Composite coating for hydrogen pipeline and preparation method thereof

Abstract

The present application discloses a composite coating for hydrogen pipelines and a preparation method thereof. The composite coating for hydrogen pipelines includes a hydrogen barrier base layer; the components of the hydrogen barrier base layer include a nano-micron multi-scale flaky filler with a crystalline phase and a semi-crystalline polymer; the multi-scale flaky filler is the hydrothermal reaction product of an inorganic flaky filler and hydrotalcite; and the composite coating effectively solves the problem that current organic or inorganic hydrogen barrier coatings cannot provide long-term protection or have poor hydrogen permeation resistance.

Description

Technical Field

[0001] The present disclosure relates to the technical field of coatings, and in particular to a coating for hydrogen pipelines. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] As an alternative energy source for realizing the energy production revolution and green energy transformation, hydrogen pipeline transportation is an important part of the development of hydrogen energy. The current problems of hydrogen embrittlement and corrosion in hydrogen transportation pipelines cannot be underestimated, which will directly lead to severe challenges to the safety of hydrogen pipeline transportation and service life. On the one hand, hydrogen embrittlement refers to the entry of hydrogen atoms into the metal lattice, which may adversely affect its mechanical properties, fracture resistance and fatigue growth rate. Existing defects will also accelerate the expansion and growth in a hydrogen-containing environment. On the other hand, the corrosion problem of metal pipelines will also greatly increase the risk of fluid leakage during transportation. Therefore, it is crucial for hydrogen transportation pipelines to develop a protective coating that has both long-term anti-corrosion properties and slows down or prevents hydrogen penetration.

[0004] Currently, most hydrogen barrier coatings are primarily used in high-temperature environments such as nuclear engineering and reactors to prevent corrosion and penetration by hydrogen isotopes. These coatings are typically composed of inorganic ceramic coatings, such as metal oxide coatings (Cr2O3, Er2O3, ZrO2, Y2O3), silicide coatings (SiC, SiN), titanium coatings (TiN, TiO2 / Ti), and aluminide coatings (FeAl3, Fe-Cr-Al). However, inorganic ceramic coatings exhibit poor corrosion resistance, are brittle, and are prone to cracking, which in turn leads to corrosion, making them unsuitable for long-term protection of hydrogen pipelines. Furthermore, the preparation methods for these ceramic coatings, including sol-gel, vapor deposition, and embedding, are cumbersome, complex, and costly, making them impractical for large-scale application in hydrogen pipeline protection.

[0005] In addition to inorganic ceramic coatings, there is little research on hydrogen-barrier composite coatings based on organic polymers. Most organic composite coatings are designed to improve the corrosion resistance of pipelines. Usually, organic substances such as epoxy resin, polyurea resin, phenolic epoxy resin, etc. are selected, which have excellent corrosion resistance. However, since they are polymers without a crystalline phase, they have no resistance to hydrogen penetration.

[0006] Furthermore, the impact of pressure during hydrogen pipeline transportation on hydrogen barrier composite coatings is an often overlooked and challenging issue. Given the small radius of hydrogen molecules, high-pressure hydrogen environments cause them to aggregate within polymer chains, plasticizing the polymer and leading to a loss of barrier properties and mechanical properties, which in turn increases the risk of hydrogen leakage.

[0007] Therefore, it is necessary to develop a coating suitable for hydrogen transportation pipelines that is both resistant to hydrogen penetration and corrosion and suitable for high-pressure hydrogen environments. This is crucial to ensuring the safety and service life of hydrogen transportation pipelines and meeting industrial needs.

[0008] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the Invention

[0009] In view of this, the present disclosure provides a composite coating for hydrogen pipelines to solve the problem that current organic or inorganic hydrogen barrier coatings cannot provide long-term protection or have poor hydrogen permeation resistance.

[0010] In addition, the present disclosure also provides a method for preparing the composite coating for the hydrogen pipeline.

[0011] In a first aspect, the composite coating for hydrogen pipelines comprises:

[0012] Hydrogen barrier bottom layer;

[0013] The components of the hydrogen barrier bottom layer include nano-micron multi-scale flake fillers with a crystalline phase and a semi-crystalline polymer;

[0014] The multi-scale plate-like filler is a hydrothermal reaction product of an inorganic plate-like filler and hydrotalcite.

[0015] In the present disclosure and possible embodiments, the inorganic flaky filler is selected from one of glass flakes, mica flakes, montmorillonite, basalt, molybdenum disulfide, graphene or boron nitride; and / or,

[0016] The semi-crystalline polymer is selected from one or more of polyketone, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polyvinylidene chloride, polyvinylidene fluoride, and high-density polyethylene.

[0017] In the present disclosure and possible embodiments, the surface of the hydrogen barrier bottom layer is provided with an anti-corrosion top layer;

[0018] The components of the anti-corrosion top layer include anti-corrosion filler and fluorine-containing organic resin.

[0019] In the present disclosure and possible embodiments, the fluorine-containing organic resin is selected from one or more of fluorosilicone resin, fluorocarbon resin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinyl fluoride; and / or,

[0020] The anti-corrosion filler is selected from one or more of graphene, graphene oxide, zirconium phosphate, boron nitride, and MXene; and / or,

[0021] The anti-corrosion filler accounts for 0.5%-20% of the mass of the fluorine-containing organic resin.

