Low-cost long-acting metal reinforced anticorrosive coating suitable for global cold region salt freeze alternating environment and preparation method

Abstract

This invention belongs to the field of spraying technology and relates to a low-cost, long-lasting metal-reinforced anti-corrosion coating and its preparation method adapted to the alternating salt and freeze environments of cold regions worldwide. The coating consists of, from the inside out, a metal substrate, an arc-sprayed pure aluminum underlayer, and a controllable, high-energy accelerated oxidation dense alumina ceramic transition layer. This invention focuses on core technologies for metal surface strengthening, using arc spraying instead of high-cost supersonic spraying, significantly reducing construction costs. It innovatively employs two exclusive high-energy accelerated oxidation processes: electric furnace oxygen-assisted high-temperature oxidation and laser in-situ oxidation. These processes can rapidly generate a highly dense, highly sealed alumina ceramic reinforcement layer on the surface of the sprayed aluminum metal layer, completely solving the industry shortcomings of existing processing technologies, such as the thinness of traditional electrophoretic coatings, easy penetration and corrosion of the substrate by chloride ions, and the porosity, insufficient density, and poor salt and freeze resistance of simple thermal spraying aluminum coatings. This solution features pure metal-ceramic reinforced protection, free from interference from organic paint coatings. It offers flexible processing, strong substrate versatility, and wide applicability. The metal coating, after high-energy oxidation reinforcement, possesses excellent salt spray resistance, freeze-thaw resistance, aging resistance, and high density and impermeability. It is specifically designed for harsh working conditions in global temperate cold regions, high-altitude permafrost regions, high-salt freeze-thaw environments, and low-temperature strong ultraviolet radiation. Its overall cost-effectiveness and service life far surpass existing traditional metal corrosion protection technologies.

Description

Technical Field

[0001] This invention belongs to the field of spraying technology, specifically relating to a method for preparing anti-corrosion coatings using arc spraying and surface oxidation. Background Technology

[0002] Most high-latitude, high-altitude regions globally experience coupled corrosion conditions involving low-temperature freeze-thaw cycles, chloride ion erosion from de-icing salts / saline soils, large diurnal temperature variations, and strong outdoor ultraviolet radiation. Metal equipment and steel structures are subjected to a complex environment of alternating ice and water, salt ion penetration, and alternating low-temperature stress, resulting in corrosion rates far exceeding those at normal temperatures. This places extremely high demands on the sealing, adhesion, low-temperature toughness, density, and long-term stability of protective coatings on metal surfaces. Currently, mainstream metal substrate spraying solutions in the industry all have significant shortcomings: 1. Electrophoretic coating: Conventional electrophoretic dry film thickness is only 10~30μm. The film is thin, the protection level is low, and the physical barrier ability is seriously insufficient. Chloride ions can easily penetrate the film and corrode the metal substrate. Under repeated freeze-thaw and salt spray environments, it is very easy to blister, perforate and rust. The service life is short and cannot meet the requirements for long-term reinforcement and protection of metal components in cold regions.

[0003] 2. Supersonic flame spraying: The coating is dense and has excellent anti-corrosion and wear resistance, but the equipment investment is huge, the unit price of consumables is high, the construction efficiency is low, the operation and maintenance costs are high, and the overall cost is expensive. It is not suitable for mass production and promotion of general workpieces, and the application scenarios are severely limited, making it difficult to popularize.

[0004] 3. Single arc spray aluminum process: Arc spray aluminum has the basic advantages of low cost, low temperature resistance and salt spray resistance. However, the original spray aluminum coating has a porous and loose structure. Salt ions and ice water can easily penetrate into the pores, making it impossible to achieve dense anti-seepage protection. Moreover, the coating surface has poor stability and no reinforced sealing structure. Under repeated freeze-thaw conditions in cold regions, it is prone to local corrosion and coating failure, resulting in insufficient protection reliability.

[0005] 4. Conventional oxidation treatment methods are limited and inefficient: Traditional passivation methods such as boiling water oxidation and weak alkali oxidation have slow film formation speed, thin film layer and limited density. They can only achieve simple surface passivation and cannot completely seal the micropores of aluminum spray coating. They are difficult to adapt to the harsh corrosion conditions of high salt freeze-thaw cycles and cannot achieve the strengthening and upgrading of metal coatings.

