Long-life inorganic coating materials, their preparation methods and radioactive waste packaging containers

Abstract

This invention discloses a long-life inorganic coating material, its preparation method, and a radioactive waste packaging container. The raw materials for the long-life inorganic coating material include the following components by weight: 10-20 parts phosphoric acid, 12-25 parts aluminum dihydrogen phosphate, 3-5 parts carbohydrates, 0.5-3 parts magnesium oxide, 3-5 parts flake aluminum powder, 25-40 parts surface passivation aluminum powder, 30-50 parts deionized water, and 0.5-1.5 parts additives; the surface passivation aluminum powder comprises spherical aluminum particles with an alumina passivation layer on their surface. The long-life inorganic coating of this invention has advantages such as water-based environmental friendliness, good stability, and excellent corrosion resistance; it can meet the requirements of sealing capacity, long-term safety, durability, and corrosion resistance for radioactive waste packaging containers.

Description

Technical Field

[0001] This invention belongs to the field of coating protection technology, specifically relating to a long-life inorganic coating material, its preparation method, and a radioactive waste packaging container. Background Technology

[0002] Because high-level radioactive waste contains radionuclides that are highly radioactive, generate a lot of heat, are highly toxic, and have long half-lives, they need to be reliably and permanently isolated from the human living environment in order to prevent them from harming the ecological environment and human health.

[0003] Currently, containers used for encapsulating high-level radioactive waste mainly employ a double-layer structure design. The inner packaging is typically made of carbon steel or cast iron, while the outer packaging can be made of nickel-chromium-manganese alloy (Alloy 22), Hastelloy, titanium alloy, pure copper, etc. However, such containers are relatively expensive. Moreover, if a packaging container design is used with a copper coating several millimeters thick over a steel substrate, damage to the copper coating could lead to galvanic corrosion as it acts as a cathode, forming a micro-battery with the steel substrate (as an anode) in the electrolyte, accelerating the corrosion of low-potential steel containers.

[0004] To reduce costs and effectively ensure the long-term integrity of high-level radioactive waste packaging containers, researchers from various countries have proposed solutions for coating the outer walls of steel containers with organic and inorganic anti-corrosion coatings. For example, the applicant has developed an epoxy-based nano-heavy-duty anti-corrosion organic coating for use as a surface anti-corrosion coating for 16MnR steel containers. However, practical application has revealed that the temperature resistance and durability of the organic coating film itself are insufficient, and oil-based organic coatings have poor environmental comfort and safety when applied in enclosed and semi-enclosed spaces.

[0005] Inorganic ceramic coatings, due to their excellent properties, have been widely used in anti-corrosion coatings, wear-resistant coatings, and thermal barrier coatings. Compared with organic coatings, inorganic ceramic coatings offer better durability and environmental comfort. Existing preparation technologies for inorganic coatings mainly include thermal spraying, vapor deposition, self-propagating high-temperature synthesis, and sol-gel technology, each with its own advantages and disadvantages. For example, self-propagating high-temperature synthesis is only suitable for large-scale, rapid production of pipeline protective coatings. Thermal spraying technology has high process requirements, low material utilization, and severe dust pollution. While sol-gel and vapor deposition technologies can significantly reduce coating cracks and improve coating performance, their complex preparation processes and high costs limit their application.

[0006] In recent years, polymer ceramic technology has gained widespread attention in the industry as a novel inorganic surface coating preparation technology. It involves pre-coating the substrate surface with coating materials using processes such as spraying and brushing, followed by room temperature curing or heat treatment to form a complete and dense coating. This technology offers numerous advantages, including simple processing, ease of operation, strong adaptability to various construction methods, high safety, and low cost. For example, researchers have proposed a water-based ceramic anti-corrosion coating containing components such as aluminum dihydrogen phosphate, magnesium oxide, zinc oxide, aluminum powder, and magnesium chromate. Coatings prepared on steel substrates using this coating can provide protection against steel substrates in both saline environments at room temperature and high-temperature oxidizing environments; however, the long-term anti-corrosion performance of this coating still needs improvement. Summary of the Invention

[0007] The main objective of this invention is to provide a long-life inorganic coating material, its preparation method, and a radioactive waste packaging container to overcome the shortcomings of the prior art.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0009] This invention provides a long-life inorganic coating material. The raw materials of the coating material include the following components calculated by weight: 10-20 parts phosphoric acid, 12-25 parts aluminum dihydrogen phosphate, 3-5 parts carbohydrates, 0.5-3 parts magnesium oxide, 3-5 parts flake aluminum powder, 25-40 parts surface passivation aluminum powder, 30-50 parts deionized water, and 0.5-1.5 parts additives; the surface passivation aluminum powder includes spherical aluminum particles with an aluminum oxide passivation layer on their surface.

