Field of the Invention

The present invention relates to a carboxylic acids based heavy-duty engine coolant/antifreeze composition, which may be used for corrosion protection of multi-metals exposed to engine coolants in automotive coolant circuit. The formulation also provides erosion protection to metals. The formulation is quite effective in providing corrosion protection even when mixed with high hardness water of upto 700ppm hardness measured in terms of

Background of the invention
This invention relates to the development of engine coolant composition for automotive cooling system applications.
Engine coolants are basically carefully designed combinations of corrosion inhibitors. These may be based on water as well as combined with alcohols etc. for providing antifreeze and boil over protection properties. Traditionally, alkylene glycols based engine coolants are most common through out the world. Various types of corrosion inhibitors are added to alkylene glycol to provide corrosion protection properties for mulit-metal system present in engine cooling system.
Formulations of engine coolants are quite complex due to multi-metal protection requirements. Today, operating severity of the automotive system is making engine coolant development more complex. Increased environmental awareness, restrictions on certain additive chemistries and different corrosion protection requirements of different automobile manufactures have also lead to the development of Original Equipment Manufacturer(OEM) specific engine coolant development. Moreover, Bureau of Indian Standard is also revising engine coolant specification, which requires engine coolant to pass corrosion test such as glassware corrosion test in 700 ppm hardness water measured in terms of CaCO3.

Keeping in view of all the above specific requirements of engine coolants, a developmental program was initiated. A Varity of corrosion inhibitors were used in different compositions for the development of disclosed engine coolant composition. Therefore, the present invention describes a composition of a heavy duty engine coolant composition.

Description of the Prior Art
Automobile industry has undergone tremendous changes in the last decades. Changes are mainly led by technology and environmental considerations. These changes have also reflected in automotive cooling system. Engine cooling system (radiator, engine block etc) consists of multi-metals including copper, solder, brass, cast iron steel and aluminium. Therefore, engine coolant should not only provide freeze protection, boil over protection but corrosion inhibition as well. The overall weight of automotive vehicles is being reduced to achieve better fuel efficiency. Lightweight aluminium and its alloys are being used for making radiator and its parts. For effective heat transfer, often the cooling system components are thin walled thus making these parts more prone to corrosion attack resulting in failure such as leakage etc. Moreover, in the absence of proper corrosion protection corrosion products can interfere with heat transfer efficacy of radiators, which may result in over heating of the engine leading to ultimate failure.
Traditionally, engine coolants are based on phosphate, silicate, borate or molybdate chemistry with ethylene gylcols. These traditional corrosion inhibitor chemistries provide excellent protection to cooling system still these have some disadvantages such as depletion with time, separation or gelling with high hardness water leading to formation of deposits etc. Besides these, a variety of inorganic inhibitors, carboxylic acids and their inorganic salts, azole compounds, glycols, alcohols, biocide, antifoam, dye etc. have been used for formulating engine coolants. As engine coolants are required to provide multi-metal corrosion protection, these can be formulated using a variety combination of chemicals and it is specific to the formulator. Most recent

