MXPA98007443A - Refrigerated inhibitor concentrate - Google Patents

Abstract

The present invention discloses a corrosion inhibitor concentrate, and a method for the preparation thereof, which can be formulated free of nitrites, amines and phosphates. The corrosion inhibitor concentrate is a synergistic combination of "individual part" of inhibitors, stabilizers and antifoaming agents, useful for the re-inhibition of antifreeze / recirculated refrigerant. The corrosion inhibitor concentrate is effective in inhibiting corrosion in refrigerants through a broad scale of glycol quality. The inhibitor concentrate comprises amounts of water, triazole, alkali metal hydroxide, borate, alkali metal silicate, silicate stabilizer and antifoam agent

Description

CONCENTRATE REFRIGERANT INHIBI DOR DESCRIPTION OF THE INVENTION Anti-freeze compositions are additives commonly used to reduce the freezing point or increase the boiling point of water. Said additives mainly consist of one or more components based on alcohol and / or glycol. Ethylene glycol is the most commonly used antifreeze component. When added to an internal combustion engine cooling system, it offers the engine coolant contained therein and freeze and anti-boil protection (typically between -37 ° C to 1 15 ° C, depending on the pressure) . It is known that from the moment the antifreeze is added to an aqueous-based motor cooling system, the glycol-based and / or alcohol-based components of the antifreeze begin to chemically break the various organic acids and aldehydes. The organic acids produced are usually glycolic, formic acids and to a lesser oxalic degree. The break is confirmed by the pH of a traditional phosphate / borate-based engine coolant composition that decreases from a pH of 10.0 to low at a pH of 7.0. As p H is reduced, corrosion proceeds at a very fast rate. Less noble metals, such as steel, iron and cast iron, are the first to go to solution via the corrosion process. A low pH also causes pitting of the aluminum, which easily weakens the wall thickness of the respective components. Also, copper corrodes and goes to solution. The zinc used to strengthen the silver solder in radiators leaches and weakens the weld so that leaks develop. The remaining impurities commonly found are products, mainly corrosion, suspended particulate matter (metal oxides), dust, cracks, and hard water sai deposits. To combat the above problems, the refrigerant compositions in circulation generally include various known corrosion inhibitors. The inhibitors are added either directly to the refrigerant or are included in an antifreeze solution added thereto, which is sold as "inhibited antifreeze". However, it has been found that a number of commonly accepted corrosion inhibitors have problems. For example, it is believed that amines and nitrites form dangerous nitrosamines when used together. In addition, it has been found that phosphates are harmful to the environment if the spent refrigerant is deposited via wastewater treatment systems. Therefore, it is generally desirable to have coolants containing corrosion inhibitors minus nitrites, amine and phosphates. But there is another additional problem in that, over a period of time, typical corrosion inhibitors such as phosphates, silicates, borates, nitrites, nitrates, azoles, and molybdates are consumed, which further contributes to the corrosion effect in the engine system. In addition, over time, the initial refrigerant accumulates dissolved impurities and suspended particulate matter and loses the effective corrosion inhibiting and freezing protection capabilities. For the purpose of supplying one or more beneficial cooling additives, which have been consumed during normal use, supplemental cooling additives (SCAs) are generally added to the circulating refrigerants, which have been of long-term use. Mainly, the SCAs are used with heavy duty diesel applications to stop the bite of the wet sleeve liner (cavitation-corrosion) as well as to avoid the development of deposits and scale in the cooling system. Several compositions of SCA are described in the following patents of E.U.A. Nos .: 3,231, 501; 3, 962, 109; 4,242,214; 4,455,248; 4,564,465; 4, 587.028; and 4,588,513. Typically, said SCAs are added directly to the refrigerant in the form of a concentrated aqueous solution of the active components of the SCA. For example, diesel truck drivers can be taught to periodically add defined amounts of such solutions to the refrigerant systems of their equipment. In certain systems, a solid ACS is included in a circulating refrigerant filter (see, for example, U.S. Patent No. 3,645,402). Although SCAs can be used to neutralize degradation products that accumulate in the system, these additives are mainly alkaline and include corrosion inhibitors, dispersants, polymers and sequestering agents. Generally, however, said compounds do not: restore depleted antifreeze components (i.e., glycol and / or alcohol); remove the impurities; increase the coolant protection or raise the boiling point of the degraded or used coolant; or inhibit further degradation of the glycol derivative. Therefore, it is generally an accepted practice to remove, replace, and dispose of the refrigerant composition after a specified period of time. However, in many