A self-repairing enamel coating for reinforcing steel and a method for preparing the same

Abstract

The application discloses a self-repairing enamel coating for reinforcing steel bars, which comprises an enamel base body and microcapsules, wherein the microcapsules comprise a shell layer, a quality layer and a core layer; the preparation ingredients of the shell layer comprise tetraethoxysilane 10-20 parts, ethanol 15-30 parts, ammonia water 1-5 parts and water 10-20 parts; the quality layer is located on the inner side of the shell layer and is selected from one or more than two of boron nitride, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide or silicon carbide; and the core layer is located on the inner side of the quality layer and is selected from sodium silicate, zirconium silicate, calcium silicate, calcium titanate or barium titanate. The application further discloses a preparation method of the self-repairing enamel coating for reinforcing steel bars. By introducing the microcapsules into the enamel coating, the service life of the coating is remarkably improved. The enamel coating with self-repairing capability can timely repair the microcracks and damages of the coating in the use process, prevent the corrosion medium from further corroding, thereby prolonging the service life of the reinforcing steel bars and the like base materials and improving the safety and stability of the building structure.

Description

Technical Field

[0001] This invention belongs to the technical field of ceramic coatings and self-healing materials, and in particular relates to a self-healing enamel coating for steel bars and its preparation method. Background Technology

[0002] In the field of materials science, enamel coatings are widely used in various industrial sectors such as construction, chemical engineering, and energy due to their excellent hardness, wear resistance, corrosion resistance, and high-temperature stability. As a protective coating, enamel coatings can effectively isolate external corrosive media, especially performing well in high-temperature and acid / alkali environments. However, the inherent brittleness of enamel materials and their high sensitivity to crack propagation have become the main bottlenecks limiting their service life and protective effectiveness. Once microcracks appear in the enamel coating, external media can easily penetrate into the substrate through the cracks, leading to coating failure. This not only affects the protective performance of the coating but may even threaten the structural safety of the protected material.

[0003] In recent years, self-healing materials, as an emerging type of smart material, have been widely researched and applied in the field of coating technology. Self-healing materials can automatically repair cracks or damage after being damaged through internal repair mechanisms, thereby restoring their original mechanical and protective properties. In the application of enamel coatings, microencapsulation technology is widely considered one of the effective methods to achieve self-healing. Microcapsules encapsulate a repair agent within a shell; when the coating is damaged, the microcapsules rupture to release the repair agent, thereby filling the cracks and restoring the coating's performance. The application of this technology not only extends the service life of the coating but also enables it to maintain long-term protective performance in harsh environments.

[0004] Nevertheless, most enamel coatings currently lack self-healing capabilities, meaning they cannot repair themselves once cracks appear during long-term use. This problem is particularly prominent in the protection of building materials such as reinforcing steel. As a crucial component of building structures, reinforcing steel is frequently exposed to the natural environment and is susceptible to corrosive substances such as acids, alkalis, and salts. The formation of cracks further accelerates the corrosion of the reinforcing steel, seriously threatening the safety and stability of the building structure.

[0005] Several patents have proposed partial solutions to this problem. For example, Chinese patent CN108531908A discloses a double-layer metal anti-corrosion coating, which mainly solves the problem of mismatch in thermal expansion coefficients between the coating and the metal substrate, thus improving the service life of the anti-corrosion coating. However, it mentions little about the self-healing function of the coating and cannot effectively solve the long-term protection problem caused by crack propagation. CN202410314291 discloses a method for preparing an acid, alkali, and salt resistant enamel coating. Although it improves the corrosion resistance of the coating to a certain extent, its production process is complex and costly, making it difficult to achieve large-scale application. CN202410377987 significantly enhances the self-healing performance of concrete by introducing polymer microcapsule technology, but the stability and repair effect of this technology in strongly alkaline environments still need to be improved. In addition, Chinese patent CN118599379A discloses a self-healing superhydrophobic nano-anti-corrosion coating, which achieves self-healing function by adding microcapsules to the coating. Although it improves the protective effect of the coating, the hydrophobicity decreases after self-healing, affecting its long-term reliability.

