Corrosion-resistant coating for color-coated aluminum plate strip and method for preparing the same

Abstract

This invention relates to the field of coating technology, specifically to a corrosion-resistant coating for color-coated aluminum sheets and strips and its preparation method. The coating comprises the following components by weight: 45-60 parts modified fluorocarbon resin emulsion, 18-28 parts composite modified anti-corrosion pigment, 8-12 parts nano-zirconia dispersion, 1-2 parts silane coupling agent, 0.5-1.5 parts anti-corrosion additive, 0.2-0.5 parts leveling agent, 0.3-0.8 parts dispersant, 0.1-0.3 parts defoamer, 10-20 parts deionized water, and 6-10 parts water-based isocyanate curing agent. The composite modified anti-corrosion pigment comprises zinc phosphate and modified zinc molybdate in a mass ratio of 6-7:3. Through reasonable formulation and synergistic effects, this corrosion-resistant coating improves the coating's corrosion resistance, adhesion, rheological properties, and long-term stability.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a corrosion-resistant coating for color-coated aluminum sheets and strips and its preparation method. Background Technology

[0002] Color-coated aluminum sheets and strips are widely used in building curtain walls, roofs, appliance housings, and interior decoration due to their advantages such as light weight, aesthetics, and high processability. However, in harsh corrosive environments such as marine climates, industrial atmospheres, or acid rain, the protective capabilities of traditional coatings face severe challenges, easily leading to problems such as chalking, discoloration, blistering, and even substrate corrosion, seriously affecting product lifespan and appearance.

[0003] Currently, the protective coatings commonly used for color-coated aluminum sheets and strips mainly include three major systems: polyester, polyurethane, and fluorocarbon. Among them, fluorocarbon resin coatings, with their excellent weather resistance and chemical stability, have become the preferred choice for high-end applications. However, traditional solvent-based fluorocarbon coatings suffer from high VOC emissions and significant environmental pollution; while water-based fluorocarbon coatings offer some improvement in environmental protection, their cured film crosslinking density, water resistance, and mechanical properties are generally inferior to solvent-based systems. More importantly, traditional fluorocarbon resins have high rigidity, and their film flexibility and adhesion still have room for improvement. During the processing and forming of aluminum sheets, the coating is prone to micro-cracks due to deformation, providing channels for the penetration of corrosive media.

[0004] In terms of corrosion protection, coatings generally rely on anti-corrosion pigments to build a protective barrier. While traditional chromate pigments offer significant anti-corrosion effects, their use is strictly limited due to their toxicity and carcinogenicity. Zinc phosphate, as one of the mainstream alternatives, has good environmental friendliness, but its anti-corrosion efficacy is relatively weak when used alone, and its stability under different pH conditions is insufficient. Furthermore, the long-term durability of a coating depends not only on its initial anti-corrosion ability but also on its resistance to ultraviolet aging. Under prolonged solar radiation, especially ultraviolet light, the resin matrix may degrade, leading to chalking, loss of gloss, and discoloration of the coating. This not only damages the appearance but also weakens the film thickness, thereby reducing the overall protective performance.

[0005] In conclusion, developing a coating with excellent overall performance, possessing superior weather resistance and corrosion resistance, as well as good mechanical properties and adhesion, is a pressing issue that needs to be addressed. Summary of the Invention

[0006] To address existing problems, this invention provides a corrosion-resistant coating for color-coated aluminum sheets and strips and its preparation method. This corrosion-resistant coating, through reasonable formulation and synergistic effects, improves the coating's corrosion resistance, adhesion, rheology, and long-term stability, solving the problem of balancing adhesion, weather resistance, and corrosion resistance in traditional coatings.

[0007] The technical solution of the present invention to solve the above problems is as follows:

[0008] A corrosion-resistant coating for color-coated aluminum sheets and strips comprises the following components by weight: 45-60 parts of modified fluorocarbon resin emulsion, 18-28 parts of composite modified anti-corrosion pigment, 8-12 parts of nano-zirconia dispersion, 1-2 parts of silane coupling agent, 0.5-1.5 parts of anti-corrosion additive, 0.2-0.5 parts of leveling agent, 0.3-0.8 parts of dispersant, 0.1-0.3 parts of defoamer, 10-20 parts of deionized water, and 6-10 parts of water-based isocyanate curing agent. The composite modified anti-corrosion pigment comprises zinc phosphate and modified zinc molybdate in a mass ratio of 6-7:3.

[0009] The preparation method of the modified zinc molybdate includes the following steps:

[0010] Step 1: Prepare molybdenum salt solution, zinc salt solution and doping solution separately. At a stirring speed of 300-600 rpm and a solution temperature of 20-30℃, add the zinc salt solution and doping solution dropwise to the molybdenum salt solution at a rate of 5-20 mL / min and react for 30-90 minutes. Adjust the pH to 8.0-8.6, then raise the temperature to 50-65℃ and age for 45-90 minutes to obtain purified material 1.

[0011] Step 2: Mix material 1 obtained in Step 1 with deionized water at 400-800 rpm for 15-30 minutes to obtain a dispersion with a solid content of 10-25%. Stir and add silica sol, adjust the pH to 9.0-9.5, stir for 40-60 minutes, adjust the pH to 4.2-4.8, add ZrOCl2 solution dropwise at a rate of 2-10 mL / min, stir at 40-50℃ for 20-40 minutes, and purify.

[0012] Step 3: Add the material obtained in Step 2 to a mixed solvent of ethanol and water, stir continuously at 400-800 rpm for 10-20 minutes, adjust the pH to 6.8-7.4 to obtain a mixture, add the phosphate coupling agent solution dropwise to the above mixture at a rate of 4-8 mL / min, react at 25-40℃ for 20-40 minutes, purify and dry to obtain the final product.

[0013] Further, in step 1, the molybdenum salt solution is an ammonium heptamolybdate solution with a concentration of 0.6-1.0 mol / L, the zinc salt solution is an aqueous solution of zinc nitrate hexahydrate or zinc acetate with a concentration of 0.6-1.0 mol / L, the doping solution is a magnesium nitrate solution with a concentration of 0.01-0.02 mol / L, and the molar ratio of zinc ions to molybdate ions and magnesium ions is 1-1.08:1:0.005-0.015.

[0014] In step 2, the mass ratio of material 1, silica sol, and ZrOCl2 is 100:1-2:005-0.15, and the concentration of ZrOCl2 solution is 0.05-0.15 mol / L.

