A method for preparing a parylene coating on a metal surface

Abstract

The present application relates to a kind of preparation methods of metal surface parylene coating, belong to polymer coating technical field.The method aims at solving the problem that parylene coating is poor in adhesion on smooth metal substrate and easy to fall off.The method includes: the surface to be plated of metal device is treated by plasma;The surface after processing is contacted with active coupling agent solution, the solution is prepared from raw materials including double bond containing silicon-based coupling agent, acid catalyst and fluorine-containing quaternary ammonium salt activator;The metal device coated with solution is treated by two-step baking process including first step normal pressure baking and second step vacuum baking;Finally, parylene film is plated.The present application significantly improves the adhesion of coating by constructing chemically bonded interface layer, and improves production efficiency and process stability by taking coupling agent treatment as off-line pretreatment process.

Description

Technical Field

[0001] This invention relates to the field of polymer coating technology, and more specifically to a method for preparing a paraffin coating on a metal surface. Background Technology

[0002] Parylene is a poly(p-xylene) polymer film formed on the surface of a substrate through chemical vapor deposition. Due to its uniform thickness, dense, pinhole-free structure, excellent electrical insulation, and chemical stability, it is widely used in high-end protective applications such as aerospace, medical devices, and precision electronics.

[0003] The bonding between the P-coating and the substrate relies primarily on physical adsorption and mechanical interlocking. However, for extremely smooth metal substrates (such as gold, silver, and highly polished stainless steel), the coating adhesion is extremely poor due to the lack of microscopic defects that can be anchored. Under conditions of friction, stress, or temperature changes, the coating is prone to delamination and peeling, severely affecting the reliability of its protective function.

[0004] Existing technologies have made various attempts to improve adhesion. For example, CN118719510A discloses an AMB-structured coupling agent, whose A-terminus contains vinyl groups that can react with phenelzine, and whose B-terminus contains carboxyl groups that can interact with metals. M is an organosilicon or polyolefin backbone, thereby enhancing the chemical bonding between phenelzine and metals. However, this approach focuses on the design of the coupling agent's molecular structure itself and does not fully address the issues of efficient activation, directional alignment, and removal of excess physically adsorbed layers on metal surfaces. The strength of the interfacial bonding and long-term stability under humid and hot conditions remain insufficient. CN110975017A discloses that plasma treatment of the substrate and the use of a silane coupling agent as an adhesion promoter can be used when preparing a hydrophilic coating, but its coupling agent activation method is conventional heating or light irradiation, which is not very efficient. CN114107974A discloses a process for coating a silane coupling agent on a copper foil surface, which uses a "105℃ heat treatment + solvent washing" method to remove the physically adsorbed coupling agent layer. However, its physical removal method using solvent washing not only introduces new processes and chemical reagents, but also makes it difficult to completely and controllably remove the weak adsorption layer at the microscopic level, and may also disturb the already formed chemical adsorption layer. Summary of the Invention

[0005] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0006] The purpose of this invention is to solve the technical problems of poor adhesion and easy peeling between the Piriton coating and the smooth metal substrate due to the lack of effective chemical bonding in the prior art, as well as the complexity and insufficient stability of the existing improvement process.

[0007] To achieve the above objectives, this application provides a method for preparing a paraffin coating on a metal surface, comprising the following steps: Cleaning of metal parts Plasma treatment is performed on the surface of metal devices to be coated; The surface of the metal device to be coated after plasma treatment is brought into contact with an active coupling agent solution, which is prepared from raw materials containing a silicon-based coupling agent with double bonds, an acid catalyst, and a fluorine-containing quaternary ammonium salt activator. The metal devices coated with the active coupling agent solution were subjected to atmospheric pressure baking and vacuum baking in sequence; The metal devices that have undergone the two-step baking process are then coated with a pyrene coating.

[0008] Furthermore, the temperature of the atmospheric pressure baking is 90~120℃, and the temperature of the vacuum baking is 80~150℃, with an absolute pressure not exceeding 10kPa.

[0009] Furthermore, the double-bonded silicon-based coupling agent is vinylsilane or acryloyloxysilane.

[0010] Furthermore, the double-bonded silicon-based coupling agent is selected from 3-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, or 3-acryloxypropyltrimethoxysilane.

