Water-based rust conversion coating and preparation method thereof

Abstract

The invention provides a water-based rust conversion coating and a preparation method thereof, and belongs to the technical field of coatings, the water-based rust conversion coating comprises the following components in parts by weight: 55-75 parts of a modified acrylic emulsion, 2-5 parts of a coalescing agent, 0.2-1.5 parts of a defoaming agent, 0.3-1 part of a wetting agent, 12.68-25.7 parts of a rust conversion system, 3-5 parts of 10% inorganic gel, 2-4 parts of a 1.5% thickening agent and 2-15 parts of water; the rust conversion system is prepared from the following raw materials in parts by weight: 0.3 to 0.8 part of citric acid, 0.1 to 0.3 part of phosphoric acid, 0.08 to 0.1 part of copper dihydrogen phosphate, 0.2 to 0.5 part of manganese dihydrogen phosphate, 2 to 5 parts of tannic acid, 2 to 4 parts of 1.5 percent thickening agent and 8 to 15 parts of water. According to the technical scheme provided by the invention, the aims of improving the component compatibility, conversion efficiency, storage stability and sagging resistance of the coating and improving the construction latitude are fulfilled.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a water-based rust-converting coating and its preparation method. Background Technology

[0002] Metal corrosion, a long-standing major technical challenge in global industry, causes direct economic losses of 20%-40% of global metal production annually. Safety accidents caused by corrosion, such as equipment failures and structural collapses, are particularly prominent in critical infrastructure sectors like shipbuilding, petrochemicals, bridge engineering, and pipeline transportation. Traditional corrosion prevention processes rely on mechanical rust removal methods such as sandblasting and grinding, or chemical pickling, followed by the application of anti-rust coatings. On the one hand, traditional corrosion prevention processes are lengthy and inefficient; on the other hand, traditional rust removal methods also have limitations. For example, traditional mechanical rust removal has significant drawbacks: the operation is cumbersome and time-consuming, accompanied by large amounts of dust and noise pollution, which not only harms the occupational health of workers but also puts ecological pressure on the surrounding environment. While chemical pickling has high rust removal efficiency, the acid is highly volatile and corrosive, requiring strict control of equipment sealing and the temperature and humidity of the operating environment; even slight operational errors can lead to metal over-corrosion. Furthermore, the treatment cost of acidic wastewater generated after pickling is high, and if discharge does not meet standards, it will cause serious water pollution, posing significant environmental risks. Therefore, developing water-based rust-converting coatings that can be applied directly to rusted surfaces and combine high-efficiency rust prevention with environmentally friendly characteristics has become a popular direction for technological upgrading in the coatings industry.

[0003] Existing water-based rust-transfer coatings mainly consist of film-forming substances, rust-transfer agents, and thickeners. Regarding the selection of film-forming substances, existing technologies typically use polyvinylidene chloride (PVDC) modified acrylic emulsions, acrylic-modified acrylic emulsions, and epoxy-modified acrylic emulsions as base materials. Alternatively, they improve coating performance by synthesizing new modified acrylic emulsions or modifying existing modified acrylic emulsions. Other methods include preparing novel modified acrylic emulsions using specific polymer synthesis routes, or adding rust-transfer components to modified acrylic emulsions to enhance their performance. Existing rust-transfer agents are mostly designed based on polyphenolic compounds, such as tannic acid and gallic acid, and are chemically modified or physically mixed with other acids to form composite rust-transfer systems. Tannic acid is widely used due to its natural source and excellent rust conversion ability. To further improve rust-transfer efficiency, researchers have tried various strategies, including but not limited to… Tannic acid can be used in combination with other organic or inorganic acids, or chemically modified to enhance its interaction with metal surfaces. The application of thickeners is relatively limited, but some representative patents disclose their use. For example, Chinese patent CN104356780A proposes a water-based rust-converting coating and its preparation method, using sodium alginate, agar, or silica gel as thickeners. CN107987591B introduces a water-based rust-converting primer coating and its preparation method, using polyester alcohol, polyvinyl alcohol, sodium alginate, and xanthan gum as thickeners. CN119529607A describes a water-based metal roof rust-converting coating and its preparation method, using cellulose as a thickener. CN118956235A, in a rust-converting water-based epoxy primer, its preparation method, and application examples, uses fumed silica and bentonite as thickeners.