places, antifreeze is considered hazardous and wasteful and several regulations are applied regarding its disposal. In an effort to protect the environment, and as an alternative to waste, the industry continues to develop methods to recycle and reuse such waste products. Examples of said recirculation of engine coolants are described in the patents of E.U.A. Nos. 4,946,595; 4, 791, 890; 4,793,403; and 5,422.008. However, the re-inhibition of recirculated antifreeze / coolant formulations presents unique complexities, which are substantially different from the addition of inhibitors to virgin grade antifreeze / coolant formulations. For example, the tendency to foaming of the recirculated glycol can be 20 times greater than that observed for the virgin fiber grade ethylene glycol. The unique complexities are due to the chemical and physical characteristics of the recirculated antifreeze / coolant. Generally, recirculated glycol / water solutions contain hard water ions, metal salts, glycol degradation products, and other destabilizing species, which may render the effectiveness of corrosion inhibitors and additives when mixed with the concentrate inhibitor. The recirculated glycol of the engine coolant or spent antifreeze contains heavy metals such as iron, lead, nickel, zinc, and copper. Heavy metals react with and form insoluble salts with corrosion inhibitor anions such as phosphates, borates, silicates and molybdates. The precipitation causes increased abrasion of the internal parts of the cooling system, particularly the water pump. Therefore, there is a need for compositions suitable for the supply of antifreeze components, such as inhibitors, for the recirculated product. This invention describes a corrosion inhibitor concentrate which can be, if desired, formulated free of nitrites, nitrates, amines and phosphates. By "concentrate" is meant that the composition is substantially free of alcohol / glycol-based freezing suppressants such as ethylene glycol and propylene glycol. The inhibitor concentrate can subsequently be mixed with the desired freezing suppressant in order to formulate a corrosion inhibited refrigerant composition. The inhibitor concentrate is a synergistic combination of "individual part" (ie, it is not necessary to store specific components separately before use), of inhibitors, stabilizers, and anti-foaming agents, useful for reinhibition of the recirculated antifreeze / coolant, which are effective through a wide quality scale of recirculated glycol. In addition, due to the synergy between the essential components of the inhibitor concentrate, the inhibitor concentrate also demonstrates a good storage life. The inhibitor concentrate comprises specific amounts of water, triazole, alkali metal hydroxide, borate, alkali metal silicate, silicate stabilizer and antifoaming agent. A further aspect of this invention includes a process for preparing the inhibitor concentrate. The corrosion inhibitor concentrate of this invention requires an amount of water of 20, preferably 25 to 90, preferably 40% by weight (hereinafter "% / p"). Unless otherwise stated, all references to% / p must mean the percentage by weight of the component observed based on a total weight of the corrosion inhibitor concentrate when formulated completely as the concentrate. Preferably, the water is substantially of metal ions, chlorides, suifatos, carbonates, or other unwanted contaminants. Most preferably, the water is distilled, deionized and / or an equivalent thereof. A second component of this invention is a triazole. The triazole is provided in an amount of 1, preferably 4 to 10, preferably 6% / p. The triazole is preferably a tolitriazole or its alkali metal salt, such as sodium tolitriazole. An advantageous means to provide the triazole is in solution with water. For example, a preferred method is to form a solution of a sodium tolitriazole at 50% by volume in water. This solution can then be added to the corrosion inhibitor concentrate. A third component of this invention is an alkali metal hydroxide. The alkali metal hydroxide is provided in an amount sufficient to provide an acceptable pH in the resulting refrigerant formulation after the corrosion inhibitor has been diluted with glycol. The preferred pH in the resulting refrigerant formulation is 10 to 11. Therefore, it is desirable that the amount of alkali metal hydroxide in the corrosion inhibitor concentrate be sufficient to provide a pH of more than 10 and preferably 11 to 14 in the concentrate. Advantageous alkali metals for use in the alkali metal hydroxide are sodium, potassium, and mixtures thereof. Potassium metal hydroxide should be used for pH control if sodium metal salts are to be used for the addition of other components. This is because the solubility of a sodium ion concentrate is less than that of the concentrated potassium or potassium and sodium compound. A lower solubility will impact the stability of the concentrate. A preferred means for providing the alkali metal hydroxide is in solution with water. For example, a desirable method is to form a 45% by volume solution of potassium hydroxide in water. This solution can then be added to the corrosion inhibitor concentrate. A fourth required component of this invention is a borate. The borate is