Antirust paint and coating

Abstract

The specific embodiment of the invention provides an anti-rust coating and a coating, the anti-rust coating comprises a water-based rust conversion agent and a water-based epoxy coating, the water-based rust conversion agent comprises a water-based acrylic emulsion and ammonium polyacrylate salt, the pH value of the water-based rust conversion agent is 6-8, Fe < 3 + > is converted into a stable complex in situ through a carboxyl chelation reaction, and the stable complex is added into the water-based epoxy coating. The water-based rust conversion agent and the epoxy coating have the advantages that the water-based rust conversion agent is added into the water-based epoxy coating, the continuous acid etching risk of a matrix is avoided, the water-based epoxy coating comprises polydopamine grafted and coated silicon dioxide, micropores can be reduced by the coating, permeation of water, oxygen and chloride ions can be inhibited, hydrolytic stripping and secondary corrosion can be prevented, and the water-based rust conversion agent and the epoxy coating have good compatibility; the formed coating is excellent in interlayer adhesive force and compact and firm in film layer, and the long-acting protection requirement in a severe corrosion environment can be met when the anti-rust coating is used for coating corrosion prevention of a steel member.

Description

Technical Field

[0001] This invention belongs to the field of steel corrosion protection, specifically relating to an anti-rust coating and coating material. Background Technology

[0002] Steel structures, as a core supporting material for modern industry and infrastructure, are widely used in bridges, buildings, and marine engineering. However, steel is highly susceptible to corrosion in humid or high-salt environments, forming a loose and porous rust layer (Fe2O3·nH2O). This not only leads to the deterioration of the material's mechanical properties (such as reduced strength) but may also pose safety hazards. Traditional anti-corrosion systems (such as painting or coating) mainly block corrosive media through physical barriers, but require strict substrate pretreatment processes, including sandblasting and grinding, to completely remove the rust layer. These processes are time-consuming, labor-intensive, and costly, and are difficult to implement in complex conditions such as high altitudes, underwater, or confined spaces. In addition, the pretreatment process generates dust pollution, which does not meet environmental protection requirements. To simplify construction, rust-converting coatings have emerged. These coatings use converting agents containing phosphoric acid or tannic acid to chelate with the rust, transforming the loose rust layer into a dense protective film (such as iron phosphate complexes), thereby directly constructing a protective layer on the surface of the rusted steel. Rust-converting coatings offer advantages such as convenient application and environmental friendliness with low toxicity. However, the conversion film itself has inherent defects: poor water resistance, easily hydrolyzed and peeled off in humid environments, leading to secondary corrosion of the substrate; limited physical barrier function, allowing corrosive media such as chloride ions and oxygen to penetrate to the substrate interface through micropores; uneven film adhesion, resulting in localized weak adhesion areas when the rust layer thickness is uneven; and due to the special nature of steel structure maintenance, commonly available acidic rust-converting agents are prone to reacting with steel structures, causing secondary corrosion. These shortcomings limit their long-term protective application in harsh environments. Summary of the Invention

[0003] Based on the problems existing in the treatment of steel components with rust-converting coatings, a specific embodiment of the present invention provides a method for coating steel components with a water-based epoxy coating in conjunction with a water-based rust-converting agent, thereby achieving long-term protection of steel components in harsh environments. The specific solution is as follows:

[0004] A rust-preventive coating comprising a water-based rust-converting agent and a water-based epoxy coating, wherein the water-based rust-converting agent comprises a water-based acrylic emulsion and an ammonium polyacrylate, wherein the pH of the water-based rust-converting agent is 6-8, and the water-based epoxy coating comprises polydopamine-grafted silica.

[0005] Optionally, the water-based rust remover may also include propylene glycol.

[0006] Optionally, the water-based rust remover may also include polyether-modified siloxane.

[0007] Optionally, the water-based rust remover may also include at least one of a leveling agent and a defoamer.

[0008] Optionally, the polydopamine-grafted silica in the waterborne epoxy coating is 0.5 to 10 wt% by weight.

[0009] Optionally, the resin matrix of the waterborne epoxy coating is a waterborne epoxy phenolic resin.

[0010] Optionally, the waterborne epoxy coating may also include aluminum tripolyphosphate.

