Environment-friendly fluorine-free anticorrosive coating for aluminum alloy surface and preparation method thereof

Abstract

The application relates to the technical field of anticorrosive coatings, and discloses an environment-friendly fluorine-free aluminum alloy surface anticorrosive coating and a preparation method thereof, which comprises the following steps: based on ion exchange, single-quaternary ammonium salt seven (salicylate group) cage polysilsesquioxane is used to perform intercalation modification treatment on sodium-based montmorillonite to obtain a stable interlayer spacing type montmorillonite loaded with salicylate groups and polysilsesquioxane groups; based on the pi-pi stacking effect between phenyl groups, the stable interlayer spacing type montmorillonite is compounded with a bisphenol A glycidyl ether type epoxy resin, and is subjected to emulsification treatment through phase inversion to obtain a corrosion-resistant and weather-resistant water-based epoxy resin emulsion; and the environment-friendly fluorine-free aluminum alloy surface anticorrosive coating is prepared by taking the corrosion-resistant and weather-resistant water-based epoxy resin emulsion as a film-forming raw material. The coating product not only has excellent corrosion resistance, but also has high weather resistance, and can resist corrosion media and environmental aging at the same time when used on the surface of an aluminum alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anticorrosive coatings, in particular to an environmentally-friendly fluorine-free anticorrosive coating for aluminum alloy surface and a preparation method thereof. BACKGROUND

[0002] Aluminum alloy has the advantages of high strength, light weight, excellent ductility, etc., and is widely used in aerospace, construction, marine engineering and other fields. Under natural conditions, a layer of Al2O3 passivation film is formed on the surface of aluminum alloy, which provides certain corrosion resistance protection to the substrate. However, the thickness uniformity of the passivation film is poor and there are pores, which can be easily damaged in humid, salt spray, acid and alkali environments, and it is difficult to meet the actual use requirements.

[0003] Coating anticorrosive coating on the surface of aluminum alloy is one of the most common, convenient and effective protection methods. Anticorrosive coatings mainly include epoxy resin coatings, fluorocarbon coatings and silicone coatings, etc. Among them, fluorocarbon coatings contain a large number of high-energy C-F bonds, which have excellent weather resistance and corrosion resistance. However, they have high cost, strict construction requirements, and long-chain perfluorinated substances with biological toxicity and biological accumulation can cause harm to the human body and the environment, resulting in poor environmental performance. Silicone coatings also contain a large number of high-energy Si-O bonds, which also have excellent weather resistance and corrosion resistance. However, they have the disadvantages of poor adhesion and high cost.

[0004] Fluorine-free waterborne epoxy resin coatings have the characteristics of low cost, strong adhesion, outstanding environmental performance and good construction adaptability, and show great application potential in the field of aluminum alloy corrosion protection. However, compared with organic solvents, water has higher evaporation heat and surface tension, and longer volatilization time, which can lead to the formation of micropores and cracks in the curing process of waterborne epoxy resin coatings, thereby significantly reducing the corrosion resistance and weather resistance of the coating film.

[0005] Research has found that adding nano fillers (such as graphene, montmorillonite, mica, etc. two-dimensional sheet materials) to epoxy resin can effectively fill the micropores and other defects in the coating, prolong the diffusion path of corrosive substances and significantly improve the corrosion resistance of the coating. However, the compatibility of inorganic nano fillers and organic epoxy resin is poor, and simply blending the fillers with epoxy resin can only improve the performance of the coating to a limited extent.

[0006] In addition, the weather resistance of the waterborne epoxy resin coating is poor, and the color is easy to change when exposed to indoor light or natural sunlight, because the epoxy resin is prone to photo-oxidation reaction leading to molecular structure damage. The prior art shows that introducing a light stabilizer (such as benzophenone, benzotriazole, salicylate, cinnamate ultraviolet absorber) into the waterborne epoxy resin coating can effectively reduce the problems of discoloration, fading, cracking, powdering and gloss retention of the coating caused by light, and improve the weather resistance of the coating. However, the small molecule light stabilizer directly added into the coating is easy to migrate from the matrix, resulting in the decrease of the performance of the coating. SUMMARY

[0007] The present application independently develops a corrosion-resistant and weather-resistant waterborne epoxy resin emulsion by composite modification of the epoxy resin. An environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating is prepared by using the waterborne epoxy resin emulsion as a film-forming raw material. The coating product not only has excellent corrosion resistance, but also shows high weather resistance. When used on the surface of aluminum alloy, it can resist both corrosion medium and environmental aging, effectively prolonging the outdoor service life of the aluminum alloy surface corrosion-resistant coating and significantly enhancing the protection of aluminum alloy.

