A method for protecting concrete structures in areas with large temperature differences and strong corrosion caused by saline soil.

Abstract

This invention discloses a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, belonging to the field of concrete structure protection technology. The method includes applying a protective coating to a surface-treated concrete surface; the protective coating comprises a three-armed star-shaped sulfide-bonded neoindocyanine green; the three-armed star-shaped sulfide-bonded neoindocyanine green comprises the product of the reaction of trimethylolpropane triglycidyl ether and mercaptolated neoindocyanine green. This invention develops a high-performance protective coating and supporting construction method that integrates strength, crack resistance, high adhesion, and high barrier properties, providing a durable protection method for concrete structures in highly corrosive saline soil environments with large temperature differences.

Description

Technical Field

[0001] This invention belongs to the field of concrete structure protection technology, specifically relating to a method for protecting concrete structures in areas with large temperature differences and strong corrosion caused by saline soil. Background Technology

[0002] Against the backdrop of the Belt and Road Initiative and the Western Development Strategy, my country's Northwest Inland Region and the Qinghai-Tibet Plateau are experiencing a massive wave of infrastructure construction. These regions are generally located in extremely harsh service environments: on the one hand, the annual temperature difference can reach 60-70℃, with drastic changes in temperature between day and night and between seasons; on the other hand, they are widely covered with highly saline soil rich in corrosive media such as high concentrations of chloride and sulfate ions. Under the combined effects of wet-dry cycles, freeze-thaw cycles, and capillary permeation, corrosive ions continuously penetrate into the concrete, causing steel reinforcement corrosion and expansion, concrete cracking and spalling, ultimately leading to a sharp decline in the structural load-bearing capacity and durability, seriously threatening the safety and service benefits of the entire life cycle of the project.

[0003] Currently, coating technology has been widely applied in high-end equipment and major engineering projects such as ships, aircraft, high-speed railways, and marine engineering. However, for the protection of concrete structures in saline soil areas, conventional methods such as epoxy resin coating, silane impregnation, and cement-based polymer mortar are still the mainstays, which still have shortcomings in extreme environments. 1. Insufficient weather resistance: The thermal expansion coefficients of ordinary epoxy coatings do not match those of the concrete substrate, making them prone to micro-cracks under large temperature difference cycles, and gradually losing their physical barrier function; 2. Limitations of passive protection: Traditional coatings can only achieve physical barrier. Once defects such as pinholes and microcracks appear, corrosive media will quickly penetrate and spread, and cannot actively inhibit the corrosion process of the already infiltrated media. 3. Poor functional synergy: It is difficult to simultaneously meet the comprehensive performance requirements of high interface adhesion, excellent resistance to ion penetration, long-term corrosion resistance and adaptability to large temperature difference deformation. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences. The technical solution for achieving the objective of this invention is as follows: A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, the method comprising the following steps: S1. Preparation of protective coating: (1) Preparation of component A: The nano-silica was dried and dehydrated, and the surface was modified with a silane coupling agent to obtain pretreated nano-silica; the pretreated nano-silica was added to an active diluent and dispersed, a three-armed star-shaped sulfide-bonded neoindocyanine green was added, and epoxy resin, triethylamine, defoamer and leveling agent were added. After vacuum degassing and filtration, component A was obtained. (2) Preparation of component B: Provide polyamide curing agent as component B for later use; S2. Concrete surface treatment: After the concrete has been cured, it is washed with high-pressure fresh water or sandblasted to remove laitance, oil stains and loose layers. S3. Protective coating construction: Mix component A and component B evenly in proportion, and after maturation, apply to the concrete surface treated in step S2. Apply 1 to 3 coats and cure at room temperature until fully dry.

[0005] Specifically, the coating process in step S3 uses one or more of the following methods: brush coating, dip coating, roller coating, and spray coating.

[0006] Specifically, the application temperature for the protective coating in step S3 is 15~35℃, and the relative humidity is ≤85%.

[0007] Specifically, in step S3, the thickness of each dry film is 30~300 μm, and the total dry film thickness of the coating is 200~600 μm.

[0008] A protective coating, by weight, comprises 100 parts epoxy resin, 2-4 parts nano silica, 0.5-1 parts silane coupling agent, 15-25 parts reactive diluent, 2-6 parts three-armed star-shaped sulfide-bonded neoindocyanine green, 0.3-0.8 parts triethylamine, 0.5-1 parts defoamer, 0.5-1 parts leveling agent, and 80-100 parts polyamide curing agent.