compositions to some of the oldest of the engine coolant compositions, as reported in literature are listed below:
Coolant for rotary engine consisting propylene glycol monomethyl ether 25-70 and water 30-75 vol.% was reported by Dow Chemical Company, USA (US 3935115 ). Otsuka Chemical Company Limited, Japan has disclosed (US 4,219,433) a metal corrosion inhibitor comprising benzoic acid and/or a benzoate, a trialkanolamine, phosphoric acid and/or a phosphate and at least one selected from mercaptobenzotriazole, its salt, benzotriazole and tolytriazole, which can exhibit excellent anti-corrosive property to various metals for a long term and can be diluted with an aqueous liquor and can be employed in combination with usual anti-freezing agents. Single-phase antifreeze or coolant concentrations containing ethylene glycol, an amino siloxane, an aminosilane or both an amino siloxane and an aminosilane and a siloxane RnSiO(4-n)/2 (R = hydrocarbyl, n = 1-3), a metal salt of carboxysilane and pH buffer preferably comprising p- or 0-HOC6H4CO2H or both was reported by BASF Wyandotte Corp., USA (US 4241011 & US 4241012). The reported coolants when used in dilutions 30-90 wt.% water provides effective corrosion protection for internal combustion engines. The coolant composition protect against corrosion of metals and alloys in heat exchangers, especially in aluminium internal-combustion engine and radiator components. Olin Corporation, USA has disclosed (US 4,306,986) selected poly(oxyalkylated) pyrazoles of the formula ##STR1## wherein R and R' are independently selected from lower alkyl groups having 1 to 4 carbon atoms; each R" is individually selected from hydrogen and methyl; and n is from 2 to about 20. These compounds are shown to be effective corrosion inhibitors in corrosive liquids such as acids, antifreezes and hydraulic fluids. BASF Aktiengesellschaft has reported (US 4,324,675) a protective additive for radiators in coolants containing water where alkylene glycol-based coolants free of nitrites, amines, and phosphates are metal corrosion inhibited with at least one nucleus-substituted benzoic acid and at least one conventional corrosion inhibitor for metals. Norchem, Inc., USA disclosed (US 4545925)an improved heat-transfer fluid (or antifreeze) comprises 0.25 wt.%
phosphate, 0.025 wt.% nitrite and the balance a polyhydroxy alcohol (e.g., ethylene glycol) with no nitrate being present in the fluid. When the heat transfer fluid is to be used as an antifreeze compn. for internal combustion engines, it can also contain a corrosion inhibitor selected from 2-mercaptobenzotriazole, tolyltriazole, benzotriazole, and alkali metal salts and a buffering agent. An anticorrosive coolant for cooler boxes, having an eutectic melting point of .approximately 10 to -8.5 deg.C. and bubbling prevention stability that prevents deformation of aluminium vessels in which it is confined, consists of an aqueous solution of KHC03 16-18, a polyhydric ale. (propylene glycol or glycerol) 1-20, a saccharide (sucrose or fructose), and a corrosion inhibitor (alkali metal silicates, metasilicates, and/or polyphosphates) 0.01-0.05% is reported by Nippon Light Metal Company Limited., Japan (US 4655951). They have disclosed thet a coolant for making ice cream was prepared by adding 100 g propylene glycol into 1 kg aqueous17% KHCO3. The corrosion of aluminium alloys A 3004 and A 1050 in this coolant with and without corrosion inhibitors [Na4SiO4, a 1:1 (wt.) Na2SiO3-Na polyphosphate mixture., Na polyphosphate, or Na2SiO3 was determined. Results of a test for coolant containing a comparative phosphate inhibitor are also discolosed. Drew Chemical Corp., USA has reported (US 4961878)an aqueous composition for inhibiting the corrosion of metals in a closed iron and aluminium -contg. aq. cooling system comprises (a) 1-20 parts of an alkali metal nitrate; (b) 1-20 parts of an alkali metal silicate; (c) 1-20 parts of an amine oxide; (d) 1-10 parts of an acrylate or methacrylate polymer of about 1000-5000 mol. wt.; (e) 1-10 parts by weight of tolyltriazole; (f) 1-20 parts of an alkali metal molybdate; and the balance water. BASF Corporation, USA has disclosed(US 5,071,582) a coolant system cleaning solution containing an EDTA salt, a polyhydroxy mono- or dicarboxylic sugar acid, and a soluble nitrate salt are effective in removing scale, corrosion and solder bloom from cooling system. A corrosion-inhibited antifreeze/coolant composition containing cyclohexane acid(s) containing 80-99 liquid alcohol freezing point depressant (e.g., ethylene glycol) and 1-20 wt.% cyclohexane acid(s) as corrosion inhibitor suitable for cooling system of internal combustion engines is disclosed by Texaco Chemical Company, USA (US 5085791). Similarly, a Corrosion-inhibited antifreeze/coolant composition comprises

