Preparation method of self-repairing coating for fretting wear of aviation aluminum alloy

Abstract

The invention relates to the technical field of aeronautical material surface protection, and discloses a preparation method of an aeronautical aluminum alloy fretting wear self-repairing coating, which comprises the following steps: pretreatment of a matrix: sequentially carrying out alkali washing, acid washing and silanization treatment on the aeronautical aluminum alloy matrix to form a silanization conversion film layer with the thickness of 0.5-1.5 mu m; preparing a primer layer, namely mixing polyamide-imide modified epoxy resin with an adhesion promoter and an anticorrosive pigment to prepare a primer, coating the silanization conversion film layer with the primer, and curing to obtain the primer layer with the thickness of 20-30 microns; and multi-element microcapsule preparation: respectively preparing a temperature control response type repairing microcapsule, a catalytic type microcapsule and a lubricating type microcapsule. The preparation method of the aviation aluminum alloy fretting wear self-repairing coating aims at solving the problems that due to a single repairing mechanism, an existing self-repairing coating is insensitive in fretting wear response, low in repairing speed, lack of collaborative protection and poor in matching performance with an aviation aluminum alloy matrix interface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface protection of aviation materials, in particular to a preparation method of an aviation aluminum alloy fretting wear self-repairing coating. BACKGROUND

[0002] Aviation aluminum alloys are widely used in aircraft structural components, fastener connection parts and landing gear assemblies due to their high specific strength, good processing performance and corrosion resistance. However, during service, small amplitude relative motion often occurs in these parts due to factors such as vibration and thermal expansion and contraction, which leads to fretting wear. Fretting wear can form microcracks and wear pits on the contact surface, which can further induce fatigue crack propagation, seriously threatening the structural integrity and service life of the aircraft. To solve this problem, researchers have developed self-repairing protective coating technology by embedding microcapsules and other repair carriers in the coating, so that the coating can automatically release repair agents to fill cracks when damaged. Existing self-repairing coatings mainly use epoxy or polyurethane matrix, combined with a single type of microcapsule repair system, such as dicyclopentadiene / Grubbs catalyst system, siloxane condensation system or superhydrophobic repair system, etc.

[0003] However, the main defects of the existing technology are that the single repair mechanism cannot simultaneously meet the requirements of rapid response, efficient repair and continuous protection under the fretting wear conditions of aviation aluminum alloys. Specifically, on the one hand, the breaking strength of existing microcapsules is usually designed to be 150-300 MPa to adapt to high stress wear environment, but aviation aluminum alloy fretting wear belongs to low stress and small amplitude contact fatigue (stress range 30-100 MPa), which makes it difficult for microcapsules to respond in time; on the other hand, single repair agent systems such as dicyclopentadiene require specific catalysts and the polymerization time is as long as 6-24 hours, and the siloxane condensation reaction requires a temperature condition of 25-80℃, which cannot achieve rapid repair in the aviation normal temperature environment, and lacks immediate lubrication protection during the wear process, which makes the coating continue to wear before the repair agent solidifies, greatly reducing the repair effect. In addition, the existing coating matrix mostly uses pure epoxy or polyurethane system, which has poor matching with the thermal expansion coefficient of aviation aluminum alloy, and is prone to interfacial stress and peeling failure under the aviation temperature cycle of-55℃ to +150℃. SUMMARY

[0004] The purpose of the present application is to solve the problems of existing self-repairing coatings caused by single repair mechanism, such as insensitive fretting wear response, slow repair speed, lack of synergistic protection and poor interface matching with aviation aluminum alloy matrix, and a preparation method of an aviation aluminum alloy fretting wear self-repairing coating is proposed.

[0005] The technical solution of the present application to solve the above technical problems is as follows:

[0006] The application discloses a preparation method of an aviation aluminum alloy fretting wear self-repairing coating.

[0007] S1: base pretreatment, sequentially performing alkali washing, acid washing and silanization treatment on the aviation aluminum alloy base to form a silanization conversion film layer with a thickness of 0.5-1.5 microns;

[0008] S2: primer layer preparation, mixing polyamide-imide modified epoxy resin, adhesion promoter and anticorrosive pigment to prepare a primer, coating the primer on the silanization conversion film layer, and curing to obtain a primer layer with a thickness of 20-30 microns;

[0009] S3: multi-element microcapsule preparation, respectively preparing temperature control responsive repair microcapsules, catalytic microcapsules and lubricating microcapsules, the temperature control responsive repair microcapsules taking epoxy pre-polymer and mercapto curing agent as a capsule core and polyurethane / polyurea hybrid material as a capsule wall, and the breaking strength being 35-80 MPa; the catalytic microcapsules taking modified nano-silicon dioxide and tertiary amine catalyst as a capsule core and polymethyl methacrylate as a capsule wall; and the lubricating microcapsules taking poly-alpha-olefin and solid lubricant as a capsule core and melamine-m-phenylenediamine-formaldehyde copolymer resin as a capsule wall;

[0010] S4: topcoat layer preparation, mixing polyamide-imide modified epoxy resin, high-temperature engineering plastic powder, functional filler and the three kinds of microcapsules to prepare a composite functional topcoat;

[0011] S5: topcoat coating, coating the composite functional topcoat on the primer layer, and segmentally curing to obtain a composite functional topcoat layer with a thickness of 60-90 microns.

[0012] On the basis of the above technical scheme, the application can be further improved as follows.

[0013] Further, the silanization treatment in S1 is specifically as follows: the aluminum alloy base is immersed or sprayed into an alcohol-water mixed solution containing an epoxy silane coupling agent, the epoxy silane coupling agent is 3-glycidyloxypropyltrimethoxysilane, the mass concentration of the epoxy silane coupling agent is 2-3 wt%, the solvent is a mixture of ethanol and deionized water, the volume ratio of the ethanol and the deionized water is (85-95):(5-15), and the pH value is adjusted to 4.0-6.0; and after the treatment, the base is cured at 120-140 DEG C for 30-50 minutes.

[0014] Further, the primer in S2 comprises, by mass percentage: polyamide-imide modified epoxy resin 55-70%, adhesion promoter 2-4%, anticorrosive pigment 5-10%, dispersant 0.5-1.5%, and the balance solvent; the adhesion promoter is phosphatized polyamide or phosphate compound; the anticorrosive pigment is one or more of nano-zinc oxide, aluminum tripolyphosphate, or zinc-aluminum hydrotalcite; and the curing process is pre-baking at 80-100℃ for 15-25 minutes, and then curing at 180-220℃ for 1.5-2.5 hours.

