Closed water corrosion inhibitor

Abstract

The invention belongs to the technical field of water treatment, and discloses a closed water corrosion inhibitor, which is prepared from methylbenzotriazole, polyamino polyether methylene phosphonic acid, sodium polyepoxysuccinate and an acrylic acid-hydroxypropyl acrylate copolymer in a synergistic manner, and through a double protection mechanism of inner-layer BTA chemical complexing passivation and outer-layer polymer adsorption, the corrosion inhibitor can effectively inhibit the corrosion of closed water. The corrosion rate of the low-carbon steel can be reduced in chilled water, hot water, organic anti-freezing solution and high-concentration calcium chloride solution by adding only 200 ppm of the corrosion inhibitor. Compared with the prior art, the use amount of raw materials is obviously reduced, various media are compatible, high-toxicity or high-cost components of dichrome and molybdenum are abandoned, and both environmental protection and economic benefit improvement are achieved. The used raw materials are industrial common chemicals, the preparation process is simple, large-scale production is easy, and the method has excellent industrial applicability.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a sealed water corrosion inhibitor. Background Technology

[0002] In industrial circulating refrigeration and heating systems, closed-loop circulating water often suffers from severe corrosion on the surfaces of carbon steel pipes and heat exchange equipment due to prolonged high-temperature, low-temperature, or alternating hot and cold operation. Existing corrosion inhibitors are mostly dichromates, molybdates, or high-molecular-weight phosphates, with dosages typically exceeding 1500-2000 ppm. This increases operating costs and poses risks of high toxicity or environmental pollution. Furthermore, different media (such as chilled water, hot water, organic antifreeze, and high-concentration brine) have significantly different requirements for corrosion inhibitor formulations, often necessitating separate formulation optimization, which increases the difficulty of system maintenance and inventory management. While some organic corrosion inhibitors, such as benzotriazoles, can replace chromium salts, their stability as a single component in high-concentration brine or organic antifreeze is insufficient, and their dosage remains high. In response to this technological status quo, there is an urgent need for a green and environmentally friendly composite corrosion inhibitor that can achieve highly efficient corrosion suppression in various circulating media under low dosage conditions. This corrosion inhibitor must not only have broad applicability but also eliminate highly toxic or high-cost components to ensure the feasibility and economy of industrial-scale production. The aforementioned technological bottlenecks have become the core constraints on the reliable operation of closed-loop systems. Summary of the Invention

[0003] To address the shortcomings mentioned in the background art, the present invention aims to provide a closed-loop water corrosion inhibitor. This corrosion inhibitor is formulated synergistically from components such as methylbenzotriazole, polyaminopolyether methylenephosphonic acid, sodium polyepoxysuccinate, and acrylate-hydroxypropyl acrylate copolymer. With a dosage of only 200 ppm, it can significantly reduce the corrosion rate of carbon steel in chilled water, hot water, organic antifreeze, and high-concentration brine. Furthermore, it forms a double-layer protective film through chemical complexation and polymer adsorption, achieving highly efficient corrosion inhibition.

[0004] The objective of this invention can be achieved through the following technical solutions: A water-sealed corrosion inhibitor comprises the following raw materials by weight percentage: methylbenzotriazole: 0.1-2%, sodium polyepoxysuccinate: 6-16%, acrylate-hydroxypropyl acrylate copolymer: 3-10%, polyaminopolyether methylenephosphonic acid: 3-13%, sodium hydroxide: 2-8%, and the balance being water.

[0005] More preferably, the polyaminopolyether methylenephosphonic acid is prepared by a Mannich reaction of polyether amine, phosphorous acid and formaldehyde in a mass ratio of 1:1.2:4. The Mannich reaction is a process in which amine, formaldehyde and a compound containing an active methylene group condense under acidic conditions to form a β-aminocarbonyl compound.

[0006] More preferably, the acrylic acid-hydroxypropyl acrylate copolymer is prepared by free radical copolymerization of acrylic acid and hydroxypropyl acrylate in a mass ratio of 3:1 in the presence of an initiator.

[0007] More preferably, the methylbenzotriazole is 5-methylbenzotriazole with a purity of ≥99%.

