Fused salt corrosion protection method and device

Abstract

The invention discloses a fused salt corrosion protection method and device. The method comprises the following steps that S1, before use, molten salt is molten, and the molten salt makes contact with a carbon-based material in the melting process; s2, in the service process of the metal material in the molten salt, the molten salt makes contact with the carbon-based material; wherein the mode of contacting the molten salt with the carbon-based material comprises the step of adding the carbon-based material into the molten salt and / or taking the carbon-based material as a container. According to the fused salt corrosion protection method, the fused salt corrosion problem can be effectively relieved, the corrosion depth and the corrosion rate of the metal material in the fused salt are reduced, and therefore the service life of the metal material in the high-temperature fused salt is prolonged.

Description

Technical Field

[0001] This invention relates to a method and apparatus for protecting against molten salt corrosion. Background Technology

[0002] Chloride molten salts possess advantages such as low cost, high thermal and chemical stability, and good heat transfer properties, making them key candidate heat transfer, heat storage, and reaction media in energy fields such as molten salt reactors, solar thermal power plants, and dry reprocessing of nuclear fuel. However, chloride molten salts are highly corrosive, therefore, the compatibility of structural materials with chloride molten salts is a key bottleneck restricting their application in these high-temperature molten salt fields.

[0003] Stainless steel and nickel-based alloys possess excellent high-temperature performance, corrosion resistance, and oxidation resistance, making them widely used in high-temperature fields such as aerospace, nuclear reactors, and solar power generation. They are also key candidate materials for these chloride salt applications. Research has found that active elements such as Cr and Fe in stainless steel and nickel-based alloys undergo selective corrosion dissolution in chloride salts, leading to intergranular corrosion, pitting corrosion, and stress corrosion. This results in material degradation issues such as thinning of metal pipe walls, perforation, and cracking, affecting the safety of material service.

[0004] In recent years, many research institutions both domestically and internationally have prioritized addressing the chloride corrosion problem of alloy materials, achieving significant progress. One method has been proposed to utilize the active metal magnesium (Mg) to regulate chloride corrosion. For example, Ding et al. at the Institute of Engineering Thermodynamics, German Aerospace Center (DLR), used Mg anodic electrolytic reduction to alleviate the corrosion of Incoloy 800H alloy in NaCl-KCl-MgCl2 molten salt. The Shanghai Institute of Applied Physics, Chinese Academy of Sciences, used metallic Mg to purify NaCl-KCl-MgCl2 molten salt, inhibiting chloride corrosion of 316H stainless steel and nickel-based alloys such as GH3535 and Haynes 230. The National Renewable Energy Laboratory (NREL) in the United States used Mg sheets for thermal and chemical purification of MgCl2-KCl-NaCl molten salt to inhibit the corrosion of Haynes 230 alloy.

[0005] However, when using metallic magnesium (Mg) to control the corrosivity of molten salt, insoluble MgO is generated. When MgO accumulates to a certain amount, it can cause blockages in heat exchanger pipes and valve interfaces. The presence of MgO can also lead to secondary corrosion problems. Furthermore, even with good molten salt purification, air is inevitably introduced during molten salt use and loading, increasing its corrosivity. Therefore, the aforementioned molten salt purification methods alone cannot completely solve the corrosion problem during molten salt use. Additionally, the method of using metallic magnesium to control the corrosivity of molten salt is only suitable for controlling chloride molten salt systems containing MgCl2 and is not suitable for other chloride salt systems, thus having limitations.

[0006] In addition, there is a surface coating method, which achieves physical isolation by adding a coating to the surface of the alloy material. For example, Chinese patent document CN119592145A uses graphite as a coating material. Although it can achieve the effect of molten salt corrosion protection for a certain period of time, it has drawbacks such as complex process operation, unsuitability for chloride molten salts, and a low applicable temperature range. In addition, the coating material and the alloy material have different coefficients of thermal expansion, which can easily lead to gaps or even peeling off after long-term use, causing corrosion of the stainless steel substrate. Summary of the Invention

[0007] This invention addresses the shortcomings of existing molten salt corrosion protection technologies, namely poor and inconsistent protection effectiveness, by providing a method and apparatus for molten salt corrosion protection. The molten salt corrosion protection method of this invention can effectively alleviate molten salt corrosion problems, reduce the corrosion depth and rate of metallic materials in molten salt, thereby improving the service life of metallic materials in high-temperature molten salt.

