CA1186298A - Coating oil compositions - Google Patents

Abstract

ABSTRACT

Useful oil compositions for coating ferrous and non-ferrous metals are provided. The coating oils are blends of an oil-soluble Group 1A alkali metal petroleum sulfonate, a polymeric fatty acid, and an inert and substantially wax-free napthenic or paraffinic hydrocarbon oil having a 100°F kinematic viscosity from 0.5 to 6 centistokes.

Description

~ fi~
The need to protect metal surfaces, particularly the surfaces of ferrous metals, during storage between operations is recognized throughout the industry. It is not uncomm~n for metal coils, for example, to be stored for ~rolonged p~riods prior to the ne~t wDrking operation, which can be stamping or another rolling operation to further reduce the thickness of the sheet and/or ~mpart the desired metallurgical properties to the metal. Very often the metal coils are stored in areas adjacent to pickling lines and as a result the metal is exposed to the corrosive action of acid vapors. To prevent, or at least minimize, deterioration of the metal surfaces protective coatings are com~only applied.
Numerous types of protective coatings are known and have been reported in the literature to protect against rusting. Typically these products form a continuous hydrophobic barrier on the metal surface, howe~er, while they may be impervious to moisture they are not totally effective in the presence of corrosive vapors. Accordingly, it is necessary to formulate products which are specifically designed to withstand the rigorous conditions encountered when sub-stantial ooncentrations of acidic vapors are present.
United States Patent 4,166,151, for example, discloses "waxy" ester compositions useful for protecting metal surfaces from acidic vapors which are derived from C10 25 aliphatic carboxylic acids and C15 40 aliphatic alcohols.
I~lese ester products are applied to the metal in an inert, volatile hydrocarbon, however, many of the waxy esters have limited solubility in the commonly used hydrocarbon carriers and must be applied as dispersions, which can present problems. For example, if the dispersions are allcwed to stand, agitation is necessary prior to use and may even be required throuyhout the application period, depending on the type of equipment used. It is also difficult to obtain uniform deposition over the entire surface area of the metal so that after ~le hydrocarbQn solvent has evaporated, discontinuities may be present in the waxy .

