Wear-resistant super-hydrophobic anti-drag coating material, preparation method and application method

Abstract

The invention discloses a wear-resistant super-hydrophobic anti-drag coating material, a preparation method and an application method, and belongs to the technical field of super-hydrophobic anti-drag coatings. Diatomite is subjected to octadecyl trichlorosilane (OTS) covalent grafting, then hydrophobically modified diatomite, PFA nano powder and absolute ethyl alcohol are compounded into a diatomite-PFA-alcohol suspension, FEVE, a polyisocyanate curing agent and absolute ethyl alcohol are compounded into a fluorocarbon resin mixed solution containing curing components, and the wear-resistant super-hydrophobic anti-drag coating material is obtained after mixing. When the coating material is applied, a laser etching technology is adopted to etch a surface texture with square micro-grooves distributed in a latticed mode on the surface of a base body, and the surface texture suitable for spraying of the wear-resistant super-hydrophobic anti-drag coating material is formed by optimizing the side length and the distance of the micro-grooves; after the wear-resistant super-hydrophobic anti-drag coating material is sprayed, the'armor-rectangular frame 'structure in the coating shows excellent wear resistance and super-hydrophobic property retention capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of super-hydrophobic drag-reducing coating, and particularly relates to a wear-resistant super-hydrophobic drag-reducing coating material, a preparation method and an application method. BACKGROUND

[0002] Research shows that the frictional resistance of a water surface ship with a speed of more than 30 knots accounts for more than 40% of the total resistance, and the frictional resistance of a torpedo, a submarine and other submerged bodies accounts for more than 80% of the total resistance under the fully submerged condition; according to theoretical calculation, if the frictional resistance is reduced by 10%, the cruising speed under the condition of equal power can be increased by about 3.57%, and the range is also increased synchronously, which has great strategic value for improving the maneuvering ability and the combat radius.

[0003] The performance of super-hydrophobic materials is derived from the synergistic effect of micro-nano hierarchical rough structure and low surface energy chemical modification. At present, the hydrophobic coating materials on the market are mostly used for self-cleaning, anti-icing and other aspects, and there is little research on super-hydrophobic drag reduction. For example, Chinese Patent 202411511601.9 discloses a hBN / Al2O3-based super-hydrophobic composite coating, which uses a polydimethylsiloxane modifier, an epoxy resin, hBN powder, Al2O3 powder and a curing agent to prepare a super-hydrophobic coating, which is tested on wood, plastic and other substrates, and the application effect on a metal surface (the metal surface has stronger water spreading ability and it is difficult to achieve super-hydrophobic effect) is not verified. For another example, Chinese Patent 202510228197.2 discloses a ZIF-8-based photo-thermal super-hydrophobic anti-corrosion and anti-icing coating applied to an aluminum alloy substrate, and a 1000-mesh sandpaper and a 100g weight are used to carry out wear resistance test. After 48 cycles of friction, the coating still has super-hydrophobic effect. Chinese Patent 202410225120.5 discloses a multi-scale wear-resistant super-hydrophobic drag-reducing surface, which uses laser processing to design large ribs and grooves with trapezoidal cross section on the metal surface, and cooperates with an octadecyltrichlorosilane super-hydrophobic emulsion to achieve hydrophobic drag reduction. However, since the structure design can only consider the drag reduction in the direction of the groove, the water flow impact in other directions has not been verified.

[0004] Therefore, it is necessary to develop a wear-resistant super-hydrophobic drag-reducing coating material, which can improve the exposure durability, wear resistance and reduce the contact angle degradation when coping with complex marine environment, and has important application value. SUMMARY

[0005] The first object of the present application is to provide a preparation method of a wear-resistant super-hydrophobic drag-reducing coating material, the second object is to provide a wear-resistant super-hydrophobic drag-reducing coating material obtained by the preparation method, and the third object is to provide an application method of the wear-resistant super-hydrophobic drag-reducing coating material.

[0006] The first object of the present application is achieved by the preparation method of the wear-resistant super-hydrophobic drag-reducing coating material as follows: 1) Preparation of hydrophobic modified diatomite: anhydrous ethanol, deionized water and ammonia water with a concentration of 25-28wt% are mixed in a volume ratio of 70-90:10-30:1-5 to obtain an alkaline alcohol-water mixture; diatomite powder is added to the alkaline alcohol-water mixture in a solid-liquid ratio of 1g:15-25mL, and mechanical stirring is carried out at a speed of 500-800r / min for 5-10min at 24-26℃ to obtain a dispersion liquid; OTS is added dropwise to the dispersion liquid at 5-15wt% of the diatomite powder, and the temperature is raised to 48-52℃ for continuous stirring at 200-400r / min for 20-24h; after the reaction is completed, the filter cake is washed with anhydrous ethanol for 3-5 times, and then dried at a vacuum degree of ≤-0.08MPa and a temperature of 38-42℃ for 20-24h; the dried product is crushed by airflow milling to D 50 ≤5μm, and OTS covalently grafted hydrophobic modified diatomite is obtained, which is sealed and dried for storage; 2) Preparation of wear-resistant super-hydrophobic drag-reducing coating material: hydrophobic modified diatomite, PFA nano-powder and anhydrous ethanol are weighed in a mass ratio of 1:2-4:7-9, mixed and then ultrasonically treated at 200-220W for 15-20min at 24-26℃, followed by magnetic stirring at a speed of 600-900r / min for 1-2h at 24-26℃ to obtain a diatomite-PFA-alcohol suspension, i.e. dispersion phase A; FEVE, a polyisocyanate curing agent and anhydrous ethanol are mixed in a mass ratio of 6-10:1:10-15, and then magnetically stirred at a speed of 600-800r / min for 1-2h at 24-26℃ to obtain a fluorocarbon resin mixture containing curing components, i.e. dispersion phase B; dispersion phase A and dispersion phase B are mixed in a volume ratio of 2-4:1, and then stirred at a speed of 600-800r / min for 20-24h at 24-26℃ in the dark to obtain a wear-resistant super-hydrophobic drag-reducing coating material.