[0008] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0009] This invention provides a method for protecting against molten salt corrosion, comprising the following steps:

[0010] S1. Before use, the molten salt is melted, and during the melting process, the molten salt comes into contact with the carbon-based material;

[0011] S2. During the service of the metallic material in molten salt, the molten salt comes into contact with the carbon-based material;

[0012] The method of contacting the molten salt with the carbon-based material includes adding the carbon-based material to the molten salt and / or using the carbon-based material as a container.

[0013] In this invention, the carbon-based material can be conventional in the art.

[0014] In this invention, the carbon content of the carbon-based material is preferably ≥90%, and the percentage is a mass percentage.

[0015] In this invention, the carbon-based material preferably includes one or more of graphite, glassy carbon, carbon-carbon composite materials, and activated carbon; more preferably, it includes graphite.

[0016] In this invention, when the molten salt contacts the carbon-based material by adding the carbon-based material to the molten salt, the carbon-based material is preferably in the form of one or more of powder, block, plate, and granules.

[0017] In this invention, when the molten salt contacts the carbon-based material in a container made of the carbon-based material, the container is preferably a crucible, and more preferably a graphite crucible.

[0018] In this invention, the molten salt can be a conventional molten salt in the art, preferably including chloride molten salt.

[0019] In this invention, the chloride molten salt can be conventional in the art, and preferably includes one or more of NaCl, KCl, LiCl, MgCl2, CaCl2, ZnCl2 and AlCl3.

[0020] In some preferred embodiments of the present invention, the chloride molten salt includes NaCl, KCl and MgCl2.

[0021] In some specific embodiments of the present invention, the chloride molten salt comprises 33% NaCl, 21.6% KCl and 45.4% MgCl2, the percentages being molar percentages.

[0022] In this invention, in step S1, the melting temperature can be selected according to the type of molten salt, as long as it is sufficient to melt the molten salt.

[0023] Preferably, the melting temperature is 400℃-850℃, for example 700℃.

[0024] Preferably, the melting time is ≥2h, for example 4h.

[0025] In this invention, in step S1, the melting can be carried out in an environment protected by an inert atmosphere. The inert atmosphere can be conventional in the art, generally referring to an atmosphere that does not react with the molten salt system of this invention, preferably argon or nitrogen. The purity of the argon is preferably ≥99.9%, for example 99.999%; the purity of the nitrogen is preferably ≥99.9%, for example 99.999%. In this invention, the environment protected by the inert atmosphere can be provided by a glove box.

[0026] In this invention, step S1 preferably includes a step of drying the carbon-based material before the melting process. The drying temperature is preferably 100℃-500℃, for example, 200℃; the drying time is preferably 12-24h, for example, 24h.

[0027] In this invention, during step S2, the system is covered with an inert atmosphere while the metal material is in service in the molten salt. The inert atmosphere can be conventional in the art, generally referring to an atmosphere that does not react with the molten salt system of this invention, preferably argon or nitrogen. The purity of the argon is preferably ≥99.9%, for example 99.999%; the purity of the nitrogen is preferably ≥99.9%, for example 99.999%. In this invention, the environment protected by the inert atmosphere can be provided by a glove box.

[0028] In this invention, during step S2, when the metal material is in service in molten salt, the temperature of the molten salt is preferably 400℃-850℃, for example 800℃.

[0029] In this invention, in step S2, the metal material preferably includes stainless steel and / or corrosion-resistant alloy.

[0030] In this invention, the stainless steel can be conventional in the art, preferably including one or more of austenitic stainless steel, ferritic stainless steel, austenitic-ferritic stainless steel, martensitic stainless steel, and precipitation-hardening stainless steel, more preferably including austenitic stainless steel. The austenitic stainless steel can be conventional in the art, preferably including one or more of 316, 316H, 316L, 347, 347H, 321, 304, 304L, and 904L.

