A corrosion-resistant coating for building aluminum formworks and a method for preparing the same

Abstract

The present application relates to the technical field of metal surface protective coating, in particular to a kind of building aluminum formwork corrosion-resistant coating and preparation method thereof, to solve the problem of coating failure under stress-corrosion synergistic effect, short service life of protection. The coating of the present application comprises: organosilicon hybrid bottom layer, double-carrier corrosion inhibitor energy storage layer, microcapsule self-repairing layer and wear-resistant super-hydrophobic top layer. The present application generates an oxide ceramic layer on the surface by micro-arc oxidation, then dip-coats organosilicon hybrid sol to form the bottom layer; then disperses the porous silica microspheres and layered double hydroxide loaded with corrosion inhibitor in water-based resin to prepare energy storage coating, forming the corrosion inhibitor energy storage layer; adds urea-formaldehyde resin microcapsules and gelatin-arabic gum microcapsules into the resin matrix to prepare self-repairing coating, forming the self-repairing layer; finally mixes fluorosilane-modified nano-alumina and nano-silica with wear-resistant organosilicon resin to form the super-hydrophobic top layer.

Description

A corrosion-resistant coating for building aluminum formwork and its preparation method Technical Field

[0001] This invention relates to the field of metal surface protective coating technology, specifically to a corrosion-resistant coating for building aluminum formwork and its preparation method. Background Technology

[0002] Aluminum alloy formwork is widely used in modern construction projects due to its advantages such as light weight and high reusability. However, aluminum alloy itself has poor chemical stability and is easily corroded by corrosive media such as cement slurry and acid rain in the construction environment. In particular, aluminum easily reacts with acids and alkalis, releasing hydrogen gas and corroding. In addition, aluminum can form complexes with cement components, causing corrosion of the formwork surface while adhering to the concrete, resulting in strong adhesion during demolding. Corrosion not only shortens the service life of aluminum formwork but also reduces the quality of concrete surface forming, producing air bubbles and increasing the difficulty of demolding. Therefore, effective corrosion protection for aluminum formwork is of great significance. Existing patent CN116285602A discloses a temperature-resistant and corrosion-resistant coating for aluminum alloy surfaces and its preparation method. The coating includes a temperature-resistant coating and a corrosion-resistant coating sequentially attached to the aluminum alloy surface. The pretreated aluminum alloy is immersed in a temperature-resistant coating liquid and cured to form a temperature-resistant coating. Then, a corrosion-resistant coating liquid is applied to the surface of the temperature-resistant coating and cured to obtain a temperature-resistant and corrosion-resistant coating attached to the aluminum alloy surface. However, single organic coatings are prone to mechanical damage and microcracks under repeated assembly and disassembly and load stress at the construction site. Corrosive media can quickly penetrate along the defects, causing the coating to fail and making it difficult to provide long-term protection.

[0003] In summary, existing technologies for aluminum formwork protection, employing single or simple combination coating systems, struggle to simultaneously meet multiple requirements such as corrosion resistance, wear resistance, and self-healing. In actual stress-corrosion alternating environments, such as mechanical impacts, bending stresses, and exposure to alkaline cement and outdoor atmospheres during formwork reuse, existing coatings often fail prematurely, failing to achieve their ideal service life. This invention addresses these shortcomings by providing a novel gradient functional composite coating system. Through a multi-layered structural design, it achieves synergistic protection, significantly extending the service life of aluminum formwork in harsh environments. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant coating for aluminum formwork and its preparation method, overcoming the technical problems of existing aluminum formwork coatings being prone to failure and having short protective lifespan under stress-corrosion combined effects. This invention's coating, through a structural gradient design, organically combines different functional layers, enabling it to adaptively prevent corrosion progression or self-repair when subjected to mechanical damage or corrosive media, thereby significantly improving the coating's reliability and durability. It is particularly suitable for surface protection of aluminum formwork in building construction.

[0005] A corrosion-resistant coating for building aluminum formwork and its preparation method are disclosed below:

[0006] S1: Select an aluminum alloy template as the substrate for degreasing. Immerse the aluminum plate in a 5% NaOH alkaline cleaning solution at 50°C for 2 minutes. After rinsing with running water, immerse the aluminum plate in a 30% HNO3 acidic solution for 1 minute. Then wash with water and dry. Use the degreased aluminum plate as the anode and place it in a micro-arc oxidation electrolyte. Use graphite as the cathode and apply current using a bipolar pulse power supply. Maintain the solution temperature at 25°C and stir. After completion, remove and wash with water to obtain a micro-arc oxidation ceramic layer.

[0007] S2: Immerse the aluminum plate with the micro-arc oxide ceramic layer into the pre-prepared organosilicon hybrid sol, and uniformly form a film using the dip coating method. Pull the sample out of the sol tank at a speed of 2 cm / min, then dry it at 80℃ for 30 minutes, then raise the temperature to 140℃ and keep it at that temperature for 1 hour. After cooling, the organosilicon hybrid bottom layer is obtained.

[0008] S3: Preparation of a dual-carrier corrosion inhibitor energy storage layer

[0009] S31: Dry silica microspheres were soaked in 0.1 mol / L benzotriazole ethanol solution for 24 hours. The ratio of silica microspheres to benzotriazole ethanol solution was 1 g: 30 mL. The microspheres were removed and dried to obtain silica microspheres loaded with benzotriazole. A metal salt solution prepared by Mg(NO3)2 and Al(NO3)3 in a molar ratio of 3:1 was added dropwise with a mixed solution of Na2MoO4 and NaOH under stirring. The mass ratio of Na2MoO4 to NaOH was 1:3, and the volume ratio of the metal salt solution to the mixed solution was 1:1.25. The pH was controlled at 10. The precipitate was filtered, washed with water, dried, and ground to obtain Mg-Al-MoO4 layered double hydroxide powder.

