PVD (Physical Vapor Deposition) multicolor coating process for metal automobile parts

Abstract

The invention relates to a PVD (Physical Vapor Deposition) multicolor coating process for metal automobile parts, which belongs to the technical field of automobile part surface treatment and comprises the following steps: S1, pretreatment: cleaning and activating a metal automobile part base material; s2, UV primer is sprayed; s3, carrying out first layer PVD film coating, and forming a PVD film layer with a first color in a vacuum environment; s4, precisely masking and etching, and arranging a mask on the first PVD film layer; s5, a second layer of PVD film coating is carried out, a PVD film layer with a second color is formed in the exposed substrate area, and then the remaining mask is removed; and S6, UV finish paint is sprayed, specifically, ultraviolet curing finish paint is sprayed on the surface with the double-color PVD film layer and cured. According to the method, the PVD coating technology and the precise mask etching technology are combined, the technical problem that clear color separation is difficult to achieve on a single part through existing PVD coating is solved, and the metal automobile part which has the distinct double-color or colorful effect, is clear in boundary and is resistant to abrasion and corrosion can be prepared.

Description

Technical Field

[0001] This invention relates to the field of automotive parts surface treatment technology, and in particular to a PVD multicolor coating process for metal automotive parts. Background Technology

[0002] PVD (Physical Vapor Deposition) technology, as an advanced surface treatment technology, has been widely used in the decoration and protection of automotive parts. The films prepared by PVD technology have the advantages of rich colors, high hardness, wear resistance and corrosion resistance.

[0003] While traditional PVD coating technology offers a variety of color options, achieving multi-color effects on a single component, especially with clear color separation, remains technically challenging. Existing technologies have attempted to achieve multi-color effects through mask coating, but these suffer from blurred boundaries and color bleeding. Other methods employ laser engraving followed by secondary coating, but these are complex and costly. For example, patent CN113463019A discloses a PVD dual-color coating method for metal parts, combining chemical etching and PVD coating to achieve two different colors and textures on two surfaces at different depths. However, this process is still insufficient for achieving more complex patterns or designs.

[0004] Existing traditional mask coating methods suffer from limitations in mask precision and edge sealing, leading to cross-penetration between different colored PVD film layers. This results in blurred and unclear color boundaries, making it impossible to achieve intricate and complex patterns. When performing secondary coatings on existing PVD film layers or different interfaces, the adhesion between layers may be insufficient. Under long-term use, friction, or thermal cycling, the second color film layer is at risk of peeling or flaking, affecting product lifespan and reliability. Traditional single-color PVD coatings offer limited color choices and struggle to provide rich, vibrant colors while ensuring the high hardness, wear resistance, and corrosion resistance required for automotive parts. On complex three-dimensional curved metal parts, relying on manual operation for pretreatment cleanliness, primer and topcoat uniformity, and precise control of PVD process parameters can easily lead to product quality fluctuations, failing to meet the stringent consistency and reproducibility requirements of large-scale industrial production. Furthermore, the PVD coating process typically requires high temperatures, which can cause thermal damage to precision metal substrates (leading to annealing deformation) or the already coated organic underlayer (leading to yellowing and degradation).

[0005] To address a series of long-standing technical challenges in achieving high-quality, durable, multi-color PVD coatings on metal automotive parts, a new process is proposed. This process enables the fabrication of multi-color PVD coatings with clear boundaries, vibrant colors, and strong adhesion on metal automotive parts. By combining PVD coating with precision mask etching technology, the technical challenge of achieving clear color separation on a single component using existing PVD coatings is solved. This process enables the fabrication of metal automotive parts with striking two- or multi-color effects, clear boundaries, and wear and corrosion resistance, significantly improving the product's appearance and decorative effect. Summary of the Invention

[0006] This invention provides a PVD multicolor coating process for metal automotive parts, which solves the problems of blurred multicolor boundaries, film adhesion and durability, single color and performance, process consistency and stability, and substrate and underlayer damage risk in achieving high-quality and durable multicolor PVD coatings on metal automotive parts in the prior art.

