Low-phosphorus organic acid composite engine coolant and preparation method thereof

Abstract

The invention discloses a low-phosphorus organic acid composite engine coolant and a preparation method thereof, and belongs to the field of coolants. The cooling liquid comprises the following components in percentage by mass: 32%-34% of ethylene glycol, 0.08%-0.15% of a dispersing agent, 0.9%-1.2% of organic acid, 0.08%-0.1% of phosphate, 0.15%-0.2% of nitrate, 0.009%-0.01% of a calcium and magnesium ion source, 0.12%-0.2% of a corrosion inhibitor, 0.6%-0.7% of a pH regulator, 0.01%-0.05% of a defoaming agent and the balance of water. Through optimal combination of low phosphorus, trace hardness ions, the dispersing agent and the organic acid, the cooling liquid can be endowed with long-acting anti-corrosion and precipitation-free performance, and the prepared low-phosphorus organic acid composite cooling liquid can meet the high-standard requirements of modern automobile engines on the aspects of freezing prevention, corrosion prevention, environmental protection and the like, and has wide application prospects.

Description

Technical Field

[0001] This invention belongs to the field of coolants, specifically relating to a low-phosphorus organic acid composite engine coolant and its preparation method. Background Technology

[0002] Engine coolant (also known as antifreeze) is typically composed of ethylene glycol, water, and various corrosion inhibitors. It is used to prevent corrosion of metal components in the engine cooling system and to improve the boiling point and low-temperature antifreeze capability of the heat transfer medium. Traditional coolant formulations mainly use inorganic salt inhibitors, such as silicates and phosphates. These phosphate-containing coolants offer some protection to metals (especially aluminum alloys) under alkaline conditions, but a significant drawback is their tendency to precipitate when in contact with hard water. When the coolant is diluted with hard water such as tap water, the phosphates react with calcium and magnesium ions in the water to form insoluble deposits that adhere to the surface of radiator pipes and can even cause blockages, thus reducing cooling efficiency. Furthermore, the long-term use of high-phosphate additives can also lead to environmental burdens; for example, the discharge of phosphorus-containing wastewater may cause eutrophication and other environmental problems. Therefore, in recent years, coolant formulations with reduced or even no phosphorus content have emerged to improve hard water compatibility and environmental performance. Simultaneously, there are also technical approaches that use organic acid corrosion inhibitors to replace traditional inorganic salt systems, namely, organic acid technology coolants (OAT antifreeze). Organic acid-based coolants do not contain easily precipitating components such as silicates or phosphates, generally providing long-term stable corrosion inhibition protection and are less prone to scaling in hard water. However, all-organic acid formulations also have some drawbacks: firstly, to meet stringent corrosion protection requirements, higher doses of corrosion inhibitors are often required, leading to increased costs; secondly, the immediate protective effect of existing all-organic acid coolants on aluminum alloys is sometimes less than ideal, with instances of blackening and discoloration observed on cast aluminum parts, indicating deficiencies in aluminum corrosion protection. For example, some literature indicates that traditional all-organic acid engine coolants easily cause black film formation on cast aluminum surfaces, making them unsuitable for all-aluminum engines, and they also offer poor cavitation protection for engine cylinder liners. To overcome these shortcomings, some improvement solutions have emerged in the industry, such as introducing additives like organic phosphates into the organic acid corrosion inhibition system to address the blackening problem of aluminum alloys.

[0003] In general, existing technologies have their advantages and disadvantages in both phosphate coolant and organic acid coolant solutions: high-phosphorus formulations have good corrosion inhibition but are prone to scaling and are not environmentally friendly, while pure organic acid formulations are clean and environmentally friendly but offer insufficient protection for certain metals and are more expensive. Therefore, there is an urgent need for a new coolant formulation that combines low phosphorus content, good corrosion and scale prevention properties, and cost-effectiveness to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] Purpose of the invention: The first purpose of this invention is to provide a low-phosphorus organic acid composite engine coolant that has both good anti-corrosion and anti-scaling properties and environmentally friendly characteristics. The second purpose of this invention is to provide a method for preparing the above-mentioned low-phosphorus organic acid composite engine coolant.

