An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, and its preparation and construction method.

Abstract

This invention discloses an inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, and its preparation and construction method. The coating, from the inside out, comprises: a high-adhesion low-zinc epoxy primer layer, a polysiloxane-modified polyurethane intermediate layer, and a nanocomposite weather-resistant polyurethane topcoat. The polysiloxane-modified polyurethane intermediate layer contains a polysiloxane intermediate and graphene nanosheets. The nanocomposite weather-resistant polyurethane topcoat contains a composite nano-UV barrier material. The composite nano-UV barrier material is a mixture of fluorinated graphene-supported nano-zinc oxide composite particles surface-modified with a silane coupling agent and nano-cerium dioxide mixed at a mass ratio of (2~4):1. This invention solves the problems of easy peeling, poor weather resistance, and short service life of traditional anti-corrosion solutions, achieving ultra-long-lasting anti-corrosion protection for outdoor steel structures, adapting to various complex outdoor corrosive environments, convenient construction, safety and environmental protection, and significantly reducing the life-cycle maintenance cost of steel structures.

Description

Technical Field

[0001] This invention relates to the field of anti-corrosion coating technology for steel structures, and in particular to an inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures and its preparation and application methods. Background Technology

[0002] Outdoor steel structures (including photovoltaic supports, power poles, offshore wind power platforms, and cross-sea bridge steel structures) are exposed to harsh environments such as high salt spray, strong ultraviolet radiation, alternating wet and dry conditions, and temperature cycles for extended periods. Corrosion failure is the primary factor affecting structural safety and service life.

[0003] Currently, the mainstream anti-corrosion solutions in the industry and their inherent defects are as follows: (1) Hot-dip galvanizing / sacrificial anode solution: only applicable to sealed or simple atmospheric environments such as underground and underwater. In outdoor atmospheric environments, the anode consumption rate is uncontrollable, and it will fail in 3-8 years under extreme conditions, which cannot support long-term protection for more than 25 years, and the maintenance cost is extremely high. (2) Traditional epoxy resin coating system: poor weather resistance, easy to powder, crack and peel off under ultraviolet radiation, and the effective protection life outdoors is only 3-10 years; poor temperature adaptability, easy to cause coating to blister and peel off due to thermal expansion and contraction; in addition, the zinc powder content in epoxy zinc-rich primer is usually as high as 70-80%, resulting in high VOC, difficult construction, high cost, and poor adhesion with subsequent coatings. (3) The existing three-layer system of “epoxy zinc-rich primer + epoxy micaceous iron oxide intermediate paint + polyurethane topcoat” (such as the invention patent with publication number CN109554064B) has improved the anti-corrosion performance to a certain extent, but still has the following synergistic defects: ① Insufficient compatibility of heterogeneous interfaces: The epoxy intermediate paint and polyurethane topcoat are different resin systems. During long-term service, the interlayer adhesion gradually decreases, resulting in the risk of interlayer peeling; ② Functional discontinuity: The epoxy micaceous iron oxide intermediate paint itself has poor resistance to ultraviolet aging. Under long-term outdoor irradiation, the resin ages, causing its function of connecting the primer and topcoat to fail, and the protective performance of the entire coating system shows a discontinuous decline; ③ Single anti-ultraviolet scheme: The topcoat only relies on the addition of a small amount of organic UV absorber, and the ultraviolet shielding rate is usually less than 80%, and it cannot protect the intermediate paint and primer from degradation after ultraviolet penetration; ④ Lack of multi-mechanism synergy: The existing scheme has failed to achieve effective synergy of multiple mechanisms of “cathode protection + physical shielding + anti-ultraviolet aging”, and cannot provide ultra-long-term protection in C5 extreme environment.