[0007] The solution of the present invention to solve the above-mentioned technical problems is as follows: a PVD multi-color coating process for metal automotive parts, the PVD multi-color coating process comprising the following steps: S1, Pretreatment, cleaning and activation treatment of metal automotive parts substrate; S2, Spray UV primer, spray UV-curable primer on the substrate surface and cure; S3, the first PVD coating, is formed by physical vapor deposition on the surface of the primer in a vacuum environment to create a PVD film with the first color. S4, Precision masking and etching: A mask is set on the first PVD film layer, and a preset pattern is formed by etching to expose part of the substrate; S5, Second PVD coating: Under vacuum, a second physical vapor deposition is performed to form a PVD film with a second color on the exposed substrate area, and then the remaining mask is removed. S6, Spray UV topcoat: Spray UV-curable topcoat onto the surface with a two-color PVD film layer and cure it.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the precision mask and etching steps include: a) coating photosensitive ink on the first PVD film layer using a photolithography process, and forming a mask with a preset pattern after exposure and development; b. The first PVD film layer in the exposed area is removed by chemical etching solution, and a micron-deep recessed structure is formed in the exposed substrate area by chemical etching. Photolithography boasts extremely high graphic resolution and edge sharpness, enabling the creation of intricate patterns (such as fine lines, complex logos, and microtext) that are impossible with traditional physical masks. It completely solves the technical challenges of blurred boundaries and mutual penetration of multi-color elements. By chemically etching micron-level recessed structures onto the substrate, it significantly increases the adhesion area of ​​the second PVD film layer, creating an "anchoring effect." This mechanically interlocked structure significantly enhances the bonding force between the second color film layer and the substrate, ensuring the reliability of the product under long-term use and friction. The micron-level recessed structure creates subtle height differences between different color areas, which not only creates a rich sense of layering and three-dimensionality visually but also provides unique tactile feedback during use (such as touch), greatly enhancing the overall texture and high-end value of the product.

[0010] Furthermore, the chemical etching solution is a mixed solution of hydrofluoric acid and hydrochloric acid, or a mixed solution of ferric chloride and hydrochloric acid, which can achieve rapid and uniform etching. At the same time, it has low corrosiveness to the photosensitive ink and UV primer used as a mask, ensuring high selectivity of the etching process, protecting areas that do not need to be etched, and making process control more precise.

[0011] Furthermore, the film materials of the first and second PVD coatings are independently selected from elemental titanium, chromium, zirconium, nitrides, carbides, or oxides. By selecting different film materials and process parameters, different color expressions can be obtained. Different materials correspond to completely different optical interference effects and intrinsic colors, thus forming a vast color system. For example, titanium nitride is golden, zirconium nitride is champagne, chromium nitride is bright silver, and titanium carbide is dark gray. By adjusting the proportion of reactive gases and coating parameters, gradient colors from blue to purple can be obtained on a single material, realizing infinite possibilities for color expression. The selected metal compounds themselves have extremely high hardness and excellent chemical inertness, which means that the final color is not only beautiful, but also extremely wear-resistant, corrosion-resistant, and scratch-resistant, perfectly meeting the stringent requirements of automotive parts for long-term use of surface treatment in harsh environments.

[0012] Furthermore, the PVD coating employs magnetron sputtering technology with a process temperature of 150-400℃ and a coating thickness of 1-5 micrometers. Magnetron sputtering technology generates high plasma density, resulting in a film layer with high density, good uniformity, low internal stress, and strong adhesion to the substrate. The resulting PVD coating has an extremely smooth surface and uniform, full color. The process temperature range of 150-400℃ is considered a low-temperature PVD process, which can effectively avoid thermal damage such as annealing and deformation to the metal substrate (especially precision parts that have undergone heat treatment). At the same time, it can also ensure that the underlying UV coating layer will not yellow or degrade due to high temperatures. The 1-5 micrometer coating thickness is the result of optimization. This thickness is sufficient to provide a full, strong hiding power color and adequate wear resistance, while avoiding excessive thickness that could affect assembly accuracy or cause excessive internal stress in the film layer, thus achieving the best balance between performance and production efficiency.

