Low-temperature curing phosphate inorganic anticorrosive coating and preparation method thereof

Abstract

The invention belongs to the technical field of inorganic anticorrosive coatings, and discloses a low-temperature curing phosphate inorganic anticorrosive coating and a preparation method thereof. The coating is prepared from the following components in parts by mass: 80 to 120 parts of aluminum phosphate binder, 5 to 18 parts of ZnO coated SiO2 core-shell structure curing agent, 0.1 to 8 parts of functional modified lamellar filler and 10 to 30 parts of deionized water. The ZnO coated SiO2 core-shell structure is constructed, the release rate of Zn < 2 + > is delayed by utilizing the physical shielding effect of the SiO2 shell layer, the problem of implosion and cracking of a phosphate system in the low-temperature curing process is solved, and stable curing of the coating at the temperature of 80 DEG C is realized. Meanwhile, the modified mica powder is introduced, the compatibility of the filler and a matrix is enhanced through interface chemical bonding, and the compactness and adhesive force of the coating are remarkably improved. The self-corrosion current density of the coating is reduced to 10 <-8 > A / cm < 2 > order of magnitude, the adhesive force reaches grade 0, and the coating has excellent long-acting corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of inorganic anti-corrosion coating technology, and relates to a low-temperature curing phosphate inorganic anti-corrosion coating and its preparation method. Background Technology

[0002] Phosphate inorganic anti-corrosion coatings, as an environmentally friendly high-performance coating, have shown great application potential in heavy-duty corrosion protection fields such as aerospace, marine engineering, and large-scale petrochemical facilities due to their excellent chemical stability, high-temperature resistance, high hardness, and non-flammability. In existing technologies, aluminum phosphate coatings mainly achieve protection of metal substrates by forming a three-dimensional network cross-linked structure through the condensation reaction between phosphate binders and hardeners. However, since this condensation reaction typically requires overcoming a high energy barrier, traditional phosphate coatings often rely on high-temperature baking above 200°C for full curing. This demanding process condition greatly limits its application in large, immovable steel structures, on-site repair work, and heat-sensitive precision metal components, becoming a key factor restricting the development of this technology.

[0003] To lower the curing temperature and adapt to a wider range of construction scenarios, researchers attempted to introduce an active curing agent into the system. While adding highly active nano-sized zinc oxide effectively catalyzes the curing of the phosphate system at around 80°C, it caused serious kinetic runaway problems in practical applications. Due to the extremely high surface energy and chemical alkalinity of nano-zinc oxide, it undergoes an extremely violent exothermic acid-base reaction and triggers explosive polymerization when in contact with acidic aluminum phosphate binders. This localized overheating-induced explosive polymerization results in enormous internal stress in the coating during the early stages of film formation. Coupled with the rapid evaporation of physical moisture, the cured coating surface is often covered with visible or microscopic cracks. These defects not only weaken the adhesion between the coating and the substrate but also allow corrosive media to directly penetrate the metal substrate surface through the cracks, leading to a decrease in corrosion resistance.

[0004] Furthermore, single inorganic film-forming systems typically exhibit brittleness and insufficient density after curing. To improve barrier properties, existing technologies often incorporate lamellar fillers. However, commonly used inorganic fillers lack active functional groups on their surfaces that can chemically bond with the phosphate matrix, resulting in a simple mechanical filling relationship between the filler and the matrix. This microscopic interfacial disconnect easily leads to the formation of continuous seepage channels within the coating. Therefore, how to achieve controlled and slow-release curing through the structural design of the curing agent, combined with surface functionalization modification of the filler to eliminate interfacial defects, is a pressing technical problem that needs to be solved in the development of high-performance low-temperature curing inorganic anti-corrosion coatings. Summary of the Invention

[0005] To address the shortcomings of existing phosphate anticorrosive coatings, such as high curing temperatures (above 200℃), uncontrolled curing kinetics leading to internal stress cracking after the introduction of active curing agents, and weak interfacial bonding between inorganic fillers and the substrate resulting in easy seepage of corrosive media, this invention provides a low-temperature curing inorganic phosphate anticorrosive coating and its preparation method. This invention achieves stable curing of the coating at 80℃ by constructing a core-shell structured curing agent with controlled-release effect and surface-functionalized lamellar shielding fillers, significantly improving the coating's density and long-term electrochemical protective capability.