80-99 liquid alcohol freezing point depressant (e.g., ethylene glycol) and 1-20 wt.% 1 hydroxyl-substituted aromatic carboxylic acid(s) having the hydroxyl radical disposed proximate to the carboxyl radical (e.g., 2-hydroxybenzoic acid) suitable for cooling system of internal combustion engines is disclosed by Texaco Chemical Co., USA (US 5085793). An alkylene glycol-based, preferably propylene glycol-based, anti-corrosive antifreeze concentrate is composed of the glycol and small but effective amounts of borate, molybdate, tolyltriazole, phosphorous acid, and optionally nitrate and silicate is disclosed (US 5240631). In combination with water it forms an internal-combustion engine coolant, which meets all ASTM testing criteria. A Phosphate-free antifreeze formulation is disclosed by Arco Chemical Technology, L.P., USA (US 5422026). The disclosed formulation comprises an alkylene glycol, preferably propylene glycol, anti-corrosive antifreeze concentrate composed of the glycol and small but effective amounts of borate, sebacate, molybdate, mercaptobenzothiazole, nitrate, tolyltriazole and silicate. The concentrate is suitably combined with water to form an internal combustion engine coolant which meets all ASTM testing criteria. R.T. Vanderbilt Company, Inc., USA has reported (US 5637251) corrosion inhibitors and stabilizers based on organic amine salts for antifreeze solutions and engine coolants. They have reported that the aqueous antifreeze or coolant solutions with polyhydric alcohols contain as antioxidants and corrosion inhibitors 0.01-5.0% 2,5-dimercapto-1,3,4-thiadiazole (I) allylamine salt and of benzoic acid (II) allylamine salt at the l:ll mol ratio of 1:1 to 2:3. The polyhydric alcohol is typically ethylene glycol, and the resulting aq. soln. at 1:1 by vol. and contg. 1000 ppm I and II at a 2:3 ratio is resistant to Copper leaching in a 380-min test at 101 deg.C. and 90 psi 02. Ashland Inc., USA has reported a (US 5702631) an aqueous corrosion inhibitor formulations for addition to glycol-based automotive antifreeze/coolant compositions. The formulations consist of a corrosion-inhibiting effective amount of a polymeric polycarboxylate, which is selected from a secondary alcohol-modified polycarboxylic acid and a Na salt of an acrylic acid-maleic acid copolymer; a nitrate selected from NaNO3, KNO3, Mg(NO3)2, Ca(NO3)2, and/or LiNO3; an azole compd. selected from Na mercaptobenzothiazole and Na tolyltriazole; a silicate compd.; a transition metal compd. selected from Na molybdate hydrate,

