Corrosion-resistant light radar wave-absorbing coating

Abstract

The invention relates to a corrosion-resistant light radar wave-absorbing coating, and belongs to the technical field of wave-absorbing coating preparation, the coating is specifically composed of a surface coating component and an inner coating component, the surface coating component comprises the following raw materials: a conductive polymer-epoxy matrix A, composite wave-absorbing particles A, a corrosion inhibitor and a solvent; the inner-layer coating is prepared from the following raw materials in parts by mass: a conductive polymer-epoxy matrix B, composite wave-absorbing particles B and a solvent. The surface layer is formed by compounding a polypyrrole powder / epoxy matrix, a ferrite-based wave-absorbing agent and nano silicon carbide, and a conductive network is blocked and high-frequency wave absorption is covered through cooperation of high magnetic conductivity of ferrite and dielectric loss of SiC; the inner layer is formed by compositing a polypyrrole fiber / epoxy matrix and carbonyl iron powder / SiC, and low-frequency wave absorption is achieved through high magnetic hysteresis loss of carbonyl iron and a SiC supporting structure. Through gradient conductive structure design and multi-component collaborative optimization, broadband wave absorption, corrosion resistance and lightweight performance of the radar wave-absorbing coating are realized.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of radar absorbing coatings, and more specifically, to a corrosion-resistant lightweight radar absorbing coating. Background Art

[0002] In modern military and civilian fields, radar detection technology is widely used in key scenarios such as target reconnaissance, air defense early warning, communication interference monitoring, etc. In order to effectively avoid radar detection, the technology of radar absorbing coatings has emerged. Radar absorbing coatings can absorb the electromagnetic wave energy projected onto their surfaces, convert it into heat energy or other forms of energy and dissipate it, thereby significantly reducing the radar cross-section of the target and improving the stealth performance of the target.

[0003] With the continuous progress of technology, the performance requirements for radar absorbing coatings are also increasing day by day. In addition to having good radar absorbing performance, it is also required to have excellent corrosion resistance and lightweight characteristics. In harsh environments such as the ocean, the coating needs to withstand the erosion of various factors such as salt spray, humidity, ultraviolet rays, etc. If the corrosion resistance is not good, it will cause the coating layer to fall off and the radar absorbing performance to decline, seriously affecting the service life and stealth effect of the equipment. At the same time, the lightweight characteristic is crucial for improving the mobility and fuel economy of the equipment. Especially in the aerospace field, reducing weight means higher payload and lower energy consumption.

[0004] However, there are still many deficiencies in the existing radar absorbing coatings. Some coatings, in order to pursue good radar absorbing performance, use a large amount of metal-based fillers, resulting in an increase in the density of the coating and making it difficult to meet the lightweight requirements; moreover, the metal-based fillers are prone to electrochemical corrosion in a corrosive environment, reducing the corrosion resistance of the coating. In addition, some coatings have a certain radar absorbing ability, but the radar absorbing frequency band is narrow and cannot adapt to the complex and changeable electromagnetic environment. There are also some coatings that are prone to the problem of attenuation of radar absorbing performance due to the instability of the internal conductive network during long-term use.

[0005] Therefore, it is of great practical significance to develop a new type of radar absorbing coating with broadband radar absorption, corrosion resistance and lightweight characteristics. Based on the above statement, the present application provides a corrosion-resistant lightweight radar absorbing coating. Summary of the Invention

[0006] In order to solve the problems raised in the background art, the present application provides a corrosion-resistant lightweight radar absorbing coating.

[0007] A corrosion-resistant lightweight radar absorbing coating is composed of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 65-70 parts of conductive polymer-epoxy matrix A, 10-15 parts of composite radar absorbing particles A, 3-5 parts of corrosion inhibitor, and 5-8 parts of solvent; The inner layer coating composition comprises the following raw materials in parts by mass: 65 - 70 parts of conductive polymer - epoxy matrix B, 20 - 25 parts of composite wave - absorbing particles B, and 8 - 10 parts of solvent; Among them, the conductive polymer - epoxy matrix A is obtained by mixing polypyrrole powder and epoxy resin, and the conductive polymer - epoxy matrix B is obtained by mixing polypyrrole fiber and epoxy resin.