[0006] Traditional microencapsulation technologies mostly employ core-shell structures, which often limit their application in complex or extreme environments. In strongly alkaline environments, the shell structure of core-shell microcapsules is relatively fragile and prone to rupture, leading to premature leakage of the repair agent and ineffective coating repair. Furthermore, the release mechanisms of existing microcapsules are relatively simple, making precise control based on the degree of coating damage difficult, further limiting the adaptability of self-healing coatings in different application scenarios. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a self-healing enamel coating for reinforcing bars and its preparation method. The coating is loaded with microcapsules with a core-shell structure. The microcapsules are dispersed in the enamel matrix, giving it a self-healing function under alkaline conditions. The preparation method significantly improves the corrosion resistance and service life of the coating, making it particularly suitable for industrial applications in harsh environments, such as corrosion protection of building structures.

[0008] The technical solution adopted by this invention to solve its technical problem is: a self-healing enamel coating for reinforcing bars, comprising:

[0009] Enamelled substrate and microcapsules, wherein the microcapsules comprise,

[0010] The shell layer is prepared by including 10-20 parts of tetraethoxysilane, 15-30 parts of ethanol, 1-5 parts of ammonia, and 10-20 parts of water.

[0011] The stromal layer, located inside the shell, is selected from one or more of boron nitride, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide, or silicon carbide.

[0012] The core layer, located inside the plasmid, is made of sodium silicate, zirconium silicate, calcium silicate, calcium titanate, or barium titanate.

[0013] During the preparation of the shell layer, a shell material with high-temperature stability is generated through a sol-gel reaction. During the preparation of the plasmid layer, heat treatment ensures that the plasmid can be completely volatilized during high-temperature calcination, reducing the impact on the coating structure. During the preparation of the core layer, the stirring speed needs to be controlled at 200-600 RPM to ensure uniform microcapsule size and prevent leakage of the core layer material.

[0014] Furthermore, the enamel matrix comprises 23-28 parts of phosphorus pentoxide, 15-20 parts of aluminum oxide, 10-15 parts of sodium oxide, 10-14 parts of potassium oxide, 8-15 parts of boron trioxide, 5-10 parts of calcium fluoride, 5-10 parts of lithium oxide, 5-10 parts of silicon dioxide, 2-5 parts of calcium oxide, 1-3 parts of nickel oxide, 1-3 parts of cobalt oxide, and 1-3 parts of zirconium dioxide.

[0015] The shell of the microcapsule is made of silica sol, specifically prepared by using tetraethoxysilane (TEOS), ethanol, ammonia as an alkaline catalyst, and water. It has good high-temperature stability, ensuring that it remains intact during the high-temperature calcination process of the enamel coating.

[0016] The microcapsule's core layer is located between the shell and core layers, exhibiting good thermal stability and completely volatilizing during calcination, ensuring that the overall performance of the coating is not affected.

[0017] The repair agent, acting as the core material, is used to repair damaged enamel enamel sections when the microcapsule shell breaks down due to alkaline corrosion, releasing the repair agent from the core. The core material must possess good chemical stability to ensure effective release of the repair agent when the coating is damaged. The selected polymer should exhibit good biocompatibility and environmental adaptability, and ensure its integrity under strongly alkaline conditions, thus providing the enamel with self-healing capabilities in alkaline environments. The selected materials meet these criteria.

[0018] Furthermore, the preparation reaction temperature of the shell layer is 25-30℃; the preparation reaction temperature of the plasmid layer is 200-300℃; and the preparation reaction temperature of the core layer is 60-70℃.

[0019] Furthermore, the coating thickness is 300-500 micrometers.

[0020] Furthermore, it exhibits self-repairing capabilities in alkaline environments.

[0021] Furthermore, the microcapsules are uniformly dispersed in the enamel matrix, and the content ratio of microcapsules to enamel matrix is ​​5-15%.