provided in an amount (calculated as B2O3) of 3, preferably 12, to 25, preferably 22% by weight. The borate is preferably provided to the concentrate of a borate source selected from boric acid, alkali metal borate, and alkali metal metaborate. The alkali metal is preferably selected from sodium, potassium and mixtures thereof. The most preferred borate is sodium tetraborate pentahydrate (Na2B407 «5H20). A fifth component of this invention is an alkali metal silicate. The alkali metal silicate is provided in an amount (calculated as an equivalent amount of the silicate in sodium metasilicate pentahydrate) of 1, preferably 3.5 to 15, preferably 10% by weight. The alkali metal is preferably selected from sodium, potassium and mixtures thereof. An advantageous means for providing the alkali metal silicate is in solution with water. For example, a preferred method is to form a solution with water so that a resulting ratio of SiO2: Na20: H20 is 3.22: 1: 7. This solution can then be added to the corrosion inhibitor concentrate. A sixth component of this invention is a silicate stabilizer. The silicate stabilizer is provided in an amount of 0-1, preferably 0.3 to 5, preferably 1.0% by weight. The purpose of the silicate stabilizer is a compound against gelation. Examples of such compounds are described in a patent issued to The Dow Chemical Company (U.S. Patent 4,333,843). A preferred silicate stabilizer is a silicon phosphonate compound. A commercially available example of the silicon phosphonate compound is available from Dow Corning Q1 -6083. A final required component of this invention is an antifoam agent. The antifoaming agent is provided in an amount of 0.02, preferably 0.05, to 5, preferably 0.5% by weight. Examples of such agents are described in a patent issued to The Dow Chemical Company (U.S. Patent No. 4,287,077). These compounds are also useful to provide additional silicate stabilization. A preferred antifoaming agent is a polymeric siloxane compound. A commercially available example of the polymeric siloxane compound is Dow Corning 2-5067. An additional component, which may be useful in automobile inhibitor concentrate, is a hard water stabilizer. The hard water stabilizer is effective in preventing hard water ions such as calcium, magnesium, and iron from precipitating alkali inhibitors such as silicate and borate. Typical stabilizers work by sequestering hard water ions. A preferred hard water stabilizer is a water soluble polyacrylate compound. Generally, the water-soluble polyacrylate compound is provided in an amount of 0.5, preferably 2, to 5, preferably 4% by weight. Examples of water-soluble polyacrylate compounds include ACUMER ™ 1100, ACUMER ™ 3100 (both available from Rohm & amp;; Hass), and POC 2020 HS (available from Degussa Chemical). Of these, ACUMER ™ 1100 is preferred. Another optional component is a water soluble dye. The dye is usually fluorescent in a way that facilitates the discovery of refrigerant system leaks during operation. For example, the specifications of both GM 1825 and GM 1899 for automotive and diesel engine coolants, respectively, specify a mixture of alizarin-cyanine green (eg, Acid Green 25) and fluorescein (eg, Acid Yellow 73) . It is desirable that the dye be stable after exposure to heat and UV radiation. It must be provided in an amount sufficient to impart a different color to the corrosion inhibitor concentrate. Preferably, it should be provided in a sufficient amount to impart a different color to a motor coolant formulation, which contains the corrosion inhibitor concentrate of this invention. Said amount is typically from 0.5 to 1.5% by weight, based on the total weight of the corrosion inhibitor concentrate. Preferred examples of the water-soluble dye include alizarin-cyanine green, FJuorescein and Rhodamin dyes. Most preferred is a mixture of Acid Green 25 and Acid Yellow 73, commercially available from Chromatech Incorporated as 15% OEM Green Liquid Dye. Another optional component is an alkali metal nitrate. The alkali metal nitrates provide increased protection against pitting for aluminum and serve as the basic formulation described above. It is desirable to add alkali metal nitrates whenever enhanced protection against corrosion of aluminum is required, such as for automotive motor applications using aluminum cylinder heads. Preferably, the alkali metal nitrate is provided in an amount of between 0, preferably 4.5, and 10, preferably 6% by weight. The alkali metal is preferably selected from sodium, potassium and mixtures thereof, wherein sodium is very preferred. Another optional component is an alkali metal molybdate. Alkali metal molybdates typically provide increased protection against cavitation-erosion for cast iron cylinder liners, especially in combination with nitrite, and this serves to improve the basic formulation described above. It is desirable to add alkali metal molybdates whenever an improved protection of the cylinder liner is required such as for heavy duty diesel engine applications. For example, practice RP 329, recommended by the Truck Maintenance Council (TMC), which governs heavy-duty diesel fleet management requires that a combined molybdate (such as Mo04"2) and nitrite (such as N02") be more of 1560 ppm, with a minimum of 600 ppm of both. With