Preparation process for eliminating performance difference of two sides of aluminum alloy matrix MFI zeolite membrane

Abstract

The invention relates to the technical field of metal anticorrosive coatings, in particular to a preparation process for eliminating performance difference of two sides of an aluminum alloy matrix MFI zeolite membrane, which comprises the following steps: preparing MFI zeolite membrane synthesis mother liquor from sodium hydroxide, deionized water, tetraethoxysilane and tetrapropylammonium hydroxide; carrying out surface treatment on the aluminum alloy matrix; the aluminum alloy matrix is placed in a reaction kettle containing mother liquor, and the aluminum alloy matrix does not make direct contact with the mother liquor initially; putting the reaction kettle into a drying oven for reaction; the reaction kettle is inverted, so that the surface of the aluminum alloy matrix is in uniform contact with the mother liquor and continuously reacts, and finally the MFI zeolite membrane with consistent properties on two sides is formed. The reaction kettle is heated until a uniform temperature field and a uniform fluid field are formed, and then the reaction kettle is inverted, so that the aluminum alloy is in uniform contact with the reaction liquid containing the primary crystal nucleus, the different-plane effect caused by the uneven temperature field, concentration field and convection in the reaction kettle in the in-situ hydrothermal synthesis process is effectively eliminated, and a foundation is laid for the in-situ hydrothermal synthesis process from laboratory research to large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of metal anti-corrosion coating technology, specifically a preparation process for eliminating the performance differences between the two sides of an MFI zeolite film on an aluminum alloy substrate. Background Technology

[0002] Aluminum-based MFI zeolite membranes exhibit great application potential in the field of metal surface corrosion protection due to their excellent chemical stability, corrosion resistance, and structural controllability. Currently, in-situ hydrothermal synthesis is the mainstream technology for preparing this membrane, which has advantages such as simple process flow, low equipment requirements, and controllable production costs, and has the foundation for large-scale promotion.

[0003] However, the existing in-situ hydrothermal synthesis method has a significant "opposite surface" effect problem when preparing flat aluminum alloy substrates. It often manifests as a continuous and dense film layer on one side, while the other side is loose, not dense, or even without a film. This results in an imbalance of anti-corrosion performance on both sides of the substrate, which seriously reduces the reliability of the product and has become a key technical bottleneck restricting aluminum-based MFI zeolite films from laboratory research to large-scale industrial application. Summary of the Invention

[0004] The purpose of this invention is to provide a preparation process that eliminates the performance differences between the two sides of an aluminum alloy substrate MFI zeolite film, in order to solve the problem that the product has a continuous and dense film layer on one side, while the other side is loose, not dense, or even without a film, resulting in an uneven anti-corrosion performance on both sides of the substrate, which seriously reduces the reliability of the product and has become a key technical bottleneck restricting the aluminum-based MFI zeolite film from laboratory research to large-scale industrial application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a preparation process for eliminating the performance differences between the two sides of an MFI zeolite film on an aluminum alloy substrate, comprising the following steps:

[0006] S1. Preparation of mother liquor: Sodium hydroxide, deionized water, tetraethyl orthosilicate and tetrapropylammonium hydroxide are used to prepare the mother liquor for MFI zeolite membrane synthesis.

[0007] S2. Surface treatment: Perform surface treatment on the aluminum alloy substrate to remove stains and foreign matter from its surface.

[0008] S3. Preparation of MFI zeolite membrane with consistent performance on both sides: The aluminum alloy substrate of step S2 is placed in a reaction vessel containing the mother liquor of step S1, and the aluminum alloy substrate is not in direct contact with the mother liquor at first.

[0009] Place the reactor in an oven, reach the target temperature, and maintain the temperature for reaction.

[0010] The reactor is inverted to allow the aluminum alloy substrate surface to come into uniform contact with the mother liquor and continue to react, ultimately forming an MFI zeolite film with consistent properties on both sides of the aluminum alloy substrate surface.

[0011] Preferably, in step S1, the molar ratio of sodium hydroxide, tetrapropylammonium hydroxide, tetraethyl orthosilicate, and deionized water is 0.64:0.16:1:92-100.

[0012] The preparation process of the mother liquor is as follows:

[0013] First, mix sodium hydroxide with deionized water and stir on a magnetic stirrer at a stirring intensity of 200-300 r / min;

[0014] After the sodium hydroxide has completely dissolved, add tetrapropylammonium hydroxide and continue stirring for 5 minutes.