[0008] A preparation method of an environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating, comprising the following steps:

[0009] Step one: preparing a single-quaternary ammonium saltized seven (salicylate group) cage-type polyhedral oligomeric silsesquioxane;

[0010] Step two: based on ion exchange, using the single-quaternary ammonium saltized seven (salicylate group) cage-type polyhedral oligomeric silsesquioxane to perform intercalation modification treatment on sodium-based montmorillonite, and adsorbing on the surface of the montmorillonite nanosheet through electrostatic attraction to prepare a stable interlamellar spacing montmorillonite loaded with salicylate groups and polyhedral oligomeric silsesquioxane groups;

[0011] Step three: based on the π-π stacking effect between phenyl groups, the stable interlamellar spacing montmorillonite is compounded with bisphenol A glycidyl ether type epoxy resin, and emulsified by phase inversion method to prepare a corrosion-resistant and weather-resistant waterborne epoxy resin emulsion;

[0012] Step four: using the corrosion-resistant and weather-resistant waterborne epoxy resin emulsion as a film-forming raw material, adding composite additives and curing agents to prepare an environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating.

[0013] Preferably, the preparation method of the single-quaternary ammonium saltized seven (salicylate group) cage-type polyhedral oligomeric silsesquioxane is as follows:

[0014] Using 3-aminopropyl triethoxysilane as a raw material, octa-aminopropyl cage-type polyhedral oligomeric silsesquioxane is synthesized by hydrolysis condensation method;

[0015] A seven(amino propyl)trisilanol cage polysilsesquioxane is synthesized by vertex-capping method using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride as capping reagent and taking the seven(amino propyl)trisilanol cage polysilsesquioxane as raw material;

[0016] A seven(amino propyl)trisilanol cage polysilsesquioxane is synthesized by vertex-capping method using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride as capping reagent and taking the seven(amino propyl)trisilanol cage polysilsesquioxane as raw material;

[0017] A seven(salicylate) cage polysilsesquioxane is synthesized by amidation reaction between 1 mole equivalent of amino functional groups of the monoquaternary ammonium saltified seven(amino propyl) cage polysilsesquioxane and 7.01-7.09 mole equivalent of carboxyl functional groups of the bis-salicylate.

[0018] Preferably, the mass ratio of the monoquaternary ammonium saltified seven(salicylate) cage polysilsesquioxane to the sodium-based montmorillonite in the interlamellar spacing stable montmorillonite is 1:(2-5).

[0019] Preferably, the flake diameter of the sodium-based montmorillonite is 5-10 μm and the thickness is 3-8 nm.

[0020] Preferably, the amount of the interlamellar spacing stable montmorillonite in the corrosion and weather resistant waterborne epoxy resin emulsion is 5-15 wt% of the amount of the bisphenol A glycidyl ether type epoxy resin.

[0021] An environmentally friendly fluorine-free aluminum alloy surface corrosion resistant coating prepared according to the above method;

[0022] Preferably, the environmentally friendly fluorine-free aluminum alloy surface corrosion resistant coating comprises A component and B component.

[0023] Preferably, the formula of the A component is: 60-70 parts by weight of the corrosion and weather resistant waterborne epoxy resin emulsion, 2-8 parts by weight of the composite additive, and 20-40 parts by weight of water.

[0024] Preferably, the formula of the B component is: 50-60 parts by weight of the curing agent and 40-50 parts by weight of water.