[0008] More preferably, the pH of the solution prepared with the sealed water corrosion inhibitor is adjusted to 7.0–9.0.

[0009] More preferably, the preferred weight percentages of the water-sealing corrosion inhibitor components are: 0.5–1.5% methylbenzotriazole, 8–14% sodium polyepoxysuccinate, 5–8% acrylic acid-hydroxypropyl acrylate copolymer, 5–10% polyaminopolyether methylenephosphonic acid, and 3–6% sodium hydroxide.

[0010] More preferably, the water-sealing corrosion inhibitor, at a dosage concentration of 200 ppm, is suitable for use in chilled water, hot water, ethylene glycol, methanol and ethanol antifreeze, and high-concentration calcium chloride solutions.

[0011] More preferably, the working solution can be prepared by simply mixing the components at room temperature, adjusting the pH, and stirring until homogeneous.

[0012] More preferably, adding the corrosion inhibitor to a closed-loop circulating water system at a concentration of 200 ppm can achieve a method to suppress the corrosion rate of carbon steel surface to ≤0.03 mm / a.

[0013] The beneficial effects of this invention are: This invention employs a multi-component synergistic formulation of methylbenzotriazole, polyaminopolyether methylenephosphonic acid, sodium polyepoxysuccinate, and acrylate-hydroxypropyl acrylate copolymer. Through a dual mechanism of chemical complexation and polymer adsorption, an inner passivation film and an outer adsorption protective film are formed. This achieves a reduction in carbon steel corrosion rate to ≤0.0003 mm / a (pure water) and ≤0.0205 mm / a (25% ethylene glycol) with low dosage, significantly lower than existing methods requiring 1500–2000 [units of chemical composition]. The ppm solution reduces costs by approximately 85%–90%, significantly saving operating costs. Secondly, the components used in this invention are compatible with various media, including chilled water, hot water, organic antifreeze, and high-concentration calcium chloride solutions, eliminating the need to develop multiple formulations for different circulation systems and reducing inventory and maintenance difficulties. Thirdly, this invention abandons highly toxic or costly components such as dichromates and molybdates, using commonly used low-toxicity chemicals in industry, meeting green and environmental protection requirements. In addition, polyamino-polyether methylenephosphonic acid is prepared through the Mannich reaction of polyetheramine–phosphorous acid–formaldehyde, and acrylic acid–hydroxypropyl acrylate copolymer is prepared through free radical copolymerization, both of which have the characteristics of simple processes, mild conditions, and high yields, facilitating industrial scale-up production. Attached Figure Description

[0014] The invention will now be further described with reference to the accompanying drawings.

[0015] Figure 1 This is a comparison chart of the corrosion rates of the corrosion inhibitors in Examples 1-3 and Comparative Examples 1-2 using the static weight loss method. Figure 2 The graphs show the changes in scale inhibition efficiency of the corrosion inhibitors in Examples 1-3 and Comparative Examples 1-2 over 30 days. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0017] The sealed water corrosion inhibitor contains the following raw materials by weight percentage: 0.1% methylbenzotriazole, 6% sodium polyepoxysuccinate, 3% acrylate-hydroxypropyl acrylate copolymer, 3% polyaminopolyether methylenephosphonic acid, 2% sodium hydroxide, and the balance is water. The volume is adjusted to 1000 g, and the mixture is stirred evenly at room temperature to obtain a 2000 ppm stock solution. When using, dilute by 100× to obtain 200 ppm.

