Preparation method of inner wall coating of hydrogen storage pressure vessel

Abstract

The invention provides a preparation method of a coating on the inner wall of a hydrogen storage pressure vessel, and relates to the technical field of coatings, the method comprises the following steps: S1, carrying out surface pretreatment on a base material to obtain a first pretreated base material; s2, the pretreated base material is subjected to electrochemical activation treatment, and a second pretreated base material is obtained; s3, preparing an Nb-P-H layer on the surface of the second pretreated base material; and S4, the Nb-P-H layer is subjected to aftertreatment, and the final coating is obtained. By adopting the method disclosed by the invention, the inner wall coating of the hydrogen storage pressure vessel, which is relatively good in hydrogen barrier property, relatively large in adhesive force, relatively good in density, relatively good in high-pressure-resistant stability and relatively good in thermal expansion coefficient matching property, can be prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coating, in particular to a preparation method of an inner wall coating of a hydrogen storage pressure container. BACKGROUND

[0002] Hydrogen embrittlement is one of the core technical problems in hydrogen energy storage and transportation. Hydrogen embrittlement is caused by the interaction of hydrogen atoms and internal defects of the metal, leading to crack propagation and material fracture. The diffusion coefficient of hydrogen in steel is relatively high. Under high pressure, hydrogen atoms enter the dislocations and grain boundaries in the metal lattice through diffusion and accumulate at defects, causing a significant decrease in the fatigue strength of the material. The diffusion rate of hydrogen atoms in the metal is closely related to temperature and pressure, especially in a high-pressure environment, the risk of hydrogen embrittlement of steel increases significantly.

[0003] Existing coating technologies mainly include metal coatings, ceramic coatings and polymer coatings. Related technologies mainly improve the hydrogen barrier performance through metal alloy coatings or ceramic coatings. Although the hydrogen barrier property of metal-based coatings (Fe, Co-based alloy coatings) is good, the adhesion between the metal-based coating and the container substrate is insufficient, which can easily peel off or fail in a high-temperature and high-pressure environment, affecting its long-term stability. Ceramic coatings (such as Al2O3, ZrO2, etc.) can theoretically effectively prevent hydrogen permeation due to their high hardness and low hydrogen permeability, but they are relatively brittle and can easily crack or break during the operation of the hydrogen storage container. This brittleness makes the coating prone to failure under the action of high-pressure hydrogen for a long time. The thickness requirement of the ceramic coating is high, and the coating needs to be sintered at a high temperature, which puts higher requirements on the density and uniformity of the coating. If the ceramic coating is not uniform or too thick, it will affect the mechanical properties of the coating, and even cause the coating to fall off. The preparation process of the ceramic coating is relatively complex, especially when coating a large area, strict control of temperature and pressure is required. In addition, the adhesion between the ceramic coating and the substrate metal is poor, and a special intermediate layer is needed to enhance the adhesion, which makes the overall production cost higher. In addition, the thermal expansion coefficient of the ceramic coating is quite different from the thermal expansion coefficient of the substrate material of the hydrogen storage pressure container (such as stainless steel, the thermal expansion coefficient is about 10 -5 / ℃), which is prone to cracking in use. Therefore, how to obtain a hydrogen storage pressure container inner wall coating with good hydrogen barrier property, good adhesion, good density, good high-pressure stability, and good thermal expansion coefficient matching has become a technical problem to be solved. SUMMARY

[0004] The problem solved by the present application is how to obtain a hydrogen storage pressure container inner wall coating with good hydrogen barrier property, good adhesion, good density, good high-pressure stability, and good thermal expansion coefficient matching.

[0005] To solve the above problems, the application provides a preparation method of an inner wall coating of a hydrogen storage pressure container, comprising the following steps: Step S1, performing surface pretreatment on a substrate to obtain a first pretreated substrate; Step S2, performing electrochemical activation treatment on the pretreated substrate to obtain a second pretreated substrate; Step S3, preparing an Nb-P-H layer on the surface of the second pretreated substrate; Step S4, performing post-treatment on the Nb-P-H layer to obtain a final coating.