protective fiLm. Areas ~lich are deficient or totally dev~id of the waxy pro-tective coating will, of course, be susceptible to the corrosive action of the acid vaFors.
m e use of coating oil formulations, such as t~ose of United States Patent 3,600,310, which contains waxes or wax-like products can also pose problems in subsequent rolling operations if aquQous rolling oils are employed.
The æ waxy coating materials are removed, at least partially, during rolling and become associated with the aqueous rolling oil. The wax, being incompatible with the aqueous system, results in emulsion inst~bility, application pro~lems and other associated difficulties, particularly as the am~unt of wax in the aql~ous rolling oil increases in the system upon recirculation. The resulting wax buildup will coat equipment, clog nozzles and give heavy localized wax deposits on the metal which can result in undesirable carbonaceous deposits if the metal is subjected to heat treatment or annealing.
Slushing oil or rust inhibiting compositions are disclosed in Uni-ted States Patent 3,857,789 which are con~rised of a Group IIA, IIIA or IV~ metal salt of a r~hogany or naphthalene sulfonic acid, an alip~atic carboxylic acid, a cosolvent selected from æc)matic hydrocarbons, methyl pyrrolidone, tetra-hydrofuran, and n~no cmd dialkyl ethers of alkylene glycols and mixtures there-of, and a paraffinic or naphthenic lubricating oil. Whereas these compositionsæe effective for preventing corrosion of iron objects, the use of costly arc~atic or heterocyclic cosolvents is ne oessary if homogeneous solutions, which do not separate upon standing, æe to be obtained~
In accordance with the present inv~ntion, there is nc~ provided improv-ed coating oil cc~ositions which do not utilize wax esters and which clo not require the use of cosolvents to c)btain stable hom~geneous solutions. It has also quite unexpectedly been discovered that improved paint adhesion is obta~n~d when the coating oil conpositions of this invention, which æe comprised of a ?~
Group IA petr~leum sulfonate, a polymeric fatty acid and a low viscosity hydro-carbon oil or hydrocarbon oil blend, are employed.
The present com~ositions are extremely useful for coating ferrous and non-ferrous metals and effectively protect the metal from the corrosive action of acidic vapors and moisture during storage. Additionally, they lubricate the metal and protect the surface from scratching during coiling and uncoiling operations. Still another advantage of the instant coating oils is the fact that they do not ccntain waxy materials or require the use of expensive organic solvents.
Oil-soluble alkali metal petroleum sulfonates, natural or synthetic are used for the ~ormulation of the protective compositions and oonstitute from 1 to about 15 wei~ht percent of the coating oil. A polymeric fatty acid is also present in an amount from about 1 to 15 weight percent of the overall coat ing oil composition. Useful polymeric fatty acids typically are tho æ obtained /6 ~
fr~m the polymerization of1~8_unsaturated fatty acids and contain at least 60%
C36 dibasic acid. Hydrocar~on oils employed with the alkali metal petroleum sulfonate and polymeric fatty acid are low viscosity naphthenic or paraffinic hydrocarbons. The viscosity (100F kinematic) of these hydrocarbons can range from 0.5 to 6 centistokes but more usually is between 1 and 5 centistokes.
Nap~lthenic and parafEinic mineral oils which are essentially wax-free are parti-cularly useful for this purpose. The hydrocarbon oil comprises 70 to 98 percent by weight of the coating oil. Most generally, the combined a~cali metal petroleum sulfonate and polymeric fatty acid constitute at least 5 weight percent and does not exceed about 20 weight percent of the coating oil. The resulting coating oils have viscosities (100 F kinematic) of less than 8 and more preferably, less than 6 centistokes. Quite unexpectedly, when a GLOUP 1~ metal petroleum sulfonate is utilized with a polymeric fatty acid and the low viscosity hydrocarbon, an aromatic or heterocyclic cosolvent is not required and metals treated with the coating oil exhibit suFIerior paint adhesion.
Petroleum sulfonates useful for the present inven-tion are the oil-~oluble Group IA alkali earth metal s~lfonates derived from petroleum fractions or their syn-thetic substitutes obtained by any of the known manufacturing pro-cedures and which are ccm~ærcially available from a variety of manufacturers.
The molecular weight and the nature of the hydrocarkon and cation portions of the molecule can be varied and are primarily governed by the requirements of the particular application and oompatibility considerations, i.e. solubility in the hydrocarbon medium of choice and compatibility with the polymeric fatty acid.
