Online treatment method and system for nanocrystallization of hot-dip surface coating

Abstract

The invention belongs to the technical field of metal material surface engineering, and particularly relates to an online treatment method and system for nanocrystallization of a hot-dip surface coating, and the method comprises the following steps: opportunity capturing: taking out a hot-dip workpiece from molten metal liquid, and conveying the workpiece to a nanometer treatment station when the surface coating is in a semi-solidified state; spraying of nano aerosol: spraying aerosol containing nano particles to the surface coating in the semi-solidified state, wherein the nano particles are embedded into the surface coating as nucleation particles; electrostatic assistance: applying an electrostatic field in the process of spraying the aerosol containing the nano-particles, driving the nano-particles to directionally move towards the surface coating and increasing the impact kinetic energy; and cooling and solidifying: cooling the workpiece after the aerosol containing the nanoparticles is sprayed, so that the nanoparticles embedded in the surface coating and the metal of the surface coating form metallurgical bonding or mechanical anchoring, and cooling and solidifying of the surface coating are completed.

Description

Technical Field

[0001] This invention belongs to the field of metal material surface engineering technology, specifically relating to an online processing method and system for nano-coating of hot-dip galvanized surfaces. Background Technology

[0002] Hot-dip galvanizing (such as zinc plating and zinc-aluminum-magnesium plating) is a widely used steel corrosion protection technology. After the traditional hot-dip galvanizing process, the coating is naturally cooled and solidified in the air, resulting in a conventional dendritic or cellular crystal structure on the surface. Although corrosion resistance has been improved, its hardness, wear resistance, and certain specific functions (such as superhydrophobicity, self-cleaning, and photocatalysis) remain limited. To impart superior performance to the coating, surface nano-sizing is an effective method. Existing technologies typically employ the following methods: 1) Post-treatment method: This usually involves coating the already formed surface with a nano-coating. This method requires an additional curing step, the coating has weak adhesion to the substrate, is easy to peel off, and may damage the integrity of the original coating.

[0003] 2) Plating solution addition method: This method usually involves pre-dispersing nanoparticles in an electroplating or chemical plating solution. This method is complex, and nanoparticles are prone to agglomeration, sedimentation, and burn-off in molten metal, making it difficult to achieve uniform dispersion and stable existence. Furthermore, it cannot be used in hot-dip plating processes involving high-temperature molten metals.

[0004] 3) Vacuum coating method: This method requires a vacuum environment, the equipment is expensive, the deposition rate is slow, and it is completely impossible to integrate with a continuous, high-speed hot-dip galvanizing production line.

[0005] Therefore, there is an urgent need in this field for a new technology that can be seamlessly integrated with existing hot-dip galvanizing production lines, operate online, and achieve nano-strengthening of surface coatings efficiently and at low cost, in order to overcome the bottlenecks of the aforementioned existing technologies. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to overcome the above-mentioned shortcomings and provide an online processing method and system for nano-scale coating of hot-dip galvanized surfaces. During the cooling stage after the hot-dip galvanized workpiece leaves the galvanizing pot, online mist cooling, mist nucleation and nanoparticle embedding are carried out simultaneously to achieve nano-scale coating of the surface, thereby solving the problem that the existing technology cannot directly, efficiently and cost-effectively achieve nano-scale coating of the surface on the hot-dip galvanizing production line.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An online method for nano-coating of hot-dip galvanized surfaces includes the following steps: Timing capture: Take the hot-dip coated workpiece out of the molten metal and transport it to the nano-processing station while the coating on its surface is in a semi-solid state; Nanoparticle aerosol spraying: spraying an aerosol containing nanoparticles into the semi-solid surface coating, wherein the nanoparticles are embedded into the surface coating as nucleation sites; Electrostatic assistance: An electrostatic field is applied during the spraying of the aerosol containing nanoparticles to drive the nanoparticles to move in an orientation toward the surface coating and increase the impact kinetic energy; Cooling and solidification: After the aerosol containing nanoparticles is sprayed, the workpiece is cooled so that the nanoparticles embedded in the surface coating form a metallurgical bond or mechanical anchor with the metal of the surface coating, thus completing the cooling and solidification of the surface coating.

