A composite coated anti-corrosion steel pipe

Abstract

This utility model discloses a composite-coated anti-corrosion steel pipe, belonging to the field of steel pipe anti-corrosion technology. It includes a steel pipe body, with a first composite coating on the inner wall and a second composite coating on the outer wall. The first composite coating comprises, in sequence, an epoxy primer layer, a graphene-modified epoxy resin coating, and a polyurethane coating. The second composite coating comprises, in sequence, an epoxy resin underlayer, a polyolefin adhesive transition layer, and a modified polyurethane toplayer. This utility model, through differentiated coating design on the inner and outer walls, addresses the issues of media corrosion and erosion on the inner wall, while the outer wall addresses soil stress and environmental aging. Combined with a coupling agent layer and anti-corrosion sealing bosses, it eliminates weak points at the coating interface and connection areas, achieving multi-dimensional improvements in corrosion resistance, wear resistance, weather resistance, and mechanical properties, providing an efficient solution for pipeline engineering in harsh service environments.

Description

Technical Field

[0001] This utility model relates to the field of steel pipe corrosion protection technology, and in particular to a composite coated anti-corrosion steel pipe. Background Technology

[0002] In industries such as petroleum, chemical, natural gas, and water conservancy, steel pipes are crucial pipelines for transporting liquids, gases, and other media. However, during use, steel pipes are susceptible to corrosion from the transported media and the external environment, leading to a shortened service life and even safety issues such as leaks. To improve the corrosion resistance of steel pipes, an anti-corrosion coating is typically applied to their surface.

[0003] However, traditional anti-corrosion steel pipes often employ a uniform coating design for both inner and outer walls (such as a single epoxy coating or polyethylene coating), making it difficult to simultaneously address the differentiated anti-corrosion requirements of the inner and outer walls. In practical applications, the inner wall needs to withstand the chemical corrosion of the transported media (such as acid and alkali solutions, sulfur-containing oil and gas). A single coating design may lead to media penetration due to insufficient chemical corrosion resistance of the inner layer (e.g., ordinary epoxy coatings are prone to pitting corrosion in chloride-containing solutions). Meanwhile, the outer wall needs to adapt to complex outdoor environments such as soil stress, ultraviolet radiation, and microbial erosion. A single coating design may present a contradiction between adhesion and weather resistance (e.g., polyethylene coatings have weak adhesion and are prone to peeling under soil stress; pure polyurethane coatings have insufficient resistance to ultraviolet aging).

[0004] Therefore, developing a composite-coated anti-corrosion steel pipe with excellent anti-corrosion performance, wear resistance and adhesion, specifically designed to meet the anti-corrosion performance requirements of both inner and outer walls, is of great practical significance. Utility Model Content

[0005] The purpose of this invention is to provide a composite coated anti-corrosion steel pipe to solve the problems in the background art.

[0006] To achieve the above objectives, this utility model provides a composite-coated anti-corrosion steel pipe, comprising a steel pipe body, wherein the inner wall of the steel pipe body is provided with a first composite coating, and the outer wall of the steel pipe is provided with a second composite coating. The first composite coating comprises an epoxy primer layer, a graphene-modified epoxy resin coating, and a polyurethane coating arranged sequentially. The second composite coating comprises an epoxy resin underlayer, a polyolefin adhesive transition layer, and a modified polyurethane top layer arranged sequentially.

[0007] Preferably, the epoxy primer layer is disposed on the inner side of the steel pipe body, and the thickness of the epoxy primer layer is 50~100μm.

[0008] Preferably, the thickness of the graphene-modified epoxy resin coating is 200~300μm.

[0009] Preferably, the thickness of the polyurethane coating is 100~150μm.

[0010] Preferably, the epoxy resin underlayer is disposed on the outer side of the steel pipe body, and the thickness of the epoxy resin underlayer is 80~150μm.

[0011] Preferably, the thickness of the polyolefin adhesive transition layer is 200~400μm.

[0012] Preferably, the thickness of the modified polyurethane surface layer is 100~200μm.