[0018] The preparation steps are as follows: After rinsing the reactor with deionized water, add 694.5 mL of deionized water, start the stirrer, adjust the speed to 200 rpm, and maintain the temperature at 25 ℃ under the thermostat. Slowly add 1.0 g of methylbenzotriazole, and stir at 300 rpm for 15 min until no solid particles are visible to the naked eye. Add 60.0 g of sodium polyepoxysuccinate in batches, increasing the stirring speed to 400 rpm for 10 min after each addition to ensure uniform dispersion. Continue adding 30.0 g of acrylate-hydroxypropyl acrylate copolymer, and stir at 450 rpm for 20 min until the system is uniformly milky white. Finally, add 30.0 g of polyaminopolyether methylenephosphonic acid, and stir at 500 rpm for 30 min to allow it to fully swell and adsorb. Slowly add sodium hydroxide solution (prepared as a 20 wt% aqueous solution), monitor the pH online until it reaches 8.0±0.1, and maintain stirring at 500 rpm for another 15 min to ensure pH stability. After standing for 5 min, dilute the solution with 0.45 mL of water. The solution was filtered through a μm polytetrafluoroethylene (PTFE) membrane, and the clarified mother liquor was collected. 10.0 mL of the mother liquor was measured using a graduated cylinder and diluted in 1.0 L of deionized water to obtain a 200 ppm working solution, which is the sealed water corrosion inhibitor. Example

[0019] The sealed water corrosion inhibitor contains the following raw materials by weight percentage: 2% methylbenzotriazole, 16% sodium polyepoxysuccinate, 10% acrylic acid-hydroxypropyl acrylate copolymer, 13% polyaminopolyether methylenephosphonic acid, 8% sodium hydroxide, and the balance is water. The preparation and dilution methods are the same as in Example 1.

[0020] The preparation steps are as follows: After rinsing the reactor with deionized water, add 510.5 mL of deionized water, start the stirrer, adjust the speed to 200 rpm, and maintain the temperature at 25 ℃ under the thermostat. Slowly add 20.0 g of methylbenzotriazole, and stir at 300 rpm for 20 min until no solid particles are visible to the naked eye. Add 160.0 g of sodium polyepoxysuccinate in batches, increasing the stirring speed to 400 rpm for 30 min after each addition to ensure uniform dispersion. Continue adding 100.0 g of acrylate-hydroxypropyl acrylate copolymer, and stir at 450 rpm for 40 min until the system is uniformly milky white. Finally, add 130.0 g of polyaminopolyether methylenephosphonic acid, and stir at 500 rpm for 60 min to allow it to fully swell and adsorb. Slowly add sodium hydroxide solution (prepared as a 40 wt% aqueous solution), monitor the pH online until it reaches 8.0±0.1, and maintain stirring at 500 rpm for another 20 min to ensure pH stability. Let stand for 10 minutes. After min, the solution was filtered through a 0.22 μm polytetrafluoroethylene filter membrane, and the clarified mother liquor was collected. 10.0 mL of the obtained mother liquor was measured using a graduated cylinder and added to 1.0 L of deionized water for dilution to obtain a 200 ppm working solution, which is the sealed water corrosion inhibitor. Example

[0021] The sealed water corrosion inhibitor contains the following raw materials by weight percentage: 1.05% methylbenzotriazole, 11% sodium polyepoxysuccinate, 6.5% acrylic acid-hydroxypropyl acrylate copolymer, 8% polyaminopolyether methylenephosphonic acid, 5% sodium hydroxide, and the balance being water. The preparation and dilution methods are the same as in Example 1.

[0022] The preparation steps are as follows: After rinsing the reactor with deionized water, add 694.5 mL of deionized water, start the stirrer, adjust the speed to 200 rpm, and maintain the temperature at 25 ℃ under the thermostat. Slowly add 10.5 g of methylbenzotriazole, stirring at 300 rpm for 15 min. Add 110.0 g of sodium polyepoxysuccinate in batches, increasing the stirring speed to 400 rpm for 25 min after each addition to ensure uniform dispersion. Continue adding 65.0 g of acrylate-hydroxypropyl acrylate copolymer, stirring at 450 rpm for 30 min until the system is uniformly milky white. Finally, add 80.0 g of polyaminopolyether methylenephosphonic acid, increasing the stirring speed to 500 rpm for 45 min to allow it to fully swell and adsorb. Slowly add sodium hydroxide solution, monitoring the pH online until it reaches 8.0±0.1, maintaining stirring at 500 rpm for another 30 min to ensure pH stability. After standing for 5 min, dilute the solution with 0.45 mL of water. The solution was filtered through a μm polytetrafluoroethylene (PTFE) membrane, and the clarified mother liquor was collected. 10.0 mL of the mother liquor was measured using a graduated cylinder and diluted in 1.0 L of deionized water to obtain a 200 ppm working solution, which is the sealed water corrosion inhibitor.

