Corrosion-resistant metal material coating as well as preparation method and application thereof

Abstract

The invention relates to the technical field of corrosion-resistant coatings, in particular to a corrosion-resistant metal material coating and a preparation method and application thereof.The preparation method comprises the following steps that a cold spraying technology is adopted, modified iron-based alloy powder is sprayed to the surface of a polished matrix, and a prefabricated iron-based alloy coating is obtained through reciprocating operation; and an induction remelting process is used for remelting the prefabricated iron-based alloy coating, plane heating is adopted for induction remelting, and the corrosion-resistant metal material coating is obtained after heating. The hydrotalcite-like compound is modified, the dispersity of the hydrotalcite-like compound after modification and the compatibility with an iron-based matrix are greatly improved, internal gaps of a coating can be evenly filled, permeation channels of a corrosive medium (chloride ions) are reduced, molybdenum elements in modified molybdate can form a compact passive film on the surface of the coating, the oxidation reaction of a metal matrix is hindered, and the corrosion resistance of the metal matrix is improved. A dual-protection system is constructed through the synergistic effect of the two components, and after the modified iron-based alloy powder is modified by a modifier, the fluidity and the spraying performance of the modified iron-based alloy powder are improved.

Description

Technical Field

[0001] This invention relates to the field of corrosion-resistant coating technology, specifically to a corrosion-resistant metal material coating, its preparation method, and its application. Background Technology

[0002] Nuclear power plant steel storage tanks, as critical facilities for storing radioactive liquid media (ASME BPVC standard), have their outer walls constantly exposed to a marine atmosphere-salt spray coupled environment (Cl). - Under harsh operating conditions such as concentrations of 3.5%-5.0%, periodic wet-dry cycles, and emergency cooling water flushing, Q245R alloy, as a core material for pressure vessels, is widely used in the main structure of storage tanks due to its excellent weldability and medium-temperature strength. However, the exposed matrix... - Under the combined effects of infiltration, microbial adhesion, and irradiation fields, localized corrosion perforation is likely to occur, threatening the inclusive safety boundary of nuclear facilities throughout their entire life cycle; In traditional coating preparation processes, poor powder dispersion leads to high porosity within the coating, allowing corrosive media to easily penetrate the substrate through the pores and cause substrate corrosion. Furthermore, the bonding strength between the coating and the substrate is limited, making the coating prone to peeling, blistering, and other failures under long-term use or external stress. Therefore, to address the problems mentioned in the background art, those skilled in the art propose a corrosion-resistant metal material coating, its preparation method, and its application. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the purpose of this invention is to provide a corrosion-resistant metal material coating, its preparation method and its application, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a corrosion-resistant metal coating includes the following steps: S1. Using a cold spraying technique with a temperature of 300-600℃ and 1-4 spray passes, modified iron-based alloy powder is sprayed onto the surface of a polished substrate. The substrate preheating temperature is 130±10℃. During spraying, the powder feed rate is 20-30g / s, the nozzle is perpendicular to the sample direction, the gas pressure is 0.7-0.9MPa, the nozzle moving speed is 8-12mm / s, and a reciprocating operation is adopted to obtain a pre-formed iron-based alloy coating. S2. The pre-made iron-based alloy coating is remelted using an induction remelting process. The induction remelting process uses planar heating with a heating temperature of 500-520℃, a heating power of 1.2-2.2KW, a frequency of 165-185kHz, and a heating time of 8-12s to obtain a corrosion-resistant metal material coating.

[0005] The modified iron-based alloy powder is prepared through the following steps: S11. Weigh the iron-based precursor raw material and add it to deionized water at 25-35℃. Stir until completely dissolved, then add PEG-6000 and stir for 15-20 minutes. Continue to add modified hydrotalcite and stir for 30-35 minutes to obtain an iron-based mixed solution. S12. Simultaneously add the precipitant solution and the modified molybdate solution dropwise to the iron-based mixed solution. During the dropwise addition, continue stirring and maintain the pH value between 7.5 and 8.0. After the dropwise addition is completed, raise the temperature to 45-50℃ and continue stirring for 1.5-2 hours to obtain the reaction system. Then cool the reaction system to room temperature. S13. The reaction system cooled in step S12 is vacuum filtered to collect the precipitate. The pH of the precipitate is washed with deionized water to 6.5-7.0. Finally, it is washed with anhydrous ethanol. After washing, the precipitate is dried and ground to obtain the precursor powder. S14. The precursor powder from step S13 is calcined under argon gas, heated to 500-550℃ at a heating rate of 4-8℃ / min and held for calcination for 2-3 hours. After calcination, the argon gas is switched to hydrogen gas, and the temperature is further increased to 800-900℃ and held for reduction for 2-3 hours. After reduction, hydrogen gas is continuously introduced to cool to room temperature. The reduced precursor powder is then ground to obtain 200-400 mesh modified iron-based alloy powder.

