A superhydrophobic coating of 304 stainless steel mesh based on SiO2 and its preparation method

Abstract

This invention discloses a 304 stainless steel mesh-based SiO2 superhydrophobic coating and its preparation method, applicable to the surface of downhole thermal recovery screens, involving surface engineering technology, superhydrophobic material preparation technology, and protection of downhole tools in oil and gas fields. The invention employs a simultaneous anodic oxidation deposition method, using a pretreated 100-mesh 304 stainless steel mesh as the anode and a platinum sheet as the cathode. The reaction is carried out in an ethylene glycol electrolyte containing 0.15 mol / L ammonium fluoride, 0.6 mol / L deionized water, and 8 g / L of 10 nm hydrophilic nano-SiO2, under constant pressure (25-85 V) and 25℃ for 20-40 min, generating a porous Fe-Cr-O oxide film in situ and embedding SiO₂ particles into the film pores. The coating is then modified with 1 vol% FAS-13 ethanol solution at room temperature in the dark for 90 min, and cured at 80-100℃ for 1-2 h. The coating prepared by this invention has an adhesion grade of 5A, a static water contact angle of >150°, and a roll-off angle of <10°. It also has excellent long-term stability, high temperature resistance, acid and alkali resistance, and self-cleaning properties. It can effectively solve the multiple failure challenges faced by downhole thermal recovery screen pipes in complex working conditions. Moreover, the preparation method is simple, easy to implement, environmentally friendly, and economical.

Description

Technical Field

[0001] This invention discloses a 304 stainless steel mesh-based SiO2 superhydrophobic coating and its preparation method, which is applied to the surface of downhole thermal recovery screen pipes and relates to surface engineering technology, superhydrophobic material preparation technology and downhole tool protection in oil and gas fields. Background Technology

[0002] Thermal recovery is a core technology for heavy oil field development globally, mainly including processes such as steam drive, steam huff and puff, and steam-assisted gravity drainage (SAGD). These processes reduce the viscosity of heavy oil by injecting high-temperature, high-pressure steam into the formation, achieving efficient extraction. Thermal recovery screens are core components of the sand control system in thermal recovery wells, playing a crucial role in blocking formation sand particles and ensuring the smooth flow of oil and gas. Their performance and service life directly determine the production efficiency of the thermal recovery well.

[0003] Under the complex conditions of downhole thermal recovery, thermal recovery screens face multiple failure challenges: First, the long-term circulation of high-temperature and high-pressure steam easily leads to oxidation and embrittlement of the screen material and a decline in mechanical properties; second, the formation water contains a large amount of corrosive media and acidic or alkaline components, which can cause severe corrosion to the screens; third, high-speed flowing formation sand particles can cause strong erosion and wear on the screen surface, leading to enlarged screen apertures, thinned wire diameters, and even breakage; fourth, heavy components such as asphaltene, gums, and waxes in heavy oil easily adhere to the screen surface, gradually clogging the screen holes, causing a sharp decline in fluid flow capacity, and in severe cases, causing complete screen failure, requiring frequent replacement and significantly increasing oilfield development costs.

[0004] Currently, the main protective technologies for downhole thermal recovery screens include surface nitriding, chrome plating, and spraying wear-resistant ceramic coatings. However, these technologies all have significant drawbacks: surface nitriding and chrome plating have high hardness but limited resistance to acid and alkali corrosion and lack self-cleaning properties, failing to fundamentally solve the problem of heavy component adhesion and blockage; while spraying wear-resistant ceramic coatings have good wear resistance and high temperature resistance, the coating has poor adhesion to the substrate and is prone to cracking and detachment under high-temperature alternating loads and sand erosion. Furthermore, the preparation process is complex, requires large equipment investment, and is costly, making it difficult to achieve large-scale industrial application.

