Anticorrosive coating based on attapulgite and method for preparing the same

Abstract

This invention relates to the field of coating technology, specifically to an anti-corrosion coating based on attapulgite and its preparation method. This invention overcomes the technical problems of poor corrosion resistance and low mechanical properties in existing coatings. The invention first prepares modified attapulgite using phytic acid and KH-560, then prepares modified hydrotalcite through sodium molybdate intercalation and dopamine coating; a mixed slurry is prepared by high-speed shear grinding of epoxy resin, modified attapulgite, and barium sulfate, followed by low-speed mixing of modified hydrotalcite and curing agent, and then coated and cured under gradient curing to obtain the anti-corrosion coating. In this invention, the modified attapulgite constructs a three-dimensional cross-linked network in the resin, significantly enhancing the mechanical properties of the coating; the modified hydrotalcite enables targeted release of corrosion inhibitors, and combined with the physical labyrinth effect of multiple fillers, greatly improves the corrosion resistance of the coating.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an anti-corrosion coating based on attapulgite and its preparation method. Background Technology

[0002] Attapulgite is a natural, layered, magnesium-aluminate silicate nanomineral with a unique microstructure exhibiting one-dimensional nanorod or fibrous forms. In the coatings industry, attapulgite has long been used as a thickener and filler due to its large specific surface area, excellent rheological regulation, outstanding anti-settling ability, and low environmentally friendly cost. In recent years, with the development of heavy-duty anti-corrosion coatings towards high performance and low cost, introducing attapulgite with natural nanoscale dimensions into anti-corrosion coatings, utilizing its physical barrier effect to prevent the penetration of corrosive media such as water, oxygen, and chloride ions, has become a hot research topic in the coatings field.

[0003] However, current attapulgite anti-corrosion coatings exhibit two major drawbacks in practical applications, leading to a significant reduction in their lifespan. Firstly, they suffer from poor corrosion resistance. Unmodified attapulgite contains numerous hydrophilic hydroxyl groups on its surface, making it highly susceptible to aggregation within the polymer matrix. This aggregation not only fails to form an effective anti-permeability barrier but also introduces numerous micropores and capillary channels into the coating, accelerating the intrusion of corrosive media. Secondly, they exhibit low mechanical properties. Natural attapulgite possesses high rigidity and a polar surface, while mainstream anti-corrosion resins (such as epoxy resins) are mostly non-polar or weakly polar, resulting in extremely poor interfacial compatibility. Under external thermal stress or mechanical impact, stress concentration easily occurs at the resin-mineral interface within the coating, triggering microcracks or even coating peeling, severely compromising the integrity of the anti-corrosion coating.

[0004] Therefore, an anti-corrosion coating based on attapulgite and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to design an anti-corrosion coating based on attapulgite and its preparation method. This invention first prepares modified attapulgite using phytic acid and KH-560, then prepares modified hydrotalcite through sodium molybdate intercalation and dopamine external coating; a mixed slurry is prepared by high-speed shear grinding of epoxy resin, modified attapulgite, and barium sulfate, followed by low-speed mixing of modified hydrotalcite and curing agent, and then coated and cured under gradient curing to obtain the anti-corrosion coating. In this invention, the modified attapulgite constructs a three-dimensional cross-linked network in the resin, significantly enhancing the mechanical properties of the coating; the modified hydrotalcite enables targeted release of corrosion inhibitors, and combined with the physical labyrinth effect of multiple fillers, greatly improves the corrosion resistance of the coating.

[0006] To achieve the above objectives, the present invention provides the following technical solution: unless otherwise specified, the parts in the solution are all parts by weight.

