A corrosion-resistant lightweight radar absorbing coating

Abstract

The present invention relates to a corrosion-resistant, lightweight radar-absorbing coating, belonging to the technical field of absorbing coating preparation. Specifically, the coating comprises a topcoat component and an innercoat component. The topcoat component includes the following raw materials: a conductive polymer-epoxy matrix A, composite absorbing particles A, a corrosion inhibitor, and a solvent; the innercoat component includes the following raw materials, in parts by weight: a conductive polymer-epoxy matrix B, composite absorbing particles B, and a solvent. The topcoat utilizes a polypyrrole powder / epoxy matrix composite with a ferrite-based absorber and nano-silicon carbide. The high magnetic permeability of the ferrite and the dielectric loss of the SiC combine to block the conductive network and cover high-frequency waves. The innercoat utilizes a polypyrrole fiber / epoxy matrix composite with carbonyl iron powder / SiC, leveraging the high hysteresis loss of the carbonyl iron and the SiC support structure to achieve low-frequency absorption. Through a gradient conductive structure design and multi-component synergistic optimization, the radar-absorbing coating achieves broadband absorption, corrosion resistance, and lightweight properties.

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 applications, radar detection technology is widely used in critical scenarios such as target reconnaissance, air defense early warning, and communication interference monitoring. To effectively evade radar detection, radar-absorbing coatings have emerged. Radar-absorbing coatings absorb electromagnetic energy projected onto their surfaces, converting it into heat or other forms of energy dissipation, thereby significantly reducing the target's radar cross section and improving its stealth capabilities.

[0003] With the continuous advancement of technology, the performance requirements for radar-absorbing coatings are also increasing. In addition to excellent absorbing properties, they are also required to have excellent corrosion resistance and lightweight properties. In harsh environments such as the ocean, coatings must withstand the erosion of various factors such as salt spray, moisture, and ultraviolet rays. Poor corrosion resistance can cause the coating layer to fall off and reduce absorbing performance, seriously affecting the service life and stealth effectiveness of the equipment. At the same time, lightweight properties are crucial for improving equipment maneuverability and fuel economy. Especially in the aerospace field, reducing weight means higher payload and lower energy consumption.

[0004] However, existing radar-absorbing coatings still have numerous shortcomings. To achieve excellent absorption performance, some coatings use a large amount of metal-based fillers, which increases the coating's density and makes it difficult to meet lightweight requirements. Furthermore, metal-based fillers are susceptible to electrochemical corrosion in corrosive environments, reducing the coating's corrosion resistance. Furthermore, while some coatings have some absorbency, their absorption frequency band is narrow, making them incapable of adapting to complex and changing electromagnetic environments. Some coatings also experience degradation of their absorption performance over long periods of use due to unstable internal conductive networks.

[0005] Therefore, developing a new radar absorbing coating with broadband absorption, corrosion resistance and light weight properties has important practical significance. Based on the above statement, the present application provides a corrosion-resistant and lightweight radar absorbing coating. Summary of the Invention

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

[0007] A corrosion-resistant lightweight radar absorbing coating, comprising a surface coating component and an inner coating component, wherein the surface coating component comprises the following raw materials in parts by weight: 65-70 parts of a conductive polymer-epoxy matrix A, 10-15 parts of composite absorbing particles A, 3-5 parts of a corrosion inhibitor, and 5-8 parts of a solvent;

[0008] The inner coating composition includes the following raw materials in parts by weight: 65-70 parts of conductive polymer-epoxy matrix B, 20-25 parts of composite absorbing particles B, and 8-10 parts of solvent;

[0009] 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.

[0010] Furthermore, the conductive polymer-epoxy matrix A is specifically prepared by the following steps:

[0011] Add polypyrrole powder to the solvent and ultrasonically mix for 20-30 minutes to obtain a polypyrrole dispersion; then heat the epoxy resin to 35-45°C, add the polypyrrole dispersion, and stir at 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 a conductive polymer-epoxy matrix A.

[0012] Further preferably, the conductive polymer-epoxy matrix A is prepared by the following steps:

[0013] Polypyrrole powder was added to a solvent (n-butanol) at a mass-to-volume ratio of 0.02 g: (1-2) mL, and ultrasonically mixed for 20-30 minutes to obtain a polypyrrole dispersion. Subsequently, the epoxy resin was heated to 35-45°C, the polypyrrole dispersion was added, and the mixture was stirred at 300-500 rpm in a magnetic stirrer for 10-15 minutes. The system temperature was then raised to 60-65°C, and stirring was continued for 2-3 hours to obtain a conductive polymer-epoxy matrix A.