[0005] Superhydrophobic materials, due to their extremely low surface energy and unique micro-nano rough structures, can significantly reduce the adhesion of liquid and solid contaminants to surfaces while simultaneously blocking contact between corrosive media and the substrate, making them a promising surface protection technology. SiO2, as an inorganic material with good chemical stability, high temperature resistance, and low cost, is an ideal raw material for preparing superhydrophobic coatings. However, most existing SiO2 superhydrophobic coatings are prepared using methods such as spraying, sol-gel, and impregnation, which suffer from weak adhesion between the coating and the substrate, poor high-temperature resistance, and insufficient long-term service stability. These methods cannot adapt to the complex working conditions of high temperature, high pressure, strong erosion, and strong corrosion in downhole thermal recovery, limiting their practical application in the protection of thermal recovery screens. Summary of the Invention

[0006] The purpose of this invention is to provide a 304 stainless steel mesh-based SiO2 superhydrophobic coating and its preparation method, which is applied to the surface of underground thermal recovery screen pipes to significantly improve the adhesion between the coating and the substrate, giving it excellent long-term stability, high temperature resistance, acid and alkali resistance and self-cleaning properties.

[0007] This invention provides the following technical solution: a 304 stainless steel mesh-based SiO2 superhydrophobic coating, comprising a 304 stainless steel mesh substrate, a porous Fe-Cr-O oxide film layer, a SiO2 nanoparticle layer, and a low surface energy modified layer. The coating surface has a micro-nano composite rough structure, a water contact angle >150°, a roll-off angle <10°, and an adhesion rating of 5A. The coating exhibits good long-term stability, high-temperature resistance, acid and alkali resistance, and self-cleaning properties.

[0008] This invention provides a method for preparing a SiO2 superhydrophobic coating on a 304 stainless steel mesh, comprising the following steps:

[0009] (1) Substrate pretreatment: The 100-mesh 304 stainless steel mesh was ultrasonically cleaned with acetone, deionized water and anhydrous ethanol in sequence, dried in a forced-air drying oven, then soaked in pickling solution and ultrasonicated for 5 minutes, and then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence, and dried in a forced-air drying oven for later use.

[0010] (2) Electrolyte preparation: Prepare an electrolyte containing 0.15 mol / L ammonium fluoride, 0.6 mol / L deionized water, 8 g / L nano SiO2, and ethylene glycol to a final volume of 200 mL. Mix well and set aside.

[0011] (3) Anodizing: Using the 304 stainless steel mesh pretreated in step (1) as the anode and the platinum sheet as the cathode, immerse it in the electrolyte prepared in step (2) and react for 20-40 minutes at a constant voltage of 25-85V and a temperature of 25℃. Then, wash the stainless steel mesh with deionized water and anhydrous ethanol in sequence, and dry it in a forced-air drying oven for later use.

[0012] (4) Low surface energy modification: Immerse the stainless steel mesh prepared in step (3) in the modification liquid for 90 min, take it out and cure it in a forced-air drying oven at 80-100℃ for 1-2 h, and then let it cool naturally to room temperature.

[0013] Preferably, the 304 stainless steel mesh has a size of 5cm*3cm;

[0014] Preferably, the volume ratio of the pickling solution in step (1) is concentrated nitric acid (65-68%): deionized water = 1:1;

[0015] Preferably, the SiO2 used in step (2) is hydrophilic SiO2 with a particle size of 10 nm, which needs to be ultrasonically dispersed in the electrolyte for 10 min;

[0016] Preferably, the area of ​​the platinum sheet in step (3) is 1 cm². 2 The distance between the two electrodes is 4 cm, and the electrolyte is continuously stirred at a speed of 400 rpm during the reaction.

[0017] Preferably, the modification solution in step (4) is a 1 vol% FAS-13 ethanol solution, and the modification is carried out at room temperature in the dark.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. This invention uses anodizing simultaneous deposition to generate a porous Fe-Cr-O oxide film on the surface of 304 stainless steel mesh, while simultaneously embedding nano-SiO2 particles directly into the pores of the oxide film to form a continuous gradient structure. This achieves a dual effect of chemical bonding and mechanical interlocking, significantly improving the adhesion between the coating and the substrate.

[0020] 2. The 304 stainless steel mesh-based SiO2 superhydrophobic coating prepared by this invention has excellent long-term stability, high temperature resistance, acid and alkali resistance and self-cleaning properties.