Mo2O3, silicoheteropolymolybdates, and/or phosphoroheteropolymolybdates; and a phosphate. Prestone Products Corporation has disclosed (US 5,742,436) organic acid corrosion inhibitors for use in antifreeze coolant compositions. The corrosion inhibitors comprise a C8 mono carboxylic acid component, or isomers and/or salts thereof, and a neo-decanoic acid, or isomers and /or salts thereof. The corrosion inhibitors of this invention provide improved corrosion protection to metal surfaces as compared to conventional inhibitors and provide surprisingly improved corrosion protection as compared to inhibitors containing only a single mono-carboxylic acid component. Shell Oil Company has disclosed (US 5,997,763) an antifreeze concentrate made by adding together at least an alkylene glycol, an effective corrosion inhibiting amount, or more, of an unsubstituted benzoic acid and an effective corrosion inhibiting amount, or more, of a C7-C14 monocarboxylic acid. The disclosed formulation is particularly effective in coolants which are free from borates, primary and secondary amines, phosphates, silicates, as well as those coolants which are free of p-tertbutyl benzoic acid. Ashland, Inc., USA has disclosed (US 6,126,852) a monobasic carboxylic acid, which is used with low levels of molybdate and a triazole compd. to produce a well balanced corrosion inhibiting formulation with very low solids to minimize potential deposits and exhibit surprising long life characteristics in engine coolant applications. A corrosion- and scale-inhibiting aqueous antifreeze coolants containing polymeric polycarboxylic acids and salts were also disclosed by Ashland Inc., USA (US 6228283). The antifreeze composion which also inhibits mineral scale formation, consists of a polymeric polycarboxylic acid, based on polyacrylic acid or a sodium polyacrylate with average molecular weight 300-12,000, 0.001-10, an inorganic nitrate salt (i.e., NaNO3, KNO3, Mg(N03)2, Ca(NO3)2, and LiNO3 0.001-10, an inorganic nitrite salt (i.e., NaNO2, KN02, Mg(NO2)2, Ca(NO2)2, and LiNO2 0.001-10, an azole 0.001-10, a stabilized polysilicate 0.001-10, an inorganic phosphate 0.001-10, and a transition metal salt 0.001-10 wt.%, with the balance being ethylene glycol, diethylene glycol, propylene glycol, and C1-3-alcs. Suitable inorg. phosphates include K2HPO4, Na2HPO4, KH2PO4, K3PO4, NaH2PO4, and Na3PO4; suitable transition metal compds. include Na2MoO4.2H2O, MoO3, silicoheteropolymolybdates, phosphoroheterpolymolybdates,

Na2MoO4, K2MoO4, Li2Mo04, (NH4)2Mo04, (NH4)2Mo2O7, and (NH4)6Mo7O24. Suitable azoles include Na mercaptobenzothiazole, Na tolyltriazole, pyrazoles, imidazoles, isooxazoles, isothiazoles, thiazoles, thiadiazole, 1,2,3-benzotriazole, 1,2,3-tolyltriazole, Na 2-mercaptobenzothiazole, and Na 2-mercaptobenzimidazole. Suitable stabilized silicate copolymers include alkali siliconate silylalkylphosphonates, arylalkyl silicon sulfonate-silicates and sulfosiloxane-silicates. Other additives can be a dye, a biocide, and a bittering agent. The formulations are especially suitable for diesel engines. Ashland Inc., USA has also disclosed (US 6290870) a monocarboxylic acid-containing glycol-based anticorrosion antifreeze composition for diesel engines. Antifreeze composition consists of a water-soluble liquid alcohol as a freezing point depressant, a monobasic carboxylic acid or alkali salt 0.1-10, an inorganic nitrite salt 0.001-10, an organic azole corrosion inhibitor 0.01-5.0, an inorg. molybdate 0.001-5.0, a silicone-silicate copolymer 0.01-10, and poly(vinylpyrrolidone) 0.001-5.0 wt.%. The inorganic nitrites and nitrates are preferably selected from the Na, K, Mg, Ca, and Li salts. The azoles are selected from tolyltriazole, hydrocarbyl triazole, benzotriazole, mercaptobenzothiazole, pyrazoles, isooxazoles, isothiazoles, thiazoles, thiadiazole salts, 1,2,3-benzotriazole, 1,2,3-tolyltriazole, and Na 2-mercaptobenzothiazole. Suitable inorg. molybdates are Na molybdate, K molybdate, Li molybdate, ammonium molybdate, ammonium dimolybdate, MoO3, heteropolymolybdates, disodium molybdate dihydrate, silicoheteropolymolybdates, and phosphoheteropolymolybdates. The monocarboxylic acids are typically C3-16-carboxylic (or fatty) acids (or the corresponding alkali metal salts), esp. hexanoic, heptanoic, isoheptanoic, octanoic, 2-ethylhexanoic, nonanoic, decanoic, undecanoic, dodecanoic, and neodecanoic acids. Prestone Products Corporation has disclosed (US 6,391,257) an antifreeze compositions comprising carboxylic acid and cyclohexenoic acid corrosion inhibitors. The compositions comprise from about 90% to about 99.89% by weight of a liquid alcohol which functions as a freezing point depressant, or mixture thereof from about 0.1% to about 5.5% by weight of a carboxylic acid selected from the group consisting of saturated and unsaturated aliphatic, and aromatic, mono-, di- and tri-carboxylic acids, and salts and isomers thereof, and any mixture thereof, and from about 0.1% to about

