An ultrahydrophobic insulating coating for metro stray current

Abstract

The application discloses a kind of super-hydrophobic insulation paint and coating for subway stray current, paint includes the following weight proportion of component: 20-60 parts of ethyl acetate, 1-5 parts of modified nickel particles, 3-5 parts of polyurea, 7-11 parts of polyurea curing agent, 1-4 parts of polydimethylsiloxane, 0.1-0.4 parts of polydimethylsiloxane curing agent;The preparation method of modified nickel particles: in the mixed solution of anhydrous ethanol and ammonia water, 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane and tetraethyl silicate are added, after stirring, hydrolysis reaction is carried out for 1-3h to nickel particles, then centrifugal separation, drying, obtain modified nickel particles.Coating is sprayed to the surface of metal matrix, curing under room temperature environment, then the matrix containing coating is magnetized using magnet, obtain coating.The coating of the application can use strong magnet to make micron nickel particles therein have certain magnetism after being made into coating, so as to enhance the stability of bonding force and super-hydrophobic structure.

Description

Technical Field

[0001] This invention relates to the field of superhydrophobic self-cleaning insulating coating technology, and in particular to a superhydrophobic insulating coating and coating for stray current in subways. Background Technology

[0002] Under normal circumstances, current flows within the designated conductor as designed. If, for some reason, a portion of the current leaves the designated conductor and flows in a conductor where no current should flow, this portion of current is called stray current. If there should be no current in a metal component, but a stray current enters the metal component from the medium in a certain area on the surface of the metal component, it will inevitably leave the metal component and return to the medium in another area on the surface of the metal component. When the stray current leaves the metal component (electronic conductor phase) and enters the medium (ionic conductor phase), it is an anodic current for that surface area of ​​the metal component, accelerating the anodic dissolution of the metal and causing "corrosion" damage caused by stray current. Stray currents mainly originate from DC electrified railways, grounding electrodes of DC electrolysis equipment, and anodic ground beds in cathodic protection systems. Stray current corrosion is concentrated in localized locations with low resistance and easy discharge, such as defects in the coating, peeling areas, and sharp corners and protruding edges.

[0003] Taking my country's subway system, which uses a DC traction power supply system, as an example, the track system cannot be completely insulated, resulting in a small portion of the current leaking into the soil and forming stray currents. The intensity of these stray currents varies depending on the locomotive's operating time, the soil's electrolyte environment, and the magnitude of the traction current. Since many metal pipes are buried in the soil, and soil has a certain degree of conductivity, these stray currents leaking into the soil can cause electrochemical corrosion to buried metal structures such as natural gas pipelines and urban water supply pipes. Long-term electrochemical corrosion can cause significant damage to these buried pipelines. Stray currents inevitably cause corrosion to structures near electric transportation systems, especially in DC urban rail transit systems. Therefore, implementing stray current protection is urgently needed.

[0004] Existing stray current protection methods include the development of anti-corrosion coatings, graphite grounding methods, the application of anti-icing and anti-corrosion coatings, and the design of stray current protection devices. However, these methods are not simple enough and suffer from problems such as difficulty in curing and surface drying of anti-stray current coatings in high humidity environments. Especially in high humidity environments like subway tracks, existing coatings cure very slowly, greatly affecting their insulation or self-cleaning properties and failing to effectively protect against stray currents; furthermore, the poor adhesion between the coating and the substrate will affect the coating's service life. Summary of the Invention

[0005] To address the problems of slow curing, poor adhesion between the coating and the substrate, and poor protection against stray current in existing anti-stray current coatings, this invention provides a superhydrophobic insulating coating for stray current in subways and a corresponding coating.

[0006] The superhydrophobic insulating coating for stray current in subways provided by this invention comprises the following components in parts by weight: 20-60 parts ethyl acetate, 1-5 parts modified nickel particles, 3-5 parts polyurea, 7-11 parts polyurea curing agent, 1-4 parts polydimethylsiloxane, and 0.1-0.4 parts polydimethylsiloxane curing agent.

