Coating, preparation method and application

Abstract

The invention discloses a coating, a preparation method and application, and relates to the technical field of anticorrosive coatings. The included angle between the plane of most of the lamellar filler in the coating and the macroscopic surface of the base material is controlled to be smaller than 45 degrees through a magnetron orientation method, that is, the lamellar filler is close to the state of being parallel to the surface of the base material, the transmission path of a corrosive medium can be longer and more zigzag, the maze effect can be further strengthened, and the corrosion resistance of the coating is improved. Therefore, the corrosion path of the corrosive medium is greatly prolonged, and the heat-conducting property of the matrix is reserved to the greatest extent. The dry film of the coating still has high corrosion resistance in the ultrathin state, the heat conduction performance of the fin base material of the heat exchanger can be reserved to the maximum degree, the service life of the heat exchanger is greatly prolonged, and the energy-saving long-term effect of the heat exchanger is greatly improved. In addition, the composite coating provided by the invention is simple in preparation process and relatively low in cost, and has extremely high market application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anticorrosive coating, in particular to a coating, a preparation method and application. BACKGROUND

[0002] Heat exchanger is a core material element of air conditioner manufacturing. The mainstream heat exchanger is a finned tube structure, and a large area of metal heat dissipation fin is wrapped outside the refrigerant pipeline. Corrosion products and stains accumulate on the surface of the fin and the refrigerant pipeline, which not only increases the thermal resistance, but also reduces the air passage area, resulting in a decrease in heat exchange efficiency and a significant increase in air conditioner energy consumption. SUMMARY

[0003] The main purpose of the present application is to develop a coating applied to the heat dissipation fin of the heat exchanger, which is coated on the surface of the heat dissipation fin of the heat exchanger and has excellent heat conductivity while taking into account corrosion resistance and weather resistance, so as to greatly improve the service life and energy saving of the heat exchanger.

[0004] To achieve the above-mentioned purpose, the present application provides a coating, which comprises a corrosion-resistant layer arranged on at least one surface of a metal substrate; the corrosion-resistant layer comprises sheet-shaped fillers; wherein the sheet-shaped fillers in the corrosion-resistant layer are arranged obliquely close to the surface of the metal substrate, and the two-dimensional plane of the sheet-shaped fillers forms a first included angle with the surface of the metal substrate.

[0005] In an embodiment, the first included angle formed by the two-dimensional plane of the sheet-shaped fillers and the surface of the metal substrate is not greater than 45°.

[0006] In an embodiment, the two-dimensional plane of the sheet-shaped fillers with a quantity ratio of not less than 80% in the corrosion-resistant layer forms the first included angle with the surface of the metal substrate.

[0007] In an embodiment, the coating used to form the corrosion-resistant layer comprises 0.05wt%-2wt% of the sheet-shaped fillers, and the balance of the base material; the base material comprises a water-based resin.

[0008] In an embodiment, the water-based resin comprises at least one of a water-based fluorocarbon resin, a water-based polyester resin, a water-based silicone resin, a water-based acrylic resin, a polyurethane resin, a modified polyurethane resin, an epoxy resin, a modified epoxy resin, and a polyamide resin.

[0009] In an embodiment, the dry film of the corrosion-resistant layer comprises 0.1wt%-6wt% of the sheet-shaped fillers.

[0010] In an embodiment, the dry film thickness of the corrosion-resistant layer is 1-2 microns.

[0011] In an embodiment, the sheet-shaped filler comprises a magnetic modified filler; wherein the magnetic modified filler comprises a two-dimensional nano filler, and magnetic nanoparticles loaded on at least one surface of the two-dimensional nano filler.

[0012] In an embodiment, the two-dimensional nano filler comprises at least one of graphene-based nanosheet, nanosheet-layer silicate, nanosheet-layer phosphate, nanosheet-layer sulfide, nanosheet-layer oxide, nanosheet-layer nitride.

[0013] In an embodiment, the magnetic nanoparticles comprise at least one of elemental and alloy nano-powder particles of iron, cobalt, nickel, nano-iron oxide particles, nano-sized ferrite powder particles, nano-sized neodymium-iron-boron powder particles.

[0014] In an embodiment, the magnetic modified filler has a particle size of the magnetic nanoparticles of 10 nm to 50 nm; and / or a sheet size of the two-dimensional nano filler of 0.5 μm to 10 μm.

[0015] In an embodiment, the magnetic modified filler has a weight ratio of the two-dimensional nano filler to the magnetic nanoparticles of 1: (1-10).

[0016] In an embodiment, the magnetic modified filler is further coated with at least one layer of a polymer shell material.

[0017] In an embodiment, the polymer shell material comprises at least one of polydopamine and polysiloxane.

[0018] In an embodiment, the weight ratio of the polymer shell material to the magnetic modified filler is (5-20):(2-11).

[0019] In an embodiment, the coating further comprises a hydrophilic layer, which is arranged on a surface of the corrosion-resistant layer away from the metal substrate.