[0011] Furthermore, the acid catalyst is acetic acid, hydrochloric acid, sulfuric acid, benzenesulfonic acid, or phosphoric acid.

[0012] Furthermore, the fluorinated quaternary ammonium salt activator is tetramethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, tetramethylammonium hexafluorophosphate, dodecyltrimethylammonium fluoride, or hexadecyltrimethylammonium fluoride.

[0013] Furthermore, the preparation of the active coupling agent solution includes: mixing and reacting the double-bonded silicon-based coupling agent, the acid catalyst, and the fluorinated quaternary ammonium salt activator in a solvent, wherein the solvent is a mixture of water and alcohol.

[0014] Further, the alcohol is selected from ethanol or isopropanol, and the alcohol accounts for 0 to 40% of the total mass of the solvent.

[0015] Furthermore, the method of contacting the active coupling agent solution with the surface to be coated is immersion or spraying.

[0016] Furthermore, the mass of the fluorinated quaternary ammonium salt activator accounts for 0.05% to 0.5% of the total mass of the active coupling agent solution.

[0017] The technical solution of this application completely reshapes the interfacial state of the metal surface through the synergistic effect of "plasma activation + specific coupling agent activated by fluorine-containing quaternary ammonium salt + two-step baking combining atmospheric pressure and vacuum". First, plasma treatment generates high-density, highly active hydroxyl groups on the metal surface. Then, based on acid-catalyzed hydrolysis of the coupling agent, a fluorine-containing quaternary ammonium salt is innovatively introduced as an activator, which can efficiently promote the condensation reaction between silanol groups and hydroxyl groups on the metal surface, forming denser and more stable Si-O-Me chemical bond anchors. Most importantly, this application adopts a two-step baking process combining "atmospheric pressure baking" and "vacuum baking". The first step, atmospheric pressure baking, fully promotes the cross-linking and interfacial anchoring of the coupling agent at a specific temperature. The second step, vacuum baking, under high temperature and negative pressure conditions, forcibly removes unreacted small molecules of the coupling agent and weakly adsorbed substances (such as water and alcohol) from the interfacial layer. This not only purifies the interface but also further promotes the condensation of residual silanol groups, transforming the interfacial layer from a mixed state of "physical adsorption + chemical bonding" into a pure, highly cross-linked chemically bonded layer. This is fundamentally different from the physical method of removing the physically adsorbed layer using "solvent washing." The vacuum baking in this application is a chemical process that strengthens chemical bonding, making it more thorough and without introducing new impurities.

[0018] Compared with the prior art, the beneficial effects of this application are as follows: 1. Significantly improves adhesion and aging resistance: Through the above synergistic effect, a stable and pure chemically bonded interface layer is constructed, which enables the adhesion of the Piriton coating on smooth metal surfaces to stably reach the 5B level of the ASTM D3359 standard, and it can still maintain extremely high strength after aging tests such as damp heat and thermal shock.

[0019] 2. Improve production efficiency and reduce energy consumption: This invention separates the coupling agent treatment step from the vacuum coating equipment as an independent pretreatment process outside the cavity, avoiding the time-consuming coupling agent evaporation (VPS) and removal process inside the vacuum cavity, and significantly shortening the occupation cycle of the main equipment.

[0020] 3. Enhanced process stability: Eliminates contamination of the CVD vacuum system by coupling agents, ensuring the cleanliness and stability of the main process of Piriton coating, thereby ensuring the reliability of coating quality and batch consistency. Detailed Implementation

[0021] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the embodiments described herein are only some, not all, embodiments of the present invention, and are merely illustrative and not intended to limit the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0022] The present invention will be described in detail below through specific embodiments. The specific implementation methods are as follows: This invention provides a method for preparing a paraffin coating on a metal surface, comprising the following steps: Cleaning of metal parts; Plasma treatment is performed on the surface of metal devices to be coated; The surface of the metal device to be coated after plasma treatment is brought into contact with an active coupling agent solution, which is prepared from raw materials containing a silicon-based coupling agent with double bonds, an acid catalyst, and a fluorine-containing quaternary ammonium salt activator. Metal devices coated with active coupling agent solution are subjected to a two-step baking process: first, atmospheric pressure baking, and second, vacuum baking. Piriton coating is applied to metal parts that have undergone two-step baking processes.