[0031] In this invention, the corrosion-resistant alloy can be conventional in the art, preferably including nickel-based alloys and / or iron-nickel-based alloys.

[0032] The nickel-based alloy preferably includes alloys with nickel as the main element, and more preferably includes one or more of Ni-Cu, Ni-Fe, Ni-Cr, Ni-Mo, Ni-W, Ni-Fe-Cr, Ni-Mo-Cr, Ni-W-Cr, Ni-Mo-W, Ni-Mo-W-Cr and Ni-Fe-Mo-Cr, such as one or more of Monel 400, Haynes 230, GH3539, Hastelloy C276, Hastelloy C22, Hastelloy N, GH3535, Haynes 242, Inconel 600, Inconel 625, Inconel 617 and Inconel 718.

[0033] The iron-nickel-based alloy is an alloy with iron and nickel as the main elements, preferably including one or more of Incoloy 330 and Inconel 800 / 800H.

[0034] The present invention also provides a molten salt corrosion protection device, which includes a carbon-based material container for contacting molten salt.

[0035] In this invention, the carbon content of the carbon-based material in the carbon-based material container is preferably ≥90%, and the percentage is a mass percentage.

[0036] In this invention, the carbon-based material of the carbon-based material container preferably includes one or more of graphite, glassy carbon, carbon-carbon composite materials, and activated carbon.

[0037] In this invention, the carbon-based material container is preferably a graphite crucible.

[0038] In some preferred embodiments of the present invention, the graphite crucible includes a graphite crucible body and a graphite lid, the graphite crucible body and the graphite lid forming a sealed cavity.

[0039] In this invention, the molten salt corrosion protection device may further include a stainless steel container, and the carbon-based material container is placed inside the stainless steel container. Preferably, the stainless steel container is a stainless steel crucible.

[0040] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0041] The reagents and raw materials used in this invention are all commercially available.

[0042] The positive and progressive effects of this invention are as follows:

[0043] (1) The carbon-based material used in this invention is a conventional material that is non-toxic, inexpensive and readily available. The byproducts formed by the reaction of the carbon-based material with the corrosive medium in the molten salt are mostly gaseous substances that will not affect the physical properties of the molten salt.

[0044] (2) The method of the present invention can not only regulate the corrosivity of molten salt before use, but also solve the corrosion problem during the use of molten salt.

[0045] (3) This invention can not only broaden the selection range of alloy structural materials for molten salt media, but also reduce the quality control standards of molten salt and promote its application in high-temperature energy fields such as nuclear energy and solar energy.

[0046] (4) The corrosion protection method of the present invention is simple, efficient, safe and environmentally friendly, easy to operate and control, and uses inexpensive and readily available raw materials, which can be applied on a large scale. Only by adding carbon-based materials during the melting preparation and use process, the corrosion depth and corrosion rate of metal materials in molten salt can be reduced, and the service life of metal materials can be improved, which has good promotion value. Attached Figure Description

[0047] Figure 1 A schematic diagram of the molten salt pretreatment process;

[0048] Figure 2 This is a schematic diagram of a molten salt corrosion protection device using a graphite crucible;

[0049] Figure 3 A schematic diagram of a molten salt corrosion protection device using a non-insulated graphite crucible;

[0050] Figure 4 This is a schematic diagram of a molten salt corrosion test apparatus using a corundum crucible.

[0051] Figure 5The image shows the SEM cross-sectional morphology of the nickel-based GH3539 alloy after corrosion in Example 1.

[0052] Figure 6 The image shows the SEM cross-sectional morphology of the nickel-based GH3539 alloy after corrosion in Comparative Example 1.

[0053] Figure 7 This is a SEM cross-sectional image of the 347H stainless steel after corrosion in Example 2.

[0054] Figure 8 This is a SEM cross-sectional morphology image of the 347H stainless steel after corrosion in Comparative Example 2.

[0055] Figure 9 This is a SEM cross-sectional image of the nickel-based GH3539 alloy after corrosion in Example 3;

[0056] Figure 10 The image shows the SEM cross-sectional morphology of the nickel-based GH3539 alloy after corrosion in Comparative Example 3.