[0020] In an embodiment, the raw material of the hydrophilic layer comprises an acrylate monomer; the acrylate monomer comprises at least one of a hydroxyl acrylate monomer, a carboxyl acrylate monomer, an amino acrylate monomer, an amido acrylate monomer, and an epoxy acrylate monomer.

[0021] In an embodiment, the coating further comprises a lubricating layer, which is arranged on a surface of the hydrophilic layer away from the substrate.

[0022] The present application further provides a preparation method of the coating, comprising the following steps: S1, preparing a coating material using a sheet-shaped filler; S2, coating the paint prepared in the step S1 on the surface of the metal substrate, curing and synchronously applying a magnetic field to form a corrosion-resistant layer, and completing the preparation of the coating.

[0023] In an embodiment, in the step S1, the method for preparing the magnetic modified filler comprises the following steps: Dispersing the two-dimensional nano filler in a solvent, adding a magnetic precursor and stirring uniformly, adjusting the pH to 7-10 under a protective atmosphere, reacting at 20-80 DEG C, filtering, and washing the filter residue to prepare the magnetic modified filler.

[0024] In an embodiment, in the step S2, at least two magnetic fields with different magnetic field strengths are applied during the curing process of the paint.

[0025] In an embodiment, in the step S2, at least three magnetic fields with different magnetic field strengths are applied during the curing process of the paint, and the magnetic field strengths of the magnetic fields show a gradient change trend.

[0026] In an embodiment, in the step S2, a first magnetic field is applied for pre-curing, and then a second magnetic field is applied for thermal curing to form the corrosion-resistant layer and complete the preparation of the coating.

[0027] In an embodiment, the magnetic field direction of the first magnetic field and the magnetic field direction of the second magnetic field are parallel to the surface of the metal substrate.

[0028] In an embodiment, the first magnetic field is a uniform magnetic field with a field strength of 0.5-1T, and the second magnetic field is a uniform magnetic field with a field strength of 0.1-0.5T.

[0029] In an embodiment, the pre-curing temperature is 20-50 DEG C, and the pre-curing time is 0.01-1h.

[0030] In an embodiment, the thermal curing temperature is 200-300 DEG C, and the thermal curing time is 0.01-0.5h.

[0031] The application also proposes the application of the coating in a heat exchanger, and the application of the coating to the heat exchanger fins of an air conditioner.

[0032] The technical scheme in the application designs a coating added with a sheet-shaped filler, the magnetic iron oxide nanoparticles are loaded on the surface of two-dimensional nanoparticles and are coated with a layer of polymer, the coating with the dispersed magnetic filler is coated into a film, and then a specific magnetic control orientation curing method is matched, so that the high dispersion stability and planar directional arrangement of the two-dimensional nano filler in the resin matrix are realized, a dense layered structure of "brick-mud" is formed, a labyrinth effect is formed in the coating, the transmission path of the corrosion medium in the coating is prolonged, and the corrosion of water and oxygen to the base material can be effectively blocked. To sum up, the dry film of the coating still has high corrosion resistance in an ultra-thin state, which is beneficial to the maximum retention of the heat conduction performance of the fin base material of the heat exchanger, and the service life and energy-saving long-effectiveness of the heat exchanger are greatly improved. In addition, the preparation process of the composite coating in the application is simple and low in cost, and has very high market application value. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the application.

[0034] It should be noted that if the embodiments of the application involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture, and if the certain posture changes, the directional indications also change accordingly.

[0035] In addition, if the embodiments of the application involve descriptions such as "first", "second", etc., the descriptions of "first", "second", etc. are only for description purposes, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include at least one of the features. In addition, "and / or" or "and / or" appearing throughout the text means that the three parallel schemes are included, for example, "A and / or B" includes A scheme, or B scheme, or A and B are satisfied at the same time. In addition, the technical solutions of each embodiment can be combined with each other, but it must be based on the realization of ordinary skilled in the art, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, and is not within the protection scope of the application.

[0036] The technical problem solved by the present application is that: the heat exchanger is the core material element of air conditioner manufacturing, the mainstream heat exchanger is a tube fin structure, the refrigerant pipeline is wrapped with a large area of metal heat dissipation fin outside, and the corrosion products and stains are accumulated on the fin surface, which not only increases the thermal resistance, but also reduces the air passage area, resulting in reduced heat exchange efficiency and greatly increased air conditioner energy consumption. In the related art, an organic coating layer of an epoxy system is coated on the metal heat dissipation fin, but the epoxy system has poor light aging resistance, and the corrosion resistance rapidly decays during service; another related art uses an organic coating layer containing a fluorine system, but the fluorine system has high cost and does not have conditions for large-scale popularization and use, and the primer layer of the fluorine system has strong hydrophobicity, and has poor compatibility with the hydrophilic topcoat layer, and has poor performance compatibility. In addition, the thermal conductivity of the organic coating layer is obviously lower than that of the metal substrate, and the coating thickening increases the energy consumption of the air conditioner, thereby causing energy waste.

