic mono and dibasic fatty acids and their derivatives and alkylated phenols, as well as their alkoxylated derivatives, having an HLB value from about 1 to 6. The favored surfactants are selected from the group consisting of fatty acid esters of sorbitol, ethoxylated alkylated phenols, ethoxylated fatty acids, ethoxylated fatty amines, including diamines and monoamines, and ethoxylated fatty amides, having the required HLB value, wherein the fatty moiety contains from 6 to 22 carbon atoms.

The preferred surfactants are the nonyl phenols ethoxylated with 2 moles of ethylene oxide, and the esters of oleic acid and sorbitol. Two preferred surfactants and their HLB values appear below.

Surfactant: Approximate HLB values Sorbitol monooleate 4.5 Nonyl phenol polyoxyalkylated with 2 moles ethylene oxide (C) Ratio of metal salt to surfactant and what constitutes a corrosion-inhibiting amount.The oil-soluble metal salt component of the corrosion-inhibiting composition must be present in excess compared to the oil-soluble surfactant. A weight ratio of 2:1 to :1 represents the practical range of metal salt to surfactant, with 4:1 to 6:1 representing the range where the most significant increase in anti-corrosive inhibition is obtained. For this reason the latter, more narrow range (4:1 to 6:1) represents the preferred weight ratio of the two components in the inventive composition.

In order to impart satisfactory corrosion inhibition to the greases and other petroleum products treated with the inventive compositions, it is not only necessary to maintain the required ratio of the two components specified supra, but in addition a certain minimal concentration of the anti-corrosive composition must be present. For some less stringent purposes, it has been found that as little as 1:5% by weight of anti-corrosive based on the total lubricant composition, represents a corrosion inhibiting amount as measured by the procedure of ASTM D-1743. However, to assure reproducible results, a concentration of at least 2% by weight of corrosion-inhibiting composition (based on the weight of the lubricant composition) is required. The upper concentration limit is a variable determined primarily by cost and the diluent effect that larger quantities of surfactant agents will have upon the physical properties of the lubricant. For most purposes this has been found to be about a 5% by weight concentration and the preferred concentration range therefore is between about 2% to about 5% by weight of the two component composition in the prescribed weight ratios.

(D) Lubricating oil base.The lubricating oils to be employed as the major component of the corrosion-inhibited greases include any of the hydrophobic oils of lubricating viscosity derived from synthetic or natural (petroleum) sources or their mixtures. The former include the aliphatic diesters such as bis-Z-ethylhexyl sebacate, bisdinonyl adipate, alkyl mixed pentaerythritol esters, alkyl silicates, polyoxyalkylene monomers and their copolymers, alkyl silicanes, alkyl and aryl phosphates such as trioctyl .4 phosphate, tributyl phosphate, tricresyl phosphate and the like.

The mineral or synthetic lubricating oils to be employed range upward in viscosity from about 50 SSU at F. The viscosity index of the oil can vary from below 0 to about 100 or higher and any mineral oil may be highly refined and/ or solvent treated.

The soaps utilized as the principal thickening or gelling agent for the greases comprise the soaps of aliphatic hydroxy fatty acids ordinarily having between about 10 and 30 carbon atoms, branched chain or straight chain. The preferred acids have between about 12 and 24 carbon atoms per molecule. These are typified by the acids derived by the saponification of the hydrogenated castor oil acids principally 12-hydroxystearic acid. The glycerides, lower alkyl (methyl, ethyl) esters may be employed in the saponification procedures. The soaps may be preformed but generally it is convenient to form them in situ. The metallic portion of the soaps may be monovalent (alkali metal), divalent (alkaline earth metal) or polyvalent metal (lead or aluminum, etc.). The alkali metal soaps are preferred, particularly the lithium soap of 12-hydroxystearic acid, referred to herein as lithium soap.

Ordinarily the metal soap is used in gelling amounts between 3-25 by weight of the base oil with 5-15 being a preferred amount.