[0015] Then, tetraethyl orthosilicate is added drop by drop to prevent it from directly coagulating.

[0016] The mixture was stirred continuously and aged for 6–24 hours to obtain the mother liquor.

[0017] Preferably, the surface treatment process of the aluminum alloy substrate in step S2 specifically includes:

[0018] Place the aluminum alloy substrate vertically in a clean beaker, ensuring that multiple aluminum alloy substrates do not overlap.

[0019] Add anhydrous ethanol to the beaker until the surface of the anhydrous ethanol completely submerges the top of the aluminum alloy substrate;

[0020] Place the beaker into an ultrasonic cleaner and ultrasonically treat for 5-10 minutes to complete the surface treatment of the aluminum alloy substrate.

[0021] Preferably, in step S3, the aluminum alloy substrate is initially not in direct contact with the mother liquor, specifically as follows:

[0022] By separating the aluminum alloy substrate from the mother liquor through a support immersed in the mother liquor, uneven nucleation on both sides of the aluminum alloy substrate due to uneven thermal conduction or flow field during the heating process is avoided.

[0023] The support is made of polytetrafluoroethylene (PTFE), and the length of the PTFE support is slightly longer than the length of the aluminum alloy substrate to ensure that the aluminum alloy substrate is stably mounted on the support and does not come into contact with the inner wall of the reactor or the mother liquor.

[0024] Preferably, in step S3, the target temperature is 175°C, the constant temperature reaction time is 0-4h, and the reaction time for uniform contact between the aluminum alloy substrate surface and the mother liquor is 10-14h.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] This invention optimizes the mother liquor preparation and aluminum alloy surface treatment processes, and employs a reactor heated to a specified temperature to form a uniform temperature and fluid field before inverting it. This allows the aluminum alloy to come into uniform contact with the reaction liquid containing primary crystal nuclei, effectively eliminating the "opposite" effect caused by uneven temperature, concentration, and convection fields within the reactor during in-situ hydrothermal synthesis. This results in differences in the microstructure, density, and corrosion resistance of the MFI zeolite film on both sides of the aluminum alloy substrate. The invention obtains an MFI zeolite film with equal density and consistent morphology on both sides, laying the foundation for its transition from laboratory research to large-scale industrial application. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the preparation process of MFI zeolite film to eliminate the performance difference between the two sides of the aluminum alloy substrate according to the present invention.

[0028] Figure 2 This is a schematic diagram of the surface morphology of the MFI zeolite films on both sides of the aluminum alloy prepared in Embodiment 1 of the present invention.

[0029] Figure 3 This is a schematic diagram of the surface morphology of the MFI zeolite films on both sides of the aluminum alloy prepared in Embodiment 2 of the present invention;

[0030] Figure 4 This is a schematic diagram of the surface morphology of the MFI zeolite films on both sides of the aluminum alloy prepared in Embodiment 3 of the present invention. Detailed Implementation

[0031] 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.

[0032] Existing technologies struggle to precisely control product quality when preparing flat aluminum alloy substrates. A prominent issue is the "non-uniform" effect: due to uneven temperature, concentration, and convection fields within the reactor during hydrothermal synthesis, significant differences in the microstructure and density of the zeolite films formed on the upper and lower surfaces of the aluminum alloy sheet occur. This often manifests as a continuous and dense film on one side, while the other side is porous, non-dense, or even lacks a film, resulting in uneven corrosion resistance on both sides of the substrate. Morphologically, this imbalance manifests as differences in grain morphology (size, packing state) on both sides. This inconsistency in grain morphology is related to the spatial inhomogeneity of MFI zeolite nucleation and growth processes on both sides of the aluminum alloy substrate during in-situ hydrothermal processes. In typical hydrothermal processes, differences in temperature and concentration fields exist between the liquids on both sides of the aluminum alloy as the oven temperature changes (from room temperature to target temperature). This difference leads to different nucleation times and densities of MFI zeolite on both sides of the aluminum alloy, which in turn affects the subsequent growth of grains within the MFI zeolite film on both sides, ultimately resulting in an uneven morphology of the zeolite film on both sides of the aluminum alloy and affecting its corrosion resistance.