[0006] Optionally, in the step S3, the Nb-P-H layer is deposited on the surface of the second pretreated substrate, comprising the following steps: performing chemical deposition on the second pretreated substrate in a mixed solution to obtain an Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; performing sintering treatment on the Nb-P layer in a hydrogen atmosphere to obtain the Nb-P-H layer.

[0007] Optionally, the thickness of the Nb-P layer is 10-15 μm.

[0008] Optionally, in the mixed solution, the concentration of the NbCl5 is 40-60 g / L, the concentration of the NaH2PO2 is 20-40 g / L, and the concentration of the ammonium citrate is 15-25 g / L.

[0009] Optionally, the sintering treatment is performed at a temperature of 600-800 ℃ for 2-3 h.

[0010] Optionally, in the step S2, the electrochemical activation treatment on the pretreated substrate comprises the following steps: taking a Pt electrode as a working electrode, and performing electrochemical reaction on the pretreated substrate in a hydrochloric acid solution; wherein the working current of the electrochemical reaction is 0.1-0.2 A / cm 2 , and the time is 100-140 s. 2

[0011] Optionally, in the step S1, the surface pretreatment on the substrate comprises the following steps: performing sand blasting treatment on the substrate, and then performing pickling and deionization flushing Optionally, in the step S4, the post-treatment comprises the following steps: sequentially performing annealing treatment and surface passivation treatment on the Nb-P-H layer.

[0012] Optionally, the annealing treatment is performed in a nitrogen atmosphere, and the annealing treatment is performed at a temperature of 280-320 ℃ for 1-2 h.

[0013] ​Optionally, the surface passivation treatment comprises: immersing the Nb-P-H layer after the annealing treatment in a CrO3 solution for immersion treatment.

[0014] The application further provides a hydrogen storage pressure vessel inner wall coating prepared by the preparation method of the hydrogen storage pressure vessel inner wall coating.

[0015] Compared with the related art, the Nb-P-H coating prepared by the application has strong interaction between the 4d orbital electrons of Nb and the 1s orbital of H, can effectively capture free protons, and generates NbH x (X<1) composite structure, thereby effectively reducing hydrogen permeation. Moreover, the NbH x The structure gap is filled with P atoms to form a Nb-H-P structure, which can further hinder proton diffusion, thereby improving the hydrogen barrier property of the coating. In addition, the application forms nanoscale pits on the surface of the substrate through electrochemical reaction, which is conducive to strengthening the bonding between the coating and the substrate and can effectively improve the adhesion of the coating. It has been found through experiments that the coating prepared by the method of the application has good compactness, and the thermal expansion coefficient of the coating and the substrate is well matched, and the coating also has good high-pressure stability. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Figure 1 is a flowchart of the preparation method of the hydrogen storage pressure vessel inner wall coating in the embodiments of the application. DETAILED DESCRIPTION

[0017] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail below with reference to the drawings. Although some embodiments of the application are shown in the drawings, it should be understood that the application can be implemented in various forms, and should not be interpreted as being limited to the embodiments described herein, on the contrary, these embodiments are provided to make the application more thorough and complete. It should be understood that the drawings and embodiments of the application are only for illustrative purposes, and are not intended to limit the scope of protection of the application.

[0018] Unless otherwise defined, all technical and scientific terms used in the application have the same meaning as commonly understood by a person skilled in the art to which the application belongs. The terms used in the specification of the application are only for the purpose of describing the specific embodiments of the application, and are not intended to limit the application.

[0019] The term "include" and variations thereof, as used in this document, is used expansively and means "including, but not limited to"; the term "based on" is meant to be "based, at least in part, on"; the term "one embodiment" is meant to be "at least one embodiment"; the term "another embodiment" is meant to be "at least one additional embodiment"; the term "some embodiments" is meant to be "at least some embodiments"; the term "optional" is meant to be "optional in at least one embodiment". Related definitions are given throughout the detailed description. It is noted that the concepts of "first", "second", etc. mentioned in the present application are used to distinguish different objects, rather than to describe a specific order or primary and secondary relationship. In addition, the terms "first", "second" are only for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can be explicitly or implicitly included one or more features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0020] It should be noted that in the present application, the coating is attached to the substrate for processing (such as annealing treatment, surface passivation treatment, etc.) and performance testing.

