A protective nanosilicon material for the inner wall of a pressure steel pipe, a preparation method thereof and a coating structure

Abstract

The application belongs to the technical field of pipeline anticorrosion materials, and particularly relates to a pressure steel pipe inner wall protection nanosilicon material, a preparation method thereof and a coating structure, which comprises the following components: 40-50 parts of an organic silicon resin matrix, 10-15 parts of nanometer silicon dioxide, 10-15 parts of silicon carbide composite particles, 3-6 parts of a silane coupling agent, 2-4 parts of silicon sol, 0.5-2 parts of a eutectic solvent and 0.5-1 part of a leveling agent. Through the synergistic chemical bonding of the methylphenyl silicon resin matrix and the silane coupling agent and the mechanical interlocking effect of the three-layer structure, the pull-off method adhesion of the coating and the steel pipe substrate can reach more than 12 MPa, and the peeling and delamination problems are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of pipeline anti-corrosion materials technology, and more specifically, it relates to a nano-silicon material for the inner wall protection of pressure steel pipes, its preparation method and coating structure. Background Technology

[0002] Pressure steel pipes are critical infrastructure in water conservancy, hydropower, and water diversion projects. Their inner walls must withstand erosion and wear from high-velocity, sand-laden water flows, frequent water hammer impacts, and the penetration and erosion of corrosive media such as chloride ions during long-term service. Therefore, extremely high requirements are placed on the wear resistance, erosion resistance, adhesion, and durability of the protective materials used on the inner walls of pressure steel pipes.

[0003] Currently, commonly used technologies for protecting the inner walls of pressure steel pipes mainly include organic coatings, such as epoxy resin and polyurethane, and inorganic composite coatings. However, existing technologies still have the following shortcomings: First, their resistance to erosion and wear is insufficient. Traditional organic coatings have low hardness and are easily worn through under long-term scouring by high-speed sand-containing water flow, with the annual erosion depth easily exceeding the standard limit. Second, the density of the coating and the interfacial bonding strength need to be improved. Single inorganic coatings or simple organic-inorganic composite coatings have micropores inside, and the interfacial pull-out strength with the steel pipe substrate is usually only 2~4MPa, making them prone to delamination and blistering during long-term service. Third, their construction performance is limited. Existing high-solids or solvent-free coatings cure slowly in low-temperature and high-humidity environments and have stringent requirements for substrate treatment. Finally, the coating structure design is too simple, making it difficult to balance adhesion, impermeability, and wear resistance.

[0004] Therefore, in view of this, we study and improve the existing structure and its shortcomings, and provide a nano-silicon material for the inner wall protection of pressure steel pipe, its preparation method and coating structure, in order to achieve a more practical value. Summary of the Invention

[0005] In view of the problems mentioned in the background art above, the present invention provides a protective nano-silicon material for the inner wall of a pressure steel pipe, its preparation method and coating structure.

[0006] On one hand, the technical solution adopted by the present invention is as follows: a nano-silicon material for the inner wall protection of a pressure steel pipe, comprising the following components by mass: 40-50 parts of organosilicon resin matrix; 10-15 parts of nano-silica; 10-15 parts of silicon carbide composite particles; 3-6 parts of silane coupling agent; 2-4 parts of silica sol; 0.5-2 parts of eutectic solvent; and 0.5-1 part of leveling agent;

[0007] The organosilicon resin matrix is ​​methylphenyl silicone resin with a viscosity of 2000~4000 mPa·s and a solid content of 85%~95%; the nano-silica has a particle size of 10~50 nm and a specific surface area ≥300 m² / g; the silicon carbide composite particles are formed by mixing solid silicon carbide with a particle size of 50~100 nm and porous silicon carbide with a particle size of 1~10 μm and a porosity of 50%~70% in a mass ratio of 1:1~2:1; the silica sol has a solid content of 40%; and the leveling agent is polyether-modified polydimethylsiloxane.

[0008] Furthermore, the eutectic solvent is prepared by reacting a hydrogen bond acceptor and a hydrogen bond donor at 70°C with stirring for 40-60 min; the hydrogen bond acceptor is menthol, and the hydrogen bond donor is decanoic acid, with a molar ratio of 1:1 to 1:2.