[0023] As a preferred embodiment, the temperature of the first step of atmospheric pressure baking is 90~120℃, and the temperature of the second step of vacuum baking is 80~150℃ and the absolute pressure is 10Pa~10kPa.

[0024] These baking conditions promote the cross-linking reaction and chemical bonding of silicon-based coupling agents on the metal surface, while thoroughly removing excess coupling agents under vacuum conditions to prevent them from interfering with coating adhesion, thereby stabilizing and improving adhesion and ensuring consistent and reliable coating quality.

[0025] In a preferred embodiment, the double-bonded silicon-based coupling agent is a vinylsilane or an acryloxysilane. During the deposition of pyrene, the nonpolar ends of the double-bonded silicon-based coupling agent can effectively bond with pyrene molecules to form a chemical bond, thereby significantly enhancing the bonding strength between the coating and the metal substrate and overcoming the problem of insufficient adhesion caused by traditional mechanical bonding alone.

[0026] As a preferred embodiment, the double-bonded silane coupling agent is selected from 3-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, or 3-acryloxypropyltrimethoxysilane.

[0027] More specifically, the double-bonded silicon-based coupling agents are selected from vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, vinyltriisopropoxysilane, vinyltriacetoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriisopropoxysilane, 3-methacryloyloxypropyltri(trimethylsiloxy)silane, or 3-acetoxypropyltrimethoxysilane. These preferred coupling agents possess moderate hydrolytic reactivity and good film-forming properties, can form stable chemical bonds with phenelzine, and simultaneously form strong interactions with metal surfaces, further enhancing the adhesion and process stability of the coating.

[0028] In a preferred embodiment, the acid catalyst is acetic acid, hydrochloric acid, sulfuric acid, benzenesulfonic acid, or phosphoric acid.

[0029] Here, the acid catalyst can regulate the pH value of the coupling agent hydrolysis reaction, promote the hydrolysis of silane into active silanol, enhance its reactivity with the metal surface, thereby improving the uniformity and adhesion of the coupling agent coating.

[0030] In a preferred embodiment, the fluorinated quaternary ammonium salt activator is tetramethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, tetramethylammonium hexafluorophosphate, dodecyltrimethylammonium fluoride, or hexadecyltrimethylammonium fluoride.

[0031] Here, fluorinated quaternary ammonium salt activators can significantly enhance the interaction between the metal surface and the silicon-based coupling agent, promote the effective adsorption and cross-linking of the coupling agent, and improve process stability and adhesion enhancement.

[0032] In a preferred embodiment, the preparation of the active coupling agent solution includes: mixing and reacting a silicon-based coupling agent containing double bonds, an acid catalyst, and a fluorinated quaternary ammonium salt activator in a solvent, wherein the solvent is a mixture of water and alcohol. Here, the water and alcohol mixture facilitates the hydrolysis reaction of the silicon-based coupling agent, forming a uniform active solution, ensuring the coupling agent is evenly distributed on the metal surface, avoiding local aggregation or incomplete reaction, thereby improving the overall adhesion performance of the coating.

[0033] In a preferred embodiment, the alcohol is selected from ethanol or isopropanol, and the alcohol accounts for 0-40% of the solvent by mass.

[0034] Here, ethanol or isopropanol can be used as a co-solvent to adjust the polarity and volatility of the solution, optimize the hydrolysis rate and coating performance of the coupling agent, ensure the wettability and film-forming properties of the solution on different metal surfaces, and improve process adaptability.

[0035] As a preferred embodiment, the active coupling agent solution is brought into contact with the surface to be coated by immersion or spraying. Immersion or spraying is simple to operate, suitable for metal devices of different shapes and sizes, and ensures that the coupling agent solution is in full contact with the surface to be coated, forming a uniform active layer and providing a good bonding foundation for subsequent coating.

[0036] In a preferred embodiment, the fluorinated quaternary ammonium salt activator is added at a mass ratio of 0.05% to 0.5% of the total mass of the active coupling agent solution. Additionally, the amount of acid catalyst added is such that the pH is ≤6, and the concentration of the double-bonded silicon-based coupling agent ranges from 0.2% to 5%.