[0022] In the present disclosure and possible embodiments, the method for preparing the multi-scale flake filler includes:

[0023] Using divalent metal nitrate and trivalent metal nitrate as precursor metal sources of hydrotalcite;

[0024] Inorganic flaky fillers are added to the mixed system of the precursor metal source and urea in a set ratio and dispersed uniformly, and the obtained dispersion is subjected to a hydrothermal reaction to obtain the multi-scale flaky fillers.

[0025] In the present disclosure and possible embodiments, the divalent metal nitrate is Zn(NO3)2·6H2O and / or Mg(NO3)2·6H2O, the trivalent metal nitrate is Al(NO3)3·9H2O and / or Ce(NO3)3·6H2O; and / or,

[0026] The set ratio is that the molar ratio of the divalent metal nitrate, the trivalent metal nitrate and the urea is 2:1:10; the concentration of the dispersion is 0.01 g / mL-0.03 g / mL; and / or,

[0027] The hydrothermal reaction temperature is set to 160°C-200°C, and the reaction time is 6h-10h; and / or,

[0028] After the hydrothermal reaction is completed and cooled to room temperature, the reaction product is filtered, washed to neutrality, and dried to obtain the multi-scale flaky filler.

[0029] In the present disclosure and possible embodiments, the multi-scale plate-shaped filler is 5% to 50% by mass of the semi-crystalline polymer.

[0030] In a second aspect, the method for preparing the composite coating for a hydrogen pipeline comprises:

[0031] The multi-scale flake filler and the semi-crystalline polymer are evenly dispersed, the evenly mixed powder is sprayed on the surface of the metal substrate, heated and oriented at a given pressure and temperature for a given time, and naturally cooled to room temperature to obtain the hydrogen barrier bottom layer described in the first aspect.

[0032] In the present disclosure and possible embodiments, a fluorine-containing organic resin and an anti-corrosion filler are uniformly mixed to obtain a dispersion, and the dispersion is coated on the surface of the hydrogen barrier bottom layer to form an anti-corrosion top layer.

[0033] In the present disclosure and possible embodiments, the thickness of the hydrogen barrier bottom layer is configured to be 100 μm-120 μm; the thickness of the anti-corrosion top layer is configured to be 90 μm-110 μm; and / or,

[0034] The given pressure, temperature and time are respectively 0-10 MPa, 150° C.-220° C. and 15 min-30 min; and / or,

[0035] The fluorine-containing organic resin and the anti-corrosion filler are uniformly mixed under gradient high-speed stirring and vacuum conditions to obtain the dispersion; and / or,

[0036] The anti-corrosion top layer is cured by baking at 120°C-300°C.

[0037] The present disclosure has the following beneficial effects:

[0038] The composite coating for hydrogen pipelines disclosed in the present invention has a micron-nano multi-scale flaky filler added to the hydrogen barrier bottom layer with a rich crystalline phase, which fills the amorphous region in the semi-crystalline polymer, can further reduce the free volume in the polymer, and improve its ability to resist hydrogen penetration; in addition, tests such as isothermal adsorption and adsorption kinetics show that the prepared multi-scale two-dimensional filler also has a certain adsorption capacity for hydrogen, so that a small amount of hydrogen is fixed on the surface, and the ability to resist hydrogen penetration is further enhanced; at the same time, it also has resistance to high-pressure hydrogen permeation, and can still maintain its ability to resist hydrogen penetration unchanged after a long time in a high-pressure hydrogen environment; the added multi-scale two-dimensional flaky filler and the semi-crystalline polymer have hydrogen bond interactions, The surface compatibility is enhanced, ensuring the dispersion of multi-scale two-dimensional fillers in the polymer; at the same time, the anti-corrosion coating used in the top layer not only ensures its anti-penetration ability to corrosive media at room temperature and pressure, but also has stable and excellent anti-corrosion ability after high-pressure hydrogen shock, and the anti-corrosion filler in the top layer can also play a physical barrier role for hydrogen molecules, further enhancing the hydrogen barrier effect, so that the hydrogen barrier performance is maximized while ensuring the anti-corrosion performance; the composite coating disclosed in the present invention can be used for the surface of hydrogen transport steel pipes, effectively reducing the rate of hydrogen penetration, effectively reducing the risk of hydrogen-induced loss of metal substrates, improving anti-corrosion performance, extending the service life of hydrogen transport pipelines, and improving the reliability and safety of pipeline hydrogen transportation processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0040] Figure 1 is a SEM photograph of the multi-scale flake filler of Example 1 of the present disclosure;

[0041] Figure 2 is the XRD diffraction peak of the multi-scale flake filler of Example 1 of the present disclosure;

[0042] Figure 3is a cross-sectional SEM photograph of the hydrogen barrier bottom layer of Example 1 of the present disclosure;

[0043] Figure 4 is a cross-sectional SEM photograph of the anti-corrosion top layer of Example 1 of the present disclosure;

