Inorganic corrosion-resistant coating and method for preparing the same

Abstract

The present application relates to the technical field of high-performance coating, in particular to an inorganic corrosion-resistant coating and a preparation method thereof.The present application overcomes the problems of poor corrosion resistance and poor thermal insulation performance of inorganic coatings.The present application obtains a composite silicate binder by mixing potassium silicate and lithium silicate, forming a dense and stable three-dimensional crosslinked network structure;obtains a thermal insulation filler by coating metal silver on the surface of hollow glass microspheres and compounding with silica aerogel, synergistically constructing a multiple thermal insulation mechanism of "reflection, blocking and inhibition";obtains a composite shielding filler by mixing a flaky filler and a two-dimensional nanosheet filler, the two forming a complementary spatial blocking structure, reducing the probability of contact between the corrosion medium and the substrate, and the flaky structure also enhancing the density of the coating;by adding an interface in-situ passivation agent, a passivation protective film can be formed at the interface between the filler and the binder, avoiding corrosion caused by interface reaction between the filler and the substrate.

Description

Technical Field

[0001] This invention relates to the field of high-performance coatings technology, specifically to an inorganic corrosion-resistant coating and its preparation method. Background Technology

[0002] In harsh industrial environments such as petrochemicals, marine engineering, energy and power, and metallurgy, metal substrates face multiple challenges, including high temperatures, high humidity, and chemical corrosion, resulting in severe corrosion problems. This not only causes huge economic losses but can also lead to serious safety accidents. Therefore, developing high-performance protective coatings is a key technical means to ensure equipment safety and extend its service life.

[0003] Traditional organic anti-corrosion coatings, such as epoxy resins and polyurethanes, while possessing good film-forming properties and physical barrier effects, have inherent drawbacks that limit their application in harsh conditions such as high temperatures. These organic coatings generally have low temperature resistance, typically softening, decomposing, and aging above 150°C, losing their protective effect. Furthermore, the chemical bonds in their molecular structure are easily broken under ultraviolet light and oxidizing agents, leading to coating chalking and cracking. In addition, the emission of volatile organic compounds during the production and application of organic coatings also poses a threat to the environment and human health.

[0004] In contrast, inorganic coatings, primarily composed of silicates and phosphates as film-forming materials, have demonstrated significant potential in high-temperature corrosion protection due to their advantages such as high temperature resistance, high hardness, non-flammability, and environmental friendliness. However, existing inorganic anti-corrosion coatings still face two major technical bottlenecks: First, their corrosion resistance needs improvement. Traditional inorganic coatings, after curing, are typically rigid and lack toughness, making them prone to micro-cracks when the substrate expands and contracts due to thermal expansion or contraction or is subjected to mechanical impact, providing channels for the penetration of corrosive media. Simultaneously, single physical barrier fillers such as mica powder and glass flakes are insufficient to construct a completely dense barrier layer, limiting the coating's impermeability. Second, their thermal insulation performance is inadequate. Most anti-corrosion coatings themselves have high thermal conductivity and lack insulation capabilities. Although some studies have attempted to reduce thermal conductivity by adding materials such as hollow glass microspheres, the poor interfacial compatibility between these insulating fillers and inorganic binders easily leads to structural defects in the coating, resulting in a decrease in mechanical strength and weakening its physical barrier ability against corrosion, failing to achieve an effective balance between corrosion resistance and thermal insulation performance.

[0005] Therefore, developing a novel inorganic coating that can synergistically improve corrosion resistance and thermal insulation is a technical problem that urgently needs to be solved in this field. To this end, an inorganic corrosion-resistant coating and its preparation method are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an inorganic corrosion-resistant coating and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] Unless otherwise specified, all parts in this invention are parts by weight.

[0009] This invention provides a method for preparing an inorganic corrosion-resistant coating, the method of which is as follows:

[0010] A composite silicate binder is obtained by mixing potassium silicate solution and lithium silicate solution at a mass ratio of 3-5:1.

[0011] A composite thermal insulation filler was prepared by mixing silver-coated hollow glass microspheres and silica aerogel.

[0012] A composite shielding filler is obtained by mixing flake-shaped filler and two-dimensional nanosheet filler at a mass ratio of 4-6:1.