[0011] Optionally, the waterborne epoxy coating may also include titanium dioxide and carbon black.

[0012] Optionally, the anti-rust coating may also include water-based polyurethane coatings or fluorocarbon resin coatings.

[0013] A rust-proof coating is formed by applying the aforementioned rust-proof paint to the surface of a steel substrate. The rust-proof coating includes a primer layer and a topcoat layer. The primer layer is formed by applying the water-based rust-removing agent to the surface of the steel substrate. The topcoat layer includes an epoxy coating formed by applying the water-based epoxy paint to the surface of the primer layer.

[0014] The water-based rust-transfer agent of this invention comprises an acrylic emulsion and an ammonium polyacrylate, wherein the pH of the water-based rust-transfer agent is 6-8, and Fe is transferred through a carboxyl chelation reaction. 3+ The waterborne epoxy coating, which is converted into a stable complex in situ to avoid the risk of continuous acid corrosion of the substrate, includes polydopamine-grafted silica. The coating can reduce microporosity, inhibit the penetration of water, oxygen and chloride ions, and prevent hydrolytic peeling and secondary corrosion. Furthermore, the waterborne rust remover and the waterborne epoxy coating have good compatibility, and the resulting coating has excellent interlayer adhesion and a dense and firm film. Using this rust-preventive coating to coat steel components can meet the long-term protection requirements under harsh corrosive environments (such as marine environments). Attached Figure Description

[0015] Figure 1 Fourier transform infrared absorption spectrum of polydopamine-grafted silica prepared in the process;

[0016] Figure 2 X-ray diffraction pattern of polydopamine-grafted silica prepared during the process;

[0017] Figure 3 XPS full spectrum of polydopamine-grafted silica prepared during the process;

[0018] Figure 4 X-ray diffraction patterns of stainless steel plates before and after applying primer;

[0019] Figure 5 SEM images of the rusted steel plate before and after applying the primer layer;

[0020] Figure 6 Photos taken after the preparation of the primer layer and the topcoat layer on the stainless steel plate during the implementation process;

[0021] Figure 7a and 7b Nyquist and Bode plots of 3.5 wt% NaCl solution after the intermediate coating was applied. Detailed Implementation

[0022] A specific embodiment of the present invention provides a rust-preventive coating, the rust-preventive coating comprising a water-based rust-converting agent and a water-based epoxy coating, the water-based rust-converting agent comprising a water-based acrylic emulsion and an ammonium polyacrylate, wherein the pH of the water-based rust-converting agent is 6-8, and the water-based epoxy coating comprises polydopamine-grafted silica.

[0023] The rust-preventive coating of this invention, in a specific embodiment, uses an acrylic emulsion as the resin matrix of the water-based rust-converting agent, with a pH value controlled within a slightly neutral range of 6-8, through the use of carboxyl groups (-COO). - ) and Fe 3+ Chelation forms a cross-linked network structure, which, upon curing, creates a physical barrier. Ammonium polyacrylate assists the chelation reaction, ensuring dispersion stability and avoiding the risk of continuous acid etching of the substrate. The waterborne epoxy coating includes polydopamine-grafted silica. While the waterborne epoxy coating provides a basic physical barrier, its molecular chain gaps (approximately 0.3–0.5 nm) still allow H2O, O2, and Cl- to pass through. - To prevent the penetration of small molecule corrosive media, the addition of polydopamine to graft and coat silica can effectively block the penetration of corrosive media such as water, oxygen, and chloride ions, thereby providing further protection for the primer layer and steel substrate formed by water-based rust converters, thus achieving long-term protection of steel components in harsh environments.

[0024] In some specific embodiments of the rust-preventive coating of the present invention, the pH of the water-based rust-converting agent is 6.5 to 7.5, specifically, it can be 6.5, 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4 or 7.5, etc.

[0025] In some specific embodiments of the rust-preventive coating of the present invention, an alkaline substance is added to control the pH value of the water-based rust-converting agent to a near-neutral range of 6 to 8.

[0026] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-converting agent further includes propylene glycol, which can form a hydrogen bond network with water and absorb water molecules generated by chelation and dehydration.