[0004] While polyurethane coatings possess excellent corrosion resistance and weather resistance potential in existing technologies, single polyurethane coatings still face the risk of aging and degradation under long-term ultraviolet radiation, and there is a lack of composite modification and systematic protection solutions for 25-year long-term outdoor service. Therefore, developing a steel structure anti-corrosion coating system that can achieve synergistic effects of multiple protection mechanisms and complementary benefits of each layer's functions has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide an inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, along with its preparation and application methods. Through a systematic synergistic design of a low-zinc primer, a polysiloxane-modified polyurethane intermediate coat, and a nano-composite weather-resistant topcoat, functional complementarity and performance enhancement between each layer are achieved. Combined with sacrificial anode joint protection, this addresses the problems of adhesion degradation, poor weather resistance, high zinc powder content, and insufficient adaptability to extreme environments inherent in traditional solutions, achieving long-term anti-corrosion protection for outdoor steel structures for over 25 years.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, which includes, from the inside to the outside: a high-adhesion low-zinc epoxy primer layer, a polysiloxane modified polyurethane intermediate layer, and a nano-composite weather-resistant polyurethane topcoat layer. The polysiloxane-modified polyurethane intermediate coating contains a polysiloxane intermediate and graphene nanosheets; the nanocomposite weather-resistant polyurethane top coating contains a composite nano UV-blocking material. The composite nano UV barrier material is a mixture of fluorinated graphene-supported nano zinc oxide composite particles (FG@ZnO) modified with silane coupling agent and nano cerium dioxide (CeO2), with a mass ratio of FG@ZnO to CeO2 of (2~4):1.

[0007] The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures provided by this invention features a complementary combination of cathodic protection effect from a high-adhesion, low-zinc primer layer and physical shielding effect from a mid-coat and top-coat layer. The high density of the mid-coat and top-coat layers slows the penetration of corrosive media, significantly reducing the consumption rate of zinc powder in the primer layer. This achieves equivalent or even better long-term cathodic protection with a zinc powder content reduction of over 20% (typically 60-80%). The polysiloxane intermediate in the mid-coat layer forms molecular-level chemical bonds with the aliphatic polyurethane resin in the top-coat layer, resulting in significantly improved interlayer adhesion compared to epoxy / polyurethane heterojunction interfaces, eliminating the risk of interlayer delamination. The UV weather resistance of the top-coat layer, combined with the UV absorption characteristics of the graphene nanosheets in the mid-coat layer, forms a double-layer UV barrier, protecting the mid-coat and primer layers from UV degradation and significantly improving the overall weather resistance, achieving 25 years of long-term anti-corrosion protection for outdoor steel structures.

[0008] In the preferred embodiment, the dry film thickness of the high-adhesion, low-zinc epoxy primer layer is 70~90 μm.

[0009] In the preferred embodiment, the raw material composition of the high-adhesion low-zinc epoxy primer layer includes, by weight: 15-25 parts epoxy resin, 40-55 parts flake zinc powder, 0.5-1 part dispersant, 1-2 parts additives, 10-15 parts polyamide curing agent, and 10-20 parts solvent.

[0010] In the preferred embodiment, the dry film thickness of the polysiloxane-modified polyurethane intermediate coating is 140~170 μm.

[0011] In the preferred embodiment, the raw material composition of the polysiloxane-modified polyurethane intermediate coating includes, by weight: 30-40 parts of hydroxyl acrylic resin, 15-20 parts of aliphatic isocyanate curing agent, 5-15 parts of polysiloxane intermediate, 2-5 parts of fumed silica, 8-15 parts of talc, 5-10 parts of anti-rust pigment, 1-3 parts of additives, 10-20 parts of solvent, and 0.5-2 parts of graphene nanosheets.

[0012] In the preferred embodiment, the dry film thickness of the nanocomposite weather-resistant polyurethane surface coating is 60~80 μm.

[0013] In the preferred embodiment, the raw material composition of the nanocomposite weather-resistant polyurethane surface coating includes, by weight: 35-45 parts aliphatic polyurethane resin, 15-20 parts isocyanate curing agent, 5-12 parts composite nano UV blocking material, 1-3 parts additives, and 10-20 parts solvent.

[0014] In a preferred embodiment, the coating further includes an aluminum-zinc-indium sacrificial anode with an installation spacing of 1.5~2.0 m and an initial protection current density of 2~5 mA / m. 2 This forms a combined system of physical barrier and electrochemical protection, suitable for extreme C5 corrosion environments such as coastal areas with high salt spray and chemical industrial zones with high pollution.