[0014] Furthermore, the mass ratio of the polypyrrole powder to the epoxy resin is (1-1.5):60.

[0015] Furthermore, the polymer-epoxy matrix B is specifically prepared by the following steps:

[0016] A1. Add hexadecyltrimethylammonium bromide to an HCl solution, stir at 0-4°C for 20-30 minutes, then add pyrrole monomer to the system, continue stirring for 20-30 minutes, then dropwise add ammonium persulfate solution to the system, continue stirring at 0-4°C for 20-24 hours, filter, wash, and dry to obtain polypyrrole fiber;

[0017] 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.

[0018] Further preferably, the polymer-epoxy matrix B is prepared by the following steps:

[0019] A1. Hexadecyltrimethylammonium bromide was added to a 1 mol / L HCl solution at a mass volume ratio of 1 g:100 mL, and the mixture was stirred at 30-90 rpm for 20-30 minutes at 0-4° C., followed by adding pyrrole monomer to the system and continuing to stir for 20-30 minutes. Then, a 0.025 mol / L ammonium persulfate solution was added dropwise to the system within 30-40 minutes, and the mixture was stirred at 0-4° C. for 20-24 hours. The filtrate was collected by suction and washed alternately with deionized water and anhydrous ethanol, and then dried in vacuo at 60-80° C. to constant weight to obtain polypyrrole fiber.

[0020] In the above reaction process, ammonium persulfate (APS) is used as an oxidant to oxidize the pyrrole monomer to generate cationic free radicals. These free radicals form dimers through coupling reactions, gradually initiating chain growth to generate polypyrrole chains. In an acidic environment, hexadecyltrimethylammonium bromide (CTAB) forms spherical micelles, whose hydrophobic core provides a polymerization microenvironment for the pyrrole monomer, and the hydrophilic shell reacts with H + Binding to the regulatory reaction interface, H + Positive charges are introduced into the polypyrrole chain to enhance the π-π conjugation between molecular chains, promote the directional arrangement and polymerization of pyrrole monomers along the micelle surface, and form a fiber structure. Ice bath conditions inhibit the excessive decomposition of APS and slow down the rate of free radical generation, so that the pyrrole monomers can be controlled and polymerized within the micelle template, avoiding random cross-linking.

[0021] A2. Heat the epoxy resin to 35-45°C, add the polypyrrole fiber obtained in step A1, stir at 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 a conductive polymer-epoxy matrix B.

[0022] Furthermore, in step A1, the usage ratio of hexadecyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution is (0.6-0.8) g: (0.3-0.4) g: (150-200) mL.

[0023] Furthermore, in step A2, the mass ratio of polypyrrole fiber to epoxy resin is (2-3):60.

[0024] Furthermore, 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).

[0025] Furthermore, the ferrite-based absorber is Ni-Zn ferrite and / or Li-Zn ferrite.

[0026] In the above technical solution, ferrite-based absorbers such as Ni-Zn ferrite and Li-Zn ferrite, with their high magnetic permeability and insulating properties, can reduce conductive pathways. When compounded with nano-silicon carbide, the ceramic properties of silicon carbide can synergistically block the conductive network in the surface coating components.

[0027] Furthermore, the corrosion inhibitor is at least one of polyaspartic acid, polyvinyl pyrrolidone and epoxy silane.

[0028] In the above technical solution, the corrosion inhibitor is preferentially adsorbed at the coating defects to form a local high-impedance area and disperse the corrosion current density.

[0029] Furthermore, 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).

[0030] Furthermore, the solvent is at least one of n-butanol, xylene and butyl acetate.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application achieves broadband absorption, corrosion resistance and lightweight performance of radar absorbing coatings through gradient conductive structure design and multi-component collaborative optimization. The surface layer is made of a composite of polypyrrole powder / epoxy matrix, ferrite-based absorber and nano-silicon carbide. The high magnetic permeability of ferrite and the dielectric loss of SiC are used to block the conductive network and cover high-frequency absorption. The inner layer is made of a composite of polypyrrole fiber / epoxy matrix and carbonyl iron powder / SiC, and the high hysteresis loss of carbonyl iron and the SiC support structure are used to achieve low-frequency absorption. The gradient conductive design optimizes impedance matching, expands the absorption bandwidth, and has a good absorption effect. At the same time, polypyrrole materials are used in the matrix for reinforcement, reducing the use of traditional metal-based fillers, reducing costs, and achieving lightweighting.