[0010] This invention also provides a method for preparing the aforementioned long-life inorganic coating material, comprising:

[0011] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of 0.05–0.2 g / mL and reacted at room temperature for 0.5–1 h to obtain surface passivated aluminum powder.

[0012] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0013] Dissolve carbohydrates in deionized water, then add additives, flake aluminum powder and surface passivation aluminum powder in sequence to form a second mixture;

[0014] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0015] The coating composition is uniformly coated onto the surface of a metal substrate and heated to 350–400°C to form the long-life inorganic coating material.

[0016] This invention also provides a long-life inorganic coating material, which is prepared by the aforementioned method.

[0017] This invention also provides a radioactive waste packaging container, including a metal container substrate, the surface of which is covered with the aforementioned long-life inorganic coating material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The long-life inorganic coating material in this invention has the advantages of being water-based and environmentally friendly, having good stability and excellent anti-corrosion performance;

[0020] (2) In the early stage of the formation of the long-life inorganic coating in this invention, only a small amount of spherical aluminum powder participates in cathodic protection, while a large amount of spherical aluminum powder participates in cathodic protection in the later stage, ensuring the cathodic protection performance of the coating; the flake aluminum powder is interspersed in the phosphate network, which also helps to improve the density of the coating. After the flake aluminum powder is completely consumed, the phosphate formed by its conversion will also be incorporated into the phosphate network, further improving the density of the coating.

[0021] (3) The present invention adds a small amount of sugar carbohydrates (such as glucose) to a long-life inorganic coating. During the process of gradually heating and curing the coating, glucose will undergo a hydrothermal reaction to generate carbon spheres, one-dimensional carbon nanomaterials, etc., thereby improving the conductivity of the coating and enhancing its corrosion resistance and cathodic protection effect.

[0022] (4) The long-life inorganic coating formed by the present invention can improve the sealing ability, long-term safety, durability and corrosion resistance of long-life waste packaging containers. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figures 1a-1b These are the appearance and pull-out adhesion test images of the long-life inorganic coating in Embodiment 1 of the present invention;

[0025] Figures 2a-2d This is a microscopic morphology diagram of the long-life inorganic coating in Embodiment 1 of the present invention;

[0026] Figures 3a-3b These are images before and after salt spray testing of the long-life inorganic coating in Embodiment 1 of the present invention;

[0027] Figures 4a-4d This is an XPS image of the long-life inorganic coating in Embodiment 1 of the present invention;

[0028] Figure 5 These are the open-circuit potential diagrams of the coatings in Examples 1-4 of this invention;

[0029] Figure 6 These are the EIS images of the coatings in Examples 1-4 of this invention;

[0030] Figure 7 These are the equivalent circuit model diagrams used in embodiments 1-4 of this invention;

[0031] Figure 8 This is a graph showing the water absorption rate of the coatings in Examples 1-4 of this invention after being immersed in 3.5wt% NaCl solution for different times;

[0032] Figure 9 These are the potentiodynamic polarization curves of the coatings in Examples 1-4 of this invention. Detailed Implementation

[0033] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0034] Specifically, as one aspect of the technical solution of this invention, a long-life inorganic coating material is involved. The raw materials of the coating material include the following components calculated by weight: 10-20 parts phosphoric acid, 12-25 parts aluminum dihydrogen phosphate, 3-5 parts carbohydrates, 0.5-3 parts magnesium oxide, 3-5 parts flake aluminum powder, 25-40 parts surface passivation aluminum powder, 30-50 parts deionized water, and 0.5-1.5 parts additives; the surface passivation aluminum powder includes spherical aluminum particles with an aluminum oxide passivation layer on their surface.

[0035] In some preferred embodiments, the additives include at least one of inorganic anti-settling agents and inorganic dispersants, but are not limited thereto.

[0036] Furthermore, the inorganic anti-settling agent includes at least one of magnesium aluminum silicate, fumed silica, and bentonite, but is not limited thereto.

[0037] Furthermore, the inorganic dispersant includes at least one of sodium hexametaphosphate, sodium polyphosphate, and potassium tripolyphosphate, but is not limited thereto.

[0038] The present invention preferably uses the above-mentioned inorganic dispersant, which can not only act as a dispersant, but also participate as a reaction raw material in the curing reaction of phosphate binder.