[0021] 3. The preparation method of the present invention is simple and easy to implement, and is both environmentally friendly and economical. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0023] Figure 1 This is a static water contact angle test diagram from Embodiment 1 of the present invention.

[0024] Figure 2These are microscopic SEM images of Embodiment 1 and Comparative Example 1 of the present invention.

[0025] Figure 3 This is a graph showing the change in static water contact angle during a high-temperature resistance test according to Embodiment 1 of the present invention.

[0026] Figure 4 This is a graph showing the change in static liquid contact angle during acid and alkali resistance testing according to Embodiment 1 of the present invention. Specific implementation methods

[0027] The technical solution of the present invention will be described more clearly and completely below with reference to specific embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing a SiO2 superhydrophobic coating on a 304 stainless steel mesh, the specific steps of which are as follows:

[0030] (1) Clean the 100 mesh 304 stainless steel mesh with a size of 5cm*3cm in sequence with acetone, deionized water and anhydrous ethanol in an ultrasonic cleaning process, dry it in a forced-air drying oven, then soak it in a pickling solution with a volume ratio of concentrated nitric acid (65-68%): deionized water = 1:1 and sonicate it for 5 minutes. Then clean it in sequence with deionized water and anhydrous ethanol in an ultrasonic cleaning process, and dry it in a forced-air drying oven for later use.

[0031] (2) Take 8 g / L of hydrophilic nano SiO2 with a particle size of 10 nm and add it to 100 mL of ethylene glycol. Disperse it by ultrasonication for 10 min. While stirring magnetically, add 0.15 mol / L ammonium fluoride and 0.6 mol / L deionized water. Make up the volume with ethylene glycol to 200 mL to obtain the electrolyte for later use.

[0032] (3) Using the 304 stainless steel mesh pretreated in step (1) as the anode, with an area of ​​1 cm² 2 The platinum sheet is used as the cathode and is immersed in the electrolyte prepared in step (2). The distance between the two electrodes is 4 cm. The reaction is carried out at a constant voltage of 55V and a temperature of 25℃ for 25 min. During the reaction, the electrolyte is continuously stirred at a speed of 400 rpm. Then, the stainless steel mesh is washed with deionized water and anhydrous ethanol in sequence and dried in a forced-air drying oven for later use.

[0033] (4) Immerse the stainless steel mesh prepared in step (3) in 1 vol% FAS-13 ethanol solution and soak it for 90 min at room temperature in the dark. After taking it out, cure it at 100°C for 1 h in a forced-air drying oven and cool it naturally to room temperature to obtain a 304 stainless steel mesh-based SiO2 superhydrophobic coating.

[0034] Performance testing: The static water contact angle is 151.09°; after 10 repeated tape peeling tests, the static water contact angle decreased by 0.90°; after 30 days of standing in air, the static water contact angle decreased by 0.63°; after 48 hours of heat preservation at 160°C, the static water contact angle decreased by 1.03°; it exhibits excellent self-cleaning properties against both solid and liquid contaminants.

[0035] Example 2

[0036] A method for preparing a SiO2 superhydrophobic coating on a 304 stainless steel mesh, the specific steps of which are as follows:

[0037] (1) Clean the 100 mesh 304 stainless steel mesh with a size of 5cm*3cm in sequence with acetone, deionized water and anhydrous ethanol in an ultrasonic cleaning process, dry it in a forced-air drying oven, then soak it in a pickling solution with a volume ratio of concentrated nitric acid (65-68%): deionized water = 1:1 and sonicate it for 5 minutes. Then clean it in sequence with deionized water and anhydrous ethanol in an ultrasonic cleaning process, and dry it in a forced-air drying oven for later use.

[0038] (2) Take 8 g / L of hydrophilic nano SiO2 with a particle size of 10 nm and add it to 100 mL of ethylene glycol. Disperse it by ultrasonication for 10 min. While stirring magnetically, add 0.15 mol / L ammonium fluoride and 0.6 mol / L deionized water. Make up the volume with ethylene glycol to 200 mL to obtain the electrolyte for later use.