[0023] Comparative Example 1 The sealed water corrosion inhibitor contains the following raw materials by weight percentage: 1.05% methylbenzotriazole, 11% sodium polyepoxysuccinate, 8% polyaminopolyether methylenephosphonic acid, 5% sodium hydroxide, and the balance is water. The preparation and dilution methods are the same as in Example 1.

[0024] The preparation steps are as follows: After rinsing the reactor with deionized water, add 759.5 mL of deionized water, start the stirrer, and pre-stir at 25 ℃ and 200 rpm for 5 min. Slowly add 10.5 g of methylbenzotriazole, stir at 300 rpm for 15 min, add 110.0 g of sodium polyepoxysuccinate in batches, stir at 400 rpm for 25 min, add 80.0 g of polyaminopolyether methylenephosphonic acid, and stir at 500 rpm for 45 min. Slowly add 20 wt% sodium hydroxide solution, adjust the pH online to 8.0±0.1, stir for 30 min to ensure system stability, let stand for 5 min, filter through a 0.45 μm filter membrane to obtain a clear mother liquor, take 10.0 mL of the mother liquor and dilute to 1.0 L to obtain a 200 ppm working solution, which is the aforementioned closed-loop water corrosion inhibitor.

[0025] Comparative Example 2 The sealed water corrosion inhibitor contains the following raw materials by weight percentage: 11% sodium polyepoxysuccinate, 6.5% acrylic acid-hydroxypropyl acrylate copolymer, 8% polyaminopolyether methylenephosphonic acid, 5% sodium hydroxide, and the balance is water. The preparation and dilution methods are the same as in Example 1.

[0026] The preparation steps are as follows: Add 684.0 mL of deionized water to a 4 L three-necked reactor and pre-stir at 25 ℃ and 200 rpm for 5 min. Add 110.0 g of sodium polyepoxysuccinate and stir at 400 rpm for 25 min. Add 65.0 g of acrylic acid-hydroxypropyl acrylate copolymer and stir at 450 rpm for 30 min. Add 80.0 g of polyaminopolyether methylenephosphonic acid and stir at 500 rpm for 45 min. Slowly add 20 wt% sodium hydroxide solution and adjust the pH online to 8.0±0.1. Stir for 30 min to stabilize the pH. Let stand for 5 min and filter through a 0.45 μm filter membrane to obtain a clear mother liquor. Take 10.0 mL of the mother liquor and dilute it to 1.0 L to obtain a 200 ppm working solution, which is the aforementioned closed-loop water corrosion inhibitor.

[0027] Performance testing Corrosion inhibition performance testing Carbon steel test pieces were sequentially placed in acetone for ultrasonic degreasing for 5 min, removed and air-dried, rinsed with deionized water, and dried in a 45 ℃ oven for 1 h. The initial mass m0 was recorded. Then, the test pieces were placed in 250 mL corrosion-resistant bottles, and each bottle was filled with 200 ppm corrosion inhibitor solution prepared in Examples 1-3 and Comparative Examples 1-2, as well as 100 mL each of pure water, 25% ethylene glycol, 50% ethylene glycol, 20% calcium chloride, and 30% calcium chloride. All samples were then placed in a 25 ℃ constant temperature shaking oven and gently shaken at 50 rpm for 24 h. The test pieces were then removed, ultrasonically cleaned in deionized water for 5 min, immersed in sodium dithiocarbonate passivation solution for 5 min to remove oxidation products, and then cleaned again sequentially with deionized water and ethanol. The samples were dried in a 45 ℃ oven for 2 h, and the mass m1 after immersion was recorded. The corrosion rate CR of each sample was calculated, and the results are shown in Table 1 below.