[0007] The second object of the application is achieved by the preparation method to obtain the wear-resistant super-hydrophobic drag-reducing coating material.

[0008] The third object of the application is achieved by the application method of the wear-resistant super-hydrophobic drag-reducing coating material as follows: A, substrate pretreatment: the substrate is immersed in an alkaline degreasing agent with a pH of 11-12, ultrasonically cleaned at 50-60℃ for 300-600s, and then rinsed with deionized water until a continuous water film is formed on the surface; the cleaned substrate is placed in a mixed solution containing 30-50g / L NaOH and 0.5-1g / L corrosion inhibitor, and immersed in etching at 40-50℃ for 30-120s to remove the natural oxide layer and expose the fresh metal surface; the etched substrate is transferred into a 10-20wt% HNO3 solution at room temperature for 10-30s to neutralize and eliminate the surface ash, and then rinsed with deionized water and dried to prepare the substrate for use; B, matrix laser etching: according to the depth of the micro-groove 20 μm, the side length 0.2~1.0mm, the groove interval 0.03~0.05mm, the surface texture of the square micro-groove grid uniform distribution is etched on the pretreated substrate surface by using ultraviolet femtosecond laser technology, then ultrasonic cleaning with anhydrous ethanol and drying with dry nitrogen; C, wear-resistant super-hydrophobic drag-reducing coating material pretreatment: the wear-resistant super-hydrophobic drag-reducing coating material is sent into a vacuum degassing kettle, and is degassed at an absolute pressure of ≤-0.09MPa until no visible bubbles escape; 500 mesh screen is used to reduce pressure filtration under 0.05~0.1MPa nitrogen pressure, and the filtrate is immediately transferred to a storage tank equipped with a 0.8mm diameter HVLP spray gun, and dry nitrogen with a dew point of ≤-40℃ is continuously introduced into the tank for protection; D, spraying and curing: the nozzle of the HVLP spray gun is corresponded to the substrate with a vertical distance of 245~255mm, and the wear-resistant super-hydrophobic drag-reducing coating material is sprayed on the substrate surface under 0.23~0.25MPa with purified compressed air as atomizing gas until the coating thickness is 200~500μm, uniform and without macroscopic defects; after spraying, the substrate is placed in a 78~82℃ air-drying oven for 10~14h, then the heating is stopped and the oven is cooled to room temperature, and then it is transferred to a dryer for 20~24h to obtain a substrate with wear-resistant super-hydrophobic drag-reducing coating.

[0009] In view of the problems existing in the prior art, the diatomite is covalently grafted with octadecyltrichlorosilane (OTS) to obtain OTS covalently grafted hydrophobic modified diatomite; then the hydrophobic modified diatomite, PFA nano powder and anhydrous ethanol are compounded to form a diatomite-PFA-alcohol suspension, and FEVE, polyisocyanate curing agent and anhydrous ethanol are compounded to form a fluorocarbon resin mixed solution containing curing components, and after mixing, a wear-resistant super-hydrophobic drag-reducing coating material composed of nano is obtained; when the wear-resistant super-hydrophobic drag-reducing coating material is applied, the surface texture of the substrate is etched in a square micro-groove grid arrangement by using laser etching technology, and by optimizing the side length and interval of the micro-groove, a substrate surface texture suitable for spraying of the wear-resistant super-hydrophobic drag-reducing coating material is formed; as shown in the drawings, the micro-groove is in the form of an open square concave pit structure (composed of opposite isosceles triangles and opposite isosceles trapezoids), with a depth of 20 μm, and the nano particles in the wear-resistant super-hydrophobic drag-reducing coating material are filled in the laser etched rectangular frame to form a "armor-rectangular frame" structure, which not only provides high specific surface area and low surface energy, but also reduces direct wear of protruding nano structures by means of "groove hiding" effect, and can disperse external friction stress to avoid the whole shear peeling of nano particles, and ensure the required nano roughness of Cassie-Baxter state.

[0010] The wear-resistant super-hydrophobic drag-reducing coating material and the 200-500 μm thick coating prepared by the method of the application have micro-grooves with a depth of 20 μm, a side length (a) of 0.2-1.0 mm, and a groove-to-groove spacing (i) of 0.03-0.05 mm. Tests show that the contact angle of the coating after formation can reach 160° or more, and the contact angle of each coating fluctuates between 130° and 160° after a 200 g load, 200 mesh sandpaper abrasion test. When i=0.03 mm and a=0.5 mm, or i=0.05 mm and a=0.8 mm, the contact angle is not less than 150° and Δθ is not more than 10° after 200 cm (40 cycles of abrasion), showing excellent wear resistance and super-hydrophobic performance retention capability.

[0011] As can be seen, the application significantly improves the mechanical durability of the super-hydrophobic drag-reducing coating and the hydrophobic performance retention capability under abrasion conditions by combining the nanoscale coating material with the microscale surface texture of the substrate surface. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 Figure 4 is the SEM micrograph of the laser-etched substrate surface of Step B of Example 1 at 100 times; Figure 2 、 3 Figure 5 is the SEM micrograph of the wear-resistant super-hydrophobic drag-reducing coating prepared in Step D of Example 1 at 50 times, 500 times, and 10,000 times; Figure 5 Figure 6 is the static contact angle of the flat substrate after pretreatment in Step A of Example 1; Figure 6 Figure 7 is the static contact angle of the laser-etched substrate in Step B of Example 1; Figure 7 Figure 8 is the static contact angle of the wear-resistant super-hydrophobic drag-reducing coating prepared in Step D of Example 1; Figure 8 Figure 9 is the static contact angle of the wear-resistant coating prepared in Comparative Example 1; Figure 9 Figure 10 is the 200 mesh sandpaper abrasion test result of the coating with a micro-groove i=0.03 mm in Test Example III; Figure 10 Figure 11 is the 200 mesh sandpaper abrasion test result of the coating with a micro-groove i=0.05 mm in Test Example III. DETAILED DESCRIPTION

[0013] The application will be further described in conjunction with the examples below, but in no way limits the application, and any transformation or replacement based on the teaching of the application also belongs to the protection scope of the application.