[0010] S32: Take 50 parts of waterborne epoxy resin as the binder, add 2-3 parts of silica microspheres loaded with benzotriazole and 1-2 parts of Mg-Al-MoO4 layered double hydroxide powder, and ultrasonically vibrate for 10 minutes. Add 0.2-0.3 parts of BYK-333 leveling agent and 0.05-0.15 parts of BYK-024 defoamer, and stir evenly to form a coating. Then add 8-12 parts of waterborne amine curing agent, stir evenly, and obtain corrosion-inhibiting energy storage coating.

[0011] S33: The prepared corrosion inhibitor coating is applied by airless spraying with a spray gun. After coating, it is left to stand for 10 minutes, and then dried at 60°C for 2 hours to obtain a dual-carrier corrosion inhibitor energy storage layer.

[0012] S4: Preparation of the microcapsule self-healing layer

[0013] S41: Type A self-healing microcapsules were prepared using an in-situ polymerization method, with urea-formaldehyde resin as the capsule wall material and liquid dicyclopentadiene monomer as the core material. Specifically, the dicyclopentadiene monomer was emulsified and dispersed in an aqueous phase to form a suspension, with a core material content of 60 wt%. The pH was adjusted to 3.5, and the mixture was heated to 50°C and stirred for 2 hours. After the reaction was completed, the mixture was cooled, centrifuged, washed, and dried to obtain urea-formaldehyde resin microcapsules, i.e., type A self-healing microcapsules.

[0014] S42: Type B catalyst microcapsules were prepared using the complex coagulation method. These microcapsules encapsulated a Grubbs II catalyst solution using gelatin-gum arabic as the capsule wall material. During preparation, the Grubbs catalyst was mixed with chloroform organic solvent at a ratio of 1 g: 8 mL to form an oil phase. The oil phase was then added dropwise to an aqueous solution of gelatin and gum arabic at a water bath of 40°C. The mass ratio of gelatin to gum arabic was 5:1, the total concentration was 3%, the pH was 4.0, and the volume ratio of the oil phase to the aqueous solution was 1:5. The mixture was stirred at high speed to emulsify and form an emulsion. The temperature was then lowered to 10°C. Finally, 6%–8% glutaraldehyde (by weight of the gelatin) was added to crosslink and solidify the capsule wall. After centrifugation, washing, and drying, gelatin-gum arabic microcapsules, i.e., type B catalyst microcapsules, were obtained.

[0015] S43: Take 100 parts by weight of waterborne epoxy resin main agent, add 8-12 parts of the above-mentioned type A microcapsules and 4-6 parts of type B microcapsules, ultrasonically disperse for 5-10 minutes, add 18-22 parts of waterborne amine curing agent and 0.5-1.5 parts of BYK-024 defoamer, and stir quickly and evenly to obtain a self-healing coating; then spray and let stand for 15 minutes, place the sample at 60℃ and dry for 4 hours to obtain a microcapsule self-healing layer;

[0016] S5: Preparation of the wear-resistant superhydrophobic top layer

[0017] S51: Nano-alumina and nano-silica powders are mixed in a 1:1 mass ratio and ultrasonically dispersed in a mixed solvent of anhydrous ethanol and deionized water in a 4:1 volume ratio to prepare a nanoparticle suspension with a solid content of 5%. Then, 5% of tridecafluorooctyltriethoxysilane by mass of the total nanoparticles is added to the suspension. The mixture is heated to 70°C and refluxed for 4 hours. The modified nanoparticles are separated by centrifugation, washed with anhydrous ethanol and dried to obtain hydrophobic nanoparticles with long-chain fluorine-containing organic groups grafted on the surface.

[0018] S52: Take 100 parts of organosilicon resin containing phenyl and vinyl functional groups as film-forming material, add 180-200 parts of xylene / butyl acetate mixed solvent to dilute, then add 18-22 parts of hydrophobic nanoparticles, stir and mix, place the mixture in a ball mill jar, use ceramic balls as the grinding medium, ball mill at 200 rpm for 2 hours to obtain superhydrophobic coating, and let stand to degas;

[0019] S53: The coating is applied using an airless spraying method with a spraying pressure of 80 bar. The spray gun is kept 25 cm away from the sample. After spraying, the coating is dried in a 90°C environment for 3 hours to obtain a robust, wear-resistant, superhydrophobic top layer, which is the corrosion-resistant coating for building aluminum formwork of this invention.

[0020] Furthermore, the micro-arc oxidation electrolyte described in step S1 is composed of silicates and tungstates, specifically: 10 g / L sodium metasilicate, 2 g / L potassium hydroxide, 2 g / L sodium tungstate, 1.5 g / L sodium hexametaphosphate, and 1.5 g / L sodium tetraborate.

[0021] Furthermore, the parameters of the bipolar pulse power supply mentioned in step S1 are set as follows: upper limit of anode voltage 450V, lower limit of cathode voltage 150V, pulse frequency 800Hz, duty cycle +30% / -20%, and oxidation time 6-10 minutes.

[0022] Further, the organosilicon hybrid sol described in step S2 has the following composition and dosage: 8-12 parts of γ-glycidoxypropyltrimethoxysilane, 10-12 parts of methyltriethoxysilane, and 10-11 parts of tetraethoxysilane are added to 70 parts of an aqueous ethanol solution, and the volume ratio of ethanol to water is 1:1. The mixture is hydrolyzed for 8 hours.

[0023] Furthermore, the spray gun described in step S33 has the following parameters: nozzle diameter 1.0 mm, spraying pressure 6 bar, and spraying distance 15 cm.