[0013] Furthermore, in the steps of spraying UV primer and UV topcoat, the film thickness of the UV-curable primer and topcoat are independently 10-20 micrometers, and the curing energy is 800-1800 mj / cm². A six-axis industrial robot, a spraying system, and a UV curing tunnel oven are used for the spraying operation. The UV curing tunnel oven has a built-in high-pressure mercury lamp or LED-UV light source and is equipped with a light intensity and energy integrator to monitor in real time and ensure that the curing energy is stable at the set value. The 10-20 micrometer UV primer provides an extremely smooth and even substrate for the PVD coating, which can cover up minor defects in the substrate, resulting in a mirror-like finish on the final PVD color film. The UV topcoat of the same thickness acts like a "transparent armor," effectively protecting the precious PVD color film underneath from scratches, UV radiation, and chemical corrosion. The use of a six-axis industrial robot for spraying completely eliminates the instability of manual operation, ensuring that the paint film thickness is uniform in every area of ​​complex three-dimensional curved parts. This is an indispensable guarantee for achieving high-end appearance quality. The use of a UV curing tunnel oven equipped with a light intensity and energy integrator for real-time monitoring can accurately ensure that the curing energy received by each product is stable within the set range. This avoids problems such as stickiness and performance degradation of the paint film due to insufficient curing, or embrittlement of the paint film due to over-curing, and achieves process controllability and traceability.

[0014] Furthermore, the pretreatment steps include wiping and degreasing with isopropanol, dry ice cleaning, and infrared preheating treatment at a temperature of 50-70°C.

[0015] Furthermore, the wiping and degreasing step utilizes an ultrasonic cleaning tank, while dry ice cleaning employs a dry ice cleaning machine. This dry ice cleaning machine includes a dry ice manufacturing system, storage tank, compressed air system, and spray gun. The infrared preheating treatment step utilizes an infrared preheating furnace equipped with a quartz tube or infrared plate radiator and a precise temperature control system. Combined with ultrasonic cleaning, dry ice cleaning, and solvent wiping, this constitutes a multi-layered cleaning system from macro to micro. Dry ice cleaning, in particular, removes stubborn contaminants in a non-contact, residue-free manner, providing a near-perfect clean surface for subsequent coatings—a prerequisite for high adhesion. Infrared preheating not only removes trace amounts of moisture and activates substrate surface molecules to enhance adhesion but also ensures the workpiece is at a stable and suitable temperature before spraying, aiding in UV paint leveling and shortening the overall production cycle, thus improving efficiency. By using standardized professional equipment (such as temperature-controlled preheating furnaces and adjustable-parameter cleaning machines) instead of purely manual operation, the impact of human factors on pretreatment quality is greatly reduced, ensuring the initial consistency of the substrate state for each batch of products and laying a solid foundation for the stability of all subsequent steps.

[0016] Furthermore, the first PVD coating step employs multi-arc ion plating or magnetron sputtering PVD equipment. The PVD equipment includes a vacuum chamber and pumping system, a cathode target source loaded with metal targets such as titanium and zirconium, a gas flow control system equipped with a mass flow controller to precisely control the input of gases such as Ar, N2, C2H2, and O2, a pulse bias power supply and an arc / sputtering power supply, and a PLC or computer-integrated control system for executing and storing process formulations. The vacuum chamber and pumping system are fundamental to the PVD process, ensuring that the coating process takes place in an oxygen-free and pollution-free environment, a prerequisite for achieving high-quality, pure films. The mass flow controller allows for precise control of each process gas at the milliliter / minute level, which is crucial for regulating the chemical composition, structure, and color of the film. The computer-integrated control system is responsible for storing and reproducing complex process formulations, ensuring that the parameters of each coating process are absolutely consistent, achieving excellent process stability and product reproducibility, and meeting the needs of large-scale industrial production.

