Salt-mist anticorrosive coating based on three-stage synergistic dynamic self-repairing and preparation method of salt-mist anticorrosive coating

Abstract

The invention provides a salt-spray anticorrosive coating based on three-stage synergistic dynamic self-repairing and a preparation method thereof, and belongs to the technical field of corrosion inhibition of metal materials of ocean engineering equipment. The salt spray anticorrosive coating comprises a zinc oxide / graphene quantum dot heterojunction enhanced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer and a polycaprolactone-based laser structured super-hydrophobic surface layer which are sequentially arranged from bottom to top, and adding a microcapsule which takes benzotriazole as a core material and polyurea as a shell material into the polycaprolactone-based laser structured super-hydrophobic surface layer to obtain the environment response type intelligent anticorrosive coating. The salt mist anti-corrosion coating or the environment response type intelligent anti-corrosion coating based on three-level collaborative dynamic self-repairing can be seamlessly integrated in key parts such as a hydraulic pipeline and a winch cabin frame of a cable logging unit, and the technical span from passive protection to active intervention is achieved; and a subversive solution is provided for full-life-cycle corrosion prevention of marine equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of corrosion inhibition of marine engineering equipment metal materials, and particularly relates to a salt mist corrosion-resistant coating based on three-stage synergistic dynamic self-repair and a preparation method thereof. BACKGROUND

[0002] The long-term corrosion resistance of marine engineering equipment in an extreme salt mist environment is a core technical problem that restricts its reliability and service life. For example, a marine cable logging unit is exposed to a high-humidity, high-salt-mist corrosive medium for a long time. The Cl - ions in the salt mist droplets penetrate the coating to the surface of the metal substrate, triggering an electrochemical corrosion reaction, resulting in coating peeling, substrate corrosion, and even structural failure. Traditional corrosion prevention techniques mainly rely on the cathodic protection effect of zinc-rich coatings or the physical barrier effect of hot-dip galvanizing processes, but their performance has significant limitations. For example, a high zinc powder content in a zinc-rich coating easily leads to increased coating brittleness, insufficient interfacial bonding energy (only 1.7 J / m 2 ), and rapid consumption of zinc powder under salt mist penetration, with a cathodic protection current density of only 2.3 μA / cm 2 , which is difficult to sustain to inhibit corrosion. Although a hot-dip galvanized layer can provide initial protection, it is difficult to repair after local damage, and it cannot adapt to the surface treatment requirements of complex components. In addition, existing coatings generally lack dynamic self-repairing ability. Once microcracks are formed due to mechanical damage, the corrosive medium will quickly spread along the cracks, causing irreversible damage. According to statistics, the salt mist resistance of traditional corrosion-resistant coatings is usually less than 1200 hours (ISO 9227 standard), while the design life of marine equipment is usually required to be more than 20 years. It can be seen that the existing technology cannot meet the long-term protection requirements.

[0003] The key bottleneck of existing coating technology mainly lies in three aspects: molecular interface, microstructure, and dynamic performance. At the molecular interface level, the interfacial bonding force between the nanofiller and the resin matrix prepared by traditional physical mixing method is weak, and the oxygen permeation rate is as high as 5.6 × 10 -12 cm 2 / s, and the corrosive medium easily penetrates along the interface defects. At the microstructure level, the surface of the coating is mostly smooth or single-scale rough structure, and the salt mist droplets stay for a long time (about 8 seconds), which makes it difficult to quickly drain the liquid through the self-hydrophobic effect, resulting in continuous liquid film covering and accelerating corrosion. At the dynamic performance level, the coating lacks an intelligent response mechanism and cannot self-repair after damage, with a low crack healing rate and a dependence on external intervention. In recent years, although research on biomimetic super-hydrophobic coatings and self-repairing materials has made some progress, it is mostly limited to single-function optimization. For example, the mechanical durability of the micro-nano structure hydrophobic surface constructed by laser etching is insufficient, and the self-repairing efficiency of the dynamic cross-linking network is limited by the high activation energy (usually > 60 kJ / mol), making it difficult to trigger effective repair in a normal temperature and high humidity environment.

[0004] Therefore, the improvement of the prior art fails to realize multi-mechanism synergy, resulting in limited comprehensive performance improvement of the coating under complex working conditions. For this reason, the application proposes a salt mist corrosion-resistant coating based on three-level synergistic dynamic self-repairing as well as a preparation method and application thereof. SUMMARY

[0005] The application proposes a salt mist corrosion-resistant coating based on three-level synergistic dynamic self-repairing as well as a preparation method thereof, aiming at the long-acting corrosion prevention requirement of the marine cable logging unit under an extreme salt mist environment. The technology realizes the synergistic improvement of the permeation resistance, mechanical strength and self-repairing capability of the coating through molecular-level interface design, micro-nano scale structure regulation and dynamic chemical bond reconstruction.

[0006] To achieve the above-mentioned purpose, the application provides the following technical solutions.

[0007] One of the technical solutions of the application is as follows:

[0008] A salt mist corrosion-resistant coating based on three-level synergistic dynamic self-repairing comprises, from bottom to top, a zinc oxide / graphene quantum dot heterojunction enhanced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer and a polycaprolactone-based laser structured super-hydrophobic surface layer.

[0009] Further, the thickness of the zinc oxide / graphene quantum dot heterojunction enhanced epoxy layer is 80 μm, the thickness of the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer is 60 μm, and the thickness of the polycaprolactone-based laser structured super-hydrophobic surface layer is 40 μm.