[0037] The range of activators in this range can effectively promote the reaction between the coupling agent and the metal surface, while avoiding side reactions or residues caused by excessive activator, ensuring that the adhesion enhancement effect is stable and controllable, and does not affect the subsequent coating process.

[0038] Example 1 This embodiment provides a method for preparing a high-adhesion Parylene C coating on a highly polished 304 stainless steel surface, the specific steps of which are as follows: Step S10, Cleaning and Drying: The high-polished 304 stainless steel sample is ultrasonically cleaned for 30 minutes with an aqueous solution containing neutral detergent, rinsed with deionized water, and then dried in a 105℃ drying oven for 1 hour.

[0039] Step S20, Plasma treatment: Place the dried sample in a plasma cleaner and treat it for 300 seconds at a discharge power of 500W to clean and activate its surface.

[0040] Step S30, preparation of active coupling agent solution: Add 840g of deionized water and 150g of ethanol to the preparation tank, add 10g of 3-methacryloyloxypropyltrimethoxysilane while stirring, adjust the pH of the solution to 5.0 by adding acetic acid dropwise, and finally add 1g of tetrabutylammonium fluoride. Stir and react at 25°C for 30 minutes to obtain the active coupling agent solution.

[0041] Step S40, Coupling agent coating: Immerse the sample treated in step S20 in the above active coupling agent solution for 30 seconds, then rinse with pure water until no water droplets remain on the surface.

[0042] Step S50, two-step baking: Step 1 (Ambient Pressure Baking): Place the sample in an ambient pressure oven at 110℃ and bake for 1 hour.

[0043] Step 2 (vacuum baking): Transfer the sample to a vacuum oven and dry it for 0.5 hours at an absolute pressure of approximately 1.3 kPa (-0.1 MPa gauge pressure) and a temperature of 120°C.

[0044] Step S60, Pyrelin Coating: Place the treated sample in the Pyrelin vacuum coating chamber, load Pyrelin C-type powder, set the pyrolysis furnace temperature to 650℃, and use a stepped heating method in the sublimation chamber to 170℃. Maintain the system base pressure at 1Pa and run the automatic coating program for 6 hours. The coupling agent evaporation device is not activated during the coating process.

[0045] Example 2 A method for preparing a high-adhesion phenelzine N coating on the surface of a gold-plated copper connector. This embodiment examines the universality of using different coupling agents, solvents, and phenelzine types. The specific steps are as follows: Steps S10-S20 are the same as in Example 1.

[0046] Step S30, preparation of active coupling agent solution: In a mixed solvent of 900g deionized water and 80g isopropanol, add 20g vinyltriethoxysilane, adjust the pH to 4.5 by adding hydrochloric acid dropwise, add 2g dodecyltrimethylammonium fluoride, and stir the reaction at 40°C for 15 minutes.

[0047] Step S40 is the same as in Example 1.

[0048] Step S50, two-step baking: the first step is atmospheric baking at 105℃; the second step is vacuum baking at 130℃, with an absolute pressure of about 0.7kPa.

[0049] Step S60, Pyrelin coating: Pyrelin N-type powder is used, the pyrolysis furnace temperature is set to 680℃, and the coating time is 12 hours.

[0050] Example 3 A method for preparing a high-adhesion paraben C coating on the surface of an aluminum alloy casing. This embodiment examines the flexibility of the coupling agent coating method, employing a spray coating method. The specific steps are as follows: Steps S10-S20 are the same as in Example 1.

[0051] Step S30: Use the same solution formulation as in Example 1, but stir the reaction at 10°C for 60 minutes.

[0052] Step S40: Use a precision spray gun to evenly spray the coupling agent solution onto the surface of the outer casing, let it stand for 10 seconds, and then rinse.

[0053] Step S50, two-step baking: the first step is atmospheric baking at 120℃; the second step is vacuum baking at 150℃, with an absolute pressure of about 1.3kPa.

[0054] Step S60, Pyrelin coating: Pyrelin HT type powder is used, the pyrolysis furnace temperature is set to 720℃, and the coating time is 8 hours.