[0006] Furthermore, the modified hydrotalcite is prepared through the following steps: S111. Add magnesium nitrate and aluminum nitrate to deionized water and stir to dissolve to obtain precursor solution A. Add sodium hydroxide and sodium carbonate to deionized water and stir to obtain precursor solution B. Heat precursor solution A to 50-60℃ and then add precursor solution B dropwise at a rate of 1.5-2 mL / min. After the addition is complete, stir for 1.5-2 h to obtain a hydrotalcite-like suspension. S112. Add silane coupling agent to the hydrotalcite-like suspension in step S111, heat to 60-70℃ and stir for 1-2 hours, centrifuge and wash with deionized water to obtain modified hydrotalcite-like suspension.

[0007] Furthermore, the modified molybdate solution is prepared through the following steps: S121. Heat deionized water to 35-45℃, add ammonium bicarbonate and stir until completely dissolved, then add anhydrous ethanol and stir to obtain the modified solvent. S122. Add ammonium molybdate to the modified solvent in step S121 and stir to dissolve to obtain a molybdate solution. Add silane coupling agent to the molybdate solution and stir for 25-35 minutes to obtain a modified molybdate solution.

[0008] Furthermore, the iron-based precursor raw material in step S11 is ferrous sulfate: ferric chloride: manganese chloride: nickel acetate in a mass ratio of (7.5-8.0):(1.5-2.0):(0.3-0.5):(0.05-0.10). The total mass of the iron-based precursor raw material is in a mass ratio of 1:(0.005-0.010) to PEG-6000. The total mass of the iron-based precursor raw material is in a mass ratio of 1:(8-10):(0.05-0.08) to deionized water and modified hydrotalcite.

[0009] Furthermore, in step S12, the mass ratio of ammonium molybdate to the iron-based precursor in the modified molybdate solution is (0.03-0.06):1, and the precipitant solution is ammonium bicarbonate, with the mass ratio of ammonium bicarbonate to all metal ions in the iron-based precursor being (1.2-1.5):1.

[0010] Furthermore, in step S111, the mass ratio of magnesium nitrate to aluminum nitrate is (2-3):1, the mass ratio of sodium hydroxide to sodium carbonate is (1.2-1.5):(0.3-0.4), the mass ratio of the total mass of magnesium nitrate and aluminum nitrate to deionized water is 1:(15-20), the mass ratio of the total mass of sodium hydroxide and sodium carbonate to deionized water is 1:(10-12), and in step S112, the mass ratio of the total mass of silane coupling agent to modified hydrotalcite is (0.02-0.03):1.

[0011] Furthermore, in step S121, the mass concentration of ammonium bicarbonate in the modified solvent is 0.1-0.2%, and the mass ratio of deionized water to anhydrous ethanol is (9.0-19.0):1.

[0012] Furthermore, in step S122, the mass ratio of silane coupling agent to ammonium molybdate is (0.05-0.07):1, and the concentration of ammonium molybdate in the modified solvent is 30-60 g / L.

[0013] Furthermore, a corrosion-resistant metallic material coating is prepared according to the aforementioned preparation method.