[0004] Although existing technologies have been studied and applied to some extent in terms of film-forming substances, rust-transfer agents and thickening systems of water-based rust-converting coatings, there are still some problems in the actual formulation design and engineering application process.

[0005] The compatibility issue between film-forming substances and rust-reducing agents is prominent. Most water-based modified acrylic emulsions (such as acrylic-modified acrylic emulsions, epoxy-modified acrylic emulsions, and PVDC-modified acrylic emulsions) are prone to intermolecular association due to hydrogen bonding, π-π stacking, or complexation reactions when coexisting with polyphenolic rust-reducing agents such as tannic acid. This leads to flocculation, stratification, or precipitation during storage. Simultaneously, the viscosity of the system gradually increases over time, and in severe cases, gelation occurs, significantly shortening the pot life of the coating, affecting its application performance and product quality consistency, and limiting its long-term stable application in industrial settings.

[0006] The following problems exist in the use of rust conversion agents: Existing technologies mostly rely on chemical complexation reactions to generate a protective layer, but the conversion products are prone to hydrolysis or oxidation in humid environments, leading to secondary activation of the rust layer and poor compatibility with subsequent coatings; the adhesion between the conversion layer and the topcoat is insufficient, especially under high humidity or low temperature conditions, problems such as interface peeling and blistering are prone to occur.

[0007] The following key issues remain in the selection of thickeners: (1) Poor compatibility with tannic acid system: Some cellulose thickeners are prone to phase separation or precipitation in high concentration polyphenol environment, losing their thickening function and causing serious sagging during construction; (2) Insufficient thickening efficiency: Thickeners such as sodium alginate and polyvinyl alcohol have weak shear thickening effect and low low shear viscosity, making it difficult to support the wet film thickness required for facade construction; (3) Poor storage stability: Inorganic thixotropic agents such as montmorillonite and bentonite are sensitive to the electrolyte of the system and are prone to flocculation or gelation due to ionic effect; while biological polysaccharide thickeners such as xanthan gum are prone to microbial degradation or viscosity decay under high temperature or long-term storage conditions, resulting in a significant decrease in viscosity.

[0008] In summary, existing water-based rust-converting coatings still face systemic technical bottlenecks in terms of component compatibility, conversion efficiency, rheological behavior control, and storage stability, and have not yet achieved a comprehensive performance balance that is efficient, stable, and suitable for engineering applications. Summary of the Invention

[0009] In view of this, the present invention provides a water-based rust-converting coating and its preparation method, which aims to improve the compatibility of coating components, conversion efficiency, storage stability and anti-sagging properties, and increase the tolerance of construction.

[0010] To achieve the above objectives, the present invention provides a water-based rust-converting coating, comprising the following components in parts by weight: 55-75 parts modified acrylic emulsion, 2-5 parts film-forming aid, 0.2-1.5 parts defoamer, 0.3-1 part wetting agent, 12.68-25.7 parts rust-converting system, 3-5 parts 10% inorganic gel, 2-4 parts 1.5% thickener, and 2-15 parts water; The rust-reducing system comprises the following raw materials in parts by weight: 0.3-0.8 parts citric acid, 0.1-0.3 parts phosphoric acid, 0.08-0.1 parts copper dihydrogen phosphate, 0.2-0.5 parts manganese dihydrogen phosphate, 2-5 parts tannic acid, 2-4 parts 1.5% thickener, and 8-15 parts water.