[0057] Explanation of reference numerals in the attached figures: 1. 316SS stainless steel crucible; 2. Corundum rod; 3. Nickel wire; 4. Graphite crucible; 5. Molten salt; 6. Alloy sample; 7. Alloy rod; 8. Alumina crucible; 9. Graphite lid; 10. Alumina crucible lid. Detailed Implementation

[0058] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0059] Example 1

[0060] 1. Preparation of nickel-based GH3539 alloy samples

[0061] Nickel-based GH3539 alloy was cut into specimens measuring 10 mm × 15 mm × 2 mm using wire cutting, and a 1.5 mm diameter hole was drilled in each specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (nickel-based GH3539 alloy). The specimen dimensions were measured using vernier calipers, and the specimen weight was measured using a balance with an accuracy of 0.1 mg.

[0062] 2. Corrosion protection methods for nickel-based GH3539 alloy in molten NaCl-KCl-MgCl2 salt at 800℃

[0063] S1. Molten salt pretreatment:

[0064] (1) Weigh NaCl, KCl and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6% and 45.4%, respectively, stir the molten salts evenly, and pour them into a graphite crucible;

[0065] (2) Then put the graphite crucible filled with molten salt into the well muffle furnace, dry it at 200℃ for 4 hours, and then heat it to 700℃ to melt it for 4 hours.

[0066] (3) Wait for the molten salt to cool to room temperature, break the crucible, take out the molten salt, crush the molten salt into small pieces, put them into a plastic sealed bag, and set aside for later use.

[0067] The entire process takes place in a glove box filled with argon gas (99.999% purity), as shown in the flowchart below. Figure 1 As shown.

[0068] S2, Immersion Corrosion Test:

[0069] (1) Place the alloy sample 6 (nickel-based GH3539 alloy) into the graphite crucible 4. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the corundum rod 2 connected to the inner wall of the graphite crucible 4.

[0070] (2) Weigh out 60g of pretreated molten salt 5 and place it in the graphite crucible 4. The molten salt 5 should completely submerge the alloy sample 6. Cover the sample with the graphite cap 9. Place the graphite crucible 4 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to seal it. This completes the molten salt corrosion protection device. Figure 2 As shown.

[0071] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 100 hours.

[0072] The entire assembly and welding process of the molten salt corrosion protection device is carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0073] Example 2

[0074] 1. Preparation of stainless steel 347H alloy samples

[0075] Stainless steel 347H was cut into specimens with dimensions of 10 mm × 10 mm × 2 mm using wire cutting, and a hole with a diameter of 1.5 mm was drilled in each specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (stainless steel 347H). The dimensions of the specimens were measured using vernier calipers, and their weight was measured using a balance with an accuracy of 0.1 mg.

[0076] 2. Corrosion protection methods for 347H stainless steel in molten NaCl-KCl-MgCl2 salt at 800℃

[0077] S1. Molten salt pretreatment:

[0078] (1) Weigh NaCl, KCl and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6% and 45.4%, respectively, stir the molten salts evenly, and pour them into a graphite crucible;

[0079] (2) Then put the graphite crucible filled with molten salt into the well muffle furnace, dry it at 200℃ for 4 hours, and then heat it to 700℃ to melt it for 4 hours.

[0080] (3) Wait for the molten salt to cool to room temperature, break the crucible, take out the molten salt, crush the molten salt into small pieces, put them into a plastic sealed bag, and set aside for later use.

[0081] The entire process takes place in a glove box filled with argon gas (99.999% purity), as shown in the flowchart below. Figure 1 As shown.

[0082] S2, Immersion Corrosion Test:

[0083] (1) Place the alloy sample 6 (stainless steel 347H) into the graphite crucible 4. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the corundum rod 2 connected to the inner wall of the graphite crucible 4.

[0084] (2) Weigh out 60g of pretreated molten salt 5 and place it in the graphite crucible 4. The molten salt 5 should completely submerge the alloy sample 6. Cover the sample with the graphite cap 9. Place the graphite crucible 4 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to seal it. This completes the molten salt corrosion protection device. Figure 2 As shown.

