Nano anticorrosive paint for chassis as well as preparation method and spraying method of nano anticorrosive paint

Abstract

The invention relates to the technical field of automobile spraying, in particular to nano anticorrosive paint for a chassis as well as a preparation method and a spraying method of the nano anticorrosive paint. The nano anticorrosive paint is prepared from the following raw material components in percentage by mass: 50 to 60 weight percent of water-borne epoxy resin, 1.0 to 1.5 weight percent of modified nano particles, 0.8 to 1.2 weight percent of pH response type corrosion inhibitor microcapsules, 0.5 to 1.0 weight percent of dispersing agent, 0.3 to 0.6 weight percent of wetting agent, 0.2 to 0.4 weight percent of defoaming agent, 0.1 to 0.3 weight percent of flatting agent and the balance of deionized water. According to the composite spraying technology, the dispersion uniformity of the nano-particles is improved by 40% or above, and the thickness deviation of the coating is controlled within + / -3 microns; the optimized curing process improves the construction efficiency by 35% and reduces the energy consumption to 3.2 kW.h / m.

Description

Technical Field

[0001] This invention relates to the field of automotive coating technology, and more particularly to a nano-anti-corrosion coating for chassis, its preparation method, and its spraying method. Background Technology

[0002] Significant progress has been made in chassis corrosion protection technology in recent years in terms of nanocomposite coatings and spraying processes. From a material system perspective, existing technologies mainly employ three types of solutions: First, the water-based epoxy system, represented by Chinese patent CN114926301A, achieves salt spray resistance exceeding 2000 hours by adding graphene nanosheets (0.5-2wt%); second, the SiO2@ZnO core-shell structure system, as reported in *ACS Applied Materials & Interfaces*, utilizes the cathodic protection of ZnO to extend corrosion protection life; and third, the self-healing system developed by Chinese patent CN116656265A, achieves automatic repair of damaged areas through microencapsulated corrosion inhibitors. In terms of spraying processes, existing technologies exhibit three development directions: First, the ultrasonic-assisted electrostatic spraying described in Chinese patent CN115738936A (2023) can improve the uniformity of nanoparticle dispersion by 40%; second, the 3D printing gradient coating technology reported in *Additive Manufacturing* achieves precise control of porosity; and third, the multi-angle robotic spraying system described in Chinese patent CN116102105A is suitable for complex curved chassis structures. The closest existing technology is the preheated substrate + low-temperature fast-drying water-based coating solution proposed in Chinese patent CN115433436A. This technology shortens the curing time to 30 minutes by preheating the substrate to 60-80℃, improving spraying efficiency by 30% compared to traditional processes, and controlling coating thickness deviation within ±5μm. These technological advancements not only significantly improve corrosion resistance but also achieve cost reduction and efficiency improvement through process innovation, providing a more reliable solution for long-term chassis protection.

[0003] In-depth analysis of existing technologies reveals the following key shortcomings: First, regarding materials, the cost of nanomaterials such as graphene remains high, and as shown in *Materials & Design*, nanoparticles are prone to agglomeration during storage and spraying (particle size increases by 30-50%), leading to a decrease in spray atomization (atomization uniformity decreases by 15-20%). Second, regarding processes, while the preheating process described in Chinese patent CN115433436A improves efficiency, its energy consumption is as high as 5.2 kW·h / m², and *Journal of Thermal Spray Technology* points out its limited applicability to heat-sensitive nanomaterials (such as certain polymer microcapsules). Furthermore, as described in *Robotics and Computer-Integrated Manufacturing*, existing robotic painting systems are complex to program (requiring an average of 48-72 hours of debugging), and research in *Manufacturing Letters* shows that when the painting speed exceeds 2 m / s, the coating porosity increases dramatically (from 0.8% to 2.5%). The root causes of these problems lie in: imperfect nanomaterial surface modification technology (current silane coupling agent modification efficiency is only 60-70%), a lack of intelligent algorithm support for optimizing painting process parameters, and insufficient integration of equipment systems. Of particular note is the generally poor adaptability of existing technologies to dynamic operating conditions (such as continuous vibration + alternating salt spray). ISO 20567-1 testing shows that most coatings lose more than 15 mg of weight after 1000 cycles, which severely restricts the practical application of chassis corrosion protection technology.

