Guanidine carbonate dispersion composition
United States Patent 3923668
A stable dispersion of guanidine carbonate and an ashless dispersing agent in mineral oil, the guanidine carbonate having a particle size in the range of 0.001 to 0.1 micron and being present at between about 1 to 50% by weight, the dispersing agent being present at between about 1 to 25% by weight; and a lubricant or hydrocarbon fuel composition containing an effective rust-inhibiting amount of the described mineral oil dispersion.
US Patent References:
Stabilized fuel oils
Catlin et al. - March 1956 - 2737452
Lubricating oil compositions containing polymeric additives
Catlin - March 1956 - 2737496
Lubricating oil compositions containing nu-dialkylaminoalkyl alkenyl succinimides
Anderson et al. - January 1962 - 3018250
/3172892.html
Le Suer et al. - March 1965 - 3172892
Polyolefin substituted polyamines and lubricants containing them
Wagenaar - September 1966 - 3275554
Stabilized fuel oils
Catlin et al. - March 1956 - 2737452
Lubricating oil compositions containing polymeric additives
Catlin - March 1956 - 2737496
Lubricating oil compositions containing nu-dialkylaminoalkyl alkenyl succinimides
Anderson et al. - January 1962 - 3018250
/3172892.html
Le Suer et al. - March 1965 - 3172892
Polyolefin substituted polyamines and lubricants containing them
Wagenaar - September 1966 - 3275554
Application Number:
05/482571
Publication Date:
12/02/1975
Filing Date:
06/24/1974
View Patent Images:
Export Citation:
Assignee:
E. I. Du Pont de Nemours and Company (Wilmington, DE)
Primary Class:
Other Classes:
252/392, 44/351, 508/550, 508/293, 252/387, 44/419, 44/347, 44/421, 44/398
International Classes:
C10L1/14; C10M133/00; C10M161/00; C10L1/18; C10L1/22; C10L1/10; C10M3/26; C10M1/32; C10L1/32; C10L1/22
Field of Search:
44/51,71 252/16,34,34.7,50,51.5A,387,392
Other References:
Chemical Abstracts, Vol. 79, 1973, 7075t..
Primary Examiner:
Gantz, Delbert E.
Assistant Examiner:
Vaughn I.
Attorney, Agent or Firm:
Costello, James A.
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows
1. A stable dispersion of guanidine carbonate and ashless dispersing agent in mineral oil comprising, based on percent by total weight,
2. A stable dispersion according to claim 1 containing from
3. to 42% guanidine carbonate
4. to 25% dispersing agent, and
5. to 85% mineral oil.
6. A stable dispersion according to claim 1 wherein the dispersing agent contains at least one amino group.
7. A stable dispersion according to claim 3 wherein the dispersing agent is aminoimide of hydrocarbylsuccinic acid wherein the hydrocarbyl group has from 50 to 150 carbon atoms.
8. A stable dispersion according to claim 3 wherein the dispersing agent is polyisobutenylsuccinimide.
9. A stable dispersion according to claim 3 wherein the dispersing agent is polyisobutenyltetraethylene pentamine.
10. A stable dispersion according to claim 3 wherein the dispersing agent is lauryl methacrylate/diethylaminoethyl methacrylate copolymer.
11. A crankcase lubricating composition comprising mineral oil of lubricating viscosity and an effective amount of the stable dispersion of claim 1 providing from about 0.5 to 5%, by total weight, of guanidine carbonate.
12. A fuel oil composition comprising hydrocarbon fuel oil and an effective amount of the stable dispersion of claim 1 providing from about 0.5 to 5%, by total weight, of guanidine carbonate.
1. A stable dispersion of guanidine carbonate and ashless dispersing agent in mineral oil comprising, based on percent by total weight,
2. A stable dispersion according to claim 1 containing from
3. to 42% guanidine carbonate
4. to 25% dispersing agent, and
5. to 85% mineral oil.
6. A stable dispersion according to claim 1 wherein the dispersing agent contains at least one amino group.
7. A stable dispersion according to claim 3 wherein the dispersing agent is aminoimide of hydrocarbylsuccinic acid wherein the hydrocarbyl group has from 50 to 150 carbon atoms.
8. A stable dispersion according to claim 3 wherein the dispersing agent is polyisobutenylsuccinimide.
9. A stable dispersion according to claim 3 wherein the dispersing agent is polyisobutenyltetraethylene pentamine.
10. A stable dispersion according to claim 3 wherein the dispersing agent is lauryl methacrylate/diethylaminoethyl methacrylate copolymer.
11. A crankcase lubricating composition comprising mineral oil of lubricating viscosity and an effective amount of the stable dispersion of claim 1 providing from about 0.5 to 5%, by total weight, of guanidine carbonate.
12. A fuel oil composition comprising hydrocarbon fuel oil and an effective amount of the stable dispersion of claim 1 providing from about 0.5 to 5%, by total weight, of guanidine carbonate.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns guanidine carbonate stably dispersed with an ashless dispersing agent in mineral oil. The invention also concerns lubricant and hydrocarbon fuel compositions containing an effective rustinhibiting amount of the guanidine carbonate/dispersing agent/mineral oil composition.
2. Description of the Prior Art
Lubricants and fuels are usually in contact with ferrous metals during storage and use. Since moisture and air are unavoidably present, corrosion of the ferrous metals will occur. In many cases, rusting and corrosion conditions are created because of the intrusion of products of combustion and/or oxidation during use of the lubricants and fuels. Thus, in the operation of an internal combustion engine, engine blowby finds its way into the crankcase. Depending upon the fuel used, blowby can contribute corrosive acids to the crankcase.
The most practical method of controlling rust and corrosion by acids is to neutralize them. Thus, automotive crankcase lubricants generally contain metal-based neutralizing additives to minimize the harmful effects of the acids. In many applications, however, the presence of metal compounds in lubricants and hydrocarbon fuels is undesirable. One objection is that the lubricants and fuels show an increased susceptibility to oxidation which necessitates the use of higher levels of antioxidants. Another objection is that metal compounds lead to metal-containing deposits, which are undesirable. In internal combustion engines, the formation of such deposits interferes with efficient operation. In fuel oil burners, the accumulation of metalcontaining deposits on the various parts eventually result in poorer burner operation.