[0014] The preparation method of the wear-resistant super-hydrophobic drag-reducing coating material is as follows: 1) Preparation of hydrophobic modified diatomite: anhydrous ethanol, deionized water and ammonia water with a concentration of 25-28wt% are mixed in a volume ratio of 70-90:10-30:1-5 to obtain an alkaline alcohol-water mixture; diatomite powder is added to the alkaline alcohol-water mixture in a solid-liquid ratio of 1g:15-25mL, and mechanical stirring is carried out at a speed of 500-800r / min for 5-10min at 24-26℃ to obtain a dispersion liquid; OTS is added dropwise to the dispersion liquid at 5-15wt% of the diatomite powder, and the temperature is raised to 48-52℃ for continuous stirring at a speed of 200-400r / min for 20-24h; after the reaction is completed, the filter cake is washed with anhydrous ethanol for 3-5 times, and dried at a vacuum degree of ≤-0.08MPa and a temperature of 38-42℃ for 20-24h, and then pulverized by airflow mill to D 50 ≤5μm to obtain OTS covalently grafted hydrophobic modified diatomite, which is sealed and dried for storage; 2) Preparation of wear-resistant super-hydrophobic drag-reducing coating material: hydrophobic modified diatomite, PFA nano-powder and anhydrous ethanol are weighed in a mass ratio of 1:2-4:7-9, mixed and then ultrasonically treated at 200-220W for 15-20min at 24-26℃, followed by magnetic stirring at a speed of 600-900r / min for 1-2h at 24-26℃ to obtain a diatomite-PFA-alcohol suspension, i.e. dispersion phase A; FEVE, a polyisocyanate curing agent and anhydrous ethanol are mixed in a mass ratio of 6-10:1:10-15, and then magnetically stirred at a speed of 600-800r / min for 1-2h at 24-26℃ to obtain a fluorocarbon resin mixture containing curing components, i.e. dispersion phase B; dispersion phase A and dispersion phase B are mixed in a volume ratio of 2-4:1, and then stirred at a speed of 600-800r / min for 20-24h at 24-26℃ in the dark to obtain a wear-resistant super-hydrophobic drag-reducing coating material.

[0015] Further, the average particle size of the diatomite powder in step 1) is 5-10μm.

[0016] Further, the average particle size of the PFA in step 1) is 250-300nm.

[0017] The wear-resistant super-hydrophobic drag-reducing coating material obtained by the preparation method.

[0018] The application of the wear-resistant super-hydrophobic drag-reducing coating material is as follows: A, substrate pretreatment: immerse the substrate in an alkaline degreasing agent with pH 11-12, ultrasonic cleaning at 50-60℃ for 300-600s, then rinse with deionized water until the surface water film is continuous; after cleaning, the substrate is placed in a mixed solution containing 30-50g / L NaOH and 0.5-1g / L corrosion inhibitor, immersed at 40-50℃ for 30-120s to remove the natural oxide layer and expose the fresh metal surface; after etching, the substrate is transferred into a 10-20wt% HNO3 solution at room temperature for 10-30s to neutralize the surface and eliminate the ash, then rinse with deionized water and dry the surface for standby; B, substrate laser etching: according to the depth of the micro-groove 20μm, the side length 0.2-1.0mm, the groove spacing 0.03-0.05mm, the ultraviolet femtosecond laser technology is used to etch the square micro-groove grid uniform distribution on the surface of the pretreated substrate, then ultrasonic cleaning with anhydrous ethanol and dry nitrogen blowing; C, pretreatment of wear-resistant super-hydrophobic drag-reducing coating material: the wear-resistant super-hydrophobic drag-reducing coating material is sent into a vacuum degassing kettle, and is placed under an absolute pressure of ≤-0.09MPa for degassing until no visible bubbles escape; a 500 mesh screen is used to reduce pressure filtration under a nitrogen pressure of 0.05-0.1MPa, and the filtrate is immediately transferred to a storage tank equipped with a 0.8mm diameter HVLP spray gun, and dry nitrogen with a dew point of ≤-40℃ is continuously introduced into the tank for protection; D, spraying and curing: the nozzle of the HVLP spray gun is corresponded to the substrate with a vertical distance of 245-255mm, and the purified compressed air is used as the atomizing gas, and the wear-resistant super-hydrophobic drag-reducing coating material is sprayed on the surface of the substrate under the intermittent mode of spraying and stopping at 0.23-0.25MPa until the coating thickness is 200-500μm, uniform and without macroscopic defects; after spraying, the substrate is placed in a 78-82℃ air drying oven for 10-14h, then the heating is stopped and the oven is cooled to room temperature, then it is transferred to a dryer for 20-24h to obtain a substrate with wear-resistant super-hydrophobic drag-reducing coating.

[0019] Further, the substrate in step A is a 7075 aluminum alloy substrate.

[0020] Further, the laser etching treatment conditions in step B are: repetition frequency 400kHz, scanning pitch 3μm, scanning speed 500mm / s, laser power 20-40W, laser off light delay 100μs and 300μs, and laser etching layer number 4 times.

[0021] Further, the screen in step B is a 316L stainless steel screen.

[0022] Further, step D sprays the wear-resistant super-hydrophobic drag-reducing coating material on the surface of the substrate in a spray-stop intermittent mode, i.e., spraying for 1-2 s and stopping for 30 s, and repeating the spraying for 15-25 times.

[0023] Further, the relative humidity of the dryer in step D is ≤20%.