[0017] The beneficial effects of this invention are as follows: This invention provides a PVD multicolor coating process for metal automotive parts, which has the following advantages: 1. It achieves precise, complex, and three-dimensional multi-color effects. By introducing photolithography, it is possible to define any complex pattern on the surface of the parts with micron-level precision, achieving clear and sharp boundaries that are impossible to achieve with traditional methods. It completely eliminates color penetration. By creating micron-level depressions on the substrate through chemical etching, a slight height difference is generated between different color areas. This not only creates a unique sense of layering and three-dimensionality visually, but also provides high-value tactile feedback, greatly enhancing the aesthetics and high-end texture of the product. 2. It ensures excellent film adhesion and long-term reliability. The micro-recessed structure etched on the substrate provides a strong "anchoring effect" for the second PVD film layer. This mechanical interlocking structure significantly enhances the adhesion between the film layer and the substrate, making the second color area as firmly "grown" on the substrate, ensuring that the product remains intact even in harsh environments throughout its entire life cycle. 3. It provides a coating system that combines rich colors with top-notch performance. By selecting metals such as titanium, chromium, and zirconium, as well as their nitrides, carbides, and oxides as film materials, and by precisely controlling process parameters, an almost unlimited color library is formed, from classic gold and silver to vibrant blue and purple. All of these PVD film materials themselves have extremely high hardness, wear resistance, and chemical inertness, which means that the final colorful surface is not only beautiful, but also has super physical and chemical protection capabilities, perfectly meeting the durability requirements of automotive parts. 4. A high-quality control system with full-process automation and digitalization has been built. From ultrasonic and dry ice cleaning to ensure atomic-level cleanliness, to six-axis robot spraying to ensure the ultimate uniformity of the paint film, and then to the mass flow controller and computer integrated system to precisely control the PVD process, the entire process has achieved a high degree of automation and digitalization. Key processes such as UV curing are equipped with energy integrators for real-time monitoring, ensuring that the curing quality of each product is stable and consistent. This system minimizes the impact of human factors and ensures extremely high consistency and traceability of product quality under large-scale production. 5. Adhering to the low-temperature, high-efficiency, and user-friendly process concept, the process employs magnetron sputtering technology and controls the process temperature within a low-temperature range of 150-400℃, effectively avoiding thermal damage to the metal substrate and destruction of the UV primer, protecting the dimensional accuracy of the workpiece and the performance of the underlying layer. The steps are closely connected, such as the infrared preheating in the pretreatment, which both activates the surface and optimizes the production cycle. UV curing is completed within seconds, making the entire process highly efficient and energy-saving, suitable for modern assembly line production.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 A process flow diagram of a PVD multicolor coating process for metal automotive parts provided in an embodiment of the present invention; Figure 2 This is a system architecture diagram of a PVD multicolor coating process for metal automotive parts, provided as an embodiment of the present invention. Detailed Implementation

