Self-repairing coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of self-repairing coatings, and particularly relates to a self-repairing coating and a preparation method and application thereof. The self-repairing coating provided by the invention comprises a micro-nano porous ceramic layer and an organic coating which are sequentially laminated on the surface of a substrate, the micro-nano porous ceramic layer contains an inorganic corrosion inhibitor; the organic coating contains a first microcapsule and a second microcapsule, the capsule core of the first microcapsule is a repairing agent, and the capsule wall of the first microcapsule is phenolic resin or urea resin; the capsule core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsule is phenolic resin or urea resin. The corrosion inhibitor is introduced into the micro-nano porous ceramic layer, so that the ceramic layer has repairing capacity. Meanwhile, microcapsules loaded with a repairing agent and microcapsules loaded with an organic corrosion inhibitor and a curing agent are introduced into the organic coating, so that the corrosion resistance, wear resistance and other properties of the self-repairing coating in different service environment systems are further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-repairing coatings, and in particular relates to a self-repairing coating and a preparation method and application thereof. Background Art

[0002] Light alloys (such as aluminum, magnesium, titanium and other non-ferrous metal alloys) and their composite materials are widely used in many fields such as aerospace, automobile manufacturing and military defense due to their excellent performance. At the same time, their service conditions are becoming more and more harsh. Surface treatment is a key way to improve the service life of light alloys in different environments. In different service environments, especially for moving parts, due to external forces (scratches, impacts, collisions, etc.) and environmental corrosion, the surface protective layer will fail in the form of damage, bubbling, peeling, etc., and in harsh service environments, it will cause rapid corrosion of the components along the damaged areas of the protective layer, thereby causing their mechanical properties and service life to decline rapidly. Coating repair technology is an important way to solve the rapid performance degradation of component protective layers after failure, but most of the existing surface treatment technologies do not have self-repair capabilities. Even if the surface protective layer has certain self-repair properties, the repair efficiency is insufficient and the degree of industrialization is limited, which limits the repair of the coating. Summary of the Invention

[0003] In view of this, the present invention provides a self-repairing coating, a preparation method and application thereof. The self-repairing coating provided by the present invention can repair itself after being damaged, which can reduce the number of secondary or subsequent overall coatings, reduce the maintenance cost of structural parts, and extend the service life of structural parts.

[0004] In order to solve the above technical problems, the present invention provides a self-repairing coating, comprising a micro-nano porous ceramic layer and an organic coating layer sequentially stacked on the surface of a substrate;

[0005] The micro-nano porous ceramic layer contains an inorganic corrosion inhibitor;

[0006] The organic coating contains first microcapsules and second microcapsules, the core of the first microcapsules is a repair agent, and the capsule wall of the first microcapsules is phenolic resin or urea-formaldehyde resin; the core of the second microcapsules is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsules is phenolic resin or urea-formaldehyde resin.

[0007] Preferably, the inorganic corrosion inhibitor includes one or more of sodium phosphate, sodium tungstate and sodium stannate;

[0008] The repair agent is epoxy resin;

[0009] The organic corrosion inhibitor includes one or more of benzotriazole, 2-mercaptobenzothiazole and 8-hydroxyquinoline;

[0010] The curing agent includes dimethylimidazole, polyetheramine or triethylenetetramine.

[0011] Preferably, the content of the inorganic corrosion inhibitor in the micro-nano porous ceramic layer is 0.01 to 0.05%;

[0012] The content of the first microcapsules in the organic coating is 0.1-0.3%, and the content of the second microcapsules in the organic coating is 0.1-0.3%;

[0013] The thickness of the micro-nano porous ceramic layer is 15 to 25 μm;

[0014] The thickness of the organic coating is 50 to 70 μm;

[0015] The thickness of the self-repairing coating is 65 to 95 μm.

[0016] The present invention also provides a method for preparing the self-repairing coating described in the above technical solution, comprising the following steps:

[0017] Plasma electrolytic oxidation is performed on the surface of the substrate to form a micro-nano porous ceramic layer; the electrolyte used for plasma electrolytic oxidation includes an inorganic corrosion inhibitor;

[0018] A modified organic coating is sprayed on the surface of the micro-nano porous ceramic layer to obtain the self-healing coating; the modified organic coating contains a first microcapsule and a second microcapsule, the core of the first microcapsule is a repair agent, and the capsule wall of the first microcapsule is a phenolic resin or a urea-formaldehyde resin; the core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin.

[0019] Preferably, the electrolyte includes a hexametaphosphate system electrolyte, a silicate system electrolyte or a metavanadate system electrolyte;

[0020] The hexametaphosphate system electrolyte includes the following components in mass concentrations: 1-40 g / L hexametaphosphate, 1-30 g / L silicate, 1-30 g / L metavanadate, 1-10 g / L tartrate, 1-8 g / L corrosion inhibitor, 1-10 g / L potassium titanium oxalate, and 1-10 g / L pH regulator.

[0021] Preferably, the plasma electrolytic oxidation process is accompanied by ultrasound;

[0022] The conditions of the plasma electrolytic oxidation include: a frequency of 100 to 5000 Hz, a duty cycle of 10 to 50%, a pulse ratio of 10 to 40:1, and an oxidation time of 10 to 60 minutes; the output mode of the power supply is a constant current output mode or a constant voltage output mode; the current density of the constant current output mode is 1 to 10 A / dm 2 , the voltage of the constant voltage output mode is 300~650V;

[0023] The power of the ultrasound is 50-1800W, and the frequency is 10-50Hz.

[0024] Preferably, the mass percentage of the first microcapsules in the modified organic coating is 0.1-0.3%, and the mass percentage of the second microcapsules in the modified organic coating is 0.1-0.3%.

[0025] Preferably, the first microcapsules and the second microcapsules are prepared in one step by in-situ polymerization.

[0026] Preferably, the spraying includes air spraying, airless spraying or electrostatic spraying;

[0027] The conditions for air spraying and airless spraying independently include: spraying pressure of 0.1 to 0.5 MPa, spraying distance of 80 to 200 mm, spraying angle of 45 to 90 degrees, and moving speed of 0.2 to 0.8 m / s;

[0028] The conditions for the electrostatic spraying include: voltage of 50-95 kV, current of 5-50 A, feed pressure of 0-0.3 MPa, air pressure of 0.05-0.4 MPa, and spraying distance of 150-200 mm.

[0029] The present invention also provides the use of the self-repairing coating described in the above technical solution or the self-repairing coating prepared by the preparation method described in the above technical solution in alloys and composite materials thereof.

[0030] The present invention provides a self-repairing coating, comprising a micro-nano porous ceramic layer and an organic coating layer sequentially stacked on the surface of a substrate; the micro-nano porous ceramic layer contains an inorganic corrosion inhibitor; the organic coating layer contains a first microcapsule and a second microcapsule, the capsule core of the first microcapsule is a repair agent, and the capsule wall of the first microcapsule is a phenolic resin or a urea-formaldehyde resin; the capsule core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin. In the present invention, the micro-nano discharge micropores in the micro-nano porous ceramic layer can effectively promote the diffusion and penetration of the organic coating, improve the bonding of the self-repairing and harmonious coating, and the present invention introduces a corrosion inhibitor into the micro-nano porous ceramic layer to enable the ceramic layer to have a repair ability, and the corrosion resistance is more than 20 times higher than that of the substrate, and the repair rate can reach 73%. At the same time, the present invention introduces microcapsules loaded with repair agents and microcapsules loaded with organic corrosion inhibitors and curing agents into the organic coating to further improve the corrosion resistance, wear resistance and other properties of the self-repairing coating in different service environment systems. When the self-repairing coating is damaged, the repair agent and corrosion inhibitor can be released in time to repair the surface of the alloy and its composite material; there is a synergistic corrosion inhibition effect between the inorganic corrosion inhibitor in the micro-nano porous ceramic layer and the organic corrosion inhibitor in the organic coating, which can further improve the corrosion resistance of the self-repairing coating. The self-repairing coating can achieve a repair efficiency of 86% under the joint action of the micro-nano porous ceramic layer and the organic coating, and the corrosion resistance of the self-repairing coating is more than 80 times higher than that of the substrate. In the present invention, the repair agent in the organic layer reacts with the released curing agent to solidify and perform intrinsic self-repair; the inorganic corrosion inhibitor in the micro-nano porous ceramic layer and the corrosion inhibitor in the organic coating work synergistically to achieve an external-aid self-repair effect. The self-repairing coating provided by the present invention can achieve intrinsic-external dual repair. The self-repairing coating provided by the present invention has a uniform, dense, firmly bonded surface and controllable thickness. It has good repairability, corrosion resistance and hydrophobicity and can be used for the surfaces of parts working under various extreme working conditions. After the coating is damaged, its self-repairing function can reduce the number of secondary or subsequent overall coatings and reduce the maintenance cost of structural parts. The raw materials used in the preparation process do not contain toxic substances harmful to the human body and the environment. It is suitable for surfaces of various sizes and complex shapes, is easy to operate and control, has a stable process, low cost, high processing efficiency, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The SEM images of the coatings prepared in Example 1 and Comparative Example 1 are shown, wherein (a) is the SEM image of the coating prepared in Comparative Example 1, and (b) is the SEM image of the self-healing coating prepared in Example 1;