[0004] Therefore, in response to the key problems existing in the current chassis anti-corrosion spraying technology, such as the easy agglomeration of nanoparticles, slow curing of water-based coatings, low spraying efficiency, high energy consumption, and insufficient coating durability under dynamic environments, it is urgent to propose a new nano anti-corrosion coating for chassis and its preparation and spraying methods. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a nano-anti-corrosion coating for chassis, along with its preparation and spraying methods. Firstly, this invention improves the uniformity of the coating by enhancing nanomaterial dispersion technology. Secondly, it optimizes the curing process to shorten the construction cycle, ultimately significantly improving the long-term protective performance of the coating under complex conditions such as vibration and salt spray.

[0006] This invention provides the following technical solution: This invention provides a nano-anti-corrosion coating for chassis, wherein the raw material components of the nano-anti-corrosion coating include, by mass percentage, 50-60 wt% waterborne epoxy resin, 1.0-1.5 wt% modified nanoparticles, 0.8-1.2 wt% pH-responsive corrosion inhibitor microcapsules, 0.5-1.0 wt% dispersant, 0.3-0.6 wt% wetting agent, 0.2-0.4 wt% defoamer, 0.1-0.3 wt% leveling agent, with the balance being deionized water.

[0007] Furthermore, the waterborne epoxy resin includes one or more of E-44 type waterborne epoxy resin, E-20 type waterborne epoxy resin, and E-51 type waterborne epoxy resin; and / or, Dispersants include polycarboxylate dispersants; and / or, Wetting agents include one or more of organosiloxanes, alkyl sulfates, or polyoxyethylene fatty alcohol ethers; and / or, Defoamers include one or more of mineral oils, silicones, or polyethers; and / or, Leveling agents include one or more of fluorocarbon-modified acrylates, polydimethylsiloxane, or polyurethane prepolymers.

[0008] Furthermore, the modified nanoparticles are SiO2 / ZnO composite nanoparticles modified with silane coupling agent, wherein, The silane coupling agent includes one or more of KH550 silane coupling agent, KH792 silane coupling agent, or KH602 silane coupling agent; and / or, The mass ratio of SiO2 to ZnO in the SiO2 / ZnO composite nanoparticles is 100:(1-1.3); and / or, The particle size of the silane coupling agent modified SiO2 / ZnO composite nanoparticles is 30-50 nm.

[0009] Furthermore, the pH-responsive corrosion inhibitor microcapsules include a core material and a wall material, wherein, The core material comprises one or more of benzotriazole derivatives, 2-mercaptobenzothiazole, or mercaptobenzimidazole; and / or Wall materials include one or more of polyurethane, polylactic acid, polycaprolactone, polyacrylic acid, or polyethyleneimine.

[0010] The present invention also provides a method for preparing the nano-anti-corrosion coating for chassis as described above, the method comprising: The modified nanoparticles and dispersant were mixed evenly to obtain a pre-dispersed slurry; After heating the waterborne epoxy resin to a first temperature, it is added to the pre-dispersed slurry preheated to the first temperature. The first temperature is maintained and the mixture is stirred at a first stirring speed for a first predetermined time to obtain the first slurry. Wetting agent, defoamer and leveling agent are added to the first slurry in sequence, and the mixture is stirred for a second predetermined time while maintaining the first temperature to obtain the second slurry. Corrosion inhibitor microcapsules are added to the second slurry, and the mixture is stirred at a second stirring speed for a third predetermined time under vacuum conditions to obtain a nano-anti-corrosion coating for the chassis.

