ALUMINUM CORROSION INHIBITORS FOR CLOSED LOOP SYSTEMS

Abstract

This disclosure provides methods for inhibiting corrosion in a closed loop systems in which a heat transfer fluid is in contact with a corrodible aluminum surface by combining a corrosion inhibitor composition with the fluid. The corrosion inhibitor composition comprises an organic acid component that includes at least one of (i) an aromatic dicarboxylic acid, an aromatic tricarboxylic acid, or salts, anions, or derivatives thereof; (ii) an organosulfonic acid or a salt or anion thereof; and (iii) an amino dicarboxylic acid or a salt or anion thereof.

Claims

1. A method of inhibiting corrosion in a closed loop system in which a heat transfer fluid recirculates and is in contact with a corrodible aluminum surface, the method comprising combining an organic acid component with the heat transfer fluid in an amount of from 5 ppm to 2,500 ppm, where the organic acid component includes at least one of (i) an aromatic dicarboxylic acid, an aromatic tricarboxylic acid, or salts, anions, or derivatives thereof; (ii) an organosulfonic acid or a salt or anion thereof; and (iii) a an amino dicarboxylic acid or a salt or anion thereof.

2. The method of claim 1, wherein the organic acid component includes a C4-C14 aromatic dicarboxylic acid, or a salt, anion, or derivative thereof.

3. The method of claim 1, wherein the organic acid component includes a C6-C10 aromatic dicarboxylic acid, or a salt, anion, or derivative thereof.

4. The method of claim 1, wherein the organic acid component includes 2,6-naphthalene dicarboxylic acid.

5. The method of claim 1, wherein the organic acid component includes at least one compound selected from the group consisting of phtalic acid, 4-sulfophthalic acid, pthalamic acid, and 1, 3, 5-benzentricarboxylic acid.

6. The method of claim 1, wherein the organic acid component includes a C4-C12 organosulfonic acid, or a salt or anion thereof.

7. The method of claim 1, wherein the organic acid component includes a C6-C10 organosulfonic acid, or a salt or anion thereof.

8. The method of claim 6, wherein the C4-C12 organosulfonic acid, or a salt or anion thereof includes at least one aromatic group.

9. The method of claim 1, wherein the organic acid component includes at least one compound selected from the group consisting of sodium caprylyl sulfonate, sodium xylene sulfonate, sodium cumene sulfonate, and sodium 1,5-naphtalene disulfonate.

10. The method of claim 1, wherein the organic acid component includes the amino dicarboxylic acid.

11. The method of claim 10, wherein the organic acid component includes L-aspartic acid.

12. The method of claim 1, further comprising combining a C6-C14 aliphatic dicarboxylic acid with the heat transfer fluid.

13. The method of claim 1, further comprising combining a C6-C14 aliphatic monocarboxylic acid with the heat transfer fluid.

14. The method of claim 1, further comprising combining an azole with the heat transfer fluid.

15. The method of claim 1, comprising combining the organic acid component with the heat transfer fluid in an amount of from 10 ppm to 1,000 ppm.

16. The method of claim 1, comprising combining the organic acid component with the heat transfer fluid in an amount of from 25 ppm to 500 ppm.

17. The method of claim 1, wherein the aluminum surface is made of aluminum metal or an aluminum-based alloy.

18. The method of claim 1, wherein the heat transfer fluid also contacts a metal surface in the closed loop system that is a steel surface or a yellow metal surface.

19. The method of claim 1, wherein the heat transfer fluid is predominantly water.

20. The method of claim 1, wherein the heat transfer fluid is predominantly glycol.

21. The method of claim 1, wherein less than 0.25 ppm of nitrate, silica, or phosphate compounds are combined with the heat transfer fluid.