[0022] This invention also discloses a method for preparing a self-healing enamel coating for reinforcing bars, comprising the following steps:

[0023] To prepare the microcapsules, 10-20 parts of tetraethoxysilane were added to a reactor, and 15-30 parts of ethanol were slowly added and stirred until homogeneous. 1-5 parts of ammonia were gradually added as an alkaline catalyst, and the reaction temperature was controlled at 25-30℃ for 4 hours, so that the silica sol formed the shell of the microcapsules.

[0024] Mix 5-15 parts boron nitride, 10-20 parts alumina and 5-15 parts zirconium oxide in a certain proportion, gradually add them to the shell material, stir evenly, and heat treat at 200-300℃.

[0025] Add 10-20 parts of sodium silicate, 10-20 parts of zirconium silicate and 10-20 parts of barium titanate to the reactor, heat to 60-70℃, and encapsulate the repair agent in the shell through interfacial polymerization technology to form a core-plasma-shell structured microcapsule.

[0026] For the preparation of the enamel substrate, 23-28 parts of phosphorus pentoxide, 15-20 parts of aluminum oxide, 10-15 parts of sodium oxide, and 10-14 parts of potassium oxide matrix raw materials are mixed in proportion, and an appropriate amount of deionized water is added and stirred evenly.

[0027] The prepared microcapsule material is uniformly dispersed in the enamel matrix to ensure thorough mixing.

[0028] Furthermore, in the preparation step of forming the core-plasma-shell structure of the microcapsules, the stirring speed is 200-600 RPM.

[0029] The prepared enamel coating is evenly applied to the surface-treated reinforcing steel. Common methods include dip coating, spray coating, or brush coating, with the specific method chosen based on the required coating thickness and uniformity. The coating thickness should be controlled between 300 and 500 micrometers to ensure good mechanical strength and corrosion resistance during application.

[0030] The mixture is poured into a mold and calcined at 800-900℃ for 30 minutes to ensure complete curing of the enamel coating and to maintain the structural stability of the microcapsules at high temperatures, while also giving the coating a self-healing function under alkaline conditions.

[0031] After calcination, the reinforcing bars should be slowly cooled to room temperature to prevent thermal stress caused by sudden temperature changes, which could lead to coating cracking. Depending on the specific needs, surface passivation or other protective treatments can also be performed to enhance the durability and corrosion resistance of the coating on the reinforcing bar surface.

[0032] Through the above steps, the enamel coating provided by this invention can not only maintain excellent mechanical strength and durability under high-temperature calcination conditions, but also has the function of automatically repairing damaged areas in alkaline environments. It is suitable for corrosion protection of building materials such as steel bars, and significantly extends their service life.

[0033] To address the problems mentioned in the background art, this invention proposes a polymer microcapsule with a core-plasma-shell three-layer structure, whose application in enamel coating self-healing technology can significantly improve the protective effect and durability of the coating. This microcapsule encapsulates the repair agent through a core layer, provides protection and release control through a plasma layer, and ensures that the microcapsule maintains high structural integrity even in extreme environments. Compared with traditional core-shell microcapsules, the core-plasma-shell microcapsule not only possesses stronger corrosion resistance and environmental adaptability, but also can precisely release the repair agent according to changes in the external environment and the degree of damage, thereby improving the self-healing effect of the coating.

[0034] This invention, through optimized design of the microcapsule structure, enables it to remain stable in strongly alkaline environments, making it particularly suitable for the protection of critical building materials such as reinforcing steel. The self-healing microcapsules in the enamel coating can promptly repair micro-cracks caused by external forces or environmental factors, preventing corrosive media from penetrating to the surface of the reinforcing steel, thereby extending the service life of the steel and improving the safety of building structures. This has significant practical implications for the sustainable development of the construction industry.