[0032] Figure 2The SEM images of the micro-nano porous ceramic layer in the self-healing coating prepared in Example 1 and the coating prepared in Comparative Example 2, wherein (a) is an SEM image of the coating prepared in Comparative Example 2, and (b) is an SEM image of the micro-nano porous ceramic layer in the self-healing coating prepared in Example 1;

[0033] Figure 3 The SEM images of the self-repairing state of the self-repairing coating prepared in Example 2 after scratching, where (a) is an artificial scratch; (b) is the morphology of the chelate formed by the reaction of the corrosion inhibitor and the aluminum matrix; (c) is the coating surface after repair;

[0034] Figure 4 The electrochemical analysis results of the coating before and after scratch repair in Example 2 are shown in Figure 2, where (a) is the electrochemical analysis result of the scratch before repair in Example 2, and (b) is the electrochemical analysis result of the scratch after self-repair in Example 2;

[0035] Figure 5 The SEM images of the surface and cross section of the self-healing coating prepared in Example 3, wherein (a) is a SEM image of the surface of the self-healing coating, and (b) is a SEM image of the cross section of the self-healing coating;

[0036] Figure 6 This is a thermogravimetric curve of the repair agent-loaded microcapsules prepared in Example 3;

[0037] Figure 7 Figure 4 shows the self-repairing state of the organic coating in the self-repairing coating prepared in Example 4 after scratching the substrate, where (a) is an artificial scratch; (b) shows the scratch filled by the repair agent seeping out; (c) is the coating surface after repair;

[0038] Figure 8 Graphs showing electrochemical analysis results of the coating before and after scratch repair in Example 4, wherein (a) shows the electrochemical analysis results of the scratch before repair in Example 4, and (b) shows the electrochemical analysis results of the scratch after self-repair in Example 4. DETAILED DESCRIPTION

[0039] The present invention provides a self-repairing coating, comprising a micro-nano porous ceramic layer and an organic coating layer sequentially stacked on the surface of a substrate;

[0040] The micro-nano porous ceramic layer contains an inorganic corrosion inhibitor;

[0041] The organic coating contains first microcapsules and second microcapsules, the core of the first microcapsules is a repair agent, and the capsule wall of the first microcapsules is phenolic resin or urea-formaldehyde resin; the core of the second microcapsules is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsules is phenolic resin or urea-formaldehyde resin.

[0042] In the present invention, the matrix preferably includes an alloy and a composite material thereof, the alloy preferably includes a light alloy or a nonferrous alloy, and the light alloy preferably includes a magnesium alloy, an aluminum alloy or a titanium alloy.

[0043] In the present invention, the self-healing coating comprises a micro-nano porous ceramic layer containing an inorganic corrosion inhibitor. In the present invention, the inorganic corrosion inhibitor preferably comprises one or more of sodium phosphate, sodium tungstate, and sodium stannate, more preferably sodium phosphate, sodium tungstate, or sodium stannate, and even more preferably sodium phosphate. In the present invention, the content of the inorganic corrosion inhibitor in the micro-nano porous ceramic layer is preferably 0.01 to 0.05%, more preferably 0.05%.

[0044] In the present invention, the self-healing coating further comprises an organic coating, which contains first and second microcapsules. In the present invention, the core of the first microcapsule is a repair agent, and the wall of the first microcapsule is a phenolic resin or urea-formaldehyde resin; the repair agent is preferably an epoxy resin. In the present invention, the content of the repair agent in the first microcapsule is preferably 0.05-0.1%, more preferably 0.05%; the content of the first microcapsule in the organic coating is preferably 0.1-0.3%, more preferably 0.15-0.2%.

[0045] In the present invention, the core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin. In the present invention, the organic corrosion inhibitor preferably includes one or more of benzotriazole, 2-mercaptobenzothiazole, and 8-hydroxyquinoline, more preferably benzotriazole, 2-mercaptobenzothiazole, or 8-hydroxyquinoline. In the present invention, the curing agent preferably includes dimethylimidazole, polyetheramine, or triethylenetetramine, more preferably dimethylimidazole. In the present invention, the content of the organic corrosion inhibitor in the second microcapsule is preferably 0.05-0.1%, more preferably 0.05%; the content of the curing agent in the second microcapsule is preferably 0.1-0.5%, more preferably 0.2-0.5%. In the present invention, the content of the second microcapsule in the organic coating is preferably 0.1-0.3%, more preferably 0.15-0.2%.

[0046] In the present invention, the thickness of the micro-nano porous ceramic layer is preferably 15-25 μm, more preferably 20 μm; the thickness of the organic coating is preferably 50-70 μm, more preferably 50-60 μm. In the present invention, the thickness of the self-healing coating is preferably 65-95 μm.

[0047] In the present invention, the inorganic corrosion inhibitor in the micro-nano porous ceramic layer can achieve self-repair by participating in the reaction with the matrix or the environment. On the other hand, the corrosion inhibitor can effectively enter the plasma discharge micropores, play the role of sealing the micropores of the porous ceramic layer, and significantly improve the corrosion resistance of the micro-nano porous ceramic layer. The present invention utilizes microcapsules to load organic corrosion inhibitors and repairing agents and loads them into the organic coating, which can achieve controlled release of organic corrosion inhibitors and repairing agents. Once the coating is damaged and the microcapsules are ruptured, the organic corrosion inhibitors and repairing agents are released, and the organic corrosion inhibitors and alloy substrates generate a passivation film layer or are adsorbed on the surface of the substrate. The repairing agent reacts and solidifies with the curing agent in the organic coating to repair the damaged coating, thereby achieving self-repair of the composite coating. This has important engineering application value for broadening the application range of light alloys, extending their service life under extreme working conditions, and reducing maintenance costs.

[0048] The present invention also provides a method for preparing the self-repairing coating described in the above technical solution, comprising the following steps:

[0049] Plasma electrolytic oxidation is performed on the surface of the substrate to form a micro-nano porous ceramic layer; the electrolyte used for plasma electrolytic oxidation includes an inorganic corrosion inhibitor;

[0050] A modified organic coating is sprayed on the surface of the micro-nano porous ceramic layer to obtain the self-healing coating; the modified organic coating contains a first microcapsule and a second microcapsule, the core of the first microcapsule is a repair agent, and the capsule wall of the first microcapsule is a phenolic resin or a urea-formaldehyde resin; the core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin.

[0051] The present invention performs plasma electrolytic oxidation on the substrate surface to form a micro-nano porous ceramic layer. In the present invention, the substrate preferably comprises an alloy and its composite material, the alloy preferably comprises a light alloy or a nonferrous alloy, and the light alloy preferably comprises a magnesium alloy, an aluminum alloy or a titanium alloy.