[0037] To solve the above technical problems, the present application provides a coating, which comprises a corrosion-resistant layer, the corrosion-resistant layer being arranged on at least one surface of a metal substrate; at least one sheet-shaped filler is stacked in the corrosion-resistant layer; wherein the sheet-shaped filler in the corrosion-resistant layer is arranged inclinedly close to the surface of the metal substrate, and a two-dimensional plane of the sheet-shaped filler forms a first included angle with the surface of the metal substrate.

[0038] It should be noted that when the two-dimensional plane of the sheet-shaped filler forms a specific size included angle with the surface of the metal substrate, each time the corrosion medium advances in the gap between the fillers will be hindered by the inclined interface, and is forced to change the penetration direction many times, thereby greatly prolonging the effective penetration path, significantly delaying the time when the medium reaches the metal substrate, and further strengthening the labyrinth effect, thereby prolonging the corrosion process.

[0039] It should be further noted that, on the one hand, the corrosion medium needs to pass through the resin gap between the fillers to reach the surface of the metal substrate, and the prolongation of the corrosion path greatly increases the total resistance of the corrosion circuit, resulting in a decrease in corrosion current and a slowdown in the corrosion rate; on the other hand, the corrosion rate is controlled by the rate of cathodic reaction, which usually requires oxygen, and due to the labyrinth effect, oxygen is difficult to reach the metal surface, resulting in strong cathodic polarization, and the corrosion potential of the whole system is negatively shifted, greatly delaying the activation time of the metal under the coating.

[0040] It should be further noted that, due to the inclined arrangement of the sheet-shaped filler close to the surface of the metal substrate in the present application, heat can be more smoothly transferred from the metal substrate to the surface of the coating along the filler, forming a heat conduction path with smaller thermal resistance, and the inclined sheet-shaped filler is more easily extended to the surface of the coating, further increasing the effective surface area of the coating in contact with air, thereby ensuring the heat exchange effect.

[0041] In an embodiment, the first included angle between the two-dimensional plane of the sheet-shaped filler and the surface of the metal substrate is not greater than 45°.

[0042] It can be understood that, by limiting the size of the first included angle to not more than 45°, on the one hand, the relatively gentle inclination angle enables the sheet-shaped filler to have more sufficient contact and anchoring effect with the surface of the substrate, thereby enhancing the adhesion; on the other hand, the sheet-shaped filler is tightly stacked in the coating, and the labyrinth effect is further strengthened and the corrosion path is prolonged.

[0043] In an embodiment, the two-dimensional plane of the sheet-shaped filler, which accounts for not less than 80% of the number of the sheet-shaped fillers in the corrosion-resistant layer, forms the first included angle with the surface of the metal substrate. It can be understood that, when more than 80% of the sheet-shaped fillers are uniformly inclined, they are overlapped with each other to form a dominant and continuous barrier network in the coating, thereby ensuring that the whole coating can play the labyrinth effect. In addition, the uniform inclination of more than 80% of the sheet-shaped fillers is conducive to forming an effective heat conduction path and facilitating rapid heat exchange between the metal substrate and the surface of the coating.

[0044] In a preferred embodiment, the two-dimensional plane of the sheet-shaped filler, which accounts for not less than 80% of the number of the sheet-shaped fillers in the corrosion-resistant layer, forms the first included angle with the surface of the metal substrate, and the first included angle is not greater than 45°.

[0045] In an embodiment, in the thickness direction of the corrosion-resistant layer, the number of layers of the sheet-shaped filler is 1-10 layers.

[0046] It should be noted that, when the surface of the sheet-shaped filler is also attached with other functional fillers or particles, the number of layers of the sheet-shaped filler is relative to the whole of the sheet-shaped filler and the functional fillers or particles attached to the surface, that is, one sheet-shaped filler and the functional fillers or particles attached to one or both surfaces of the sheet-shaped filler are collectively regarded as one layer in the thickness direction of the corrosion-resistant layer.

[0047] In an embodiment, the coating used to form the corrosion-resistant layer comprises 0.05wt%-2wt% of the sheet-shaped filler, and the balance of the base material; the base material comprises a water-based resin.

[0048] It can be understood that, the coating in the present application only needs 0.05wt%-2wt% of the sheet-shaped filler for low loading to achieve a coating with high barrier performance, which has a relatively low raw material cost and preparation cost. In addition, the base material of the corrosion-resistant layer adopts a water-based resin, which contains a large number of polar groups and has good compatibility and binding force with the hydrophilic layer, thereby further strengthening the protection of the coating to the substrate.

[0049] In a preferred embodiment, the coating for forming the corrosion-resistant layer comprises 0.05wt%-1wt% of the lamellar filler, and the balance of a base material; the base material comprises a water-based resin.

[0050] In a more preferred embodiment, the coating for forming the corrosion-resistant layer comprises 0.1wt%-1wt% of the lamellar filler, and the balance of a base material; the base material comprises a water-based resin.