[0013] Add 30-50 parts of composite silicate binder and 25 parts of deionized water to a mixing tank, start high-speed dispersion, and then add 15-25 parts of composite shielding filler, 20-30 parts of composite thermal insulation filler, 1-3 parts of interface in-situ passivating agent sodium hexametaphosphate and 0.5 parts of wetting and dispersing agent in sequence. Disperse at 1800-2200 rpm for 30-50 minutes to form a slurry. Add 5 parts of curing agent and stir at 500 rpm for 20 minutes to obtain inorganic corrosion resistant coating; the wetting and dispersing agent is BYK-190.

[0014] Preferably, the composite thermal insulation filler is prepared as follows: silver-coated hollow glass microspheres and silica aerogel (particle size 1-5μm) are mixed at a mass ratio of 2-4:1 and ultrasonically dispersed in ethanol; silane coupling agent KH-550 is added dropwise under stirring conditions, the temperature is raised to 60-70℃ and reacted for 4-6 hours, the stirring rate is 250rpm, and after filtration, washing and drying, the composite thermal insulation filler is obtained.

[0015] The preferred method for preparing silver-coated hollow glass microspheres is as follows: Hollow glass microspheres (particle size 50-80 μm) are pretreated and then added to a sensitizing solution of stannous chloride. Sensitization is carried out at 250 rpm for 20-30 min at room temperature. The surface of the microspheres is rinsed with deionized water to remove residual sensitizing solution. The sensitized hollow glass microspheres are then transferred to an activation solution of palladium chloride and ultrasonically activated at 300 W for 15-25 min. The microspheres are then rinsed with deionized water until no Cl is visible in the effluent. -The activated hollow glass microspheres were dried at 70℃ for 1 hour. The activated hollow glass microspheres were then added to a silver ammonia solution (solid-liquid ratio 1:20-25, g:mL) and stirred at 200 rpm for 15 minutes at 30-40℃. A reducing agent glucose solution was added dropwise at a rate of 2 mL / min, with continuous stirring during the addition process. The stirring rate was increased to 300 rpm, and the reaction temperature was controlled at 30℃ for 20-30 minutes. The microspheres were rinsed with deionized water until the effluent was neutral, and then rinsed with anhydrous ethanol to remove residual plating solution from the surface. Finally, the microspheres were vacuum dried at 80℃ for 2 hours to obtain silver-coated hollow glass microspheres.

[0016] Preferably, the flake-shaped filler is mica powder with an average particle size of 10 μm and an aspect ratio ≥80; the two-dimensional nanosheet filler is modified graphene oxide.

[0017] The preferred method for preparing modified graphene oxide is as follows: 10 parts of graphene oxide (CAS: 2640657-49-2) are added to 900 parts of ethanol aqueous solution and ultrasonically treated at 400W for 40 min to obtain a dispersion; a silane coupling agent KH-550 solution is added dropwise under stirring at 500 rpm, with the dropwise addition rate controlled at 1 mL / min. After the addition is complete, the temperature is raised to 60-70℃, the rotation speed is increased to 650 rpm, and the reflux condenser is turned on to react for 4-6 h; the mixture is cooled to room temperature, centrifuged, washed, and dried to obtain modified graphene oxide.

[0018] Preferably, the curing agent is obtained by mixing active zinc oxide and aluminum dihydrogen phosphate in a mass ratio of 1.5:1; the active zinc oxide is purchased from Shandong Xingya New Material Co., Ltd.

[0019] Another aspect of the present invention provides an inorganic corrosion-resistant coating, which is prepared by any of the above preparation methods; the raw materials for preparing the inorganic corrosion-resistant coating include a composite silicate binder, a composite thermal insulation filler, a composite shielding filler, a curing agent, and an in-situ interface passivating agent.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. This invention uses potassium silicate and lithium silicate as a binder and introduces graphene oxide. Potassium silicate provides the main framework and hardness of the coating, while lithium ions with smaller radii can fill the micropores of the potassium silicate network structure, achieving ion-level filling and reinforcement, which significantly improves the density and toughness of the binder after curing. At the same time, the graphene oxide sheets with large specific surface area and oxygen-containing functional groups can be strongly bonded to the silicate binder through hydrogen bonds and chemical bonds, and physically divide and fill the micropores in the coating. It forms a maze + nano barrier effect with micron-sized mica powder, which greatly extends the penetration path of corrosive media and jointly constructs a physically and chemically dense anti-corrosion barrier.