[0024] Example 1: Preparation of a substrate with a wear-resistant super-hydrophobic drag-reducing coating I. Preparation of a wear-resistant super-hydrophobic drag-reducing coating material: 1) Preparation of hydrophobically modified diatomite: mix anhydrous ethanol, deionized water and ammonia water with a concentration of 25 wt% according to a volume ratio of 70:10:1 to obtain an alkaline alcohol-water mixture; add diatomite powder with an average particle size of 5 μm to the alkaline alcohol-water mixture according to a solid-liquid ratio of 1 g:15 mL, and mechanically stir at 500 r / min for 5 min at 25 °C to obtain a dispersion liquid; add octadecyltrichlorosilane (OTS) dropwise to the dispersion liquid according to 5 wt% of the diatomite powder, and continuously stir at 48 °C and 200 r / min for 20 h; after the reaction is completed, filter the filter cake, wash it with ethanol for 3 times, dry it at a vacuum degree of ≤-0.08 MPa and 38 °C for 20 h, and crush it by airflow milling to D 50 ≤5 μm to obtain OTS covalently grafted hydrophobically modified diatomite, which is sealed and dried for storage; 2) Preparation of a wear-resistant super-hydrophobic drag-reducing coating material: weigh the hydrophobically modified diatomite, PFA nano-powder (average particle size of 250 nm) and anhydrous ethanol according to a mass ratio of 1:2:7, mix them, and then ultrasonically treat at 200 W for 15 min at 25 °C, followed by magnetic stirring at 600 r / min for 1 h at 24 °C to obtain a diatomite-PFA-alcohol suspension, i.e., dispersion phase A; weigh the FEVE, polyisocyanate curing agent and anhydrous ethanol according to a mass ratio of 6:1:10, mix them, and then magnetically stir at 600 r / min for 1 h at 24 °C to obtain a fluorocarbon resin mixture containing curing components, i.e., dispersion phase B; mix dispersion phase A and dispersion phase B according to a volume ratio of 2:1, and stir at 600 r / min for 20 h at 24 °C in the dark to obtain a wear-resistant super-hydrophobic drag-reducing coating material.

[0025] II. Preparation of a wear-resistant super-hydrophobic drag-reducing coating: A. Substrate pretreatment: immerse a 7075 aluminum alloy substrate with a smooth surface in an alkaline degreasing agent with a pH of 11, ultrasonically clean it at 50 °C for 300 s, then rinse it with deionized water until a continuous water film is formed on the surface; immerse the cleaned substrate in a mixed solution containing 30 g / L NaOH and 0.5 g / L corrosion inhibitor, and etch it at 40 °C for 30 s to remove the natural oxide layer and expose the fresh metal surface; transfer the etched substrate into a 10 wt% HNO3 solution at room temperature, neutralize it for 10 s, eliminate the surface dust, rinse it with deionized water, and then dry the surface for standby use; B, matrix laser etching: using ultraviolet femtosecond laser technology to etch a square microgroove grid arrangement surface texture on the pretreated 7075 aluminum alloy substrate surface, the microgroove depth is 20 μm, the side length (a) is 0.5 mm, the groove spacing (i) is 0.03 mm, then ultrasonic cleaning with anhydrous ethanol and drying with dry nitrogen; the laser etching treatment conditions are: repetition frequency 400 kHz, scanning pitch 3 μm, scanning speed 500 mm / s, laser power 20 W, laser off light delay 100 μs and 300 μs, laser etching layer number 4 times; C, pretreatment of wear-resistant super-hydrophobic drag-reducing coating material: the wear-resistant super-hydrophobic drag-reducing coating material is put into a vacuum degassing kettle, and is degassed at an absolute pressure of ≤-0.09 MPa until no visible bubbles escape; 500 mesh 316L stainless steel screen is used to reduce pressure filtration under 0.05 MPa nitrogen pressure, and the filtrate is immediately transferred to a storage tank equipped with a 0.8 mm diameter HVLP spray gun, and dry nitrogen with a dew point of ≤-40 ℃ is continuously introduced into the tank for protection; D, spraying and curing: the nozzle of the HVLP spray gun is corresponded to the substrate with a vertical distance of 245 mm, and the purified compressed air is used as the atomizing gas. The wear-resistant super-hydrophobic drag-reducing coating material is sprayed on the substrate surface by using spray-stop intermittent mode under 0.23 MPa until the coating thickness is 200 μm, uniform and without macroscopic defects. After spraying, the substrate is placed in a 78 ℃ air drying oven for 10 h, then the heating is turned off and the oven is cooled to room temperature, and then it is transferred to a desiccator (relative humidity ≤20%) for 20 h to obtain a substrate with wear-resistant super-hydrophobic drag-reducing coating (the substrate is provided with a coating on one side).

[0026] Example 2 Preparation of a substrate with wear-resistant super-hydrophobic drag-reducing coating I, preparation of wear-resistant super-hydrophobic drag-reducing coating material: 1) Preparation of hydrophobic modified diatomite: mix anhydrous ethanol, deionized water and ammonia water with a concentration of 26.5 wt% according to a volume ratio of 80:20:3 to obtain an alkaline alcohol-water mixture; add diatomite powder with an average particle size of 8 μm to the alkaline alcohol-water mixture according to a solid-liquid ratio of 1 g:20 mL, and mechanically stir at 24 ℃ and 700 r / min for 8 min to obtain a dispersion liquid; add octadecyltrichlorosilane (OTS) dropwise to the dispersion liquid according to 10 wt% of the diatomite powder, and continuously stir at 50 ℃ and 300 r / min for 22 h; after the reaction is completed, the filter cake is washed with ethanol for 4 times, and then dried at a vacuum degree of ≤-0.08 MPa and 40 ℃ for 22 h; the dried filter cake is crushed by air flow mill to D 50 ≤5 μm to obtain OTS covalently grafted hydrophobic modified diatomite, which is sealed and stored dry; 2) Preparation of wear-resistant super-hydrophobic drag-reducing coating material: hydrophobic modified diatomite, PFA nano-powder (average particle size 255 nm), and anhydrous ethanol were weighed according to a mass ratio of 1:3:8, mixed, and then treated with ultrasonic waves at 24°C for 18 min at 210 W, followed by magnetic stirring at 700 r / min at 25°C for 1.5 h to obtain a diatomite-PFA-alcohol suspension, i.e., the dispersion phase A; FEVE, a polyisocyanate curing agent, and anhydrous ethanol were weighed according to a mass ratio of 8:1:13, mixed, and then magnetically stirred at 700 r / min at 25°C for 1.5 h to obtain a fluorocarbon resin mixture containing a curing component, i.e., the dispersion phase B; the dispersion phase A and the dispersion phase B were mixed according to a volume ratio of 3:1, and then stirred at 700 r / min at 25°C for 22 h in the dark to obtain the wear-resistant super-hydrophobic drag-reducing coating material.