22. The method of claim 1, further comprising combining a buffer with the heat transfer fluid.

23. The method of claim 22, wherein the buffer is selected from at least one of triethanolamine and borax.

24. The method of claim 1, wherein the closed loop system is an engine coolant system.

25. The method of claim 1, wherein the closed loop system is an industrial water system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The drawing is a graph that illustrates the reduction in corrosion on aluminum surfaces using an organic acid corrosion inhibitor composition according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0007] The corrosion inhibitor compositions described herein were discovered to be effective in inhibiting corrosion in closed loop systems with corrodible aluminum surfaces. The corrosion inhibitor compositions can be added to any aqueous- or glycol-based heat transfer fluids that are used to transfer heat in closed loop systems. A closed loop system as used herein refers to a system in which a fluid is recirculated in a loop for an extended period of time without adding significant makeup fluid to the loop or removing blowdown of the loop, e.g., boiler water systems, engine coolant systems, air conditioning chilled water systems, etc. Closed loop systems can be characterized in that evaporation does not occur in closed loop cooling systems by design, unlike in open cooling systems. The purpose of a closed loop is to transfer heat, from a process or equipment to a second process or equipment. For example, removing heat from a combustion engine and transferring it to an air cooled radiator or transferring heat from an electric boiler to a plastic injected blow mold.

Corrosion Inhibitor Composition

[0008] The corrosion inhibitor compositions can include an organic acid component that is effective to inhibit corrosion on aluminum surfaces. The organic acid component used as the corrosion inhibitor can include at least one of (i) aromatic dicarboxylic acids, aromatic tricarboxylic acids, or salts, anions, or derivatives thereof; (ii) organosulfonic acids or salts or anions thereof; and (iii) amino dicarboxylic acids or salts or anions thereof. The organic acid component can also include combinations of any of the foregoing organic acids.

[0009] The aromatic dicarboxylic acid or aromatic tricarboxylic acid can be a C4-C14 or C6-C10 carboxylic acid compound or salts, anions or monoamide derivates thereof. These compounds can have one or two aromatic groups. Examples of the dicarboxylic acid compound include phtalic acid, 4-sulfophthalic acid, and pthalamic acid, and an example of the tricarboxylic acid compound includes 1, 3, 5-benzentricarboxylic acid.

[0010] The organosulfonic acid compound can include C4-C12 or C6-C10 organosulfonic acids or salts or anions thereof. The organosulfonic acid can include aromatic or aliphatic groups. Examples of the sulfonic acid compound include sodium caprylyl sulfonate, sodium xylene sulfonate, sodium cumene sulfonate, and sodium 1,5-naphtalene disulfonate.

[0011] The amino dicarboxylic acid can include C4-C8 dicarboxylic acid with one or more amine groups. The amino dicarboxylic acid can include aspartic acid or glutamic acid, for example.

[0012] The corrosion inhibitor composition can be provided as a solution having from 0.05 wt. % to 25 wt. % of the organic acid component, 0.1 wt. % to 5 wt. % of the organic acid component, or 0.2 wt. % to 1 wt. % of the organic acid component. The solution can be an aqueous solution that is primarily water and/or glycol. The corrosion inhibitor composition can have a combined amount of water and glycol that is at least 50 wt. %, at least 75 wt. % or at least 90 wt. %.

[0013] The corrosion inhibitor composition can include other additives, including other corrosion inhibitor agents such as a C6-C14 aliphatic dicarboxylic acid (e.g., sebacic acid, dodecanedioic acid), a C6-C14 aliphatic monocarboxylic acid (e.g., hexanoic acid, 2-ethyl hexanoic acid, heptanoic acid, isoheptanoic acid, octanoic acid, nonanoic acid, neodecanoic acid, decanoic acid dodecanoic acid), an azole (e.g., tolyltriazole, benzotriazole, chlorinated tolyltriazoles, and brominated tolytriazoles), or any combinations of these additional corrosion inhibitor agents. In some aspects, the corrosion inhibitor composition can include or be administered together with any of the compositions described in Provisional Application No. 63/680,296, filed on Aug. 7, 2024, the entirety of which is incorporated by reference herein. These additional corrosion inhibitor agents may improve corrosion inhibition when the closed loop system includes components made of mild steel or yellow metals, in addition to aluminum.

