Composite protective coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of coating protection, in particular to a composite protective coating as well as a preparation method and application thereof. The invention provides a composite protective coating. The composite protective coating comprises a photopolymerization precursor mixed solution, graphene oxide and a nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial, the photopolymerization precursor mixed solution is prepared from triethylene glycol dimethacrylate, 3, 4-epoxycyclohexyl methyl-3, 4-epoxycyclohexyl formate, 2-hydroxy-2-methyl propiophenone and carbonic acid acetate, and the photopolymerization precursor mixed solution is prepared from the following raw materials: triethylene glycol dimethacrylate, 3, 4-epoxycyclohexyl methyl-3, 4-epoxycyclohexyl formate, 2-hydroxy-2-methyl propiophenone and carbonic acid acetate. A protective coating prepared from the composite protective paint has high corrosion resistance and weather resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating protection, in particular to a composite protective coating material and a preparation method and application thereof. BACKGROUND

[0002] Metal materials play a vital role in the construction of national economy (such as building, transportation, etc.) and national defense (such as aerospace, weapons and equipment, etc.). However, most of the metal materials are prone to corrosion during use, resulting in structural damage and loss of function. According to statistics, the direct economic loss caused by metal corrosion worldwide is more than 3 trillion US dollars per year. Therefore, metal corrosion and protection are still major scientific and technological problems faced by the academic and industrial communities.

[0003] Coating protection technology is one of the most widely used and effective means to solve the problem of metal material corrosion. However, compared with civilian equipment, the service environment of military equipment such as aircraft, tanks, ships and artillery is significantly more complex and uncontrollable. It is usually required to be used in severe salt spray humid environment, harsh weather and intense battlefield environment. The problems of corrosion, wear, aging, mold and other problems faced by equipment will be more prominent. One of the key problems in using conventional coating technology to achieve protection of military equipment is that the protection characteristics are single, and it is difficult to meet the application requirements of long-term complex environment in multiple scenes. The coating technology developed based on inorganic-organic hybrid composite can effectively integrate the characteristics of inorganic materials and organic materials, and is considered to be the most promising technology to achieve comprehensive improvement in stability, corrosion resistance, mechanical properties, adhesion, and impact resistance of the coating. However, it usually lacks weather resistance. Therefore, it is urgent to develop protective coatings with weather resistance and corrosion resistance. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a composite protective coating material and a preparation method and application thereof. The protective coating prepared from the composite protective coating material has high corrosion resistance and weather resistance.

[0005] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions: The present application provides a composite protective coating material, which comprises a photopolymerization precursor mixed solution, graphene oxide and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. The photopolymerization precursor mixed solution comprises triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylmethyl carboxylate, 2-hydroxy-2-methylbenzophenone and ethyl acetate carbonate.

[0006] Preferably, the mass percentage of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials in the photopolymerization precursor mixed solution is 0.05-0.08%. The mass percentage of the graphene oxide in the photopolymerization precursor mixed solution is 0.05-0.08%.

[0007] Preferably, the triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate, 2-hydroxy-2-methylpropiophenone and ethyl acetate are used in a ratio of (4-6) g:(4-6) g:(0.1-0.2) g:(5-10) mL.

[0008] Preferably, the preparation method of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial comprises the following steps: Mixing cadmium sulfide, water and dopamine, and performing polymerization coating under alkaline conditions to obtain a polydopamine-coated cadmium sulfide composite material; Mixing the polydopamine-coated cadmium sulfide composite material, a soluble cobalt salt and water, and performing cobalt ion doping to obtain a cobalt ion-doped polydopamine-coated cadmium sulfide composite material; Calcining the cobalt ion-doped polydopamine-coated cadmium sulfide composite material to obtain the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial.

[0009] Preferably, the cadmium sulfide, dopamine and water are used in a ratio of (28-33) g:(2.8-3.2) g:(4.8-5.2) L; The pH value of the alkaline condition is 8.5-9.5; The temperature of the polymerization coating is 28-32℃, and the time is 3.5-4.5h.