[0025] Preferably, the composite additive comprises 1-3 parts by weight of wetting agent, 0.5-3 parts by weight of defoaming agent, and 0.5-2 parts by weight of thickening agent.

[0026] Beneficial effects:

[0027] The present application is based on the principle of molecular design, and a cage-type polysilsesquioxane with excellent corrosion resistance and weather resistance is used as a basic connecting framework, the cage-type siloxane framework is opened by a vertex opening method, and then the cage-type siloxane framework is re-closed by a vertex capping method to introduce a quaternary ammonium salt group, and then a salicylate group with ultraviolet light absorption function is modified on the cage-type polysilsesquioxane framework by an amino-carboxyl amidation reaction to prepare a mono-quaternary ammonium salt seven (salicylate group) cage-type polysilsesquioxane;

[0028] Based on ion exchange, the mono-quaternary ammonium salt seven (salicylate group) cage-type polysilsesquioxane is used for intercalation modification treatment of sodium-based montmorillonite, and is adsorbed on the surface of the montmorillonite nanosheet by electrostatic attraction to prepare a stable interlamellar spacing montmorillonite loaded with salicylate groups and polysilsesquioxane groups;

[0029] Based on the π-π stacking of phenyl groups, the stable interlamellar spacing montmorillonite is compounded with a bisphenol A glycidyl ether type epoxy resin, and then a corrosion-resistant and weather-resistant water-based epoxy resin emulsion is prepared by phase inversion under the action of an emulsifier;

[0030] The environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating is prepared by using the corrosion-resistant and weather-resistant water-based epoxy resin emulsion as a film-forming raw material and adding a composite additive and a curing agent;

[0031] It is found through experimental results that the water-based epoxy resin coating product prepared by compounding and modifying the epoxy resin with the stable interlamellar spacing montmorillonite loaded with salicylate groups and polysilsesquioxane groups has a significant improvement in corrosion resistance and weather resistance compared with the conventional water-based epoxy resin coating without modification;

[0032] The environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating prepared by the present application has excellent comprehensive performance and practical application value. DETAILED DESCRIPTION

[0033] The present application develops a stable interlamellar spacing montmorillonite loaded with salicylate groups and polysilsesquioxane groups, which is used for modifying the epoxy resin, can significantly enhance the compatibility of inorganic fillers (montmorillonite) and organic matrix (epoxy resin), and effectively avoid the migration and precipitation of light stabilizers (salicylate) in the epoxy resin system.

[0034] Experimental example:

[0035] The mono-quaternary ammonium salt seven (salicylate group) cage-type polysilsesquioxane is prepared, and the preparation process is as follows:

[0036] Step one: 3-aminopropyl triethoxysilane (KH-550) as raw material, by hydrolysis condensation method to synthesize eight aminopropyl cage polysilsesquioxane, its chemical structural formula is:

[0037] ;

[0038] Step two: eight aminopropyl cage polysilsesquioxane as raw material, using tetraethylammonium hydroxide as opening reagent, by vertex-opening method to synthesize seven (aminopropyl) trisilanol cage polysilsesquioxane, its chemical structural formula is:

[0039] ;

[0040] Step three: seven (aminopropyl) trisilanol cage polysilsesquioxane as raw material, using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride as capping reagent, by vertex-capping method to synthesize single quaternary ammonium salt seven (aminopropyl) cage polysilsesquioxane, its chemical structural formula is:

[0041] ;

[0042] Step four: by 1 mole equivalent of single quaternary ammonium salt seven (aminopropyl) cage polysilsesquioxane amino functional group and 7.02 mole equivalent of double salicylate carboxyl functional group amide reaction, to generate single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane, its chemical structural formula is:

[0043] ;

[0044] The specific experimental steps of preparing single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane are as follows:

[0045] 90 mL of deionized water, 40 mL of ethanol, 10 mL of acetonitrile, 5 mL of triethylamine and 2 mL of 35wt% tetraethylammonium hydroxide aqueous solution were added into a three-necked flask, and the mixture was stirred at 50℃ for 30 min. Then 200 mL of 3-aminopropyl triethoxysilane was added dropwise into the three-necked flask, and the reaction was carried out at 50℃ for 24 h. After cooling to room temperature, the mixture was concentrated by rotary evaporation and then added dropwise into petroleum ether. After standing, suction filtration, and repeated washing with acetone and deionized water, the product was dried under vacuum to obtain eight aminopropyl cage polysilsesquioxane;