[0021] As shown in Figure 1 The present application provides a preparation method of a hydrogen storage pressure vessel inner wall coating, comprising: Step S1, surface pretreatment of the substrate to obtain a first pretreated substrate; Step S2, electrochemical activation treatment of the pretreated substrate to form nanoscale pits on the pretreated substrate to obtain a second pretreated substrate; Step S3, preparation of a Nb-P-H layer on the surface of the second pretreated substrate; Step S4, post-treatment of the Nb-P-H layer to obtain a final coating.

[0022] The Nb-P-H coating prepared by the present application has strong interaction between the 4d orbital electrons of Nb and the 1s orbital of H in the coating, which can effectively capture free protons and generate NbH x (X<1) composite structure, so as to effectively reduce hydrogen permeation. Moreover, the NbH x structure gap is filled with P atoms to form a Nb-H-P structure, which can further hinder proton diffusion, thereby improving the hydrogen barrier performance of the coating. In addition, the present application forms nanoscale pits on the surface of the substrate through electrochemical reaction, which is beneficial to strengthening the bonding between the coating and the substrate, and can effectively improve the adhesion of the coating. It is found through experiments that the coating prepared by the method of the present application has good compactness, and the thermal expansion coefficient matching of the coating and the substrate is good, and the coating also has good high-pressure stability.

[0023] In some embodiments of the present application, in the step S3, the depositing of the Nb-P-H layer on the surface of the second pretreated substrate comprises: chemically depositing the second pretreated substrate in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; sintering the Nb-P layer in a hydrogen atmosphere to obtain the Nb-P-H layer; wherein the sintering temperature is 600-800℃ and the sintering time is 2-3h.

[0024] In the chemical deposition process, NbCl5 provides Nb ions for coating deposition, NaH2PO2 acts as a reducing agent, which can effectively promote the reduction deposition of Nb ions, and at the same time form a Nb-P coating with Nb, ammonium citrate helps to adjust the pH value of the mixed solution, and can play a chelating effect, which is conducive to maintaining the stable state of Nb and P elements in the solution. Sintering the Nb-P layer in a hydrogen atmosphere generates a Nb-P-H layer, which solidifies the coating and ensures the pressure stability and adhesion of the coating.

[0025] In some embodiments of the present application, in the step S3, the depositing of the Nb-P-H layer on the surface of the second pretreated substrate can also be implemented by a plasma enhanced chemical vapor deposition (PECVD) method, specifically, the substrate is subjected to plasma enhanced chemical vapor deposition; wherein the plasma used in the plasma enhanced chemical vapor deposition is composed of NbCl5, H2 and PH3, the radio frequency power is 300W, and the working temperature is 250℃.

[0026] In some embodiments of the present application, in the step S3, the thickness of the Nb-P layer is 10-15μm.

[0027] In some embodiments of the present application, in the step S3, the deposition rate of the chemical deposition is 2.0-2.3μm / h, which is conducive to ensuring the uniformity of the coating.

[0028] In some embodiments of the present application, in the step S3, in the mixed solution, the concentration of the NbCl5 is 40-60g / L, the concentration of the NaH2PO2 is 20-40g / L, and the concentration of the ammonium citrate is 15-25g / L. In this embodiment, the concentration of the NbCl5 is controlled to be 40-60g / L, the concentration of the NaH2PO2 is controlled to be 20-40g / L, and the concentration of the ammonium citrate is controlled to be 15-25g / L, which can provide sufficient Nb ions and P ions for coating deposition, In some embodiments of the present application, in the step S3, the pH of the mixed solution is 3-4, and the temperature of the mixed solution is 60-70℃. In this embodiment, the pH of the mixed solution is controlled to be 3-4, so that the NbCl5 solution can be kept stable and unstable chlorides can be avoided; and the temperature of the mixed solution is controlled to be 60-70℃, so that a good deposition rate can be kept.