[0009] Specifically, the nano-silica is selected from one or two of fumed nano-silica and hollow nano-silica microspheres; the silane coupling agent is selected from aminosilane coupling agents; the reactive diluent is selected from one or two of monofunctional or difunctional glycidyl ethers; the defoamer is selected from one or more of polysiloxane defoamers, polyether defoamers, and polyacrylate defoamers; the leveling agent is selected from one of organosilicon leveling agents and acrylic leveling agents; and the polyamide curing agent is selected from one or more of polyamide 650, polyamide 651, polyamide 140, and polyamide 300.

[0010] The preparation method of the three-armed star-shaped sulfide-bonded neoindocyanine green includes the following steps: (1) Synthesis of thiolized neoindocyanine green: Dithiol compound and neoindocyanine green were dissolved in solvents respectively; triethylamine was added to the dithiol compound solution while stirring, and then the neoindocyanine green solution was added dropwise to the dithiol compound solution; after the reaction was completed, the thiolized neoindocyanine green was obtained by purification. (2) Synthesis of three-armed star-shaped sulfide-bonded neoindocyanine green: Thiolized neoindocyanine green and triethylamine were dissolved in a solvent and stirred to activate; trimethylolpropane triglycidyl ether was dissolved in a solvent and added dropwise to the above solution to react. After the reaction was completed, the solution was purified and dried under vacuum to obtain three-armed star-shaped sulfide-bonded neoindocyanine green.

[0011] Specifically, the preparation conditions for the three-armed star-shaped sulfide-bonded neoindocyanine green are: inert gas protection and light avoidance; the dithiol compound is selected from one or both of 2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-1-thiol) and bis(2-mercaptoethyl) ether; the molar ratio of the dithiol compound to neoindocyanine green is (1.1~1.5):1; the molar ratio of the mercapto-modified neoindocyanine green to trimethylolpropane triglycidyl ether is (3.0~3.2):1; the amount of triethylamine used is 1~2 times the molar amount of neoindocyanine green in step (1), and 0.8~1.5 times the molar amount of mercapto-modified neoindocyanine green in step (2).

[0012] A protective coating for concrete in highly corrosive saline soil areas with large temperature differences comprises a three-armed star-shaped sulfide-bonded neoindocyanine green prepared by the method described above.

[0013] This invention develops a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences. Its core mechanism is as follows: First, the sulfonyl and hydroxyl groups in the molecule have strong hydrophilicity, which can improve the wettability and interfacial adhesion between the coating and the concrete substrate. At the same time, they may help to hinder the penetration of corrosive anions through electrostatic repulsion. The thioether bond has good chemical stability and a certain degree of chain flexibility, which helps to improve the flexibility and fatigue resistance of the coating. The flexible ether chain improves molecular flexibility and promotes the dispersion of the three-arm star-shaped thioether bonded neoindocyanine green in the epoxy system.

[0014] II. Reinforcing and Barrier Effects of Nano-Silica Silane-modified nano-silica can be uniformly dispersed in resin. On the one hand, it can enhance cross-linking density, extend the penetration path of corrosive ions, and strengthen physical barrier by utilizing the nano-size effect. On the other hand, it can improve the hardness and wear resistance of coating as a rigid nanofiller, inhibit crack initiation and propagation, and complement the flexible structure of the three-armed star-shaped sulfide-bonded new indocyanine green.

[0015] III. Interfacial Bridging Effect of Silane Coupling Agents The silane terminus of the aminosilane coupling agent hydrolyzes to generate silanol, which condenses with the silanol groups on the concrete surface to form Si-O-Si covalent bonds; its amino terminus reacts with the epoxy groups of the epoxy resin to form chemical bonds. This "molecular bridging" effect enhances the adhesion between the coating and the concrete substrate and seals the interfacial water seepage channels. Simultaneously, the silane coupling agent modifies the surface of nano-silica, improving its dispersibility and interfacial bonding.

[0016] IV. Film Formation and Barrier Effects of Epoxy-Polyamide Curing Systems Epoxy resin reacts with polyamide curing agents to form a highly cross-linked, chemically stable three-dimensional network, providing the coating with basic corrosion resistance and a physical barrier. Three-armed star-shaped sulfide-bonded neoindocyanine green participates in the formation of the cross-linked network through the reaction of the secondary hydroxyl groups at the arm ends with the epoxy groups of the epoxy resin, while simultaneously introducing sulfide bond structures to improve the network's chemical stability. Nano-silica fills the pores, and coupling agents strengthen the interface, together constructing a multi-layered, ion-barrier, highly interfacially bonded, and temperature-resistant integrated synergistic protection system.

