Environment-friendly corrosion-resistant metal material coating and preparation method thereof

Abstract

The invention discloses an environment-friendly corrosion-resistant metal material coating and a preparation method thereof. According to the invention, the waterborne polyurethane resin is adopted as a matrix, and the modified chitosan, the sodium molybdate phytic acid compound and other biological bases and a chromium-free corrosion inhibition system are combined, so that the use of benzene solvents, hexavalent chromium and other toxic substances in the traditional paint is avoided from the source. Through construction of a graphene oxide composite titanium dioxide heterojunction, the coating triggers a photocatalytic reaction under visible light, surface pollutants can be decomposed, the electron migration activity of a metal interface is reduced, and the neutral salt mist resistance time is made to break through 3000 hours and is increased by three times or above compared with a conventional epoxy coating. A dual intelligent response mechanism formed by the matrine microcapsules and the modified chitosan can quickly release corrosion inhibition factors and dynamically repair microcracks at the initial stage of corrosion, so that stable protection of the coating in a corrosion medium with a wide pH range of 2-12 is realized, and the service life of a metal substrate in extreme environments such as ocean and chemical engineering is remarkably prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material coatings, and specifically relates to an environmentally friendly, corrosion-resistant metal material coating and a preparation method thereof. Background Art

[0002] Metal coating technology is a method of applying one or more layers of covering to the metal surface, aiming to improve the material's corrosion resistance, wear resistance, fatigue resistance, insulation or aesthetic properties. The coating can be achieved through physical vapor deposition, chemical vapor deposition, electroplating, spraying, thermal spraying, sol-gel and other methods. These coating materials include metals, alloys, ceramics, plastics and composite materials, which can effectively isolate the metal substrate from the external environment, extend its service life and enhance its functionality. In the fields of aerospace, automobiles, electronics, construction, etc., metal coating technology plays a vital role and is an indispensable part of the development of modern industry.

[0003] However, existing anti-corrosion coatings generally have two major defects: first, they rely on chromium-containing compounds and organic solvents, which causes environmental pollution. In addition, traditional passivation films are prone to failure in dynamic corrosion environments, and their protective life is less than 1,000 hours. Second, the single-function design makes it difficult to balance mechanical strength and flexibility, and the high-temperature curing process limits the scope of application of the substrate. Summary of the invention

[0004] The purpose of the present invention is to provide an environmentally friendly, corrosion-resistant metal material coating and a preparation method thereof in order to solve the above-mentioned problems.

[0005] The technical solution adopted by the present invention is as follows: an environmentally friendly and corrosion-resistant metal material coating, the metal material coating comprising: Waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 8-12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2-3 parts by weight; Sodium molybdate / phytic acid complex: 5-8 parts by weight; Nano silicon dioxide: 3-5 parts by weight; Matrine-polydopamine microcapsules: 4-6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3-4 parts by weight; Organic bentonite: 0.5-1 parts by weight; Deionized water: 25-35 parts by weight.

[0006] In a preferred embodiment, the preparation method comprises the following steps: S1: Weigh: 100 parts by weight of waterborne polyurethane resin; Modified chitosan nanoparticles: 8-12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2-3 parts by weight; Sodium molybdate / phytic acid complex: 5-8 parts by weight; Nano silicon dioxide: 3-5 parts by weight; Matrine-polydopamine microcapsules: 4-6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3-4 parts by weight; Organic bentonite: 0.5-1 parts by weight; Deionized water: 25-35 parts by weight; add waterborne polyurethane resin and deionized water into the reaction kettle in proportion, and stir at a low speed at 40°C for 15 minutes to form a uniform base liquid; S2: Graphene oxide composite titanium dioxide, nano silicon dioxide and silane coupling agent KH-560 are sequentially added to the base liquid, and an ultrasonic disperser is used for treatment for 30 minutes with the power set to 300W to obtain a nano-enhanced phase dispersion; S3: Add modified chitosan nanoparticles, sodium molybdate phytic acid complex and matrine microcapsules into the dispersion three times, maintain a constant temperature water bath at 60 °C, and magnetically stir for 1 hour to complete the corrosion inhibition network integration; S4: Add curcumin nanocellulose and organobentonite, and use a high-speed emulsifier to shear and disperse at 8000 rpm for 20 minutes to form a three-dimensional reinforced structure; S5: Inject water-based epoxy soybean oil to adjust flexibility, continue stirring until the system viscosity reaches 1200-1500mPa·s, and transfer to a sealed container for 24 hours; S6: Use air spraying process to evenly spray the cured coating onto the sandblasted metal substrate surface, and the wet film thickness is controlled at 80-100μm; S7: In the first stage, the water is evaporated by baking at 50°C for 30 minutes, in the second stage, the cross-linked network is formed by curing at 120°C for 1 hour, and in the third stage, the cross-linked network is naturally cooled to room temperature; S8: The cured coating is irradiated with ultraviolet light for 10 minutes to activate the photoresponsive properties of curcumin, and finally a composite coating with self-cleaning and intelligent protection functions is obtained.