[0055] Example 4 A method for preparing a high-adhesion pyrene D coating on the surface of a silver electrode. This embodiment investigates the substitutability of different acid catalysts and activators. The specific steps are as follows: Steps S10-S20 are the same as in Example 1.

[0056] Step S30: The active coupling agent solution is prepared by reacting 5g of 3-acryloyloxypropyltrimethoxysilane, phosphoric acid (adjusted to pH 6.0), and 0.5g of hexadecyltrimethylammonium fluoride in an appropriate amount of alcohol-water solvent.

[0057] Step S40 is the same as in Example 1.

[0058] Step S50, two-step baking: the first step is atmospheric pressure baking at 115℃; the second step is vacuum baking at 140℃, with an absolute pressure of approximately 0.7kPa.

[0059] Step S60, Pyrelin coating: Pyrelin D-type powder is used, the pyrolysis furnace temperature is set to 660℃, and the coating time is 10 hours.

[0060] Example 5 This embodiment provides a method for preparing a high-adhesion Pyrelin C coating on the surface of an iron sheet, the specific steps of which are as follows: Steps S10-S20 are the same as in Example 1.

[0061] Step S30, preparation of active coupling agent solution: Add 800g of deionized water and 120g of ethanol to the preparation tank, add 10g of 3-acetoxypropyltrimethoxysilane while stirring, adjust the pH of the solution to 5.0 by adding phosphoric acid dropwise, and finally add 1g of tetrabutylammonium fluoride. Stir and react at 25°C for 30 minutes to obtain the active coupling agent solution.

[0062] Step S40 is the same as in Example 1.

[0063] Step S50, two-step baking: The first step is atmospheric pressure baking at 90℃ for 2 hours. The second step is vacuum baking, where the sample is transferred to a vacuum oven and dried at an absolute pressure of approximately 1.3 kPa and a temperature of 80℃ for 1.5 hours.

[0064] Step S60, Pyrelin Coating: Place the treated sample in the Pyrelin vacuum coating chamber, load Pyrelin C-type powder, set the pyrolysis furnace temperature to 650℃, and use a stepped heating method in the sublimation chamber to 170℃. Maintain the system base pressure at 1Pa and run the automatic coating program for 6 hours. The coupling agent evaporation device is not activated during the coating process.

[0065] Comparative Example 1 A method for preparing a high-adhesion paraffin C coating on a highly polished stainless steel surface differs from Example 1 in that: in step S30, its carboxyl-organosilicon-vinyl coupling agent (CaSiVi, Mw=780) is prepared as a 1.5 wt% isopropanol immersion solution. The stainless steel sheet, which has undergone the same pretreatment (cleaning + plasma) process, is immersed for 0.5 hours and then dried in a 65°C, atmospheric pressure oven for 1 hour. The remaining steps are identical to those in Example 1.

[0066] Comparative Example 2 A method for preparing a high-adhesion Parylene C coating on a highly polished stainless steel surface differs from Example 1 in that: tetrabutylammonium fluoride is not added to the coupling agent solution in step S30; and after coating the coupling agent, vacuum baking (120°C, 1.3 kPa, 0.5 hours) is performed directly in step S50, without the "atmospheric pressure baking" step. The remaining steps are exactly the same as in Example 1.

[0067] Comparative Example 3 A method for preparing a high-adhesion para-rein C coating on a highly polished stainless steel surface differs from Example 1 in that, in step S50, after applying the coupling agent and rinsing, only atmospheric pressure baking (110°C, 1 hour) is performed, without subsequent vacuum baking. The remaining steps are exactly the same as in Example 1.

[0068] Comparative Example 4 A method for preparing a Parylene C coating on a highly polished stainless steel surface differs from Example 1 in that: in step S30, tetrabutylammonium fluoride is not added; that is, the active coupling agent solution consists only of 840g deionized water, 150g ethanol, and 10g 3-methacryloyloxypropyltrimethoxysilane, with the pH adjusted to 5.0 using acetic acid, and the reaction is stirred at 25°C for 30 minutes. The remaining steps are exactly the same as in Example 1.

