Heat transfer fluids containing synergistic blends of corrosion inhibitor formulations

1. A heat transfer fluid comprising:

greater than or equal to about 89 wt. % of a freezing point depressant that is selected from the group consisting of methanol, ethanol, propanol, butanol, furfurol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethoxylated furfuryl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, butylene glycol, glycerol, glycerol-1,2-dimethyl ether, glycerol-1,3-dimethyl ether, monoethylether of glycerol, sorbitol, 1,2,6-hexanetriol, trimethylopropane, methoxyethanol, and a combination thereof;

a corrosion inhibitor formulation comprising:

an optionally substituted benzoic acid or a salt thereof, wherein the salt of the optionally substituted benzoic acid comprises sodium benzoate, potassium benzoate, or a combination thereof;

a first n-alkyl monocarboxylic acid selected from heptanoic acid, octanoic acid, a salt thereof, and mixtures thereof;

a second n-alkyl monocarboxylic acid selected from nonanoic acid, decanoic acid, a salt thereof, and mixtures thereof; and

an azole compound selected from the group consisting of benzotriazole, tolyltriazole, mercaptobenzothiazole, tetrahydro tolyltriazole, and a combination thereof;

wherein the heat transfer fluid has a pH between about 6.8 and about 10.0;

wherein a ratio of weight percent of the first n-alkyl monocarboxylic acid or the salt thereof to weight percent of the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:0.75 to about 1:2.00;

wherein a ratio of weight percent of the optionally substituted benzoic acid or the salt thereof to combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof and the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:0.30 to about 1:2.25; and

wherein the heat transfer fluid is free of silicates, borates, amines, branched carboxylates, dibasic—aliphatic carboxylates, dibasic-aromatic carboxylates, and acrylate based polymers.

2. The heat transfer fluid of claim 1 , wherein the salt of the first n-alkyl monocarboxylic acid and the salt of the second n-alkyl monocarboxylic acid each comprises an alkali metal.

3. The heat transfer fluid of claim 1 , wherein one of the first n-alkyl monocarboxylic acid comprises heptanoic acid and the second n-alkyl monocarboxylic acid comprises nonanoic acid.

4. The heat transfer fluid of claim 1 , wherein the first n-alkyl monocarboxylic acid comprises octanoic acid and the second n-alkyl monocarboxylic acid comprises decanoic acid.

5. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the first n-alkyl monocarboxylic acid or the salt thereof to the weight percent of the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:1.00 to about 1:2.00.

6. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the first n-alkyl monocarboxylic acid or the salt thereof to the weight percent of the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:1.00 to about 1:1.50.

7. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the first n-alkyl monocarboxylic acid or the salt thereof to the weight percent of the second n-alkyl monocarboxylic acid or the salt thereof is about 1:1.

8. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the benzoic acid or the salt thereof to the combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof and the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:0.50 to about 1:2.25.

9. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the benzoic acid or the salt thereof to the combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof and the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:0.75 to about 1:2.00.

10. The heat transfer fluid of claim 1 , wherein the ratio of the weight percent of the benzoic acid or the salt thereof to the combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof and the second n-alkyl monocarboxylic acid or the salt thereof is about 1:1.

11. The heat transfer fluid of claim 1 , further comprising a water-soluble molybdate salt.

12. The heat transfer fluid of claim 1 , further comprising sodium molybdate, potassium molybdate, or a combination thereof.

13. The heat transfer fluid of claim 1 , further comprising an additional component selected from the group consisting of an inorganic phosphate, an organophosphate, a water-soluble alkaline earth metal salt, a water-soluble alkali metal salt, a water-soluble zinc salt, a nitrite, a nitrate, a phosphonate, a phosphinate, and a combination thereof.

14. The heat transfer fluid of claim 1 , further comprising an alkaline earth metal oxide, an alkaline earth metal hydroxide, or a combination thereof.

15. The heat transfer fluid of claim 14 , wherein the alkaline earth metal comprises calcium, magnesium, strontium, or a combination thereof.

16. The heat transfer fluid of claim 1 , further comprising lithium oxide, lithium hydroxide, or a combination thereof.

17. The heat transfer fluid of claim 13 further comprising an additional component selected from the group consisting of a colorant, a biocide, an antifoaming agent, a surfactant, an additional corrosion inhibitor, a dispersant, or a combination thereof.

18. The heat transfer fluid of claim 13 further comprising at least one additional n-alkyl monocarboxylic acid or a salt thereof.

19. The heat transfer fluid of claim 18 wherein the ratio of the weight percent of the benzoic acid or the salt thereof to a combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof, the second n-alkyl monocarboxylic acid or the salt thereof, and the at least one additional carboxylic acid or the salt thereof ranges from about 1:0.50 to about 1:2.25.

20. The heat transfer fluid of claim 1 , further comprising an inorganic phosphate, an organophosphate, or a combination thereof.