[0020] The following is in conjunction with the appendix Figure 1-2 The principles and features of the present invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Examples, such as Figure 1-2 As shown, the present invention provides a PVD multicolor coating process for metal automotive parts, which includes the following steps; S1, Pretreatment, the purpose of this step is to obtain an absolutely clean and uniformly active substrate surface, providing a solid foundation for subsequent coatings; 1. First, wipe and degrease: The operator uses a lint-free cloth dipped in high-purity isopropyl alcohol to thoroughly wipe the metal automotive parts (such as aluminum alloy gear shift knob) to remove macroscopic grease and fingerprints; 2. Perform dry ice cleaning: Place the workpiece into the working chamber of the dry ice cleaning machine. Through the nozzle of the equipment, solid dry ice particles are sprayed at high speed onto the surface of the workpiece under the drive of compressed air. The dry ice particles will cause a "micro-explosion" at the moment of impact. Through the thermal shock contraction and sublimation gas expansion, the micro-contaminants are peeled off from the surface of the substrate and blown clean. This process is non-contact and no secondary waste liquid is generated. 3. Finally, perform infrared preheating: transfer the cleaned workpiece to an infrared preheating oven and maintain it at a set temperature (e.g., 60°C) for several minutes to completely evaporate any residual trace amounts of moisture and solvent on the surface and raise the overall temperature of the workpiece, which helps with the leveling and adhesion of the subsequent UV primer. S2, Spray UV primer: Spray a UV-curable primer onto the substrate surface and cure it. This step is designed to provide a smooth, flat base layer with excellent adhesion for the PVD coating. 1. Loading and electrostatic dust removal: The preheated workpiece is fixed on the conveyor fixture of the spraying line and passes through the electrostatic dust removal area equipped with ion air bars to neutralize and blow away static electricity and dust that may be generated on the surface due to friction. 2. Robotic spraying: A six-axis industrial robot (such as KUKA or FANUC) holds a high-pressure mixed air spray gun and sprays the workpiece evenly according to a preset trajectory. The robot path program ensures the uniformity of coverage of complex three-dimensional curved surfaces. 3. Leveling: After spraying, the workpiece enters a low-temperature (e.g., 60°C) leveling zone for 3 minutes to balance the surface tension of the paint film and achieve a mirror-like smooth effect. 4. UV curing: The workpiece enters the UV curing tunnel oven and is irradiated with ultraviolet light of a specific wavelength (usually 365nm or 395nm). After the photoinitiator absorbs the photon energy, it generates active groups, which initiates a rapid chain polymerization reaction of the unsaturated double bonds in the UV resin, forming a three-dimensional cross-linked solid paint film in seconds. S3, the first PVD coating, is formed by physical vapor deposition on the surface of the primer in a vacuum environment to form a PVD film layer with a first color. This step deposits the first functional film with a specific color in a vacuum environment. 1. Loading and vacuuming: Load the workpiece onto the planetary carrier of the PVD equipment cavity, close the cavity door, and start the multi-stage vacuum pump group (usually composed of a mechanical pump and a molecular pump connected in series) to evacuate the cavity background vacuum to a high vacuum level (e.g., 5.0×10⁻³Pa) to completely eliminate gas contamination; 2. Argon ion bombardment cleaning: A small amount of high-purity argon gas is introduced into the chamber, and a pulsed bias voltage is applied to the workpiece. The argon gas is ionized into Ar⁺ and bombarded on the surface of the workpiece under the acceleration of the electric field, sputtering away the last few atomic layers of contaminants to achieve atomic-level cleaning. 3. Deposition of coating: First, turn on the power supply of the titanium target and perform short-term metallic titanium sputtering in an argon atmosphere to form an extremely thin (about 0.2 μm) titanium underlayer to enhance the adhesion of the transition layer; then, introduce high-purity nitrogen into the chamber as a reactive gas, and titanium atoms are sputtered out in the plasma, react with nitrogen atoms to form titanium nitride, which is deposited on the surface of the workpiece to form the first golden PVD film; S4, Precision masking and etching: A mask is set on the first PVD film layer, and a preset pattern is formed by etching to expose part of the substrate. This is the core technical step to achieve accurate color separation. 1. Coating with photosensitive ink: The workpiece is uniformly coated with a layer of liquid photosensitive ink that is sensitive to light of a specific wavelength by passing it through a precision coating equipment; 2. Exposure: Using a high-precision digital exposure machine, a digital graphic file containing a preset pattern (such as a brand logo) is input into the device. The device uses a DMD chip or a direct laser imaging system to precisely project ultraviolet laser onto the photosensitive ink layer. The ink in the illuminated area undergoes a photochemical reaction, and its solubility changes. 3. Development: The exposed workpiece is immersed or sprayed with a specific weak alkaline developing solution. The ink in the unexposed areas is dissolved and removed, thus precisely exposing the logo area of ​​the underlying gold PVD film layer on the surface of the workpiece, while other areas are tightly protected by the remaining ink layer. 4. PVD layer etching: The workpiece is immersed in a mixed etching solution of hydrofluoric acid and hydrochloric acid. The solution precisely etches away the exposed gold titanium nitride layer of the logo area, but does not damage the underlying UV primer and the surrounding ink mask. Subsequently, the workpiece can be transferred to a mixture of ferric chloride and hydrochloric acid, which performs controlled micron-level etching on the exposed aluminum alloy substrate to form a recessed step with a depth of about 5 microns. Digital image processing and path planning algorithm: Before exposure, the original vector graphics need to be processed by the "raster image processor" algorithm. This algorithm converts the vector path into the scanning path of the exposure device and automatically performs "dose compensation calculation". Based on the graphic position and focal length, it fine-tunes the exposure energy of different areas to ensure the consistency, sharpness and dimensional accuracy of the graphic boundary throughout the exposure area. S5, Second PVD coating: Under vacuum, a second physical vapor deposition is performed to form a PVD film with a second color on the exposed substrate area. The remaining mask is then removed. This step deposits a second color in the defined pattern area. Detailed steps: 1. Secondary PVD deposition: The workpiece with a precision mask is put back into the PVD equipment and the process is repeated similar to the third step, but the target material and reaction gas are changed. For example, a zirconium target is used and reacted in a nitrogen atmosphere to deposit a black zirconium nitride film. This film will be deposited on the aluminum substrate of the etched recessed logo area, as well as on the gold PVD layer of other areas that are not protected by the mask. 2. Mask Removal: After the workpiece is removed from the PVD equipment, it is immersed in a special stripping solution. The stripping solution completely removes the photosensitive ink mask that protects the first gold PVD area through swelling and decomposition, thus perfectly revealing the underlying gold layer. S6, Apply UV topcoat: Apply UV-cured topcoat to the surface with the two-color PVD film layer and cure it. This step provides the final protection and gloss to the entire coating system. The detailed steps are as follows: secondary electrostatic dust removal, robot spraying of UV topcoat, leveling and UV curing. The process is exactly the same as the second step, ensuring that the topcoat covers the area evenly and seals the two-color PVD pattern under a transparent, high-hardness protective layer. After the landline is completed, a final inspection is carried out: using automatic optical inspection equipment in conjunction with machine vision color and defect detection algorithms, the image of the finished product is compared with a standard template. The algorithm automatically determines whether the color is qualified, whether the color separation boundary is clear and sharp, and whether there are any defects by calculating the color difference ΔE value of the image and extracting the edge contour.