[0024] Furthermore, the aqueous phase described in step S41 contains 2 wt% urea, 1 wt% formaldehyde, and 1 wt% OP-10 surfactant.

[0025] Furthermore, the spraying described in step S43 has the following parameters: air pressure 4 bar and nozzle-to-surface distance 20 cm.

[0026] Further, the xylene / butyl acetate mixed solvent mentioned in step S52 specifically has a xylene to butyl acetate volume ratio of 1:1. Compared with existing patents, the present invention has the following beneficial effects:

[0027] 1. This invention significantly extends the protective life of the coating through multi-layer synergistic effects; the micro-arc oxidation ceramic layer provides excellent basic corrosion resistance and adhesion; the corrosion inhibitor storage layer releases effective components in the early stages of corrosion to passivate the metal surface and delay corrosion; the self-healing layer repairs the coating structure in time when damage occurs, preventing further corrosion; and the superhydrophobic top layer blocks most of the moisture. Through synergistic effects, the coating can maintain its corrosion resistance even in the event of scratches or localized failure, greatly improving its service life.

[0028] 2. The present invention has excellent mechanical properties through the underlying ceramic / organosilicon hybrid structure; the nanoparticles added to the superhydrophobic top layer improve the surface hardness and wear resistance.

[0029] 3. The coating of this invention belongs to the category of smart coatings, which has the ability to respond to changes in the environment, ensuring the reliability of the coating in complex environments and greatly reducing maintenance costs.

[0030] 4. This invention reduces the adhesion of concrete to aluminum formwork by utilizing the superhydrophobic and low surface energy properties of the outermost layer of the coating, which is beneficial for demolding and surface cleaning. Attached Figure Description

[0031] Figure 1 is a flow chart of the preparation process of a corrosion-resistant coating for building aluminum formwork according to the present invention.

[0032] Figure 2 shows the physical results of neutral salt spray tests in Examples 1-3 and Comparative Examples 1-4.

[0033] Figure 3 shows the physical results of the water contact angle test in Examples 1-3 and Comparative Examples 1-4.

[0034] Figure 4 is a comparison chart of the self-healing rate and water contact angle test results of Examples 1-3 and Comparative Examples 1-4. Detailed Implementation

[0035] The following embodiments further explain and illustrate the technical solutions of the present invention. It is particularly noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention. As shown in Figure 1, a process flow for preparing a corrosion-resistant coating for building aluminum formwork is provided, and its detailed preparation steps are as follows:

[0036] This invention's coating system is a biomimetic intelligent composite protection system that mimics the multi-layered protection and self-repair mechanisms of biological organisms, constructing an integrated, adaptive, and long-life surface protection system. It consists of four functionally distinct and synergistically functioning structural layers: an organosilicon hybrid bottom layer, a dual-carrier corrosion inhibitor energy storage layer, a microcapsule self-repair layer, and a wear-resistant superhydrophobic top layer. The organosilicon hybrid bottom layer generates a porous oxide ceramic layer on the aluminum alloy surface through micro-arc oxidation, which is then filled and cured by organosilicon hybrid sol dipping, forming a transitional structure similar to a biological substrate membrane. The interface is integrated and transitioned; the dual-carrier corrosion inhibitor energy storage layer releases corrosion inhibitors when corrosive media invade, forming a protective film on the metal surface to achieve chemical immunity, similar to the biomimetic immune system / drug slow release of a biological organism, enabling intelligent response and chemical inhibition; the microcapsule self-repair layer simulates the self-healing process of biological tissue after damage, similar to the biomimetic dermis / coagulation mechanism of a biological organism, achieving self-healing and structural reinforcement; the wear-resistant superhydrophobic top layer constructs a micro-nano rough structure and a low surface energy chemical layer similar to the surface of a lotus leaf, which can achieve water repellency and wear resistance.

[0037] 1. Substrate pretreatment

[0038] Aluminum alloy templates were selected as the substrate. First, the substrate underwent routine pretreatment to ensure surface cleanliness and activation. Pretreatment included: degreasing by immersing the aluminum plate in an alkaline cleaning solution to remove oil and the initial oxide film; rinsing thoroughly with running water followed by neutralization and acid pickling activation by immersing the aluminum plate in an acidic solution to remove surface passivation products generated by alkaline washing and activate the surface; and finally, thorough rinsing with deionized water and drying. After these treatments, the aluminum template surface was clean and exhibited a micro-roughened activated state, which is beneficial for the adhesion of subsequent coatings.

[0039] Next, micro-arc oxidation is performed. The pretreated aluminum plate is placed in the micro-arc oxidation electrolyte, with stainless steel or graphite as the cathode. A bipolar pulsed power supply is used to apply current, generating a micro-arc discharge effect on the aluminum plate surface. During the process, tiny arc lights can be seen emanating from the aluminum surface, and a uniform grayish-white ceramic film is formed. After completion, the aluminum plate is removed, and the surface is rinsed with deionized water to remove residual electrolyte, yielding the micro-arc oxidized ceramic layer.

[0040] 2. Preparation of Organosilicon Hybrid Substrates

[0041] The bottom layer is composed of an alumina ceramic layer formed by micro-arc oxidation of an aluminum substrate and a silicone hybrid coating. This layer provides a hard, wear-resistant inner layer of protection, filling in surface defects on the substrate, and enhances the bonding with the upper organic coating through the silicone network. The dense, non-porous hybrid bottom layer acts as the first barrier to prevent corrosive media from entering and improves the adhesion of the entire coating system to the substrate.