[0022] 2. The hollow structure of hollow glass microspheres mainly blocks heat conduction and convection through the internal static air layer. In this invention, a layer of metallic silver is coated on its surface, and the surface of the microsphere becomes a highly efficient infrared reflector. When high-temperature heat radiation is transmitted to the inside of the coating, it will be scattered and reflected in all directions by these countless tiny reflectors, which greatly hinders the penetration of heat radiation.

[0023] 3. This invention uses hollow glass microspheres and silica aerogel particles, and modifies their surface with a silane coupling agent. The multi-scale insulating filler achieves efficient stacking. The aerogel fills the gaps between the microspheres, maximizing the construction of a static air layer and the interruption of the solid heat conduction path, thereby obtaining extremely low thermal conductivity. In addition, through the bridging effect of the silane coupling agent, a strong chemical bond is formed between the surface of the insulating filler and the inorganic silicate binder, turning the filler / matrix interface, which was originally a mechanically weak point, into an effective stress transfer point. This ensures that the coating maintains excellent mechanical strength and structural integrity while achieving efficient insulation, avoiding the problem of sacrificing anti-corrosion performance due to the addition of insulating materials.

[0024] 4. The composite shielding filler of this invention is composed of flake-shaped filler and two-dimensional nanosheet filler, which form a complementary spatial barrier structure. The flake-shaped filler can construct a multi-layered parallel physical barrier inside the coating, extending the penetration path of corrosive media. The two-dimensional nanosheet filler, with its nanoscale size advantage, can fill the tiny gaps between the flake-shaped filler, further blocking the penetration channels of water molecules, oxygen, and corrosive ions. This synergistic effect significantly reduces the probability of contact between corrosive media and the substrate. At the same time, the sheet structure can also enhance the density of the coating and reduce the porosity inside the coating, significantly improving the corrosion resistance of the coating from the perspective of physical barrier and effectively delaying the oxidation and corrosion process of the substrate.

[0025] 5. The addition of the in-situ passivating agent at the interface of this invention can form a passivation protective film at the interface between the filler and the binder, preventing corrosion caused by interfacial reaction between the filler and the substrate. At the same time, the modification treatment of the two-dimensional nanosheet filler can enhance its compatibility with the binder and reduce interface defects. This interface optimization treatment not only improves the overall bonding strength of the coating, but also prevents corrosive media from accumulating and penetrating at the interface, avoiding coating failure caused by interfacial peeling. Moreover, the modified filler has better dispersibility and can be evenly distributed in the coating, ensuring that each area has consistent anti-corrosion capability, extending the service life of the coating in harsh environments, and improving the stability and durability of corrosion resistance. Attached Figure Description

[0026] Figure 1 The figures show the test results of thermal insulation performance of Embodiments 3, 5-6 and Comparative Examples 3-6 of the present invention. Detailed Implementation

[0027] 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.

[0028] Please see Figure 1 This invention provides an inorganic corrosion-resistant coating and its preparation method, the technical solution of which is as follows:

[0029] Example 1

[0030] Hollow glass microspheres were placed in a 6 wt% sodium hydroxide solution (solid-liquid ratio 1:10, g:mL) and stirred at 300 rpm for 30 min at 45 °C to remove surface oil and impurities. They were then repeatedly rinsed with deionized water until neutral, dried in an 85 °C oven for 2 h, and cooled to room temperature for later use. The pretreated hollow glass microspheres were added to a sensitizing solution of stannous chloride (solid-liquid ratio 1:10, g:mL) and sensitized at 250 rpm for 20 min at room temperature. The microspheres were rinsed with deionized water to remove residual sensitizing solution. The sensitized hollow glass microspheres were then transferred to an activation solution of palladium chloride (solid-liquid ratio 1:10, g:mL) and ultrasonically activated at 300 W for 15 min. The microspheres were then rinsed with deionized water until no Cl- was visible in the effluent. - The hollow glass microspheres were dried at 70℃ for 1 hour. The activated microspheres were then added to a silver ammonia solution (solid-liquid ratio 1:20, g:mL), and stirred at 200 rpm for 15 minutes at 30℃. A reducing agent, a glucose aqueous solution (75 g / L concentration, 1:1 volume ratio to the silver ammonia solution), was added dropwise at a rate of 2 mL / min, with continuous stirring at a rate increased to 300 rpm. The reaction temperature was maintained at 30℃, and the reaction was allowed to proceed for 20 minutes. The microspheres were rinsed with deionized water until the effluent was neutral, and then rinsed with anhydrous ethanol to remove surface residues. The plating solution was vacuum dried at 80℃ for 2 hours to obtain silver-coated hollow glass microspheres. The silver-coated hollow glass microspheres and silica aerogel were mixed at a mass ratio of 2:1 and then ultrasonically dispersed in ethanol (solid-liquid ratio 1:10, g:mL). Under stirring conditions, a silane coupling agent KH-550 solution (6% of the total solid mass of silane coupling agent KH-550, diluted with 10 times the mass of anhydrous ethanol) was added dropwise. The temperature was raised to 60℃ and the reaction was carried out for 4 hours with a stirring rate of 250 rpm. After filtration, washing, and drying, the composite thermal insulation filler was obtained.