[0006] 5. Traditional metal + paint composite structure: It relies on organic paint layer to achieve pore sealing and weather protection. The paint layer is prone to aging, powdering, cracking and peeling. It has poor low-temperature toughness and is very easy to fail under freeze-thaw cycle conditions in cold regions. Moreover, it cannot achieve the strengthening and modification of the metal body coating, thus limiting the protective life and stability.

[0007] In summary, existing metal surface protection technologies cannot simultaneously meet the core requirements of low cost, thick metal protection, high-sealing pores, and resistance to low-temperature freeze-thaw cycles, and are therefore insufficient to meet the requirements for long-term use in harsh salt-freezing conditions in cold regions around the world. Summary of the Invention

[0008] To address the aforementioned issues, this invention provides a low-cost, long-lasting metal-reinforced anti-corrosion coating and its preparation method adapted to the alternating salt-freezing environments of cold regions worldwide. This invention employs a thick-layer arc-sprayed aluminum coating combined with a high-energy in-situ ceramic reinforcement structure. This constructs a composite coating consisting of an arc-sprayed pure aluminum underlayer and an alumina ceramic reinforcement layer formed by in-situ high-energy accelerated oxidation. It abandons the traditional organic paint protection system, overcomes the shortcomings of traditional electrophoretic coatings (such as excessively thin film, susceptibility to chloride ion penetration and corrosion in salt-freezing environments), and addresses the weaknesses of conventional aluminum spray coatings (such as porosity, lack of reinforcement, and poor protective stability). Simultaneously, it avoids the industry's shortcomings of high cost and limited mass production of supersonic spraying.

[0009] This invention develops a metal-reinforced anti-corrosion coating system suitable for various general-purpose metal substrates such as carbon steel, cast iron, and alloy steel in harsh outdoor environments including cold regions, high-altitude permafrost regions, saline permafrost regions, low-temperature and high-salt freeze-thaw cycles, and strong ultraviolet radiation. It can be widely used for surface strengthening and long-term anti-corrosion protection of engineering machinery, outdoor steel structures, road and bridge equipment, agricultural and forestry machinery, cold-region power equipment, and outdoor general-purpose metal components.

[0010] To achieve the above technical objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, comprising: A pure aluminum underlayer is arc-sprayed onto the surface of a metal substrate, wherein the porosity of the pure aluminum underlayer is 5%–15%. The pure aluminum substrate is subjected to high-temperature oxidation or in-situ oxidation under laser scanning to grow an alumina ceramic reinforced transition layer, which is then cooled to obtain a composite coating.

[0011] The composite reinforced anti-corrosion coating of this invention consists of two core layers from the substrate outward: a metal substrate → an arc-sprayed pure aluminum underlayer → a controllable high-energy accelerated oxidation alumina ceramic reinforcement layer. There is no organic paint coating throughout the process, and the pure metal-ceramic structure achieves substrate reinforcement and long-term anti-corrosion.

[0012] A second aspect of the present invention provides an anti-corrosion coating prepared by the above-described method. The coating comprises, from the metal substrate outwards: an arc-sprayed pure aluminum underlayer and an alumina ceramic reinforcing layer formed by in-situ high-energy accelerated oxidation; the arc-sprayed pure aluminum underlayer has a thickness of 150-300 μm and is prepared using an arc-spraying process; the alumina ceramic reinforcing layer is generated in-situ by high-energy accelerated oxidation via electric furnace oxygen-flushing high-temperature oxidation or laser in-situ oxidation; the composite coating is a pure metal-ceramic protective structure, without any organic paint coating, and is suitable for surface strengthening and anti-corrosion protection of general-purpose metal substrates such as carbon steel, cast iron, and alloy steel in high-latitude cold regions, high-altitude permafrost regions, and saline freeze-thaw regions worldwide.

[0013] A third aspect of this invention provides the application of the aforementioned anti-corrosion coating in the machining of precision workpieces, irregularly shaped workpieces, or critical load-bearing components. Applicable substrates include general-purpose metal materials such as carbon steel, gray cast iron, ductile iron, and low-alloy steel. The substrates are widely applicable and suitable for most general-purpose machinery and steel structural components in cold regions.