(E) Test procedure for evaluating corrosion inhibitors.-The test procedure used throughout this application this application to evaluate the corrosion inhibition properties of the inventive compositions in ASTM Designaton: D-1743-64 entitled Rust Preventive Properties of Lubricating Greases. The test is run twice, the duplicate run being designated as check. In this procedure three clean new bearings are lubricated with the lubricant system to be evaluated, then run under a light thrust load for 60 seconds so as to distribute the lubricant in a pattern that might be found in service. The bearings are then subsequetnly stored for two weeks at 77 F. and 100 percent reltaive humidity. After cleaning, the bearings are examined for evidence of corrosion and rated as follows according to the degree of corrosion found. A hearing showing no corrosion is rated 1. Incipient corrosion no more than three spots of a size to be visible to the naked eye is rated 2. Anything more severe is rated 3 and considered as a failure. If the ratings on two or three of the three bearings agree, this number is reported for the sam ple. If all three ratings are different, the test is repeated. For the purposes of this invention, to be considered passing, both the original and rerun (check) tests must give passing results.

In order to present the invention in the greatest possible detail, the following illustrative examples showing the preparation of corrosion-inhibited grease compositions and summarizing the results obtained in corrosion inhibition test are submitted.

EXAMPLE 1 Preparation of a corrosion-inhibited lithium grease A grease kettle equipped with heating, cooling and stirring means is charged with 2225 parts by weight of a base grease containing 133.5 parts by weight of lithium -12-hydroxy stearate blended with 2091.5 parts by Weight of a base oil having the following properties: API Gravity 24.4; Viscosity SUS at 100 F. and 84 SUS at 310 F.; Flash 450 F.; and Pour +20 F. To this base grease is added 45.4 parts by weight of a previously blended (210 F.) corrosion inhibitor composition comprising 45.4 parts by weight of a composition comprising 85.7 parts by weight of commercial lead naphthenate and 14.3 parts by weight of sorbitan monooleate. (This represents a weight ratio of metal salt to surfactant of about 6:1). The grease containing the corrosion inhibitor composition is heated with stirring to 210220 F., is stirred at this temperature for 30 minutes, then milled using a colloid mill to grease consistency.

EXAMPLE 2-13 v pared using the procedure, order of addition, reaction Preparation and evaluation of other greases I temperatures, base oil, lithium soap and surfactant (sorbitol monooleate) of Example 1. The only difference is that in the P P P Order Of t q reaction the lead naphthenate component is replaced on a weightconditlons described 111 Example 1, corrosion-resistant and by.weight basis with the f ll i salts;

control greases are prepared using different combinations of lead naphthenate and barium dinonyl naphthalene sul- Barium dinonyl naphthalene sulfonate fonate and different oil-soluble surfactants in weight ratios sodufm dmonyl naphthalene Sulfonate of approximately 6: 1. The results of evaluation of these Calcmm Octadecyl benzene Sulfonate greases and that of Example 1 are presented in Table I which follows. All parts are by weight.

In all these instances, satisfactory corrosion inhibition is obtained when evaluated according to the procedure of ASTM D-l743-64.

TABLE I Example Number 1 2 3 4 5 6 7 8 9 10 11 12 Batch Number. 1014 1034 1063 1047 Composition, parts by Weight:

Lithium soap grease 100. 98. 0 98. 0 98. 0 98. 0

Lead naphthenate 2. O 1. 7

Barium dinonyl naphthalene sulfonate. 2. 0

Sorbitol monooleate polyoxyethylated th 6 moles ethylene oxide Sorbitol monooleate polyoxyethylated with 20 moles ethylene oxide Nonyl phenol polyoxyethylated with 2 moles ethylene oxide Nonyl phenol polyoxyethylated with 6 moles ethylene oxide Nonyl phenol polyoxyethylated with 30 moles ethylene oxide 0, 3 Approximate HLB value 4 4 5 5 11 17 4 5 10 Rust test (ASTM D-1743-64 Overall rating Fall Fall Fall Fail Pass Pass Pass Fail Fail Pass Fail Fail Individual bearing ratings 3,3,3 ,3,3 3,3, 3,3,3 1, ,1 1,3,1 1,1,1 3,3,1 3,3,1 1,3,1 3,3,3 2,3,3 Check rust test (D-1743-64):