[0044] Figure 5-1 is the XRD diffraction peak of the ethylene-vinyl alcohol copolymer in Example 2 of the present disclosure;

[0045] Figure 5-2 is the XRD diffraction peak of the hydrogen barrier bottom layer in Example 2 of the present disclosure;

[0046] Figure 6-1 is an impedance graph of the composite coating of Example 2 of the present disclosure after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days;

[0047] Figure 6-2 is the Nyquist plot of the composite coating of Example 2 of the present disclosure after being immersed in a 3.5 wt % NaCl solution for 90 days at room temperature;

[0048] Figure 7 is the hydrogen permeation curve of the composite coating of Example 2 of the present disclosure;

[0049] Figure 8-1 This is an impedance graph of the composite coating of Example 4 of the present disclosure after being placed in a 4 MPa high-pressure hydrogen environment for 7 days and then immersed in a 3.5 wt % NaCl solution at room temperature for 60 days;

[0050] Figure 8-2 This is the Nyquist plot of the composite coating of Example 4 of the present disclosure after being placed in a 4 MPa high-pressure hydrogen environment for 7 days and then immersed in a 3.5 wt % NaCl solution at room temperature for 60 days;

[0051] Figure 9 This is the hydrogen permeation curve of the composite coating of Example 4 of the present disclosure after being placed in a 4 MPa high-pressure hydrogen environment for 7 days;

[0052] Figure 10 This is an adsorption kinetics test curve of Example 4 of the present disclosure, in which the prepared multi-scale flake filler is placed in a 4 MPa high-pressure hydrogen environment;

[0053] Figure 11-1 This is an impedance graph of the hydrogen barrier bottom layer of Comparative Example 1 of the present disclosure after being immersed in a 3.5 wt % NaCl solution for 90 days;

[0054] Figure 11-2 This is the Nyquist plot of the hydrogen barrier bottom layer of Comparative Example 1 of the present disclosure after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days;

[0055] Figure 12is the hydrogen permeation curve of the hydrogen barrier bottom layer of Comparative Example 1 of the present disclosure;

[0056] Figure 13-1 is an impedance graph of the coating of Comparative Example 2 of the present disclosure after being immersed in a 3.5 wt % NaCl solution for 90 days;

[0057] Figure 13-2 is the Nyquist plot of the coating of Comparative Example 2 of the present disclosure after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days;

[0058] Figure 14 is the hydrogen permeation curve of the coating of Comparative Example 3 of the present disclosure;

[0059] Figure 15-1 This is an impedance graph of the composite coating of Comparative Example 4 of the present disclosure after being placed in an 8 MPa high-pressure hydrogen environment for 15 days and then immersed in a 3.5 wt % NaCl solution at room temperature for 60 days;

[0060] Figure 15-2 This is the Nyquist plot of the composite coating of Comparative Example 4 of the present disclosure after being placed in an 8 MPa high-pressure hydrogen environment for 15 days and then immersed in a 3.5 wt % NaCl solution at room temperature for 60 days;

[0061] Figure 16 This is the hydrogen permeation curve of the composite coating of Comparative Example 4 of the present disclosure after being placed in an 8 MPa high-pressure hydrogen environment for 15 days. DETAILED DESCRIPTION

[0062] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts not described in detail, those skilled in the art can also fully understand the present disclosure.

[0063] In addition, persons of ordinary skill in the art will appreciate that the drawings are provided only to illustrate the objects, features, and advantages of the present disclosure and are not drawn to scale. Furthermore, unless the context clearly requires otherwise, the words "include," "comprising," and similar expressions throughout the specification and claims should be interpreted as including, rather than exclusive or exhaustive; that is, as meaning "including but not limited to."

[0064] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.

[0065] The composite coating for hydrogen transport pipelines prepared in the following embodiments of the present disclosure is a double-layer organic / inorganic hybrid hydrogen barrier and anti-corrosion coating, specifically composed of a hydrogen barrier bottom layer and an anti-corrosion top layer.

[0066] The hydrogen barrier bottom layer described in the embodiment of the present disclosure is based on multi-scale flake fillers and semi-crystalline polymers.

[0067] In the disclosed embodiment, the multi-scale flaky filler is a hydrothermal reaction product of one of glass flakes, mica flakes, montmorillonite, basalt, molybdenum disulfide, graphene, or boron nitride and hydrotalcite. Preferably, the multi-scale flaky filler is prepared by a hydrothermal reaction method.

[0068] In the embodiment of the present disclosure, the semi-crystalline polymer is selected from one or more of polyketone, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polyvinylidene chloride, polyvinylidene fluoride, and high-density polyethylene.

[0069] The anti-corrosion layer described in the embodiment of the present disclosure is composed of anti-corrosion filler and fluorine-containing organic resin.

[0070] In the embodiments of the present disclosure, the anti-corrosion filler is selected from one or more of graphene, graphene oxide, zirconium phosphate, boron nitride, and MXene.

[0071] In the embodiment of the present disclosure, the fluorine-containing organic resin is selected from one or more of fluorosilicone resin, fluorocarbon resin, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinyl fluoride.