[0039] In some preferred embodiments, the surface passivation aluminum powder is formed by passivating spherical aluminum particles with at least one of chromic acid, chromate, dichromic acid, and dichromate.

[0040] In some preferred embodiments, the raw material for the coating material includes 30 to 35 parts of surface passivating aluminum powder.

[0041] In some preferred embodiments, the carbohydrate includes at least one of glucose, fructose, and sucrose, but is not limited thereto.

[0042] Furthermore, the carbohydrate in question is glucose. When glucose is used, a higher proportion of it is converted into carbon materials.

[0043] In some preferred embodiments, the spherical aluminum particles have a purity of 99 wt% or higher and a particle size of 300–900 nm.

[0044] In some preferred embodiments, the flake aluminum powder has a purity of 99 wt% or higher, a flake diameter of 3–10 μm, and a thickness of 20–100 nm.

[0045] In some preferred embodiments, the magnesium oxide has a particle size of 3–5 μm.

[0046] Another aspect of the present invention provides a method for preparing the aforementioned long-life inorganic coating material, comprising:

[0047] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of 0.05–0.2 g / mL and reacted at room temperature for 0.5–1 h to obtain surface passivated aluminum powder.

[0048] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0049] Dissolve carbohydrates in deionized water, then add additives, flake aluminum powder and surface passivation aluminum powder in sequence to form a second mixture;

[0050] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0051] The coating composition is uniformly coated onto the surface of a metal substrate and heated to 350–400°C to form the long-life inorganic coating material.

[0052] In some preferred embodiments, the preparation method specifically includes: uniformly coating the coating composition onto the surface of a metal substrate, baking it at 60-80°C for 0.5-1.5 hours, then heating it to 200-240°C at a rate of 3-5°C / min and holding it at that temperature for 1-3 hours, and then heating it to 350-400°C at a rate of 10-15°C / min and holding it at that temperature for more than 1 hour to form the long-life inorganic coating material.

[0053] In this invention, baking at 60–80°C is used to remove moisture from the surface of the coating (i.e., surface drying), while retaining moisture inside the coating. This moisture is essential for the hydrothermal reaction of the sugar. The surface-dried coating essentially forms a closed reaction vessel, thus satisfying the conditions for the hydrothermal reaction.

[0054] In this invention, a slow heating rate of 3–5 °C / min is used to promote the continued slow drying of the coating and to allow the sugar to gradually undergo a hydrothermal reaction, transforming it into carbon nanomaterials. Subsequently, a rapid heating rate of 10–15 °C / min is used to accelerate the reaction rate between phosphoric acid, aluminum dihydrogen phosphate, and magnesium oxide. Initially, the phosphoric acid also reacts with the alumina passivation layer of the surface passivated aluminum powder, consuming a portion of the alumina and exposing the internal metallic aluminum portion. The resulting aluminum dihydrogen phosphate and aluminum monohydrogen phosphate accumulate on the surface of the metallic aluminum, continuing to play a role in slow release, and also undergo a condensation reaction with phosphoric acid, more firmly fixing the aluminum powder within the phosphate network structure.

[0055] Another aspect of the present invention provides a long-life inorganic coating material, which is prepared by the aforementioned method.

[0056] In this invention, only a small amount of spherical aluminum powder participates in cathodic protection in the early stage after the coating is formed, while a larger amount of spherical aluminum powder participates in cathodic protection in the later stage, ensuring the cathodic protection performance of the coating. At the same time, the flake-shaped aluminum powder interspersed in the phosphate network also helps to improve the density of the coating. After the flake-shaped aluminum powder is completely consumed, the phosphate formed by its conversion will also be incorporated into the phosphate network, further improving the density of the coating.

[0057] In this invention, a small amount of glucose is added to the coating. During the gradual heating and curing process of the coating, the glucose undergoes a hydrothermal reaction, generating carbon spheres, one-dimensional carbon nanomaterials, etc., which improves the conductivity, corrosion resistance, and cathodic protection of the coating. Compared to directly adding carbon spheres and one-dimensional carbon materials to the coating, the dispersibility is better.

[0058] Another aspect of the present invention provides a radioactive waste packaging container, comprising a metal container substrate, the surface of which is covered with the aforementioned long-life inorganic coating material.

[0059] In some preferred embodiments, the metal container substrate includes a steel substrate, but is not limited thereto.