[0009] Furthermore, it also contains 3 to 8 parts of micron-sized silicon carbide, wherein the particle size of the micron-sized silicon carbide is 1 to 5 μm.

[0010] Furthermore, it also includes a mixed solvent for adjusting viscosity, wherein the mixed solvent is a mixture of xylene and butyl acetate in a volume ratio of 1:1, and the amount of the mixed solvent added satisfies the following condition: after the nano-silicon material is mixed with the mixed solvent, the spraying viscosity reaches 25~35s of Fore-4 cup.

[0011] Secondly, the technical solution adopted by the present invention is as follows: a method for preparing a protective nano-silicon material for the inner wall of a pressure steel pipe, comprising the following steps:

[0012] S51: Porous silicon carbide particles are immersed in a silane coupling agent alcohol solution with a mass fraction of 5-15%, and after standing for 5-8 hours, they are dried at 45-55℃ for 3-5 hours to obtain pretreated porous silicon carbide.

[0013] S52: Mix nano-silica, the pretreated porous silicon carbide, solid silicon carbide and 30%~50% of silane coupling agent, and ball mill at 300~500 rpm for 3~5 hours to obtain blended powder;

[0014] S53: Add the blended powder to the organosilicon resin matrix, and then add the remaining silane coupling agent, silica sol, eutectic solvent and leveling agent in sequence. After stirring evenly, vacuum degas for 10-20 minutes to obtain the nano-silicon material.

[0015] Furthermore, in step S52, micron-sized silicon carbide is added, wherein the particle size of the micron-sized silicon carbide is 1~5μm, and the amount added is 3~8 parts by mass.

[0016] Furthermore, the alcohol in the silane coupling agent alcohol solution described in S51 is anhydrous ethanol; the ball milling in S52 adopts a planetary ball mill with a ball-to-material ratio of 3:1 to 5:1.

[0017] Thirdly, the technical solution adopted by the present invention is as follows: a protective coating structure for the inner wall of a pressure steel pipe, characterized in that: it comprises a bottom layer, a particle anchoring layer, and a top layer sequentially disposed on the inner wall surface of the steel pipe, wherein the bottom layer and the top layer are both formed by curing the protective coating material; the particle anchoring layer is a porous ceramic particle layer embedded between the bottom layer and the top layer, wherein the particle size of the porous ceramic particles is 50~80μm and the spreading density is 1.0~1.5kg / m²; the dry film thickness of the bottom layer is 200~350μm, and the dry film thickness of the top layer is 150~250μm.

[0018] Furthermore, at least one of the bottom layer and the top layer also contains a curing accelerator accounting for 0.5 to 2% of the total mass of the coating material in that layer, wherein the curing accelerator is an organotin compound or a tertiary amine compound.

[0019] Fourthly, the technical solution adopted by the present invention is as follows: a construction method using a protective coating structure, comprising the following steps:

[0020] S101: Sandblasting and rust removal treatment on the inner wall of the pressure steel pipe;

[0021] S102: The nano-silicon material described in claim 1 is mixed with a mixed solvent according to the construction viscosity requirements, and coated onto the inner wall of the steel pipe using an airless spraying process to form a base layer, with the dry film thickness of the base layer controlled at 200~350μm.

[0022] S103: Within 30 to 60 minutes after the base coat is applied, evenly spread porous ceramic particles at a density of 1.0 to 1.5 kg / m², and gently tap the outer wall of the steel pipe to remove excess particles.

[0023] S104: After the bottom layer is surface dry, spray the top layer coating, and control the dry film thickness of the top layer to be 150~250μm;

[0024] S105: Cures at room temperature, requiring 7-14 days of curing at 25℃, or 3-7 days of curing after adding a curing accelerator.

[0025] The beneficial effects of this invention are:

[0026] 1. Through the synergistic chemical bonding between the methylphenyl silicone resin matrix and the silane coupling agent, combined with the mechanical interlocking effect of the three-layer structure, the coating has high adhesion to the steel pipe substrate by pull-out method, effectively solving the problems of peeling and delamination.

[0027] 2. Introduce silicon carbide composite particles to construct a multi-level wear-resistant system and enhance service life.