[0046] Into a three-necked flask, 8.8 g of octakis(aminopropyl)cage polysilsesquioxane and 100 mL of tetrahydrofuran were added, and stirred at room temperature until completely dissolved, then 10 mL of 30 wt% aqueous tetraethylammonium hydroxide solution was added to the flask, and the reaction was carried out at 70°C for 5 h under reflux with stirring, and then cooled to room temperature, and the pH was adjusted to neutral with 0.1 mol / L dilute hydrochloric acid, and then tetrahydrofuran was removed by rotary evaporation, and then dissolved in diethyl ether, and dried with anhydrous magnesium sulfate, filtered, and then diethyl ether was removed by rotary evaporation, and then vacuum dried to obtain incompletely condensed octakis(aminopropyl)trisilanol cage polysilsesquioxane;

[0047] Into a three-necked flask, 4.0 g of incompletely condensed octakis(aminopropyl)trisilanol cage polysilsesquioxane and 50 mL of tetrahydrofuran were added, and stirred at room temperature until completely dissolved, then placed in an ice water bath, and 1.4 mL of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride was added dropwise to the flask, and stirred in the ice water bath for 1 h, then removed from the ice water bath, and continued to stir at room temperature for 8 h, and then the solvent was removed by rotary evaporation, and then vacuum dried to obtain monoquaternary ammonium saltified octakis(aminopropyl) cage polysilsesquioxane;

[0048] Into a three-necked flask, 3.2 g of monoquaternary ammonium saltified octakis(aminopropyl) cage polysilsesquioxane and 30 mL of tetrahydrofuran were added, and stirred at room temperature until completely dissolved, then 40 mL of a tetrahydrofuran solution containing 6.0 g of disalicylate and 10 mL of a tetrahydrofuran solution containing 1.5 g of N,N'-dicyclohexyl carbodiimide catalyst were sequentially added to the flask, and the reaction was carried out at 70°C for 6 h under reflux with stirring, and then cooled to room temperature, and then the solvent was removed by rotary evaporation, and then sequentially washed with ethanol and deionized water, and then vacuum dried to obtain monoquaternary ammonium saltified octakis(salicylato) cage polysilsesquioxane;

[0049] The proton nuclear magnetic resonance spectrum of the monoquaternary ammonium saltified octakis(salicylato) cage polysilsesquioxane was characterized as follows: 1 H NMR (CDCI3, 400 MHz) δ: 0.63-0.66 (t, 14H), 0.80-0.83 (t, 2H), 1.61-1.81 (m, 16H), 3.18-3.32 (m, 14H), 3.43 (s, 9H), 3.49-3.53 (t, 2H), 6.90-7.91 (m, 56H, Ar-H).

[0050] Example One:

[0051] Preparation of the interlamellar spacing stable montmorillonite loaded with salicylate groups and polysilsesquioxane groups: The sodium-based montmorillonite is intercalated and modified by using the mono-quaternary ammonium salt of seven (salicylate group) cage-type polysilsesquioxane, and the ammonium cation of the mono-quaternary ammonium salt of seven (salicylate group) cage-type polysilsesquioxane first undergoes ion exchange with the interlamellar sodium cation of the sodium-based montmorillonite, and then the salicylate groups and polysilsesquioxane groups are loaded on the surface of the montmorillonite nanosheet through electrostatic interaction to prepare the interlamellar spacing stable montmorillonite, and the specific experimental steps are as follows: 5 g of sodium-based montmorillonite (5-10 μm in diameter and 3-8 nm in thickness), 90 mL of tetrahydrofuran and 10 mL of deionized water are added to a three-necked flask, ultrasonic treatment is performed for 30 min, and then the mixture is stirred and dispersed at 60°C for 2 h. Then 10 mL of tetrahydrofuran solution containing 2 g of mono-quaternary ammonium salt of seven (salicylate group) cage-type polysilsesquioxane is added to the three-necked flask, and the mixture is stirred at 60°C for 8 h. Filtration is performed, and the obtained product is washed with ethanol until no precipitate is detected in silver nitrate solution. Vacuum drying is performed to obtain the interlamellar spacing stable montmorillonite loaded with salicylate groups and polysilsesquioxane groups.