[0007] This invention provides a method for preparing an anti-corrosion coating based on attapulgite, comprising the following steps: A mixed slurry was prepared by mixing epoxy resin, mixed solvent, dispersant, modified attapulgite, and barium sulfate. Modified hydrotalcite, supplementary mixed solvent, leveling defoamer, and curing agent were added to the mixed slurry, which was then coated onto the substrate surface and subjected to gradient curing treatment to obtain an anti-corrosion coating. The modified attapulgite was obtained by modifying attapulgite with phytic acid and KH-560. The modified hydrotalcite was obtained by modifying hydrotalcite with sodium molybdate and dopamine hydrochloride.

[0008] Preferred method for preparing modified attapulgite: 100 parts of attapulgite powder (specific surface area of ​​150-250 m² / g, average particle size of 400 mesh) are added to 1000 parts of 1 mol / L HCl solution. The temperature is set at 60℃, the mechanical stirring speed is 500 rpm, and the reaction is carried out for 2 hours. Then, the mixture is filtered, washed with deionized water until neutral, dried at 80℃, and pulverized through a 400-mesh sieve to obtain pretreated powder. 45-55 parts of the pretreated powder are dispersed in 500 parts of ethanol-water solution (volume ratio 1:1), sonicated for 20 minutes, and then 2-6 parts of phytic acid (50%-70% by mass aqueous solution) are added. The temperature is raised to 70℃, and the mixture is stirred under reflux for 4 hours. After the reaction is completed, the mixture is filtered and washed three times with deionized water to remove impurities. Unreacted free phytic acid in the system yielded a chelated intermediate. The chelated intermediate was redispersed in a 500-part ethanol-water mixture (anhydrous ethanol to deionized water volume ratio of 4:1) to obtain a chelate solution. 1-3 parts of KH-560 were pre-dissolved in a 20-part ethanol-water mixture (pH adjusted to 4.5 with glacial acetic acid) and hydrolyzed for 30 min. The solution was then added dropwise to the chelate solution (at a rate of 1-2 drops / s). The temperature was raised to 50 °C and the reaction continued for 5 h. After the reaction was completed, the solution was filtered, washed, and vacuum dried at 50 °C for 12 h. After pulverization, modified attapulgite was obtained.

[0009] Preferred method for preparing modified hydrotalcite: Boil deionized water for at least 30 minutes, continuously purging with high-purity nitrogen during cooling to obtain carbonate-free decarbonated deionized water; all subsequent solutions are prepared using this water. Dissolve 51 parts magnesium nitrate and 37 parts aluminum nitrate in 200 parts decarbonated deionized water to obtain a metal salt solution. Add 50 parts decarbonated deionized water to a three-necked flask beforehand, purging with nitrogen throughout the process. Under mechanical stirring (800 rpm), simultaneously add the metal salt solution and 2 mol / L NaOH solution dropwise to the flask, maintaining the pH of the system constant between 9.5 and 10.0. After the addition is complete, continue stirring for 30 minutes, transfer to a polytetrafluoroethylene reactor, and hydrothermally age at 100°C for 12 hours. After the reaction, centrifuge and repeatedly wash with decarbonated deionized water until the supernatant is neutral. The lower layer... The precipitate was dried in a vacuum drying oven at 60℃ to obtain LDH powder; 500 parts of 0.1 mol / L sodium molybdate solution were prepared, and the pH was adjusted to 8 with NaOH solution. 15 parts of LDH powder were added and sonicated for 20 min. Under nitrogen protection (CO2 exclusion), the mixture was stirred at 60℃ for 24 h. After centrifugation and washing, the pretreated LDH was obtained after vacuum drying at 60℃; 8-12 parts of the pretreated LDH were dispersed in 400 parts of Tris-HCl buffer solution (pH adjusted to 8.5 with NaOH or HCl solution), and sonicated for 30 min. 0.5-1.5 parts of dopamine hydrochloride were added, and the mixture was magnetically stirred for 10-14 h under ambient temperature (25℃), light-proof and open conditions. After centrifugation, the mixture was washed three times alternately with deionized water and anhydrous ethanol, and then freeze-dried for 48 h to obtain modified hydrotalcite.

