Magnesium-based controlled-release corrosion inhibitor of chloride molten salt medium and preparation method and application of magnesium-based controlled-release corrosion inhibitor

Abstract

The invention belongs to the technical field of material corrosion protection, and particularly relates to a magnesium-based controllable-release corrosion inhibitor of a chloride molten salt medium and a preparation method and application of the magnesium-based controllable-release corrosion inhibitor. The corrosion inhibitor comprises an inner layer which is a magnesium-nickel alloy inner core; the middle layer is a metal nickel slow release layer; and an outer layer which is a magnesium oxide barrier layer. The preparation method comprises the following steps: S1, preparing a magnesium-nickel alloy; s2, crushing the magnesium-nickel alloy into particles; s3, electroplating a metal nickel layer on the surface of the magnesium-nickel alloy core by adopting an electroplating method to obtain a metal nickel slow-release layer; and S4, heating and oxidizing the magnesium-nickel alloy core with the metal nickel slow-release layer in an air atmosphere to obtain the magnesium oxide barrier layer. The corrosion inhibitor not only can effectively remove water and oxygen impurities in the chlorate and reduce the corrosivity of the chlorate, but also can avoid the problem of local destructive corrosion caused by direct contact between a liquid magnesium corrosion inhibitor and a container material, and greatly improves the corrosion resistance of the container material in the chlorate.

Description

Technical Field

[0001] The present invention belongs to the technical field of material corrosion protection, and particularly relates to a magnesium-based controlled-release corrosion inhibitor for chloride molten salt medium, a preparation method thereof, and an application thereof. Background Art

[0002] In a solar thermal power generation system, molten salt is widely used as an efficient heat transfer and heat storage medium. Among them, chloride molten salt is widely regarded as the most promising heat storage and heat transfer material in the next-generation molten salt technology due to its good heat capacity and thermal conductivity, low melting point, high stability, and wide working temperature range, and has great development potential. However, due to the strong water absorption of chloride salts and the easy formation of strongly corrosive oxidation impurities at high temperatures, which will cause serious corrosion to the container material, the strong corrosion problem of chloride molten salt to the container material has become one of the key bottlenecks restricting the development of solar thermal power generation technology.

[0003] Reducing the concentration of oxidizing impurities in chloride salts can significantly improve the corrosion resistance and service life of container materials. At present, common chloride salt purification methods include heat treatment, electrochemical reduction, and adding corrosion inhibitors, etc. Among them, adding Mg corrosion inhibitor to chloride salts has received attention. In order to achieve good purification effects, Mg metal is usually added in excess to remove impurities in chloride salts. However, the working temperature of chloride salts is usually higher than 700 °C, while the melting point of Mg metal is about 650 °C, which means that in the chloride salt environment, the Mg metal corrosion inhibitor exists in a liquid state. In addition, due to the lower density of liquid Mg metal than that of chloride salts, it will float in the molten salt and directly contact the container material. At present, the commonly used container materials are mainly Fe-Cr-Ni-based alloys, and Mg metal is extremely easy to alloy with Ni elements. Therefore, when liquid Mg metal contacts the container material, it will cause liquid metal corrosion, resulting in serious destructive corrosion to the local area of the material. This degree of corrosion is extremely significant, and the corrosion depth of the container material may even be dozens of times higher than its corrosion depth in chloride salts without adding corrosion inhibitors. Thus, developing a new type of magnesium-based corrosion inhibitor that will not cause serious liquid metal corrosion to the container material is of crucial significance for promoting the development of chloride salt solar thermal power generation technology. Summary of the Invention

[0004] To solve the deficiencies of the prior art, the present invention provides a magnesium-based controlled-release corrosion inhibitor for chloride molten salt medium, a preparation method thereof, and an application thereof. This corrosion inhibitor can not only effectively remove water and oxygen impurities in chloride salts and reduce their corrosiveness, but also avoid the problem of local destructive corrosion caused by direct contact between liquid magnesium corrosion inhibitor and container materials, and greatly improve the corrosion resistance of container materials in chloride salts.

[0005] The technical solutions provided by the present invention are as follows: A magnesium-based controlled-release corrosion inhibitor in a molten chloride salt medium, comprising: An inner layer, which is a magnesium-nickel alloy core; A middle layer, which is a metal nickel slow-release layer; And an outer layer, which is a magnesium oxide barrier layer.