[0015] Further, the core composition of the temperature-controlled responsive repair microcapsule in S3 comprises, by mass percentage: epoxy-terminated polyether prepolymer 55-65%, multifunctional epoxy resin 15-25%, aliphatic or aromatic mercapto curing agent 18-28%, and promoter 1-3%;

[0016] The epoxy value of the epoxy-terminated polyether prepolymer is 0.40-0.60 mol / 100g; the multifunctional epoxy resin is trimethylolpropane triglycidyl ether, pentaerythritol glycidyl ether, or neopentyl glycol diglycidyl ether;

[0017] The mercapto curing agent is pentaerythritol tetramercaptoacetate, trimethylolpropane trimercaptoacetate, or polymeric mercapto compound;

[0018] The average particle size of the microcapsule is 8-25μm, the glass transition temperature is -20℃ to 0℃, and the core accounts for 60-75% of the mass of the microcapsule.

[0019] Further, the core composition of the catalytic microcapsule in S3 comprises, by mass percentage: modified nano-silica 70-82%, tertiary amine catalyst 15-22%, dispersion stabilizer 3-6%, and antioxidant 1-3%;

[0020] The modified nano-silica is obtained by modifying the surface of nano-silica with amino silane or epoxy silane, and the nano-silica has a particle size of 10-30nm;

[0021] The tertiary amine catalyst is triethylenediamine, dimethylbenzylamine, or 1,4-diazabicyclo[2.2.2]octane; and the average particle size of the microcapsule is 3-10μm, and the breaking strength is 25-60MPa.

[0022] Further, the core composition of the lubricating microcapsule in S3 includes, by mass percentage: poly-alpha-olefin or synthetic ester base oil 65-78%, solid lubricant 20-30%, dispersant 3-6%, antioxidant 2-4%; the solid lubricant is one or more of nano-molybdenum disulfide, nano-tungsten disulfide, graphene or boron nitride; the kinematic viscosity (100℃) of the poly-alpha-olefin is 4-10 mm² / s; the average particle size of the microcapsule is 5-15 μm, the breaking strength is 40-90 MPa, and the capsule wall is composed of melamine-resorcinol-formaldehyde copolymer resin with a molar ratio of 1:(0.8-1.2):(2.5-3.5).

[0023] Further, the composition of the composite functional topcoat in S4 includes, by mass percentage: film-forming material 40-48%, microcapsule repair system 15-22%, functional filler 18-25%, auxiliary agent 5-8%, and the balance is solvent; the film-forming material includes polyamide-imide modified epoxy resin 28-35%, high-temperature engineering plastic powder 8-12%, and fluoropolymer powder 4-6%; the high-temperature engineering plastic powder is one or more of polyether ether ketone, polyphenylene sulfide or polyimide, and the particle size is 5-20 μm; the fluoropolymer powder is fluorinated polyimide, polytetrafluoroethylene or polyvinylidene fluoride.

[0024] Further, the functional filler includes, by mass percentage: fibrous reinforcing agent 6-10%, layered solid lubricant 7-11%, nano-ceramic particles 3-5%, and layered double hydroxide 2-4%; the fibrous reinforcing agent is potassium titanate whisker, carbon fiber chopped fiber or silicon carbide whisker; the layered solid lubricant is amino-functionalized boron nitride nanosheet, organic hexagonal boron nitride or modified graphene; the nano-ceramic particles are α-Al2O3, ZrO2 or TiO2; the layered double hydroxide is zinc-aluminum hydrotalcite, magnesium-aluminum hydrotalcite or zinc-magnesium-aluminum hydrotalcite.

[0025] Further, the microcapsule repair system in S4 includes, by mass percentage: temperature-responsive repair microcapsule 8-12%, catalytic microcapsule 5-8%, and lubricating microcapsule 2-4%; the addition order of the three kinds of microcapsules is to add the temperature-responsive repair microcapsule first, and then add the catalytic microcapsule and the lubricating microcapsule in turn, and after adding each kind of microcapsule, low-speed stirring is adopted for 15-25 minutes, and the stirring speed is controlled at 200-500 rpm to ensure the integrity of the microcapsules.

[0026] Further, the topcoat coating in S5 is specifically: 2-3 times of construction by air spraying or electrostatic spraying, spraying air pressure is 0.3-0.5 MPa, interval of each time is 15-25 minutes, and total thickness of wet film is controlled to be 120-200 μm; the segmented curing process is: first, pre-drying at 60-80 DEG C for 20-35 minutes to volatilize solvent, then, primary curing at 150-170 DEG C for 0.8-1.2 hours, finally, complete curing at 200-230 DEG C for 2-3.5 hours, and naturally cooling to room temperature and aging for 24-72 hours.

[0027] Compared with the prior art, the technical scheme of the application has the following beneficial technical effects:

[0028] The temperature control response type repair microcapsule designed in the application has a rupture strength of 35-80 MPa, accurately matches the fretting wear stress range of the aviation aluminum alloy, ensures that the microcapsule can be broken and release the repair agent at the initial stage of microcrack initiation, and the capsule core adopts a combination of epoxy prepolymer and mercapto curing agent, uses mercapto-epoxy click chemistry reaction, and can be rapidly cured at normal temperature without additional catalyst, so that the repair time is shortened to 2-4 hours, and catalytic type microcapsules and lubricating type microcapsules are introduced: the released tertiary amine catalyst of the former further accelerates the repair reaction, and the modified nanosilica fills the crack to provide secondary reinforcement; the poly-alpha-olefin and solid lubricant released by the latter at the moment of rupture immediately reduce the friction coefficient, gain time for structure repair, and realize the three-level linkage of instant protection-catalytic acceleration-structure repair. In view of the poor matching of the coating and the aluminum alloy substrate, the application improves the interface bonding strength and the matching of the thermal expansion coefficient through the three-layer interface design of the silanized conversion film layer, the polyamide-imide modified epoxy resin primer and the adhesion promoter; the polyamide-imide modified epoxy resin substrate combines the curing performance of the epoxy resin and the temperature resistance and toughness of the polyamide-imide, cooperates with the high-temperature engineering plastic powder, so that the coating remains stable under the aviation temperature cycle of-55 DEG C to + 150 DEG C, and effectively prevents peeling failure. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic diagram of the multi-element microcapsule structure of the application;

[0030] Figure 2 It is a schematic diagram of the microcapsule repair mechanism of the application;

[0031] Figure 3 It is a schematic diagram of the topcoat layer composition ratio of the application. DETAILED DESCRIPTION

[0032] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0033] Embodiment 1

[0034] The present embodiment provides a preparation method of a fretting wear self-repairing coating of an aviation aluminum alloy, comprising the following steps:

[0035] S1: substrate pretreatment

[0036] (1) alkali washing: the 7075 aviation aluminum alloy substrate (size 100 mm x 100 mm x 3 mm) is sequentially ultrasonically cleaned with acetone, ethanol and deionized water for 10 minutes, and is immersed in a 10wt% sodium hydroxide solution at 80℃ for 5 minutes for alkali washing, and is washed with deionized water.