[0014] The beneficial effects of this invention are as follows: (1) It is economically efficient and solves the core pain points of two major industries. This invention uses electric arc spraying to replace expensive supersonic spraying, significantly reducing equipment, consumables, and labor costs; it replaces the traditional ultra-thin electrophoretic coating with a thick metal coating and an in-situ ceramic reinforcement structure, completely solving the defects of thin electrophoretic films, easy penetration by salt ions, and short lifespan in cold regions. The pure metal reinforcement structure requires no paint or consumables, resulting in lower overall costs and more stable protection.

[0015] (2) Dual-mode high-energy oxidation enhancement, far exceeding traditional passivation processes This invention pioneers two high-energy accelerated strengthening schemes: overall oxidation via electric furnace oxygenation and precise local oxidation via laser. These schemes are suitable for mass production and customized precision irregular parts. The in-situ generated alumina ceramic film has a density, hardness, and stability far exceeding that of traditional boiling water and weak alkali passivation films. It completely blocks the microporous permeation channels of the aluminum spray layer, thereby achieving structural strengthening of the metal coating.

[0016] (3) Pure metal-ceramic integrated protection, without the drawbacks of organic coatings This invention abandons the traditional paint composite structure and adopts a metal + ceramic oxide layer for protection throughout the process, eliminating problems such as paint aging, powdering, cracking and peeling. It also significantly improves the resistance to high and low temperature alternation and UV aging, making it suitable for long-term harsh working conditions in cold regions.

[0017] (4) The coating has high bonding strength and good stability. This invention utilizes high-energy oxidation to reconstruct the microstructure of the aluminum layer surface, optimizes the coating interface bonding state, eliminates defects in porous coating structures, significantly improves the overall stability of the metal coating, eliminates the risk of delamination and peeling, and is suitable for long-term freeze-thaw stress alternation conditions.

[0018] (5) Extremely wide range of working conditions adaptability The enhanced metal-ceramic coating of this invention is resistant to ultra-low temperature freeze-thaw cycles, high salt spray, strong ultraviolet aging, and alternating temperature differences, and can be adapted to various harsh environments such as high-latitude cold regions, high-altitude permafrost regions, saline soil regions, and outdoor equipment for winter de-icing and salt removal.

[0019] (6) The process is flexible, versatile, and adaptable to large-scale production. This invention enables mass production of furnace body oxidation for overall strengthening, as well as laser precision local strengthening. It can accommodate the production of standard parts, irregular parts, and precision parts. It is applicable to all types of conventional metal substrates and is suitable for the surface strengthening and corrosion protection needs of various metal components.

[0020] (7) The method of the present invention is simple, easy to operate, highly practical, and easy to promote. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 A. Front view, B. Top view, and C. Side view of the arc-sprayed pure aluminum substrate prepared in Comparative Example 1 of this invention. Figure 2 The coating prepared by laser in-situ scanning oxidation method in Embodiment 6 of the present invention is shown in the following views: A. Front view, B. Top view, and C. Side view. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] As described in the background section, metal surface protection technologies often struggle to simultaneously achieve low cost, thick-layer metal protection, highly sealable pores, and resistance to low-temperature freeze-thaw cycles. This invention provides a method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating suitable for alternating salt-freezing environments in cold regions worldwide, comprising: A pure aluminum underlayer is arc-sprayed onto the surface of a metal substrate, wherein the porosity of the pure aluminum underlayer is 5%–15%. The pure aluminum substrate is subjected to high-temperature oxidation or in-situ oxidation under laser scanning to grow an alumina ceramic reinforced transition layer, which is then cooled to obtain a composite coating.

[0026] In the laser oxidation process of this invention, it is necessary to ensure that the aluminum metal is oxidized but not melted, and to achieve pore sealing during the oxidation process. Therefore, the porosity of the initial pure aluminum substrate cannot be too high to ensure the subsequent sealing effect. At the same time, the laser energy cannot be too high or too low to avoid melting of the aluminum or difficulty in forming a dense ceramic oxide layer. Therefore, this invention has conducted long-term research and experimental exploration on the parameter conditions of each process, as detailed below: This invention breaks through the traditional, single, and inefficient passivation and oxidation methods, abandons the use of organic coatings for auxiliary protection, and innovatively adopts two high-energy, controllable, and accelerated oxidation processes: electric furnace oxygen-flushed high-temperature oxidation and laser in-situ oxidation. The appropriate process can be flexibly selected based on workpiece size, structural morphology, and batch production requirements. It generates a continuous, uniform, highly dense, and high-hardness ceramic-phase alumina reinforced film in situ on the surface of the porous aluminum-coated metal layer, achieving structural strengthening and complete pore sealing of the metal coating. Preferably, the conditions for the in-situ oxidation under laser scanning are: laser power: 1000–1500W, scanning speed: 800–1500mm / min, spot size: φ5–8mm defocused spot, overlap rate: 30%–50%, powder feeding system off, atmosphere: air.