[0011] The rust conversion system provided by this invention integrates phosphating theory with the conventional tannic acid + phosphoric acid conversion theory, and enhances the rust conversion effect through the synergistic effect of multiple components. The specific composition and function are as follows: Copper dihydrogen phosphate: Its mechanism of action is based on the oxidizing property of copper ions. During rust conversion, copper ions can oxidize the ferrous ions in the rust to ferric ions, while being reduced to elemental copper. Since the combination and complexation stability of ferric ions with tannic acid or phosphoric acid is significantly better than that with ferrous ions, this reaction can greatly improve the structural stability of the conversion product. Simultaneously, tannic acid complexes with ferric ions to form a black substance, and with ferrous ions to form a blue substance; the participation of copper ions can promote the deepening of the conversion film color and optimize the coating appearance. It should be noted that copper dihydrogen phosphate has certain negative effects; excessive addition can easily lead to the oxidation of the metal substrate to produce ferrous ions, accelerating substrate corrosion. Therefore, its addition amount should be referenced to the amount added in the phosphating solution and controlled at 0.08%-0.1% of the total system mass. Citric acid, as a phosphating accelerator, primarily works in phosphating solutions by forming complexes with ferrous ions to reduce sludge. In rust conversion systems, it slows the reaction rate of tannic acid, phosphoric acid, and ferrous ions, preventing the conversion film from becoming loose due to excessively vigorous reactions. This regulatory effect ensures a more uniform rust conversion process, guaranteeing a tight bond between the conversion film and the substrate, while also reducing bubble formation during the reaction and improving coating density. Manganese dihydrogen phosphate: Introducing a manganese-based phosphating mechanism enhances the toughness of the conversion coating. The manganese-based phosphating film itself is black, which synergistically complements the black color of the tannic acid-iron complex, accelerating the blackening process of the conversion coating and shortening the post-construction appearance adjustment period. Furthermore, the phosphating layer formed by manganese dihydrogen phosphate can form a complementary structure with the conversion coating, further improving the coating's corrosion resistance, abrasion resistance, and adhesion to subsequent coatings. Optionally, the modified acrylic emulsion is Qingdao Enze Chemical's 8712 type emulsion.

[0012] Optionally, the 1.5% thickener comprises the following raw materials by weight percentage: 1.5% thickener, 0.2% bactericide, and 98.3% water.

[0013] Optionally, the thickener is N-TKN thickener from Henan Jincheng Agricultural Technology Development Co., Ltd.

[0014] Optionally, the 10% inorganic gel comprises the following raw materials by weight percentage: 10% inorganic gel, 0.2% bactericide, and 89.8% water.

[0015] Optionally, the inorganic gel is FZ-S30 from Mingguang Feizhou New Materials Co., Ltd.

[0016] The thickener used in this application increases the viscosity of the coating, but it is prone to separation. However, the thickener used in this application is used in conjunction with the inorganic gel, which provides excellent suspension properties, making the system less prone to separation and achieving a synergistic suspension-thickening effect.

[0017] To achieve the above objectives, the present invention provides a method for preparing a water-based rust-converting coating, comprising the following steps: adding water to a modified acrylic emulsion under medium-speed stirring, then adding a film-forming aid and stirring at high speed, then adding an antifoaming agent and a wetting agent in sequence and dispersing them evenly; then adding the rust-converting system, 1.5% thickener, 10% inorganic gel and the remaining water under medium-speed stirring and stirring evenly to obtain a water-based rust-converting coating.

[0018] Optionally, the speed of the medium-speed stirring is 800~1000 rpm, and the speed of the high-speed stirring is 1100~1400 rpm; when the defoamer and wetting agent are added in sequence and dispersed evenly, the fineness is ≤20 micrometers.

[0019] Optionally, the preparation of the rust-converting system includes the following steps: first, add water, then add citric acid, phosphoric acid, copper dihydrogen phosphate, manganese dihydrogen phosphate and tannic acid in sequence and stir at high speed until evenly dispersed, then add 1.5% thickener and stir evenly to obtain the rust-converting system.

[0020] Optionally, the preparation of the 1.5% thickener includes the following steps: adding water and bactericide and stirring at medium speed, then adding the thickener and stirring at high speed to obtain the 1.5% thickener.

[0021] Optionally, the preparation of the 10% inorganic gel includes the following steps: adding water and bactericide and stirring at medium speed, then adding inorganic gel and stirring at high speed to obtain 10% inorganic gel.

[0022] The above-described technical solution of the present invention has at least the following beneficial effects: 1. This invention, through systematic formulation optimization and synergistic design, focuses on overcoming technical challenges such as sedimentation and performance degradation during long-term storage, achieving synergistic performance enhancement, and ultimately preparing a water-based rust-converting coating with excellent storage stability and no clumping during long-term storage, significantly extending the product's shelf life and applicability for construction.

[0023] 2. The composite rust conversion system used in this invention has broad adaptability to different types and thicknesses of rust. The converted composite film is uniform and dense. It is highly compatible with various types of topcoats, including solvent-based and water-based ones, achieving Level 1 interlayer adhesion (cross-cut test), with no wrinkling or peeling. The overall protective effect of the coating system, when combined with the rust-converting paint, is significantly improved, and its service life is relatively extended.