[0069] Comparative Example 5 A method for preparing a Piriton C coating on a highly polished stainless steel surface differs from Example 1 in that the two baking steps in step S50 are reversed: first, the sample coated with the coupling agent and rinsed is placed in a vacuum oven and dried at an absolute pressure of approximately 1.3 kPa and a temperature of 120°C for 0.5 hours; then, it is transferred to an oven at 110°C and atmospheric pressure for 1 hour. The remaining steps are exactly the same as in Example 1.

[0070] Comparative Example 6 A method for preparing a Parylene C coating on a highly polished stainless steel surface differs from Example 1 in that: in step S30, acetic acid is not added to adjust the pH; instead, after mixing deionized water, ethanol, 3-methacryloyloxypropyltrimethoxysilane, and tetrabutylammonium fluoride, the natural pH of the solution is approximately 6.5-7.0, and no acidification treatment is performed. The stirring reaction conditions are the same as in Example 1. The remaining steps are exactly the same as in Example 1.

[0071] Comparative Example 7 A method for preparing a Parylene C coating on a highly polished stainless steel surface differs from Example 1 in that: in step S30, 3-aminopropyltriethoxysilane (KH550) without double bonds is used instead of 3-methacryloyloxypropyltrimethoxysilane, and the amount added remains 10g. The remaining steps are exactly the same as in Example 1.

[0072] Comparative Example 8 A method for preparing a Pyrelin C coating on a highly polished stainless steel surface differs from Example 1 in that the amount of tetrabutylammonium fluoride added in step S30 is increased from 1g to 6g (accounting for approximately 0.6% of the total mass of the active coupling agent solution, exceeding the upper limit of 0.05%-0.5% as described in claim 10). The remaining steps are exactly the same as in Example 1.

[0073] The metal products coated with Pyrelin, prepared in the above examples and comparative examples, were subjected to adhesion testing using ASTM D3359 (cross-cut adhesion test). Test conditions included the initial state 2 hours after baking and the state after a "double 85" aging test (85°C, 85% relative humidity, 168 hours). The test results are summarized in Table 1. Table 1. Test results of metal products coated with Pyrelin coating According to Examples 1-5, this invention can achieve high-adhesion coatings on various metal substrates (high-polished 304 stainless steel, gold-plated copper connectors, aluminum alloy shells, silver electrodes, iron sheets) and various types of Piriton (Type C, Type N, Type HT, Type D). All examples use a silicon-based coupling agent containing double bonds (such as 3-methacryloyloxypropyltrimethoxysilane, vinyltriethoxysilane, etc.), an acid catalyst (acetic acid, hydrochloric acid, or phosphoric acid), and a fluorinated quaternary ammonium salt activator (tetrabutylammonium fluoride, dodecyltrimethylammonium fluoride, or hexadecyltrimethylammonium fluoride) to prepare an active coupling agent solution. The solvent is a mixture of deionized water and ethanol or isopropanol. The coating method includes immersion or spraying, followed by a two-step baking treatment of "first step atmospheric pressure baking, second step vacuum baking," and finally Piriton vacuum coating. The coatings in Examples 1-5 were uniform and defect-free, and the adhesion remained at 4B-5B 2 hours after furnace exposure. They showed no degradation after double 85 testing and had an intact appearance, proving that the process window could withstand reflow soldering and damp heat aging.

[0074] In contrast, Comparative Examples 1-8, deviating from the key process conditions of this invention, all failed to obtain coatings with high adhesion (adhesion <3B or obvious defects). The adhesion was generally ≤3B after 2 hours in the oven, and further deteriorated to ≤2B or even 1B after the double 85 test. Defects such as blistering, peeling, whitening, and cracking appeared, indicating that the absence of any one of the key technologies (activator, acid, double bond, two-step baking sequence / integrity) prevents the achievement of reliable long-term protective performance.