[0005] Technical solution: The low-phosphorus organic acid composite engine coolant of the present invention comprises the following components by mass percentage: ethylene glycol 32-34%, dispersant 0.08-0.15%, organic acid 0.9-1.2%, phosphate 0.08-0.1%, nitrate 0.15-0.2%, calcium and magnesium ion source 0.009-0.01%, corrosion inhibitor 0.12-0.2%, pH adjuster 0.6-0.7%, defoamer 0.01-0.05%, and the remainder is water.

[0006] Furthermore, the ethylene glycol is high-purity (≥99.9%) polyester-grade ethylene glycol; the water is deionized water treated by two-stage reverse osmosis with a conductivity not exceeding 5 μS / cm, in order to avoid introducing hardness impurities.

[0007] Furthermore, the elemental mass ratio of calcium ions to magnesium ions in the calcium-magnesium ion source is 1.8-2.2:1, preferably 2:1.

[0008] Furthermore, the calcium and magnesium ion source includes calcium nitrate tetrahydrate and magnesium nitrate hexahydrate.

[0009] Furthermore, the nitrate is one or more of sodium nitrate and potassium nitrate; nitrate ions have a certain cathodic corrosion inhibition effect, and unlike nitrites, they do not require high doses to be effective and may cause instability. Therefore, adding an appropriate amount of nitrate helps to improve the overall corrosion resistance of materials such as cast iron and steel.

[0010] Furthermore, the dispersant is a phosphonocarboxylic acid copolymer or 2-phosphonobutane-1,2,4-tricarboxylic acid, which has excellent chelating and dispersing properties and can combine with calcium and magnesium ions to prevent inorganic salt scaling, thereby inhibiting the precipitation and agglomeration that may occur from phosphates.

[0011] Furthermore, the organic acid is an aliphatic dicarboxylic acid, including sebacic acid, adipic acid, azelaic acid, etc. Organic dicarboxylic acids can form a dense adsorption film on the metal surface, which has a corrosion inhibition effect on steel and aluminum alloys. They also have good thermal stability, slow consumption rate, and can provide long-term anti-corrosion protection.

[0012] Furthermore, the phosphate is a soluble alkali metal phosphate, including one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, or trisodium phosphate. This invention, by strictly controlling the amount of phosphate added and using a calcium and magnesium ion source, ensures that the elemental content in the coolant does not exceed 200 ppm. The controlled formation of trace amounts of "phosphate-calcium / magnesium" precipitates within the coolant system adheres in situ to the aluminum alloy surface, forming a dense protective film, thereby inhibiting further corrosion of the aluminum. Simultaneously, only a small amount of precipitate is generated during hard water resistance testing.

[0013] Furthermore, the corrosion inhibitor is composed of methylbenzotriazole and benzotriazole in a mass ratio of 1-1.5:1. The composite corrosion inhibitor has excellent corrosion inhibition effect on copper and its alloys, and can form a protective film on the copper / brass surface to prevent soft corrosion and discoloration of copper; at the same time, it also has an auxiliary protective effect on aluminum when combined with organic acids.

[0014] Furthermore, the pH adjuster is one or both of potassium hydroxide or sodium hydroxide. By adding an appropriate amount of alkali metal hydroxide, the pH of the coolant is adjusted to an alkaline range of 8-9, which is beneficial for the corrosion inhibitor to play its role and maintain the chemical stability of the system.

[0015] Furthermore, the defoamer is a polyether siloxane-based silicone defoamer, such as a polydimethylsiloxane copolymer containing a block polyether structure, which can effectively eliminate bubbles generated during the preparation and use of the coolant, ensuring the system is uniform and stable, and not affecting the heat transfer performance of the coolant.

[0016] The preparation method of the above-mentioned engine coolant includes the following steps: first, the calcium and magnesium ion source and the dispersant are mixed according to the mass percentage, and then ethylene glycol, dispersant, organic acid, phosphate, nitrate, corrosion inhibitor, pH adjuster, defoamer and water are fully mixed to obtain the coolant. By mixing the calcium and magnesium ion source with the dispersant first, it can be prevented that the calcium and magnesium ions will react with the pH adjuster or phosphate to form insoluble substances during the preparation process.