Typical oil-soluble petroleum sulfonates correspond to the yeneric Eormula CnH2n 1oS03 Me where Me represents the alkali metal, m~st usually lithium, sodium or potassium and n is an integer greater than 20. Sodium petroleum sulfonates are particularly useful. Sodium petroleum sulfonates are oommercial-1~ available and obtained as solutions in hyd~ocarb3n oils and typically contaLn 50 -80% of the active ingredient.
Necessarily present with the alkali metal petroleum sulfonate is a Folymeric fatty acid. I have quite unexpectedly found that, while both products are recogm zed rust preventatives~ effective protection against the corrosive action of acid vapors and the other attendant advantages are obtained only if koth materials are present in the prescribed ooncentration ranges and utilized with a low visoosity hydrocarbon oil or hydrocarkon oil blend.
Polymeric fatty acids are well known and are obtainable from commercial suppliers. These products and pro oe sses for their preparation are described extensively in the literature. Typically they are obtained by polymerizing unsaturated mDnocarbo~ylic acids containing from 16 to 20 carbon atoms. Depending on the conditions employed dimer, trimer and higher polymer acids are obtained, however, for the purpo æ of this invention ~le polymeric acids will contain at least 60 percent by weight dibasic (dimer) acid which is preferably a C36 dimer acid obtained by the dimerization of Cl~ fatty acids such as oleic acid, linoleic acid or mixtures thereof. Particularly useful are polymeric fatty acids having 75% or more C36 dibasic acid. The remainder of the polymeric fatty acid consists primarily of C54 trimer acid and higher oligomers. Small amDunts of unreacted monomer, i.e. m~nocarboxylic acid, may also be present. In addition to the prescribed C36 dLmer acid content, useful polymeric fatty acids for this invention have acid values and saponification values in the range 180 to 215.
me alkali metal pet~oleum sulfonate and polymeric fatty acid are combined with a hydrccarbon diluent or carrier which facilitates application to the metal and also imparts useful lubrication properties. Useful hydrocarbon oils for this purpo æ are any of the commonly used naphthenic, paraffinic or synthetic oils which are substantially inert, substan-tially wax-free and relat-ively volatile and which have 100F kinematic viscosities from about 0.5 to 6 centistokes. Whereas the foreg~ing viscosity data is determined in accordance with the kinematic method, primarily due to the low viscosity of the hydrocarbonoil which are utilized for the invention, it will be understood that this data can be readily converted to other viscon~etric units, such as Saybolt Universal Seconds (SUS), by referring to available conversion tables. One such chart for determining equivalent viscosities at 100F is found at page 36 of "me Lubrication Manual", First edition (1971) r published by the United States SteelCorpora-tion. m us, by way of exa~ple, the upper visoosity limit of -the hydr3-carbon oil used for the preparation of the present improved coating oil con~-positions, represented in SUS units, is appr~ximately 46.
me viscosity of the hydrocarbon(s) to be used is dictated primarily by the method of application, i.e. whether the coating oil is sprayed, wiped, rolled or brushed onto the surface of the metal, whether tile metal is immersed in a bath containing the oil, etc. Hydrxarbon oils wi-th kinematic viscosities m the range 1 to 5 centistokes at 100F are most useful for ~ost applications and are therefore particularly advantageous. By judicious blending it is possible to employ a hydrocarbon havm g a viscosity greater -~han 5 centistokes so long as the viscosity of the resulting hydrocarbon blend is within the ranges prescribed above.
By the terms "substantially inert" and "substantially wax-free"
is meant that the hydrocarbon oil does not chemically react with the metal surface or otherwise impair the efficiency of the active components and the wax content of the oil is such that it will not inter~ere with aqueous rolling oil formulas which might subsequently be used for rolling the coated metal. me term "relatively volatile" indicates that the oil has a vapor pressure such that it can evaporate under ambient conditio~s leaving a protective coating of the polymeric fatty acid and petroleum sulfonate on the surface of the metc~l.
Commonly available paraffinic oils and petroleum naphthas having suitable viscosities and u æ ful for the prep~ration of the present improved coating oils include kerosene, No. 2 fuel oil, Stoddard solvent, mineral spirits mineral seal oil, and the like. Especially useful hydrocarbons are the solvent extracted "de-waxedl' oils which typically have pour points of 10F or lower.