2% by weight of a cyclohexenoic acid, or salt, isomer or mixture thereof, having the formula: ##STR1## wherein each of R 1, R2 and R3 is, independently, selected from the group consisting of H, OH, COOH, C1 to C10 alkyl groups, glycol esters, or combinations thereof. The antifreeze compositions provide surprisingly improved corrosion protection to aluminum surfaces, and in particular protection from cavitation-erosion corrosion, as compared to compositions containing only the carboxylic acid component or the cyclohexenoic acid component alone. Texaco Inc. , USA has reported (US 6,398,984) corrosion inhibitors and synergistic inhibitor combinations for the protection of light metals in heat-transfer fluids and engine coolants. They have disclosed that corrosion protection of magnesium and aluminum alloys in engine coolants and heat-exchange fluids is achieved by the use of a select group of aliphatic and aromatic carboxylate acids or the alkaline metal, ammonium or amine salts thereof in combination with a fluoride and/or a fluorocarboxylic acid or salt thereof. These compositions have been found to significantly improve the high temperature magnesium corrosion protection properties of coolants, and are of use in automobile engine coolant systems. BetzDearborn, Inc., USA has disclosed (US 6,585,933) a method and composition for controlling corrosion of metals, particularly ferrous-based metals in contact with aqueous systems is disclosed, which includes treating industrial waters with a combination of a tetrazolium salt of the general formula: ##STR1## where R1, R2 and R3 may be various organic or inorganic substitutents, where n may be 1 or 2, and at least one other aqueous system treatment material. Ashland Inc., USA has disclosed (US 6,676,847) a carboxylic acid based antifreeze coolant formulation for heavy duty applications such as for diesel engines which may be used for inhibition and prevention erosion and corrosion of aluminum and the corrosion of other metals exposed to an aqueous liquid in automotive coolant systems. The formulation further inhibits mineral scale. It may be packaged as an ethylene glycol based additive for use in new engines or in a concentrated inhibition package as an additive as for re-inhibition of used coolant. The combination of a mixture of ethylene or propylene glycol, a monobasic carboxylic organic acid, azoles, low levels of molybdates, a nitrite salt and/or nitrate salt and/or siloxane stabilized silicate, and combinations thereof,

polyvinylpyrrolidone, provide a synergistic protective effect against the cavitation corrosion of aluminum in aqueous liquids reducing the corrosion rate and is effective at relatively low concentrations and varying pH ranges. Texaco USA has developed (US 6,676, 848) a corrosion inhibitors and synergistic inhibitor combinations for protection of magnesium and aluminum alloys in engine coolants and heat-exchange fluids is achieved by the use of a select group of aliphatic and aromatic carboxylate acids or the alkaline metal, ammonium or amine salts thereof in combination with a fluoride and/or a fluorocarboxylic acid or salt thereof. These compositions have been found to significantly improve the high temperature magnesium corrosion protection properties of coolants, and are of use in automobile engine coolant systems. Fleetguard Inc., USA has disclosed (US 6,733,687) a supplemental coolant additive for use in cooling systems, for example, in diesel engine cooling systems. The supplemental coolant additive includes a C4 to C6 dicarboxylic acid, preferably adipic acid, and optionally a C9 to C12 aliphatic dicarboxylic acid an aromatic monocarboxylic acid, an aromatic dicarboxylic acid and salts of these acids. The supplemental coolant additive can also include a variety of other additives including molybdate salts, nitrate salts, nitrite salts, silicate salts and buffering agents. The supplemental coolant additive is preferably provided as a solid additive or a liquid concentrate. The supplemental coolant additive is preferably added to the liquid coolant over time to provide increased coolant life. Further the supplemental coolant additive provides enhanced anti-corrosion protection in cooling systems that include hard water. Diversified Natural Products Inc., USA has disclosed (US 6,846, 431) an environmentally benign, non-toxic, non-corrosive liquid engine coolant/antifreeze which is produced from renewable resources, and which is biodegradable, non-toxic, and is non-corrosive to engines. The disclosed antifreeze composition for use as an engine coolant in a dilute or concentrate form comprises a water soluble salt of succinic acid, a water soluble salt of acetic acid, ethanol, and water, wherein the composition has a freezing point of greater than -30.degree. C. in the engine.

