A composite anticorrosive coating for incinerator wall surface and its preparation method

Abstract

The present application belongs to the technical field of boiler corrosion prevention treatment, and particularly relates to a composite anticorrosion coating for incinerator wall surface and a preparation method thereof. The composite anticorrosion coating is a composite structure layer combined on a pipe base, and has a double-layer structure or a triple-layer structure. The composite anticorrosion coating with the double-layer structure is sequentially formed with a bottom layer and a surface layer along the thickness direction; the composite anticorrosion coating with the triple-layer structure is sequentially formed with a bottom layer, a middle layer and a surface layer along the thickness direction. The bottom layer material is Ni-22Cr-10Al alloy, the middle layer material is Al2O3, and the surface layer material is yttrium stabilized zirconium oxide. The present application realizes differential protection of different corrosion degrees by designing two kinds of composite structures: the double-layer structure is suitable for moderate corrosion environment and provides economic and effective protection; the triple-layer structure significantly enhances the penetration resistance by introducing the Al2O3 intermediate layer and is suitable for more severe corrosion environment.

Description

Technical Field

[0001] This invention belongs to the field of boiler corrosion protection technology, specifically relating to a composite anti-corrosion coating for incinerator walls and its preparation method. Background Technology

[0002] During incinerator operation, combustion products contain elements such as sulfur, chlorine, and alkali metals, which are key factors causing high-temperature corrosion of the incinerator's heating surfaces. For economic reasons, conventional 20G or 12Cr1MoVG tubing is typically used for incinerator heating surfaces. However, this type of tubing has relatively weak resistance to high-temperature corrosion. When the concentration of corrosive gases (such as HCl and SO2) inside the furnace is high, the tubing walls will suffer severe corrosion. This not only shortens the service life of the tubing but also leads to uncontrollable safety risks such as leaks due to thinning and breakage of the tubing walls.

[0003] In existing technologies, there are two main approaches to improving the high-temperature corrosion resistance of incinerator heating surfaces: one is to enhance the corrosion resistance of the heating surface substrate itself, and the other is to form a coating with high-temperature corrosion resistance on the substrate surface through spraying technology. Compared to replacing the entire high-performance alloy material, coating technology is more cost-effective and has therefore become a research hotspot. Currently, most anti-corrosion coatings applied to incinerator heating surfaces are Ni-based alloy coatings. By adding Cr and Al alloying elements, a dense oxide protective layer is formed at high temperatures to resist corrosion.

[0004] However, existing Ni-based coatings have a simple structure, making it difficult to provide effective protection against the complex and variable corrosive environment inside incinerators. Especially in harsh environments with high concentrations of HCl or SO2, single-structure coatings often fail due to the rapid penetration of corrosive media, failing to meet the requirements for long-term, stable protection. Summary of the Invention

[0005] This invention aims to address the problem that existing anti-corrosion coatings for incinerator pipes, with their single-structure design, are insufficient to cope with complex and variable high-temperature corrosive environments and offer inadequate protection. This invention provides a composite anti-corrosion coating for incinerator walls and its preparation method. Different coating structures are designed to address varying degrees of corrosion within the incinerator, adapting to different corrosive environments and thereby improving the durability and safety of the incinerator's heated surfaces under diverse corrosive conditions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a composite anti-corrosion coating for incinerator walls. The composite anti-corrosion coating is a composite structural layer bonded to a pipe substrate. The composite anti-corrosion coating has a double-layer structure or a triple-layer structure. The double-layer composite anti-corrosion coating is composed of a bottom layer and a top layer formed sequentially along the thickness direction. The triple-layer composite anti-corrosion coating is composed of a bottom layer, a middle layer, and a top layer formed sequentially along the thickness direction. The bottom layer material is Ni-22Cr-10Al alloy, the top layer material is yttrium-stabilized zirconium oxide, and the middle layer material is Al2O3.