[0017] Invention principle: The design points of the formulation of this invention are as follows: 1. Low-phosphorus, scale-resistant, and environmentally friendly: This invention reduces the total phosphorus content in the coolant to below 200 ppm, which is only one-third or even less of that in traditional phosphate antifreeze (phosphorus content above 600 ppm). This significant reduction in phosphate content significantly lowers the risk of hard water precipitation. Experiments show that the coolant of this invention is less prone to deposit formation in hard water (total hardness > 2.5 mmol / L), thus avoiding the problem of scale buildup and blockage in radiator pipes. Simultaneously, the low-phosphorus formula reduces phosphorus-containing wastewater discharge, making it more environmentally friendly.

[0018] 2. Micro-precipitate film protection for aluminum: This invention uniquely introduces trace amounts of calcium and magnesium ions combined with a low dose of phosphate. During normal use, these calcium and magnesium ions only react with a small amount of phosphate to form in-situ precipitates, adhering to the aluminum alloy surface as an extremely thin film. This dense and uniform phosphate film effectively prevents direct contact between the coolant and the metal, thus protecting the aluminum from pitting corrosion and oxidation. Experimental results show that the coolant of this invention exhibits extremely low corrosion weight loss in cast aluminum alloy thermal corrosion tests, and the aluminum sheet surface retains its metallic luster without black spots after the test. This mechanism of forming a protective film through "controlled precipitation" differs from the uncontrolled precipitation of traditional high-phosphorus formulations, making it more effective and safer.

[0019] 3. Enhanced Stability in Hard Water Through Scale Inhibition: Due to the addition of a highly efficient phosphonate dispersant to the formula, the coolant of this invention does not exhibit significant flocculent precipitation even when stored or operated under certain hard water conditions. In comparative experiments, the formula without dispersant showed a large amount of sedimentation in hard water, while the sediment volume of this invention, with the addition of dispersant, was far below the national standard limit, significantly improving the coolant's stability in adapting to water quality. This indicates that the formula of this invention can effectively prevent the aggregation of small amounts of phosphate precipitates into scale, maintaining system cleanliness.

[0020] 4. Synergistic Corrosion Inhibition by Organic Acids, Preventing Black Film: This invention incorporates a suitable amount of organic dicarboxylic acid (such as sebacic acid) and a low amount of phosphate in its formulation for synergistic corrosion inhibition. Compared to all-organic acid coolants, this invention, due to the presence of trace amounts of phosphate, avoids the problem of black film formation on the aluminum surface caused by organic acids. Test results show that under the same cast aluminum corrosion test conditions, pure organic acid coolants easily produce black films on the surface of the test pieces, while aluminum test pieces using the coolant of this invention remain bright and new, without discoloration. This formulation combines the advantages of long-term protection by organic acids and immediate passivation by phosphates, ensuring that the aluminum alloy surface is both free from blackening and adequately protected.

[0021] 5. Excellent Comprehensive Corrosion Resistance: Besides aluminum alloys, the coolant of this invention provides excellent protection for various metals involved in the engine cooling system. Experimental data shows that the corrosion rates of materials such as copper, brass, solder, low-carbon steel, and cast iron meet or exceed the requirements of the national standard GB 29743.1-2022. The protection of cast iron is particularly outstanding; no rust or "rust sludge" caused by the coolant was observed during static corrosion. There was also no over-corrosion or excessive weight loss in soft metals such as copper and solder. This is attributed to the synergistic effect of the triazole corrosion inhibitor and the multi-element organic acid in the formula, which forms an effective corrosion-inhibiting film on various metals.

[0022] 6. Moderate cost and good compatibility: The coolant of this invention uses ethylene glycol-water as the base fluid and employs readily available and mature corrosion inhibitors (phosphates, diacids, corrosion inhibitors, etc.). Compared to a fully organic acid system, this significantly reduces the amount of expensive specialized corrosion inhibitors required, resulting in a more economical overall cost. Furthermore, this coolant has similar material compatibility to traditional antifreeze and will not adversely affect commonly used rubber seals or plastic parts, making it easy to replace in existing vehicle cooling systems.