the corrosion inhibitor concentrate of this invention, the alkali metal molybdate is preferably provided in an amount of between O, preferably 3, and 7, preferably 5% by weight. The alkali metal is preferably selected from sodium, potassium and mixtures thereof, wherein sodium is very preferred. Most preferably, the alkali metal molybdate is provided in the form of sodium molybdate dihydrate (Na2Mo04 »2 H20). Another optional component is an alkali metal nitrite. Alkali metal nitrites, such as alkali metal molybdates, typically provide improved protection against cavitation-erosion for cast iron cylinder liners. It is desirable to add alkali metal nitrites whenever cylinder liner protection such as heavy-duty diesel engine applications is required. For example, practice RP 329, recommended by the Truck Maintenance Council (TMC), which governs the handling of heavy-duty diesel fleet, requires that a nitrite concentration (such as N02") be more than 2400 ppm when no molybdate is added. With the corrosion inhibitor concentrate of this invention, the alkali metal nitrite is preferably provided in an amount of between 0, preferably 8.5, and 25, preferably 12% by weight. The alkali metal is preferably selected from sodium, potassium and mixtures thereof, wherein sodium is very preferred. It has been found that it is desirable to formulate the corrosion inhibitor concentrate of this invention using a specific procedure. The first step of this method comprises adding to a first container, and mixing for a sufficient period to ensure the complete dissolution of all the contents of the first container, the following components: a first aliquot of the water in an amount of 20 to 90% in weight; the triazole; a first aliquot of the alkali metal hydroxide in an amount of 2 to 20% by weight; and borate. Generally, each component is completely dissolved before proceeding to the next component addition. If desired, the optional alkali metal nitrate, molybdate and nitrite can also be added during the first step as additional components. A second step of the process comprises adding to a second container, and mixing for a period sufficient to ensure complete dissolution of all the contents of the second container, the following components: the alkali metal silicate; a second aliquot of water in an amount of between 0 and 10% by weight; a second aliquot of alkali metal hydroxide in a second amount between 0 and 5% by weight; and the silicate stabilizer. A third step comprises adding the contents of the second container to the contents of the first container and mixing to form a combined mixture. The final step involves adding the antifoam to the blended mixture and mixing for a sufficient period to ensure complete dissolution. If desired, the optional water-soluble dye and polyacrylate can be added during this final step before mixing. The corrosion inhibitor concentrate of this invention can then be mixed with alcohol freeze suppressants such as ethylene glycol, propylene glycol, and mixtures thereof, to form a corrosion inhibition engine coolant formulation. It has been discovered that the components of the corrosion inhibitor concentrate work in a particularly synergistic manner when used to re-inhibit alcohol freeze suppressors recirculated from antifreeze / coolants. The corrosion inhibitor concentrate of this invention has been tested on a variety of ethylene glycol streams obtained by recirculating the spent engine coolant using a variety of commercially available methods such as: industrial scale distillation, portable distillation (garage unit), nano -filtration, ion exchange, and chemical treatment with filtration. In all cases, the addition of the recirculated ethylene glycol corrosion inhibitor concentrate produced an engine coolant, which satisfies all the performance requirements listed by ASTM D3306-95 and D5345-95. The concentration of alcohol freeze suppressant present in the spent engine coolant typically ranges from 25 to 60% by volume. The refrigerant recirculation technology based on distillation will typically increase the glycol concentration on a scale of 75 to 100% by volume. Most recirculation technologies produce an alcohol freeze suppressant concentration of 40 to 60% by volume of the solution with water. The corrosion inhibitor concentrate can then be mixed with the solution in an amount sufficient to provide desirable corrosion inhibiting properties. For example, in a water solution with 50% by volume of ethylene glycol, the corrosion inhibitor concentrate can be provided in an amount sufficient to provide a volume-volume ratio of the concentrate to the glycol solution of 1:48 to 1:72, the highly preferred scale being 1:60. This relationship has been found to produce an engine coolant or antifreeze, which satisfies ASTM D5345-95. Other ratios can be used for different volume percentages of ethylene glycol or for alcohol freeze suppressants, such as propylene glycol. However, typically, a weight-to-weight ratio of corrosion inhibitor concentrate to pure freezing point suppressor (either EG, PG or other) from 1:20 to 1:30, preferably from 1:22 to 1:28 , the highly preferred ratio being 1:25, produces a coolant or engine antifreeze, which satisfies the accepted performance standards in the industry such as ASTM.