[0052] The present invention preferably further includes pre-treating the substrate before performing plasma electrolytic oxidation; the pre-treatment preferably includes the following steps: polishing the substrate with sandpaper and then cleaning and drying in sequence. The present invention has no special requirements for the polishing, and conventional methods in this field can be used. The present invention can increase the micro-roughness of the substrate surface through polishing, which helps to improve the mechanical bite strength between the oxide film (micro-nano porous ceramic layer) and the substrate, making the formed oxide film more firm. In the present invention, the cleaning includes organic solvent washing and water washing in sequence; the organic solvent used for the organic solvent washing is preferably acetone or anhydrous ethanol, more preferably anhydrous ethanol; the water used for the water washing is preferably deionized water. In the present invention, the drying is preferably blow-dried with cold air.

[0053] In the present invention, the plasma electrolytic oxidation electrolyte includes an inorganic corrosion inhibitor; the inorganic corrosion inhibitor preferably includes one or more of sodium phosphate, sodium tungstate, and sodium stannate, more preferably sodium phosphate, sodium tungstate, or sodium stannate. The mass concentration of the inorganic corrosion inhibitor in the electrolyte is preferably 1-8 g / L, more preferably 3-6 g / L, and even more preferably 4-5 g / L. In the present invention, the electrolyte preferably includes a hexametaphosphate electrolyte, a silicate electrolyte, or a metavanadate electrolyte, more preferably a hexametaphosphate electrolyte. In the present invention, the solvent of the electrolyte is preferably water, preferably deionized water. In the present invention, the hexametaphosphate electrolyte preferably includes the following components in the following mass concentrations: hexametaphosphate 1-40 g / L, tartrate 1-10 g / L, inorganic corrosion inhibitor 1-8 g / L, potassium titanium oxalate 1-10 g / L, and pH adjuster 1-10 g / L. In the present invention, the silicate electrolyte preferably includes the following components at the following mass concentrations: 1-30 g / L silicate, 1-10 g / L tartrate, 1-8 g / L inorganic corrosion inhibitor, 1-10 g / L potassium titanium oxalate, and 1-10 g / L pH adjuster. In the present invention, the metavanadate electrolyte preferably includes the following components at the following mass concentrations: 1-40 g / L metavanadate, 1-10 g / L tartrate, 1-8 g / L inorganic corrosion inhibitor, 1-10 g / L potassium titanium oxalate, and 1-10 g / L pH adjuster. In the present invention, the hexametaphosphate is preferably sodium hexametaphosphate or potassium hexametaphosphate; the tartrate is preferably sodium tartrate or potassium tartrate; and the pH adjuster is preferably an alkali metal hydroxide, more preferably sodium hydroxide or potassium hydroxide. In the present invention, the electrolyte is preferably prepared by mixing an electrolyte and a solvent under ultrasonic conditions. In the present invention, the power of the ultrasound is preferably 50 to 1000 W, more preferably 300 to 900 W, and even more preferably 350 to 400 W; the frequency of the ultrasound is preferably 30 to 50 Hz, and more preferably 35 to 40 Hz.

[0054] In the present invention, the plasma electrolytic oxidation process is preferably accompanied by ultrasound. In the present invention, the conditions of the plasma electrolytic oxidation preferably include a frequency of 100 to 5000 Hz, a duty cycle of 10 to 50%, a pulse ratio of 10 to 40:1, and an oxidation time of 10 to 60 min; more preferably, a frequency of 500 to 800 Hz, a duty cycle of 30 to 40%, a pulse ratio of 20 to 25:1, and an oxidation time of 15 to 30 min. In the present invention, the power output mode of the plasma electrolytic oxidation is preferably a constant current output mode or a constant voltage output mode, more preferably a constant current output mode. In the present invention, the current density of the constant current output mode is preferably 1 to 10 A / dm 2 , more preferably 5 to 8 A / dm 2; The voltage of the constant voltage output mode is preferably 300-650V, more preferably 350-600V. In the present invention, the anode for the plasma electrolytic oxidation is a substrate, and the cathode is preferably graphite or stainless steel, more preferably graphite. In the present invention, the power of the ultrasound is preferably 50-1800W, more preferably 500-1000W; the frequency of the ultrasound is preferably 10-50Hz, more preferably 20-30Hz. In the present invention, the addition of ultrasonic assistance in the plasma electrolytic oxidation process can effectively improve the oxidation conditions and promote the uniformity of the reaction, thereby forming a more uniform and excellent performance ceramic layer.

[0055] In the present invention, after the plasma electrolytic oxidation, the process preferably further comprises: washing the micro-nano porous ceramic layer obtained by the plasma electrolytic oxidation with water and then drying it. In the present invention, the water used for washing is preferably deionized water. In the present invention, the drying is preferably performed by blowing with cold air.

[0056] After obtaining the micro-nano porous ceramic layer, the present invention sprays a modified organic coating on the surface of the micro-nano porous ceramic layer to obtain the self-healing coating. In the present invention, the modified organic coating contains a first microcapsule and a second microcapsule. In the present invention, the modified coating is preferably obtained by mixing the first microcapsule, the second microcapsule and the organic coating. In the present invention, the organic coating is preferably an epoxy resin or a polyurethane, more preferably an epoxy resin. In the present invention, the mixing is preferably carried out under stirring conditions. The present invention has no special requirements for the stirring, as long as it can be stirred evenly. In the present invention, after the mixing, it is preferably further included: ultrasonically treating the mixed system and then letting it stand. The present invention removes bubbles in the mixed system by ultrasonic treatment. The present invention has no special requirements for the ultrasonic treatment, and conventional methods in the art can be used. In the present invention, the standing time is preferably 10 to 30 minutes, more preferably 15 to 25 minutes.

[0057] In the present invention, the core of the first microcapsule is a repair agent, and the wall of the first microcapsule is a phenolic resin or a urea-formaldehyde resin; the repair agent is preferably an epoxy resin. In the present invention, the mass percentage of the first microcapsule in the organic coating is preferably 0.1 to 0.3%, and more preferably 0.15 to 0.2%. In the present invention, the core of the second microcapsule is an organic corrosion inhibitor and a curing agent, and the wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin. In the present invention, the organic corrosion inhibitor preferably includes one or more of benzotriazole, 2-mercaptobenzothiazole, and 8-hydroxyquinoline, and more preferably benzotriazole, 2-mercaptobenzothiazole, or 8-hydroxyquinoline. In the present invention, the curing agent preferably includes dimethylimidazole, polyetheramine, or triethylenetetramine, and more preferably dimethylimidazole. In the present invention, the mass percentage of the second microcapsule in the organic coating is 0.1 to 0.3%.

[0058] The present invention preferably utilizes an in-situ polymerization method to prepare the first microcapsule and the second microcapsule in one step. In the present invention, taking urea-formaldehyde resin as the capsule wall material as an example, the preparation method of the first microcapsule preferably includes the following steps:

[0059] Dissolving urea in formaldehyde solution, adjusting the pH to 8-9 with triethanolamine, and then performing polymerization reaction to obtain a urea-formaldehyde resin prepolymer solution;

[0060] The repair agent, emulsifier and water are mixed and emulsified to obtain a core material emulsion;

[0061] The urea-formaldehyde resin prepolymer solution and the core material emulsion are mixed, and the pH value is adjusted to 3-4 using dilute hydrochloric acid, followed by a first stirring to obtain the first microcapsule.

[0062] The present invention dissolves urea in a formaldehyde solution and then uses triethanolamine to adjust the pH value to 8-9 before conducting a polymerization reaction to obtain a urea-formaldehyde resin prepolymer solution. In the present invention, the mass concentration of the formaldehyde solution is preferably 20-40%, more preferably 25-30%. In the present invention, the volume ratio of the mass of the urea to the formaldehyde solution is preferably 5-10 g:15-30 mL, more preferably 10 g:30 mL. The present invention has no special limitation on the dissolution, as long as it can be completely dissolved. In the present invention, the temperature of the polymerization reaction is preferably 65-75°C, more preferably 70°C; the time of the polymerization reaction is preferably 35-45 min, more preferably 40 min. In the present invention, the polymerization reaction is preferably accompanied by stirring. The present invention has no special requirements for the stirring, as long as the polymerization reaction can be completed.