[0027] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-removing agent further includes a polyether-modified siloxane surfactant, which can reduce surface tension and increase the permeability to the micropores of the rust layer.

[0028] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-converting agent further includes a leveling agent, which helps to eliminate brush marks.

[0029] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-converting agent further includes a defoamer, which helps to suppress bubbles during production or construction.

[0030] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-converting agent, by weight, comprises: 35-45 parts of water-based acrylic emulsion, specifically, for example, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, or 45 parts, etc.; 0.1-5 parts of ammonium polyacrylate, more specifically, 0.5-2 parts, specifically, for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc.; and 0.1-5 parts of propylene glycol, more specifically, 0.5-2 parts, specifically, for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc. The ether-modified siloxane surfactant is 0.1 to 5 parts, more preferably 0.5 to 2 parts, specifically for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc.; the leveling agent is 0.1 to 5 parts, more preferably 0.5 to 2 parts, specifically for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc.; the defoamer is 0.1 to 5 parts, more preferably 0.5 to 2 parts, specifically for example, 0.5 parts, 1 part, 1.5 parts, or 2 parts, etc.; and the water is 50 to 60 parts, specifically for example, 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, or 60 parts, etc.

[0031] In some specific embodiments of the rust-preventive coating of the present invention, the water-based rust-converting agent is composed of water-based acrylic emulsion, ammonium polyacrylate, propylene glycol, polyether-modified siloxane surfactant, leveling agent, defoamer and water.

[0032] The anti-rust coating of the present invention, wherein the water-based rust-converting agent achieves rust conversion through a mild chelation mechanism rather than relying on a highly corrosive environment, gives it significant advantages in terms of substrate compatibility, coating compatibility, environmental safety and adaptability to humid environments, and is especially suitable for non-dismantling maintenance of high-value metal structures.

[0033] The anti-rust coating of this invention, specifically the water-based epoxy coating, comprises polydopamine-grafted silica. Silica, due to its high hardness, high temperature resistance, and good chemical inertness, enhances the physical barrier properties of the coating. Polydopamine, with its abundant polar groups, can form a hydrogen bond network with the topcoat, enhancing the dispersibility and interfacial bonding of the filler. Furthermore, polydopamine, through its phenolic hydroxyl groups, can bind with Fe... 3+ It can coordinate to form a chemical passivation layer. Therefore, through the synergistic effect of physical barrier enhancement, interfacial bonding enhancement and chemical passivation of polydopamine grafted with silica, the physical barrier function of epoxy coating is effectively improved, providing further protection for the primer layer formed by water-based rust converter and steel substrate, thereby achieving long-term protection of steel components in harsh environments.

[0034] In some specific embodiments of the rust-preventive coating of the present invention, the polydopamine-grafted silica is prepared by in-situ polymerization of fumed silica dispersed in an aqueous solution with dopamine.

[0035] In some specific embodiments of the rust-preventive coating of the present invention, the polydopamine-grafted silica in the water-based epoxy coating has a weight percentage of 0.5 to 10 wt%, specifically, it can be 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, etc., with 3 wt% having a particularly superior effect.

[0036] In some specific embodiments of the rust-preventive coating of the present invention, the resin matrix of the waterborne epoxy coating is waterborne epoxy phenolic resin, and the curing agent is waterborne epoxy curing agent.

[0037] In some specific embodiments of the rust-preventive coating of the present invention, the water-based epoxy coating further includes aluminum tripolyphosphate, which can be hydrolyzed to generate [PO4]. 3- with Fe 3+ The formation of a passivation film helps improve protective performance.

[0038] In some specific embodiments of the rust-preventive coating of the present invention, the water-based epoxy coating further includes titanium dioxide and carbon black, which can synergistically improve the ultraviolet shielding efficiency of the coating.