[0035] The enamel coating of this invention employs a core-mass-shell three-phase microcapsule structure, which provides stronger structural stability compared to traditional enamel coatings. This three-layer microcapsule structure effectively resists external mechanical forces and chemical erosion, reducing the breakage rate of the microcapsules during use, thereby improving the overall durability and reliability of the enamel coating.

[0036] The core-shell structure endows the microcapsules with better environmental responsiveness, enabling precise control of the release of the repair agent when enamel is damaged in a strongly alkaline environment. This controllability ensures that the repair agent is activated only when the enamel coating is damaged, improving repair efficiency and material lifespan, allowing the enamel coating to self-repair in a timely and effective manner.

[0037] The microcapsule shell is made of silica, which exhibits excellent stability at high temperatures. The enamel coating of this invention undergoes high-temperature calcination during preparation. The silica shell ensures the integrity of the microcapsules during coating preparation, preventing premature rupture or failure of the repair agent due to high temperatures, thus ensuring that the enamel coating maintains good performance even at high temperatures.

[0038] The polymer material selected for the core layer not only possesses excellent chemical stability but also exhibits biocompatibility and environmental adaptability. This allows the enamel coating to maintain its repair function even in strongly alkaline environments, broadening its application range and enabling it to function stably in various complex environments.

[0039] By introducing the microcapsules of this invention into the enamel coating, the service life of the coating is significantly improved. The self-healing enamel coating can promptly repair microcracks and damage that occur during use, preventing further erosion by corrosive media, thereby extending the service life of substrates such as reinforcing steel and improving the safety and stability of building structures. Attached Figure Description

[0040] Figure 1 This is a schematic diagram illustrating the self-healing process of the enamel coating containing self-healing capsules under alkaline conditions according to the present invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions in 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 a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0042] Example 1

[0043] A self-healing enamel coating for reinforcing bars includes: an enamel substrate and microcapsules. The microcapsules include: a shell layer, the preparation of which comprises 10-20 parts tetraethoxysilane, 15-30 parts ethanol, 1-5 parts ammonia, and 10-20 parts water; a core layer, located inside the shell layer, selected from one or more of boron nitride, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide, or silicon carbide; and a core layer, located inside the core layer, selected from sodium silicate, zirconium silicate, calcium silicate, calcium titanate, or barium titanate.

[0044] The enamel matrix comprises 23-28 parts of phosphorus pentoxide, 15-20 parts of aluminum oxide, 10-15 parts of sodium oxide, 10-14 parts of potassium oxide, 8-15 parts of boron trioxide, 5-10 parts of calcium fluoride, 5-10 parts of lithium oxide, 5-10 parts of silicon dioxide, 2-5 parts of calcium oxide, 1-3 parts of nickel oxide, 1-3 parts of cobalt oxide, and 1-3 parts of zirconium dioxide.

[0045] In this embodiment, the content ratio of microcapsules to enamel matrix is ​​8%.

[0046] The coating material is calcined at high temperature, and the microcapsules maintain their structural stability, ensuring that the coating has the function of self-repair in alkaline environment, which significantly improves the anti-corrosion performance of the coating.

[0047] Before applying the coating, the surface of the reinforcing steel needs to be pretreated to ensure that the coating can adhere firmly. Common surface treatment steps include:

[0048] Cleaning: Use degreasers, acidic solutions or alkaline solutions to clean the surface of the steel bars to remove grease, oxides, rust and other contaminants.

[0049] Pickling: Remove surface rust by pickling (such as using dilute sulfuric acid or hydrochloric acid), and rinse after cleaning.

[0050] Surface passivation: Treatment with passivating agents (such as phosphoric acid or passivating solution) to reduce the activity of the steel reinforcement surface and increase the adhesion of the coating.