[0051] By adopting the above technical means, the lamellar filler can be better uniformly dispersed in the base material, the probability of the orientation of the lamellar filler in the coating being consistent with the surface of the base material during coating and shaping is improved, the excellent barrier property of the two-dimensional material is fully utilized, the shielding and barrier effect of the coating is improved, and the corrosion resistance of the coating is further improved.

[0052] In an embodiment, the water-based resin comprises at least one of a water-based fluorocarbon resin, a water-based polyester resin, a water-based silicone resin, a water-based acrylic resin, a polyurethane resin, a modified polyurethane resin, an epoxy resin, a modified epoxy resin, and a polyamide resin.

[0053] In an embodiment, the dry film of the corrosion-resistant layer comprises 0.1wt%-6wt% of the lamellar filler.

[0054] It can be understood that, by further limiting the content of the lamellar filler in the dry film of the corrosion-resistant layer, the dry film of the corrosion-resistant layer can be detected and verified after the coating is prepared, so that a proper amount of the lamellar filler is ensured to overlap and lap with each other in the coating to form a continuous and effective barrier network. The content of the lamellar filler in the dry film is prevented from being too low to cause the lamellar filler to be stacked and unable to completely cover the metal base material. Meanwhile, the content of the lamellar filler is prevented from being too high, and the cohesive strength of the continuous phase of the resin is not enough, thereby causing the coating to peel off or powder.

[0055] In an embodiment, the dry film of the corrosion-resistant layer has a thickness of 1μm-2μm. For example, the dry film of the corrosion-resistant layer can have a thickness of 1μm, 1.1μm, 1.2μm, 1.5μm, or 2μm, and the present application is not limited in this regard.

[0056] It should be noted that, by controlling the amount and stacking mode of the lamellar filler, the lamellar filler is stacked in a specific form in the coating, so that the total thickness of the lamellar filler in the cured coating dry film is only 0.8μm-1.6μm. By adopting the above technical means, the coating dry film still has high corrosion resistance in an ultra-thin state, which is beneficial to the heat conduction performance of the fin base material of the heat exchanger.

[0057] In an embodiment, the sheet-shaped filler comprises a magnetic modified filler; wherein the magnetic modified filler comprises a two-dimensional nano filler, and a magnetic nanoparticle loaded on at least one surface of the two-dimensional nano filler.

[0058] It should be noted that in the embodiment, the magnetic modified filler is prepared by loading the magnetic nanoparticle on the surface of the two-dimensional nano filler, i.e. nanosheet, by in-situ synthesis. The magnetic modified filler can respond to the magnetic field and can be arranged under the guidance of the magnetic field. By controlling the direction of the magnetic field, the angle between the sheet structure of the magnetic modified filler and the surface of the substrate is smaller, so that the sheet structure of the magnetic modified filler in the corrosion-resistant layer has a smaller angle, thereby better protecting the surface of the substrate.

[0059] In an embodiment, the two-dimensional nano filler comprises at least one of a graphene-based nanosheet, a nanosheet-layered silicate, a nanosheet-layered phosphate, a nanosheet-layered sulfide, a nanosheet-layered oxide, and a nanosheet-layered nitride. The graphene-based nanosheet can be graphene, graphene oxide, reduced graphene oxide, aminated graphene, fluorinated graphene, hydrogenated graphene, and other two-dimensional sheet materials that can be surface modified. The two-dimensional nano filler is a material with a single-atom thickness and excellent chemical stability. By selecting graphene and its derivatives as the two-dimensional nano filler, a continuous multi-layer structure can be constructed in the direction perpendicular to the sheet layer by using the single-atom thickness and chemical inertness of graphene and its derivatives, thereby effectively blocking the penetration path of the corrosion medium.

[0060] In an embodiment, the magnetic nanoparticle comprises at least one of a nano-powder particle of an element and an alloy of iron, cobalt, and nickel, a nano-iron oxide particle, a nano-sized ferrite powder particle, and a nano-sized neodymium-iron-boron powder particle.

[0061] In an embodiment, the magnetic nanoparticle in the magnetic modified filler has a particle size of 10 nm to 50 nm; and / or the two-dimensional nano filler has a sheet size of 1 μm to 10 μm.

[0062] It can be understood that in the embodiment, the two-dimensional nano filler can be approximately regarded as the sheet size of the sheet-shaped filler.

[0063] It can be understood that by accurately controlling the particle size of the magnetic nanoparticle in a specific range, the magnetic nanoparticle has appropriate superparamagnetic properties, can quickly respond and directionally arrange under the applied magnetic field, thereby avoiding the problems of slow response or uneven arrangement of the filler caused by improper particle size.

[0064] In an embodiment, the weight ratio of the two-dimensional nano filler to the magnetic nanoparticle is 1: (1-10).