[0037] (2) acid washing: the substrate after alkali washing is immersed in a 15vol% nitric acid solution at room temperature for 30 seconds for neutralization and ash removal, and is washed with deionized water.

[0038] (3) silanization treatment: a silanization solution is prepared, in which the mass concentration of 3-glycidoxypropyltrimethoxysilane is 2.5wt%, the solvent is a mixture of ethanol and deionized water with a volume ratio of 90:10, and the pH value is adjusted to 5.0 with glacial acetic acid; the aluminum alloy substrate after acid washing is treated in the silanization solution for 20 minutes, and is cured at 130℃ for 40 minutes after being taken out, to form a silanization conversion film layer with a thickness of 1.0μm.

[0039] S2: primer layer preparation

[0040] The primer is prepared according to the mass percentage: polyamide-imide modified epoxy resin 62%, phosphonated polyamide adhesion promoter 3%, nano-zinc oxide anticorrosion pigment 7.5%, dispersant 1%, and the rest is a mixed solvent of dimethylbenzene and butanol (mass ratio 1:1). After the primer is fully stirred and mixed uniformly, it is coated on the silanization conversion film layer by brushing, and is pre-baked at 90℃ for 20 minutes, and then is cured at 200℃ for 2 hours, to obtain a primer layer with a thickness of 25μm.

[0041] As shown in Figure 1 S3: preparation of multi-component microcapsules

[0042] (3.1) preparation of temperature-responsive repair microcapsules:

[0043] Core formulation (mass percent): epoxy-terminated polyether prepolymer (epoxy value 0.50 mol / 100g) 60%, trimethylolpropane triglycidyl ether 20%, pentaerythritol tetramercaptoacetate 18%, triphenylphosphine accelerator 2%.

[0044] Preparation by interfacial polymerization: the core material and emulsifier (polyvinyl alcohol, 3wt% of the core mass) were emulsified in deionized water at high speed (8000 rpm, 20 min), then the isocyanate monomer and diamine monomer were added, and reacted at 50°C for 3 hours to form a polyurethane / polyurea hybrid capsule wall. After filtration, washing, and freeze-drying, temperature-responsive repair microcapsules with an average particle size of 15 μm, a rupture strength of 58 MPa, and a core content of 68% were obtained, with a glass transition temperature of -10°C.

[0045] As shown in Figure 2 , (3.2) catalytic microcapsule preparation:

[0046] Core formulation (mass percent): amino-silane modified nano-silica (particle size 20 nm) 76%, triethylenediamine 18%, dispersion stabilizer 4%, antioxidant 2%.

[0047] Preparation by suspension polymerization: the core material and methyl methacrylate monomer, initiator were suspended in the aqueous phase and polymerized at 70°C for 4 hours to obtain catalytic microcapsules with an average particle size of 6 μm and a rupture strength of 42 MPa.

[0048] (3.3) Lubricating microcapsule preparation:

[0049] Core formulation (mass percent): poly-alpha-olefin (kinematic viscosity at 100°C 6 mm² / s) 70%, nano-molybdenum disulfide 25%, dispersant 3.5%, antioxidant 1.5%.

[0050] Preparation by in-situ polymerization: melamine, resorcinol, and formaldehyde were pre-polymerized at a molar ratio of 1:1.0:3.0 at pH 8.5 and 70°C for 45 minutes to obtain a pre-polymer, then the core material was emulsified and added to the pre-polymer, the pH was adjusted to 3.5, and the reaction was carried out at 55°C for 2 hours, the capsule wall was crosslinked on the surface of the core to obtain lubricating microcapsules with an average particle size of 10 μm and a rupture strength of 65 MPa.

[0051] As shown in Figure 3 , S4: topcoat layer preparation

[0052] Prepare a composite functional topcoat according to the mass percent:

[0053] Film-forming material: polyamide-imide modified epoxy resin 31%, polyether ether ketone powder (particle size 10 μm) 10%, fluorinated polyimide powder 5%

[0054] Microcapsule repair system: thermoregulation responsive repair microcapsule 10%, catalytic microcapsule 6.5%, lubricating microcapsule 3%

[0055] Functional filler: potassium titanate whisker 8%, amino-functionalized boron nitride nanosheet 9%, α-Al2O3 nanoparticle 4%, zinc aluminum hydrotalcite 3%

[0056] Auxiliary agent: dispersant 2%, leveling agent 1.5%, defoaming agent 0.5%, curing agent 3.5%

[0057] The balance is a mixed solvent of xylene and butanone

[0058] Preparation process: first, mix the polyamide-imide modified epoxy resin with the solvent, add the high-temperature engineering plastic powder and the fluorine-containing polymer powder, and stir and disperse at medium speed for 30 minutes; then add the functional filler and stir and disperse for 40 minutes; then add the thermoregulation responsive repair microcapsule, the catalytic microcapsule, and the lubricating microcapsule in sequence, and mix each microcapsule after addition by low-speed stirring (300 rpm) for 20 minutes; finally, add the auxiliary agent and the curing agent, stir at low speed for 15 minutes, and stand for defoaming for 30 minutes.

[0059] S5: topcoat painting

[0060] The air spraying method is used for 3-pass construction, the spraying air pressure is 0.4 MPa, the interval between each pass is 20 minutes, and the total wet film thickness is controlled at 150 μm. The segmented curing process is as follows: first, volatilize the solvent at 70°C for 25 minutes, then perform primary curing at 160°C for 1 hour, finally, perform complete curing at 220°C for 3 hours, naturally cool to room temperature, and then age for 48 hours, to obtain a composite functional topcoat layer with a thickness of 75 μm.