[0006] Based on the above technical solution: At the working temperature of the chloride salt, the magnesium corrosion inhibitor is in a liquid state and has fluidity, and can directly contact the container material. However, magnesium is extremely easy to alloy with nickel in the container material, and this reaction will cause the material to suffer from liquid metal corrosion, resulting in local severe damage. Melting magnesium and nickel metals into a magnesium-nickel alloy with a higher melting point can not only ensure that magnesium can react with impurities in the chloride salt to reduce the impurity concentration, but also make the corrosion inhibitor solid at the working temperature of the chloride salt, avoiding liquid metal corrosion of the container material; at the same time, using the magnesium-nickel alloy as the core of the corrosion inhibitor can effectively reduce the concentration of magnesium in the core, making it not easy to alloy with nickel elements in the container material; The metal nickel coating on the surface of the magnesium-nickel alloy can effectively control the diffusion rate of magnesium in the core outward, achieving the purpose of controlled release of the magnesium corrosion inhibitor. In addition, the nickel coating can further reduce the concentration of magnesium on the surface of the corrosion inhibitor to prevent the alloying reaction between magnesium and the container material; and, at the molten salt working temperature, a certain outward diffusion rate of magnesium in the core can be maintained, thus ensuring the reaction between magnesium and impurities; Since magnesium continuously diffuses outward, oxidizing the nickel-plated magnesium-nickel alloy can form a non-dense and insulating oxide film protection layer on the surface of the corrosion inhibitor particles, which can prevent the magnesium-nickel alloy from contacting the container material to cause galvanic corrosion and does not affect the reaction between magnesium and molten salt impurities.

[0007] Specifically, the material of the magnesium-nickel alloy core is MgNi2, Mg2Ni or a mixture of the two.

[0008] The above magnesium-nickel alloy has a relatively high melting point and is solid at the molten salt working temperature, and will not cause liquid metal corrosion to the container material. At the same time, it can also react with impurities in the chloride salt. The impurities include but are not limited to water, oxygen, HCl or MgOHCl.

[0009] Specifically, in the magnesium-nickel alloy, the molar ratio of magnesium to nickel is (2:1)~(1:2).

[0010] Specifically, the size of the magnesium-nickel alloy core is 0.05 mm - 10 mm.

[0011] Based on the above technical solution, if the magnesium-nickel alloy core is too small, the content of Mg will be less and it will be consumed quickly. If it is too large, the specific surface area of the corrosion inhibitor will be small, resulting in a low reaction active area.

[0012] Specifically, the thickness of the nickel metal slow-release layer is 0.5 - 10 μm.

[0013] Based on the above technical solution, if the thickness of the nickel metal slow-release layer is too small, magnesium in the magnesium-nickel alloy core will diffuse outward too quickly, resulting in its inability to play a good slow-release role. If it is too large, it will cause difficulty in the outward diffusion of Mg.

[0014] Specifically, the thickness of the magnesium oxide barrier layer is 0.5 - 10 μm.

[0015] Based on the above technical solution, if the thickness of the magnesium oxide barrier layer is too small, it will not be able to play a good barrier role, and if it is too large, it will cause difficulty in the outward diffusion of Mg.

[0016] The present invention also provides a preparation method of a magnesium-based controlled-release corrosion inhibitor in a molten chloride salt medium, including the following steps: S1. Mix magnesium and nickel metals in proportion, heat and melt them into a magnesium-nickel alloy in an inert atmosphere, and cool to room temperature; S2. Crush the magnesium-nickel alloy into particles to obtain a magnesium-nickel alloy core; S3. Electroplate a layer of nickel metal layer on the surface of the magnesium-nickel alloy core by electroplating to obtain a nickel metal slow-release layer; S4. Heat and oxidize the magnesium-nickel alloy core with a nickel metal slow-release layer in an air atmosphere to obtain a magnesium oxide barrier layer.

[0017] Based on the above technical solution, each layer can be conveniently prepared in sequence from the inside to the outside.

[0018] Specifically: in step S1, heat to 1500 - 2000 °C and melt it into a magnesium-nickel alloy. Preferably, it is 1500 - 1800 °C.

[0019] Further: in step S3, deposit a carbon transition layer with a thickness of 10 - 50 nm on the surface of the magnesium-nickel alloy core by chemical vapor deposition method in an acetylene atmosphere at 600 - 700 °C.