[0008] Furthermore, in the timing capture step, the temperature range of the semi-solidified surface coating corresponds to the temperature of the solid-liquid coexistence region of the coating metal.

[0009] Furthermore, in the nano-aerosol spraying step, the droplet size of the aerosol is controlled at 5-10 μm, and the carrier gas flow rate is controlled at 5-10 m / s.

[0010] Furthermore, the nanoparticles are selected from at least one of aluminum, zinc, alumina, zinc oxide, silicon dioxide, or carbon nanotubes, and their particle size is 10-100 nm.

[0011] Furthermore, in the electrostatic assist step, the applied electrostatic field voltage is 5kV-10kV.

[0012] On the other hand, the present invention also provides an online processing system for nano-coating of hot-dip galvanized surfaces, comprising: A nanoparticle supply unit is used to store and uniformly disperse nanoparticles; An aerosol generation and delivery unit, connected to the nanoparticle supply unit, is used to generate and spray an aerosol containing nanoparticles onto the surface coating. An electrostatic auxiliary unit is used to generate an electrostatic field during aerosol spraying. An online monitoring and control unit is used to monitor aerosol parameters and surface coating temperature in real time, and to adjust the injection parameters of the aerosol generation and delivery unit through closed-loop feedback.

[0013] Furthermore, the aerosol generation and delivery unit includes a gas-solid delivery subsystem, an aqueous mixed liquid device, and a fog generating device, which are sequentially connected to the nanoparticle supply unit. The fog generating device is the ultrasonic atomizer or a pressure nozzle. The oscillation frequency of the ultrasonic atomizer is 1.8MHz-2.5MHz.

[0014] Furthermore, the electrostatic auxiliary unit includes a high-voltage electrostatic generator and an integrated electrostatic nozzle that matches the high-voltage electrostatic generator; The integrated electrostatic nozzle includes: The aerosol channel, located at the center of the integrated electrostatic nozzle, is a rectangular airflow channel arranged along the axis; The channel is arranged around the mist channel, and multiple needle-shaped electrodes matching the high-voltage electrostatic generator are provided inside to generate an electrostatic field. The tips of the electrodes protrude towards the outlet of the mist channel, and ceramic insulating layers are covered on the electrode spacing and the electrodes. Cooling channels are arranged around the periphery of the arrangement channels, and the electrodes are cooled by air cooling or water cooling. A grounded shielding shell, wrapped around the outermost layer, is used to limit the range of the electric field; The integrated electrostatic nozzles consist of multiple pairs, arranged in an array along the running direction and width direction of the workpiece to be processed, to form an integrated electrostatic assisted uniform device.

[0015] Furthermore, the online monitoring and control unit integrates a laser particle size analyzer, which detects the droplet size signal of the aerosol and adjusts the power of the fog generating device in conjunction with a PID algorithm to stabilize the droplet size of the aerosol within the range of 6±3μm.

[0016] Furthermore, it also includes a post-processing unit, which includes an aerosol rapid cooling device and an air cooling device for completing the solidification process of the surface coating.

[0017] The beneficial effects of this invention are as follows: This invention achieves highly efficient online processing for nano-scale coating by simultaneously performing aerosol spraying, electrostatic assisted embedding, and cooling solidification of nanoparticles online within a short time window during the semi-solid state of the coating after hot-dip plating. This seamlessly integrates with existing hot-dip plating production lines, resulting in nano-scale surface coatings. Compared to existing offline post-processing, plating solution addition, or vacuum coating technologies, this invention offers the following significant advantages: 1. Truly integrated online production This invention directly embeds nano-processing into existing hot-dip galvanizing production lines. During the cooling stage after the workpiece is removed from the molten metal, aerosol spraying and nanoparticle embedding are completed simultaneously, eliminating the need for any offline secondary processing steps. This achieves seamless integration with continuous high-speed production lines, thereby significantly improving production efficiency (estimated >40%) and significantly reducing equipment investment and production costs.