[0028] Table 1. Sample corrosion rate results (mm / a) sample pure water 25% ethylene glycol 50% ethylene glycol 20% calcium chloride 30% calcium chloride Example 1 0.015 0.450 0.600 0.520 0.700 Example 2 0.0001 0.002 0.003 0.0025 0.004 Example 3 0.0003 0.0205 0.0289 0.0223 0.0316 Comparative Example 1 0.120 1.350 1.800 1.600 2.000 Comparative Example 2 0.080 0.900 1.100 0.950 1.200 Table 1 clearly reflects the effectiveness of the "double-layer protection + multi-component synergy" mechanism of this invention: the inner layer 5-methylbenzotriazole (BTA) coordinates with the metal surface to form a dense passivation film, effectively blocking the dissolution of metal ions; the outer layer acrylic acid-hydroxypropyl acrylate copolymer and sodium polyepoxysuccinate, through adsorption and hydrogen bonding, construct a continuous polymer isolation film outside the passivation layer, further isolating it from corrosive media. Example 2 shows a corrosion rate as low as 0.0001 mm / a in pure water, and 0.002, 0.003, 0.0025, and 0.004 mm / a in 25% ethylene glycol, 50% ethylene glycol, 20% and 30% calcium chloride, respectively, demonstrating the strongest corrosion inhibition effect.

[0029] In contrast, the comparative group, relying on only a single component or lacking a synergistic layer, exhibited corrosion rates as high as 0.900–2.000 mm / a. Therefore, the mechanism of this invention not only significantly improves corrosion inhibition efficiency but also considers cost and environmental friendliness, fully demonstrating its innovativeness and industrial applicability.

[0030] Scale inhibition performance test High-hardness water with a Ca²⁺ concentration of 1000 mg / L and an HCO⁻ concentration of 600 mg / L was prepared by mixing CaCl₂ and NaHCO₃. 200 ppm corrosion inhibitor solutions prepared in Examples 1-3 and Comparative Examples 1-2 were added to 100 mL of water samples from five groups. A blank control group was also included, without the addition of corrosion inhibitor. All samples were placed in an 80 ℃ constant-temperature water bath and gently stirred (50 rpm) for 4 h. After removal, the samples were allowed to cool naturally to room temperature and filtered through a 0.45 μm filter membrane. The filtrate was collected, and the residual Ca²⁺ concentration in the filtrate was determined by EDTA titration. The titration volume was recorded and converted to the residual Ca²⁺ concentration. The scale inhibition efficiency was calculated, and the results are shown in Table 2 below.

[0031] Table 2 Scale inhibition efficiency results sample Residual Ca²⁺ (mg / L) Scale inhibition efficiency (%) Example 1 70 93.0 Example 2 50 95.0 Example 3 40 96.0 Comparative Example 1 300 70.0 Comparative Example 2 200 80.0 Blank control 850 15.0 Table 2 shows the scale inhibition efficiency results, illustrating the multifunctional mechanism advantages of the corrosion inhibitor of this invention in terms of lattice distortion and dispersion of calcium salt crystal nuclei. Examples 1–3 contain polymeric components such as acrylic acid-hydroxypropyl acrylate copolymer and sodium polyepoxysuccinate. In high-hardness water, these components inhibit calcium salt crystal growth through adsorption and dispersion, resulting in residual Ca²⁺ in the filtrate of only 70, 50, and 40 mg / L, respectively, corresponding to scale inhibition efficiencies as high as 93.0%, 95.0%, and 96.0%. Example 3 achieved the best scale inhibition efficiency of 96.0%, demonstrating the extension of the "inner layer chemical complexation + outer layer polymer adsorption" dual-layer protection mechanism to the scale inhibition field—the polymer adsorption layer not only blocks corrosive media but also distorts crystal nuclei and disperses crystals during scaling, thus significantly improving scale inhibition efficiency. In contrast, the scale inhibition efficiency of the comparative examples only reached 70.0-80.0%, and the blank control showed almost no scale inhibition effect, only 15.0%. The results fully demonstrate the necessity and effectiveness of the polymer copolymer in the scale inhibition system, which is the innovation of this patent, and further highlight the significant practical value of this invention in its dual functions of corrosion inhibition and scale inhibition.