[0020] Based on the above technical solution, since the mutual diffusion rate of magnesium and nickel is relatively fast, depositing a carbon transition layer between the magnesium-nickel alloy core and the nickel metal slow-release layer can further control the outward diffusion rate of magnesium.

[0021] Specifically: in step S4, oxidize in an air atmosphere at 400 - 700 °C for 10 - 300 min to obtain a magnesium oxide barrier layer.

[0022] Based on the above technical solution, it can ensure that the obtained magnesium oxide barrier layer has a suitable density.

[0023] The present invention also provides an application of a magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium as a corrosion inhibitor for the chloride molten salt medium in the molten salt solar thermal power generation technology.

[0024] Specifically, the container material of the molten salt solar thermal power generation device is one of iron-based alloys and nickel-based alloys. Examples of iron-based alloys include 310 stainless steel, 316 stainless steel, 321 stainless steel, etc. Examples of nickel-based alloys include Inconel 625, Inconel 617, Hastelloy C276, etc.

[0025] Compared with the prior art, the present invention has the following characteristics and beneficial effects: The corrosion inhibitor provided by the present invention can not only effectively remove water and oxygen impurities in the chloride salt, reduce its corrosiveness, but also avoid the problem of local destructive corrosion caused by direct contact between the liquid Mg corrosion inhibitor and the container material, and greatly improve the corrosion resistance of the container material in the chloride salt; The synthesis method provided by the present invention is simple, has remarkable effects, has stable physical and chemical properties, and has no obvious influence on the heat storage performance of the chloride salt system. Detailed Embodiments

[0026] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0027] Unless otherwise specified, the test methods used in the examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, are reagents and materials that can be obtained from commercial channels.

[0028] The specific composition of the chloride salt is MgCl2 - NaCl - KCl (molar ratio 60:20:20).

[0029] Example 1 Mix Mg and Ni metals in a molar ratio of 2:1, heat them to 1500 °C in an inert (argon) atmosphere to melt them into a magnesium-nickel alloy, and cool it to room temperature; crush the magnesium-nickel alloy into particles with a size of 0.05 mm; then electroplate a 0.5-μm-thick nickel metal layer on the surface of the magnesium-nickel alloy particles by electroplating; oxidize the nickel-plated magnesium-nickel alloy particles in an air atmosphere at 400 °C for 50 min to prepare a 2-μm-thick magnesium oxide layer.

[0030] After uniformly mixing the obtained magnesium-based controlled-release corrosion inhibitor with the chloride salt, a high-temperature corrosion experiment is carried out by heating to 700 °C in an argon atmosphere. The 316 stainless steel plate is immersed in the chloride salt. After 1000 h, the weight, corrosion products, and cross-sectional morphology of the stainless steel are analyzed to observe its corrosion situation. It can be seen from the scanning electron microscope observation that there is no local severe corrosion phenomenon caused by liquid metal corrosion on the surface of the 316 stainless steel, and the annual corrosion rate of the 316 stainless steel plate in the chloride salt containing Mg-based controlled-release corrosion inhibitor particles is less than 10 μm / year.

[0031] Example 2 Mix Mg:Ni metals in a molar ratio of 1:2, melt them into a magnesium-nickel alloy by heating to 1600 °C in an inert atmosphere, and cool to room temperature; crush the magnesium-nickel alloy into particles of 0.5 mm; deposit a carbon transition layer with a thickness of 30 nm on the surface of the magnesium-nickel alloy particles by chemical vapor deposition method in an acetylene atmosphere at 700 °C; subsequently, electroplate a metal nickel layer with a thickness of 0.2 μm on the surface of the magnesium-nickel alloy particles wrapped by carbon; oxidize the nickel-plated magnesium-nickel alloy particles in an air atmosphere at 500 °C for 10 min to prepare a magnesium oxide layer with a thickness of 0.5 μm.

[0032] After uniformly mixing the obtained magnesium-based controlled-release corrosion inhibitor with the chloride salt, a high-temperature corrosion experiment is carried out by heating to 700 °C in an argon atmosphere. The 316 stainless steel plate is immersed in the chloride salt. After 1000 h, the weight, corrosion products, and cross-sectional morphology of the stainless steel are analyzed to observe its corrosion situation. It can be seen from the scanning electron microscope observation that there is no local severe corrosion phenomenon caused by liquid metal corrosion on the surface of the 316 stainless steel, and the annual corrosion rate of the 316 stainless steel plate in the chloride salt containing Mg-based controlled-release corrosion inhibitor particles is less than 10 μm / year.