[0018] 2. Excellent interface integration By cleverly utilizing the plastic fluidity of the coating in its semi-solid state (the temperature range of solid-liquid coexistence), combined with the electrostatic field driving the directional movement of nanoparticles and high-energy impact, the nanoparticles are embedded deep into the interior of the coating in a way that is not simply a surface coating, forming a strong metallurgical bond or mechanical anchoring. The interfacial bonding strength is increased by more than 3 times, and the coating has excellent durability and anti-peeling performance.

[0019] 3. Comprehensive improvement in functionality and performance Embedded nanoparticles act as nucleation sites, inducing the coating to form a refined nanostructure surface, which significantly improves the coating's corrosion resistance (salt spray resistance time increased by 200%), hardness, and wear resistance. At the same time, depending on the type of nanoparticles selected (such as alumina, zinc oxide, silicon dioxide, carbon nanotubes, etc.), additional functions such as photocatalysis, superhydrophobicity, antibacterial properties, and self-cleaning can be flexibly imparted, thereby achieving a multi-functional improvement in coating performance.

[0020] 4. Precise and reliable process control The system is equipped with an online monitoring and control unit to monitor key parameters such as aerosol droplet size, carrier gas flow rate and coating temperature in real time. It also dynamically adjusts the ultrasonic atomizer power and spray parameters through closed-loop feedback (such as PID algorithm) to ensure that the droplet size is stable within the set range (such as 6±3μm), thereby ensuring the high uniformity of nanoparticle distribution and embedding effect and process stability.

[0021] 5. Wide applicability This method has good compatibility with various coating metals (such as zinc, zinc-aluminum-magnesium, Al-Zn-Si, etc.), does not depend on specific plating solution composition or high-temperature melting environment, and is suitable for various hot-dip plating production lines, with strong versatility and industrial promotion value.

[0022] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of an online processing system for nano-coating of hot-dip galvanized surfaces, as described in Example 1. Figure 2 This is a schematic diagram of the integrated electrostatic nozzle in Example 1.

[0024] Attached reference numerals: 1-Aerosol channel; 2-Arrangement channel; 3-Cooling channel; 4-Grounded shielding shell. Detailed Implementation

[0025] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0027] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0028] like Figure 1 The image shows an online method for nano-coating of hot-dip galvanized surfaces, comprising the following steps: Timing capture: Take the hot-dip coated workpiece out of the molten metal and transport it to the nano-processing station while the coating on its surface is in a semi-solid state; Nanoparticle aerosol spraying: spraying an aerosol containing nanoparticles into the semi-solid surface coating, wherein the nanoparticles are embedded into the surface coating as nucleation sites; Electrostatic assistance: An electrostatic field is applied during the spraying of the aerosol containing nanoparticles to drive the nanoparticles to move in an orientation toward the surface coating and increase the impact kinetic energy; Cooling and solidification: After the aerosol containing nanoparticles is sprayed, the workpiece is cooled so that the nanoparticles embedded in the surface coating form a metallurgical bond or mechanical anchor with the metal of the surface coating, thus completing the cooling and solidification of the surface coating.

[0029] Furthermore, in the timing capture step, the temperature range of the semi-solidified surface coating corresponds to the temperature of the solid-liquid coexistence region of the coating metal.

[0030] Furthermore, in the nano-aerosol spraying step, the droplet size of the aerosol is controlled at 5-10 μm, and the carrier gas flow rate is controlled at 5-10 m / s.

[0031] Furthermore, the nanoparticles are selected from at least one of aluminum, zinc, alumina, zinc oxide, silicon dioxide, or carbon nanotubes, and their particle size is 10-100 nm.

[0032] Furthermore, in the electrostatic assist step, the applied electrostatic field voltage is 5kV-10kV.

[0033] On the other hand, such as Figure 2 As shown, the present invention also provides an online processing system for nano-coating of hot-dip galvanized surfaces, comprising: A nanoparticle supply unit is used to store and uniformly disperse nanoparticles; An aerosol generation and delivery unit, connected to the nanoparticle supply unit, is used to generate and spray an aerosol containing nanoparticles onto the surface coating. An electrostatic auxiliary unit is used to generate an electrostatic field during aerosol spraying. An online monitoring and control unit is used to monitor aerosol parameters and surface coating temperature in real time, and to adjust the injection parameters of the aerosol generation and delivery unit through closed-loop feedback.