As can be seen form the prior art that a variety of corrosion inhibitors including combinations of organic and/or inorganic inhibitors have been used successfully for making antifreeze/engine coolants. However, none of the references have provided a composition for corrosion protection of multi metal cooling system of engine in the presence of high hardness water of about 700 ppm hardness measured in terms of CaCO3 as claimed by the applicant inventor's.
Efforts have therefore, made to develop a heavy-duty engine coolant for automotive application.

The Object of the Invention
The object of the present invention is to propose an engine coolant composition, which provides excellent corrosion protection, when diluted with water, for engine cooling system.
Another object of this invention is to propose a engine coolant composition that gives corrosion protection in hard water containing 700 ppm Calcium Sulphate solution when measured in term of CaCOs.
Yet another object of this invention is to propose a engine composition, which can give excellent antifreeze properties.
A further object of this invention is to propose a engine coolant composition which when used in engine cooling system, provides excellent boil-over protection.
A still further object of this invention is to propose a engine coolant composition which provides long term corrosion protection to the cooling system.

Yet another object of this invention is to propose an engine coolant composition, which provides excellent hard water stability.
A further object of this invention is to propose an engine coolant composition which is based on organic acid chemistry.
Another object of this invention is to propose an engine coolant composition, which does not contain amines, phosphates, nitrites, silicates and molybdates.
A still further object of this invention is to propose an engine coolant composition, which is also suitable for heavy duty diesel engine application.
A still further object of this invention is to propose an engine coolant concentrate which when diluted with distilled water from 20% volume to 50% volume, provides excellent corrosion protection to engine cooling system.

Summary of the Invention

The engine coolant composition disclosed in the present invention is an optimised combination of alkylene glycol selected from ethylene glycol, propylene glycol or commercially available mixtures largely ethylene glycol and a small amount of diethylene glycol and carefully selected combination of an alkali metal nitrate, along with a combination of poly carboxylic acid substituted triazine and/ sodium/potassium salt, mono and/or dicarboxylic acids and at least one conventional corrosion inhibitor selected from aromatic carboxylic acids and also a triazole compound, dye and alkali metal hydroxides for pH and/or buffering action. Some amount of water is also added to get better solubility of additives.
The engine coolant composition provides multi-metal corrosion protection in corrosion tests conducted in laboratory. It also provides excellent corrosion protection in the

presence of 700 ppm hardness water and also dilutions as low as 20%. Excellent corrosion protection was also observed for more than 1100 hrs glassware corrosion test conducted at 20 % dilution in 700ppm hardness water.