[0010] Preferably, the polydopamine-coated cadmium sulfide composite material, the soluble cobalt salt and water are used in a ratio of (2-3) g:(2-3) g:(1-1.3) L; The soluble cobalt salt comprises cobalt nitrate; The calcination is performed in a protective atmosphere, the temperature of the calcination is 700-900℃, and the time is 1.5-2.5h.

[0011] Preferably, the preparation method of the cadmium sulfide comprises the following steps: Mixing a soluble cadmium salt, thiourea and an aqueous solution of ethylenediamine, and performing hydrothermal reaction to obtain the cadmium sulfide.

[0012] Preferably, the soluble cadmium salt, thiourea and the aqueous solution of ethylenediamine are used in a ratio of (2.7-3.2) g:(2.1-2.5) g:(28-32) mL; The mass concentration of the aqueous solution of ethylenediamine is 40%; The temperature of the hydrothermal reaction is 150-170℃, and the time is 44-50h.

[0013] This invention also provides a method for preparing the composite protective coating described in the above technical solution, comprising the following steps: Under light-protected conditions, a photopolymerization precursor mixture, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials are mixed to obtain the composite protective coating.

[0014] The present invention also provides the application of the composite protective coating described in the above technical solution or the composite protective coating prepared by the preparation method described in the above technical solution in the field of coating protection.

[0015] This invention provides a composite protective coating comprising a photopolymerization precursor mixture, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. The photopolymerization precursor mixture comprises triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone, and acetate carbonate. The nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials in this composite protective coating exhibit excellent visible / ultraviolet light absorption and form a strong reducing environment, which can control the photopolymerization process and enhance the coating's weather resistance. Simultaneously, the introduction of graphene oxide enhances the coating's corrosion resistance and adhesion, and also absorbs ultraviolet light, further enhancing its weather resistance. Therefore, this composite protective coating not only possesses excellent corrosion resistance but also good weather resistance. According to the embodiments, the composite protective coating prepared by this invention exhibits salt spray resistance >500h and weather resistance >500h. Attached Figure Description

[0016] Figure 1 Optical images of the coating prepared by the composite protective coating described in Example 1 before and after salt spray testing; Figure 2 Optical images of the coating prepared from the photopolymerization precursor mixture described in Comparative Example 1 before and after salt spray testing; Figure 3 Optical images of the coating prepared by the composite protective coating described in Example 1 before and after aging tests; Figure 4 Optical images of the coating prepared from the photopolymerization precursor mixture described in Comparative Example 1 before and after aging tests. Detailed Implementation

[0017] This invention provides a composite protective coating comprising a photopolymerization precursor mixture, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. The photopolymerization precursor mixture includes triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone, and acetate carbonate.

[0018] In this invention, unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0019] In this invention, the photopolymerization precursor mixture comprises triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone, and acetate carbonate; the preferred ratio of triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone, and acetate carbonate is (4~6) g:(4~6) g:(0.1~0.2) g:(5~10) mL, more preferably 4 g. : 4g: 0.1g: (5~10) mL, 4g: 5g: 0.1g: (5~10) mL, 4g: 6g: 0.1g: (5~10) mL, 5g: 4g: 0.1g: (5~10) mL, 5g: 5g: 0.1g: (5~10) mL, 5g: 6g: 0.1g: (5~10) mL, 6g: 4g: 0.1g: (5~10) mL, 6g: 6g: 0.1g: (5~10) mL or 6g: 6g: 0.1g: (5~10) mL. In embodiments of the present invention, the ratio of triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone and acetic acid carbonate can be 5g:5g:0.1g:7mL or 5g:4g:0.1g:5mL.

[0020] In this invention, the graphene oxide content in the photopolymerization precursor mixture is preferably 0.05-0.08% by mass, more preferably 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, or 0.08%. In an embodiment of this invention, the graphene oxide content in the photopolymerization precursor mixture is 0.06% or 0.08% by mass.