[0029] In some embodiments of the present application, in the step S1, the material of the substrate is stainless steel; for example, the material of the substrate is 316L steel.

[0030] In some embodiments of the present application, in the step S1, the substrate is subjected to surface pretreatment, including: sandblasting treatment, and then acid pickling and deionized water rinsing. The sandblasting treatment is used to remove the oxide film on the surface of the substrate, and the surface roughness Ra is controlled to be 3-5 μm; and the acid pickling is used to remove the passivation film on the surface of the substrate.

[0031] In some embodiments of the present application, in the step S2, the electrochemical activation treatment of the pretreated substrate includes: taking a Pt electrode as a working electrode, and performing electrochemical reaction on the pretreated substrate in a hydrochloric acid solution.

[0032] In some embodiments of the present application, the concentration of the hydrochloric acid solution is 1-2 mol / L, the working current of the electrochemical reaction is 0.1-0.2 A / cm2, and the time is 100-140 s. 2 2

[0033] In some embodiments of the present application, in the step S4, the post-treatment includes: sequentially performing annealing treatment and surface passivation treatment on the Nb-P-H layer. The annealing treatment is performed in a nitrogen atmosphere, the temperature of the annealing treatment is 280-320℃, and the time is 1-2 h. The surface passivation treatment includes: immersing the Nb-P-H layer after the annealing treatment in a CrO3 solution for soaking treatment; wherein the mass fraction of the CrO3 solution is 5-8%, and the time of the soaking treatment is 10-30 min. In this embodiment, the annealing treatment is used to remove the internal stress in the coating, so that the stability and adhesion of the coating can be enhanced; and the surface passivation treatment is used to form a stable oxide film on the surface of the coating, for example, the CrO3 can react with the Nb and P elements on the surface of the coating to generate a composite oxide film, which is beneficial to improving the corrosion resistance of the coating.

[0034] The present application also provides a hydrogen storage pressure vessel inner wall coating prepared by the method described above.

[0035] ​​The application will be further described in connection with specific embodiments.

[0036] Example 1 A1, the substrate is sandblasted, then pickled and deionized rinsed to obtain a first pretreated substrate; wherein the material of the substrate is 316L steel, the surface roughness Ra after sandblasting is controlled to be 4 μm, the acid solution used for pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60 ℃, and the pickling time is 8 min.

[0037] A2, a Pt electrode is used as a working electrode, and the pretreated substrate is subjected to an electrochemical reaction in a hydrochloric acid solution to form a nanoscale pit on the pretreated substrate, thereby obtaining a second pretreated substrate; the concentration of the hydrochloric acid solution is 1 mol / L, the working current of the electrochemical reaction is 0.1 A / cm 2 , and the time is 140 s. A3, the second pretreated substrate is subjected to chemical deposition in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 50 g / L, the concentration of the NaH2PO2 is 30 g / L, and the concentration of the ammonium citrate is 20 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65 ℃, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the Nb-P layer is 12.5 μm.

[0038] A4, the Nb-P layer is subjected to sintering treatment in a hydrogen atmosphere to obtain a Nb-P-H layer; wherein the sintering treatment temperature is 700 ℃, and the time is 2.5 h.

[0039] A5, the Nb-P-H layer is subjected to annealing treatment in a nitrogen atmosphere and then immersed in a CrO3 solution for immersion treatment to obtain a final coating; the annealing treatment temperature is 300 ℃, the time is 1.5 h, the mass fraction of the CrO3 solution is 6.5%, and the immersion treatment time is 20 min.

[0040] Example 2 A1, the substrate is sandblasted, then pickled and deionized rinsed to obtain a first pretreated substrate; wherein the material of the substrate is 316L steel, the surface roughness Ra after sandblasting is controlled to be 4 μm, the acid solution used for pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60 ℃, and the pickling time is 8 min.