[0008] Further, the conductive polymer - epoxy matrix A is specifically prepared by the following steps: Add polypyrrole powder into the solvent, ultrasonically mix for 20 - 30 minutes to obtain a polypyrrole dispersion; then heat the epoxy resin to 35 - 45 °C, add the polypyrrole dispersion, stir at a rate of 300 - 500 rpm for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C, and continue to stir for 2 - 3 hours to obtain the conductive polymer - epoxy matrix A.

[0009] Further preferably, the conductive polymer - epoxy matrix A is specifically prepared by the following steps: Add polypyrrole powder into the solvent (n - butanol) according to the mass - volume ratio of 0.02 g:(1 - 2) mL, ultrasonically mix for 20 - 30 minutes to obtain a polypyrrole dispersion; then heat the epoxy resin to 35 - 45 °C, add the polypyrrole dispersion, stir in a magnetic stirrer at a rate of 300 - 500 rpm for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C, and continue to stir for 2 - 3 hours to obtain the conductive polymer - epoxy matrix A.

[0010] Further, the mass ratio of polypyrrole powder to epoxy resin is (1 - 1.5):60.

[0011] Further, the polymer - epoxy matrix B is specifically prepared by the following steps: A1. Add cetyltrimethylammonium bromide into the HCl solution, stir at 0 - 4 °C for 20 - 30 minutes, then add pyrrole monomer into the system, continue to stir for 20 - 30 minutes, then dropwise add ammonium persulfate solution into the system, and continue to stir and react at 0 - 4 °C for 20 - 24 hours, filter, wash, and dry to obtain polypyrrole fiber; A2. Heat the epoxy resin to 35 - 45 °C, add the polypyrrole fiber obtained in step A1, stir for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C, and continue to stir for 2 - 3 hours to obtain the conductive polymer - epoxy matrix B.

[0012] Further preferably, the polymer - epoxy matrix B is specifically prepared by the following steps: A1. Add cetyltrimethylammonium bromide to 1 mol / L HCl solution at a mass-volume ratio of 1 g:100 mL, stir at a rate of 30 - 90 rpm for 20 - 30 minutes at 0 - 4 °C. Subsequently, add pyrrole monomer to the system and continue stirring for 20 - 30 minutes. Then, add 0.025 mol / L ammonium persulfate solution dropwise to the system, complete the dropwise addition within 30 - 40 minutes and continue stirring and reacting at 0 - 4 °C for 20 - 24 hours. Filter by suction to collect the filtrate and wash the product alternately with deionized water and absolute ethanol. Then, dry it under vacuum at 60 - 80 °C to constant weight to obtain polypyrrole fibers. During the above reaction process, ammonium persulfate (APS) is used as an oxidant to oxidize pyrrole monomers to generate cationic radicals. These radicals form dimers through coupling reactions, gradually initiate chain growth, and generate polypyrrole chains. In an acidic environment, cetyltrimethylammonium bromide (CTAB) forms spherical micelles, whose hydrophobic core provides a polymerization microenvironment for pyrrole monomers, and the hydrophilic outer shell binds to H + to regulate the reaction interface, and H + introduces positive charges on the polypyrrole chain, enhances the π-π conjugation between molecular chains, promotes the directional arrangement and polymerization of pyrrole monomers along the micelle surface, and forms a fiber structure. The ice bath condition inhibits the excessive decomposition of APS, slows down the radical generation rate, enables the controlled polymerization of pyrrole monomers within the micelle template, and avoids random crosslinking.

[0013] A2. Heat the epoxy resin to 35 - 45 °C, add the polypyrrole fibers obtained in step A1, stir at a rate of 300 - 500 rpm in a magnetic stirrer for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C and continue stirring for 2 - 3 hours to obtain the conductive polymer-epoxy matrix B.

[0014] Furthermore, in step A1, the dosage ratio of cetyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution is (0.6 - 0.8) g:(0.3 - 0.4) g:(150 - 200) mL.

[0015] Furthermore, in step A2, the mass ratio of polypyrrole fibers to epoxy resin is (2 - 3):60.

[0016] Furthermore, the composite absorbing particles A are obtained by mixing a ferrite-based absorbing agent and nano silicon carbide in a mass ratio of (6 - 7):(3 - 4).

[0017] Furthermore, the ferrite-based absorbing agent is Ni-Zn ferrite and / or Li-Zn ferrite.