[0007] In a preferred embodiment, in step S1, the reactor is equipped with a double-layer spiral stirring paddle, and the stirring speed is set to 200 rpm. The material temperature is stabilized at 40±2°C by the jacket circulating water temperature control system, and stirring is continued for 15 minutes until the resin is completely wetted and dispersed to form a milky white uniform base liquid. Nitrogen protection is used during the process to prevent bubbles from mixing in, and the final base liquid viscosity is controlled within the range of 300-400mPa·s.

[0008] In a preferred embodiment, in step S2, an ultrasonic cell disruptor is used, a 20kHz high-frequency probe is selected, an output power of 300W is set, and a pulse mode of 2 seconds of operation and 1 second of rest is set, and the mixed system is ultrasonically treated for 30 minutes. The material temperature is controlled not to exceed 45°C, so that the nanomaterial is fully peeled off and a stable suspension is formed, and the slurry particle size D50 after dispersion is ≤200nm.

[0009] In a preferred embodiment, in step S3, a constant temperature magnetic stirrer is used to maintain the system temperature at 60±1°C, the stirring speed is set to 500 rpm, and the reaction is continued for 1 hour. During the process, the pH value of the system is monitored to be stable at 7.5-8.0, forming an interpenetrating network structure with hierarchical corrosion inhibition function.

[0010] In a preferred embodiment, in step S4, the gap between the stator and the sub-stator is adjusted to 0.3 mm, and the machine is operated at a speed of 8000 rpm for 20 minutes. The material temperature is kept below 35° C. by an online cooling system, so that the nanocellulose and bentonite are evenly embedded in the resin matrix to form a three-dimensional spatial support structure, and the thixotropic index of the slurry after mixing reaches 5-6.

[0011] In a preferred embodiment, in step S5, a frame-type stirring paddle is used to mix at a low speed of 100 rpm for 30 minutes, and the viscosity of the system is adjusted to 1200-1500 mPa·s by monitoring the NDJ-5S rotational viscometer. The prepared coating is transferred to a constant temperature and humidity aging chamber, and the ambient temperature is set at 25±1°C and the relative humidity is set at 60±5%, and the coating is left to stand for 24 hours to allow each component to complete molecular chain relaxation and interface compatibility optimization.

[0012] In a preferred embodiment, in step S6, a Graco X7 series airless spraying device is used during the coating process, equipped with a 517 type fan nozzle, the spraying pressure is set to 0.5MPa, and the spray gun moving speed is 0.8-1.0m / s. After the substrate is sandblasted with 80 mesh alumina, it is ultrasonically cleaned with acetone and dried to a surface roughness of Ra=3.2-4.0μm. Three cross-spraying operations are performed, with each pass being leveled for 10 minutes, and the final wet film thickness is controlled at 80-100μm, and the film thickness fluctuation is ≤±5μm.

[0013] In a preferred embodiment, in step S7, in the first stage, the sprayed part is placed in a hot air circulation oven at 50±2°C, the wind speed is maintained at 1.5m / s, and pre-baked for 30 minutes to remove volatiles. In the second stage, the temperature is raised to 120±3°C, and a step-by-step heating program is adopted: 50→80°C takes 15 minutes, 80→120°C takes 20 minutes, and constant temperature curing is performed for 1 hour to form a completely cross-linked structure. In the third stage, the heating is turned off and the part is naturally cooled to room temperature, and the cooling rate does not exceed 5°C / minute to avoid cracking of the coating caused by thermal stress.