[0033] This severe quality inconsistency significantly reduces product reliability, becoming a key technological bottleneck restricting the transition of aluminum-based MFI zeolite membranes from laboratory research to large-scale industrial applications. Therefore, developing a new method to eliminate two-sided differences and achieve controllable preparation of uniformly dense MFI zeolite membranes on both sides is of urgent and significant importance for promoting the practical application of this high-performance anti-corrosion coating technology.

[0034] Please see Figure 1-4 This invention provides a technical solution: a preparation process for eliminating the performance differences between the two sides of an MFI zeolite film on an aluminum alloy substrate, comprising the following steps:

[0035] S1. Preparation of mother liquor: Take sodium hydroxide, deionized water, tetraethyl orthosilicate and tetrapropylammonium hydroxide, wherein the molar ratio of sodium hydroxide, tetrapropylammonium hydroxide, tetraethyl orthosilicate and deionized water is 0.64:0.16:1:92-100;

[0036] First, mix sodium hydroxide with deionized water and stir on a magnetic stirrer at a stirring intensity of 200-300 r / min;

[0037] After the sodium hydroxide has completely dissolved, add tetrapropylammonium hydroxide and continue stirring for 5 minutes.

[0038] Then, tetraethyl orthosilicate is added drop by drop to prevent it from directly coagulating.

[0039] The mixture was stirred and aged for 6–24 h to obtain the mother liquor for preparing MFI zeolite membranes.

[0040] S2. Surface Treatment: Surface treatment is performed on the aluminum alloy substrate to remove stains and foreign matter. Specifically:

[0041] Place the aluminum alloy substrate vertically in a clean beaker, ensuring that multiple aluminum alloy substrates do not overlap.

[0042] Add anhydrous ethanol to the beaker until the surface of the anhydrous ethanol completely submerges the top of the aluminum alloy substrate;

[0043] Place the beaker into the ultrasonic cleaner, set the ultrasonic power to 800W and the frequency to 40kHz, and ultrasonically treat for 5 to 10 minutes to complete the surface treatment of the aluminum alloy substrate.

[0044] S3. Preparation of MFI zeolite membrane with consistent performance on both sides: The aluminum alloy substrate from step S2 is placed in a reactor containing the mother liquor from step S1. The reactor is sealed. The aluminum alloy substrate is separated from the mother liquor by a support immersed in the mother liquor, so that the aluminum alloy substrate does not directly contact the mother liquor at first. This avoids uneven nucleation on both sides of the aluminum alloy substrate due to uneven thermal conduction or flow field during the heating process. The support is made of polytetrafluoroethylene (PTFE), and the length of the PTFE support is slightly longer than the length of the aluminum alloy substrate to ensure that the aluminum alloy substrate is stably mounted on the support and does not contact the inner wall of the reactor or the mother liquor.

[0045] The sealed reactor was placed in an oven and kept at 175°C for 0-4 hours to form a uniform and stable temperature and fluid field in the reaction solution.

[0046] The reactor was then inverted to allow the aluminum alloy substrate surface to come into uniform contact with the mother liquor and continue to react for 12-14 hours. This process ensures uniform contact between the aluminum alloy substrate surface and the reaction liquid containing primary crystal nuclei (silicate nanoparticles), which is beneficial for the homogenization of nucleation on both sides of the aluminum alloy plate. Ultimately, an MFI zeolite film with consistent performance on both sides is formed on the aluminum alloy substrate surface.

[0047] Example 1

[0048] A preparation process for eliminating the property differences between the two sides of an MFI zeolite film on an aluminum alloy substrate includes the following steps:

[0049] S1. Preparation of mother liquor: Take 0.51g of sodium hydroxide solid (NaOH), 30mL of deionized water, 4.47mL of tetraethyl orthosilicate (TEOS) and 2.60mL of tetrapropylammonium hydroxide (TPAOH).

[0050] Accurately weigh 0.51g of sodium hydroxide solid (NaOH) into a clean beaker, and add 30mL of deionized water to the beaker. Next, measure 2.60mL of tetrapropylammonium hydroxide (TPAOH) and 4.47mL of tetraethyl orthosilicate (TEOS) in sequence. The specific operation procedure is as follows: First, thoroughly mix the sodium hydroxide and deionized water, add a stir bar, place the beaker on a magnetic stirrer, and set the stirring intensity to 200-300r / min;

[0051] After the sodium hydroxide has completely dissolved, use a pipette to accurately measure tetrapropylammonium hydroxide and add it to the mixture, then continue stirring for 5 minutes.