[0018] In the above technical solution, ferrite-based microwave absorbing agents such as Ni-Zn ferrite and Li-Zn ferrite have high magnetic permeability and insulating properties, which can reduce the conductive path. After being compounded with nano silicon carbide, the ceramic properties of silicon carbide can be synergistically used to block the conductive network in the surface coating components.

[0019] Further, the corrosion inhibitor is at least one of polyaspartic acid, polyvinylpyrrolidone and epoxy silane.

[0020] In the above technical solution, the corrosion inhibitor preferentially adsorbs at the coating defects, forms a local high-impedance region, and disperses the corrosion current density.

[0021] Further, the composite microwave absorbing particle B is obtained by mixing carbonyl iron powder and nano silicon carbide in a mass ratio of (6-7):(3-4).

[0022] Further, the solvent is at least one of n-butanol, xylene and butyl acetate.

[0023] In summary, the present application has the following beneficial effects: 1. Through the gradient conductive structure design and multi-component synergistic optimization, the present application realizes the broadband microwave absorption, corrosion resistance and lightweight performance of the radar absorbing coating. The surface layer is composed of polypyrrole powder / epoxy matrix, ferrite-based microwave absorbing agent and nano silicon carbide. Through the synergy of the high magnetic permeability of ferrite and the dielectric loss of SiC, the conductive network is blocked and high-frequency microwave absorption is achieved. The inner layer is composed of polypyrrole fiber / epoxy matrix, carbonyl iron powder / SiC. The high magnetic hysteresis loss of carbonyl iron and the supporting structure of SiC are used to achieve low-frequency microwave absorption. By optimizing the impedance matching through gradient conductive design, the microwave absorption bandwidth is extended, and good microwave absorption effect is obtained. At the same time, polypyrrole material is used in the matrix for reinforcement, reducing the use of traditional metal-based fillers, reducing the cost and achieving lightweight.

[0024] 2. By using polypyrrole material to enhance epoxy resin as the matrix component of the coating, the present application can make the inner and outer components have a stable bonding effect. Utilize the excellent mechanical strength and chemical corrosion resistance of epoxy resin and the conductive polymer material of polypyrrole to form a conductive path through π-π conjugation, and regulate the conductivity of the inner and outer layers through wave-absorbing agents and corrosion inhibitors to form a composite coating structure with low conductivity on the surface layer and high conductivity on the inner layer. The silicon carbide component in the composite wave-absorbing particle A can block the conductive network, and the conductive polymer-epoxy matrix A provides dielectric loss, which can inhibit the formation of the conductive network while improving the anti-corrosion performance, thereby prolonging the service life of the wave-absorbing coating in harsh environments such as the ocean. In the composite wave-absorbing particle B, the conductivity of carbonyl iron powder is better than that of ferrite, which is also beneficial to form a gradient conductive structure. At the same time, when the two wave-absorbing particles are used in combination, using ferrite to dominate the high frequency and carbonyl iron to cover the low frequency can better improve the wave-absorbing effect of the coating in the full frequency band. A corrosion inhibitor is also added to the outer component, which has the effects of isolating the penetration of chloride ions and O2, reducing the corrosion current density, and reducing the concentration of local current. At the same time, it can also prevent the formation of a strong conductive network by conductive polymers and composite wave-absorbing particles, resulting in enhanced electromagnetic wave reflection, so that the coating material can better achieve the wave-absorbing function while achieving the anti-corrosion effect. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] In the following detailed implementation manners, all raw materials used are chemically pure. In addition, the particle size of the used nano-silicon carbide is 50-100 nm; the average particle size of the used carbonyl iron powder is 3-5 μm; the model of the used epoxy resin is E-44; Ni-Zn ferrite: nickel-zinc ferrite magnetic powder, Chunguang Magnetoelectricity, model CN4012; polyvinylpyrrolidone: Shanghai Macklin PVP40000, purity >99%; epoxy silane: Dow Corning Z-6040.