Metal-free rust inhibitors are known such as those based on long chain aliphatic amines, low molecular weight alkenylsuccinic acids, alkylthioacetic acids and substituted imidazolines. These metal-free rust inhibitors have not been entirely satisfactory because of limited effectiveness in the presence of acids. A need therefore exists for an effective, ashless, rust inhibitor for lubricants and hydrocarbon fuels that is useful in acidic environments. The novel compositions of this invention fulfill this need.
Guanidine carbonate, although known in the art, is not known to be a rust inhibitor. Nor is guanidine carbonate known in combination with mineral oil or dispersing agent. The present invention is based on the discovery that stable dispersions of guanidine carbonate in mineral oils using certain ashless dispersing agents provide effective antirust protection for lubricants and hydrocarbon fuels.
SUMMARY OF THE INVENTION
This invention concerns a stable dispersion of guanidine carbonate and ashless dispersing agent in mineral oil comprising, based on percent by total weight,
i. from 1 to 50% guanidine carbonate having a particle size in the range of from 0.001 to 0.1 micron,
ii. from 1 to 25% of at least one oil-soluble, ashless dispersing agent selected from the group consisting of
a. an aliphatic hydrocarbylsuccinic acid and derivatives thereof wherein the hydrocarbyl group has 30 to 200 carbon atoms, said derivative being selected from the group consisting of anhydride, ester, amide and aminoimide,
b. an aliphatic hydrocarbyl-substituted polyalkylene polyamine of the formula ##EQU1## wherein R is selected from the group consisting of hydrogen, lower alkyl, and aliphatic hydrocarbyl containing from 30 to 200 carbon atoms, at least one R being said hydrocarbyl group, R' is an alkylene radical having 2 to 3 carbon atoms and x is 0 to 5, and
c. a basic amino nitrogen-containing addition type copolymer containing in copolymerized form at least one polymerizable ethylenically unsaturated monomer, free of amino-nitrogen and containing an aliphatic hydrocarbyl chain of from 8 to 18 carbon atoms, and at least one polymerizable ethylenically unsaturated monomer containing basic amino nitrogen, said copolymer containing 0.1 to 3.0% by weight of said basic amino nitrogen, said copolymer having an inherent viscosity of 0.1 to 3.0 as determined at 0.1% weight volume concentration in benzene at 25°C., and
iii. from 25 to 98% of mineral oil having a 100°F. viscosity of from 30 to 1,500 SUS.
A preferred mineral oil dispersion contains from 10 to 42% of guanidine carbonate, from 5 to 25% of the dispersing agent and from 33 to 85% of the mineral oil, based on total weight. Preferred dispersing agents are the amino nitrogen-containing derivatives of hydrocarbylsuccinic acid.
The preferred ashless dispersing agents are characterized by the presence of one or more amino groups, which can be primary, secondary or tertiary amino groups. Thus, the preferred dispersants of the hydrocarbylsuccinic class (a) are those prepared with a polyalkylene polyamine, so as to contain at least one amino nitrogen. The hydrocarbyl-substituted polyalkylene polyamines (b) and the amino nitrogen-containing copolymeric dispersing agents (c) inherently contain one or more amino groups. These preferred dispersants are known in the art as additives for lubricating oils to disperse sludge and deposits.
The most preferred dispersing agent is the aminoimide derivative of hydrocarbylsuccinic acid wherein the hydrocarbyl has from 50 to 150 carbon atoms.
This invention also concerns compositions comprising a major proportion of a crankcase lubricant or fuel oil together with an effective rust inhibiting amount of the mineral oil dispersion. An "effective amount" of the mineral oil dispersion for inhibiting rust and corrosion will usually be such as to provide between about 0.5 to 5% of guanidine carbonate based on the total weight of the composition. It should be appreciated, however, that amounts of the mineral oil dispersion that provide more than 0.1% of guandine carbonate and less than 0.5% will provide some rust and corrosion-inhibiting properties, which properties will improve as the percentage of guanidine carbonate approaches the most effective range of 0.5 to 5%.
In this invention, by "stable dispersion" is meant one that shows little or no settling of guanidine carbonate when stored at 25°C. for one week.
DETAILS OF THE INVENTION
Guanidine carbonate is a carbonic acid salt, 2CH 5 N 3 .H 2 CO 3 , of guanidine which is a strong base. Guanidine carbonate can be prepared from guanidine and carbonic acid, but since guanidine is isolated only with difficulty, the carbonate is usually prepared by other known methods such as (1) heating dicyandiamide with ammonium carbonate or (2) heating cyanamide with ammonium carbonate.
Guanidine carbonate has a density of about 1.25 and melts at 241°C. It is soluble in water (45 g per 100 g water at 20°C. ) and is sparingly soluble in nonpolar organic liquids such as benzene, toluene, hexane, petroleum oils, and the like. To be an effective anitrustant in lubricants and fuel oils, guanidine carbonate must be provided in a suitable form. Since guanidine carbonate itself is insufficiently soluble in lubricants and hydrocarbon fuels to be effective, it is provided herein as a stable dispersion in mineral oil.
Stable dispersions of guanidine carbonate in mineral oil are obtained when the average particle size of guanidine carbonate is in the range of 0.001 to 0.1 micron, and certain ashless dispersing agents are used. When the average particle size is greater than about 0.1 micron, the dispersions are turbid and the guanidine carbonate settles out more rapidly than is desired. Thus, a stable dispersion has an average particle size of about 0.1 micron or less. The preferred particle size is about 0.05 micron or less.
Numerous methods are known for making solid guanidine carbonate finely divided. These methods include grinding and ball milling in liquid media with and without dispersing agents. These mechanical methods, however, are generally time consuming and costly. It has been found that stable dispersions of guanidine carbonate can be prepared by emulsifying an aqueous guanidine carbonate solution in a mineral oil in the presence of a suitable dispersing agent and (2) removing the water by azeotropic distillation at low temperature. By this process, guanidine carbonate stably dispersed in mineral oil and having an average particle size of about 0.05 micron is readily and economically prepared.