Synthetic hydrocarbon oils obtained by oliyomerizing olefins having up to 20 carbon atoms in the presence of peroxide or Friedel-Crafts catalysts can also be employed. Coating oil compositions exhibiting superior characteristics are obtained using Stoddard solvent or a h~drocarbon oil blend where Stoddard solvent is the major component oil.
As was pointed out previously, it will be understood that mixtures of hydrocarbon oils are equally satisfactory for the practice of this invention, in fact, it is sometimes advantageous to utilize blends of t~ or more petroleum and/or synthetic hydrocarbons. This is particularly advantayeous for tne user since he can "customize" the coating oils to fit his part-icular needs. Also P~ B
this feature makes it possible for the supplier to provide a mul-ti-purpose ooating oil "concentrate" which can later be diluted to suit the needs of the user. T~le compositions of this invention are particularly suited for preparation of concentrates since both the polymeric fatty acid and alkali metal petroleum sulfonate are readily soluble in the hydrocarbon oils even at high concentrations.
The polymeric acid and pet~leum sulfonate are added, individually or in oo~bination to the hydrocarbon oil or hydrocarbon oil blend and are readily soluble therein without any special processing. Conventional mi~ing is sufficient to achieve solution and the resulting solutions are stable and do not detexiorate or separate under ambient conditions even when allcwed to stand for prolonged periods. Additives such as stabilizers, fungicides, bacteriocides, and the like may be present in small amounts, however, they are not necessary for most applications.
Useful coating oils will contain from 1 to 15 weight percent of the oil-soluble alkali metal petroleum sulfonate, 1 to 15 weight percent polym~ric fatty acid and 70 to 98 weight percent hydrocarbon oil. Particularly useful compositions oontain 2 to 12 weight percent sodium petroleum sulfonate, 2 to lQ
weight percent polymer acid and 78 to 96 weight percent hydrocarbon oil. The active components (sulfonate and polymer acid) most generally constitute from 5 to 20 weight percent: of the coating oil form~ations. Especially useful coat-ing oil formulations of this invention have viscosities (100F kinematic) of less than 8 centistokes and, more preferably, less than 6 centistokes.
The coating oils of this invention represent a significant improvement over the slushing oils of United States Patent 3,857,789. In addition to being low viscosity fluids readily adaptable for application to metal sheet moving on a mill line at high rates of speed, the oils evaporate quickly to fonn an ; effective oontinuous protective barrier over the ~reated metal surface. Furth~r-more, this is accomplished wlthout the use of costl~ aromatic, heterocyclic, or s~
glycol ether solvents as are required for the prior art compositions. Quite unexpectedly, lt has al~so been discovered that metals coated with the present oils, con~rised of a low viscosity hydroc æbon, a polymeric fatty acid and rr.ono-valent metal petroelum sulfonate, exhibit significantly improved paint adhesion compared to the metals coated with the oils of United States patent 3,857,789.
While the coating oils of this invention æe primarily used with ferrous metals, they may also be employed to protect nonferrous metals. mis and other aspects of the invention, will be more fully illustrated in the follow-ing examples which are not intended to limit the irrvention~ In these examples all pæ ts and percentages are on a weight basis unless otherwise indicated.
Resistance to corrosion is deter~ined by suspending a one inch by one inch steel strip cut from can stock in a loosely covered 600 ml glass beaker containing approximately 100 mls. 5~ hydrochloric acid solution, heat-ing the beaker and its contents at 200F for 4 hours, removing the strip and allowing to stand exposed to the atmosphere for 16 hours and then visually examining and rating the strip for corrosion. The following ratings æe employ-ed: clear (no corrosion), light, moderate and heavy corrosion. me oonditions of this test are considered to be much more severe than are normally encounter-ed in actual industrial use since the pH of the hot vapors in the beaker is approximately 2. Pri.or to testing, the steel strips are solvent washed and soaked in dilute hydx~chloric acid to remove any protective film applied by the manufacturer and to insure that a fresh clean metal surface is provided for the test. m e cleaned steel strips are dipped in the coating oil, suspended and allowed to drain for several hours before~eingevaluated in the corrosion test.
EX~E 1 A series of coating oils were prepared varying the amounts of sodium petroleum sulfonate (Alox ~ 319FX) and dirrer acid (Empol ~ 1018 Dimer acid D ~ ~