[0017] Beneficial effects

[0018] This invention develops a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences. By applying a protective coating to the concrete surface, it achieves the following beneficial effects: 1. Achieving a balance between the physical barrier effect and durability of the rigid framework: The core three-arm star-shaped sulfide-bonded neo-indocyanine green permanently anchors the rigid conjugated framework of indocyanine green in the cross-linked network through chemical bonds, transforming the traditional easily migrating and failing exogenous functional additive into a stable and durable intrinsic structural component; the rigid conjugated framework is uniformly dispersed in the cross-linked network, forming a nanoscale physical barrier, extending the penetration path of corrosive media, and combined with the chemical stability of the sulfide bond, making it difficult for corrosive media to wet and penetrate.

[0019] 2. Constructing a high-performance coating system that combines rigidity and flexibility: The three-armed star-shaped sulfide bonded neo-indocyanine green achieves a synergistic effect of rigidity and flexibility at the molecular level. The rigid conjugated skeleton is combined with flexible ether chains and sulfide bonds, giving the coating both high strength and high crosslinking density, as well as excellent flexibility and deformation ability. It can effectively absorb and release the thermal stress generated by large temperature differences, and its anti-cracking and anti-peeling properties surpass those of traditional rigid epoxy coatings, making it suitable for environments with severe temperature changes.

[0020] 3. Formation of multiple synergistic reinforcement and barrier mechanisms: sulfonyl and hydroxyl groups enhance wetting performance, silane coupling agents construct molecular bridges to achieve high-strength chemical bonding and physical anchoring between the coating and the concrete substrate, blocking interfacial penetration channels; surface-modified nano-silica is uniformly dispersed and synergistically reinforces with star molecules, refining the coating microstructure and extending the diffusion path of corrosive media; highly cross-linked epoxy-polyamide network provides basic chemical inertness, and thioether bonds enhance network stability, together forming a robust corrosion-resistant barrier.

[0021] 4. Excellent comprehensive protective performance and long service life: The synergistic effect of various mechanisms makes the coating perform well in key indicators such as resistance to chloride ion penetration, resistance to dry and wet conditions and freeze-thaw cycles; accelerated aging tests show that its protective performance decays slowly and its expected service life is longer than that of conventional epoxy coatings, which can withstand the long-term harsh environmental test of saline soil areas.

[0022] 5. Mature construction technology and wide applicability: The coating is a two-component system, which is stable in storage and can be applied using conventional coating processes. It is compatible with general concrete substrate treatment methods and matching primers, and is suitable for both preventive protection of new projects and repair and reinforcement of existing facilities.

[0023] In summary, this invention develops a high-performance protective coating and supporting construction method that integrates strength, crack resistance, high adhesion, and high barrier properties, providing a method for protecting concrete structures in highly corrosive saline soil environments with large temperature differences. Attached Figure Description

[0024] Figure 1 Synthetic route for the three-armed star-shaped sulfide-bonded novel indocyanine green 1.

[0025] Figure 2 The 1H NMR spectrum of thiolized neoindocyanine green 1 is shown. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0028] The raw materials and equipment used in the examples and comparative examples are described below, where eq represents molar equivalent: New Indocyanine Green: CAS No. 172616-80-7, commercially available.

[0029] Nano silica: Vapor phase nano silica, particle size 7~40 nm, commercially available.

[0030] Silane coupling agent: selected from γ-aminopropyltriethoxysilane, commercially available.

[0031] Epoxy resin: Bisphenol A type epoxy resin, epoxy equivalent 170~190 g / eq, commercially available.

[0032] Polyamide curing agent: Selected from polyamide curing agent 650, amine value 200~240 mgKOH / g, commercially available.

[0033] Reactive diluent: Allyl glycidyl ether, commercially available.

[0034] Defoamer: Selected from BYK-066N, commercially available.

[0035] Leveling agent: BYK-333, commercially available.