[0023] In summary, the low-phosphorus organic acid composite coolant provided by this invention has excellent anti-settling ability under hard water conditions, provides high-level anti-corrosion protection for aluminum alloys and other metals without discoloration, and takes into account both environmental protection and cost controllability, making it suitable for long-term use in modern automotive engine cooling systems.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention significantly reduces the phosphorus content in the coolant formulation to below 200 ppm, thereby eliminating the risk of hard water scaling and environmental burden caused by phosphate precipitation; at the same time, through the combination of various additives, it compensates for the possible decrease in corrosion inhibition performance caused by the reduction in phosphorus content, ensuring sufficient protection for metal materials such as aluminum alloys in the engine cooling system and avoiding black film and pitting corrosion on cast aluminum parts; furthermore, the present invention takes into account the economy and long-term stability of the coolant, making it suitable for long-term use in the cooling systems of modern automotive engines such as all-aluminum engines. Detailed Implementation

[0025] The present invention will now be further described with reference to specific embodiments.

[0026] Example 1: The specific formulation of the low-phosphorus organic acid composite coolant provided in this example is as follows (by weight percentage): 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% phosphonocarboxylic acid copolymer dispersant (English name: POCA-Phosphino Carboxylic Acid Copolymer), 0.9% sebacic acid, 0.0825% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, the elemental mass ratio of calcium ions to magnesium ions in the calcium-magnesium ion source is 2:1, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% organosilicon defoamer - polypropylene glycol 2000, and the balance is deionized water (conductivity ≤5 μS / cm).

[0027] Example 2: The dosage of dispersant was changed, and the formulation of Example 1 was slightly adjusted while the other components remained unchanged. The specific formulation was as follows: 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.10% phosphonocarboxylic acid copolymer dispersant, 0.9% sebacic acid, 0.0825% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, calcium ion to magnesium ion mass ratio of 2:1 in the calcium-magnesium ion source, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% organosilicon defoamer - polypropylene glycol 2000, and the balance was water (conductivity ≤5 μS / cm).

[0028] Example 3: The specific formulation of the low-phosphorus organic acid composite coolant provided in this example is as follows (by weight percentage): 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% 2-phosphonobutane-1,2,4-tricarboxylic acid dispersant, 1.20% adipic acid, 0.09% sodium dihydrogen phosphate, 0.20% potassium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, the elemental mass ratio of calcium ions to magnesium ions in the calcium-magnesium ion source is 2:1, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.70% sodium hydroxide, 0.05% organosilicon defoamer—polypropylene glycol 2000, and the balance is deionized water (conductivity ≤5 μS / cm).

[0029] Example 4: The specific formulation of the low-phosphorus organic acid composite coolant provided in this example is as follows (by weight percentage): 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.15% phosphonocarboxylic acid copolymer dispersant, 0.90% sebacic acid, 0.1% trisodium phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, the elemental mass ratio of calcium ions to magnesium ions in the calcium-magnesium ion source is 2:1, 0.11% methylbenzotriazole, 0.09% benzotriazole, 0.60% potassium hydroxide, 0.01% organosilicon defoamer—polypropylene glycol 2000, and the balance is deionized water (conductivity ≤5 μS / cm).

[0030] Comparative Example 1: A control formulation without dispersant was used to evaluate the effect of dispersant on hard water precipitation. The formulation was as follows: 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.9% sebacic acid, 0.0875% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% defoamer, and the balance being water (all other conditions were the same as in Example 1).

[0031] The difference between the formulation of Comparative Example 1 and Example 1 is that it does not include a dispersant.

[0032] Comparative Example 2: A comparative formulation with reduced phosphate content was used to evaluate the effect of phosphorus content on aluminum corrosion. The formulation consisted of: 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% phosphonocarboxylic acid copolymer dispersant, 0.9% sebacic acid, 0.0875% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.0076% magnesium nitrate hexahydrate, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% defoamer, and the balance being water.

[0033] The formulation of Comparative Example 2 reduced the amount of phosphate compared to Example 1, thereby lowering the phosphorus content to 100-120 ppm.

[0034] Comparative Example 3: A comparative formulation with calcium and magnesium ions removed was used to evaluate the effect of calcium and magnesium ions. The formulation was as follows: 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% phosphonocarboxylic acid copolymer dispersant, 0.9% sebacic acid, 0.0875% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% defoamer, and the balance being water.

[0035] The formulation of Comparative Example 3 was based on Example 1 but with calcium and magnesium ions removed.