[0014] The corrosion inhibitor composition preferably does not include nitrate, phosphate, or silica compounds, or includes only insignificant amounts of those compounds, e.g. less than 0.01 wt. %. In these embodiments, the corrosion inhibitor composition is considered to be non-fouling since it is free of these type of inorganic corrosion inhibitors, and the risk of fouling caused by inorganic scale deposition or micro biofouling can be substantially minimized.

Treatment Methods

[0015] This disclosure also provides methods of inhibiting corrosion on aluminum surfaces in closed loop systems by combining one or more of the organic acid compounds described above with a heat transfer fluid that contacts the aluminum surfaces. As shown below, the treatment compositions have been shown to provide excellent corrosion protection on aluminum metal. The term aluminum as used herein includes aluminum and aluminum-based alloys. In some embodiments, the organic acid shows efficacy in inhibiting corrosion on other types of metal in addition to aluminum. In these embodiments, the treatment methods can be useful in closed loop systems with mixed metals, such as where the heat transfer fluid is in contact with aluminum and at least one other type of metal such as steel, copper, or brass.

[0016] The treatment method can include adding the corrosion inhibitor composition with the organic acid directly to the fluid that recirculates in the closed loop system, including adding it to the fluid when the system is offline, while the fluid is circulating, and/or by adding the composition to the makeup fluid, for example.

[0017] The heat transfer fluid can be cooling water or other aqueous fluid that is typically predominantly water or can be predominantly glycol. The heat transfer fluid is in contact with corrodible aluminum surfaces in the system that are part of conduits or equipment. In some cases, the fluid may have a pH that is in a range of from 5 to 12, from 7 to 11, or from 8 to 10, for example. Aqueous fluids can have a temperature in the closed loop system that is maintained in a range of from 25 to 100 C. or from 50 C. to 80 C., for example, and up to 350 C. in pressurized loops. Glycol-based fluids in the closed system can have temperatures of from 25 to 200 C., for example. Aqueous fluids can have a Malk (total alkalinity as CaCo3) in a range of from 5 to 10,000 ppm or from 25 to 250 ppm, for example, can have chlorides in an amount of from 1 ppm to 2000 ppm or from 5 ppm to 100 ppm, for example, and can have sulfate in an amount of from 5 ppm to 100 ppm or from 20 ppm to 50 ppm, for example.

[0018] The treatment methods include adding a sufficient amount of the organic acid component described above so that it is present in the recirculating fluid in an amount of at least 5 ppm, such as from 5 ppm to 2,500 ppm, 10 ppm to 2,000 ppm, 20 ppm to 1000 ppm, from 25 ppm to 500 ppm, or from 40 ppm to 250 ppm, for example.

[0019] The methods can provide excellent corrosion inhibition over long periods of time in closed loop systems. For example, even with a single dosing of the corrosion inhibitor, the corrosion rate can be maintained to be less than 1 mpy, less than 0.5 mpy, less than 0.15 mpy, or less 0.10 mpy over at least a consecutive eight hour period.

[0020] In embodiments, the recirculating fluid can be treated to inhibit corrosion without the presence of nitrates, phosphates, or silica compounds, or with only insignificant amounts of those components such as less than 0.25 ppm of each.

[0021] In embodiments, a buffer can also be added to the heat transfer fluid, either as part of the corrosion inhibitor composition or separately. The buffer can be thriethanolamine or borax, for example.

Example 1

[0022] The following experiments are intended to be predictive of corrosion inhibition behavior in an engine coolant closed loop system. Several corrosion inhibitor compositions identified in Table 1 below were prepared by adding 0.15 wt. % of an organic acid compound in ethylene glycol/water solutions that also contain solvent PMA, potassium hydroxide, sebacic acid, octanoic/decanoic acid, sodium tolytriazole, borax, and an antifoam agent (L-61). Also, instead of an organic acid, a 0.15 wt. % aqueous solution of sodium nitrate was prepared for comparison. All values are in wt. %.