[0051] A method for preparing a self-healing enamel coating for reinforcing bars includes the following steps:

[0052] 1) Surface treatment of reinforcing bars:

[0053] First, cut 10mm diameter steel bars into 1-meter long samples. To ensure good coating adhesion, the steel bar surface needs to be thoroughly cleaned. Use a degreaser to clean the steel bar surface to remove oil and impurities. After cleaning, immerse the steel bar in a 10% dilute sulfuric acid solution for 30 minutes to effectively remove oxides and rust from the steel bar surface. After pickling, rinse the surface thoroughly with clean water. Next, immerse the steel bar in a phosphoric acid solution for passivation for 5 minutes. This step reduces the activity of the steel bar surface and increases the adhesion of the coating. After passivation, the steel bar needs to be air-dried for later use.

[0054] 2) Preparation of microcapsule shells:

[0055] To enhance the self-healing function of the coating, microencapsulation technology was employed. 15 parts tetraethoxysilane (TEOS), 25 parts ethanol, 3 parts ammonia, and 15 parts water were sequentially added to a reactor and stirred at 28°C for 4 hours. During this process, the generated silica sol forms a microcapsule shell with high-temperature stability, which remains intact during subsequent high-temperature calcination, ensuring the stability of the coating.

[0056] 3) Preparation of the plasmolayer:

[0057] To ensure the microcapsules can perform self-healing under high-temperature conditions, 10 parts boron nitride, 15 parts alumina, and 10 parts zirconium oxide were mixed in a specific ratio and gradually added to the prepared shell material, stirring until homogeneous. The shell material was then heated at 250°C for 1 hour to ensure complete volatilization during the high-temperature calcination process, minimizing its impact on the coating structure.

[0058] 4) Preparation of the core layer:

[0059] Next, 15 parts of sodium silicate, 15 parts of zirconium silicate, and 15 parts of barium titanate were stirred at 65°C at a stirring speed of 200-600 RPM. Interfacial polymerization was used to encapsulate the repair agent within a shell, forming a core-plasma-shell three-layer microcapsule structure. This process requires ensuring uniform stirring speed to prevent leakage of the core material. The prepared microcapsules were dried at 100°C and then sieved to obtain microcapsule products with uniform particle size.

[0060] 5) Preparation and coating of enamel substrate:

[0061] A mixture of 25 parts phosphorus pentoxide, 18 parts alumina, 12 parts sodium oxide, 12 parts potassium oxide, 10 parts boron trioxide, 8 parts calcium fluoride, 6 parts lithium oxide, 7 parts silicon dioxide, 3 parts calcium oxide, 2 parts nickel oxide, and 2 parts cobalt oxide was prepared according to the formula to form an enamel matrix slurry. The prepared microcapsules were added to the enamel matrix at 5% of the total weight and stirred until uniformly distributed. The mixture was then uniformly coated onto the surface of a surface-treated steel reinforcement, with the coating thickness controlled at 400 micrometers.

[0062] 6) High-temperature calcination and cooling:

[0063] After coating, the reinforcing steel is placed in a high-temperature furnace and calcined at 850°C for 30 minutes. At this temperature, the enamel coating fully cures and ensures the structural stability of the microcapsules, giving the coating self-healing capabilities in alkaline environments. After calcination, the reinforcing steel needs to be slowly cooled to room temperature to prevent the coating from cracking or peeling due to a sudden drop in temperature.

[0064] The self-healing enamel coating for steel bars prepared by the method in Example 1 not only has excellent anti-corrosion performance, but also can automatically release repair agent when the coating is subjected to minor damage, repair cracks in time, and extend the service life of the coating.

[0065] Example 2

[0066] Based on Example 1, 5 parts of titanium dioxide were added to the shell material of the microcapsules to enhance their high-temperature stability. The preparation method of the microcapsules was the same as in Example 1, and the plasma and core materials remained unchanged.

[0067] In this embodiment, 5 parts of titanium dioxide were added to the shell material of the microcapsules. The introduction of titanium dioxide enhances the mechanical strength and chemical resistance of the microcapsules under high-temperature environments. This is because titanium dioxide possesses excellent heat resistance and stability, which can improve the structural integrity of the shell during calcination, thereby preventing the microcapsule shell from cracking or being damaged due to high temperatures. In addition, titanium dioxide can also improve the crack resistance of the shell, enabling the microcapsules to maintain their functionality during calcination, ultimately improving the self-healing performance and corrosion resistance of the coating under extreme environments.