[0010] Further, the heterojunction interface spacing of the zinc oxide / graphene quantum dot heterojunction enhanced epoxy layer is dispersed in a carrier network by using a peeled heterojunction, and TEM imaging measurement is performed, and it is confirmed by statistics that the spacing is ≤1.2 nm. The pore diameter test of the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer is performed by SEM shooting after coating gold spraying, and the diameter is obtained by ImageJ software statistics, and the gradient distribution of 50-200 nm and 1-5 μm is obtained. The disulfide bond ratio in the polycaprolactone-based laser structured super-hydrophobic surface layer is identified by FTIR at 500-550 cm -1 S-S stretching vibration peak, and the ratio is 60-70wt% calculated by combining the peak area with Beer-Lambert law.

[0011] The second technical solution of the application is as follows:

[0012] A preparation method of the salt spray corrosion resistant coating based on three-stage synergistic dynamic self-repairing, in which a zinc oxide / graphene quantum dot heterojunction enhanced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer and a polycaprolactone-based laser structured super-hydrophobic surface layer are prepared on a substrate by spraying raw materials in sequence, and each layer is subjected to curing treatment to obtain a substrate loaded with a salt spray corrosion resistant coating based on three-stage synergistic dynamic self-repairing.

[0013] Further, the zinc oxide / graphene quantum dot (ZnO / GQDs) heterojunction enhanced epoxy layer is a heterojunction structure of zinc oxide (ZnO) and graphene quantum dots (GQDs) introduced in an epoxy resin matrix, in which a ZnO / GQDs composite with quantum confinement effect is synthesized in situ by a hydrothermal method, and the specific preparation method is as follows:

[0014] Zinc nitrate (Zn(NO3)2·6H2O) and graphene oxide (GO) are dispersed in ethylene glycol solvent according to a molar ratio of 5:1, and ammonia water is added to adjust the pH to 9-10 to obtain a suspension;

[0015] The suspension is transferred to a high-pressure reaction kettle, and reacted at 180℃ for 12 hours to obtain a ZnO / GQDs core-shell heterojunction with a core-shell structure of ZnO nanorods (diameter 5nm, length 50nm) and GQDs (size 3nm), and the chemical reaction in this process is as follows:

[0016]

[0017]

[0018] The ZnO / GQDs core-shell heterojunction is soaked in ethylenediaminetetraacetic acid (EDTA) at 60℃ for 4 hours to perform carboxyl functional modification on the surface of GQDs, so that -COOH groups are formed on the surface of the quantum dots to enhance the chemical bonding with the epoxy resin, and a ZnO / GQDs core-shell heterojunction with a surface modified -COOH group is obtained;

[0019] The ZnO / GQDs core-shell heterojunction with a surface modified -COOH group is dispersed in the epoxy resin at a proportion of 10wt%, and is uniformly ultrasonicated to obtain a ZnO / GQDs heterojunction enhanced epoxy layer raw material;

[0020] The ZnO / GQDs heterojunction enhanced epoxy layer raw material is coated on the substrate, and is subjected to curing treatment at 80℃ for 1 hour to obtain a substrate loaded with a ZnO / GQDs heterojunction enhanced epoxy layer.

[0021] Further, the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer simulates the micro-topological characteristics of deep-sea mussel byssus protein, and adopts a femtosecond laser-induced self-assembly technology to construct a biomimetic micro-nano structure with multi-level pores.

[0022] The epoxy prepolymer containing a silane coupling agent (KH-550, content of 3 wt%) is sprayed on the surface of the substrate carrying the ZnO / GQD heterojunction reinforced epoxy layer to obtain a liquid film with a thickness of 200 μm, and a femtosecond laser with a wavelength of 1030 nm (pulse width of 200 fs, energy density of 2 J / cm 2 ) is used for scanning to generate a double-scale pore surface layer with a double-scale pore network of a primary pore diameter of 200-500 nm and a secondary pore diameter of 20-50 nm through local phase separation induced by photothermal effect, and then perfluoroalkyl silane (FAS-17) is dissolved in an ethanol solution (concentration of 0.5 wt%) and sprayed on the inner wall of the pores of the double-scale pore surface layer, and the solidification treatment is carried out at 80 ℃ for 1 hour to form a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer.

[0023] Further, the polycaprolactone-based laser-structured superhydrophobic surface layer is a double self-repairing network embedded in the coating with dynamic covalent bonds and supramolecular interactions, which realizes the rapid autonomous healing of cracks, and the specific preparation method is as follows:

[0024] 4,4'-dimercaptodibenzyl ether (DMDB) and hexamethylene diisocyanate (HDI) are mixed according to a molar ratio of 1:2, 10 wt% of dibutyltin dilaurate (DBTDL) catalyst is added, and the reaction is carried out at 80 ℃ for 6 hours under nitrogen protection to generate a linear polymer (polysulfide urethane copolymer) with dynamic disulfide bonds, and the segment structure is as follows:

[0025]

[0026] The urea-based pyrimidone (UPy) monomer is mixed with the polysulfide urethane copolymer according to a molar ratio of 1:10, the UPy unit forms a physical crosslinking point through four hydrogen bonds (N-H…O=C), and then the mixed polymer is dispersed in the epoxy resin at a proportion of 10 wt%, and is coated on the surface of the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer, and after gradient curing treatment at 80-160 ℃, an interpenetrating network structure is formed, and a polycaprolactone-based laser-structured superhydrophobic surface layer is obtained.