[0052] Measure out tetraethyl orthosilicate and add it dropwise to avoid direct coagulation. Continue stirring for 6 hours to obtain the mother liquor for preparing MFI zeolite membrane.

[0053] S2. Surface Treatment: Surface treatment is performed on the aluminum alloy substrate to remove stains and foreign matter. Specifically:

[0054] Select an aluminum alloy of the appropriate size to the reactor liner, carefully peel off the protective film on its surface, and place the aluminum alloy substrate vertically in a clean beaker, ensuring that multiple aluminum alloy substrates do not overlap.

[0055] Add anhydrous ethanol to the beaker until the surface of the anhydrous ethanol completely submerges the top of the aluminum alloy substrate;

[0056] Place the beaker into the ultrasonic cleaner, set the ultrasonic power to 800W and the frequency to 40kHz, and ultrasonically treat for 5 minutes to complete the surface treatment of the aluminum alloy substrate, thereby obtaining a clean aluminum alloy substrate.

[0057] S3. Preparation of MFI zeolite membrane with consistent performance on both sides: The aluminum alloy substrate from step S2 is placed in a reactor containing the mother liquor from step S1. The reactor is sealed. The aluminum alloy substrate is separated from the mother liquor by a support immersed in the mother liquor, so that the aluminum alloy substrate does not directly contact the mother liquor at first. This avoids uneven nucleation on both sides of the aluminum alloy substrate due to uneven thermal conduction or flow field during the heating process. The support is made of polytetrafluoroethylene (PTFE), and the length of the PTFE support is slightly longer than the length of the aluminum alloy substrate to ensure that the aluminum alloy substrate is stably mounted on the support and does not contact the inner wall of the reactor or the mother liquor.

[0058] The sealed reactor was placed in an oven and kept at 175°C for 24 hours to form a uniform and stable temperature and fluid field in the reaction solution.

[0059] The reactor was then inverted to allow the aluminum alloy substrate surface to come into uniform contact with the mother liquor and continue to react for 14 hours. This process ensures uniform contact between the aluminum alloy substrate surface and the reaction liquid containing primary crystal nuclei (silicate nanoparticles), which is beneficial for the homogenization of nucleation on both sides of the aluminum alloy plate. Ultimately, an MFI zeolite film with consistent performance on both sides is formed on the aluminum alloy substrate surface.

[0060] Example 2

[0061] The difference from Example 1 is:

[0062] S3. Preparation of MFI zeolite membrane with consistent performance on both sides: The aluminum alloy substrate from step S2 is placed in a reactor containing the mother liquor from step S1. The reactor is sealed. The aluminum alloy substrate is separated from the mother liquor by a support immersed in the mother liquor, so that the aluminum alloy substrate does not directly contact the mother liquor at first. This avoids uneven nucleation on both sides of the aluminum alloy substrate due to uneven thermal conduction or flow field during the heating process. The support is made of polytetrafluoroethylene (PTFE), and the length of the PTFE support is slightly longer than the length of the aluminum alloy substrate to ensure that the aluminum alloy substrate is stably mounted on the support and does not contact the inner wall of the reactor or the mother liquor.

[0063] The sealed reactor was placed in an oven and inverted after reaching 175°C to allow the aluminum alloy substrate surface to come into uniform contact with the mother liquor and continue to react for 16 hours. This process ensures uniform contact between the aluminum alloy substrate surface and the reaction liquid containing primary crystal nuclei (silicate nanoparticles), which is beneficial for the homogenization of nucleation on both sides of the aluminum alloy plate. Ultimately, an MFI zeolite film with consistent performance on both sides is formed on the aluminum alloy substrate surface.

[0064] Example 3

[0065] The difference from Example 1 is:

[0066] S3, MFI zeolite membrane preparation: Place aluminum alloy in a reaction vessel, add mother liquor so that the liquid level is slightly higher than the top of the aluminum alloy, place it in an oven, set it to 175℃ and bake for 16 hours. After the reaction is completed, the aluminum alloy with film is obtained.

[0067] A schematic diagram of the surface morphology of the MFI zeolite films on both sides of the aluminum alloy prepared in Example 3 is shown below. Figure 4 As shown, due to the imbalance of temperature-density fields on both sides of the aluminum alloy during the heating process, the nucleation time and density differ greatly, ultimately resulting in a fragmented morphology of the two film layers: one side has loosely packed grains with uneven sizes, and even some areas without film; the other side, although dense, has poor overall consistency. This can be seen from the schematic diagrams of the surface morphology of the MFI zeolite films on both sides of the aluminum alloy obtained in Examples 1 and 2. Figure 2 and attached Figure 3 It is evident that the zeolite films on both sides of the aluminum alloy have uniform grain size and are densely and orderly packed, with no loose or unfilmed areas, completely eliminating the "opposite" differences of traditional methods and achieving a high degree of uniformity in the double-sided film structure.