[0010] Preferably, the preparation method of the mixed slurry is as follows: In a clean dispersion tank, add 45-55 parts of E-44 epoxy resin and 15 parts of mixed solvent, turn on the disperser, adjust the speed to 600 rpm and stir for 5 min, add 1.5 parts of polycarboxylate dispersant (BYK-110), and while stirring, slowly add 5-7 parts of modified attapulgite and 13-17 parts of barium sulfate (average particle size of 800 mesh), increase the disperser speed to 2300-2700 rpm, and perform high-speed shearing for 30 min. Then, pump the slurry into a horizontal sand mill (using 0.8 mm zirconia beads, with a grinding media filling rate of 70%) and grind it 3 times. Control the cooling water flow rate to ensure that the discharge temperature is <55℃ (to prevent local cross-linking of epoxy resin at high temperature). The fineness is measured by a scraper fineness gauge to reach ≤25μm to obtain the mixed slurry.

[0011] Preferably, the mixed solvent comprises xylene and n-butanol, wherein the weight ratio of xylene to n-butanol is 7:3.

[0012] Preferably, the preparation method of the anti-corrosion coating is as follows: the mixed slurry is transferred to a low-speed mixing tank, and under low shear conditions at a speed of 500-800 rpm, 3-5 parts of modified hydrotalcite are slowly added in two batches, followed by 5 parts of mixed solvent and 0.5 parts of silicone leveling defoamer (BYK-320). The mixture is stirred at low speed for 30 minutes, filtered through a 100-mesh filter, and then 25 parts of polyamide 650 curing agent (average amine value of 200 mg KOH / g) are added. After curing at room temperature for 10-20 minutes, the mixture is applied to the substrate by spraying and subjected to gradient curing treatment: first, pre-curing at 60℃ for 2 hours (to allow the solvent to evaporate smoothly and the ATP skeleton to be shaped to prevent filler sedimentation), and then post-curing at 80-100℃ for 2 hours to obtain the anti-corrosion coating.

[0013] Another aspect of the present invention provides an anti-corrosion coating based on attapulgite, the raw materials for which include E-44 epoxy resin, modified attapulgite, modified hydrotalcite, dispersant, barium sulfate, leveling defoamer and curing agent.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention prepares modified hydrotalcite through a pre-defined modification process. The molybdate ions loaded between the hydrotalcite layers act as highly efficient anodic corrosion inhibitors, releasing them through ion exchange upon the intrusion of corrosive media to form a stable passivation film on the metal substrate surface. Simultaneously, the outer polydopamine coating layer exhibits excellent pH responsiveness, undergoing permeability changes when the coating is damaged or the local microenvironment becomes acidic, thereby promoting the targeted exchange and release of molybdate ions. This mechanism overcomes the passive defense defects of traditional anti-corrosion coatings and solves the problem of rapid substrate corrosion once the coating is damaged.

[0015] 2. This invention utilizes phytic acid and a silane coupling agent to perform dual modification on one-dimensional rod-shaped attapulgite. The modified attapulgite is not only uniformly dispersed in the resin matrix, but its surface KH-560 epoxy groups can also react with the epoxy resin matrix during the subsequent curing stage. This combination of "rigid inorganic nanorods + flexible organic chemical bonds" constructs a strong and tough three-dimensional stress network within the coating, playing a toughening and strengthening role and significantly improving the mechanical properties of the coating.

[0016] 3. In this invention, the polydopamine on the surface of the modified hydrotalcite is rich in catechol and amino groups, and the surface of the modified attapulgite is grafted with organosiloxane segments. This significantly reduces the surface energy of the inorganic particles, enabling them to obtain good wetting and spreading in mixed solvents and epoxy resins, and enhances the adhesion of the coating.