[0023] These treatment compositions were dosed at 33.3 wt. % and the corrosion loss (mg) was determined according to the test parameters outlined in ASTM D1384 (2019) on various metallurgies. The results are shown below in Table 1 below.

TABLE-US-00001 TABLE 1 Component Closed Loop Engine Coolant Composition (%) Dosed at 33.3% RO Water 5.03 4.88 4.88 4.88 4.88 4.88 4.88 4.88 4.88 4.88 4.88 4.88 4.88 Ethylene Glycol 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 90.00 PMA 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 50% KOH 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 2.36 Sebacic Acid 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 1.47 Octanoic/Decanoic 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 0.63 Acid Sodium Tolytriazole 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 Borax 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 L-61 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 4-Sulfophthalic Acid 0.15 Phthalamic Acid 0.15 Sodium Nitrate 0.15 1,3,5- 0.15 Benzenetricarboxylic Acid Sodium Caprylyl 0.15 Sulfonate Phthalic Acid 0.15 Sodium Xylene 0.15 Sulfonate Naphthalene 0.15 Disulfonate Sulfamic Acid 0.15 Citric Acid 0.15 L-Aspartic Acid 0.15 Sodium 0.15 Glucoheptonate Solder Loss (mg) 7.6 6.1 5.1 5.4 4.7 3.3 5.9 5.9 3.8 5.4 8.4 6.4 4.3 Cast Aluminum Loss 3.2 0.6 5.9 0.1 0.7 0.1 0 3.2 3.4 20.6 60.8 0.3 9.9 (mg) Copper Loss (mg) 1.2 1.2 1.3 1.6 1.2 1.1 1 0.8 1 0.8 1.7 2.2 0.9 Brass Loss (mg) 0.4 1 0.6 0.5 0.5 0.8 0.6 0.2 0.3 0.3 3 3.3 0.5 Cast Iron Loss (mg) 0.8 0.4 0.3 0 0.2 0.5 0.3 0.6 0.6 0.4 13.4 0.5 0 Steel Loss (mg) 2.7 2.5 2.3 2.8 2.6 2.7 1.9 0.5 0.7 0.3 18.6 0.4 0.3

[0024] It can be seen from the above results that the organic acid corrosion inhibitor compositions corresponding to aromatic dicarboxylic acids, aromatic tricarboxylic acids, organosulfonic acids and salts thereof, and amino dicarboxylic acids and salts thereof are effective to substantially reduce the corrosion loss of cast aluminum as compared to the control. Furthermore, many of the compositions show comparable or better result as the conventional nitrate-based corrosion inhibitor.

[0025] These experiments also show that the performance of corrosion inhibitor on other metals is not necessarily predictive of the ability to successfully inhibit corrosion on aluminum surfaces. For example, sulfamic acid, citric acid, and sodium glucoheptanate performed relatively poorly on aluminum surfaces but exhibited good corrosion inhibition on one or more of solder, copper, brass, iron, and steel.

Example 2

[0026] The following experiments are intended to be predictive of heat-transfer corrosion of aluminum cylinder heads during engine operation. The corrosion inhibitor composition was prepared as shown in Table 2 below (amounts in wt. %). Two samples were dosed at 25 wt. % and measured for heat-transfer corrosion rate (mg/cm2/week) according to ASTMD430 (2019) on cast aluminum alloy. The initial pH of the heat transfer fluid with both samples was measured at 8.5 and the final pH of the heat transfer fluid with both samples was measured at 7.9. The corrosion results are shown below in Table 2.

TABLE-US-00002 TABLE 2 Component Amount RO Water 3.889 Ethylene Glycol 90.000 Triethanolamine 0.500 50% KOH 2.100 Sebacic Acid 1.470 Octanoic/Decanoic Acid 0.630 50% Sodium Tolytriazole 0.396 L-61 0.015 40% Sodium Xylene Sulfonate 1.000 Heat transfer Corrosion Rate (Replicate 1) 0.0 Heat transfer Corrosion Rate (Replicate 2) 0.0

[0027] It can be seen from the above results that the organic acid corrosion inhibitor compositions described herein effectively inhibit heat-transfer corrosion of cast aluminum alloys.