[0041] A2, taking the Pt electrode as a working electrode, and performing electrochemical reaction on the pretreated substrate in a hydrochloric acid solution to form nanoscale pits on the pretreated substrate to obtain a second pretreated substrate; the concentration of the hydrochloric acid solution is 1 mol / L, and the working current of the electrochemical reaction is 0.2 A / cm 2 , and the time is 100 s. A3, performing chemical deposition on the second pretreated substrate in a mixed solution to obtain an Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2, and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 40 g / L, the concentration of the NaH2PO2 is 20 g / L, and the concentration of the ammonium citrate is 15 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65℃, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the Nb-P layer is 12.5 μm.

[0042] A4, performing sintering treatment on the Nb-P layer in a hydrogen atmosphere to obtain an Nb-P-H layer; wherein the temperature of the sintering treatment is 600℃, and the time is 3 h.

[0043] A5, after performing annealing treatment on the Nb-P-H layer in a nitrogen atmosphere, immersing the Nb-P-H layer in a CrO3 solution to obtain a final coating layer; the temperature of the annealing treatment is 280℃, the time is 2 h, the mass fraction of the CrO3 solution is 5%, and the time of the immersion treatment is 30 min.

[0044] Example 3 A1, performing sand blasting treatment on a substrate, and then performing pickling and deionization rinsing to obtain a first pretreated substrate; wherein the material of the substrate is 316L steel, the surface roughness Ra after the sand blasting treatment is controlled to be 4 μm, the acid solution used for the pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60℃, and the time of the pickling is 8 min.

[0045] A2, taking the Pt electrode as a working electrode, and performing electrochemical reaction on the pretreated substrate in a hydrochloric acid solution to form nanoscale pits on the pretreated substrate to obtain a second pretreated substrate; the concentration of the hydrochloric acid solution is 1 mol / L, and the working current of the electrochemical reaction is 0.15 A / cm 2 , and the time is 120 s. A3, performing chemical deposition on the second pretreated substrate in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 60 g / L, the concentration of the NaH2PO2 is 40 g / L, and the concentration of the ammonium citrate is 25 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65°C, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the Nb-P layer is 12.5 μm.

[0046] A4, performing sintering treatment on the Nb-P layer in a hydrogen atmosphere to obtain a Nb-P-H layer; wherein the temperature of the sintering treatment is 800°C, and the time is 2 h.

[0047] A5, after performing annealing treatment on the Nb-P-H layer in a nitrogen atmosphere, immersing the Nb-P-H layer in a CrO3 solution to obtain a final coating layer; the temperature of the annealing treatment is 320°C, the time is 1 h, the mass fraction of the CrO3 solution is 8%, and the time of the immersion treatment is 10 min.

[0048] Comparative Example 1 (lacking the electrochemical activation treatment step) performing sand blasting treatment on a substrate, and then performing acid pickling and deionized water rinsing to obtain a first pretreated substrate; wherein the material of the substrate is 316L steel, the surface roughness Ra after the sand blasting treatment is controlled to be 4 μm, the acid solution used for the acid pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60°C, and the time of the acid pickling is 8 min.

[0049] performing chemical deposition on the first pretreated substrate in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 50 g / L, the concentration of the NaH2PO2 is 30 g / L, and the concentration of the ammonium citrate is 20 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65°C, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the Nb-P layer is 12.5 μm.

[0050] performing sintering treatment on the Nb-P layer in a hydrogen atmosphere to obtain a Nb-P-H layer; wherein the temperature of the sintering treatment is 700°C, and the time is 2.5 h.

[0051] after performing annealing treatment on the Nb-P-H layer in a nitrogen atmosphere, immersing the Nb-P-H layer in a CrO3 solution to obtain a final coating layer; the temperature of the annealing treatment is 300°C, the time is 1.5 h, the mass fraction of the CrO3 solution is 6.5%, and the time of the immersion treatment is 20 min.

[0052] Comparative Example 2 (no NaH2PO2in the mixed solution) The substrate was subjected to sand blasting treatment, and then was subjected to acid pickling and deionized water rinsing to obtain a first pretreated substrate; wherein the material of the substrate was 316L steel, the surface roughness Ra after sand blasting treatment was controlled to be 4 μm, the acid solution used for acid pickling was a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution was 60°C, and the acid pickling time was 8 min.