[0021] In this invention, the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial accounts for 0.05-0.08% of the mass percentage of the photopolymerization precursor mixture, more preferably 0.05%, 0.055%, 0.06%, 0.065%, 0.07%, 0.075%, or 0.08%. In an embodiment of this invention, the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial accounts for 0.06% or 0.08% of the mass percentage of the photopolymerization precursor mixture.

[0022] In this invention, the preparation method of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial preferably includes the following steps: Cadmium sulfide, water and dopamine are mixed and polymerized under alkaline conditions to obtain polydopamine-coated cadmium sulfide composite material. The polydopamine-coated cadmium sulfide composite material, soluble cobalt salt, and water are mixed to perform cobalt ion doping, wherein the cobalt ion doped polydopamine-coated cadmium sulfide composite material is used. The cobalt ion-doped polydopamine-coated cadmium sulfide composite material was calcined to obtain the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial.

[0023] This invention involves mixing cadmium sulfide, water, and dopamine, and then polymerizing and coating them under alkaline conditions to obtain a polydopamine-coated cadmium sulfide composite material.

[0024] In this invention, the method for preparing cadmium sulfide preferably includes the following steps: An aqueous solution of soluble cadmium salt, thiourea, and ethylenediamine is mixed and subjected to a hydrothermal reaction to obtain the cadmium sulfide.

[0025] In this invention, the soluble cadmium salt preferably includes cadmium nitrate tetrahydrate.

[0026] In this invention, the preferred ratio of the aqueous solution of the soluble cadmium salt, thiourea, and ethylenediamine is (2.7~3.2) g:(2.1~2.5) g:(28~32) mL, more preferably 2.7 g:(2.1~2.5) g:(28~32) mL, 2.8 g:(2.1~2.5) g:(28~32) mL, 2.9 g:(2.1~2.5) g:(28~32) mL, 3.0 g:(2.1~2.5) g:(28~32) mL, 3.1 g: The dosages are (2.1~2.5)g:(28~32)mL, 3.2g:(2.1~2.5)g:(28~32)mL, (2.7~3.2)g:2.1g:(28~32)mL, (2.7~3.2)g:2.2g:(28~32)mL, (2.7~3.2)g:2.3g:(28~32)mL, (2.7~3.2)g:2.4g:(28~32)mL, or (2.7~3.2)g:2.5g:(28~32)mL. In this invention, the mass concentration of the aqueous solution of ethylenediamine is preferably 40%. In the embodiments of this invention, the ratio of the soluble cadmium salt, thiourea, and the aqueous solution of ethylenediamine can be 3.05g:2.3g:30mL or 3.05g:2.5g:30mL.

[0027] In this invention, the mixing is preferably carried out under stirring conditions. The stirring process is not particularly limited and can be performed using a process well-known to those skilled in the art. In embodiments of this invention, the stirring time can be 25 minutes or 30 minutes.

[0028] In this invention, the temperature of the hydrothermal reaction is preferably 150~170℃, more preferably 150℃, 155℃, 160℃, 165℃ or 170℃; the time is preferably 44~50h, more preferably 44h, 45h, 46h, 47h, 48h, 49h or 50h. In embodiments of this invention, the temperature of the hydrothermal reaction can be 160℃ or 180℃, and the time can be 48h or 44h.

[0029] After the hydrothermal reaction is completed, the present invention preferably includes sequential filtration, washing and drying. The washing method is preferably rinsing with deionized water. The present invention does not have any special limitations on the filtration, rinsing and drying process, and any process known to those skilled in the art can be used.

[0030] In this invention, the water is preferably deionized water.