21. The heat transfer fluid of claim 1 , further comprising an ethylene glycol phosphate ester, 1,2,3-propanetriol phosphate, a phosphate polyether ester, a C 6 -C 12 alkyl alcohol ethoxylate phosphoric acid, an alkali metal salt of phosphate ester of cresyl ethoxylate, potassium cresyl phosphate, octylphenoxypolyethoxyethyl phosphate, octylphenoxy polyethyl phosphate, olyethylene glycol mono(octylphenyl) ether phosphate, an alkali metal salt of alkylphenoxypolyethoxyethyl phosphoric acid of R-phenyl(CH 2 CH 2 O)xphosphate, wherein R is hydrogen or a C 1 -C 20 alkyl and x is an integer from 1 to 30, or a combination thereof.

22. The heat transfer fluid of claim 1 , further comprising at least one additional n-alkyl monocarboxylic acid or a salt thereof.

23. The heat transfer fluid of claim 22 , wherein the salt of the at least one additional n-alkyl monocarboxylic acid comprises an alkali metal, and wherein the at least one additional n-alkyl monocarboxylic acid comprises a C 6 -C 20 mono-aliphatic or aromatic carboxylic acid.

24. The heat transfer fluid of claim 1 , further comprising a water-soluble alkaline earth metal salt that will produce at least one of Ca 2+ , Mg 2+ , and Sr 2+ upon dissolving in water.

25. The heat transfer fluid of claim 1 , further comprising a water-soluble alkaline earth metal salt that will produce magnesium ions.

26. The heat transfer fluid of claim 1 wherein the optionally substituted benzoic acid comprises p-toluic acid, t-butyl benzoic acid, an alkoxybenzoic acid, 1,3,5-benzene tricarboxylic acid, 1,2,4-benzene tricaboxylic acid, 1,2,3-benzene tricarboxylic acid, or a combination thereof.

27. A heat transfer fluid comprising:

greater than or equal to about 89 wt. % of a freezing point depressant that is selected from the group consisting of methanol, ethanol, propanol, butanol, furfurol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethoxylated furfuryl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, butylene glycol, glycerol, glycerol-1,2-dimethyl ether, glycerol-1,3-dimethyl ether, monoethylether of glycerol, sorbitol, 1,2,6-hexanetriol, trimethylopropane, methoxyethanol, and a combination thereof;

a corrosion inhibitor formulation comprising:

benzoic acid or an alkali metal salt thereof, wherein the salt of the optionally substituted benzoic acid comprises sodium benzoate, potassium benzoate, or a combination thereof;

a first n-alkyl monocarboxylic acid selected from heptanoic acid, octanoic acid, an alkali metal salt thereof, and mixtures thereof;

a second n-alkyl monocarboxylic acid selected from nonanoic acid, decanoic acid, or an alkali metal salt thereof, and mixtures thereof;

an azole compound selected from the group consisting of benzotriazole, tolyltriazole, mercaptobenzothiazole, tetrahydro tolyltriazole, and a combination thereof; and

a molybdate salt comprising sodium molybdate, potassium molybdate, or a combination thereof;

wherein the heat transfer fluid has a pH between about 6.8 and about 10.0;

wherein a ratio of weight percent of the first n-alkyl monocarboxylic acid or the salt thereof to weight percent of the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:1.00 to about 1:1.75; and

wherein a ratio of weight percent of the benzoic acid or the salt thereof to combined weight percent of the first n-alkyl monocarboxylic acid or the salt thereof and the second n-alkyl monocarboxylic acid or the salt thereof ranges from about 1:0.50 to about 1:2.00

wherein the heat transfer fluid is free of silicates, borates, amines, branched carboxylates, dibasic-aliphatic carboxylates, dibasic-aromatic carboxylates, and acrylate based polymers.

28. The heat transfer fluid of claim 27 , further comprising an additional component selected from the group consisting of an inorganic phosphate, an organophosphate, a water-soluble alkaline earth metal salt, a water-soluble alkali metal salt, a water-soluble zinc salt, a nitrite, a nitrate, an acrylate-based polymer, a phosphonate, a phosphinate, and a combination thereof.

29. A method of preventing corrosion in a heat transfer system, the method comprising contacting at least a portion of the heat transfer system with the heat transfer fluid of claim 1 .

30. The method of claim 29 , wherein the heat transfer system comprises a component made by controlled atmosphere brazing, a component comprising compacted graphite iron (CGI), a component comprising aluminum, or a combination thereof.

31. The fluid of claim 20 , further comprising an alkaline earth metal oxide, an alkaline earth metal hydroxide, or a combination thereof.

32. The heat transfer fluid of claim 31 , wherein the alkaline earth metal comprises calcium, magnesium, strontium, or a combination thereof.

33. The heat transfer fluid of claim 20 , further comprising lithium oxide, lithium hydroxide, or a combination thereof.