A method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel

Abstract

A method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel: Step (1) Prepare a pseudo-boehmite aqueous solution, disperse it ultrasonically, add nitric acid solution dropwise to form a semi-transparent aluminum sol, add a preset amount of PEG, and continue stirring to obtain a stable aluminum sol; Step (2) Clean the 310S stainless steel with ethanol and deionized water, immerse it in the aluminum sol, chemical bath at 60~90℃ for 1~4 h, wash with ethanol and dry to obtain 310S stainless steel with surface-modified aluminum sol; Step (3) Heat treat the stainless steel obtained above in an air atmosphere, and cool it with the furnace to obtain 310S stainless steel with a uniform and dense alumina coating; Step (4) Add tetraethyl orthosilicate, or nano ZrC, or nano ZrB2 particles to the aluminum sol in step (1), stir to obtain silicon-doped aluminum sol, or ZrC-alumina sol, or ZrB2-alumina sol; Repeat step (3) to obtain 310S stainless steel with a uniform and dense coating.

Description

Technical Field

[0001] This invention relates to the preparation technology of functional coatings, specifically to the preparation technology of alumina-based anti-corrosion coatings on stainless steel surfaces. Background Technology

[0002] Nitrate salts are commonly used in solar thermal power generation technology, with system operating temperatures typically between 280-560℃. However, current tower-type solar thermal power generation systems can achieve concentration temperatures exceeding 800℃, making nitrate salts insufficient to fully meet system requirements. Chloride molten salts, due to their superior properties, hold promise as the next-generation heat storage molten salt for solar thermal power generation systems. However, chloride molten salts are extremely corrosive, placing higher demands on the corrosion resistance of metal components used in solar thermal power generation in high-temperature chloride molten salt environments.

[0003] With the development of alloy materials, the potential for further improving the high-temperature performance and corrosion resistance of nickel-based alloys through material modification methods is very limited. Although high-temperature alloys such as Inconel 625 have good resistance to molten salt corrosion, their high cost restricts their widespread use in CSP systems. Therefore, depositing high-temperature resistant and corrosion-resistant coatings on stainless steel surfaces as key components in solar thermal power plants to extend their service life and prevent surface corrosion and high-temperature oxidation in chloride molten salts has become the most effective approach. Aluminide coatings, with their low density, high melting point, excellent mechanical properties, and high-temperature corrosion resistance, have become one of the most promising coatings.

[0004] Currently, there are various methods for preparing aluminide coatings, mainly including physical vapor deposition (PVD), chemical vapor deposition (CVD), magnetron sputtering, thermal spraying, cold spraying, plasma spraying, laser cladding, hot-dip aluminizing, and 3D printing. Each of these methods has its own advantages, such as strong adhesion between the coating and the substrate, dense coating, and controllable composition, but also some disadvantages, such as high equipment requirements, high preparation costs, and limited coating thickness. Therefore, there is a need to develop a simple, convenient, and low-cost method for preparing coatings.

[0005] Patent CN201910026394.0 proposes a method for preparing a high-frequency induction-assisted self-propagating NiAl-based intermetallic compound coating. The preparation process is relatively complex, requiring mixing, pressing, high-frequency induction heating, drying for 15 hours, a high-vacuum environment, and generating 20-40 MPa high pressure, which carries certain risks. Patent CN202011410297.0 proposes a method for modifying NiAl with the active element Hf. β -NiAl coating and its preparation process: The method involves: electroplating a Ni-Hf layer onto a substrate; depositing an Al layer on the obtained Ni-Hf layer using arc ion plating; and then annealing the obtained electroplated Ni-Hf + arc ion-plated Al layer in a vacuum annealing furnace to obtain Hf modification. β-NiAl coating involves a complex process and requires sophisticated equipment. Chemical bath coating, a simpler technique combining immersion-coating-coating, is simple to operate and requires less equipment. Its application to the preparation of aluminide coatings on stainless steel surfaces would be highly effective. The preparation of aluminide sol using a chemical bath is a prerequisite for aluminide coatings. Patent 202310444877.9 proposes a modified aluminide sol and its preparation method. This method uses aluminum chloride to prepare an aluminum trichloride solution, then adds concentrated ammonia for precipitation, filtration, and washing. The aluminum trichloride solution is then added again, and the mixture is heated to 60°C for gelation to obtain an aluminide sol. Auxiliary components are added under stirring, and the reaction is maintained at this temperature for 3 hours to finally obtain the modified aluminide sol. Traditional aluminide sol preparation requires steps such as precipitation, filtration, washing, re-acidification, gelation, and aging. This application directly utilizes boehmite (SB powder) to acidify the gel with nitric acid, then adds a PEG stabilizer to obtain a stable aluminide sol in one step. Then, 310S stainless steel is immersed in aluminum sol through a chemical bath, followed by drying and calcination to obtain 310S stainless steel with an alumina coating that exhibits excellent corrosion resistance. Furthermore, the corrosion resistance of the coating is further enhanced by adding nano-ceramic powders such as Si, nano-ZrC, and ZrB2 to the aluminum sol. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel.