[0065] By controlling the specific proportion of the two-dimensional nanofiller and the magnetic nanoparticles, on the one hand, the magnetic modified filler can reach a sufficient magnetization intensity, and on the other hand, the two-dimensional nanofiller can retain more adsorption sites to ensure the adsorption performance of the filler. In addition, if the content of the magnetic nanoparticles is too high, the magnetic nanoparticles are prone to agglomeration, which leads to a decrease in the magnetic performance and a decrease in the functional sites.

[0066] In an embodiment, the surface of the magnetic modified filler is further coated with at least one polymer shell material, and the polymer shell material includes at least one of polydopamine and polysiloxane.

[0067] It should be noted that, in the present application, the polydopamine or polysiloxane is coated on the surface of the magnetic modified particles to form a core-shell structure filler by in-situ polymerization or solution blending method. The active groups such as hydroxyl, amino, and siloxane bond of the shell layer high molecule can be bonded with the polar matrix such as epoxy resin and polyurethane, so as to reduce the interface energy, enhance the interface bonding force, and avoid stress concentration. The polydopamine has adhesion and secondary reaction activity, and can be further grafted with functional molecules such as conductive polymer and flame retardant, so as to realize multifunctionalization. The polysiloxane provides flexibility and high temperature resistance, and improves the thermal stability of the composite material.

[0068] In a specific embodiment, the weight ratio of the polymer shell material to the magnetic modified filler is (5-20):(2-11).

[0069] In an embodiment, the coating further includes a hydrophilic layer, and the hydrophilic layer is arranged on the surface of the corrosion-resistant layer away from the metal base material.

[0070] In a specific embodiment, the raw material of the hydrophilic layer includes the following components in mass percentage: hydroxy acrylate monomer: 1wt%-10wt%; carboxyl acrylate monomer: 8wt%-30wt%; other acrylate monomers: 0wt%-40wt%; initiator: 0.5wt%-3wt%; auxiliary agent: 0.5wt%-2wt%; and the rest is solvent; the other acrylate monomers include at least one of amino acrylate monomer, amide acrylate monomer, and epoxy acrylate monomer. The coating of the hydrophilic layer is an acrylic emulsion, and is a thermosetting acrylic emulsion.

[0071] By using the above technical solution, the strong hydrophilic functional groups and the reactive active sites are introduced into the hydrophilic layer, the strong hydrophilic groups are anchored in the coating by chemical means, and a high-strength crosslinked network is constructed, so as to obtain a high-performance and long-life hydrophilic coating.

[0072] In a specific embodiment, the dry film thickness of the hydrophilic layer is 0.3μm-0.6μm.

[0073] In an embodiment, the coating further comprises a lubricating layer, which is arranged on the surface of the hydrophilic layer away from the substrate. The material of the lubricating layer can be a conventional paint used for the top coating of metal substrates. In this embodiment, HD5330 or HW6550 purchased from Guangdong Huigu Chemical Co., Ltd. is stirred uniformly and then coated on the surface of the hydrophilic layer away from the substrate to form the lubricating layer after curing and cross-linking.

[0074] In a specific embodiment, the dry film thickness of the lubricating layer is 0.3-0.6 μm.

[0075] The application further provides a preparation method of the coating, comprising the following steps: S1, preparing a coating using the sheet-shaped filler; S2, coating the coating prepared in step S1 on the surface of a metal substrate, curing and synchronously applying a magnetic field to form a corrosion-resistant layer, thereby completing the preparation of the coating.

[0076] In a specific embodiment, step S1 specifically comprises the following steps: mixing the sheet-shaped filler and the base material, stirring at a speed of 800-1000 rpm for 15-30 min, and standing for 2-12 h for defoaming.

[0077] In an embodiment, the preparation method of the magnetic modified filler in step S1 comprises the following steps: dispersing the two-dimensional nanofiller in a solvent, adding a magnetic precursor and stirring uniformly, adjusting the pH to 7-10 under a protective atmosphere, reacting at 20-80 °C, filtering, and washing the filter residue to obtain the magnetic modified filler.

[0078] In a specific embodiment, the magnetic precursor comprises a ferric salt and a ferrous salt, wherein the molar ratio of the iron ions in the ferric salt to the ferrous ions in the ferrous salt is (2-4):1.

[0079] It should be noted that the magnetic modified filler is prepared by in-situ co-precipitation in this embodiment, so that the metal ions are hydrolyzed and co-precipitated into magnetic oxides, thereby growing magnetic nanoparticles in-situ on the surface of the two-dimensional nanosheet to form the magnetic modified filler. By controlling the ratio of the iron ions to the ferrous ions in the magnetic precursor, the crystal structure and phase purity can be further controlled, the generation of Fe(OH)2 impurities is inhibited, and the loss of Fe 2+ during the reaction is reduced; secondly, the magnetic modified particles can be controlled in size. The inventors have found in the research process that when the ratio of the iron ions to the ferrous ions is too high, the magnetic modified particles are too large, the magnetic saturation strength increases, but the coercive force decreases; when the ratio of the iron ions to the ferrous ions is too low, the magnetic modified particles are too small, the magnetic saturation strength decreases, but the coercive force increases. 2+ 3+ When the ratio of the iron ions to the ferrous ions is increased, smaller and more uniform particle size distribution can be obtained.