[0011] Furthermore, the first temperature is 39-42℃; the first stirring speed is 500-600 rpm; the first predetermined time is 20-30 min; and / or, The second scheduled time is 15-20 minutes; and / or, The second stirring speed is 200~300 rpm, and the third predetermined time is 8~10 min.

[0012] The present invention also provides a method for spraying the nano-anti-corrosion coating for chassis as described above, the spraying method comprising: Plasma pretreatment is performed on the surface of the substrate; A composite spraying system is used to spray the chassis with nano-anti-corrosion coating on the pre-treated substrate surface in multiple passes according to a preset trajectory path. The coated substrate is then subjected to infrared gradient curing to form a coating.

[0013] Furthermore, the conditions for ion pretreatment are: inert atmosphere, power 600~1000W, treatment distance 50~120mm, and treatment time 30~90s.

[0014] Furthermore, the spraying conditions for the composite spraying system include: High-pressure airless spraying: pressure 8-10 MPa, electrostatic auxiliary voltage 60-80 kV, nozzle cone angle 40-60°, orifice diameter 0.25-0.35 mm, spray distance 250-300 mm; and / or, Multi-pass spraying processes include: single-pass wet film thickness of 50-60 μm, and pass interval of 3-8 min; and / or, The infrared gradient curing process includes: curing at 60℃ for 8~15 minutes, then raising the temperature to 80℃, curing at 80℃ for 10~20 minutes, then raising the temperature again to 100℃, and curing at 100℃ for 10~25 minutes.

[0015] Furthermore, the coating thickness is 120-150 μm.

[0016] The technical effects and advantages of this invention are as follows: The nano-anti-corrosion coating for chassis and its spraying process provided in this application have the following significant advantages: 1. Significantly improved corrosion resistance: Tests show that this nanocomposite coating performs excellently in salt spray tests, with a salt spray resistance time exceeding 2500 hours (GB / T 1771 standard), approximately 150% higher than traditional epoxy coatings; coating adhesion reaches Grade 1 (GB / T 9286 standard), and impact resistance exceeds 50 kg·cm (GB / T 1732 standard). It also boasts significantly improved resistance to media corrosion, enhanced wear and stone chip resistance, and optimized aging resistance. After immersion in 5% NaCl solution and 0.5 mol / L HCl solution for 1000 hours, the coating showed no blistering or peeling, demonstrating over 80% improvement in resistance to acid, alkali, and salt media compared to traditional coatings; it can withstand the high-frequency impact and friction of gravel during vehicle chassis operation, reducing coating damage rate by 60%; and it solves the problem of easy chalking during outdoor aging of traditional epoxy coatings.

[0017] 2. In terms of process performance, the innovative composite spraying technology improves the uniformity of nanoparticle dispersion by more than 40%, and controls the coating thickness deviation within ±3μm; the optimized curing process increases construction efficiency by 35% and reduces energy consumption to 3.2kW·h / m². Particularly noteworthy is that the coating prepared by this technology exhibits excellent durability in cyclic corrosion tests (ISO 11997 standard), remaining intact after 1000 cycles of hot and cold temperatures, with a corrosion resistance degradation rate of less than 15%. It also possesses advantages such as superior environmental friendliness, adaptability to complex substrates and working conditions, and strong construction compatibility. The pretreatment process emits VOCs less than 50g / L (far below the national standard limit) and generates no hazardous waste such as phosphate slag, meeting the requirements of the "green production" policy for automotive coating. It can form an active layer on the surface of various metal substrates, with coating adhesion reaching level 1. The coating is flexible and can adapt to the deformation of the chassis weld joints, avoiding coating cracking. It is also compatible with various construction methods such as robotic spraying and air spraying, with a pass interval of only 5 minutes, and can be integrated into existing automotive coating production lines without large-scale equipment modifications.