[0033] 2. This application uses polypyrrole material to reinforce epoxy resin as the matrix component of the coating, which can make the inner and outer layer components have a stable bonding effect, and utilizes 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 regulates the conductivity of the inner and outer layers through absorbers and corrosion inhibitors to form a composite coating structure with low conductivity on the surface and high conductivity on the inner layer. The silicon carbide component in the composite absorbing particle A can block the conductive network, and the conductive polymer-epoxy matrix A provides dielectric loss, which inhibits the formation of the conductive network while improving the anti-corrosion performance, thereby extending the service life of the absorbing coating in harsh environments such as the ocean. In the composite absorbing particle B, the conductivity of carbonyl iron powder is better than that of ferrite, which is also conducive to forming a gradient conductive structure. At the same time, the two absorbing particles are used in combination, with ferrite dominating the high frequency and carbonyl iron covering the low frequency, which can better improve the absorbing effect of the coating in the entire frequency band. Corrosion inhibitors are also added to the outer layer components, which have the effect of isolating chloride ion and O2 penetration, reducing corrosion current density, and reducing local current concentration. At the same time, it can also avoid the conductive polymer and composite absorbing particles from forming a strong conductive network that leads to enhanced electromagnetic wave reflection, so that the coating material can better realize the absorbing function while achieving the anti-corrosion effect. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0035] The raw materials used in the following specific embodiments are all chemically pure. In addition, the particle size of the nano-silicon carbide used is 50-100 nm; the average particle size of the carbonyl iron powder used is 3-5 μm; the model of the epoxy resin used is E-44; Ni-Zn ferrite: nickel-zinc ferrite magnetic powder, Chunguang Magnetoelectric, model CN4012; polyvinyl pyrrolidone: Shanghai McLean PVP40000, purity >99%; epoxy silane: Dow Corning Z-6040.

[0036] Example 1

[0037] The present application provides a corrosion-resistant lightweight radar absorbing coating, which is composed of a surface coating component and an inner coating component, wherein the surface coating component includes the following raw materials in parts by weight: 65 parts of conductive polymer-epoxy matrix A, 10 parts of composite absorbing particles A, 3 parts of corrosion inhibitor, and 5 parts of solvent;

[0038] The conductive polymer-epoxy matrix A used is specifically prepared by the following steps:

[0039] Polypyrrole powder was added to n-butanol solvent at a mass-to-volume ratio of 0.02 g:1 mL, and ultrasonic mixing was performed for 20 minutes at an ultrasonic frequency of 28 kHz to obtain a polypyrrole dispersion. Subsequently, epoxy resin was heated to 35°C, the polypyrrole dispersion was added, and stirring was carried out in a magnetic stirrer at 300 rpm for 10 minutes. The system temperature was then raised to 60°C and stirring was continued for 2 hours to obtain a conductive polymer-epoxy matrix A. The mass ratio of polypyrrole powder to epoxy resin was 1:60.

[0040] The composite absorbing particles A used are obtained by mixing a ferrite-based absorber and nano-silicon carbide in a mass ratio of 6:3, and the ferrite-based absorber is Ni-Zn ferrite;

[0041] The corrosion inhibitor used is epoxy silane.

[0042] Wherein, the solvent used is n-butanol.

[0043] The polymer-epoxy matrix B used is specifically prepared by the following steps:

[0044] A1. Cetyltrimethylammonium bromide was added to a 1 mol / L HCl solution at a mass volume ratio of 1 g:100 mL, and the mixture was stirred at 90 rpm for 20 minutes at 0°C. Subsequently, a pyrrole monomer was added to the system and the stirring was continued for 20 minutes. Subsequently, a 0.025 mol / L ammonium persulfate solution was added dropwise to the system within 30 minutes, and the mixture was stirred at 0°C for 20 hours. The filtered product was collected by suction and washed alternately with deionized water and anhydrous ethanol, and then dried under vacuum at 60°C to constant weight to obtain polypyrrole fiber; the amount ratio of cetyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution was 0.6 g:0.3 g:150 mL;

[0045] A2. Heat the epoxy resin to 35°C, add the polypyrrole fiber obtained in step A1, and stir at 300 rpm in a magnetic stirrer for 15 minutes. Then, raise the system temperature to 60°C and continue stirring for 2 hours to obtain a conductive polymer-epoxy matrix B; the mass ratio of polypyrrole fiber to epoxy resin is 2:60.