[0023] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Content not described in detail in this specification is prior art known to those skilled in the art.

[0024] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A PVD multi-color coating process for metal automotive parts, characterized in that, The PVD multi-color coating process comprises the following steps: S1, pretreatment, cleaning and activating the metal automobile parts substrate; S2, spraying UV primer, spraying and curing UV-curable primer on the substrate surface; S3, first layer PVD coating, physical vapor deposition on the primer surface in a vacuum environment to form a PVD film layer with a first color; S4, precision mask and etching, setting a mask on the first layer PVD film layer, forming a pre-set pattern by etching and exposing part of the substrate; S5, second layer PVD coating, second layer physical vapor deposition in a vacuum environment to form a PVD film layer with a second color on the exposed substrate area, and then remove the remaining mask; S6, spraying UV topcoat, spraying and curing UV-curable topcoat on the surface with double-color PVD film layer.

2. The PVD multi-color coating process of metal automotive parts according to claim 1, characterized in that, The precision mask and etching step comprises: a. coating a photosensitive ink on the first layer PVD film layer by a photolithography process, and forming a mask with a pre-set pattern after exposure and development; b. removing the first layer PVD film layer of the exposed area by using a chemical etching solution to form a micron-level deep recess structure on the exposed substrate area by chemical etching.

3. The PVD multi-color coating process of metal automotive parts according to claim 2, characterized in that, The chemical etching solution is a mixed solution of hydrofluoric acid and hydrochloric acid, or a mixed solution of ferric chloride and hydrochloric acid.

4. The PVD multi-color coating process of metal automotive parts according to claim 1, characterized in that, The film layer materials of the first layer PVD coating and the second layer PVD coating are independently selected from the group consisting of metal elements, nitrides, carbides or oxides of titanium, chromium and zirconium; different color performances are obtained by selecting different film layer materials and process parameters.

5. The PVD multi-color coating process of metal automotive parts according to claim 1 or 4, characterized in that, The PVD coating adopts a magnetic control sputtering technology, the process temperature is 150-400℃, and the coating thickness is 1-5 microns.

6. The PVD multi-color coating process of metal automotive parts according to claim 1, characterized in that, In the steps of spraying UV primer and spraying UV topcoat, the film thickness of the UV-curable primer and topcoat is independently 10-20 microns, the curing energy is 800-1800 mj / cm², a six-axis industrial robot and a spraying system are used for spraying operation, and a UV curing tunnel furnace is used for curing operation, the UV curing tunnel furnace is built-in high-pressure mercury lamp or LED-UV light source, and is equipped with light intensity and energy integrator to monitor and ensure that the curing energy is stable at the set value.

7. The PVD multi-color coating process of metal automotive parts according to claim 1, wherein, The pretreatment step comprises wiping degreasing with isopropyl alcohol, dry ice cleaning and infrared preheating, and the preheating temperature is 50-70℃.

8. The PVD multi-color coating process of metal automotive parts according to claim 7, characterized in that, The wiping degreasing step uses an ultrasonic cleaning tank, the dry ice cleaning uses a dry ice cleaning machine which comprises a dry ice manufacturing system, a storage tank, a compressed air system and a spray gun, and the infrared preheating step uses an infrared preheating furnace which is equipped with a quartz tube or an infrared plate radiator and has a precise temperature control system.

9. The PVD multi-color coating process of metal automotive parts according to claim 1, wherein, The first layer PVD coating step uses a multi-arc ion plating or a magnetic control sputtering PVD device, the PVD device comprises a vacuum cavity and a gas extraction system, a cathode target source loaded with titanium, zirconium and other metal target materials, a gas flow control system for precisely controlling the input of Ar, N2, C2H2, O2 and other gases, a pulse bias power supply and an arc / sputtering power supply, and a PLC or computer integrated control system for executing and storing process formulas.

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