[0015] In step 3, the mass ratio of the material obtained in step 2 to the mixed solvent of ethanol and water is 100:150-300, the volume ratio of ethanol to water in the mixed solvent is 1-3:7-9, the mass ratio of the phosphate coupling agent to the material obtained in step 2 is 0.25-0.60:100, the concentration of the phosphate coupling agent solution is 3-8%, and the solvent in the phosphate coupling agent solution is a mixed solvent of ethanol and water, wherein the volume ratio of ethanol to water is 1-3:7-9.

[0016] Furthermore, the preparation method of the modified fluorocarbon resin includes the following steps:

[0017] Step a: Mix silane coupling agent KH-560 with methyltrimethoxysilane, add to deionized water at 35-45℃, adjust pH to 4.5-5.5 with glacial acetic acid solution, stir at 400-600 rpm for 40-80 minutes, add pre-hydrolyzed solution to fluorocarbon resin emulsion at 300-500 rpm and 70-75℃ at a rate of 1.0-2.0 mL / min, then add catalyst dibutyltin dilaurate, keep the reaction at the temperature for 2.5-4.0 hours, then cool to below 40℃, adjust pH to 7.5-8.5 with ammonia solution to obtain organosilicon hybrid fluorocarbon emulsion with solid content of 45-50%;

[0018] Step b: Disperse nanocellulose whiskers in deionized water to obtain a nanocellulose whisker aqueous dispersion. Dilute silane coupling agent KH-550 with deionized water, adjust the pH to 4-5, and hydrolyze for 20-30 minutes to obtain a hydrolysate. Add the hydrolysate to the nanocellulose whisker dispersion and react at 52-62℃ and 500-700 rpm for 1.5-2.5 hours to obtain a pretreated dispersion. Heat the organosilicon hybrid fluorocarbon emulsion obtained in step a to 58-63℃, and add the pretreated dispersion dropwise to the organosilicon hybrid fluorocarbon emulsion at a dropping rate of 1.5-3.0 mL / min while stirring at 350-550 rpm. Maintain the temperature for 2.0-3.0 hours, cool to room temperature, and filter through a 250-400 mesh filter to obtain a reinforced organosilicon hybrid fluorocarbon emulsion with a solid content of 40-47%.

[0019] Step c: Heat the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b to 78-84℃ at 250-450 rpm. Mix methacrylic acid, ammonium persulfate, and deionized water to obtain a mixed solution of methacrylic acid and ammonium persulfate, controlling the pH to 7.8-8.5. Add the mixed solution of methacrylic acid and ammonium persulfate dropwise to the enhanced organosilicon hybrid fluorocarbon emulsion at a drop rate of 0.3-0.8 mL / min. After the addition is complete, maintain the pH at 7.8-8.5 and keep the reaction at 80-85℃ for 1.5-2.5 hours. Then cool to below 40℃, adjust the pH to 8.0-9.0, and filter to obtain the final product.

[0020] In step a, the solid content of the aqueous fluorocarbon resin emulsion is 43-50%, and the mass ratio of the solid component in the aqueous fluorocarbon resin emulsion to the silane coupling agent KH-560, methyltrimethoxysilane, deionized water, and catalyst dibutyltin dilaurate is 100:3.0-6.0:1.5-4.0:10-20:0.05-0.15.

[0021] In step b, the mass ratio of the solid component in the organosilicon hybrid fluorocarbon emulsion to the nanocellulose whisker aqueous dispersion and the silane coupling agent KH-550 is 100:5.0-15.0:0.5-1.5, the solid content of the nanocellulose whisker aqueous dispersion is 2-5%, and the mass ratio of the silane coupling agent KH-550 to deionized water is 1:5-10.

[0022] In step c, the mass ratio of the solid component to methacrylic acid in the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b is 100:2.0-5.0, and the mass ratio of methacrylic acid, ammonium persulfate, and deionized water in the mixed solution of methacrylic acid and ammonium persulfate is 1:0.003-0.005:3-8.

[0023] Furthermore, the corrosion inhibitor includes benzotriazole and alkyl imidazoline, wherein the mass ratio of benzotriazole to alkyl imidazoline is 1:1.5-2.5; the leveling agent is a polyether siloxane copolymer leveling agent; the dispersant is a polyacrylate ammonium salt dispersant; and the defoamer is an organosilicon defoamer.

[0024] The preparation method of the corrosion-resistant coating for color-coated aluminum sheets and strips mentioned above specifically includes: First, in a dispersion vessel, a modified fluorocarbon resin emulsion, 60-80% of deionized water, a dispersant, and 40-50% of a defoamer are added sequentially. Stirring is started, and at a speed of 300-500 rpm, a modified zinc molybdate and nano-zirconia dispersion are added. Then, the speed is increased to 800-1200 rpm, and high-speed dispersion is carried out for 20-40 minutes. The stirring speed is reduced to 400-600 rpm, and a silane coupling agent, an organic corrosion inhibitor, a leveling agent, the remaining defoamer, and deionized water are added sequentially to the vessel. Stirring is continued for 15-30 minutes. The mixture is then filtered using a 200-400 mesh filter cloth to remove any possible coarse particles or gels, resulting in a uniform and fine slurry. Before coating, the prepared slurry is mixed with a water-based isocyanate curing agent to obtain the final product.

[0025] The present invention has the following beneficial effects:

[0026] The corrosion-resistant coating for color-coated aluminum sheets and strips of this invention improves the corrosion resistance, adhesion, rheological properties, and long-term stability of the coating through reasonable formulation and synergistic effects, solving the problem of balancing adhesion, weather resistance, and corrosion resistance in traditional coatings. Specifically, in step a of the modified zinc molybdate process, magnesium ion doping significantly enhances the semiconductor corrosion resistance and ion dissolution behavior of zinc molybdate to the responsiveness of the corrosion microenvironment (such as pH and potential) by introducing lattice defects and altering the electronic structure, achieving "on-demand release" and efficient passivation of molybdate corrosion-inhibiting ions. Step 2: Under alkaline conditions, silica sol deposits a SiO2 film on the surface of zinc molybdate particles. Subsequently, under acidic conditions, ZrOCl2 hydrolyzes to generate Zr(OH)4 and ultimately transforms into ZrO2, which combines with the SiO2 layer. The resulting SiO2-ZrO2 composite coating effectively slows down the solubility of zinc molybdate in the coating, avoiding bubbling and coating failure caused by excessively rapid dissolution, achieving long-term, controllable slow release. ZrO2 itself is chemically extremely stable and has high hardness, further enhancing the shielding effect of the pigment and the wear resistance of the coating. Step 3: The phosphate group at one end of the phosphate coupling agent chemically bonds with ZrO2, SiO2, and zinc molybdate on the pigment surface, while the long-chain organic group at the other end is compatible with fluorocarbon resin, solving the fundamental problem of poor compatibility between inorganic pigments and organic resins. The modified pigment can be uniformly and stably dispersed in the resin without agglomeration or sedimentation, thus forming a uniform protective phase in the coating. The coupling agent, acting as a "molecular bridge," strengthens the interfacial bonding between the pigment and the resin, preventing the interface from becoming a weak point for corrosive media penetration. The modified zinc molybdate pigment can efficiently passivate aluminum materials by slowly releasing molybdate ions, and its own composite coating layer and excellent dispersibility constitute an excellent physical barrier. The combination of zinc phosphate and modified zinc molybdate constructs a highly efficient synergistic anti-corrosion system. Zinc phosphate forms a dense physical shielding layer on the metal substrate through hydrolysis, providing stable initial protection. Modified zinc molybdate acts as a smart slow-release unit, releasing molybdate ions specifically when corrosion occurs to form a stable passivation film in the active anolyte region, achieving precise long-term protection. The combination of these two components results in complementary ion release peaks: the initial zinc phosphate rapidly forms a film to build "comprehensive defense," while the subsequent modified zinc molybdate releases ions for targeted repair. This synergistic effect achieves full-cycle protection of "shielding-passivation-self-healing," significantly improving salt spray resistance lifespan.

[0027] While traditional fluorocarbon resins possess excellent weather resistance and chemical inertness, their film-forming properties, adhesion, and mechanical properties are sometimes insufficient to withstand extreme corrosive environments. This invention comprehensively improves their performance through a three-step modification. In step a, the silane coupling agent KH-560 and methyltrimethoxysilane hydrolyze under acidic conditions to generate silanols. Subsequently, under the action of a catalyst, these silanols undergo a condensation reaction with functional groups such as hydroxyl groups on the fluorocarbon resin molecular chain. Simultaneously, the silanols also self-condense to form a Si-O-Si inorganic network. The epoxy groups of KH-560 react with the resin, while the silanols formed after the methoxy group hydrolysis form strong covalent bonds with the hydroxyl groups on the aluminum plate surface, greatly improving the adhesion between the coating and the aluminum substrate and enhancing corrosion resistance. Furthermore, the introduced Si-O-Si inorganic network forms an "organic-inorganic hybrid" structure with the fluorocarbon organic phase. This structure, embedded in the polymer chain, effectively improves the coating's crosslinking density, hardness, heat resistance, and compactness, preventing the penetration of corrosive media. Step b: After pretreatment with KH-550 (containing amino groups), amine groups are introduced onto the surface of the nanocellulose whiskers. When dispersed in an organosilicon hybrid fluorocarbon emulsion containing negatively charged groups such as carboxyl groups, these whiskers can interact strongly with the resin matrix through electrostatic interactions or hydrogen bonding. The nanocellulose whiskers possess extremely high specific strength and modulus. Their uniform dispersion in the resin effectively pins polymer chains, hindering the propagation of microcracks, thereby simultaneously improving the coating's hardness, strength, and toughness, preventing damage due to impact or deformation. The highly dispersed nanofibers construct a tortuous physical barrier in the coating, significantly extending the penetration path of corrosive media such as water, oxygen, and chloride ions, and significantly improving the coating's shielding and barrier properties. Step c: Under the action of an initiator, methacrylic acid undergoes graft copolymerization with the fluorocarbon resin molecular chains, introducing carboxyl groups. The introduction of carboxyl anions enhances the double-layer repulsion of the emulsion particles, improving the chemical and mechanical stability of the emulsion, and facilitating storage and application. Carboxyl groups can react with subsequently added waterborne isocyanate curing agents, increasing crosslinking points and forming a denser network. Simultaneously, an appropriate amount of carboxyl groups can regulate the rheological properties of the coating, improve its leveling properties, and result in a smoother, more uniform paint film. Through these three steps of modification, the fluorocarbon resin forms a coating matrix with good adhesion, high density, excellent mechanical properties, and stability, providing a reliable physical barrier for long-term corrosion protection.

[0028] Modified zinc molybdate and modified fluorocarbon resin, the two components are coated with a "phosphate ester-Zr" process. 4+ -COOH" covalent bridging: Zr-OP bonds on the pigment surface crosslink with the carboxyl and hydroxyl groups of the resin simultaneously, forming an inorganic-organic gradient transition layer. This layer both locks in the pigment to prevent exudation and transmits the corrosion inhibition signal to the entire network. When the corrosive agent penetrates, the modified zinc molybdate releases MoO4 according to the potential requirement. 2-The modified fluorocarbon resin rapidly forms an Fe-Mo passivation film at the defect site, achieving active corrosion inhibition; while the modified fluorocarbon resin passively blocks water, oxygen, and ultraviolet rays for a long time thanks to its organosilicon-cellulose skeleton. The synergy of active and passive functions greatly enhances the corrosion resistance of the coating.

[0029] This invention achieves superior comprehensive performance through component and structural design. Modified fluorocarbon resin constructs a strong, dense, and tough organic-inorganic hybrid coating framework, providing excellent physical shielding and weather resistance. Composite modified anti-corrosion pigments and nano-zirconia work synergistically to form multiple protective barriers within the coating, enabling both intelligent slow-release of passivating ions for active corrosion protection and enhancing the coating's wear resistance and stability. A silane coupling agent further enhances the interfacial bonding between components and the adhesion between the coating and the substrate. Ultimately, this coating exhibits long-lasting salt spray and chemical resistance, as well as good mechanical strength, significantly improving the service life of color-coated aluminum sheets in harsh environments. Attached Figure Description

[0030] Figure 1 The results of the salt spray test (1000h) - scratch corrosion width test for Examples 1-3 and Comparative Examples 1-10 are shown in the figure.