[0046] The composite wave-absorbing particles B used are obtained by mixing carbonyl iron powder and nano-silicon carbide in a mass ratio of 6:3.

[0047] Wherein, the solvent used is n-butanol.

[0048] Example 2

[0049] The present application provides a corrosion-resistant lightweight radar absorbing coating, which is composed of a surface coating component and an inner coating component, wherein the surface coating component includes the following raw materials in parts by weight: 68 parts of conductive polymer-epoxy matrix A, 13 parts of composite absorbing particles A, 4 parts of corrosion inhibitor, and 7 parts of solvent;

[0050] The conductive polymer-epoxy matrix A used is specifically prepared by the following steps:

[0051] Polypyrrole powder was added to n-butanol solvent at a mass-to-volume ratio of 0.02 g:1.5 mL, and ultrasonic mixing was performed for 30 minutes at an ultrasonic frequency of 28 kHz to obtain a polypyrrole dispersion. Subsequently, epoxy resin was heated to 40°C, the polypyrrole dispersion was added, and stirring was carried out in a magnetic stirrer at 400 rpm for 15 minutes. The system temperature was then raised to 65°C and stirring was continued for 3 hours to obtain a conductive polymer-epoxy matrix A. The mass ratio of polypyrrole powder to epoxy resin was 1.2:60.

[0052] The composite absorbing particles A used are obtained by mixing a ferrite-based absorber and nano-silicon carbide in a mass ratio of 6.5:3.5, and the ferrite-based absorber is Ni-Zn ferrite;

[0053] The corrosion inhibitor used is epoxy silane.

[0054] Wherein, the solvent used is n-butanol.

[0055] The inner coating composition includes the following raw materials in parts by weight: 68 parts of conductive polymer-epoxy matrix B, 23 parts of composite absorbing particles B, and 9 parts of solvent;

[0056] The polymer-epoxy matrix B used is specifically prepared by the following steps:

[0057] A1. Cetyltrimethylammonium bromide was added to a 1 mol / L HCl solution at a mass volume ratio of 1 g:100 mL, and the mixture was stirred at 90 rpm for 30 minutes at 0°C. Subsequently, a pyrrole monomer was added to the system and the stirring was continued for 30 minutes. Subsequently, a 0.025 mol / L ammonium persulfate solution was added dropwise to the system within 30-40 minutes, and the mixture was stirred at 0°C for 24 hours. The filtrate was collected by suction filtration and the product was washed alternately with deionized water and anhydrous ethanol, and then dried in vacuo at 80°C to constant weight to obtain polypyrrole fiber; the amount ratio of cetyltrimethylammonium bromide, pyrrole monomer, and ammonium persulfate solution was 0.7 g:0.35 g:180 mL;

[0058] A2. Heat the epoxy resin to 40°C, add the polypyrrole fiber obtained in step A1, and stir at 400 rpm in a magnetic stirrer for 15 minutes. Then, raise the system temperature to 65°C and continue stirring for 3 hours to obtain a conductive polymer-epoxy matrix B; the mass ratio of polypyrrole fiber to epoxy resin is 2.5:60.

[0059] The composite wave-absorbing particles B used are obtained by mixing carbonyl iron powder and nano-silicon carbide in a mass ratio of 6.5:3.5.

[0060] Wherein, the solvent used is n-butanol.

[0061] Example 3

[0062] The present application provides a corrosion-resistant lightweight radar absorbing coating, which is composed of a surface coating component and an inner coating component, wherein the surface coating component includes the following raw materials in parts by weight: 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;

[0063] The conductive polymer-epoxy matrix A used is specifically prepared by the following steps:

[0064] Polypyrrole powder was added to n-butanol solvent at a mass-to-volume ratio of 0.02 g:2 mL, and ultrasonic mixing was performed for 30 minutes at an ultrasonic frequency of 28 kHz to obtain a polypyrrole dispersion. Subsequently, epoxy resin was heated to 45°C, the polypyrrole dispersion was added, and stirring was carried out in a magnetic stirrer at 500 rpm for 15 minutes. The system temperature was then raised to 65°C and stirring was continued for 3 hours to obtain a conductive polymer-epoxy matrix A. The mass ratio of polypyrrole powder to epoxy resin was 1.5:60.