[0031] Take 800 parts deionized water, slowly add 30 parts concentrated hydrochloric acid and stir until homogeneous. Add 15 parts stannous chloride to the above dilute hydrochloric acid solution and stir until completely dissolved. Dilute the solution to 1000 parts with deionized water to obtain a stannous chloride solution. Mix 0.2 parts palladium chloride with 8 parts concentrated hydrochloric acid. After the palladium chloride is completely dissolved, slowly add this solution to 900 parts deionized water while stirring continuously. Dilute the solution to 1000 parts with deionized water to obtain a palladium chloride solution. Slowly add ammonia water dropwise to a 2.5 wt% silver nitrate aqueous solution while stirring at 200 rpm until the brown precipitate in the solution is completely dissolved. The final solution pH should be controlled at 9.5-10.0, and the solution should be transparent and free of precipitate to obtain a silver ammonia solution, which should be prepared and used immediately.

[0032] A composite silicate binder was obtained by mixing potassium silicate solution (potassium silicate:deionized water mass ratio = 1:1.2) and lithium silicate solution (lithium silicate:deionized water mass ratio = 1:1.5) at a mass ratio of 3:1; a composite shielding filler was obtained by mixing flake filler and two-dimensional nanosheet filler at a mass ratio of 4:1; and a curing agent was obtained by mixing active zinc oxide and aluminum dihydrogen phosphate at a mass ratio of 1.5:1. The flake filler was mica powder, and the two-dimensional nanosheet filler was modified graphene oxide.

[0033] Ten parts of graphene oxide were added to 900 parts of an aqueous ethanol solution (ethanol:deionized water mass ratio = 1:3), and ultrasonicated at 400W for 40 min to obtain a dispersion. A silane coupling agent KH-550 solution was added dropwise under stirring at 500 rpm at a rate of 1 mL / min. After the addition was complete, the temperature was raised to 60℃, the stirring speed was increased to 650 rpm, and the reflux condenser was turned on for 4 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain modified graphene oxide. The silane coupling agent KH-550 solution was prepared by dissolving 2 parts of silane coupling agent KH-550 in 80 parts of anhydrous ethanol.

[0034] Add 30 parts of composite silicate binder and 25 parts of deionized water to a mixing tank, start high-speed dispersion, run at 500 rpm for 2 minutes, then at 1000 rpm for 3 minutes, and finally increase to 1500 rpm; add 15 parts of composite shielding filler, 20 parts of composite thermal insulation filler, 1 part of interface in-situ passivating agent sodium hexametaphosphate and 0.5 parts of wetting and dispersing agent in sequence, disperse at 1800 rpm for 30 minutes to form a slurry, add 5 parts of curing agent, stir at 500 rpm for 20 minutes to obtain inorganic corrosion resistant coating; the wetting and dispersing agent is BYK-190.

[0035] Example 2

[0036] The preparation method and parameters of Example 1 are the same, except that the mass ratio of potassium silicate solution to lithium silicate solution is 4:1; the amount of composite silicate binder is 35 parts; and the components are mixed and dispersed at 1900 rpm for 35 min to form a slurry.

[0037] Example 3

[0038] The preparation method and parameters of Example 1 are the same, except that the mass ratio of potassium silicate solution to lithium silicate solution is 5:1; the amount of composite silicate binder is 40 parts; and the components are mixed and dispersed at a speed of 2000 rpm for 40 min to form a slurry.