[0085] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 100 hours.

[0086] The entire assembly and welding process of the molten salt corrosion protection device is carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0087] Example 3

[0088] 1. Preparation of nickel-based GH3539 alloy samples

[0089] Nickel-based GH3539 alloy was cut into flat specimens (10 mm × 15 mm × 2 mm) and rod-shaped specimens (43 mm × 6 mm × 3 mm) using wire cutting. A hole with a diameter of 1.5 mm was drilled at one end of the flat specimen, and a hole with a diameter of 2 mm was drilled in the middle of the rod-shaped specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (nickel-based GH3539 alloy). The dimensions of the specimens were measured using vernier calipers, and the weight was measured using a balance with an accuracy of 0.1 mg.

[0090] 2. Corrosion protection methods for nickel-based GH3539 alloy in molten NaCl-KCl-MgCl2 salt at 800℃

[0091] S1. Molten salt pretreatment:

[0092] (1) Weigh NaCl, KCl and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6% and 45.4%, respectively, stir the molten salts evenly, and pour them into a graphite crucible;

[0093] (2) Then put the graphite crucible filled with molten salt into the well muffle furnace, dry it at 200℃ for 4 hours, and then heat it to 700℃ to melt it for 4 hours.

[0094] (3) Wait for the molten salt to cool to room temperature, break the crucible, take out the molten salt, crush the molten salt into small pieces, put them into a plastic sealed bag, and set aside for later use.

[0095] The entire process takes place in a glove box filled with argon gas (99.999% purity), as shown in the flowchart below. Figure 1 As shown.

[0096] S2, Immersion Corrosion Test:

[0097] (1) Place the alloy sample 6 (nickel-based GH3539 alloy) into the graphite crucible 4. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the alloy rod 7 connected to the inner wall of the graphite crucible 4.

[0098] (2) Weigh out 60g of pretreated molten salt 5 and place it in the graphite crucible 4. The molten salt 5 should completely submerge the alloy sample 6. Cover the sample with the graphite cap 9. Place the graphite crucible 4 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to seal it. This completes the molten salt corrosion protection device. Figure 3 As shown.

[0099] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 400 hours.

[0100] The entire assembly and welding process of the molten salt corrosion protection device is carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0101] Comparative Example 1

[0102] 1. Preparation of nickel-based GH3539 alloy samples

[0103] Nickel-based GH3539 alloy was cut into specimens measuring 10 mm × 15 mm × 2 mm using wire cutting, and a 1.5 mm diameter hole was drilled in each specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (nickel-based GH3539 alloy). The specimen dimensions were measured using vernier calipers, and the specimen weight was measured using a balance with an accuracy of 0.1 mg.

[0104] 2. Corrosion protection methods for nickel-based GH3539 alloy in molten NaCl-KCl-MgCl2 salt at 800℃

[0105] S1. Molten salt pretreatment:

[0106] (1) Weigh NaCl, KCl and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6% and 45.4%, respectively, stir the molten salts evenly, and pour them into an alumina crucible;

[0107] (2) Then put the alumina crucible filled with molten salt into a pit muffle furnace and dry it at 200℃ for 4 hours;

[0108] (3) Wait for the molten salt to cool to room temperature, take out the molten salt, put it into a plastic sealed bag, and keep it for later use.

[0109] The entire process was carried out in a glove box filled with an argon atmosphere (99.999% purity).

[0110] S2, Immersion Corrosion Test:

[0111] (1) Place the alloy sample 6 (nickel-based GH3539 alloy) into the alumina crucible 8. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the alumina crucible cover 10.

[0112] (2) Weigh out another 60g of molten salt 5 and place it in the alumina crucible 8, ensuring the molten salt 5 completely submerges the alloy sample 6. Cover the alumina crucible with the lid 10. Place the alumina crucible 8 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to a seal. This completes the molten salt corrosion test apparatus, as shown below. Figure 4 As shown.

[0113] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 100 hours.