EXAMPLES The invention will be further clarified by considering the following examples, which are intended to be purely illustrative for the use of the invention.

EXAMPLE 1 An automotive inhibitor concentrate was prepared using the components and procedure described below: Component Quantity% / P (grams per 100 100 grams of final product) 1 . Distilled water (aliquot # 1) 32.4 2. NaNO3 5.2 3. 50% sodium tolitriazole 5.2 4. 45% KOH (aliquot # 1) 17.7 5. Na2B407 «5H20 19.5 6. N sodium silicate solution 7 7 7 Distilled water (aliquot # 2) 5.7 8. 45% KOH (aliquot # 2) 2.2 9. Dow Corning Q1 -6083 0.52 10. Dow Corning 2-5967 0.62 1 1. ACUMER 1 100 2.6 12. Green coloring 15% OEM 0.8 Procedure In a first vessel (# 1), the first one to the water plate, followed by the nitrate, the tolitriazole, the first aliquot of alkali metal hydroxide and finally the borate were added. Each component dissolved completely before proceeding to the next. The contents of vessel # 1 were kept above a temperature of 35 ° C and mixed overnight to ensure complete dissolution. In a separate vessel (# 2), the alkali metal silicate, the second aliquot of water, the second aliquot of alkali metal hydroxide, and the silicate stabilizer (antifoaming agent) were added. Each component dissolved completely before proceeding to the following. After the components of both vessels dissolved, the contents of vessel # 2 were added to vessel # 1 and mixed. Finally, the antifoaming agent, the polymeric hard water stabilizer and the colorant were added to vessel # 1 and mixed thoroughly to produce the automotive inhibitor concentrate.

When diluted with virgin ethylene glycol and water in a ratio of 1 part of inhibitor concentrate to 60 parts of a 50% glycol / water solution on a volume-volume basis, an antifreeze / coolant was produced having a pH of between 10 to 1 1 and satisfying the operating standard ASTM D4656-95 (light duty cars and diesel). See Example 3 for specific operating data.