[0017] 4. This invention employs a two-step processing technique in coating preparation: First, the easily agglomerated modified attapulgite crystal bundles are thoroughly broken up through high-speed shearing and grinding to construct a stable thixotropic rheological framework; then, modified hydrotalcite is added under low-speed, low-shear conditions. This differentiated mechanical processing strategy ensures the formation of a dense physical barrier framework while avoiding damage to the layered structure of hydrotalcite and the dopamine coating layer caused by strong mechanical forces.

[0018] 5. This invention employs a gradient curing process, combining barium sulfate and modified attapulgite. Low-temperature pre-curing utilizes the thixotropic network established by the modified attapulgite to prevent the sedimentation of high-density fillers. High-temperature post-curing allows the mixed solvent in the system to evaporate smoothly, avoiding microporous defects caused by solvent boiling, while simultaneously promoting cross-linking of functional groups at each interface. The labyrinth effect formed by the one-dimensional modified attapulgite, two-dimensional modified hydrotalcite, and barium sulfate significantly extends the penetration path of corrosive media, further strengthening the corrosion resistance of the coating from a physical barrier perspective. Attached Figure Description

[0019] Figure 1 The diagram shows the impact strength of Example 1 and Comparative Examples 1-7 in this invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] For details, please refer to [link / reference]. Figure 1 This invention provides an anti-corrosion coating based on attapulgite and its preparation method, the technical solution of which is as follows:

[0022] Example 1 100 parts of attapulgite powder were added to 1000 parts of 1 mol / L HCl solution. The temperature was set at 60℃, the mechanical stirring speed was 500 rpm, and the reaction was carried out for 2 hours. Afterward, the mixture was filtered, washed with deionized water until neutral, dried at 80℃, and pulverized through a 400-mesh sieve to obtain pretreated powder. 50 parts of the pretreated powder were dispersed in 500 parts of ethanol-water solution (volume ratio 1:1), sonicated for 20 minutes, and then 4 parts of phytic acid were added. The temperature was raised to 70℃, and the mixture was stirred under reflux for 4 hours. After the reaction was completed, the mixture was filtered and washed three times with deionized water to remove unreacted free phytic acid from the system. A chelated intermediate was obtained; the chelated intermediate was redispersed in a 500-part ethanol-water mixture (the volume ratio of anhydrous ethanol to deionized water was 4:1) to obtain a chelate solution; 2 parts of KH-560 were pre-dissolved in a 20-part ethanol-water mixture (the pH was adjusted to 4.5 with glacial acetic acid) and hydrolyzed for 30 min, and then added dropwise to the chelate solution (at a rate of 1-2 drops / s), and the temperature was raised to 50℃ and the reaction continued for 5 h. After the reaction was completed, the mixture was filtered, washed, vacuum dried at 50℃ for 12 h, and pulverized to obtain modified attapulgite.

[0023] Deionized water was boiled for at least 30 minutes, and high-purity nitrogen was continuously purged during cooling to obtain carbonate-free decarbonated deionized water. All subsequent solutions were prepared using this water. 51 parts magnesium nitrate and 37 parts aluminum nitrate were dissolved in 200 parts decarbonated deionized water to obtain a metal salt solution. 50 parts decarbonated deionized water were pre-added to a three-necked flask, and nitrogen was purged throughout the process. Under mechanical stirring (800 rpm), the metal salt solution and 2 mol / L NaOH solution were simultaneously added dropwise to the flask, maintaining the pH of the system constant between 9.5 and 10.0. After the addition was complete, stirring was continued for 30 minutes. The mixture was then transferred to a polytetrafluoroethylene reactor and hydrothermally aged at 100°C for 12 hours. After the reaction, the mixture was centrifuged and repeatedly washed with decarbonated deionized water until the supernatant was neutral. The precipitate was dried in a vacuum drying oven at 60℃ to obtain LDH powder; 500 parts of 0.1 mol / L sodium molybdate solution were prepared, and the pH was adjusted to 8 with NaOH solution. 15 parts of LDH powder were added and sonicated for 20 min. Under nitrogen protection, the mixture was stirred at 60℃ for 24 h, centrifuged and washed, and then vacuum dried at 60℃ to obtain pretreated LDH; 10 parts of pretreated LDH were dispersed in 400 parts of Tris-HCl buffer solution (the pH was adjusted to 8.5 with NaOH solution or HCl solution), sonicated for 30 min, and then 1 part of dopamine hydrochloride was added. The mixture was magnetically stirred for 12 h at room temperature (25℃), in the dark and in an open environment. After centrifugation, the mixture was washed three times alternately with deionized water and anhydrous ethanol, and then freeze-dried for 48 h to obtain modified hydrotalcite.