[0072] The preparation method of the composite coating for hydrogen transport pipelines used in the following embodiments of the present disclosure is summarized as follows:

[0073] (1) Preparation of multi-scale flake fillers

[0074] According to the molar ratio of divalent metal nitrate, trivalent metal nitrate and urea of ​​2:1:10, divalent metal nitrate Zn(NO3)2·6H2O and / or Mg(NO3)2·6H2O, trivalent metal nitrate Al(NO3)3·9H2O and / or Ce(NO3)3·6H2O and urea are dissolved in deionized water, stirred evenly, and one of glass flakes, mica flakes, montmorillonite, basalt, molybdenum disulfide, graphene or boron nitride is added, and stirring is continued to obtain a uniform dispersion, and the concentration of the dispersion is controlled to be 0.01g / mL-0.03g / mL;

[0075] The uniform dispersion is transferred to a hydrothermal reactor with a filling level of 70%-80%. The uniform dispersion is hydrothermally reacted at 160-200°C for 6-10 hours. The reaction product is cooled to room temperature, removed, filtered, repeatedly washed with deionized water until neutral, and dried to obtain the multi-scale flaky filler. The product is preferably dried in a forced air drying oven for 3-8 hours.

[0076] (2) Preparation of hydrogen barrier bottom layer

[0077] The metal substrate used in the embodiments of the present disclosure may be Q235 carbon steel, stainless steel, copper foil, aluminum foil, etc. The metal substrate is pretreated before use. Specifically, the metal substrate is coarsely ground or sandblasted with 400#, 800#, or 1000# sandpaper until the roughness is approximately 2.5μm. The metal substrate is then washed sequentially with solvents such as acetone, ethanol, and ethyl acetate, and dried in an 80°C oven.

[0078] The multi-scale flake filler and the semi-crystalline polymer prepared in step (1) are mixed uniformly in a disperser, wherein the amount of the multi-scale flake filler is 5%-50% by weight of the semi-crystalline polymer. The uniformly mixed powder is sprayed onto the surface of a pretreated metal substrate and heated for orientation under a given pressure and temperature, wherein the pressure is 0-10 MPa, the temperature is 150-220°C, and the time is 15-30 minutes. The substrate is then cooled naturally to room temperature to obtain a hydrogen barrier base layer having a thickness of approximately 100-120 μm.

[0079] (3) Preparation of anti-corrosion top layer

[0080] A mixture of a fluorine-containing organic resin and an anti-corrosion filler, wherein the anti-corrosion filler accounts for 0.5%-20% of the mass of the fluorine-containing organic resin, is uniformly dispersed under gradient high-speed stirring and vacuum conditions to obtain a dispersion; the obtained dispersion is applied to the surface of a hydrogen barrier bottom layer by a spraying method, baked and solidified at 120-300°C, and after heat preservation, taken out and placed at room temperature for cooling to form a stable surface anti-corrosion top layer with a thickness of about 90-110μm.

[0081] Example 1

[0082] (1) Preparation of multi-scale flake fillers

[0083] Take 1.28g of magnesium nitrate hexahydrate, 0.94g of aluminum nitrate nonahydrate, and 1.5g of urea and dissolve them in 200mL of deionized water. Then stir continuously until they are completely dissolved. Then add 2g of glass flakes and continue to disperse to obtain a uniform dispersion.

[0084] The dispersion was transferred to a hydrothermal reactor, and after a hydrothermal reaction at 160° C. for 10 h, the reaction product was cooled to room temperature and filtered, repeatedly washed with deionized water until neutral, and dried to obtain a multi-scale flake filler.

[0085] Figure 1 : is an SEM photograph of the multi-scale flake filler prepared in Example 1. It can be observed that small-sized flake hydrotalcite grows on larger-sized flake materials. Figure 2 The XRD diffraction peaks of the multi-scale flaky filler prepared in this Example 1 show multiple crystalline diffraction peaks, which proves that the multi-scale flaky filler has a rich crystalline phase.

[0086] (2) Preparation of hydrogen barrier bottom layer

[0087] The multi-scale flaky filler prepared in step (1) and the polyketone resin are placed in a disperser and mixed evenly, wherein the multi-scale flaky filler accounts for 10% of the mass of the polyketone resin; the evenly mixed powder is sprayed on the surface of the pretreated metal substrate, and heated and oriented under the conditions of a pressure of 2 MPa, a heating temperature and a heating time of 220° C. and 15 minutes respectively; and naturally cooled to room temperature to obtain a hydrogen barrier bottom layer with a thickness of approximately 100-120 μm.

[0088] Figure 3 This is a cross-sectional SEM photograph of the hydrogen barrier bottom layer. It can be observed that the cross-section is dense and defect-free, and the composite flake fillers are embedded in the polymer matrix.

[0089] (3) Preparation of anti-corrosion top layer

[0090] After adding 4 g of fluorosilicone resin and graphene oxide into a material cup, a uniform dispersion is obtained under gradient high-speed stirring and vacuum conditions, in which the graphene oxide accounts for 0.5% of the mass of the fluorosilicone resin.

[0091] The dispersion is applied to the surface of the hydrogen barrier bottom layer by spraying, and then cured by baking at 150°C. After keeping warm for 30 minutes, it is taken out and placed at room temperature to cool to form a stable surface anti-corrosion top layer with a thickness of about 90-110μm.