It is recognized that the stability of dispersions in general depends upon the particle size and the nature of the solid, the nature of the solid surface, the properties of the liquid medium and the characteristics of the dispersing agent. Dispersing agents are generally surface active agents characterized by having lipophilic and hydrophilic groups. Dispersing agents useful in the present invention should be oil-soluble, that is soluble to the extent of at least 0.05 g. per 100 g. of mineral oil. Oil-soluble dispersing agents generally contain at least one oil-solubilizing group, usually an alkyl or an alkenyl group of at least about 8 carbon atoms, more usually at least 12 carbon atoms. Since the dispersions of the invention will find applications in systems which are desirably ash-free or of very low ash, the dispersing agents should also be ash-free, that is, be substantially free of metallic components.
Since the preferred method for preparing stable guanidine carbonate dispersions includes the preparation of an emulsion of aqueous guanidine carbonate in mineral oil, it is desirable that the dispersing agent also be effective as an emulsifying agent in the above process. Those skilled in the art can easily determine the suitability of a surface active compound as an emulsifying agent and as a dispersing agent by a simple experiment as described in Example 1.
Dispersing agents useful in the present invention include high molecular weight hydrocarbylsuccinic acid and certain derivatives thereof. In the present context, the term "hydrocarbyl" includes alkyl and alkenyl groups. The hydrocarbylsuccinic acids are known in the art. They are prepared by the reaction of maleic anhydride with high molecular weight aliphatic olefins or with chlorinated high molecular weight aliphatic olefins to provide in each case a high molecular weight aliphatic hydrocarbylsuccinic anhydride. The high molecular weight olefin can be any olefin but is preferably a polymer of a C 3 to C 6 olefin, most preferably polypropylene or polyisobutylene. To provide oil solubility to the hydrocarbylsuccinic acid the olefin should contain at least 30 carbon atoms, preferably in the range of 50 to 200 carbon atoms. The hydrocarbylsuccinic anhydride obtained as described above can be (a) hydrolyzed to the acid, (b) condensed with a hydroxyl-containing compound such as sorbitol to provide either the mono- or diester, or (c) reacted with a polyalkylene polyamine having at least one amino hydrogen to provide derivatives which include corresponding substituted amides and imides.
The preferred dispersing agent is the imide reaction product of a hydrocarbylsuccinic acid and a substantially equimolar amount of a polyalkylene polyamine having a free NH 2 group and is represented by the formula ##EQU2## wherein R is an aliphatic hydrocarbyl group of 30 to 200 carbon atoms, R 1 is an alkylene group of 2 to 3 carbon atoms, R 2 and R 3 are selected from the group consisting of hydrogen and lower alkyl groups and x is 0 to 5.
The particularly preferred dispersing agents are imides of the above formula wherein R is a hydrocarbyl group of 50 to 150 carbon atoms, R 1 is an alkylene group of 2 carbon atoms, R 2 and R 3 are hydrogens and x is 4. Specific polyalkylene polyamines suitable for the preparation of such imides include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, 1,2-propylenediamine, 1,3-propylenediamine, di-1,2-propylenetriamine, tri-1,2-propylenetetramine, di-1,3-propylenetriamine, tri-1,3-propylenetetramine, N,N-dimethylethylenediamine, N,N-diethylpropylenediamine and the like. It is understood that while the above reaction product is described in terms of aminoimide, the product can also contain amides as well as amine carboxylates.
Another class of useful dispersing agents comprises certain high molecular weight oil-soluble aliphatic hydrocarbyl substituted polyamines. This type of dispersing agent is usually prepared by halogenation of a high molecular weight olefin such as polypropylene or polyisobutylene, to form an alkyl or alkenyl halide which is then used to alkylate a polyalkylene polyamine having a replaceable aminohydrogen. To provide sufficient oil solubility to the resulting hydrocarbylated polyalkylene polyamine, the olefin should contain at least about 30 carbon atoms preferably 50 to 200 carbon atoms. Depending upon the molar proportions and the reaction conditions, the resulting alkylated polyalkylene polyamine contains one or more high molecular weight hydrocarbyl group(s). This type of dispersing agent is represented by the formula ##EQU3## wherein R is selected from the group consisting of hydrogen, lower alkyl, and aliphatic hydrocarbyl containing from 30 to 200 carbon atoms, at least one R being said hydrocarbyl group, R' is an alkylene radical having 2-3 carbon atoms and x is 0 to 5. Usually only one of the R groups is hydrocarbyl. Polyalkylene polyamines suitable for the preparation of such hydrocarbyl derivatives include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, 1,2- and 1,3-propylenediamine, di-1,2- and 1,3-propylenetriamine, tri-1,2-propylenetetramine, N-methylethylenediamine, N-methyl-1,3-propylenediamine, N,N-dimethylethylenediamine, N,N-dimethyl-1,3-propylenediamine and the like.
Another useful class of ashless dispersing agent for the preparation of the novel compositions comprises basic nitrogen-containing addition type copolymers containing in copolymerized form at least one ethylenically unsaturated polymerizable monomer, free of amino nitrogen and containing an aliphatic hydrocarbyl chain of from 8 to 18 carbon atoms, and at least one ethylenically unsaturated polymerizable monomer containing basic amino nitrogen, the copolymer containing 0.1 to 3.0% by weight of the basic amino nitrogen and having an inherent viscosity of 0.1 to 3.0 as determined at 0.1% weight-volume concentration in benzene at 25°C.
Useful polymers include copolymers of lauryl methacrylate and diethylaminoethyl methacrylate, n-octyl methacrylate and diethylaminoethyl methacrylate, tridecyl methacrylate and dimethylaminoethyl methacrylate, octadecyl methacrylate and dimethylaminoethyl methacrylate, lauryl methacrylate and p-dimethylaminomethylstyrene and the like. The preferred copolymer contains 90% by weight of lauryl methacrylate and 10% by weight of diethylaminoethyl methacrylate.
The mineral oil of the composition is characterized by having a 100°F. viscosity in the range of 30 to 1500 SUS. The choice of the particular mineral oil depends partially on the intended use of the composition. When the composition is to be added to a lubricating oil such as crankcase oil, the mineral oil will preferably have its 100°F. SUS viscosity in the range 50 to 600. When the composition is to be added to a hydrocarbon fuel oil, the mineral oil will preferably have a 100°F. viscosity in the range 30 to 60.
The substrates to which the composition of the invention can be added to provide antirust protection include lubricants and hydrocarbon fuels. Lubricants include greases, crankcase lubricants for internal combustion engines, turbine oils, hydraulic oils, gear oils and slushing oils, derived either from mineral oil or from various synthetic sources such as polymerized olefins and ester-type compositions.