[0031] In this invention, the preferred ratio of cadmium sulfide, dopamine, and water is (28~33) g:(2.8~3.2) g:(4.8~5.2) L, more preferably 28 g:(2.8~3.2) g:(4.8~5.2) L, 29 g:(2.8~3.2) g:(4.8~5.2) L, 30 g:(2.8~3.2) g:(4.8~5.2) L, 31 g:(2.8~3.2) g:(4.8~5.2) L, 32 g:(2.8~3.2) g:(4.8~5.2) L, etc. 8~3.2)g:(4.8~5.2)L, 33g:(2.8~3.2)g:(4.8~5.2)L, (28~33)g:2.8g:(4.8~5.2)L, (28~33)g:2.9g:(4.8~5.2)L, (28~33)g:3.0g:(4.8~5.2)L, (28~33)g:3.1g:(4.8~5.2)L, or (28~33)g:3.2g:(4.8~5.2)L. In embodiments of the present invention, the ratio of cadmium sulfide, dopamine, and water can be 30g:3g:5L or 30g:3.2g:5L.

[0032] In this invention, the mixing of cadmium sulfide, water, and dopamine is preferably carried out by ultrasonically mixing cadmium sulfide and water before adding dopamine. In this invention, the ultrasonic mixing time is preferably 25-35 minutes, more preferably 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 34 minutes, or 35 minutes. In embodiments of this invention, the ultrasonic mixing time can be 25 minutes or 30 minutes. This invention does not impose any special limitations on the dopamine addition process; any process well-known to those skilled in the art can be used.

[0033] In this invention, the pH value of the alkaline condition is preferably 8.5 to 9.5, more preferably 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, or 9.5. In an embodiment of this invention, the pH value of the alkaline condition can be 9.0. In this invention, the alkaline condition is preferably achieved by adding ammonia.

[0034] In this invention, the polymerization coating temperature is preferably 28~32℃, more preferably 28℃, 29℃, 30℃, 31℃ or 32℃; the time is preferably 3.5~4.5h, more preferably 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4.0h, 4.1h, 4.2h, 4.3h, 4.4h or 4.5h. In an embodiment of this invention, the polymerization coating temperature can be 30℃ and the time can be 4h.

[0035] After the polymerization coating is completed, the present invention preferably includes sequential filtration, washing and drying. The washing method is preferably rinsing with deionized water. The present invention does not have any special limitations on the filtration, rinsing and drying process, and any process known to those skilled in the art can be used.

[0036] After obtaining the polydopamine-coated cadmium sulfide composite material, the present invention mixes the polydopamine-coated cadmium sulfide composite material, soluble cobalt salt and water, and performs cobalt ion doping to obtain cobalt ion-doped polydopamine-coated cadmium sulfide composite material.

[0037] In this invention, the preferred ratio of the polydopamine-coated cadmium sulfide composite material, the soluble cobalt salt, and water is (2~3) g:(2~3) g:(1~1.3) L, more preferably 2 g:(2~3) g:(1.2~1.3) L, 2.5 g:(2~3) g:(1.2~1.3) L, 3 g:(2~3) g:(1.2~1.3) L, (2~3) g:2 g:(1.2~1.3) L, (2~3) g:2.5 g:(1.2~1.3) L, or (2~3) g:3 g:(1.2~1.3) L. In embodiments of this invention, the preferred ratio of the polydopamine-coated cadmium sulfide composite material, the soluble cobalt salt, and water is 2.5 g:2.5 g:1.25 L or 2 g:3 g:1 L.

[0038] In this invention, the soluble cobalt salt preferably includes cobalt nitrate.

[0039] In this invention, the water is preferably deionized water.

[0040] In this invention, the mixing is preferably performed by ultrasonically mixing the polydopamine-coated cadmium sulfide composite material with water, then adding a soluble cobalt salt, and continuing ultrasonication. In this invention, the ultrasonic mixing and continued ultrasonication times are independently preferably 25-35 min, more preferably 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, or 35 min. In embodiments of this invention, the ultrasonic mixing time can be 30 min or 25 min, and the continued ultrasonication time can be 30 min or 25 min. In this invention, the continued ultrasonication process is the cobalt ion doping process.

[0041] After the cobalt ion doping is completed, the present invention preferably includes sequential filtration, washing and drying. The washing method is preferably rinsing with deionized water. The present invention does not have any special limitations on the filtration, rinsing and drying process, and any process known to those skilled in the art can be used.