containing approximately 83% C36 dibasic acid) used. Stoddard solvent (petro-leum naptha; boiling range 315-334 F; 100 F viscosity 1.20 centistokes) was u~sed as the diluent for all the formulations. Each formulation was evaluated for resistance to corrosion and the results were as follows:

% Pet.
Sulfona~e ~SIODDA~D Coating Oil 1 (60% active)/%Dimer/Solvent Viscosity Corrosion =. . _ IA 3 / 2 / 95 1.35 Clear IB 4 / 2 / 94 1~36 Clear 10 IC 5 / 2 / 93 1.38 Clear ID 3 / 4 / 93 1.40 Clear IE 4 / 4 / g2 1.41 Clear IF 4 / 4 / 92 1.42 Clear IG 12 / 10 / 78 4.28 Clear 00F kinematic ID demonstrate the need to have both the petroleum sulfonate and polymeric fatty acid present with the hydrocarbon oil to achieve corrosion resistance, the follawing formulations were prepared for co~parative purposes and gave the following results:

% Pet. %Stoddard Sul~onate/%Dimer/ Solvent Gbrrosion .. ..... _ O / O / 100 Heavy 0 / 0 5 / 99.5 Heavy 0 / 2 / 98 Heavy O / 4 / 96 Heavy ; 0 / 12 / 88 Heavy 4 / 0 / 96 Heavy 12 / O / 88 Heavy The above results clearly demonstrate the superior results obt~ined with the _ g _ coating oils of this invention and the need for both the polymeric acid and the alkali metal petroleum sulfonate if resistance to the corrosive action of the acid vapors is to be obtained.
In addition to forming an effective continuous protective barrier on the surface of metal treated therewith it was also observed that the surface of the metal was not exoessively oily or sticky and that it was not necessary to solvent wash the metal in order to obtain good paint adhesion. ~o demonstrate this point, 2 x 8 inch steel Q-panels (SAE 1010 low carbon cold rolled steel, approximate RDckwell B65-70, smooth finish) coated with each of the formulationsprepared a~ove (containing dimer and sodium petroleum sulfonate) were air-dried for 24 hours and then spray painted with white enamel (Dutch soy Supra-Swift).P~ter being allowed to dry for 24 hours, the tenacity of the paint film to the metal surface was tested by firmly applying 3/4" wide transparent tape (Scotch ~
brand) to the panel. Upon removal of the tape, none of the paint was lifted from the metal wit~ the tape.
EXAMPLE II
Employing the petroleum sulfonate and polymeric fatty acid of Example I in varying amounts, a series of coating oils were prepared using hydrocarkon oil blends comprised of Stoddard solvent and solvent extracted neutral paraffinic hydrocar~on oil (pour point 0F; viscosity (100F) 31.9 centistokes). Ilhe hydro-carbon oil blends utilized all had 100F kinematic viscosities belaw 5 centi-stokes. me resulting coating oils were applied to steel strips and evaluated for resistance to the coxxosive action of HCl vapor. The aomFositions and results of the corrosion test were as follcws:
% Pet.
Sulfonate %Stoddard %Parafflmc (60% active)/Dimer/ Solvent / Oil Corrosion . _ . _ ~ ... . .
IIA2 / 4 / 69 / 25 Clear IIB12 / 2 / 61 / 25 Clear % Pet.
Sulfonate %Stoddard %ParafEinic (60% active)/~Dlmer/ Solv t / Oil Corr~sion .
IIC 12 / 4 / 59 / 25 Clear me viscosity of prod~lct IIC, which was -~he most viscous coating oil of those prepared, was 5.89 centistokes.
Resistanoe to corrosion is also obtained with the above formulatio~s when metal strips treated with the coating oils are exposed to sulfuric acid vapors under similar test conditions.
Panels coated with the oils also exhibited good paint adhesion when evaluated in accordance with the pro oedure of Example I. Ib demonstra e the criticality of the composition and viscosity oE the coating oil, formulations were prepared usmg similar hydrocarhon oils obtained by blending Stoddard solvent with 31.9 CSt paraffinic oil. The viscosity of ~he hydrocarhon carrier oil was, in all instan oes, less than 5 centistokes. Compositions and coating oil visoosities were as follows:

~O % %Stoddard %Paraffinic Coating Oil Sulfonat~ / Dimer / Solvent / Oil Viscosity (centistokes) .. . . .... .. ... .. . _ . . ..... ..... .. .

2~ / 12 / 39 / 25 19.9 12 / 24 / 39 / 25 17.5 24 / 4 / 47 / 25 8.6 Whereas all of these products provided effective corrosion resistance when applied to the metal, paint adhesion to the treated surfaces was unacceptable.
With each of the latter coating oils, paint in contact with the t~ansparent tape was lifted when the tape was removed from the painted surface.