[0007] The modified nickel particles are prepared as follows:

[0008] Add 1H,1H,2H,2H-perfluorodecyltriethoxysilane and tetraethyl silicate to a mixture of anhydrous ethanol and ammonia. After stirring for 1-5 min, add nickel particles with a particle size of 1-5 μm. Perform hydrolysis reaction at room temperature (25 °C) for 1-3 h, then centrifuge and dry to obtain low surface energy modified micron nickel particles, i.e., modified nickel particles. A preferred preparation method is as follows: 20-40 ml of anhydrous ethanol and 5-12 ml of ammonia water are added to a beaker and stirred evenly. Then, 0.5-1.0 ml of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and 0.2-0.8 ml of tetraethyl silicate are added and stirred for 1-5 min. Then, nickel particles with a particle size of 20-50 nm are added and hydrolyzed for 1-3 h. The mixture is then centrifuged at 4000-6000 rpm and dried at 50-90 °C for 20-60 min to obtain low surface energy modified micron nickel particles, i.e., modified nickel particles.

[0009] Preferably, the weight ratio of the modified nickel particles to ethyl acetate is 1:10.

[0010] Preferably, the weight ratio of the polyurea to the polyurea curing agent is 1:2. The weight ratio of the polydimethylsiloxane to the polydimethylsiloxane curing agent is 10:1.

[0011] The preparation method of the superhydrophobic insulating coating is as follows: First, the modified nickel particles are added to ethyl acetate and stirred for 20-40 minutes to disperse them evenly; then polyurea and polyurea curing agent are added and stirred evenly. Then, polydimethylsiloxane and polydimethylsiloxane curing agent are added, and all the mixtures are stirred thoroughly for 5-10 minutes to ensure sufficient cross-linking, thus obtaining the coating.

[0012] The coating is sprayed onto the surface of a metal substrate and cured at room temperature for 20-30 minutes. Then, the substrate containing the coating is magnetized with a magnet to make the modified nickel particles magnetic, thus obtaining a superhydrophobic insulating coating for stray current in subways.

[0013] The metal substrate can be a steel substrate. Before spraying, the steel substrate undergoes pretreatment, which includes four steps: grinding and rust removal, shot peening, ultrasonic cleaning, and drying. First, the steel substrate is ground and rust removed using metallographic sandpaper. Then, shot peening is performed using cast steel shot ASH230 and ceramic shot AZB300 at pressures of 0.1-0.4 MPa and 0.1-0.3 MPa respectively, for 5-10 minutes. High-speed micro-shots bombard the surface of Q235 steel for shot peening. Shot peening can prevent bending fatigue of components, improve surface strength, and enhance resistance to stress corrosion. The continuous bombardment of the surface by high-speed shot causes micro-plastic deformation on the steel surface, increasing compressive stress and decreasing tensile stress, effectively preventing the formation of micro-cracks. Furthermore, this micro-plastic deformation provides a "mechanical interlocking" capability for the bonding between the coating and the substrate, improving the adhesion between the coating and the substrate, reducing the likelihood of peeling off, and increasing the service life of the coating.

[0014] After pretreatment, the coating is transferred to a spray gun with a nozzle diameter of 0.3-1 mm and sprayed evenly onto the steel substrate from a distance of 10-40 cm under a pressure of approximately 0.5-0.7 MPa. The sample is then placed at room temperature for curing, achieving surface dryness in approximately 20-30 minutes. Next, the micron-sized nickel particles in the coating are magnetized using a strong magnet, enhancing the adhesion between the coating and the substrate through magnetic force. This results in a rapid-curing, superhydrophobic, self-cleaning insulating coating that resists stray currents and is suitable for use in subway operations.

[0015] Compared with the prior art, the advantages of the present invention are:

[0016] (1) This invention uses polyurea as the main binder and takes advantage of the rapid curing function of polyurea. It combines low surface energy modified nickel micron particles to construct a micro-protrusion surface structure and designs a superhydrophobic self-cleaning insulating coating that can be applied to the protection of stray currents in subways. The coating can be further made to have a certain magnetic properties by using a strong magnet, thereby enhancing the bonding force and the stability of the superhydrophobic structure.