[0063] The present invention mixes a repair agent, an emulsifier and water and then emulsifies them to obtain a core material emulsion. In the present invention, the emulsifier is preferably one of a polyvinyl alcohol aqueous solution, Tween 80, and sodium lauryl sulfate, more preferably a polyvinyl alcohol aqueous solution; the mass percentage of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is preferably 5-30%, more preferably 10-15%. In the present invention, the mass ratio of the repair agent to the emulsifier is preferably 10-25g:10mL, more preferably 10-17g:10mL. In the present invention, the volume ratio of the emulsifier to water is preferably 0.5-1g:100mL, more preferably 1g:100mL. The present invention has no special requirements for the emulsification method, and the conventional method in the field can be used.

[0064] After obtaining a urea-formaldehyde resin prepolymer solution and a core material emulsion, the present invention mixes the urea-formaldehyde resin prepolymer solution and the core material emulsion, adjusts the pH to 3-4 using dilute hydrochloric acid, and then stirs the mixture to obtain the first microcapsules. In the present invention, the temperature for the first stirring is preferably 60-70°C, more preferably 65°C; the speed for the first stirring is preferably 900-1100 rpm, more preferably 1000 rpm; and the time for the first stirring is preferably 1.8-2.2 hours, more preferably 2 hours.

[0065] The present invention preferably uses an optical microscope to observe the state of the product during the first stirring process. Once stable microcapsules are formed, the pH value of the system is adjusted to 7 with NaOH solution, and then stirring is stopped. After standing and stratification, it is cooled to room temperature and then filtered, washed and dried in sequence to obtain the first microcapsules.

[0066] In the present invention, taking the capsule wall material as urea-formaldehyde resin as an example, the preparation method of the second microcapsule preferably includes the following steps:

[0067] The polyvinyl alcohol aqueous solution, urea, ammonium chloride, resorcinol and water are mixed and the pH value is adjusted to 7 to 8 to obtain a wall material solution;

[0068] dissolving a corrosion inhibitor and a curing agent in xylene to obtain a core material solution;

[0069] mixing and emulsifying the wall material solution and the core material solution to obtain an emulsion;

[0070] The emulsion and formaldehyde solution are mixed, and then the pH value of the system is adjusted to 3-4 using a hydrochloric acid solution to obtain the second microcapsules.

[0071] The present invention mixes a polyvinyl alcohol aqueous solution, urea, ammonium chloride, resorcinol, and water, and then adjusts the pH to 7-8 to obtain a wall material solution. In the present invention, the volume concentration of the polyvinyl alcohol aqueous solution is preferably 4.5-5.5%, more preferably 5%. In the present invention, polyvinyl alcohol is preferably dissolved in water to obtain the polyvinyl alcohol aqueous solution. In the present invention, the volume ratio of the polyvinyl alcohol aqueous solution to water is preferably 15:115-125, more preferably 15:120. In the present invention, the volume ratio of the polyvinyl alcohol aqueous solution to urea is preferably 15 mL:4.5-5.5 g, more preferably 15 mL:5 g. In the present invention, the mass ratio of urea, ammonium chloride, and resorcinol is preferably 4.5-5.5:0.25-0.35:0.25-0.35, more preferably 5:0.3:0.3. In the present invention, the mixing is preferably carried out under stirring conditions, and the stirring is preferably carried out using an electric stirrer. The present invention has no particular restrictions on the speed and time of the stirring, as long as uniform stirring is achieved. The present invention preferably uses sodium hydroxide solution to adjust the pH of the mixed system. The present invention has no special limitation on the amount of the sodium hydroxide solution used, as long as the desired pH value can be achieved.

[0072] The present invention dissolves a corrosion inhibitor and a curing agent in xylene to obtain a core material solution. In the present invention, the mass ratio of the corrosion inhibitor to the curing agent is preferably 0.8 to 1.2:1, more preferably 1:1. In the present invention, the mass ratio of the corrosion inhibitor to the volume of xylene is preferably 1 g:20 to 30 mL, more preferably 1 g:25 mL. The present invention has no special requirements for the dissolution, as long as complete dissolution is achieved.

[0073] After obtaining the wall material solution and the core material solution, the present invention mixes and emulsifies the wall material solution and the core material solution to obtain an emulsion. The present invention has no special requirements for the emulsification, and conventional methods in the art can be used.

[0074] After obtaining the emulsion, the present invention mixes the emulsion and formaldehyde solution and then uses hydrochloric acid solution to adjust the pH of the system to 3-4 to obtain the second microcapsules. In the present invention, the mass concentration of the formaldehyde solution is preferably 20% to 40%, more preferably 25% to 30%. In the present invention, the mass concentration of the hydrochloric acid solution is preferably 4-6%, more preferably 5%. In the present invention, the volume ratio of the emulsion to the formaldehyde solution is preferably 2-5:1, more preferably 3-5:1. In the present invention, the mixing is preferably carried out under stirring conditions, the stirring speed is preferably 500-1000 rpm, more preferably 500-800 rpm; the stirring time is preferably 25-35 minutes, more preferably 30 minutes. The present invention has no special requirements for the amount of hydrochloric acid solution used, as long as it can achieve the required pH value of the mixed system.

[0075] The present invention preferably uses an optical microscope to observe the state of the product during the mixing process. Once stable microcapsules are formed, stirring is stopped, the mixture is allowed to stand and separate into layers, and the upper layer product is filtered, washed and dried in sequence to obtain the second microcapsules.

[0076] In the present invention, the spraying preferably includes air spraying, airless spraying or electrostatic spraying, more preferably air spraying. In the present invention, the conditions of the air spraying preferably include: a spraying pressure of 0.1 to 0.5 MPa, a spraying distance of 80 to 200 mm, a spraying angle of 45 to 90 °, and a moving speed of 0.2 to 0.8 m / s; more preferably, a spraying pressure of 0.2 to 0.4 MPa, a spraying distance of 85 to 100 mm, a spraying angle of 50 to 60 °, and a moving speed of 0.3 to 0.5 m / s. In the present invention, the conditions of the airless spraying independently include: a spraying pressure of 0.1 to 0.5 MPa, a spraying distance of 80 to 200 mm, a spraying angle of 45 to 90 °, and a moving speed of 0.2 to 0.8 m / s. In the present invention, the conditions for electrostatic spraying preferably include: voltage of 50-95kV, current of 5-50A, feed pressure of 0-0.3Mpa, air pressure of 0.05-0.4Mpa, and spraying distance of 150-200mm, more preferably voltage of 55-90kV, current of 20-40A, feed pressure of 0.2-0.3Mpa, air pressure of 0.1-0.3Mpa, and spraying distance of 170-190mm.

[0077] In the present invention, after spraying, the process preferably further comprises: drying the sprayed product to obtain the self-repairing coating. In the present invention, the drying is preferably oven drying, the oven drying temperature is preferably 40-70°C, more preferably 45-50°C, and the oven drying time is preferably 7-12 hours, more preferably 8-10 hours.

[0078] The present invention utilizes a plasma electrolytic oxidation method to produce a micro-nanoporous ceramic layer. Its microporous structure not only increases the surface area but also provides abundant diffusion channels, allowing the organic coating to penetrate deeply into the porous interior, forming a strong physical and chemical bond and significantly improving the bonding strength between the coating and the substrate. This not only enhances the coating's adhesion but also creates space for the storage and release of corrosion inhibitors. Once the coating sustains minor damage, the repair agent in the microcapsules can rapidly migrate to the damaged area, enabling self-repair and effectively delaying performance degradation. The present invention directly enhances the corrosion resistance of the substrate material by introducing an inorganic corrosion inhibitor into the micro-nanoporous ceramic layer. The corrosion inhibitor loading rate is as high as 76%, meaning the coating contains sufficient corrosion inhibitor to activate before the corrosive medium contacts the substrate, forming a protective layer that prevents or slows the corrosion reaction and significantly improves corrosion resistance by more than 20 times that of the substrate material. Even if the coating sustains local damage, the loaded corrosion inhibitor continues to function, maintaining the material's corrosion resistance. The self-repairing capabilities of the self-repairing coating provided by the present invention reduce maintenance costs. Once the coating is physically damaged, the embedded microcapsules rupture and release a repair agent, instantly sealing the damaged area and preventing further corrosion. This mechanism significantly extends the coating's service life and reduces the need for re-coating, thereby alleviating the high cost and inconvenience of periodic maintenance.