[0024] 3. This invention, by introducing specific thickeners and inorganic gels, synergistically achieves high viscosity under low shear conditions, effectively suppressing wet film dripping during vertical surface application. In actual construction, the wet film thickness can be stably maintained at 50-200 μm, meeting the film thickness requirements for rust conversion coatings. Sufficient film thickness not only provides ample space for the rust conversion reaction, ensuring its full progress, but also significantly enhances the coating's physical barrier against corrosive media. Simultaneously, the high application tolerance reduces the requirements for the operating environment and personnel skills, enabling uniform coating even on complex conditions such as vertical and inclined surfaces. Attached Figure Description

[0025] Figure 1 The image shows the actual wetting effect of the coating prepared in Example 1 of this invention. Figure 2 The actual wetting effect of competing products in the market is shown in the diagram. Figure 3 This is an actual effect diagram of the conversion film of the coating prepared in Example 1 of the present invention; Figure 4 Actual effect diagram of the conversion film of competing products in the market; Figure 5 The images show the actual effects of Group B and Group D after being left to stand overnight.

[0026] In the figure: Group B is the coating with 0.1 parts thickener added; Group D is the coating with 0.1 parts thickener + 0.4 parts inorganic gel added. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will be described in conjunction with the accompanying drawings of the embodiments of the present invention. Figures 1-5 The technical solutions of the embodiments of the present invention will be clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0028] The raw material types used in the embodiments of this invention are as follows: The modified acrylic emulsion is Qingdao Enze Chemical's 8712 type emulsion; the film-forming aid is alcohol ester twelve; defoamer 1 is mineral oil defoamer NXZ (Shengnuopco); defoamer 2 is BYK Chemical's BYK-024; the wetting agent is Yueyang Kaimen Chemical's Greesol A04PG; phosphoric acid, citric acid, and manganese dihydrogen phosphate are from Xilong Scientific Co., Ltd.; copper dihydrogen phosphate is from Hubei Tuobang Chemical Co., Ltd.; tannic acid is from Wufeng Chicheng Biotechnology Co., Ltd.; the thickener is Henan Jincheng Agricultural Technology Development Co., Ltd.'s thickening and suspending agent N-TKN; the inorganic gel is Mingguang Feizhou New Materials Co., Ltd.'s FZ-S30; and the bactericide is Hoffmann Chemical's Defros CP15.

[0029] Example 1 This invention provides a water-based rust-converting coating, comprising the following components in parts by weight: 70 parts modified acrylic emulsion, 3 parts film-forming aid, 0.1 parts defoamer 1, 0.2 parts defoamer 2, 0.6 parts wetting agent, 15.5 parts rust-converting system, 3.6 parts 10% inorganic gel, 5 parts 1.5% thickener, and 2 parts water; The rust-converting system comprises the following raw materials in parts by weight: 0.3 parts citric acid, 0.15 parts phosphoric acid, 0.1 parts copper dihydrogen phosphate, 0.4 parts manganese dihydrogen phosphate, 3 parts tannic acid, 3 parts 1.5% thickener, and 8.55 parts water; The 1.5% thickener comprises the following ingredients by weight percentage: 1.5% thickener, 0.2% bactericide, and 98.3% water; The 10% inorganic gel comprises the following raw materials by weight percentage: 10% inorganic gel, 0.2% bactericide, and 89.8% water.

[0030] This invention provides a method for preparing a water-based rust-converting coating: A modified acrylic emulsion is added to water under medium-speed stirring at 900 rpm, then a film-forming aid is added and stirred at high-speed stirring at 1300 rpm, followed by the sequential addition of an antifoaming agent and a wetting agent to disperse evenly; then, a rust-converting system, 1.5% thickener, 10% inorganic gel, and the remaining water are added under medium-speed stirring at 1000 rpm and stirred evenly to obtain the water-based rust-converting coating. The preparation of the rust-converting system includes the following steps: first, add water, then add citric acid, phosphoric acid, copper dihydrogen phosphate, manganese dihydrogen phosphate and tannic acid in sequence and stir at 1400 rpm. After the mixture is evenly dispersed, add 1.5% thickener and stir evenly to obtain the rust-converting system. The preparation of 1.5% thickener includes the following steps: adding water and bactericide and stirring at a medium speed of 800 rpm, then adding thickener and stirring at a high speed of 1100 rpm to obtain 1.5% thickener; The preparation of 10% inorganic gel includes the following steps: adding water and bactericide and stirring at a medium speed of 1000 rpm, then adding inorganic gel and stirring at a high speed of 1400 rpm to obtain 10% inorganic gel.