[0042] Specifically, an aluminum plate with a micro-arc oxidation ceramic layer is immersed in a pre-prepared organosilicon hybrid sol, and a uniform film is formed using a dip-coating method. The hybrid sol is prepared by co-hydrolysis and condensation of a silane coupling agent and an organic resin; an epoxy-containing silane is selected and hydrolyzed with an organosilicon resin precursor to form the sol. After dip coating, the plate is placed in an oven for segmented curing to promote solvent evaporation and initial sol curing. The temperature is then increased to allow the organosilicon network to fully cross-link and cure. After cooling, a transparent and dense micro-arc oxidation-organosilicon hybrid underlayer is obtained. This seals most of the micropores in the ceramic layer, while the organic functional groups of the silane provide active anchoring sites for subsequent organic layers.

[0043] 3. Preparation of a dual-carrier corrosion inhibitor energy storage layer

[0044] The corrosion inhibitor reservoir layer contains two types of corrosion inhibitor carriers: porous silica microspheres and layered double hydroxides. The porous silica microspheres are internally loaded with corrosion inhibitors, while the layered double hydroxides contain intercalated corrosion-inhibiting anions. When corrosive media penetrates this layer, the carriers release corrosion-inhibiting anions or organic corrosion-inhibiting molecules, which are adsorbed onto the metal surface or neutralize the corrosive media, thereby actively inhibiting the corrosion reaction. This layer acts as a corrosion inhibitor reservoir, providing chemical protection when the coating is damaged, delaying the occurrence and spread of corrosion.

[0045] Specifically, the process involves preparing an intermediate coating containing corrosion inhibitor microcapsules and applying it over the underlying layer. First, a corrosion inhibitor carrier is prepared: silica microspheres are immersed in a corrosion inhibitor solution to adsorb and load the corrosion inhibitor. The corrosion inhibitor selected is a compound with good corrosion inhibition effect on aluminum. After drying, the microspheres are ready for use. Then, a Mg-Al-MoO4 layered double hydroxide powder is prepared using a co-precipitation method, introducing corrosion-inhibiting anions such as molybdate into the interlayer. Next, a corrosion-inhibiting and energy-storing coating is formulated: water-based epoxy resin is selected as the binder. The aforementioned corrosion inhibitor carrier—Mg-Al-MoO4 layered double hydroxide powder, a leveling agent, a small amount of defoamer, and a curing agent are added to the epoxy emulsion base agent and stirred evenly to form the corrosion-inhibiting and energy-storing coating. This coating is then applied to the surface of the aluminum plate with the previously prepared underlying layer using an airless spraying method. The coating is allowed to stand and dry to allow the epoxy resin to fully cure and cross-link. This yields a dual-carrier corrosion inhibitor energy-storing layer.

[0046] 4. Preparation of microcapsule self-repair layer

[0047] The microcapsule self-healing layer disperses microcapsules A containing a self-healing agent and microcapsules B containing a catalyst. When external mechanical stress causes cracks in the coating, the microcapsules at the crack tips rupture: capsule A releases liquid dicyclopentadiene monomer, and capsule B releases Grubbs catalyst. The two rapidly contact at the crack and undergo a ring-opening polymerization reaction, generating a cured polymer product that fills the crack, thereby repairing the coating structure. This self-healing surface layer ensures that even if microscopic damage occurs during use, the coating can heal promptly and restore its barrier performance.

[0048] Specifically, type A self-healing microcapsules are prepared by in-situ polymerization, with urea-formaldehyde resin as the capsule wall material and liquid dicyclopentadiene monomer as the core material. The specific method is as follows: dicyclopentadiene monomer is emulsified and dispersed in an aqueous phase to form a suspension. The aqueous phase contains urea, formaldehyde and OP-10 surfactant. The condensation reaction of urea-formaldehyde under acidic conditions is used to form a polymer film shell on the surface of the droplets. After the reaction is completed, the mixture is cooled, centrifuged, washed and dried to obtain urea-formaldehyde resin microcapsules, i.e., type A self-healing microcapsules.

[0049] Type B catalyst microcapsules were prepared using a complex coagulation method. These microcapsules encapsulated a Grubbs II catalyst solution using gelatin-gum arabic as the capsule wall material. During preparation, the Grubbs II catalyst was mixed with chloroform to form an oil phase. This oil phase was then dropped into an aqueous solution of gelatin and gum arabic, and the mixture was stirred at high speed to emulsify and form an emulsion. The temperature was then lowered to 10°C to induce complex coagulation of the gelatin and gum arabic, which deposited as a solidified film on the surface of the oil droplets. Finally, glutaraldehyde was added to crosslink and solidify the capsule wall. After centrifugation, washing, and drying, the gelatin-gum arabic microcapsules, i.e., type B catalyst microcapsules, were obtained.

[0050] The epoxy resin main agent, the above-mentioned type A microcapsules and type B microcapsules are mixed, ultrasonically dispersed, and then a curing agent and defoamer are added. The mixture is then stirred quickly and evenly to obtain a self-healing coating. The self-healing coating is applied to the surface of the cured corrosion inhibitor layer by spraying. Multiple thin sprays are used to gradually cover and form a wet film. After the solvent evaporates, the coating is dried to obtain the microcapsule self-healing layer.

[0051] 5. Preparation of wear-resistant superhydrophobic top layer

[0052] The outermost layer is a wear-resistant coating with superhydrophobic properties. By introducing fluorosilane-modified nano-alumina and silica particles into the silicone resin, a micro-nano rough structure is formed, giving the coating low surface energy. This makes water droplets exhibit a high contact angle on the surface, making it difficult to wet. This not only constructs the micro-nano structure but also significantly improves the coating's hardness and wear resistance. This superhydrophobic surface greatly reduces the intrusion of water and chloride ions; at the same time, the selected wear-resistant silicone resin allows the top layer to maintain its structural integrity during friction. The top layer also has a non-sticking and anti-adhesion effect, making it difficult for concrete slurry to adhere to it, thus facilitating demolding. Even if a small amount of dirt adheres, the self-cleaning effect of the superhydrophobic surface allows it to be automatically cleaned by rainwater.