[0007] This invention achieves differentiated protection for incinerator tubes by designing two different composite structures. The core of this invention lies in the functional combination of different material layers: a Ni-22Cr-10Al alloy is used as the bottom layer, which has good thermal expansion coefficient matching with common boiler tube substrates (such as 20G and 12Cr1MoVG), forming a strong bonding layer and providing a solid foundation for the entire anti-corrosion system. Yttrium-stabilized zirconium oxide (YSZ) is used as the top layer, possessing excellent high-temperature stability, chemical inertness, and low thermal conductivity, effectively isolating direct corrosion from external high-temperature corrosive media (such as HCl and SO2 gases). In the three-layer structure, a dense Al2O3 ceramic material is further introduced as the middle layer, constructing an additional physical barrier, significantly extending the path of inward diffusion of corrosive media, and greatly enhancing the coating's anti-permeability.

[0008] Preferably, in the double-layer composite anti-corrosion coating, the top layer is formed by spraying a top layer material onto the bottom layer surface that has been heated to a red-hot state.

[0009] Preferably, in the three-layer composite anti-corrosion coating, the middle layer is formed by spraying a top layer material onto the bottom layer surface heated to a red-hot state, and the top layer is formed by spraying a top layer material onto the middle layer surface after sandblasting.

[0010] Preferably, in the double-layer composite anti-corrosion coating, the thickness of the bottom layer is 0.2mm to 0.5mm, and the thickness of the top layer is 0.8mm to 1.2mm.

[0011] Preferably, in the three-layer composite anti-corrosion coating, the thickness of the bottom layer is 0.2mm to 0.5mm, the thickness of the middle layer is 0.5mm to 0.7mm, and the thickness of the top layer is 0.8mm to 1.2mm.

[0012] Preferably, the particle size of the bottom layer material, the middle layer material and the top layer material is 15μm to 45μm.

[0013] This invention provides a method for preparing a composite anti-corrosion coating, comprising the following steps: The pipe substrate is first sandblasted, and then a base material is sprayed onto the surface of the pipe substrate to form a base layer; the pipe substrate with the base layer is heated to a red-hot state; a top layer material is sprayed onto the surface of the red-hot pipe substrate to form a top layer, resulting in a double-layer composite anti-corrosion coating.

[0014] Alternatively, a middle layer material can be sprayed onto the surface of the pipe substrate in a red-hot state to form a middle layer; the pipe substrate with the bottom and middle layers sprayed is cooled to room temperature, the middle layer surface is subjected to a second sandblasting treatment, and then a top layer material is sprayed to form a top layer, resulting in a three-layer composite anti-corrosion coating.

[0015] The present invention heats the pipe substrate coated with the base material to a red-hot state, and then sprays the top layer material in the red-hot state, which helps to release the stress of the base layer and enhance the bonding strength between the base layer and the subsequent top layer.

[0016] To address the challenge of bonding the middle and top layers in ceramic materials, a sandblasting process after cooling is employed to improve the surface roughness of the middle layer, thereby significantly enhancing the mechanical bonding force between the middle and top layers.

[0017] Preferably, the spraying conditions are as follows: the carrier gas pressure of the powder supply system is 3.5MPa to 4.5MPa, the turntable speed is 20 to 25 rpm, the stirrer speed is 60 to 65 rpm, the distance between the spray gun and the sample is 130 mm to 135 mm, and the spray gun moving speed is 500 mm / s to 550 mm / s.

[0018] Preferably, the conditions for the first or second sandblasting treatment are: the compressed air pressure is maintained at 0.5MPa to 0.8MPa, the sandblasting distance is maintained at 100mm to 300mm, and the spraying angle is controlled between 15° and 75°.

[0019] Preferably, the double-layer composite anti-corrosion coating is suitable for corrosive environments with HCl concentration less than 300 ppm or SO2 concentration less than 50 ppm; the triple-layer composite anti-corrosion coating is suitable for corrosive environments with HCl concentration greater than 300 ppm or SO2 concentration greater than 50 ppm.

[0020] Compared with the prior art, the present invention has the following technical effects: This invention addresses varying degrees of corrosion within incinerators by designing a double-layer or triple-layer composite structure on the pipe substrate. The double-layer composite anti-corrosion coating consists of a base layer and a top layer sequentially along the thickness direction; the triple-layer composite coating consists of a base layer, a middle layer, and a top layer sequentially along the thickness direction. The base layer material is a Ni-22Cr-10Al alloy, which has good thermal expansion coefficient matching with the pipe substrate and can form a good metallurgical or mechanical bond, providing a solid base for the entire composite anti-corrosion coating system. The top layer material is yttrium-stabilized zirconium oxide, which has excellent high-temperature stability and low thermal conductivity, effectively isolating high-temperature corrosive media. In the triple-layer structure, the Al2O3 middle layer further blocks the diffusion of corrosive elements. Through the synergistic effect of materials and structure, the composite anti-corrosion coating of this invention significantly improves the high-temperature corrosion resistance of the pipe; it solves the problem that existing single-coat structures cannot adequately address different corrosive environments and have poor protective effects, achieving differentiated and adaptive protection for the heated surfaces of the incinerator.