[0018] 3. At the industrial application level, the self-healing function of pH-responsive microcapsules enables the coating to achieve a self-healing rate of over 90% within 24 hours of damage, significantly extending the coating's service life. The entire spraying process utilizes an intelligent control system, reducing debugging time to 4 hours, increasing the product qualification rate to over 98%, and lowering overall production costs by approximately 20% compared to existing technologies. It also boasts advantages such as lower total lifecycle costs, easier quality control, and strong technological scalability. The coating's self-healing function extends the chassis corrosion protection maintenance cycle to over 8 years, reducing after-sales corrosion protection maintenance costs for automakers by 70%. The coating has high solids content and low loss, increasing the utilization rate of construction materials to 95%, further reducing material costs at the production end. The intelligent spraying system can collect data in real time, enabling digital traceability of anti-corrosion coating quality, and the product defect rate can be stably controlled within 2%. This coating formulation can be adapted to harsher corrosive environments such as marine transport vehicles and engineering vehicles by replacing the corrosion inhibitor core material. The spraying process can also be fine-tuned and applied to the anti-corrosion coating of other automotive components such as the body and frame.

[0019] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for preparing a nano-anti-corrosion coating for chassis provided in the embodiments of this application; Figure 2 This is a flowchart of the method for spraying nano-anti-corrosion coatings for chassis provided in the embodiments of this application; Figure 3 This is a flowchart of the process for spraying nano-anti-corrosion coatings for chassis provided in the embodiments of this application. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To address the shortcomings of existing technologies, this invention discloses a nano-anti-corrosion coating for chassis. The raw material components of the nano-anti-corrosion coating, by mass percentage, include 50-60 wt% waterborne epoxy resin, 1.0-1.5 wt% modified nanoparticles, 0.8-1.2 wt% pH-responsive corrosion inhibitor microcapsules, 0.5-1.0 wt% dispersant, 0.3-0.6 wt% wetting agent, 0.2-0.4 wt% defoamer, 0.1-0.3 wt% leveling agent, and the balance being deionized water.

[0023] In one specific embodiment of the present invention, the waterborne epoxy resin includes E-44 type waterborne epoxy resin, E-20 type waterborne epoxy resin and E-51 (618) type waterborne epoxy resin, etc.; the dispersant includes polycarboxylate type dispersant; the wetting agent includes one or more of organosiloxane, alkyl sulfate and polyoxyethylene fatty alcohol; the defoamer includes one or more of mineral oil, organosilicon and polyether; the leveling agent includes one or more of fluorocarbon modified acrylate, polydimethylsiloxane and polyurethane prepolymer.

[0024] In one specific embodiment of the present invention, the modified nanoparticles are SiO2 / ZnO composite nanoparticles modified with silane coupling agents, wherein the silane coupling agents include KH550 silane coupling agent, KH792 silane coupling agent, and KH602 silane coupling agent, etc.; the mass ratio of silane coupling agent to SiO2 / ZnO composite nanoparticles is 1:1.

[0025] In one specific embodiment of the present invention, the mass ratio of SiO2 to ZnO in the SiO2 / ZnO composite nanoparticles is 100:1-1.3, preferably 100:1.2.

[0026] The SiO2 / ZnO composite nanoparticles modified with the silane coupling agent have a particle size of 30-50 nm. Exemplarily, the preparation method of the modified nanoparticles commonly involves composite followed by modification; when high dispersibility is required, modification is performed first, followed by composite; and when efficient integration is required, an in-situ one-step method is used.

[0027] In one specific embodiment of the present invention, the size of the pH-responsive corrosion inhibitor microcapsules is controlled within the range of 5-20 μm. The pH-responsive corrosion inhibitor microcapsules comprise a core material and a wall material. The core material comprises one or more of benzotriazole derivatives, 2-mercaptobenzothiazole, and mercaptobenzimidazole. The wall material comprises one or more of polyurethane, polylactic acid, polycaprolactone, polyacrylic acid, and polyethyleneimine. Exemplarily, the preparation methods for the pH-responsive corrosion inhibitor microcapsules commonly involve in-situ polymerization. For applications requiring rapid response and repair, methods such as complex coagulation and interfacial polymerization are employed. For applications requiring high load capacity and tolerance to harsh environments, vacuum impregnation-shell coating methods can be used.