[0027] II, Preparation of the wear-resistant super-hydrophobic drag-reducing coating: A, Substrate pretreatment: a 7075 aluminum alloy substrate with a smooth surface was immersed in an alkaline degreasing agent with a pH of 11.5, ultrasonically cleaned at 55°C for 450 s, and then rinsed with deionized water until a continuous water film was formed on the surface; the cleaned substrate was placed in a mixed solution containing 40 g / L NaOH and 0.8 g / L corrosion inhibitor, and immersed in etching at 45°C for 75 s to remove the natural oxide layer and expose the fresh metal surface; the etched substrate was transferred into a 15 wt% HNO3 solution at room temperature for 20 s to neutralize the surface and eliminate the grayish appearance, and then rinsed with deionized water and dried with dry nitrogen for standby; B, Laser etching of the substrate: ultraviolet femtosecond laser technology was used to etch a square micro-groove grid-shaped surface texture on the pretreated 7075 aluminum alloy substrate, with a micro-groove depth of 20 μm, a side length (a) of 0.8 mm, and a groove spacing (i) of 0.05 mm, and then ultrasonically cleaned with anhydrous ethanol and dried with dry nitrogen; the laser etching treatment conditions were as follows: a repetition frequency of 400 kHz, a scanning pitch of 3 μm, a scanning speed of 500 mm / s, a laser power of 30 W, a laser-off delay of 100 μs and 300 μs, and 4 times of laser etching layer; C, Pretreatment of the wear-resistant super-hydrophobic drag-reducing coating material: the wear-resistant super-hydrophobic drag-reducing coating material was placed in a vacuum degassing kettle and degassed at an absolute pressure of ≤-0.09 MPa until no visible bubbles escaped; a 500-mesh 316L stainless steel screen was used to reduce pressure filtration at a nitrogen pressure of 0.08 MPa, and the filtrate was immediately transferred to a storage tank equipped with a 0.8 mm diameter HVLP spray gun, and dry nitrogen with a dew point of ≤-40°C was continuously introduced into the tank for protection; D. Spraying and curing: the nozzle of the HVLP spray gun corresponds to the substrate with a vertical distance of 250 mm, purifies compressed air as atomizing gas, sprays the wear-resistant super-hydrophobic drag-reducing coating material on the surface of the substrate at 0.24 MPa using the spray-stop intermittent mode until the coating thickness is 300 μm, uniform and the surface is free of macroscopic defects; after spraying is completed, the substrate is placed in an 80°C air-drying oven for curing for 12 h, then the heating is turned off and the oven is cooled to room temperature, and then transferred to a desiccator (relative humidity ≤ 20%) for standing for 22 h, to obtain a substrate with a wear-resistant super-hydrophobic drag-reducing coating (the substrate is provided with a coating on one side).

[0028] Example 3 Preparation of a substrate with a wear-resistant super-hydrophobic drag-reducing coating I. Preparation of a wear-resistant super-hydrophobic drag-reducing coating material: 1) Preparation of hydrophobically modified diatomite: mix anhydrous ethanol, deionized water and ammonia water with a concentration of 28 wt% according to a volume ratio of 90:30:5 to obtain an alkaline alcohol-water mixture; add diatomite powder with an average particle size of 10 μm to the alkaline alcohol-water mixture according to a solid-liquid ratio of 1 g:25 mL, and mechanically stir at 800 r / min for 10 min at 26°C to obtain a dispersion liquid; add octadecyltrichlorosilane (OTS) dropwise to the dispersion liquid according to 15 wt% of the diatomite powder, and continuously stir at 400 r / min for 24 h while the temperature is raised to 52°C; after the reaction is completed, the filter cake is washed with ethanol for 5 times, and then dried at a vacuum degree of ≤-0.08 MPa and a temperature of 42°C for 24 h; and then pulverized by an air flow mill to D 50 ≤5 μm to obtain OTS covalently grafted hydrophobically modified diatomite, which is sealed and stored dry; 2) Preparation of a wear-resistant super-hydrophobic drag-reducing coating material: weigh hydrophobically modified diatomite, PFA nano powder (average particle size 300 nm) and anhydrous ethanol according to a mass ratio of 1:4:9, mix and then ultrasonically treat at 26°C for 20 min at 220 W, and then magnetically stir at 26°C at a speed of 900 r / min for 2 h to obtain a diatomite-PFA-alcohol suspension, i.e. dispersion phase A; weigh FEVE, a polyisocyanate curing agent and anhydrous ethanol according to a mass ratio of 10:1:15, mix and then magnetically stir at 26°C at a speed of 800 r / min for 2 h to obtain a fluorocarbon resin mixture containing curing components, i.e. dispersion phase B; mix dispersion phase A and dispersion phase B according to a volume ratio of 4:1, and stir at 26°C at a speed of 800 r / min for 24 h in the dark to obtain a wear-resistant super-hydrophobic drag-reducing coating material.