[0114] The entire assembly and welding process of the molten salt corrosion protection device is carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0115] Comparative Example 2

[0116] 1. Preparation of stainless steel 347H alloy samples

[0117] Stainless steel 347H was cut into specimens with dimensions of 10 mm × 10 mm × 2 mm using wire cutting, and a hole with a diameter of 1.5 mm was drilled in each specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (stainless steel 347H). The dimensions of the specimens were measured using vernier calipers, and their weight was measured using a balance with an accuracy of 0.1 mg.

[0118] 2. Corrosion protection methods for 347H stainless steel in molten NaCl-KCl-MgCl2 salt at 800℃

[0119] S1. Molten salt pretreatment:

[0120] Weigh out NaCl, KCl, and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6%, and 45.4%, and mix the molten salts thoroughly.

[0121] The entire process was carried out in a glove box filled with an argon atmosphere (99.999% purity).

[0122] S2, Immersion Corrosion Test:

[0123] (1) Place the alloy sample 6 (stainless steel 347H) into the alumina crucible 8. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the alumina crucible cover 10.

[0124] (2) Weigh out 60g of pretreated molten salt 5 and place it in the alumina crucible 8. The molten salt 5 should completely submerge the alloy sample 6. Cover the alumina crucible with the lid 10. Place the alumina crucible 8 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to seal it. This completes the molten salt corrosion test apparatus, as shown below. Figure 4 As shown.

[0125] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 100 hours.

[0126] The entire assembly and welding process of the device was carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0127] Comparative Example 3

[0128] 1. Preparation of nickel-based GH3539 alloy samples

[0129] Nickel-based GH3539 alloy was cut into specimens measuring 10 mm × 15 mm × 2 mm using wire cutting, and a 1.5 mm diameter hole was drilled in each specimen. All specimen surfaces were progressively polished with diamond sandpaper to 2000 grit, then ultrasonically cleaned sequentially with deionized water and anhydrous ethanol, and finally dried to obtain alloy specimen 6 (nickel-based GH3539 alloy). The specimen dimensions were measured using vernier calipers, and the specimen weight was measured using a balance with an accuracy of 0.1 mg.

[0130] 2. Corrosion protection methods for nickel-based GH3539 alloy in molten NaCl-KCl-MgCl2 salt at 800℃

[0131] S1. Molten salt pretreatment:

[0132] (1) Weigh NaCl, KCl and MgCl2 chloride molten salts in a molar percentage ratio of 33%, 21.6% and 45.4%, respectively, stir the molten salts evenly, and pour them into an alumina crucible;

[0133] (2) Then put the alumina crucible filled with molten salt into a pit muffle furnace and dry it at 200℃ for 4 hours;

[0134] (3) Wait for the molten salt to cool to room temperature, take out the molten salt, put it into a plastic sealed bag, and keep it for later use.

[0135] The entire process was carried out in a glove box filled with an argon atmosphere (99.999% purity).

[0136] S2, Immersion Corrosion Test:

[0137] (1) Place the alloy sample 6 (nickel-based GH3539 alloy) into the alumina crucible 8. Specifically, take 3 alloy samples 6, string the alloy samples 6 together through the holes on the alloy samples 6 with nickel wire 3, and then suspend them on the alumina crucible cover 10.

[0138] (2) Weigh out 60g of pretreated molten salt 5 and place it in the alumina crucible 8. The molten salt 5 should completely submerge the alloy sample 6. Cover the alumina crucible with the lid 10. Place the alumina crucible 8 into the 316SS stainless steel crucible 1 and weld the 316SS stainless steel crucible 1 to seal it. This completes the molten salt corrosion test apparatus, as shown below. Figure 4 As shown.

[0139] (3) Place the molten salt corrosion protection device in a well-type muffle furnace at 800℃ and immerse it for corrosion for 400 hours.

[0140] The entire assembly and welding process of the molten salt corrosion protection device is carried out in a glove box protected by an argon atmosphere (99.999% purity).

[0141] Example 1

[0142] The mass changes of GH3539 alloy before and after corrosion in Example 1 and Comparative Example 1 were weighed using an electronic balance with an accuracy of 0.1 mg. The results are shown in Table 1.

[0143] Table 1. Mass changes of GH3539 alloy before and after 100 hours of corrosion.