[0021] The double-layer composite anti-corrosion coating of this invention provides economical and effective protection for moderately corrosive environments, while the triple-layer composite anti-corrosion coating, by adding an Al2O3 intermediate layer, significantly enhances the isolation and anti-permeability in more severe corrosive environments, thereby making the protection work more targeted and improving the overall ability of the incinerator to cope with variable corrosive environments. Attached Figure Description

[0022] Figure 1 The images show actual pictures of the composite anti-corrosion coatings prepared in Examples 1 and 2; where a is an actual picture of the composite anti-corrosion coating prepared in Example 1, and b is an actual picture of the composite anti-corrosion coating prepared in Example 2.

[0023] Figure 2 This is a flowchart of the preparation of the composite anti-corrosion coating in Example 1.

[0024] Figure 3 This is a flowchart of the preparation of the composite anti-corrosion coating in Example 2.

[0025] Figure 4 These are the corrosion weight gain curves of the composite anti-corrosion coatings of Examples 1 and 2. Detailed Implementation

[0026] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0027] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0028] Example 1 A method for preparing a double-layer composite anti-corrosion coating includes the following steps: The preparation flow chart of the double-layer composite anti-corrosion coating is as follows: Figure 2 Substrate preparation: 12Cr1MoVG pipe is selected as the substrate. The pipe surface is sandblasted to clean and roughen the surface, improving adhesion. Sandblasting conditions: Compressed air pressure is maintained between 0.5MPa and 0.8MPa, sandblasting distance is maintained between 100mm and 300mm, and the spray angle is controlled between 15° and 75°.

[0029] Primer application: Using atmospheric plasma spraying equipment, Ni-22Cr-10Al alloy powder with a particle size of 15μm~45μm was sprayed onto the sandblasted pipe surface to form the primer. The spraying parameters were: carrier gas pressure of the powder supply system 3.5MPa, rotary table speed 20 rpm, stirrer speed 60 rpm, spray gun distance from the sample 135mm, and spray gun movement speed 500mm / s. The coating thickness was controlled to approximately 0.5mm.

[0030] Intermediate treatment: After the base coat is applied, use a flame gun to heat the pipe with the base coat until it reaches a red-hot state.

[0031] Topcoat: While the pipe remains red-hot, yttrium-stabilized zirconia powder with a particle size of 15μm to 45μm is sprayed onto the base layer using atmospheric plasma spraying equipment to form a topcoat, resulting in a double-layer composite anti-corrosion coating. A physical image of the double-layer composite anti-corrosion coating is shown below. Figure 1 As shown in a. The spraying parameters are: carrier gas pressure of the powder supply system 3.5MPa, turntable speed 20 rpm, stirrer speed 60 rpm, spray gun distance from sample 135mm, spray gun moving speed 500mm / s, and control surface layer thickness of approximately 1.2mm.

[0032] Example 2 A method for preparing a three-layer composite anti-corrosion coating includes the following steps: The preparation flow chart of the three-layer composite anti-corrosion coating is as follows: Figure 3 Substrate preparation: 12Cr1MoVG pipe is selected as the substrate. The surface of the pipe is sandblasted to clean and roughen the surface and improve the bonding force. Sandblasting conditions: compressed air pressure is maintained at 0.5MPa~0.8MPa, sandblasting distance is maintained at 100mm~300mm, and spraying angle is controlled between 15°~75°.

[0033] Primer application: Using atmospheric plasma spraying equipment, Ni-22Cr-10Al alloy powder with a particle size of 15μm~45μm was sprayed onto the sandblasted pipe surface to form the primer. The spraying parameters were: carrier gas pressure of the powder supply system 3.5MPa, rotary table speed 20 rpm, stirrer speed 60 rpm, spray gun distance from the sample 135mm, and spray gun movement speed 500mm / s. The coating thickness was controlled to approximately 0.5mm.