[0061] The total thickness of the finally obtained coating is 101 μm (silanization conversion film layer 1.0 μm + primer layer 25 μm + topcoat layer 75 μm).

[0062] Example 2

[0063] The preparation method of the aviation aluminum alloy fretting wear self-repairing coating provided in this example is basically the same as the preparation method of Example 1, and the difference lies in that:

[0064] Silanization treatment in S1: the mass concentration of 3-glycidyloxypropyltrimethoxysilane is 2 wt%, the volume ratio of solvent ethanol to deionized water is 85:15, the pH value is 4.5, and the silanization conversion film layer with a thickness of 0.5 μm is formed after curing at 120°C for 50 minutes.

[0065] S2: Primer composition: polyamide-imide modified epoxy resin 55%, phosphate ester adhesion promoter 2%, aluminum tripolyphosphate corrosion pigment 5%, dispersant 0.5%, and the balance solvent. Curing process: pre-baking at 80°C for 15 minutes, curing at 180°C for 1.5 hours to obtain a primer layer with a thickness of 20 μm.

[0066] S3: Temperature-controlled responsive repair microcapsule core composition: epoxy-terminated polyether prepolymer (epoxy value 0.40 mol / 100g) 55%, pentaerythritol glycidyl ether 15%, aliphatic mercapto curing agent 27%, and accelerator 3%. The average particle size of the microcapsule is 8 μm, the breaking strength is 35 MPa, and the glass transition temperature is -20°C. The mercapto curing agent is pentaerythritol tetramercaptoacetate, trimethylolpropane trimercaptoacetate, or a polymercaptan compound.

[0067] Catalytic microcapsule core composition: modified nano-silica (particle size 10 nm) 70%, dimethylbenzylamine 15%, dispersing stabilizer 3%, and antioxidant 12%. The average particle size is 3 μm, and the breaking strength is 25 MPa.

[0068] Lubricating microcapsule core composition: poly-alpha-olefin (kinematic viscosity at 100°C 4 mm² / s) 71%, nano-tungsten disulfide 20%, dispersant 6%, and antioxidant 3%. The average particle size is 5 μm, the breaking strength is 40 MPa, and the molar ratio of melamine-resorcinol-formaldehyde is 1:0.8:2.5.

[0069] S4: Composite functional topcoat composition: film-forming material 40% (polyamide-imide modified epoxy resin 28%, polyphenylene sulfide powder 8%, and polytetrafluoroethylene powder 4%), microcapsule repair system 15% (temperature-controlled response type 8%, catalytic type 5%, and lubricating type 2%), functional filler 18% (carbon fiber chopped fiber 6%, organic hexagonal boron nitride 7%, ZrO2 nanoparticles 3%, and magnesium-aluminum hydrotalcite 2%), and auxiliary agent 5%, and the balance solvent.

[0070] S5: Topcoat coating: two passes, spray pressure 0.3 MPa, interval between passes 15 minutes, and total wet film thickness 120 μm. Curing process: pre-baking at 60°C for 20 minutes, curing at 150°C for 0.8 hours, curing at 200°C for 2 hours, and aging for 24 hours to obtain a topcoat layer with a thickness of 60 μm.

[0071] The total thickness of the final coating is 80.5 μm.

[0072] Example 3

[0073] The preparation method of the aviation aluminum alloy fretting wear self-repairing coating provided in this example is basically the same as the preparation method of Example 1, except that:

[0074] Silanization treatment in S1: 3-glycidyloxypropyltrimethoxysilane mass concentration of 3wt%, volume ratio of solvent ethanol to deionized water of 95:5, pH value of 6.0, curing at 140℃ for 30 minutes to form a silanized conversion film layer with a thickness of 1.5μm.

[0075] Primer composition in S2: polyamide-imide modified epoxy resin 70%, phosphonated polyamide adhesion promoter 4%, zinc-aluminum hydrotalcite anticorrosion pigment 10%, dispersant 1.5%, and the rest solvent. Curing process: pre-baking at 100℃ for 25 minutes, curing at 220℃ for 2.5 hours to obtain a primer layer with a thickness of 30μm.

[0076] Temperature-controlled responsive repair microcapsule core composition in S3: epoxy-terminated polyether prepolymer (epoxy value 0.60 mol / 100g) 65%, neopentyl glycol diglycidyl ether 25%, trimethylolpropane trimercaptoacetate 8%, and accelerator 2%. Average particle size of microcapsule 25μm, rupture strength 80MPa, core content 60%, and glass transition temperature 0℃.

[0077] Catalytic microcapsule core composition: epoxy-silane modified nano-silica (particle size 30nm) 70%, 1,4-diazabicyclo[2.2.2]octane 22%, dispersion stabilizer 6%, and antioxidant 2%. Average particle size 10μm, rupture strength 60MPa.

[0078] Lubricating microcapsule core composition: synthetic ester base oil 66%, graphene 28%, dispersant 4%, and antioxidant 2%. Average particle size 15μm, rupture strength 90MPa, and melamine-resorcinol-formaldehyde molar ratio 1:1.2:3.5.

[0079] Composite functional topcoat composition in S4: film-forming material 48% (polyamide-imide modified epoxy resin 35%, polyimide powder 12%, and polyvinylidene fluoride powder 6%), microcapsule repair system 22% (temperature-controlled responsive type 12%, catalytic type 8%, and lubricating type 4%), functional filler 25% (silicon carbide whisker 10%, modified graphene 11%, TiO2 nanoparticle 5%, and zinc-magnesium-aluminum hydrotalcite 4%), and auxiliary agent 8%, and the rest solvent. Stirring speed 500rpm when adding microcapsules, and each mixing for 25 minutes.

[0080] Topcoat coating in S5: electrostatic spraying in 3 passes, spraying air pressure 0.5MPa, interval between each pass 25 minutes, and total wet film thickness 200μm. Curing process: pre-baking at 80℃ for 35 minutes, curing at 170℃ for 1.2 hours, curing at 230℃ for 3.5 hours, and aging for 72 hours to obtain a topcoat layer with a thickness of 90μm.

[0081] Total thickness of the final coating is 121.5μm.

[0082] Example 4

[0083] The present example provides a preparation method of a fretting wear self-repairing coating for an aviation aluminum alloy, which is basically the same as the preparation method of Example 1, except that:

[0084] In S1, the silanization treatment: the mass concentration of 3-glycidyloxypropyltrimethoxysilane is 2.2wt%, the volume ratio of solvent ethanol to deionized water is 88:12, the pH value is 4.0, and the silanization conversion film layer with a thickness of 0.8μm is formed at 125℃ for 45 minutes.