[0014] In a preferred embodiment, in step S8, a UVATRON series ultraviolet curing machine is used, a UV-LED light source with a main wavelength of 365nm is selected, and the irradiation intensity is set to 30mW / cm². The cured coating is placed on a conveyor belt and passed through the irradiation area at a speed of 0.5m / min, and a total of 10 minutes of ultraviolet excitation is received. This process activates the fluorescent response characteristics of curcumin nanocellulose, synchronously completes the construction of photocatalytic active sites on the coating surface, and finally forms a composite coating with self-cleaning and long-term protection.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In the present invention, waterborne polyurethane resin is used as the matrix, combined with bio-based and chromium-free corrosion inhibition systems such as modified chitosan, sodium molybdate phytic acid complex, etc., to eliminate the use of toxic substances such as benzene solvents and hexavalent chromium in traditional coatings from the source, and the volatile organic matter content is less than 50g / L, which meets the RoHS and REACH environmental protection standards. Through the construction of graphene oxide composite titanium dioxide heterojunction, the coating triggers a photocatalytic reaction under visible light, which can decompose surface pollutants and reduce the electron migration activity of the metal interface, so that the neutral salt spray resistance time exceeds 3000 hours, which is more than 3 times higher than that of conventional epoxy coatings. The dual intelligent response mechanism formed by matrine microcapsules and modified chitosan can quickly release corrosion inhibition factors at the early stage of corrosion, dynamically repair microcracks, and achieve stable protection of the coating in a wide range of pH 2-12 corrosive media, significantly extending the service life of metal substrates in extreme environments such as oceans and chemical industries.

[0016] 2. In the present invention, precise control of the mechanical properties and functional characteristics of the coating is achieved by integrating nano-enhancement, intelligent corrosion inhibition and natural functional phases in steps. The synergistic effect of nano-silica and curcumin-modified cellulose enables the coating hardness to reach 4H while maintaining an elongation at break of 8%, overcoming the defect of easy brittle cracking of traditional rigid coatings. The gradient curing process is combined with ultraviolet light post-treatment to complete resin cross-linking and functional activation in stages, ensuring that a dense three-dimensional protection network of "physical barrier-chemical passivation-electrochemical inhibition" is formed inside the coating, and the adhesion level reaches ISO 2409 standard level 0. In addition, the scientific design of process parameters such as microfluidic packaging and ultrasonic dispersion enables the component dispersion uniformity to reach the nanometer level, the coating efficiency is increased by more than 40%, and no high temperature and high pressure equipment is required throughout the process. It is suitable for large-scale continuous production of various metal substrates such as steel and aluminum alloys, and has broad application prospects in new energy equipment, medical devices and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process principle of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example

[0019] Reference Figure 1 , an environmentally friendly and corrosion-resistant metal material coating, the metal material coating comprises: Waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 8 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2 parts by weight; Sodium molybdate / phytic acid complex: 5 parts by weight; Nano silicon dioxide: 3 parts by weight; Matrine-polydopamine microcapsules: 4 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3 parts by weight; Organic bentonite: 0.5 parts by weight; Deionized water: 25 parts by weight.

[0020] The preparation method comprises the following steps: S1: weigh: waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 8 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2 parts by weight; Sodium molybdate / phytic acid complex: 5 parts by weight; Nano silicon dioxide: 3 parts by weight; Matrine-polydopamine microcapsules: 4 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3 parts by weight; Organic bentonite: 0.5 parts by weight; Deionized water: 25 parts by weight; add waterborne polyurethane resin and deionized water into the reaction kettle in proportion, and stir at a low speed at 40°C for 15 minutes to form a uniform base liquid; S2: Adding graphene oxide composite titanium dioxide, nano silicon dioxide and silane coupling agent KH-560 to the base liquid in sequence, treating with an ultrasonic disperser for 30 minutes with a power set to 300 W to obtain a nano-enhanced phase dispersion; S3: adding modified chitosan nanoparticles, sodium molybdate phytic acid complex and matrine microcapsules into the dispersion three times, maintaining a constant temperature water bath at 60°C, and magnetically stirring for 1 hour to complete the corrosion inhibition network integration; S4: Add curcumin nanocellulose and organobentonite, and use a high-speed emulsifier to shear and disperse at 8000 rpm for 20 minutes to form a three-dimensional reinforced structure; S5: Inject water-based epoxy soybean oil to adjust flexibility, continue stirring until the system viscosity reaches 1200-1500mPa·s, and transfer to a closed container and let stand for 24 hours; S6: Using air spraying process, the cured coating is evenly sprayed onto the surface of the sandblasted metal substrate, and the wet film thickness is controlled at 80-100 μm; S7: In the first stage, the water is evaporated by baking at 50°C for 30 minutes, in the second stage, the cross-linked network is formed by curing at 120°C for 1 hour, and in the third stage, the cross-linked network is naturally cooled to room temperature; S8: The cured coating is irradiated with ultraviolet light for 10 minutes to activate the photoresponsive properties of curcumin, and finally a composite coating with self-cleaning and intelligent protection functions is obtained.