[0031] Figure 2 The graph shows the xenon lamp aging (1000h) - ΔE (color difference) test results for Examples 1-3 and Comparative Examples 1-10. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0033] All the following raw materials are commercially available. Alkyl imidazoline, 99% purity, Hubei Jiufenglong Chemical Co., Ltd.; Organosilicon defoamer, viscosity (25℃) 235 mPa·s, Langfang Demei Chemical Fireproof Materials Co., Ltd.; Water-based isocyanate curing agent, viscosity 22±10 mPa.s (25℃), Guangzhou Yourun Synthetic Materials Co., Ltd.; Silica sol, active ingredient content 40%, Jinan Jiuzhouyuan Biotechnology Co., Ltd.; Ammonium polyacrylate, brand, Solpro (Netherlands), Foshan Koller Building Materials Co., Ltd.; HY-245 leveling agent is a specially modified polyether siloxane copolymer, appearance: pale yellow. Transparent liquid, active ingredient (%): 100, Shanghai Huiyan New Materials Co., Ltd.; Nano-zirconia dispersion, solid content ≥20%, particle size 50nm, Huzhou Mister New Materials Co., Ltd.; Waterborne fluorocarbon resin emulsion (hydroxyl type): solid content 45%, fluorine content >10%, hydroxyl content approximately 2.2% solid content, Greenlink (Jining) Chemical Technology Co., Ltd.; Cellulose nano whiskers, diameter 10-50nm, active ingredient 99.9%, Beijing Deco Island Gold Technology Co., Ltd.; Phosphate ester coupling agent, active ingredient ≥98%, Tianchang Green Chemical Additives Factory.

[0034] Example 1

[0035] A corrosion-resistant coating for color-coated aluminum sheets and strips comprises the following components by weight: 52 parts modified fluorocarbon resin emulsion, 23 parts composite modified anti-corrosion pigment, 10 parts nano-zirconia dispersion, 1.5 parts silane coupling agent KH-560, 1.0 part anti-corrosion additive, 1.5 parts leveling agent, 0.5 parts dispersant, 0.2 parts defoamer, 15 parts deionized water, and 8 parts waterborne isocyanate curing agent; the anti-corrosion additive includes benzotriazole and alkyl imidazoline, wherein the mass ratio of benzotriazole to 2-undecylimidazoline is 1:2; the leveling agent is a polyether siloxane copolymer leveling agent; the dispersant is an ammonium polyacrylate dispersant; and the defoamer is an organosilicon defoamer; the composite modified anti-corrosion pigment includes zinc phosphate and modified zinc molybdate, wherein the mass ratio of the two is 6.5:3;

[0036] The preparation method of the modified zinc molybdate includes the following steps:

[0037] Step 1: Prepare molybdenum salt solution, zinc salt solution, and doping solution separately. At a stirring speed of 450 rpm and a solution temperature of 25°C, add the zinc salt solution and doping solution dropwise to the molybdenum salt solution at a rate of 12 mL / min and react for 60 minutes. During this process, adjust the pH to 8.0-8.6 with ammonia water (28% concentration). Then, raise the temperature to 53°C and age for 65 minutes, maintaining the pH at 8.0-8.6. Centrifuge (4500g) and wash with deionized water to obtain material 1. The molybdenum salt solution is a 0.8 mol / L ammonium heptamolybdate solution; the zinc salt solution uses zinc nitrate hexahydrate as a raw material with a concentration of 0.8 mol / L; the doping solution is a 0.015 mol / L magnesium nitrate solution; and the zinc ions (Zn...)... 2+ ) and molybdate ions (MoO4) 2- ), magnesium ions (Mg 2+ The molar ratio of () is 1.02:1:0.010;

[0038] Step 2: Mix material 1 obtained in Step 1 with deionized water at 600 rpm for 22 minutes to obtain a dispersion with a solid content of 18%. Stir and add silica sol, adjust the pH to 9.0-9.5, stir for 50 minutes, adjust the pH of the reaction solution to 4.2-4.8 with dilute nitric acid, add ZrOCl2 solution dropwise at a rate of 5 mL / min, stir at 45℃ for 30 minutes, centrifuge, filter, and wash with deionized water; the mass ratio of material 1, silica sol, and ZrOCl2 is 100:1.5:0.10, and the concentration of ZrOCl2 solution is 0.10 mol / L.

[0039] Step 3: Add the material obtained in Step 2 to a mixed solvent of ethanol and water, stir continuously at 600 rpm for 15 minutes, and adjust the pH to 6.8-7.4 (using 28% ammonia water and 3% glacial acetic acid solution) to obtain a mixed solution. Add the phosphate coupling agent solution dropwise to the above mixed solution at a rate of 6 mL / min, react at 32°C for 30 minutes, centrifuge, wash with deionized water, dry at 100°C for 3 hours, and pulverize to 22 μm using an airflow at a pressure of 0.8 MPa. The mass ratio of the material obtained in Step 2 to the mixed solvent of ethanol and water is 100:220, the volume ratio of ethanol to water in the mixed solvent is 2:8, the mass ratio of the phosphate coupling agent to the material obtained in Step 2 is 0.40:100, the concentration of the phosphate coupling agent solution is 5%, and the solvent in the phosphate coupling agent solution is a mixed solvent of ethanol and water with a volume ratio of 2:8.

[0040] The preparation method of the modified fluorocarbon resin includes the following steps:

[0041] Step a: Mix silane coupling agent KH-560 with methyltrimethoxysilane, slowly add to deionized water at 40°C, adjust pH to 4.5-5.5 with 8% glacial acetic acid solution, stir at 500 rpm for 60 minutes, and slowly add the pre-hydrolyzed solution to the fluorocarbon resin emulsion at 1.5 mL / min at 400 rpm and 72°C. Then add the catalyst dibutyltin dilaurate, keep the reaction at this temperature for 3 hours, and then cool to below 40°C. Adjust the pH to 7.5-8.5 with 28% ammonia solution to obtain an organosilicon hybrid fluorocarbon emulsion with a solid content of 46%. The solid content of the aqueous fluorocarbon resin emulsion is 48%, and the mass ratio of the solid component to silane coupling agent KH-560, methyltrimethoxysilane, deionized water, and catalyst dibutyltin dilaurate in the aqueous fluorocarbon resin emulsion is 100:5:3:15:0.10.