[0042] After obtaining the cobalt ion-doped polydopamine-coated cadmium sulfide composite material, the present invention calcines the cobalt ion-doped polydopamine-coated cadmium sulfide composite material to obtain the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial.

[0043] In this invention, the calcination is preferably carried out in a protective atmosphere, preferably a nitrogen atmosphere; the calcination temperature is preferably 700~900℃, more preferably 700℃, 750℃, 800℃, 850℃ or 900℃; the calcination time is preferably 1.5~2.5h, more preferably 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h. In an embodiment of this invention, the calcination temperature can be 800℃ or 850℃, and the time can be 2h or 1.8h.

[0044] This invention also provides a method for preparing the composite protective coating described in the above technical solution, comprising the following steps: Under light-protected conditions, a photopolymerization precursor mixture, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials are mixed to obtain the composite protective coating.

[0045] In this invention, the mixing is preferably carried out under stirring conditions. This invention does not impose any special limitations on the stirring process, and any process well known to those skilled in the art can be used.

[0046] This invention also provides the application of the composite protective coating described in the above-described technical solutions or the composite protective coating prepared by the preparation method described in the above-described technical solutions in the field of coating protection. This invention does not impose any special limitations on the method of application; any method well-known to those skilled in the art can be used.

[0047] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0048] Example 1 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 160 °C for 48 h. After filtration, deionization rinsing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 30min. Then add 0.3g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, deionize, rinse and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 30min. 1.5g of cobalt nitrate was added and ultrasonicated for 30min. The mixture was then filtered, rinsed with deionized water, and dried to obtain the cobalt ion-doped polydopamine-coated cadmium sulfide composite material. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. Six mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial and six mg of graphene oxide were mechanically dispersed in 10.1 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 7 mL of ethylene carbonate) under light-shielded conditions to obtain a composite protective coating.

[0049] Example 2 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 180 °C for 44 h. After filtration, deionization washing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 30min. Then add 0.32g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, deionize, rinse and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 30min. 1.5g of cobalt nitrate was added and ultrasonicated for 30min. The mixture was then filtered, rinsed with deionized water, and dried to obtain the cobalt ion-doped polydopamine-coated cadmium sulfide composite material. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. 8 mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial and 6 mg of graphene oxide were mechanically dispersed in 10 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 7 mL of ethylene carbonate) under light-shielded conditions to obtain a composite protective coating.

[0050] Example 3 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 160 °C for 48 h. After filtration, deionization rinsing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 30min. Then add 0.3g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, deionize, rinse and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 30min. 1g of cobalt nitrate was added and ultrasonically dispersed for 30min. After filtration, rinsing with deionized water, and drying, cobalt ion-doped polydopamine-coated cadmium sulfide composite material was obtained. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. 8 mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial and 8 mg of graphene oxide were mechanically dispersed in 10 g of photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 7 mL of ethylene carbonate) under light-shielded conditions to obtain a composite protective coating.

[0051] Example 4 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 160 °C for 48 h. After filtration, deionization rinsing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 30min. Then add 0.3g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, deionize, rinse and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 30min. 1.5g of cobalt nitrate was added and ultrasonicated for 30min. The mixture was then filtered, rinsed with deionized water, and dried to obtain the cobalt ion-doped polydopamine-coated cadmium sulfide composite material. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. Six mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial and six mg of graphene oxide were mechanically dispersed in 10.1 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 4 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 5 mL of ethylene carbonate) under light-shielded conditions to obtain a composite protective coating.

[0052] Example 5 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 25 min, the solution was transferred to a hydrothermal reactor and reacted at 160 °C for 48 h. After filtration, deionization washing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 25min. Then add 0.3g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, rinse with deionized water and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 25min. 1g of cobalt nitrate was added and ultrasonicated for 25min. After filtration, rinsing with deionized water, and drying, cobalt ion-doped polydopamine-coated cadmium sulfide composite material was obtained. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. Six mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial and six mg of graphene oxide were mechanically dispersed in 10 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 7 mL of ethylene carbonate) under light-shielded conditions to obtain a composite protective coating.