[0027] The alumina ceramic reinforcing layer is used to comprehensively seal the micropores and through-pores of the arc-sprayed aluminum layer, blocking the penetration channels of salt ions and ice water. Simultaneously, it reconstructs the microstructure of the aluminum layer surface, improving the surface hardness, wear resistance, and overall structural stability of the metal coating, thus achieving a surface strengthening upgrade. Preferably, the conditions for in-situ oxidation under laser scanning are: laser power: 1800–2200W, scanning speed: 1200–2000mm / min, spot size: φ8–12mm, overlap rate: 30%–50%, powder feeding system off, atmosphere: air. A high-energy laser beam is used to perform controllable uniform scanning of the aluminum layer surface, achieving rapid localized high-temperature oxidation, instantly generating a high-hardness, high-density alumina ceramic reinforcing film. This results in a minimal heat-affected zone, no substrate deformation, and no loss of precision, enabling precise localized strengthening. It is suitable for localized strengthening and protection of irregularly shaped parts, precision parts, and critical load-bearing metal components.

[0028] The core functions of this ceramic reinforcement layer are: first, to completely seal the surface micropores and through pores of the arc-sprayed aluminum layer, thereby completely blocking the penetration channels of salt ions and ice water, and solving the core defect of traditional arc-sprayed aluminum coatings that are porous and leaky; second, to generate a ceramic phase oxide film in situ, which greatly improves the surface hardness, wear resistance and structural stability of the metal coating, and achieves surface strengthening upgrade of the metal coating; and third, the oxide film has extremely strong chemical and thermal stability, is resistant to high and low temperature alternation and strong ultraviolet aging, and is suitable for extreme working conditions such as repeated freeze-thaw cycles and high salt corrosion in cold regions around the world, achieving long-term stable protection without the need for organic paint auxiliary protection.

[0029] Preferably, the high-temperature oxidation conditions are as follows: in a closed electric furnace, the heating rate is 5-10℃ / min; first, the temperature is raised to 300℃-350℃ and held for 1-1.5 hours, then raised to 500℃-600℃ and held for 1.5-2 hours. Oxygen is continuously introduced during the process at a flow rate of 5-10 L / min. After the holding period, the furnace is cooled to room temperature. Placing the aluminum-sprayed workpiece inside the closed electric furnace and continuously introducing high-purity oxygen drives the overall uniform oxidation of the aluminum layer under a controllable constant temperature environment. This results in a highly dense film, thorough micropore sealing, and uniform overall coating strengthening, suitable for standardized mass production strengthening of large batches of regular-structure metal workpieces. Preferably, the total thickness of the pure aluminum substrate is 150–300 μm, and it is formed by cross-spraying in 3–5 layers.

[0030] This method employs arc spraying, replacing high-cost supersonic spraying, significantly reducing overall construction costs and improving mass production efficiency. It is suitable for large-scale reinforcement and protection of numerous metal components. Preferably, the arc spraying conditions are: material: pure aluminum wire; voltage: 28–32V; current: 180–220A; compressed air pressure: 0.6–0.7MPa; spraying distance: 150–180mm; spraying angle: 60°–90°; multi-layer cross-hatching. Relying on the excellent cathodic protection characteristics and low-temperature stability of aluminum, it withstands low-temperature freeze-thaw cycles, salt ion corrosion, and alternating moisture erosion. As the base metal anti-corrosion layer of the entire reinforcement system, it provides a high-quality substrate for subsequent anodizing reinforcement.

[0031] Preferably, the metal substrate is pretreated by sandblasting to Sa2.5 grade with a roughness of 50–100 μm, and is thoroughly degreased and derusted.

[0032] Preferably, the metal substrate is selected from carbon steel, gray cast iron, ductile iron, and low alloy steel.

[0033] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0034] In the following examples and comparative examples, the metal substrate is carbon steel.

[0035] Hardness was tested according to GB / T4340.1-2018 "Metallic materials Vickers hardness test - Part 1: Test method".