[0028] 3. The high solids content system can adjust the viscosity by mixing solvents to adapt to airless spraying; the spread particles form an anchoring layer, eliminating the interlayer sanding step of traditional multi-layer coating, making construction convenient and highly adaptable. Attached Figure Description

[0029] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings;

[0030] Figure 1 This is a schematic diagram of the coating structure layer on the inner wall of the pressure steel pipe according to the present invention;

[0031] The attached diagram is labeled as follows:

[0032] Pressure steel pipe 1, bottom layer 2, particle anchoring layer 3, surface layer 4. Detailed Implementation

[0033] A nano-silicon material for the inner wall protection of pressure steel pipes, comprising the following components by weight: 40-50 parts of organosilicon resin matrix; 10-15 parts of nano-silica; 10-15 parts of silicon carbide composite particles; 3-6 parts of silane coupling agent; 2-4 parts of silica sol; 0.5-2 parts of eutectic solvent; and 0.5-1 part of leveling agent. The above parts represent the weighing weight of commercially available raw materials, not on a dry basis. Since this coating material is a high-solids content system, a mixed solvent is added on-site during construction to adjust the viscosity.

[0034] Specifically, the above-mentioned components are:

[0035] The silicone resin matrix is ​​methylphenyl silicone resin, with a viscosity of 2000~4000 mPa·s and a solid content of 85%~95%;

[0036] The particle size of nano-silica is 10~50nm, and the specific surface area is ≥300m² / g;

[0037] Silicon carbide composite particles are made by mixing solid silicon carbide with a particle size of 50~100nm and porous silicon carbide with a particle size of 1~10μm and a porosity of 50%~70% in a mass ratio of 1:1~2:1.

[0038] The silane coupling agent is selected from KH-550;

[0039] The solid content of the silica sol is 40%.

[0040] The leveling agent is polyether-modified polydimethylsiloxane.

[0041] The eutectic solvent is obtained by mixing menthol and decanoic acid in a molar ratio of 1:1 to 1:2, stirring at 70°C for 40 to 60 minutes, and cooling to room temperature to obtain a colorless to pale yellow transparent liquid.

[0042] To ensure the formation of a eutectic solvent, Fourier transform infrared spectroscopy analysis revealed that the OH stretching vibration peak of menthol was located at 3350 cm⁻¹. -1 Displaced to 3280cm -1 The C=O stretching vibration peak of decanoic acid is from 1710 cm⁻¹. -1 Displaced to 1695cm -1 This indicates the formation of hydrogen bonds. Differential scanning calorimetry shows that the liquid exhibits a single glass transition temperature below -20°C, while the individual melting points of each component are 43°C and 31°C, respectively, confirming the formation of hydrogen bonds.

[0043] A protective coating structure for the inner wall of a pressure steel pipe includes a base layer, a particle anchoring layer, and a top layer sequentially disposed on the inner wall surface of the steel pipe. Both the base layer and the top layer are formed by curing the aforementioned nano-silicon material. The particle anchoring layer is a porous ceramic particle layer embedded between the base layer and the top layer, with a particle size of 50-80 μm and a spreading density of 1.0-1.5 kg / m². The dry film thickness of the base layer is 200-350 μm, and the dry film thickness of the top layer is 150-250 μm. If a thicker coating is required for the project, the base layer, anchoring layer, and top layer can be used as a basic unit, and 2-3 units can be repeatedly coated to achieve the required total thickness.

[0044] A method for preparing a nano-silicon material for the inner wall protection of a pressure steel pipe:

[0045] Porous silicon carbide particles were placed in a KH-550 / ethanol solution with a mass fraction of 5-15% and allowed to stand for 5-8 hours. Then they were dried at 45-55℃ for 3-5 hours to obtain pretreated porous silicon carbide.

[0046] Nano-silica, pretreated porous silicon carbide, solid silicon carbide, and 30% to 50% of silane coupling agent are added to a planetary ball mill with a ball-to-material ratio of 3:1 to 5:1. The mixture is ball-milled at 300 to 500 rpm for 3 to 5 hours to obtain a blended powder.

[0047] Add the blended powder to the silicone resin matrix, then add the remaining silane coupling agent, silica sol, eutectic solvent, and leveling agent in sequence. Stir evenly using a high-speed disperser, and then degas under vacuum for 10-20 minutes to obtain the finished product.