[0079] The present invention also provides the use of the self-healing coating described in the above technical solution or the self-healing coating prepared by the preparation method described in the above technical solution in alloys and composite materials thereof. In the present invention, the alloy preferably comprises a light alloy or a non-ferrous alloy, more preferably a light alloy. In the present invention, the light alloy preferably comprises a magnesium alloy, an aluminum alloy, or a titanium alloy.

[0080] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0081] Example 1

[0082] Substrate pretreatment: The magnesium alloy substrate was polished with sandpaper, cleaned with acetone, and then washed with deionized water; the washed product was dried with cold air to obtain the pretreated magnesium alloy, and the self-repairing coating was prepared according to the following method.

[0083] Step 1: Prepare a micro-nano porous ceramic layer on the pretreated magnesium alloy surface by ultrasound-assisted plasma electrolytic oxidation:

[0084] (1) Preparation of electrolyte: Sodium silicate, sodium tartrate, sodium phosphate, potassium titanium oxalate, sodium hydroxide and deionized water were mixed under ultrasonic frequency of 30 Hz and power of 300 W to obtain an electrolyte; the specific composition of the electrolyte was: sodium silicate 20 g / L, sodium tartrate 10 g / L, sodium phosphate (inorganic corrosion inhibitor) 3 g / L, potassium titanium oxalate 6 g / L, and sodium hydroxide 5 g / L;

[0085] (2) Plasma electrolytic oxidation: The pretreated magnesium alloy is used as the anode and the stainless steel is used as the cathode. The plasma electrolytic oxidation is carried out by constant current output. The product after the plasma electrolytic oxidation is rinsed with deionized water and then dried with cold air to obtain a micro-nano porous ceramic layer with a thickness of 20 μm. The conditions for plasma electrolytic oxidation are: current density 5A / dm 2 , frequency 500 Hz, duty cycle 10%, pulse ratio 10:1, oxidation time 10 min; the plasma electrolytic oxidation process is accompanied by ultrasonic treatment with an ultrasonic frequency of 50 Hz and a power of 800 W;

[0086] Step 2: Spraying an organic layer on the surface of the micro-nano porous ceramic layer:

[0087] (1) Preparing a first microcapsule containing a repair agent: dissolving 5 g of urea in 15 mL of a 37% formaldehyde solution, adjusting the pH of the system to 8.5 with triethanolamine, and performing a polymerization reaction at 70° C. (with stirring) for 40 min to obtain a urea-formaldehyde resin prepolymer solution;

[0088] 10 mL of a 10 wt.% aqueous solution of polyvinyl alcohol (emulsifier) and 80 mL of pure water were placed in a reaction vessel, and an electric stirrer was turned on. Then, 14.5 g of epoxy resin was added to the reaction vessel and stirred with an electric stirrer for 1 h to form a core material emulsion;

[0089] The urea-formaldehyde resin prepolymer solution and the core material emulsion are stirred to form a uniform emulsion, and then the pH value of the system is adjusted to 3.5 using a hydrochloric acid solution with a mass concentration of 5%. The mixture is heated to 65°C in a water bath and stirred at a constant temperature of 1000 rpm for 2 hours. The product state is observed using an optical microscope during the reaction. Once stable microcapsules are formed, the pH value is adjusted to 7 using a NaOH solution, and stirring is stopped. After the mixture is allowed to stand and stratify to cool to room temperature, the lower layer product is filtered, washed, and dried to obtain the first microcapsules loaded with the repair agent.

[0090] (2) Preparation of second microcapsules containing organic corrosion inhibitor and curing agent:

[0091] In a reaction vessel, 15 mL of a 5% polyvinyl alcohol aqueous solution was dissolved in 120 mL of water, and then 5 g of urea was added thereto. 0.3 g of ammonium chloride and 0.3 g of resorcinol were then added to the reaction vessel in sequence and mixed uniformly. The mixture was stirred with an electric stirrer to form a wall material solution, and the pH of the system was adjusted to 8.0 with a NaOH solution.

[0092] Dissolve 1g of organic corrosion inhibitor 8-hydroxyquinoline and 1g of curing agent dimethylimidazole in 25mL of xylene to obtain a core material solution;

[0093] The wall material solution and the core material solution were mixed and stirred for 30 minutes to emulsify to obtain an emulsion;

[0094] To the emulsion, 13.57 g of a 37% formaldehyde solution was added, and stirring was adjusted to 500 rpm at 65°C for 3 hours. The pH of the system was then adjusted to 3.5 using 5% hydrochloric acid. During the reaction, the product was observed under an optical microscope. Once stable microcapsules were formed, stirring was stopped. After stratification, the upper layer was filtered, washed, and dried to obtain the second microcapsules loaded with both the corrosion inhibitor and the curing agent.

[0095] (3) Preparation of modified organic coating: 0.02 g of the first microcapsule, 0.03 g of the second microcapsule, and 50 mL of epoxy resin organic coating were mixed uniformly with an electric stirrer, and then ultrasonically cleaned to remove bubbles. The mixture was allowed to stand for 10 min to obtain a modified organic coating.

[0096] (4) Spraying an organic coating: spraying a modified organic coating on the surface of the micro-nano porous ceramic layer prepared in step 1 by an air spraying method to obtain an organic coating with a thickness of 50 μm; the spraying parameters are: spraying pressure 0.2 MPa, spraying distance 85 mm, spraying angle 45°, and moving speed 0.3 m / s;

[0097] The sprayed product was placed in an oven for drying to obtain a magnesium alloy containing a self-repairing coating; the drying temperature was 50° C. and the drying time was 8 h.

[0098] Example 2

[0099] Substrate pretreatment: The aluminum alloy substrate was polished with sandpaper, cleaned with acetone, and then washed with deionized water; the washed product was blown dry with cold air to obtain the pretreated aluminum alloy, and the self-repairing coating was prepared according to the following method.

[0100] Step 1: Prepare a micro-nano porous ceramic layer on the pretreated aluminum alloy surface by ultrasound-assisted plasma electrolytic oxidation:

[0101] (1) Preparation of electrolyte: Potassium hexametaphosphate, sodium tartrate, sodium tungstate, potassium titanium oxalate, sodium hydroxide and deionized water were mixed under ultrasonic frequency of 35 Hz and power of 350 W to obtain an electrolyte; the specific composition of the electrolyte was: 30 g / L potassium hexametaphosphate, 8 g / L potassium tartrate, 4 g / L sodium tungstate, 8 g / L potassium titanium oxalate, and 6 g / L sodium hydroxide;

[0102] (2) Plasma electrolytic oxidation: The pretreated aluminum alloy is used as the anode and the stainless steel is used as the cathode. The plasma electrolytic oxidation is carried out by constant current output. The product after the plasma electrolytic oxidation is rinsed with deionized water and then dried with cold air to obtain a micro-nano porous ceramic layer with a thickness of 15 μm. The conditions for plasma electrolytic oxidation are: current density 8A / dm 2 , frequency 800 Hz, duty cycle 30%, pulse ratio 20:1, oxidation time 15 min; the plasma electrolytic oxidation process is accompanied by ultrasonic treatment with an ultrasonic frequency of 30 Hz and a power of 500 W;

[0103] Step 2: Spraying an organic layer on the surface of the micro-nano porous ceramic layer:

[0104] (1) Preparing a first microcapsule containing a repair agent: dissolving 7 g of urea in 21 mL of a 30% formaldehyde solution, adjusting the pH of the system to 8.5 with triethanolamine, and performing a polymerization reaction at 70° C. (with stirring) for 40 min to obtain a urea-formaldehyde resin prepolymer solution;

[0105] 15 mL of a 10 wt.% emulsifier-containing PVA solution and 100 mL of pure water were placed in a reaction vessel, and an electric stirrer was turned on. 25 g of epoxy resin was then added to the reaction vessel, and stirred with an electric stirrer for 1 hour to form a core material emulsion.