EXAMPT~ III

Follcwing the procedure of Example II, a coating oil was prepared except that in this instance the polymeric fatty acidused contained 92% C36 dimer acid. The coating oil oontained 12% sodium petroleum sulfonate (60%
active), 4% dimer, 59% Stoddard solvent and 25% of the solvent extracted neutral paraffinic oil. me hydrocarkon oil (Stoddard solvent and paraffinic oil) blend had a viscosity of 3.3 centistokes and the vlscosity of the resulting coating oil was less than 7 centistokes. The coating oil provided excellent protection for the steel strip in the corrosion test and there was no evidence of corrosion at the oonclusion of the test period. Metal panels treated with the coating oil gave good paint adhesion.
EXAMPLE IV
Ib demonstrate the ability of the coating oils to be used with non-ferrous metals, aluminum strips were coated with a coating oil having a 100F
viscosity less than 7 centistokes and comprised of 12% sodium petroleum sulfona-te (60% active), 4% dimer acid containing 83% C36 dibasic acids, 6% naphthenic bright stock, 25% solvent extract d neutral paraffinic oil and 53% petroleum naphtha. The viscosity (100F) of the h~drocarbon oil (without the petroleum sulfonate and dimer acid) was less than 5 centistokes. Cbated aluminum strip was subjected to the corrosion test and compared with an untreated aluminum strip. Whereas the untreated control was slightly etched and had a dull, dis-colored finish, the treated aluminum strip remained bright with no eviden oe of discoloration or any change in appearance.

EX~MPLE V
m e coating oil of Example IV was applied to a clean brass bar which was exposed to the corrosive action of HCl vapors in accordance ~ith the test procedure. The treated bar was unchanged in appearance after tlle test period -it remained bright and there was no disooloration. An untreated control was slightly e-tched and the surface was dull and discolored.

EX~MæLE VI
To further demonstrate the invention and the imoroved results obtained ~ 3~
herewithl two coating oils containing 12% sodium petrole~ sulfonate (60%
active) and 4% dimer acid were prepared. The petroleum sulfonate and dimer were the same as used in Example I. m e remainder of the formulation for ~le first coating oil camposition consisted of 6% nc~phthenic bright stock c~nd 78%
pc~raffinic petroleum oil (150 SUS) and for the second fonmulation consisted of 6% naphthenic bright stock and 78% Stoddard solvent. me viscosities of -the resulting coating oil formulations were significantly different, 64.5 centistokes and 2.86 centistokes, respectively. Both coating oils provided excellent resist-anoe to corrosion when steel strips treated with these coating oils were subject-ed to the corrosive action of HCl in accordance with the test procedure, however, acceptable paint adhesion was obtained only with the 2.86 centistoke coating oil. The paint applied to metal panels coated with the 64.5 centistoke product pulled off the metal surface when the tape was removed.
EXAMELE VII
A highly effective coating oil was prepared in accordance with the following formulation:
4 Parts dimer acid (83% C36 dibasic acid) 12 Parts sodium petroleum sulfonate (60% active) 6 Parts naphthenic bright stock 25 Parts paraffinic oil (32 centistokes at 100F) 53 Parts petroleum naphtha (1.2-1.4 centistokes at 100F) The viscosity of the combined hydrocarbon oils was 2.63 centistokes and the resuIting coating oil had a viscosity of 5.11 centistokes. Steel strip -treated with the coating oil com~osition shcwed no evidence of oorrosion when subjected to the corrosion test. me coating oil also provided an effective protective barrier for aluminwm, copper and brass.
m e coating oil was sprayed on the surface of steel sheet mDving at a high rate of speed (8 to lQ ft. per second) and provided a highly effective eorrosion resistant proteetive coating over the entire surfaoe of the metal.
Coils of the coated steel sheet stored in the mill for an extended period under adverse c~nditions (high hu~idity and high concentration of acidie vapors), shcwed no evidence of oorrosion. Upon uncoiling, the surface of the metal was bright, free of discoloration, rust and pitting.
A spray mist of the coating oil was similarly applied to eold rolled lc~ earbon steel sheet (26" wide) and c~ils of the treated sheet stored out-doors ~uncovered) for 45 days. When the sheet was uncoiled there was no evidenee of eorrosion. The sheet was then passed through a lead bath and into a slitter where it was eut into narrow bands. The metal banding had good surfaee quanti-ties and uniformly accepted paint without difficulty.