[0039] (3) Using the 304 stainless steel mesh pretreated in step (1) as the anode, with an area of ​​1 cm² 2 The platinum sheet is used as the cathode and is immersed in the electrolyte prepared in step (2). The distance between the two electrodes is 4 cm. The reaction is carried out at a constant voltage of 45V and a temperature of 25℃ for 25 min. During the reaction, the electrolyte is continuously stirred at a speed of 400 rpm. Then, the stainless steel mesh is washed with deionized water and anhydrous ethanol in sequence and dried in a forced-air drying oven for later use.

[0040] (4) Immerse the stainless steel mesh prepared in step (3) in 1 vol% FAS-13 ethanol solution and soak it for 90 min at room temperature in the dark. After taking it out, cure it at 100°C for 1 h in a forced-air drying oven and cool it naturally to room temperature to obtain a 304 stainless steel mesh-based SiO2 superhydrophobic coating.

[0041] Performance test: Static water contact angle is 144.64°.

[0042] Example 3

[0043] A method for preparing a SiO2 superhydrophobic coating on a 304 stainless steel mesh, the specific steps of which are as follows:

[0044] (1) Clean the 100 mesh 304 stainless steel mesh with a size of 5cm*3cm in sequence with acetone, deionized water and anhydrous ethanol in an ultrasonic cleaning process, dry it in a forced-air drying oven, then soak it in a pickling solution with a volume ratio of concentrated nitric acid (65-68%): deionized water = 1:1 and sonicate it for 5 minutes. Then clean it in sequence with deionized water and anhydrous ethanol in an ultrasonic cleaning process, and dry it in a forced-air drying oven for later use.

[0045] (2) Take 8 g / L of hydrophilic nano SiO2 with a particle size of 10 nm and add it to 100 mL of ethylene glycol. Disperse it by ultrasonication for 10 min. While stirring magnetically, add 0.15 mol / L ammonium fluoride and 0.6 mol / L deionized water. Make up the volume with ethylene glycol to 200 mL to obtain the electrolyte for later use.

[0046] (3) Using the 304 stainless steel mesh pretreated in step (1) as the anode, with an area of ​​1 cm² 2 The platinum sheet is used as the cathode and is immersed in the electrolyte prepared in step (2). The distance between the two electrodes is 4 cm. The reaction is carried out at a constant voltage of 55V and a temperature of 25℃ for 35 min. During the reaction, the electrolyte is continuously stirred at a speed of 400 rpm. Then, the stainless steel mesh is washed with deionized water and anhydrous ethanol in sequence and dried in a forced-air drying oven for later use.

[0047] (4) Immerse the stainless steel mesh prepared in step (3) in 1 vol% FAS-13 ethanol solution and soak it for 90 min at room temperature in the dark. After taking it out, cure it at 100°C for 1 h in a forced-air drying oven and cool it naturally to room temperature to obtain a 304 stainless steel mesh-based SiO2 superhydrophobic coating.

[0048] Performance test: Static water contact angle is 141.87°.

[0049] Comparative Example 1

[0050] 100-mesh 304 stainless steel mesh without any surface treatment, measuring 5cm x 3cm.

[0051] Performance testing: The static water contact angle is 76.83°; it is extremely susceptible to contamination by both solid and liquid pollutants.

[0052] Comparative Example 2

[0053] A method for preparing a stainless steel mesh-based superhydrophobic coating, the specific steps of which are as follows:

[0054] A 250-mesh 316L stainless steel mesh was ultrasonically cleaned for 10 minutes each in anhydrous ethanol and deionized water, and then dried with cold air. A 5 vol% perchloric acid-ethylene glycol solution was prepared as the anodizing electrolyte. The stainless steel mesh sample was used as the anode, connected to the positive terminal of the power supply, and the graphite sheet was used as the cathode, connected to the negative terminal of the power supply, with a distance of 4.5 cm between the anode and cathode. The prepared electrolyte was placed in a low-temperature magnetic stirrer, and the temperature was controlled at 5°C. The anodizing apparatus was placed in the electrolyte, the DC power supply was turned on, and the oxidation voltage was set to 40V for 300s. After anodizing, the sample was removed, rinsed with plenty of deionized water, and dried with cold air. The anodized stainless steel mesh was then immersed in a 0.1M perfluorooctanoic acid aqueous solution for 48 hours, and then dried at room temperature.