[0080] ​In a preferred embodiment, in step S2, at least two magnetic fields with different magnetic field strengths are applied during the curing process of the coating.

[0081] In another preferred embodiment, in step S2, at least three magnetic fields with different magnetic field strengths are applied during the curing process of the coating, and the magnetic field strengths of the magnetic fields show a gradient change trend.

[0082] It should be noted that the present application mixes the magnetic modified filler with the water-based resin matrix, forms a uniform coating through dispersion and mechanical stirring; and under the action of a gradient magnetic field, the filler is induced to arrange in the plane direction, and finally a dense "brick-mud" layered structure is formed through heat curing, so that the material has excellent water vapor barrier property, heat exchange performance and corrosion resistance.

[0083] In an embodiment, in step S2, the coating is pre-cured by applying a first magnetic field, and then heat-cured by applying a second magnetic field, to complete the curing and form the coating.

[0084] In an embodiment, in step S2, the magnetic field direction of the first magnetic field and the magnetic field direction of the second magnetic field are parallel to the surface to be coated of the metal substrate.

[0085] In an embodiment, in step S2, the first magnetic field is a uniform magnetic field with a field strength of 0.5T~1T, and the second magnetic field is a uniform magnetic field with a field strength of 0.1T~0.5T.

[0086] In an embodiment, in step S2, the pre-curing temperature is 20℃~50℃, and the pre-curing time is 0.01h~1h; and / or, the heat curing temperature is 200℃~300℃, and the heat curing time is 0.01h~0.5h.

[0087] In a preferred embodiment, the preparation method of the corrosion-resistant layer comprises the following steps: The corrosion-resistant coating is applied to the surface of the substrate, a first magnetic field parallel to the surface of the substrate is applied and controlled to have a size of 0.1T~1T, and pre-curing is performed at 20℃~50℃ for 0.01h~1h; then a second magnetic field parallel to the surface is applied and controlled to have a size of 0.1T~1T, and heat curing is performed at 200℃~300℃ for 0.01h~0.5h to form a coating.

[0088] It should be noted that, in the coating preparation process, a staged curing mechanism is adopted: the pre-curing stage maintains the mobility of the filler, and the thermal curing stage locks the orientation structure by cross-linking the resin; at the same time, a strong magnetic field is applied during the pre-curing stage to achieve rapid orientation, and the magnetic field strength is reduced during the thermal curing stage to maintain the stability of the coating. The probability of the orientation of the sheet-shaped filler being consistent with the surface of the substrate during coating and shaping is improved, the included angle is generally maintained at a low state, the excellent barrier performance of the two-dimensional material is fully utilized, the shielding and barrier effect of the coating is improved, and the corrosion resistance of the coating is further improved.

[0089] In another preferred embodiment, in step S2, the coating prepared in step S1 is coated on a metal substrate, a first magnetic field parallel to the surface is applied and controlled to have a size of 0.6T~1T, and a first step curing is performed at 20℃~50℃ for 0.1h~1h; then a second magnetic field parallel to the surface is applied and controlled to have a size of 0.4T~0.6T, and a second step curing is performed at 50℃~200℃ for 0.1h~0.5h; then a third magnetic field parallel to the surface is applied and controlled to have a size of 0.1T~0.5T, and a third step curing is performed at 200℃~300℃ for 0.01h~0.5h, to form a coating.

[0090] The application also proposes an application of the above-mentioned coating in the field of heat exchangers.

[0091] In a specific embodiment, the coating in the application is applied to the surface of the heat exchanger fins and / or refrigerant pipes, especially the surface of the heat exchanger fins of an air conditioner, and the performance attenuation of the air conditioner is smaller after long-term operation, and the user experience is better.

[0092] The application will be further described below through specific embodiments: The raw materials, reagents or devices used in the embodiments of the application are commercially available, and the application does not make any limitation on the source of the raw materials unless otherwise specified.

[0093] Embodiment 1 Embodiment 1 is a fin coated with a corrosion-resistant layer, and the fin substrate is aluminum foil.

[0094] The preparation method of the sheet-shaped filler in embodiment 1 includes the following steps: 1g of graphene was dispersed in 200 mL of deionized water at a power of 200W for 20min; 0.8g of FeCl2·4H2O and 2.16g of FeCl3·6H2O were added, and ammonia water was added dropwise under nitrogen protection until the pH was about 10, and the reaction was carried out at 70℃ for 2 hours, and then magnetic separation and washing were performed to prepare Fe3O4 loaded graphene; the product was dispersed in Tris buffer and the pH was controlled to be about 8.5, 2g of dopamine hydrochloride was added, and stirring was performed for 12 hours to prepare a polydopamine coated magnetic modified filler.