[0053] A Pt electrode was used as a working electrode, and the pretreated substrate was subjected to electrochemical reaction in a hydrochloric acid solution to form nanoscale pits on the pretreated substrate, thereby obtaining a second pretreated substrate; the concentration of the hydrochloric acid solution was 1 mol / L, the working current of the electrochemical reaction was 0.1 A / cm 2 , and the time was 140 s.

[0054] The second pretreated substrate was subjected to chemical deposition in a mixed solution to obtain a first coating layer; the mixed solution included NbCl5 and ammonium citrate; in the mixed solution, the concentration of the NbCl5 was 50 g / L, and the concentration of the ammonium citrate was 20 g / L; the pH of the mixed solution was 3.5, the temperature of the mixed solution was 65°C, the deposition rate of the chemical deposition was 2.1 μm / h, and the thickness of the first coating layer was 12.5 μm.

[0055] The first coating layer was subjected to sintering treatment in a hydrogen atmosphere to obtain a second coating layer; wherein the sintering treatment temperature was 700°C, and the time was 2.5 h.

[0056] After the second coating layer was subjected to annealing treatment in a nitrogen atmosphere, the second coating layer was immersed in a CrO3 solution to obtain a final coating layer; the annealing treatment temperature was 300°C, the time was 1.5 h, the mass fraction of the CrO3 solution was 6.5%, and the immersion treatment time was 20 min.

[0057] Comparative Example 3 (no ammonium citrate in the mixed solution) The substrate was subjected to sand blasting treatment, and then was subjected to acid pickling and deionized water rinsing to obtain a first pretreated substrate; wherein the material of the substrate was 316L steel, the surface roughness Ra after sand blasting treatment was controlled to be 4 μm, the acid solution used for acid pickling was a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution was 60°C, and the acid pickling time was 8 min.

[0058] A Pt electrode was used as a working electrode, and the pretreated substrate was subjected to electrochemical reaction in a hydrochloric acid solution to form nanoscale pits on the pretreated substrate, thereby obtaining a second pretreated substrate; the concentration of the hydrochloric acid solution was 1 mol / L, the working current of the electrochemical reaction was 0.1 A / cm 2 , and the time was 140 s.

[0059] The second pretreated substrate is subjected to chemical deposition in a mixed solution to obtain a first coating layer; the mixed solution comprises NbCl5 and NaH2PO2; in the mixed solution, the concentration of the NbCl5 is 50 g / L, and the concentration of the NaH2PO2 is 30 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65 ℃, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the first coating layer is 12.5 μm.

[0060] The first coating layer is subjected to sintering treatment in a hydrogen atmosphere to obtain a second coating layer; wherein the temperature of the sintering treatment is 700 ℃, and the time of the sintering treatment is 2.5 h.

[0061] The second coating layer is subjected to annealing treatment in a nitrogen atmosphere and then is subjected to immersion treatment in a CrO3 solution to obtain a final coating layer; the temperature of the annealing treatment is 300 ℃, the time of the annealing treatment is 1.5 h, the mass fraction of the CrO3 solution is 6.5%, and the time of the immersion treatment is 20 min.

[0062] Comparative Example 4 (lacking the hydrogen atmosphere sintering treatment on the Nb-P layer) A substrate is subjected to sand blasting treatment, and then is subjected to acid pickling and deionized water rinsing to obtain a first pretreated substrate; wherein the material of the substrate is 316L steel, the surface roughness Ra after the sand blasting treatment is controlled to be 4 μm, the acid solution used for the acid pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60 ℃, and the time of the acid pickling is 8 min.

[0063] A Pt electrode is used as a working electrode, and the pretreated substrate is subjected to electrochemical reaction in a hydrochloric acid solution to form a nanoscale pit on the pretreated substrate to obtain a second pretreated substrate; the concentration of the hydrochloric acid solution is 1 mol / L, the working current of the electrochemical reaction is 0.1 A / cm 2 , and the time of the electrochemical reaction is 140 s.