[0027] Example 1 The present application provides a corrosion-resistant lightweight radar wave-absorbing coating, which is composed of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 65 parts of conductive polymer-epoxy matrix A, 10 parts of composite wave-absorbing particle A, 3 parts of corrosion inhibitor, and 5 parts of solvent. The specific preparation method of the used conductive polymer-epoxy matrix A is as follows: The polypyrrole powder was added to the n-butanol solvent at a mass-to-volume ratio of 0.02 g:1 mL, and ultrasonically mixed for 20 minutes at an ultrasonic frequency of 28 kHz to obtain a polypyrrole dispersion; subsequently, the epoxy resin was heated to 35 °C, the polypyrrole dispersion was added, and after stirring in a magnetic stirrer at a rate of 300 rpm for 10 minutes, the system temperature was raised to 60 °C and stirring continued for 2 hours to obtain the conductive polymer-epoxy matrix A; the mass ratio of the polypyrrole powder to the epoxy resin was 1:60.

[0028] The composite wave-absorbing particles A used were obtained by mixing a ferrite-based wave-absorbing agent and nano-silicon carbide in a mass ratio of 6:3, and the ferrite-based wave-absorbing agent was Ni-Zn ferrite; The corrosion inhibitor used was epoxy silane.

[0029] Among them, the solvent used was n-butanol.

[0030] The conductive polymer-epoxy matrix B used was specifically prepared by the following steps: A1. Cetyltrimethylammonium bromide was added to a 1 mol / L HCl solution at a mass-to-volume ratio of 1 g:100 mL, stirred at a rate of 90 rpm at 0 °C for 20 minutes, then pyrrole monomer was added to the system and stirring continued for 20 minutes, then a 0.025 mol / L ammonium persulfate solution was added dropwise to the system, the addition was completed within 30 minutes and stirring reaction continued at 0 °C for 20 hours, the filtrate was collected by filtration and the product was washed alternately with deionized water and absolute ethanol, and then vacuum dried at 60 °C to constant weight to obtain polypyrrole fibers; the dosage ratio of cetyltrimethylammonium bromide, pyrrole monomer and ammonium persulfate solution was 0.6 g:0.3 g:150 mL; A2. The epoxy resin was heated to 35 °C, the polypyrrole fibers obtained in step A1 were added, and after stirring in a magnetic stirrer at a rate of 300 rpm for 15 minutes, the system temperature was raised to 60 °C and stirring continued for 2 hours to obtain the conductive polymer-epoxy matrix B; the mass ratio of the polypyrrole fibers to the epoxy resin was 2:60.

[0031] The composite wave-absorbing particles B used were obtained by mixing carbonyl iron powder and nano-silicon carbide in a mass ratio of 6:3.

[0032] Among them, the solvent used was n-butanol.

[0033] Example 2 This application provides a corrosion-resistant lightweight radar-absorbing coating, which consists of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 68 parts of conductive polymer-epoxy matrix A, 13 parts of composite wave-absorbing particles A, 4 parts of corrosion inhibitor, and 7 parts of solvent; The conductive polymer-epoxy matrix A used was specifically prepared by the following steps: The polypyrrole powder was added to the n-butanol solvent according to a mass-to-volume ratio of 0.02 g:1.5 mL, and ultrasonically mixed for 30 minutes at an ultrasonic frequency of 28 kHz to obtain a polypyrrole dispersion; subsequently, the epoxy resin was heated to 40 °C, the polypyrrole dispersion was added, and after stirring in a magnetic stirrer at a rate of 400 rpm for 15 minutes, the system temperature was raised to 65 °C and stirring was continued for 3 hours to obtain the conductive polymer-epoxy matrix A; the mass ratio of the polypyrrole powder to the epoxy resin was 1.2:60.

[0034] The composite wave-absorbing particles A used were obtained by mixing a ferrite-based wave-absorbing agent and nano-silicon carbide according to a mass ratio of 6.5:3.5, and the ferrite-based wave-absorbing agent was Ni-Zn ferrite; The corrosion inhibitor used was epoxy silane.

[0035] Among them, the solvent used was n-butanol.