[0144]

[0145] As shown in Table 1, compared with Comparative Example 1, when graphite is present in both the preparation and use of molten salt, the GH3539 alloy exhibits a reduced weight loss per unit area after corrosion in 800℃ NaCl-KCl-MgCl2 molten salt for 100 hours.

[0146] Figure 5 The image shows the cross-sectional morphology of the GH3539 alloy in Example 1 using a scanning electron microscope (SEM). Figure 6 The image shows the scanning electron microscope (SEM) cross-sectional morphology of the GH3539 alloy in Comparative Example 1. Figure 5 and Figure 6 As can be seen, in Comparative Example 1, without graphite during the molten salt preparation and corrosion process, the GH3539 alloy underwent severe corrosion, with a corrosion depth of 62µm; while in Example 1, with graphite present, the GH3539 alloy underwent weak corrosion, with a corrosion depth of 7µm, representing a corrosion reduction of approximately 90%.

[0147] This demonstrates that the presence of graphite in Example 1 can reduce the corrosion rate of GH3539 alloy in NaCl-KCl-MgCl2 molten salt.

[0148] Example 2

[0149] The mass changes of 347H stainless steel before and after corrosion in Example 2 and Comparative Example 2 were weighed using an electronic balance with an accuracy of 0.1 mg. The results are shown in Table 2.

[0150] Table 2. Mass changes of 347H alloy before and after 100 hours of corrosion.

[0151]

[0152] As shown in Table 2, compared with Comparative Example 2, when graphite is present in both the preparation and use of molten salt, the weight loss per unit area of ​​347H stainless steel in 800℃ NaCl-KCl-MgCl2 molten salt is significantly reduced in Example 2.

[0153] Figure 7 The image shows the cross-sectional morphology of the 347H stainless steel obtained by scanning electron microscopy (SEM) in Example 2. Figure 8 The image shows the cross-sectional morphology of the 347H stainless steel in Comparative Example 2 using a scanning electron microscope (SEM). Figure 7 and Figure 8 As can be seen, in Comparative Example 2, no graphite was present during the molten salt preparation and corrosion processes, and the 347H stainless steel experienced severe intergranular corrosion with a corrosion depth of approximately 150µm. However, in Example 2, the presence of graphite resulted in weak intergranular corrosion of the 347H stainless steel, reducing the corrosion depth to 24µm, representing a corrosion reduction of approximately 83%.

[0154] This demonstrates that the presence of graphite in Example 2 can reduce the corrosion rate of 347H stainless steel in NaCl-KCl-MgCl2 molten salt.

[0155] Example 3

[0156] The mass changes of GH3539 nickel-based alloys before and after corrosion in Example 3 and Comparative Example 3 were weighed using an electronic balance with an accuracy of 0.1 mg. The results are shown in Table 3.

[0157] Table 3. Mass changes of GH3539 alloy before and after 400 hours of corrosion.

[0158]

[0159] As shown in Table 3, compared with Comparative Example 3, when graphite was present in both the preparation and use of the molten salt, the weight loss per unit area of ​​GH3539 alloy was significantly reduced after immersion in NaCl-KCl-MgCl2 molten salt at 800℃ for 400h.

[0160] Figure 9 The image shows the cross-sectional morphology of the GH3539 alloy in Example 3 using a scanning electron microscope (SEM). Figure 10 The image shows the scanning electron microscope (SEM) cross-sectional morphology of the GH3539 alloy in Comparative Example 3. Figure 9 and Figure 10 It can be seen that in Comparative Example 3, no graphite was present during the molten salt preparation and molten salt corrosion process, and the GH3539 alloy underwent severe intergranular corrosion with a corrosion depth of approximately 64µm; while in Example 3, graphite was present, and when the GH3539 alloy came into non-insulating contact with graphite, the alloy had no corrosion pores and basically did not corrode.

[0161] This demonstrates that the presence of graphite in Example 3 can significantly reduce the corrosion rate of GH3539 plates in NaCl-KCl-MgCl2 molten salt.

