A method for preparing a hydrophilic-hydrophobic adjustable anticorrosive coating

Abstract

This invention relates to the field of functional coating materials technology, and particularly to a method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating, comprising: hydrolyzing methyltrimethoxysilane to obtain a hydrolysate; adding the hydrolysate dropwise to a nano-SiO2 suspension, reacting and drying to obtain superhydrophobic SiO2 powder; mixing the superhydrophobic SiO2 powder with a hydrophilic filler to obtain a filler suspension; dissolving epoxy resin A in anhydrous ethanol to obtain an epoxy resin liquid; mixing the epoxy resin liquid with the filler suspension, adding epoxy resin B to obtain a homogeneous spraying liquid; spraying a primer onto the substrate surface, atomizing the homogeneous spraying liquid onto the primer surface, and curing to obtain a hydrophilic-hydrophobic adjustable anti-corrosion coating; not only avoiding the use of expensive fluorinated compounds and using green and environmentally friendly low surface energy materials, but also achieving the transformation of coating wettability from superhydrophobic to hydrophilic through simple filler ratio control, and significantly enhancing the adhesion between the coating and the substrate.

Description

Technical Field

[0001] This invention relates to the field of functional coating materials technology, and in particular to a method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating. Background Technology

[0002] Superhydrophobic surfaces (static water contact angle > 150°, roll-off angle < 10°) have become a research hotspot in materials science due to their broad application prospects in self-cleaning, corrosion prevention, anti-icing, drag reduction, and oil-water separation. Meanwhile, with the development of emerging fields such as microfluidics, biosensors, and controllable liquid transport, single superhydrophobic surfaces are no longer sufficient to meet practical needs. For example, in microfluidic chips, the directional transport and precise manipulation of liquids can be achieved through regionalized control of the wettability of channel surfaces; in oil-water separation, separation membranes with hydrophilic-hydrophobic gradient properties can improve separation efficiency; and in the biomedical field, tunable hydrophilic-hydrophobic surfaces help regulate cell adhesion and proliferation behavior.