[0014] Furthermore, the corrosion-resistant metal material coating is used as a coating material for steel storage tanks in nuclear power plants.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention modifies hydrotalcite-like materials, which significantly improves their dispersibility and compatibility with iron-based substrates. This allows for uniform filling of the internal voids of the coating, reducing the penetration channels of corrosive media (chloride ions). The molybdenum element in the modified molybdate can form a dense passivation film on the coating surface, hindering the oxidation reaction of the metal substrate. The synergistic effect of these two elements constructs a dual protection system. 2. The present invention improves the flowability and spraying performance of modified iron-based alloy powder by modifying it with a modifier. During cold spraying, it can be deposited more uniformly on the substrate surface. The addition of the modifier reduces the porosity in the cold spray pre-coated layer. After induction remelting, a tighter metallurgical bond is formed between the coating and the substrate, which can stably obtain a coating with uniform thickness and consistent structure, and reduce the incidence of coating defects (such as cracks and inclusions) caused by poor powder characteristics during the preparation process. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the preparation process of the corrosion-resistant metal material coating of the present invention; Figure 2 This is a schematic diagram of the preparation process of the modified iron-based alloy powder of the present invention; Figure 3 This is a schematic diagram of the preparation process of the modified hydrotalcite of the present invention; Figure 4 This is a schematic diagram of the preparation process of the modified molybdate solution of the present invention; Figure 5 The microstructure morphology of the metal material coating cross sections at different spraying temperatures is shown below: (a, b) is the microstructure morphology of the coating at 300℃ in Example 1; (c, d) is the microstructure morphology of the coating at 400℃ in Example 2; (e, f) is the microstructure morphology of the coating at 500℃ in Example 3; and (g, h) is the microstructure morphology of the coating at 600℃ in Example 4. Figure 6 These are the hardness values ​​of the metal coating at different spraying temperatures; Figure 7 The microstructure morphology of the metal material coating cross section for different spraying passes is as follows: (a, b) is the microstructure morphology of the first pass in Example 1; (c, d) is the microstructure morphology of the second pass in Example 5; (e, f) is the microstructure morphology of the third pass in Example 5; (g, h) is the microstructure morphology of the fourth pass in Example 5. Figure 8 Hardness values ​​of metal coatings for different spray passes; Figure 9 The optical microstructures of the metal coatings after induction remelting at different spraying temperatures are as follows: (a) Optical microstructure of the coating at 300℃ in Example 1; (b) Optical microstructure of the coating at 400℃ in Example 2; (c) Optical microstructure of the coating at 500℃ in Example 3; (d) Optical microstructure of the coating at 600℃ in Example 4. Figure 10SEM images of metal coatings after induction remelting at different spraying temperatures: (a) SEM image of the coating at a spraying temperature of 300℃ in Example 1; (b) SEM image of the coating at a spraying temperature of 400℃ in Example 2; (c) SEM image of the coating at a spraying temperature of 500℃ in Example 3; (d) SEM image of the coating at a spraying temperature of 600℃ in Example 4; (a1), (b1), (c1), and (d1) are magnified views of (a), (b), (c), and (d), respectively; (a2), (b2), (c2), and (d2) are magnified views of (a1), (b1), (c1), and (d1), respectively. Figure 11 SEM images of the cross-section of the metal material coating after induction remelting at different spraying temperatures: (a) is the SEM image of the coating cross-section at a spraying temperature of 300℃ in Example 1; (b) is the SEM image of the coating cross-section at a spraying temperature of 400℃ in Example 2; (a1) and (b1) are magnified views of (a) and (b), respectively. Figure 12 SEM images of the cross-section of the metal material coating after induction remelting at different spraying temperatures: (c) is the SEM image of the coating cross-section at a spraying temperature of 500℃ in Example 3; (d) is the SEM image of the coating cross-section at a spraying temperature of 600℃ in Example 4; (c1) and (d1) are magnified views of (c) and (d), respectively. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-12 The present invention provides a technical solution: Example 1: A method for preparing a corrosion-resistant metal coating includes the following steps: Preparation of modified hydrotalcite-like material: 66.67 g of magnesium nitrate and 33.33 g of aluminum nitrate were weighed and added to 1500 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution A. 80 g of sodium hydroxide and 20 g of sodium carbonate were weighed and added to 1000 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution B. Precursor solution A was heated to 60 °C, and precursor solution B was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 2 h to obtain a hydrotalcite-like suspension. 1 g of silane coupling agent was added to the hydrotalcite-like suspension, the temperature was raised to 70 °C, and the mixture was stirred for 1 h. After centrifugation and washing, modified hydrotalcite-like material was obtained. Preparation of modified molybdate solution: Take 1000g of deionized water and heat it to 40℃. Add 1g of ammonium bicarbonate and stir to dissolve. Then add 10.1g of anhydrous ethanol and stir evenly to obtain the modified solvent. Add 30.3g of ammonium molybdate to the modified solvent and stir to dissolve. Then add 1.52g of silane coupling agent and stir for 30min to obtain the modified molybdate solution. Preparation of modified iron-based alloy powder: Weigh 78.07g ferrous sulfate, 16.04g ferric chloride, 3.21g manganese chloride, and 0.68g nickel acetate. Add 800g deionized water and stir to dissolve at 30℃. Add 0.5g PEG-6000 and stir for 15min. Then add 5g modified hydrotalcite and stir for 30min. Simultaneously, add a precipitant (4.11g ammonium bicarbonate) and a modified molybdate solution (containing 3g ammonium molybdate) dropwise to maintain pH. 8.0, after the addition was complete, the temperature was raised to 50℃ and stirred for 1.5h, cooled to room temperature, the precipitate was vacuum filtered, washed with deionized water until pH 7.0, then washed with anhydrous ethanol, dried under vacuum at 80℃ and -0.09MPa for 12h, and then ground to obtain precursor powder. The precursor powder was calcined at 550℃ for 2h by passing argon gas through it and raising the temperature at 5℃ / min, then reduced by switching to hydrogen gas and raising the temperature to 850℃ for 3h. After cooling, it was ground and sieved to obtain 200-mesh modified iron-based alloy powder. Coating preparation: Cold spraying technology was used. After grinding the substrate, it was preheated to 120℃. The spraying temperature was set to 300℃, the number of spray passes was 1, the powder feed rate was 25g / s, the gas pressure was 0.8MPa, and the nozzle moving speed was 10mm / s. The nozzle was perpendicular to the sample and sprayed back and forth to obtain a pre-formed iron-based alloy coating. The pre-formed coating was remelted using an induction remelting process. The gap between the planar coil and the substrate was set to 10mm, the heating temperature was 510℃, the power was 1.2KW, the frequency was 175kHz, and the heating time was 10s to obtain a corrosion-resistant metal material coating.