[0092] Figure 4 This is a cross-sectional SEM photo of the anti-corrosion top layer. It can be observed that the graphene oxide sheets are embedded in the polymer matrix and are basically arranged in parallel.

[0093] Example 2

[0094] (1) Preparation of multi-scale flake fillers

[0095] 0.595 g of zinc nitrate hexahydrate, 0.32 g of aluminum nitrate nonahydrate, 0.1 g of cerium nitrate hexahydrate, and 0.5 g of urea were dissolved in 200 mL of deionized water and stirred continuously until completely dissolved. 2 g of sericite was added and dispersed continuously to obtain a uniform dispersion.

[0096] The dispersion was transferred to a hydrothermal reactor, and after a hydrothermal reaction at 150° C. for 8 h, the reaction product was cooled to room temperature and filtered, repeatedly washed with deionized water until neutral, and dried to obtain a multi-scale flake filler.

[0097] (2) Preparation of hydrogen barrier bottom layer

[0098] The multi-scale flaky filler prepared in step (1) and the ethylene-vinyl alcohol copolymer are placed in a disperser and mixed evenly, wherein the multi-scale flaky filler accounts for 30% of the mass of the ethylene-vinyl alcohol copolymer.

[0099] The uniformly mixed powder is sprayed onto the surface of the pretreated metal substrate, and heated for orientation at a pressure of 4 MPa, a heating temperature of 190°C, and a heating time of 20 minutes respectively; it is naturally cooled to room temperature to obtain a hydrogen barrier bottom layer with a thickness of about 100-120 μm.

[0100] Figure 5-1 is the XRD diffraction peak of the ethylene-vinyl alcohol copolymer in Example 2 of the present disclosure, Figure 5-2 It is the XRD diffraction peak of the hydrogen barrier layer in Example 2 of the present disclosure. Due to the doping of multi-scale flake fillers, obvious crystalline diffraction peaks belonging to hydrotalcite and sericite can be observed, which proves that the composite coating has a higher degree of crystallization. The introduction of flake fillers fills the original amorphous area of ​​the polymer and has a better gas barrier effect.

[0101] (3) Preparation of anti-corrosion top layer

[0102] After adding 5g of fluorocarbon resin and graphene into a material cup, a uniform dispersion is obtained under gradient high-speed stirring and vacuum conditions, in which the graphene accounts for 5% of the mass of the fluorocarbon resin.

[0103] The dispersion is applied to the surface of the hydrogen barrier bottom layer by spraying, and then cured by baking at 160°C. After keeping warm for 30 minutes, it is taken out and placed at room temperature to cool to form a stable surface anti-corrosion top layer with a thickness of about 90-110 μm.

[0104] Figure 6-1 This is an impedance graph of the composite coating of Example 2 of the present disclosure after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days. Figure 6-2 This is the Nyquist plot of the composite coating after being immersed in a 3.5wt% NaCl solution at room temperature for 90 days. Figure 7 This is the hydrogen permeation curve of Example 2.

[0105] in, Figure 6-1 The impedance value in the low and medium frequency region remains at 10 11 Ωcm 2 , proving its long-term anti-corrosion ability; Figure 6-2 The semicircle of the medium impedance arc is incomplete and has a large radius, which also proves its long-term corrosion protection ability; Figure 7 The penetration time of the composite coating is as long as 70,000 s, and the pressure in the lower chamber is less than 100 Pa, which proves that the hydrogen penetration rate is very slow. The composite coating prepared in Example 2 has excellent hydrogen barrier capability.

[0106] Example 3

[0107] (1) Preparation of multi-scale flake fillers

[0108] 0.595 g of zinc nitrate hexahydrate, 0.434 g of cerium nitrate hexahydrate, and 1.3 g of urea were dissolved in 200 mL of deionized water and stirred continuously for 30 minutes to completely dissolve them. 2 g of montmorillonite was then added and dispersed to obtain a uniform dispersion.

[0109] The dispersion was transferred to a hydrothermal reactor and subjected to a hydrothermal reaction at 200° C. for 6 h. The reaction product was cooled to room temperature and filtered, repeatedly washed with deionized water until neutral, and dried to obtain a multi-scale flake filler.

[0110] (2) Preparation of hydrogen barrier bottom layer

[0111] The multi-scale flaky filler prepared in step (1) and polyvinylidene chloride are placed in a disperser and mixed evenly, wherein the multi-scale flaky filler accounts for 40% of the mass of the polyvinylidene chloride; the evenly mixed powder is sprayed on the surface of the pretreated metal substrate, and heated and oriented under the conditions of a pressure of 8 MPa, a heating temperature and a heating time of 180° C. and 15 minutes respectively; and naturally cooled to room temperature to obtain a hydrogen barrier bottom layer with a thickness of about 100-120 μm.