[0033] Example 3 Mix Mg:Ni metals in a molar ratio of 2:1, melt them into a magnesium-nickel alloy by heating to 1500 °C in an inert atmosphere, and cool to room temperature; crush the magnesium-nickel alloy into particles of 4 mm; subsequently, electroplate a metal nickel layer with a thickness of 1 μm on the surface of the magnesium-nickel alloy particles; oxidize the nickel-plated magnesium-nickel alloy particles in an air atmosphere at 600 °C for 100 min to prepare a magnesium oxide layer with a thickness of 5 μm.

[0034] After uniformly mixing the obtained magnesium-based controlled-release corrosion inhibitor with the chloride salt, a high-temperature corrosion experiment is carried out by heating to 700 °C under an argon atmosphere. The 316 stainless steel plate is immersed in the chloride salt. After 1000 h, the weight, corrosion products and cross-sectional morphology of the stainless steel are analyzed to observe its corrosion situation. It can be seen from the scanning electron microscope observation that there is no local severe corrosion phenomenon caused by liquid metal corrosion on the surface of 316 stainless steel. The annual corrosion rate of the 316 stainless steel plate in the chloride salt containing Mg-based controlled-release corrosion inhibitor particles is less than 10 μm / year.

[0035] Example 4 Mix Mg:Ni metals in a molar ratio of 1:2, melt them into a magnesium-nickel alloy by heating to 1600 °C in an inert atmosphere, and cool to room temperature; crush the magnesium-nickel alloy into particles of 0.2 mm; subsequently, electroplate a metal nickel layer with a thickness of 0.1 μm on the surface of the magnesium-nickel alloy particles by electroplating; oxidize the nickel-plated magnesium-nickel alloy particles in an air atmosphere at 650 °C for 20 min to prepare a magnesium oxide layer with a thickness of 1 μm.

[0036] After uniformly mixing the obtained magnesium-based controlled-release corrosion inhibitor with the chloride salt, a high-temperature corrosion experiment is carried out by heating to 700 °C under an argon atmosphere. The 316 stainless steel plate is immersed in the chloride salt. After 1000 h, the weight, corrosion products and cross-sectional morphology of the stainless steel are analyzed to observe its corrosion situation. It can be seen from the scanning electron microscope observation that there is no local severe corrosion phenomenon caused by liquid metal corrosion on the surface of 316 stainless steel. The annual corrosion rate of the 316 stainless steel plate in the chloride salt containing Mg-based controlled-release corrosion inhibitor particles is less than 10 μm / year.

[0037] Example 5 Referring to Example 1, the difference is that the 316 stainless steel plate is replaced by Inconel 617. The result is that it can be seen from the scanning electron microscope observation that there is no local severe corrosion phenomenon caused by liquid metal corrosion on the surface of the container, and the annual corrosion rate of Inconel 617 is less than 10 μm / year.

[0038] Comparative Example 1 Mix an excessive amount of Mg metal with the chloride salt, carry out a high-temperature corrosion experiment by heating to 700 °C under an argon atmosphere, immerse the 316 stainless steel plate in the chloride salt, and after 1000 h, analyze the weight, corrosion products and cross-sectional morphology of the stainless steel to observe its corrosion situation. It can be seen from the scanning electron microscope observation that there is a local severe corrosion phenomenon caused by liquid metal corrosion on the surface of 316 stainless steel. The annual corrosion rate of the 316 stainless steel plate in the chloride salt containing an excessive amount of Mg metal is 2000 μm / year.

[0039] Comparative Example 2 The chloride salt was heated to 700 °C under an argon atmosphere for a high-temperature corrosion experiment. The 316 stainless steel plate was immersed in the chloride salt. After 1000 h, the weight, corrosion products, and cross-sectional morphology of the stainless steel were analyzed to observe its corrosion situation. The annual corrosion rate of the 316 stainless steel plate in the chloride salt without an inhibitor was 700 μm / year.

[0040] Comparative Example 3 Referring to Example 1, the difference is that the magnesium oxide layer is not prepared.