[0039] Example 4

[0040] The preparation method and parameters of Example 1 are the same, except that the mass ratio of potassium silicate solution to lithium silicate solution is 4:1; the amount of composite silicate binder is 50 parts; and the components are mixed and dispersed at 2200 rpm for 50 min to form a slurry.

[0041] Comparative Example 1

[0042] The preparation method and parameters of Example 1 are the same, except that only potassium silicate solution is used as silicate binder, and the amount is 30 parts.

[0043] Comparative Example 2

[0044] The preparation method and parameters of Example 1 are the same, except that only lithium silicate solution is used as silicate binder, and the amount is 30 parts.

[0045] Experiment Example 1: Corrosion Resistance Test

[0046] The metal substrate was sandblasted to Sa2.5 level to remove surface oil and rust. The prepared inorganic corrosion-resistant coating was then uniformly applied to the substrate surface by spraying, followed by a stepped temperature program curing process: first, leveling at room temperature for 30 minutes, then holding at 80℃ for 1 hour, then raising the temperature to 160℃ and holding for 2 hours, and finally raising the temperature to 260℃ and holding for 1 hour. The coating was then cooled to room temperature in the furnace to obtain the coating. The corrosion resistance of the coating was tested; the salt spray resistance was tested according to the standard GB / T1771-2007. The results are shown in Table 1.

[0047] Table 1. Corrosion resistance test results of Examples 1-4 and Comparative Examples 1-2

[0048] Group Acid resistance (5% HCl) 25℃, 30 days Alkali resistance (5% NaOH) 25℃, 30d Salt spray resistance Example 1 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Example 2 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Example 3 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Example 4 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Comparative Example 1 Localized blistering with slight detachment at the edges Fine cracks appeared Rust spots appeared after 850 hours. Comparative Example 2 A small number of tiny bubbles appeared Slight swelling occurred Rust spots appeared after 1000 hours.

[0049] As can be seen from Table 1, in Examples 1-4, the composite silicate binder can form a denser and more stable three-dimensional cross-linked network structure by combining potassium silicate and lithium silicate: potassium silicate can improve the initial bonding strength of the coating, while lithium silicate can enhance the chemical stability and resistance to ion erosion of the coating. The two work synergistically to significantly improve the coating's anti-permeability and structural stability. The resulting coating does not bubble or peel off in acid and alkali resistance tests, and shows no rust spots in salt spray resistance test ≥1200h. In Comparative Example 1, only potassium silicate solution was used as the silicate binder. The silicon-oxygen bonds in the structure of potassium silicate are prone to react with hydrogen ions in an acidic environment to generate water-soluble silicic acid, which causes the coating structure to gradually become loose. In the acid resistance test, it could not achieve the stable state of "no bubbling and no peeling" as in Example 1. In terms of alkali resistance, although potassium silicate is more resistant to alkali than acid, the crosslinking density of the coating formed by a single binder is low. 5% NaOH solution will still slowly penetrate into the interior of the coating, destroying the interfacial bond between the binder and the filler. In terms of salt spray resistance, the porosity of the single potassium silicate coating is high. Chloride ions in the salt spray can easily reach the substrate surface through the pores, causing substrate corrosion and rust spots, and shortening its salt spray resistance time. In Comparative Example 2, only lithium silicate solution was used as the silicate binder. In the acid resistance test, although the coating formed by lithium silicate could resist the corrosion of 5% HCl to a certain extent, the ionic stability of the single binder was insufficient. Hydrogen ions easily exchanged with lithium ions in the coating, resulting in damage to the integrity of the coating structure. In the alkali resistance test, the cross-linking network strength of the single lithium silicate coating was weak, and the coating would swell slightly under the long-term action of 5% NaOH solution. In terms of salt spray resistance, the barrier ability of the single lithium silicate coating was insufficient, and corrosive ions in the salt spray could easily penetrate the coating.

[0050] Example 5

[0051] Referring to the preparation method and parameters of Example 3, the difference is that in preparing silver-coated hollow glass microspheres, the stirring sensitization was performed for 25 min, followed by ultrasonic activation for 20 min; the activated hollow glass microspheres were added to a silver ammonia solution with a solid-liquid ratio of 1:22, and stirred at 200 rpm for 15 min at 35°C; a reducing agent glucose solution was added dropwise, and the reaction was carried out for 25 min; in preparing the composite thermal insulation filler, the mass ratio of silver-coated hollow glass microspheres to silica aerogel was 3:1, and after adding silane coupling agent KH-550, the temperature was raised to 65°C and reacted for 5 h; the amount of composite thermal insulation filler used was 25 parts.