[0068] The double-sided dense and uniform film layer prepared by this invention can uniformly block corrosive media such as water and oxygen from penetrating into the aluminum alloy substrate, avoiding the risk of "one-sided corrosion". Moreover, the chemical stability (inherent characteristics of MFI zeolite) of the double-sided film layer is consistent with its physical density, which can ensure the synchronous anti-corrosion effect on the entire surface of the aluminum alloy component, greatly improving the service life and performance stability of the product in actual working conditions, and solving the pain point of "low reliability" of traditional products.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A preparation process for eliminating the difference in properties between the two sides of an MFI zeolite film on an aluminum alloy substrate, characterized in that: Includes the following steps: S1. Preparation of mother liquor: Sodium hydroxide, deionized water, tetraethyl orthosilicate and tetrapropylammonium hydroxide are used to prepare the mother liquor for MFI zeolite membrane synthesis. S2. Surface treatment: Perform surface treatment on the aluminum alloy substrate to remove stains and foreign matter from its surface. S3. Preparation of MFI zeolite membrane with consistent performance on both sides: The aluminum alloy substrate of step S2 is placed in a reaction vessel containing the mother liquor of step S1, and the aluminum alloy substrate is not in direct contact with the mother liquor at first. Place the reactor in an oven, reach the target temperature, and maintain the temperature for reaction. The reactor is inverted to allow the aluminum alloy substrate surface to come into uniform contact with the mother liquor and continue to react, ultimately forming an MFI zeolite film with consistent properties on both sides of the aluminum alloy substrate surface.

2. The preparation process for eliminating the difference in properties between the two sides of an MFI zeolite film on an aluminum alloy substrate according to claim 1, characterized in that: In step S1, the molar ratio of sodium hydroxide, tetrapropylammonium hydroxide, tetraethyl orthosilicate, and deionized water is 0.64:0.16:1:92-100. The preparation process of the mother liquor is as follows: First, mix sodium hydroxide with deionized water and stir on a magnetic stirrer at a stirring intensity of 200-300 r / min; After the sodium hydroxide has completely dissolved, add tetrapropylammonium hydroxide and continue stirring for 5 minutes. Then, tetraethyl orthosilicate is added drop by drop to prevent it from directly coagulating. The mixture was stirred continuously and aged for 6–24 hours to obtain the mother liquor.

3. The preparation process for eliminating the difference in properties between the two sides of an MFI zeolite film on an aluminum alloy substrate according to claim 1, characterized in that: The surface treatment process of the aluminum alloy substrate in step S2 is as follows: Place the aluminum alloy substrate vertically in a clean beaker, ensuring that multiple aluminum alloy substrates do not overlap. Add anhydrous ethanol to the beaker until the surface of the anhydrous ethanol completely submerges the top of the aluminum alloy substrate; Place the beaker into an ultrasonic cleaner and ultrasonically treat for 5-10 minutes to complete the surface treatment of the aluminum alloy substrate.

4. The preparation process for eliminating the difference in properties between the two sides of an MFI zeolite film on an aluminum alloy substrate according to claim 1, characterized in that: In step S3, the aluminum alloy substrate is initially not in direct contact with the mother liquor, specifically as follows: By separating the aluminum alloy substrate from the mother liquor through a support immersed in the mother liquor, uneven nucleation on both sides of the aluminum alloy substrate due to uneven thermal conduction or flow field during the heating process is avoided. The support is made of polytetrafluoroethylene (PTFE), and the length of the PTFE support is slightly longer than the length of the aluminum alloy substrate to ensure that the aluminum alloy substrate is stably mounted on the support and does not come into contact with the inner wall of the reactor or the mother liquor.

5. The preparation process for eliminating the difference in properties between the two sides of an MFI zeolite film on an aluminum alloy substrate according to claim 1, characterized in that: In step S3, the target temperature is 175℃, the constant temperature reaction time is 0-4h, and the reaction time for uniform contact between the aluminum alloy substrate surface and the mother liquor is 10-14h.

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