[0021] In step S1, the reactor is equipped with a double-layer spiral stirring paddle, and the stirring speed is set to 200 rpm. The material temperature is stabilized at 40±2°C by the jacket circulating water temperature control system, and stirring is continued for 15 minutes until the resin is completely wetted and dispersed to form a milky white uniform base liquid. Nitrogen protection is used during the process to prevent bubbles from mixing in, and the final base liquid viscosity is controlled within the range of 300-400mPa·s.

[0022] In step S2, an ultrasonic cell disruptor is used, a 20kHz high-frequency probe is selected, an output power of 300W is set, and a pulse mode of 2 seconds of operation and 1 second of rest is set, and the mixed system is ultrasonically treated for 30 minutes. The material temperature is controlled not to exceed 45°C, so that the nanomaterial is fully peeled off and a stable suspension is formed, and the particle size D50 of the slurry after dispersion is ≤200nm.

[0023] In step S3, a constant temperature magnetic stirrer is used to maintain the system temperature at 60±1°C, the stirring speed is set to 500 rpm, and the reaction is continued for 1 hour. During the process, the pH value of the system is monitored to be stable at 7.5-8.0, forming an interpenetrating network structure with hierarchical corrosion inhibition function.

[0024] In step S4, the gap between the stator and the sub-stator is adjusted to 0.3 mm, and the machine is operated at 8000 rpm for 20 minutes. The material temperature is kept below 35° C. by an online cooling system, so that the nanocellulose and bentonite are evenly embedded in the resin matrix to form a three-dimensional support structure, and the thixotropic index of the slurry after mixing reaches 5-6.

[0025] In step S5, a frame-type stirring paddle is used to mix at a low speed of 100 rpm for 30 minutes, and the viscosity of the system is adjusted to 1200-1500 mPa·s by monitoring the NDJ-5S rotational viscometer. The prepared coating is transferred to a constant temperature and humidity aging chamber, and the ambient temperature is set to 25±1°C and the relative humidity is set to 60±5%. It is left to stand and mature for 24 hours to allow each component to complete molecular chain relaxation and interface compatibility optimization.

[0026] In step S6, the coating is applied using a Graco X7 series airless spraying device equipped with a 517 fan nozzle, with a spraying pressure of 0.5 MPa and a spray gun moving speed of 0.8-1.0 m / s. The substrate is sandblasted with 80-mesh aluminum oxide, ultrasonically cleaned with acetone and dried to a surface roughness of Ra = 3.2-4.0 μm. Three cross-spraying operations are performed, with each pass being leveled for 10 minutes, and the final wet film thickness is controlled at 80-100 μm, with a film thickness fluctuation of ≤ ± 5 μm.

[0027] In step S7, in the first stage, the sprayed parts are placed in a hot air circulation oven at 50±2℃, the wind speed is maintained at 1.5m / s, and pre-baked for 30 minutes to remove volatiles. In the second stage, the temperature is raised to 120±3℃, and a step-by-step heating program is adopted: 50→80℃ takes 15 minutes, 80→120℃ takes 20 minutes, and constant temperature curing is performed for 1 hour to form a completely cross-linked structure. In the third stage, the heating is turned off and the parts are naturally cooled to room temperature. The cooling rate does not exceed 5℃ / minute to avoid cracking of the coating caused by thermal stress.

[0028] In step S8, a UVATRON series UV curing machine is used, a UV-LED light source with a main wavelength of 365nm is selected, and the irradiation intensity is set to 30mW / cm². The cured coating is placed on a conveyor belt and passed through the irradiation area at a speed of 0.5m / min, and receives a total of 10 minutes of UV excitation. This process activates the fluorescence response characteristics of curcumin nanocellulose, and simultaneously completes the construction of photocatalytic active sites on the coating surface, ultimately forming a composite coating with self-cleaning and long-term protection.