[0003] Currently, the preparation of hydrophilic-hydrophobic tunable coatings usually involves complex surface modification processes or multi-step modification treatments. For example, Chinese invention patents with application numbers 201810408735.6 and 202311398489.8 respectively use fluorinated organosilicon polymers, fluorinated silane modified nanoparticles and fluorocarbon surfactants, as well as perfluorooctanoic acid and fluorinated surfactants. All of these rely on expensive fluorinated reagents as low surface energy materials, which not only increases manufacturing costs but may also bring environmental and health risks. In addition, existing coatings generally have problems such as insufficient adhesion to the substrate and poor mechanical durability, making it difficult to meet the long-term use requirements under actual working conditions.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating, which not only avoids the use of expensive fluorine-containing compounds and adopts green and environmentally friendly low surface energy materials, but also achieves the transformation of coating wettability from superhydrophobic to hydrophilic through simple filler ratio control, and significantly enhances the adhesion between the coating and the substrate, effectively solving the problems in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a hydrophilic / hydrophobic tunable anti-corrosion coating, the method comprising: S1 hydrolyzes methyltrimethoxysilane (MTMS) to obtain a hydrolysate; the hydrolysate is added dropwise to a nano-SiO2 suspension, heated to react, and then dried to obtain superhydrophobic SiO2 powder; More specifically, in this step, MTMS undergoes a hydrolysis reaction under weakly acidic conditions to generate hydrolysis products with active silanol groups. After the hydrolysate is added dropwise to the nano-SiO2 suspension, the silanol groups of the hydrolysis products undergo a dehydration condensation reaction with the silanol groups on the surface of the nano-SiO2, causing the silane structural units with inert hydrophobic methyl groups to be uniformly anchored on the surface of the nano-SiO2 particles. This significantly reduces the surface energy of the SiO2 powder without using fluorine-containing substances, resulting in SiO2 powder with stable superhydrophobic properties. The process is divided into the following stages: 1. Hydrolysis stage: Si-OCH3 is converted to Si-OH; 2. Adsorption stage: MTMS silanol forms hydrogen bonds with Si-OH on the SiO2 surface; 3. Grafting stage: Heating and curing transform hydrogen bonds into strong Si-O-Si covalent bonds, introducing low surface energy methyl groups (-CH3) into the SiO2 surface, thereby achieving hydrophobicity. S2 mixes superhydrophobic SiO2 powder with a hydrophilic filler, disperses it in anhydrous ethanol, and then sonicates it to obtain a filler suspension; wherein the hydrophilic filler is a mixture of polyethylene glycol 400 monooleate (PEG400MO) and hydrophilic SiO2. More specifically, PEG400MO, with its strongly hydrophilic long polyethylene glycol chains, can synergistically enhance the hydrophilic properties of the coating surface with hydrophilic SiO2. By controlling the mass ratio of superhydrophobic SiO2 powder to hydrophilic fillers, the ratio of hydrophobic and hydrophilic groups and the distribution of micro / nano structures on the coating surface can be altered, thereby achieving the control of coating wettability from superhydrophobic to hydrophilic. Specifically, PEG400MO molecules possess long-chain polyethylene glycol structures containing numerous strongly hydrophilic ether bonds and terminal hydroxyl groups, which can form high-density hydrogen bonds with water molecules, making them strongly hydrophilic organic units; simultaneously, its long carbon chain structure forms a film-forming matrix with epoxy resin. It exhibits excellent biocompatibility and can be uniformly dispersed in the coating system, avoiding uneven wettability caused by phase separation. The hydrophilic SiO2 surface has a large number of active silanol groups, which are strong hydrophilic inorganic units. It has good interfacial compatibility with hydrophobic SiO2 powder, which can achieve a uniform and non-agglomerated distribution of hydrophilic groups on the coating surface. As the amount of hydrophilic filler added increases, the proportion of hydrophobic methyl groups on the coating surface continues to decrease, while the proportion of hydrophilic groups (ether bonds, hydroxyl groups, silanol groups) increases. The inherent surface energy of the coating continuously increases, and it smoothly transitions from a low surface energy hydrophobic state to a high surface energy hydrophilic state, thereby achieving continuous regulation of wettability from the source. S3 dissolves epoxy resin A in anhydrous ethanol to obtain epoxy resin solution; More specifically, epoxy resin A is the main component of epoxy resin. Epoxy resin has excellent film-forming properties, mechanical strength and anti-corrosion barrier properties, and can provide a stable carrier matrix for functional fillers. At the same time, anhydrous ethanol can be used as a solvent to adjust the viscosity of the system and make it suitable for subsequent spraying. S4 mixes epoxy resin liquid with filler suspension, stirs and ultrasonically disperses the mixture, adds epoxy resin agent B, and ultrasonically disperses it again to obtain a homogeneous spraying liquid. More specifically, epoxy resin agent B is a curing agent. The filler and resin are mixed first to avoid uneven coating performance caused by filler agglomeration. The curing agent is added later to prevent premature cross-linking and curing of the epoxy resin. S5 sprays a primer onto the substrate surface. When the primer is in a semi-cured viscous state, a homogeneous spraying liquid is atomized and sprayed onto the primer surface. After curing, a hydrophilic and hydrophobic adjustable anti-corrosion coating is obtained. More specifically, this step employs a semi-cured primer spraying process. The semi-cured primer has excellent adhesion, which allows the sprayed functional coating fillers and resin to be effectively embedded in the primer layer, forming an interpenetrating anchoring structure between the primer and the functional coating. This significantly improves the interlayer adhesion of the coating system and prevents the coating from peeling off during service. At the same time, the curing process allows the epoxy resin to fully cross-link, forming a dense and stable anti-corrosion coating.

[0007] Furthermore, the method for preparing the hydrolysate includes: Q1. Add an organic acid dropwise to a mixed solvent containing 9-12 parts by mass of an alcohol solvent and 3-5 parts by mass of deionized water to adjust the pH value to 4-5. In this step, the mixed solvent provides a homogeneous reaction environment for the hydrolysis of MTMS. The weakly acidic environment can make the hydrolysis reaction of MTMS proceed smoothly, avoiding excessively strong acidity that leads to excessively fast hydrolysis rate and product self-aggregation and turbidity, and also avoiding incomplete hydrolysis due to insufficient acidity. Q2 Under constant temperature and stirring conditions, 6-12 parts by mass of methyltrimethoxysilane are added dropwise in multiple batches, with an interval of 2-3 minutes between two consecutive additions. The reaction is stirred at room temperature until the solution is clear to obtain a hydrolysate. In this step, the stepwise addition can avoid excessively high local concentrations of MTMS and ensure that each batch of MTMS is fully hydrolyzed. Finally, the solution is stirred at room temperature until it is clear to obtain a hydrolysate with uniform activity and good stability.