[0006] The technical solution of the present invention: A low-temperature curing phosphate inorganic anti-corrosion coating, comprising the following components by weight: 80-120 parts of aluminum phosphate binder; 5-18 parts of ZnO@SiO2 core-shell structure curing agent; 0.1-8 parts of functionalized modified lamellar filler; 10-30 parts deionized water.

[0007] Preferably, in the aluminum phosphate binder, the molar ratio of phosphorus to aluminum (P / Al) is 2.5-3.5; Preferably, the P / Al molar ratio of the aluminum phosphate binder is 2.8-3.2; Preferably, the P / Al molar ratio of the aluminum phosphate binder is 3.0.

[0008] Preferably, the ZnO@SiO2 core-shell structure curing agent comprises an active core and an inorganic shell layer; Preferably, the active core is at least one of nano-sized ZnO, nano-sized MgO, and nano-sized CuO; Preferably, the active core is nano-zinc oxide with an average particle size of 50-100 nm.

[0009] Preferably, the inorganic shell is at least one of SiO2, TiO2, and Al2O3; Preferably, the inorganic shell is SiO2.

[0010] Preferably, the mass ratio of the active core to the inorganic shell in the ZnO@SiO2 core-shell structure curing agent is 1:(0.5-2.0); Preferably, the mass ratio of the active core to the inorganic shell is 1:(1.0-1.5).

[0011] Preferably, the functionalized modified sheet filler is selected from at least one of modified mica powder, modified talc powder, and modified glass microspheres; Preferably, the functionalized modified sheet filler is mica powder.

[0012] Preferably, the mica powder has a mesh size of 800-2000 mesh; Preferably, the mica powder has a mesh size of 1250.

[0013] Preferably, the surface treatment agent used for the modified mica powder is a silane coupling agent; Preferably, the silane coupling agent is selected from at least one of KH550, KH560, and KH570; Preferably, the silane coupling agent is KH550.

[0014] A method for preparing a low-temperature curing phosphate inorganic anti-corrosion coating includes the following steps: (1) Preparation of aluminum phosphate binder: Dilute phosphoric acid to the required concentration, heat to 80°C, add aluminum hydroxide powder according to the P / Al molar ratio of 2.5-3.5, stir continuously at constant temperature, and after the solution becomes completely clear and transparent, cool to room temperature to obtain aluminum phosphate binder for later use; (2) Preparation of core-shell curing agent: First, nano zinc oxide powder was added to anhydrous ethanol and ultrasonically treated; ammonia and deionized water were added successively under continuous stirring at room temperature and aging continued; under constant temperature and continuous stirring, a mixture of TEOS and anhydrous ethanol was added dropwise to the system and the reaction was continued under constant temperature and stirring; the reaction solution was centrifuged, washed and dried to obtain ZnO@SiO2 core-shell curing agent; wherein, the mass ratio of anhydrous ethanol, deionized water, ammonia, zinc oxide and TEOS was 88:17:3:1:12. (3) Mixing and blending of aluminum phosphate binder and ZnO@SiO2 core-shell curing agent: Add ZnO@SiO2 core-shell curing agent to aluminum phosphate binder and continue stirring until ZnO@SiO2 core-shell curing agent is evenly distributed to obtain initial mixed slurry; (4) Preparation of modified mica powder: First, glacial acetic acid was added dropwise to a 90% ethanol aqueous solution to adjust the pH to acidic; then silane coupling agent was added dropwise and stirred at room temperature; mica powder was added and ultrasonically dispersed, then heated to 80°C and stirred continuously; the reaction solution was centrifuged, washed and dried to obtain modified mica powder; the mass ratio of ethanol aqueous solution, mica powder and silane coupling agent was 80:1:0.1. (5) Introduction and compounding of modified filler: Add the modified lamellar filler and deionized water obtained in step (4) to the initial mixed slurry obtained in step (3), and stir evenly to obtain phosphate inorganic coating.

[0015] The beneficial effects of this invention are: (1) The ZnO@SiO2 core-shell structure curing agent constructed by the Stöber method in this invention fundamentally optimizes the curing process of the phosphate system. Due to the physical isolation effect of the SiO2 shell on the active sites of the core ZnO, the curing process of ZnO is effectively inhibited. 2+ The intense acid-base reaction with the aluminum phosphate matrix in the early stages of film formation smooths out the exothermic peak of the reaction. This mechanism successfully avoids the huge internal stress caused by explosive polymerization in existing technologies, enabling the coating to achieve stable and uniform polymerization at a low temperature of 80°C. The resulting coating surface is macroscopically dense and microscopically crack-free, providing a structural integrity basis for long-term corrosion protection.