Overall rating Fall P858 Fall Fail Pass Fall Pass Pass Pass Pass Pass Fail Individual bearing ratings 3,3,3 1,2,1 3,1,3 1,1,1 1,1,1 1,3,1 1,1,1 1,1,2 3,1,3 Water absorption, percent 50 20 25 25 20 50 80 Penetration, original. 274 258 246 258 256 2&8 254 256 254 Emubion 300 67 267 276 274 267 300 319 343 As can be seen from the data summarized in Table I, As the specification, including the numerous examples, greases containing only the lithium base grease (Example 35 indicates, this invention offers several advantages com- 1) or the grease plus the lead naphthenate salt (Example pared to the prior art, for example, by utilizing the novel 2) or the grease plus barium dinonyl naphthalene sulformulations of this invention it is possible to increase fonate (Example 3) or the grease plus only the oil-soluble the corrosion inhibition of greases and lubricants protected surfactants (Example 4) fail to give adequate corrosion by the metal salt contained in the formulation. In addition, control. In contrast, Examples 5, 7 and 10, which utilize the oil-soluble, low HLB surfactants are low in cost and both an anti-corrosive agent and an oil-soluble surfactant function at low concentration levels. Two unexpected to protect the lithium base grease, give satisfactory proaspects of the subject invention are (1) the gain in the tection against corrosion when the HLB value is between water resistance of greases protected by both barium 1 and 6. Note that none of the grease compositions comdinonyl naphthalene sulfonate and surfactant compared bining an anti-corrosive agent with an oil-soluble surto those protected by this metal salt alone, and (2) the factant having an HLB value above 6 provide the recorrosion resistance of greases protected by both comquired passing results in both the original test and the ponents of the corrosion-inhibiting system is substantially check or rerun tests and therefore cannot be considered increased compared to the corrosion resistance of greases containing only one of the two components.

As the numerous examples demonstrate, various modifications, changes and substitutions in materials, reaction conditions and sequence of addition can be made without departing from the inventive concept. The metes and as satisfactory anti-corrosive greases.

EXAMPLES 13-17 Preparation of different weight ratios of metal salt to surfactant boun of thi inv ntio ar b st determ' aim 'Usmg the order of addmon reactlon conwhicl l follow reail in onimit'on 'th il 2 i i ii zition drtlons, base oil (lithlum soap), metal salt and surfactant 0 l C J 1 W1 pe described in Example 1, corrosion-inhibited greases are What 15 1S1 prepared utilizing the same metal salt (lead naphthenate) A lubrlfiatlflg composltloll C tmg Of a and oil-soluble surfactant (sorbitan monooleate) but com- 1ubnat1ng 011 thlckened t0 coflslstem'fiy bined in diflEerent weight ratios. The formulations are Wlth hthlum lz-hydfoxysteafflte d containing synergistic corrosion-inhibiting proportions of:

T bl 11. shown below m a e (a) one member selected from the group consisting of TABLE II lead naphthenate, barium dinonyl naphthalene sul- Example Number 13 14 15 16 17 fonate sodium dinonyl naphthalene sulfonate, and Lithium soap grease 97.2 97.5 97.6 97.75 97.8 calcium octadecyl benzene sulfonate and ffiilti iftlifiiiai: 5:3 3:2 3:2 3'22 313 one member h ving an HLB value between 1 and 6 selected from the group consisting of sorbitan In all instances, the above formulations gave satismonooleate and nonyl phenol ethoxylated with two factory corrosion-inhibiting properties when tested under moles of ethylene oxide.

conditions specified in ASTM D-1743-64. 2. The grease of claim 1 wherein (a) is lead naphthen- X a I I ate. E PLE 18 3. The grease of claim 1 wherein (a) is barium dinonyl Preparation of other corrosion-inhibiting greases naphthalene sulfonata utlhzmg metal salts 4. The grease of claim 1 wherein (a) is sodium dinonyl In this example, corrosion-inhibiting greases are prenaphthalene sulfonate.

5. The grease of claim 1 wherein (a) is calcium octadecyl benzene sulfonate.

References Cited UNITED OTHER REFERENCES Polar-Type Riist Inhibitors by' Baker ef'all in Industrial and Engineering Chemistry, vol. 40, No. 12,

pp. 2338-2346. STATES PATENTS Fraser 252*36 5 DANIEL E. WYMAN, Primary Examiner Moore I. VAUGHN, Assistant Examiner Woods et a1. 25240 Sproule et a1. 252-40 US. Cl. X.R. Panzer et a1. 252-332 10 25236, 41, 389

Greenwood et a1. 252-36 Scott 25236