[0095] The magnetic separation and washing parameters are as follows: the magnetic field strength is 0.1 T, and the rising water speed is 0.5 cm / s to 1 cm / s.

[0096] The preparation method of the corrosion-resistant layer of the fin in Example 1 includes the following steps: The corrosion-resistant layer coating was prepared by mixing 1 g of the sheet-shaped filler with the water-based silicone resin at a mass ratio of 1:999, mechanically stirring at a speed of 800 r / min for 20 min, and standing for 12 h. The corrosion-resistant layer coating was roll-coated on the aluminum foil, pre-cured at 30 DEG C for 0.3 h, and simultaneously applied with a uniform magnetic field of 0.8 T parallel to the substrate direction, and then heat-cured at 280 DEG C for 0.05 h while simultaneously applying a uniform magnetic field of 0.3 T parallel to the substrate direction. After curing, a corrosion-resistant layer with a dry film thickness of about 1.2 pm was formed on the surface of the fin.

[0097] It was determined that the percentage of the sheet-shaped filler with an angle less than 45 DEG with the macroscopic surface of the aluminum foil in Example 1 was about 84%.

[0098] Comparative Example 1 The preparation method of the corrosion-resistant layer of the fin in Comparative Example 1 includes the following steps: S1, 1 g of graphene oxide was dispersed in 200 mL of deionized water, ultrasonically treated (200 W, 20 min), filtered out, dried, and directly mixed with a water-based silicone resin (mass ratio 1:999), mechanically stirred (800 rpm for 20 min), and stood for 12 h to prepare a coating; S2, the coating was roll-coated on the aluminum foil, pre-cured at 40 DEG C for 0.5 h, and heat-cured at 280 DEG C for 0.1 h to form a corrosion-resistant layer with a dry film thickness of about 7.6 pm.

[0099] It was determined that the sheet-shaped filler in the coating in Comparative Example 1 was randomly stacked, and the percentage of the sheet-shaped filler with an angle less than 45 DEG with the macroscopic surface of the aluminum foil was only 31%.

[0100] Performance detection: (1) The low-frequency impedance values (|Z| and |Z|) of the corrosion-resistant layers prepared in Example 1 and Comparative Example 1 were measured, respectively. 10 mHz / Ω·cm 2 The measurement results are shown in Table 1. (2) The salt spray corrosion resistance of the coatings prepared in Example 1 and Comparative Example 1 was determined according to the standard GB / T 1771-2007 "Color Paint and Varnish - Determination of Neutral Salt Spray Resistance"; the hardness of the coatings formed in Example 1 and Comparative Example 1 was determined according to the standard GB / T 6739-2006 "Color Paint and Varnish - Determination of Film Hardness by Pencil Method"; the adhesion of the coatings formed in Example 1 and Comparative Example 1 was determined according to the standard GB / T 9286-2021 "Color Paint and Varnish - Cross-cut Test"; the measurement results are shown in Table 2.

[0101] Table 1

[0102] Table 2

[0103] Through the analysis of the data in Table 1, it can be known that, under the premise of the same amount of addition, the electrochemical impedance value of the coating in the preparation example is obviously one order of magnitude higher than that of the preparation comparative example, and it can be seen that the corrosion-resistant layer prepared in the application has higher barrier performance.

[0104] Through the analysis of the data in Table 2, it can be known that the coating prepared in the application has strong salt spray resistance, and can effectively prolong the service life of the heat exchanger when coated on the surface of the heat exchanger.

[0105] In summary, by controlling the included angle between the plane of more than 80% of the sheet-shaped filler and the macroscopic surface of the substrate to be less than 45°, most of the filler sheet layers are in a "lying flat" state close to parallel to the surface of the substrate, which can make the transmission path of the corrosive medium longer and more tortuous, and can further strengthen the labyrinth effect, thereby prolonging the corrosion process.

[0106] The above only describes exemplary embodiments of the application, and does not limit the patent scope of the application, and any equivalent structural transformation made by the application specification, or direct / indirect application in other related technical fields under the technical concept of the application is included in the patent protection scope of the application.

Claims

1. A coating, characterized in that, The coating includes a corrosion-resistant layer disposed on at least one surface of the metal substrate; The corrosion-resistant layer contains at least one layer of sheet-like filler. The lamellar filler in the corrosion-resistant layer is inclined and close to the surface of the metal substrate, and the two-dimensional plane of the lamellar filler forms a first angle with the surface of the metal substrate.

2. The coating as described in claim 1, characterized in that, The first angle formed between the two-dimensional plane of the lamellar filler and the surface of the metal substrate is no greater than 45°.

3. The coating as described in claim 1, characterized in that, The two-dimensional plane of the lamellar filler, which constitutes no less than 80% of the corrosion-resistant layer, forms the first included angle with the surface of the metal substrate.

4. The coating as described in claim 1, characterized in that, In the corrosion-resistant layer, the number of lamellar filler layers is 1 to 10.