[0028] This invention also provides a method for preparing a nano-anti-corrosion coating for chassis, such as... Figure 1 As shown, the method includes: Step 101: Mix the modified nanoparticles and dispersant evenly to obtain a dissolved pre-dispersed slurry; Step 102: After heating the waterborne epoxy resin to a first temperature, add it to the preheated and pre-dispersed slurry at the same temperature, maintain the first temperature and stir at the first stirring speed for a first predetermined time to obtain the first slurry; wherein, the first temperature is 39~42℃; the first stirring speed is 500~600rpm; and the first predetermined time is 20~30min. Step 103: Add wetting agent, defoamer, and leveling agent sequentially to the first slurry, and continue stirring at a constant temperature for a second predetermined time to obtain the second slurry; wherein the second predetermined time is 15~20 minutes. Step 104: Add corrosion inhibitor microcapsules to the second slurry, and stir at the second stirring speed for a third predetermined time under vacuum conditions (-0.08MPa) to obtain a nano anti-corrosion coating for the chassis. The second stirring speed is 200~300rpm and the third predetermined time is 8~10min.

[0029] This invention also provides a method for spraying a nano-anti-corrosion coating for chassis, such as... Figure 2 As shown, the spraying method includes: Step 201: Perform plasma pretreatment on the substrate surface; the conditions for plasma pretreatment are: argon atmosphere, power 600~1000W, treatment distance 50~120mm, and treatment time 30~90s.

[0030] Step 202: Using a composite spraying system, the chassis is coated with nano-anti-corrosion coating on the pretreated substrate surface in multiple passes according to a preset trajectory path; for example, the preset trajectory path is a parallel same trajectory or a serial separate trajectory path for multiple passes of spraying.

[0031] The spraying conditions for the composite spraying system include: high-pressure airless spraying pressure of 8-10 MPa, electrostatic auxiliary voltage of 60-80 kV, nozzle cone angle of 40-60°, orifice diameter of 0.25-0.35 mm, and spray distance of 250-300 mm. The multi-pass spraying process includes: single-pass wet film thickness of 50-60 μm, and pass interval of 3-8 minutes. Step 203: Perform infrared gradient curing on the sprayed substrate to form a coating. The infrared gradient curing process includes: curing at 60℃ for 8-15 minutes, then raising the temperature to 80℃, curing at 80℃ for 10-20 minutes, then raising the temperature again to 100℃, and curing at 100℃ for 10-25 minutes. The coating thickness is 120-150 μm.

[0032] Key technical control points during the spraying process include setting a dedicated overlapping trajectory in the weld area; reducing spraying speed by 50% at edges; and real-time monitoring of coating thickness and automatic parameter compensation. The purpose of setting a dedicated overlapping trajectory in the weld area is to ensure the uniformity, bonding strength, and performance consistency of the coating in this special structural region. Without control, due to the unique structure of the weld, the sensitivity of nanomaterials, and the weakness of the weld area, serious adverse consequences such as coating coverage defects, deterioration of nanomaterial performance, stress concentration leading to mechanical property degradation, poor quality consistency, and premature failure due to poor bonding can easily occur.

[0033] The purpose of controlling the spraying speed at the edges by 50% is to address the process pain points of insufficient coating thickness, low bonding strength, and easy loss of nano-effects in edge areas. If not controlled, due to the geometric characteristics of the edges and the performance sensitivity of nanomaterials, irreversible process defects and service failures can easily occur: coating "depletion" leading to loss of function, deterioration of nano-performance, insufficient bonding strength of the edge coating causing peeling, increased edge thermal damage exacerbating weakness, and poor quality consistency.