[0060] The long-life inorganic coating material of this invention has the advantages of being water-based and environmentally friendly, having good stability and excellent corrosion resistance. In view of the heavy corrosion resistance requirements of packaging containers for radioactive waste containing long-life, highly toxic radionuclides, the long-life inorganic coating formed by this invention can improve the sealing ability, long-term safety, durability and corrosion resistance of long-life waste packaging containers.

[0061] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0062] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0063] Example 1

[0064] The raw materials for a long-life inorganic coating material include the following components in parts by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 3 parts glucose, 1.5 parts magnesium oxide, 3 parts flake aluminum powder, 35 parts surface passivation aluminum powder, 35 parts deionized water, 0.5 parts fumed silica and 0.5 parts sodium polyphosphate.

[0065] A method for preparing a long-life inorganic coating material includes the following steps:

[0066] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.1 g / mL and reacted at room temperature for about 1 hour to obtain surface passivated aluminum powder.

[0067] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0068] Glucose is dissolved in deionized water, and then fumed silica, sodium polyphosphate, flake aluminum powder and surface passivation aluminum powder are added in sequence to form a second mixture.

[0069] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0070] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 60℃ for about 1 hour, then heated to 220℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, and then heated to 380℃ at a heating rate of 12℃ / min and held at that temperature for 1 hour to form a long-life inorganic coating material.

[0071] Characterization: The long-life inorganic coating material prepared in this embodiment was tested, and the appearance and pull-out adhesion of the coating formed on Q345 steel plate were tested as follows. Figures 1a-1b As shown, the surface of the Q345 steel is smooth and flat, with a cross-cut adhesion grade of 0 and a pull-out adhesion ≥10MPa. The microstructure of the long-life inorganic coating on Q345 steel was observed using scanning electron microscopy (e.g., ...). Figures 2a-2d As shown in the figure, the surface passivated aluminum powder in the coating is spherical, and the paint film is dense and uniform, without visible agglomeration or other defects. Salt spray resistance tests were conducted on the formed long-life inorganic coating, and the results before and after 5000 hours of salt spray are shown in the figure. Figures 3a-3b As shown, the coating did not change significantly during the long-term salt spray test, and no visible defects were observed in the coating.

[0072] XPS analysis was performed on the surface of the formed long-life inorganic coating, such as... Figures 4a-4d As shown, the coating contains C, O, Al, Cr, and P (e.g., Figure 4a (As shown). In Figure 4b In the inorganic phosphate coating, the C 1s fine spectrum decomposes into four peaks at 284.8 eV, 286.2 eV, 287.7 eV, and 289.3 eV, originating from C / C=C, C-OH, C=O, and OC=O bonds, respectively. The carbon component in the sample mainly originates from carbon materials formed by the conversion of glucose. The characteristic peak observed at 75.0 eV is attributed to Al₂O₃, while the characteristic peak observed at 76.9 eV is characteristic of Al-OP (e.g., ...). Figure 4c (As shown). Since the 2p1 / 2 and 2p3 / 2 characteristic peaks of Cr 2p always appear as split peaks with a spacing of 9.3 eV, therefore in Figure 4d The analysis focused on Cr 2p 3 / 2 The characteristic peaks at 576.7 eV and 578.4 eV originate from Cr₂O₃ and Cr(OH)₃, respectively. Cr(OH)₃ is formed during the passivation process by a reaction between Al and chromate, and then transforms into Cr₂O₃ upon heating. The presence of Cr₂O₃ indicates that the surface passivation aluminum powder in the coating has been passivated by chromate.

[0073] Comparative Example 1

[0074] The method is the same as in Example 1, except that glucose is missing from the raw materials;

[0075] An inorganic coating material comprises the following components by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 1.5 parts magnesium oxide, 3 parts flake aluminum powder, 35 parts surface passivation aluminum powder, 35 parts deionized water, 0.5 parts fumed silica, and 0.5 parts sodium polyphosphate.

[0076] A method for preparing an inorganic coating material includes the following steps:

[0077] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.1 g / mL and reacted at room temperature for about 1 hour to obtain surface passivated aluminum powder.

[0078] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0079] Deionized water is mixed with fumed silica, sodium polyphosphate, flake aluminum powder and surface passivation aluminum powder to form a second mixture.

[0080] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0081] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 60℃ for about 1 hour, then heated to 220℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, and then heated to 380℃ at a heating rate of 12℃ / min and held at that temperature for 1 hour to form an inorganic coating material.

[0082] Comparative Example 2

[0083] The method is the same as in Example 1, except that, following the method described in the literature, the same mass of glucose is first converted into carbon quantum dots, and then added to the raw material system.