[0042] Step b: Disperse nanocellulose whiskers in deionized water to obtain a nanocellulose whisker aqueous dispersion. Dilute silane coupling agent KH-550 with deionized water, adjust the pH to 4-5 with 8% glacial acetic acid solution, and hydrolyze for 25 minutes to obtain a hydrolysate. Add the hydrolysate to the nanocellulose whisker dispersion and react at 55℃ and 600 rpm for 2 hours to obtain a pretreated dispersion. Heat the organosilicon hybrid fluorocarbon emulsion to 60℃, and add the pretreated dispersion to the organosilicon hybrid fluorocarbon emulsion at a dropping rate of 2.2 mL / min while stirring at 400 rpm. Maintain the temperature for 2.5 hours, cool to room temperature, and filter through a 300-mesh filter to obtain a reinforced organosilicon hybrid fluorocarbon emulsion with a solid content of 45%. The solid components in the organosilicon hybrid fluorocarbon emulsion are... The mass ratio of nanocellulose whisker aqueous dispersion to silane coupling agent KH-550 is 100:10:1.0, the solid content of nanocellulose whisker aqueous dispersion is 2.8%, and the mass ratio of silane coupling agent KH-550 to deionized water is 1:8. The preparation method of nanocellulose whisker aqueous dispersion in step b is as follows: weigh cellulose nanocrystals and add them to deionized water, stir at 650 rpm for 45 minutes to obtain a coarse suspension with a solid content of 3%. The coarse suspension is homogenized 8 times under a pressure of 800 bar using a high-pressure homogenizer until it gradually changes from a milky white turbid liquid to a translucent, milky colloidal dispersion. The pH of the dispersion is adjusted to 7.0-9.0 with NaOH or dilute hydrochloric acid, and then filtered through a 200-mesh filter to obtain the final product.

[0043] Step c: The enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b is heated to 80°C at 320 rpm. Methacrylic acid, ammonium persulfate, and deionized water are mixed to obtain a mixed solution of methacrylic acid and ammonium persulfate, and the pH is controlled at 7.8-8.5 (adjusted with 3% sodium hydroxide solution). The mixed solution of methacrylic acid and ammonium persulfate is added dropwise to the enhanced organosilicon hybrid fluorocarbon emulsion at a rate of 0.5 mL / min. After the addition is complete, the pH is controlled at 7.8-8.5 (adjusted with 3% sodium hydroxide solution). The reaction is carried out at 82°C for 2 hours, then cooled to below 40°C. The pH of the emulsion is adjusted to 8.0-9.0 with 28% ammonia water, and filtered through a 200-mesh filter to obtain the final product. In the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b, the mass ratio of the solid component to methacrylic acid is 100:3.5, and the mass ratio of methacrylic acid, ammonium persulfate, and deionized water in the mixed solution of methacrylic acid and ammonium persulfate is 1:0.004:5.

[0044] The preparation method of the corrosion-resistant coating for color-coated aluminum sheets and strips mentioned above specifically includes: First, in a dispersion vessel, a modified fluorocarbon resin emulsion, 70% of deionized water, a dispersant, and 50% of a defoamer are added sequentially. Stirring is started, and at a speed of 400 rpm, a modified zinc molybdate and nano-zirconia dispersion are added. Then, the speed is increased to 900 rpm, and high-speed dispersion is carried out for 30 minutes. The stirring speed is reduced to 500 rpm, and a silane coupling agent, corrosion inhibitor, leveling agent, and the remaining defoamer and deionized water are added sequentially to the vessel. Stirring is continued for 22 minutes. The mixture is filtered using a 300-mesh filter cloth to remove any possible coarse particles or gels, resulting in a uniform and fine slurry. Before coating, the prepared slurry is mixed with a water-based isocyanate curing agent to obtain the final product.

[0045] Example 2

[0046] A corrosion-resistant coating for color-coated aluminum sheets and strips comprises the following components by weight: 60 parts modified fluorocarbon resin emulsion, 18 parts composite modified anti-corrosion pigment, 12 parts nano-zirconia dispersion, 1 part silane coupling agent KH-560, 0.5 parts anti-corrosion additive, 0.5 parts leveling agent, 0.3 parts dispersant, 0.1 parts defoamer, 20 parts deionized water, and 6 parts waterborne isocyanate curing agent; the anti-corrosion additive includes benzotriazole and alkyl imidazoline, wherein the mass ratio of benzotriazole to 2-undecylimidazoline is 1:2.5; the leveling agent is a polyether siloxane copolymer leveling agent; the dispersant is an ammonium polyacrylate dispersant; and the defoamer is an organosilicon defoamer; the composite modified anti-corrosion pigment includes zinc phosphate and modified zinc molybdate, wherein the mass ratio of the two is 6:3.

[0047] The preparation method of the modified zinc molybdate includes the following steps:

[0048] Step 1: Prepare molybdenum salt solution, zinc salt solution, and doping solution separately. At a stirring speed of 600 rpm and a solution temperature of 20°C, add the zinc salt solution and doping solution dropwise to the molybdenum salt solution at a rate of 5 mL / min and react for 30 minutes. During this process, adjust the pH to 8.0-8.6 with ammonia water (28% concentration). Then, raise the temperature to 50°C and age for 90 minutes, maintaining the pH at 8.0-8.6. Centrifuge (3000g) and wash with deionized water to obtain material 1. The molybdenum salt solution is a 0.6 mol / L ammonium heptamolybdate solution; the zinc salt solution uses zinc nitrate hexahydrate as a raw material with a concentration of 0.6 mol / L; the doping solution is a 0.02 mol / L magnesium nitrate solution; and the zinc ions (Zn...)... 2+ ) and molybdate ions (MoO4) 2- ), magnesium ions (Mg 2+ The molar ratio of ) is 1:1:0.015;

[0049] Step 2: Mix material 1 obtained in Step 1 with deionized water at 800 rpm for 15 minutes to obtain a dispersion with a solid content of 10%. Stir and add silica sol, adjust the pH to 9.0-9.5, stir for 60 minutes, adjust the pH of the reaction solution to 4.2-4.8 with dilute nitric acid or hydrochloric acid, add ZrOCl2 solution dropwise at a rate of 10 mL / min, stir at 40℃ for 20 minutes, centrifuge, filter, and wash with deionized water; the mass ratio of material 1, silica sol, and ZrOCl2 is 100:2:005, and the concentration of ZrOCl2 solution is 0.05 mol / L.

[0050] Step 3, wherein the mass ratio of the material obtained in step 2 to the mixed solvent of ethanol and water is 100:300, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 1:9, the mass ratio of the phosphate coupling agent to the material obtained in step 2 is 0.25:100, the concentration of the phosphate coupling agent solution is 8%, and the solvent in the phosphate coupling agent solution is a mixed solvent of ethanol and water, wherein the volume ratio of ethanol to water is 1:9, and the rest is the same as in Example 1.