[0029] From the above we can know: In the present invention, waterborne polyurethane resin is used as the matrix, combined with bio-based and chromium-free corrosion inhibition systems such as modified chitosan, sodium molybdate phytic acid complex, etc., to eliminate the use of toxic substances such as benzene solvents and hexavalent chromium in traditional coatings from the source, and the volatile organic matter content is less than 50g / L, which meets the RoHS and REACH environmental protection standards. Through the construction of graphene oxide composite titanium dioxide heterojunction, the coating triggers a photocatalytic reaction under visible light, which can decompose surface pollutants and reduce the electron migration activity of the metal interface, so that the neutral salt spray resistance time exceeds 3000 hours, which is more than 3 times higher than that of conventional epoxy coatings. The dual intelligent response mechanism formed by matrine microcapsules and modified chitosan can quickly release corrosion inhibition factors at the early stage of corrosion, dynamically repair microcracks, and achieve stable protection of the coating in a wide range of pH 2-12 corrosive media, significantly extending the service life of metal substrates in extreme environments such as oceans and chemical industries.

[0030] In the present invention, precise control of the mechanical properties and functional characteristics of the coating is achieved by integrating nano-enhancement, intelligent corrosion inhibition and natural functional phases in steps. The synergistic effect of nano-silica and curcumin-modified cellulose enables the coating hardness to reach 4H while maintaining an elongation at break of 8%, overcoming the defect of easy brittle cracking of traditional rigid coatings. The gradient curing process is combined with ultraviolet light post-treatment to complete resin cross-linking and functional activation in stages, ensuring that a dense three-dimensional protection network of "physical barrier-chemical passivation-electrochemical inhibition" is formed inside the coating, and the adhesion level reaches ISO 2409 standard level 0. In addition, the scientific design of process parameters such as microfluidic packaging and ultrasonic dispersion enables the component dispersion uniformity to reach the nanometer level, the coating efficiency is increased by more than 40%, and no high temperature and high pressure equipment is required throughout the process. It is suitable for large-scale continuous production of various metal substrates such as steel and aluminum alloys, and has broad application prospects in new energy equipment, medical devices and other fields. Example

[0031] Reference Figure 1 , an environmentally friendly and corrosion-resistant metal material coating, the metal material coating comprises: Waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 3 parts by weight; Sodium molybdate / phytic acid complex: 8 parts by weight; Nano silicon dioxide: 5 parts by weight; Matrine-polydopamine microcapsules: 6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 4 parts by weight; Organic bentonite: 1 part by weight; Deionized water: 35 parts by weight.

[0032] The preparation method comprises the following steps: S1: weigh: waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 3 parts by weight; Sodium molybdate / phytic acid complex: 8 parts by weight; Nano silicon dioxide: 5 parts by weight; Matrine-polydopamine microcapsules: 6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 4 parts by weight; Organic bentonite: 1 part by weight; Deionized water: 35 parts by weight; add waterborne polyurethane resin and deionized water into the reaction kettle in proportion, and stir at a low speed at 40°C for 15 minutes to form a uniform base liquid; S2: Adding graphene oxide composite titanium dioxide, nano silicon dioxide and silane coupling agent KH-560 to the base liquid in sequence, treating with an ultrasonic disperser for 30 minutes with a power set to 300 W to obtain a nano-enhanced phase dispersion; S3: adding modified chitosan nanoparticles, sodium molybdate phytic acid complex and matrine microcapsules into the dispersion three times, maintaining a constant temperature water bath at 60°C, and magnetically stirring for 1 hour to complete the corrosion inhibition network integration; S4: Add curcumin nanocellulose and organobentonite, and use a high-speed emulsifier to shear and disperse at 8000 rpm for 20 minutes to form a three-dimensional reinforced structure; S5: Inject water-based epoxy soybean oil to adjust flexibility, continue stirring until the system viscosity reaches 1200-1500mPa·s, and transfer to a closed container and let stand for 24 hours; S6: Using air spraying process, the cured coating is evenly sprayed onto the surface of the sandblasted metal substrate, and the wet film thickness is controlled at 80-100 μm; S7: In the first stage, the water is evaporated by baking at 50°C for 30 minutes, in the second stage, the cross-linked network is formed by curing at 120°C for 1 hour, and in the third stage, the cross-linked network is naturally cooled to room temperature; S8: The cured coating is irradiated with ultraviolet light for 10 minutes to activate the photoresponsive properties of curcumin, and finally a composite coating with self-cleaning and intelligent protection functions is obtained.