[0084] An inorganic coating material comprises the following components by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 3 parts carbon quantum dots, 1.5 parts magnesium oxide, 3 parts flake aluminum powder, 35 parts surface passivation aluminum powder, 35 parts deionized water, 0.5 parts fumed silica, and 0.5 parts sodium polyphosphate.

[0085] A method for preparing an inorganic coating material includes the following steps:

[0086] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.1 g / mL and reacted at room temperature for about 1 hour to obtain surface passivated aluminum powder.

[0087] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0088] Carbon quantum dots are dissolved in deionized water, and then fumed silica, sodium polyphosphate, flake aluminum powder and surface passivation aluminum powder are added in sequence to form a second mixture.

[0089] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0090] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 60℃ for about 1 hour, then heated to 220℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, and then heated to 380℃ at a heating rate of 12℃ / min and held at that temperature for 1 hour to form an inorganic coating material.

[0091] Comparative Example 3

[0092] The method is the same as in Example 1, except that the surface passivated aluminum powder is replaced with unpassivated spherical aluminum powder.

[0093] An inorganic coating material comprises the following components in parts by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 3 parts glucose, 1.5 parts magnesium oxide, 3 parts flake aluminum powder, 35 parts spherical aluminum powder, 35 parts deionized water, 0.5 parts fumed silica, and 0.5 parts sodium polyphosphate.

[0094] A method for preparing an inorganic coating material includes the following steps:

[0095] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0096] Glucose is dissolved in deionized water, and then fumed silica, sodium polyphosphate, flake aluminum powder and spherical aluminum powder are added in sequence to form a second mixture.

[0097] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0098] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 60℃ for about 1 hour, then heated to 220℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, and then heated to 380℃ at a heating rate of 12℃ / min and held at that temperature for 1 hour to form an inorganic coating material.

[0099] Comparative Example 4

[0100] The method is the same as in Example 1, except that flake aluminum powder is missing from the raw materials;

[0101] An inorganic coating material comprises the following components in parts by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 3 parts glucose, 1.5 parts magnesium oxide, 35 parts surface passivation aluminum powder, 35 parts deionized water, 0.5 parts fumed silica and 0.5 parts sodium polyphosphate.

[0102] A method for preparing an inorganic coating material includes the following steps:

[0103] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.1 g / mL and reacted at room temperature for about 1 hour to obtain surface passivated aluminum powder.

[0104] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0105] Glucose is dissolved in deionized water, and then fumed silica, sodium polyphosphate and surface passivation aluminum powder are added in sequence to form a second mixture.

[0106] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0107] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 60℃ for about 1 hour, then heated to 220℃ at a heating rate of 4℃ / min and held at that temperature for 2 hours, and then heated to 380℃ at a heating rate of 12℃ / min and held at that temperature for 1 hour to form an inorganic coating material.

[0108] Comparative Example 5

[0109] The method is the same as in Example 1, except that after baking, the temperature is directly increased to 350-400°C at a rate of 12°C / min and kept warm for 1 hour.

[0110] An inorganic coating material comprises the following components in parts by weight: 12 parts phosphoric acid, 15 parts aluminum dihydrogen phosphate, 3 parts glucose, 1.5 parts magnesium oxide, 3 parts flake aluminum powder, 35 parts surface passivated aluminum powder, 35 parts deionized water, 0.5 parts fumed silica, and 0.5 parts sodium polyphosphate.

[0111] A method for preparing an inorganic coating material includes the following steps:

[0112] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.1 g / mL and reacted at room temperature for about 1 hour to obtain surface passivated aluminum powder.

[0113] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0114] Glucose is dissolved in deionized water, and then fumed silica, sodium polyphosphate, flake aluminum powder and surface passivation aluminum powder are added in sequence to form a second mixture.

[0115] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0116] After uniformly coating the surface of Q345 steel plate with the coating composition, the temperature is raised to 380℃ at a heating rate of 12℃ / min and held for 1 hour to form an inorganic coating material.

[0117] The coatings prepared in Example 1 and Comparative Examples 1-5 were tested, and the results are shown in Table 1:

[0118] Table 1 Performance tests of the coatings in Example 1 and Comparative Examples 1-5

[0119]

[0120] Coating test standards: ① Water resistance: ≥1200h, GB / T 1733; ② Heat resistance: 600℃, 24 hours, coating intact, no blistering, GB / T 1735; ③ Salt spray resistance: ≥1200h, GB / T 1771; ④ Coating adhesion to steel substrate ≤ Grade 1, GB / T1720

[0121] Example 2

[0122] The method is the same as in Example 1, except that the amount of surface passivation aluminum powder used in the raw materials is 29 parts by weight.