EXAMPLE VIII
To demonstrate the need for the polymerie fatty acid with the alkali metal sulfonate for the compositions of this invention, oleic acid was substitut-ed for the polymeric fatty acid in Produet IA. Whereas the viseosity of the resulting coating oil eontaining the oleic acid was essentially the same as that of produet I~, heavy rusting and eorrosion was obtained with metal ooated with the oleie-eontaining produet. Similarly, when linoleic aeid, ricinoleic aeid or s-tearic acid was combined with sodi~n petroleum sulEonate in Stoddard solvent, heavy oorrosion was observed upon expos~e of the treated metal to the acid atmosphere.
E~Z~PIE IX
To illustrate the neeessity of employing an alkali metal, i.e. mono-valent metal, petroleum sulfonate for the eoating oils of this inventio~, a ooating oil was prepared for comparative purposes utilizing a synthetie petro-leum sulfonate of a divalent metal. For this ooating oil formulation synthetic barium dinonyl-naphthalene sulfonate (N~-SUL ~ BSN) was substituted for the sodium sulfonate in Prc~uct IIC. Whereas it was possibl~ to obtain a substantial--ly ho~ogeneous coating oil solution when the product was stirred at 150F, noticeable phase separation of the components was evident within a very short time when the oil was allowed to stand at r~om temperature. In order to obtain a homogeneous solution, which did not separate upon standing at ambient condi-tions using the divalent metal sulfonate, required the addition of several parts of a cosolvent of the type employed for the oompositions of United States Patent

3,857,789.
EX~MPLE X
Tb further demonstrate the advantages of the coating oils of this invention over the compositions of United States Patent 3,857,789 the formula-tions A-C were prepared as follows:

Weight Percent A _ C
Sodium Petroleum Sulfonate 4 Barium Petroleum Sulfonate - 4 4 Dim~er Acid 2 2 2 Butyl Cellosolve - - 3 Stoddard Solvent 94 Pale Oil (100 SUS) - 94 91 1100 F kinematic viscosity 1.3 centistokes 100 F kinematic viscosity 20.3 centistokes Product A, a coating oil prepared in accordan oe with this invention, was a ho~ogeneous yellow liquid (100F kine~atic viscosity 1.52 centistokes) which did not se~arate upon standing at ambient conditions for up to three ~onths.
Product B, prepared using a divalent metal sulfonate in accordance with United States Patent 3,857,789, but with~ut a cosolvent produced an incompatible system. Due to the separation of phases product B could not be utilized for ~ ~ ~t~

subsequent testing. Product C, prepared following the teachings of United S-tates Patent 3,857,789 gave a homogeneous amber solution having a 100 kinematic viscosity of 31.5 centistokes (148 SUS). Products A and C were uni~nrmly applied to both sides of 6 3/4 x 3 inch steel panels. The panel coated with product A was essentially dry to the touch with no undesirable oily sticky film after 15 minutes whereas the pcmel coated with product C had an oily residue even after drying for 24 hours. After 24 hours the panels coated with Product A retained 5.2% of the weight of the original oil applied whereas panels coat-ed with Product C retained 29% of the original weigh-t of applied oil. In spite of the fact that amDunt of the protective residue on the metal was approximately five ti~es less with Product A versus Product C, no rust or corrosion was observed on the panels coated with Product A when they were exposed to the acid corrosion test. Panels coated with both products were spray painted after being allowed to dry for up to five days with the follcwing results:

Drying Time Product A Product C
1 day no peeling heavy peeling 2 days no peeling heavy peeling 5 days no peeling heavy peeling When sodium petroleum sulfonate was substituted for barium sulfonate in the preparation of Product C, there was no appreciable improvement in the paint adhesion of panels coated therewith.

Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coating oil coMposition conprising (a) 1 to 15% polymeric fatty acid obtained from the polymerization of unsaturated Cl6-20 monocarboxylic acids and containing at least 60% C36 dimer acid, (b) 1 to 15% oil-soluble Group IA alkali metal petroleum sulfonate and (c) 70 to 98% inert and substantial-ly wax-free naphthenic or paraffinic hydrocarbon oil having a 100°F kinematic viscosity from 0.5 to 6 centistokes.

2. The coating oil of claim 1 wherein the Group IA alkali metal petroleum sulfonate is a sodium petroleum sulfonate.

3. The coating oil of claim 1 wherein the polymeric fatty acid contains 75% or more C36 dimer acid and has an acid value of 180 to 215 and saponification value of 180 to 215.

4. The coating oil of claim 1 containing 2 to 10% polymeric fatty acid, 2 to 12% sodium petroleum sulfonate and 78 to 96% hydrocarbon oil.

5. The coating oil of claim 2 wherein the hydrocarbon oil has a 100°F kinematic viscosity of 1 to 5 centistokes and the viscosity (100 F
kinematic) of the coating oil is less than 8 centistokes.

6. The coating oil of claim 5 wherein the hydrocarbon oil is Stoddard solvent or a blend of hydrocarbon oils wherein Stoddard solvent is the major component oil.

7. A method of protecting a metal surface which comprises treating a metal with a coating oil having a 100°F kinematic viscosity of less than 8 centistokes and comprised of (a) 1 to 15% polymeric fatty acid obtained from the polymerization of unsaturated C16-20 monocarboxylic acids and containing at least 60% C36 dimer acid,(b) 1 to 15% oil-soluble Group IA alkali metal petroleum sulfonate and (c) 70 to 98% inert and substantially wax-free naphthenic or paraffinic hydrocarbon oil having a 100°F kinematic viscosity of 0.5 to 6 centistokes so as to obtain a continuous protective coating on the exposed metal surfaces.

8. The method of claim 7 wherein the Group IA alkali metal petroleum sulfonate is a sodium petroleum sulfonate.

9. The method of claim 8 wherein the hydrocarbon oil is Stoddard solvent or a hydrocarbon blend wherein Stoddard solvent is the major component oil and substantially all of said hydrocarbon oil is evaporated.

10. The method of claim 9 wherein the coating oil is applied to rolled metal sheet.

11. The method of claim 10 wherein the coating oil is sprayed on the metal surface.

12. A metal article having supplied to its surface a coating oil compris-ing (a) 1 to 15% polymeric fatty acid obtained from the polymerization of unsaturated C16-20 monocarboxylic acids and containing at least 60% C36 dimer acid, (b) 1 to 15% oil-soluble Group IA alkali metal petroleum sulfonate and (c) 70 to 98% inert and substantially wax-free naphthenic or paraffinic hydro-carbon oil having a 100°F kinematic viscosity from 0.5 to 6 centistokes.

13. The metal article of claim 12 wherein the hydrocarbon oil is Stoddard solvent or a hydrocarbon oil blend wherein Stoddard solvent is the major component oil and all or a portion of said hydrocarbon oil is evaporated to provide a substantially continuous protective film resistant to moisture and acid vapors.

14. The metal article of claim 13 wherein the Group IA alkali metal petroleum sulfonate is a sodium petroleum sulfonate.

15. The metal article of claim 14 wherein the coating oil contains 2 to 10%
polymeric fatty acid containing 75% or more C36 dimer acid, 2 to 12% sodium petroleum sulfonate and 78 to 96% hydrocarbon oil.