External anti-corrosion structure of prestressed concrete cylinder pipe and construction method of external anti-corrosion structure

Abstract

The invention relates to the technical field of corrosion prevention of pipes, in particular to an external corrosion prevention structure of a prestressed concrete cylinder pipe and a construction method of the external corrosion prevention structure. The concrete pipe body is covered with the outer anti-corrosion structure, the outer anti-corrosion structure and the concrete pipe body are coaxially arranged, the outer anti-corrosion structure comprises an anti-corrosion layer, a middle layer and a surface layer which are sequentially arranged from inside to outside, the surface layer comprises a first protective coating, a reinforcing structure and a second protective coating, and the first protective coating, the reinforcing structure and the second protective coating are sequentially arranged from inside to outside. The occlusion opening is formed in the reinforcing structure, then the first protective coating is cured to form the occlusion head which is mechanically interlocked with the occlusion opening, the first protective coating and the occlusion head form a whole, and at the moment, the reinforcing structure can be tightly combined with the middle layer through the first protective coating; therefore, the problem that the reinforcing structure and the middle layer are difficult to combine due to incompatibility of the reinforcing structure and the middle layer is solved, and the anti-puncture capacity of the surface layer is improved through the reinforcing structure.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe anti-corrosion, and specifically, to an external anti-corrosion structure for a prestressed concrete cylinder pipe and a construction method thereof. Background Art

[0002] Prestressed concrete cylinder pipes (PCCP) are widely used in major water conservancy projects in the national infrastructure construction. The durability of PCCP is closely related to social undertakings and public safety. Affected by the saline environment, some PCCP have serious corrosive broken wires, posing serious potential safety hazards to the operation of the entire water conveyance project.

[0003] The mortar protective layer is the first line of defense for PCCP anti-corrosion, protecting the prestressed steel wires from corrosion in a highly saline corrosive environment. The commonly used anti-corrosion measure in engineering is epoxy coal tar pitch. However, epoxy coal tar pitch is prone to aging and peeling under the influence of the external environment. In the field of metal steel pipes, a protective layer is provided outside the anti-corrosion layer. For example:

[0004] Chinese Patent Publication No.: CN221196408U discloses a 3PE anti-corrosion pipe treated by fused epoxy powder spraying, including a metal steel pipe, an anti-corrosion layer, an isolation layer, and a protective layer. The outer layer of the metal steel pipe is sprayed with an anti-corrosion layer. An isolation layer is provided outside the anti-corrosion layer, and a protective layer is provided outside the isolation layer. Among them, the anti-corrosion layer includes an epoxy layer, an adhesive layer is wound outside the epoxy layer, and a first polyethylene layer is wound outside the adhesive layer. The isolation layer includes a second polyethylene layer and a steel wire mesh; the anti-corrosion layer is composed of a fused epoxy coating and a polyethylene layer, with good anti-corrosion effect and certain wear resistance; the anti-corrosion layer is protected by the isolation layer, and the protective effect is further enhanced in cooperation with the outer protective layer to avoid affecting the anti-corrosion layer inside the isolation layer.

[0005] However, PCCP uses epoxy coal tar pitch as an anti-corrosion coating and is further combined with coatings such as polyurethane and polyurea as protective coatings because the outer wall of the PCCP pipe is covered by a cement mortar layer, and the epoxy coal tar pitch coating has good adhesion to the concrete surface. In contrast, fused epoxy powder (FBE) usually requires a metal substrate and needs to be melted and cured at high temperature, which is not suitable for direct application to concrete or a cured cement mortar layer;

[0006] Moreover, for PCCP pipes, the coating cures at room temperature. If a steel wire mesh is to be used, it is difficult for the coating to penetrate into the steel wire mesh to form a complete protection system, and at the same time, it is necessary to ensure that the steel wire mesh is not corroded to achieve the expected anti-corrosion effect.

[0007] Therefore, to protect the anti-corrosion layer of PCCP, the above problems need to be urgently overcome. Summary of the Invention

[0008] The object of the present invention is to provide an external anti-corrosion structure for a prestressed concrete cylinder pipe and its construction method. Through the setting of an intermediate layer, the anti-corrosion layer and the surface layer are closely combined together, and a strengthening structure is arranged in the surface layer to improve the protection ability for the anti-corrosion layer.