[0019] Example 2: A method for preparing a corrosion-resistant metal coating includes the following steps: Preparation of modified hydrotalcite-like material: 77.67 g of magnesium nitrate and 33.77 g of aluminum nitrate were weighed and added to 1864 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution A. 81.25 g of sodium hydroxide and 22.81 g of sodium carbonate were weighed and added to 1134 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution B. Precursor solution A was heated to 60 °C, and precursor solution B was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 2 h to obtain a hydrotalcite-like suspension. 2.45 g of silane coupling agent was added to the hydrotalcite-like suspension, and the mixture was heated to 70 °C and stirred for 1 h. After centrifugation and washing, modified hydrotalcite-like material was obtained. Preparation of modified molybdate solution: Take 1000g of deionized water and heat it to 40℃. Add 1.5g of ammonium bicarbonate and stir to dissolve. Then add 26.3g of anhydrous ethanol and stir evenly to obtain a modified solvent. Add 45.45g of ammonium molybdate to the modified solvent and stir to dissolve. Then add 2.54g of silane coupling agent and stir for 30min to obtain a modified molybdate solution. Preparation of modified iron-based alloy powder: Weigh 78.41g ferrous sulfate, 17.31g ferric chloride, 3.56g manganese chloride, and 0.71g nickel acetate. Add 850g deionized water and stir to dissolve at 30℃. Add 0.65g PEG-6000 and stir for 15min. Then add 6g modified hydrotalcite and stir for 30min. Simultaneously, add a precipitant (4.45g ammonium bicarbonate) and a modified molybdate solution (containing 3.75g ammonium molybdate) dropwise, maintaining the temperature... pH 8.0, after the addition is complete, the temperature is raised to 50℃ and stirred for 1.5h, cooled to room temperature, the precipitate is vacuum filtered, washed with deionized water until pH 7.0, then washed with anhydrous ethanol, dried under vacuum at 80℃ and -0.09MPa for 12h, and then ground to obtain precursor powder. The precursor powder is calcined at 550℃ for 2h by passing argon gas through it and raising the temperature at 5℃ / min, then reduced by hydrogen gas at 850℃ for 3h, cooled, ground and sieved to obtain 200 mesh modified iron-based alloy powder. Coating preparation: Spraying temperature 400℃, other parameters are the same as in Example 1, to obtain a corrosion-resistant metal material coating.

[0020] Example 3: A method for preparing a corrosion-resistant metal coating includes the following steps: Preparation of modified hydrotalcite-like material: 71.43 g of magnesium nitrate and 28.57 g of aluminum nitrate were weighed and added to 1750 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution A. 78.95 g of sodium hydroxide and 21.05 g of sodium carbonate were weighed and added to 1100 g of deionized water. The mixture was stirred and dissolved to obtain precursor solution B. Precursor solution A was heated to 60 °C, and precursor solution B was added dropwise at a rate of 2 mL / min. After the addition was complete, the mixture was stirred for 2 h to obtain a hydrotalcite-like suspension. 2.5 g of silane coupling agent was added to the hydrotalcite-like suspension, the temperature was raised to 70 °C, and the mixture was stirred for 1 h. After centrifugation and washing, modified hydrotalcite-like material was obtained. Preparation of modified molybdate solution: Take 1000g of deionized water and heat it to 40℃. Add 2g of ammonium bicarbonate and stir to dissolve. Then add 34g of anhydrous ethanol and stir evenly to obtain a modified solvent. Add 60.6g of ammonium molybdate to the modified solvent and stir to dissolve. Then add 3.64g of silane coupling agent and stir for 30min to obtain a modified molybdate solution. Preparation of modified iron-based alloy powder: Weigh 78.79 g of ferrous sulfate, 18.18 g of ferric chloride, 4.04 g of manganese chloride, and 0.81 g of nickel acetate. Add 900 g of deionized water and stir to dissolve at 30 °C. Add 0.8 g of PEG-6000 and stir for 15 min. Then add 7 g of modified hydrotalcite and stir for 30 min. Simultaneously, add a precipitant (4.62 g of ammonium bicarbonate) and a modified molybdate solution (containing 4.5 g of ammonium molybdate) dropwise to maintain pH. H8.0 was added, and the temperature was raised to 50℃ and stirred for 1.5h. After cooling to room temperature, the precipitate was vacuum filtered, washed with deionized water until pH 7.0, and then washed with anhydrous ethanol. After drying under vacuum at 80℃ and -0.09MPa for 12h, the precursor powder was ground to obtain precursor powder. The precursor powder was calcined at 550℃ for 2h by passing argon gas through it and raising the temperature at 5℃ / min. Then, hydrogen gas was switched and the temperature was raised to 850℃ for 3h for reduction. After cooling, the powder was ground and sieved to obtain 200-mesh modified iron-based alloy powder. Coating preparation: Spraying temperature 500℃, other parameters are the same as in Example 1, to obtain a corrosion-resistant metal material coating.