[0013] Preferably, connecting flanges are welded to both ends of the steel pipe body, and an annular sealing boss is provided on the outer side of the welding position between the connecting flange and the steel pipe body. The outer surface of the annular sealing boss is coated with an anti-corrosion layer, and the surface of the boss is flush with the outer wall of the steel pipe body.

[0014] Preferably, a nano-silica coupling agent layer is provided between the epoxy primer layer and the graphene-modified epoxy resin coating, and the thickness of the nano-silica coupling agent layer is 10~20μm.

[0015] Preferably, the modified polyurethane surface layer is provided with an anti-UV aging layer with a thickness of 50~80μm.

[0016] Therefore, the composite coated anti-corrosion steel pipe of this utility model with the above-mentioned structure has the following beneficial effects:

[0017] (1) The inner wall adopts a three-layer structure of epoxy primer layer - graphene modified epoxy resin coating - polyurethane coating. The epoxy primer layer forms a chemical anchor with the steel pipe body through epoxy groups, which solves the problem of interface adhesion between metal substrate and organic coating. The graphene modified epoxy resin coating utilizes the "maze effect" of graphene sheets to form a three-dimensional network barrier structure inside the coating, which extends the diffusion path of corrosive media and improves the salt spray resistance time compared with ordinary epoxy resin coating. At the same time, the high conductivity of graphene evenly disperses the charge and inhibits electrochemical corrosion. The polyurethane coating provides wear-resistant protection, resists the scouring and wear of particles (such as mineral sand and mud) in the transport medium, and also has a certain chemical resistance to protect the lower anti-corrosion layer.

[0018] (2) The outer wall adopts a three-layer structure of epoxy resin bottom layer - polyolefin adhesive transition layer - modified polyurethane surface layer. The epoxy resin bottom layer blocks the penetration of water and oxygen in the soil through the cross-linking structure of epoxy resin, and provides chemical bonding force with the steel pipe body and the upper polyolefin layer. The polyolefin adhesive transition layer uses the flexibility of polyolefin molecular chains to absorb the mechanical stress caused by soil settlement and temperature changes, and avoids the coating from cracking due to stress concentration. At the same time, it acts as an adhesive to connect the rigid epoxy resin bottom layer and the flexible polyurethane surface layer. The modified polyurethane surface layer has an improved UV aging resistance time compared with ordinary polyurethane by adding antioxidants and light stabilizers, and is suitable for long-term outdoor service.

[0019] (3) An annular sealing boss is set on the outside of the welding position of the connecting flange and the steel pipe body. The surface of the boss is coated with the same composite coating as the steel pipe to cover the welding heat-affected zone and avoid coating failure caused by stress concentration. A nano silica coupling agent layer is added between the inner wall epoxy primer layer and the graphene modified epoxy resin coating. Through the bridging effect of the silane coupling agent, the interlayer adhesion is improved and the coating is prevented from peeling off. An anti-ultraviolet aging layer is set on the outside of the outer wall modified polyurethane surface layer to form an anti-aging system of "hard protection + soft buffer" to extend the outdoor service life.

[0020] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of an embodiment of the present utility model;

[0022] Figure 2 This is a schematic diagram of the structure between the two ends of the steel pipe body and the connecting flange in an embodiment of this utility model;

[0023] Figure label:

[0024] 1. Steel pipe body; 2. Epoxy primer layer; 3. Graphene modified epoxy resin coating; 4. Polyurethane coating; 5. Epoxy resin underlayer; 6. Polyolefin adhesive transition layer; 7. Modified polyurethane top layer; 8. Connecting flange; 9. Annular sealing boss; 10. Nano silica coupling agent layer; 11. Anti-UV aging layer. Detailed Implementation

[0025] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] Example

[0028] like Figures 1-2 As shown, this utility model provides a composite coated anti-corrosion steel pipe, including a steel pipe body 1, which is made of Q235B steel. Both ends are welded with connecting flanges 8 (made of Q345B) using an automatic welding process. An annular sealing boss 9 is provided on the outer side of the welding area between the connecting flanges 8 and the steel pipe body 1. The surface of the boss is sequentially coated with an epoxy resin underlayer 5, a polyolefin adhesive transition layer 6, and a modified polyurethane top layer 7, consistent with the outer wall coating structure, forming a continuous anti-corrosion barrier. Furthermore, the surface of the boss is flush with the outer wall of the steel pipe body 1, used to cover the weld heat-affected zone. In actual manufacturing, the surface of the steel pipe body 1 can also be sandblasted to Sa2.5 standard, forming a roughness Ra5.0μm uneven interface to enhance the mechanical interlocking between the coating and the substrate.