[0075] Comparative Example 1 used an isopropanol solution of carboxyl-organosilicon-vinyl coupling agent (CaSiVi), and was only baked at 65°C under normal pressure, without two-step baking or activator; adhesion <3B. Comparative Example 2 did not add tetrabutylammonium fluoride to the coupling agent solution, and after coating, only vacuum baking was performed without normal pressure baking; adhesion <3B. Comparative Example 3 contained an activator but only underwent normal pressure baking without subsequent vacuum baking; the coating showed bubbles and adhesion <3B. Comparative Example 4 retained two-step baking but completely lacked fluorinated quaternary ammonium salt activator; the coupling layer was uneven, adhesion <3B, and it peeled off completely after aging. Comparative Example 5 reversed the two-step baking order to vacuum baking followed by normal pressure baking; the coating showed microcracks, peeled off in flakes, and adhesion <3B. Comparative Example 6 did not add an acid catalyst to the active coupling agent solution; the coupling agent was insufficiently hydrolyzed and mainly existed through physical adsorption; adhesion <3B and poor solvent resistance. Comparative Example 7 used a conventional silane coupling agent KH550 without double bonds instead of a coupling agent containing double bonds. Although the two-step baking was retained, the interface peeled off and the adhesion was <3B because it could not form a covalent bond with Pyrelin. Comparative Example 8 increased the amount of fluorinated quaternary ammonium salt activator to 0.6% of the total mass of the solution (exceeding the upper limit of the preferred range of 0.5%), which led to precipitation and surface contamination in the solution. After coating, the coating produced white haze and pinholes, and the adhesion was <3B.

[0076] This invention requires a three-component active coupling agent solution consisting of a silicon-based coupling agent containing double bonds, an acid catalyst, and a fluorinated quaternary ammonium salt activator. Combined with a correct two-step baking process of "first baking under normal pressure, then baking under vacuum," a high-density, highly reactive coupling layer can be formed on the metal surface. This achieves a strong chemical bond between the phenelzine coating and the substrate, resulting in excellent adhesion. The absence, substitution, or incorrect process sequence of any single factor will lead to a significant decrease in adhesion or coating failure. By combining external pretreatment of the coupling agent with phenelzine vacuum coating, a stable chemically bonded interface layer is constructed on the metal surface, significantly improving coating adhesion and aging resistance, while also increasing production efficiency, reducing energy consumption, and enhancing process stability and batch consistency.

[0077] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing a paraffin coating on a metal surface, characterized in that, Includes the following steps: Cleaning of metal parts; Plasma treatment is performed on the surface of the cleaned metal parts to be coated. The surface of the metal device to be coated after plasma treatment is brought into contact with an active coupling agent solution, which is prepared from raw materials containing a silicon-based coupling agent with double bonds, an acid catalyst, and a fluorine-containing quaternary ammonium salt activator. The metal devices coated with the active coupling agent solution were subjected to atmospheric pressure baking and vacuum baking in sequence. The metal devices that have undergone the two-step baking process are then coated with a pyrene coating.

2. The method according to claim 1, characterized in that, The temperature of the first step of atmospheric pressure baking is 90~120℃, and the temperature of the second step of vacuum baking is 80~150℃, with an absolute pressure not exceeding 10kPa.

3. The method according to claim 1 or 2, characterized in that, The silicon-based coupling agent containing double bonds is vinylsilane or acryloyloxysilane.

4. The method according to claim 3, characterized in that, The double-bonded silane coupling agent is selected from 3-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, or 3-acryloxypropyltrimethoxysilane.

5. The method according to claim 1, characterized in that, The acid catalyst is acetic acid, hydrochloric acid, sulfuric acid, benzenesulfonic acid, or phosphoric acid.

6. The method according to claim 1, characterized in that, The fluorinated quaternary ammonium salt activator is tetramethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride, tetramethylammonium hexafluorophosphate, dodecyltrimethylammonium fluoride, or hexadecyltrimethylammonium fluoride.

7. The method according to claim 1, characterized in that, The preparation of the active coupling agent solution includes: mixing and reacting the double-bonded silicon-based coupling agent, the acid catalyst, and the fluorinated quaternary ammonium salt activator in a solvent, wherein the solvent is a mixture of water and alcohol.

8. The method according to claim 7, characterized in that, The alcohol is selected from ethanol or isopropanol, and the alcohol accounts for 0 to 40% of the total mass of the solvent.

9. The method according to claim 1, characterized in that, The method of contacting the active coupling agent solution with the surface to be coated is immersion or spraying.

10. The method according to claim 1, characterized in that, The added fluorine-containing quaternary ammonium salt activator accounts for 0.05% to 0.5% of the total mass of the active coupling agent solution.

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