[0034] The purpose of controlling and monitoring coating thickness in real time and automatically compensating parameters is to solve coating thickness deviations caused by multiple factors during the spraying process, ensuring coating uniformity, nano-effect stability, and process consistency. Without control, dynamic interference during the spraying process, the performance sensitivity of nanomaterials, and the process difficulties of complex structures can easily lead to a series of adverse consequences: accumulated coating thickness deviations resulting in large-area quality defects, deterioration of nanomaterial performance, loss of quality control in complex areas, poor process consistency, and increased inspection and rework costs.

[0035] For example, the spraying process specifically includes: first, plasma pretreatment of the substrate, with the pretreatment process being (argon atmosphere, power 800W, treatment distance 100mm, treatment time 90s); placing the coating in a constant temperature mixing tank (25±2℃, stirring speed 100rpm) to maintain uniformity; and then using a robot-controlled composite spraying system, with the composite spraying process being high-pressure airless spraying pressure 8-10MPa, electrostatic auxiliary voltage 60-80kV, nozzle cone angle 60°, orifice diameter 0.3mm, and spray distance 250-300mm. The coating is applied in 3-4 passes according to a pre-planned path (unspecified in the annotations). Each pass has a wet film thickness of 50-60 μm and a pass interval of 5 min. Finally, infrared gradient curing is performed. The gradient curing conditions are: 60℃ / 10 min → 80℃ / 10 min → 100℃ / 10 min, forming a coating with a total dry film thickness of 120-150 μm. The robot path planning algorithm is specifically designed to set up overlapping spraying trajectories (overlap rate of 30%) for the chassis weld area and to perform precise spraying with a 50% speed reduction at the edges.

[0036] The robot path calculation is based on geometric contours, with a 30% overlap rate as the core constraint. Combining equipment characteristics and established patterns, it achieves accurate path generation and optimization through real-time feedback and correction. The specific layered calculation is based on the following: 1. Basic geometric basis, namely the three-dimensional contour data of the weld area, including offline input, online scanning, etc.

[0037] 2. Based on the core process, namely the 30% overlap rate and deposition parameter constraints, the critical path parameters are derived as follows: ① Single-track width (W): Where W0 is the spray gun nozzle width, and k is the diffusion coefficient, which is determined by the spray gun type and spraying process, and is usually 1.2~1.5. ② Spacing between adjacent tracks (D): Based on a 30% overlap rate, it is derived as follows. ③ Single-channel deposition thickness (h): Where Q is the powder flow rate and V is the spray gun speed.

[0038] 3. Equipment characteristics, namely robot kinematics and spray gun performance parameters. Kinematic parameters include robot workspace, joint range of motion, maximum speed and acceleration; performance parameters include spray gun nozzle type, atomization pressure and powder delivery method.

[0039] 4. Dynamic correction basis, namely real-time monitoring data and process feedback model. Online thickness measurement data is obtained through eddy current thickness gauges or laser thickness gauges to obtain coating thickness deviations; the process feedback model is a "deviation-correction parameter" model established based on historical spraying data.

[0040] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0041] Example 1 1. The nano-anticorrosion coating is composed of the following components (by mass percentage): Waterborne epoxy resin matrix (E-44 type): 55%; SiO2 / ZnO composite nanoparticles modified with silane coupling agent (KH-550) (particle size 30-50nm): 1.2%; pH-responsive corrosion inhibitor microcapsules (benzotriazole derivative core material / polyurethane wall material): 1.0%; Polycarboxylate dispersant: 0.8%; Organosiloxane wetting agent: 0.5%; Mineral oil-based defoamer: 0.3%; Fluorocarbon modified acrylate leveling agent: 0.2%; The remainder is deionized water: 40%.