EXAMPLE 2 A heavy duty diesel inhibitor concentrate was prepared using the components and procedure described below. Nitrite and molybdate were added to meet the typical heavy duty diesel OEM demands: Component Quantity% / P (grams per 100 100 grams of final product) 1. Distilled water (aliquot # 1) 34.0 2. Na2MoO4.2H20 3.9 2. NaNO3 3.9 5. NaNOz 10.4 3. Tolitriazole sodium 50% 5.2 4. KOH 45% (aliquot # 1) 14.4 5. Na2B4O7 «5H2O 1 5.6 6. N sodium silicate solution 4.4 7. Distilled water (aliquot # 2) 3.6 8. 45% KOH (aliquot # 2) 1 .3 9. Dow Corning Q 1 -6083 0.52 10. Dow Corning 2-5067 0.26 eleven . ACUMER 1 100 2.6 12. Green coloring 15% OEM 0.8 Procedure In a first vessel (# 1), the first one to the water plate, followed by the molybdate, the nitrite, the tolitriazole, the first aliquot of alkali metal hydroxide and finally the borate were added. Each component dissolved completely before proceeding to the next. The contents of vessel # 1 were kept above a temperature of 35 ° C and mixed overnight to ensure complete dissolution. In a separate vessel (# 2), the alkali metal silicate, the second aliquot of water, the second aliquot of alkali metal hydroxide, and the silicate stabilizer (antifoaming agent) were added. Each component dissolved completely before proceeding to the following. After the components of both vessels dissolved, the contents of vessel # 2 were added to vessel # 1 and mixed. Finally, the antifoam agent, the polymeric hard water stabilizer and the colorant were added to vessel # 1 and mixed thoroughly to produce the heavy duty diesel inhibitor concentrate. When diluted with virgin ethylene glycol and water in a ratio of 1 part of inhibitor concentrate to 60 parts of a 50% glycol / water solution on a volume-volume basis, an antifreeze / coolant was produced satisfying the ASTM D5345-95 operating standard (heavy duty diesel). Specifically, the following results illustrate the typical operation of a refrigerant prepared from the above heavy duty diesel injector concentrate: Test Method Results ASTM D1881 tendency to < 5 sec (breaking time) foaming < 50 ml (volume of foam) ASTM D1287-91 pH 10 to 1 1 (50% solution) ASTM D4340-89 Thermal Rejection Aluminum 0.1 1 mg / cm2 / week ASTM D1384-94 Cu test = + 3.0 mg; solder = 17.9 mg; corrosion of bronze glassware = + 0.1 mg; steel = + 0.3mg; cast iron = + 0.1 mg; Al = + 0.1 mg ASTM D2809-94 water pump cavitation by Al classification 9 EXAMPLE 3 The refrigerant inhibitor concentrate of Example 1 (hereinafter "Conc. Inhib.") Was mixed with a solution of ethylene glycol (EG) antifreeze (virgin or recovered) and water so that the refrigerant inhibitor concentrate was present in the weight in an amount of 1 part of inhibitor concentrate to 25 parts of pure EG. For example, in a solution of 100 grams of EG in water, if it is determined that 33 grams are pure EG, then approximately 1.32 grams of inhibitor concentrate are added to the solution. Performance data using various sources of EG (as presented later in Table 1) are set out in Tables 2 to 6.

Table 1 Characterization of the Glycol Quality Used for Evaluation in Tables 2 to 6 This Table represents a compositional analysis of commercially available ethylene glycols, including "virgin" EG and several recirculated glycols. The recirculated glycols (identified as "A" through "G") were each independently produced from a normal spent refrigerant using different recirculation methods such as distillation, nano-filtration, ultra-filtration, ion exchange, and filtration with treatment chemical (in a non-particular correspondence order). The Table represents the concentration in parts per million (PPM) unless otherwise indicated.

N-) Ol O Oí Oí Table 2 Corrosion of Cast Aluminum Alloys in Engine Coolants under Thermal Rejection Conditions This Table represents three separate operations of a resulting refrigerant test produced through the addition of the corrosion inhibitor concentrate for the various sources of EG (as specifically it is established in "Table 1"). The Table reflects the weight loss in mg / cm2 / week of SAE 329 aluminum alloy as for the test conditions set forth in ASTM D4340-89 (maximum allowable loss = 1.0 mg / cm2 / week). containing hard water stabilizer Table 3 Corrosion Test of Engine Coolants in Glassware This Table represents the average of three separate operations of a resulting refrigerant test produced through the addition of the corrosion inhibitor concentrate to the various sources of EG (as specifically stated in "Table 1"). The Table reflects the current weight losses and the maximum allowable losses in milligrams for 6 different types of metal alloys as for the test conditions set forth in ASTM D1384-94. denotes the formulation of concentrated corrosion inhibitor containing hard water stabilizer Table 4 Simulated Service Corrosion Test of Engine Coolants This Table represents the test of resulting refrigerants produced through the addition of the corrosion inhibitor concentrate to two sources of EG (ie virgin and recirculated giicol generically identified as procedure G) . Specifically, this Table reflects the actual weight losses and the maximum allowable losses in milligrams for 6 different types of metal alloys as for the test conditions established in ASTM D2570-94. (the data are averages of tests in duplicate / triplicate) * denotes the formulation of concentrated corrosion inhibitor containing hard water stabilizer Table 5 Erosion-Corrosion Cavitation Characteristics of Aluminum Pumps with Engine Coolants (classification on a scale of 1 to 10) This Table represents the resulting refrigerant test produced by the addition of the corrosion inhibitor concentrate to three sources of EG (ie say, virgin and recirculated, as specifically stated in "Table 1" as E and G). The Table reflects a classification of the appearance of the water pump and the quality as for the test conditions and the classification system established in ASTM D2809-94 (the minimum acceptable classification is 8). denotes the formulation of corrosion inhibitor concentrate containing hard water stabilizer Table 6 Trends of Foam Formation of Engine Coolants in Glassware This Table represents the test of resulting refrigerants produced through the addition of the corrosion inhibitor concentrate to two sources of EG (ie, virgin and recirculated, as specifically stated in "Table 1" as G). In addition, the data for the G glycol process without the corrosion inhibitor concentrate are listed for comparison. The Table represents an average of three separate operations and reflects the foaming characteristics for the antifreeze composition as for the test conditions set forth in ASTM D 1 881-86. With respect to the tendency to foaming, the comparison of virgin glycol with the glycol G of the process reflects a total scale of glycol qualities (ie, from the best to the oil respectively).