[0039] In some specific embodiments of the rust-preventive coating of the present invention, the waterborne epoxy coating comprises, by weight, 50-60 parts of waterborne phenolic epoxy resin, specifically, for example, 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, or 60 parts, etc.; the weight ratio of the waterborne epoxy curing agent to the waterborne phenolic epoxy resin is 1:3 to 1:6, specifically, for example, 1:3, 1:4, 1:5, or 1:6, etc.; and the aluminum tripolyphosphate is 0.1-5 parts, more specifically, 1-3 parts, etc. For example, the amount of titanium dioxide can be 1 part, 2 parts, or 3 parts, etc. The amount of titanium dioxide is 15 to 25 parts, specifically for example, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, or 25 parts, etc. The amount of titanium dioxide is 1 to 10 parts, specifically for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, or 10 parts, etc. The amount of water is 10 to 20 parts, specifically for example, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts, etc.

[0040] In some specific embodiments of the rust-preventive coating of the present invention, the waterborne epoxy coating is composed of waterborne phenolic epoxy resin, waterborne epoxy curing agent, polydopamine grafted silica, aluminum tripolyphosphate, titanium dioxide, carbon black and additives, wherein the additives include dispersants, leveling agents, defoamers, anti-settling agents and film-forming agents.

[0041] In some specific embodiments of the rust-preventive coating of the present invention, the rust-preventive coating further includes a waterborne polyurethane coating. The active hydroxyl groups in the waterborne polyurethane coating undergo a cross-linking reaction with the epoxy groups after the epoxy coating is cured, forming a dense interpenetrating network. Its aliphatic structure can resist ultraviolet degradation and make up for the shortcomings of the epoxy coating in terms of weather resistance.

[0042] In some specific embodiments of the rust-preventive coating of the present invention, the rust-preventive coating further includes a fluorocarbon resin coating. The CF bond in the fluorocarbon resin coating can provide excellent weather resistance and is suitable for areas with high UV exposure (such as bridge railings). The carboxyl groups of the fluorocarbon resin and the epoxy coating can form hydrogen bonds, but a silane coupling agent needs to be added to enhance adhesion.

[0043] A specific embodiment of the present invention also provides a rust-preventive coating, which is formed by applying the aforementioned rust-preventive coating to the surface of a steel substrate. The rust-preventive coating includes a primer layer and a topcoat layer. The primer layer is formed by applying the water-based rust converter to the surface of the steel substrate, and the topcoat layer is formed by applying the epoxy coating to the surface of the primer layer. In some specific embodiments, the topcoat layer comprises multiple layers. For example, in some specific embodiments, the topcoat layer consists of an epoxy coating formed by applying the water-based epoxy coating to the primer layer and a polyurethane coating formed by applying a water-based polyurethane coating to the surface of the epoxy coating. In some specific embodiments, the topcoat layer consists of an epoxy coating formed by applying the water-based epoxy coating to the primer layer and a fluorocarbon resin coating formed by applying a fluorocarbon resin coating to the surface of the epoxy coating.

[0044] The present invention will be further illustrated by specific embodiments below.

[0045] Example

[0046] Preparation of polydopamine grafted silica

[0047] At room temperature, 0.50 g of dopamine hydrochloride and 1 g of fumed silica were dispersed in 130 mL of deionized water, and then mechanically stirred at 300 rpm for 30 min to form a homogeneous suspension. Subsequently, a mixture of 3 mL of concentrated ammonia (28 wt%) and 50 mL of anhydrous ethanol was added dropwise to the suspension at a rate of 2 mL / min using a peristaltic pump. The mixture was stirred at 150 rpm for 24 h under light-protected conditions to complete the preparation of polydopamine / fumed silica. After the reaction was completed, the product was purified by centrifugation (8000 rpm, 15 min) and washing with deionized water, and finally dried in a vacuum drying oven at 60 °C for 24 h to obtain a black solid powder.