[0068] Example 3

[0069] Based on Example 1, the base coat material was changed to 7 parts magnesium oxide, 10 parts aluminum oxide, and 5 parts silicon carbide. The base coat material completely volatilizes at high temperatures, ensuring that the microcapsules do not rupture during calcination. This change in base coat material aims to improve the volatility of the microcapsules during high-temperature calcination, ensuring complete volatilization under high-temperature conditions without affecting the overall structure of the coating. Magnesium oxide and silicon carbide, as base coat materials, possess good high-temperature resistance and volatility, ensuring stable decomposition of the base coat during calcination. This improvement not only ensures complete volatilization of the base coat but also enhances the mechanical stability of the coating through the addition of silicon carbide, reducing crack formation and thus improving the protective effect of the coating.

[0070] Example 4

[0071] In this embodiment, the surface treatment process of the reinforcing steel was adjusted, shortening the pickling time to 20 minutes and extending the passivation time to 10 minutes. Shortening the pickling time avoids corrosion damage to the reinforcing steel surface due to excessive pickling; while extending the passivation time further enhances the adhesion between the coating and the reinforcing steel surface, improving the coating's durability. This improvement is because properly controlling the pretreatment process of the reinforcing steel surface not only reduces surface defects but also increases coating adhesion, thereby improving the coating's mechanical strength and corrosion resistance.

[0072] Example 5

[0073] In this embodiment, the coating thickness is adjusted from 400 micrometers to 500 micrometers. The reason for increasing the coating thickness is that a thicker coating provides a better physical barrier, reducing the chance of corrosive media penetrating the steel reinforcement surface. A thicker coating improves corrosion resistance and enhances the wear resistance of the steel reinforcement. However, increasing the coating thickness also requires precise control of temperature and time during the calcination process to avoid excessive thickness leading to cracking or peeling. Therefore, this improved coating thickness enhances protective performance while avoiding the problems caused by excessive thickness.

[0074] Example 6

[0075] In this embodiment, barium titanate in the microcapsule core material is replaced with calcium silicate. Calcium silicate, as a core material, exhibits higher chemical stability, especially demonstrating excellent corrosion resistance in strongly alkaline environments. Calcium silicate can release a repair agent upon microcapsule rupture and react rapidly upon contact with alkaline media to form a protective layer, effectively repairing coating cracks. Therefore, replacing it with calcium silicate not only improves self-healing efficiency but also enhances the coating's protective effect in extremely corrosive environments.

[0076] Example 7

[0077] In this embodiment, the composition of the base coat material was adjusted to a combination of 8 parts boron nitride, 12 parts alumina, and 10 parts zirconium oxide. This adjustment aims to further enhance the volatility and thermal stability of the base coat material during calcination. The increased proportion of alumina helps enhance the heat resistance of the base coat, while the increased boron nitride improves its thermal conductivity, allowing for more uniform volatilization during high-temperature calcination and ensuring complete disappearance of the base coat material. The stability of zirconium oxide provides better mechanical strength to the base coat, preventing structural damage to the microcapsules during calcination. This optimized composition, by enhancing the volatility and stability of the base coat material, further improves the coating's self-healing and corrosion-resistant properties, particularly demonstrating greater stability under extreme temperature conditions.

[0078] Example 8

[0079] In this embodiment, the core layer material was adjusted from 15 parts zirconium silicate and 10 parts barium titanate to 12 parts calcium silicate and 15 parts calcium titanate. The combination of calcium silicate and calcium titanate provides higher self-healing efficiency. Calcium silicate exhibits excellent reactivity in alkaline media, enabling rapid crack filling, while the addition of calcium titanate provides stronger structural support and crack resistance to the core layer. Calcium titanate possesses good chemical corrosion resistance and thermal stability, forming a robust protective layer while repairing cracks, preventing secondary corrosion. This improvement in the core layer material significantly enhances the self-healing effect of the microcapsules in strongly alkaline environments, further improving the corrosion resistance of the coating, making it suitable for reinforced steel structures exposed to harsh environments for extended periods.