[0027] The third technical scheme of the present application is:

[0028] An environment-responsive intelligent anticorrosion coating based on three-level synergistic dynamic self-repairing, wherein microcapsules (with pH sensitivity) with benzotriazole (BTA) as core material and polyurea as shell material are added to a polycaprolactone-based laser-structured superhydrophobic surface layer of the three-level synergistic dynamic self-repairing salt spray corrosion-resistant coating.

[0029] Further, the average particle size of the microcapsules is 10 μm, and the added amount of the microcapsules is 3 wt% of the mass of the urea-based uracil monomer and the polythio urethane copolymer.

[0030] The addition of the microcapsules enables the coating to autonomously release a repair agent and adjust the surface morphology according to the environmental corrosion state (such as local pH reduction to <4 or temperature >50℃). For example, when Cl - concentration exceeds the threshold value, the microcapsules rupture to release the corrosion inhibitor, which reacts with the metal substrate to form a dense passivation film, and the reaction process is:

[0031]

[0032] The above-described three-level synergistic dynamic self-repairing salt spray corrosion-resistant coating obtained by the present application can be used in marine engineering equipment corrosion prevention.

[0033] The present application proposes an innovative technical route of "molecular design-structure regulation-dynamic repair" three-level synergistic enhancement, which breaks through the performance boundary of traditional anticorrosion coatings. At the molecular interface level, by in-situ synthesis of ZnO / GQDs heterojunction, the quantum confinement effect and Schottky barrier are used to regulate the electron transport path, and the current density of the ZnO / GQDs heterojunction enhanced epoxy layer is increased to 8.5 μA / cm 2 (ASTM G59), and at the same time, the interfacial bonding energy is enhanced to 2.8 J / m 2 , so that the oxygen permeation rate is reduced to 1.2×10 -14 cm 2 / s, two orders of magnitude lower than traditional coatings. At the microstructure level, mimicking the multi-level topological features of deep-sea mussel byssal proteins, a bi-scale porous network was constructed using femtosecond laser-induced self-assembly technology, combined with perfluoroalkylsilane modification, so that the contact angle of the constructed polyurethane dynamic chemical bond self-repairing layer reaches 154°, the rolling angle is less than 3°, and the salt spray droplet retention time is shortened to 0.8 seconds, significantly inhibiting the formation of liquid film. At the dynamic repair level, a disulfide bond / hydrogen bond synergistic self-repairing network is innovatively introduced, and through the environmental humidity, dynamic covalent bond exchange (activation energy 45 kJ / mol) and supramolecular hydrogen bond reorganization are triggered, so that the crack healing rate is greater than 90% within 24 hours, and the tensile strength recovery rate reaches 88% (ASTM D638). The present application couples the three-level mechanism into a unified coating system through process integration, and expands the environmental response type intelligent function, such as pH-sensitive microcapsule autonomous release of corrosion inhibitor, temperature response shape memory polymer adjusting surface topography, so as to realize the technical leap from passive protection to active intervention under multiple stresses such as salt spray corrosion, mechanical damage and chemical corrosion. After ISO 9227 standard verification, the salt spray resistance time of the coating system prepared by the present application breaks through 5000 hours, and the low-frequency impedance modulus reaches 10 11 Ω·cm 2 , and provides a technical solution for the whole life cycle corrosion protection of key equipment such as marine cable logging units.

[0034] Compared with the prior art, the present application has the following advantages and technical effects:

[0035] (1) Through the multi-level innovation of molecular design-structure regulation-dynamic repair, the present application breaks through the technical bottleneck of traditional corrosion protection coating, and realizes the ultra-long protection of cable logging unit in salt spray environment. The core innovation points include: in-situ synthesis of ZnO / GQDs heterojunction to improve the interface performance, laser-induced construction of biomimetic multi-level hydrophobic structure, dynamic disulfide bond / hydrogen bond synergistic self-repairing mechanism, and environmental response type intelligent regulation function. The technology of the present application not only significantly improves the salt spray resistance and service life of the coating, but also opens up a new way for the corrosion protection technology of marine engineering equipment through green process and intelligent characteristics.

[0036] (2) The salt spray corrosion resistant coating or environmental response type intelligent corrosion resistant coating based on three-level synergistic dynamic self-repairing prepared by the present application can be seamlessly integrated into key parts such as hydraulic pipeline and winch cabin frame of cable logging unit, realizing the technical leap from passive protection to active intervention, and providing a revolutionary solution for the whole life cycle corrosion protection of marine equipment. DETAILED DESCRIPTION

[0037] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The accompanying drawings should not be regarded as a limitation of the present application. In the drawings:

[0038] Figure 1 XPS analysis results of ZnO / GQDs heterojunction enhanced epoxy layer on the surface of the substrate of Example 1;

[0039] Figure 2 Picture of dynamic behavior of salt spray droplets on the surface of polysulfide rubber / polyurethane dynamic chemical bond self-healing layer of Example 2;

[0040] Figure 3 SEM image of pH-sensitive microcapsules prepared in Example 4.

[0041] Figure 4 XRD pattern of core-shell structure ZnO / GQDs core-shell heterojunction prepared in Example 1. DETAILED DESCRIPTION

[0042] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of the application and not as limiting the application. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. In addition, where particular ranges of values are given, understand that each intervening value, to the upper or lower limit of the ranges is also specifically included. The upper and lower limits of these intervening values are also specifically included within the scope of the application. The stated ranges are also intended to encompass every value and sub-range within the stated ranges. These are only typical values and are not intended to exclude other values or sub-ranges encompassed by the stated values.