[0036] Thiol-modified neoindocyanine green 1: prepared in-house, the preparation method is as follows: Under nitrogen protection and in the dark, 1.5 eq of 2,2'-(ethane-1,2-dimethylbis(oxy))bis(ethane-1-thiol) was dissolved in anhydrous N,N-dimethylformamide to prepare a 30 mL / mmol thiol solution, which was stirred thoroughly at 30 °C. 1.0 eq of neoindocyanine green was dissolved in anhydrous N,N-dimethylformamide to prepare a 5 mL / mmol neoindocyanine green solution, which was transferred to a constant-pressure dropping funnel for later use. Before starting the addition of the neoindocyanine green solution, 1.2 eq of triethylamine was added to the thiol solution while stirring. Then, the neoindocyanine green solution was slowly added dropwise to the thiol solution at a rate of approximately 2.5 mL / h, for a total addition time of 2 h. After the addition was complete, the reaction mixture was stirred at 30 °C for 6 hours. h, the reaction was monitored by thin-layer chromatography until the raw materials were completely consumed; after the reaction was completed, the reaction solution was concentrated under reduced pressure, and the resulting concentrate was slowly added dropwise to 10 times its volume of ice-cold ether under stirring. The precipitated dark green solid was collected by filtration, washed thoroughly with cold ether, and finally dried under vacuum to obtain mercapto-modified neoindocyanine green 1.

[0037] Thiolized Neoindocyanine Green 2: Prepared in-house, the preparation method is the same as that of Thiolized Neoindocyanine Green 1, except that 2,2'-(ethane-1,2-dimethylbis(oxy))bis(ethane-1-thiol) is replaced with bis(2-mercaptoethyl) ether, and all other conditions remain unchanged, to obtain Thiolized Neoindocyanine Green 2.

[0038] Three-armed star-shaped sulfide-bonded neoindocyanine green 1: self-prepared, the preparation method is as follows: Under nitrogen protection and light-protected conditions, 3.0 eq of mercapto-indocyanine green 1 and 3.0 eq of triethylamine were dissolved in anhydrous N,N-dimethylformamide to prepare a 20 mL / mmol mercapto-indocyanine green solution, which was then activated by stirring at 30 °C for 10 min. 1.0 eq of trimethylolpropane triglycidyl ether was dissolved in anhydrous N,N-dimethylformamide to prepare a 10 mL / mmol trimethylolpropane triglycidyl ether solution, which was added dropwise to the above solution at a rate of approximately 2 mL / h, completing the addition over 1.5 h. After the addition was complete, the reaction was continued at 30 °C with stirring for 12 minutes. h, the epoxy groups were monitored by infrared spectroscopy until they were completely consumed; after the reaction was completed, the reaction solution was concentrated under reduced pressure to remove most of the solvent, and the concentrated solution was slowly added dropwise to 10 times the volume of ice-cold diethyl ether under vigorous stirring. The precipitated solid was collected by filtration, washed thoroughly with cold diethyl ether, and the crude product was purified by silica gel column chromatography. Finally, it was dried under vacuum to obtain the three-armed star-shaped thioether-bonded neoindocyanine green 1.

[0039] Three-armed star-shaped sulfide-bonded neoindocyanine green 2: prepared in-house. The preparation method is the same as that of three-armed star-shaped sulfide-bonded neoindocyanine green 1, except that thiolated neoindocyanine green 1 is replaced with thiolated neoindocyanine green 2, while other conditions remain unchanged, to obtain three-armed star-shaped sulfide-bonded neoindocyanine green 2.

[0040] Single-arm thioether-bonded neoindocyanine green: prepared in-house, the preparation method is the same as that of three-arm star-shaped thioether-bonded neoindocyanine green 1, the difference is that 3.0 eq of thiolated neoindocyanine green 1 is replaced with 1 eq, and trimethylolpropane triglycidyl ether is replaced with n-butyl glycidyl ether, while other conditions remain unchanged, to obtain single-arm thioether-bonded neoindocyanine green.