The mineral oil-lubricant composition which has a major proportion of mineral oil of lubricating viscosity can also contain conventional additives such as viscosity index improvers, dispersants, pour point depressants, antioxidants, corrosion inhibitors, antiwear agents, rust inhibitors, antifoam agents, metal deactivators and the like. Hydrocarbon fuels include kerosene, diesel fuel, home heating oil and residual fuel. Hydrocarbon fuels can also contain additives commonly used therein such as dispersants, antioxidants, antirust agents, antiwear agents, and the like.
The compositions of the invention, particularly those having amino-containing ashless dispersants, are unexpectedly effective to inhibit rusting of ferrous metals in severely corroding acid environments. Such an environment exists, for example, in an automotive engine crankcase where water, hydrochloric acid, hydrobromic acid, sulfuric acid and organic acids are introduced in the blowby. These acids are formed in the combustion process from ethylene chloride, and ethylene dibromide, sulfur in the fuel, and incomplete combustion of the fuel components. Exposed to such conditions, ferrous metals rapidly corrode and rust. Neither guanidine carbonate alone nor the amine-containing dispersant alone provides adequate protection. It is surprising, therefore, that the combination does provide such good protection.
A particularly useful combination is that of the invention compositions with ashless amino nitrogen-containing sludge and deposit dispersants for lubricating oils. Such combination provides enhanced rust protection. Since certain of these ashless amino nitrogen-containing dispersant additives for lubricating oils are also the preferred dispersants for the present composition, the desirable combination can be made by incorporating additional amounts of such dispersants in the present compositions or by adding the present composition to lubricants already containing such dispersants.
The following Examples are meant to illustrate the invention.
EXAMPLE 1
Polyisobutenylsuccinic anhydride (30 g) (polyisobutenyl formula weight=1,400) was dissolved in a mixture of 90 g. of mineral oil of 125 SUS viscosity at 100°F. and 50 ml. of toluene. The oil solution was added to an homogenizer of 1 liter capacity, and, with the blender operating at the medium speed, 160 g. of a 25% aqueous solution of guanidine carbonate was added over a period of 2 to 3 minutes. The blender was then operated at high speed for 8 to 10 minutes to produce a stable emulsion. The emulsion was transferred to a distillation flask equipped with an agitator, a thermometer and a Dean-Stark water separator. The contents of the flask was heated to 50°-60°C. at 550 to 600 mm pressure to remove water azeotropically. After all of the water had been removed, toluene was removed at 70°C. and 700 mm pressure.
The product remaining was a dark amber liquid composition containing 25% by weight of dispersed guanidine carbonate, 19% by weight of the dispersing agent and 56% by weight of the mineral oil. The dispersion stored at room temperature for one week showed no sign of separation of guanidine carbonate. Electron microscopic examination of the dispersion showed that the average size of the guanidine carbonate particles was in the range 0.05 to 0.1 micron.
EXAMPLES 2 to 10
Using the procedure as described in Example 1 and the appropriate amounts of the guanidine carbonate solution and the mineral oil used in Example 1, stable guanidine carbonate dispersions were prepared as listed below. Particularly notable is the composition of Example 7 which provided a very clear dispersion.
TABLE ____________________________________________________________ ______________ Dispersing Guanidine Dispersing Mineral Example Agent Carbonate Agent Oil No. Used Wt.% Wt.% Wt.% ____________________________________________________________ ______________ 2 of Example 1 20 10 70 3 of Example 1 10 5 85 4 of Example 1 42 17 41 5 Polypropenylsuccinic 10 5 85 anhydride (1) 6 Polyisobutenylsuccinic 10 5 85 acid-sorbitol ester (2) 7 Polyisobutenylsuccinimide (3) 20 25 55 8 Polyisobutenylsuccimimide (3) 19 9 72 9 Polyisobutenylsuccinimide (3) 50 25 25 10 Polyisobutenyltetraethylene pentamine (4) 20 10 70 11 LM/DEAM Copolymer (5) 20 10 70 ____________________________________________________________ ______________ (1) Formula weight (FW) of polypropenyl group = 800 (2) Diester, FW of polyisobutenyl group = 1400 (3) Monoimide of tetraethylene pentamine, FW of polyisobutenyl group = 1400 (4) FW of polyisobutenyl group = 1200 (5) Copolymer of 90% (by weight) lauryl methacrylate and 10% (by weight) of diethylaminoethyl methacrylate.
EXAMPLE 12
The antirust properties of the invention composition in fuel oil were determined according to the modified method of ASTM D665, Procedure A, employing the composition of Example 7.
In this test, 300 ml. of No. 2 fuel oil containing the additive under test was stirred with 30 ml of distilled water at a temperature of 32°C. (90°F.) with a cylindrical steel specimen completely immersed therein. The test was carried out for 20 hours. At the conclusion of the test, the condition of the steel specimen was rated as rust-free, light rusting, moderate rusting or severe rusting. The results summarized below show that the novel composition when added to fuel oil in such amount to produce a total weight percent of guanidine carbonate of 0.5% was effective in preventing the rusting of steel.
______________________________________ Additive (Wt.%) Steel Specimen ______________________________________ None (Control Fuel Oil) Moderate rusting 0.1% Moderate rusting 0.5% Rust-free ______________________________________
EXAMPLE 13
The utility of the compositions of the present invention as ashless antirust additives was demonstrated in automotive crankcase lubricant. Two lubricating oil blends were prepared, each one containing viscosity index improver, ashless dispersant, antioxidant, and pour point depressant. The blends were identical except that one lubricating oil blend contained 0.5% of commerically used ashless antirust agent while the second blend contained enough guanidine carbonate composition of Example 8 to provide 1% of guanidine carbonate, by total weight.
Evaluation of rusting and corrosion characteristics of the blended oils was carried out according to industry-known Reference Sequence IIC Test Method. In this test a carefully cleaned and assembled engine is operated on a dynamometer test stand for a total of 32 hours under controlled conditions of engine speed, coolant temperature, and air-fuel ratio. At the completion of the test, the engine is disassembled and five parts, namely, lifter bodies, plungers, balls, relief valve plungers and push rods are each rated for rusting and corrosion by reference to a standard color chart wherein 10 is a perfect rating. The average value of the ratings of the parts characterizes the performance of the lubricating oil. The test results indicated that the composition of this invention improved the rusting and corrosion characteristics of lubricating oil since a rating of 7.3 was achieved by an oil blend containing the composition of this invention whereas a rating of only 4.7 was achieved employing a conventional ashless antirustant.