[0017] (2) Polyurea is produced by the polymerization of cyanate esters and amino groups. The molecular chain segments are composed of alternating hard and soft segments. The soft segments with lower glass transition temperatures have good flexibility and form the basic phase, while the hard segments with higher glass transition temperatures form the hard phase under the action of hydrogen bonds, playing the role of physical cross-linking and reinforcing filler. Polyurea has the characteristics of rapid solidification, excellent mechanical properties, good insulation, and is not sensitive to humidity and temperature, and can be applied at -28℃. This invention utilizes this characteristic and combines it with surface microstructure design to prepare this fast-curing superhydrophobic insulating coating that can be applied to stray currents in subways. For the subway environment, the humidity is generally >90% and the temperature is generally around 10℃, which poses a great challenge to the workability of the coating. On the one hand, the construction cycle is long and the cost is high; on the other hand, the inability to achieve rapid curing makes the coating unable to meet the requirements of the construction unit, and the coating is easily damaged during the long curing time, causing the coating to lose its protective value.

[0018] (3) Due to exposure to air, the surface of nickel particles generates certain hydroxyl groups from the NiO metal oxide on the surface during the hydrolysis reaction. These hydroxyl groups are then grafted with 1H,1H,2H,2H-perfluorodecyltriethoxysilane to form micron-sized nickel particles with low surface energy modification. These particles have long CF bonds and can produce excellent hydrophobic properties. Furthermore, nickel exhibits ferromagnetism and can be magnetized into permanent magnets. When applied to coatings, these particles can be magnetically adsorbed onto the surface of the rails to a certain extent, thus enhancing the bonding force.

[0019] (4) The resistance to stray current mainly involves two aspects: self-cleaning performance and insulation. According to relevant simulation studies and research on the influence of contaminant layers on transition resistance, the insulation resistance between the rail and the base plate is determined by the insulation resistance of the contaminant layer. Furthermore, the thicker the contaminant layer, the smaller the insulation resistance of the fastener to ground, which greatly increases the likelihood of stray current in the rail. Therefore, this invention designs a functional coating with a surface microstructure, utilizing the low surface energy of PDMS and low surface energy-modified micron-sized nickel particles as the main raw materials to provide a multi-level microstructure. This design creates an insulating anti-stray current coating with superhydrophobic self-cleaning properties, effectively preventing microcurrents from forming loops between the rail and the ground, and greatly reducing the corrosion hazards associated with stray currents. Moreover, the self-cleaning ability effectively prevents contaminants from adhering to the rail surface, keeping the rail clean and maintaining its insulation. The polyurea used in this invention has excellent resistivity, and insulation is an inherent property of polyurea.

[0020] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0021] Figure 1This is a schematic diagram illustrating the preparation principle of the superhydrophobic insulating coating for stray current in subways according to the present invention.

[0022] Figure 2 This is a comparison chart of the self-cleaning capabilities of the coatings.

[0023] Figure 3 The images show the acid and alkali resistance test results for different samples.

[0024] Figure 4 The figures show the results of water resistance tests on different samples.

[0025] Figure 5 The images show salt spray test results for different samples.

[0026] Figure 6 The figures show the test results of Tesla magnetic field strength and bonding force for different samples.

[0027] Figure 7 The water contact angle of the coatings in Comparative Example 3(a) and Example 1(b) is shown in the experimental diagram. Detailed Implementation

[0028] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0029] Example 1

[0030] like Figure 1 As shown, a method for preparing a fast-curing superhydrophobic insulating coating for use with stray currents in subways is as follows:

[0031] (1) Pretreatment of Q235 steel substrate surface

[0032] The pretreatment of the steel sheet substrate includes four steps in sequence: grinding and rust removal, shot peening, ultrasonic cleaning and impurity removal, and drying. First, the steel sheet is ground and rust removed using metallographic sandpaper of different purposes. Then, shot peening is performed using cast steel shot (ASH230) and ceramic shot (AZB300) at pressures of 0.1-0.4 MPa and 0.1-0.3 MPa, respectively, for 5-10 minutes.