[0052] Example 2

[0053] Preparation of the corrosion-resistant and weather-resistant water-based epoxy resin emulsion I: First, the phenyl groups in the salicylate groups loaded on the interlamellar spacing stable montmorillonite undergo π-π stacking with the phenyl groups rich in the molecular backbone of the bisphenol A glycidyl ether type epoxy resin, and then 0.5 parts by weight of the interlamellar spacing stable montmorillonite loaded with salicylate groups and polysilsesquioxane groups is compounded with 10 parts by weight of the bisphenol A glycidyl ether type epoxy resin. Then, the corrosion-resistant and weather-resistant water-based epoxy resin emulsion I is prepared by phase inversion method under the action of an emulsifier.

[0054] The specific experimental steps for preparing the corrosion-resistant and weather-resistant water-based epoxy resin emulsion I are as follows: 10 g of bisphenol A glycidyl ether type epoxy resin (model E-51) and 100 mL of acetone are added to a beaker, and the mixture is stirred at 50°C until it is completely dissolved. Then, 0.5 g of the interlamellar spacing stable montmorillonite loaded with salicylate groups and polysilsesquioxane groups is added to the beaker, and the mixture is stirred at 50°C for 4 h. The solvent is removed by rotary evaporation, and the mixture is dried in an oven at 60°C for 5 h. After cooling to room temperature, the mixture is again added to a beaker, and 10 mL of propylene glycol butyl ether cosolvent and 1.2 g of emulsifier (model OP-10) are added. The mixture is stirred uniformly at 100°C at a speed of 600 r / min. The temperature is reduced to 50°C, and the speed is increased to 2000 r / min. Deionized water is added to the system at a speed of 4 drops per second under the action of high-speed shearing, and the viscosity of the system is observed. When the viscosity of the system instantaneously jumps and completely phase inverts, the addition of deionized water is continued until the solid content of the system reaches 55%. The corrosion-resistant and weather-resistant water-based epoxy resin emulsion I is obtained.

[0055] Example three:

[0056] A corrosion and weather resistant waterborne epoxy resin emulsion II is prepared, which is only different from the corrosion and weather resistant waterborne epoxy resin emulsion I in that the amount of the interlamellar spacing stabilized montmorillonite loaded with salicylate groups and polysilsesquioxane groups is 1.0 parts by weight.

[0057] Example four:

[0058] A corrosion and weather resistant waterborne epoxy resin emulsion III is prepared, which is only different from the corrosion and weather resistant waterborne epoxy resin emulsion I in that the amount of the interlamellar spacing stabilized montmorillonite loaded with salicylate groups and polysilsesquioxane groups is 1.5 parts by weight.

[0059] Example five:

[0060] An environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating, comprising A component and B component;

[0061] The A component comprises the following raw materials in parts by weight: 65 parts of the corrosion and weather resistant waterborne epoxy resin emulsion, 2 parts of the wetting agent (model BYK-346), 2 parts of the defoaming agent (model BYK-011), 1 part of the thickening agent (model BYK-428), and 30 parts of water.

[0062] The B component comprises the following raw materials in parts by weight: 55 parts of the curing agent (model AB-HGA-50) and 45 parts of water.

[0063] The corrosion and weather resistant waterborne epoxy resin emulsion is one of the corrosion and weather resistant waterborne epoxy resin emulsion I, the corrosion and weather resistant waterborne epoxy resin emulsion II, and the corrosion and weather resistant waterborne epoxy resin emulsion III.