[0123] Example 3

[0124] The method is the same as in Example 1, except that the amount of surface passivation aluminum powder used in the raw materials is 32 parts by weight.

[0125] Example 4

[0126] The method is the same as in Example 1, except that the amount of surface passivation aluminum powder used in the raw materials is 38 parts by weight.

[0127] The long-life inorganic coatings prepared in Examples 1-4 were analyzed. The coatings with different contents of surface passivation aluminum powder were designated as 29%-AHP coating, 32%-AHP coating, 35%-AHP coating and 38%-AHP coating, respectively. The protective effect of the prepared waterborne inorganic phosphate coating on Q345 steel was evaluated using an electrochemical workstation.

[0128] like Figure 5As shown, both the 29%-AHP and 35%-AHP coatings exhibited potential values ​​less than -0.78V after immersion for 2 hours, then gradually shifted positive and remained near -0.70V. The 32%-AHP coating showed an open-circuit potential of -0.69V after immersion for 2 hours, then shifted negative to -0.86V after immersion for 4 hours, and then gradually shifted positive to around -0.70V. The open-circuit potential of the 38%-AHP coating fluctuated between -0.7±0.05V. This indicates that the 29%-AHP and 35%-AHP coatings exhibited cathodic protection as sacrificial anodes from the initial immersion stage; the 32%-AHP coating exhibited cathodic protection after immersion for 4 hours, but gradually lost its sustained cathodic protection capability after 12 hours as the potential shifted positively. In contrast, the cathodic protection of the 38%-AHP coating was not obvious, possibly because the relatively significant cathodic protection had ended before immersion for 2 hours, and the potential began to shift positively (self-corrosion potential higher than -0.78V). For all coatings, the open circuit potential after 14 days of immersion did not show a significant negative shift, but remained around -0.70V, indicating that all coatings still maintained protection of the Q345 steel substrate after 14 days of immersion, and there was no significant difference between the coatings.

[0129] Figure 6 (The Nyquist and Bode plots for each coated sample during the 14-day immersion process are given for 29%-AHP(a1, a2), 32%-AHP(b1, b2), 35%-AHP(c1, c2), and 38%-AHP(d1, d2)). During the 14-day immersion process, the capacitive arc radius of all coatings decreased slightly but did not shrink significantly, indicating that the coatings maintained good protective performance. The impedance spectrum results were fitted using ZSimpWin software, and the corresponding equivalent circuit model is shown below. Figure 7 As shown, where R s R represents the resistance of the solution. C and R ct These represent the coating resistance and the charge transfer resistance of the metal surface, respectively, while CPE C and CPE dl The figures represent the coating capacitance and the double-layer capacitance generated during the charge transfer process, respectively. Due to the unavoidable porosity and defects in the coating, a constant-phase element (CPE) was used instead of an ideal capacitor. The electrochemical parameters obtained by ZSimpWin fitting are shown in Table 2.

[0130] Table 2. EIS fitting results of coatings with different surface passivation aluminum powder contents.

[0131]

[0132] During the soaking process, all coatings of CPE C The values ​​all increase with prolonged immersion time, which is due to the continuous penetration of NaCl solution into the coating during immersion. During immersion, on the one hand, the continuous penetration of NaCl solution reduces the coating resistance; on the other hand, the aluminum powder, acting as a sacrificial anode, is continuously consumed and generates corrosion products with poor conductivity, thus increasing the coating resistance. For 29%-AHP coatings with a low content of surface passivation aluminum powder, its R... C The value is 64.2 Ω·cm 2 Up to 145.7 Ω·cm 2 The fluctuations between these values ​​indicate that the consumption of surface passivation aluminum powder in the coating is significant, and its impact on coating resistance is greater than that of NaCl solution penetration. For 32%-AHP, 35%-AHP, and 38%-AHP coatings with high surface passivation aluminum powder content, their R... C The values ​​all decreased significantly as the immersion process continued, indicating that the consumption of surface passivation aluminum powder in the coating was relatively slow, and the penetration of NaCl solution had a more significant impact on the coating resistance.

[0133] R of phosphate coatings with different surface passivation aluminum powder contents ct The values ​​showed different trends. It can be seen that the R... of the 29%-AHP coating... ct The value increased significantly after immersion for 2 days and remained at a high level. Meanwhile, the R value of the 32%-AHP coating... ct The value decreased significantly after immersion for 2 days and continued to decrease gradually. The R value of the 35%-AHP coating... ct The R value of the 38%-AHP coating decreases slowly with immersion time. ct The value is 30000 Ω·cm 2 Fluctuating left and right.