[0048] Figure 1 Fourier transform infrared absorption spectra of polydopamine-grafted silica, such as Figure 1 As shown, 3341cm -1 The absorption peak at 1613 cm⁻¹ is due to the stretching vibrations of NH and OH. -1 The nearby peak is the C=C stretching vibration peak of the aromatic ring, 1518 cm⁻¹. -1 The peak of CN stretching vibration is located at 1101 cm⁻¹. -1 The broad absorption band at this location belongs to the Si-O-Si stretching vibration mode in the silica structure, confirming that polydopamine was successfully grafted onto the silica surface. Figure 2 The X-ray diffraction pattern of polydopamine grafted onto silica is shown below. Figure 2As shown, the broad peak appearing at around 22℃ belongs to amorphous SiO2, and the diffraction peak pattern of polydopamine-grafted silica (SiO2@PDA) is completely consistent with that of SiO2, confirming that polydopamine does not affect the structure of SiO2. Figure 3 XPS full spectrum of polydopamine-grafted silica, such as Figure 3 As shown, the N 1s characteristic peak is clearly distinguishable, indicating the successful synthesis of SiO2@PDA. The Si 2p (103 eV) peak is attributed to the silicon element characteristic peak of fumed silica (SiO2), and the N 1s characteristic peak (C-NH2) appears at 400 eV, revealing that polydopamine is successfully coated on the SiO2 surface. Furthermore, peaks such as CO, C=C, and OC=O in the polydopamine structure were also detected, further confirming the successful grafting and coating of polydopamine onto the silica surface.

[0049] Preparation of rusted steel plates

[0050] A 7-day salt spray test was conducted according to GB / T 1771–2007 "Determination of resistance to neutral salt spray in paints and varnishes". After removal, a 7-day damp heat test was conducted according to GB / T 1740–2007 "Determination of resistance to damp heat in paint films". After removing the test plates, the surface oil was cleaned with distilled water, anhydrous ethanol and ethyl acetate in sequence. Finally, the plates were dried at (105 ± 2)℃ for 1 hour.

[0051] Primer preparation

[0052] The primer was prepared according to the following components and weight percentages: 41.5 wt% waterborne acrylic emulsion (BASF 1558), 1 wt% ammonium polyacrylate, 0.5 wt% Y-2089 leveling agent, 1 wt% DC-65 defoamer, 1 wt% propylene glycol, 1 wt% polyether-modified siloxane surfactant (HLB12-14), and 54 wt% water. The pH was adjusted to 7.15 with alkali. The primer was applied evenly to the surface of the rusted steel plate and baked at (105 ± 2) °C for 12 h.

[0053] Figure 4 X-ray diffraction patterns of rusted steel plates before and after applying a primer layer, such as Figure 4As shown, before coating, the (220), (311), (400), and (440) crystal planes of the mixed valence state corrosion products of iron oxide were displayed, indicating that the composition of the rusted steel plate was locally composed of mixed valence state compounds of iron oxide. The main reason for this formation was that the rusted plate was accelerated to form a magnetite rust layer under the low oxygen environment of the laboratory. After coating, the X-ray diffraction pattern of the rusted plate after being coated with the rust-converting agent and left to stand for 24 hours showed that the characteristic peaks of (220), (311), (400), and (440) of iron oxide disappeared. This indicates that the rust-converting agent reacted and complexed with the mixed valence state compounds of iron oxide. Moreover, the complex has high stability, which transforms the active rust into a stable compound and firmly bonds it with the coating film, forming a closed protective layer and an impermeable barrier. Figure 5 SEM images of the rusted steel plate before and after applying a primer layer, such as... Figure 5 As shown, the surface before coating is rough and loose, with obvious pores and irregular structure, indicating that it is still mixed with active γ-FeOOH and other active iron ions, which makes it easy for corrosive media to penetrate. After coating, the surface is relatively smooth and dense, effectively filling the rust layer defects and providing better shielding protection for the substrate. This shows that rust-converting agent treatment can improve the rust layer structure and enhance protective performance.

[0054] Topcoat layer preparation

[0055] The topcoat is prepared according to the following components and parts by weight: 55 parts by weight of waterborne phenolic epoxy resin (Allnex DTM 6919), 20 parts by weight of titanium dioxide, 5 parts by weight of carbon black, 2 parts by weight of aluminum tripolyphosphate, polydopamine-grafted silica (added at 0 wt%, 1 wt%, 3 wt%, 5 wt%, and 7 wt% of the total weight of the topcoat excluding the curing agent), 2 parts by weight of dispersant (BYK190), 0.5 parts by weight of Y-2089 leveling agent, 0.5 parts by weight of DC-65 defoamer, 1 part by weight of anti-settling agent (PUR65), 2 parts by weight of propylene glycol methyl ether, and 13 parts by weight of water. The mixture is then magnetically stirred until homogeneous. Then, 20 parts by weight of waterborne epoxy curing agent (Allnex 613W) are added and magnetically stirred until homogeneous. One coat is applied evenly to the surface of the primer layer using a craft brush and baked at (105 ± 2)℃ for 72 h.