[0106] The urea-formaldehyde resin prepolymer solution and the core material emulsion are stirred to form a uniform emulsion, and then the pH value of the system is adjusted to 3.5 using a hydrochloric acid solution with a mass concentration of 5%. The mixture is heated to 65°C in a water bath and stirred at a constant temperature of 1000 rpm for 2 hours. The product state is observed using an optical microscope during the reaction. Once stable microcapsules are formed, the pH value is adjusted to 7 using a NaOH solution, and stirring is stopped. After the mixture is allowed to stand and stratify to cool to room temperature, the lower layer product is filtered, washed, and dried to obtain the first microcapsules loaded with the repair agent.

[0107] (2) Preparation of second microcapsules containing organic corrosion inhibitor and curing agent:

[0108] In a reaction vessel, 15 mL of 8% polyvinyl alcohol solution was dissolved in 120 mL of water, and then 5 g of urea was added thereto. 0.3 g of ammonium chloride and 0.3 g of resorcinol were then added to the reaction vessel in sequence and mixed uniformly. The mixture was stirred with an electric stirrer to form a wall material solution, and the pH value of the system was adjusted to 8.0 with a NaOH solution.

[0109] Dissolve 1g of organic corrosion inhibitor 8-hydroxyquinoline and 1g of curing agent dimethylimidazole in 25mL of xylene to obtain a core material solution;

[0110] The wall material solution and the core material solution were mixed and stirred for 30 minutes to emulsify to obtain an emulsion;

[0111] To the emulsion, 20g of a 30% formaldehyde solution was added, and stirring was adjusted to 500 rpm at 65°C for 3 hours. The pH of the system was then adjusted to 3.5 using a 5% hydrochloric acid solution. During the reaction, the product was observed under an optical microscope. Once stable microcapsules were formed, stirring was stopped. After stratification, the upper layer was filtered, washed, and dried to obtain the second microcapsules loaded with both the corrosion inhibitor and the curing agent.

[0112] (3) Preparation of modified organic coating: 0.02 g of the first microcapsule, 0.02 g of the second microcapsule, and 50 mL of epoxy resin organic coating were mixed uniformly with an electric stirrer, and then ultrasonically cleaned to remove bubbles. The mixture was allowed to stand for 15 min to obtain a modified organic coating.

[0113] (4) Spraying an organic coating: spraying a modified organic coating on the surface of the micro-nano porous ceramic layer prepared in step 1 by air spraying to obtain an organic coating with a thickness of 55 μm; the spraying parameters are: spraying pressure 0.3 MPa, spraying distance 100 mm, spraying angle 60°, and moving speed 0.5 m / s;

[0114] The sprayed product was placed in an oven for drying to obtain an aluminum alloy containing a self-repairing coating; the drying temperature was 45°C and the drying time was 10 hours.

[0115] Example 3

[0116] Substrate pretreatment: The titanium alloy substrate was polished with sandpaper, cleaned with acetone, and then washed with deionized water; the washed product was blown dry with cold air to obtain the pretreated titanium alloy, and the self-repairing coating was prepared according to the following method.

[0117] Step 1: Prepare a micro-nano porous ceramic layer on the pretreated titanium alloy surface by ultrasound-assisted plasma electrolytic oxidation:

[0118] (1) Preparation of electrolyte: Sodium hexametaphosphate, sodium tartrate, sodium phosphate, potassium titanium oxalate, potassium hydroxide, and deionized water were mixed under ultrasonic conditions of 40 Hz and 400 W to obtain an electrolyte; the specific composition of the electrolyte was: 35 g / L sodium hexametaphosphate, 7 g / L sodium tartrate, 6 g / L sodium phosphate, 9 g / L potassium titanium oxalate, and 7 g / L potassium hydroxide;

[0119] (2) Plasma electrolytic oxidation: The pretreated titanium alloy was used as the anode and the stainless steel was used as the cathode. Plasma electrolytic oxidation was performed in a constant voltage output mode. The product after plasma electrolytic oxidation was rinsed with deionized water and then dried with cold air to obtain a micro-nano porous ceramic layer with a thickness of 20 μm. The conditions of plasma electrolytic oxidation were: voltage of 350 V, frequency of 600 Hz, duty cycle of 35%, pulse ratio of 25:1, and oxidation time of 20 min. The plasma electrolytic oxidation process was accompanied by ultrasonic treatment with an ultrasonic frequency of 20 Hz and a power of 1000 W.

[0120] Step 2: Spraying an organic layer on the surface of the micro-nano porous ceramic layer:

[0121] (1) Preparing a first microcapsule containing a repair agent: dissolving 7 g of urea in 21 mL of a 30% formaldehyde solution, adjusting the pH of the system to 8.5 with triethanolamine, and performing a polymerization reaction at 70° C. (with stirring) for 40 min to obtain a urea-formaldehyde resin prepolymer solution;

[0122] 15 mL of a 10 wt.% emulsifier-containing PVA solution and 100 mL of pure water were placed in a reaction vessel, and an electric stirrer was turned on. 25 g of epoxy resin was then added to the reaction vessel, and stirred with an electric stirrer for 1 hour to form a core material emulsion.

[0123] The urea-formaldehyde resin prepolymer solution and the core material emulsion are stirred to form a uniform emulsion, and then the pH value of the system is adjusted to 3.5 using a hydrochloric acid solution with a mass concentration of 5%. The mixture is heated to 65°C in a water bath and stirred at a constant temperature of 1000 rpm for 2 hours. The product state is observed using an optical microscope during the reaction. Once stable microcapsules are formed, the pH value is adjusted to 7 using a NaOH solution, and stirring is stopped. After the mixture is allowed to stand and stratify to cool to room temperature, the lower layer product is filtered, washed, and dried to obtain the first microcapsules loaded with the repair agent.

[0124] (2) Preparation of second microcapsules containing organic corrosion inhibitor and curing agent:

[0125] In a reaction vessel, 15 mL of 8% polyvinyl alcohol solution was dissolved in 120 mL of water, and then 5 g of urea was added thereto. 0.3 g of ammonium chloride and 0.3 g of resorcinol were then added to the reaction vessel in sequence and mixed uniformly. The mixture was stirred with an electric stirrer to form a wall material solution, and the pH value of the system was adjusted to 8.0 with a NaOH solution.

[0126] Dissolve 1 g of organic corrosion inhibitor 2-mercaptobenzothiazole and 1 g of curing agent dimethylimidazole in 25 mL of xylene to obtain a core material solution;

[0127] The wall material solution and the core material solution were mixed and stirred for 30 minutes to emulsify to obtain an emulsion;

[0128] To the emulsion, 20g of a 30% formaldehyde solution was added, and stirring was adjusted to 500 rpm at 65°C for 3 hours. The pH of the system was then adjusted to 3.5 using a 5% hydrochloric acid solution. During the reaction, the product was observed under an optical microscope. Once stable microcapsules were formed, stirring was stopped. After stratification, the upper layer was filtered, washed, and dried to obtain the second microcapsules loaded with both the corrosion inhibitor and the curing agent.

[0129] (3) Preparation of modified organic coating: 0.02 g of the first microcapsule, 0.02 g of the second microcapsule, and 50 mL of epoxy resin coating were mixed uniformly with an electric stirrer, and then ultrasonically cleaned to remove bubbles. The mixture was allowed to stand for 15 min to obtain a modified organic coating.

[0130] (4) Spraying an organic coating: The modified organic coating was sprayed on the surface of the micro-nano porous ceramic layer prepared in step 1 by an airless spraying method to obtain an organic coating with a thickness of 65 μm; the spraying parameters were: spraying pressure 0.4 MPa, spraying distance 80 mm, spraying angle 50°, and moving speed 0.4 m / s;

[0131] The sprayed product was placed in an oven for drying to obtain a titanium alloy containing a self-repairing coating; the drying temperature was 50°C and the drying time was 9 hours.

[0132] Example 4

[0133] Substrate pretreatment: The magnesium alloy substrate was polished with sandpaper, cleaned with acetone, and then washed with deionized water; the washed product was dried with cold air to obtain the pretreated magnesium alloy, and the self-repairing coating was prepared according to the following method.