[0024] In a clean dispersion tank, add 50 parts of E-44 epoxy resin and 15 parts of mixed solvent. Turn on the disperser and stir at 600 rpm for 5 minutes. Add 1.5 parts of polycarboxylate dispersant. While stirring, slowly add 6 parts of modified attapulgite and 15 parts of barium sulfate. Increase the disperser speed to 2500 rpm and shear at high speed for 30 minutes. Then pump the slurry into a horizontal sand mill (using 0.8 mm zirconia beads and a grinding media filling rate of 70%) and grind it 3 times. Control the cooling water flow rate to ensure that the discharge temperature is <55℃. The fineness of the scraper fineness gauge is ≤25μm to obtain a mixed slurry. The mixed slurry was transferred to a low-speed mixing tank. Under low shear conditions at a speed of 650 rpm, 4 parts of modified hydrotalcite were slowly added in two batches. Then, 5 parts of mixed solvent and 0.5 parts of silicone leveling defoamer (BYK-320) were added. The mixture was stirred at low speed for 30 minutes. The mixture was then filtered through a 100-mesh filter. Subsequently, 25 parts of polyamide 650 curing agent were added. After curing at room temperature for 15 minutes, the mixture was applied to the substrate by spraying. Gradient curing treatment was used: first, pre-curing at 60℃ for 2 hours, and then post-curing at 90℃ for 2 hours to obtain the anti-corrosion coating.

[0025] Examples 2-5 refer to the parameter conditions in Example 1, with specific differences shown in Table 1.

[0026] Table 1 Parameters and conditions for Examples 1-5

[0027] Comparative Example 1 follows the same parameters and conditions as in Example 1, except that KH-560 was not used in the modification of the prepared modified attapulgite.

[0028] Comparative Example 2 follows the same parameters and conditions as in Example 1, except that the chelation process of phytic acid is omitted when preparing modified attapulgite.

[0029] Comparative Example 3 follows the same parameters and conditions as in Example 1, except that no modification treatment is applied to the attapulgite.

[0030] Comparative Example 4 follows the same parameters and conditions as in Example 1, except that modified attapulgite is not added.

[0031] Comparative Example 5 follows the same parameters and conditions as in Example 1, except that the sodium molybdate ion exchange step is omitted when preparing the modified hydrotalcite.

[0032] Comparative Example 6 follows the same parameters and conditions as in Example 1, except that the dopamine coating step is omitted when preparing the modified hydrotalcite.

[0033] Comparative Example 7 follows the same parameters and conditions as in Example 1, except that no modified hydrotalcite is added.

[0034] Comparative Example 8 follows the same parameters and conditions as in Example 1, except that modified hydrotalcite and modified attapulgite are added together when preparing the mixed slurry.

[0035] Comparative Example 9 follows the same parameters and conditions as in Example 1, except that the 60°C pre-curing stage is omitted.

[0036] Experimental Example 1: Adhesion and Mechanical Property Testing The adhesion of Examples 1-5 and Comparative Examples 1-9 was tested according to GB / T 1720-2020; the impact strength of Examples 1-5 and Comparative Examples 1-9 was tested according to GB / T 1732-2020; the hardness of Examples 1-5 and Comparative Examples 1-9 was tested according to GB / T 6739-2022; the results are shown in Table 2. The impact strength of Examples 1 and Comparative Examples 1-7 is as follows: Figure 1 As shown.