[0051] The preparation method of the modified fluorocarbon resin includes the following steps:

[0052] Step a: Mix silane coupling agent KH-560 with methyltrimethoxysilane, and slowly add the mixture to deionized water at 35°C. Adjust the pH to 4.5-5.5 with 8% glacial acetic acid solution, and stir at 600 rpm for 40 minutes. Then, at 500 rpm and 70°C, slowly add the pre-hydrolyzed solution to the fluorocarbon resin emulsion at a rate of 2.0 mL / min, followed by the addition of the catalyst dibutyltin dilaurate. Incubate the reaction for 2.5 hours, and then... The solution is cooled to below 40°C, and the pH is adjusted to 7.5-8.5 with a 28% ammonia solution to obtain an organosilicon hybrid fluorocarbon emulsion with a solid content of 50%. The aqueous fluorocarbon resin emulsion has a solid content of 48%, and the mass ratio of the solid component to the silane coupling agent KH-560, methyltrimethoxysilane, deionized water, and catalyst dibutyltin dilaurate in the aqueous fluorocarbon resin emulsion is 100:6.0:1.5:10:0.15.

[0053] Step b, wherein the mass ratio of the solid component in the organosilicon hybrid fluorocarbon emulsion to the nanocellulose whisker aqueous dispersion and the silane coupling agent KH-550 is 100:5.0:1.5, the solid content of the nanocellulose whisker aqueous dispersion is 2.8%, and the mass ratio of the silane coupling agent KH-550 to deionized water is 1:10; the rest is the same as in Example 1;

[0054] Step c, wherein the mass ratio of the solid component to methacrylic acid in the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b is 100:2.0-5.0, and the mass ratio of methacrylic acid, ammonium persulfate and deionized water in the mixed solution of methacrylic acid and ammonium persulfate is 1:0.003:8, and the rest is the same as in Example 1.

[0055] The preparation method of the corrosion-resistant coating for the above-mentioned color-coated aluminum sheet and strip is the same as in Example 1.

[0056] Example 3

[0057] A corrosion-resistant coating for color-coated aluminum sheets and strips comprises the following components by weight: 45 parts modified fluorocarbon resin emulsion, 28 parts composite modified anti-corrosion pigment, 8 parts nano-zirconia dispersion, 2 parts silane coupling agent KH-560, 1.5 parts anti-corrosion additive, 0.2 parts leveling agent, 0.8 parts dispersant, 0.3 parts defoamer, 10 parts deionized water, and 10 parts waterborne isocyanate curing agent; the anti-corrosion additive includes benzotriazole and alkyl imidazoline, wherein the mass ratio of benzotriazole to 2-undecylimidazoline is 1:1.5; the leveling agent is a polyether siloxane copolymer leveling agent; the dispersant is an ammonium polyacrylate dispersant; and the defoamer is an organosilicon defoamer; the composite modified anti-corrosion pigment includes zinc phosphate and modified zinc molybdate, wherein the mass ratio of the two is 7:3.

[0058] The preparation method of the modified zinc molybdate includes the following steps:

[0059] Step 1: Prepare molybdenum salt solution, zinc salt solution, and doping solution separately. At a stirring speed of 300 rpm and a solution temperature of 30°C, add the zinc salt solution and doping solution dropwise to the molybdenum salt solution at a rate of 20 mL / min and react for 90 minutes. During this process, adjust the pH to 8.0-8.6 with ammonia water (28% concentration). Then, raise the temperature to 50-65°C and age for 45 minutes, maintaining the pH at 8.0-8.6. Centrifuge (6000g) and wash with deionized water to obtain material 1. The molybdenum salt solution is a 1.0 mol / L ammonium heptamolybdate solution; the zinc salt solution uses zinc nitrate hexahydrate as a raw material with a concentration of 1.0 mol / L; the doping solution is a 0.01 mol / L magnesium nitrate solution; and the zinc ions (Zn...)... 2+ ) and molybdate ions (MoO4) 2- ), magnesium ions (Mg 2+ The molar ratio of () is 1.08:1:0.015;

[0060] Step 2: Mix material 1 obtained in Step 1 with deionized water at 400 rpm for 30 minutes to obtain a dispersion with a solid content of 25%. Stir and add silica sol, adjust the pH to 9.0-9.5, and stir for 40 minutes. Adjust the pH of the reaction solution to 4.2-4.8 with dilute nitric acid or hydrochloric acid. Add ZrOCl2 solution dropwise at a rate of 2 mL / min, stir at 50°C for 40 minutes, centrifuge, filter, and wash with deionized water. The mass ratio of material 1, silica sol, and ZrOCl2 is 100:1:0.15, and the concentration of ZrOCl2 solution is 0.15 mol / L.

[0061] Step 3, wherein the mass ratio of the material obtained in step 2 to the mixed solvent of ethanol and water is 100:150, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3:7, the mass ratio of the phosphate coupling agent to the material obtained in step 2 is 0.60:100, the concentration of the phosphate coupling agent solution is 3%, and the solvent in the phosphate coupling agent solution is a mixed solvent of ethanol and water, wherein the volume ratio of ethanol to water is 3:7, and the rest is the same as in Example 1.

[0062] The preparation method of the modified fluorocarbon resin includes the following steps:

[0063] Step a: Mix silane coupling agent KH-560 with methyltrimethoxysilane, and slowly add the mixture to deionized water at 35-45℃. Adjust the pH to 4.5-5.5 with 8% glacial acetic acid solution, and stir at 400 rpm for 80 minutes. Then, at 300 rpm and 75℃, slowly add the pre-hydrolyzed solution to the fluorocarbon resin emulsion at a rate of 1.0 mL / min. Subsequently, add the catalyst dibutyltin dilaurate, and maintain the reaction temperature for 4.0 hours. Then, the solution is cooled to below 40°C, and the pH is adjusted to 7.5-8.5 with a 28% ammonia solution to obtain an organosilicon hybrid fluorocarbon emulsion with a solid content of 45%. The solid content of the aqueous fluorocarbon resin emulsion is 48%, and the mass ratio of the solid component to the silane coupling agent KH-560, methyltrimethoxysilane, deionized water, and catalyst dibutyltin dilaurate in the aqueous fluorocarbon resin emulsion is 100:3.0:4.0:20:0.15.

[0064] Step b, wherein the mass ratio of the solid component in the organosilicon hybrid fluorocarbon emulsion to the nanocellulose whisker aqueous dispersion and the silane coupling agent KH-550 is 100:15.0:0.5, the solid content of the nanocellulose whisker aqueous dispersion is 2.8%, and the mass ratio of the silane coupling agent KH-550 to deionized water is 1:5; the rest is the same as in Example 1;

[0065] Step c, wherein the mass ratio of the solid component to methacrylic acid in the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b is 100:2.0-5.0, and the mass ratio of methacrylic acid, ammonium persulfate and deionized water in the mixed solution of methacrylic acid and ammonium persulfate is 1:0.005:3, and the rest is the same as in Example 1.