[0134] Step 1: Prepare a micro-nano porous ceramic layer on the pretreated magnesium alloy surface by ultrasound-assisted plasma electrolytic oxidation:

[0135] (1) Preparation of electrolyte: Sodium metavanadate, sodium tartrate, sodium stannate, potassium titanium oxalate, sodium hydroxide, and deionized water were mixed under ultrasonic conditions of 50 Hz and 1000 W to obtain an electrolyte; the specific composition of the electrolyte was: 40 g / L sodium metavanadate, 5 g / L potassium tartrate, 5 g / L sodium stannate, 7 g / L potassium titanium oxalate, and 9 g / L sodium hydroxide;

[0136] (2) Plasma electrolytic oxidation: The pretreated magnesium alloy was used as the anode and graphene was used as the cathode. Plasma electrolytic oxidation was performed in a constant voltage output mode. The product after plasma electrolytic oxidation was rinsed with deionized water and then dried with cold air to obtain a micro-nano porous ceramic layer with a thickness of 20 μm. The conditions of plasma electrolytic oxidation were: voltage of 650 V, frequency of 700 Hz, duty cycle of 40%, pulse ratio of 40:1, and oxidation time of 30 min. The plasma electrolytic oxidation process was accompanied by ultrasonic treatment with an ultrasonic frequency of 30 Hz and a power of 900 W.

[0137] Step 2: Spraying an organic layer on the surface of the micro-nano porous ceramic layer:

[0138] (1) Preparing a first microcapsule containing a repair agent: dissolving 7 g of urea in 21 mL of a 30% formaldehyde solution, adjusting the pH of the system to 8.5 with triethanolamine, and performing a polymerization reaction at 70° C. (with stirring) for 40 min to obtain a urea-formaldehyde resin prepolymer solution;

[0139] 15 mL of a 10 wt.% emulsifier-containing PVA solution and 100 mL of pure water were placed in a reaction vessel, and an electric stirrer was turned on. 25 g of epoxy resin was then added to the reaction vessel, and stirred with an electric stirrer for 1 hour to form a core material emulsion.

[0140] The urea-formaldehyde resin prepolymer solution and the core material emulsion are stirred to form a uniform emulsion, and then the pH value of the system is adjusted to 3.5 using a hydrochloric acid solution with a mass concentration of 5%. The mixture is heated to 65°C in a water bath and stirred at a constant temperature of 1000 rpm for 2 hours. The product state is observed using an optical microscope during the reaction. Once stable microcapsules are formed, the pH value is adjusted to 7 using a NaOH solution, and stirring is stopped. After the mixture is allowed to stand and stratify to cool to room temperature, the lower layer product is filtered, washed, and dried to obtain the first microcapsules loaded with the repair agent.

[0141] (2) Preparation of second microcapsules containing organic corrosion inhibitor and curing agent:

[0142] In a reaction vessel, 15 mL of 8% polyvinyl alcohol solution was dissolved in 120 mL of water, and then 5 g of urea was added thereto. 0.3 g of ammonium chloride and 0.3 g of resorcinol were then added to the reaction vessel in sequence and mixed uniformly. The mixture was stirred with an electric stirrer to form a wall material solution, and the pH value of the system was adjusted to 8.0 with a NaOH solution.

[0143] Dissolve 1g of organic corrosion inhibitor benzotriazole and 1g of curing agent dimethylimidazole in 25mL of xylene to obtain a core material solution;

[0144] The wall material solution and the core material solution were mixed and stirred for 30 minutes to emulsify to obtain an emulsion;

[0145] To the emulsion, 20g of a 37% formaldehyde solution was added, stirring was adjusted to 800 rpm, and stirring was continued at 65°C for 3 hours. The pH of the system was then adjusted to 3.5 using a 5% hydrochloric acid solution. During the reaction, the product was observed under an optical microscope. Once stable microcapsules were formed, stirring was stopped. After stratification, the upper layer was filtered, washed, and dried to obtain the second microcapsules loaded with both the corrosion inhibitor and the curing agent.

[0146] (3) Preparation of modified organic coating: 0.01 g of the first microcapsule, 0.01 g of the second microcapsule, and 50 mL of epoxy resin organic coating were mixed uniformly with an electric stirrer, and then ultrasonically cleaned to remove bubbles. The mixture was allowed to stand for 30 min to obtain a modified organic coating.

[0147] (4) Spraying an organic coating: The modified organic coating was sprayed on the surface of the micro-nano porous ceramic layer prepared in step 1 by an electrostatic spraying method to obtain an organic coating with a thickness of 55 μm; the spraying parameters were: electrostatic high voltage of 55 kV, electrostatic current of 20 A, feed pressure of 0.2 MPa, air pressure of 0.3 MPa, and spraying distance of 170 mm;

[0148] The sprayed product was placed in an oven for drying to obtain a magnesium alloy containing a self-repairing coating; the drying temperature was 50° C. and the drying time was 8 h.

[0149] Comparative Example 1

[0150] The coating was prepared according to the method of Example 1, except that the organic modified organic coating was directly sprayed on the surface of the magnesium alloy substrate to obtain an organic coating with a thickness of 75 μm, which did not contain a micro-nano porous ceramic layer.

[0151] Comparative Example 2

[0152] The coating was prepared according to the method of Example 1, except that the inorganic corrosion inhibitor sodium phosphate was not contained in the electrolyte during the plasma electrolytic oxidation process.

[0153] The coatings prepared in Example 1 and Comparative Example 1 were subjected to scanning electron microscopy and EDS analysis, and the results were as follows: Figure 1 , wherein (a) is the SEM image of the coating prepared in Comparative Example 1, and (b) is the SEM image of the self-repairing coating prepared in Example 1. Figure 1 The SEM scanning morphology shows that the surface of the magnesium alloy contains only organic coatings and there is cracking on the substrate surface, and the bonding strength is poor. The plasma electrolytic oxidation composite organic synergistic coating has a jagged interlaced pattern with the substrate and has a good bonding strength.

[0154] The micro-nano porous ceramic layer in the self-repairing coating prepared in Example 1 and the coating prepared in Comparative Example 2 were examined by scanning electron microscopy. Figure 2 , wherein (a) is the SEM image of the coating prepared in Comparative Example 2, and (b) is the SEM image of the micro-nano porous ceramic layer in the self-repairing coating prepared in Example 1. Figure 2 It can be seen that the surface of the unmodified plasma electrolytic oxidation layer (without inorganic corrosion inhibitor) has plasma discharge micropores of varying sizes. The plasma electrolytic oxidation self-repairing coating prepared by the ultrasonic-assisted method after corrosion inhibitor modification has fewer surface micropores, and the corrosion inhibitor plays a role in sealing the plasma discharge micropores. On the other hand, when the coating cracks, the corrosion inhibitor is released and reacts with the substrate to repair the defects. Therefore, after modification with the corrosion inhibitor, the coating repair rate and corrosion resistance are significantly improved.

[0155] The self-repairing coating prepared in Example 2 was scratched and its self-repairing state was observed. Figure 3 The SEM images of the self-repairing process are shown in Figure 2, where (a) is an artificial scratch; (b) is the morphology of the chelate generated by the reaction between the corrosion inhibitor and the aluminum matrix; and (c) is the surface of the coating after repair. Figure 3 It can be seen that after the self-repairing coating is scratched, the two corrosion inhibitors in the composite coating will begin to be released from the cracks and repair the damaged areas. The compound corrosion inhibitors can produce a synergistic corrosion inhibition effect on the substrate, which can effectively prevent the further expansion of corrosion and improve the corrosion resistance of the coating.

[0156] A Bruker Dimension ICON atomic force microscope was used to perform micro-area electrochemical testing on the coating before and after repair after scratching in Example 2. The test mode adopts the KPFM mode. The probe first tests the surface morphology of the sample, and then is lifted to a certain height to test the surface potential of the sample. Using the compensation voltage method, a DC compensation voltage is added to the probe or sample surface to offset the electrostatic force generated by the potential difference between the probe and the sample. The required compensation voltage is equivalent to the potential difference between the probe and the sample. The repair condition of the sample is analyzed by comparing the changes in the potential difference of the sample. The electrochemical analysis results are shown as follows: Figure 4As shown, (a) is the electrochemical analysis result of the scratch before repair in Example 2, and (b) is the electrochemical analysis result of the scratch after self-repair in Example 2. Figure 4 From the data shown, it can be seen that before repair, the potential difference between the scratched area and the coating surface is 0.35V. After repair, the potential difference between the repaired area and the coating surface is 0.095V. The self-healing efficiency (η) of the coating can be calculated according to the formula η = (V1-V2) ÷ V1 × 100%, where V2 is the potential difference after repair and V1 is the potential difference before repair. The coating repair rate is 73%.