EXAMPLE 14
The utility of a composition of the present invention to protect ferrous metals under severe corrosion and rusting conditions was demonstrated in the following test. A 1020 mild steel billet, 1/8 × 1/2 × 6, inches, is placed in a 4 oz. glass bottle, and 30 ml of test oil blend is added to the bottle making sure that the entire billet is coated with the test oil. To the bottle, 3 ml of an aqueous acid solution containing 0.97 wt. % each of hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid and acetic acid as well as 0.02 wt. % of lead chloride and lead bromide is added. The bottle is closed, placed in an oven at 140° ± 5°F., then alternately rotated and allowed to stand for 4-hour periods for a total of 24 hours. At the conclusion of the test, the billet is removed from the bottle, rinsed free of oil and visually examined for rust and corrosion.
Three oil blends were prepared, each having a total base number (TBN) of 9.5. Total base number is determined by ASTM D2896 Method wherein the oil blend is titrated with perchloric acid in glacial acetic acid and is defined as the "quantity of perchloric acid expressed in terms of equivalent number of milligrams of potassium hydroxide required to neutralize all basic constituents in 1 g of sample" (ASTM D2896, 1973).
Blend A contained 9.22% by weight of the guanidine carbonate dispersion of Example 2(1.84 wt. % guanidine carbonate) TBN=9.5.
Blend B contained 11.5 wt. % of a polyisobutenylsuccinimide derived from tetraethylenepentamine. (Formula weight of polyisobutenyl group = 1,400) TBN = 9.5.
Blend C contained 1.12 wt. % of the guanidine carbonate used in Blend A and 4.5 wt. % of the polyisobutenylsuccinimide used in Blend B, TBN = 9.5.
Each of the blends A, B, and C was tested as described above and compared with the control oil (no additive). The results are summarized below.
______________________________________ Blend Condition of Billet ______________________________________ Control Oil Black A Brownish-Black B Black C Clean ______________________________________
The results demonstrate that Blend C, a combination of guanidine carbonate and an amine-containing dispersing agent, provides unexpected protection for ferrous metal in a severely corroding and rusting acid environment. Blend A is also somewhat effective in protecting the steel billet although not to the extent of Blend C.
1. Field of the Invention
This invention concerns guanidine carbonate stably dispersed with an ashless dispersing agent in mineral oil. The invention also concerns lubricant and hydrocarbon fuel compositions containing an effective rustinhibiting amount of the guanidine carbonate/dispersing agent/mineral oil composition.
2. Description of the Prior Art
Lubricants and fuels are usually in contact with ferrous metals during storage and use. Since moisture and air are unavoidably present, corrosion of the ferrous metals will occur. In many cases, rusting and corrosion conditions are created because of the intrusion of products of combustion and/or oxidation during use of the lubricants and fuels. Thus, in the operation of an internal combustion engine, engine blowby finds its way into the crankcase. Depending upon the fuel used, blowby can contribute corrosive acids to the crankcase.
The most practical method of controlling rust and corrosion by acids is to neutralize them. Thus, automotive crankcase lubricants generally contain metal-based neutralizing additives to minimize the harmful effects of the acids. In many applications, however, the presence of metal compounds in lubricants and hydrocarbon fuels is undesirable. One objection is that the lubricants and fuels show an increased susceptibility to oxidation which necessitates the use of higher levels of antioxidants. Another objection is that metal compounds lead to metal-containing deposits, which are undesirable. In internal combustion engines, the formation of such deposits interferes with efficient operation. In fuel oil burners, the accumulation of metalcontaining deposits on the various parts eventually result in poorer burner operation.
Metal-free rust inhibitors are known such as those based on long chain aliphatic amines, low molecular weight alkenylsuccinic acids, alkylthioacetic acids and substituted imidazolines. These metal-free rust inhibitors have not been entirely satisfactory because of limited effectiveness in the presence of acids. A need therefore exists for an effective, ashless, rust inhibitor for lubricants and hydrocarbon fuels that is useful in acidic environments. The novel compositions of this invention fulfill this need.
Guanidine carbonate, although known in the art, is not known to be a rust inhibitor. Nor is guanidine carbonate known in combination with mineral oil or dispersing agent. The present invention is based on the discovery that stable dispersions of guanidine carbonate in mineral oils using certain ashless dispersing agents provide effective antirust protection for lubricants and hydrocarbon fuels.
SUMMARY OF THE INVENTION
This invention concerns a stable dispersion of guanidine carbonate and ashless dispersing agent in mineral oil comprising, based on percent by total weight,
i. from 1 to 50% guanidine carbonate having a particle size in the range of from 0.001 to 0.1 micron,
ii. from 1 to 25% of at least one oil-soluble, ashless dispersing agent selected from the group consisting of
a. an aliphatic hydrocarbylsuccinic acid and derivatives thereof wherein the hydrocarbyl group has 30 to 200 carbon atoms, said derivative being selected from the group consisting of anhydride, ester, amide and aminoimide,
b. an aliphatic hydrocarbyl-substituted polyalkylene polyamine of the formula ##EQU1## wherein R is selected from the group consisting of hydrogen, lower alkyl, and aliphatic hydrocarbyl containing from 30 to 200 carbon atoms, at least one R being said hydrocarbyl group, R' is an alkylene radical having 2 to 3 carbon atoms and x is 0 to 5, and
c. a basic amino nitrogen-containing addition type copolymer containing in copolymerized form at least one polymerizable ethylenically unsaturated monomer, free of amino-nitrogen and containing an aliphatic hydrocarbyl chain of from 8 to 18 carbon atoms, and at least one polymerizable ethylenically unsaturated monomer containing basic amino nitrogen, said copolymer containing 0.1 to 3.0% by weight of said basic amino nitrogen, said copolymer having an inherent viscosity of 0.1 to 3.0 as determined at 0.1% weight volume concentration in benzene at 25°C., and
iii. from 25 to 98% of mineral oil having a 100°F. viscosity of from 30 to 1,500 SUS.