[0029] The inner wall of the steel pipe body 1 is provided with a first composite coating, which includes an epoxy primer layer 2, a graphene-modified epoxy resin coating 3, and a polyurethane coating 4 arranged sequentially. The epoxy primer layer 2 is applied to the inner side of the steel pipe body 1 in close contact with the surface, using a solvent-free epoxy primer (solid content ≥95%), and is applied to the surface of the steel pipe body 1 by a high-pressure airless spraying process. The thickness of the epoxy primer layer 2 is 50~100μm. The primer contains a phenolic amine curing agent, which forms a chemical anchor with the steel surface to ensure that the coating does not peel off during long-term service. When the thickness of this layer is set to 80μm, the adhesion reaches grade 0 in the cross-cut adhesion test (GB / T9286), and the coating porosity is ≤3%.

[0030] A graphene-modified epoxy resin coating 3 is applied to the surface of the epoxy primer layer 2. After the primer layer dries, a dense coating with a thickness of 200-300 μm is formed using an electrostatic spraying process. The sheet structure of graphene creates a "maze effect" within the coating, extending the diffusion path of corrosive media (such as Cl⁻). Adding 1.2% (mass fraction) of graphene oxide (sheet diameter 5-10 μm, thickness 5-10 nm) to the epoxy resin, followed by ultrasonic dispersion and mixing with the curing agent, results in a coating conductivity of 10⁻³ S / cm, forming a conductive and corrosion-resistant barrier.

[0031] Finally, polyurethane coating 4 is applied to the surface of graphene-modified epoxy resin coating 3 using an air spraying process, with a thickness of 100~150μm. This coating contains 10% tungsten carbide wear-resistant filler, which effectively resists the erosion and wear of particulate matter in the conveying medium. When the layer thickness is 120μm, the Shore hardness is A85, the wear loss is ≤0.06g / 1000 cycles (Taber test), and it can withstand immersion in 30% hydrochloric acid for ≥1000h.

[0032] The outer wall of the steel pipe is coated with a second composite coating, which includes an epoxy resin underlayer 5, a polyolefin adhesive transition layer 6, and a modified polyurethane top layer 7, arranged sequentially. The epoxy resin underlayer 5 is applied to the outer side of the steel pipe body 1, with a thickness of 80-150 μm. It is made of epoxy resin containing 15% glass flakes and applied by brushing. The glass flakes are arranged in parallel, forming a "layered shielding effect." When the thickness is 100 μm, the water permeability of this coating is ≤5×10⁻⁻⁻⁶. 9 g / (cm・h), effectively blocking the penetration of water and oxygen in the soil.

[0033] A polyolefin adhesive transition layer 6 is coated on the surface of the epoxy resin base layer 5, with a thickness of 200~400μm. It is coated with ethylene-vinyl acetate copolymer (EVA) hot melt adhesive at a melting temperature of 140℃. When the thickness is 300μm, its elongation at break is 450%, and its peel strength from the epoxy resin base layer 5 is ≥18N / cm. It can absorb the mechanical stress caused by soil settlement and prevent the coating from cracking.

[0034] A modified polyurethane topcoat 7 is coated onto the surface of the polyolefin adhesive transition layer 6, with a thickness of 100~200μm. This layer contains 0.8% hindered amine light stabilizer (HALS) and is applied by roller coating. At a thickness of 150μm, after QUV aging test (1000h), the coating color difference ΔE≤3 and chalking grade 0 (GB / T 1865) are suitable for long-term outdoor service.

[0035] In some embodiments, a γ-aminopropyltriethoxysilane solution is coated between the epoxy primer layer 2 and the graphene-modified epoxy resin coating 3 to form a 10-20 μm thick nano-silica coupling agent layer 10, creating a chemical transition interface. One end of the coupling agent molecule reacts with the hydroxyl groups of the epoxy primer, while the other end crosslinks with the epoxy groups of the graphene epoxy coating, thereby improving interlayer adhesion and preventing coating delamination.