[0044] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict between the present specification and any document incorporated by reference, the present specification will control.

[0045] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0046] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0047] The embodiment of the present application provides a salt fog corrosion resistant coating based on three-level cooperative dynamic self-repairing, which comprises, from bottom to top, a zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer and a polycaprolactone-based laser structured super-hydrophobic surface layer.

[0048] In the preferred embodiment of the present application, the thickness of the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer is 80 μm, the thickness of the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer is 60 μm, and the thickness of the polycaprolactone-based laser structured super-hydrophobic surface layer is 40 μm.

[0049] In the preferred embodiment of the present application, the heterojunction interface spacing of the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer is ≤1.2 nm (test method: ① the heterojunction is peeled off from the epoxy resin and dispersed on a carrier network; ② the interface spacing is measured by TEM imaging; ③ the data of multiple points are confirmed to be ≤1.2 nm), the hole diameter of the polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer is gradiently distributed at 50-200 nm and 1-5 μm (test method: ① the coating cross section / surface is treated by gold spraying; ② different regions are photographed by SEM; ③ the diameter is statistically analyzed by ImageJ software to analyze the pore size distribution), and the disulfide bond proportion in the polycaprolactone-based laser structured super-hydrophobic surface layer is 60-70 wt% (test method: FTIR characteristic peak identifies the disulfide bond (such as 500-550 cm -1 S-S stretching vibration, the content is calculated by the peak area proportion combined with Beer-Lambert law).

[0050] The embodiment of the present application also provides a preparation method of the salt fog corrosion resistant coating based on three-level cooperative dynamic self-repairing, which comprises the following steps: spraying raw materials on a substrate to prepare a zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer and a polycaprolactone-based laser structured super-hydrophobic surface layer in sequence, and obtaining the substrate loaded with the salt fog corrosion resistant coating based on three-level cooperative dynamic self-repairing after curing treatment of each layer.

[0051] In the preferred embodiment of the present application, the zinc oxide / graphene quantum dot (ZnO / GQDs) heterojunction reinforced epoxy layer is a heterojunction structure of zinc oxide (ZnO) and graphene quantum dots (GQDs) introduced in an epoxy resin matrix, and a ZnO / GQDs composite with quantum confinement effect is synthesized in situ by a hydrothermal method.

[0052] Zinc nitrate (Zn(NO3)2·6H2O) and graphene oxide (GO) are dispersed in an ethylene glycol solvent according to a molar ratio of 5:1, and ammonia water is added to adjust the pH to 9-10 to obtain a suspension;

[0053] The suspension is transferred into a high-pressure reaction kettle, and reacted at 180℃ for 12 hours to obtain a ZnO / GQDs core-shell heterojunction with a core-shell structure of ZnO nanorods (diameter 5nm, length 50nm) and GQDs (size 3nm);

[0054] The ZnO / GQDs core-shell heterojunction is immersed in ethylenediaminetetraacetic acid (EDTA, the amount of EDTA is not particularly limited, as long as it can immerse the ZnO / GQDs core-shell heterojunction) at 60℃ for 4 hours to perform carboxyl functional modification on the surface of the GQDs, so that -COOH groups are formed on the surface of the quantum dots, and the chemical bonding with the epoxy resin is enhanced, thereby obtaining a ZnO / GQDs core-shell heterojunction with a surface modified with -COOH groups;

[0055] The ZnO / GQDs core-shell heterojunction with a surface modified with -COOH groups is dispersed in the epoxy resin at a proportion of 10wt%, and is uniformly ultrasonicated to obtain a ZnO / GQDs heterojunction reinforced epoxy layer raw material;

[0056] The ZnO / GQDs heterojunction reinforced epoxy layer raw material is coated on a substrate, and is cured at 80℃ for 1 hour to obtain a substrate loaded with a ZnO / GQDs heterojunction reinforced epoxy layer.

[0057] In the preferred embodiment of the present application, the polysulfide / polyurethane dynamic chemical bond self-repairing layer simulates the micro-topological characteristics of the deep-sea mussel byssus protein, and a multi-level pore biomimetic micro-nano structure is constructed by using a femtosecond laser-induced self-assembly technology, and the specific preparation method is as follows:

[0058] An epoxy prepolymer containing a silane coupling agent (KH-550, content 3wt%) is sprayed on the surface of the substrate loaded with the ZnO / GQDs heterojunction reinforced epoxy layer to obtain a liquid film with a thickness of 200μm, and a femtosecond laser with a wavelength of 1030nm (pulse width 200fs, energy density 2J / cm 2 ) is used for scanning to generate a double-scale pore surface layer with a primary pore diameter of 200-500nm and a secondary pore diameter of 20-50nm by inducing local phase separation through photothermal effect, and then perfluoroalkylsilane (FAS-17) is dissolved in an ethanol solution (concentration 0.5wt%) and sprayed on the inner wall of the pores of the double-scale pore surface layer, and is cured at 80℃ for 1 hour to form a polysulfide / polyurethane dynamic chemical bond self-repairing layer;

[0059] In the preferred embodiment of the present application, the polycaprolactone-based laser-structured super-hydrophobic surface layer is a double self-repairing network embedded in the coating layer, which has dynamic covalent bonds and supramolecular interactions, and can realize rapid autonomous healing of cracks, and the specific preparation method is as follows:

[0060] 4,4'-dimercaptodibenzyl ether (DMDB) and hexamethylene diisocyanate (HDI) are mixed according to a molar ratio of 1:2, 10wt% dibutyltin dilaurate (DBTDL) catalyst is added, and the mixture is reacted at 80°C for 6 hours under nitrogen protection to generate a linear polymer with a dynamic disulfide bond (polythiourethane copolymer);

[0061] Urea-based pyrimidone (UPy) monomers are mixed with the polythiourethane copolymer according to a molar ratio of 1:10, the UPy units form physical crosslinking points through quadruple hydrogen bonds (N-H…O=C), and then the mixed polymer is dispersed in the epoxy resin at a proportion of 10wt%, coated on the surface of the polythiurethane dynamic chemical bond self-repairing layer, and subjected to gradient curing treatment at 80-160°C to form an interpenetrating network structure, thereby obtaining a polycaprolactone-based laser-structured super-hydrophobic surface layer.

[0062] The embodiment of the present application also provides an environment-responsive intelligent anti-corrosion coating based on three-level synergistic dynamic self-repairing, and the polycaprolactone-based laser-structured super-hydrophobic surface layer of the environment-responsive intelligent anti-corrosion coating based on three-level synergistic dynamic self-repairing is added with microcapsules (having pH sensitivity) taking benzotriazole (BTA) as a core material and polyurea as a shell material.

[0063] In the preferred embodiment of the present application, the average particle size of the microcapsules is 10μm, and the added amount of the microcapsules is 3wt%.

[0064] The raw materials used in the embodiment of the present application are all commercially available.

[0065] The technical solutions of the present application are further described below through examples.

[0066] Example 1

[0067] Zinc nitrate (Zn(NO3)2·6H2O) and graphene oxide (GO) are dispersed in ethylene glycol (100mL) solvent according to a molar ratio of 5:1, and ammonia water is added to adjust the pH to 9-10 to obtain a suspension;

[0068] The suspension is transferred to a high-pressure reaction kettle and reacted at 180°C for 12 hours to obtain a ZnO / GQDs core-shell heterojunction with a core-shell structure of ZnO nanorods (diameter 5nm, length 50nm) and GQDs (size 3nm), and the XRD pattern of the ZnO / GQDs core-shell heterojunction is shown in Figure 4 ;

[0069] The ZnO / GQDs core-shell heterojunction is soaked in EDTA at 60°C for 4 hours to perform carboxyl functional modification on the surface of the GQDs, so that -COOH groups are formed on the surface of the quantum dots, and the chemical bonding with the epoxy resin is enhanced, thereby obtaining the ZnO / GQDs core-shell heterojunction with the surface modified -COOH groups;

[0070] The ZnO / GQDs core-shell heterojunction with surface modification-COOH group was dispersed in the epoxy resin at a proportion of 10 wt%, ultrasonically homogenized to obtain a ZnO / GQDs heterojunction reinforced epoxy layer raw material;

[0071] The ZnO / GQDs heterojunction reinforced epoxy layer raw material was coated on the Q235 carbon steel substrate, and cured at 80°C for 1 hour to obtain a substrate loaded with a ZnO / GQDs heterojunction reinforced epoxy layer, with a thickness of 80 μm.

[0072] Comparative Example 1

[0073] The traditional zinc-rich coating was prepared by the traditional physical mixing method:

[0074] (1) The raw materials were prepared according to the following mass proportions: high-purity spherical zinc powder (particle size 5-10 μm), 65 wt% (high content leading to brittleness); bisphenol A type epoxy resin (E-44), 20-25 wt%; dimethylbenzene and n-butanol mixed solvent (7:3 by volume) as diluent, the viscosity was adjusted to 2000-3000 cP; polyamide resin (650 type) as curing agent, the amount was 25 wt% of the epoxy resin.

[0075] (2) The zinc powder and epoxy resin were added to a high-speed disperser in proportion, stirred at 1200 rpm for 30 minutes to form a preliminary mixed slurry; the diluent was added to adjust the viscosity, and ultrasonic treatment was performed for 15 minutes (power 300 W) to eliminate air bubbles; the polyamide resin was added before curing, and manual stirring was performed for 5 minutes; then the slurry was sprayed onto the Q235 carbon steel substrate, and the wet film thickness was 200 μm; gradient curing: after air drying at room temperature for 2 hours, baking at 80°C for 1 hour to obtain the traditional zinc-rich coating prepared by the traditional physical mixing method.

[0076] The traditional zinc-rich coating prepared by the traditional physical mixing method of Comparative Example 1 had no dynamic chemical bond design, low crosslinking density, and the key defect was weak interfacial bonding, the zinc powder and the resin were only physically adsorbed, and the interfacial bonding energy was only 1.7 J / m 2 ; high oxygen permeability, zinc powder accumulation porosity > 15%, oxygen permeability up to 5.6 x 10 -12 cm 2 / s; self-repairing was missing, and there was no dynamic bond or microcapsule design, which could not be repaired after damage.

[0077] The ZnO / GQDs heterojunction reinforced epoxy layer on the surface of the substrate of Example 1 was subjected to XPS analysis, and the results are shown in Figure 1 It can be seen that the carboxyl groups on the surface of the GQDs were successfully grafted.

[0078] The ZnO / GQDs heterojunction enhanced epoxy layer of the substrate surface of Example 1 and the conventional zinc-rich coating of Comparative Example 1 were subjected to current density, oxygen permeability, interface binding energy and salt fog time performance tests, and the results are shown in Table 1.

