Surface treatment method for valve seat combined with liner interface of type IV hydrogen storage bottle

Abstract

The invention provides a surface treatment method for a valve seat combined with an inner container interface of a type IV hydrogen storage bottle, and relates to the technical field of metal surface treatment. Performing surface adjustment and secondary cleaning; performing anode electrolysis to form an aluminum oxide film; performing acid pickling and hole expanding treatment to form a micron-sized pore structure; carrying out phosphate chemical sealing treatment on the gas contact area; and coating and curing the polyimide-based anode electrophoretic paint on the area combined with the plastic liner. Gas permeation can be prevented, and the bonding strength of the metal cylinder valve seat and the plastic inner container can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment, and in particular to a method for treating the surface of a valve seat of a type IV hydrogen storage bottle that is bonded to an interface with an inner tank. Background Art

[0002] The demand for high-pressure hydrogen storage vessels in the commercial vehicle and energy storage sectors is increasingly urgent. As the "cleanest" secondary energy source, hydrogen energy is a clean energy source that demands accelerated development and utilization. Hydrogen storage is a crucial component of its development. Type IV hydrogen storage bottles, due to their lightweight, high-strength, and fatigue-resistant properties, have become a core technology focus for hydrogen storage and transportation in the hydrogen energy sector.

[0003] Due to the small molecular weight and flammable and explosive physical and chemical properties of hydrogen, the sealing of Type IV hydrogen storage bottles is crucial. It is the cornerstone of hydrogen storage bottle quality assurance. The plastic liner (liner) technology of Type IV hydrogen storage bottles is relatively mature, ensuring the hydrogen storage bottles meet standard airtightness. However, because the plastic liner of a Type IV hydrogen storage bottle is made of, the interface between it and the metal valve seat (typically aluminum alloy, 6061) at the cylinder mouth remains a vulnerable link, prone to leakage risks. Therefore, the interface between the two materials is particularly critical.

[0004] Especially under the complex operating conditions of Type IV hydrogen storage bottles, such as cyclic charging and discharging, vibration, and thermal expansion, due to differences in the mechanical or thermal properties (elongation, thermal expansion coefficient, etc.) of the plastic liner and the metal valve seat, under the action of cyclic dynamic loads, the plastic liner and the metal valve seat may peel off from each other at their interface, resulting in relative slip and cracks. Hydrogen can penetrate through the interfacial gaps, leading to leakage and even explosion risks, making this interface a weak point prone to leakage risks. Therefore, specific processing is required for the valve seat of Type IV hydrogen storage bottles and the location where it meets the liner.

[0005] Traditional surface treatment technologies for metal bottle valve seats mainly include mechanical grinding, chemical etching and simple anodizing to enhance the bonding strength between metal and plastic.

[0006] The surface treatment of metal bottle valve seats in the prior art has the following defects and deficiencies: The surface structure formed by traditional surface treatment methods is single and lacks sufficient mechanical bite area, resulting in insufficient interface bonding strength between metal and plastic. Interface separation is prone to occur under high-pressure environments, causing safety hazards of gas leakage.

[0007] The pore structure of the oxide film formed by the existing anodizing process is uneven, and it is impossible to achieve precise control of the pore size and distribution, making it difficult to meet the functional requirements of different regions, especially the inability to simultaneously take into account both air tightness and interface bonding strength.

[0008] Current surface treatment methods lack differentiated treatment strategies for areas in contact with gas and areas bonding with plastic. Using the same treatment process makes it difficult to simultaneously meet the dual requirements of preventing gas penetration and enhancing bonding strength, resulting in bonding strength attenuation or gas leakage problems during long-term use. Summary of the Invention

[0009] The embodiment of the present invention provides a surface treatment method for a metal bottle valve seat bonded to the interface of a plastic liner in a Type IV hydrogen storage bottle, which can solve the problems of insufficient bonding strength and possible gas leakage in the prior art.

[0010] A first aspect of an embodiment of the present invention provides a method for treating the surface of a valve seat of a Type IV hydrogen storage bottle in conjunction with an inner tank, comprising the following steps: 1) Use spray degreasing liquid to pre-degrease the metal bottle valve seat, and then perform main degreasing on the pre-degreased metal bottle valve seat by immersion combined with ultrasonic vibration. Use deionized water to clean the degreased metal bottle valve seat once to remove residual degreasing agent. 2) The surface of the metal bottle valve seat after the primary cleaning is adjusted using phosphoric acid to remove trace metal impurities on the surface. The metal bottle valve seat after the surface adjustment is then cleaned again using deionized water combined with ultrasonic vibration to form a uniform active layer on the surface of the metal bottle valve seat for the subsequent formation of the aluminum oxide film. 3) Using the secondary cleaned metal bottle valve seat as the anode, electrolysis is performed using a mixture of phosphoric acid and oxalic acid as the electrolyte. By regulating the voltage, current density, electrolyte temperature, and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the aluminum oxide film is then rinsed with pure water to remove impurities in the initial pores. 4) The aluminum oxide film with initial pores is pickled and expanded, and anodized and pickled repeatedly until a micron-sized pore structure is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the micron-sized pore structure is cleaned with pure water; 5) preparing a chemical sealant (such as potassium dichromate or phosphate), and using the chemical sealant to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the area in contact with the gas to prevent gas penetration; 6) Apply high-temperature resistant polyimide-based anodic electrophoretic paint and perform graded temperature-raising curing treatment to form a polyimide paint film in the area bonded to the plastic liner to improve the bonding strength.

[0011] Specifically, in step 2), phosphoric acid is used to condition the surface of the metal bottle valve seat after the primary cleaning to remove trace metal impurities on the surface. Deionized water combined with ultrasonic vibration is then used to perform a secondary cleaning on the surface-conditioned metal bottle valve seat to form a uniform active layer on the surface of the metal bottle valve seat for subsequent formation of an aluminum oxide film, including: A phosphoric acid solution of a preset concentration is prepared, heated to a preset temperature, and the metal bottle valve seat is immersed in the phosphoric acid solution for a preset time for surface treatment, so that the phosphoric acid solution and the surface of the metal bottle valve seat undergo a step-by-step chemical reaction to produce a reaction product layer and surface impurities: aluminum atoms on the surface of the metal bottle valve seat react with hydrogen ions to produce aluminum ions and hydrogen gas, the hydrogen gas escapes from the solution, and the aluminum ions react with phosphate ions to produce aluminum phosphate; The metal bottle valve seat after the reaction is cleaned by fixed-frequency ultrasonic cleaning, whereby cavitation bubbles are formed on the surface of the metal bottle valve seat by the fixed-frequency ultrasonic cleaning, and the cavitation bubbles collapse under the action of the acoustic pressure and generate shock waves, which clean the reaction product layer and surface impurities on the surface of the metal bottle valve seat; After the reaction product layer is cleaned by the fixed-frequency ultrasonic cleaning, the aluminum phosphate reaction product remains on the surface of the metal bottle valve seat to form an active layer, and the active layer is used for the subsequent generation of an aluminum oxide film.

[0012] In step 3), the metal bottle valve seat after secondary cleaning is used as the anode, and a mixture of phosphoric acid and oxalic acid is used as the electrolyte for electrolysis. By regulating the voltage, current density, electrolyte temperature and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat, including: Prepare an oxalic acid solution and place it in a reaction vessel, slowly add the phosphoric acid solution dropwise while continuously stirring, monitor the pH value during the addition process, stop adding when the pH value drops to the target range, let it stand until the solution becomes clear, and then filter to obtain a mixed electrolyte; Precooling the mixed electrolyte to below room temperature, immersing the metal bottle valve seat as an anode in the mixed electrolyte, applying an electric field in a constant voltage mode, and then gradually increasing the voltage to a first preset voltage at a fixed rate, during which ions in the mixed electrolyte directionally migrate under the drive of the electric field, and aluminum atoms on the surface of the metal bottle valve seat undergo an oxidation-reduction reaction with hydrogen ions that migrate to the surface to generate aluminum ions. The aluminum ions, under the action of the local electric field, directionally combine with anions in the electrolyte to form aluminum oxide, and are deposited on the surface of the metal bottle valve seat to form an initial aluminum oxide film; The temperature of the mixed electrolyte is maintained constant. When the monitored current drops to half of the initial value, the voltage is lowered to a second preset voltage and maintained constant, while the electrolyte temperature is increased to a predetermined temperature. At this time, the initial aluminum oxide film continues to deposit and thicken under the action of the electric field, while the surface layer is partially dissolved under the action of the electrolyte. By regulating the dynamic balance of deposition and dissolution, a uniformly distributed honeycomb pore structure is formed on the surface of the initial aluminum oxide film, and an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat.