[0029] II. Preparation of a wear-resistant super-hydrophobic drag-reducing coating: A, substrate pretreatment: immerse the 7075 aluminum alloy substrate with smooth surface in an alkaline degreasing agent with pH 12, ultrasonic cleaning at 60°C for 600s, then rinse with deionized water until the surface water film is continuous; place the cleaned substrate in a mixed solution containing 50g / L NaOH and 1g / L corrosion inhibitor, immerse and etch at 50°C for 120s to remove the natural oxide layer and expose the fresh metal surface; transfer the etched substrate into a 20wt% HNO3 solution at room temperature for 30s to neutralize and eliminate the surface ash, then rinse with deionized water and dry the surface; B, substrate laser etching: use ultraviolet femtosecond laser technology to etch a square microgroove grid-shaped surface texture on the surface of the pretreated 7075 aluminum alloy substrate, the microgroove depth is 20μm, the side length (a) is 0.6mm, and the groove spacing (i) is 0.03mm; then ultrasonic clean with anhydrous ethanol and dry with dry nitrogen; the laser etching treatment conditions are: repetition frequency 400kHz, scanning pitch 3μm, scanning speed 500mm / s, laser power 40W, laser off light delay 100μs and 300μs, and laser etching layer number 4 times; C, pretreatment of wear-resistant super-hydrophobic drag-reducing coating material: place the wear-resistant super-hydrophobic drag-reducing coating material in a vacuum degassing kettle, and degas at an absolute pressure ≤-0.09MPa until no visible bubbles escape; use a 500-mesh 316L stainless steel screen under 0.1MPa nitrogen pressure to reduce pressure filtration, and immediately transfer the filtrate to a storage tank equipped with a 0.8mm diameter HVLP spray gun, and continuously introduce dry nitrogen with a dew point ≤-40°C into the tank for protection; D, spraying and curing: the nozzle of the HVLP spray gun corresponds to the substrate at a vertical distance of 255mm, and uses purified compressed air as the atomizing gas to spray the wear-resistant super-hydrophobic drag-reducing coating material on the substrate surface at 0.25MPa in a spray-stop intermittent mode until the coating thickness is 500μm, uniform and free of macroscopic defects; after spraying, the substrate is placed in an 82°C air-drying oven for 14h, then the heating is turned off and the oven is cooled to room temperature, then it is transferred to a desiccator (relative humidity ≤20%) for 24h to obtain a substrate with a wear-resistant super-hydrophobic drag-reducing coating (the substrate has a coating on one side).

[0030] In examples 4-6, the side length (a) of the microgroove in step B is 0.2mm, 0.3mm, 0.4mm respectively, and the others are the same as example 1.

[0031] In examples 7-12, the side length (a) of the microgroove in step B is 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 1.0mm respectively, and the others are the same as example 2.

[0032] Comparative example 1: prepare a wear-resistant coating with a commercially available super-hydrophobic spray can wear-resistant coating emulsion M The 7075 aluminum alloy substrate was pretreated according to step A in Example 1, and the pretreated substrate was placed horizontally on an operation table. The nozzle of the HVLP spray gun was vertically positioned at a distance of 250 mm from the substrate, and the bottom coat and top coat materials of the super-hydrophobic spray can wear-resistant coating emulsion M were sprayed on the surface of the substrate using compressed air as the atomizing gas in a spray-stop intermittent mode at 0.24 MPa. The total thickness of the coating was 300 μm, and the surface was uniform and free of macroscopic defects. After spraying, the substrate was placed in a 80°C air-drying oven for curing for 12 h, then the heating was turned off and the substrate was cooled to room temperature in the oven, and then transferred to a desiccator (relative humidity ≤ 20%) for 22 h, to obtain a substrate with a wear-resistant coating.

[0033] Test Example Based on Examples 1-12 and Comparative Example 1, the following tests were conducted: Test I The static contact angle of the wear-resistant coating prepared in Comparative Example 1 was measured using a static contact angle instrument.

[0034] Test II II-I, the laser-etched substrate in step B of Example 1 was observed under 100x magnification using a scanning electron microscope (SEM), and the wear-resistant super-hydrophobic drag-reducing coating prepared in step D of Example 1 was observed under 50x, 500x, and 10,000x magnification using a scanning electron microscope (SEM); II-II, the static contact angles of the pretreated substrate (i.e., bare flat substrate) in step A of Example 1, the laser-etched substrate (i.e., bare laser-etched substrate) in step B, and the wear-resistant super-hydrophobic drag-reducing coating in step D were measured using a static contact angle instrument.

[0035] Test III was a sandpaper abrasion test Test object grouping: The first group used the substrates prepared in Examples 4, 5, 6, 1, and 3 as test objects, and the laser-etched micro-grooves on the substrate had i = 0.03 mm and a of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.6 mm, respectively. The second group used the substrates prepared in Examples 7-11 and Examples 2 and 12 as test objects, and the laser-etched micro-grooves on the substrate had i = 0.05 mm and a of 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.8 mm, and 1.0 mm, respectively.

[0036] Test operation: with 200g standard weight as constant load, 200g standard weight is vertically pressed and pasted on the center point of each test object without coating (so that the contact surface pressure is uniformly distributed on the substrate) by 3M tape (make the contact surface pressure uniformly distributed on the substrate), the substrate with coating is pasted and placed on the 200-mesh aluminum oxide sandpaper; Before the test, the initial contact angle of the wear surface of each test object is measured by a static contact angle instrument; Then move the substrate on the aluminum oxide sandpaper at a constant speed for 200 cm in one direction, and measure the contact angle of the wear surface at different wear cycles during movement: wherein: Wear surface refers to the coating area corresponding to the bottom surface of the 200g standard weight; Wear cycle refers to moving 5cm as one wear cycle, moving 200cm for 40 wear cycles, and immediately measuring the contact angle of the wear surface after each wear cycle with a static contact angle instrument every 5cm. The change (Δθ) of the contact angle from the initial wear surface to the end of movement is used to evaluate the degradation of the hydrophobic performance of the coating after wear, and then the wear resistance of the wear-resistant super-hydrophobic drag-reducing coating is judged.

[0037] Test results: Test example I: as shown in Figure 8 The static contact angle of the wear-resistant coating of the substrate prepared by Comparative Example 1 is 135.3°.

[0038] Test example II: II-I: as shown in Figure 1 Under SEM 100 times, it can be clearly observed that through the laser etching of step B of Example 1, the surface texture of the substrate is uniformly arranged in the form of square micro-groove grid. Figure 1 The micro-groove is a concave bucket structure composed of opposite isosceles triangles and opposite isosceles trapezoids (open square), with a depth of 20μm, a being the side length, and i being the slot spacing.