[0053] Specifically, the process involves: mixing nano-alumina and nano-silica powders, ultrasonically dispersing them in a mixed solvent of anhydrous ethanol and deionized water to prepare a nanoparticle suspension; then adding tridecafluorooctyltriethoxysilane to the suspension, heating and refluxing the mixture, centrifuging to separate the modified nanoparticles, washing with anhydrous ethanol and drying to obtain hydrophobic nanoparticles with long-chain fluorinated organic groups grafted onto their surface; using an organosilicon resin containing phenyl and vinyl functional groups as a film-forming agent, diluting it with a mixed solvent of xylene / butyl acetate, then adding the hydrophobic nanoparticles, stirring and mixing, placing the mixture in a ball mill jar, using ceramic balls as the grinding medium to obtain a superhydrophobic coating, and allowing it to stand to degas; gradually covering the surface with multiple thin sprays to form a wet film, allowing the solvent to evaporate, resulting in a robust, wear-resistant, superhydrophobic top layer, which is the corrosion-resistant coating for aluminum formwork of this invention.

[0054] Example 1

[0055] Table 1 Raw Material Information Table

[0056]

[0057]

[0058] A corrosion-resistant coating for building aluminum formwork and its preparation method are disclosed, comprising the following steps:

[0059] S1: Select 6061-T6 aluminum alloy template sheet as the substrate for degreasing. Immerse the aluminum sheet in a 50℃, 5% (w / w) NaOH alkaline cleaning solution for 2 minutes to remove oil and initial oxide film. After rinsing thoroughly with running water, immerse the aluminum sheet in a 30% (w / w) HNO3 acidic solution for 1 minute. Rinse thoroughly again with deionized water and dry. Then perform micro-arc oxidation treatment. Use the degreased aluminum sheet as the anode and place it in a micro-arc oxidation electrolyte composed of silicates and tungstates, specifically: 10g / L sodium metasilicate. 2 g / L potassium hydroxide, 2 g / L sodium tungstate, 1.5 g / L sodium hexametaphosphate, and 1.5 g / L sodium tetraborate were used. Graphite was used as the cathode, and a bipolar pulse power supply was used to apply current to generate a micro-arc discharge effect on the surface of an aluminum plate. The parameters were set as follows: upper limit of anode voltage 450V, lower limit of cathode voltage 150V, pulse frequency 800Hz, duty cycle +30% / -20%, oxidation time 8 minutes, solution temperature maintained at 25℃ and stirred. After completion, the aluminum plate was removed, and the surface residual electrolyte was rinsed with deionized water to obtain a micro-arc oxidation ceramic layer with a thickness of 12 μm.

[0060] S2: Immerse an aluminum plate with a micro-arc oxidation ceramic layer into a pre-prepared organosilicon hybrid sol and uniformly form a film using a dip coating method; Organosilicon hybrid sol: Take 10 parts of γ-glycidoxypropyltrimethoxysilane, 11 parts of methyltriethoxysilane, and 10.5 parts of tetraethoxysilane and add them to 70 parts of an ethanol aqueous solution. The volume ratio of ethanol to water is 1:1. Mix and hydrolyze for more than 8 hours to prepare a sol; Dip coating is performed. The sample is pulled out of the sol tank at a speed of 2 cm / min, then dried at 80℃ for 30 minutes, then heated to 140℃ and kept at that temperature for 1 hour. After cooling, an organosilicon hybrid underlayer with a thickness of 8 μm is obtained;

[0061] S3: Preparation of a dual-carrier corrosion inhibitor energy storage layer

[0062] S31: Dry silica microspheres were soaked in 0.1 mol / L benzotriazole ethanol solution for 24 hours. The ratio of silica microspheres to benzotriazole ethanol solution was 1 g: 30 mL. The microspheres were removed and dried to obtain silica microspheres loaded with benzotriazole. Magnesium-aluminum layered double hydroxides were prepared by co-precipitation method. A metal salt solution prepared by Mg(NO3)2 and Al(NO3)3 in a molar ratio of 3:1 was added dropwise with a mixed solution of Na2MoO4 and NaOH under stirring. The mass ratio of Na2MoO4 to NaOH was 1:3, and the volume ratio of metal salt solution to mixed solution was 1:1.25. The pH was controlled at 10. The precipitate was filtered, washed with water and dried, and then ground to obtain Mg-Al-MoO4 layered double hydroxide powder.

[0063] S32: Take 50 parts of waterborne epoxy resin as the binder, add 2.5 parts of silica microspheres loaded with benzotriazole and 1.5 parts of Mg-Al-MoO4 layered double hydroxide powder, and ultrasonically vibrate for 10 minutes. Add 0.25 parts of BYK-333 leveling agent and 0.1 parts of BYK-024 defoamer, and stir evenly to form a coating. Then add 10 parts of waterborne amine curing agent and stir quickly and evenly to obtain corrosion-inhibiting energy storage coating.

[0064] S33: The prepared corrosion inhibitor coating is applied to the surface of the aluminum plate with the previously completed base layer by airless spraying. The spray gun nozzle diameter is 1.0 mm, the spraying pressure is 6 bar, the spraying distance is 15 cm, and the coating is sprayed back and forth evenly to make the wet film thickness reach 50 μm. After coating, let it stand for 10 minutes to allow the coating to self-level, and then place it in a 60°C environment to dry for 2 hours to obtain a dual-carrier corrosion inhibitor energy storage layer.