[0036] In addition, polyvinylidene fluoride (PVDF) is coated onto the exterior of the modified polyurethane surface layer 7 using a thermal spraying process to form an anti-UV aging layer 11 with a thickness of 50~80μm. When the thickness is 60μm, the coating tensile strength retention rate is ≥85% after a xenon lamp aging test (3000h), making it suitable for high-UV environments such as plateaus and coastal areas.

[0037] The actual thickness and composition of each coating can be selected according to the specific application. For example, in the high-salt, high-humidity environment of marine splash zones, the polyolefin adhesive transition layer 6 uses a seawater-resistant formula with added magnesium hydroxide flame retardant, and its thickness is set to 400 μm. 1% nano-zinc oxide is added to the modified polyurethane surface layer 7 to enhance its resistance to chloride ion penetration. Without departing from the structural design of the inner and outer coatings of the steel pipe in this invention, equivalent substitutions can be made for the coating material (such as other modified polyolefins), the specifications of the connecting flange, and the type of coupling agent (such as titanate coupling agent).

[0038] Therefore, this utility model adopts a composite coated anti-corrosion steel pipe with the above-mentioned structure, featuring differentiated coatings on the inner and outer walls: the inner wall uses an "epoxy primer-graphene epoxy-polyurethane" coating to solve the problems of media corrosion and wear, while the outer wall uses an "epoxy resin-polyolefin transition-modified polyurethane coating" to cope with environmental stress and aging, breaking the performance limitations of traditional isomorphic coatings; moreover, the annular sealing boss covers the welding defect area, the coupling agent layer enhances the interlayer bonding force, and the UV-resistant layer strengthens outdoor weather resistance, forming a complete structural protection without weak points; the thickness of each coating and the material formula can be flexibly adjusted within the scope of the claims, adapting to the needs of multiple scenarios such as chemical, marine, and municipal applications, combining engineering practicality with the flexibility of patent protection.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solution of this utility model, and these modifications or equivalent substitutions cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of this utility model.

Claims

1. A composite-coated anti-corrosion steel pipe, characterized in that: The device includes a steel pipe body, the inner wall of which is provided with a first composite coating, and the outer wall of which is provided with a second composite coating. The first composite coating includes an epoxy primer layer, a graphene-modified epoxy resin coating, and a polyurethane coating arranged in sequence. The second composite coating includes an epoxy resin underlayer, a polyolefin adhesive transition layer, and a modified polyurethane top layer arranged in sequence.

2. A composite coated corrosion resistant steel pipe as claimed in claim 1, wherein: The epoxy primer layer is applied to the inner side of the steel pipe body, and the thickness of the epoxy primer layer is 50~100μm.

3. The composite coated corrosion resistant steel pipe of claim 1, wherein: The thickness of the graphene-modified epoxy resin coating is 200~300μm.

4. The composite coated corrosion resistant steel pipe of claim 1, wherein: The thickness of the polyurethane coating is 100~150μm.

5. The composite-coated anti-corrosion steel pipe according to claim 1, characterized in that: The epoxy resin underlayer is disposed on the outer side of the steel pipe body, and the thickness of the epoxy resin underlayer is 80~150μm.

6. The composite-coated anti-corrosion steel pipe according to claim 1, characterized in that: The thickness of the polyolefin adhesive transition layer is 200~400μm.

7. The composite coated anti-corrosion steel pipe according to claim 1, characterized in that: The thickness of the modified polyurethane surface layer is 100~200μm.

8. The composite-coated anti-corrosion steel pipe according to claim 1, characterized in that: The steel pipe body is welded to both ends with connecting flanges, and an annular sealing boss is provided on the outside of the welding position between the connecting flange and the steel pipe body.

9. The composite-coated anti-corrosion steel pipe according to claim 1, characterized in that: A nano-silica coupling agent layer is disposed between the epoxy primer layer and the graphene-modified epoxy resin coating.

10. The composite-coated anti-corrosion steel pipe according to claim 1, characterized in that: The modified polyurethane surface layer is provided with an anti-UV aging layer on the outside.

Images