[0080] Comparative Example 1

[0081] In this comparative example, the preparation of the enamel coating on the reinforcing steel bars did not use microencapsulation technology; other process steps were consistent with Example 1. By comparison, the impact of microcapsules on self-healing ability and corrosion resistance can be evaluated.

[0082] Reinforcing bar surface treatment: Same as in Example 1, clean, pickle and passivate the reinforcing bar surface.

[0083] Preparation of the enamel substrate: Phosphorus pentoxide, aluminum oxide, sodium oxide, potassium oxide, and other substrate raw materials were mixed in a specific ratio, and an appropriate amount of deionized water was added and stirred until homogeneous. Since this comparative example does not use microcapsules, no microcapsule materials were added.

[0084] Coating application: The enamel substrate slurry is evenly applied to the surface of the treated steel bars, and the coating thickness is controlled at 400 micrometers.

[0085] High-temperature calcination: calcined at 850℃ for 30 minutes, then slowly cooled to room temperature.

[0086] In this comparative example, the self-healing ability of the coating is significantly reduced due to the absence of microcapsules. If cracks or damage occur during use, the enamel coating cannot automatically recover through its self-healing mechanism. Furthermore, its corrosion resistance also decreases due to the lack of release of repair agents, especially under prolonged exposure to corrosive environments, resulting in poor coating durability.

[0087] Comparative Example 2

[0088] In this comparative example, the reinforcing bars were not subjected to pickling and passivation treatment; other process steps were consistent with Example 1. By comparison, the impact of reinforcing bar surface pretreatment on coating adhesion and corrosion resistance can be evaluated.

[0089] Surface treatment of reinforcing bars: pickling and passivation steps are omitted, and only basic surface cleaning is performed.

[0090] Microcapsule preparation and coating: Similar to Example 1, microcapsules were prepared and dispersed in an enamel substrate, and the enamel substrate was coated on the surface of the reinforcing steel. The coating thickness was controlled at 400 micrometers.

[0091] High-temperature calcination: calcined at 850℃ for 30 minutes, then slowly cooled to room temperature.

[0092] This comparative example, by omitting the pickling and passivation steps on the rebar surface, resulted in a significant reduction in the adhesion between the coating and the rebar surface. During use, the coating is more prone to peeling or blistering, leading to a decrease in corrosion resistance. Furthermore, rebar lacking surface passivation treatment is more susceptible to corrosion in corrosive media, thus shortening the coating's service life.

[0093] To comprehensively evaluate the corrosion resistance and self-healing effect of the self-healing enamel coating on reinforcing bars in different embodiments, polarization resistance (Rp) was mainly used as the detection index for corrosion resistance. A higher polarization resistance value indicates that the coating has better corrosion resistance. The evaluation process first involved measuring the polarization resistance using an electrochemical workstation with a three-electrode system. The working electrode was the sample with the enamel coating, the reference electrode was a saturated calomel electrode, and the auxiliary electrode was a platinum electrode. A sodium hydroxide solution with a pH of 13.4 was used as the corrosive medium, ensuring that the reinforcing bar sample was completely immersed in the solution. Next, the test parameters were set using the electrochemical workstation, controlling the scan range to be within ±10mV to ±20mV near the corrosion potential, and the scan rate was set to 0.1mV / s or 0.5mV / s to start the polarization curve scan. The electrochemical workstation recorded the changes in sample potential and current, generating a polarization curve. By analyzing the slope of the linear region of the curve, the polarization resistance (Rp) was calculated, and this was used to evaluate the corrosion resistance performance of the coating. To ensure the reliability of the data, the polarization resistance test for each embodiment was repeated at least three times, and the average value was taken as the final result.