[0008] Furthermore, the preparation method of superhydrophobic SiO2 powder includes: Weigh out dried nano-SiO2 particles, the mass of which is 8 to 12 times that of methyltrimethoxysilane in step Q2. Add deionized water and stir to disperse to obtain a nano-SiO2 suspension. In this step, the mass of nano-SiO2 particles is 8 to 12 times that of methyltrimethoxysilane. This ensures that there are sufficient silanol grafting sites on the surface of nano-SiO2, which can not only make the MTMS hydrolysis products uniformly grafted on the surface of SiO2 particles to achieve stable hydrophobic modification, but also avoid self-agglomeration caused by excessive MTMS. The hydrolysate was dropped into the nano-SiO2 suspension, heated to 80~95℃ and stirred to react. After standing and cooling, the solid phase was separated and dried to obtain superhydrophobic SiO2 powder. In this step, the temperature range of 80~95℃ can effectively promote the dehydration condensation reaction between silanol groups, so that the hydrophobic segments of MTMS can form stable covalent bonds with nano-SiO2, and avoid the hydrophobic groups from falling off during subsequent use.

[0009] Furthermore, the particle size of nano-SiO2 is 10nm~10μm; the organic acid is any one of acetic acid, formic acid, propionic acid or butyric acid; and the alcohol solvent is any one of anhydrous ethanol, methanol, propanol or butanol.

[0010] More specifically, the aforementioned particle size range can construct a micro-nano composite rough structure on the coating surface to achieve superhydrophobic properties. SiO2 particles of different sizes can be combined to form a more stable and less easily damaged rough structure. The aforementioned organic acids are all weak acids, which can stably adjust the pH value of the reaction system. They are not highly corrosive, the raw materials are readily available and inexpensive, and they are suitable for industrial production. The aforementioned alcohol solvents are all miscible with water, providing a homogeneous environment for MTMS hydrolysis. Moreover, different alcohol solvents have different evaporation rates, which can be flexibly selected according to the needs of the actual spraying process.

[0011] Further, by weight, in step S2, the superhydrophobic SiO2 powder is 0.5-2.5 parts, the anhydrous ethanol is 10-15 parts, the polyethylene glycol 400 monooleate and the hydrophilic SiO2 are both 0.1-0.6 parts, and the mass ratio of the two is 1-2:1-2.

[0012] More specifically, the above solid-liquid ratio ensures that the superhydrophobic SiO2 powder is fully dispersed in the solvent, avoiding filler agglomeration due to excessive solid content. By adjusting the amount of hydrophilic filler added, the proportion of hydrophilic groups on the coating surface is continuously changed. As the amount of hydrophilic filler added increases, the water contact angle of the coating can continuously decrease from a superhydrophobic state of over 155° to a hydrophilic state, thus achieving wettability control. Among them, PEG400MO and hydrophilic SiO2 work synergistically. PEG400MO provides strong hydrophilic groups, while hydrophilic SiO2 can adjust the microstructure of the coating surface. The combination of the two can achieve stable control of wettability and avoid abrupt changes in the contact angle.

[0013] Preferably, the mass ratio of polyethylene glycol 400 monooleate to hydrophilic SiO2 is 1:1. At this mass ratio, the strongly hydrophilic organic segments provided by polyethylene glycol 400 monooleate form spatial complementarity and hydrogen bond synergy with the active silanol groups enriched on the surface of hydrophilic SiO2, resulting in the most uniform distribution of hydrophilic groups on the coating surface. At the same time, when the two are of equal mass, after being compounded with superhydrophobic SiO2 powder, the ratio of hydrophobic methyl groups to hydrophilic groups on the coating surface exhibits the most stable gradient change, which can achieve continuous and non-abrupt control of wettability from superhydrophobic to hydrophilic. In addition, at this ratio, the interfacial compatibility between organic and inorganic components is the best, and the dispersion stability in the epoxy resin matrix is ​​the highest, avoiding local wettability differences or coating mechanical property degradation caused by uneven distribution of hydrophilic components.