[0015] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0016] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 70~90 μm, and it is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 140~170 μm, and cured at room temperature for 24~48 h. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 60~80 μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0017] In the preferred embodiment, an aluminum-zinc-indium sacrificial anode is installed after the coating application is completed. This provides supplementary protection in extreme environments such as coastal areas and chemical industrial zones.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention introduces graphene nanosheets into the intermediate coating and constructs a superhydrophobic surface (contact angle > 120°) in the topcoat to form a shielding compensation effect. The layered labyrinth structure of graphene extends the penetration path of corrosive media by 5 to 10 times, and the superhydrophobic topcoat further prevents water penetration. The two work together to reduce the zinc powder consumption rate of the primer layer to 45% to 55%, solving the defect in traditional technology where a zinc powder content of less than 60% is considered insufficient cathodic protection, and achieving a technological leap in reducing zinc and increasing efficiency.

[0019] 2. In this invention, the coating is made of polysiloxane-modified polyurethane, which is a homogeneous resin system with the aliphatic polyurethane topcoat. Molecular-level chemical bonds are formed between the layers, and the adhesion retention rate is greater than 80% after 3000 h QUV aging.

[0020] 3. This invention constructs a dual-layer UV protection system consisting of an ultra-high shielding topcoat and an intrinsic absorption midcoat: the FG@ZnO composite particles in the topcoat provide both physical shielding and chemical absorption, while nano-CeO2 provides free radical scavenging capabilities, synergistically achieving a UV shielding rate of ≥99.6%; the graphene nanosheets in the midcoat absorb residual UV rays penetrating the topcoat; after 3000 h QUV aging, the gloss retention rate of Examples 1-3 still reaches 91%-93%, the color difference ΔE ≤2.0, and there is no powdering or cracking; the weather resistance life is greatly improved.

[0021] 4. This invention organically combines the physical barrier of the coating with the electrochemical protection of the sacrificial anode to form a dual insurance mechanism: the coating blocks more than 99% of the corrosive medium, reducing the consumption rate of the sacrificial anode by more than 60%; the sacrificial anode provides immediate protection for the exposed metal at the coating defects.

[0022] 5. All coatings in this application are cured at room temperature, requiring no special treatment between layers, and are easy to repair. They are also suitable for both factory prefabrication and on-site construction. When used with sacrificial anodes, they can cover extreme C5 environments such as coastal areas with high salt spray and chemical industrial zones with high pollution, overcoming the technical contradiction of traditional solutions that cannot balance long-term protection with ease of construction. Detailed Implementation

[0023] The technical solution of the present invention will be further described and illustrated below through examples. All raw materials used in the examples are commercially available or prepared using conventional methods.

[0024] Example 1 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 50 parts flake zinc powder (approximately 47.6% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15 parts solvent; dry film thickness 80 μm. The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 1 part graphene nanosheets, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; the dry film thickness is 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts composite nano UV blocking material (of which the mass ratio of FG@ZnO to CeO2 is 3:1), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm.

[0025] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0026] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0027] The performance of the samples was tested according to certain standards, and the results are shown in Table 1.

[0028] Table 1 Performance of the samples prepared in Example 1

[0029] Table 1 shows the zinc powder consumption rate (accelerated aging for 1 year) test, which was conducted in accordance with GB / T 32088-2015 "Accelerated Aging Test Method for Automotive Non-metallic Parts and Materials under Xenon Lamp" and GB / T 20853-2007 "Corrosion Test of Metals and Alloys under Artificial Atmospheres - Outdoor Accelerated Test under Intermittent Salt Spray (Crust Test)". One cycle includes: salt spray: 4 h, 35℃±2℃, 5% NaCl solution, sedimentation rate 1~2 mL / 80cm. 2 • h; UV-A ultraviolet light irradiation: 4 h, 60℃±2℃, irradiance 0.83W / m 2@340nm; Condensation (no light, high humidity): 4 h, 50℃±2℃, relative humidity 100%; Total test time: 2000 h (equivalent to simulating 1 year of natural outdoor exposure, acceleration factor approximately 4.38 times). Cross-sectional samples were taken from the coating of the specimens before and after the accelerated aging test. The morphology of the primer layer was observed using a scanning electron microscope (SEM) in backscattered electron mode, with an accelerating voltage of 15 kV and a working distance of 10 mm. Surface scanning or point analysis of the primer layer was performed using energy dispersive spectroscopy (EDS, Oxford X-max 50), and the mass fraction (wt%) of zinc was collected. At least 5 different regions were selected for each specimen, and the average value was taken as the zinc content of that specimen. The zinc powder consumption rate = (C... 初始 -C 老化 ) / C 初始 The formula calculates the zinc powder consumption rate, where: C 初始 To accelerate the aging test, the mass fraction (%) of zinc in the primer layer was determined by C. 老化 The mass fraction (%) of zinc in the primer layer after accelerated aging test.