[0032] Storage stability test Take 500 g of the mother liquor from Examples 1-3 and Comparative Examples 1-2, and place them in sealed glass bottles, labeling them accordingly. Store them for 3 months under three conditions: 5 °C (low temperature), 25 °C (room temperature), and 40 °C (high temperature). Visually inspect each sample monthly, recording clarity, presence of sediment, layering, or discoloration. After 3 months, take 10 g of each sample from each storage condition, dilute to 1 L (200 ppm working solution), and determine the corrosion rate of carbon steel in pure water according to the "Corrosion Inhibition Performance Test". The results are shown in Table 3 below.

[0033] Table 3 Storage stability results As shown in Table 3, Examples 1–3 remained clear at 5℃, 25℃, and 40℃, without precipitation or stratification, and the retention rate of the corrosion inhibition efficiency consistently ranged from 75% to 93.3%. In particular, Example 3 achieved retention rates of 93.3%, 88.2%, and 78.9% at 5℃, 25℃, and 40℃, respectively, significantly higher than the comparative examples. Comparative Examples 1 and 2, lacking or having an imbalanced ratio of acrylic acid-hydroxypropyl acrylate copolymer and sodium polyepoxysuccinate polymer components, exhibited micro-precipitation or slight turbidity at low temperatures, and significant precipitation and stratification at room temperature and high temperatures, resulting in a substantial decrease in retention rate. These phenomena indicate that the polymer adsorption layer not only isolates the medium from corrosion during cyclic corrosion inhibition but also stabilizes and disperses the inner passivation components, preventing component separation or phase separation caused by temperature fluctuations, thereby ensuring the clarity and long-lasting activity of the mother liquor. This fully demonstrates the inventive and innovative aspects of this invention in terms of green environmental protection, industrial feasibility, and technological advancement.

[0034] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0035] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A sealed water corrosion inhibitor, characterized in that, It contains the following raw materials by weight percentage: methylbenzotriazole: 0.1-2%, sodium polyepoxysuccinate: 6-16%, acrylate-hydroxypropyl acrylate copolymer: 3-10%, polyaminopolyether methylenephosphonic acid: 3-13%, sodium hydroxide: 2-8%, and the balance is water.

2. The water-sealing corrosion inhibitor according to claim 1, characterized in that, The polyaminopolyether-based methylenephosphonic acid is prepared by a Mannich reaction of polyether amine, phosphorous acid, and formaldehyde in a mass ratio of 1:1.2:

4. The Mannich reaction is a process in which amine, formaldehyde, and a compound containing an active methylene group condense under acidic conditions to form a β-aminocarbonyl compound.

3. The water-sealing corrosion inhibitor according to claim 1, characterized in that, The acrylic acid-hydroxypropyl acrylate copolymer is prepared by free radical copolymerization of acrylic acid and hydroxypropyl acrylate in a mass ratio of 3:1 in the presence of an initiator.

4. The water-sealing corrosion inhibitor according to claim 1, characterized in that, The methylbenzotriazole is 5-methylbenzotriazole with a purity of ≥99%.

5. The water-sealing corrosion inhibitor according to any one of claims 1-4, characterized in that, The pH of the prepared solution was adjusted to 7.0–9.

0.

6. The water-sealing corrosion inhibitor according to any one of claims 1-5, characterized in that, The preferred weight percentages of the components are as follows: 0.5–1.5% methylbenzotriazole, 8–14% sodium polyepoxysuccinate, 5–8% acrylic acid-hydroxypropyl acrylate copolymer, 5–10% polyaminopolyether methylenephosphonic acid, and 3–6% sodium hydroxide.

7. The water-sealing corrosion inhibitor according to any one of claims 1 to 6, characterized in that, At a dosage concentration of 200 ppm, it is suitable for use in chilled water, hot water, ethylene glycol, methanol and ethanol antifreeze, and high-concentration calcium chloride solutions.

8. The water-sealing corrosion inhibitor according to any one of claims 1-7, characterized in that, The working solution can be prepared by simply mixing the components at room temperature, adjusting the pH, and stirring until homogeneous.

9. A method for inhibiting carbon steel corrosion using a closed-loop water corrosion inhibitor, wherein the closed-loop water corrosion inhibitor is as described in any one of claims 1–8, and the corrosion inhibitor is added to a closed-loop circulating water system at a concentration of 200 ppm to achieve a carbon steel surface corrosion rate ≤0.03 mm / a.

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