[0021] Example 4: A method for preparing a corrosion-resistant metal coating includes the following steps: Preparation of modified hydrotalcite-like material: Weigh 75g of magnesium nitrate and 25g of aluminum nitrate, add 2000g of deionized water, and stir to dissolve to obtain precursor solution A; weigh 78.95g of sodium hydroxide and 21.05g of sodium carbonate, add 1200g of deionized water, and stir to dissolve to obtain precursor solution B; heat precursor solution A to 60℃, add precursor solution B dropwise at a rate of 2mL / min, and stir for 2h after the addition is complete to obtain hydrotalcite-like suspension; add 3g of silane coupling agent to hydrotalcite-like suspension, heat to 70℃ and stir for 1h; after centrifugation and washing, obtain modified hydrotalcite-like material. Preparation of modified molybdate solution: Take 1000g of deionized water and heat it to 40℃. Add 2g of ammonium bicarbonate and stir to dissolve. Then add 52.6g of anhydrous ethanol and stir evenly to obtain the modified solvent. Add 60.6g of ammonium molybdate to the modified solvent and stir to dissolve. Then add 4.24g of silane coupling agent and stir for 30min to obtain the modified molybdate solution. Preparation of modified iron-based alloy powder: Weigh 75.47g ferrous sulfate, 18.87g ferric chloride, 4.72g manganese chloride, and 0.94g nickel acetate. Add 1000g deionized water and stir to dissolve at 30℃. Add 1.0g PEG-6000 and stir for 15min. Then add 5g modified hydrotalcite and stir for 30min. Simultaneously, add a precipitant (5.13g ammonium bicarbonate) and a modified molybdate solution (containing 6g ammonium molybdate) dropwise to maintain pH. 8.0, after the addition was complete, the temperature was raised to 50℃ and stirred for 1.5h, cooled to room temperature, the precipitate was vacuum filtered, washed with deionized water until pH 7.0, then washed with anhydrous ethanol, dried under vacuum at 80℃ and -0.09MPa for 12h, and then ground to obtain precursor powder. The precursor powder was calcined at 550℃ for 2h by passing argon gas through it and raising the temperature at 5℃ / min, then reduced by switching to hydrogen gas and raising the temperature to 850℃ for 3h. After cooling, it was ground and sieved to obtain 200-mesh modified iron-based alloy powder. Coating preparation: Spraying temperature 600℃, other parameters are the same as in Example 1, to obtain a corrosion-resistant metal material coating.

[0022] Example 5: Corrosion-resistant metal coatings were prepared by applying 2, 3, and 4 spray passes respectively, with other parameters the same as in Example 1.

[0023] Comparative Example 1 Compared to Example 3, Comparative Example 1 replaced the modified hydrotalcite with conventional hydrotalcite, and the remaining steps were exactly the same as in Example 3.

[0024] Comparative Example 2 Comparative Example 2 differs from Example 3 in that the modified molybdate solution is replaced with a conventional ammonium molybdate solution, while the remaining steps are exactly the same as in Example 3.

[0025] Comparative Example 3 Compared to Example 3, Comparative Example 3 replaced the modified iron-based alloy powder with conventional iron-chromium-boron-silicon alloy powder.

[0026] Ten different metal material coatings were obtained through Examples 1-5 and Comparative Examples 1-3. The performance of the ten different metal material coatings was tested, specifically static immersion test, electrochemical test and wet-dry alternating corrosion test. Static immersion test: 3.5% NaCl solution (simulating marine salt spray), immersion period 1000h, immersion temperature room temperature; Electrochemical testing: The corrosive medium was a neutral 3.5% NaCl solution with pH=7, and the test temperature was 25ºC at room temperature. A three-electrode system was used, with the sample serving as the working electrode and an exposure area of ​​1 cm². 2The saturated calomel electrode is used as the reference electrode, and the Pt electrode is used as the auxiliary electrode. The scanning range of the electrode potential in the polarization test is from -2V to +1V relative to the open circuit potential, and the scanning rate is 1mV / s.

[0027] Wet-dry corrosion test: Simulating the working conditions of a nuclear power plant storage tank, the test involved 8 hours of immersion followed by 4 hours of drying, repeated 50 times. The specific test results are shown in Table 1 below. Table 1: Performance of Metallic Material Coatings in Each Embodiment Table 1 shows the effects of spraying temperature, number of spray passes, and powder type on coating hardness and porosity. In Examples 1-4 (spraying temperatures 300-600℃), hardness first increases and then decreases, reaching a peak at 500℃, while porosity continuously decreases, reaching its lowest point at 600℃. Example 3 (500℃) exhibits the best overall performance. Example 5, based on Example 1, uses 2, 3, and 4 spray passes respectively. Hardness continuously increases with increasing number of passes, while porosity gradually decreases. Comparing the data in Comparative Example 1 (conventional hydrotalcite) with the data in Example 3 demonstrates that the dispersibility and compatibility advantages of the modified hydrotalcite effectively fill pores, reduce corrosive media channels, and address the lack of... The density of the post-coating decreased significantly. Comparing the data in Comparative Example 2 (conventional ammonium molybdate solution) with the data in Example 3, it is shown that the dense passivation film formed by the modified molybdate can improve the coating strength. The lack of the post-coating structure reduces stability. The synergistic effect of the modified hydrotalcite and the modified molybdate is the core of the coating's high performance. The absence of either component alone will lead to significant performance degradation. The performance of Comparative Example 3 (conventional iron-chromium-boron-silicon alloy powder) deteriorated across the board, highlighting the core advantages of the modified iron-based alloy powder. Overall, the modified iron-based alloy powder, combined with a spraying temperature of 500°C and 4 spray passes, can obtain a high-hardness, low-porosity, high-quality coating, providing support for protection in harsh environments.