[0157] The surface and cross section of the self-repairing coating prepared in Example 3 were examined by scanning electron microscopy to obtain SEM images, as shown in FIG. Figure 5 As shown, (a) is the SEM image of the self-repairing coating surface, and (b) is the SEM image of the cross section of the self-repairing coating. Figure 5 The self-healing coating is uniform, dense, and well-bonded to the substrate. The microcapsules are evenly dispersed within the self-healing coating and enable controlled release of organic corrosion inhibitors and repair agents. When the coating cracks, the microcapsules quantitatively release the organic corrosion inhibitor, depending on the crack size, and react with the substrate to repair the defect. Therefore, the plasma-electrolytic oxidation composite organic self-healing synergistic coating significantly improves the corrosion resistance and self-healing efficiency of titanium alloys.

[0158] Thermogravimetric analysis was performed on the microcapsules loaded with the repair agent prepared in Example 3 to obtain a thermogravimetric curve, as shown in FIG. Figure 6 As shown. Figure 6 The microcapsules lost approximately 7.86% of their mass between 251°C and 316°C, indicating thermal decomposition of the capsule wall. Between 316°C and 475°C, they lost approximately 76% of their mass, indicating thermal decomposition of the repair agent core. Therefore, the mass of the repair agent core accounts for 76% of the total mass of the microcapsules, indicating a 76% loading rate.

[0159] The self-repairing coating prepared in Example 4 was scratched onto the substrate and its self-repairing state was observed. Figure 7 The self-repairing process is shown in Figure 1, where (a) is an artificial scratch; (b) is the scratch filled by the repair agent; and (c) is the coating surface after repair. Figure 7 It can be seen that after the organic coating in the self-repairing coating is scratched, the repair agent will be released from the cracks to fill the scratches. After the repair is completed, the coating surface is relatively smooth, and the repair effect of the Concorde coating is good.

[0160] A Bruker DimensionICON atomic force microscope was used to perform micro-area electrochemical testing on the organic coating of Example 4 before and after repair after scratches. The test mode adopts the KPFM mode. The probe first tests the surface morphology of the sample, and then is lifted to a certain height to test the surface potential of the sample. Using the compensation voltage method, a DC compensation voltage is added to the probe or sample surface to offset the electrostatic force generated by the potential difference between the probe and the sample. The required compensation voltage is equivalent to the potential difference between the probe and the sample. The repair condition of the sample is analyzed by comparing the changes in the potential difference of the sample. The electrochemical analysis results are as follows: Figure 8 As shown, (a) is the electrochemical analysis result of the scratch before repair in Example 4, and (b) is the electrochemical analysis result of the scratch after self-repair in Example 4. Figure 8 From the data shown, it can be seen that before repair, the potential difference between the scratched part and the coating surface is 0.38V. After repair, the potential difference between the repaired part and the coating surface is 0.055V. The self-healing efficiency (η) of the coating can be calculated according to the formula η = (V1-V2) ÷ V1 × 100%, where V2 is the potential difference after repair and V1 is the potential difference before repair. It can be concluded that the repair efficiency of the Concorde coating is 86%.

[0161] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A self-repairing coating, characterized in that: It includes a micro-nano porous ceramic layer and an organic coating layer sequentially stacked on the surface of a substrate; The micro-nano porous ceramic layer contains an inorganic corrosion inhibitor; The organic coating contains first microcapsules and second microcapsules, the core of the first microcapsules is a repair agent, and the capsule wall of the first microcapsules is phenolic resin or urea-formaldehyde resin; the core of the second microcapsules is an organic corrosion inhibitor and a curing agent, and the capsule wall of the second microcapsules is phenolic resin or urea-formaldehyde resin.

2. The self-repairing coating according to claim 1, characterized in that: The inorganic corrosion inhibitor includes one or more of sodium phosphate, sodium tungstate and sodium stannate; The repair agent is epoxy resin; The organic corrosion inhibitor includes one or more of benzotriazole, 2-mercaptobenzothiazole and 8-hydroxyquinoline; The curing agent includes dimethylimidazole, polyetheramine or triethylenetetramine.

3. The self-repairing coating according to claim 1 or 2, characterized in that: The content of the inorganic corrosion inhibitor in the micro-nano porous ceramic layer is 0.01-0.05%; The content of the first microcapsules in the organic coating is 0.1-0.3%, and the content of the second microcapsules in the organic coating is 0.1-0.3%; The thickness of the micro-nano porous ceramic layer is 15 to 25 μm; The thickness of the organic coating is 50 to 70 μm; The thickness of the self-repairing coating is 65-95 μm.

4. The method for preparing the self-repairing coating according to any one of claims 1 to 3, characterized in that: The following steps are involved: Plasma electrolytic oxidation is performed on the surface of the substrate to form a micro-nano porous ceramic layer; the electrolyte used for plasma electrolytic oxidation includes an inorganic corrosion inhibitor; spraying a modified organic coating on the surface of the micro-nano porous ceramic layer to obtain the self-repairing coating; The modified organic coating contains a first microcapsule and a second microcapsule, wherein the core of the first microcapsule is a repairing agent and the capsule wall of the first microcapsule is a phenolic resin or a urea-formaldehyde resin; the core of the second microcapsule is an organic corrosion inhibitor and a curing agent and the capsule wall of the second microcapsule is a phenolic resin or a urea-formaldehyde resin.

5. The preparation method according to claim 4, characterized in that: The electrolyte includes a hexametaphosphate system electrolyte, a silicate system electrolyte or a metavanadate system electrolyte; The hexametaphosphate system electrolyte includes the following components in mass concentrations: 1-40 g / L hexametaphosphate, 1-30 g / L silicate, 1-30 g / L metavanadate, 1-10 g / L tartrate, 1-8 g / L corrosion inhibitor, 1-10 g / L potassium titanium oxalate, and 1-10 g / L pH regulator.

6. The preparation method according to claim 4 or 5, characterized in that: The plasma electrolytic oxidation process is accompanied by ultrasound; The conditions of the plasma electrolytic oxidation include: a frequency of 100 to 5000 Hz, a duty cycle of 10 to 50%, a pulse ratio of 10 to 40:1, and an oxidation time of 10 to 60 minutes; the output mode of the power supply is a constant current output mode or a constant voltage output mode; the current density of the constant current output mode is 1 to 10 A / dm 2 , the voltage of the constant voltage output mode is 300~650V; The power of the ultrasound is 50-1800W, and the frequency is 10-50Hz.

7. The preparation method according to claim 4, characterized in that: The mass percentage of the first microcapsules in the modified organic coating is 0.1-0.3%, and the mass percentage of the second microcapsules in the modified organic coating is 0.1-0.3%.

8. The preparation method according to claim 4 or 7, characterized in that: The first microcapsule and the second microcapsule are prepared in one step by an in-situ polymerization method.

9. The preparation method according to claim 4, characterized in that: The spraying includes air spraying, airless spraying or electrostatic spraying; The conditions for air spraying and airless spraying independently include: spraying pressure of 0.1 to 0.5 MPa, spraying distance of 80 to 200 mm, spraying angle of 45 to 90 degrees, and moving speed of 0.2 to 0.8 m / s; The conditions for the electrostatic spraying include: voltage of 50-95 kV, current of 5-50 A, feed pressure of 0-0.3 MPa, air pressure of 0.05-0.4 MPa, and spraying distance of 150-200 mm.

10. Use of the self-repairing coating according to any one of claims 1 to 3 or the self-repairing coating prepared by the preparation method according to any one of claims 4 to 9 in alloys and composite materials thereof.

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