[0064] The second pretreated substrate is subjected to chemical deposition in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 50 g / L, the concentration of the NaH2PO2 is 30 g / L, and the concentration of the ammonium citrate is 20 g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65 ℃, the deposition rate of the chemical deposition is 2.1 μm / h, and the thickness of the Nb-P layer is 12.5 μm.

[0065] The Nb-P layer is placed in a CrO3 solution for immersion treatment after annealing treatment under a nitrogen atmosphere, to obtain a final coating; the annealing treatment is at a temperature of 300°C for 1.5h, the mass fraction of the CrO3 solution is 6.5%, and the immersion treatment is for 20min.

[0066] Comparative Example 5 (lacking the nitrogen atmosphere sintering treatment of the Nb-P-H layer) The substrate is subjected to sand blasting treatment, and then to acid pickling and deionized rinsing, to obtain a first pretreated substrate; the substrate is made of 316L steel, the surface roughness Ra after sand blasting treatment is controlled to be 4μm, the acid solution used for acid pickling is a nitric acid solution with a mass fraction of 10%, the temperature of the acid solution is 60°C, and the acid pickling time is 8min.

[0067] A Pt electrode is used as a working electrode, and the pretreated substrate is subjected to electrochemical reaction in a hydrochloric acid solution, to form nanoscale pits on the pretreated substrate, to obtain a second pretreated substrate; the concentration of the hydrochloric acid solution is 1mol / L, the working current of the electrochemical reaction is 0.1A / cm 2 , and the time is 140s.

[0068] The second pretreated substrate is subjected to chemical deposition in a mixed solution, to obtain an Nb-P layer; the mixed solution includes NbCl5, NaH2PO2, and ammonium citrate; in the mixed solution, the concentration of the NbCl5 is 50g / L, the concentration of the NaH2PO2 is 30g / L, and the concentration of the ammonium citrate is 20g / L; the pH of the mixed solution is 3.5, the temperature of the mixed solution is 65°C, the deposition rate of the chemical deposition is 2.1μm / h, and the thickness of the Nb-P layer is 12.5μm.

[0069] The Nb-P layer is subjected to sintering treatment under a hydrogen atmosphere, to obtain an Nb-P-H layer; the sintering treatment is at a temperature of 700°C for 2.5h.

[0070] The Nb-P-H layer is placed in a CrO3 solution for immersion treatment, to obtain a final coating; the annealing treatment is at a temperature of 300°C for 1.5h, the mass fraction of the CrO3 solution is 6.5%, and the immersion treatment is for 20min.

[0071] Experimental Example The final coating prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was measured for hydrogen permeation coefficient, adhesion, difference in thermal expansion coefficient from the substrate, density and high-pressure stability, and the results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1 to 5, the final coating prepared in Examples 1 to 3 has smaller hydrogen permeation coefficient, greater adhesion, smaller difference in thermal expansion coefficient from the substrate, better density and better high-pressure stability; compared with Example 1, the final coating prepared in Comparative Example 1 has significantly reduced adhesion, significantly increased hydrogen permeation coefficient and reduced high-pressure stability, indicating that the electrochemical activation treatment is beneficial to improving the adhesion, high-pressure stability of the coating and reducing the hydrogen permeation coefficient. Compared with Example 1, the final coating prepared in Comparative Example 2 has significantly increased hydrogen permeation coefficient, reduced high-pressure stability and significantly increased difference in thermal expansion coefficient from the substrate, because the lack of NaH2PO2 in the mixed solution cannot form the Nb-P-H ternary synergistic structure, and there is no P in the coating, so the hydrogen atoms are easy to diffuse through the Nb lattice gap, resulting in reduced hydrogen permeation coefficient; in addition, the Nb-P solid solution is absent in the coating, the difference in thermal expansion coefficient between the coating and the substrate is large, and the thermal matching property is deteriorated, thereby reducing the high-pressure stability. Compared with Example 1, the final coating prepared in Comparative Example 3 has significantly increased hydrogen permeation coefficient, because the lack of ammonium citrate in the mixed solution causes the Nb ions to be easy to hydrolyze to form unstable chlorides, the uneven distribution of Nb ions causes the increase of the pores in the coating, and the pores become the hydrogen permeation channels. Compared with Example 1, the final coating prepared in Comparative Example 4 has significantly increased hydrogen permeation coefficient and reduced high-pressure stability, because the lack of the “hydrogen trapping” effect of the Nb-H bond allows the free hydrogen atoms to directly diffuse to the substrate; because of the lack of hydrogen sintering process at high temperature, the crystal structure of the coating is loose, and micro-cracks are easy to occur under high pressure.