[0028] Figure 5 These figures show the microstructure of metal coatings applied at different spraying temperatures. (a), (c), (e), and (g) represent the microstructure of metal coatings applied by supersonic cold spraying at temperatures of 300℃, 400℃, 500℃, and 600℃, respectively. (b), (d), (f), and (h) are corresponding magnified views. The pore-free area at the bottom of the figures represents the substrate of the coating. The figures show numerous small pores in the coating, with diameters ranging from 3 to 5 µm. These pores are porosity, shrinkage cavities, and defects generated during the coating preparation process. Figure 5It is known that after spraying, the modified iron-based alloy powder has a flat surface distribution and many pores. During this process, gaps exist at the junctions of the modified iron-based alloy powder particles. This may be due to the different particle sizes, resulting in insufficient powder deformation during spraying and thus incomplete overlap, leading to numerous pores. The size and number of pores directly affect the coating quality, causing a decrease in mechanical and corrosion resistance. At a spraying temperature of 500℃, the internal structure of the coating is relatively uniform, with a small number of pores on the surface. This is because some gas dissolves within the high-speed particles during cold spraying, and the gas released during deformation forms pores on the surface. A comparison of the surface morphology of coatings at different spraying temperatures shows that the modified iron-based alloy powder prepared by the supersonic cold spraying process at 500℃ has significantly fewer pores than that prepared at other temperatures. These pores directly affect the mechanical and corrosion resistance of the coating.

[0029] Depend on Figure 6 It is known that as the spraying gas temperature increases, the microhardness of the coating gradually increases. The mechanism by which gas temperature affects the microhardness of the coating is mainly attributed to the fact that the increase in gas temperature can improve the acceleration effect of the airflow on the particles. The higher the particle velocity, the greater its compaction impact on the coating, the more obvious the work hardening effect within the coating, and the higher the coating hardness. In addition, the increase in gas temperature will cause a thermal softening effect on the particles. When the gas temperature rises from 300℃ to 500℃, the microhardness value of the coating increases significantly. At this time, the thermal softening effect of the particles is not obvious. When the gas temperature reaches 500℃, the airflow acceleration effect is better, but the thermal softening of the particles offsets part of the work hardening effect inside the coating, resulting in a decrease in the increase in coating hardness. When the spraying temperature is 600℃, the hardness decreases. This is because the spraying temperature is too high, and the internal thermal stress of the coating is too high, resulting in cracks and reducing the hardness of the coating.

[0030] Figure 7The images show the cross-sectional microstructure of metal coatings prepared using supersonic cold spraying technology under different spraying passes. (a), (c), (e), and (g) show the microstructure of the coating cross-sections under different spraying passes in Example 1 (pass 1), Example 5 (pass 2), Example 5 (pass 3), and Example 5 (pass 4), respectively. (b), (d), (f), and (h) are enlarged views of (a), (c), (e), and (g). When the spraying passes are 1-3, the supersonic cold sprayed modified iron-based alloy powder is extremely unevenly distributed on the substrate, failing to completely cover it. Coatings prepared under these conditions tend to have poor performance. Exposure of the substrate in the required environment can lead to a large cathode and small anode situation, accelerating substrate corrosion. As the coating thickness increases, the powder is distributed in layers on the coating surface, and the coating bonds well to the substrate through mechanical bonding. However, the modified iron-based alloy powder prepared under this process... During the layered deposition process, pores exist, and the porosity is relatively high. When the number of spray passes reaches 4, a few pores can be observed inside the coating from the cross-sectional morphology. This may be because the powder velocity is too high during the spraying process, which dissolves some gas. When the gas that has been released cannot escape from the particles in time, a certain amount of pores are generated inside them. These pores will directly cause the solution to enter the interior of the coating, thereby corroding the substrate and significantly reducing its performance. When the number of spray passes is 4, the metal material coating prepared by the supersonic cold spraying process has a low porosity, and there is an obvious bonding line "bright line" between the coating and the substrate, indicating that mutual solubility has occurred between the elements of the coating and the substrate. Under this process, the metal material coating has good protection for the substrate. As the thickness increases, the coating quality remains relatively stable. This shows that increasing the number of spray passes can enhance the deformation of particles during the impact process, thereby improving the bonding between particles and reducing porosity.

[0031] like Figure 8 As shown, the microhardness of the coating surface increases with the increase of the number of spraying passes. This is because the coating thickness gradually increases with the increase of the number of spraying passes. It can also be observed that the hardness increase is the largest from the first to the second pass. This is because when the number of spraying passes is low, metal powder is easier to deposit. As the number of spraying passes increases, the difficulty of metal powder deposition increases, the coating thickness changes less, and therefore the increase in hardness is relatively small.