[0041] Examples 1-4 and Comparative Examples 1-4 Example 1

[0042] A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences 1 S1. Preparation of protective coating 1: (1) Preparation of component A: Under nitrogen protection, 3 parts of nano silica were dried and dehydrated at 120℃ for 2 h, and then surface modified with 0.75 parts of silane coupling agent at 60℃ for 1.5 h to obtain pretreated nano silica; the pretreated nano silica was added to 20 parts of reactive diluent and dispersed by high-speed shearing at 40℃ for 30 min; 4 parts of three-arm star-shaped sulfide-bonded neoindocyanine green 1 were added and ultrasonically dissolved at 40℃ for 30 min; 100 parts of epoxy resin were added, heated to 60℃ and stirred evenly, and then cooled to 40℃; 0.55 parts of triethylamine, 0.75 parts of defoamer and 0.75 parts of leveling agent were added, and defoaming was carried out under vacuum degree ≤ -0.08 MPa for 15 min, filtered and packaged to obtain component A; (2) Component B: Prepare 90 parts of polyamide curing agent; S2. Concrete surface treatment: After the concrete has been cured for 28 days, it is washed with high-pressure fresh water to remove laitance, oil stains and loose layers. S3. Protective Coating Application: Application temperature 25℃, relative humidity ≤75%; prepare the coating according to the mass ratio of epoxy resin to polyamide curing agent 100:90, mechanically stir evenly, and cure for 20 min; use airless spraying method, first apply one coat of protective coating with a dry film thickness of 50μm, and cure for 24 h; then apply two more coats of protective coating, each with a dry film thickness of 175μm, with an interval of 24 h; total dry film thickness 400 μm; cure at room temperature for 7 days.

[0043] Example 2

[0044] A second method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences: Compared with the first method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, the difference lies in step S1, where nano-silica is replaced with 2 parts, silane coupling agent is replaced with 0.5 parts, reactive diluent is replaced with 15 parts, three-arm star-shaped sulfide-bonded neoindocyanine green 1 is replaced with 2 parts, triethylamine is replaced with 0.3 parts, defoamer is replaced with 0.5 parts, leveling agent is replaced with 0.5 parts, and polyamide curing agent is replaced with 80 parts, while other conditions remain unchanged. This is a second method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences.

[0045] Example 3

[0046] A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, method 3: Compared with method 1, the difference lies in step S1, where nano-silica is replaced with 4 parts, silane coupling agent is replaced with 1 part, reactive diluent is replaced with 25 parts, three-arm star-shaped sulfide-bonded neoindocyanine green 1 is replaced with 6 parts, triethylamine is replaced with 0.8 parts, defoamer is replaced with 1 part, leveling agent is replaced with 1 part, and polyamide curing agent is replaced with 100 parts, while other conditions remain unchanged. This method serves as a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, method 3.

[0047] Example 4

[0048] A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, method 4: Compared with method 1, the difference is that the three-armed star-shaped sulfide-bonded new indocyanine green 1 is replaced with three-armed star-shaped sulfide-bonded new indocyanine green 2, while other conditions remain unchanged. This method is used as a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences.

[0049] Comparative Example 1 A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, method 5: Compared with method 1, the difference is that the three-armed star-shaped sulfide-bonded neoindocyanine green 1 is replaced with a single-armed sulfide-bonded neoindocyanine green, while other conditions remain unchanged. This method is used as a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences.

[0050] Comparative Example 2 A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences: Compared with a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, the difference is that a three-armed star-shaped sulfide-bonded neoindocyanine green 1 is not added, while other conditions remain unchanged. This method is used as a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences.

[0051] Comparative Example 3 A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences 7: Compared with a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences 1, the difference is that no nano-silica is added, while other conditions remain unchanged. This is a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences 7.

[0052] Comparative Example 4 A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences (8): Compared with a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences (1), the difference is that the three-armed star-shaped sulfide-bonded neoindocyanine green 1 is replaced with the raw material neoindocyanine green, while other conditions remain unchanged. This method is used as a method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences (8).

[0053] Table 1. Formulations of Examples 1-4 and Comparative Examples 1-4 (by weight)

[0054] The following are the test methods for performance parameters involved in this invention: 1. Nuclear magnetic resonance hydrogen spectrum test: Characterization was performed using a nuclear magnetic resonance spectrometer (Bruker AM-600, Avance 600), with dimethyl sulfoxide-d6 as the deuterated reagent.

[0055] 2. Chloride Ion Permeability Test: Following the test methods for chloride ion permeability of coatings in the current industry standards "Code for Construction of Corrosion Protection of Waterway Engineering Structures" (JTS / T 209-2020) and "Standard for Durability Design of Waterway Engineering Structures" (JTS 153), the protective coatings prepared in the examples and comparative examples were tested for chloride ion permeability. The coatings of each example and comparative example were uniformly applied to a flat glass plate, cured, and then peeled off to form a uniformly thick movable coating sheet with a dry film thickness of 300 μm. The coating sheet was cut into specimens with a diameter of 60 mm and installed in a double-chamber permeation tank, with one side of the coating in contact with a 3.0% sodium chloride solution and the other side in contact with distilled water. The test was conducted at room temperature (23℃) for 30 days. After the test, the chloride ion concentration in the distilled water was measured, and the chloride ion permeation amount was calculated according to the standard formula. The results are expressed as mg / (cm²·d). Three specimens were tested in each group, and the results are shown in Table 2.