Detailed Description of the Invention
The engine coolant composition of the present invention comprises: 82.1 to 94.3 wt% of alkylene glycol, 1.0 to 3.4 wt% of poly carboxylic acid substituted triazine and/ sodium/potassium salt, 0.5 to 2.5 wt% of dicarboxylic acid , 0.2 to 2.5 wt% of alkali metal nitrate, 0.69 to 3.57 wt% of PH control agent, 2.0 to 6.5 wt% of conventional corrosion inhibitor selected from aromatic carboxylic acids, 0.01 to 0.05 wt% of antifoam, 0.1 to 0.5 wt% of triazole inhibitor, 0.01 to 0.03 wt% of dye and 0.5 to 5.0 wt% of water to get the desired multi-metal corrosion protection in high hardness water along with good antifreeze and high boil over characteristics.
The process of evaluating and identifying the composition of engine coolant is further described below:
EXPERIMENTAL EVALUATION
In order to establish the suitability of the developed engine coolant composition, a number of laboratory compositions of engine coolants using various components comprising alkylene glycol, carboxylic acids, nitrate of alkali metals, triazole inhibitor, antifoam, dye etc. were prepared and evaluated for pH, reserve alkalinity and for multi-metal corrosion protection in glassware corrosion tests.
It can be appreciated that only combination of alkylene glycol and carboxylic acids does not provide desired engine coolant characteristics. Therefore, an optimised combination of the alkylene glycol, carboxylic acids, other corrosion inhibitors, anti-foam agent etc., is required to get engine coolant formulation with specific characteristics..

In order to make different engine coolant compositions, the alkylene glycol was taken in a beaker and heated to 35 to 40 deg.C and different combinations of carboxylic acids/corrosion inhibitors were added one by one after complete dissolution of previous ingredient. pH of the solution is adjusted in the range of 7.0 to 10.0 using solution of caustic or potash in water. After adjusting pH, silicon compound and dyes are added. The clear blends were evaluated for metal corrosion property in glassware corrosion (ASTM D 1384). and aluminium corrosion (ASTM D 4340) tests). The formulation(s) meeting the requirements of ASTM D 1384 and ASTM D 4340 tests were evaluated for complete physico-chemical tests. The formulation meeting all the above requirements was subjected for circulatory corrosion tests as per ASTM D 2570 test.
The following examples are presented to illustrate the claimed invention and are not intended to be otherwise limiting.
Chemical names of the compounds are as follows
(Table Removed)
Example 1
Various engine coolant compositions comprising various combinations of aromatic carboxylic acid, cinnamic acid, dicarboxylic acid, Poly Carboxylic acid substituted triazine, pH control agent, alkali nitrate, triazole inhibitor, antifoam, water and dye. Test results are given below:
(Table Removed)

# All the components were taken in percentage weight
(*) Corrosive water as per JIS K 22341ASTM D1384 test methods
(**) + sign indicate weight loss
Example 2
In order to get optimum performance of the engine coolant compositions in glassware corrosion test and aluminium corrosion tests, more blends with different compositions were developed and tested. Test results are given below:
(Table Removed)
# All the components were taken in percentage weight
(*) Corrosive water as per JIS K 22341ASTM D1384 test methods
(**) + sign indicate weight loss
It can be seen form the test results given in example-2 that a heavy-duty engine coolant composition can be obtained when the concentration of alkylene glycol is 87.5 to 93 wt%, concentration of water is 2.0 to 3.8 wt%, concentration of poly carboxylic acid substituted triazine and/ or sodium/potassium salt is 1.4 to 2.2 wt%, concentration of dicarboxylic acid is 0.9 to 1.5 wt%, concentration of conventional corrosion inhibitor i.e. aromatic carboxylic acid is 3.5 to 4.5 wt%, concentration of alkali metal nitrate is 0.4 to 0.7 wt%, triazole inhibitor is 0.18 to 0.3 wt%, concentration of antifoam is 0.02 to 0.04wt%, concentration of dye is 0.01 to 0.02wt% and the concentration of pH control agent is 1.0 to 1.50wt%.
It can also be seen from the examples that the heavy-duty engine coolant composition provide excellent corrosion protection to copper, solder brass, steel, cast iron and cast aluminium in glassware corrosion test even with water of 700ppm hardness when