[0036] Comparative Example 4: A comparative formulation with excess calcium and magnesium ions was used to evaluate the effect of calcium and magnesium ions. The formulation was as follows: 33% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% phosphonocarboxylic acid copolymer dispersant, 0.021% calcium nitrate tetrahydrate, 0.076% magnesium nitrate hexahydrate, 0.9% sebacic acid, 0.0875% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.06% methylbenzotriazole, 0.06% benzotriazole, 0.6% potassium hydroxide, 0.01% defoamer, and the balance being water.

[0037] The formulation of Comparative Example 4 increased the calcium and magnesium ion content by 10 times compared to Example 1.

[0038] Comparative Example 5: The calcium-to-magnesium ion source had an elemental mass ratio of 1:1 to investigate the effect of this ratio on performance. The formulation was as follows: 3% high-purity (≥99.9%) polyester-grade ethylene glycol, 0.08% phosphonocarboxylic acid copolymer dispersant, 0.90% sebacic acid, 0.0875% disodium hydrogen phosphate, 0.15% sodium nitrate, 0.0021% calcium nitrate tetrahydrate, 0.00228% magnesium nitrate hexahydrate (calculated based on Mg:Ca = 1:1), 0.11% methylbenzotriazole, 0.09% benzotriazole, 0.60% potassium hydroxide, 0.01% silicone defoamer, and the balance being deionized water (conductivity ≤5 μS / cm).

[0039] The formulation of Comparative Example 5 was based on Example 1, but the elemental mass ratio of calcium and magnesium ions was adjusted to 1:1.

[0040] For the coolant samples of Examples 1-4 and Comparative Examples 1-5 above, key performance tests were conducted according to the test methods in the national standard GB 29743.1–2022 "Motor Vehicle Engine Coolant", including appearance, storage stability, hard water resistance stability, and cast aluminum alloy thermal corrosion test. Some test results are summarized in Table 1.

[0041] As can be seen from the data in Table 1, Embodiments 1, 2, 3, and 4 of the present invention meet or exceed the requirements of national standards in all aspects of performance, demonstrating excellent comprehensive performance.

[0042] Table 1 shows the test results of the coolant in Examples 1-4 and Comparative Examples 1-5.

[0043] .

[0044] Hard water stability: The sediment volumes of Examples 1, 2, 3, and 4 were 0.4 mL, 0.3 mL, 0.3 mL, and 0.05 mL, respectively, all below the upper limit of 0.5 mL, indicating that almost no visible precipitation was produced under the formulation of this invention. Comparative Example 1, without dispersant, produced as much as 1.0 mL of sediment, exceeding the limit, confirming that phosphate precipitates significantly in hard water without dispersant, further verifying the role of dispersant in preventing sediment aggregation. Although Comparative Example 2 produced only 0.2 mL of sediment, the low phosphate content prevented the formation of an effective protective film on the aluminum surface, resulting in blackening of the cast aluminum sample (see appearance results in Table 1). Comparative Example 3 (without calcium and magnesium ions) produced 0.4 mL of sediment, comparable to the examples, but also showed blackening of the sample, indicating that the lack of trace calcium and magnesium ion sources weakens aluminum protection. In Comparative Example 4, after the calcium and magnesium ion content was increased tenfold, the sediment volume rose to 0.5 mL, which was on the edge of the limit. This shows that although excessive calcium and magnesium ions can maintain the luster of aluminum sheets, they significantly increase the risk of precipitation. In Comparative Example 5 (Mg:Ca = 1:1), the sediment volume was 0.3 mL, which met the limit, but the appearance was "grayish," indicating that when the Mg:Ca ratio deviates from 2:1, the density and appearance stability of the interfacial protective film are slightly reduced compared to the system in the example. In summary, it can be seen that under low phosphorus dosage, by using "dispersant + appropriate amount of calcium and magnesium ion source" and controlling nitrate and calcium and magnesium ion source separately, a formulation balance with low precipitation and no blackening of aluminum sheets can be achieved: it controls precipitation aggregation while retaining sufficient phosphate and calcium and magnesium ions to form a stable protective film and avoid aluminum corrosion and discoloration.