[0055] Performance testing: The static water contact angle was 154.66°; after 10 repeated tape peeling tests, the static water contact angle decreased to 149.25°.

[0056] The performance test comparison between Example 1 and Comparative Examples 1 and 2 shows that the SiO2 superhydrophobic coating prepared on the surface of 304 stainless steel mesh by the anodizing simultaneous deposition method of the present invention has a strong bonding force with the substrate and has excellent long-term stability, high temperature resistance, acid and alkali resistance and self-cleaning properties.

[0057] The performance test comparison between Examples 1, 2, and 3 shows that the 304 stainless steel mesh-based SiO2 superhydrophobic coating prepared by the present invention under the condition of constant voltage 55V reaction for 25 minutes has the best hydrophobic performance.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, various equivalent substitutions, improvements, and modifications can be made without departing from the principles of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A superhydrophobic SiO2 coating on a 304 stainless steel mesh base, characterized in that, The coating consists of a 304 stainless steel mesh substrate, a porous Fe-Cr-O oxide film layer, a SiO2 nanoparticle layer, and a low surface energy modified layer.

2. A superhydrophobic SiO2 coating on a 304 stainless steel mesh base, characterized in that, The coating surface has a micro-nano composite rough structure, a water contact angle >150°, a roll-off angle <10°, and an adhesion rating of 5A.

3. A SiO2 superhydrophobic coating on a 304 stainless steel mesh base, characterized in that, The coating has good long-term stability, high temperature resistance, acid and alkali resistance, and self-cleaning properties, and can be applied to the surface of downhole thermal recovery screen pipes.

4. A method for preparing the coating according to claims 1-3, characterized in that, Includes the following steps: (1) Substrate pretreatment: The 100-mesh 304 stainless steel mesh was ultrasonically cleaned with acetone, deionized water and anhydrous ethanol in sequence, dried in a forced-air drying oven, then soaked in pickling solution and ultrasonicated for 5 minutes, and then ultrasonically cleaned with deionized water and anhydrous ethanol in sequence, and dried in a forced-air drying oven for later use. (2) Electrolyte preparation: Prepare an electrolyte containing 0.15 mol / L ammonium fluoride, 0.6 mol / L deionized water, 8 g / L nano SiO2, and ethylene glycol to a final volume of 200 mL. Mix well and set aside. (3) Anodizing: Using the 304 stainless steel mesh pretreated in step (1) as the anode and the platinum sheet as the cathode, immerse it in the electrolyte prepared in step (2) and react for 20-40 minutes at a constant voltage of 25-85V and a temperature of 25℃. Then, wash the stainless steel mesh with deionized water and anhydrous ethanol in sequence, and dry it in a forced-air drying oven for later use. (4) Low surface energy modification: Immerse the stainless steel mesh prepared in step (3) in the modification liquid for 90 min, take it out and cure it in a forced-air drying oven at 80-100℃ for 1-2 h, and then let it cool naturally to room temperature.

5. The preparation method according to claim 4, characterized in that, The 304 stainless steel mesh measures 5cm x 3cm.

6. The preparation method according to claim 4, characterized in that, The pickling solution volume ratio in step (1) is concentrated nitric acid (65-68%): deionized water = 1:

1.

7. The preparation method according to claim 4, characterized in that, The SiO2 used in step (2) is hydrophilic SiO2 with a particle size of 10 nm, which needs to be ultrasonically dispersed in the electrolyte for 10 min.

8. The preparation method according to claim 4, characterized in that, In step (3), the area of ​​the platinum sheet is 1 cm². 2 The distance between the two electrodes is 4 cm, and the electrolyte is continuously stirred at a speed of 400 rpm during the reaction.

9. The preparation method according to claim 4, characterized in that, The modification solution mentioned in step (4) is a 1 vol% FAS-13 ethanol solution, and the modification is carried out at room temperature in the dark.

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