[0016] (2) This invention achieves a leap from physical mixing to chemical bonding between inorganic fillers and phosphate matrix by performing surface functionalization modification of mica sheets in a general sense. The amino functional groups on the modified mica surface can form a strong chemical anchor with the aluminum phosphate molecular chains, greatly enhancing interfacial compatibility. This enhanced interfacial effect not only eliminates the seepage path formed by poor wettability at the filler edge, but also fundamentally improves the adhesion of the coating. Even under harsh temperature changes or humid and hot environments, the coating is not prone to peeling or blistering.

[0017] (3) This invention constructs a highly efficient physical labyrinth shielding system within the coating by optimizing the addition ratio of modified mica. The micro- and nano-sized sheet mica is arranged in parallel layers within the coating, significantly extending the diffusion path of corrosive media such as water molecules, oxygen, and chloride ions to the metal substrate. Experimental results show that the coating obtained by this invention can reduce the self-corrosion current density in 3.5 wt.% NaCl solution by two orders of magnitude, demonstrating excellent long-term electrochemical inhibition capability. Attached Figure Description

[0018] Figure 1 These are surface morphology diagrams of Embodiment 1 and Comparative Example 1 of the present invention; wherein, (a) Embodiment 1; (b) Comparative Example 1.

[0019] Figure 2 These are thermal performance comparison graphs of Embodiment 1 and Comparative Example 1 of the present invention; wherein, (a) TG curve; (b) DTG curve.

[0020] Figure 3 These are contact angle test results of Embodiment 1, Comparative Example 1, Embodiment 2, Comparative Example 2, and Comparative Example 3 of the present invention; wherein, (a) Embodiment 1; (b) Comparative Example 1; (c) Embodiment 2; (d) Comparative Example 2; and (e) Comparative Example 3.

[0021] Figure 4These are adhesion test results of Examples 1, 1, 2, 2 and 3 of the present invention; wherein, (a) Example 1; (b) 1, 2, 3; (c) Example 2; (d) 2, 3; and (e) 3.

[0022] Figure 5 These are polarization curve test results of Embodiment 1, Comparative Example 1, Embodiment 2, Comparative Example 2, and Comparative Example 3 of the present invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0024] The research logic of this invention is divided into two stages: the first stage focuses on verifying the regulatory effect of ZnO@SiO2 core-shell structure curing agent on the curing kinetics of phosphate system; the second stage, based on the stable curing of core-shell structure, introduces functionalized modified lamellar filler, and improves the adhesion and protective performance of coating through the synergistic effect of interfacial chemical bonding and physical shielding effect.

[0025] Example 1 1 g of nano-zinc oxide powder was placed in a beaker. 100 ml of anhydrous ethanol was added as a dispersion medium, and the beaker was ultrasonically treated in an ultrasonic cleaner for 30 min. 3 ml of concentrated ammonia and 17 ml of deionized water were added sequentially under stirring at 500 rpm, and the mixture was aged for 10 min under constant temperature and stirring conditions. Subsequently, a mixture of 12 ml of TEOS and 12 ml of anhydrous ethanol was added dropwise to the system, and the reaction was continued under constant temperature and stirring for 2 h. The reaction solution was centrifuged, washed, and dried at 80℃ for 6 h to obtain the ZnO@SiO2 core-shell curing agent.

[0026] Weigh 100 ml of a 90% (w / w) ethanol aqueous solution and add an appropriate amount of glacial acetic acid to adjust the pH of the solution to approximately 4. Weigh 1 ml of coupling agent and add it dropwise to the above acidic solvent. Place the beaker on a magnetic stirrer and stir at 500 r / min for 60 min at 25°C. Weigh 10 g of raw mica powder and place it in a 500 mL flask, then slowly pour in the pre-hydrolyzed silane solution. Disperse the mixture ultrasonically for 20 min, then stir at 500 r / min for 60 min at 80°C. Centrifuge, wash, and dry at 80°C for 6 h to obtain the modified mica powder. Take 100 parts by weight of aluminum phosphate binder, add 10 parts of ZnO@SiO2 core-shell curing agent, and stir evenly. Then add 5 parts of silane coupling agent modified mica powder and 20 parts of deionized water, and stir at 500 r / min for 60 min. Spray the evenly mixed coating evenly onto the surface of the metal substrate, allow it to dry and level at room temperature for 30 min, and then transfer it to a constant temperature oven for curing at 80℃ for 6 hours.