[0007] This invention relates to a method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel, comprising the following steps:

[0008] Step (1) Prepare a pseudoboehmite aqueous solution with a concentration of 0.1~10 mol / L; after ultrasonic dispersion, add nitric acid solution with a concentration of 0.01~0.5 mol / L, and continue stirring at 85 ℃ for 2~4 h to form a translucent aluminum sol. Add a preset amount of PEG with a molecular weight of 2000 and a mass fraction of PEG of 0.1~1 wt.% and continue stirring to obtain a stable aluminum sol.

[0009] Step (2) After cleaning the 310S stainless steel with ethanol and deionized water, immerse it in the aluminum sol obtained in the above step, chemical bath at 60~90 ℃ for 1~4 h, wash with ethanol and dry to obtain 310S stainless steel with surface modified aluminum sol.

[0010] Step (3) The stainless steel obtained above is heat-treated in an air atmosphere, held at 550 ℃ for 4 h, and then heated to 800~1100 ℃ for 2 h. The heating rate is 5 degrees / minute. After cooling in the furnace, 310S stainless steel with a uniform and dense alumina coating on the surface is obtained.

[0011] Step (4) Add a preset amount of tetraethyl orthosilicate, or nano ZrC, or nano ZrB2 particles to the aluminum sol in step (1), with a doping / composite amount of 1 wt.%~5 wt.%. After stirring for a preset time, silicon-doped aluminum sol, or ZrC-aluminum sol, or ZrB2-aluminum sol can be obtained. Repeat step (3) to obtain 310S stainless steel with uniform and dense silicon-alumina, ZrC-alumina, or ZrB2-alumina coatings.

[0012] The beneficial effects of this invention are as follows: a stable aluminum sol can be obtained through a one-step acidification sol treatment, and an aluminum compound coating can be applied to the surface of 310S stainless steel using a chemical bath followed by heat treatment. Furthermore, adding tetraethyl orthosilicate, ZrC, ZrB2, and other nano-ceramic powders to the aluminum sol can yield an alumina corrosion-resistant coating reinforced with Si-doped alumina and ZrC / ZrB2 nano-ceramic phases. This invention is simple, rapid, and low-cost, and has promising prospects for industrial application in the preparation of corrosion-resistant coatings for stainless steel surfaces. Attached Figure Description

[0013] Figure 1 The aluminum sol prepared in Example 1 Figure 2 The Si-doped aluminum sol prepared in Example 2 Figure 3 The ZrC-aluminum sol prepared in Example 3, Figure 4 The ZrB2-aluminum sol prepared in Example 4 Figures 1-4 It is a set of comparative samples for experiments; Figure 5 The 310S stainless steel modified with an alumina coating obtained in Example 1. Figure 6 The 310S stainless steel modified with Si-Al2O3 coating obtained in Example 2. Figure 7 The 310S stainless steel modified with a ZrC-Al2O3 coating obtained in Example 3. Figure 8 The 310S stainless steel modified with the ZrB2-Al2O3 coating obtained in Example 4. Figures 5-8 It is a set of comparative samples for experiments; Figure 9 Weight loss of coated stainless steel under high-temperature chloride molten salt corrosion at 800 ℃. Implementation

[0014] This invention relates to a method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel, comprising the following steps:

[0015] Step (1) Prepare a pseudoboehmite aqueous solution with a concentration of 0.1~10 mol / L; after ultrasonic dispersion, add nitric acid solution with a concentration of 0.01~0.5 mol / L, and continue stirring at 85 ℃ for 2~4 h to form a translucent aluminum sol. Add a preset amount of PEG with a molecular weight of 2000 and a mass fraction of PEG of 0.1~1 wt.% and continue stirring to obtain a stable aluminum sol.