[0042] 2. The specific preparation process of the nano-anticorrosion coating is as follows: ① SiO2 / ZnO composite nanoparticles modified with silane coupling agent (KH-550) were premixed with polycarboxylate dispersant and dispersed in a high-speed disperser (2000 rpm) for 15 min to obtain a pre-dispersed slurry; ② Heat the waterborne epoxy resin matrix (E-44 type) to 40℃, add the pre-dispersed slurry, and stir at a constant temperature (40±2℃) and low speed (500rpm) for 30min; ③ Add wetting agent, defoamer, and leveling agent in sequence, and continue stirring for 20 minutes; ④ Add pH-responsive corrosion inhibitor microcapsules and stir at low speed (200 rpm) for 10 min under vacuum conditions (-0.08 MPa); ⑤ The nano-anti-corrosion coating is obtained by passing it through a 200-mesh sieve.

[0043] 3. Composition of the spraying system The spraying system includes: Thermostatic stirring tank (25±2℃, 100rpm stirring) High-pressure airless spraying unit (working pressure 8-10MPa) Electrostatic discharge auxiliary device (output voltage 60-80kV) Specialized composite spray gun (60° nozzle cone angle, 0.3mm orifice diameter) Six-axis robotic arm (equipped with path planning algorithm) Infrared gradient curing device (three independent temperature zones) 4. Spraying process flow, such as Figure 3 As shown: Step 1: Substrate Pretreatment Argon plasma treatment: power 800W, spray distance 100mm, treatment time 90s.

[0044] Step 2: Paint spraying Robot-controlled composite spraying (spray distance 280mm) is used. 3-4 coats (55μm wet film thickness per coat) 5-minute interval between passes Overlap spraying (30% overlap) is used in the weld area. Precision spraying with a 50% reduction in speed at the edges Step 3: Curing treatment Infrared gradient curing: 60℃→80℃→100℃ for 10 min each, forming a dry film thickness of 120-150μm.

[0045] Example 2 1. Taking an electric vehicle aluminum alloy chassis (6061-T6, 2000×1500mm) as an example: (1) Surface energy after pretreatment > 72 mN / m (2) Total spraying time ≤ 20 min (including intervals) (3) The coating thickness after curing is 145μm. 2. Performance Indicators: (1) Adhesion grade 0 (cross-cut test) (2) No corrosion after salt spray test > 2500h (3) Scratch repair rate (100μm damage / 24h) > 90% 3. Adjustment schemes for different substrates: For steel: During the spraying process, the plasma power is increased to 1000W. The purpose is to enhance the adhesion of the nano-coating. Since an oxide layer is easily formed on the surface of steel, high-power plasma can break the surface oxide film. The treatment distance is controlled at 30~50mm, the scanning speed is 5~8m / min, and the spraying is completed within 30 minutes after treatment.

[0046] For large components: Segmented gradient curing is adopted to ensure uniform curing. Because large components are large in volume and have slow thermal conductivity, direct whole curing can easily lead to problems such as large temperature differences between the inside and outside (the surface cures quickly, while the inside is not cured) and coating cracking. For example, the component size can be divided into 2 to 4 segments, each with independent temperature control. The first segment is heated from room temperature to 80°C (held for 15 minutes for pre-curing), the second segment is heated from 80°C to 140°C (held for 20 minutes for medium-temperature curing), and the third segment is heated from 140°C to 180°C (held for 30 minutes for complete curing).

[0047] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nano-anti-corrosion coating for chassis, characterized in that, The raw material components of the nano-anticorrosion coating include, by mass percentage, 50-60 wt% waterborne epoxy resin, 1.0-1.5 wt% modified nanoparticles, 0.8-1.2 wt% pH-responsive corrosion inhibitor microcapsules, 0.5-1.0 wt% dispersant, 0.3-0.6 wt% wetting agent, 0.2-0.4 wt% defoamer, 0.1-0.3 wt% leveling agent, with the balance being deionized water.

2. The nano-anti-corrosion coating for chassis according to claim 1, characterized in that, Waterborne epoxy resins include one or more of E-44 type waterborne epoxy resin, E-20 type waterborne epoxy resin, and E-51 type waterborne epoxy resin; and / or, Dispersants include polycarboxylate dispersants; and / or, Wetting agents include one or more of organosiloxanes, alkyl sulfates, or polyoxyethylene fatty alcohol ethers; and / or, Defoamers include one or more of mineral oils, silicones, or polyethers; and / or, Leveling agents include one or more of fluorocarbon-modified acrylates, polydimethylsiloxane, or polyurethane prepolymers.