[0030] Example 2 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 50 parts flake zinc powder (approximately 47.6% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15.7 parts solvent; dry film thickness 80 μm; The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 1 part graphene nanosheets, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; the dry film thickness is 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts composite nano UV blocking material (of which the mass ratio of FG@ZnO to CeO2 is 3:1), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm. The coating also includes an aluminum-zinc-indium sacrificial anode with an installation spacing of 1.5~2.0 m and an initial protection current density of 2~5 mA / m. 2 .

[0031] The preparation method of inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0032] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness is controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured. P5. After the surface layer construction is completed, install the aluminum-zinc-indium sacrificial anode.

[0033] The performance test results are shown in Table 2.

[0034] Table 2 Performance of the samples prepared in Example 2

[0035] Example 3 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 40 parts flake zinc powder (approximately 47.6% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15 parts solvent; dry film thickness 80 μm. The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 1 part graphene nanosheets, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; the dry film thickness is 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts composite nano UV blocking material (of which the mass ratio of FG@ZnO to CeO2 is 3:1), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm.

[0036] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0037] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0038] The performance test results are shown in Table 3.

[0039] Table 3 Performance of the samples prepared in Example 3

[0040] Comparative Example 1 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 50 parts flake zinc powder (approximately 47.6% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15 parts solvent; dry film thickness 80 μm. The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 1 part graphene nanosheets, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; the dry film thickness is 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts nano zinc oxide (ZnO), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm.

[0041] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, nano zinc oxide, additives and solvent evenly according to the formula, and grind to a fineness of ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0042] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0043] The performance test results are shown in Table 4.

[0044] Table 4 Performance of the sample prepared in Comparative Example 1

[0045] Comparative Example 2 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 50 parts flake zinc powder (approximately 47.6% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15 parts solvent; dry film thickness 80 μm. The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; dry film thickness 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts composite nano UV blocking material (of which the mass ratio of FG@ZnO to CeO2 is 3:1), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm.

[0046] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0047] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0048] The performance test results are shown in Table 5.

[0049] Table 5 Performance of the samples prepared in Comparative Example 2

[0050] Comparative Example 3 An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, comprising, from the inside out: The high-adhesion, low-zinc epoxy primer comprises, by weight parts: 20 parts epoxy resin, 30 parts flake zinc powder (approximately 37.8% by weight), 0.8 parts dispersant, 1.5 parts additives, 12 parts polyamide curing agent, and 15 parts solvent; dry film thickness 80 μm; The polysiloxane-modified polyurethane intermediate coating comprises, by weight parts: 35 parts hydroxyl acrylic resin, 10 parts polysiloxane intermediate, 18 parts aliphatic isocyanate curing agent, 1 part graphene nanosheets, 3 parts fumed silica, 12 parts talc, 8 parts anti-rust pigment, 2 parts additives, and 15 parts solvent; the dry film thickness is 160 μm. The nanocomposite weather-resistant polyurethane topcoat comprises, by weight parts: 40 parts aliphatic polyurethane resin, 18 parts isocyanate curing agent, 8 parts composite nano UV blocking material (of which the mass ratio of FG@ZnO to CeO2 is 3:1), 2 parts additives, and 15 parts solvent; the dry film thickness is 70 μm.

[0051] The method for preparing the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to fineness ≤50μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

[0052] The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 80 μm, and the primer is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 160μm, and the coating should be cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 70μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

[0053] The performance test results are shown in Table 6.

[0054] Table 6 Performance of the sample prepared in Comparative Example 3

[0055] Analysis of Experimental Results 1. Adhesion and interlayer bonding performance analysis Adhesion is a key indicator for evaluating the long-term reliability of a coating system. Especially for outdoor steel structures, the bonding strength between the coating and the substrate, as well as between different layers of the coating, directly affects the protective effect.

[0056] As shown in Tables 1-3, the initial adhesion of Examples 1-3 were 13.2 MPa, 13.5 MPa, and 12.5 MPa, respectively, all significantly higher than the 12.0-12.8 MPa range of Comparative Examples 1-3, and far exceeding the 6-8 MPa of existing technologies such as CN109554064B in the background art. More importantly, after 3000 h of QUV accelerated aging, the adhesion retention rates of Examples 1-3 were 87%, 87%, and 84%, respectively, while the adhesion of Comparative Example 1 dropped sharply from 12.0 MPa to 5.5 MPa, with a retention rate of only 46%, and obvious peeling of the intermediate coat / topcoat interface was observed.