[0053] Comparative Example 1 5g of triethylene glycol dimethacrylate, 5g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1g of 2-hydroxy-2-methylphenylacetone and 7mL of ethylene carbonate were mixed to obtain a photopolymerization precursor mixture.

[0054] Comparative Example 2 6.1 g of cadmium nitrate tetrahydrate and 4.6 g of thiourea were added to 60 mL of ethylenediamine aqueous solution (mass concentration of 40%). After stirring for 30 min, the solution was transferred to a hydrothermal reactor and reacted at 160 °C for 48 h. After filtration, deionization rinsing and drying, cadmium sulfide nanoparticles were obtained. Add 3g of the cadmium sulfide to 500mL of deionized water and sonicate for 30min. Then add 0.3g of dopamine and adjust the pH to 9 with ammonia. React at 30℃ for 4h. Filter, deionize, rinse and dry to obtain polydopamine-coated cadmium sulfide composite material. 1g of the polydopamine-coated cadmium sulfide composite material was ultrasonically dispersed in 500mL of deionized water for 30min. 1.5g of cobalt nitrate was added and ultrasonicated for 30min. The mixture was then filtered, rinsed with deionized water, and dried to obtain the cobalt ion-doped polydopamine-coated cadmium sulfide composite material. 1g of the cobalt ion-doped polydopamine-coated cadmium sulfide composite material was placed in a tube furnace under nitrogen protection and calcined at 800°C for 2h to obtain nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials. Six mg of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial was mechanically dispersed in 10.1 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylacetone and 7 mL of ethylene carbonate) under light-protected conditions to obtain a composite protective coating.

[0055] Comparative Example 3 6 mg of graphene oxide was mechanically dispersed in 10.1 g of a photopolymerization precursor mixture (containing 5 g of triethylene glycol dimethacrylate, 5 g of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 0.1 g of 2-hydroxy-2-methylphenylacetone and 7 mL of ethylene carbonate) under light-protected conditions to obtain a composite protective coating.

[0056] Test case Salt spray test: The composite protective coatings described in Examples 1-5 and Comparative Examples 2-3, and the photopolymerization precursor mixture described in Comparative Example 1, were uniformly applied to the surface of steel sheets and cured under light. After obtaining the coatings, a salt spray test was conducted according to national standard GB / T1771-1991 at 35°C, 100% relative humidity, and a 5% (w / w) NaCl solution. The test results are shown in Table 1 and... Figures 1-2 As shown: Among them, Figure 1 Optical images of the coating prepared by the composite protective coating described in Example 1 before and after salt spray testing; Figure 2 Optical images of the coating prepared from the photopolymerization precursor mixture described in Comparative Example 1 before and after salt spray testing; Table 1. Salt spray test results of the coatings prepared from the composite protective coatings described in Examples 1-5 and Comparative Examples 2-3 and the photopolymerization precursor mixture described in Comparative Example 1.

[0057] From Table 1 and Figures 1-2 It can be seen that the composite protective coatings described in Examples 1 to 5 did not exhibit blistering or peeling after 504 to 576 hours of salt spray testing. However, the composite protective coatings described in Comparative Examples 2 and 3 and the photopolymerization precursor mixture described in Comparative Example 1 showed obvious corrosion and peeling after 168 to 360 hours, indicating that the composite protective coatings described in this invention effectively enhance the corrosion resistance of the coating.