[0013] In step 4), the aluminum oxide film with initial pores is pickled and expanded, and anodized and pickled and expanded repeatedly until a micron-scale pore structure is formed on the surface of the metal bottle valve seat, including: The aluminum oxide film having initial pores is immersed in an acidic solution for pickling. By controlling the concentration and temperature of the acidic solution, different dissolution rates are generated at the pore walls of the initial pores. Driven by the difference in dissolution rates, the initial pores evolve into a circular shape to form a regular array of pits. The metal bottle valve seat is anodized using the regular pit array as a nucleation site, and a constant voltage is applied to cause the oxidation reaction to proceed preferentially at the regular pit array. The geometric morphology of the regular pit array guides the growth orientation of the aluminum oxide layer, forming a new aluminum oxide layer at the regular pit array. The pores in the new aluminum oxide layer inherit the spatial distribution characteristics of the regular pit array and grow directionally in a vertical direction, forming a periodically arranged pore structure. The anodizing treatment and the pickling treatment are repeated, wherein the voltage value of the anodizing treatment controls the spacing between adjacent pores, and the voltage value is positively correlated with the resulting spacing; the time of the pickling treatment controls the degree of expansion of the pores, and the treatment time is positively correlated with the resulting pore size; by gradually increasing the voltage value and extending the pickling treatment time, the pore structure is gradually enlarged and maintained in a regular arrangement under the drive of surface energy, until a uniformly distributed micron-scale pore structure is formed on the surface of the metal bottle valve seat.

[0014] In step 5), a chemical sealant (such as potassium dichromate or phosphate) is prepared and used to perform gradient penetration sealing on the micron-scale pore structure in the area in contact with the gas to prevent gas penetration, including: dissolving a sealing agent salt in deionized water according to a preset mass fraction to prepare a salt-based liquid, adding a surfactant dropwise to the salt-based liquid under constant temperature stirring conditions, monitoring the surface tension of the salt-based liquid in real time using a surface tension tester, and stopping the addition when the surface tension drops to a level sufficient to generate capillary force on the pore size of the micron-sized pore structure, thereby preparing a chemical sealing agent; The chemical sealant is applied to the gas contact area of ​​the valve seat of the metal bottle. The chemical sealant spontaneously penetrates into the micron-scale pore structure under the action of capillary force. By controlling the infiltration time and temperature of the chemical sealant, the chemical sealant forms a concentration gradient distribution along the depth direction of the micron-scale pore structure and fills the micron-scale pore structure to a predetermined depth. The metal bottle valve seat that has completed gradient infiltration is heat-treated to form a chemical bond between the chemical sealant and the aluminum oxide on the surface of the micron-scale pore structure, thereby forming a sealing layer with a dense structure in the gas contact area to prevent gas penetration.

[0015] In step 6), a high-temperature resistant polyimide-based anodic electrophoretic paint coating and a graded temperature-raising curing treatment are performed to form a polyimide paint film in the area bonded to the plastic liner to improve the bonding strength, including: preparing an anodic electrophoretic paint containing a preset content of polyimide resin, measuring the mobility of charged particles of the anodic electrophoretic paint, and determining a voltage control parameter in electrophoresis according to the mobility of the charged particles; Electrophoretic coating is performed using a three-stage voltage control method according to the voltage control parameters, and the switching time of each stage is determined by real-time monitoring of the electrophoretic current: in the initial stage, a first preset voltage is applied to cause the charged colloid particles to migrate to the surface of the metal bottle valve seat to form an initial covering layer; in the middle stage, the voltage is increased to a second preset voltage to maintain a constant deposition rate to allow the initial covering layer to grow; and in the final stage, the voltage is reduced to a third preset voltage to enhance the density of the initial covering layer to a preset degree; The metal bottle valve seat after electrophoresis is subjected to a graded temperature-raising curing treatment, wherein the graded temperature-raising curing treatment includes: a first preset temperature is used in the primary stage to flatten the paint film surface by solvent volatilization; a second preset temperature is used in the intermediate stage to catalyze the cross-linking of polyimide molecular chains to increase the paint film strength to a preset degree; and a third preset temperature is used in the advanced stage to cure the paint film and form a polyimide paint film on the surface of the metal bottle valve seat; The polar groups on the surface of the polyimide paint film undergo molecular chain entanglement with the liner material and form chemical bonds. At the same time, the microscopic roughness of the paint film surface provides a mechanical interlocking effect, thereby improving the bonding strength between the metal bottle valve seat and the plastic liner material.

[0016] According to a second aspect of the embodiments of the present invention, An electronic device is provided, comprising: processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the aforementioned method.

[0017] According to a third aspect of the embodiments of the present invention, A computer-readable storage medium is provided, on which computer program instructions are stored. When the computer program instructions are executed by a processor, the method described above is implemented.

[0018] The beneficial effects of the present invention are as follows: The present invention forms an oxide film layer with a micron-scale pore structure on the surface of the metal bottle valve seat of the IV type hydrogen storage bottle through a surface treatment process, effectively increasing the interface bonding strength between the metal bottle valve seat and the plastic liner, and solving the problem that the joint between the plastic liner and the metal bottle valve seat in the IV type hydrogen storage bottle is weak and prone to failure when subjected to high pressure and periodic dynamic loads.

[0019] Phosphate-based chemical sealants are used to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the area in contact with gas, effectively preventing high-pressure gas from penetrating through the micropores to the metal-plastic interface, improving the airtightness and safety of Type IV hydrogen storage bottle products and extending their service life.

[0020] High-temperature resistant polyimide-based anodic electrophoretic paint and graded temperature curing treatment are applied to the area combined with the plastic liner to form a stable polyimide paint film. This not only enhances the interfacial adhesion between metal and plastic, but also improves the stability of the overall structure of the Type IV hydrogen storage bottle in high and low temperature alternating environments, significantly enhancing the product's adaptability in extreme environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of a method for treating the surface of a valve seat integrated with the inner tank interface of a Type IV hydrogen storage bottle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0023] The following specific embodiments are used to describe the technical solution of the present invention in detail. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0024] Figure 1 This is a flow chart of a method for treating the surface of a valve seat of a type IV hydrogen storage bottle in conjunction with the inner tank according to an embodiment of the present invention. Figure 1 As shown, the method includes the following steps: 1) Use spray degreasing liquid to pre-degrease the metal bottle valve seat, and then perform main degreasing on the pre-degreased metal bottle valve seat by immersion combined with ultrasonic vibration. Use deionized water to clean the degreased metal bottle valve seat once to remove residual degreasing agent. 2) The surface of the metal bottle valve seat after the primary cleaning is adjusted using phosphoric acid to remove trace metal impurities on the surface. The metal bottle valve seat after the surface adjustment is then cleaned again using deionized water combined with ultrasonic vibration to form a uniform active layer on the surface of the metal bottle valve seat for the subsequent formation of the aluminum oxide film. 3) Using the secondary cleaned metal bottle valve seat as the anode, electrolysis is performed using a mixture of phosphoric acid and oxalic acid as the electrolyte. By regulating the voltage, current density, electrolyte temperature, and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the aluminum oxide film is then rinsed with pure water to remove impurities in the initial pores. 4) The aluminum oxide film with initial pores is pickled and expanded, and anodized and pickled repeatedly until a micron-sized pore structure is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the micron-sized pore structure is cleaned with pure water; 5) preparing a phosphate-based chemical sealant, and using the phosphate-based chemical sealant to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the area in contact with the gas to prevent gas penetration; 6) Apply high-temperature resistant polyimide-based anodic electrophoretic paint and perform graded temperature-raising curing treatment to form a polyimide paint film in the area bonded to the plastic liner to improve the bonding strength.