[0064] Example six:

[0065] A preparation method of an environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating, comprising the following steps:

[0066] Step one, preparing the A component: according to the formula of the A component, mix water, a wetting agent, and a defoaming agent, stir at a speed of 600 r / min for 5 min, then add a corrosion and weather resistant waterborne epoxy resin emulsion, keep stirring at a speed of 600 r / min for 15 min, finally add a thickening agent and stir for 5 min, reduce the speed to 200 r / min, and defoam at a low speed for 30 min to obtain the A component of the environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating;

[0067] Step two, preparing the B component: according to the formula of the B component, mix a curing agent and water, and stir to dissolve at a speed of 100 r / min for 30 min to obtain the B component of the environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating;

[0068] Step three, preparation of environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint: A component and B component are mixed uniformly according to the mass ratio of 4:1 to prepare environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint;

[0069] When the corrosion-resistant and weather-resistant waterborne epoxy resin emulsion is corrosion-resistant and weather-resistant waterborne epoxy resin emulsion I, the prepared paint product is marked as environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint I;

[0070] When the corrosion-resistant and weather-resistant waterborne epoxy resin emulsion is corrosion-resistant and weather-resistant waterborne epoxy resin emulsion II, the prepared paint product is marked as environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint II;

[0071] When the corrosion-resistant and weather-resistant waterborne epoxy resin emulsion is corrosion-resistant and weather-resistant waterborne epoxy resin emulsion III, the prepared paint product is marked as environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint III.

[0072] Comparative example:

[0073] A conventional waterborne epoxy resin paint is prepared, which is different from the environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant paint I only in that the conventional waterborne epoxy resin emulsion is used instead of the corrosion-resistant and weather-resistant waterborne epoxy resin emulsion I;

[0074] The preparation method of the conventional waterborne epoxy resin emulsion is as follows: 10 g of bisphenol A glycidyl ether type epoxy resin (model E-51), 10 mL of propylene glycol butyl ether cosolvent and 1.2 g of emulsifier (model OP-10) are added to a beaker, heated to 100°C, and stirred uniformly at a speed of 600 r / min. The temperature is reduced to 50°C and the speed is increased to 2000 r / min. Deionized water is added to the system at a rate of 4 drops per second under high-speed shearing, and the viscosity of the system is observed. Until the system viscosity instantaneously jumps and completely phase inverts, continue to add deionized water until the system solid content is 55%, to obtain a conventional waterborne epoxy resin emulsion.

[0075] Performance test:

[0076] Aluminum alloy (size 150 mm x 70 mm x 0.28 mm, model 2024) is used as the experimental substrate. First, the aluminum alloy is pretreated: the surface of the aluminum alloy is polished with 800# silicon carbide sandpaper, and then the polished aluminum alloy is washed with deionized water and anhydrous ethanol in turn and dried. Then the paint product is sprayed on the surface of the aluminum alloy using an adjustable pressure spray gun (spray gun caliber 2.0 mm, air pressure 0.4 MPa, spraying distance 20 cm) (each sample is sprayed for an average of two rounds, and the coating thickness is controlled at 50 μm). After curing, an environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating is formed, and the corrosion resistance and weather resistance are tested, and the results are shown in Table 1.

[0077] Table 1 Performance test results of the environment-friendly fluorine-free aluminum alloy surface corrosion-resistant paint

[0078]

[0079] Note: The weather resistance test parameters in Table 1 are set as: light source wavelength 340 nm, light irradiation intensity 0.51 W / m 2 , light temperature 60℃, light cycle 4h, condensation temperature 50℃, condensation cycle 4h;

[0080] The following conclusions can be drawn from the experimental results in Table 1:

[0081] The present application utilizes the independently developed sheet layer spacing stable montmorillonite carrying salicylate groups and polysilsesquioxane groups to perform composite modification treatment on epoxy resin, and the water-based epoxy resin coating product prepared thereby has significantly improved beneficial technical effects in corrosion resistance and weather resistance compared to conventional water-based epoxy resin coating without modification treatment;

[0082] The basic performance of the environment-friendly fluorine-free aluminum alloy surface corrosion-resistant paint was tested, and the test results are shown in Table 2 as follows:

[0083] Table 2 Performance test results of the environment-friendly fluorine-free aluminum alloy surface corrosion-resistant paint

[0084]

[0085] The following conclusions can be drawn from the experimental results in Table 2: The environment-friendly fluorine-free aluminum alloy surface corrosion-resistant paint prepared by the present application has excellent comprehensive performance and practical application value.