[0057] The fundamental reason for this difference lies in the fact that Examples 1-3 and Comparative Examples 1-3 all used a homogeneous resin system of polysiloxane-modified polyurethane intermediate coating and aliphatic polyurethane top coating, forming molecular-level chemical bonds between the layers, thus resulting in high initial adhesion. However, the top coating of Comparative Example 1 only added single nano-zinc oxide (ZnO), lacking the complex system of fluorinated graphene-supported nano-zinc oxide (FG@ZnO) and nano-cerium dioxide (CeO2). Under long-term ultraviolet irradiation, the top coating resin degraded, leading to the destruction of its chemical bond with the intermediate coating and a significant decrease in adhesion. In contrast, in the top coatings of Examples 1-3, FG@ZnO provided efficient ultraviolet shielding and absorption, while CeO2 provided free radical scavenging ability, effectively protecting the molecular chain integrity of the top coating resin and thus maintaining the stability of the interlayer chemical bonds.

[0058] 2. Corrosion resistance performance (neutral salt spray test) analysis The neutral salt spray test (NSS) is a standard method for evaluating the ability of a coating system to resist the penetration of corrosive media. The test results directly reflect the long-term anti-corrosion performance of the coating.

[0059] Data shows that the NSS lifetime of Example 1 reached 10,000 h, Example 2 (with sacrificial anode) was further increased to 12,000 h, and Example 3 (40 parts of zinc powder) was 9,000 h. The NSS lifetimes of Comparative Examples 1 to 3 were 7,000 h, 6,500 h and 5,000 h, respectively, all significantly lower than those of the Examples.

[0060] From the corrosion morphology, the corrosion diffusion at the scratches in Examples 1-3 was ≤1.5~2.0 mm, and there was no blistering; while in Comparative Examples 1-3, varying degrees of blistering, edge corrosion (diffusion ≥3.0 mm), and even localized rusting were observed. This indicates that the coating system of the present invention has significant advantages in shielding against corrosive media.

[0061] This is because: First, the graphene nanosheets in the intermediate coating (present in Examples 1-3, absent in Comparative Example 2) significantly extend the penetration path of the corrosive medium through the layered maze effect; second, the FG@ZnO / CeO2 composite system in the topcoat not only provides UV protection, but its superhydrophobic properties (contact angle >120°) further prevent the penetration of moisture and chloride ions; the two work synergistically to form a highly efficient physical shielding layer. Example 2, by additionally installing a sacrificial anode on top of the coating, achieves dual protection of physical barrier and electrochemical protection, further increasing the NSS lifetime by 20%. Comparative Example 3, due to its excessively low zinc powder content (only 30 parts, content 37.8%), suffers from insufficient cathodic protection, resulting in an NSS lifetime of 5000 h, verifying the necessity of the lower limit of the 40%~55% zinc powder range specified in this invention.

[0062] 3. Analysis of UV aging resistance The QUV (Quick UV) test is used to evaluate the weather resistance of coatings under outdoor sunlight, with gloss retention and color difference being the core indicators.

[0063] After 3000 h of QUV aging, Examples 1-3 maintained gloss retention rates of 92%, 93%, and 91%, respectively, with color differences ΔE of 1.8, 1.6, and 2.0, respectively. The coatings showed no chalking or cracking. Comparative Example 1 had a gloss retention rate of only 65%, a color difference as high as 4.5, significant chalking of the topcoat, and slight loss of gloss in the intermediate coating. Comparative Example 2 had a gloss retention rate of 90% and a color difference of 2.2. Although the topcoat showed acceptable UV resistance, the intermediate coating showed slight aging. Comparative Example 3 had a gloss retention rate of 91% and a color difference of 2.0. The topcoat exhibited good UV resistance, but its corrosion resistance decreased due to insufficient zinc powder.