[0056] Figure 6 Photos of the rusted steel plate, after the preparation of the primer layer and the topcoat layer (with a polydopamine-grafted silica addition of 3wt%), as shown. Figure 5 As shown, the coating is dense and firm, without cracking, peeling, or blistering, indicating that the primer and topcoat layers have good compatibility. Furthermore, the interlayer adhesion of the coating, tested by the pull-out method, is excellent (>6 MPa), far exceeding the industry standard. Figure 7a and 7bThe images show Nyquist and Bode plots for a 3.5 wt.% NaCl solution after coating. A larger Nyquist plot (Nyquist) indicates a higher capacitive arc diameter, signifying higher corrosion resistance of the coating. Figure 7a and 7b As shown, in the initial stage of immersion, all coatings exhibit a large-diameter capacitive arc. With prolonged immersion time, the radius of the capacitive arc decreases. The coating with 3wt.% SiO2@PDA (polydopamine-grafted silica) consistently maintains the largest capacitive arc radius, indicating that the coating with 3wt.% SiO2@PDA exhibits the best corrosion resistance. The low-frequency impedance modulus (|Z|) in the Bode plot is also shown. 0.01Hz The low-frequency impedance modulus (|Z|) is a semi-quantitative indicator for evaluating the protective performance of coatings. Coatings with different proportions of SiO2@PDA have varying low-frequency impedance moduli. 0.01Hz All are greater than 10 8 Ω·cm 2 As the soaking time increased, the unmodified coating showed a decrease in |Z| after 1 day of soaking. 0.01Hz The sudden drop of three orders of magnitude may be due to the continuous penetration of corrosive media such as chloride ions, forming corrosion channels, and the contact between the corrosive media and the metal substrate causing localized corrosion. The |Z| of the coating with added SiO2@PDA... 0.01Hz The decrease was only one or two orders of magnitude, with the coating containing 3 wt.% SiO2@PDA still maintaining a high |Z|. 0.01Hz This indicates that adding SiO2@PDA to the water-based phenolic epoxy resin in the topcoat layer can effectively enhance the corrosion resistance of the coating.

[0057] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A rust preventive coating, characterized by, The rust-proof coating comprises a water-based rust converter and a water-based epoxy coating, the water-based rust converter comprises a water-based acrylic emulsion and a polyacrylate ammonium salt, wherein the pH of the water-based rust converter is 6-8, and the water-based epoxy coating comprises polydopamine grafted coated silica.

2. The rust preventive paint according to claim 1, characterized by The water-based rust converter further comprises propylene glycol.

3. The rust preventive paint according to claim 1, characterized by The water-based rust converter further comprises polyether-modified siloxane.

4. The rust preventive coating according to claim 1, characterized by The water-based rust converter further comprises at least one of a leveling agent and a defoaming agent.

5. The rust preventive coating according to claim 1, characterized by The weight percentage of the polydopamine grafted coated silica in the epoxy coating is 0.5-10 wt%.

6. The rust preventive coating according to claim 1, characterized by The resin matrix of the water-based epoxy coating is a water-based epoxy phenolic resin.

7. The rust preventive coating according to claim 1, characterized by The water-based epoxy coating further comprises aluminum tripolyphosphate.

8. The rust preventive coating according to claim 1, characterized by, The water-based epoxy coating further comprises titanium white and carbon black.

9. The rust preventive coating according to claim 1, characterized by, The rust-proof coating further comprises a water-based polyurethane coating or a fluorocarbon resin coating.

10. A rust-preventive coating characterized by comprising: The rust-proof coating is formed by coating the rust-proof coating of any one of claims 1-9 on the surface of a steel substrate, wherein the rust-proof coating comprises a primer layer and a topcoat layer, the primer layer is formed by coating the water-based rust converter on the surface of the steel substrate, and the topcoat layer comprises an epoxy coating formed by coating the water-based epoxy coating on the surface of the primer layer.

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