[0052] Example 6

[0053] Referring to the preparation method and parameters of Example 3, the difference is that in preparing silver-coated hollow glass microspheres, the stirring sensitization was performed for 30 min, followed by ultrasonic activation for 25 min; the activated hollow glass microspheres were added to a silver ammonia solution with a solid-liquid ratio of 1:25, and stirred at 200 rpm for 15 min at 40°C; a reducing agent glucose solution was added dropwise, and the reaction was carried out for 30 min; in preparing the composite thermal insulation filler, the mass ratio of silver-coated hollow glass microspheres to silica aerogel was 4:1, and after adding silane coupling agent KH-550, the temperature was raised to 70°C and reacted for 6 h; the amount of composite thermal insulation filler used was 30 parts.

[0054] Comparative Example 3

[0055] The preparation method and parameters of Example 3 were used, except that the hollow glass microspheres were not coated with silver.

[0056] Comparative Example 4

[0057] The preparation method and parameters of Example 3 were used, except that the composite insulating filler was not treated with a silane coupling agent.

[0058] Comparative Example 5

[0059] The preparation method and parameters of Example 3 were used in accordance with the same method and parameters, except that only silica aerogel treated with silane coupling agent was used as the insulating filler, and the amount was 20 parts.

[0060] Comparative Example 6

[0061] The preparation method and parameters of Example 3 were used in accordance with the same method and parameters, except that only silver-coated hollow glass microspheres treated with silane coupling agent were used as the heat insulation filler, and the amount was 20 parts.

[0062] Experiment Example 2: Thermal Insulation Performance Test

[0063] The experiment was conducted using a self-made simulated thermal insulation tester, referring to Chapter 2.3.1 of the master's thesis "Preparation and Performance Study of Thermal Insulation Coatings for Buildings" (Zhang Ling, 2014). Following the method for determining the thermal conductivity of the coating in Chapter 2.3.4, the thermal conductivity of the coating was tested at an average temperature of 25℃. Three parallel tests were performed for each group, and the average value was taken. The results are shown in Table 2 and... Figure 1 As shown.

[0064] Table 2 Thermal insulation performance tests of Examples 3, 5-6 and Comparative Examples 3-6

[0065] Group Thermal conductivity / W / m·K Thermal insulation temperature difference / ℃ Example 3 0.135 7.4 Example 5 0.122 8.5 Example 6 0.125 8.0 Comparative Example 3 0.167 5.4 Comparative Example 4 0.155 6.0 Comparative Example 5 0.180 4.5 Comparative Example 6 0.148 6.7

[0066] From Table 2 and Figure 1As can be seen, in Examples 3 and 5-6, the composite thermal insulation filler uses silver-coated hollow glass microspheres and silica aerogel as core components, which combine to form an excellent multilayer thermal insulation system. The sealed cavity inside the hollow glass microspheres can trap still air, utilizing the low thermal conductivity of air to achieve basic thermal insulation; the silica aerogel, with its extremely high porosity and nanoscale pore structure, further inhibits air convection and heat conduction, while its three-dimensional network structure can reduce heat radiation transfer; the silver coating layer can reflect some external heat radiation, reducing heat absorption; the three components work together to construct a multi-layer thermal insulation mechanism of "reflection-blocking-inhibition", significantly reducing the thermal conductivity of the coating, improving the overall thermal insulation performance, effectively maintaining the stability of the substrate surface temperature, and reducing the impact of ambient temperature fluctuations on the substrate. The obtained coating has a thermal conductivity of 0.122-0.135 W / m·K and a thermal insulation temperature difference of 7.4-8.5℃. In Comparative Example 3, the hollow glass microspheres were not silver-coated, lacking the heat-reflective effect of the silver layer. Basic insulation relied solely on the cavities within the microspheres, resulting in a significant decrease in the coating's ability to reflect environmental heat radiation. Furthermore, heat was more easily transferred into the coating via radiation, disrupting the insulation balance. In Comparative Example 4, the composite insulating filler was not treated with a silane coupling agent. Its surface compatibility with the binder was poor, leading to agglomeration in the coating. This resulted in thermal bridges between the fillers, accelerating heat conduction. The absence of the silane coupling agent also created gaps at the filler-binder interface, reducing air convection and heat conduction resistance, significantly weakening the insulation performance. In Comparative Example 5, only silica aerogel treated with a silane coupling agent was used as the insulating filler. While single silica aerogel possesses a nanoscale porous structure, its low mechanical strength made it susceptible to pressure damage in the coating, causing partial collapse of the pore structure and loss of insulation capacity. In Comparative Example 6, only silver-coated hollow glass microspheres treated with silane coupling agent were used as thermal insulation fillers. Although the single silver-coated hollow glass microspheres retained heat reflection ability, they lacked the nanoscale pore barrier effect of silica aerogel. Heat was easily transferred through the gaps between the microspheres in the form of air convection. Moreover, the lack of aerogel prevented the formation of a dual "reflection-barrier" mechanism inside the coating, resulting in insufficient suppression of heat convection and weakened thermal insulation performance compared with the example.