[0039] As shown in Figure 2 Under SEM 50 times, it can be clearly observed that the surface texture of the substrate etched by laser in step B of Example 1 forms a rectangular frame array (i.e. rectangular frame) of micro-grooves, which is regularly arranged with a certain spacing. The wear-resistant super-hydrophobic drag-reducing coating material prepared by the present application is uniformly filled in the rectangular frame, with a filling rate of more than 85%, thereby forming a "armor-rectangular frame" structure on the surface of the substrate; as shown in Figure 3 Under SEM 500 times, it can be clearly observed that the coating surface obtained in step D of Example 1 presents a "cabbage" shaped cluster structure with numerous lateral branches and dense arrangement; further magnified to 10000 times under SEM, as shown in Figure 4 The details of the cluster structure are clear and identifiable, the binder tightly binds the nano PFA particles, and the PFA nanoparticles impart hydrophobicity to the coating, and the binder significantly improves the durability of the coating by firmly adhering the hydrophobic nanoparticles.

[0040] II-II: As shown in Figure 5 , the static contact angle of the substrate (bare flat substrate) after pretreatment in Step A of Example 1 is only 72°; as shown in Figure 6 , the static contact angle of the substrate (bare laser-etched substrate) after laser etching in Step B of Example 1 is increased to 130.1°; as shown in Figure 7 , the static contact angle of the prepared coating in Step D of Example 1 reaches 158.0°; it is obvious that the laser etching of the flat substrate to form a square micro-groove grid uniformly arranged has greatly improved the hydrophobic property of the substrate (the static contact angle is increased by nearly 60°), and the further increase of the static contact angle by nearly 30° by matching the prepared wear-resistant super-hydrophobic drag-reducing coating material with the surface texture of the substrate shows excellent super-hydrophobic property, and the drag-reducing effect is also significantly improved.

[0041] Test Example III: After 200 cm of sandpaper abrasion, the hydrophobic properties of each test object are degraded to some extent, Figure 9 , 10 shows the abrasion contact angle test data of the coating with micro-groove i = 0.03 mm or 0.05 mm and different side length a (0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm) when contacting with 200 mesh sandpaper Figure 9 , 10 The data of 40 cycles are not completely shown, only part of the data showing the trend of the reaction contact angle change is shown: As shown in Figure 9 , according to the operation of Test III, when the micro-groove i = 0.03 mm and the side length a is 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 0.6 mm, the contact angle changes in the range of 138°~160° during the abrasion process, i.e., the coating can still maintain ideal hydrophobic property after abrasion, and has good wear resistance; among them, the coating prepared in Example 1 (micro-groove i = 0.03 mm, a = 0.5 mm) has an initial contact angle of 158.0° (see Test II-II), and after 40 cycles of abrasion, the final contact angle is greater than 150°, and Δθ < 8°, which is obviously the lowest degree of hydrophobic property degradation and the best wear resistance among the coatings with other side lengths (i = 0.03 mm); in combination with Figure 9It can be seen that when a=0.4mm, 0.3mm, 0.2mm, the hydrophobicity gradually decreases and the decrease is large, because the space structure of the micro-groove becomes small due to the same interval i and the gradually decreasing side length a, the filling rate of the coating material increases during spraying, thereby affecting the hydrophobicity and wear resistance of the coating; when a=0.6mm, although the contact angle after abrasion is still higher than that of a=0.2mm, the space change of the micro-groove and the increase of the coating material capacity due to the increasing side length do not bring better wear resistance, but cause the degradation of the hydrophobicity and the decrease of the wear resistance; therefore, the preparation of the wear-resistant super-hydrophobic drag-reducing coating material in cooperation with the suitable surface texture (such as the micro-groove i=0.03mm, a=0.5mm) of the substrate is a key factor for maintaining the hydrophobicity and improving the wear resistance of the coating.

[0042] As shown in Figure 10 , according to the operation of Test III, when the micro-groove i=0.05mm and the side length a is 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm and 1.0mm respectively, the contact angle during the abrasion process changes in the range of 133°~161°, that is, the ideal hydrophobicity can be maintained after abrasion, and the wear resistance is good; the initial contact angle of the coating prepared in Example 2 (micro-groove i=0.05mm, a=0.8mm) is not less than 160°, after 40 cycles of abrasion, the final contact angle is not less than 150°, and Δθ is not more than 10°, which is obviously the lowest degradation of the hydrophobicity and the best wear resistance of the coating relative to other side lengths (i=0.05mm). Figure 10 It can be seen that although the initial contact angle is not less than 156°, the hydrophobicity decreases greatly after 40 cycles of abrasion when the side length a is 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm and 1.0mm, which also proves that the preparation of the wear-resistant super-hydrophobic drag-reducing coating material in cooperation with the suitable surface texture (such as the micro-groove i=0.05mm, a=0.8mm) of the substrate is a key factor for maintaining the hydrophobicity and improving the wear resistance of the coating.

[0043] It can be seen that although the initial contact angle is not less than 156°, the hydrophobicity decreases greatly after 40 cycles of abrasion when the side length a is 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm and 1.0mm, which also proves that the preparation of the wear-resistant super-hydrophobic drag-reducing coating material in cooperation with the suitable surface texture (such as the micro-groove i=0.05mm, a=0.8mm) of the substrate is a key factor for maintaining the hydrophobicity and improving the wear resistance of the coating. Figure 9 , 10 It can be seen that although the initial contact angle is not less than 156°, the hydrophobicity decreases greatly after 40 cycles of abrasion when the side length a is 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm and 1.0mm, which also proves that the preparation of the wear-resistant super-hydrophobic drag-reducing coating material in cooperation with the suitable surface texture (such as the micro-groove i=0.05mm, a=0.8mm) of the substrate is a key factor for maintaining the hydrophobicity and improving the wear resistance of the coating.