A preferred mineral oil dispersion contains from 10 to 42% of guanidine carbonate, from 5 to 25% of the dispersing agent and from 33 to 85% of the mineral oil, based on total weight. Preferred dispersing agents are the amino nitrogen-containing derivatives of hydrocarbylsuccinic acid.
The preferred ashless dispersing agents are characterized by the presence of one or more amino groups, which can be primary, secondary or tertiary amino groups. Thus, the preferred dispersants of the hydrocarbylsuccinic class (a) are those prepared with a polyalkylene polyamine, so as to contain at least one amino nitrogen. The hydrocarbyl-substituted polyalkylene polyamines (b) and the amino nitrogen-containing copolymeric dispersing agents (c) inherently contain one or more amino groups. These preferred dispersants are known in the art as additives for lubricating oils to disperse sludge and deposits.
The most preferred dispersing agent is the aminoimide derivative of hydrocarbylsuccinic acid wherein the hydrocarbyl has from 50 to 150 carbon atoms.
This invention also concerns compositions comprising a major proportion of a crankcase lubricant or fuel oil together with an effective rust inhibiting amount of the mineral oil dispersion. An "effective amount" of the mineral oil dispersion for inhibiting rust and corrosion will usually be such as to provide between about 0.5 to 5% of guanidine carbonate based on the total weight of the composition. It should be appreciated, however, that amounts of the mineral oil dispersion that provide more than 0.1% of guandine carbonate and less than 0.5% will provide some rust and corrosion-inhibiting properties, which properties will improve as the percentage of guanidine carbonate approaches the most effective range of 0.5 to 5%.
In this invention, by "stable dispersion" is meant one that shows little or no settling of guanidine carbonate when stored at 25°C. for one week.
DETAILS OF THE INVENTION
Guanidine carbonate is a carbonic acid salt, 2CH 5 N 3 .H 2 CO 3 , of guanidine which is a strong base. Guanidine carbonate can be prepared from guanidine and carbonic acid, but since guanidine is isolated only with difficulty, the carbonate is usually prepared by other known methods such as (1) heating dicyandiamide with ammonium carbonate or (2) heating cyanamide with ammonium carbonate.
Guanidine carbonate has a density of about 1.25 and melts at 241°C. It is soluble in water (45 g per 100 g water at 20°C. ) and is sparingly soluble in nonpolar organic liquids such as benzene, toluene, hexane, petroleum oils, and the like. To be an effective anitrustant in lubricants and fuel oils, guanidine carbonate must be provided in a suitable form. Since guanidine carbonate itself is insufficiently soluble in lubricants and hydrocarbon fuels to be effective, it is provided herein as a stable dispersion in mineral oil.
Stable dispersions of guanidine carbonate in mineral oil are obtained when the average particle size of guanidine carbonate is in the range of 0.001 to 0.1 micron, and certain ashless dispersing agents are used. When the average particle size is greater than about 0.1 micron, the dispersions are turbid and the guanidine carbonate settles out more rapidly than is desired. Thus, a stable dispersion has an average particle size of about 0.1 micron or less. The preferred particle size is about 0.05 micron or less.
Numerous methods are known for making solid guanidine carbonate finely divided. These methods include grinding and ball milling in liquid media with and without dispersing agents. These mechanical methods, however, are generally time consuming and costly. It has been found that stable dispersions of guanidine carbonate can be prepared by emulsifying an aqueous guanidine carbonate solution in a mineral oil in the presence of a suitable dispersing agent and (2) removing the water by azeotropic distillation at low temperature. By this process, guanidine carbonate stably dispersed in mineral oil and having an average particle size of about 0.05 micron is readily and economically prepared.
It is recognized that the stability of dispersions in general depends upon the particle size and the nature of the solid, the nature of the solid surface, the properties of the liquid medium and the characteristics of the dispersing agent. Dispersing agents are generally surface active agents characterized by having lipophilic and hydrophilic groups. Dispersing agents useful in the present invention should be oil-soluble, that is soluble to the extent of at least 0.05 g. per 100 g. of mineral oil. Oil-soluble dispersing agents generally contain at least one oil-solubilizing group, usually an alkyl or an alkenyl group of at least about 8 carbon atoms, more usually at least 12 carbon atoms. Since the dispersions of the invention will find applications in systems which are desirably ash-free or of very low ash, the dispersing agents should also be ash-free, that is, be substantially free of metallic components.
Since the preferred method for preparing stable guanidine carbonate dispersions includes the preparation of an emulsion of aqueous guanidine carbonate in mineral oil, it is desirable that the dispersing agent also be effective as an emulsifying agent in the above process. Those skilled in the art can easily determine the suitability of a surface active compound as an emulsifying agent and as a dispersing agent by a simple experiment as described in Example 1.
Dispersing agents useful in the present invention include high molecular weight hydrocarbylsuccinic acid and certain derivatives thereof. In the present context, the term "hydrocarbyl" includes alkyl and alkenyl groups. The hydrocarbylsuccinic acids are known in the art. They are prepared by the reaction of maleic anhydride with high molecular weight aliphatic olefins or with chlorinated high molecular weight aliphatic olefins to provide in each case a high molecular weight aliphatic hydrocarbylsuccinic anhydride. The high molecular weight olefin can be any olefin but is preferably a polymer of a C 3 to C 6 olefin, most preferably polypropylene or polyisobutylene. To provide oil solubility to the hydrocarbylsuccinic acid the olefin should contain at least 30 carbon atoms, preferably in the range of 50 to 200 carbon atoms. The hydrocarbylsuccinic anhydride obtained as described above can be (a) hydrolyzed to the acid, (b) condensed with a hydroxyl-containing compound such as sorbitol to provide either the mono- or diester, or (c) reacted with a polyalkylene polyamine having at least one amino hydrogen to provide derivatives which include corresponding substituted amides and imides.
The preferred dispersing agent is the imide reaction product of a hydrocarbylsuccinic acid and a substantially equimolar amount of a polyalkylene polyamine having a free NH 2 group and is represented by the formula ##EQU2## wherein R is an aliphatic hydrocarbyl group of 30 to 200 carbon atoms, R 1 is an alkylene group of 2 to 3 carbon atoms, R 2 and R 3 are selected from the group consisting of hydrogen and lower alkyl groups and x is 0 to 5.