[0027] Comparative Example 1 This comparative example provides a phosphate inorganic anti-corrosion coating.

[0028] The preparation steps are basically the same as in Example 1. The difference is that 10 parts of untreated nano-zinc oxide curing agent are directly added to replace the ZnO@SiO2 core-shell curing agent in Example 1. The remaining raw materials, proportions, and process steps are completely consistent with those in Example 1.

[0029] Example 2 This embodiment provides a phosphate inorganic anti-corrosion coating.

[0030] The preparation steps are basically the same as in Example 1. The difference is that, by mass, 120 parts of aluminum phosphate binder, 18 parts of ZnO@SiO2 core-shell curing agent, 8 parts of silane coupling agent modified mica powder, and 30 parts of deionized water are used. The remaining raw materials, proportions, and process steps are completely consistent with those in Example 1.

[0031] Example 3 This embodiment provides a phosphate inorganic anti-corrosion coating.

[0032] The preparation steps are basically the same as in Example 1. The difference is that, by mass, 80 parts of aluminum phosphate binder, 5 parts of ZnO@SiO2 core-shell curing agent, 0.1 parts of silane coupling agent modified mica powder, and 10 parts of deionized water are used. The remaining raw materials, proportions, and process steps are completely consistent with those in Example 1.

[0033] Comparative Example 2 This comparative example provides a phosphate inorganic anti-corrosion coating.

[0034] The preparation steps are basically the same as in Example 2. The difference is that 8 parts of unmodified mica powder are added to replace the silane coupling agent-modified mica powder in Example 2. The remaining raw materials, proportions, and process steps are completely consistent with Example 2.

[0035] Comparative Example 3 This comparative example provides a phosphate inorganic anti-corrosion coating.

[0036] The preparation steps are basically the same as in Example 2. The difference is that the proportion of silane coupling agent modified mica powder exceeds the limits of this invention. By mass fraction, 12 parts of silane coupling agent modified mica powder are used to replace 8 parts in Example 2. The remaining raw materials, proportions, and process steps are completely consistent with Example 2.

[0037] Performance tests were performed on Examples 1, 2, 1, 2, 3, 4, and 5. Microstructure tests were performed on Examples 1 and 1, as follows: Figure 1 As shown, the thermal performance test is as follows: Figure 2 As shown; wettability tests were performed on Example 1, Comparative Example 1, Example 2, Comparative Example 2, and Comparative Example 3 as follows. Figure 3 As shown, the adhesion test is as follows: Figure 4 As shown, the polarization curve test is as follows: Figure 5 As shown, electrochemical impedance spectroscopy and immersion tests were performed. Table 1 summarizes the results of wettability, adhesion, electrochemical tests, and immersion tests.

[0038] Table 1 Performance test results of the examples and comparative examples

[0039] according to Figure 1 The microstructure of the coating surface is shown in the comparison. Figure 1 (b) The coating surface of Comparative Example 1 exhibits obvious, wide, and penetrating cracks. This indicates that the uncoated nano-zinc oxide, due to its excessively high curing activity, reacts too violently with the phosphate matrix, resulting in the generation and instantaneous release of enormous internal stress during film formation. Figure 1 (a) The coating surface of Example 1 is dense and crack-free. This demonstrates that the ZnO@SiO2 core-shell structure achieves controllable regulation of the reaction rate and eliminates internal stress in film formation by physically shielding the activity of the curing agent.

[0040] according to Figure 2 As shown in the thermal performance comparison curves, the weight loss process of Example 1's TG curve is smoother compared to Comparative Example 1. Figure 2 As shown in the DTG curve in (b), the peak weight loss rate of Example 1 is significantly reduced and shifts towards higher temperatures. This confirms that the core-shell structure curing agent effectively suppresses the intense exothermic reaction and instantaneous moisture evaporation during the initial curing stage. By slowing down the chemical reaction kinetics, it ensures that the coating can achieve stable curing with structural integrity at a low temperature of 80°C. As shown in Table 1, the low-temperature curing phosphate inorganic anti-corrosion coating prepared in this invention possesses excellent comprehensive performance. The ZnO@SiO2 core-shell structure curing agent prepared using the Stöber method regulates the release rate of the active zinc oxide center through the physical barrier effect of the silica shell, achieving low-temperature curing at 80℃ while avoiding film cracking caused by excessively rapid acid-base reactions, thus ensuring the density and structural integrity of the coating surface. By using a silane coupling agent to modify the surface of lamellar mica powder, chemical bonding replaces the traditional physical mixing, significantly improving the interfacial compatibility between the inorganic filler and the aluminum phosphate matrix. This results in an increase in coating adhesion from grade 3 to grade 0, and a significant increase in contact angle. The silane coupling agent-modified mica powder, working in conjunction with the core-shell curing agent, constructs a dense physical labyrinth shielding system within the coating, effectively extending the penetration path of corrosive media. This enables the coating to achieve a self-corrosion current density as low as 2.02 × 10⁻⁶. - 8 A / cm 2 And a immersion failure period of up to 40 days.