[0094] Besides measuring polarization resistance, self-healing performance is also an important indicator for evaluating coating quality. Microcracks are created on the coating surface, and the sample is re-immersed in an alkaline corrosive medium. After a certain period, the change in polarization resistance is measured again. If the coating has a significant self-healing effect, the polarization resistance should partially recover to its original state after repair, indicating that the repair agent within the microcapsules is released at the crack and effectively seals the fissure. Furthermore, abrasion resistance and adhesion tests further verify the mechanical properties of the coating and its bond strength with the substrate. In the abrasion resistance test, an abrasion testing machine is used to simulate the wear of reinforcing steel during use, and the abrasion resistance of the coating is evaluated by recording the amount of wear. The adhesion test uses a pull-out testing machine to test the bond strength between the coating and the reinforcing steel substrate, ensuring that the coating will not peel or detach during long-term use.

[0095]

[0096] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A self-healing enamel coating for reinforcing steel, characterized in that, The enamel base and the microcapsule, the microcapsule comprises, The shell layer is prepared from 10-20 parts of tetraethoxysilane, 15-30 parts of ethanol, 1-5 parts of ammonia water and 10-20 parts of water; The core layer is prepared from one or more than two of boron nitride, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide or silicon carbide; The core layer is prepared from one or more than two of boron nitride, aluminum oxide, zirconium oxide, titanium dioxide, magnesium oxide or silicon carbide; The enamel base comprises 23-28 parts of phosphorus pentoxide, 15-20 parts of aluminum oxide, 10-15 parts of sodium oxide, 10-14 parts of potassium oxide, 8-15 parts of boron trioxide, 5-10 parts of calcium fluoride, 5-10 parts of lithium oxide, 5-10 parts of silicon dioxide, 2-5 parts of calcium oxide, 1-3 parts of nickel oxide, 1-3 parts of cobalt oxide and 1-3 parts of zirconium dioxide; The microcapsule is uniformly dispersed in the enamel base, and the content ratio of the microcapsule and the enamel base is 5-15%. The preparation reaction temperature of the shell layer is 25-30℃, the preparation reaction temperature of the core layer is 200-300℃, and the preparation reaction temperature of the core layer is 60-70℃.

2. The self-healing enamel coating for reinforcing steel according to claim 1, characterized in that: The coating thickness is 300-500 microns.

3. The self-healing enamel coating for reinforcing steel according to claim 1, characterized in that: The self-repairing function is realized in an alkaline environment.

4. The self-healing enamel coating for reinforcing steel according to claim 1, characterized in that: The preparation steps of the microcapsule include:

5. A method for preparing a self-repairing enamel coating for reinforcing steel, characterized in that, The shell layer of the microcapsule is prepared by adding 10-20 parts of tetraethoxysilane into a reactor, slowly adding 15-30 parts of ethanol, stirring uniformly, gradually adding 1-5 parts of ammonia water as an alkaline catalyst, controlling the reaction temperature at 25-30℃, and reacting for 4 hours to form a silica sol; 5-15 parts of boron nitride, 10-20 parts of aluminum oxide and 5-15 parts of zirconium oxide are mixed in proportion, gradually added into the shell layer material, stirred uniformly, and heated at 200-300℃; 10-20 parts of sodium silicate, 10-20 parts of zirconium silicate and 10-20 parts of barium titanate are added into the reactor, heated to 60-70℃, and the repairing agent is wrapped in the shell layer by interface polymerization technology to form a microcapsule with a core-shell structure; The enamel base is prepared by mixing 23-28 parts of phosphorus pentoxide, 15-20 parts of aluminum oxide, 10-15 parts of sodium oxide, 10-14 parts of potassium oxide, and adding a proper amount of deionized water and stirring uniformly; The prepared microcapsule material is uniformly dispersed in the enamel base to ensure sufficient mixing. In the preparation step of the microcapsule with a core-shell structure, the stirring speed is 200-600 RPM.

6. The method for preparing a self-healing enamel coating for reinforcing steel according to claim 5, characterized in that: ​

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