The particularly preferred dispersing agents are imides of the above formula wherein R is a hydrocarbyl group of 50 to 150 carbon atoms, R 1 is an alkylene group of 2 carbon atoms, R 2 and R 3 are hydrogens and x is 4. Specific polyalkylene polyamines suitable for the preparation of such imides include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, 1,2-propylenediamine, 1,3-propylenediamine, di-1,2-propylenetriamine, tri-1,2-propylenetetramine, di-1,3-propylenetriamine, tri-1,3-propylenetetramine, N,N-dimethylethylenediamine, N,N-diethylpropylenediamine and the like. It is understood that while the above reaction product is described in terms of aminoimide, the product can also contain amides as well as amine carboxylates.
Another class of useful dispersing agents comprises certain high molecular weight oil-soluble aliphatic hydrocarbyl substituted polyamines. This type of dispersing agent is usually prepared by halogenation of a high molecular weight olefin such as polypropylene or polyisobutylene, to form an alkyl or alkenyl halide which is then used to alkylate a polyalkylene polyamine having a replaceable aminohydrogen. To provide sufficient oil solubility to the resulting hydrocarbylated polyalkylene polyamine, the olefin should contain at least about 30 carbon atoms preferably 50 to 200 carbon atoms. Depending upon the molar proportions and the reaction conditions, the resulting alkylated polyalkylene polyamine contains one or more high molecular weight hydrocarbyl group(s). This type of dispersing agent is represented by the formula ##EQU3## wherein R is selected from the group consisting of hydrogen, lower alkyl, and aliphatic hydrocarbyl containing from 30 to 200 carbon atoms, at least one R being said hydrocarbyl group, R' is an alkylene radical having 2-3 carbon atoms and x is 0 to 5. Usually only one of the R groups is hydrocarbyl. Polyalkylene polyamines suitable for the preparation of such hydrocarbyl derivatives include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, 1,2- and 1,3-propylenediamine, di-1,2- and 1,3-propylenetriamine, tri-1,2-propylenetetramine, N-methylethylenediamine, N-methyl-1,3-propylenediamine, N,N-dimethylethylenediamine, N,N-dimethyl-1,3-propylenediamine and the like.
Another useful class of ashless dispersing agent for the preparation of the novel compositions comprises basic nitrogen-containing addition type copolymers containing in copolymerized form at least one ethylenically unsaturated polymerizable monomer, free of amino nitrogen and containing an aliphatic hydrocarbyl chain of from 8 to 18 carbon atoms, and at least one ethylenically unsaturated polymerizable monomer containing basic amino nitrogen, the copolymer containing 0.1 to 3.0% by weight of the basic amino nitrogen and having an inherent viscosity of 0.1 to 3.0 as determined at 0.1% weight-volume concentration in benzene at 25°C.
Useful polymers include copolymers of lauryl methacrylate and diethylaminoethyl methacrylate, n-octyl methacrylate and diethylaminoethyl methacrylate, tridecyl methacrylate and dimethylaminoethyl methacrylate, octadecyl methacrylate and dimethylaminoethyl methacrylate, lauryl methacrylate and p-dimethylaminomethylstyrene and the like. The preferred copolymer contains 90% by weight of lauryl methacrylate and 10% by weight of diethylaminoethyl methacrylate.
The mineral oil of the composition is characterized by having a 100°F. viscosity in the range of 30 to 1500 SUS. The choice of the particular mineral oil depends partially on the intended use of the composition. When the composition is to be added to a lubricating oil such as crankcase oil, the mineral oil will preferably have its 100°F. SUS viscosity in the range 50 to 600. When the composition is to be added to a hydrocarbon fuel oil, the mineral oil will preferably have a 100°F. viscosity in the range 30 to 60.
The substrates to which the composition of the invention can be added to provide antirust protection include lubricants and hydrocarbon fuels. Lubricants include greases, crankcase lubricants for internal combustion engines, turbine oils, hydraulic oils, gear oils and slushing oils, derived either from mineral oil or from various synthetic sources such as polymerized olefins and ester-type compositions.
The mineral oil-lubricant composition which has a major proportion of mineral oil of lubricating viscosity can also contain conventional additives such as viscosity index improvers, dispersants, pour point depressants, antioxidants, corrosion inhibitors, antiwear agents, rust inhibitors, antifoam agents, metal deactivators and the like. Hydrocarbon fuels include kerosene, diesel fuel, home heating oil and residual fuel. Hydrocarbon fuels can also contain additives commonly used therein such as dispersants, antioxidants, antirust agents, antiwear agents, and the like.
The compositions of the invention, particularly those having amino-containing ashless dispersants, are unexpectedly effective to inhibit rusting of ferrous metals in severely corroding acid environments. Such an environment exists, for example, in an automotive engine crankcase where water, hydrochloric acid, hydrobromic acid, sulfuric acid and organic acids are introduced in the blowby. These acids are formed in the combustion process from ethylene chloride, and ethylene dibromide, sulfur in the fuel, and incomplete combustion of the fuel components. Exposed to such conditions, ferrous metals rapidly corrode and rust. Neither guanidine carbonate alone nor the amine-containing dispersant alone provides adequate protection. It is surprising, therefore, that the combination does provide such good protection.
A particularly useful combination is that of the invention compositions with ashless amino nitrogen-containing sludge and deposit dispersants for lubricating oils. Such combination provides enhanced rust protection. Since certain of these ashless amino nitrogen-containing dispersant additives for lubricating oils are also the preferred dispersants for the present composition, the desirable combination can be made by incorporating additional amounts of such dispersants in the present compositions or by adding the present composition to lubricants already containing such dispersants.
The following Examples are meant to illustrate the invention.
EXAMPLE 1
Polyisobutenylsuccinic anhydride (30 g) (polyisobutenyl formula weight=1,400) was dissolved in a mixture of 90 g. of mineral oil of 125 SUS viscosity at 100°F. and 50 ml. of toluene. The oil solution was added to an homogenizer of 1 liter capacity, and, with the blender operating at the medium speed, 160 g. of a 25% aqueous solution of guanidine carbonate was added over a period of 2 to 3 minutes. The blender was then operated at high speed for 8 to 10 minutes to produce a stable emulsion. The emulsion was transferred to a distillation flask equipped with an agitator, a thermometer and a Dean-Stark water separator. The contents of the flask was heated to 50°-60°C. at 550 to 600 mm pressure to remove water azeotropically. After all of the water had been removed, toluene was removed at 70°C. and 700 mm pressure.