[0034] Furthermore, the aerosol generation and delivery unit includes a gas-solid delivery subsystem, an aqueous mixed liquid device, and a fog generating device, which are sequentially connected to the nanoparticle supply unit. The fog generating device is the ultrasonic atomizer or a pressure nozzle, or an ultrasonic atomizer and a pressure nozzle arranged in parallel.

[0035] Furthermore, the oscillation frequency of the ultrasonic atomizer is 1.8MHz-2.5MHz.

[0036] Furthermore, the electrostatic auxiliary unit includes a high-voltage electrostatic generator and an integrated electrostatic nozzle that matches the high-voltage electrostatic generator; The integrated electrostatic nozzle includes: The aerosol channel, located at the center of the integrated electrostatic nozzle, is a rectangular airflow channel arranged along the axis; The channel is arranged around the mist channel, and multiple needle-shaped electrodes matching the high-voltage electrostatic generator are provided inside to generate an electrostatic field. The tips of the electrodes protrude towards the outlet of the mist channel, and ceramic insulating layers are covered on the electrode spacing and the electrodes. Cooling channels are arranged around the periphery of the arrangement channels, and the electrodes are cooled by air cooling or water cooling. A grounded shielding shell, wrapped around the outermost layer, is used to limit the range of the electric field; The integrated electrostatic nozzles consist of multiple pairs, arranged in an array along the running direction and width direction of the workpiece to be processed, to form an integrated electrostatic assisted uniform device.

[0037] Furthermore, the online monitoring and control unit integrates a laser particle size analyzer, which detects the droplet size signal of the aerosol and adjusts the power of the fog generating device in conjunction with a PID algorithm to stabilize the droplet size of the aerosol within the range of 6±3μm.

[0038] Example 1 This embodiment provides an online processing method and system for nano-coating of hot-dip galvanized surfaces. Figure 1 The schematic diagram of the online processing system of this embodiment is shown. Figure 2 A schematic diagram of the integrated electrostatic nozzle in this embodiment is shown.

[0039] The online processing system includes a nanoparticle supply unit, an aerosol generation and delivery unit, an electrostatic auxiliary unit, and an online monitoring and control unit.

[0040] The nanoparticle supply unit is used to store and uniformly disperse nanoparticles, and includes a storage tank, a dispersing agitator, and a precision flow controller to prevent nanoparticle agglomeration.

[0041] The aerosol generation and delivery unit is connected to the nanoparticle supply unit and is used to generate and spray an aerosol containing nanoparticles onto the surface coating. The aerosol generation and delivery unit includes a gas-solid delivery subsystem, an aqueous mixing liquid device, and a fog generating device, all connected in sequence to the nanoparticle supply unit. The fog generating device is an ultrasonic atomizer with an oscillation frequency of 1.8MHz to 2.5MHz. In other embodiments, a pressure nozzle may also be used as the fog generating device.

[0042] It should be noted that the storage tank, dispersing agitator, precision flow controller, gas-solid conveying subsystem, aqueous mixed liquid device, and mist generating device described in this application can be conventional devices in the prior art, therefore their specific structures will not be described in detail in this application. Specifically, in this embodiment, the gas-solid conveying subsystem includes a carrier gas source, a flow meter, and a nozzle, used to spray the dried nanoparticles in the form of an airflow into the aqueous mixed liquid device, thereby enabling the nanoparticles to mix better with the carrier medium in the aqueous mixed liquid device. The carrier gas source used to convey the nanoparticles in the gas-solid conveying subsystem is nitrogen or air, and the carrier medium used by the aqueous mixed liquid device and the mist generating device to generate the aerosol is a volatile solvent such as ethanol.

[0043] The electrostatic auxiliary unit includes a high-voltage electrostatic generator and an integrated electrostatic nozzle that matches the high-voltage electrostatic generator. The voltage of the high-voltage electrostatic generator is 5kV-10kV.