[0036] The inner layer coating composition comprises the following raw materials in parts by mass: 68 parts of conductive polymer-epoxy matrix B, 23 parts of composite wave-absorbing particles B, and 9 parts of solvent; The polymer-epoxy matrix B used was specifically prepared by the following steps: A1. Cetyltrimethylammonium bromide was added to a 1 mol / L HCl solution according to a mass-to-volume ratio of 1 g:100 mL, stirred at a rate of 90 rpm for 30 minutes at 0 °C, then pyrrole monomer was added to the system, and stirring was continued for 30 minutes. Subsequently, a 0.025 mol / L ammonium persulfate solution was added dropwise to the system, and the addition was completed within 30 - 40 minutes and stirring reaction was continued at 0 °C for 24 hours. The filtrate was collected by filtration and the product was washed alternately with deionized water and absolute ethanol, and then vacuum dried at 80 °C to constant weight to obtain polypyrrole fibers; the dosage ratio of cetyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution was 0.7 g:0.35 g:180 mL; A2. The epoxy resin was heated to 40 °C, the polypyrrole fibers obtained in step A1 were added, and after stirring in a magnetic stirrer at a rate of 400 rpm for 15 minutes, the system temperature was raised to 65 °C and stirring was continued for 3 hours to obtain the conductive polymer-epoxy matrix B; the mass ratio of the polypyrrole fibers to the epoxy resin was 2.5:60.

[0037] The composite wave-absorbing particles B used were obtained by mixing carbonyl iron powder and nano-silicon carbide according to a mass ratio of 6.5:3.5.

[0038] Among them, the solvent used was n-butanol.

[0039] Example 3 The present application provides a corrosion-resistant lightweight radar absorbing coating, which is composed of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 70 parts of conductive polymer-epoxy matrix A, 15 parts of composite absorbing particles A, 5 parts of corrosion inhibitor, and 8 parts of solvent; The conductive polymer-epoxy matrix A used is specifically prepared by the following steps: Add polypyrrole powder into n-butanol solvent according to the mass-volume ratio of 0.02g:2mL, ultrasonically mix for 30 minutes, and the ultrasonic frequency is 28kHz to obtain a polypyrrole dispersion; then heat the epoxy resin to 45°C, add the polypyrrole dispersion, stir in a magnetic stirrer at a rate of 500rpm for 15 minutes, then raise the system temperature to 65°C, and continue stirring for 3 hours to obtain the conductive polymer-epoxy matrix A; the mass ratio of polypyrrole powder to epoxy resin is 1.5:60.

[0040] The composite absorbing particles A used are obtained by mixing a ferrite-based absorbing agent and nano silicon carbide according to a mass ratio of 7:4, and the ferrite-based absorbing agent is Ni-Zn ferrite; The corrosion inhibitor used is polyvinylpyrrolidone.

[0041] Among them, the solvent used is n-butanol.

[0042] The inner coating component includes the following raw materials in parts by mass: 70 parts of conductive polymer-epoxy matrix B, 25 parts of composite absorbing particles B, and 10 parts of solvent; The conductive polymer-epoxy matrix B used is specifically prepared by the following steps: A1. Add cetyltrimethylammonium bromide into 1mol / L HCl solution according to the mass-volume ratio of 1g:100mL, stir at a rate of 90rpm at 0°C for 30 minutes, then add pyrrole monomer into the system, continue stirring for 30 minutes, then dropwise add 0.025mol / L ammonium persulfate solution, finish dropping within 30 - 40 minutes and continue stirring and reacting at 0°C for 24 hours, filter and collect the filtrate, and wash the product alternately with deionized water and absolute ethanol, then vacuum dry at 80°C to constant weight to obtain polypyrrole fibers; the dosage ratio of cetyltrimethylammonium bromide, pyrrole monomer and ammonium persulfate solution is 0.8g:0.4g:200mL; A2. Heat the epoxy resin to 45°C, add the polypyrrole fibers obtained in step A1, stir in a magnetic stirrer at a rate of 500rpm for 15 minutes, then raise the system temperature to 65°C, and continue stirring for 3 hours to obtain the conductive polymer-epoxy matrix B; the mass ratio of polypyrrole fibers to epoxy resin is 3:60.

[0043] The composite absorbing particles B used are obtained by mixing carbonyl iron powder and nano silicon carbide according to a mass ratio of 7:4.

[0044] Among them, the solvent used is n-butanol.

[0045] Comparative Example 1 The difference between this comparative example and Example 2 is that the same conductive polymer-epoxy matrix A is used as the coating component for both the inner and outer layers. Specifically, a corrosion-resistant lightweight radar-absorbing coating is composed of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 68 parts of conductive polymer-epoxy matrix A, 13 parts of composite radar-absorbing particles A, 4 parts of corrosion inhibitor, and 7 parts of solvent; the inner coating component includes the following raw materials in parts by mass: 68 parts of conductive polymer-epoxy matrix A, 23 parts of composite radar-absorbing particles B, and 9 parts of solvent.