[0066] The preparation method of the corrosion-resistant coating for the above-mentioned color-coated aluminum sheet and strip is the same as in Example 1.

[0067] Online automatic coating: The prepared slurry and water-based isocyanate curing agent are continuously pumped into a static mixer. After a residence time of 3-8 seconds, the mixture is immediately sent to the coating roller through a closed pipeline. The total residence time from mixing to coating is ≤15 seconds. After coating, the board surface is immediately placed in a drying oven at 230-250℃ for 60-90 seconds to cure.

[0068] Comparative Example 1

[0069] A corrosion-resistant coating for color-coated aluminum sheets and strips, wherein the composite modified anti-corrosion pigment is replaced with zinc phosphate and commercially available zinc molybdate, and the rest is the same as in Example 1.

[0070] Comparative Example 2

[0071] A corrosion-resistant coating for color-coated aluminum sheets and strips, wherein the composite modified anti-corrosion pigment is replaced with zinc phosphate, and the rest is the same as in Example 1.

[0072] Comparative Example 3

[0073] A corrosion-resistant coating for color-coated aluminum sheets and strips, wherein the composite modified anti-corrosion pigment is replaced with commercially available zinc molybdate, and the rest is the same as in Example 1.

[0074] Comparative Example 4

[0075] A corrosion-resistant coating for color-coated aluminum sheets and strips, wherein the composite modified anti-corrosion pigment is replaced with modified zinc molybdate, and the rest is the same as in Example 1.

[0076] Comparative Example 5

[0077] A corrosion-resistant coating for color-coated aluminum sheets and strips, wherein the modified fluorocarbon resin is replaced with a common commercially available fluorocarbon resin, and the rest is the same as in Example 1.

[0078] Comparative Examples 6-10

[0079] The modified fluorocarbon resins in Comparative Examples 1-5 were replaced with ordinary commercially available fluorocarbon resins, and were subsequently labeled as Comparative Examples 6-10.

[0080] Performance testing:

[0081] After coating using the above method, the resulting sample was tested as follows:

[0082] Coating thickness: The test method is based on GB / T13452.2-2008 "Determination of film thickness of paints and varnishes";

[0083] Corrosion resistance: Neutral salt spray test, conducted according to GB / T1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes", salt spray solution: 5% NaCl solution (pH 6.5~7.2), temperature: 35±2℃, spray rate: 1.0-2.0mL / h·80cm 2 Test duration: 1000 hours;

[0084] Aging resistance: Tested according to GB-T1865-2009 "Artificial weathering and artificial radiation exposure of paints and varnishes with filtered xenon arc radiation"; blackboard temperature: 65±3℃, chamber temperature: 47±3℃, relative humidity: 50±5%, light / spray cycle: 102 minutes of light exposure, 18 minutes of light exposure + spray cycle, test cycle: 1000 hours;

[0085] Impact resistance: Tested according to GB / T1732-1993 "Test Method for Impact Resistance of Coating Films";

[0086] Adhesion: Tested according to GB / T9286-2021 "Paints and Varnishes - Cross-cut Test". A cross-cut tester is used to evenly cut 6×6 squares (1mm spacing) on ​​the sample surface, cutting through the coating until the substrate is exposed. Then, pressure-sensitive tape of the specified type is applied to the cut area and quickly peeled off at a constant angle and speed. The coating peeling within the cut area is graded according to GB / T9286-2021 (grade 0 to 5), where grade 0 indicates the best adhesion with no significant peeling.

[0087] The test results are shown in Table 1.

[0088] Table 1. Test Results

[0089]

[0090] From Table 1, Figure 1 and Figure 2 It is evident that modified fluorocarbon resin, through organosilicon hybridization, nanocellulose whisker reinforcement, and methacrylic acid grafting, significantly improves the UV resistance, crosslinking density, cohesive strength, and adhesion to the substrate of the resin matrix. Specifically, the samples of Examples 1-3 exhibit superior ΔE color difference, gloss retention, impact resistance, and adhesion compared to the comparative example. This indicates that the modified resin is the decisive factor in resisting chalking, loss of gloss, and discoloration, while also providing excellent flexibility and adhesion. Examples 1-3 and Comparative Example 4 demonstrate the best corrosion resistance due to the presence of modified zinc molybdate, proving that the modified zinc molybdate, through Mg... 2+ Doping and SiO2 / ZrO2 coating enhance its chemical stability and synergistic passivation ability; however, the aging resistance of Comparative Example 4 is worse than that of Comparative Examples 1-3, and the overall performance of Comparative Example 2 is also worse than that of Examples 1-3, further illustrating the synergistic effect of the composite modified anti-corrosion pigment (zinc phosphate + modified zinc molybdate).

[0091] Examples 1-3, containing both modified fluorocarbon resin and composite modified anti-corrosion pigments, performed best in all test items. The modified fluorocarbon resin primarily determines the coating's long-term durability (aging resistance) and mechanical properties (adhesion, impact resistance). Without it, the coating's "skeleton" is unstable, leading to premature failure. The composite modified anti-corrosion pigment is key to corrosion resistance: it constructs an efficient active and passive protection system, significantly delaying the corrosion process of the substrate. Without it, the coating's "protective ability" is greatly reduced. Together, they provide a perfect combination of a robust "skeleton" and an efficient "protective layer," significantly improving overall performance. The absence or degradation of either will lead to a significant decrease in the coating's overall performance.

[0092] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0093] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A corrosion-resistant coating for color-coated aluminum sheets and strips, characterized in that, The composition by weight includes the following components: 45-60 parts modified fluorocarbon resin emulsion, 18-28 parts composite modified anticorrosive pigment, 8-12 parts nano-zirconia dispersion, 1-2 parts silane coupling agent, 0.5-1.5 parts anticorrosive additive, 0.2-0.5 parts leveling agent, 0.3-0.8 parts dispersant, 0.1-0.3 parts defoamer, 10-20 parts deionized water, and 6-10 parts water-based isocyanate curing agent. The composite modified anticorrosive pigment comprises zinc phosphate and modified zinc molybdate in a mass ratio of 6-7:

3. The preparation method of the modified zinc molybdate includes the following steps: Step 1: Prepare molybdenum salt solution, zinc salt solution, and doping solution separately. At 20-30℃, add the zinc salt solution and doping solution dropwise to the molybdenum salt solution and react for 30-90 minutes. Adjust the pH to 8.0-8.6, then raise the temperature to 50-65℃ and age for 45-90 minutes to obtain material 1. The molybdenum salt solution is a 0.6-1.0 mol / L ammonium heptamolybdate solution; the zinc salt solution is an aqueous solution of zinc nitrate hexahydrate or zinc acetate with a concentration of 0.6-1.0 mol / L; the doping solution is a 0.01-0.02 mol / L magnesium nitrate solution; and the molar ratio of zinc ions to molybdate ions and magnesium ions in the zinc salt solution is 1-1.08:1:0.005-0.