The above examples demonstrate that this invention provides the desirable corrosion inhibitor properties in anticoagulants / coolants using a very broad scale of glycol grades. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention described herein. It is intended that the specification and examples be considered as illustrative only; with the true scope and spirit of the invention being indicated by the following claims.

Claims (10)

1. - A corrosion inhibitor concentrate comprising: (a) from 20 to 90% by weight of water; (b) from 1 to 10% by weight of triazole; (c) from 2 to 20% by weight of an alkali metal hydroxide; (d) from 3 to 25% by weight of a borate, calculated as B2O3; (e) from 1 to 15% by weight of an alkali metal silicate, calculated as an equivalent amount of silicate in sodium metasilicate pentahydrate; (f) from 0.1 to 5% by weight of a silicate stabilizer; and (g) from 0.05 to 5% by weight of an antifoam agent; wherein all percentages by weight are based on the total weight of the corrosion inhibitor concentrate.

2. The corrosion inhibitor concentrate according to claim 1, wherein the alkali metal hydroxide is provided in an amount sufficient to provide a pH greater than 10.

3. The corrosion inhibiting concentrate according to claim 1 , wherein the alkali metal silicate is sodium silicate, potassium silicate, or mixtures thereof.

4. The corrosion inhibitor concentrate according to claim 1, characterized in that it further comprises an alkali metal nitrate, which is present in an amount of between 0 and 10% by weight, based on the total weight of the inhibitor concentrate of corrosion.

5. The corrosion inhibitor concentrate according to claim 1, characterized in that it further comprises an alkali metal molybdate, which is present in an amount of between 0 to 7% by weight, based on the total weight of the inhibitor concentrate of corrosion.

6. The corrosion inhibitor concentrate according to claim 1, characterized in that it further comprises an alkali metal nitrite, which is present in an amount of between 0 and 25% by weight, based on the total weight of the inhibitor concentrate of corrosion.

7. An engine coolant formulation comprising an alcohol freeze suppressant and the corrosion inhibitor concentrate of claim 1.

8. The corrosion inhibitor concentrate according to claim 1, wherein the concentrate is prepared through of a process comprising: (a) adding water in an amount of 20 to 90% by weight, the triazole, the alkali metal hydroxide in an amount of 2 to 20% by weight, and the borate in a first container and mixing for a sufficient period to ensure complete dissolution; (b) adding the alkali metal silicate, a second aliquot of water in an amount of between 0 and 10% by weight, a second aliquot of alkali metal hydroxide in an amount of between 0 and 5% by weight, and the stabilizer of silicate in a second container and mixing for a sufficient period to ensure complete dissolution; (c) adding the contents of the second container to the contents of the first container and mixing to form a combined mixture; and (d) adding the antifoam to the blended mixture and mixing for a sufficient period to ensure complete dissolution.

9. The corrosion inhibitor concentrate according to claim 8, wherein step (a) further comprises adding alkali metal nitrate prior to mixing.

10. The corrosion inhibitor concentrate according to claim 8, wherein step (a) further comprises adding alkali metal molybdate and alkali metal nitrite prior to mixing.