[0009] To achieve the above object, first, an external anti-corrosion structure for a prestressed concrete cylinder pipe is provided. It covers the outside of the concrete pipe body and is coaxially arranged with the concrete pipe body. The external anti-corrosion structure includes an anti-corrosion layer, an intermediate layer, and a surface layer arranged in sequence from inside to outside. The surface layer includes a first protective coating, a strengthening structure, and a second protective coating. The first protective coating, the strengthening structure, and the second protective coating are arranged in sequence from inside to outside;

[0010] Wherein, the strengthening structure is provided with a biting opening, and the cured first protective coating forms a biting head that mechanically interlocks with the biting opening;

[0011] The strengthening structure and the first protective coating become an integral whole to utilize the close combination of the first protective coating and the intermediate layer.

[0012] As a further improvement of the technical solution, the anti-corrosion layer adopts solvent-free epoxy coal tar pitch.

[0013] As a further improvement of the technical solution, the intermediate layer adopts epoxy primer.

[0014] As a further improvement of the technical solution, the first protective coating and the second protective coating are respectively formed by spraying polyurethane coatings twice.

[0015] As a further improvement of the technical solution, the strengthening structure adopts fiberglass mesh cloth and is made in a multi-layer composite manner.

[0016] As a further improvement of the technical solution, the thickness of the strengthening structure is less than the thickness of the first spraying of polyurethane coating.

[0017] As a further improvement of the technical solution, the biting opening adopts a conical shape;

[0018] The area of the outer surface of the formed biting head is larger than the area of the inner surface.

[0019] As a further improvement of the technical solution, the biting openings on the strengthening structure are connected to each other.

[0020] As a further improvement of the technical solution, a polyol coating is attached to the pointed surface of the strengthening structure;

[0021] The thickness of the first spraying of polyurethane coating is lower than the pointed part;

[0022] When the second polyurethane coating is sprayed, it reacts with the polyol coating, causing the interface between the tip and the second protective coating to expand and form a rigid foam-like structure.

[0023] Secondly, a construction method for the external anti-corrosion structure of any one of the above prestressed concrete cylinder pipes is provided, including the following steps:

[0024] S1. Cover the surface of the concrete pipe body with an anti-corrosion layer;

[0025] S2. Spray an intermediate layer with a thickness of 30 - 50 μm on the surface of the anti-corrosion layer;

[0026] S3. After the epoxy seal primer is cured, perform the first spraying on its surface to obtain a layer of polyurethane coating with a thickness of 400 - 500 μm. Immediately wind the strengthening structure around the surface of the polyurethane coating. At this time, the polyurethane coating is not fully cured and will fill the bite opening. When the polyurethane coating is cured, the strengthening structure adheres to the polyurethane coating on one side of the intermediate layer and cures to form a first protective coating with a thickness of 20 - 30 μm;

[0027] Among them, the thickness of the strengthening structure is 300 - 400 μm;

[0028] The polyurethane coating located inside the bite opening cures to form a bite head, and the bite head bites with the bite opening to achieve mechanical interlocking;

[0029] S4. Perform the second spraying on the surface of the strengthening structure to obtain a layer of polyurethane coating with a thickness of 600 - 1000 μm. After the polyurethane coating of the second spraying is cured, it forms a second protective coating.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. In the external anti-corrosion structure of the prestressed concrete cylinder pipe and its construction method, by providing a bite opening on the strengthening structure, and then the first protective coating cures to form a bite head that mechanically interlocks with the bite opening, making the two into a whole. At this time, the strengthening structure can closely combine with the intermediate layer by using the first protective coating (polyurethane coating), thus solving the problem of difficult combination caused by the incompatibility between the strengthening structure and the intermediate layer (epoxy seal primer), and improving the anti-puncture ability of the surface layer by the strengthening structure.