[0085] In S3, the composition of the temperature-controlled responsive repair microcapsule core: epoxy-terminated polyether prepolymer (epoxy value 0.52 mol / 100g) 58%, trimethylolpropane triglycidyl ether 20%, pentaerythritol tetramercaptoacetate 20%, accelerator 2%. The average particle size of the microcapsule is 12μm, the breaking strength is 50MPa, the core content is 65%, and the glass transition temperature is -15℃.

[0086] The composition of the lubricating microcapsule core: poly-alpha-olefin (kinematic viscosity at 100℃ is 8 mm² / s) 65%, mixed nano-molybdenum disulfide and boron nitride (mass ratio 1:1) 28%, dispersant 4%, antioxidant 3%. The average particle size is 8μm, and the breaking strength is 75MPa.

[0087] In S4, the microcapsule repair system: temperature-controlled responsive repair microcapsule 9%, catalytic microcapsule 7%, lubricating microcapsule 3.5%, stirring speed 200rpm when adding, each mixed for 15 minutes.

[0088] In S5, the topcoat coating: the total wet film thickness is 160μm, the curing process: pre-baking at 65℃ for 30 minutes, curing at 155℃ for 1 hour, curing at 210℃ for 2.5 hours, aging for 36 hours, to obtain a topcoat layer with a thickness of 80μm.

[0089] The total thickness of the final coating is 105.8μm.

[0090] Example 5

[0091] The present example provides a preparation method of a fretting wear self-repairing coating for an aviation aluminum alloy, which is basically the same as the preparation method of Example 1, except that:

[0092] In S2, the composition of the primer: polyamide-imide modified epoxy resin 65%, phosphate ester adhesion promoter 3.5%, mixed nano-zinc oxide and aluminum tripolyphosphate corrosion-resistant pigment (mass ratio 1:1) 8%, dispersant 1.2%, and the rest is solvent. Curing process: pre-baking at 95℃ for 18 minutes, curing at 210℃ for 2.2 hours, to obtain a primer layer with a thickness of 28μm.

[0093] S3 in the catalytic microcapsule core composition: amino silane modified nano silicon dioxide (particle size 25 nm) 78%, triethylene diamine and dimethyl benzyl amine mixed (mass ratio 1:1) 19%, dispersion stabilizer 4.5%, antioxidant 2%. The average particle size is 7 μm, and the breaking strength is 50 MPa.

[0094] S4 in the functional filler: potassium titanate whisker and carbon fiber chopped fiber mixed (mass ratio 1:1) 9%, amino functional boron nitride nanosheet 8%, α-Al2O3 and ZrO2 mixed nanoparticles 3.5%, zinc aluminum hydrotalcite 3%.

[0095] S5 in the topcoat coating: the total thickness of the wet film is 135 μm, the curing process is 75℃ pre-drying for 28 minutes, 165℃ curing for 0.9 hours, 215℃ curing for 2.8 hours, aging for 60 hours, and the topcoat layer with a thickness of 68 μm is obtained.

[0096] The total thickness of the final coating is 97 μm.

[0097] Example 6

[0098] The present embodiment provides a preparation method of an aviation aluminum alloy fretting wear self-repairing coating, which is basically the same as the preparation method of Example 1, except that:

[0099] S1 in the silanization treatment: the mass concentration of 3-glycidyloxypropyltrimethoxysilane is 2.8 wt%, the volume ratio of solvent ethanol to deionized water is 92:8, the pH value is 5.5, and the silanization conversion film layer with a thickness of 1.2 μm is formed at 135℃ for 35 minutes.

[0100] S3 in the temperature-controlled responsive repair microcapsule core composition: epoxy-terminated polyether prepolymer (epoxy value 0.55 mol / 100g) 62%, pentaerythritol glycidyl ether 22%, aromatic mercapto curing agent 14%, accelerator 2.5%. The average particle size of the microcapsule is 20 μm, the breaking strength is 70 MPa, the core content is 75%, and the glass transition temperature is -5℃.

[0101] The catalytic microcapsule core composition: epoxy silane modified nano silicon dioxide (particle size 15 nm) 75%, 1,4-diazabicyclo[2.2.2]octane 20%, dispersion stabilizer 4%, antioxidant 1%. The average particle size is 5 μm, and the breaking strength is 35 MPa.

[0102] The core of the lubricating microcapsule is composed of 68% poly-alpha-olefin (kinematic viscosity at 100℃ is 10 mm² / s), 30% mixed nano-tungsten disulfide and graphene (mass ratio 1:1), 3.5% dispersant, and 2.5% antioxidant. The average particle size is 12 μm, the breaking strength is 55 MPa, and the molar ratio of melamine-resorcinol-formaldehyde is 1:1.0:3.0.

[0103] The film-forming material in S4 is composed of 32% polyamide-imide modified epoxy resin, 11% mixed powder of polyether ether ketone and polyimide (mass ratio 1:1, particle size 5-20 μm), and 5% mixed powder of fluorinated polyimide and polytetrafluoroethylene. The microcapsule repair system is composed of 11% temperature-responsive type, 7.5% catalytic type, and 3.2% lubricating type.

[0104] In S5, the topcoat is sprayed at an air pressure of 0.45 MPa, and the total wet film thickness is 180 μm. The curing process is pre-baking at 72℃ for 32 minutes, curing at 162℃ for 1.1 hours, curing at 225℃ for 3.2 hours, and aging for 54 hours, resulting in a topcoat layer with a thickness of 85 μm.

[0105] The total thickness of the final coating is 112.2 μm.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating in Example 1, except that:

[0108] In S1, no silanization treatment is performed, and the acid washing is directly followed by coating the primer.

[0109] The other steps are the same as in Example 1. The total thickness of the final coating is 100 μm.

[0110] Comparative Example 2

[0111] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating in Example 1, except that:

[0112] In S2, the primer layer preparation step is omitted, and the topcoat is directly coated on the silanized conversion film layer.

[0113] The other steps are the same as in Example 1. The total thickness of the final coating is 76 μm.

[0114] Comparative Example 3

[0115] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating in Example 1, except that:

[0116] In S3, only temperature-responsive type repair microcapsules are prepared, and no catalytic type microcapsules and lubricating type microcapsules are prepared.