[0112] (3) Preparation of anti-corrosion top layer

[0113] After adding 6g of polyvinyl fluoride resin and zirconium phosphate into a material cup, a uniform dispersion is obtained under gradient high-speed stirring and vacuum conditions, wherein the zirconium phosphate accounts for 15% of the mass of the polyvinyl fluoride resin;

[0114] The dispersion is applied to the surface of the hydrogen barrier bottom layer by spraying, and then cured by baking at 250°C. After keeping warm for 30 minutes, it is taken out and placed at room temperature to cool to form a stable surface anti-corrosion top layer with a thickness of about 90-110μm.

[0115] Example 4

[0116] (1) Preparation of multi-scale flake fillers

[0117] 1.49 g of zinc nitrate hexahydrate, 0.94 g of cerium nitrate hexahydrate, and 0.6 g of urea were dissolved in 200 mL of deionized water and stirred continuously for 30 minutes to completely dissolve them. 2 g of basalt was then added and dispersed to obtain a uniform dispersion.

[0118] The dispersion was transferred to a hydrothermal reactor, and after a hydrothermal reaction at 200° C. for 8 h, the reaction product was cooled to room temperature and filtered, repeatedly washed with deionized water until neutral, and dried to obtain a multi-scale flake filler.

[0119] (2) Preparation of hydrogen barrier bottom layer

[0120] The multi-scale flaky filler prepared in step (1) and polyvinyl alcohol are placed in a disperser and mixed evenly, wherein the multi-scale flaky filler accounts for 50% of the mass of the polyvinyl alcohol; the evenly mixed powder is sprayed on the surface of the pretreated metal substrate, and heated and oriented under the conditions of a pressure of 4 MPa, a heating temperature and a heating time of 200°C and 15 minutes respectively; and naturally cooled to room temperature to obtain a hydrogen barrier bottom layer with a thickness of approximately 100-120 μm.

[0121] (3) Preparation of anti-corrosion top layer

[0122] After adding 6g of tetrafluoroethylene-hexafluoropropylene copolymer and MXene into the material cup, a uniform dispersion was obtained under gradient high-speed stirring and vacuum conditions, in which MXene accounted for 1% of the mass of the tetrafluoroethylene-hexafluoropropylene copolymer resin;

[0123] The dispersion is applied to the surface of the hydrogen barrier bottom layer by spraying, and then cured by baking at 280°C. After keeping warm for 30 minutes, it is taken out and placed at room temperature to cool to form a stable surface anti-corrosion top layer with a thickness of about 90-110μm.

[0124] Figure 8-1 This is the impedance graph of the composite coating of Example 4 of the present disclosure after being placed in a 4MPa high-pressure hydrogen environment for 7 days and then immersed in a 3.5wt% NaCl solution at room temperature for 60 days. Figure 8-2 This is the Nyquist plot of the composite coating after being placed in a 4MPa high-pressure hydrogen environment for 7 days and then immersed in a 3.5wt% NaCl solution at room temperature for 60 days. Figure 9 This is the hydrogen permeation curve of the composite coating after being placed in a 4MPa high-pressure hydrogen environment for 7 days. Figure 10 This is the adsorption kinetics test curve of placing the prepared multi-scale flake filler in a 4MPa high-pressure hydrogen environment.

[0125] Among them, from Figure 8-1 It can be observed that after high pressure hydrogen shock, the low frequency impedance value of the coating can still be maintained at 10 11 Ωcm 2 , proving that high-pressure hydrogen environment has no effect on the long-term anti-corrosion ability of the coating. Figure 8-2 It can be seen that the impedance arc radius is large and incomplete, which also proves that its long-term anti-corrosion ability is not affected by the impact of high-pressure hydrogen environment. Figure 9 During the penetration time of 25,000 s, the pressure in the lower chamber was less than 50 Pa, which proved that the hydrogen penetration rate was slow and the high-pressure hydrogen environment had no effect on the hydrogen penetration resistance of Example 4. Figure 10 It can be observed that the adsorption amount gradually increases with time, proving that the prepared multi-scale flake filler has a certain ability to adsorb and fix hydrogen.

[0126] Comparative Example 1

[0127] The polyketone resin powder is sprayed on the surface of the pretreated metal substrate, and then heated and oriented under the conditions of a pressure of 2 MPa, a heating temperature of 220° C. and a heating time of 15 minutes, respectively, to obtain a hydrogen barrier bottom layer with a thickness of about 100-120 μm.

[0128] Figure 11-1 This is the impedance graph of the hydrogen barrier bottom layer of comparative example 1 after being immersed in a 3.5wt% NaCl solution for 90 days. Figure 11-2 This is the Nyquist plot of the hydrogen barrier bottom layer of Comparative Example 1 after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days. Figure 12 This is the hydrogen permeation curve of the hydrogen barrier bottom layer of Comparative Example 1.

[0129] in, Figure 11-1 The impedance value in the low and medium frequency area is already lower than 10 8 Ωcm 2 , and loses its shielding ability against corrosive media; Figure 11-2 The small semicircle radius of the medium impedance arc also proves that the anti-corrosion ability of the coating gradually fails; Figure 12 When the permeation time is about 5000s, the pressure in the lower chamber has increased to nearly 400Pa, and the hydrogen permeation rate is greatly increased compared with Example 2.

[0130] Comparative Example 2

[0131] The method of Example 2 is used to directly coat the anti-corrosion top layer on the metal substrate.