[0046] Comparative Example 2 The difference between this comparative example and Example 2 is that composite radar-absorbing particles B are used instead of composite radar-absorbing particles A.

[0047] Comparative Example 3 The difference between this comparative example and Example 2 is that benzotriazole is used as the corrosion inhibitor.

[0048] Comparative Example 4 The difference between this comparative example and Example 2 is that barium petroleum sulfonate is used as the corrosion inhibitor.

[0049] Performance Test Now, performance tests are carried out on the coating samples prepared in Examples 1-3 and Comparative Examples 1-4. The coating samples in different groups are cured on the substrate surface. Specifically, first, the inner coating component is mixed with polyamide 650 curing agent. The mass ratio of the curing agent to the epoxy resin is 0.8:1. After stirring for 10-15 minutes, it is coated on the surface of a 120mm×120mm×2mm steel plate. The surface layer is thinly coated with 50μm, and the inner layer is thickly coated with 150μm. It is vacuum dried in a vacuum drying oven at 0.08 Mpa and 80°C for 12 hours.

[0050] Radar Absorbing Performance Test: Referring to the methods described in GJB 2038A-2011 and ASTM D4935, the radar absorbing performance of the samples is tested. The test frequency range is 1-40 GHz; the effective radar absorbing bandwidth of the samples is tested, and the test reflectivity threshold is ≤ -10 dB; the test angle is 0° (normal incidence). The specific performance test results are shown in Table 1 below.

[0051] Table 1

[0052] As can be seen from the results shown in Table 1 above: Through the gradient design of low surface conductivity and high inner-layer conductivity in Examples 1-3, the broadband wave absorption is better than that of the comparative examples, that is, within the scope of the technical solutions defined in this application, the polyester fiber cushion materials prepared have excellent comprehensive performance.

[0053] Now, corrosion resistance tests are carried out on the samples prepared in Examples 1-3 and Comparative Examples 1-4.

[0054] Salt spray corrosion resistance test: Referring to the method described in ASTM B117, a 5wt% NaCl solution with a pH value of 6.5 is used as the test solution, the test temperature is 35 ± 2 °C, the treatment time is 2000 hours, and the salt spray resistance of the samples is judged by the surface blistering area.

[0055] Damp heat resistance test: The samples in different groups are treated in an environment of 85 °C and 85% RH for 1000 hours, and the damp heat resistance of the samples is judged by the surface state of the coating. The specific evaluation criteria for the surface state are as follows: Grade A: There is no visible change on the coating surface, and the original luster and color are maintained; there are no blisters, cracks, rust or peeling; the cross-cut adhesion test is at level 0 (no peeling), and the equilibrium water absorption rate ≤ 1%.

[0056] Grade B: The coating surface shows slight discoloration, color difference ΔE ≤ 1.5; there are a small number of micro-bubbles, and the total area of micro-bubbles is less than 5%; there are no cracks or peeling, the cross-cut adhesion test is at level 1, and the equilibrium water absorption rate ≤ 1.5%.

[0057] Grade C: The coating surface shows obvious discoloration, color difference ΔE > 1.5; the blistering area accounts for 5% - 15%; local cracks appear, the crack length ≤ 5 mm, the cross-cut adhesion test is at level 2, and the equilibrium water absorption rate is 1.5% - 2%.

[0058] Grade D: The coating shows severe discoloration, color difference ΔE > 3; the blistering area > 15%; through cracks appear, the cross-cut adhesion test is at level 2, and the equilibrium water absorption rate > 2%.

[0059] Solvent resistance test: The samples in different groups are soaked in toluene solvent for 24 hours, and the mass loss rate of the samples is measured to judge the solvent resistance of the samples.

[0060] Each group of samples is tested 5 times, and the average value is recorded. The specific test results are shown in Table 2.