[0032] 2. In the external anti-corrosion structure of the prestressed concrete cylinder pipe and its construction method, the engaging opening adopts a conical design. On the one hand, it increases the surface area inside the strengthening structure. When the strengthening structure is wound, it can increase the contact area with the first sprayed polyurethane coating. A larger contact area helps to more evenly disperse the external forces applied to the system (such as the pressure during the winding process), thereby reducing the risk that the strengthening structure breaks through the polyurethane coating and directly contacts the intermediate layer due to local stress concentration, ensuring the effective formation of the first protective coating. Moreover, increasing the contact area will also improve the better bonding performance between the first protective coating and the strengthening structure.

[0033] On the other hand, it increases the contact area between the engaging head and the polyurethane coating during the second spraying, thereby improving the bonding force between the two layers of materials. This is particularly effective for surfaces composed of polyurethane because similar materials usually have better chemical compatibility, thus promoting a closer combination.

[0034] 3. In the external anti-corrosion structure of the prestressed concrete cylinder pipe and its construction method, all the engaging openings can be connected to each other. During the second spraying, the isocyanate group (-N=C=O) in the sprayed polyurethane coating will react with the hydroxyl group (-OH) and water in the polyol to form a urethane bond and release carbon dioxide gas. With the generation of carbon dioxide, the interface between the pointed head and the second protective coating begins to expand and form a foamy structure.

[0035] At the same time, with the formation of more cross-linking points, it gradually hardens and finally forms a solid foam body. At this time, the foam body can also block spiky objects. Moreover, under the extrusion of the foam body, the engaging head and the inner surface of the engaging opening can be closely fitted, thereby improving the sealing effect. Not only that, the foam body can also achieve mechanical interlocking with the second protective coating, improving the bonding strength between the second protective coating and the strengthening structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the overall structure of the anti-corrosion structure of the present invention;

[0037] Figure 2 It is a schematic diagram of the composition structure of the surface layer of the present invention;

[0038] Figure 3 It is a schematic diagram of the composition structure of the anti-corrosion structure of the present invention;

[0039] Figure 4 It is a schematic diagram of the structure of the engaging opening and the engaging head of the present invention;

[0040] Figure 5 It is a schematic diagram of the split structure of the fiberglass mesh cloth of the strengthening structure of the present invention;

[0041] Figure 6 The first side structure schematic diagram of the anti-corrosion structure of the present invention;

[0042] Figure 7 The stress analysis schematic diagram of the anti-corrosion structure of the present invention;

[0043] Figure 8 The second side structure schematic diagram of the anti-corrosion structure of the present invention. Detailed implementation manners

[0044] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0045] During the construction process, due to the problem of many sharp gravels in the backfill soil, it will cause spiky damage to the anti-corrosion layer. Once the external anti-corrosion layer of the PCCP pipe is damaged, it cannot be repaired, which brings great potential safety hazards to the operation of the PCCP pipe and directly shortens the service life of the project.

[0046] For this reason, the first embodiment provides an external anti-corrosion structure for a prestressed concrete cylinder pipe, as Figure 1 and Figure 2 shown. This structure includes a concrete pipe body 100. An anti-corrosion layer 200 is provided outside the concrete pipe body 100. The anti-corrosion layer 200 uses solvent-free epoxy coal tar pitch with a thickness of 300 - 600 μm. A surface layer 400 is further provided outside the solvent-free epoxy coal tar pitch. Figure 2 Among them, the surface layer 400 includes a first protective coating 410, a strengthening structure 420, and a second protective coating 430. The first protective coating 410, the strengthening structure 420, and the second protective coating 430 are arranged in sequence from the inside out. By sandwiching the strengthening structure 420 with the first protective coating 410 and the second protective coating 430, the sealing of the strengthening structure 420 is realized.

[0047] The background technology mentions the concrete pipe body 100, whose core is composed of concrete, and prestressed steel wires are wound outside, and then a layer of mortar is covered, and then a layer of solvent-free epoxy coal tar pitch (i.e., the anti-corrosion layer 200) is covered on the surface of the mortar. Thus, it can be seen that the surface of the anti-corrosion layer 200 is as rough as the surface of the concrete pipe body 100. In order to make the strengthening structure 420 closely combine with the concrete pipe body 100 with a rough surface, the following technical solutions are specifically disclosed:

[0048] First, an epoxy primer with a thickness of 30 - 50 μm is sprayed on the surface of the anti-corrosion layer 200. After the epoxy primer cures to form an intermediate layer 300, the function of the intermediate layer 300 is to tightly bond the anti-corrosion layer 200 and the surface layer 400 together. In this embodiment, both the first protective coating 410 and the second protective coating 430 are made of polyurethane paint. After the epoxy primer cures, the first spraying is carried out on its surface to obtain a layer of polyurethane paint with a thickness of 400 - 500 μm. Immediately afterwards, the strengthening structure 420 is wound around the surface of the polyurethane paint once. Refer to Figure 3 As shown, the strengthening structure 420 is provided with a bite opening 421. When the strengthening structure 420 is wound once, the polyurethane paint will fill the bite opening 421. When the polyurethane paint cures, the polyurethane paint on the side of the strengthening structure 420 that adheres to the intermediate layer 300 cures to form a first protective coating 410 with a thickness of 20 - 30 μm; As Figure 4 shown, the polyurethane paint located within the bite opening 421 cures to form a bite head 411. The bite head 411 engages with the bite opening 421 to achieve mechanical interlocking, making the strengthening structure 420 and the first protective coating 410 into a whole. In this way, the strengthening structure 420 can be tightly bonded to the intermediate layer 300 by means of the first protective coating 410.

[0049] It should be noted here that the thickness of the strengthening structure 420 is 300 - 400 μm, and its thickness is less than the thickness of the first sprayed polyurethane paint, ensuring that the polyurethane paint can fully fill the bite opening 421 while also forming the first protective coating 410.

[0050] Furthermore, the strengthening structure 420 is made of fiberglass mesh cloth, and in order to be able to design the shape of the bite opening 421, the strengthening structure 420 is made by means of multi-layer lamination. As Figure 5 shown, multiple thinner fiberglass mesh cloths are used for superposition, and an adhesive or resin can be used for bonding between each layer, so as to obtain a bite opening 421 with a predetermined shape through multi-layer superposition. However, the bonding strength between the fiberglass mesh cloth and the intermediate layer 300 formed by the epoxy primer is insufficient. For precisely this reason, in this embodiment, as mentioned above, by forming a first protective coating 410 (the material is polyurethane paint) on the side of the strengthening structure 420 that adheres to the intermediate layer 300, the bonding strength between the strengthening structure 420 and the intermediate layer 300 is improved.

[0051] Because polyurethane coatings and epoxy primer have a certain chemical compatibility, and both are high-performance polymers that can form stable chemical bonds at the interface. In addition, the first protective coating 410 and the reinforcing structure 420 form a mechanical interlock, making the first protective coating 410 and the reinforcing structure 420 an integral whole. Therefore, when the first protective coating 410 is tightly bonded to the intermediate layer 300, it is equivalent to the reinforcing structure 420 also being tightly bonded to the intermediate layer 300.

[0052] In addition, the reinforcing structure 420 only strengthens the mechanical properties of the surface layer 400. Therefore, a second spraying is required on the surface of the reinforcing structure 420 to obtain a polyurethane coating with a thickness of 600 - 1000 μm. After the polyurethane coating sprayed for the second time is cured, a second protective coating 430 is formed. As the outermost line of defense, the second protective coating 430 can play a role in preventing ultraviolet rays, preventing needle punctures, and resisting scratches, effectively protecting the internal anti-corrosion layer 200.

[0053] Preferably, the second spraying needs to be completed within 24 hours after the first spraying. Moreover, before the second spraying, the outer surface of the reinforcing structure 420 will be slightly polished to increase the surface roughness, and the surface cleanliness will be ensured after polishing, so as to improve the adhesion during the second spraying.

[0054] In this embodiment, as Figure 6 shown, the engaging opening 421 adopts a conical design, which can be a pyramid, a cone, etc. The conical design can achieve mechanical interlock, and the area of the outer surface 421a of the engaging head 411 is larger than the area of the inner surface 421b. On the one hand, it increases the surface area inside the reinforcing structure 420. When the reinforcing structure 420 is wound, it can increase the contact area with the polyurethane coating sprayed for the first time. The larger contact area helps to more evenly disperse the external forces applied to the system (such as the pressure during the winding process), thereby reducing the risk that the reinforcing structure 420 breaks through the polyurethane coating and directly contacts the intermediate layer 300 due to local stress concentration, ensuring the effective formation of the first protective coating 410, and increasing the contact area will also improve the better bonding performance between the first protective coating 410 and the reinforcing structure 420.