[0065] The composite absorbing particles A used are obtained by mixing a ferrite-based absorber and nano-silicon carbide in a mass ratio of 7:4, and the ferrite-based absorber is Ni-Zn ferrite;

[0066] The corrosion inhibitor used is polyvinyl pyrrolidone.

[0067] Wherein, the solvent used is n-butanol.

[0068] The inner coating composition includes the following raw materials in parts by weight: 70 parts of conductive polymer-epoxy matrix B, 25 parts of composite absorbing particles B, and 10 parts of solvent;

[0069] The polymer-epoxy matrix B used is specifically prepared by the following steps:

[0070] A1. Cetyltrimethylammonium bromide was added to a 1 mol / L HCl solution at a mass volume ratio of 1 g:100 mL, and the mixture was stirred at 90 rpm for 30 minutes at 0°C. Subsequently, a pyrrole monomer was added to the system and the stirring was continued for 30 minutes. Subsequently, a 0.025 mol / L ammonium persulfate solution was added dropwise to the system within 30-40 minutes, and the reaction was continued at 0°C with stirring for 24 hours. The filtrate was collected by suction filtration and the product was alternately washed with deionized water and anhydrous ethanol, and then vacuum dried at 80°C to constant weight to obtain polypyrrole fiber; the amount ratio of cetyltrimethylammonium bromide, pyrrole monomer and ammonium persulfate solution was 0.8 g:0.4 g:200 mL;

[0071] A2. Heat the epoxy resin to 45°C, add the polypyrrole fiber obtained in step A1, and stir at 500 rpm in a magnetic stirrer for 15 minutes. Then, raise the system temperature to 65°C and continue stirring for 3 hours to obtain a conductive polymer-epoxy matrix B; the mass ratio of polypyrrole fiber to epoxy resin is 3:60.

[0072] The composite wave-absorbing particles B used are obtained by mixing carbonyl iron powder and nano-silicon carbide in a mass ratio of 7:4.

[0073] Wherein, the solvent used is n-butanol.

[0074] Comparative Example 1

[0075] This comparative example differs from Example 2 in 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 comprises a topcoat component and an innercoat component. The topcoat component comprises the following raw materials by weight: 68 parts conductive polymer-epoxy matrix A, 13 parts composite absorbing particles A, 4 parts corrosion inhibitor, and 7 parts solvent; the innercoat component comprises the following raw materials by weight: 68 parts conductive polymer-epoxy matrix A, 23 parts composite absorbing particles B, and 9 parts solvent.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 2 is that composite wave-absorbing particles B are used instead of composite wave-absorbing particles A.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 2 is that benzotriazole is used as the corrosion inhibitor.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 2 is that barium petroleum sulfonate is used as the corrosion inhibitor.

[0082] Performance Testing

[0083] The coating samples prepared in Examples 1-3 and Comparative Examples 1-4 were now subjected to performance testing. The coating samples from different groups were cured on the surface of a substrate. Specifically, the inner coating component was first mixed with a polyamide 650 curing agent at a curing agent to epoxy resin mass ratio of 0.8:1. After stirring for 10-15 minutes, the coating was applied to the surface of a 120 mm × 120 mm × 2 mm steel plate. The outer layer was applied thinly to a thickness of 50 μm, and the inner layer was applied thickly to a thickness of 150 μm. The coating was then dried in a vacuum oven at 0.08 MPa and 80°C for 12 hours.

[0084] Radar absorption performance test:

[0085] The radar absorption performance of the samples was tested according to the methods described in GJB 2038A-2011 and ASTM D4935. The test frequency range was 1-40 GHz, the effective absorption bandwidth was tested, the reflectivity threshold was ≤-10 dB, and the test angle was 0° (normal incidence). Specific performance test results are shown in Table 1.

[0086] Table 1

[0087]

[0088] From the results shown in Table 1 above, it can be seen that Examples 1-3 achieve broadband wave absorption better than the control example through the gradient design of low conductivity of the surface layer and high conductivity of the inner layer. That is, within the technical solution defined in this application, the polyester fiber mat material obtained has excellent comprehensive performance.

[0089] The corrosion resistance of the samples prepared in Examples 1-3 and Comparative Examples 1-4 is now tested.

[0090] Salt spray corrosion resistance test: Refer to the method described in ASTM B117, use 5wt% NaCl solution with a pH value of 6.5 as the test solution, the test temperature is 35±2℃, the treatment time is 2000 hours, and the salt spray resistance of the sample is judged by the surface blister area.