[0064] This is because the present invention achieves excellent weather resistance through a dual-layer UV protection strategy. In the first layer, the FG@ZnO composite particles in the topcoat block most UV rays through both physical shielding (reflection / scattering) and chemical absorption. Simultaneously, nano-CeO2 acts as a free radical scavenger, capturing free radicals generated by photodegradation, synergistically achieving a UV shielding rate of ≥99.8%. In the second layer, the graphene nanosheets in the intermediate coating possess intrinsic UV absorption properties, absorbing residual UV rays that penetrate the topcoat. Comparative Example 1, because its topcoat only contains ZnO and lacks the physical shielding enhancement of FG@ZnO and the free radical scavenging effect of CeO2, has a UV shielding rate of only 82%, leading to rapid degradation of the topcoat. Comparative Example 2, although its topcoat exhibits good UV resistance, lacks graphene in its intermediate coating, failing to absorb UV rays penetrating the topcoat, resulting in slight aging of the intermediate coating. This comparison directly demonstrates the synergistic effect of the dual-layer UV protection between the graphene in the intermediate coating and the FG@ZnO / CeO2 in the topcoat.

[0065] 4. Analysis of the relationship between hydrophobicity and zinc powder consumption rate The water contact angle test reflects the hydrophobic properties of the coating surface. High hydrophobicity helps reduce the adsorption and penetration of moisture and corrosive ions.

[0066] The water contact angles of Examples 1-3 were 123°, 124°, and 122°, respectively, all greater than 120°, exhibiting superhydrophobic properties. The water contact angle of Comparative Example 1 was only 105°, showing a significant decrease in hydrophobicity; Comparative Examples 2-3 maintained a high hydrophobic angle of around 122°. The decrease in the contact angle of Comparative Example 1 is because its surface coating only contains ZnO, lacking the fluorinated graphene superhydrophobic surface structure provided by FG@ZnO.

[0067] Zinc powder consumption rate is a quantitative indicator that directly reflects the synergistic effect of "low zinc without reduced efficiency". The zinc powder consumption rate in Example 1 was only 48%, in Example 2 it was further reduced to 45%, and in Example 3 it was 55%, all achieving a reduction of 45%~55% in zinc powder consumption rate. Comparative Example 1 (topcoat lacking composite UV blocking) had a rate of 60%, Comparative Example 2 (intermediate coating lacking graphene) had a rate of 65%, and Comparative Example 3 (too low zinc powder) had a rate as high as 78%. These data clearly show that when the physical shielding and UV protection functions of the intermediate and topcoats are complete (Example 1), even with a zinc powder content reduced to 47.6%, the zinc powder consumption rate is only half that of the traditional high-zinc system; however, once the intermediate coating lacks graphene or the topcoat lacks composite UV blocking material, the zinc powder consumption rate increases significantly; if the zinc powder content is below 40%, even with a complete shielding layer, sufficient cathodic protection cannot be provided, and the zinc powder consumption rate rises sharply to 78%.

[0068] In the neutral salt spray accelerated corrosion test (GB / T 10125-2021), the coating system of Example 1 showed corrosion diffusion ≤1.5 mm at the scratch after 10,000 h with no blistering, while Example 2 (including sacrificial anode) achieved corrosion diffusion ≤1.0 mm after 12,000 h. The gloss retention rate of Examples 1-3 remained at 91%-93%, with a color difference ΔE ≤2.0, and the coating showed no chalking or cracking. In contrast, the industry generally considers a gloss retention rate below 80% after 1000 h of QUV aging to be a failure. The examples still far exceeded the failure threshold after 3000 h, indicating that their weather resistance life is at least three times that of conventional methods. Furthermore, after 3000 h of comprehensive aging (UV + condensation + salt spray cycling), the interlayer adhesion of Example 1 remained as high as 11.5 MPa, and the zinc powder consumption rate was only 48% of that of the traditional high-zinc system. These data collectively demonstrate that the coating's three main functions—physical shielding, interfacial bonding, and cathodic protection—did not show significant deterioration during long-term, multi-factor aging. Based on the experience of the heavy-duty anti-corrosion coating industry in assessing the lifespan of similar high-performance coating systems, Example 1 of this invention (10,000 h NSS + 3,000 h QUV gloss retention >90%) already provides a foundation for 25 years of protection, while Example 2 (12,000 h NSS) further verifies that ultra-long-lasting protection of over 30 years can be achieved under sacrificial anode combined protection. Therefore, based solely on the accelerated aging data from the embodiments of this invention, through cross-verification using different experimental methods and industry-recognized lifespan estimation conventions, it is sufficient to reasonably support the claim of a 25-year long-lasting anti-corrosion protection technology for outdoor steel structures.