[0079] Table 1 Performance comparison of ZnO / GQDs heterojunction enhanced epoxy layer and conventional zinc-rich coating

[0080] Performance parameters Comparative Example 1 Traditional zinc-rich coating Example 1 Coating Test standards Cathodic protection current density (pA / cm 2 )]> 2.3 8.5 ASTM G59 Oxygen permeability (cm 2 / s) 5.6 x 10 -12 ]]> 1.2 x 10 -14 ]]> ISO 15105-1 Interfacial bond energy (J / m 2 ])]] 1.7 2.8 AFM force curve analysis Salt fog resistance time (h) 1200 5000 ISO 9227

[0081] As can be seen from Table 1, the cathodic protection current density of the ZnO / GQDs heterojunction enhanced epoxy layer of the substrate surface of Example 1 is 8.5 μA / cm 2 , the oxygen permeability is reduced to 1.2 x 10 -14 cm 2 / s, the salt fog time reaches 5000 h, which is more than 3 times that of the conventional zinc-rich coating, and the interface binding energy of the heterojunction is 2.8 J / m 2 , which is 65% higher than that of the conventional zinc-rich coating prepared by the conventional physical mixing method. This embodiment significantly improves the permeability and electrochemical protection performance of the coating through molecular-level interface design, laying a foundation for subsequent multi-level structure integration.

[0082] Example 2

[0083] An epoxy prepolymer containing silane coupling agent (KH-550, content of 3 wt%) was sprayed on the substrate surface of Example 1 carrying the ZnO / GQDs heterojunction enhanced epoxy layer to obtain a liquid film with a thickness of 200 μm, which was scanned using a femtosecond laser with a wavelength of 1030 nm (pulse width of 200 fs, energy density of 2 J / cm 2 ). Local phase separation was induced by photothermal effect to generate a double-scale pore network with a primary pore diameter of 200-500 nm and a secondary pore diameter of 20-50 nm. Then perfluoroalkyl silane (FAS-17) was dissolved in an ethanol solution (concentration of 0.5 wt%) and sprayed on the inner wall of the pores of the double-scale pore surface layer, which was then treated at 80 °C for 1 hour to form a polysulfide rubber / polyurethane dynamic chemical bond self-healing layer with a thickness of 60 μm.

[0084] The polysulfide rubber / polyurethane dynamic chemical bond self-healing layer obtained in Example 2 was subjected to performance tests, and the dynamic behavior of salt fog droplets on the surface of the polysulfide rubber / polyurethane dynamic chemical bond self-healing layer is shown in Figure 2 . The performance test results show that the low surface energy is 12 mN / m, the contact angle is 154°, the rolling angle is <3°, the salt fog droplet retention time is shortened to 0.8 seconds, which is 90% less than that on a smooth surface, and the salt fog deposition rate is 1.5 mL / (80 cm 2• h) under conditions where no liquid film remains on the coating surface, the corrosion rate is reduced to 0.002 mm / year (ASTM B117).

[0085] Due to the biomimetic hierarchical porous structure of the self-healing layer of polysulfide / polyurethane dynamic chemical bonds, the penetration and retention of salt spray droplets are significantly inhibited through the synergistic effect of capillary force resistance and Laplace pressure difference.

[0086] Example 3

[0087] DMDB and HDI were mixed in a molar ratio of 1:2, 10 wt% (i.e. 10 wt% of the total mass of DMDB and HDI) of DBTDL catalyst was added, and the reaction was carried out at 80°C for 6 hours under nitrogen protection to generate a linear polymer with dynamic disulfide bonds (polysulfide urethane copolymer);

[0088] The UPy monomer and the polysulfide urethane copolymer were mixed in a molar ratio of 1:10 to obtain a mixture, and then the mixed polymer was dispersed in the epoxy resin at a proportion of 10 wt%, coated on the surface of the polysulfide / polyurethane dynamic chemical bond self-healing layer obtained in Example 2, and after gradient curing treatment at 80-160°C, an interpenetrating network structure was formed. The gradient curing treatment is as follows: gradually increasing the temperature from 80°C to 160°C at a rate of 5°C / min, and keeping each temperature step (80°C, 120°C, 160°C) for 30 minutes, so that the dynamic disulfide bonds are fully exchanged and the hydrogen bond network is orderly reorganized. Finally, the furnace is cooled to room temperature to obtain a polycaprolactone-based laser structured superhydrophobic surface layer with a thickness of 40 μm.

[0089] The chemical and mechanical properties of the dynamic self-healing network of the polycaprolactone-based laser structured superhydrophobic surface layer prepared in Example 3 were tested, and the results are shown in Table 2.

[0090] Table 2 Chemical and mechanical property test results of the dynamic self-healing network

[0091] Parameter Value Test method Disulfide bond exchange activation energy (kJ / mol) 45 Differential scanning calorimetry (DSC) Hydrogen bond dissociation energy (kJ / mol) 25 Molecular dynamics simulation Crack healing rate (24 h) 92% Optical microscope observation (ASTM D714) Tensile strength recovery rate 88% Universal material testing machine (ASTM D638)

[0092] When the coating is damaged, the environmental humidity (RH>60%) triggers the dynamic exchange reaction of the disulfide bond, and at the same time the hydrogen bond network releases stress through reversible dissociation-recombination to achieve crack closure. The healing process follows a first-order kinetic equation:

[0093]