[0132] Figure 13-1 This is the impedance graph of the coating of Comparative Example 2 after being immersed in a 3.5wt% NaCl solution for 90 days. Figure 13-2 This is the Nyquist plot of the coating of Comparative Example 2 after being immersed in a 3.5 wt % NaCl solution at room temperature for 90 days.

[0133] in, Figure 13-1 The impedance value in the low and medium frequency area is lower than 10 11 Ωcm 2 , has a certain anti-corrosion ability, but a platform area gradually appears in the low-frequency area, proving that the barrier ability to corrosive media is weakened; Figure 13-2 The radius of the medium impedance arc is significantly smaller than that of Example 2. Considering that the anti-corrosion filler used is graphene, it is proved that the preparation of the hydrogen barrier bottom layer is beneficial to inhibiting the galvanic corrosion between the graphene and the substrate.

[0134] Comparative Example 3

[0135] 6g of polyvinyl fluoride resin and zirconium phosphate, wherein the zirconium phosphate accounts for 2% of the mass of the polyvinyl fluoride resin, are stirred at a gradient high speed and vacuum conditions to obtain a uniform dispersion; the obtained dispersion is applied to the surface of the hydrogen barrier bottom layer by a spraying method, baked and cured at a temperature of 200°C, kept warm for 30 minutes, then taken out and allowed to cool at room temperature to form a stable anti-corrosion top layer with a surface thickness of approximately 90-110μm.

[0136] Figure 14 This is the hydrogen permeation curve of the coating of comparative example 3 of the present disclosure. In a short period of time of about 200 seconds, the pressure in the lower cavity has quickly risen to about 1200Pa, and then the permeation process ends, proving that the anti-corrosion layer has no ability to resist hydrogen penetration.

[0137] Comparative Example 4

[0138] (1) Preparation of hydrogen barrier bottom layer

[0139] Polyvinyl alcohol powder was sprayed on the surface of the pretreated metal substrate under the conditions of a pressure of 4 MPa, a heating temperature of 200°C and a heating time of 15 minutes, and then naturally cooled to room temperature to obtain a hydrogen barrier bottom layer with a thickness of about 100-120 μm.

[0140] (2) Preparation of anti-corrosion top layer

[0141] After 6g of tetrafluoroethylene-hexafluoropropylene copolymer is obtained under gradient high-speed stirring and vacuum conditions to obtain a uniform dispersion, the bottom layer coating is completely cooled to room temperature, and then the dispersion is applied to the bottom layer surface by spraying, baked and cured at 280°C, kept warm for 30 minutes, taken out, and placed at room temperature to cool to form a stable surface anti-corrosion top layer with a thickness of about 90-110μm.

[0142] Figure 15-1 This is the impedance graph of the composite coating of Comparative Example 4 of the present disclosure after being placed in an 8MPa high-pressure hydrogen environment for 15 days and then immersed in a 3.5wt% NaCl solution at room temperature for 60 days. Figure 15-2 This is the Nyquist plot of the composite coating after being placed in an 8MPa high-pressure hydrogen environment for 15 days and then immersed in a 3.5wt% NaCl solution at room temperature for 60 days. Figure 16 This is the hydrogen permeation curve of the composite coating after being placed in an 8MPa high-pressure hydrogen environment for 15 days.

[0143] from Figure 15-1 and 15-2 It can be seen that a platform area has appeared in the low-frequency region of the impedance diagram, and the impedance arc radius has been significantly reduced, proving that the anti-corrosion performance of the double-layer composite coating has been weakened and damaged without the addition of the prepared multi-scale flaky filler. Figure 16When the penetration time is about 25000s, the pressure in the lower chamber is close to 80Pa. Compared with the addition of multi-scale flaky fillers in the hydrogen barrier layer in Example 2, the anti-hydrogen penetration ability has also been damaged to a certain extent, but it can still maintain a certain hydrogen barrier effect.

[0144] Performance Testing

[0145] The coatings of Examples 1-4 and Comparative Examples 1-4 were tested for performance, and the specific testing methods are as follows:

[0146] 1. Electrochemical testing

[0147] The electrochemical behavior of the coated metal substrates after 90 days of immersion in a 3.5wt% NaCl solution was tested using an electrochemical workstation (at room temperature and pressure). Electrochemical testing was performed using a traditional three-electrode system, with a platinum sheet serving as the counter electrode, a saturated calomel electrode serving as the reference electrode, and the coated metal substrate serving as the working electrode. Low-frequency impedance values ​​were recorded for samples soaked for different times to assess the coating's corrosion resistance.

[0148] 2. Hydrogen permeability test

[0149] First, apply some vacuum grease around the test cavity and cover it with filter paper. Then, place the film sample on the test bench and make sure that the size of the covered area is larger than the size of the cavity area. Finally, evacuate the inner and outer cavities of the container and the entire system until the target vacuum degree is reached. The vacuuming process will last for at least 2 hours to eliminate any gas and water vapor adsorbed by the sample. The test gas is introduced into the outer cavity of the container. During this process, permeation occurs under the action of the pressure gradient. By monitoring the pressure on the low-pressure side, the value of the hydrogen permeation rate is calculated through a plot generated by the software connected to the machine. The unit of the gas permeation rate is cm 3 / (m 2 ·24h·0.1MPa).