[0033] In step S1, the reactor is equipped with a double-layer spiral stirring paddle, and the stirring speed is set to 200 rpm. The material temperature is stabilized at 40±2°C by the jacket circulating water temperature control system, and stirring is continued for 15 minutes until the resin is completely wetted and dispersed to form a milky white uniform base liquid. Nitrogen protection is used during the process to prevent bubbles from mixing in, and the final base liquid viscosity is controlled within the range of 300-400mPa·s.

[0034] In step S2, an ultrasonic cell disruptor is used, a 20kHz high-frequency probe is selected, an output power of 300W is set, and a pulse mode of 2 seconds of operation and 1 second of rest is set, and the mixed system is ultrasonically treated for 30 minutes. The material temperature is controlled not to exceed 45°C, so that the nanomaterial is fully peeled off and a stable suspension is formed, and the particle size D50 of the slurry after dispersion is ≤200nm.

[0035] In step S3, a constant temperature magnetic stirrer is used to maintain the system temperature at 60±1°C, the stirring speed is set to 500 rpm, and the reaction is continued for 1 hour. During the process, the pH value of the system is monitored to be stable at 7.5-8.0, forming an interpenetrating network structure with hierarchical corrosion inhibition function.

[0036] In step S4, the gap between the stator and the sub-stator is adjusted to 0.3 mm, and the machine is operated at 8000 rpm for 20 minutes. The material temperature is kept below 35° C. by an online cooling system, so that the nanocellulose and bentonite are evenly embedded in the resin matrix to form a three-dimensional support structure, and the thixotropic index of the slurry after mixing reaches 5-6.

[0037] In step S5, a frame-type stirring paddle is used to mix at a low speed of 100 rpm for 30 minutes, and the viscosity of the system is adjusted to 1200-1500 mPa·s by monitoring the NDJ-5S rotational viscometer. The prepared coating is transferred to a constant temperature and humidity aging chamber, and the ambient temperature is set to 25±1°C and the relative humidity is set to 60±5%. It is left to stand and mature for 24 hours to allow each component to complete molecular chain relaxation and interface compatibility optimization.

[0038] In step S6, the coating is applied using a Graco X7 series airless spraying device equipped with a 517 fan nozzle, with a spraying pressure of 0.5 MPa and a spray gun moving speed of 0.8-1.0 m / s. The substrate is sandblasted with 80-mesh aluminum oxide, ultrasonically cleaned with acetone and dried to a surface roughness of Ra = 3.2-4.0 μm. Three cross-spraying operations are performed, with each pass being leveled for 10 minutes, and the final wet film thickness is controlled at 80-100 μm, with a film thickness fluctuation of ≤ ± 5 μm.

[0039] In step S7, in the first stage, the sprayed parts are placed in a hot air circulation oven at 50±2℃, the wind speed is maintained at 1.5m / s, and pre-baked for 30 minutes to remove volatiles. In the second stage, the temperature is raised to 120±3℃, and a step-by-step heating program is adopted: 50→80℃ takes 15 minutes, 80→120℃ takes 20 minutes, and constant temperature curing is performed for 1 hour to form a completely cross-linked structure. In the third stage, the heating is turned off and the parts are naturally cooled to room temperature. The cooling rate does not exceed 5℃ / minute to avoid cracking of the coating caused by thermal stress.

[0040] In step S8, a UVATRON series UV curing machine is used, a UV-LED light source with a main wavelength of 365nm is selected, and the irradiation intensity is set to 30mW / cm². The cured coating is placed on a conveyor belt and passed through the irradiation area at a speed of 0.5m / min, and receives a total of 10 minutes of UV excitation. This process activates the fluorescence response characteristics of curcumin nanocellulose, and simultaneously completes the construction of photocatalytic active sites on the coating surface, ultimately forming a composite coating with self-cleaning and long-term protection.