[0037] Table 2 Adhesion and mechanical properties of Examples 1-5 and Comparative Examples 1-9

[0038] From Table 2 and Figure 1 It can be observed that, compared with Example 1, the impact strength of Comparative Example 1 decreased significantly, and the hardness also decreased. This is because the participation of the silane coupling agent KH-560 was lacking, and the attapulgite surface could not be grafted with epoxy groups, thus failing to react with the epoxy resin matrix during curing. The nano-inorganic particles could not play a role, and when subjected to external impact, they not only failed to transfer stress but also became stress concentration points, inducing microcracks. The performance of Comparative Example 2 was significantly lower than that of Example 1 because the chelation process of phytic acid was omitted. Although KH-560 was added, the lack of oxygen-rich bridging sites on the attapulgite surface resulted in a low grafting rate of KH-560 and weak inorganic-organic interfacial bonding, causing the coating's toughness and strength to fail to reach the optimal synergistic state. The adhesion of Comparative Example 3 dropped to level 2, and the impact strength also decreased. Unmodified attapulgite is hydrophilic and oleophobic, and it will undergo severe agglomeration in mixed solvents and resins with low polarity. The large agglomerates formed defects in the paint film, destroying the coating's density and stress uniformity. The impact strength of Comparative Example 4 was severely reduced, which fully demonstrates that the toughening effect of modified attapulgite as a microscopic physical steel skeleton in the system is irreplaceable. Without the three-dimensional network support of one-dimensional nanomaterials, the pure epoxy coating exhibits extreme brittleness and is extremely susceptible to damage by external physical forces.

[0039] Comparative Example 5 maintained optimal adhesion and hardness, with slight fluctuations in impact strength. This is because sodium molybdate acts as an intercalation corrosion inhibitor, primarily responsible for chemical corrosion protection; its absence has minimal impact on the macroscopic mechanics and interfacial bonding of the coating. Comparative Example 6 showed decreased adhesion and impact strength. Omitting the dopamine coating resulted in the absence of a catechol and amino-rich polydopamine layer on the hydrotalcite surface, hindering its compatibility with the epoxy resin. The hydrotalcite was directly exposed to the resin, leading to extremely poor interfacial bonding and weakening the coating's adhesion and stress transfer. Comparative Example 7 exhibited slightly reduced adhesion and impact strength. The lack of modified hydrotalcite with strong interfacial adhesion affected the overall coating adhesion. Furthermore, the absence of an important two-dimensional sheet-like rigid filler for synergistic stress distribution meant the system's overall mechanical performance could not match that of Example 1.

[0040] Comparative Example 8 showed a comprehensive reduction in all mechanical properties. Adding the modified hydrotalcite at an early stage and subjecting it to high-speed and high-pressure shearing in a sand mill not only completely destroyed the layered structure of the hydrotalcite but also forcibly peeled off the surface polydopamine organic layer. The resulting fragmented particles were randomly distributed, losing their proper interfacial bonding ability and severely damaging the resin cross-linking network, leading to a soft and brittle paint film. Comparative Example 9 eliminated the 60℃ pre-curing process and directly baked the film, placing the freshly sprayed wet film containing the mixed solvent directly into a 90℃ environment, resulting in a severe imbalance in the coating film-forming kinetics.

[0041] Experiment Example 2: Corrosion Resistance and Aging Resistance Test According to GB / T 9274-1988, the acid resistance of Examples 1-5 and Comparative Examples 1-9 was tested under the condition of 50 g / L H2SO4 / 24h. The coatings did not crack, blister, peel, or rust, and the test results were qualified. According to GB / T 9274-1988, the alkali resistance was tested under the condition of 50 g / L NaOH / 168h. The coatings did not crack, blister, peel, or rust, and the test results were qualified. According to GB / T 1865-2009, the aging resistance of Examples 1-5 and Comparative Examples 1-9 was tested for a total duration of 1200h. The results are shown in Table 3.