[0025] Regarding step 2), that is, the surface of the metal bottle valve seat after the primary cleaning is adjusted using phosphoric acid to remove trace metal impurities on the surface, and the surface-adjusted metal bottle valve seat is secondary cleaned using deionized water combined with ultrasonic vibration to form a uniform active layer on the surface of the metal bottle valve seat for subsequent formation of the aluminum oxide film. An optional embodiment thereof includes the following steps: The first step is to prepare a phosphoric acid solution of a predetermined concentration. The concentration can range from 5% to 20%, with 10% being preferred. To prepare the solution, take 100 grams (equivalent to 53.5 milliliters) of analytical grade phosphoric acid, add 900 milliliters of deionized water, and stir thoroughly to obtain a 10% solution. It is important to note that the preparation process should be performed in a fume hood, wearing protective gloves and goggles to prevent damage to the skin and eyes. The selection of the phosphoric acid solution concentration has been rigorously verified: below 5%, the reaction rate on the metal bottle valve seat surface is too slow to form a sufficiently thick active layer within 15 minutes; above 20%, the surface reaction is too intense, easily leading to localized excessive corrosion. Orthogonal experiments have shown that at a concentration of 10%, the reaction rate is moderate, allowing a uniform active layer of 0.5 to 2 microns to form within the specified time.

[0026] The second step is to heat the prepared phosphoric acid solution to a preset temperature. The preset temperature can be between 40°C and 70°C, preferably 60°C. A constant temperature water bath can be used for heating. Place the container containing the phosphoric acid solution in the water bath, set the temperature to 60°C, and wait for the solution temperature to reach the preset value. Use a thermometer to monitor the solution temperature in real time to ensure that the temperature is stable within a range of 2°C above and below the preset value. The temperature is controlled using a PID system to control the fluctuation range within ±1°C. Experiments have shown that when the temperature is below 40°C, the reaction activity on the surface of the metal bottle valve seat is insufficient, and the active layer grows slowly and unevenly; when the temperature is above 70°C, the volatilization of the phosphoric acid solution intensifies, which is not conducive to the stable progress of the reaction. A process temperature of 60°C ensures a moderate and controllable reaction rate.

[0027] The third step is to immerse the metal bottle valve seat in a heated phosphoric acid solution for surface treatment. The immersion time can be set to 5 minutes to 30 minutes, preferably 15 minutes. During this process, the phosphoric acid solution undergoes a step-by-step chemical reaction with the surface of the metal bottle valve seat. The aluminum atoms on the surface of the metal bottle valve seat react with the hydrogen ions in the solution to generate aluminum ions and hydrogen. The generated hydrogen escapes the solution in the form of bubbles. The aluminum ions further react with phosphate ions to generate aluminum phosphate. Through this series of reactions, a reaction product layer containing aluminum phosphate is formed on the surface of the metal bottle valve seat, and the metal impurities on the surface are also dissolved or loosened.

[0028] After the soaking treatment is complete, remove the valve seat from the metal bottle and briefly rinse it with deionized water to remove any phosphoric acid solution adhering to the surface. The deionized water used for rinsing should be kept between room temperature (20°C and 25°C). Repeat this rinse process three times, using 50 ml of deionized water each time.

[0029] The fourth step is to perform fixed-frequency ultrasonic cleaning on the metal bottle valve seat after the reaction. The metal bottle valve seat is placed in an ultrasonic cleaner filled with deionized water, and the ultrasonic frequency is set to 40kHz, the power is set to 300W, and the cleaning time is 10 minutes. Under the action of ultrasound, a large number of tiny bubbles, namely cavitation bubbles, are generated in the cleaning liquid. These cavitation bubbles expand and contract rapidly under the action of sound pressure, and eventually collapse and generate powerful shock waves. The shock wave acts on the surface of the metal bottle valve seat, which can effectively remove the loose reaction product layer and surface impurities, while retaining the firmly attached aluminum phosphate active layer. The selection of a frequency of 40kHz is based on the optimization of the cavitation effect: the average diameter of the cavitation bubbles generated at this frequency is 30 microns, and a local pressure of 100MPa can be generated when collapsing. The microjet velocity generated by the collapse of the cavitation bubble reaches 150m / s. The combination of these parameters can effectively remove surface impurities without destroying the already formed aluminum phosphate active layer.

[0030] During the cleaning process, you can observe that the cleaning solution becomes slightly turbid. This is because surface impurities and some reaction products are stripped away and dispersed in the cleaning solution. To improve the cleaning effect, you can replace the deionized water once during the cleaning process, and keep the total cleaning time at 10 minutes.

[0031] After constant-frequency ultrasonic cleaning, the aluminum phosphate reaction product remains firmly attached to the surface of the metal cylinder valve seat, forming a uniform active layer. This active layer possesses excellent chemical activity and surface roughness, providing an ideal foundation for the subsequent formation of an aluminum oxide film. The active layer is approximately 0.5 to 2 microns thick and exhibits a uniform light gray color.

[0032] After treatment, the metal bottle valve seat can be rinsed with anhydrous ethanol and then dried at 60°C for 10 minutes to remove surface moisture. The surface active layer of the metal bottle valve seat treated in this way is uniform and stable, and can be directly used in the subsequent aluminum oxide film formation process.

[0033] Regarding step 3), the metal bottle valve seat after secondary cleaning is used as the anode, and a mixture of phosphoric acid and oxalic acid is used as the electrolyte for electrolysis. By regulating the voltage, current density, electrolyte temperature and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat. An optional implementation method includes: Prepare an oxalic acid solution and place it in a reaction vessel, slowly add the phosphoric acid solution dropwise while continuously stirring, monitor the pH value during the addition process, stop adding when the pH value drops to the target range, let it stand until the solution becomes clear, and then filter to obtain a mixed electrolyte; Precooling the mixed electrolyte to below room temperature, immersing the metal bottle valve seat as an anode in the mixed electrolyte, applying an electric field in a constant voltage mode, and then gradually increasing the voltage to a first preset voltage at a fixed rate, during which ions in the mixed electrolyte directionally migrate under the drive of the electric field, and aluminum atoms on the surface of the metal bottle valve seat undergo an oxidation-reduction reaction with hydrogen ions that migrate to the surface to generate aluminum ions. The aluminum ions, under the action of the local electric field, directionally combine with anions in the electrolyte to form aluminum oxide, and are deposited on the surface of the metal bottle valve seat to form an initial aluminum oxide film; As the aluminum oxide film forms, the conductivity of the valve seat decreases, causing the current to slowly drop. The mixed electrolyte temperature is maintained constant. When the monitored current drops to half of its initial value, the voltage is lowered to a second preset voltage and held constant, while the electrolyte temperature is raised to a predetermined temperature. At this point, the initial aluminum oxide film continues to deposit and thicken under the action of the electric field, while the surface layer partially dissolves under the action of the electrolyte. By regulating the dynamic balance between deposition and dissolution, a uniformly distributed honeycomb pore structure forms on the surface of the initial aluminum oxide film, forming an aluminum oxide film with initial pores on the surface of the metal bottle valve seat.

[0034] Before electrolysis, the metal cylinder valve seat needs to be masked to ensure that only the areas where the aluminum oxide film is to be formed are anodized. Masking can be done in two ways: First, use acid- and alkali-resistant polyimide tape to carefully cover the areas not to be anodized, ensuring a tight fit between the tape and the metal surface to prevent electrolyte penetration. Second, use a custom silicone protective sleeve to completely cover the areas not to be treated. The silicone protective sleeve should have good sealing and corrosion resistance, and remain stable during the electrolysis process. The choice of masking material and the accuracy of the masking operation directly affect the quality and effectiveness of the anodizing process.