[0061] Table 2

[0062] As can be seen from the results in Table 2, the samples in Examples 1-3 showed better corrosion resistance. The results of Comparative Example 1 and Comparative Example 2 verified that the SiC skeleton blocked the penetration of Cl⁻. Combining with the gradient conductive structure designed in the present invention, the corrosion current density was reduced. As can be seen from the results of Comparative Example 3 and Comparative Example 4, benzotriazole-based nitrogen-containing heterocyclic corrosion inhibitors can form coordination bonds with the metal surface through N atoms to generate a dense passivation film, isolating corrosion media such as chloride ions. Organic acid salt corrosion inhibitors such as barium petroleum sulfonate can chelate with metal ions through carboxylate groups to inhibit anodic dissolution, and the non-polar long chain blocks the penetration of corrosion media. However, in the technical solution of the present invention, they cannot be adapted to the multi-layer composite design to exert a good anti-corrosion effect.

[0063] In the description of the specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0064] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should fall within the protection scope of the present invention.

Claims

1. A corrosion-resistant lightweight radar-absorbing coating, characterized in that, It is composed of a surface coating component and an inner coating component. Among them, the surface coating component includes the following raw materials in parts by mass: 65 - 70 parts of conductive polymer - epoxy matrix A, 10 - 15 parts of composite wave - absorbing particles A, 3 - 5 parts of corrosion inhibitor, and 5 - 8 parts of solvent; the inner coating component includes the following raw materials in parts by mass: 65 - 70 parts of conductive polymer - epoxy matrix B, 20 - 25 parts of composite wave - absorbing particles B, and 8 - 10 parts of solvent. Among them, the conductive polymer - epoxy matrix A is obtained by mixing polypyrrole powder and epoxy resin, and the conductive polymer - epoxy matrix B is obtained by mixing polypyrrole fiber and epoxy resin. The composite wave - absorbing particles A are obtained by mixing a ferrite - based wave - absorbing agent and nano - silicon carbide in a mass ratio of 6 - 7:3 - 4, and the composite wave - absorbing particles B are obtained by mixing carbonyl iron powder and nano - silicon carbide in a mass ratio of 6 - 7:3 - 4.

2. The corrosion-resistant lightweight radar-absorbing coating according to claim 1, wherein, The conductive polymer - epoxy matrix A is specifically prepared by the following steps: Add polypyrrole powder into the solvent, ultrasonically mix for 20 - 30 minutes to obtain a polypyrrole dispersion; then heat the epoxy resin to 35 - 45 °C, add the polypyrrole dispersion, stir at a rate of 300 - 500 rpm for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C, and continue stirring for 2 - 3 hours to obtain the conductive polymer - epoxy matrix A.

3. The corrosion-resistant and lightweight radar-absorbing coating according to claim 2, wherein, The mass ratio of polypyrrole powder to epoxy resin is 1 - 1.5:

60.

4. A corrosion-resistant lightweight radar-absorbing coating according to claim 1, wherein, The polymer - epoxy matrix B is specifically prepared by the following steps: A1. Add cetyltrimethylammonium bromide into the HCl solution, stir at 0 - 4 °C for 20 - 30 minutes, then add pyrrole monomer into the system, continue stirring for 20 - 30 minutes, then dropwise add ammonium persulfate solution into the system, and continue stirring and reacting at 0 - 4 °C for 20 - 24 hours, filter, wash, and dry to obtain polypyrrole fiber. A2. Heat the epoxy resin to 35 - 45 °C, add the polypyrrole fiber obtained in step A1, stir for 10 - 15 minutes, then raise the system temperature to 60 - 65 °C, and continue stirring for 2 - 3 hours to obtain the conductive polymer - epoxy matrix B.

5. The corrosion-resistant and lightweight radar-absorbing coating according to claim 4, characterized in that In step A1, the dosage ratio of cetyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution is 0.6 - 0.8 g:0.3 - 0.4 g:150 - 200 mL.

6. The corrosion-resistant and lightweight radar-absorbing coating according to claim 4, wherein In step A2, the mass ratio of polypyrrole fiber to epoxy resin is 2 - 3:

60.

7. An anti-corrosion and lightweight radar absorbing coating according to claim 1, characterized in that The corrosion inhibitor is at least one of polyaspartic acid, polyvinylpyrrolidone, and epoxy silane.

8. An anti-corrosion and lightweight radar absorbing coating according to claim 1, characterized in that, In the surface coating component and the inner coating component, the solvent is at least one of n - butanol, xylene, and butyl acetate.

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