[0031] Example 2 The difference from Example 1 is that it includes the following components in parts by weight: 65 parts modified acrylic emulsion, 3.28 parts film-forming aid, 0.1 parts defoamer 1, 0.2 parts defoamer 2, 0.5 parts wetting agent, 17.42 parts rust-converting system, 4 parts 10% inorganic gel, 7 parts 1.5% thickener, and 3.28 parts water; The rust-converting system comprises the following raw materials in parts by weight: 0.4 parts citric acid, 0.12 parts phosphoric acid, 0.1 parts copper dihydrogen phosphate, 0.3 parts manganese dihydrogen phosphate, 3.5 parts tannic acid, 3 parts 1.5% thickener, and 10 parts water. The remaining raw materials and steps are the same as in Example 1.

[0032] Example 3 The difference from Example 1 is that it includes the following components in parts by weight: 60 parts modified acrylic emulsion, 2 parts film-forming aid, 0.1 parts defoamer 1, 0.2 parts defoamer 2, 0.4 parts wetting agent, 17.4 parts rust-converting system, 4 parts 10% inorganic gel, 11 parts 1.5% thickener, and 4.9 parts water; The rust-converting system comprises the following raw materials in parts by weight: 0.4 parts citric acid, 0.1 parts phosphoric acid, 0.1 parts copper dihydrogen phosphate, 0.3 parts manganese dihydrogen phosphate, 3.5 parts tannic acid, 3 parts 1.5% thickener, and 10 parts water. The remaining raw materials and steps are the same as in Example 1.

[0033] Example 4 The difference from Example 1 is that it includes the following components in parts by weight: 56 parts modified acrylic emulsion, 2 parts film-forming aid, 0.1 parts defoamer 1, 0.2 parts defoamer 2, 0.3 parts wetting agent, 18 parts rust-converting system, 4.2 parts 10% inorganic gel, 10 parts 1.5% thickener, and 9.2 parts water; The rust-converting system comprises the following raw materials in parts by weight: 0.4 parts citric acid, 0.1 parts phosphoric acid, 0.1 parts copper dihydrogen phosphate, 0.3 parts manganese dihydrogen phosphate, 4 parts tannic acid, 3 parts 1.5% thickener, and 10 parts water. The remaining raw materials and steps are the same as in Example 1.

[0034] The performance of the coatings prepared in Examples 1-4 was tested, and the results are shown in Table 1.

[0035] Table 1. Performance test results of coatings prepared in Examples 1-4

[0036] As shown in Table 1, the coating obtained in the embodiments of the present invention exhibits excellent performance in terms of viscosity, anti-sagging properties, storage stability, hardness, and compatibility. The system viscosity can be controlled within 20-40 s / 25℃, the wet film thickness on vertical surfaces is >50 μm, it has strong anti-sagging properties, and high application tolerance, adapting to various complex working conditions. Furthermore, the coating has good compatibility with various topcoats, without issues such as color bleeding, and provides excellent overall protective effect, meeting the high-efficiency and environmentally friendly requirements of the metal protection field.

[0037] The inorganic gel and thickener from Example 1 were added to the rust-converting system and allowed to stand for 30 days to test its performance. The results showed that after 30 days of standing, only a small amount of loose suspended particles remained at the bottom, which easily returned to a uniform state. After standing at 50°C for 30 days, there was no sedimentation, indicating a significant rust-converting effect. The rust-converting system can efficiently convert rust, producing a uniform and dense conversion film that does not crack, has good adhesion to the substrate, and exhibits excellent compatibility.

[0038] The wettability of the coating prepared in Example 1 was tested under the same conditions as that of competing products on the market, and the results were obtained respectively. Figure 1 , Figure 2 . Figure 1 This is a diagram showing the actual wetting effect of the coating prepared in Example 1. Figure 2 This is a diagram illustrating the actual wetting properties of competing products in the market. Figure 1 and Figure 2 The comparison shows that the coating prepared by the present invention has strong wettability and more uniform coating distribution.