[0035] The preparation of electrolyte is one of the key steps of this method. In actual operation, 0.3mol / L oxalic acid solution is first prepared, 37.8g oxalic acid dihydrate is dissolved in deionized water, placed in a 1000mL volumetric flask and deionized water is added to the scale, while using a magnetic stirrer to continuously stir with a speed of 300rpm. Under stirring, a phosphoric acid solution with a volume percentage of 85% is slowly added dropwise using a titration funnel, and the drop rate is controlled at 2mL per minute. The pH value of the solution is monitored in real time using a pH meter during the addition process, and the addition is stopped when the pH value drops to 1.5. The mixed solution is then left to stand for 2 hours, and after the solution is completely clarified, it is filtered using a 0.45μm polytetrafluoroethylene filter membrane to obtain a clear and transparent mixed electrolyte. The selection of the mixed electrolyte ratio is based on the electrolytic reaction kinetics: the oxalic acid concentration of 0.3 mol / L is determined based on its dissolution rate of the aluminum oxide film. Concentrations below this level result in slow pore formation, while concentrations above this level tend to cause excessive dissolution. The amount of phosphoric acid added is controlled by the pH value of 1.5, at which the mixed solution has optimal conductivity and dissolution capacity. Experiments have shown that the oxide film formed at this ratio has the best pore uniformity and aspect ratio.

[0036] The mixed electrolyte requires temperature control before electrolysis. The prepared mixed electrolyte is placed in an electrolytic cell equipped with a temperature control system. A refrigeration cycle is used to cool the electrolyte to a constant temperature of 5°C. The cleaned metal bottle valve seat is secured to a custom anode fixture to ensure a good connection with the anode. A high-purity graphite plate is used as the cathode, with an area approximately three times the anode surface area, and the distance between the cathode and the cathode is maintained at 5 cm. The secured metal bottle valve seat is completely immersed in the pre-cooled mixed electrolyte to a depth that ensures the treated surface is completely immersed and held vertically. Temperature control during the electrolysis process is crucial for the formation of pore structures. An initial low temperature of 5°C helps suppress the dissolution rate of the oxide film, ensuring the formation of a dense base layer. Later, heating to 15°C promotes moderate dissolution and forms a regular pore structure. A PID control system is used to control temperature fluctuations within ±0.5°C to ensure uniformity during the dissolution process.

[0037] The initial electrolysis phase is performed in constant voltage mode. The DC power supply is started and the voltage is gradually increased at a fixed rate from the initial voltage setting to the first preset voltage, while the initial current density is recorded. During this process, H⁺ ions in the electrolyte migrate toward the cathode, driven by the electric field, while anions such as C₂O₄²⁻ migrate toward the anode. Aluminum atoms on the surface of the metal bottle valve seat lose electrons and are oxidized to Al⁺. Simultaneously, H⁺ ions are reduced at the cathode to produce hydrogen, causing the solution acidity to decrease. Under weakly acidic or neutral conditions, aluminum ions form Al₂O₃, which deposits on the surface of the metal bottle valve seat to form an initial aluminum oxide film. During the electrolysis process, a stirrer is used to maintain a uniform electrolyte temperature at 100 rpm. The voltage regulation strategy is designed based on the kinetics of oxide film growth: an initial voltage of 5V is used to activate the surface and form a uniform oxide layer, and a voltage ramp rate of 0.5V / min ensures a dynamic balance between ion migration and oxidation reactions. When the current drops to half of its initial value, it indicates that the oxide film has reached a certain thickness. At this time, lowering the voltage is beneficial to controlling the pore growth rate and avoiding local breakdown.

[0038] When the monitored current drops to half its initial value, the voltage is lowered to a second preset voltage and held constant. Simultaneously, the electrolyte temperature is increased from 5°C to 15°C at a rate of 1°C / min. During this phase, the growth and dissolution of the aluminum oxide film reach a dynamic equilibrium. The aluminum oxide film continues to deposit and thicken on the surface of the metal bottle valve seat. Simultaneously, the phosphoric acid and oxalic acid in the electrolyte partially dissolve the surface of the aluminum oxide film, forming a uniformly distributed honeycomb pore structure.

[0039] In a specific example, a metal bottle valve seat made of a high-purity aluminum alloy with a mass percentage of 99.5% was used as a sample. After cleaning, it was placed in a mixed electrolyte of oxalic acid and phosphoric acid at a temperature of 5°C. The initial voltage was 5V, and it was increased to 30V at a rate of 5V / min. The current density was initially 5mA / cm² and increased to 25mA / cm². When the current dropped to 12.5mA / cm², the voltage was adjusted to 20V, the temperature was raised to 15°C, and electrolysis was continued for 6 minutes. Finally, an aluminum oxide film with a thickness of 20μm was formed on the surface of the metal bottle valve seat. The surface of the film had a uniform honeycomb structure, a pore diameter of 60nm, a pore depth of 12μm, and a pore density of 5×10 9 Scanning electron microscope observation shows that the pores are evenly distributed and the structure is stable, providing an ideal foundation for subsequent sealing treatment.

[0040] After the electrolysis is complete, the metal bottle valve seat is removed from the electrolyte and immediately rinsed with deionized water at least three times, each time for at least 1 minute, to remove residual electrolyte. The sample is then immersed in deionized water for ultrasonic cleaning for 5 minutes, rinsed again with deionized water, and finally dried at 80°C for 30 minutes to obtain a metal bottle valve seat with an aluminum oxide film with initial porosity.

[0041] Regarding step 4), that is, performing pickling and pore enlargement treatment on the aluminum oxide film with initial pores, and repeatedly performing anodizing and pickling and pore enlargement treatment until a micron-scale pore structure is formed on the surface of the metal bottle valve seat, an optional implementation method includes: The aluminum oxide film having initial pores is immersed in an acidic solution for pickling. By controlling the concentration and temperature of the acidic solution, different dissolution rates are generated at the pore walls of the initial pores. Driven by the difference in dissolution rates, the initial pores evolve into a circular shape to form a regular array of pits. The metal bottle valve seat is anodized using the regular pit array as a nucleation site, and a constant voltage is applied to cause the oxidation reaction to proceed preferentially at the regular pit array. The geometric morphology of the regular pit array guides the growth orientation of the aluminum oxide layer, forming a new aluminum oxide layer at the regular pit array. The pores in the new aluminum oxide layer inherit the spatial distribution characteristics of the regular pit array and grow directionally in a vertical direction, forming a periodically arranged pore structure. The anodizing treatment and the pickling treatment are repeated, wherein the voltage value of the anodizing treatment controls the spacing between adjacent pores, and the voltage value is proportional to the resulting spacing; the time of the pickling treatment controls the degree of expansion of the pores, and the treatment time is proportional to the resulting pore diameter; by gradually increasing the voltage value and extending the pickling treatment time, the pore structure is gradually enlarged and maintained in a regular arrangement under the drive of surface energy, until a uniformly distributed micron-scale pore structure is formed on the surface of the metal bottle valve seat.

[0042] In a specific example, an aluminum oxide film with initial pores is first obtained by performing a first anodizing treatment on the metal bottle valve seat: the metal bottle valve seat is placed in a 0.3M oxalic acid solution, the temperature is controlled at 10°C, and a constant voltage of 40V is applied for 6 minutes of anodizing treatment to form an aluminum oxide film with initial pores on the surface of the metal bottle valve seat. The pore diameter of the initial pores is about 100~200nm, and the pore arrangement is disordered.

[0043] The alumina membrane with initial pores was immersed in a 0.5M phosphoric acid solution for pickling and pore expansion treatment. The solution temperature was controlled at 35°C and the treatment time was 10 minutes. During the pickling process, the dissolution rate was different due to the uneven stress distribution at different positions of the pore wall of the initial pores. Specifically, the dissolution rate of the area with greater stress on the pore wall was faster, and the dissolution rate of the area with less stress was slower. This difference in dissolution rate drives the initial pores to gradually evolve into a circle, eventually forming a regular array of pits. After this step of treatment, the diameter of the pits expanded to about 200~220nm, and the arrangement became more regular.