[0014] Furthermore, 0.1 to 0.3 parts of silane coupling agent are added to the packing suspension in step S2; Preferably, the silane coupling agent used is KH-550.

[0015] Silane coupling agents are bifunctional compounds. The alkoxy group at one end can be hydrolyzed to generate silanol groups, which can undergo a condensation reaction with the silanol groups on the surface of inorganic SiO2 fillers to form stable covalent bonds. The active organic group at the other end can react with the epoxy groups of epoxy resin, thereby forming a stable molecular bridge between the inorganic filler and the organic resin matrix, which greatly improves the interfacial compatibility between the inorganic filler and the organic resin.

[0016] Further, the epoxy resin A agent is selected from any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin or phenolic epoxy resin; the epoxy resin B agent is selected from any one of polyamide curing agent, aliphatic amine curing agent or alicyclic amine curing agent; the mass ratio of the two is (1.5~3):(0.5~1).

[0017] Furthermore, the primer is acrylic, the spraying distance is 10~15cm, and the spraying thickness is 20~50μm.

[0018] More specifically, acrylic primers possess excellent substrate adhesion, corrosion resistance, and compatibility. They can effectively seal micropores and defects on the surface of metal substrates, isolate corrosive media from direct contact with the substrate, and form a good interlayer bond with the subsequently sprayed epoxy functional coating. The above-mentioned spraying distance ensures uniform atomization of the primer, avoiding sagging and uneven thickness caused by excessively close distance. The above-mentioned thickness range ensures that the primer fully seals the substrate, while avoiding problems such as excessively long primer curing time and reduced interlayer bonding due to excessive thickness.

[0019] Furthermore, the substrate in S5 is degreased and pickled before spraying.

[0020] More specifically, by degreasing and pickling, various impurities on the surface of the substrate can be completely removed, exposing a fresh and clean metal substrate, allowing the primer to bond directly and tightly with the metal substrate, and greatly improving the adhesion between the coating system and the substrate.

[0021] Furthermore, the curing temperature in S5 is 50~70℃, and the curing time is 10~14h.

[0022] More specifically, 50~70℃ is a medium to low temperature, which allows the epoxy resin system to complete the cross-linking reaction stably and fully, avoiding defects such as pinholes, bubbles or cracks in the coating caused by excessively rapid solvent evaporation.

[0023] The technical solution of this invention can achieve the following technical effects: (1) By adjusting the mass ratio of superhydrophobic SiO2 powder to hydrophilic filler, the wettability of the coating can be controlled from superhydrophobic to hydrophilic, and the anti-corrosion performance can be optimized under different service environments: In humid or corrosive media environments, adjusting to a superhydrophobic state can form a stable air barrier layer, which can significantly delay the intrusion of corrosive media; In scenarios where the interface bonding between the coating and the substrate is required to be high, the appropriate introduction of hydrophilic components can enhance the interface anchoring force between the coating and the primer or metal substrate, and avoid local corrosion caused by coating peeling; Through this hydrophilic-hydrophobic synergistic control mechanism, the coating of the present invention exhibits a better anti-corrosion effect than single superhydrophobic.

[0024] (2) The present invention adopts a primer semi-curing spraying technology to ensure that micro-nano particles are effectively embedded in the coating, further enhancing the bonding force and structural density between the coating and the substrate; the overall preparation process is simple, the equipment is readily available, and it is easy to achieve large-scale production, and has good industrial promotion value.