[0048] The porous ceramic particles are alumina-based or silicon carbide-based porous ceramics.

[0049] Construction method:

[0050] The inner wall of the pressure steel pipe is sandblasted to remove rust, achieving a cleanliness level of Sa2.5 and a surface roughness of Ra40~60μm;

[0051] The above-mentioned nano-silicon material was mixed with a xylene:butyl acetate = 1:1 solvent according to the spraying viscosity requirement of 25~35s (Ford Cup 4). The mixture was then applied to the inner wall of the steel pipe using an airless spraying process, with the underlying dry film thickness controlled at 200~350μm. The airless spraying parameters were: nozzle diameter 0.021~0.025 inches, spraying pressure 2000~2500psi, and spraying distance 200~300mm.

[0052] Within 30 to 60 minutes after the base coat is applied, evenly spread porous ceramic particles at a density of 1.0 to 1.5 kg / m². Gently tap the outer wall of the steel pipe to remove excess particles and form a particle anchoring layer.

[0053] After the bottom layer is completely dry, the top layer is coated using the same spraying process, controlling the dry film thickness of the top layer to be 150~250μm.

[0054] Curing can be carried out at 25℃ for 7-14 days, or by adding 1-3% of a curing accelerator, such as dibutyltin dilaurate or triethylamine, and then curing for 3-7 days. During the curing period, the ambient temperature should be kept no lower than 15℃ and the relative humidity no higher than 85%, and direct rainwater should be avoided.

[0055] If the project requires a higher total dry film thickness, the second set of bottom layer, anchoring layer and top layer can be formed again after the first layer has cured, and so on.

[0056] Example 1:

[0057] Composition: By mass: 45 parts silicone resin, 12 parts nano silica, 12 parts silicon carbide composite particles, wherein the mass ratio of solid silicon carbide to porous silicon carbide is 1.5:1, 5 parts silane coupling agent, 3 parts silica sol, 1 part eutectic solvent, wherein the molar ratio of menthol to decanoic acid is 1:1, 0.8 parts leveling agent, and 5 parts micron-sized silicon carbide.

[0058] Preparation method: Porous silicon carbide particles were immersed in 10wt% KH-550 anhydrous ethanol solution for 6h and dried at 50℃ for 4h to obtain pretreated porous silicon carbide; nano-silica, pretreated porous silicon carbide, solid silicon carbide, micron-sized silicon carbide and 40% of KH-550 were added to a planetary ball mill at a ball-to-particle ratio of 4:1 to obtain a blended powder; the blended powder was added to methylphenyl silicone resin, and the remaining KH-550, silica sol, eutectic solvent and leveling agent were added in sequence, dispersed at high speed and degassed under vacuum for 15min to obtain nano-silicon material.

[0059] Construction method:

[0060] Q235 steel plate, easy to clamp for testing, with no significant difference from pressure steel pipe, sandblasted to Sa2.5 cleanliness level, surface roughness Ra50μm; the above nano-silicon material is mixed with xylene:butyl acetate = 1:1 mixed solvent according to the spraying viscosity requirement of Forecast cup 4 30s, and coated using airless spraying process, controlling the dry film thickness of the bottom layer to 280μm.

[0061] Within 45 minutes after the base coat is applied, porous ceramic particles are evenly spread at a density of 1.2 kg / m². The outer wall of the steel pipe is gently tapped to remove excess particles, forming a particle anchoring layer.

[0062] After the bottom layer is completely dry, apply the top layer using the same spraying process, controlling the dry film thickness of the top layer to 220μm; then cure and maintain.

[0063] Example 2

[0064] Composition: By mass: 40 parts silicone resin, 10 parts nano silica, 10 parts silicon carbide composite particles, wherein the mass ratio of solid silicon carbide to porous silicon carbide is 1:1, 3 parts silane coupling agent, 2 parts silica sol, 0.5 parts eutectic solvent, wherein the molar ratio of menthol to decanoic acid is 1:1, 0.5 parts leveling agent, and 3 parts micron-sized silicon carbide.