[0044] The metal bottle valve seat was anodized for the second time using the above-mentioned regular pit array as the nucleation site. The metal bottle valve seat was placed in a 0.3M oxalic acid solution again, the temperature was controlled at 10°C, and a constant voltage of 40V was applied for anodization for 8 minutes. During this process, the oxidation reaction preferentially occurs at the regular pit array, and the geometric morphology of the pits guides the aluminum oxide layer to grow in a specific direction. The pores in the newly generated aluminum oxide layer inherit the spatial distribution characteristics of the regular pit array and grow directionally in a direction perpendicular to the surface of the metal bottle valve seat, forming a periodically arranged pore structure. After this step of treatment, the obtained aluminum oxide film has a thickness of about 7 microns, a pore diameter of about 40nm, and a spacing between adjacent pores of about 100nm.

[0045] The alumina membrane with periodic pore structure was immersed in 0.5M phosphoric acid solution for a second pickling treatment. The temperature was controlled at 35°C and the treatment time was extended to 15 minutes. During this pickling process, the pore diameter was further expanded to about 800~1000nm, reaching the submicron level. During the third anodization treatment, the voltage was increased to 60V, the 0.3M oxalic acid solution was still used, the temperature was controlled at 10°C, and the treatment time was 10 minutes. As the voltage increased, the spacing between adjacent pores increased to approximately 150nm, and the pore diameter also increased accordingly. The voltage and pore spacing showed a linear positive correlation: at a voltage of 40V, the pore spacing was approximately 100nm; at a voltage of 60V, the pore spacing was approximately 150nm; and at a voltage of 80V, the pore spacing was approximately 200nm.

[0046] The third pickling treatment uses a 0.5M phosphoric acid solution at 35°C for 20 minutes. During this process, the pore diameter expands to approximately 300-350nm (1.2-1.5μm), reaching the micron level.

[0047] Through repeated anodizing and pickling pore-expanding treatments, a uniformly distributed micron-scale pore structure is formed on the surface of the metal bottle valve seat. The pore diameter is 1.2-1.5μm, the spacing between adjacent pores is approximately 300nm, and the pore depth is approximately 10μm. This micron-scale pore structure has good regularity and uniformity, with a relative standard deviation of pore size less than 5%. It can meet the special functional requirements of the metal bottle valve seat surface, such as improving surface wettability, enhancing surface adhesion, and improving heat exchange efficiency.

[0048] In practical applications, the anodizing voltage, pickling time, and number of repetitions can be adjusted according to specific needs to achieve micron-scale pore structures of varying sizes and depths. For example, if a larger pore diameter is desired, the pickling time can be appropriately extended; if a larger pore spacing is desired, the anodizing voltage can be appropriately increased.

[0049] Regarding step 5), i.e., preparing a chemical sealant, and using the chemical sealant to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the area in contact with the gas to prevent gas penetration, an optional implementation method includes: dissolving phosphate in deionized water according to a preset mass fraction to prepare a phosphate-based liquid, adding a surfactant dropwise to the phosphate-based liquid under constant temperature stirring conditions, monitoring the surface tension of the phosphate-based liquid in real time using a surface tension tester, and stopping the addition when the surface tension drops to a level sufficient to generate capillary force on the pore size of the micron-sized pore structure, thereby preparing a phosphate-based chemical sealant; Applying the phosphate-based chemical sealant to the gas contact area of ​​the valve seat of the metal bottle, wherein the phosphate-based chemical sealant spontaneously penetrates into the micron-sized pore structure under the action of capillary force, and controlling the infiltration time and temperature of the phosphate-based chemical sealant to form a concentration gradient distribution along the depth direction of the micron-sized pore structure and fill the micron-sized pore structure to a predetermined depth; The metal bottle valve seat that has completed gradient infiltration is heat-treated to allow the phosphate in the phosphate-based chemical sealant to chemically react with the aluminum oxide on the surface of the micron-sized pore structure and form a chemical bond, thereby forming a phosphate sealing layer with a dense structure in the gas contact area to prevent gas infiltration.

[0050] In this embodiment, a gradient permeation sealing method for the micron-scale pore structure of a metal bottle valve seat is described in detail. By preparing a special phosphate-based chemical sealant, the gas contact area is effectively sealed to prevent gas permeation and leakage.

[0051] The preparation process of phosphate-based chemical sealers includes two key steps: base liquid preparation and surface activity control. In the base liquid preparation stage, analytically pure sodium dihydrogen phosphate, disodium hydrogen phosphate, and trisodium phosphate are mixed in a mass ratio of 3:5:2, and the total mass percentage is 12% and dissolved in deionized water. In the specific operation, 400ml of deionized water is added to a 500ml beaker, and 14.4g of sodium dihydrogen phosphate, 24.0g of disodium hydrogen phosphate, and 9.6g of trisodium phosphate are weighed using a precision electronic balance, and slowly added to the water. Use a magnetic stirrer to stir at a rate of 250rpm at room temperature for 30 minutes to ensure that the phosphate is completely dissolved to form a uniform and transparent base liquid.

[0052] During the surface activity regulation stage, sodium lauryl sulfate surfactant was added dropwise to the phosphate base liquid at a constant temperature of 25°C using a magnetic stirrer maintained at a stirring rate of 200 rpm. A JYW-200C surface tension tester was used to monitor the surface tension changes of the base liquid in real time. The initial surface tension was 72.5 mN / m, and the surface tension gradually decreased with the addition of surfactant. When the added surfactant reached 0.08% of the base liquid mass, the surface tension dropped to 32.5 mN / m, at which point sufficient capillary force could be generated for pore structures with a diameter of 1-10 μm, and the addition of surfactant was stopped. Stirring was continued for 15 minutes to fully mix the solution to obtain a phosphate-based chemical sealant.

[0053] Before the gradient penetration sealing treatment, the metal cylinder valve seat was pretreated. First, the gas contact area was polished with 80# sandpaper to remove surface impurities and oxide layers. Then, ultrasonic cleaning was performed with acetone for 5 minutes to remove surface oil. Finally, the surface was rinsed with deionized water and allowed to air dry. After pretreatment, the micron-scale pore structure of the metal cylinder valve seat surface was clearly visible, which facilitated the penetration of the sealant.

[0054] The gradient penetration sealing process is implemented by the immersion method. Pour the prepared phosphate-based chemical sealant into the immersion container so that the liquid level reaches 20mm. Place the pretreated metal bottle valve seat on a special fixing rack so that the gas contact area is immersed in the sealant, and the liquid level is 5mm higher than the upper edge of the gas contact area. Immerse for 30 minutes at room temperature. At this time, the sealant spontaneously penetrates into the micron-scale pore structure to a depth of about 50μm under capillary force. Continue to raise the temperature to 40°C and maintain immersion at constant temperature for 60 minutes. The sealant further penetrates to a depth of about 120μm. Take out the metal bottle valve seat, gently wipe off the excess liquid on the surface with a soft cloth, and let it dry naturally at room temperature for 30 minutes.

[0055] After gradient infiltration, heat treatment and curing are performed. The treated metal bottle valve seat is placed in an oven preheated to 80°C and heated at a rate of 2°C / min to 120°C, held for 30 minutes, and then heated to 180°C at a rate of 2°C / min for 60 minutes. During this heat treatment, the phosphate reacts chemically with the aluminum oxide on the surface of the micron-sized porous structure, forming a stable aluminum-phosphate compound and a chemically bonded, hermetic sealing layer. After heat treatment, the valve seat is allowed to cool naturally to room temperature.

[0056] The gradient permeation sealing effect was verified by airtightness test. The test used a helium mass spectrometer leak detector to compare the metal bottle valve seat before and after treatment. The average leakage rate of the metal bottle valve seat before treatment was 1.2×10 -5 Pa·m³ / s; after gradient penetration sealing treatment with phosphate-based chemical sealant, under the same test conditions, the average leakage rate dropped to 3.5×10-9 Pa·m³ / s, which is reduced by about 3400 times and reaches the application standard of high-pressure gas.