[0025] (3) The hydrophobic and hydrophobic adjustable anti-corrosion coating of the present invention does not require the use of expensive fluorinated compounds, but only green and environmentally friendly organosilicon materials and conventional epoxy resins, which is inexpensive and in line with the development trend of green and environmental protection. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The characterization of hydrophilic and hydrophobic coatings is compared with that of superhydrophobic coatings. Among them, a1 and a2 are the characterization and EDS distribution diagrams of hydrophilic and hydrophobic coatings, and b1 and b2 are the characterization and EDS distribution diagrams of superhydrophobic coatings. Figure 2 An electrochemical Tafel diagram of the prepared hydrophilic-hydrophobic coating; Figure 3 XRD comparison diagram of the prepared superhydrophobic powder and ordinary silica powder; Figure 4 The graph shows the change in contact angle of the prepared superhydrophobic coating with the amount of superhydrophobic SiO2 powder added. Figure 5 The structural formula of PEG400MO; Figure 6 The graph shows the change in contact angle of the prepared hydrophilic-hydrophobic coating with the amount of polyethylene glycol 400 monooleate added. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application.

[0031] Example 1:

[0032] This embodiment provides a method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating. The specific preparation steps are as follows: Preparation of S1 superhydrophobic SiO2 powder First, a hydrolysis pretreatment of methyltrimethoxysilane (MTMS) was performed: a mixed solvent containing 12g of anhydrous ethanol and 3g of deionized water was prepared, and acetic acid was added dropwise to adjust the pH of the system to 4.5. Under constant temperature and stirring conditions at 25℃, 9g of MTMS was added dropwise in 6 portions, with each addition being 1.5mL and an interval of 2.5min between adjacent additions. After the addition was completed, the reaction was continued at room temperature until the solution was completely clear, thus obtaining the MTMS hydrolysate. It should be noted that during the experiment, the degree of hydrolysis was determined by observing the turbidity of the solution: if the reaction system remained clear and transparent, it was considered that the hydrolysis was complete; if turbidity appeared, it indicated that the hydrolysis was insufficient and the solution needed to be prepared again. Because the MTMS hydrolysate has high reactivity, it is easy to undergo condensation polymerization and become ineffective as the standing time increases, so the hydrolysate must be prepared and used immediately. Subsequently, a nano-SiO2 suspension was prepared: dried nano-SiO2 particles with a particle size of 30 nm were weighed, and their mass was 10 times that of the MTMS mentioned above. Deionized water was added, and the mixture was stirred at high speed until it was evenly dispersed to obtain a nano-SiO2 suspension. Finally, grafting modification was carried out: the above MTMS hydrolysate was added dropwise to the nano SiO2 suspension at a uniform rate, heated to 90℃ and stirred for 4 hours. After the reaction was completed, the mixture was allowed to stand and cool to room temperature, filtered to obtain the solid phase, and dried in an oven at 105℃ to constant weight to obtain superhydrophobic SiO2 powder. X-ray diffraction (XRD) tests were performed on the above-mentioned superhydrophobic SiO2 powder and unmodified ordinary nano-SiO2 powder to obtain... Figure 3 From the appendix Figure 3 It can be seen that both the modified and unmodified SiO2 powders exhibit characteristic diffraction peaks of amorphous SiO2 in the 20°~30° range, with no other impurity peaks. This indicates that the MTMS modification is only surface covalent grafting and does not change the bulk crystal structure of SiO2. The modification process does not introduce impurities, thus ensuring the stability of the filler performance.