[0072] Table 1

[0073] The performance detection method involved in the present application is as follows: Hydrogen permeation coefficient: detected by electrochemical hydrogen permeation method, and the smaller the hydrogen permeation coefficient, the better the hydrogen barrier property of the coating.

[0074] Adhesion: refer to GB / T 9286-1998.

[0075] Difference in thermal expansion coefficient from the substrate: thermal mechanical analysis method.

[0076] Density: Archimedes drainage method, which characterizes the internal porosity of the coating, and the higher the value (tending to 1), the higher the density.

[0077] High pressure stability: high pressure hydrogen gas circulation test (50 MPa, 100 cycles), characterized by detecting the intact rate of the coating after 100 cycles, 100% represents no crack / peeling.

[0078] Although the present application is disclosed as above, the protection scope of the present application is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and these changes and modifications will fall within the protection scope of the present application.

Claims

1. A method for preparing a coating for the inner wall of a hydrogen storage pressure vessel, characterized by, The application relates to a method for preparing a Nb-P-H coating on a substrate. The method comprises the following steps: S1, surface pretreatment of the substrate to obtain a first pretreated substrate; S2, electrochemical activation treatment of the pretreated substrate to obtain a second pretreated substrate; S3, preparation of a Nb-P-H layer on the surface of the second pretreated substrate; 2. The method of claim 1, wherein the method further comprises: S4, post-treatment of the Nb-P-H layer to obtain a final coating. In the step S3, the Nb-P-H layer is deposited on the surface of the second pretreated substrate, which comprises the following steps: chemical deposition of the second pretreated substrate in a mixed solution to obtain a Nb-P layer; the mixed solution comprises NbCl5, NaH2PO2 and ammonium citrate; 3. The method of claim 2, wherein the method further comprises: sintering treatment of the Nb-P layer in a hydrogen atmosphere to obtain the Nb-P-H layer.

4. The method of claim 2, wherein the method further comprises: The thickness of the Nb-P layer is 10-15 mu m.

5. The method of claim 2, wherein the method further comprises: In the mixed solution, the concentration of the NbCl5 is 40-60 g / L, the concentration of the NaH2PO2 is 20-40 g / L, and the concentration of the ammonium citrate is 15-25 g / L.

6. The method of claim 1, wherein the method further comprises: In the step S2, the electrochemical activation treatment of the pretreated substrate comprises: taking a Pt electrode as a working electrode, and performing electrochemical reaction on the pretreated substrate in a hydrochloric acid solution; wherein a working current of the electrochemical reaction is 0.1 A / cm 2 to 0.2 A / cm 2 and a time is 100 s to 140 s.

7. The method of claim 1, wherein the method further comprises: The sintering treatment is carried out at a temperature of 600-800 DEG C for 2-3 hours.

8. The method of claim 1, wherein the method further comprises: In the step S1, the surface pretreatment of the substrate comprises sand blasting treatment, acid pickling and deionized water rinsing.

9. The method of claim 8, wherein the method further comprises the step of: In the step S4, the post-treatment comprises annealing treatment and surface passivation treatment of the Nb-P-H layer in sequence.

10. The method of claim 8, wherein the method further comprises: The annealing treatment is carried out in a nitrogen atmosphere, and the annealing treatment is carried out at a temperature of 280-320 DEG C for 1-2 hours. The surface passivation treatment comprises immersion treatment of the Nb-P-H layer after the annealing treatment in a CrO3 solution.

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