[0033] (2) Preparation of modified nickel particles: 40 ml of anhydrous ethanol and 10 ml of ammonia water were added to a beaker and stirred evenly. Then, 1.0 ml of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and 0.8 ml of tetraethyl silicate were added and stirred for 5 min. Then, 3 g of nickel particles with a particle size of 20-50 nm were added and hydrolyzed at room temperature (25 °C) for 1 h. Then, the particles were centrifuged at 6000 rpm and dried at 90 °C for 60 min to obtain micron-sized nickel particles with low surface energy modification, i.e., modified nickel particles.

[0034] (3) Preparation of coating: Weigh 60g of ethyl acetate as solvent, then weigh 5g of modified nickel particles and place them in ethyl acetate, mechanically stirring for 30min to ensure uniform dispersion. Weigh 5g of polyurea, 10g of polyurea curing agent (isocyanate), 4g of PDMS, and 0.4g of PDMS curing agent (dibutyl phthalate DBP). Stir all the mixture thoroughly for 5min to ensure sufficient cross-linking. Then transfer the mixture to a spray gun with a nozzle diameter of 0.3-1mm and spray it evenly onto the surface of the substrate at a pressure of about 0.5-0.7Mpa, at a distance of 10-40cm. Place the sample at room temperature for curing treatment, which takes about 20-30min for surface drying. Finally, magnetize the sample with the coating using a strong magnet. After the magnet is attached to the back of the substrate for a period of time, about 30min, remove the magnet to make the micron-sized nickel particles have a certain magnetism.

[0035] Example 2

[0036] A method for preparing a fast-curing superhydrophobic insulating coating for use with stray currents in subways:

[0037] (1) Pretreatment of Q235 steel substrate surface

[0038] The pretreatment of the steel sheet substrate includes four steps in sequence: grinding and rust removal, shot peening, ultrasonic cleaning and impurity removal, and drying. First, the steel sheet is ground and rust removed using metallographic sandpaper of different purposes. Then, shot peening is performed using cast steel shot (ASH230) and ceramic shot (AZB300) at pressures of 0.1-0.4 MPa and 0.1-0.3 MPa, respectively, for 5-10 minutes.

[0039] (2) Preparation of modified nickel particles: 20 ml of anhydrous ethanol and 5 ml of ammonia water were added to a beaker and stirred evenly. Then, 0.5 ml of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and 0.2 ml of tetraethyl silicate were added and stirred for 5 min. Then, 1 g of nickel particles with a particle size of 20-50 nm were added and hydrolyzed at room temperature (25 °C) for 3 h. Then, the particles were centrifuged at 4000 rpm and dried at 50 °C for 60 min to obtain micron-sized nickel particles with low surface energy modification, i.e., modified nickel particles.

[0040] (3) Preparation of coating: Weigh 20g of ethyl acetate as solvent, then weigh 1g of modified nickel particles and add them to the ethyl acetate, stirring mechanically for 30min to ensure uniform dispersion. Weigh 3g of polyurea, 6g of polyurea curing agent (isocyanate), 1g of PDMS, and 0.1g of PDMS curing agent (dibutyl phthalate DBP). Stir all the mixture thoroughly for 5min to ensure sufficient cross-linking. Then transfer the mixture to a spray gun with a nozzle diameter of 0.3-1mm and spray it evenly onto the surface of the substrate at a pressure of approximately 0.5-0.7MPa, at a distance of 10-40cm. Place the sample at room temperature for curing, which takes about 20-30min for surface drying. Finally, use a strong magnet to magnetize the coated sample, giving the micron-sized nickel particles a certain degree of magnetism.

[0041] Comparative Example 1

[0042] In order to demonstrate the rapid curing characteristics of using polyurea as the main binder and make it more suitable for stray current protection in subways, based on Example 1, the polyurea and polyurea curing agent were replaced with the same amount of epoxy resin and its curing agent (specific type) to obtain a coating, which was then further made into a coating layer.