[0033] Preparation of S2 packing suspension Weigh 2.0g of the superhydrophobic SiO2 powder obtained in step S1, mix it with 0.3g of polyethylene glycol 400 monooleate (PEG400MO) and 0.3g of hydrophilic SiO2, disperse them together in 15mL of anhydrous ethanol, add 0.2g of silane coupling agent KH-550, and sonicate at 400W for 30min to obtain a uniformly dispersed filler suspension. The molecular structure of PEG400MO is as follows: Figure 5As shown, the long-chain polyethylene glycol structure at one end of the molecule has a large number of highly hydrophilic ether bonds and terminal hydroxyl groups, which can form high-density hydrogen bonds with water molecules and are the core groups for achieving hydrophilicity control; the long carbon chain of oleic acid at the other end has excellent compatibility with the epoxy resin matrix, which can ensure that the hydrophilic components are uniformly dispersed in the coating without agglomeration or phase separation problems, and ensure that the wettability of the coating can be stably and linearly controlled. Preparation of S3 epoxy resin solution Weigh 2.0g of bisphenol A type epoxy resin E-51 (epoxy resin agent A), dissolve it in 15mL of anhydrous ethanol, and ultrasonically dilute it for 20min at 300W power to obtain a uniform and transparent epoxy resin solution. Preparation of S4 spraying liquid The epoxy resin liquid obtained in step S3 is mixed with the filler suspension obtained in step S2, and stirred continuously at room temperature for 30 min. Then, it is ultrasonically dispersed at 400W power for 20 min. Subsequently, 0.7 g of 650 type low molecular weight polyamide curing agent (epoxy resin agent B) is added, with a mass ratio of 2:0.7. The mixture is then ultrasonically dispersed for another 10 min to obtain a homogeneous spraying liquid. S5 Substrate Pretreatment and Coating Q235 iron sheet was selected as the metal substrate. The substrate was first degreased and pickled: first, it was ultrasonically cleaned with anhydrous ethanol for 10 minutes to remove surface oil stains, then pickled with 10wt% hydrochloric acid for 5 minutes to remove surface oxide scale and rust products, rinsed with deionized water and dried with hot air; then, acrylic primer was sprayed on the dried substrate surface at a distance of 12cm and the dry film thickness was controlled to be 30μm; after the primer was sprayed, it was left at room temperature for 15 minutes and was in a semi-cured viscous state. Then, the homogeneous spraying liquid prepared in step S4 was uniformly atomized and sprayed onto the primer surface using a spray gun. The thickness of each spray was controlled to be 12μm, and it was applied in 3 thin coats to reach the target total thickness.

[0034] S6 Curing Molding The sprayed sample was placed in a 60°C forced-air oven and cured at a constant temperature for 12 hours. After the solvent had completely evaporated and the resin had fully cross-linked, it was taken out and cooled to room temperature to obtain the hydrophilic and hydrophobic adjustable anti-corrosion coating of the present invention.

[0035] For the hydrophilic-hydrophobic coating prepared in Example 1, a control sample of a pure superhydrophobic coating without hydrophilic filler was simultaneously set up. Scanning electron microscopy (SEM) morphology characterization and energy dispersive spectroscopy (EDS) elemental distribution analysis were performed to obtain... Figure 1 Where a1 and a2 are the SEM morphology and EDS elemental distribution diagrams of the hydrophilic-hydrophobic coating in this embodiment, respectively, and b1 and b2 are the SEM morphology and EDS elemental distribution diagrams of the pure superhydrophobic control sample, respectively; from the appendix Figure 1As can be seen, a uniform micro-nano rough structure was formed on the coating surface in this embodiment. The Si, C, and O elements were evenly distributed and there was no filler agglomeration. This indicates that PEG400MO and hydrophilic SiO2 can be uniformly dispersed in the coating system, ensuring the uniformity of wettability control. There was no significant difference in the element distribution between the two groups of coatings. Only the C element content of the hydrophilic and hydrophobic coating was slightly increased, corresponding to the successful introduction of PEG400MO. The hydrophilic / hydrophobic coating prepared in this embodiment and the pure superhydrophobic coating as a control sample were subjected to three-electrode electrochemical tests in a 3.5 wt% NaCl aqueous solution corrosive medium to obtain Tafel polarization curves, as shown in the attached figure. Figure 2 From the appendix Figure 2 As can be seen, compared with the control sample of pure superhydrophobic coating, the corrosion potential of the hydrophilic-hydrophobic coating in this embodiment is significantly positively shifted and the corrosion current density is lower. This indicates that the present invention enables the coating to have a better ability to block corrosive media through synergistic regulation of hydrophilicity and hydrophobicity, and its anti-corrosion performance is better than that of a single superhydrophobic coating.

[0036] The hydrophilic-hydrophobic coating prepared in this embodiment was tested according to GB / T9286-1998. The adhesion between the coating and the metal substrate was grade 0. After 800 hours of neutral salt spray testing, there was no blistering, no rust, and no peeling. It has both excellent interfacial bonding and anti-corrosion performance.