[0134] In addition, to analyze the barrier properties of the coating during the immersion process, the water absorption rate of the coating was calculated using the Brasher and Kingsbury formula (1), such as... Figure 8 As shown.

[0135]

[0136] Among them, X V (%) represents the volume fraction of water in the coating, C C (0) and C C(t) represents the capacitance of the coating at the initial time and at immersion time t, respectively. Due to the hydrophilic nature of the coating, it quickly absorbs a large amount of water at the initial immersion. During subsequent immersion, the water absorption rate increases with the penetration of the aqueous solution, but also decreases due to the accumulation of corrosion products caused by the self-corrosion of the aluminum powder in the coating. Notably, the water absorption rate of the 38%-AHP coating actually decreased to a negative value in the early stage of immersion. This is because excessive penetration of the aqueous solution in the initial stage of immersion causes the corrosion products of the passivated aluminum powder on the surface to fill the coating defects, thus reducing the water absorption rate. However, overall, the water absorption rate of the coating gradually increases with increasing immersion time, indicating that the aqueous solution gradually penetrates into the interior of the coating.

[0137] Figure 9 The potentiodynamic polarization curves of each coating after immersion in 3.5 wt% NaCl solution for 20 days are shown in Table 3, and the corresponding Tafel parameters are also presented. The Et values ​​for the 29%-AHP coating and the 32%-AHP coating are shown in Table 3. corr It has lower E than other coatings, followed by the 38%-AHP coating, while the 35%-AHP coating has lower E. corr Keep it in the correct position. This may be because the 35%-AHP and 38%-AHP coatings contain more surface passivating aluminum powder, resulting in more insoluble corrosion products formed after long-term immersion compared to the 29%-AHP and 32%-AHP coatings. This leads to a stronger filling effect on micro-defects in the coating, thus improving its corrosion resistance. However, the 38%-AHP coating has a small number of cracks on its surface, making it more susceptible to NaCl penetration, hence the lower ET of the 38%-AHP coating. corr The β value is more negative compared to the 35%-AHP coating. This can also be demonstrated by the cathodic slope of the potentiodynamic polarization curves of each coating. The |β value of the 29%-AHP and 32%-AHP coatings is... c All are at 100V·dec -1 Around 100%, while 35%-AHP coatings and 38%-AHP coatings have a larger |β value. c |(approximately 190V·dec) -1 This indicates a lower diffusion rate.

[0138] Table 3 Electrochemical parameters of the coating under different surface passivation aluminum powder contents obtained by Tafel extrapolation method

[0139]

[0140] Based on the results of the above open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization curve tests, it can be seen that when the content of surface passivation aluminum powder is 35%, the coating has the best anti-corrosion effect on Q345 steel.

[0141] Example 5

[0142] The raw materials for a long-life inorganic coating material include the following components in parts by weight: 10 parts phosphoric acid, 12 parts aluminum dihydrogen phosphate, 4 parts fructose, 0.5 parts magnesium oxide, 4 parts flake aluminum powder, 25 parts surface passivation aluminum powder, 30 parts deionized water, 0.5 parts magnesium aluminum silicate, and 1.5 parts sodium hexametaphosphate.

[0143] A method for preparing a long-life inorganic coating material includes the following steps:

[0144] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.05 g / mL and reacted at room temperature for about 0.5 h to obtain surface passivated aluminum powder.

[0145] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0146] Fructose is dissolved in deionized water, and then magnesium aluminum silicate, sodium hexametaphosphate, flake aluminum powder and surface passivated aluminum powder are added in sequence to form a second mixture.

[0147] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0148] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 80℃ for about 0.5h, then heated to 200℃ at a heating rate of 3℃ / min and held for 3h, then heated to 350℃ at a heating rate of 10℃ / min and held for 5h to form a long-life inorganic coating material.

[0149] Example 6

[0150] The raw materials for a long-life inorganic coating material include the following components in parts by weight: 20 parts phosphoric acid, 25 parts aluminum dihydrogen phosphate, 5 parts sucrose, 3 parts magnesium oxide, 5 parts flake aluminum powder, 40 parts surface passivation aluminum powder, 50 parts deionized water, 1 part bentonite and 0.5 parts potassium tripolyphosphate.