[0065] S4: Preparation of the microcapsule self-healing layer

[0066] S41: Dicyclopentadiene monomer was emulsified and dispersed in an aqueous phase to form a suspension, with a core material content of 60 wt%. The aqueous phase contained 2 wt% urea, 1 wt% formaldehyde, and 1 wt% OP-10 surfactant. The pH was adjusted to 3.5, and the mixture was heated to 50°C and stirred for 2 hours. After the reaction was completed, the mixture was cooled, centrifuged, washed, and dried to obtain type A self-healing microcapsules.

[0067] S42: Grubbs catalyst and chloroform organic solvent were mixed at a ratio of 1 g: 8 mL to form an oil phase; the oil phase was added dropwise to an aqueous solution of gelatin and gum arabic at a water bath of 40 °C. The mass ratio of gelatin to gum arabic was 5:1, the total concentration was 3%, the pH was 4.0, and the volume ratio of oil phase to aqueous solution was 1:5. The mixture was stirred at high speed to emulsify and form an emulsion. The temperature was then lowered to 10 °C, and finally 7% glutaraldehyde (by weight of gelatin) was added to crosslink and solidify the capsule wall. After centrifugation, washing, and drying, type B catalyst microcapsules were obtained.

[0068] S43: Take 100 parts of waterborne epoxy resin main agent, add 10 parts of the above-mentioned type A microcapsules and 5 parts of type B microcapsules, ultrasonically disperse for 8 minutes, add 20 parts of waterborne amine curing agent and 1 part of BYK-024 defoamer, and stir quickly and evenly to obtain self-healing coating; apply the self-healing coating to the surface of the cured corrosion inhibitor layer by spraying, with an air pressure of 4 bar and a nozzle distance of 20 cm from the surface, and gradually cover the surface by multiple thin sprays to form a uniform coating with a wet film thickness of 50 μm. After standing for 15 minutes to evaporate the solvent, place the sample at 60℃ to dry for 4 hours to obtain the microcapsule self-healing layer;

[0069] S5: Preparation of the wear-resistant superhydrophobic top layer

[0070] S51: Nano-alumina and nano-silica powders are mixed in a 1:1 mass ratio and ultrasonically dispersed in a mixed solvent of anhydrous ethanol and deionized water in a 4:1 volume ratio to prepare a nanoparticle suspension with a solid content of 5%. Then, 5% of tridecafluorooctyltriethoxysilane by mass of the total nanoparticles is added to the suspension. The mixture is heated to 70°C and refluxed for 4 hours. The modified nanoparticles are separated by centrifugation, washed with anhydrous ethanol and dried to obtain hydrophobic nanoparticles with long-chain fluorine-containing organic groups grafted on the surface.

[0071] S52: Take 100 parts of organosilicon resin containing phenyl and vinyl functional groups as film-forming material, add 190 parts of xylene / butyl acetate mixed solvent to dilute with organic solvent, the volume ratio of xylene and butyl acetate is 1:1, then add 20 parts of hydrophobic nanoparticles, stir and mix, place the mixture in a ball mill jar, use ceramic balls as the grinding medium, ball mill at 200 rpm for 2 hours to obtain superhydrophobic coating, let stand to degas;

[0072] S53: The coating is applied using an airless spraying method with a spraying pressure of 80 bar. The spray gun is kept 25 cm away from the sample, and the coating is applied to a thickness of 20 μm. After the coating is completed, the sample is dried at 90°C for 3 hours to obtain a robust, wear-resistant, superhydrophobic top layer, which is the corrosion-resistant coating for building aluminum formwork of this invention.

[0073] Example 2

[0074] The preparation method is the same as in Example 1, but with the following differences:

[0075] In step S1: oxidation time is 6 minutes;

[0076] In step S2: Organosilicon hybrid sol: Take 8 parts of γ-glycidoxypropyltrimethoxysilane, 10 parts of methyltriethoxysilane, and 10 parts of tetraethoxysilane and add them to 70 parts of ethanol aqueous solution;

[0077] In step S32: Take 50 parts of waterborne epoxy resin as the adhesive base, add 2 parts of silica microspheres loaded with benzotriazole and 1 part of Mg-Al-MoO4 layered double hydroxide powder, 0.2 parts of BYK-333 leveling agent and 0.05 parts of BYK-024 defoamer, and 8 parts of waterborne amine curing agent;

[0078] In step S42: 6% glutaraldehyde (by weight of gelatin) is added to cross-link and cure the capsule wall;

[0079] In step S43: Take 100 parts of waterborne epoxy resin main agent, add 8 parts of the above-mentioned type A microcapsules and 4 parts of type B microcapsules, ultrasonically disperse for 5 minutes, add 18 parts of waterborne amine curing agent and 0.5 parts of BYK-024 defoamer;

[0080] In step S52: Take 100 parts of organosilicon resin containing phenyl and vinyl functional groups as film-forming material, add 180 parts of xylene / butyl acetate mixed solvent, and 18 parts of hydrophobic nanoparticles.

[0081] Example 3

[0082] The preparation method is the same as in Example 1, but with the following differences:

[0083] In step S1: oxidation time is 10 minutes;

[0084] In step S2: Organosilicon hybrid sol: Take 12 parts of γ-glycidoxypropyltrimethoxysilane, 12 parts of methyltriethoxysilane, and 11 parts of tetraethoxysilane and add them to 70 parts of ethanol aqueous solution;

[0085] In step S32: Take 50 parts of waterborne epoxy resin as the binder, add 3 parts of silica microspheres loaded with benzotriazole and 2 parts of Mg-Al-MoO4 layered double hydroxide powder, 0.3 parts of BYK-333 leveling agent and 0.15 parts of BYK-024 defoamer, and 12 parts of waterborne amine curing agent;

[0086] In step S42: Add 8% glutaraldehyde (by weight of gelatin) to crosslink and cure the capsule wall;

[0087] In step S43: Take 100 parts of waterborne epoxy resin main agent, add 12 parts of the above-mentioned type A microcapsules and 6 parts of type B microcapsules, ultrasonically disperse for 10 minutes, add 22 parts of waterborne amine curing agent and 1.5 parts of BYK-024 defoamer;

[0088] In step S52: 100 parts of organosilicon resin containing phenyl and vinyl functional groups are taken as film-forming material, and 200 parts of xylene / butyl acetate mixed solvent and 22 parts of hydrophobic nanoparticles are added.