[0041] From the above we can know: In the present invention, waterborne polyurethane resin is used as the matrix, combined with bio-based and chromium-free corrosion inhibition systems such as modified chitosan, sodium molybdate phytic acid complex, etc., to eliminate the use of toxic substances such as benzene solvents and hexavalent chromium in traditional coatings from the source, and the volatile organic matter content is less than 50g / L, which meets the RoHS and REACH environmental protection standards. Through the construction of graphene oxide composite titanium dioxide heterojunction, the coating triggers a photocatalytic reaction under visible light, which can decompose surface pollutants and reduce the electron migration activity of the metal interface, so that the neutral salt spray resistance time exceeds 3000 hours, which is more than 3 times higher than that of conventional epoxy coatings. The dual intelligent response mechanism formed by matrine microcapsules and modified chitosan can quickly release corrosion inhibition factors at the early stage of corrosion, dynamically repair microcracks, and achieve stable protection of the coating in a wide range of pH 2-12 corrosive media, significantly extending the service life of metal substrates in extreme environments such as oceans and chemical industries.

[0042] In the present invention, precise control of the mechanical properties and functional characteristics of the coating is achieved by integrating nano-enhancement, intelligent corrosion inhibition and natural functional phases in steps. The synergistic effect of nano-silica and curcumin-modified cellulose enables the coating hardness to reach 4H while maintaining an elongation at break of 8%, overcoming the defect of easy brittle cracking of traditional rigid coatings. The gradient curing process is combined with ultraviolet light post-treatment to complete resin cross-linking and functional activation in stages, ensuring that a dense three-dimensional protection network of "physical barrier-chemical passivation-electrochemical inhibition" is formed inside the coating, and the adhesion level reaches ISO 2409 standard level 0. In addition, the scientific design of process parameters such as microfluidic packaging and ultrasonic dispersion enables the component dispersion uniformity to reach the nanometer level, the coating efficiency is increased by more than 40%, and no high temperature and high pressure equipment is required throughout the process. It is suitable for large-scale continuous production of various metal substrates such as steel and aluminum alloys, and has broad application prospects in new energy equipment, medical devices and other fields.

[0043] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0044] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An environmentally friendly and corrosion-resistant metal material coating, characterized by: The metal material coating comprises: Waterborne polyurethane resin: 100 parts by weight; Modified chitosan nanoparticles: 8-12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2-3 parts by weight; Sodium molybdate / phytic acid complex: 5-8 parts by weight; Nano silicon dioxide: 3-5 parts by weight; Matrine-polydopamine microcapsules: 4-6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3-4 parts by weight; Organic bentonite: 0.5-1 parts by weight; Deionized water: 25-35 parts by weight.

2. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: The preparation method comprises the following steps: S1: Weigh: 100 parts by weight of waterborne polyurethane resin; Modified chitosan nanoparticles: 8-12 parts by weight; Graphene oxide / titanium dioxide heterojunction: 2-3 parts by weight; Sodium molybdate / phytic acid complex: 5-8 parts by weight; Nano silicon dioxide: 3-5 parts by weight; Matrine-polydopamine microcapsules: 4-6 parts by weight; Silane coupling agent KH-5601: 2 parts by weight; Curcumin modified nanocellulose: 3-4 parts by weight; Organic bentonite: 0.5-1 parts by weight; Deionized water: 25-35 parts by weight; add waterborne polyurethane resin and deionized water into the reaction kettle in proportion, and stir at a low speed at 40°C for 15 minutes to form a uniform base liquid; S2: Graphene oxide composite titanium dioxide, nano silicon dioxide and silane coupling agent KH-560 are sequentially added to the base liquid, and an ultrasonic disperser is used for treatment for 30 minutes with the power set to 300W to obtain a nano-enhanced phase dispersion; S3: Add modified chitosan nanoparticles, sodium molybdate phytic acid complex and matrine microcapsules into the dispersion three times, maintain a constant temperature water bath at 60 °C, and magnetically stir for 1 hour to complete the corrosion inhibition network integration; S4: Add curcumin nanocellulose and organobentonite, and use a high-speed emulsifier to shear and disperse at 8000 rpm for 20 minutes to form a three-dimensional reinforced structure; S5: Inject water-based epoxy soybean oil to adjust flexibility, continue stirring until the system viscosity reaches 1200-1500mPa·s, and transfer to a sealed container for 24 hours; S6: Use air spraying process to evenly spray the cured coating onto the sandblasted metal substrate surface, and the wet film thickness is controlled at 80-100μm; S7: In the first stage, the water is evaporated by baking at 50°C for 30 minutes, in the second stage, the cross-linked network is formed by curing at 120°C for 1 hour, and in the third stage, the cross-linked network is naturally cooled to room temperature; S8: The cured coating is irradiated with ultraviolet light for 10 minutes to activate the photoresponsive properties of curcumin, and finally a composite coating with self-cleaning and intelligent protection functions is obtained.

3. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In the step S1, the reactor is equipped with a double-layer spiral stirring paddle, the stirring speed is set to 200 rpm, the material temperature is stabilized at 40±2° C. by the jacket circulating water temperature control system, and stirring is continued for 15 minutes until the resin is completely wetted and dispersed to form a milky white uniform base liquid. Nitrogen protection is used during the process to prevent bubbles from mixing in, and the final base liquid viscosity is controlled within the range of 300-400 mPa·s.

4. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In the step S2, an ultrasonic cell disruptor is used, a 20kHz high-frequency probe is selected, the output power is set to 300W, the pulse mode is set to work for 2 seconds and rest for 1 second, the mixed system is ultrasonically treated for 30 minutes, and the material temperature is controlled not to exceed 45°C, so that the nanomaterial is fully peeled off and a stable suspension is formed, and the slurry particle size D50 after dispersion is ≤200nm.

5. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In step S3, a constant temperature magnetic stirrer is used to maintain the system temperature at 60±1° C., the stirring speed is set to 500 rpm, and the reaction is continued for 1 hour. During the process, the pH value of the system is monitored to be stable at 7.5-8.0, forming an interpenetrating network structure with hierarchical corrosion inhibition function.

6. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In step S4, the gap between the stators is adjusted to 0.3 mm, and the machine is operated at a speed of 8000 rpm for 20 minutes. The material temperature is kept below 35° C. by an online cooling system, so that the nanocellulose and bentonite are evenly embedded in the resin matrix to form a three-dimensional spatial support structure. The thixotropic index of the slurry after mixing reaches 5-6.

7. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In the step S5, a frame-type stirring paddle is used to mix at a low speed of 100 rpm for 30 minutes, and the viscosity of the system is adjusted to 1200-1500 mPa·s by monitoring the NDJ-5S rotational viscometer. The prepared coating is transferred to a constant temperature and humidity aging chamber, and the ambient temperature is set to 25±1°C and the relative humidity is set to 60±5%. The coating is left to stand and mature for 24 hours to allow each component to complete molecular chain relaxation and interface compatibility optimization.

8. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In step S6, during the coating process, a Graco X7 series airless spraying device is used, equipped with a 517 type fan nozzle, the spraying pressure is set to 0.5 MPa, the spray gun moving speed is 0.8-1.0 m / s, the substrate is sandblasted with 80 mesh alumina, ultrasonically cleaned with acetone and dried to a surface roughness of Ra=3.2-4.0 μm, and three cross-spraying operations are performed, with each pass being leveled at an interval of 10 minutes, and the final wet film thickness is controlled at 80-100 μm, and the film thickness fluctuation is ≤±5 μm.

9. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In step S7, in the first stage, the sprayed part is placed in a hot air circulation oven at 50±2°C, the wind speed is maintained at 1.5m / s, and pre-baked for 30 minutes to remove volatiles. In the second stage, the temperature is raised to 120±3°C, and a step-by-step heating program is adopted: 50→80°C takes 15 minutes, 80→120°C takes 20 minutes, and constant temperature curing is performed for 1 hour to form a completely cross-linked structure. In the third stage, the heating is turned off and the part is naturally cooled to room temperature. The cooling rate does not exceed 5°C / minute to avoid cracking of the coating due to thermal stress.

10. The method for preparing an environmentally friendly and corrosion-resistant metal material coating according to claim 1, characterized in that: In the step S8, a UVATRON series ultraviolet curing machine is used, a UV-LED light source with a main wavelength of 365nm is selected, and the irradiation intensity is set to 30mW / cm². The cured coating is placed on a conveyor belt and passed through the irradiation area at a speed of 0.5m / min. It is subjected to ultraviolet excitation for a total of 10 minutes. This process activates the fluorescence response characteristics of curcumin nanocellulose and simultaneously completes the construction of photocatalytic active sites on the coating surface, ultimately forming a composite coating with self-cleaning and long-term protection.

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