[0042] Table 3. Corrosion resistance and aging resistance of Examples 1-5 and Comparative Examples 1-9

[0043] Table 3 shows that Comparative Example 1 lacks the participation of KH-560, resulting in a lack of chemical cross-linking bonds between attapulgite and the epoxy matrix. This leads to microscopic gaps at the inorganic-organic interface, making it easy for acid and alkali corrosive media to penetrate capillarily along these weak interfacial channels, causing blistering in the coating during acid and alkali tests. Simultaneously, the decreased resin cross-linking density resulted in slight chalking of the coating after 1200 hours of aging. In Comparative Example 2, the absence of the phytic acid chelation process significantly reduced the grafting rate of KH-560 on the attapulgite surface. Although it barely passed the short-term acid resistance test, the remaining interfacial defects still became the entry point for alkali intrusion during the 168-hour alkali resistance test, leading to edge blistering. Insufficient interfacial adhesion also caused slight loss of gloss under long-term UV aging. In Comparative Example 3, the unmodified attapulgite in the coating exhibited severe agglomeration, forming large structural defects on a macroscopic scale. Under acid and alkali immersion, corrosive media directly penetrated these loose agglomerates, reaching the substrate and causing severe blistering and peeling. In UV aging tests, the stress concentration effect generated by the agglomerates led to rapid powdering and macroscopic cracking of the coating. Comparative Example 4 lacked the modified attapulgite, a one-dimensional nanorod material. The coating lost its labyrinthine barrier effect, significantly shortening the downward penetration path of corrosive media, causing the substrate to be corroded and rusted by acid in a short time. Simultaneously, during the 1200-hour aging process of pure epoxy resin, the lack of inorganic rigid framework support led to the release of internal stress, resulting in microcracks on the paint film surface.

[0044] Comparative Example 5 verified the core role of molybdate. Due to the lack of an anodic corrosion inhibitor with an intercalation layer, the coating was penetrated by acid to the substrate, losing its ability to actively passivate and target repair, leading to rapid corrosion and its spread. Since the hydrotalcite and outer polydopamine were still present, its alkali resistance and UV aging resistance were not significantly affected. In Comparative Example 6, omitting the polydopamine coating resulted in direct exposure of the hydrotalcite, leading to poor interfacial compatibility and easy penetration of acid and alkali solutions, causing blistering. More seriously, without the shielding effect of polydopamine, the epoxy resin underwent severe molecular chain breakage under 1200 hours of UV irradiation, exhibiting severe yellowing and loss of gloss. In Comparative Example 7, without the addition of modified hydrotalcite, the coating lost both its ability to actively release molybdate for corrosion protection and the strong adhesion and UV resistance provided by polydopamine. Under acid and alkali immersion, the single physical defense was breached, resulting in rapid rusting and blistering. In the aging test, due to the lack of UV absorption shielding from polydopamine, the coating showed significant yellowing.

[0045] In Comparative Example 8, the high shear rate broke down the layered structure of the hydrotalcite and peeled off the polydopamine shell, causing the water-soluble sodium molybdate to be released prematurely into the coating system. This not only resulted in the loss of corrosion inhibition function, but the free salt also created a huge osmotic pressure inside the coating, causing the paint film to absorb water and blister or even peel off on a large scale when immersed in acids and alkalis. The broken polydopamine also lost its UV protection for the overall system, resulting in obvious yellowing and chalking. In Comparative Example 9, the pre-curing was eliminated and baking was carried out directly, which accelerated the cross-linking speed of the surface polyamide and epoxy resin, causing the paint film surface to form a skin quickly. This dense skin sealed off the evaporation channels of the underlying solvent, causing the residual solvent to form a large number of microscopic chambers (dark bubbles) inside the coating, weakening the coating's density and physical barrier ability. Moisture and acid and alkali media could easily enter through these micro-defects.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing an anti-corrosion coating based on attapulgite, characterized in that, Includes the following steps: A mixed slurry was prepared by mixing epoxy resin, mixed solvent, dispersant, modified attapulgite, and barium sulfate. Modified hydrotalcite, supplementary mixed solvent, leveling defoamer and curing agent are added to the mixed slurry, then coated on the substrate surface, and the anti-corrosion coating is obtained by gradient curing treatment; The modified attapulgite was obtained by modifying attapulgite with phytic acid and KH-560. The modified hydrotalcite was obtained by modifying hydrotalcite with sodium molybdate and dopamine hydrochloride.