[0036] Porosity was determined using GB / T39852-2021 "Metallographic Image Analysis Method for Testing Porosity of Thermal Spray Coatings".

[0037] The neutral salt spray test (NSS) was conducted according to GB / T10125-2021. The conditions were: 5% NaCl solution, pH 6.5~7.2, test chamber 35℃, continuous spraying, and no red rust, no coating blistering or peeling, and no substrate corrosion.

[0038] The high and low temperature freeze-thaw cycle test was conducted according to GB / T2423.22-2022. The conditions were: low temperature -40℃ for 4 hours, high temperature 60℃ for 4 hours, single cycle 8 hours, cycle switching rate ≤3℃ / min, no cracking, peeling, or bulging of the coating, and no peeling at the interface.

[0039] The accelerated UV aging test was conducted according to GB / T16422.3-2014, under the following conditions: UV irradiation of 0.63 W / (m²). 2 •nm), light exposure at 60℃ / 4h, condensation at 50℃ / 4h, 8h cycle, no chalking, loss of gloss, cracking, or coating peeling, color difference ΔE≤3.

[0040] The alternating temperature and humidity damp heat test was conducted according to GB / T2423.4-2008. The conditions were: high temperature 55℃, 95%RH for 12h; low temperature -10℃, 30%RH for 12h, with a cycle of 24h. No bubbling, peeling, rust spots, or delamination were observed.

[0041] Example 1 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0042] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 28V, Current: 180A. Air pressure conditions: Compressed air pressure: 0.7MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 150mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0043] A 150 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 15%, an adhesion strength of 9 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0044] 3. High-energy controllable accelerated oxidation enhancement treatment High-temperature oxidation with oxygen in an electric furnace: The aluminum-sprayed workpiece is placed in a sealed electric furnace. The furnace temperature rises at a rate of 5℃ / min, first reaching 300℃ and holding for 1.5 hours to relieve stress, then rising to 500℃ and holding for 2 hours. During the process, oxygen is continuously introduced (flow rate 10L / min, slight positive pressure inside the furnace). After holding, the workpiece is cooled to room temperature with the furnace to prevent coating cracking. This constant-temperature controlled oxidation method ensures a uniform and dense alumina ceramic strengthening film is formed on the aluminum surface, completing the overall coating reinforcement and sealing process. 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0045] Example 2 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0046] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 28V, Current: 180A. Air pressure conditions: Compressed air pressure: 0.7MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 150mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0047] A 150 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 15%, an adhesion strength of 9 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0048] 3. High-energy controllable accelerated oxidation enhancement treatment High-temperature oxidation in an electric furnace with oxygen: The aluminum-sprayed workpiece is placed in a sealed electric furnace. The furnace temperature rises at a rate of 10℃ / min, first reaching 350℃ and holding for 1 hour to relieve stress, then rising to 600℃ and holding for 1.5 hours. During this process, oxygen is continuously introduced (flow rate 5L / min, slight positive pressure inside the furnace). After holding, the workpiece is cooled to room temperature with the furnace to prevent coating cracking. This constant-temperature controlled oxidation method ensures a uniform and dense alumina ceramic strengthening film is formed on the aluminum surface, completing the overall coating reinforcement and sealing process. 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0049] Example 3 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0050] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0051] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0052] 3. High-energy controllable accelerated oxidation enhancement treatment Laser in-situ scanning oxidation: 4000W laser equipment, laser power: 1000W, scanning speed: 1500mm / min, spot size: φ8mm defocused large spot size, overlap rate: 50%, powder feeding speed: 0 (powder feeding system off), atmosphere: natural air oxidation, no protective gas required.

[0053] A high-energy laser with preset parameters is used to scan the surface of the aluminum spray layer at a uniform speed, quickly generating a high-density, high-hardness alumina ceramic reinforced transition layer in situ. This ensures that the substrate is free from deformation, thermal damage, and loss of precision, achieving accurate reinforcement.

[0054] Experimental results show that the coating surface is uniformly matte gray-black with no metallic shine, no melting, no peeling, and no ablation, successfully sealing the micropores of the aluminum spray and significantly improving corrosion resistance, wear resistance, and stability.