[0055] On the other hand, it increases the contact area between the engaging head 411 and the polyurethane coating during the second spraying, thereby improving the bonding force between the two layers of materials. This is especially effective for surfaces composed of polyurethane, because similar materials usually have better chemical compatibility, thus promoting a closer combination.

[0056] From the perspective of force analysis, as Figure 7As shown, when an external force F1 is applied to the second protective coating 430, the second protective coating 430 buffers to form a force F2 on the strengthening structure 420. Then, because the inner surface of the engaging opening 421 is beveled, the force F2 can be dispersed to obtain a force F3 on the first protective coating 410. Finally, after being buffered by the first protective coating 410, a force F4 is formed on the intermediate layer 300 and the anti-corrosion layer 200, and F1 > F2 > F3 > F4. Thus, it can be seen that the anti-corrosion layer 200 is protected by weakening the force through multiple levels.

[0057] In addition, when a sharp object in the external environment pierces the second protective coating 430, it will be blocked by the strengthening structure 420 to prevent damage to the anti-corrosion layer 200. At the same time, the first protective coating 410 can also seal the anti-corrosion layer 200 to protect it.

[0058] In this embodiment, the performance tables of solvent-free epoxy coal tar pitch, epoxy seal primer, and polyurethane coating are also disclosed, which are specifically as follows:

[0059] Performance table of solvent-free epoxy coal tar pitch,

[0060]

[0061]

[0062] Performance table of epoxy seal primer,

[0063]

[0064] Performance table of polyurethane coating,

[0065]

[0066]

[0067]

[0068] This embodiment also provides a construction method for the external anti-corrosion structure of a prestressed concrete cylinder pipe, and the specific steps are as follows:

[0069] S1. Cover the anti-corrosion layer 200 on the surface of the concrete pipe body 100;

[0070] S2. Spray an intermediate layer 300 with a thickness of 30 - 50 μm on the surface of the anti-corrosion layer 200;

[0071] S3. After the epoxy sealant primer is cured, perform the first spraying on its surface to obtain a layer of polyurethane coating with a thickness of 400 - 500 μm. Immediately wind the strengthening structure 420 around the surface of the polyurethane coating once. At this time, the polyurethane coating is not fully cured and will fill the engaging opening 421. When the polyurethane coating is cured, the strengthening structure 420 adheres to the polyurethane coating on one side of the intermediate layer 300 and cures to form the first protective coating 410 with a thickness of 20 - 30 μm.

[0072] Among them, the thickness of the strengthening structure 420 is 300 - 400 μm.

[0073] The polyurethane coating located within the engaging opening 421 cures to form the engaging head 411, and the engaging head 411 engages with the engaging opening 421 to achieve mechanical interlocking.

[0074] S4. Perform the second spraying on the surface of the strengthening structure 420 to obtain a layer of polyurethane coating with a thickness of 600 - 1000 μm. After the polyurethane coating of the second spraying is cured, it forms the second protective coating 430.

[0075] When the above steps are carried out, spraying should not be performed when any of the following situations exist and there are no effective protective measures:

[0076] 1. Rain, fog, snow, or sandy weather.

[0077] 2. Wind force reaches level 5 or above.

[0078] 3. Relative humidity is greater than 85%.

[0079] 4. When the surface temperature of the substrate is 3℃ above the dew point temperature or lower than the recommended temperature of the paint manufacturer.

[0080] Preferably, the spraying of the polyurethane coating should be carried out using a two-component airless thermal spraying device.

[0081] The second embodiment is as Figure 8 shown. In this embodiment, the engaging opening 421 still adopts a conical design. However, different from the first embodiment, the outer opening of the engaging opening 421 in this embodiment is larger, so that all the engaging openings 421 can be connected to each other, and a polyol coating is attached to the surface of the pointed head 422 of the strengthening structure 420, making the thickness of the first protective coating 410 of the first spraying lower than that of the pointed head 422.