[0065] Preparation method: Porous silicon carbide particles were immersed in 5wt% KH-550 anhydrous ethanol solution for 5h and dried at 45℃ for 3h to obtain pretreated porous silicon carbide; nano-silica, pretreated porous silicon carbide, solid silicon carbide, micron-sized silicon carbide and 30% of KH-550 were added to a planetary ball mill at a ball-to-particle ratio of 3:1 to obtain a blended powder; after adding methylphenyl silicone resin to the blended powder, the remaining KH-550, silica sol, eutectic solvent and leveling agent were added in sequence, dispersed at high speed and degassed under vacuum for 10min to obtain nano-silicon material.

[0066] Construction method:

[0067] Q235 steel plate, easy to clamp for testing, with no significant difference from pressure steel pipe, sandblasted to Sa2.5 cleanliness level, surface roughness Ra50μm; the above nano-silicon material is mixed with xylene:butyl acetate = 1:1 mixed solvent according to the spraying viscosity requirement of Forecast cup 4 30s, and coated using airless spraying process, controlling the dry film thickness of the bottom layer to 200μm.

[0068] Within 30 minutes after the base coat is applied, porous ceramic particles are evenly spread at a density of 1.0 kg / m². The outer wall of the steel pipe is gently tapped to remove excess particles, forming a particle anchoring layer.

[0069] After the bottom layer is completely dry, apply the top layer using the same spraying process, controlling the dry film thickness of the top layer to 150μm; then cure and maintain.

[0070] Example 3:

[0071] Composition: By mass: 50 parts silicone resin, 15 parts nano silica, 15 parts silicon carbide composite particles, wherein the mass ratio of solid silicon carbide to porous silicon carbide is 2:1, 6 parts silane coupling agent, 4 parts silica sol, 2 parts eutectic solvent, wherein the molar ratio of menthol to decanoic acid is 1:1, 1 part leveling agent, and 8 parts micron-sized silicon carbide.

[0072] Preparation method: Porous silicon carbide particles were immersed in 15wt% KH-550 anhydrous ethanol solution for 8 hours and dried at 55℃ for 5 hours to obtain pretreated porous silicon carbide; nano-silica, pretreated porous silicon carbide, solid silicon carbide, micron-sized silicon carbide and 50% of the formula amount of KH-550 were put into a planetary ball mill at a ball-to-particle ratio of 5:1 to obtain a blended powder; the blended powder was added to methylphenyl silicone resin, and the remaining KH-550, silica sol, eutectic solvent and leveling agent were added in sequence, dispersed at high speed and degassed under vacuum for 20 minutes to obtain nano-silicon material.

[0073] Construction method:

[0074] Q235 steel plate, easy to clamp for testing, with no significant difference from pressure steel pipe, sandblasted to Sa2.5 cleanliness level, surface roughness Ra50μm; the above nano-silicon material is mixed with xylene:butyl acetate = 1:1 mixed solvent according to the spraying viscosity requirement of Forecast cup 4 30s, and coated using airless spraying process, controlling the dry film thickness of the bottom layer to 350μm.

[0075] Within 60 minutes after the base coat is applied, porous ceramic particles are evenly spread at a density of 1.5 kg / m². The outer wall of the steel pipe is gently tapped to remove excess particles, forming a particle anchoring layer.

[0076] After the bottom layer is completely dry, apply the top layer using the same spraying process, controlling the dry film thickness of the top layer to 250μm; then cure and maintain.

[0077] Example 4:

[0078] The preparation and construction methods are the same as in Example 1, but the components do not contain micron-sized silicon carbide.

[0079] Example 5:

[0080] The preparation and construction methods are the same as in Example 1, but the mass ratio of solid silicon carbide to porous silicon carbide in the silicon carbide composite particles is 1:1.

[0081] Example 6:

[0082] The preparation and application methods are the same as in Example 1, but the molar ratio of menthol to decanoic acid in the eutectic solvent is 1:2.

[0083] Example 7:

[0084] The composition and preparation method are the same as in Example 1, but no mixed solvent is added in the construction method. The original liquid is directly sprayed, and the spraying pressure and nozzle diameter are adjusted to suit the construction.

[0085] Comparative Example 1:

[0086] The preparation and application methods are the same as in Example 1, but no eutectic solvent is added to the components.