[0055] 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0056] Example 4 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0057] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0058] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0059] 3. High-energy controllable accelerated oxidation enhancement treatment Laser in-situ scanning oxidation: 4000W laser equipment, laser power: 1500W, scanning speed: 800mm / min, spot size: φ5mm defocused large spot size, overlap rate: 30%, powder feeding speed: 0 (powder feeding system off), atmosphere: natural air oxidation, no protective gas required.

[0060] A high-energy laser with preset parameters is used to scan the surface of the aluminum spray layer at a uniform speed, quickly generating a high-density, high-hardness alumina ceramic reinforced transition layer in situ. This ensures that the substrate is free from deformation, thermal damage, and loss of precision, achieving accurate reinforcement.

[0061] Experimental results show that the coating surface is uniformly matte gray-black with no metallic shine, no melting, no peeling, and no ablation, successfully sealing the micropores of the aluminum spray and significantly improving corrosion resistance, wear resistance, and stability.

[0062] 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0063] Example 5 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0064] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0065] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0066] 3. High-energy controllable accelerated oxidation enhancement treatment Laser in-situ scanning oxidation: 12000W laser equipment (for large and high-efficiency applications), laser power: 1800W, scanning speed: 2000mm / min, spot size: φ12mm large spot, overlap rate: 50%, powder feeding speed: 0 (powder feeding off), atmosphere: natural air.

[0067] A high-energy laser with preset parameters is used to scan the surface of the aluminum spray layer at a uniform speed, quickly generating a high-density, high-hardness alumina ceramic reinforced transition layer in situ. This ensures that the substrate is free from deformation, thermal damage, and loss of precision, achieving accurate reinforcement.

[0068] 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0069] Example 6 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0070] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0071] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0072] 3. High-energy controllable accelerated oxidation enhancement treatment Laser in-situ scanning oxidation: 12000W laser equipment (for large and high-efficiency applications), laser power: 2200W, scanning speed: 1200mm / min, spot size: φ8mm large spot, overlap rate: 30%, powder feeding speed: 0 (powder feeding off), atmosphere: natural air.

[0073] A high-energy laser with preset parameters is used to scan the surface of the aluminum spray layer at a uniform speed, quickly generating a high-density, high-hardness alumina ceramic reinforced transition layer in situ. This ensures that the substrate is free from deformation, thermal damage, and loss of precision, achieving accurate reinforcement.

[0074] 4. Cooling stabilization treatment The anodized and strengthened workpiece is naturally and slowly cooled to room temperature to fully stabilize the alumina ceramic layer structure, eliminate internal stress in the coating, and complete the metal surface strengthening and anti-corrosion construction.

[0075] Comparative Example 1 The difference from Example 6 is that steps 3 and 4 are omitted. Specifically, it includes: 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0076] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0077] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0078] Comparative Example 2 The difference from Example 6 is that step 3 uses laser cladding to prepare the alumina ceramic coating. Specifically, it includes: 1. Substrate pretreatment The metal substrate is sandblasted to a Sa2.5 grade to thoroughly remove surface oil, rust, scale and impurities, and the surface roughness is controlled at 50~100μm, providing a good bonding foundation for subsequent arc spraying of aluminum and anodizing.

[0079] 2. Arc spraying pure aluminum base layer Arc spraying is employed, with the equipment spraying pure aluminum wire. The coating material is ≥99.5% pure aluminum wire with a diameter of Φ2.0mm. Electrical parameters: Voltage: 32V, Current: 220A. Air pressure conditions: Compressed air pressure: 0.6MPa (dry and oil-free). Spraying operation parameters: Spraying distance: 180mm, Spraying angle: vertical. Gun travel speed: uniform and stable, multi-layer cross-hatching spraying.

[0080] A 300 μm thick pure aluminum metal underlayer was formed on the substrate surface. The performance of the underlayer was tested, showing a porosity of 9%, an adhesion strength of 12 MPa, and a rough, porous surface structure, which facilitates subsequent laser / electric furnace accelerated oxidation sealing and strengthening.

[0081] 3. Laser cladding coating Equipment: 12000W fiber laser cladding system, equipped with a synchronous powder feeder and a sealed argon gas protection chamber; Ceramic powder: α-Al2O3, particle size 15~45μm; Laser power: 1400W; Scanning speed: 2200 mm / min; Spot size: φ8mm focused spot (no positive defocus); Overlap rate: 30%; Powder feeding rate: 4g / min; Protective gas: Argon 25L / min, to prevent oxidation by air; Process method: single-layer single-scan, precise control of deposition amount.