[0044] like Figure 2 As shown, the integrated electrostatic nozzle includes: Aerosol channel 1, located at the center of the integrated electrostatic nozzle, is a rectangular airflow channel set along the axis, used to transport aerosol containing nanoparticles; Arrange channel 2, which is set around aerosol channel 1, and has multiple needle-shaped electrodes inside. The needle-shaped electrodes are matched with a high-voltage electrostatic generator to generate an electrostatic field. The tip of the electrode protrudes towards the outlet of the aerosol channel, and the electrode spacing and the electrode are covered with a ceramic insulating layer. Cooling channel 3 is arranged around the arrangement channel 2 and cools the electrodes by air cooling or water cooling. The grounding shield shell 4, which is wrapped around the outermost layer, is used to limit the range of the electric field.

[0045] The integrated electrostatic nozzles consist of multiple pairs, arranged in an array along the running direction and width direction of the workpiece to be processed, forming an integrated electrostatic assisted uniform device.

[0046] The online monitoring and control unit integrates a laser particle size analyzer for real-time monitoring of aerosol parameters and surface coating temperature, and provides closed-loop feedback to adjust the injection parameters of the aerosol generation and delivery unit. Specifically, by detecting the aerosol droplet size signal and using a PID algorithm to adjust the power of the mist generator, the aerosol droplet size is stabilized within the range of 6±3μm.

[0047] The online processing method for nano-coating of hot-dip galvanized surfaces using the above system includes the following steps: First, a timing capture step is performed: the hot-dip coated workpiece (e.g., steel strip) is removed from the molten metal and transported to the nanoprocessing station while the surface coating is in a semi-solid state. The temperature of the semi-solid surface coating corresponds to the temperature range of the solid-liquid coexistence zone of the coating metal. At this time, the coating has sufficient plastic fluidity to facilitate the subsequent embedding of nanoparticles.

[0048] Next, a nano-aerosol spraying step is performed: an aerosol containing nanoparticles is sprayed onto the semi-solid surface coating. The nanoparticles are selected from at least one of aluminum, zinc, alumina, zinc oxide, silicon dioxide, or carbon nanotubes, and have a particle size of 10-100 nm, serving as nucleation sites embedded in the surface coating. The aerosol droplet size is controlled at 5-10 μm, and the carrier gas flow rate is controlled at 5-10 m / s.

[0049] The aerosol generation process is as follows: nanoparticles from the nanoparticle supply unit are transported to the water-containing mixed liquid device through the gas-solid transport subsystem to form a uniformly dispersed mixture; the mixture enters the mist generating device (an ultrasonic atomizer in this embodiment), and aerosols containing nanoparticles are obtained by ultrasonic atomization; the aerosols enter the mist channel (1) of the integrated electrostatic nozzle, and are uniformly sprayed onto the surface coating by multiple pairs of arrayed integrated electrostatic nozzles.

[0050] In another embodiment, a pressure nozzle can be used for ultra-high pressure atomization to obtain an aerosol containing nanoparticles.

[0051] Simultaneously with the nano-aerosol spraying step, an electrostatic auxiliary step is performed: a 5kV-10kV electrostatic field is applied during the spraying process using a high-voltage electrostatic generator and needle electrodes, driving the nanoparticles to move oriented toward the surface coating and increasing the impact kinetic energy, so that the nanoparticles are partially embedded in the coating metal which is still in a soft state.

[0052] Finally, a cooling and solidification step is performed by a post-processing unit, which includes an aerosol rapid cooling device and an air cooling device to complete the coating solidification process. After the aerosol containing nanoparticles is sprayed, the workpiece is cooled so that the nanoparticles embedded in the surface coating form a metallurgical bond or mechanical anchor with the coating metal, thus completing the cooling and solidification of the surface coating.

[0053] This embodiment achieves online nano-processing that is seamlessly integrated with the hot-dip galvanizing production line through the above-described method and system. The nanoparticles have high embedding and bonding strength, and the surface coating has a refined nanostructure, which significantly improves corrosion resistance, hardness and functionality.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An online processing method for nano-coating of hot-dip galvanized surfaces, characterized in that, Includes the following steps: Timing capture: Take the hot-dip coated workpiece out of the molten metal and transport it to the nano-processing station while the coating on its surface is in a semi-solid state; Nanoparticle aerosol spraying: spraying an aerosol containing nanoparticles into the semi-solid surface coating, wherein the nanoparticles are embedded into the surface coating as nucleation sites; Electrostatic assistance: An electrostatic field is applied during the spraying of the aerosol containing nanoparticles to drive the nanoparticles to move in an orientation toward the surface coating and increase the impact kinetic energy; Cooling and solidification: After the aerosol containing nanoparticles is sprayed, the workpiece is cooled so that the nanoparticles embedded in the surface coating form a metallurgical bond or mechanical anchor with the metal of the surface coating, thus completing the cooling and solidification of the surface coating.