[0034] Intermediate Layer Coating: After the base coat is applied, the pipe surface is heated using a flame torch until it reaches a red-hot state. Then, using atmospheric plasma spraying equipment, Al2O3 powder with a particle size of 15μm–45μm is sprayed onto the base coat surface to form the intermediate layer. The spraying parameters are: carrier gas pressure of the powder supply system 3.5MPa, rotary table speed 20 rpm, stirrer speed 60 rpm, spray torch distance from the sample 135mm, and spray torch moving speed 500mm / s. The coating thickness is controlled to be approximately 0.5mm.

[0035] Pretreatment before spraying the topcoat: After the pipe with the base coat and intermediate coat has cooled naturally to room temperature, the surface of the pipe is sandblasted to improve the surface roughness of the intermediate coat and enhance the mechanical bonding between the intermediate coat and the topcoat. Sandblasting conditions: the compressed air pressure is maintained at 0.5MPa to 0.8MPa, the sandblasting distance is maintained at 100mm to 300mm, and the spraying angle is controlled between 15° and 75°.

[0036] Topcoat: Using atmospheric plasma spraying equipment, yttrium-stabilized zirconia powder with a particle size of 15μm to 45μm is sprayed onto the sandblasted intermediate layer surface to form the topcoat, resulting in a three-layer composite anti-corrosion coating. A physical image of the three-layer composite anti-corrosion coating is shown below. Figure 1 As shown in b. The spraying parameters are: carrier gas pressure of the powder supply system 3.5 MPa, rotary table speed 20 rpm, stirrer speed 60 rpm, spray gun distance from the sample 135 mm, and spray gun moving speed 500 mm / s. The controlled spray thickness is approximately 0.5 mm. The controlled surface layer thickness is approximately 1.2 mm.

[0037] Test 1: To verify the high-temperature corrosion resistance of the composite anti-corrosion coatings prepared in Examples 1 and 2, simulated corrosion experiments were conducted. Test conditions: temperature 230℃, corrosion duration 60 days. Corrosion atmosphere: HCl, gas flow rate 25 mL / min, water vapor flow rate 0.5 mL / min.

[0038] Test samples: 12Cr1MoVG pipes, pipes coated with the double-layer composite anti-corrosion coating of Example 1, and pipes coated with the triple-layer composite anti-corrosion coating of Example 2.

[0039] Test method: Samples were taken out on days 10, 20, 30, 40, and 60 after the start of the experiment, and the corrosion weight gain per unit area was measured. The results are as follows: Figure 3 As shown.

[0040] Depend on Figure 4 It can be seen that after 30 days, the corrosion weight gain of both the double-layer composite anti-corrosion coating (Example 1) and the triple-layer composite anti-corrosion coating (Example 2) was significantly lower than that of the uncoated pipe, thus proving that the composite anti-corrosion coating effectively improves the resistance to high-temperature corrosion. Throughout the entire experimental period, the corrosion weight gain of the triple-layer composite anti-corrosion coating was consistently lower than that of the double-layer composite anti-corrosion coating, demonstrating superior long-term protective performance. Due to its additional Al2O3 barrier layer, the triple-layer composite anti-corrosion coating has stronger resistance to corrosive gases such as HCl, making it suitable for harsher corrosive environments. Therefore, the triple-layer composite anti-corrosion coating is applied for situations where the HCl concentration is greater than 300 ppm or the SO2 concentration is greater than 50 ppm. For moderately corrosive environments with HCl concentrations less than 300 ppm or SO2 concentrations less than 50 ppm, the double-layer composite anti-corrosion coating provides sufficient protection and is more economical.

[0041] To further verify the adaptability of the composite anti-corrosion coating provided by this invention under different corrosive atmospheres, particularly its corrosion resistance in sulfur-containing atmospheres, simulated high-temperature corrosion experiments with SO2 were conducted on the composite anti-corrosion coatings prepared in Examples 1 and 2. When the SO2 concentration was greater than 50 ppm, the sample coated with the three-layer composite anti-corrosion coating exhibited excellent sulfur corrosion resistance. This demonstrates that the composite anti-corrosion coating prepared by this invention can significantly delay the diffusion of corrosive media into the substrate, providing longer-lasting protection for the pipe.