[0150] The specific test results of the above comparative examples and embodiments are shown in Table 1:

[0151] Table 1 Hydrogen permeation rate and low frequency impedance value

[0152]

[0153]

[0154] Through the above-mentioned examples, this disclosure explores the effects of a high-pressure hydrogen environment on the hydrogen barrier and corrosion resistance of the composite coating of the present invention. The results show that both the hydrogen barrier bottom layer and the corrosion-resistant top layer can maintain their original excellent performance and are not affected by the high-pressure environment. A mechanism analysis was conducted from the perspectives of the coating's crystallinity, morphology, chemical structure, and composition, revealing the scientific basis for its resistance to high-pressure hydrogen at a microscopic level. Molecular dynamics was used to theoretically simulate the effects of a high-pressure hydrogen environment on the performance of the composite coating, demonstrating that the composite coating has good high-pressure hydrogen tolerance.

[0155] The above-described embodiments are merely examples of implementation methods of the present disclosure, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art may make various modifications, equivalent substitutions, and improvements without departing from the scope of the present disclosure, and these modifications are all within the scope of protection of the present disclosure. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A composite coating for a hydrogen pipeline, characterized in that: include: Hydrogen barrier bottom layer; The components of the hydrogen barrier bottom layer include nano-micron multi-scale flake fillers with a crystalline phase and a semi-crystalline polymer; The multi-scale flake filler is a hydrothermal reaction product of an inorganic flake filler and hydrotalcite; The inorganic flaky filler is selected from one of glass flakes, mica flakes, montmorillonite, basalt, molybdenum disulfide, graphene or boron nitride; The semi-crystalline polymer is selected from one or more of polyketone, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyethylene terephthalate, polyvinylidene chloride, polyvinylidene fluoride, and high-density polyethylene; The surface of the hydrogen barrier bottom layer is provided with an anti-corrosion top layer; The components of the anti-corrosion top layer include anti-corrosion filler and fluorine-containing organic resin; The method for preparing the multi-scale flaky filler comprises: Using divalent metal nitrate and trivalent metal nitrate as precursor metal sources of hydrotalcite; Adding an inorganic flaky filler to the mixed system of the precursor metal source and urea in a set ratio and dispersing the filler uniformly, and subjecting the obtained dispersion to a hydrothermal reaction to obtain the multi-scale flaky filler; The set ratio is that the molar ratio of the divalent metal nitrate, the trivalent metal nitrate and the urea is 2:1:10; the concentration of the dispersion is 0.01 g / mL-0.03 g / mL; The temperature of the hydrothermal reaction is set to 160°C-200°C, and the reaction time is 6 h-10 h; After the hydrothermal reaction is completed and cooled to room temperature, the reaction product is filtered, washed to neutrality, and dried to obtain the multi-scale flaky filler; The multi-scale plate-like filler is 5% to 50% by mass of the semi-crystalline polymer.

2. The composite coating for hydrogen pipeline according to claim 1, characterized in that: The fluorine-containing organic resin is selected from one or more of fluorosilicone resin, fluorocarbon resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinyl fluoride.

3. The composite coating for hydrogen pipeline according to claim 1, characterized in that: The anti-corrosion filler is selected from one or more of graphene, graphene oxide, zirconium phosphate, boron nitride, and MXene.

4. The composite coating for hydrogen pipeline according to claim 1, characterized in that: The anti-corrosion filler accounts for 0.5%-20% of the mass of the fluorine-containing organic resin.

5. The composite coating for hydrogen pipeline according to claim 1, characterized in that: The divalent metal nitrate is Zn(NO3)2·6H2O and / or Mg(NO3)2·6H2O, and the trivalent metal nitrate is Al(NO3)3·9H2O and / or Ce(NO3)3·6H2O.

6. The method for preparing the composite coating for hydrogen pipeline according to any one of claims 1 to 5, characterized in that: include: The multi-scale flake filler and the semi-crystalline polymer are evenly dispersed, the evenly mixed powder is sprayed on the surface of the metal substrate, heated and oriented for a given time at a given pressure and temperature, and naturally cooled to room temperature to obtain the hydrogen barrier bottom layer.

7. The method for preparing a composite coating for a hydrogen pipeline according to claim 6, characterized in that: The fluorine-containing organic resin and the anti-corrosion filler are uniformly mixed to obtain a dispersion liquid, and the dispersion liquid is coated on the surface of the hydrogen barrier bottom layer to form an anti-corrosion top layer.

8. The method for preparing a composite coating for a hydrogen pipeline according to claim 7, characterized in that: The thickness of the hydrogen barrier bottom layer is configured to be 100 μm-120 μm; the thickness of the anti-corrosion top layer is configured to be 90 μm-110 μm; The given pressure, temperature and time are respectively 0-10 MPa, 150°C-220°C and 15-30 min. The fluorine-containing organic resin and the anti-corrosion filler are uniformly mixed under gradient high-speed stirring and vacuum conditions to obtain the dispersion; The anti-corrosion top layer is cured by baking at 120°C-300°C.

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