[0082] Post-processing appearance: light grayish-white cladding patterns, extremely thin film layer; micro-cracks exist at the fusion interface between the aluminum layer and the ceramic layer, and slight thermal warping occurs on thin-walled workpieces.

[0083] 4. Cooling stabilization treatment The laser-clad workpiece is then allowed to cool naturally to room temperature.

[0084] Table 1. Hardness and porosity test results of embodiments and comparative examples of the present invention.

[0085] Table 2 Performance test results of embodiments and comparative examples of the present invention

[0086] The coatings prepared by Examples 1-6 have good hardness, sealing rate and corrosion resistance, and have excellent resistance to ultra-low temperature freeze-thaw, high salt spray, strong ultraviolet aging and temperature difference alternation. They can be adapted to various harsh environments such as high latitude cold regions, high altitude permafrost regions, saline soil regions and outdoor equipment for winter de-icing and salt removal.

[0087] As can be seen from the comparison of Examples 1-6 and Comparative Example 1, the controllable high-energy accelerated oxidation alumina ceramic reinforcement layer prepared by the present invention effectively improves the hardness, pore sealing rate and corrosion resistance of the coating, and also significantly improves the resistance to ultra-low temperature freeze-thaw, high salt spray, strong ultraviolet aging and temperature difference alternation.

[0088] A comparison of Examples 6 and 2 shows that the alumina ceramic coating prepared by laser in-situ oxidation has better hardness and sealing effect, and its resistance to ultra-low temperature freeze-thaw, high salt spray, strong ultraviolet aging and temperature difference alternation is significantly improved.

[0089] As can be seen from the comparison between Example 6 and Comparative Example 2, compared with the laser cladding coating, the alumina ceramic coating prepared by the laser in-situ oxidation method of the present invention has better hardness and pore sealing effect, and its resistance to ultra-low temperature freeze-thaw, high salt spray, strong ultraviolet aging and temperature difference alternation is also significantly improved.

[0090] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, characterized in that, include: A pure aluminum underlayer is arc-sprayed onto the surface of a metal substrate, wherein the porosity of the pure aluminum underlayer is 5%–15%. The pure aluminum substrate is subjected to high-temperature oxidation or in-situ oxidation under laser scanning to grow an alumina ceramic reinforced transition layer, which is then cooled to obtain a composite coating.

2. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The conditions for in-situ oxidation under laser scanning are: laser power: 1000–1500W, scanning speed: 800–1500mm / min, spot size: φ5–8mm defocused spot, overlap rate: 30%–50%, powder feeding system off, atmosphere: air.

3. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The conditions for in-situ oxidation under laser scanning are: laser power: 1800–2200W, scanning speed: 1200–2000mm / min, spot size: φ8–12mm, overlap rate: 30%–50%, powder feeding system off, atmosphere: air.

4. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The conditions for high-temperature oxidation are as follows: in a closed electric furnace, the heating rate is 5~10℃ / min, first heating to 300℃-350℃ and holding for 1-1.5h, then heating to 500℃-600℃ and holding for 1.5-2h, during which oxygen is continuously introduced at a flow rate of 5~10L / min, and after the holding period, the furnace is cooled to room temperature.

5. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The total thickness of the pure aluminum base layer is 150–300 μm, and it is formed by cross-spraying in 3–5 layers.

6. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The conditions for arc spraying are as follows: material: pure aluminum wire, voltage: 28–32V, current: 180–220A, compressed air pressure: 0.6–0.7MPa, spraying distance: 150–180mm, spraying angle: 60°–90°, and multi-layer cross-spraying.

7. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The metal substrate is first pretreated by sandblasting to Sa2.5 grade with a roughness of 50–100 μm, and is then thoroughly cleaned of oil and rust.

8. The method for preparing a low-cost, long-lasting metal-reinforced anti-corrosion coating adapted to the alternating salt-freezing environment of cold regions worldwide, as described in claim 1, is characterized in that... The metal substrate is selected from one of carbon steel, gray cast iron, ductile iron, and low alloy steel.

9. The anti-corrosion coating prepared by the method according to any one of claims 1-8.

10. The application of the anti-corrosion coating of claim 9 in the processing of precision workpieces, irregularly shaped workpieces or critical load-bearing components.

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