[0032] Figure 9 These are optical micrographs of the surface microstructure of pre-coated samples after induction remelting at different spraying temperatures. Figure 9 As can be seen in (a)-(d), the surface of the coating after induction remelting is uneven and contains a large number of pores. Figure 9As can be seen in (a), when the cold spraying temperature is 300℃, after induction remelting, many small, regularly shaped granular substances appear on the surface of the coating, most of which are square. When the spraying temperature reaches 400℃, after induction remelting, the shape of the granular substances on the surface of the coating changes from the original squares to irregular circles. At the same time, a small number of small triangular substances can be found on the surface of the coating, such as... Figure 9 As shown in (b), with further increases in spraying temperature, the number of triangular materials on the coating surface increases, such as... Figure 9 As shown in (c), when the spraying temperature reaches 600℃, it can be observed that the number of triangular substances on the coating surface further increases, and the size difference is relatively large, such as... Figure 9 As shown in (d).

[0033] To further clarify the microstructure morphology of the coating surface after remelting, scanning electron microscopy (SEM) was used to characterize the microstructure morphology of the coating surface. Figure 10 SEM images of the coating after induction remelting at different spraying temperatures show that as the spraying temperature increases, the porosity of the sample surface gradually decreases, and the sample surface becomes smoother and more uniform. This is because as the spraying temperature increases, the plasticity of the metal powder is enhanced, allowing the metal powder to undergo sufficient plastic deformation and thus better bond with the matrix. After induction remelting, the cold-sprayed coating is fully remelted, and cooling in air further improves the density of the coating, thereby improving the coating quality. Figure 10 As shown in (a), after induction remelting, the surface of the sample contains a large number of layered metal particles. Magnified observation of the depressions in the coating reveals numerous fine particles, such as... Figure 10 As shown in (a1), upon further magnification, the layered morphology of the stacked metal particles can be clearly observed, such as... Figure 10 As shown in (a2), a large number of fine, round particles are present in the pit of the sample, and they are concentrated in one area. Larger square particles are distributed around these particles. Furthermore, from... Figure 10 As can be seen in (b)-(d), approximately triangular blocky substances are distributed on the surface of the coating. As the spraying temperature increases, the number of these triangular blocky substances gradually increases, and their size also increases.

[0034] Figures 11-12 SEM images of the cross-sections of the coatings after induction remelting at different spraying temperatures are shown. It is evident from the images that the coating thickness decreases after induction remelting. No obvious cracks are found within the coating, but a small number of pores are present. The interface between the substrate and the coating is relatively smooth, exhibiting metallurgical bonding characteristics. This improves the bonding strength between the coating and the substrate. Figure 11(a) It can be observed that there are very small gaps at the interface between the coating and the substrate surface. Upon further magnification, it can be seen that the structure of the remelted coating is not uniform. Figure 11 As can be observed in (b), after induction remelting, the coating thickness on the surface is very small and it is fused with the substrate material. This is because the coating thickness is small at 400°C. During the induction remelting process, the skin effect affects the interface between the coating surface and the substrate surface, which concentrates the input heat at the interface, causing the substrate material to melt into the coating material. This is also the reason why the coating thickness decreases after induction remelting. Meanwhile, it can be observed that when the spraying temperature is 300℃, induction remelting has a significant impact on the substrate material, and many pores and cracks can be found in the substrate material. As the spraying temperature increases, the number of pores inside the substrate material decreases. When the spraying temperature increases to 600℃, the number of pores and cracks in the substrate material is minimal. This is because, as the spraying temperature increases, the thickness of the cold spray coating also increases. Under the same remelting conditions, the greater the coating thickness, the smaller the impact on the substrate material during rapid heating and melting.

[0035] This invention fundamentally solves the technical pain points of traditional coatings, such as high porosity, easy penetration of corrosive media, and insufficient bonding strength, through the synergistic protective design of modified hydrotalcite and modified molybdate, combined with a composite preparation process of cold spraying and induction remelting. Modified hydrotalcite fills the pores and blocks corrosion channels, while modified molybdate forms a passivation film and inhibits oxidation reactions. The combination of these two with modified iron-based alloy powder and an optimized spraying-remelting process enables the coating to exhibit excellent corrosion resistance under harsh conditions such as simulated marine salt spray and alternating wet and dry conditions, making it particularly suitable for long-term protection of iron-based alloy materials such as nuclear power plant storage tanks.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a corrosion-resistant metallic material coating, characterized in that, Includes the following steps: S1. Using a cold spraying technique with a temperature of 300-600℃ and 1-4 spray passes, modified iron-based alloy powder is sprayed onto the surface of a polished substrate. The substrate preheating temperature is 130±10℃. During spraying, the powder feed rate is 20-30g / s, the nozzle is perpendicular to the sample direction, the gas pressure is 0.7-0.9MPa, the nozzle moving speed is 8-12mm / s, and a reciprocating operation is adopted to obtain a pre-formed iron-based alloy coating. S2. The pre-made iron-based alloy coating is remelted using an induction remelting process. The induction remelting process uses planar heating with a heating temperature of 500-520℃, a heating power of 1.2-2.2KW, a frequency of 165-185kHz, and a heating time of 8-12s to obtain a corrosion-resistant metal material coating. The modified iron-based alloy powder is prepared through the following steps: S11. Weigh the iron-based precursor raw material and add it to deionized water at 25-35℃. Stir until completely dissolved, then add PEG-6000 and stir for 15-20 minutes. Continue to add modified hydrotalcite and stir for 30-35 minutes to obtain an iron-based mixed solution. S12. Simultaneously add the precipitant solution and the modified molybdate solution dropwise to the iron-based mixed solution. During the dropwise addition, continue stirring and maintain the pH value between 7.5 and 8.