[0041] The above-described embodiments are merely illustrative of the implementation methods of the present invention, but should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A low-temperature curing phosphate inorganic anti-corrosion coating, characterized in that, This low-temperature curing phosphate inorganic anti-corrosion coating comprises the following components by weight: 80-120 parts of aluminum phosphate binder; 5-18 parts of ZnO@SiO2 core-shell structure curing agent; 0.1-8 parts of functionalized modified lamellar filler; 10-30 parts deionized water.

2. The low-temperature curing phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, In the aluminum phosphate binder, the molar ratio of phosphorus to aluminum, P / Al, is 2.5-3.

5.

3. The low-temperature curing phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The ZnO@SiO2 core-shell structure curing agent includes an active core and an inorganic shell layer; The active core is at least one of nano-sized ZnO, nano-sized MgO, and nano-sized CuO; The inorganic shell is at least one of SiO2, TiO2, and Al2O3; The mass ratio of the active core to the inorganic shell in the ZnO@SiO2 core-shell structure curing agent is 1:(0.5-2.0).

4. The low-temperature curing phosphate inorganic anti-corrosion coating according to claim 1, characterized in that, The functionalized modified sheet filler is selected from at least one of modified mica powder, modified talc powder, and modified glass microspheres.

5. The low-temperature curing phosphate inorganic anti-corrosion coating according to claim 4, characterized in that, The functionalized modified sheet filler is modified mica powder; The modified mica powder has a mesh size of 800-2000 mesh; The modified mica powder uses a silane coupling agent as its surface treatment agent. The silane coupling agent is selected from at least one of KH550, KH560, and KH570.

6. A method for preparing a low-temperature curing phosphate inorganic anti-corrosion coating according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Preparation of aluminum phosphate binder: Dilute phosphoric acid to the required concentration, heat to 80°C, add aluminum hydroxide powder according to the P / Al molar ratio of 2.5-3.5, stir continuously at constant temperature, and after the solution becomes completely clear and transparent, cool to room temperature to obtain aluminum phosphate binder for later use; (2) Preparation of core-shell curing agent: First, nano zinc oxide powder was added to anhydrous ethanol and ultrasonically treated; ammonia water and deionized water were added successively under continuous stirring at room temperature and aging continued; under constant temperature and continuous stirring, a mixture of TEOS and anhydrous ethanol was added dropwise to the system and the reaction was continued under constant temperature and stirring; the reaction solution was centrifuged, washed and dried to obtain ZnO@SiO2 core-shell curing agent; (3) Mixing and blending of aluminum phosphate binder and ZnO@SiO2 core-shell curing agent: Add ZnO@SiO2 core-shell curing agent to aluminum phosphate binder and continue stirring until ZnO@SiO2 core-shell curing agent is evenly distributed to obtain initial mixed slurry; (4) Preparation of modified mica powder: First, glacial acetic acid was added dropwise to a 90% ethanol aqueous solution to adjust the pH to acidic; then silane coupling agent was added dropwise and stirred at room temperature; mica powder was added and ultrasonically dispersed, then the temperature was raised to 80°C and stirred continuously; the reaction solution was centrifuged, washed and dried to obtain modified mica powder. (5) Introduction and compounding of modified filler: Add the modified lamellar filler and deionized water obtained in step (4) to the initial mixed slurry obtained in step (3), and stir evenly to obtain phosphate inorganic coating.

7. The method for preparing the low-temperature curing phosphate inorganic anti-corrosion coating according to claim 6, characterized in that, In step (2), the mass ratio of anhydrous ethanol, deionized water, ammonia, zinc oxide, and TEOS is 88:17:3:1:

12.

8. The method for preparing the low-temperature curing phosphate inorganic anti-corrosion coating according to claim 6, characterized in that, In step (2), the mass ratio of ethanol aqueous solution, mica powder, and silane coupling agent is 80:1:0.1.

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