[0039] The rust conversion film effect of the coating prepared in Example 1 was tested against that of competing products on the market under the same conditions, and the results were obtained respectively. Figure 3 , Figure 4 . Figure 3 This is an image showing the actual effect of the conversion film of the coating prepared in Example 1. Figure 4 These are actual effect images of conversion coatings from competing products in the market. Figure 3 and Figure 4 The comparison shows that the coating prepared by the present invention has good conversion efficiency and the conversion film does not crack.

[0040] Synergistic effect of thickeners and inorganic gels: experimental examples Four portions of coating were taken and divided into groups A, B, C, and D. Group A served as the blank control group. Group B was supplemented with 0.1 parts thickener, Group C with 0.4 parts inorganic gel, and Group D with a mixture of 0.1 parts thickener and 0.4 parts inorganic gel. After thoroughly mixing the four groups of coating, they were allowed to stand overnight (12 hours) before their viscosity and state were measured. The results are shown in Table 2. The actual effects of Group B and Group D after standing overnight are shown in the figures below. Figure 5 .

[0041] Table 2. Viscosity and State Results of Four Groups of Coatings

[0042] Combined with Table 2 Figure 5 As can be seen, this application employs a synergistic effect of thickener and inorganic gel, simultaneously achieving both thickening and suspension effects. This can significantly improve the product's application performance and storage stability.

[0043] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water-based rust-converting coating, characterized in that, The product comprises the following components in parts by weight: 55-75 parts modified acrylic emulsion, 2-5 parts film-forming aid, 0.2-1.5 parts defoamer, 0.3-1 part wetting agent, 12.68-25.7 parts rust-converting system, 3-5 parts 10% inorganic gel, 2-4 parts 1.5% thickener, and 2-15 parts water; The rust-reducing system comprises the following raw materials in parts by weight: 0.3-0.8 parts citric acid, 0.1-0.3 parts phosphoric acid, 0.08-0.1 parts copper dihydrogen phosphate, 0.2-0.5 parts manganese dihydrogen phosphate, 2-5 parts tannic acid, 2-4 parts 1.5% thickener, and 8-15 parts water.

2. The water-based rust-converting coating according to claim 1, characterized in that, The 1.5% thickener comprises the following raw materials by weight percentage: 1.5% thickener, 0.2% bactericide, and 98.3% water.

3. The water-based rust-converting coating according to claim 1, characterized in that, The 10% inorganic gel comprises the following raw materials by weight percentage: 10% inorganic gel, 0.2% bactericide, and 89.8% water.

4. A method for preparing a water-based rust-converting coating as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Add water to the modified acrylic emulsion under medium-speed stirring, then add film-forming aid and stir at high speed, then add defoamer and wetting agent in sequence and disperse evenly; then add rust conversion system, 1.5% thickener, 10% inorganic gel and the remaining water under medium-speed stirring and stir evenly to obtain water-based rust conversion coating.

5. The method for preparing the water-based rust-converting coating according to claim 4, characterized in that, The speed of the medium-speed stirring is 800~1000 rpm, and the speed of the high-speed stirring is 1100~1400 rpm; when the defoamer and wetting agent are added in sequence and dispersed evenly, the fineness is ≤20 micrometers.

6. The method for preparing the water-based rust-converting coating according to claim 4, characterized in that, The preparation of the rust-converting system includes the following steps: first, add water, then add citric acid, phosphoric acid, copper dihydrogen phosphate, manganese dihydrogen phosphate and tannic acid in sequence and stir at high speed until evenly dispersed, then add 1.5% thickener and stir evenly to obtain the rust-converting system.

7. The method for preparing the water-based rust-converting coating according to claim 4, characterized in that, The preparation of the 1.5% thickener includes the following steps: adding water and bactericide and stirring at medium speed, then adding the thickener and stirring at high speed to obtain the 1.5% thickener.

8. The method for preparing the water-based rust-converting coating according to claim 4, characterized in that, The preparation of the 10% inorganic gel includes the following steps: adding water and bactericide and stirring at medium speed, then adding inorganic gel and stirring at high speed to obtain 10% inorganic gel.

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