[0067] Example 7

[0068] The preparation method and parameters of Example 5 are the same, except that when preparing modified graphene oxide, the temperature is raised to 65°C after adding silane coupling agent and refluxed for 5 hours; the flake filler and two-dimensional nanosheet filler are mixed at a mass ratio of 5:1 to obtain composite shielding filler; the amount of composite shielding filler is 20 parts; and the amount of interface in-situ passivating agent is 2 parts.

[0069] Example 8

[0070] The preparation method and parameters of Example 5 are the same, except that when preparing modified graphene oxide, the temperature is raised to 70°C after adding silane coupling agent and refluxed for 6 hours; the flake filler and two-dimensional nanosheet filler are mixed at a mass ratio of 6:1 to obtain composite shielding filler; the amount of composite shielding filler is 25 parts; and the amount of interface in-situ passivating agent is 3 parts.

[0071] Comparative Example 7

[0072] The preparation method and parameters of Example 5 were used, except that no in-situ passivating agent was added to the interface.

[0073] Comparative Example 8

[0074] The preparation method and parameters of Example 5 are the same, except that only flake-shaped filler is used as the shielding filler, and the amount is 15 parts.

[0075] Comparative Example 9

[0076] The preparation method and parameters of Example 5 are the same, except that only two-dimensional nanosheet filler is used as the shielding filler, and the amount is 15 parts.

[0077] Comparative Example 10

[0078] The preparation method and parameters of Example 5 were used, except that the graphene oxide was not modified.

[0079] Comparative Example 11

[0080] The preparation method and parameters of Example 5 were used, except that no composite shielding filler was added.

[0081] Experiment Example 3: Corrosion Resistance Test

[0082] The corrosion resistance performance was tested according to the method in Experiment Example 1; the results are shown in Table 3.

[0083] Table 3 Corrosion resistance tests of Examples 5, 7-8 and Comparative Examples 7-11

[0084] Group Acid resistance (5% HCl) 25℃, 30 days Alkali resistance (5% NaOH) 25℃, 30d Salt spray resistance Example 5 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Example 7 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Example 8 No bubbling or peeling No bubbling or peeling ≥1200h, no rust spots Comparative Example 7 Localized blistering with slight peeling at the edges Fine cracks appeared, and some filler was exposed. Rust spots appeared after 850 hours. Comparative Example 8 A small number of bubbles appeared, but there was no obvious shedding. Mild swelling occurred in some areas. Rust spots appeared after 940 hours. Comparative Example 9 Numerous bubbles appeared, and some areas detached. Surface cracks are obvious Rust spots appeared after 720 hours. Comparative Example 10 Bubbles appear in the clustered area Delamination occurs around the aggregates Rust spots appeared after 800 hours. Comparative Example 11 Bubbling and detachment occurred after 15 days. The surface swelled severely after 10 days. Rust appeared after 330 hours.