5. The coating as described in claim 1, characterized in that, The coating used to form the corrosion-resistant layer comprises 0.05 wt% to 2 wt% of the lamellar filler and the balance being a matrix material, wherein the matrix material comprises an aqueous resin.

6. The coating as described in claim 5, characterized in that, The waterborne resin includes at least one of waterborne fluorocarbon resin, waterborne polyester resin, waterborne silicone resin, waterborne acrylic resin, polyurethane resin, modified polyurethane resin, epoxy resin, modified epoxy resin, and polyamide resin.

7. The coating as described in claim 1, characterized in that, The dry film of the corrosion-resistant layer comprises 0.1 wt% to 6 wt% of the lamellar filler.

8. The coating as described in claim 1, characterized in that, The dry film thickness of the corrosion-resistant layer is 1μm~2μm.

9. The coating as claimed in claim 1, characterized in that, The lamellar packing includes magnetically modified packing; The magnetically modified filler includes a two-dimensional nanofiller and magnetic nanoparticles loaded on at least one surface of the two-dimensional nanofiller.

10. The coating as claimed in claim 9, characterized in that, The two-dimensional nanofiller includes at least one of graphene-based nanosheets, nanosheet silicates, nanosheet phosphates, nanosheet sulfides, nanosheet oxides, and nanosheet nitrides. And / or, the magnetic nanoparticles include at least one of the following: elemental iron, cobalt, nickel, and alloy nanoparticles; nano-iron oxide particles; nano-ferrite powder particles; and nano-neodymium iron boron powder particles.

11. The coating as claimed in claim 9, characterized in that, In the magnetically modified filler, the magnetic nanoparticles have a particle size of 10 nm to 50 nm; and / or, the two-dimensional nanofiller has a sheet diameter of 0.5 μm to 10 μm; And / or, in the magnetically modified filler, the weight ratio of the two-dimensional nanofiller to the magnetic nanoparticles is 1:(1~10).

12. The coating as claimed in claim 9, characterized in that, The surface of the magnetically modified filler is also coated with at least one layer of polymer shell material.

13. The coating as claimed in claim 12, characterized in that, The polymer shell material includes at least one of polydopamine and polysiloxane; And / or, the weight ratio of the polymer shell material to the magnetically modified filler is (5~20):(2~11).

14. The coating as claimed in claim 1, characterized in that, The coating further includes a hydrophilic layer disposed on the surface of the corrosion-resistant layer away from the metal substrate.

15. The coating as claimed in claim 14, characterized in that, The raw material for the hydrophilic layer includes acrylate monomers; The acrylate monomers include at least one of hydroxy acrylate monomers, carboxy acrylate monomers, amino acrylate monomers, amide acrylate monomers, and epoxy acrylate monomers.

16. The coating as claimed in claim 14, characterized in that, The coating further includes a lubricating layer disposed on the surface of the hydrophilic layer away from the substrate.

17. A method for preparing a coating as described in any one of claims 1 to 16, characterized in that, The method for preparing the coating includes the following steps: S1. Coatings are prepared using lamellar fillers; S2. Apply the coating obtained in step S1 to the surface of the metal substrate, cure it, and simultaneously apply a magnetic field to form a corrosion-resistant layer, thus completing the preparation of the coating.

18. The method for preparing the coating as described in claim 17, characterized in that, In step S1, the layered packing includes magnetically modified packing, and the preparation method of the magnetically modified packing includes the following steps: Two-dimensional nanofillers were dispersed in a solvent, a magnetic precursor was added and stirred, the pH was adjusted to 7-10 under a protective atmosphere, the reaction was carried out at 20℃-80℃, the mixture was filtered, and the filter residue was washed to obtain the magnetically modified filler.

19. The method for preparing the coating as described in claim 17, characterized in that, In step S2, during the curing process of the coating, at least two magnetic fields with different magnetic field strengths are applied.

20. The method for preparing the coating as described in claim 17, characterized in that, In step S2, during the curing process of the coating, at least three magnetic fields with different strengths are applied, and the strength of the magnetic fields shows a gradient change trend.

21. The method for preparing the coating as described in claim 17, characterized in that, In step S2, during the curing process, the coating is pre-cured by applying a first magnetic field, and then thermally cured by applying a second magnetic field to form the corrosion-resistant layer, thus completing the preparation of the coating.

22. The method for preparing the coating as described in claim 21, characterized in that, The magnetic field directions of the first magnetic field and the second magnetic field are parallel to the surface of the metal substrate; And / or, the first magnetic field is a magnetic field with a field strength of 0.5T to 1T, and the second magnetic field is a magnetic field with a field strength of 0.1T to 0.5T; And / or, the pre-curing temperature is 20℃~50℃, and the pre-curing time is 0.01h~1h; And / or, the thermosetting temperature is 200℃~300℃, and the thermosetting time is 0.01h~0.5h.

23. The application of a coating as described in any one of claims 1 to 16 in a heat exchanger, characterized in that, The coating is applied to the heat exchanger fins of the air conditioner.

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