[0082] During the second spraying, the isocyanate group (-N=C=O) in the sprayed polyurethane coating reacts with the hydroxyl group (-OH) and moisture in the polyol to form a urethane bond and release carbon dioxide gas. As carbon dioxide is generated, the interface between the tip 422 and the second protective coating 430 begins to expand to form a foamy structure. At the same time, as more cross-linking points are formed, it gradually hardens and finally forms a solid foam body. At this time, the foam body can also block the spiky objects. Moreover, under the extrusion of the foam body, the inner surfaces of the engaging head 411 and the engaging opening 421 can be closely attached, thereby improving the sealing effect. Not only that, the foam body can also achieve mechanical interlocking with the second protective coating 430, improving the bonding strength between the second protective coating 430 and the reinforcing structure 420.

[0083] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. An external anti-corrosion structure of a prestressed steel cylinder concrete pipe, which covers the outside of a concrete pipe body (100) and is coaxially arranged with the concrete pipe body (100), the external anti-corrosion structure comprising an anti-corrosion layer (200), an intermediate layer (300) and a surface layer (400) arranged in sequence from the inside to the outside, characterized in that: The surface layer (400) comprises a first protective coating (410), a reinforcement structure (420), and a second protective coating (430), wherein the first protective coating (410), the reinforcement structure (420), and the second protective coating (430) are arranged in sequence from the inside to the outside; The reinforcing structure (420) is provided with a bite opening (421), and the first protective coating (410) after solidification forms a bite head (411) that is mechanically interlocked with the bite opening (421); The reinforcing structure (420) and the first protective coating (410) are integrated into one body, so as to tightly combine the first protective coating (410) and the intermediate layer (300).

2. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 1 is characterized in that: The anti-corrosion layer (200) is made of solvent-free epoxy coal tar.

3. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 1 is characterized in that: The intermediate layer (300) is made of epoxy sealing primer.

4. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 1 is characterized in that: The first protective coating (410) and the second protective coating (430) are respectively formed by spraying polyurethane coating twice.

5. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 1 is characterized in that: The reinforcement structure (420) is made of glass fiber mesh cloth in a multi-layer composite manner.

6. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 4 is characterized in that: The thickness of the reinforcing structure (420) is smaller than the thickness of the first polyurethane coating sprayed.

7. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 1 is characterized in that: The engagement opening (421) is tapered; The outer surface area of ​​the engaging head (411) is formed to be larger than the inner surface area.

8. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 7 is characterized in that: The bite openings (421) on the reinforcement structure (420) are connected to each other.

9. The external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to claim 8 is characterized in that: A polyol coating is attached to the tip surface of the reinforcement structure (420); The first spray of polyurethane coating is made with a thickness lower than the tip; When the polyurethane coating is sprayed for the second time, it reacts with the polyol coating, causing the interface between the tip and the second protective coating to expand and form a hard foam-like structure.

10. A construction method for the external anti-corrosion structure of the prestressed steel cylinder concrete pipe according to any one of claims 1 to 9, characterized in that: The steps include: S1. Covering the surface of the concrete pipe body (100) with an anti-corrosion layer (200); S2. Spraying an intermediate layer (300) having a thickness of 30 to 50 μm on the surface of the anti-corrosion layer (200); S3, after the epoxy sealing primer is cured, the first spraying is performed on the surface to obtain a layer of polyurethane coating with a thickness of 400-500 μm, and then the reinforcing structure (420) is wrapped around the surface of the polyurethane coating. At this time, the polyurethane coating is not completely cured, and the bite (421) will be filled. When the polyurethane coating is cured, the reinforcing structure (420) is attached to the polyurethane coating on one side of the intermediate layer (300) and cured to form a first protective coating (410) with a thickness of 20-30 μm; Wherein, the thickness of the reinforcement structure (420) is 300-400 μm; The polyurethane coating in the bite opening (421) is cured to form a bite head (411), and the bite head (411) is engaged with the bite opening (421) to achieve mechanical interlocking; S4. Perform a second spraying on the surface of the reinforcement structure (420) to obtain a layer of polyurethane coating with a thickness of 600-1000 μm, and after the polyurethane coating sprayed for the second time is cured, a second protective coating (430) is formed.

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