[0057] Microstructural analysis shows that within the gas contact area, the phosphate concentration reaches 10.5% from the surface to a depth of 20 μm, forming a tightly sealed layer. From 20 to 80 μm, the phosphate concentration gradually decreases to 6.8%, forming a transition layer. From 80 to 120 μm, the phosphate concentration further decreases to 2.3%, forming a diffusion layer. This gradient distribution structure not only ensures the compactness of the surface sealing layer, but also strengthens the bond between the sealing layer and the substrate through the transition and diffusion layers, effectively preventing gas permeation.

[0058] Through the precise preparation of the above-mentioned chemical sealants and the gradient penetration sealing process, the micron-level pore structure of the metal bottle valve seat is effectively sealed, which significantly improves the airtightness of the metal bottle valve seat, prevents gas penetration and leakage, and ensures the safety of high-pressure gas storage.

[0059] Regarding step 6), a high-temperature resistant polyimide-based anodic electrophoretic paint coating and a graded temperature-raising curing process are performed to form a polyimide paint film in the area bonded to the plastic liner, thereby improving the bonding strength. An optional implementation method includes: preparing an anodic electrophoretic paint containing a preset content of polyimide resin, measuring the mobility of charged particles of the anodic electrophoretic paint, and determining a voltage control parameter in electrophoresis according to the mobility of the charged particles; Electrophoretic coating is performed using a three-stage voltage control method according to the voltage control parameters, and the switching time of each stage is determined by real-time monitoring of the electrophoretic current: in the initial stage, a first preset voltage is applied to cause the charged colloid particles to migrate to the surface of the metal bottle valve seat to form an initial covering layer; in the middle stage, the voltage is increased to a second preset voltage to maintain a constant deposition rate to allow the initial covering layer to grow; and in the final stage, the voltage is reduced to a third preset voltage to enhance the density of the initial covering layer to a preset degree; The metal bottle valve seat after electrophoresis is subjected to a graded temperature-raising curing treatment, wherein the graded temperature-raising curing treatment includes: a first preset temperature is used in the primary stage to flatten the paint film surface by solvent volatilization; a second preset temperature is used in the intermediate stage to catalyze the cross-linking of polyimide molecular chains to increase the paint film strength to a preset degree; and a third preset temperature is used in the advanced stage to cure the paint film and form a polyimide paint film on the surface of the metal bottle valve seat; The polar groups on the surface of the polyimide paint film undergo molecular chain entanglement with the liner material and form chemical bonds. At the same time, the microscopic roughness of the paint film surface provides a mechanical interlocking effect, thereby improving the bonding strength between the metal bottle valve seat and the plastic liner material.

[0060] In this embodiment, a method of high-temperature resistant polyimide-based anodic electrophoretic paint coating and graded temperature-raising curing treatment is provided to improve the bonding strength between the metal bottle valve seat and the plastic liner.

[0061] When preparing anodic electrophoretic paint, high-performance polyimide resin is selected as the main film-forming material, and the resin solid content is controlled within the range of 25%-35%. Specifically, 20kg of polyimide resin is mixed with 5kg of modified epoxy resin, 2kg of dispersant and 1kg of cosolvent are added, and the mixture is dispersed at 2000rpm in a high-speed disperser for 30 minutes to obtain a uniform resin mixture. Subsequently, 72kg of deionized water is added and stirring is continued for 15 minutes to form a stable emulsion system. In order to adjust the pH value to the appropriate range of 5.5-6.5, acetic acid solution is slowly added dropwise while monitoring the pH change until it stabilizes. After the preparation is completed, the average particle size of the colloid particles is measured using a laser particle size analyzer to ensure that it is within the range of 50-150nm, which is conducive to stable migration during the electrophoresis process. The resin system formulation process requires strict control of the following conditions: The mixing process temperature is maintained at 40±5°C, a range that ensures thorough mixing without pre-cooking the resin. The dispersion process utilizes a 100mm diameter high-speed dispersing impeller at 2000rpm, ensuring sufficient shear without overheating the system. The mass ratio of polyimide to modified epoxy resin is maintained at 4:1, a ratio that has demonstrated the optimal balance between temperature resistance and adhesion in experimental verification.

[0062] Measuring the mobility of charged particles is crucial for determining voltage control parameters. Using an electrophoretic mobility tester, an electric field strength of 10 V / cm was applied under standard conditions (25°C, 60% relative humidity) to measure the migration distance of the particles within 10 seconds. In a practical case, the mobility of polyimide particles was measured to be 2.8×10 -4 cm² / (V·s). Based on this mobility, combined with the surface area of ​​the metal bottle valve seat (approximately 120 cm²) and the desired initial deposition time (60 seconds), the appropriate voltage for the first stage is calculated to be 50-80V, 180-220V for the middle stage, and 100-130V for the final stage. During electrophoresis, the migration rate of the colloid particles is linearly related to the electric field strength. When the electrode spacing is fixed at 15cm, the actual migration rate of the colloid particles at 60V is approximately 0.11cm / s, which ensures sufficient coverage without causing a loose film. As the paint film forms, the resistance gradually increases, necessitating a corresponding increase in voltage to maintain an appropriate deposition rate. This is the fundamental reason for adopting three-stage voltage control.

[0063] The electrophoretic coating process adopts a three-stage voltage control strategy to achieve precise film thickness and quality control. In the electrophoretic tank, the temperature of the anodic electrophoretic paint is adjusted to 28±2°C, the pH value is maintained at 6.0±0.2, and the conductivity is controlled at 1200-1400μS / cm. The metal bottle valve seat serves as the cathode and the stainless steel plate serves as the anode. In the initial stage, a voltage of 60V is applied for 70 seconds to allow the charged colloid particles to migrate to the metal surface to form an initial covering layer. By real-time monitoring of the current change, when the current drops from the initial 3.6A to 2.8A, it indicates that the initial coverage has been formed, and the intermediate stage is entered. In the intermediate stage, the voltage is increased to 200V and maintained for 120 seconds to maintain a relatively stable deposition rate, so that the paint film gradually thickens. During this stage, the current is maintained in the range of 2.5-2.7A. When the current drops to 2.2A, the final stage begins, and the voltage is reduced to 110V for 80 seconds to enhance film density. During this stage, the current slowly decreases to 1.8A and stabilizes, indicating that the film has reached the desired thickness of 20-25μm and has good density. During the three-stage voltage control process, the film growth status is determined by real-time monitoring of current density changes: the initial current density starts at 0.03A / cm² and enters the intermediate stage when it drops to 0.023A / cm²; the intermediate stage is maintained at around 0.02A / cm² to ensure stable deposition; and the final stage, the current density gradually decreases to 0.015A / cm² and stabilizes, indicating that film growth is essentially complete. Throughout the process, if the current density fluctuates by more than ±10%, the electrophoretic fluid condition and electrode connections should be immediately checked.

[0064] After electrophoresis, the metal bottle valve seat undergoes a simple water wash to remove any unadhered paint liquid from the surface before entering the staged temperature-increasing curing process. The curing oven utilizes a combination of infrared and hot air heating to ensure uniform heating. The primary stage temperature is set at 120±5°C for 30 minutes. This temperature allows the solvent in the paint film to evaporate slowly, preventing bubbles and promoting surface smoothness. Experience has shown that this stage increases the solids content of the paint film from the initial 85% to 93%. The secondary stage temperature is raised to 200±5°C for 45 minutes. This temperature initiates cross-linking of the polyimide molecular chains, increasing the film hardness from a pencil hardness of 2H to 5H, demonstrating significant film strength enhancement. The advanced stage temperature is further increased to 280±5°C for 60 minutes. At this temperature, the polyimide is fully cured, forming a highly cross-linked three-dimensional network structure. The film hardness reaches 7H and its temperature resistance increases to over 300°C. During the staged temperature-increasing curing process, the film structure undergoes significant changes: at 120°C, solvent volatilization and initial molecular chain movement occur, increasing the solids content to 93% while surface tension smoothes the film. At 200°C, the polyimide molecular chains partially crosslink, forming a preliminary network structure, and the film exhibits excellent mechanical strength. At 280°C, final crosslinking is achieved, and the molecular chains form a stable three-dimensional network, endowing the film with excellent temperature resistance and chemical stability. The hold times for each temperature stage are optimized to ensure sufficient reaction without wasting energy.