[0043] The coatings prepared in Example 1 and Comparative Example 1 were placed in an environment with an ambient temperature of 25°C and a humidity of 90%, and the surface drying time and related performance evaluations were recorded. The test data are shown in Table 1.

[0044] Table 1. Surface drying time and complete drying time for different types of coatings

[0045]

[0046] Comparative Example 2

[0047] Based on the preparation method of Example 1, step (2) was removed, and modified nickel particles were not added in step (3) to obtain pure coating.

[0048] The coatings prepared in Example 1 and Comparative Example 2 were tested for superhydrophobicity and self-cleaning ability. The test method was as follows: both samples were placed at an angle, and some graphite powder was sprinkled on their surfaces. Water was then dripped onto the surfaces of both samples using a plastic dropper. The test substrate was a 12*5*0.1cm tinplate, and the solution was water. The test results are shown below. Figure 2 .Depend on Figure 2 In the middle, the left figure is a coating made with the paint of Comparative Example 2, and the right figure is a coating made with the paint of Example 1. It can be seen from the water droplet adhesion on the surface that the water droplets on the coating of Example 1 can carry away the graphite powder and play a self-cleaning role.

[0049] The coatings prepared in Example 1 and Comparative Example 2 were subjected to tests for acid and alkali resistance, as well as water resistance. Test methods: a) Acid resistance: The coating was immersed in a 5% HCl solution for 168 hours, and the surface was visually inspected for any abnormalities; b) Alkali resistance: The coating was immersed in a 5% NaOH solution for 168 hours, and the surface was visually inspected for any abnormalities; c) Water resistance: The coating was immersed in water for 168 hours, and the presence of blistering, cracking, peeling, powdering, significant discoloration, or significant loss of gloss was visually inspected. Test results are shown below. Figure 3 and Figure 4 In the figure, the pure coating refers to the coating prepared in Comparative Example 2, and the superhydrophobic coating represents the coating prepared in Example 1. As can be seen from the figure, the coating of Example 1 of this invention did not peel off in the acid and alkali resistance test, demonstrating excellent acid and alkali resistance. In the 400-hour water resistance test, the surface of the coating of Example 1 of this invention remained clean. The acid and alkali resistance and water resistance of the coating prepared in Example 1 of this invention are superior to those of the coating in Comparative Example 2. This proves that the addition of modified nickel particles to the coating of this invention improves its acid and alkali resistance and water resistance.

[0050] The coatings prepared in Example 1 and Comparative Example 2 were subjected to salt spray (5% wt NaCl) tests. The experimental method involved placing the steel substrate, the coating of Comparative Example 2, and the coating of Example 1 in a salt spray chamber for 15 days. The test results are shown below. Figure 5 As shown in the figure, the coating of Example 1 did not show corrosion during the 15-day salt spray test.

[0051] To demonstrate that magnetization of modified nickel particles enhances the adhesion of the coating, tests were conducted on the coatings of Example 1 before and after magnetization. The magnetic field strength of both samples was measured using a Tesla meter, and the adhesion of the coatings was tested using the cross-cut adhesion test. The test results are shown in [Figure number missing]. Figure 6The two figures above and below represent the unmagnetized and magnetized coatings, respectively. The unmagnetized micron-sized nickel coating measured 0.35 mT using a Tesla meter, while the magnetized coating measured 1.02 mT, demonstrating that the nickel particles were magnetized to a certain extent. The magnetized particles can generate a magnetic attraction effect with the metal substrate, thereby enhancing the bonding force. Moreover, the experimental results show that the coating prepared in Example 1 has twice the stray current resistance of Comparative Example 2.

[0052] Comparative Example 3

[0053] Based on the preparation method of Example 1, step (2) was removed, and unmodified original nickel particles were directly added in step (3) to obtain the coating.