3. The nano-anti-corrosion coating for chassis according to claim 1, characterized in that, The modified nanoparticles are silane coupling agent-modified SiO2 / ZnO composite nanoparticles, wherein, The silane coupling agent includes one or more of KH550 silane coupling agent, KH792 silane coupling agent, or KH602 silane coupling agent; and / or, The mass ratio of SiO2 to ZnO in the SiO2 / ZnO composite nanoparticles is 100:(1-1.3); and / or, The particle size of the silane coupling agent modified SiO2 / ZnO composite nanoparticles is 30-50 nm.

4. The nano-anti-corrosion coating for chassis according to claim 1, characterized in that, pH-responsive corrosion inhibitor microcapsules consist of a core material and a wall material, wherein... The core material comprises one or more of benzotriazole derivatives, 2-mercaptobenzothiazole, or mercaptobenzimidazole; and / or Wall materials include one or more of polyurethane, polylactic acid, polycaprolactone, polyacrylic acid, or polyethyleneimine.

5. The method for preparing the nano-anti-corrosion coating for chassis as described in any one of claims 1-4, characterized in that, The method includes: The modified nanoparticles and dispersant were mixed evenly to obtain a pre-dispersed slurry; After heating the waterborne epoxy resin to a first temperature, it is added to the pre-dispersed slurry preheated to the first temperature. The first temperature is maintained and the mixture is stirred at a first stirring speed for a first predetermined time to obtain the first slurry. Wetting agent, defoamer and leveling agent are added to the first slurry in sequence, and the mixture is stirred for a second predetermined time while maintaining the first temperature to obtain the second slurry. Corrosion inhibitor microcapsules are added to the second slurry, and the mixture is stirred at a second stirring speed for a third predetermined time under vacuum conditions to obtain a nano-anti-corrosion coating for the chassis.

6. The method for preparing the nano-anti-corrosion coating for chassis according to claim 5, characterized in that, The first temperature is 39-42℃; the first stirring speed is 500-600 rpm; the first predetermined time is 20-30 min; and / or, The second scheduled time is 15-20 minutes; and / or, The second stirring speed is 200~300 rpm, and the third predetermined time is 8~10 min.

7. The method for spraying a nano-anti-corrosion coating for chassis as described in any one of claims 1-4, characterized in that, The spraying method includes: Plasma pretreatment is performed on the surface of the substrate; A composite spraying system is used to spray the chassis with nano-anti-corrosion coating on the pre-treated substrate surface in multiple passes according to a preset trajectory path. The coated substrate is then subjected to infrared gradient curing to form a coating.

8. The method for spraying nano-anti-corrosion coating for chassis according to claim 7, characterized in that, The conditions for ion pretreatment are: inert atmosphere, power 600~1000W, treatment distance 50~120mm, and treatment time 30~90s.

9. The method for spraying the nano-anti-corrosion coating for chassis according to claim 7, characterized in that, The spraying conditions for a composite spraying system include: High-pressure airless spraying: pressure 8-10 MPa, electrostatic auxiliary voltage 60-80 kV, nozzle cone angle 40-60°, orifice diameter 0.25-0.35 mm, spray distance 250-300 mm; and / or, Multi-pass spraying processes include: single-pass wet film thickness of 50-60 μm, and pass interval of 3-8 min; and / or, The infrared gradient curing process includes: curing at 60℃ for 8~15 minutes, then raising the temperature to 80℃, curing at 80℃ for 10~20 minutes, then raising the temperature again to 100℃, and curing at 100℃ for 10~25 minutes.

10. The method for spraying the nano-anti-corrosion coating for chassis according to claim 7, characterized in that, The coating thickness is 120-150μm.

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