015. Step 2: Mix material 1 obtained in Step 1 with deionized water and stir for 15-30 minutes to obtain a dispersion with a solid content of 10-25%. Then add silica sol, adjust the pH to 9.0-9.5, stir for 40-60 minutes, adjust the pH to 4.2-4.8, add ZrOCl2 solution, and stir at 40-50℃ for 20-40 minutes to purify. Step 3: Add the material obtained in Step 2 to a mixed solvent of ethanol and water, stir for 10-20 minutes, adjust the pH to 6.8-7.4 to obtain a mixture, add the phosphate coupling agent solution dropwise to the above mixture, react at 25-40℃ for 20-40 minutes, purify and dry to obtain the final product; The preparation method of the modified fluorocarbon resin includes the following steps: Step a: Mix silane coupling agent KH-560 with methyltrimethoxysilane, add to deionized water at 35-45℃, adjust pH to 4.5-5.5 with glacial acetic acid solution, stir at 400-600 rpm for 40-80 minutes, add pre-hydrolyzed solution to fluorocarbon resin emulsion at 300-500 rpm and 70-75℃ at a rate of 1.0-2.0 mL / min, then add catalyst dibutyltin dilaurate, keep the reaction at the temperature for 2.5-4.0 hours, then cool to below 40℃, adjust pH to 7.5-8.5 with ammonia solution to obtain organosilicon hybrid fluorocarbon emulsion with solid content of 45-50%; Step b: Disperse nanocellulose whiskers in deionized water to obtain a nanocellulose whisker aqueous dispersion. Dilute silane coupling agent KH-550 with deionized water, adjust the pH to 4-5, and hydrolyze for 20-30 minutes to obtain a hydrolysate. Add the hydrolysate to the nanocellulose whisker dispersion and react at 52-62℃ and 500-700 rpm for 1.5-2.5 hours to obtain a pretreated dispersion. Heat the organosilicon hybrid fluorocarbon emulsion obtained in step a to 58-63℃, and add the pretreated dispersion dropwise to the organosilicon hybrid fluorocarbon emulsion at a dropping rate of 1.5-3.0 mL / min while stirring at 350-550 rpm. Maintain the temperature for 2.0-3.0 hours, cool to room temperature, and filter through a 250-400 mesh filter to obtain a reinforced organosilicon hybrid fluorocarbon emulsion with a solid content of 40-47%. Step c: Heat the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b to 78-84℃ at 250-450 rpm. Mix methacrylic acid, ammonium persulfate, and deionized water to obtain a mixed solution of methacrylic acid and ammonium persulfate, controlling the pH to 7.8-8.

5. Add the mixed solution of methacrylic acid and ammonium persulfate dropwise to the enhanced organosilicon hybrid fluorocarbon emulsion at a drop rate of 0.3-0.8 mL / min. After the addition is complete, maintain the pH at 7.8-8.5 and keep the reaction at 80-85℃ for 1.5-2.5 hours. Then cool to below 40℃, adjust the pH to 8.0-9.0, and filter to obtain the final product.

2. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, In step 2, the mass ratio of material 1, silica sol, and ZrOCl2 is 100:1-2:005-0.15, and the concentration of ZrOCl2 solution is 0.05-0.15 mol / L.

3. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, In step 3, the mass ratio of the material obtained in step 2 to the mixed solvent of ethanol and water is 100:150-300, the volume ratio of ethanol to water in the mixed solvent is 1-3:7-9, the mass ratio of the phosphate coupling agent to the material obtained in step 2 is 0.25-0.60:100, the concentration of the phosphate coupling agent solution is 3-8%, and the solvent in the phosphate coupling agent solution is a mixed solvent of ethanol and water, wherein the volume ratio of ethanol to water is 1-3:7-9.

4. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, In step a, the solid content of the fluorocarbon resin emulsion is 43-50%, and the mass ratio of the solid component in the fluorocarbon resin emulsion to the silane coupling agent KH-560, methyltrimethoxysilane, deionized water, and catalyst dibutyltin dilaurate is 100:3.0-6.0:1.5-4.0:10-20:0.05-0.

15.

5. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, In step b, the mass ratio of the solid component in the organosilicon hybrid fluorocarbon emulsion to the nanocellulose whisker aqueous dispersion and the silane coupling agent KH-550 is 100:5.0-15.0:0.5-1.5, the solid content of the nanocellulose whisker aqueous dispersion is 2-5%, and the mass ratio of the silane coupling agent KH-550 to deionized water is 1:5-10.

6. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, In step c, the mass ratio of the solid component to methacrylic acid in the enhanced organosilicon hybrid fluorocarbon emulsion obtained in step b is 100:2.0-5.0, and the mass ratio of methacrylic acid, ammonium persulfate, and deionized water in the mixed solution of methacrylic acid and ammonium persulfate is 1:0.003-0.005:3-8.

7. The corrosion-resistant coating for color-coated aluminum sheets and strips according to claim 1, characterized in that, The corrosion inhibitors include benzotriazole and alkyl imidazoline, wherein the mass ratio of benzotriazole to alkyl imidazoline is 1:1.5-2.5; the leveling agent is a polyether siloxane copolymer leveling agent; the dispersant is an ammonium polyacrylate dispersant; and the defoamer is an organosilicon defoamer.

8. The method for preparing corrosion-resistant coatings for color-coated aluminum sheets and strips as described in any one of claims 1-7, characterized in that, Specifically, it includes: First, in a dispersion vessel, add the modified fluorocarbon resin emulsion, 60-80% of deionized water, dispersant, and 40-50% of defoamer in sequence. Start stirring and add the modified zinc molybdate and nano-zirconia dispersion at a speed of 300-500 rpm. Then increase the speed to 800-1200 rpm and disperse at high speed for 20-40 minutes. Reduce the stirring speed to 400-600 rpm and add the silane coupling agent, organic preservative, leveling agent, and the remaining defoamer and deionized water in sequence. Continue stirring for 15-30 minutes. Filter using a 200-400 mesh filter cloth to remove any coarse particles or gels, obtaining a uniform and fine slurry. Before coating, mix the prepared slurry with an aqueous isocyanate curing agent to obtain the final product.

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