[0117] S4 contains only 19.5% of temperature-responsive repair microcapsules, and the proportions of other components are adjusted accordingly.

[0118] The other steps are the same as in Example 1.

[0119] Comparative Example 4

[0120] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating of Example 1, except that:

[0121] The breaking strength of the temperature-responsive repair microcapsules in S3 is 20 MPa (lower than the range of the claim).

[0122] The other steps are the same as in Example 1.

[0123] Comparative Example 5

[0124] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating of Example 1, except that:

[0125] No microcapsule repair system is added in S4, only film-forming materials, functional fillers, and additives are contained.

[0126] The other steps are the same as in Example 1.

[0127] Comparative Example 6

[0128] This comparative example provides a method for preparing a coating, which is basically the same as the method for preparing the coating of Example 1, except that:

[0129] In S5, a one-step curing process is used: the pre-baking and initial curing steps are omitted, and direct curing at 220°C for 3 hours is performed.

[0130] The other steps are the same as in Example 1.

[0131] Test Example 1: Coating thickness and adhesion test

[0132] A magnetic thickness gauge was used to test the thickness of the coatings prepared in Examples 1-6 and Comparative Examples 1-6. Ten points were measured for each sample, and the average value and standard deviation were calculated.

[0133] The cross-cut method (GB / T 9286-2021) was used to test the adhesion of the coating. A total of 36 squares were cut on the surface of the coating, each with a side length of 1 mm. After being quickly peeled off with adhesive tape, the coating was observed for peeling. The adhesion was evaluated on a scale of 0-5 (0 being the best and 5 being the worst).

[0134] The test results are shown in Table 1.

[0135] Table 1. Coating thickness and adhesion test results

[0136] Sample Silane Film Layer Thickness (μm) Primer Layer Thickness (μm) Topcoat Layer Thickness (μm) Total Thickness (μm) Adhesion Rating Example 1 1.0 25 75 101.0 0 Example 2 0.5 20 60 80.5 0 Example 3 1.5 30 90 121.5 0 Example 4 0.8 25 80 105.8 0 Example 5 1.0 28 68 97.0 0 Example 6 1.2 25 85 111.2 0 Comparative Example 1 0 25 75 100.0 3 Comparative Example 2 1.0 0 75 76.0 2 Comparative Example 3 1.0 25 75 101.0 0 Comparative Example 4 1.0 25 75 101.0 0 Comparative Example 5 1.0 25 75 101.0 0 Comparative Example 6 1.0 25 75 101.0 1

[0137] Test Example 2: Fretting wear self-repairing performance test

[0138] The coatings prepared in Examples 1-6 and Comparative Examples 1-6 were subjected to fretting wear test using a fretting wear tester (SRV-4 type). Test conditions: reciprocating frequency 25 Hz, amplitude 1 mm, normal load 50 N, counter material GCr15 steel ball (diameter 10 mm), room temperature environment, test time 30 minutes. After the test, the wear track width and depth were measured.

[0139] Self-repairing performance test: the worn samples were respectively placed at room temperature for 24 hours and at 80°C environment for 2 hours, and then the wear track width and depth were measured again, and the repair rate was calculated.

[0140] Repair rate (%) = (wear depth after wear - wear depth after repair) / wear depth after wear × 100%

[0141] The test results are shown in Table 2.

[0142] Table 2. Fretting wear self-repairing performance test results

[0143] Sample Wear Scratch Width (mm) Wear Scratch Depth (μm) Depth after Room Temperature Repair (μm) Room Temperature Repair Rate (%) Depth after 80°C Repair (μm) 80°C Repair Rate (%) Friction Coefficient Example 1 1.82 28.5 12.3 56.8 5.8 79.6 0.28 Example 2 1.88 32.1 14.5 54.8 7.2 77.6 0.31 Example 3 1.75 25.8 10.8 58.1 4.5 82.6 0.25 Example 4 1.80 29.2 13.1 55.1 6.5 77.7 0.29 Example 5 1.78 27.6 11.5 58.3 5.2 81.2 0.27 Example 6 1.76 26.8 11.2 58.2 5.0 81.3 0.26 Comparative Example 1 2.15 42.5 35.8 15.8 32.5 23.5 0.45 Comparative Example 2 2.08 38.6 32.2 16.6 29.8 22.8 0.42 Comparative Example 3 1.95 35.2 22.5 36.1 18.5 47.4 0.35 Comparative Example 4 1.92 33.8 25.8 23.7 22.5 33.4 0.38 Comparative Example 5 2.22 45.8 42.5 7.2 40.2 12.2 0.52 Comparative Example 6 1.98 36.5 28.2 22.7 24.8 32.1 0.39

[0144] Test Example 3: Cycle wear-repairing performance test

[0145] The coatings of Examples 1, 3 and 6 were subjected to cycle wear-repairing performance test using a reciprocating friction and wear tester. Test method: 1000 mesh sandpaper was used as the counter material, the normal load was 100 g, the water contact angle and friction coefficient of the coating surface were measured after 10 times of reciprocating wear (10 cm each time), then the sample was placed at 80°C environment for 2 hours for repair, and the water contact angle and friction coefficient were measured again. This was repeated for 10 cycles.

[0146] The water contact angle of the coating in the initial state should be ≥ 90° to characterize its hydrophobic property, and the lower the friction coefficient, the better the lubricating property.

[0147] The test results are shown in Table 3.

[0148] Table 3. Cycle wear-repairing performance test results

[0149] Cycle Number Example 1 Water Contact Angle (°) Example 1 Friction Coefficient Example 3 Water Contact Angle (°) Example 3 Friction Coefficient Example 6 Water Contact Angle (°) Example 6 Friction Coefficient Initial 108.5 0.28 112.3 0.25 110.8 0.26 After 1st Wear 85.2 0.42 88.5 0.38 86.8 0.40 After 1st Repair 102.8 0.31 106.5 0.28 104.2 0.29 After 2nd Wear 83.5 0.43 86.8 0.39 85.2 0.41 After 2nd Repair 100.5 0.32 104.2 0.29 102.5 0.30 After 3rd Wear 82.1 0.44 85.5 0.40 83.8 0.42 After 3rd Repair 98.8 0.33 102.5 0.30 100.8 0.31 After 4th Wear 80.5 0.45 84.2 0.41 82.5 0.43 After 4th Repair 96.5 0.34 100.8 0.31 98.5 0.32 After 5th Wear 78.8 0.46 82.5 0.42 80.8 0.44 After 5th Repair 94.2 0.35 98.5 0.32 96.2 0.33 After 6th Wear 77.2 0.47 80.8 0.43 79.2 0.45 After 6th Repair 92.5 0.36 96.8 0.33 94.5 0.34 After 7th Wear 75.5 0.48 79.2 0.44 77.5 0.46 After 7th Repair 90.2 0.37 94.5 0.34 92.2 0.35 After 8th Wear 73.8 0.49 77.5 0.45 75.8 0.47 After 8th Repair 88.5 0.38 92.8 0.35 90.5 0.36 After 9th Wear 72.2 0.50 75.8 0.46 74.2 0.48 After 9th Repair 86.8 0.39 90.5 0.36 88.2 0.37 After 10th Wear 70.5 0.51 74.2 0.47 72.5 0.49 After 10th Repair 84.5 0.40 88.2 0.37 86.5 0.38