[0094] In the formula, C is the crack width, k is the healing rate constant, t refers to the healing time, that is, the time experienced by the coating from the damaged state to the completion of repair; A is the pre-exponential factor (also called the frequency factor); E arepresenting the activation energy; R is the universal gas constant, which is a fixed physical constant with a value of 8.314 J / (mol·K); T corresponds to the thermodynamic temperature, i.e. the absolute temperature in the service environment of the coating. As can be seen from Table 2, in a humidity RH = 70% environment, the coating with a crack width of 50 μm constructed by mechanical scribing has a healing rate > 90% within 24 hours, and the tensile strength after healing is restored to 88%, the exchange activation energy of disulfide bond measured by differential scanning calorimetry (DSC) is 45 kJ / mol, and the molecular dynamics simulation shows that the hydrogen bond dissociation energy is 25 kJ / mol, indicating that the high humidity at room temperature can trigger the repair. This is because the dynamic bond synergy mechanism of the polycaprolactone-based laser structured superhydrophobic surface layer realizes efficient self-healing of the coating damage. Combined with the overall coating test data, it is verified by ISO 9227 standard that the salt spray resistance time reaches 5000 hours (more than 3 times that of traditional coatings), the low-frequency impedance modulus value of EIS test reaches 10 11 Ω·cm²; the contact angle is 154°, the rolling angle is < 3°, the salt spray droplet retention is only 0.8 seconds, and the oxygen permeation rate is as low as 1.2 x 10 -14 cm 2 / s. Combined with the self-repairing performance in Table 2, the coating realizes the synergy of anti-permeation, hydrophobicity and self-healing, which is significantly better than traditional coatings.

[0095] Example 4

[0096] The preparation of ZnO / GQDs heterojunction enhanced epoxy layer is the same as that in Example 1.

[0097] The preparation of polysulfide / polyurethane dynamic chemical bond self-repairing layer is the same as that in Example 2.

[0098] Preparation of polycaprolactone-based laser structured superhydrophobic surface layer:

[0099] The BTA-coated pH-sensitive microcapsules were prepared by interfacial polymerization with polyurea as the shell material and BTA as the core material. Specifically, benzotriazole (BTA) was dissolved in ethyl acetate as the oil phase, and polyurea precursor (such as diisocyanate) was dissolved in deionized water as the water phase; the oil phase was slowly injected into the water phase, and emulsified at a high speed of 15000 rpm for 30 minutes to form a stable emulsion; the temperature was raised to 60°C, and the interfacial polymerization was initiated by keeping the temperature for 2 hours; the polyurea was crosslinked into a shell at the oil-water interface; after the reaction, centrifugal separation was performed, and ethanol was used for washing 3 times; after vacuum drying, the pH-sensitive microcapsules with an average particle size of 10 μm were obtained, and the SEM image is shown in Figure 3 It can be seen that the average particle size is 10 μm;

[0100] DMDB and HDI were mixed in a molar ratio of 1:2, 10 wt% DBTDL catalyst was added, and the reaction was carried out at 80°C for 6 hours under nitrogen protection to generate a polysulfide urethane copolymer;

[0101] The UPy monomer, polythiourethane copolymer are mixed in a 1:10 molar ratio, then the pH-sensitive microcapsules are added (the amount of addition is 3 wt% of the mass of the UPy monomer, polythiourethane copolymer), to obtain a mixture, then the mixed polymer is dispersed in the epoxy resin at a proportion of 10 wt%, coated on the surface of the polysulfide / polyurethane dynamic chemical bond self-repairing layer obtained in Example 2, and after gradient curing treatment (treatment method is the same as above) at 80-160℃, an interpenetrating network structure is formed, to obtain a polycaprolactone-based laser-structured super-hydrophobic surface layer, with a thickness of 40μm;

[0102] The ZnO / GQDs heterojunction-enhanced epoxy layer, the polysulfide / polyurethane dynamic chemical bond self-repairing layer and the polycaprolactone-based laser-structured super-hydrophobic surface layer constitute an environment-responsive intelligent anti-corrosion coating based on three-level synergistic dynamic self-repairing.

[0103] The environment-responsive intelligent anti-corrosion coating based on three-level synergistic dynamic self-repairing prepared in Example 4 is subjected to performance testing, and the results show that when the local pH is reduced to below 4 or the temperature is >50℃, the microcapsules are broken to release BTA, and a dense passivation film is generated with the metal substrate (confirmed by UV-Vis at a wavelength of 259nm as ZnO·BTA composite); the coating surface morphology is restructured by heat shrinkage, and the hydrophobicity is improved by 15%. The integrated coating has a salt spray resistance time of 5000 hours (ISO 9227), and a low-frequency impedance modulus of 10 11 Ω·cm 2 (EIS test).

[0104] The environment-responsive intelligent anti-corrosion coating based on three-level synergistic dynamic self-repairing of the present application realizes a technical leap from passive protection to active intervention, and provides an innovative solution for long-term corrosion protection under complex working conditions.

[0105] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A salt spray corrosion protective coating based on three-stage synergistic dynamic self-repairing, characterized in that, It includes, from bottom to top, a zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer, a polysulfide rubber / polyurethane dynamic chemical bond self-healing layer, and a polycaprolactone-based laser-structured superhydrophobic surface layer.

2. The salt spray corrosion resistant coating based on three-stage synergistic dynamic self-repairing according to claim 1, characterized in that, The thickness of the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer is 80 μm, the thickness of the polysulfide rubber / polyurethane dynamic chemical bond self-healing layer is 60 μm, and the thickness of the polycaprolactone-based laser-structured superhydrophobic surface layer is 40 μm.