[0056] 3.28d Salt Freeze Resistance Spalling Test: The test was conducted according to GB / T 50082-2024 "Standard for Test Methods of Long-Term Performance and Durability of Concrete". The single-sided freeze-thaw method was used. The test specimens were 150mm×120mm×70mm cubic specimens mixed in the same batch and cured under the same conditions. Five specimens were used in each group. The results are shown in Table 2.

[0057] 4. Adhesion test: The adhesion of the protective coatings prepared in the examples and comparative examples was tested according to GB / T 9286-2021 "Paints and Varnishes Cross-cut Test". The test panels were concrete test panels coated with protective coatings with a thickness of 10 mm and a dry film thickness of 100 μm. The coatings were cut manually, with three test panels in each group. The results are shown in Table 2.

[0058] 5. Salt spray resistance test: The salt spray resistance of the protective coatings prepared in the examples and comparative examples was tested according to GB / T 1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes". The test panels were concrete test panels coated with protective coatings with a thickness of 10 mm and a dry film thickness of 100 μm. There were six test panels in each group. The results are shown in Table 2.

[0059] 6. Impact resistance test: The impact resistance of the protective coatings prepared in the examples and comparative examples was tested according to GB / T1732-2020 "Test Method for Impact Resistance of Coating Film". The substrate was a steel plate of 150mm×70mm×0.5mm and the dry film thickness of the coating was 100μm. The results are expressed as the maximum height at which no cracks, wrinkles and peeling were observed in three tests. The results are shown in Table 2.

[0060] Table 2 Performance test results of Examples 1-4 and Comparative Examples 1-4

[0061] As shown in Table 2, Example 1, as the baseline formulation, exhibits the best overall performance. This is attributed to the fact that the flexible segments in the three-armed star-shaped sulfide-bonded neoindocyanine green 1 used in Example 1 can form a dense cross-linked network, and nano-silica fills the micropores to extend the penetration path of corrosive ions. Example 2, by reducing the amount of three-armed star-shaped sulfide-bonded neoindocyanine green 1, shows a slight decrease in various performance aspects, but it is still significantly better than the comparative example and is suitable for general saline soil environments. Example 3, by increasing the amount of three-armed star-shaped sulfide-bonded neoindocyanine green 1, achieves the best protective performance, but the cost increases accordingly. Example 4, using three-armed star-shaped sulfide-bonded neoindocyanine green 2 containing shorter flexible segments, has performance similar to but less than that of Example 1, confirming the important influence of flexible segment length on stress release. Comparative Example 1 uses a single-armed star molecule. Although the single-armed molecule can participate in cross-linking, the cross-linking density is insufficient, resulting in better performance than the unadded system, but significantly lower performance than the three-armed system. Comparative Example 2, without the addition of three-armed star molecules, has poor protective performance. Comparative Example 3, without the addition of nano-silica, exhibited the worst resistance to chloride ion penetration, increased salt freeze peeling, decreased impact resistance and adhesion, and edge blistering and detachment. This indicates that the physical filling of nano-silica and the interfacial enhancement effect of the silane coupling agent are crucial. The lack of nano-fillers leads to increased coating porosity, reduced interfacial bonding, and accelerated penetration of corrosive media. Comparative Example 4 used a physical blend of the raw material neo-indocyanine green. The results showed that the unmodified neo-indocyanine green had poor compatibility with epoxy resin and was prone to migration and aggregation in the cured network, failing to form a stable and uniform protective barrier. This demonstrates the necessity of anchoring functional molecules in the cross-linked network through chemical bonds. In summary, the three-armed star-shaped molecule can significantly improve the protective efficacy of the coating. Its unique three-arm structure, by constructing a three-dimensional dense network, providing high-density functional groups and dynamic connecting bonds, achieves synergistic protection of the coating with large temperature difference adaptability and strong corrosion barrier.