[0150] Comprehensive performance evaluation

[0151] Table 4. Summary of comparison of comprehensive performance of coatings

[0152] Sample Adhesion Wear Resistance Self-repairing Ability Friction Coefficient Overall Evaluation Example 1 Excellent Good Good 0.28 Meets requirements, excellent performance Example 2 Excellent Good Good 0.31 Meets requirements, parameters at lower limit Example 3 Excellent Excellent Excellent 0.25 Meets requirements, best performance Example 4 Excellent Good Good 0.29 Meets requirements, excellent performance Example 5 Excellent Good Excellent 0.27 Meets requirements, excellent performance Example 6 Excellent Excellent Excellent 0.26 Meets requirements, excellent performance Comparative Example 1 Poor Poor Poor 0.45 No silane treatment, insufficient adhesion Comparative Example 2 Average Poor Poor 0.42 No primer layer, poor adhesion and wear resistance Comparative Example 3 Excellent Average Average 0.35 Lack of catalytic and lubricating microcapsules, limited repair effect Comparative Example 4 Excellent Average Poor 0.38 Microcapsule rupture strength too low, poor repair effect Comparative Example 5 Excellent Poor Very poor 0.52 No microcapsule repair system, no self-repairing ability Comparative Example 6 Good Average Average 0.39 Improper curing process, coating performance decreased

[0153] Conclusion

[0154] From the above examples and test examples, it can be seen that:

[0155] The coating prepared according to the technical solution of the claim in Examples 1-6 all exhibit excellent adhesion (0 level), good wear resistance and excellent self-repairing ability. After fretting wear, the repair rate can reach 77.6%-82.6% at 80℃ for 2 hours, and the friction coefficient is controlled between 0.25-0.31, which is significantly better than the comparative examples.

[0156] Comparative Example 1 does not perform silanization treatment, resulting in a significant decrease in coating adhesion (3 level) and poor repair effect after wear, which verifies the importance of silanization conversion film layer to the adhesion and overall performance of the coating.

[0157] Comparative Example 2 omits the primer layer, and the coating adhesion decreases to level 2, and the wear resistance and repair performance are both significantly decreased, which shows that the primer layer plays a key role in the coating system.

[0158] Comparative Example 3 only uses a single repair microcapsule, which has a certain repair ability, but the repair rate is only 47.4%, which is much lower than the synergistic repair effect of the examples, proving the necessity of the synergistic effect of multiple microcapsules.

[0159] Comparative Example 4 has a low rupture strength (20 MPa) of the temperature-responsive repair microcapsule, which breaks prematurely during fretting wear, and cannot achieve effective stress-responsive repair, with a repair rate of only 33.4%.

[0160] Comparative Example 5 does not contain any microcapsule repair system, and the coating is the most severely worn, with the highest friction coefficient (0.52) and a repair rate of only 12.2%, completely lacking self-repairing ability.

[0161] Comparative Example 6 uses an improper one-step curing process, resulting in high internal stress in the coating and damage to the integrity of the microcapsule, which leads to a decrease in adhesion and repair performance.

[0162] The cycle test shows that the coating prepared in the examples can still maintain good hydrophobicity and lubricity after 10 cycles of wear-repair, among which Example 3 has the most outstanding performance, verifying the excellent long-term use stability of the coating.

[0163] In summary, the aviation aluminum alloy fretting wear self-repairing coating preparation method provided by the present application realizes excellent adhesion, wear resistance and self-repairing ability of the coating through the synergistic effect of silanization treatment, primer layer, multiple microcapsule repair system and functional filler, which can effectively prolong the service life of aviation aluminum alloy parts and has important engineering application value.

[0164] 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; it is not intended to exclude myriad other embodiments of the present application that other inventors can develop based on the same general inventive concepts embodied by the described embodiments. That is, although the present application is described in terms of particular embodiments and implementations, it is to be understood that the terminology used is for the purpose of descriptive clarity and that it should be taken in a descriptive sense and not a limiting sense.

[0165] While the embodiments of the application have been shown and described herein, it is to be understood that the application is not limited to these embodiments. Rather, it is to be understood that various modifications, changes, substitutions and alterations can be made to the embodiments of the application without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A method for preparing a fretting wear self-repairing coating for an aerospace aluminum alloy, characterized in that, The method comprises the following steps: S1: pretreatment of the substrate, sequentially performing alkali cleaning, acid cleaning and silanization treatment on the aviation aluminum alloy substrate to form a silanized conversion film layer with a thickness of 0.5-1.5 μm; S2: preparation of the primer layer, mixing polyamide-imide modified epoxy resin, adhesion promoter and anticorrosive pigment to prepare a primer, coating the primer on the silanized conversion film layer, and curing to obtain a primer layer with a thickness of 20-30 μm; S3: preparation of the multi-component microcapsule, respectively preparing temperature control responsive repair microcapsules, catalytic microcapsules and lubricating microcapsules, the temperature control responsive repair microcapsules taking epoxy pre-polymer and mercapto curing agent as the capsule core and polyurethane / polyurea hybrid material as the capsule wall, and the breaking strength being 35-80 MPa; the catalytic microcapsules taking modified nano-silicon dioxide and tertiary amine catalyst as the capsule core and polymethyl methacrylate as the capsule wall; and the lubricating microcapsules taking poly-alpha-olefin and solid lubricant as the capsule core and melamine-m-phenol-formaldehyde copolymer resin as the capsule wall; S4: preparation of the topcoat layer, mixing polyamide-imide modified epoxy resin, high-temperature engineering plastic powder, functional filler and the above three kinds of microcapsules to prepare a composite functional topcoat; S5: topcoat coating, coating the composite functional topcoat on the primer layer, and segmentally curing to obtain a composite functional topcoat layer with a thickness of 60-90 μm.