[0087] Comparative Example 2:

[0088] The preparation and construction methods are the same as in Example 1, but the components are replaced with solid silicon carbide instead of silicon carbide composite particles.

[0089] Comparative Example 3:

[0090] The composition and preparation method are the same as in Example 1, but the construction method does not involve sprinkling porous ceramic particles after the base coat is applied.

[0091] Comparative Example 4:

[0092] The composition and construction method are the same as in Example 1, but step S51 is omitted in the preparation method, that is, the porous silicon carbide is not pretreated.

[0093] The coatings of each embodiment and comparative example were subjected to performance tests. The test standards are shown in Table 1, and the test results are shown in Table 2.

[0094] Table 1: Test Standards

[0095] Test Project Test standards / methods Main equipment Remark Adhesion GB / T 5210 Pull-out adhesion tester Test the adhesion strength between the coating and the substrate Impact resistance GB / T 1732 Drop hammer impact tester direct impact abrasion resistance GB / T 1768 Abrasion testing machine quality loss Erosion wear rate Establish a water flow containing quartz sand, with a flow velocity of 15 m / s and an angle of attack of 30°, for 24 hours. Erosion testing machine Measuring coating thickness loss Salt water resistance GB / T 9274 Immersion test Observe for blistering, rusting, and peeling.

[0096] Table 2: Test Results

[0097] Test case Adhesion MPa Impact resistance (cm) abrasion resistance mg Erosion wear resistance (mm / a) Salt water resistance (3% NaCl, 720h) Example 1 14.5 55 18 0.012 No abnormalities Example 2 12.8 50 22 0.018 No abnormalities Example 3 15.2 58 16 0.01 No abnormalities Example 4 13.1 52 20 0.015 No abnormalities Example 5 13.5 53 19 0.014 No abnormalities Example 6 14.2 54 18 0.013 No abnormalities Example 7 13.8 53 19 0.015 Microbubbling at the edges Comparative Example 1 10.2 40 35 0.045 Slight bubbling Comparative Example 2 10.8 35 32 0.052 Slight rust Comparative Example 3 6.5 48 21 0.025 Bubbling at the edges Comparative Example 4 11.5 45 28 0.032 Slight loss of light

[0098] Results analysis:

[0099] Examples 1-7 all exhibited excellent adhesion and extremely low erosion wear rate, significantly outperforming all comparative examples.

[0100] Comparing Example 1 and Comparative Example 1, it was found that the addition of a eutectic solvent significantly improved adhesion, impact resistance, and salt water resistance. This is because the eutectic solvent improved filler dispersion and coating density.

[0101] Comparing Example 1 and Comparative Example 2, it was found that the silicon carbide composite particles showed significantly improved wear resistance and erosion resistance compared to pure solid particles, which is attributed to the stress absorption and lubrication effect of porous particles.

[0102] Comparing Example 1 and Comparative Example 3, it was found that the presence of the particle anchoring layer increased the adhesion from 6.5 MPa to 14.5 MPa, verifying the key role of the mechanical interlocking effect.

[0103] Comparing Example 1 and Comparative Example 4, it was found that the adhesion and wear resistance of porous silicon carbide were improved after pretreatment with silane coupling agent, indicating that the pretreatment improved the interfacial bonding between the filler and the resin.

[0104] The present invention has been described in detail above. The specific embodiments are provided only to help understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A nano-silicon material for protecting the inner wall of a pressure steel pipe, characterized in that: By weight, it includes the following components: 40-50 parts of silicone resin matrix; 10-15 parts of nano-silica; 10-15 parts of silicon carbide composite particles; 3-6 parts of silane coupling agent; 2-4 parts of silica sol; 0.5-2 parts of eutectic solvent; and 0.5-1 part of leveling agent. The organosilicon resin matrix is ​​methylphenyl silicone resin with a viscosity of 2000~4000 mPa·s and a solid content of 85%~95%; the nano-silica has a particle size of 10~50 nm and a specific surface area ≥300 m² / g; the silicon carbide composite particles are formed by mixing solid silicon carbide with a particle size of 50~100 nm and porous silicon carbide with a particle size of 1~10 μm and a porosity of 50%~70% in a mass ratio of 1:1~2:1; the silica sol has a solid content of 40%; and the leveling agent is polyether-modified polydimethylsiloxane.