0. After the dropwise addition is completed, raise the temperature to 45-50℃ and continue stirring for 1.5-2 hours to obtain the reaction system. Then cool the reaction system to room temperature. S13. The reaction system cooled in step S12 is vacuum filtered to collect the precipitate. The pH of the precipitate is washed with deionized water to 6.5-7.

0. Finally, it is washed with anhydrous ethanol. After washing, the precipitate is dried and ground to obtain the precursor powder. S14. The precursor powder from step S13 is calcined under argon gas, heated to 500-550℃ at a heating rate of 4-8℃ / min and held for calcination for 2-3 hours. After calcination, the argon gas is switched to hydrogen gas, and the temperature is further increased to 800-900℃ and held for reduction for 2-3 hours. After reduction, hydrogen gas is continuously introduced to cool to room temperature. The reduced precursor powder is then ground to obtain 200-400 mesh modified iron-based alloy powder.

2. The method for preparing a corrosion-resistant metallic material coating according to claim 1, characterized in that, The modified hydrotalcite is prepared through the following steps: S111. Add magnesium nitrate and aluminum nitrate to deionized water and stir to dissolve to obtain precursor solution A. Add sodium hydroxide and sodium carbonate to deionized water and stir to obtain precursor solution B. Heat precursor solution A to 50-60℃ and then add precursor solution B dropwise at a rate of 1.5-2 mL / min. After the addition is complete, stir for 1.5-2 h to obtain a hydrotalcite-like suspension. S112. Add silane coupling agent to the hydrotalcite-like suspension in step S111, heat to 60-70℃ and stir for 1-2 hours, centrifuge and wash with deionized water to obtain modified hydrotalcite-like suspension.

3. The method for preparing a corrosion-resistant metallic material coating according to claim 1, characterized in that, The modified molybdate solution is prepared by the following steps: S121. Heat deionized water to 35-45℃, add ammonium bicarbonate and stir until completely dissolved, then add anhydrous ethanol and stir to obtain the modified solvent. S122. Add ammonium molybdate to the modified solvent in step S121 and stir to dissolve to obtain a molybdate solution. Add silane coupling agent to the molybdate solution and stir for 25-35 minutes to obtain a modified molybdate solution.

4. The method for preparing a corrosion-resistant metallic material coating according to claim 1, characterized in that, The iron-based precursor raw material in step S11 is ferrous sulfate: ferric chloride: manganese chloride: nickel acetate in a mass ratio of (7.5-8.0):(1.5-2.0):(0.3-0.5):(0.05-0.10). The total mass of the iron-based precursor raw material is in a mass ratio of 1:(0.005-0.010) to PEG-6000. The total mass of the iron-based precursor raw material is in a mass ratio of 1:(8-10):(0.05-0.08) to deionized water and modified hydrotalcite.

5. The method for preparing a corrosion-resistant metallic material coating according to claim 1, characterized in that, In step S12, the mass ratio of ammonium molybdate to the iron-based precursor in the modified molybdate solution is (0.03-0.06):1, and the precipitant solution is ammonium bicarbonate, with the mass ratio of ammonium bicarbonate to all metal ions in the iron-based precursor being (1.2-1.5):

1.

6. The method for preparing a corrosion-resistant metallic material coating according to claim 2, characterized in that, In step S111, the mass ratio of magnesium nitrate to aluminum nitrate is (2-3):1, the mass ratio of sodium hydroxide to sodium carbonate is (1.2-1.5):(0.3-0.4), the mass ratio of the total mass of magnesium nitrate and aluminum nitrate to deionized water is 1:(15-20), and the mass ratio of the total mass of sodium hydroxide and sodium carbonate to deionized water is 1:(10-12). In step S112, the mass ratio of silane coupling agent to modified hydrotalcite is (0.02-0.03):

1.

7. The method for preparing a corrosion-resistant metallic material coating according to claim 3, characterized in that, In step S121, the mass concentration of ammonium bicarbonate in the modified solvent is 0.1-0.2%, and the mass ratio of deionized water to anhydrous ethanol is (9.0-19.0):

1.

8. The method for preparing a corrosion-resistant metallic material coating according to claim 3, characterized in that, In step S122, the mass ratio of silane coupling agent to ammonium molybdate is (0.05-0.07):1, and the concentration of ammonium molybdate in the modified solvent is 30-60 g / L.

9. A corrosion-resistant metal material coating, characterized in that, It is prepared according to the preparation method according to any one of claims 1-8 above.

10. The application of the corrosion-resistant metal material coating as described in claim 9 as a coating material for steel storage tanks in nuclear power plants.

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