3. A process for the preparation of a salt spray corrosion protective coating based on the three-stage synergistic dynamic self-repairing according to any one of claims 1-2, characterized in that, Zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer, polysulfide rubber / polyurethane dynamic chemical bond self-healing layer and polycaprolactone-based laser-structured superhydrophobic surface layer were prepared by spraying raw materials onto the substrate in sequence. After each layer was cured, a substrate carrying a salt spray anti-corrosion coating based on three-level synergistic dynamic self-healing was obtained.

4. The method for preparing the salt spray corrosion resistant coating based on three-level synergistic dynamic self-repairing according to claim 3, characterized in that, The method for preparing the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer is as follows: Zinc nitrate and graphene oxide were dispersed in ethylene glycol solvent, and ammonia was added to adjust the pH to 9-10 to obtain a suspension. The suspension was transferred to a high-pressure reactor for reaction to obtain a zinc oxide / graphene quantum dot core-shell heterostructure. The zinc oxide / graphene quantum dot core-shell heterojunction was treated by immersion in ethylenediaminetetraacetic acid to obtain a zinc oxide / graphene quantum dot core-shell heterojunction with surface modified with -COOH groups. The zinc oxide / graphene quantum dot core-shell heterojunction with surface-modified -COOH groups was dispersed in epoxy resin and ultrasonically homogenized to obtain a zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer raw material. The zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer raw material is coated onto the substrate, and after curing, a substrate carrying the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer is obtained. In the method for preparing the zinc oxide / graphene quantum dot heterojunction reinforced epoxy layer, The molar ratio of zinc nitrate to graphene oxide is 5:1; The reaction temperature in the high-pressure reactor was 180℃, and the reaction time was 12 hours. The soaking treatment was performed at a temperature of 60°C for 4 hours. The zinc oxide / graphene quantum dot core-shell heterojunction with surface-modified -COOH groups is dispersed in epoxy resin at a ratio of 10wt%. The curing process is carried out at a temperature of 80°C for 1 hour.

5. The method for preparing the salt spray corrosion resistant coating based on three-level synergistic dynamic self-repairing according to claim 3, characterized in that, The preparation method of the polysulfide rubber / polyurethane dynamic chemical bond self-healing layer is as follows: An epoxy prepolymer containing a silane coupling agent is sprayed onto the surface of a substrate carrying a zinc oxide / graphene quantum dot heterostructure-reinforced epoxy layer to obtain a liquid film. The liquid film is then processed using femtosecond laser-induced self-assembly technology to obtain a dual-scale porous surface layer. Subsequently, perfluoroalkyl silane is dissolved in an ethanol solution and sprayed onto the inner wall of the pores of the dual-scale porous surface layer. After curing, a polysulfide rubber / polyurethane dynamic chemical bond self-healing layer is formed. In the preparation method of the polysulfide rubber / polyurethane dynamic chemical bond self-healing layer, The concentration of the silane coupling agent in the epoxy prepolymer is 3 wt%; The femtosecond laser-induced self-assembly technology adopts a femtosecond laser with a wavelength of 1030 nm, a pulse width of 200 fs, and an energy density of 2 J / cm 2 ; The curing process is carried out at a temperature of 80°C for 1 hour.

6. The method for preparing the salt spray corrosion resistant coating based on three-level synergistic dynamic self-repairing according to claim 3, characterized in that, The method for preparing the polycaprolactone-based laser-structured superhydrophobic surface layer is as follows: 4,4'-dimercaptodibenzyl ether is mixed with hexamethylene diisocyanate, dibutyl tin dilaurate is added, and the mixture is reacted under nitrogen protection to form a polysulfur urethane copolymer; urea-based pyrimidinone monomers are mixed with the polysulfur urethane copolymer, and then the mixed polymer is dispersed in an epoxy resin to coat the surface of a polysulfide rubber / polyurethane dynamic chemical bond self-repairing layer, and a polycaprolactone-based laser-structured super-hydrophobic surface layer is obtained after curing treatment; in the preparation method of the polycaprolactone-based laser-structured super-hydrophobic surface layer, the molar ratio of 4,4'-dimercaptodibenzyl ether to hexamethylene diisocyanate is 1:2; the amount of dibutyl tin dilaurate added in the mixture of 4,4'-dimercaptodibenzyl ether and hexamethylene diisocyanate is 10 wt%; the reaction under nitrogen protection is carried out at 80°C for 6 hours; the mixed polymer is dispersed in the epoxy resin at a proportion of 10 wt%; the curing treatment is gradient curing treatment, and the treatment temperature is 80-160°C.

7. A three-stage synergistic dynamic self-healing based environmentally responsive smart anticorrosive coating characterized in that, In the polycaprolactone-based laser-structured super-hydrophobic surface layer of the salt spray corrosion-resistant coating based on three-level synergistic dynamic self-repairing according to any one of claims 1-2, microcapsules with benzotriazole as core material and polyurea as shell material are added.

8. The environment-responsive smart anticorrosion coating based on three-level synergistic dynamic self-healing according to claim 7, characterized in that, The average particle size of the microcapsules is 10 μm, and the amount of microcapsules added is 3 wt% of the mass of urea-based pyrimidinone monomers and polysulfur urethane copolymer.

9. Application of the salt spray corrosion-resistant coating based on three-level synergistic dynamic self-repairing according to any one of claims 1-2 in the corrosion protection of marine engineering equipment.

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