2. The nano-silicon material for protecting the inner wall of a pressure steel pipe according to claim 1, characterized in that: The eutectic solvent is prepared by reacting a hydrogen bond acceptor and a hydrogen bond donor at 70°C with stirring for 40-60 min; the hydrogen bond acceptor is menthol, and the hydrogen bond donor is decanoic acid, with a molar ratio of 1:1 to 1:

2.

3. The nano-silicon material for protecting the inner wall of a pressure steel pipe according to claim 1, characterized in that: It also contains 3 to 8 parts of micron-sized silicon carbide, wherein the particle size of the micron-sized silicon carbide is 1 to 5 μm.

4. The nano-silicon material for protecting the inner wall of a pressure steel pipe according to claim 1, characterized in that: It also includes a mixed solvent for adjusting viscosity, wherein the mixed solvent is a mixture of xylene and butyl acetate in a volume ratio of 1:

1.

5. A method for preparing a protective nano-silicon material for the inner wall of a pressure steel pipe as described in any one of claims 1-4, characterized in that: Includes the following steps: S51: Porous silicon carbide particles are immersed in a 5-15% (w / w) silane coupling agent alcohol solution, left to stand for 5-8 hours, and then dried at 45-55℃ for 3-5 hours to obtain pretreated porous silicon carbide. S52: Mix nano-silica, the pretreated porous silicon carbide, solid silicon carbide and 30%~50% of silane coupling agent, and ball mill at 300~500 rpm for 3~5 hours to obtain blended powder; S53: Add the blended powder to the organosilicon resin matrix, and then add the remaining silane coupling agent, silica sol, eutectic solvent and leveling agent in sequence. After stirring evenly, vacuum degas for 10-20 minutes to obtain the nano-silicon material.

6. The method for preparing a protective nano-silicon material for the inner wall of a pressure steel pipe according to claim 5, characterized in that: In step S52, micron-sized silicon carbide is also added, wherein the particle size of the micron-sized silicon carbide is 1~5μm, and the amount added is 3~8 parts by mass.

7. The method for preparing a protective nano-silicon material for the inner wall of a pressure steel pipe according to claim 6, characterized in that: The alcohol in the silane coupling agent alcohol solution described in S51 is anhydrous ethanol; the ball milling in S52 uses a planetary ball mill with a ball-to-material ratio of 3:1 to 5:

1.

8. A protective coating structure for the inner wall of a pressure steel pipe according to any one of claims 1-4, characterized in that: It includes a bottom layer, a granular anchoring layer, and a top layer, which are sequentially installed on the inner surface of the steel pipe. Both the bottom layer and the top layer are formed by curing the protective coating material; The particle anchoring layer is a porous ceramic particle layer embedded between the bottom layer and the top layer. The particle size of the porous ceramic particles is 50~80μm and the spreading density is 1.0~1.5kg / m². The dry film thickness of the bottom layer is 200~350μm, and the dry film thickness of the top layer is 150~250μm.

9. The protective coating structure for the inner wall of a pressure steel pipe according to claim 8, characterized in that: At least one of the bottom layer and the top layer further comprises a curing accelerator accounting for 0.5 to 2% of the total mass of the coating material in that layer, wherein the curing accelerator is an organotin compound or a tertiary amine compound.

10. A construction method employing a protective coating structure, characterized in that: Includes the following steps: S101: Sandblasting and rust removal treatment on the inner wall of the pressure steel pipe; S102: The nano-silicon material described in claim 1 is mixed with a mixed solvent according to the construction viscosity requirements, and coated onto the inner wall of the steel pipe using an airless spraying process to form a base layer, with the dry film thickness of the base layer controlled at 200~350μm. S103: Within 30 to 60 minutes after the base coat is applied, evenly spread porous ceramic particles at a density of 1.0 to 1.5 kg / m², and gently tap the outer wall of the steel pipe to remove excess particles. S104: After the bottom layer is surface dry, spray the top layer coating, and control the dry film thickness of the top layer to be 150~250μm; S105: Cures at room temperature, requiring 7-14 days of curing at 25℃, or 3-7 days of curing after adding a curing accelerator.

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