2. The online processing method for nano-coating of hot-dip galvanized surfaces according to claim 1, characterized in that: In the timing capture step, the temperature range of the semi-solidified surface coating corresponds to the temperature of the solid-liquid coexistence region of the coating metal.

3. The online processing method for nano-coating of hot-dip galvanized surfaces according to claim 1, characterized in that: In the nano-aerosol spraying step, the droplet size of the aerosol is controlled at 5-10 μm, and the carrier gas flow rate is controlled at 5-10 m / s.

4. The online processing method for nano-coating of hot-dip galvanized surfaces according to claim 3, characterized in that: The nanoparticles are selected from at least one of aluminum, zinc, alumina, zinc oxide, silicon dioxide, or carbon nanotubes, and their particle size is 10-100 nm.

5. The online processing method for nano-coating of hot-dip galvanized surfaces according to claim 1, characterized in that: In the electrostatic assist step, the applied electrostatic field voltage is 5kV-10kV.

6. An online processing system for implementing the method according to any one of claims 1 to 5, characterized in that, include: A nanoparticle supply unit is used to store and uniformly disperse nanoparticles; An aerosol generation and delivery unit, connected to the nanoparticle supply unit, is used to generate and spray an aerosol containing nanoparticles onto the surface coating. An electrostatic auxiliary unit is used to generate an electrostatic field during aerosol spraying. An online monitoring and control unit is used to monitor aerosol parameters and surface coating temperature in real time, and to adjust the injection parameters of the aerosol generation and delivery unit through closed-loop feedback.

7. The online processing system for nano-coating of hot-dip galvanized surfaces according to claim 6, characterized in that: The aerosol generation and delivery unit includes a gas-solid delivery subsystem, an aqueous mixed liquid device, and a fog generating device, which are connected in sequence to the nanoparticle supply unit. The fog generating device is the ultrasonic atomizer or the pressure nozzle, or an ultrasonic atomizer and a pressure nozzle arranged in parallel. The oscillation frequency of the ultrasonic atomizer is 1.8MHz-2.5MHz.

8. The online processing system for nano-coating of hot-dip galvanized surfaces according to claim 7, characterized in that: The electrostatic auxiliary unit includes a high-voltage electrostatic generator and an integrated electrostatic nozzle that matches the high-voltage electrostatic generator. The integrated electrostatic nozzle includes: The mist channel (1) is located at the center of the integrated electrostatic nozzle and is a rectangular airflow channel arranged along the axis. Arrange channel (2) around the mist channel (1), and provide multiple needle-shaped electrodes inside that match the high voltage electrostatic generator to generate an electrostatic field. The tip of the electrode protrudes toward the outlet of the mist channel, and the electrode spacing and the electrode are covered with a ceramic insulating layer. Cooling channel (3) is arranged around the arrangement channel (2) and the electrodes are cooled by air cooling or water cooling. The grounding shield shell (4) is wrapped around the outermost layer to limit the range of the electric field; The integrated electrostatic nozzles consist of multiple pairs, arranged in an array along the running direction and width direction of the workpiece to be processed, to form an integrated electrostatic assisted uniform device.

9. The online processing system for nano-coating of hot-dip galvanized surfaces according to claim 7, characterized in that: The online monitoring and control unit integrates a laser particle size analyzer. By detecting the droplet size signal of the aerosol and coordinating with a PID algorithm, the power of the fog generating device is adjusted to stabilize the droplet size of the aerosol within the range of 6±3μm.

10. The online processing system for nano-coating of hot-dip galvanized surfaces according to claim 7, characterized in that: It also includes a post-processing unit, which includes an aerosol rapid cooling device and an air cooling device to complete the solidification process of the surface coating.

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