[0037] Example 2:

[0038] In this embodiment, the superhydrophobic SiO2 powder prepared in Example 1 was used to prepare six groups of superhydrophobic SiO2 powder gradient samples with a weight of 0.5g, 1.0g, 1.5g, 2.0g, 2.5g and 3.0g. No hydrophilic filler was added to any of them, and six groups of coating samples were prepared. Static water contact angle tests were conducted on six groups of coating samples, and the results were obtained. Figure 4 ;from Figure 4 It can be seen that as the amount of superhydrophobic SiO2 powder added increases from 0.5g to 2.0g, the static water contact angle of the coating increases from 82° to 155°, reaching the superhydrophobic standard; if the amount is further increased to 3.0g, the contact angle decreases slightly.

[0039] This embodiment verifies the effectiveness of the hydrophobic modification of the superhydrophobic SiO2 powder prepared by MTMS fluorine-free grafting modification according to the present invention.

[0040] Example 3:

[0041] In this embodiment, 2.0 g of the superhydrophobic SiO2 powder prepared in Example 1 was used. Only the amount of PEG400MO and hydrophilic SiO2 added in step S2 was adjusted. Seven gradient samples were set with PEG400MO addition amounts of 0.0 g, 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g and 0.6 g. The mass ratio of PEG400MO to hydrophilic SiO2 was 1:1. Seven hydrophilic and hydrophobic coatings were prepared. Other process parameters were the same as in Example 1. Static water contact angle tests were performed on 7 groups of samples, and the results were obtained. Figure 6 ,from Figure 6 It can be seen that as the amount of PEG400MO added increases from 0.0g to 0.6g, the static water contact angle of the coating decreases linearly from 155° to 10°, realizing the continuous control of the coating wettability across the entire range from superhydrophobic to hydrophobic to hydrophilic, without any abrupt change in wettability. This verifies that the present invention can precisely control the coating wettability by adjusting the ratio of hydrophilic filler and superhydrophobic SiO2 powder.

[0042] Comparative Example 1: Using hydrophilic SiO2 alone as a hydrophilic filler The difference from Example 1 is that in step S2, polyethylene glycol 400 monooleate was not added; only 0.6 parts of hydrophilic SiO2 were added, while the remaining components and process parameters remained unchanged. The resulting coating, after static water contact angle testing, showed a contact angle of 132°, still within the hydrophobic range, failing to achieve hydrophilic properties. Simultaneously, localized uneven hydrophilicity was observed on the coating surface. EDS spectroscopy revealed slight aggregation of hydrophilic SiO2 within the coating, resulting in uneven wettability distribution. This indicates that the synergistic effect of polyethylene glycol 400 monooleate and hydrophilic SiO2 is crucial for achieving uniform, continuous, and controllable hydrophilicity.

[0043] Comparative Example 2: Polyethylene glycol 400 monooleate was used alone as a hydrophilic filler. The difference from Example 1 is that hydrophilic SiO2 was not added in step S2, only 0.6 parts of polyethylene glycol 400 monooleate were added, and the remaining components and process parameters remained unchanged; the resulting coating had a static water contact angle of 28°, achieving hydrophilic properties, but obvious oily precipitates appeared on the coating surface. SEM observation showed separation of the organic and inorganic phases, and the coating density decreased; local blistering appeared after 300 hours of neutral salt spray testing, and the adhesion test result was level 2, indicating that adding organic hydrophilic components alone would lead to poor coating compatibility and a significant decrease in anti-corrosion performance.

[0044] Comparative Example 3: The amount of superhydrophobic SiO2 powder added exceeds the scope of this invention. The difference from Example 1 is that the amount of superhydrophobic SiO2 powder added in step S2 was adjusted to 3.5 parts, while the ratio of hydrophilic filler remained unchanged. During the spraying process, the resulting coating experienced spray gun clogging, a significant increase in surface roughness, and powdering in some areas. The static water contact angle was 148°, which did not meet the superhydrophobic standard (>150°), and the coating adhesion dropped to level 2. This indicates that excessive addition of superhydrophobic SiO2 powder will damage the film-forming properties and interfacial bonding of the coating, making it impossible to achieve stable superhydrophobic performance.