[0085] As shown in Table 3, the excellent corrosion resistance in Examples 5 and 7-8 stems from the synergistic effect of "interface passivation-composite shielding": the in-situ passivating agent eliminates interface defects, and the flake-like and two-dimensional nanosheet fillers form a multi-level barrier of "macroscopic barrier + microscopic sealing." Modification treatment ensures uniform dispersion of the nanofillers, resulting in coatings that do not bubble or peel off in acid and alkali resistance tests, and show no rust spots in salt spray tests ≥1200h. In Comparative Example 7, no in-situ passivating agent was added, and micro-gaps easily formed at the filler-binder interface, becoming channels for corrosive media penetration. In Comparative Example 8, only flake-like fillers were used as shielding fillers. Although a physical barrier was formed, it could not fill the tiny pores between its layers, allowing corrosive media to slowly penetrate through the pores. The lack of the synergistic sealing effect of the two-dimensional nanosheet fillers significantly weakened the barrier effect compared to the examples. In Comparative Example 9, only two-dimensional nanosheet fillers were used as shielding fillers. Single two-dimensional nanosheet fillers are difficult to form a continuous macroscopic barrier network, and at high dosages, they are prone to agglomeration and defects. Without the interlayer shielding of flake fillers, the microscopic barrier of the nanosheets is insufficient to resist long-distance media penetration. In Comparative Example 10, no modification was made to the graphene oxide. The surface contained many oxygen-containing groups, resulting in poor compatibility with the inorganic binder and a tendency to agglomerate and form defects. After 30 days of acid resistance testing, bubbles appeared first in the agglomerated areas; after 30 days of alkali resistance testing, peeling occurred around the agglomerates. The lack of modification treatment led to uneven dispersion of the nanofillers, creating localized corrosion entry points. In Comparative Example 11, no composite shielding filler was added. The coating relied solely on the density of the binder itself to resist corrosion, resulting in extremely weak protection. Corrosive media could directly penetrate the coating, leaving the substrate without effective protection. After 15 days of acid resistance testing, large-area blistering and peeling occurred; after 10 days of alkali resistance testing, the surface severely swelled.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an inorganic corrosion-resistant coating, characterized in that: The preparation method is as follows: A composite silicate binder is obtained by mixing potassium silicate solution and lithium silicate solution; A composite thermal insulation filler was prepared by mixing silver-coated hollow glass microspheres and silica aerogel. A composite shielding filler is obtained by mixing flake-shaped fillers and two-dimensional nanosheet fillers; The composite silicate binder and deionized water are added to a mixing tank, and stirring is started. The composite shielding filler, the composite thermal insulation filler, the interface in-situ passivating agent and the wetting and dispersing agent are added in sequence to disperse and form a slurry. The curing agent is added and stirred to obtain the inorganic corrosion-resistant coating.

2. The method for preparing an inorganic corrosion-resistant coating according to claim 1, characterized in that: The composite thermal insulation filler is prepared as follows: the silver-coated hollow glass microspheres and the silica aerogel are mixed and ultrasonically dispersed in ethanol; a silane coupling agent is added dropwise under stirring conditions; after reaction, the mixture is filtered, washed, and dried to obtain the composite thermal insulation filler.

3. The method for preparing an inorganic corrosion-resistant coating according to claim 2, characterized in that: The method for preparing the silver-coated hollow glass microspheres is as follows: after pretreatment, the hollow glass microspheres are added to a stannous chloride solution and stirred for sensitization; after rinsing with the deionized water, they are transferred to a palladium chloride solution for ultrasonic activation, rinsed with the deionized water, dried, and then added to a silver ammonia solution for stirring. A glucose solution was added dropwise to initiate the reaction, followed by washing and drying to obtain the silver-coated hollow glass microspheres.

4. The method for preparing an inorganic corrosion-resistant coating according to claim 1, characterized in that: The flake-shaped filler is mica powder, and the two-dimensional nanosheet filler is modified graphene oxide.

5. The method for preparing an inorganic corrosion-resistant coating according to claim 4, characterized in that: The modified graphene oxide is prepared as follows: graphene oxide is added to an ethanol aqueous solution and ultrasonically treated to obtain a dispersion; a silane coupling agent solution is added dropwise under stirring and refluxed; the mixture is cooled to room temperature, centrifuged, washed, and dried to obtain the modified graphene oxide.

6. The method for preparing an inorganic corrosion-resistant coating according to claim 1, characterized in that: The curing agent is obtained by mixing active zinc oxide and aluminum dihydrogen phosphate.

7. An inorganic corrosion-resistant coating, characterized in that: The inorganic corrosion-resistant coating is prepared by the preparation method described in any one of claims 1-6; the raw materials for preparing the inorganic corrosion-resistant coating include composite silicate binder, composite thermal insulation filler, composite shielding filler, curing agent and in-situ interface passivating agent.

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