Example 3

[0028] The following experiments are intended to be predictive of corrosion inhibition behavior in an industrial coolant closed loop system. Several corrosion inhibitor compositions identified in Table 3 below were prepared by combining 2.0 wt. % of an organic acid in a water solution that also contains triethanolamine, potassium hydroxide, sebacic acid, octanoic/decanoic acid, sodium tolytriazole, an antifoam agent (L-61), and sodium nitrate. A composition with sodium nitrate and without organic acid was prepared for comparison, and a control sample of 100 wt. % water was also analyzed.

[0029] The corrosion inhibitor composition was added to test water at a 5,000 ppm dose. The test water included 100 ppm sulfate, 100 ppm chloride, 150 ppm Malk as CaCO3, 25 ppm Ca as CaCO3, and 10 ppm Mg as CaCO3. The pH was adjusted to 8.0-8.2 and the water was heated to 176 F. Aluminum coupons (Al1100) were submerged in the test water for 3 days and the corrosion rate measured (mpy). The results are shown in Table 3 below

TABLE-US-00003 TABLE 3 Component Closed Loop Composition (%) 5000 ppm Dosage RO Water 100.0 54.9 53.3 51.3 51.3 51.3 51.3 51.3 51.3 Triethanolamine 4.0 4.0 4.0 4.0 4.0 4.0 4.0 4.0 50% KOH 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 Sebacic Acid 14.0 14.0 14.0 14.0 14.0 14.0 14.0 14.0 Octanoic/Decanoic Acid 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 Sodium Tolytriazole 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 L-61 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Sodium Nitrate 1.6 1.6 1.6 1.6 1.6 1.6 1.6 4-Sulfophthalic Acid 2.0 Sodium Caprylyl 2.0 Sulfonate Phthalic Acid 2.0 Sodium Xylene Sulfonate 2.0 Naphthalene Disulfonate 2.0 1,3,6,8- 2.0 Pyrenetetrasulfonic Acid Corrosion Rate (mpy) 14.7 17.7 15.2 5.5 6.9 4.1 5.4 7.3 20.4

[0030] It can be seen from the above results that the organic acid corrosion inhibitor compositions corresponding to aromatic dicarboxylic acids, aromatic tricarboxylic acids, and organosulfonic acids and salts thereof were effective to substantially reduce the corrosion loss of the aluminum coupons in this experiment as compared to untreated water, and as compared to a corrosion inhibition composition with other organic acids (e.g., sebacic acid, octanoic acid, decanoic acid) and nitrate alone.

Example 4

[0031] The following experiment is intended to illustrate corrosion inhibition behavior on aluminum in an industrial coolant closed loop system. The corrosion inhibitor composition identified in Table 4 below was prepared (amounts in wt. %). The composition was added to test water at a 7,500 ppm dose. The test water was prepared as described above in Example 3. Aluminum coupons (Al1100) were submerged in the test water for 20 days and the corrosion rate was continuously measured (mpy). A control sample of 100 wt. % water was also analyzed. The results are shown in the Drawing.

TABLE-US-00004 TABLE 4 Component Amount RO Water 35.26 Triethanolamine 2.64 50% KOH 12.64 Sebacic Acid 9.36 Octanoic/Decanoic Acid 4.00 50% Sodium Tolytriazole 2.64 L-61 0.10 40% Sodium Xylene Sulfonate 33.36

[0032] It can be seen from the Drawing that the organic acid corrosion inhibitor compositions described herein exhibit prolonged protection against corrosion of aluminum in closed loop systems as compared to a control sample.

[0033] It will be apparent to those skilled in the art that variations of the methods and compositions described herein are possible and are intended to be encompassed within the scope of the present invention.