[0041] The Mg:Ni metals were mixed in a molar ratio of 2:1 and melted into a magnesium-nickel alloy by heating to 1500 °C in an inert (argon) atmosphere and then cooled to room temperature; the magnesium-nickel alloy was crushed into particles with a size of 0.05 mm; subsequently, a 0.5-μm-thick metallic nickel layer was electroplated on the surface of the magnesium-nickel alloy particles by an electroplating method.

[0042] After the obtained inhibitor was mixed evenly with the chloride salt, a high-temperature corrosion experiment was carried out by heating to 700 °C under an argon atmosphere. The 316 stainless steel plate was immersed in the chloride salt. After 1000 h, the weight, corrosion products, and cross-sectional morphology of the stainless steel were analyzed to observe its corrosion situation. Observed by scanning electron microscopy, the annual corrosion rate of the 316 stainless steel plate in the chloride salt containing inhibitor particles was 40 μm / year.

[0043] Comparative Example 4 Referring to Example 1, the difference is that the magnesium oxide layer and the metallic nickel layer are not prepared.

[0044] The Mg:Ni metals were mixed in a molar ratio of 2:1 and melted into a magnesium-nickel alloy by heating to 1500 °C in an inert (argon) atmosphere and then cooled to room temperature; the magnesium-nickel alloy was crushed into particles with a size of 0.05 mm.

[0045] After the obtained inhibitor was mixed evenly with the chloride salt, a high-temperature corrosion experiment was carried out by heating to 700 °C under an argon atmosphere. The 316 stainless steel plate was immersed in the chloride salt. After 1000 h, the weight, corrosion products, and cross-sectional morphology of the stainless steel were analyzed to observe its corrosion situation. Observed by scanning electron microscopy, the annual corrosion rate of the 316 stainless steel plate in the chloride salt containing inhibitor particles was 50 μm / year.

[0046] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnesium-based controlled-release corrosion inhibitor in a molten chloride salt medium, characterized in that, Comprising: An inner layer, which is a magnesium-nickel alloy core; A middle layer, which is a metal nickel slow-release layer; And an outer layer, which is a magnesium oxide barrier layer.

2. The magnesium-based controlled-release corrosion inhibitor for chloride molten salt medium according to claim 1, characterized in that: The material of the magnesium-nickel alloy core is MgNi2, Mg2Ni or a mixture of both; In the magnesium-nickel alloy, the molar ratio of magnesium to nickel is (2:1) to (1:2); The size of the magnesium-nickel alloy core is 0.05 - 4 mm.

3. The magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to claim 1, characterized in that: The thickness of the metal nickel slow-release layer is 0.1 - 1 μm.

4. The magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to claim 1, characterized in that: The thickness of the magnesium oxide barrier layer is 0.5 - 5 μm.

5. A preparation method of a magnesium-based controlled-release corrosion inhibitor for a chloride molten salt medium according to any one of claims 1 to 4, characterized in that, Including the following steps: S1. Mix magnesium and nickel metals in proportion, heat and melt them into a magnesium-nickel alloy in an inert atmosphere, and cool to room temperature; S2. Crush the magnesium-nickel alloy into particles to obtain a magnesium-nickel alloy core; S3. Electroplate a layer of metal nickel layer on the surface of the magnesium-nickel alloy core by electroplating to obtain a metal nickel slow-release layer; S4. Heat and oxidize the magnesium-nickel alloy core with a metal nickel slow-release layer in an air atmosphere to obtain a magnesium oxide barrier layer.

6. The preparation method of the magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to claim 5, characterized in that: In step S1, heat to 1500 - 2000 °C and melt it into a magnesium-nickel alloy.

7. The preparation method of the magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to claim 5, characterized in that: In step S3, deposit a carbon transition layer with a thickness of 10 - 50 nm on the surface of the magnesium-nickel alloy core by chemical vapor deposition in an acetylene atmosphere at 600 - 700 °C.

8. The preparation method of the magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to claim 5, characterized in that: In step S4, oxidize in an air atmosphere at 400 - 700 °C for 10 - 300 min to obtain a magnesium oxide barrier layer.

9. Use of a magnesium-based controlled-release corrosion inhibitor in a chloride molten salt medium according to any one of claims 1 to 4, characterized in that: As a corrosion inhibitor for chloride molten salt medium in molten salt solar thermal power generation.

10. The application according to claim 9, wherein: The container material of the molten salt solar thermal power generation device is one of iron-based alloys or nickel-based alloys.