[0042] To further verify the structural advantages of the Al2O3 intermediate layer in the three-layer composite anti-corrosion coating of this invention, a comparative experiment was designed while keeping the total coating thickness basically consistent.

[0043] Control group: bottom layer (Ni-22Cr-10Al): thickness 0.3mm; top layer (yttrium stabilized zirconia): thickness 1.2mm.

[0044] Experimental group: Bottom layer (Ni-22Cr-10Al): thickness 0.2mm; Middle layer (Al2O3): thickness 0.5mm; Top layer (yttrium stabilized zirconia): thickness 0.8mm.

[0045] Test conditions: Temperature 230℃, corrosion time 60 days. Corrosion atmosphere: HCl, gas flow rate 25 mL / min, water vapor flow rate 0.5 mL / min.

[0046] Test results show that, under the condition of the same total coating thickness, the three-layer composite anti-corrosion coating has better corrosion resistance and protection effect.

[0047] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0048] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A composite anti-corrosion coating for incinerator walls, characterized in that, Composite anti-corrosion coatings have a double-layer or triple-layer structure; The double-layer composite anti-corrosion coating consists of a base layer and a top layer formed sequentially along the thickness direction; The three-layer composite anti-corrosion coating consists of a base layer, a middle layer, and a top layer formed sequentially along the thickness direction. The bottom layer material is Ni-22Cr-10Al alloy, the top layer material is yttrium-stabilized zirconium oxide, and the middle layer material is Al2O3.

2. The composite anti-corrosion coating for incinerator walls according to claim 1, characterized in that, In a double-layer composite anti-corrosion coating, the top layer is formed by spraying a top layer material onto the bottom layer surface that has been heated to a red-hot state.

3. The composite anti-corrosion coating for incinerator walls according to claim 1, characterized in that, In a three-layer composite anti-corrosion coating, the middle layer is formed by spraying the top layer material onto the bottom layer surface heated to a red-hot state, and the top layer is formed by spraying the top layer material onto the middle layer surface after sandblasting.

4. The composite anti-corrosion coating for incinerator walls according to claim 1, characterized in that, In the double-layer composite anti-corrosion coating, the thickness of the bottom layer is 0.2mm to 0.5mm, and the thickness of the top layer is 0.8mm to 1.2mm.

5. The composite anti-corrosion coating for incinerator walls according to claim 1, characterized in that, In the three-layer composite anti-corrosion coating, the thickness of the bottom layer is 0.2mm to 0.5mm, the thickness of the middle layer is 0.5mm to 0.7mm, and the thickness of the top layer is 0.8mm to 1.2mm.

6. The composite anti-corrosion coating for incinerator walls according to claim 1, characterized in that, The particle size of the bottom layer, middle layer and top layer materials is 15μm to 45μm.

7. A method for preparing the composite anti-corrosion coating according to any one of claims 1 to 5, characterized in that, Includes the following steps: The pipe substrate is first sandblasted, and then a base material is sprayed onto the surface of the pipe substrate to form a base layer; the pipe substrate with the base layer is heated to a red-hot state. A surface layer material is sprayed onto the surface of the pipe substrate in a red-hot state to form a surface layer, resulting in a double-layer composite anti-corrosion coating. Alternatively, a middle layer material can be sprayed onto the surface of the pipe substrate in a red-hot state to form a middle layer; the pipe substrate with the bottom and middle layers sprayed is cooled to room temperature, the middle layer surface is subjected to a second sandblasting treatment, and then a top layer material is sprayed to form a top layer, resulting in a three-layer composite anti-corrosion coating.

8. The method for preparing the composite anti-corrosion coating according to claim 7, characterized in that, The spraying conditions are as follows: the carrier gas pressure of the powder supply system is 3.5MPa to 4.5MPa, the turntable speed is 20 to 25 rpm, the stirrer speed is 60 to 65 rpm, the distance between the spray gun and the sample is 130 mm to 135 mm, and the spray gun moving speed is 500 mm / s to 550 mm / s.

9. The method for preparing the composite anti-corrosion coating according to claim 8, characterized in that, The conditions for the first or second sandblasting treatment are: The compressed air pressure is maintained between 0.5MPa and 0.8MPa, the sandblasting distance is maintained between 100mm and 300mm, and the spray angle is controlled between 15° and 75°.

Images