[0016] Step (2) After cleaning the 310S stainless steel with ethanol and deionized water, immerse it in the aluminum sol obtained in the above step, chemical bath at 60~90 ℃ for 1~4 h, wash with ethanol and dry to obtain 310S stainless steel with surface modified aluminum sol.

[0017] Step (3) The stainless steel obtained above is heat-treated in an air atmosphere, held at 550 ℃ for 4 h, and then heated to 800~1100 ℃ for 2 h. The heating rate is 5 degrees / minute. After cooling in the furnace, 310S stainless steel with a uniform and dense alumina coating on the surface is obtained.

[0018] Step (4) Add a preset amount of tetraethyl orthosilicate, or nano ZrC, or nano ZrB2 particles to the aluminum sol in step (1), with a doping / composite amount of 1 wt.%~5 wt.%. After stirring for a preset time, silicon-doped aluminum sol, or ZrC-aluminum sol, or ZrB2-aluminum sol can be obtained. Repeat step (3) to obtain 310S stainless steel with uniform and dense silicon-alumina, ZrC-alumina, or ZrB2-alumina coatings.

[0019] The preparation method described above uses 30 nm ZrC nanoparticles and 20 nm ZrB2 nanoparticles.

[0020] The above-described preparation method, when the 310S stainless steel modified with the alumina-based coating obtained above is subjected to a high-temperature chloride molten salt corrosion test at 800℃, shows that compared with the unmodified stainless steel, the coated stainless steel exhibits excellent resistance to high-temperature chloride molten salt corrosion.

[0021] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0022] Example 1: In this example, the concentration of SB powder was 1 mol / L, and the concentration of nitric acid was 0.5 mol / L. Stirring was continued at 85 °C for 4 hours to form a translucent aluminum sol. A certain amount of PEG (molecular weight 2000), with a PEG mass fraction of 0.1 wt.%, was added, and stirring continued to obtain a stable aluminum sol (Al). Figure 1As shown. The cleaned 310S stainless steel was placed in the aforementioned alumina sol and immersed at 85 ℃ for 4 hours. It was then rinsed with ethanol and deionized water, and subsequently heat-treated in air atmosphere at 550 ℃ for 4 hours, followed by a further increase to 1000 ℃ and holding for 2 hours at a heating rate of 5 degrees / minute. After furnace cooling, a 310S stainless steel with a uniform and dense alumina coating was obtained. Figure 5 As shown.

[0023] Example 2: In this example, the concentration of SB powder was 5 mol / L, and 0.25 mol / L tetraethyl orthosilicate and 1 mol / L nitric acid were added. The mixture was stirred at 85 °C for 4 h to form a translucent aluminum sol. A certain amount of PEG (molecular weight 2000) with a mass fraction of 0.5 wt.% was added, and stirring continued to obtain a stable silicon-doped aluminum sol (Si-Al). Figure 2 As shown. The cleaned 310S stainless steel was placed in the aforementioned alumina sol and immersed at 90 °C for 4 h. It was then rinsed with ethanol and deionized water, and subsequently heat-treated in air atmosphere at 550 °C for 4 h, followed by a further increase to 1100 °C and holding for 2 h at a heating rate of 5 °C / min. After furnace cooling, a Si-doped alumina coating-modified 310S stainless steel was obtained. Figure 6 .