[0091] Moisture and heat resistance test: Samples from different groups are treated at 85°C and 85% RH for 1000 hours. The moisture and heat resistance of the samples is judged by the surface condition of the coating. The specific surface condition grade evaluation standards are as follows:

[0092] Grade A: No visible changes to the coating surface, maintaining the original gloss and color; no blistering, cracking, rusting or peeling; cross-hatch adhesion test level 0 (no peeling), equilibrium water absorption ≤1%.

[0093] Grade B: The coating surface is slightly discolored, with a color difference ΔE ≤ 1.5; there are a small number of microbubbles, and the total area of ​​the microbubbles is less than 5%; there are no cracks or peeling, the cross-hatch adhesion test is level 1, and the equilibrium water absorption rate is ≤ 1.5%.

[0094] Grade C: The coating surface is obviously discolored, with a color difference ΔE>1.5; the blister area accounts for 5%-15%; local cracks appear, with a crack length of ≤5 mm; the cross-hatch adhesion test is level 2, and the equilibrium water absorption rate is 1.5%-2%.

[0095] Grade D: The coating is severely discolored, with a color difference ΔE>3; the blister area is>15%; through cracks appear, the cross-hatch adhesion test is level 2, and the equilibrium water absorption rate is>2%.

[0096] Solvent resistance test: Samples from different groups were immersed in toluene solvent for 24 hours, and the mass loss rate of the samples was measured to determine the solvent resistance of the samples.

[0097] Each group of samples was tested 5 times, and the average value was recorded. The specific test results are shown in Table 2.

[0098] Table 2

[0099]

[0100] As can be seen from the results in Table 2, the samples in Examples 1-3 exhibited better corrosion resistance. The results in Comparative Examples 1 and 2 verified that the SiC skeleton blocked Cl⁻ penetration, and combined with the gradient conductive structure designed in the present invention, the corrosion current density was reduced. As can be seen from the results in Comparative Examples 3 and 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 corrosive media such as chloride ions. Organic acid salt corrosion inhibitors such as barium petroleum sulfonate can chelate with metal ions through carboxylates to inhibit anodic dissolution, and non-polar long chains can block the penetration of corrosive media. However, in the technical solution of the present invention, they cannot be adapted to a multi-layer composite design to exert a good anti-corrosion effect.

[0101] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0102] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in similar ways. As long as they do not deviate from the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A corrosion-resistant lightweight radar absorbing coating, characterized in that: The invention is composed of a surface layer component and an inner layer component, wherein the surface layer component comprises the following raw materials in parts by weight: 65-70 parts of conductive polymer-epoxy matrix A, 10-15 parts of composite absorbing particles A, 3-5 parts of corrosion inhibitor, and 5-8 parts of solvent; the inner layer component comprises the following raw materials in parts by weight: 65-70 parts of conductive polymer-epoxy matrix B, 20-25 parts of composite absorbing particles B, and 8-10 parts of solvent; 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 corrosion inhibitor is at least one of polyaspartic acid, polyvinyl pyrrolidone and epoxy silane.

2. The corrosion-resistant lightweight radar absorbing coating according to claim 1, characterized in that: The conductive polymer-epoxy matrix A is specifically prepared by the following steps: Add polypyrrole powder to the solvent and ultrasonically mix for 20-30 minutes to obtain a polypyrrole dispersion; then heat the epoxy resin to 35-45°C, add the polypyrrole dispersion, and stir at 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 a conductive polymer-epoxy matrix A.

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

60.

4. The corrosion-resistant lightweight radar absorbing coating according to claim 1, characterized in that: The polymer-epoxy matrix B is specifically prepared by the following steps: A1. Add hexadecyltrimethylammonium bromide to an HCl solution, stir at 0-4°C for 20-30 minutes, then add pyrrole monomer to the system, continue stirring for 20-30 minutes, then dropwise add ammonium persulfate solution to the system, continue stirring 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 lightweight radar absorbing coating according to claim 4, characterized in that: In step A1, the usage 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 lightweight radar absorbing coating according to claim 4, characterized in that: In step A2, the mass ratio of polypyrrole fiber to epoxy resin is 2-3:

60.

7. The corrosion-resistant lightweight radar absorbing coating according to claim 1, characterized in that: 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.

8. The corrosion-resistant lightweight radar absorbing coating according to claim 1, characterized in that: 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.

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

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