[0058] Aging test: The composite protective coatings described in Examples 1-5 and Comparative Examples 2-3, along with the photopolymerization precursor mixture described in Comparative Example 1, were uniformly applied to the surface of steel sheets and cured under light. After obtaining the coatings, an aging test was conducted according to national standard GB / T1865-2009, at 38±3℃ and 40-60% relative humidity, simulating outdoor full-spectrum sunlight. The test results are shown in Table 2 and... Figures 3-4 As shown: Figure 3 Optical images of the coating prepared by the composite protective coating described in Example 1 before and after aging tests; Figure 4 Optical images of the coating prepared from the photopolymerization precursor mixture described in Comparative Example 1 before and after aging tests. Table 2. Aging test results of the coatings prepared from the composite protective coatings described in Examples 1-5 and Comparative Examples 2-3 and the photopolymerization precursor mixture described in Comparative Example 1.

[0059] From Table 2 and Figures 3-4 It can be seen that after aging tests of 504-624 hours, no blistering or chalking occurred in Examples 1-5, only the color darkened. However, the composite protective coatings described in Comparative Examples 2-3 and the photopolymer precursor mixture described in Comparative Example 1 showed blistering and chalking problems after 336-480 hours, indicating that the present invention effectively improves the weather resistance of the coating.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A composite protective coating, characterized in that, Including photopolymerization precursor mixtures, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials; The photopolymerization precursor mixture comprises triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone, and acetate carbonate.

2. The composite protective coating as described in claim 1, characterized in that, The nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial accounts for 0.05~0.08% of the mass of the photopolymerization precursor mixture; The graphene oxide accounts for 0.05~0.08% of the mass percentage of the photopolymerization precursor mixture.

3. The composite protective coating as described in claim 1 or 2, characterized in that, The ratio of triethylene glycol dimethacrylate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 2-hydroxy-2-methylphenylacetone and acetic acid carbonate is (4~6) g: (4~6) g: (0.1~0.2) g: (5~10) mL.

4. The composite protective coating as described in claim 1 or 2, characterized in that, The preparation method of the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial includes the following steps: Cadmium sulfide, water and dopamine are mixed and polymerized under alkaline conditions to obtain polydopamine-coated cadmium sulfide composite material. The polydopamine-coated cadmium sulfide composite material, soluble cobalt salt, and water were mixed to perform cobalt ion doping, thereby obtaining a cobalt ion-doped polydopamine-coated cadmium sulfide composite material. The cobalt ion-doped polydopamine-coated cadmium sulfide composite material was calcined to obtain the nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterial.

5. The composite protective coating as described in claim 4, characterized in that, The ratio of cadmium sulfide, dopamine, and water is (28~33) g : (2.8~3.2) g : (4.8~5.2) L; The pH value of the alkaline conditions is 8.5~9.5; The polymerization coating temperature is 28~32℃, and the time is 3.5~4.5h.

6. The composite protective coating as described in claim 4, characterized in that, The ratio of the polydopamine-coated cadmium sulfide composite material, the soluble cobalt salt, and water is (2~3) g: (2~3) g: (1~1.3) L; The soluble cobalt salt includes cobalt nitrate; The calcination is carried out in a protective atmosphere at a temperature of 700-900°C for 1.5-2.5 hours.

7. The composite protective coating as described in claim 4, characterized in that, The method for preparing cadmium sulfide includes the following steps: An aqueous solution of soluble cadmium salt, thiourea, and ethylenediamine is mixed and subjected to a hydrothermal reaction to obtain the cadmium sulfide.

8. The composite protective coating as described in claim 7, characterized in that, The ratio of the aqueous solution of the soluble cadmium salt, thiourea, and ethylenediamine is (2.7~3.2) g : (2.1~2.5) g : (28~32) mL; The aqueous solution of ethylenediamine has a mass concentration of 40%. The hydrothermal reaction is carried out at a temperature of 150-170℃ for 44-50 hours.

9. A method for preparing the composite protective coating according to any one of claims 1 to 8, characterized in that, Includes the following steps: Under light-protected conditions, a photopolymerization precursor mixture, graphene oxide, and nitrogen-doped carbon-coated cobalt-doped cadmium sulfide composite nanomaterials are mixed to obtain the composite protective coating.

10. The application of the composite protective coating according to any one of claims 1 to 8 or the composite protective coating prepared by the preparation method according to claim 9 in the field of coating protection.

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