measured in terms of CaCO3. The composition is quiet effective in the range of 20% to 50% volume of its dilution with water of 700ppm hardness.
The composition so obtained was also evaluated in glassware corrosion test for 1130+2 hours at 20% dilution in 700 ppm hardness water and was able to provide excellent corrosion protection to all metals. Same composition was also evaluated in circulatory corrosion test as per ASTM D 2570 test at 20% dilution in 700 ppm hardness water and it was able to provide excellent corrosion protection to all the six metals viz. copper solder, brass, steel, cast iron and cast aluminium.
Specific compositions, methods, or embodiments discussed are intended to be only illustrative of the invention disclosed by this specification. Variation on these compositions, methods, or embodiments are readily apparent to a person of skill in the art based upon the teachings of this specification and are therefore intended to be included as part of the inventions disclosed herein.
The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood there from, for modification will become obvious to those skilled in the art upon reading this disclosure and may be made upon departing from the spirit of the invention and scope of the appended claims. Accordingly, this invention is not intended to be limited by the specific exemplifications presented hereinabove. Rather, what is intended to be covered is within the spirit and scope of the appended claims.

We Claim:
1. A heavy duty engine coolant composition for corrosion protection of multi-metal
automotive coolant system comprising -:
82.1 to 94.3 wt% of alkylene glycol, 1.0 to 3.4 wt% of poly carboxylic acid substituted triazine and/or sodium/potassium salt, 0.5 to 2.5 wt% of dicarboxylic acid , 0.2 to 2.5 wt% of alkali metal nitrate, 0.69 to 3.57 wt% of PH control agent, 2.0 to 6.5 wt% of conventional corrosion inhibitor selected from aromatic carboxylic acids, 0.01 to 0.05 wt% of antifoam, 0.1 to 0.5 wt% of triazole inhibitor, 0.01 to 0.03 wt% of dye and 0.5 to 5.0 wt% of water.
2. A composition as claimed in claim 1 wherein the concentration of alkylene
glycol is preferably 87.5 to 93 wt%.
3. A composition as claimed in claim 1 wherein the concentration of water is
preferably 2.0 to 3.8 wt%.
4. A composition as claimed in claim 1 wherein the concentration of poly
carboxylic acid substituted triazine and/ or sodium/potassium salt is
preferably 1.4 to 2.2 wt%.
5. A composition as claimed in claim 1 wherein the concentration of
dicarboxylic acid is preferably 0.9 to 1.5 wt%.

6. A composition as claimed in claim 1 wherein the concentration
conventional corrosion inhibitor selected from aromatic carboxylic acids
is preferably 3.5 to 4.5 wt%.
7. A composition as claimed in claim 1 wherein the concentration of alkali
metal nitrate is preferably 0.4 to 0.7 wt%.
8. A composition as claimed in claim 1 wherein the concentration of triazole
inhibitor is preferably 0.18 to 0.3 wt%.
9. A composition as claimed in claim 1 wherein the concentration of antifoam
is preferably 0.02 to 0.04wt%
10. A composition as claimed in claim 1 wherein the concentration of dye is
preferably 0.01 to 0.02wt%.
11. A composition as claimed in claim 1 wherein the concentration of pH
control agent is preferably 1.0 to 1.50wt%.
12. A composition as claimed in claim 1 wherein the said alkali metal nitrate is
selected from the nitrates of lithium, sodium and potassium.
13. A composition as claimed in claim 1 wherein the said pH control agent is
selected from the hydroxides of sodium or potassium.

14. A composition as claimed in claim 1 wherein the 20% to 50% volume of its
dilution with water provide excellent corrosion protection to copper, solder
brass, steel, cast iron and cast aluminium in glassware corrosion test.
15. A composition as claimed in claim 1 wherein the 20% to 50% volume of its
dilution with water provide excellent corrosion protection to copper, solder
brass, steel, cast iron and cast aluminium in glassware corrosion test even
with water of 700ppm hardness when measured in terms of CaCOa.
16. A composition as claimed in claim 1 wherein the disclosed composition is
particularly suitable for diesel engines.

17. A heavy duty engine coolant composition for corrosion protection of multi-metal automotive coolant system substantially as herein described with references to the foregoing description, examples and tables.