Claims

1. A method of making a wear resistant, superhydrophobic, drag reducing coating material, characterized by, The preparation method is as follows: 1) Preparation of hydrophobic modified diatomite: anhydrous ethanol, deionized water and ammonia water with a concentration of 25-28 wt% were mixed in a volume ratio of 70-90:10-30:1-5 to obtain an alkaline alcohol-water mixture; diatomite powder was added to the alkaline alcohol-water mixture in a solid-liquid ratio of 1 g:15-25 mL, and mechanical stirring was carried out at a speed of 500-800 r / min for 5-10 min at 24-26 ℃ to obtain a dispersion liquid; OTS was added dropwise to the dispersion liquid at 5-15 wt% of the diatomite powder, and the temperature was raised to 48-52 ℃ for continuous stirring at 200-400 r / min for 20-24 h; after the reaction was completed, the filter cake was washed with anhydrous ethanol for 3-5 times, and then dried at a vacuum degree of ≤-0.08 MPa, 38-42 ℃ for 20-24 h; the dried product was crushed by air jet mill to D 50 ≤5 μm to obtain OTS covalently grafted hydrophobic modified diatomite, which was sealed and stored dry; 2) Preparation of wear-resistant super-hydrophobic drag-reducing coating material: hydrophobic modified diatomite, PFA nano-powder and anhydrous ethanol are weighed according to the mass ratio of 1:2-4:7-9, mixed, and then treated with ultrasonic waves at 200-220 W for 15-20 min at 24-26 DEG C, followed by magnetic stirring at 600-900 r / min for 1-2 h at 24-26 DEG C to obtain diatomite-PFA-alcohol suspension, i.e. dispersion phase A; FEVE, polyisocyanate curing agent and anhydrous ethanol are weighed according to the mass ratio of 6-10:1:10-15, mixed, and then stirred with a magnetic stirrer at 600-800 r / min for 1-2 h at 24-26 DEG C to obtain a fluorocarbon resin mixture containing curing components, i.e. dispersion phase B; dispersion phase A and dispersion phase B are mixed according to the volume ratio of 2-4:1, and then stirred with a magnetic stirrer at 600-800 r / min for 20-24 h at 24-26 DEG C in the dark to obtain the wear-resistant super-hydrophobic drag-reducing coating material.

2. The production method according to claim 1, characterized by, The average particle size of the diatomite micro-powder in step 1) is 5-10 μm.

3. The preparation method according to claim 1, characterized in that, The average particle size of the PFA in step 1) is 250-300 nm.

4. A wear-resistant super-hydrophobic drag-reducing coating material obtained based on the preparation method according to claim 1, 2 or 3.

5. A method of applying the wear resistant, superhydrophobic, drag reducing coating material of claim 4, characterized in that, The application method is as follows: A, substrate pretreatment: immerse the substrate in an alkaline degreasing agent with a pH of 11-12, ultrasonically clean at 50-60 DEG C for 300-600 s, and then rinse with deionized water until a continuous water film is formed on the surface; place the cleaned substrate in a mixed solution containing 30-50 g / L NaOH and 0.5-1 g / L corrosion inhibitor, immerse and etch at 40-50 DEG C for 30-120 s to remove the natural oxide layer and expose the fresh metal surface; transfer the etched substrate into a 10-20 wt% HNO3 solution at room temperature for 10-30 s to neutralize, eliminate surface dust, rinse with deionized water, and then dry the surface for standby; B, substrate laser etching: according to the depth of the micro-groove of 20 μm, the side length of 0.2-1.0 mm, and the groove spacing of 0.03-0.05 mm, use ultraviolet femtosecond laser technology to etch a square micro-groove grid-shaped uniform arrangement on the surface of the pretreated substrate, and then ultrasonically clean with anhydrous ethanol and dry with dry nitrogen; C, wear-resistant super-hydrophobic drag-reducing coating material pretreatment: place the wear-resistant super-hydrophobic drag-reducing coating material into a vacuum degassing kettle, and degas at an absolute pressure of ≤-0.09 MPa until no visible bubbles escape; use a 500-mesh sieve to perform reduced-pressure filtration under a nitrogen pressure of 0.05-0.1 MPa, and immediately transfer the filtrate to a storage tank equipped with a 0.8 mm diameter HVLP spray gun, and continuously introduce dry nitrogen with a dew point of ≤-40 DEG C into the tank for protection; D, spraying and curing: correspond the nozzle of the HVLP spray gun to the substrate at a perpendicular distance of 245-255 mm, use purified compressed air as the atomizing gas, and spray the wear-resistant super-hydrophobic drag-reducing coating material on the substrate surface under a pressure of 0.23-0.25 MPa until the coating thickness is 200-500 μm, the coating is uniform, and there are no macroscopic defects on the surface. After the spraying is completed, the substrate is placed in a blast drying oven at 78-82 DEG C for curing for 10-14 hours, then the heating is stopped and the oven is cooled to room temperature, and then the substrate is transferred to a desiccator for standing for 20-24 hours to obtain the substrate with the wear-resistant super-hydrophobic drag-reducing coating.

6. The method of use of claim 5, wherein, The substrate in step A is a 7075 aluminum alloy substrate.

7. The method of claim 5, wherein the compound is administered in an amount of about 0.1 to 10 mg / kg. The laser etching treatment conditions in step B are as follows: a repetition frequency of 400 kHz, a scanning interval of 3 microns, a scanning speed of 500 mm / s, a laser power of 20-40 W, a laser-off delay time of 100 microseconds and 300 microseconds, and a laser etching layer number of 4 times.

8. The use according to claim 5, characterized in that, The screen in step B is a 316L stainless steel screen.

9. The use according to claim 5, characterized in that, In step D, the wear-resistant super-hydrophobic drag-reducing coating material is sprayed on the surface of the substrate in a spray-stop intermittent mode, the spray-stop intermittent mode is single spraying for 1-2 seconds, interval standing for 30 seconds, and the cycle spraying is 15-25 times.

10. The use according to claim 5, characterized in that, The relative humidity of the desiccator in step D is less than or equal to 20%.

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