[0045] Comparative Example 4: The total amount of hydrophilic filler exceeds the scope of this invention. The difference from Example 1 is that in step S2, the amount of polyethylene glycol 400 monooleate and hydrophilic SiO2 was adjusted to 0.8 parts each, with a total amount of 1.6 parts, while the amount of superhydrophobic SiO2 powder remained at 2.0 parts. The resulting coating had a static water contact angle of 5°, exhibiting a superhydrophilic state, but the coating surface showed obvious cracking and peeling. Electrochemical testing showed that its corrosion current density was about 1.5 orders of magnitude higher than that of Example 1, indicating a significant deterioration in anti-corrosion performance. This indicates that excessive hydrophilic filler will destroy the continuity and density of the epoxy resin matrix, leading to coating structural defects and failing to achieve both hydrophilicity control and anti-corrosion performance.

[0046] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the spirit and scope of this application. Accordingly, this specification and drawings are merely exemplary illustrations of the application as defined herein, and are to be considered as covering any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for preparing a hydrophilic / hydrophobic tunable anti-corrosion coating, characterized in that, The method includes: S1 hydrolyzes methyltrimethoxysilane to obtain a hydrolysate; the hydrolysate is added dropwise to a nano-SiO2 suspension, heated to react, and then dried to obtain superhydrophobic SiO2 powder; S2 mixes the superhydrophobic SiO2 powder with a hydrophilic filler, disperses it in anhydrous ethanol, and then sonicates it to obtain a filler suspension; wherein the hydrophilic filler is a mixture of polyethylene glycol 400 monooleate and hydrophilic SiO2. S3 dissolves epoxy resin A in anhydrous ethanol to obtain epoxy resin solution; S4 mixes the epoxy resin liquid with the filler suspension, stirs and ultrasonically disperses the mixture, adds epoxy resin agent B, and ultrasonically disperses it again to obtain a homogeneous spraying liquid. S5. Apply a primer to the substrate surface. When the primer is in a semi-cured viscous state, atomize the homogeneous spraying liquid and spray it onto the primer surface. After curing, the hydrophilic and hydrophobic adjustable anti-corrosion coating is obtained.

2. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, The method for preparing the hydrolysate includes: Q1 Add an organic acid dropwise to a mixed solvent containing 9-12 parts by mass of alcohol solvent and 3-5 parts by mass of deionized water, and adjust the pH value to 4-5; Q2 Under constant temperature and stirring conditions, 6-12 parts by mass of methyltrimethoxysilane were added dropwise in multiple batches, with an interval of 2-3 minutes between two consecutive additions. The reaction was stirred at room temperature until the solution became clear, thus obtaining the hydrolysate.

3. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 2, characterized in that, The method for preparing the superhydrophobic SiO2 powder includes: Weigh out dried nano-SiO2 particles, the mass of which is 8 to 12 times that of methyltrimethoxysilane in step Q2, add deionized water, and stir to disperse to obtain a nano-SiO2 suspension. The hydrolysate was dropped into a nano-SiO2 suspension, heated to 80-95°C and stirred to react. After standing and cooling, the solid phase was separated and dried to obtain the superhydrophobic SiO2 powder.

4. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 3, characterized in that, The nano-SiO2 has a particle size of 10 nm to 10 μm; the organic acid is any one of acetic acid, formic acid, propionic acid or butyric acid; the alcohol solvent is any one of anhydrous ethanol, methanol, propanol or butanol.

5. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, By weight, in step S2, the superhydrophobic SiO2 powder is 0.5-2.5 parts, anhydrous ethanol is 10-15 parts, polyethylene glycol 400 monooleate and hydrophilic SiO2 are both 0.1-0.6 parts, and the mass ratio of the two is 1-2:1-2.

6. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 5, characterized in that, In step S2, 0.1 to 0.3 parts of silane coupling agent are also added to the packing suspension.

7. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, The epoxy resin A agent is selected from any one of bisphenol A type epoxy resin, bisphenol F type epoxy resin or phenolic epoxy resin; the epoxy resin B agent is selected from any one of polyamide curing agent, aliphatic amine curing agent or alicyclic amine curing agent, and the mass ratio of the two is (1.5~3):(0.5~1).

8. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, The primer is acrylic, the spraying distance is 10~15cm, and the spraying thickness is 20~50μm.

9. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, The substrate in S5 is degreased and pickled before spraying.

10. The method for preparing a hydrophilic-hydrophobic adjustable anti-corrosion coating according to claim 1, characterized in that, The curing temperature for S5 is 50~70℃, and the curing time is 10~14h.

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