[0024] Example 3: In this example, the concentration of SB powder was 5 mol / L, and the concentration of nano-ZrC was 0.25 mol / L. The concentration of nitric acid was 1 mol / L. Stirring was continued at 85 °C for 4 h to form a translucent aluminum sol. A certain amount of PEG (molecular weight 2000), with a PEG mass fraction of 0.5 wt.%, was added. Stirring continued to obtain a stable ZrC composite aluminum sol (ZrC-Al). Figure 3 As shown. The cleaned 310S stainless steel was placed in the aforementioned alumina sol and immersed at 90 °C for 4 hours. It was then rinsed with ethanol and deionized water, and subsequently heat-treated in air atmosphere at 550 °C for 4 hours, followed by a further increase to 1100 °C and holding for 2 hours at a heating rate of 5 °C / min. After furnace cooling, a ZrC composite alumina coating-modified 310S stainless steel was obtained. Figure 7 As shown.

[0025] Example 4: In this example, the concentration of SB powder was 5 mol / L, and the concentration of nano ZrB2 was 0.25 mol / L. The concentration of nitric acid was 1 mol / L. Stirring was continued at 85 °C for 4 h to form a translucent aluminum sol. A certain amount of PEG (molecular weight 2000), with a PEG mass fraction of 0.5 wt.%, was added. Stirring continued to obtain a stable ZrB2 composite aluminum sol (ZrB2-Al). Figure 4As shown. The cleaned 310S stainless steel was placed in the aforementioned alumina sol and immersed at 90 °C for 4 hours. It was then rinsed with ethanol and deionized water, and subsequently heat-treated in air atmosphere at 550 °C for 4 hours, followed by a further increase to 1100 °C and holding for 2 hours at a heating rate of 5 °C / min. After furnace cooling, a ZrB2 composite alumina coating-modified 310S stainless steel was obtained. Figure 8 As shown.

[0026] The 310S stainless steel modified with alumina-based coatings obtained in Examples 1-4 was subjected to a high-temperature chloride molten salt corrosion test. The chloride molten salt composition was NaCl / MgCl2 / KCl (24.5 : 55.0 : 20.5, wt.%), the temperature was 800℃, and the corrosion time was 10 h. The weight loss of the sample after corrosion was as follows: Figure 9 As shown, the coated stainless steel has less weight loss, indicating its superior resistance to high-temperature chloride molten salt corrosion.

Claims

1. A method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel, characterized in that the steps include... include: Step (1) Prepare a pseudoboehmite aqueous solution with a concentration of 0.1–10 mol / L; After ultrasonic dispersion, nitric acid solution with a concentration of 0.01–0.5 mol / L is added dropwise. Stirring is continued at 85°C for 2–4 hours to form a translucent aluminum sol. A predetermined amount of PEG with a molecular weight of 2000 and a mass fraction of 0.1–1 wt.% is added and stirring is continued to obtain a stable aluminum sol. Add a predetermined amount of tetraethyl orthosilicate, or nano ZrC, or nano ZrB2 particles to the aluminum sol in step (1), with a doping / composite amount of 1wt.% to 5wt.% and stir for a predetermined time to obtain silicon-doped aluminum sol, or ZrC-aluminum sol, or ZrB2-aluminum sol. Step (2) After cleaning the 310S stainless steel with ethanol and deionized water, immerse it in the silicon-doped aluminum sol, or ZrC-aluminum sol, or ZrB2-aluminum sol obtained in the above steps, in a chemical bath at 60-90℃ for 1-4 hours, and then wash and dry with ethanol to obtain surface-modified 310S stainless steel. Step (3) The stainless steel obtained above is heat-treated in an air atmosphere, held at 550°C for 4 hours, and then heated to 800-1100°C for 2 hours. The heating rate is 5 degrees / minute. After cooling in the furnace, 310S stainless steel with uniform and dense silicon-alumina, ZrC-alumina or ZrB2-alumina coating is obtained. When the 310S stainless steel modified with the alumina-based coating obtained above was subjected to a high-temperature chloride molten salt corrosion test at 800℃, the coated stainless steel showed excellent resistance to high-temperature chloride molten salt corrosion compared to the unmodified stainless steel.

2. The method for preparing an alumina-based anti-corrosion coating on the surface of 310S stainless steel according to claim 1, characterized in that... Nano ZrC consists of 30nm particles, and nano ZrB2 consists of 20nm particles.

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