[0065] After this treatment, a uniform, dense polyimide film with a thickness of 22±3μm forms on the surface of the metal bottle valve seat. Its adhesion reaches level 0 (optimal), and its wear resistance exceeds 2,000 reciprocating friction cycles without noticeable damage. Atomic force microscopy reveals a surface microroughness of 50-200nm, a microstructure that facilitates mechanical interlocking with the plastic liner material. X-ray photoelectron spectroscopy analysis reveals that the film surface is rich in polar groups such as carbonyl and amide groups, accounting for 32% of the total surface groups.

[0066] When a metal bottle valve seat is bonded to a plastic liner material (such as polypropylene), at injection molding temperatures (220-240°C), polar groups on the paint film surface form molecular chain entanglements with the liner material, forming secondary chemical bonds such as hydrogen bonds. Tensile testing results show that the bond strength between the treated metal bottle valve seat and the plastic liner reached 2.8 MPa, a 366% increase compared to the untreated sample (0.6 MPa). After cyclic thermal shock testing (-40°C to 120°C, 500 cycles), the bond strength remained above 2.5 MPa, demonstrating the excellent long-term stability and temperature resistance of the bond interface.

[0067] Regarding the process implementation sequence of the present invention, a specific implementation method is as follows: The degreasing process removes grease and other impurities from the valve seat surface. Degreasing is divided into two steps: pre-degreasing and main degreasing. Spraying degreasing liquid is used to pre-remove some grease and impurities. The main degreasing process uses immersion and ultrasonic waves to remove grease and impurities on the metal valve seat surface. Deionized water is then used to wash away the remaining degreasing agent before entering the next process.

[0068] Use acid (such as phosphoric acid or nitric acid) to remove impurities on the valve seat surface, thereby obtaining a uniform and stable aluminum oxide film during the oxidation step. Use water washing again and ultrasonic waves to remove the acid in the pores.

[0069] During the oxidation process, a mixture of phosphoric acid and oxalic acid is used as the electrolyte, and the metal valve seat serves as the anode. As the aluminum oxide film forms, the valve seat's conductivity decreases until the anode potential drops to a specific value due to resistance loss, at which point the film thickness stops increasing. Strict control of voltage, current density, bath temperature, and bath concentration allows for precise control of the film thickness. The valve seat surface is then rinsed with pure water. Because the aluminum oxide film has a microporous structure, pure water is essential for cleaning to prevent impurities from tap water from settling in the film's pores.

[0070] The pores of the aluminum oxide film generated by oxidation are small. The pores are expanded by pickling and soaking, the barrier layer is removed, and then anodizing is used. The two steps are alternated to obtain micron-level pores.

[0071] Because the aluminum oxide film has pores on its surface, these pores are sealed using a potassium dichromate solution chemical sealant. The portion of the valve port that comes into direct contact with hydrogen needs to be completely sealed. The aluminum oxide film combined with pore sealing significantly blocks hydrogen erosion of the valve seat. Conversely, the interface between the valve seat and the liner does not need to be sealed. During the rotational molding process, the molten plastic liner material can fill the nano- and micron-scale pores, thereby promoting a close bond between the liner and the valve seat.

[0072] During the implementation process, it is not necessary to perform masking operations on the anodized area. The masking material can be covered with polyimide tape or with a silicone shell to cover the area that does not need to be treated.

[0073] Regarding the process implementation sequence of the present invention, another specific embodiment is as follows, including five steps: degreasing, pickling activation, passivation, electrophoresis, and curing: A degreasing process is used to remove grease and other impurities from the valve seat surface. Degreasing is divided into two steps: pre-degreasing and main degreasing. Spraying degreasing liquid is used to pre-remove some grease and impurities. The main degreasing process uses immersion and ultrasonic treatment to remove grease from the metal valve seat surface, which may affect the adhesion of the electrophoretic paint film. Deionized water is then used to wash away the remaining degreasing agent before proceeding to the next process.

[0074] Place the metal valve seat in a pickling solution (phosphoric acid / nitric acid) to remove the surface oxide layer or other impurities, then rinse with water again and use ultrasonic waves to remove the acid in the pores.

[0075] The passivation process uses trivalent chromium passivation solution. This process creates a dense aluminum oxide film on the valve seat surface. The trivalent chromium passivation layer also increases the density of active sites on the aluminum alloy surface, facilitating the adhesion of electrophoretic paint. The passivated valve seat is sprayed and soaked with pure water to remove any residual passivation solution.

[0076] The electrophoretic coating process uses polyimide-based electrophoretic paint. By precisely controlling the coating voltage, unit current density, and the concentrations of its components, the thickness of the polyimide coating film can be precisely controlled. Polyimide offers excellent performance and can withstand the high temperatures (around 300°C) encountered during the rotational molding process. Furthermore, the carbonyl and amino functional groups contained in polyimide can form an interfacial bond with the amino and carboxylic acid groups at the ends of the PA11 molecular chain through hydrogen bonding or chemical crosslinking.

[0077] After temperature gradient curing (80°C, 120°C, and 160°C), the resulting valve seat electrophoresis component has a polyimide coating film thickness of approximately 20 microns. The valve seat has threads at the bottle mouth. During electrophoresis, silicone plugs can be used to mask the threaded holes to prevent the polyimide-based electrophoretic paint from being applied to the threads, thus avoiding subsequent assembly problems with other parts. Other areas not requiring coating can be masked with high-temperature tape. If the head material used is susceptible to hydrogen corrosion, the voltage can be reduced and the electrophoresis time shortened to create a "thin coating" treatment. This procedure improves the valve seat's resistance to hydrogen corrosion without affecting assembly.

[0078] According to a second aspect of an embodiment of the present invention, an electronic device is provided, including: processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the aforementioned method.

[0079] According to a third aspect of an embodiment of the present invention, a computer-readable storage medium is provided, on which computer program instructions are stored. When the computer program instructions are executed by a processor, the method described above is implemented.

[0080] The present invention may be a method, an apparatus, a system and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for executing various aspects of the present invention.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for treating the surface of the valve seat of a type IV hydrogen storage bottle in conjunction with the inner tank, characterized in that: include: The metal bottle valve seat is pre-degreased by spraying degreasing liquid, and the pre-degreased metal bottle valve seat is subjected to main degreasing treatment by immersion combined with ultrasonic vibration. The degreased metal bottle valve seat is cleaned once with deionized water to remove residual degreasing agent. The surface of the metal bottle valve seat after the primary cleaning is adjusted using phosphoric acid to remove trace metal impurities on the surface. The metal bottle valve seat after the surface adjustment is then cleaned again using deionized water combined with ultrasonic vibration to form a uniform active layer on the surface of the metal bottle valve seat for the subsequent formation of the aluminum oxide film. The metal bottle valve seat after secondary cleaning is used as the anode, and a mixture of phosphoric acid and oxalic acid is used as the electrolyte for electrolysis. By regulating the voltage, current density, electrolyte temperature and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the aluminum oxide film is then cleaned with pure water to remove impurities in the initial pores. The aluminum oxide film with initial pores is pickled and expanded, and anodized and pickled repeatedly until a micron-sized pore structure is formed on the surface of the metal bottle valve seat. The metal bottle valve seat with the micron-sized pore structure is cleaned with pure water. A phosphate-based chemical sealant is prepared and used to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the area in contact with the gas to prevent gas penetration.