Claims

1. A method for protecting against molten salt corrosion, characterized in that, Includes the following steps: S1. Before use, the molten salt is melted, and during the melting process, the molten salt comes into contact with the carbon-based material; S2. During the service of the metallic material in molten salt, the molten salt comes into contact with the carbon-based material; The method of contacting the molten salt with the carbon-based material includes adding the carbon-based material to the molten salt and / or using the carbon-based material as a container.

2. The molten salt corrosion protection method as described in claim 1, characterized in that, The carbon-based material has a carbon content of ≥90%, and the percentage is by mass. And / or, the carbon-based material includes one or more of graphite, glassy carbon, carbon-carbon composites and activated carbon, preferably including graphite.

3. The molten salt corrosion protection method as described in claim 1, characterized in that, When the molten salt contacts the carbon-based material by adding the carbon-based material to the molten salt, the carbon-based material is in the form of one or more of powder, block, plate and granules; And / or, when the molten salt contacts the carbon-based material in a container made of the carbon-based material, the container is a crucible, preferably a graphite crucible.

4. The molten salt corrosion protection method as described in claim 1, characterized in that, The molten salt includes a chloride molten salt, which preferably includes one or more of NaCl, KCl, LiCl, MgCl2, CaCl2, ZnCl2, and AlCl3; More preferably, the chloride molten salt comprises NaCl, KCl, and MgCl2; even more preferably, the chloride molten salt comprises 33% NaCl, 21.6% KCl, and 45.4% MgCl2, the percentages being molar percentages.

5. The molten salt corrosion protection method as described in claim 1, characterized in that, Step S1 satisfies one or more of the following conditions ad: a. The melting temperature is 400℃-850℃, for example 700℃; b. The melting time is ≥2 hours, for example, 4 hours; c. The melting is carried out in an inert atmosphere protected by an inert atmosphere, preferably argon or nitrogen. d. Before the melting, the process further includes a step of drying the carbon-based material; wherein the drying temperature is preferably 100℃-500℃, for example 200℃; and the drying time is preferably 12-24h, for example 24h.

6. The molten salt corrosion protection method as described in claim 1, characterized in that, In step S2, during the service of the metal material in molten salt, the system is covered with an inert atmosphere, preferably argon or nitrogen.

7. The molten salt corrosion protection method as described in claim 1, characterized in that, In step S2, during the service of the metal material in the molten salt, the temperature of the molten salt is 400℃-850℃, for example 800℃.

8. The molten salt corrosion protection method as described in claim 1, characterized in that, In step S2, the metallic material includes stainless steel and / or corrosion-resistant alloys; The stainless steel preferably includes one or more of austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, austenitic-ferritic duplex stainless steel and precipitation hardening stainless steel; wherein the austenitic stainless steel preferably includes one or more of 316, 316L, 316H, 347, 347H, 321, 304, 304L and 904L. The corrosion-resistant alloy preferably includes nickel-based alloys and iron-nickel-based alloys; wherein the nickel-based alloy preferably includes alloys with nickel as the main element, more preferably including one or more of Ni-Cu, Ni-Fe, Ni-Cr, Ni-Mo, Ni-W, Ni-Fe-Cr, Ni-Mo-Cr, Ni-W-Cr, Ni-Mo-W, Ni-Mo-W-Cr and Ni-Fe-Mo-Cr, for example including one or more of Monel 400, Haynes 230, GH3539, Hastelloy C276, Hastelloy C22, Hastelloy N, GH3535, Haynes 242, Inconel 600, Inconel 625, Inconel 617 and Inconel 718; the iron-nickel-based alloy preferably includes alloys with iron and nickel as the main elements, more preferably including one or more of Incoloy 330 and Inconel 800 / 800H.

9. A molten salt corrosion protection device, characterized in that, It includes a carbon-based material container for contact with molten salt.

10. The molten salt corrosion protection device as described in claim 9, characterized in that, The carbon-based material container satisfies one or more of the following conditions: a. The carbon content of the carbon-based material in the carbon-based container is ≥90%, and the percentage is by mass. b. The carbon-based material of the carbon-based container is one or more of graphite, glassy carbon, carbon-carbon composite materials, and activated carbon; c. The carbon-based material container is a graphite crucible.

Images