[0062] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for protecting concrete structures in highly corrosive saline soil areas with large temperature differences, characterized in that, The method includes the following steps: S1. Preparation of protective coating: (1) Preparation of component A: The nano-silica was dried and dehydrated, and the surface was modified with a silane coupling agent to obtain pretreated nano-silica; the pretreated nano-silica was added to an active diluent and dispersed, a three-armed star-shaped sulfide-bonded neoindocyanine green was added, and epoxy resin, triethylamine, defoamer and leveling agent were added. After vacuum degassing and filtration, component A was obtained. (2) Preparation of component B: Provide polyamide curing agent as component B for later use; S2. Concrete surface treatment: After the concrete has been cured, it is washed with high-pressure fresh water or sandblasted to remove laitance, oil stains and loose layers. S3. Protective coating construction: Mix component A and component B evenly in proportion, and after maturation, apply to the concrete surface treated in step S2. Apply 1 to 3 coats and cure at room temperature until fully dry.

2. The method for protecting concrete in highly corrosive saline soil areas with large temperature differences as described in claim 1, characterized in that, The coating process in step S3 can be one or more of the following methods: brush coating, dip coating, roller coating, and spray coating.

3. The method for protecting concrete in highly corrosive saline soil areas with large temperature differences as described in claim 1, characterized in that, The application temperature for the protective coating in step S3 is 15~35℃, and the relative humidity is ≤85%.

4. The method for protecting concrete in highly corrosive saline soil areas with large temperature differences as described in claim 1, characterized in that, In step S3, the thickness of each dry film is 30~300μm, and the total dry film thickness of the coating is 200~600μm.

5. A protective coating for use in the protection method of concrete in highly corrosive saline soil areas with large temperature differences as described in any one of claims 1 to 4, comprising, by weight, 100 parts epoxy resin, 2 to 4 parts nano silica, 0.5 to 1 part silane coupling agent, 15 to 25 parts reactive diluent, 2 to 6 parts three-armed star-shaped sulfide-bonded neoindocyanine green, 0.3 to 0.8 parts triethylamine, 0.5 to 1 part defoamer, 0.5 to 1 part leveling agent, and 80 to 100 parts polyamide curing agent.

6. The protective coating as described in claim 5, characterized in that, The nano-silica is selected from one or two of fumed nano-silica and hollow nano-silica microspheres; the silane coupling agent is selected from aminosilane coupling agents; the reactive diluent is selected from one or two of monofunctional or difunctional glycidyl ethers; the defoamer is selected from one or more of polysiloxane defoamers, polyether defoamers, and polyacrylate defoamers; the leveling agent is selected from one of organosilicon leveling agents and acrylic leveling agents; and the polyamide curing agent is selected from one or more of polyamide 650, polyamide 651, polyamide 140, and polyamide 300.

7. The protective coating as described in claim 5, characterized in that, The three-armed star-shaped sulfide-bonded neoindocyanine green is prepared by a method comprising the following steps: (1) Synthesis of thiolized neoindocyanine green: Dithiol compound and neoindocyanine green were dissolved in solvents respectively; triethylamine was added to the dithiol compound solution while stirring, and then the neoindocyanine green solution was added dropwise to the dithiol compound solution; after the reaction was completed, the thiolized neoindocyanine green was obtained by purification. (2) Synthesis of three-armed star-shaped sulfide-bonded neoindocyanine green: Thiolized neoindocyanine green and triethylamine were dissolved in a solvent and stirred to activate; trimethylolpropane triglycidyl ether was dissolved in a solvent and added dropwise to the above solution to react. After the reaction was completed, the solution was purified and dried under vacuum to obtain three-armed star-shaped sulfide-bonded neoindocyanine green.

8. The protective coating as described in claim 7, characterized in that, The preparation conditions for the three-armed star-shaped sulfide-bonded neoindocyanine green are: inert gas protection and light avoidance; the dithiol compound is selected from one or two of 2,2'-(ethane-1,2-diylbis(oxy))bis(ethane-1-thiol) and bis(2-mercaptoethyl) ether; the molar ratio of the dithiol compound to neoindocyanine green is (1.1~1.5):1; the molar ratio of the mercapto-modified neoindocyanine green to trimethylolpropane triglycidyl ether is (3.0~3.2):1; the amount of triethylamine used is 1~2 times the molar amount of neoindocyanine green in step (1), and 0.8~1.5 times the molar amount of mercapto-modified neoindocyanine green in step (2).

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