[0069] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. An inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures, characterized in that, From the inside out, it includes: a high-adhesion low-zinc epoxy primer layer, a polysiloxane-modified polyurethane intermediate layer, and a nano-composite weather-resistant polyurethane topcoat. The polysiloxane-modified polyurethane intermediate coating contains a polysiloxane intermediate and graphene nanosheets; the nanocomposite weather-resistant polyurethane top coating contains a composite nano UV-blocking material. The composite nano UV barrier material is a mixture of fluorinated graphene-supported nano zinc oxide composite particles modified with silane coupling agent and nano cerium dioxide mixed at a mass ratio of (2~4):

1.

2. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The dry film thickness of the high-adhesion, low-zinc epoxy primer layer is 70~90 μm.

3. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The raw material composition of the high-adhesion low-zinc epoxy primer layer, by weight, includes: 15-25 parts epoxy resin, 40-55 parts flake zinc powder, 0.5-1 part dispersant, 1-2 parts additives, 10-15 parts polyamide curing agent, and 10-20 parts solvent.

4. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The dry film thickness of the polysiloxane-modified polyurethane intermediate coating is 140~170 μm.

5. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The raw material composition of the polysiloxane-modified polyurethane intermediate coating includes, by weight: 30-40 parts of hydroxyl acrylic resin, 15-20 parts of aliphatic isocyanate curing agent, 5-15 parts of polysiloxane intermediate, 2-5 parts of fumed silica, 8-15 parts of talc, 5-10 parts of anti-rust pigment, 1-3 parts of additives, 10-20 parts of solvent, and 0.5-2 parts of graphene nanosheets.

6. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The dry film thickness of the nanocomposite weather-resistant polyurethane topcoat is 60~80 μm.

7. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The raw material composition of the nanocomposite weather-resistant polyurethane surface coating, by weight, includes: 35-45 parts aliphatic polyurethane resin, 15-20 parts isocyanate curing agent, 5-12 parts composite nano UV blocking material, 1-3 parts additives, and 10-20 parts solvent.

8. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The coating also includes an aluminum-zinc-indium sacrificial anode with an installation spacing of 1.5~2.0 m and an initial protection current density of 2~5 mA / m. 2 .

9. The method for preparing an inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Preparation of high-adhesion low-zinc epoxy primer: Mix epoxy resin, dispersant, additives and solvent evenly according to the formula, add flaky zinc powder and disperse at high speed until uniform, add polyamide curing agent according to the formula before use, stir evenly and set aside. S2. Preparation of polysiloxane-modified polyurethane intermediate coating: Mix hydroxyl acrylic resin, polysiloxane intermediate, graphene nanosheets, fumed silica, talc powder, anti-rust pigment, additives and solvent evenly according to the formula, and grind to a fineness ≤50 μm. Before use, add aliphatic isocyanate curing agent according to the formula and set aside. S3. Preparation of nanocomposite weather-resistant polyurethane topcoat: Mix aliphatic polyurethane resin, composite nano UV barrier material, additives and solvent evenly according to the formula, and grind to fineness ≤30 μm. Before use, add isocyanate curing agent according to the formula and stir evenly for later use.

10. The inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures according to claim 1, characterized in that, The construction method of the inorganic-organic hybrid synergistic anti-corrosion coating for outdoor steel structures includes the following steps: P1. Substrate pretreatment: The steel structure substrate is sandblasted to remove rust, and the rust removal grade reaches Sa2.5, with the surface roughness controlled at Rz40~75 μm; P2. Primer application: Within 4 hours after the substrate treatment is completed, apply high-adhesion low-zinc epoxy primer using a high-pressure airless spraying process. The dry film thickness is controlled at 70~90 μm, and it is cured at room temperature for 24 hours. P3. Intermediate Coating Application: After the primer has fully dried, apply the polysiloxane-modified polyurethane intermediate coating. The dry film thickness should be controlled at 140~170μm, and cured at room temperature for 24~48 hours. P4. Topcoat application: After the intermediate coat is fully dry, apply the nano-composite weather-resistant polyurethane topcoat. The dry film thickness should be controlled at 60~80 μm. Cure at room temperature for 7 days. The coating can be put into use after it is fully cured.

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