2. The method of claim 1, wherein the method further comprises: In the silanization treatment in S1, the aluminum alloy substrate is immersed or sprayed with an alcohol-water mixed solution containing an epoxy silane coupling agent, the epoxy silane coupling agent is 3-glycidyloxypropyltrimethoxysilane with a mass concentration of 2-3 wt%, the solvent is a mixture of ethanol and deionized water with a volume ratio of (85-95):(5-15), and the pH value is adjusted to 4.0-6.0; after the treatment, the substrate is cured at 120-140℃ for 30-50 minutes.

3. The method of claim 1, wherein the method further comprises: In the primer in S2, the composition includes, by mass percentage, polyamide-imide modified epoxy resin 55-70%, adhesion promoter 2-4%, anticorrosive pigment 5-10%, dispersant 0.5-1.5%, and the balance is solvent; the adhesion promoter is phosphatized polyamide or phosphate compound; the anticorrosive pigment is one or more of nano-zinc oxide, aluminum tripolyphosphate or zinc-aluminum hydrotalcite; and the curing process is pre-baking at 80-100℃ for 15-25 minutes, and then curing at 180-220℃ for 1.5-2.5 hours.

4. The method of claim 1, wherein the method further comprises: In the temperature control responsive repair microcapsule in S3, the capsule core composition includes, by mass percentage, epoxy-terminated polyether pre-polymer 55-65%, multifunctional epoxy resin 15-25%, aliphatic mercapto curing agent or aromatic mercapto curing agent 18-28%, and promoter 1-3%; The epoxy value of the epoxy-terminated polyether pre-polymer is 0.40-0.60 mol / 100g; the multifunctional epoxy resin is trimethylolpropane triglycidyl ether, pentaerythritol glycidyl ether or neopentyl glycol diglycidyl ether; The mercapto curing agent is pentaerythritol tetramercaptoacetate, trimethylolpropane trimercaptoacetate or polymercaptan compound; The average particle size of the microcapsule is 8-25 μm, the glass transition temperature is -20℃ to 0℃, and the core of the microcapsule accounts for 60-75% of the mass of the microcapsule.

5. The method of claim 4, wherein the method further comprises: The core of the catalytic microcapsule in S3 includes, by mass percentage: modified nano-silicon dioxide 70-82%, tertiary amine catalyst 15-22%, dispersion stabilizer 3-6%, and antioxidant 1-3%; The modified nano-silicon dioxide is obtained by modifying the surface of nano-silicon dioxide with amino silane or epoxy silane, and the particle size of the nano-silicon dioxide is 10-30 nm; The tertiary amine catalyst is triethylenediamine, dimethylbenzylamine, or 1,4-diazabicyclo[2.2.2]octane; the average particle size of the microcapsule is 3-10 μm, and the breaking strength is 25-60 MPa.

6. The method of claim 1, wherein the method further comprises: The core of the lubricating microcapsule in S3 includes, by mass percentage: poly-alpha-olefin or synthetic ester base oil 65-78%, solid lubricant 20-30%, dispersant 3-6%, and antioxidant 2-4%; the solid lubricant is one or more of nano-molybdenum disulfide, nano-tungsten disulfide, graphene, or boron nitride; the kinematic viscosity (100℃) of the poly-alpha-olefin is 4-10 mm² / s; the average particle size of the microcapsule is 5-15 μm, the breaking strength is 40-90 MPa, and the capsule wall is composed of melamine-resorcinol-formaldehyde copolymer resin with a molar ratio of 1:(0.8-1.2):(2.5-3.5).

7. The method of claim 4, wherein the method further comprises: The composition of the composite functional topcoat in S4 includes, by mass percentage: film-forming material 40-48%, microcapsule repair system 15-22%, functional filler 18-25%, auxiliary agent 5-8%, and the balance is solvent; the film-forming material includes polyamide-imide modified epoxy resin 28-35%, high-temperature engineering plastic powder 8-12%, and fluoropolymer powder 4-6%; the high-temperature engineering plastic powder is one or more of polyether ether ketone, polyphenylene sulfide, or polyimide, and the particle size is 5-20 μm; the fluoropolymer powder is fluorinated polyimide, polytetrafluoroethylene, or polyvinylidene fluoride.

8. The method of claim 7, wherein the method further comprises: The functional filler includes, by mass percentage: fibrous reinforcing agent 6-10%, layered solid lubricant 7-11%, nano-ceramic particles 3-5%, and layered double hydroxide 2-4%; the fibrous reinforcing agent is potassium titanate whisker, carbon fiber short fiber, or silicon carbide whisker; the layered solid lubricant is amino-functionalized boron nitride nanosheet, organically modified hexagonal boron nitride, or modified graphene; the nano-ceramic particles are α-Al2O3, ZrO2, or TiO2; and the layered double hydroxide is zinc-aluminum hydrotalcite, magnesium-aluminum hydrotalcite, or zinc-magnesium-aluminum hydrotalcite.

9. The method of claim 1, wherein the method further comprises: The S4 microcapsule repair system comprises, by mass percentage: temperature control responsive repair microcapsules 8-12%, catalytic microcapsules 5-8%, and lubricating microcapsules 2-4%. The three kinds of microcapsules are added in the following order: first, the temperature control responsive repair microcapsules, then the catalytic microcapsules and the lubricating microcapsules in sequence. After each kind of microcapsule is added, low-speed stirring is adopted for 15-25 minutes, and the stirring speed is controlled at 200-500 rpm, so as to ensure the integrity of the microcapsules.

10. The method of claim 1, wherein the method further comprises: The S5 topcoat painting is specifically as follows: air spraying or electrostatic spraying is adopted for 2-3 passes, the spraying air pressure is 0.3-0.5 MPa, the interval between each pass is 15-25 minutes, and the total wet film thickness is controlled at 120-200 μm. The segmented curing process is as follows: first, pre-drying at 60-80 ℃ for 20-35 minutes to volatilize the solvent, then primary curing at 150-170 ℃ for 0.8-1.2 hours, finally, complete curing at 200-230 ℃ for 2-3.5 hours, and naturally cooling to room temperature and aging for 24-72 hours.

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