[0054] The coatings prepared from the coatings of Example 1 and Comparative Example 3 were subjected to water contact angle tests. The test results are shown in [Figure Number]. Figure 7 The water contact angle of the coating in Comparative Example 3 was 93°, while that of the coating in Example 1 was 153°. This demonstrates that the coating prepared using low surface energy modified micron-sized nickel particles in this invention exhibits superior superhydrophobic properties.

[0055] In summary, this invention provides a fast-curing superhydrophobic self-cleaning insulating coating for use in subway rail service environments with stray currents. Performance tests of the fast-curing superhydrophobic coating were conducted through salt spray, acid and alkali resistance, and water resistance tests. The coating did not peel off, exhibiting excellent acid and alkali resistance and good corrosion resistance; no corrosion was observed in the 15-day salt spray test. In the 400-hour water resistance test, the superhydrophobic coating surface remained clean, with a water contact angle of 153°, demonstrating excellent hydrophobic properties. Furthermore, the coating exhibits excellent self-cleaning properties, preventing dirt adhesion and corrosion. Using low surface energy modified micron-sized nickel metal particles as filler and magnetizing them not only achieves superhydrophobicity but also, as demonstrated by the cross-cut adhesion test, the magnetized nickel particles enhance the adhesion between the coating and the metal substrate. The tiny powder particles at the scratched edges fill the scratches, thus protecting the substrate.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A superhydrophobic insulating coating for stray currents in subway systems, characterized in that, The preparation method is as follows: Superhydrophobic insulating coating is sprayed onto the surface of a metal substrate and cured at room temperature for 20-30 minutes. Then, the substrate with the coating is magnetized with a magnet to make the modified nickel particles magnetic, thus obtaining a superhydrophobic insulating coating for stray current in subways. The superhydrophobic insulating coating comprises the following components in parts by weight: 20-60 parts ethyl acetate, 1-5 parts modified nickel particles, 3-5 parts polyurea, 7-11 parts polyurea curing agent, 1-4 parts polydimethylsiloxane, and 0.1-0.4 parts dibutyl phthalate. The modified nickel particles are prepared as follows: Add 1H,1H,2H,2H-perfluorodecyltriethoxysilane and tetraethyl silicate to a mixture of anhydrous ethanol and ammonia. After stirring for 1-5 min, add nickel particles with a particle size of 20-50 nm. Perform hydrolysis reaction at room temperature (25°C) for 1-3 h. Then centrifuge and dry to obtain low surface energy modified micron nickel particles, i.e. modified nickel particles. The preparation method of the superhydrophobic insulating coating is as follows: First, add modified nickel particles to ethyl acetate and stir for 20-40 minutes to make them uniformly dispersed; then add polyurea and polyurea curing agent, polydimethylsiloxane and dibutyl phthalate, and stir all the mixture thoroughly for 5-10 minutes to make them fully crosslinked to obtain the coating.

2. The superhydrophobic insulating coating for stray currents in subways as described in claim 1, characterized in that, The modified nickel particles are used in a weight ratio of 1:10 to ethyl acetate.

3. The superhydrophobic insulating coating for stray currents in subways as described in claim 1, characterized in that, The weight ratio of the polyurea to the polyurea curing agent is 1:

2.

4. The superhydrophobic insulating coating for stray currents in subways as described in claim 1, characterized in that, The weight ratio of polydimethylsiloxane to dibutyl phthalate is 10:

1.

5. The superhydrophobic insulating coating for stray currents in subways as described in claim 1, characterized in that, The metal substrate is a steel substrate. Before spraying, the steel substrate is pretreated, which includes four steps in sequence: grinding and rust removal, shot peening, ultrasonic cleaning and impurity removal, and drying.

6. The superhydrophobic insulating coating for stray currents in subways as described in claim 5, characterized in that, First, the steel substrate is polished and rust removed using metallographic sandpaper. Then, shot peening is performed using cast steel shot ASH230 and ceramic shot AZB300 at pressures of 0.1-0.4 MPa and 0.1-0.3 MPa, respectively, for 5-10 minutes.

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