2. The method according to claim 1, characterized in that The surface of the metal bottle valve seat after the first cleaning is adjusted with phosphoric acid to remove trace metal impurities on the surface, and the metal bottle valve seat after the surface adjustment is cleaned for the second time with deionized water combined with ultrasonic vibration to form a uniform active layer on the surface of the metal bottle valve seat for the subsequent formation of the aluminum oxide film. The process includes: A phosphoric acid solution of a preset concentration is prepared, heated to a preset temperature, and the metal bottle valve seat is immersed in the phosphoric acid solution for a preset time for surface treatment, so that the phosphoric acid solution and the surface of the metal bottle valve seat undergo a step-by-step chemical reaction to produce a reaction product layer and surface impurities: aluminum atoms on the surface of the metal bottle valve seat react with hydrogen ions to produce aluminum ions and hydrogen gas, the hydrogen gas escapes from the solution, and the aluminum ions react with phosphate ions to produce aluminum phosphate; The metal bottle valve seat after the reaction is cleaned by fixed-frequency ultrasonic cleaning, whereby cavitation bubbles are formed on the surface of the metal bottle valve seat by the fixed-frequency ultrasonic cleaning, and the cavitation bubbles collapse under the action of the acoustic pressure and generate shock waves, which clean the reaction product layer and surface impurities on the surface of the metal bottle valve seat; After the reaction product layer is cleaned by the fixed-frequency ultrasonic cleaning, the aluminum phosphate reaction product remains on the surface of the metal bottle valve seat to form an active layer, and the active layer is used for the subsequent generation of an aluminum oxide film.

3. The method according to claim 1, characterized in that The metal bottle valve seat after secondary cleaning is used as the anode, and a mixture of phosphoric acid and oxalic acid is used as the electrolyte for electrolysis. By regulating the voltage, current density, electrolyte temperature and electrolyte concentration, an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat. The following steps are involved: Prepare an oxalic acid solution and place it in a reaction vessel, slowly add the phosphoric acid solution dropwise while continuously stirring, monitor the pH value during the addition process, stop adding when the pH value drops to the target range, let it stand until the solution becomes clear, and then filter to obtain a mixed electrolyte; Precooling the mixed electrolyte to below room temperature, immersing the metal bottle valve seat as an anode in the mixed electrolyte, applying an electric field in a constant voltage mode, and then gradually increasing the voltage to a first preset voltage at a fixed rate, during which ions in the mixed electrolyte directionally migrate under the drive of the electric field, and aluminum atoms on the surface of the metal bottle valve seat undergo an oxidation-reduction reaction with hydrogen ions that migrate to the surface to generate aluminum ions. The aluminum ions, under the action of the local electric field, directionally combine with anions in the electrolyte to form aluminum oxide, and are deposited on the surface of the metal bottle valve seat to form an initial aluminum oxide film; The temperature of the mixed electrolyte is maintained constant. When the monitored current drops to half of the initial value, the voltage is lowered to a second preset voltage and maintained constant, while the electrolyte temperature is increased to a predetermined temperature. At this time, the initial aluminum oxide film continues to deposit and thicken under the action of the electric field, while the surface layer is partially dissolved under the action of the electrolyte. By regulating the dynamic balance of deposition and dissolution, a uniformly distributed honeycomb pore structure is formed on the surface of the initial aluminum oxide film, and an aluminum oxide film with initial pores is formed on the surface of the metal bottle valve seat.

4. The method according to claim 1, wherein The aluminum oxide film with initial pores is pickled and pore-enlarged, and anodized and pickled repeatedly until a micron-scale pore structure is formed on the surface of the metal bottle valve seat. The aluminum oxide film having initial pores is immersed in an acidic solution for pickling. By controlling the concentration and temperature of the acidic solution, different dissolution rates are generated at the pore walls of the initial pores. Driven by the difference in dissolution rates, the initial pores evolve into a circular shape to form a regular array of pits. The metal bottle valve seat is anodized using the regular pit array as a nucleation site, and a constant voltage is applied to cause the oxidation reaction to proceed preferentially at the regular pit array. The geometric morphology of the regular pit array guides the growth orientation of the aluminum oxide layer, forming a new aluminum oxide layer at the regular pit array. The pores in the new aluminum oxide layer inherit the spatial distribution characteristics of the regular pit array and grow directionally in a vertical direction, forming a periodically arranged pore structure. The anodizing treatment and the pickling treatment are repeated, wherein the voltage value of the anodizing treatment controls the spacing between adjacent pores, and the voltage value is proportional to the resulting spacing; the time of the pickling treatment controls the degree of expansion of the pores, and the treatment time is proportional to the resulting pore diameter; by gradually increasing the voltage value and extending the pickling treatment time, the pore structure is gradually enlarged and maintained in a regular arrangement under the drive of surface energy, until a uniformly distributed micron-scale pore structure is formed on the surface of the metal bottle valve seat.

5. The method according to claim 1, characterized in that The method comprises preparing a phosphate-based chemical sealant, and using the phosphate-based chemical sealant to perform gradient penetration sealing and heat treatment on the micron-scale pore structure in the gas contact area to prevent gas penetration, comprising: dissolving phosphate in deionized water according to a preset mass fraction to prepare a phosphate-based liquid, adding a surfactant dropwise to the phosphate-based liquid under constant temperature stirring conditions, monitoring the surface tension of the phosphate-based liquid in real time using a surface tension tester, and stopping the addition when the surface tension drops to a level sufficient to generate capillary force on the pore size of the micron-sized pore structure, thereby preparing a phosphate-based chemical sealant; Applying the phosphate-based chemical sealant to the gas contact area of ​​the valve seat of the metal bottle, wherein the phosphate-based chemical sealant spontaneously penetrates into the micron-sized pore structure under the action of capillary force, and controlling the infiltration time and temperature of the phosphate-based chemical sealant to form a concentration gradient distribution along the depth direction of the micron-sized pore structure and fill the micron-sized pore structure to a predetermined depth; The metal bottle valve seat that has completed gradient infiltration is heat-treated to allow the phosphate in the phosphate-based chemical sealant to chemically react with the aluminum oxide on the surface of the micron-sized pore structure and form a chemical bond, thereby forming a phosphate sealing layer with a dense structure in the gas contact area to prevent gas infiltration.

6. The method according to claim 1, characterized in that Apply high-temperature resistant polyimide-based anodic electrophoretic paint and perform graded temperature-raising curing to form a polyimide paint film in the area bonded to the plastic liner, thereby improving the bonding strength. This includes: preparing an anodic electrophoretic paint containing a preset content of polyimide resin, measuring the mobility of charged particles of the anodic electrophoretic paint, and determining a voltage control parameter in electrophoresis according to the mobility of the charged particles; Electrophoretic coating is performed using a three-stage voltage control method according to the voltage control parameters, and the switching time of each stage is determined by real-time monitoring of the electrophoretic current: in the initial stage, a first preset voltage is applied to cause the charged colloid particles to migrate to the surface of the metal bottle valve seat to form an initial covering layer; in the middle stage, the voltage is increased to a second preset voltage to maintain a constant deposition rate to allow the initial covering layer to grow; and in the final stage, the voltage is reduced to a third preset voltage to enhance the density of the initial covering layer to a preset degree; The metal bottle valve seat after electrophoresis is subjected to a graded temperature-raising curing treatment, wherein the graded temperature-raising curing treatment includes: a first preset temperature is used in the primary stage to flatten the paint film surface by solvent volatilization; a second preset temperature is used in the intermediate stage to catalyze the cross-linking of polyimide molecular chains to increase the paint film strength to a preset degree; and a third preset temperature is used in the advanced stage to cure the paint film and form a polyimide paint film on the surface of the metal bottle valve seat; The polar groups on the surface of the polyimide paint film undergo molecular chain entanglement with the liner material and form chemical bonds. At the same time, the microscopic roughness of the paint film surface provides a mechanical interlocking effect, thereby improving the bonding strength between the metal bottle valve seat and the plastic liner material.

7. An electronic device, characterized in that: include: processor; a memory for storing processor-executable instructions; The processor is configured to call the instructions stored in the memory to execute the method according to any one of claims 1 to 6.

8. A computer-readable storage medium having computer program instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, the method according to any one of claims 1 to 6 is implemented.

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