2. The method for preparing an anti-corrosion coating based on attapulgite according to claim 1, characterized in that, The modified attapulgite is prepared by adding attapulgite powder to an HCl solution, stirring and reacting, then filtering, washing, drying and pulverizing to obtain a pretreated powder; dispersing the pretreated powder in an ethanol aqueous solution, sonicating and adding the phytic acid, refluxing and reacting, filtering and washing to obtain a chelated intermediate. The chelating intermediate was dispersed in an ethanol-water mixture to obtain a chelating solution; KH-560 was pre-dissolved in the ethanol-water mixture and hydrolyzed, then added dropwise to the chelating solution. After the reaction was completed, the mixture was filtered, washed, vacuum dried, and pulverized to obtain the modified attapulgite.

3. The method for preparing an anti-corrosion coating based on attapulgite according to claim 1, characterized in that, The modified hydrotalcite is prepared as follows: magnesium nitrate and aluminum nitrate are dissolved in decarbonized deionized water to obtain a metal salt solution; the decarbonized deionized water is added to a three-necked flask, nitrogen gas is introduced for protection, and the metal salt solution and NaOH solution are simultaneously added dropwise to the flask. After the addition is complete, stirring is continued, followed by hydrothermal aging at 100°C, washing, and vacuum drying to obtain LDH powder; the LDH powder is added to a sodium molybdate solution and sonicated, stirred under nitrogen protection, washed, and vacuum dried to obtain pretreated LDH; the pretreated LDH is dispersed in a Tris-HCl buffer solution, sonicated, and then dopamine hydrochloride is added, the reaction is stirred, centrifuged and washed, and freeze-dried to obtain the modified hydrotalcite.

4. The method for preparing an anti-corrosion coating based on attapulgite according to claim 1, characterized in that, The preparation method of the mixed slurry is as follows: E-44 epoxy resin and the mixed solvent are added to a dispersion tank, and polycarboxylate dispersant, modified attapulgite and barium sulfate are added while stirring. After stirring, the mixture is pumped into a sand mill for grinding to obtain the mixed slurry.

5. The method for preparing an anti-corrosion coating based on attapulgite according to claim 1, characterized in that, The mixed solvent includes xylene and n-butanol, with the weight ratio of xylene to n-butanol being 7:

3.

6. The method for preparing an anti-corrosion coating based on attapulgite according to claim 1, characterized in that, The preparation method of the anti-corrosion coating is as follows: the mixed slurry is transferred to a mixing tank, and the modified hydrotalcite, the supplementary mixed solvent and the organosilicon leveling defoamer are added under shear conditions at a speed of 500-800 rpm. After stirring, the mixture is filtered, and then polyamide 650 curing agent is added. After curing at room temperature, the mixture is applied to the substrate by spraying and gradient curing treatment is adopted: first, pre-curing at 60℃ for 2 hours, and then post-curing at 80-100℃ for 2 hours to obtain the anti-corrosion coating.

7. An anti-corrosion coating based on attapulgite, characterized in that, The anti-corrosion coating is prepared by the preparation method described in any one of claims 1-6; the raw materials for preparing the anti-corrosion coating include E-44 epoxy resin, modified attapulgite, modified hydrotalcite, dispersant, barium sulfate, leveling defoamer and curing agent.

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