[0151] A method for preparing a long-life inorganic coating material includes the following steps:

[0152] Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of approximately 0.2 g / mL and reacted at room temperature for about 0.8 h to obtain surface passivated aluminum powder.

[0153] Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture;

[0154] Dissolve sucrose in deionized water, then add bentonite, potassium tripolyphosphate, flake aluminum powder and surface passivation aluminum powder in sequence to form a second mixture.

[0155] The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition;

[0156] After uniformly coating the surface of Q345 steel plate with the coating composition, it is first baked at 70℃ for about 1.5 hours, then heated to 240℃ at a heating rate of 5℃ / min and held for 1 hour, and then heated to 400℃ at a heating rate of 15℃ / min and held for 2 hours to form a long-life inorganic coating material.

[0157] Furthermore, the long-life inorganic coating of this invention exhibits a salt water resistance of ≥5000h and a salt spray resistance of ≥5000h. Compared to the foreign competitor SERMETEL-W coating, the phosphate coating shows a self-corrosion current of 16.218 μA·cm after immersion in a 3.5wt% NaCl solution for 10 days. -2 This is far lower than the 46.026 μA·cm of SERMETEL-W coating. -2 Compared with the TW-7 water-based high-temperature resistant coating from Zhonghao Northern Coatings Industry Research and Design Institute Co., Ltd. in China, this product has advantages such as high density and good resistance to salt spray and salt water. Meanwhile, SERMETEL-W coating is priced at 2000 RMB / kg in China, while TW-7 water-based high-temperature resistant coating is priced at approximately 1200 RMB / kg. The cost price of this product is approximately 500 RMB / kg, giving it a significant cost advantage.

[0158] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0159] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A long-life inorganic coating material, characterized in that, The raw materials for the coating material include the following components by weight: 10-20 parts phosphoric acid, 12-25 parts aluminum dihydrogen phosphate, 3-5 parts carbohydrates, 0.5-3 parts magnesium oxide, 3-5 parts flake aluminum powder, 25-40 parts surface passivation aluminum powder, 30-50 parts deionized water, and 0.5-1.5 parts additives; the surface passivation aluminum powder comprises spherical aluminum particles with an aluminum oxide passivation layer on their surface; the additives include at least one of inorganic anti-settling agents and inorganic dispersants; the inorganic dispersant includes at least one of sodium hexametaphosphate, sodium polyphosphate, and potassium tripolyphosphate; the carbohydrates include at least one of glucose, fructose, and sucrose. The preparation method of the long-life inorganic coating material includes: Spherical aluminum powder was dispersed in a chromic acid solution with a concentration of 0.05~0.2 g / mL and reacted at room temperature for 0.5~1 h to obtain surface passivated aluminum powder. Phosphoric acid, aluminum dihydrogen phosphate and magnesium oxide are mixed evenly to form the first mixture; Dissolve carbohydrates in deionized water, then add additives, flake aluminum powder and surface passivation aluminum powder in sequence to form a second mixture; The second mixture is added to the first mixture in batches and mixed evenly to obtain a coating composition; After uniformly coating the coating composition onto the surface of the metal substrate, it is first baked at 60~80℃ for 0.5~1.5h, then heated to 200~240℃ at a heating rate of 3~5℃ / min and held at that temperature for 1~3h, and then heated to 350~400℃ at a heating rate of 10~15℃ / min and held at that temperature for more than 1h to form the long-life inorganic coating material.

2. The long-life inorganic coating material according to claim 1, characterized in that: The inorganic anti-settling agent includes at least one of magnesium aluminum silicate, fumed silica, and bentonite.

3. The long-life inorganic coating material according to claim 1, characterized in that: The raw materials for the coating material include 30-35 parts of surface passivation aluminum powder.

4. The long-life inorganic coating material according to claim 1, characterized in that: The carbohydrate mentioned is glucose.

5. The long-life inorganic coating material according to claim 1, characterized in that: The spherical aluminum particles have a purity of over 99 wt% and a particle size of 300~900 nm.

6. The long-life inorganic coating material according to claim 1, characterized in that: The purity of the flake-shaped aluminum powder is above 99wt%, the flake diameter is 3~10μm, and the thickness is 20~100nm.

7. The long-life inorganic coating material according to claim 1, characterized in that: The magnesium oxide has a particle size of 3~5μm.

8. A radioactive waste packaging container, comprising a metal container base, characterized in that: The surface of the metal container substrate is covered with a long-life inorganic coating material as described in any one of claims 1-7.

9. The radioactive waste packaging container according to claim 8, characterized in that: The metal container substrate includes a steel substrate.

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