[0045] Thermal corrosion of cast aluminum: In the aluminum alloy corrosion test conducted according to SH / T 0620 standard, the mass change of aluminum by each coolant was within ±1.0 mg / cm³. 2 Within this range, the requirements are met. However, from a more rigorous comparison, although Comparative Example 2 shows a mass change of −0.60 mg / cm³, 2 The sample was still within acceptable limits, but a visible black film appeared, indicating that the low phosphate content weakened the protection of aluminum, causing organic acids to form a colored film on the aluminum surface. Comparative Example 3 (without calcium and magnesium ions) showed a mass change of −0.20 mg / cm³. 2 Similarly, a black film appeared, indicating that even with normal phosphate content, a lack of trace amounts of calcium and magnesium ions weakens the protective effect of aluminum. In Comparative Example 4, although the amount of calcium and magnesium ions added was increased tenfold, the sample maintained a metallic luster and showed no black film. However, combined with the increase in hard water precipitation to 0.5 mL, it is evident that excessive hardness ions are not conducive to the cleanliness and stability of the system. The mass change in Comparative Example 5 (Mg:Ca = 1:1) was −0.20 mg / cm³. 2Although it met the standards, its appearance was grayish, and its metallic luster was slightly inferior to that of the system in the example (Mg:Ca = 2:1). In contrast, the mass changes of Examples 1, 2, 3, and 4 were -0.05 mg / cm³. 2 -0.10 mg / cm 2 -0.20 mg / cm 2 and -0.30 mg / cm 2 None of the samples showed a black film, indicating that colorless passivation protection of the aluminum surface was achieved on the basis of a low corrosion rate. At the same time, the amount of precipitation after the test of all samples did not exceed the standard, indicating that even under the harsh conditions of high temperature metal presence, the coolant of the present invention will not precipitate additional solids and has good chemical stability.

[0046] Other properties: The appearance and storage stability of the examples and comparative examples were clear and transparent without precipitation, proving that the formulation can remain stable for a long time after preparation and will not precipitate due to incompatibility of additives.

[0047] Based on the experimental data, the coolant of this invention still achieves the inhibition of hard water scaling and effective protection of cast aluminum under low phosphorus conditions. The results of the embodiments verify the feasibility and superiority of the technical solution described in the invention: through the optimized combination of low phosphorus, trace hardness ions, dispersants, and organic acids, the coolant can be endowed with long-lasting anti-corrosion and precipitation-free properties. This low-phosphorus organic acid composite coolant can meet the high standards of modern automotive engines in terms of antifreeze, corrosion prevention, and environmental protection, and has broad application prospects.

Claims

1. A low-phosphorus organic acid composite engine coolant, characterized in that, The composition by mass percentage includes: 32-34% ethylene glycol, 0.08-0.15% dispersant, 0.9-1.2% organic acid, 0.08-0.1% phosphate, 0.15-0.2% nitrate, 0.009-0.01% calcium and magnesium ion source, 0.12-0.2% corrosion inhibitor, 0.6-0.7% pH adjuster, 0.01-0.05% defoamer, and the remainder is water.

2. The engine coolant according to claim 1, characterized in that, The elemental mass ratio of calcium ions to magnesium ions in the calcium-magnesium ion source is 1.8-2.2:

1.

3. The engine coolant according to claim 1, characterized in that, The calcium and magnesium ion source includes calcium nitrate tetrahydrate and magnesium nitrate hexahydrate.

4. The engine coolant according to claim 1, characterized in that, The dispersant is a phosphonocarboxylic acid copolymer or 2-phosphonobutane-1,2,4-tricarboxylic acid.

5. The engine coolant according to claim 1, characterized in that, The organic acid is an aliphatic dicarboxylic acid.

6. The engine coolant according to claim 1, characterized in that, The phosphate is a soluble alkali metal phosphate.

7. The engine coolant according to claim 1, characterized in that, The corrosion inhibitor is composed of methylbenzotriazole and benzotriazole in a mass ratio of 1-1.5:

1.

8. The engine coolant according to claim 1, characterized in that, The pH adjuster is one or both of potassium hydroxide and sodium hydroxide.

9. The engine coolant according to claim 1, characterized in that, The defoamer is a polyether siloxane-based silicone defoamer.

10. A method for preparing engine coolant according to any one of claims 1-9, characterized in that, The steps are as follows: First, mix the calcium and magnesium ion source with the dispersant according to the mass percentage, and then thoroughly mix the ethylene glycol, dispersant, organic acid, phosphate, nitrate, corrosion inhibitor, pH adjuster, defoamer and water to obtain the final product.