Claims

1. A method for preparing an environmentally friendly fluorine-free anticorrosive coating for aluminum alloy surfaces, characterized by, The method comprises the following steps: Step 1: preparing a single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane, whose chemical structural formula is as follows: ； Step 2: based on ion exchange, using the single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane to modify the sodium-based montmorillonite by intercalation, and adsorbing on the surface of the sodium-based montmorillonite by electrostatic attraction, to obtain a stable interlayer spacing montmorillonite loaded with salicylate groups and polysilsesquioxane groups; Step 3: based on the π-π stacking effect between phenyl groups, the stable interlayer spacing montmorillonite is compounded with bisphenol A glycidyl ether type epoxy resin, and emulsified by phase inversion to obtain a corrosion-resistant and weather-resistant water-based epoxy resin emulsion; Step 4: using the corrosion-resistant and weather-resistant water-based epoxy resin emulsion as a film-forming raw material, adding a composite additive and a curing agent to prepare an environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating.

2. The preparation method of the environmentally friendly fluorine-free aluminum alloy surface anticorrosive coating according to claim 1, characterized in that, The preparation method of the single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane is as follows: Using 3-aminopropyl triethoxysilane as a raw material, eight aminopropyl cage polysilsesquioxane is synthesized by hydrolysis condensation; Using eight aminopropyl cage polysilsesquioxane as a raw material, using tetraethylammonium hydroxide as an opening reagent, seven (aminopropyl) trisilanol cage polysilsesquioxane is synthesized by vertex-opening method; Using seven (aminopropyl) trisilanol cage polysilsesquioxane as a raw material, using N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride as a capping reagent, single quaternary ammonium salt seven (aminopropyl) cage polysilsesquioxane is synthesized by vertex-capping method; Through the amidation reaction between 1 mole equivalent of the amino functional group of the single quaternary ammonium salt seven (aminopropyl) cage polysilsesquioxane and 7.01-7.09 mole equivalents of the carboxyl functional group of bisalicylate, the single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane is generated.

3. The preparation method of the environment-friendly fluorine-free aluminum alloy surface anticorrosive coating of claim 1, characterized in that, The mass ratio of the single quaternary ammonium salt seven (salicylate) cage polysilsesquioxane to the sodium-based montmorillonite in the stable interlayer spacing montmorillonite is 1:(2-5).

4. The preparation method of the environment-friendly fluorine-free aluminum alloy surface anticorrosive coating of claim 3, characterized in that, The flake diameter of the sodium-based montmorillonite is 5-10 μm, and the thickness is 3-8 nm.

5. The preparation method of the environmentally friendly fluorine-free aluminum alloy surface anticorrosive coating of claim 1, characterized in that, The amount of the stable interlayer spacing montmorillonite in the corrosion-resistant and weather-resistant water-based epoxy resin emulsion is 5-15 wt% of the amount of the bisphenol A glycidyl ether type epoxy resin.

6. The environmentally friendly fluorine-free anticorrosive coating for aluminum alloy surface prepared by the method according to any one of claims 1-5, characterized in that, The environmentally friendly fluorine-free aluminum alloy surface corrosion-resistant coating comprises an A component and a B component; The formula of the A component is: 60-70 parts by weight of the corrosion-resistant and weather-resistant water-based epoxy resin emulsion, 2-8 parts by weight of the composite additive, and 20-40 parts by weight of water; The formula of the B component is: 50-60 parts by weight of the curing agent and 40-50 parts by weight of water.

7. The environmentally friendly fluorine-free aluminum alloy surface anticorrosive coating of claim 6, characterized in that, The composite additive comprises 1-3 parts by weight of a wetting agent, 0.5-3 parts by weight of a defoaming agent, and 0.5-2 parts by weight of a thickening agent.

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