The product remaining was a dark amber liquid composition containing 25% by weight of dispersed guanidine carbonate, 19% by weight of the dispersing agent and 56% by weight of the mineral oil. The dispersion stored at room temperature for one week showed no sign of separation of guanidine carbonate. Electron microscopic examination of the dispersion showed that the average size of the guanidine carbonate particles was in the range 0.05 to 0.1 micron.
EXAMPLES 2 to 10
Using the procedure as described in Example 1 and the appropriate amounts of the guanidine carbonate solution and the mineral oil used in Example 1, stable guanidine carbonate dispersions were prepared as listed below. Particularly notable is the composition of Example 7 which provided a very clear dispersion.
TABLE ____________________________________________________________ ______________ Dispersing Guanidine Dispersing Mineral Example Agent Carbonate Agent Oil No. Used Wt.% Wt.% Wt.% ____________________________________________________________ ______________ 2 of Example 1 20 10 70 3 of Example 1 10 5 85 4 of Example 1 42 17 41 5 Polypropenylsuccinic 10 5 85 anhydride (1) 6 Polyisobutenylsuccinic 10 5 85 acid-sorbitol ester (2) 7 Polyisobutenylsuccinimide (3) 20 25 55 8 Polyisobutenylsuccimimide (3) 19 9 72 9 Polyisobutenylsuccinimide (3) 50 25 25 10 Polyisobutenyltetraethylene pentamine (4) 20 10 70 11 LM/DEAM Copolymer (5) 20 10 70 ____________________________________________________________ ______________ (1) Formula weight (FW) of polypropenyl group = 800 (2) Diester, FW of polyisobutenyl group = 1400 (3) Monoimide of tetraethylene pentamine, FW of polyisobutenyl group = 1400 (4) FW of polyisobutenyl group = 1200 (5) Copolymer of 90% (by weight) lauryl methacrylate and 10% (by weight) of diethylaminoethyl methacrylate.
EXAMPLE 12
The antirust properties of the invention composition in fuel oil were determined according to the modified method of ASTM D665, Procedure A, employing the composition of Example 7.
In this test, 300 ml. of No. 2 fuel oil containing the additive under test was stirred with 30 ml of distilled water at a temperature of 32°C. (90°F.) with a cylindrical steel specimen completely immersed therein. The test was carried out for 20 hours. At the conclusion of the test, the condition of the steel specimen was rated as rust-free, light rusting, moderate rusting or severe rusting. The results summarized below show that the novel composition when added to fuel oil in such amount to produce a total weight percent of guanidine carbonate of 0.5% was effective in preventing the rusting of steel.
______________________________________ Additive (Wt.%) Steel Specimen ______________________________________ None (Control Fuel Oil) Moderate rusting 0.1% Moderate rusting 0.5% Rust-free ______________________________________
EXAMPLE 13
The utility of the compositions of the present invention as ashless antirust additives was demonstrated in automotive crankcase lubricant. Two lubricating oil blends were prepared, each one containing viscosity index improver, ashless dispersant, antioxidant, and pour point depressant. The blends were identical except that one lubricating oil blend contained 0.5% of commerically used ashless antirust agent while the second blend contained enough guanidine carbonate composition of Example 8 to provide 1% of guanidine carbonate, by total weight.
Evaluation of rusting and corrosion characteristics of the blended oils was carried out according to industry-known Reference Sequence IIC Test Method. In this test a carefully cleaned and assembled engine is operated on a dynamometer test stand for a total of 32 hours under controlled conditions of engine speed, coolant temperature, and air-fuel ratio. At the completion of the test, the engine is disassembled and five parts, namely, lifter bodies, plungers, balls, relief valve plungers and push rods are each rated for rusting and corrosion by reference to a standard color chart wherein 10 is a perfect rating. The average value of the ratings of the parts characterizes the performance of the lubricating oil. The test results indicated that the composition of this invention improved the rusting and corrosion characteristics of lubricating oil since a rating of 7.3 was achieved by an oil blend containing the composition of this invention whereas a rating of only 4.7 was achieved employing a conventional ashless antirustant.
EXAMPLE 14
The utility of a composition of the present invention to protect ferrous metals under severe corrosion and rusting conditions was demonstrated in the following test. A 1020 mild steel billet, 1/8 × 1/2 × 6, inches, is placed in a 4 oz. glass bottle, and 30 ml of test oil blend is added to the bottle making sure that the entire billet is coated with the test oil. To the bottle, 3 ml of an aqueous acid solution containing 0.97 wt. % each of hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid and acetic acid as well as 0.02 wt. % of lead chloride and lead bromide is added. The bottle is closed, placed in an oven at 140° ± 5°F., then alternately rotated and allowed to stand for 4-hour periods for a total of 24 hours. At the conclusion of the test, the billet is removed from the bottle, rinsed free of oil and visually examined for rust and corrosion.
Three oil blends were prepared, each having a total base number (TBN) of 9.5. Total base number is determined by ASTM D2896 Method wherein the oil blend is titrated with perchloric acid in glacial acetic acid and is defined as the "quantity of perchloric acid expressed in terms of equivalent number of milligrams of potassium hydroxide required to neutralize all basic constituents in 1 g of sample" (ASTM D2896, 1973).
Blend A contained 9.22% by weight of the guanidine carbonate dispersion of Example 2(1.84 wt. % guanidine carbonate) TBN=9.5.
Blend B contained 11.5 wt. % of a polyisobutenylsuccinimide derived from tetraethylenepentamine. (Formula weight of polyisobutenyl group = 1,400) TBN = 9.5.
Blend C contained 1.12 wt. % of the guanidine carbonate used in Blend A and 4.5 wt. % of the polyisobutenylsuccinimide used in Blend B, TBN = 9.5.
Each of the blends A, B, and C was tested as described above and compared with the control oil (no additive). The results are summarized below.
______________________________________ Blend Condition of Billet ______________________________________ Control Oil Black A Brownish-Black B Black C Clean ______________________________________
The results demonstrate that Blend C, a combination of guanidine carbonate and an amine-containing dispersing agent, provides unexpected protection for ferrous metal in a severely corroding and rusting acid environment. Blend A is also somewhat effective in protecting the steel billet although not to the extent of Blend C.