[0089] Comparative Example 1

[0090] The preparation method of Example 1 is followed, but the preparation of the organosilicon hybrid underlayer is omitted, i.e., step S2 is not performed. The remaining steps are the same.

[0091] Comparative Example 2

[0092] The preparation method of Example 1 is followed, but the corrosion inhibitor energy storage layer is not prepared, i.e., step S3 is not performed. The remaining steps are the same.

[0093] Comparative Example 3

[0094] The preparation method of Example 1 is followed, but the self-healing layer is not prepared, i.e., step S4 is not performed. The remaining steps are the same.

[0095] Comparative Example 4

[0096] The preparation method of Example 1 is followed, but the superhydrophobic top layer is not prepared, i.e., step S5 is omitted. The remaining steps are the same.

[0097] The comprehensive performance of the corrosion-resistant coatings for aluminum formwork prepared in Examples 1-3 and Comparative Examples 1-4 was determined.

[0098] Neutral salt spray test: The test was conducted in accordance with the standard GB / T 10125-2021 "Civilization test of artificial atmosphere - salt spray test". The test conditions were: 5% NaCl solution, pH value 6.5-7.2, chamber temperature (35±2)℃, and after continuous spraying for 3000 hours, the corrosion of the sample surface was observed and recorded.

[0099] Scratch self-healing test: A scratch hardness tester was used to create a self-healing layer with a width of 80 μm and a depth to the coating surface. The scratched sample was then placed in a constant temperature environment of (50±2)℃ for 24 hours to accelerate the repair reaction. After repair, the repair efficiency (%) was calculated using the formula: Repair efficiency (%) = (Initial scratch width - Repaired scratch width) / Initial scratch width × 100%.

[0100] Water droplet contact angle test: The test was conducted in accordance with the standard GB / T 30693-2014 "Measurement of contact angle between plastic film and water" using an optical contact angle meter and ultrapure water as the test solution.

[0101] Adhesion test: The test is conducted according to standard GB / T 9286-2021 "Cross-cut test for paints and varnishes". A 6×6 grid of 1mm spaced squares is created on the coating surface using a multi-bladed cutting tool, cutting through to the substrate. After removing debris with a soft brush, pressure-sensitive adhesive tape conforming to the standard is applied and quickly peeled off at a 60° angle. The adhesion grade is determined based on the proportion of coating peeled off in the grid areas (0-5, with 0 being the best).

[0102] The specific test comparison results are shown in Table 2, Figure 2, Figure 3, and Figure 4:

[0103] Table 2. Comparison of overall performance between Examples 1-3 and Comparative Examples 1-4

[0104]

[0105] The comparison results show that in Comparative Example 1, without the preparation of the organosilicon hybrid underlayer, large-area corrosion and poor adhesion occurred in the salt spray test. This indicates that the organosilicon hybrid underlayer effectively sealed the pores and enhanced the interlayer bonding, providing a stable foundation. Without this layer, the coating easily peels off from the substrate, and the protection quickly fails. In Comparative Example 2, without the preparation of the corrosion inhibitor energy storage layer, dozens of scattered corrosion spots appeared in the salt spray test. The active passivation effect of the corrosion inhibitor energy storage layer is crucial for delaying the occurrence and spread of corrosion. Without this active protection, the corrosion process is accelerated. In Comparative Example 3, without the preparation of the self-healing layer, a small number of tiny bubbles appeared on the surface in the salt spray test, with fine corrosion points around the bubbles. This proves the key role of the self-healing layer in timely repairing damage and preventing corrosion expansion. In Comparative Example 4, without the preparation of the superhydrophobic top layer, a layer of corrosion products was uniformly covered on the surface in the salt spray test, accompanied by dense micro-pits. The surface also became hydrophilic, meaning that water and corrosive media could spread and penetrate more easily on the surface, weakening the overall barrier performance of the system.

Claims

1. A corrosion-resistant coating for building aluminum formwork, comprising a multi-layer protective coating, characterized in that, From the inside out, the structure comprises an organosilicon hybrid bottom layer, a dual-carrier corrosion inhibitor energy storage layer, a microcapsule self-healing layer, and a wear-resistant superhydrophobic top layer. The organosilicon hybrid bottom layer is based on an aluminum alloy template substrate with a micro-arc oxidation ceramic layer; the pores and surface of the micro-arc oxidation ceramic layer are loaded with organosilicon hybrid sol. The dual-carrier corrosion inhibitor energy storage layer consists of multi-level porous silica microspheres and layered double hydroxides dispersed in a resin substrate. Corrosion inhibitors are loaded within the pores of the silica microspheres, and corrosion-inhibiting anions are inserted between the layers of the layered double hydroxides. The microcapsule self-healing layer is a resin... Two types of microcapsules are dispersed in a lipid substrate, each carrying a repair agent and a repair catalyst, respectively. The wear-resistant superhydrophobic top layer is composed of fluorosilane-modified low surface energy nano-oxides dispersed in wear-resistant organosilicon resin. The microcapsule self-repairing layer is prepared by: preparing type A self-repairing microcapsules using in-situ polymerization, and encapsulating liquid dicyclopentadiene monomer as the core material with urea-formaldehyde resin as the capsule wall material; specifically, the dicyclopentadiene monomer is emulsified and dispersed in an aqueous phase to form a suspension, with the core material content at 60 wt%, the pH adjusted to 3.5, and the temperature raised to 50°C. Stirring at ℃ for 2 hours, after the reaction is complete, cooling, centrifugation, washing, and drying yields type A self-healing microcapsules. Type B catalyst microcapsules are prepared using the complex coagulation method, encapsulating Grubbs II catalyst solution with gelatin-gum arabic as the capsule wall material. During preparation, the Grubbs II catalyst is mixed with chloroform organic solvent at a ratio of 1 g:8 mL to form an oil phase. The oil phase is then added dropwise to an aqueous solution of gelatin and gum arabic at a water bath of 40℃. The mass ratio of gelatin to gum arabic is 5:1, the total concentration is 3%, the pH is 4.0, and the volume ratio of oil phase to aqueous solution is 1:

5. High-speed stirring is used to emulsify the solution. The mixture is converted into an emulsion, then the temperature is lowered to 10°C. Finally, 6%–8% glutaraldehyde (by weight of gelatin) is added to crosslink and cure the capsule walls. After centrifugation, washing, and drying, type B catalyst microcapsules are obtained. 100 parts by weight of waterborne epoxy resin are taken, and 8–12 parts of the above type A microcapsules and 4–6 parts of type B microcapsules are added. The mixture is ultrasonically dispersed for 5–10 minutes, and 18–22 parts of waterborne amine curing agent and 0.5–1.5 parts of BYK-024 defoamer are added. The mixture is quickly stirred until homogeneous to obtain a self-healing coating. The coating is then sprayed and allowed to stand for 15 minutes. The sample is then dried at 60°C for 4 hours to obtain a microcapsule self-healing layer.

2. The corrosion-resistant coating for building aluminum formwork according to claim 1, characterized in that, The organosilicon hybrid sol is composed of γ-glycidoxypropyltrimethoxysilane, methyltriethoxysilane, tetraethoxysilane, and an aqueous ethanol solution; the layered double hydroxide is a Mg-Al-MoO4 layered double hydroxide.

3. A method for preparing a corrosion-resistant coating for building aluminum formwork according to any one of claims 1-2, characterized in that, Includes the following steps: S1: Select an aluminum alloy template as the substrate for degreasing. Immerse the aluminum plate in a 5% NaOH alkaline cleaning solution at 50°C for 2 minutes. After rinsing with running water, immerse the aluminum plate in a 30% HNO3 solution for 1 minute. Then wash with water and dry. Use the degreased aluminum plate as the anode and place it in a micro-arc oxidation electrolyte. Use graphite as the cathode and apply current using a bipolar pulse power supply. Maintain the solution temperature at 25°C and stir. After completion, remove and wash with water to obtain a micro-arc oxidation ceramic layer. S2: An aluminum plate with a micro-arc oxide ceramic layer was immersed in a pre-prepared organosilicon hybrid sol. A uniform film was formed using a dip coating method. The sample was pulled out of the sol bath at a speed of 2 cm / min, dried at 80℃ for 30 minutes, then heated to 140℃ and held for 1 hour. After cooling, the organosilicon hybrid underlayer was obtained. S3: Preparation of the dual-carrier corrosion inhibitor energy storage layer S31: Dry silica microspheres were immersed in a 0.1 mol / L benzotriazole ethanol solution for 24 hours. The ratio of silica microspheres to benzotriazole ethanol solution was 1 g: 30 mL. The microspheres were removed and dried to obtain silica microspheres loaded with benzotriazole. Mg(NO3)2 was added to the sol. 3) A metal salt solution prepared by mixing Al(NO3)3 and Na2MoO4 with NaOH in a molar ratio of 3:1 was added dropwise under stirring. The mass ratio of Na2MoO4 to NaOH was 1:3, and the volume ratio of the metal salt solution to the mixed solution was 1:1.

25. The pH was controlled at 10. The precipitate was filtered, washed with water, dried, and ground to obtain Mg-Al-MoO4 layered double hydroxide powder. S32: 50 parts of water-based epoxy resin were used as the binder, 2-3 parts of silica microspheres loaded with benzotriazole and 1-2 parts of Mg-Al-MoO4 layered double hydroxide powder were added, and the mixture was ultrasonically vibrated for 10 minutes.

0. 2-0.3 parts of BYK-333 leveling agent and 0.05-0.15 parts of BYK-024 defoamer are stirred evenly to form a coating; then 8-12 parts of water-based amine curing agent are added and stirred evenly to obtain a corrosion-inhibiting and energy-storing coating; S33: The prepared corrosion-inhibiting coating is applied using an airless spray gun, and after coating, it is left to stand for 10 minutes, and then dried at 60℃ for 2 hours to obtain a dual-carrier corrosion inhibitor energy-storing layer; S4: Preparation of microcapsule self-healing layer S41: Type A self-healing microcapsules are prepared by in-situ polymerization, with urea-formaldehyde resin as the capsule wall material and liquid dicyclopentadiene monomer as the core material; the specific method is: dicyclopentadiene monomer emulsion The core material was dispersed in an aqueous phase to form a suspension, with a core material content of 60 wt%. The pH was adjusted to 3.5, and the mixture was heated to 50°C and stirred for 2 hours. After the reaction was completed, the mixture was cooled, centrifuged, washed, and dried to obtain type A self-healing microcapsules. S42: Type B catalyst microcapsules were prepared using the complex coagulation method. Gelatin-gum arabic was used as the capsule wall material to encapsulate the Grubbs II catalyst solution into microcapsules. During preparation, the Grubbs II catalyst was mixed with chloroform organic solvent at a ratio of 1 g: 8 mL to form an oil phase. The oil phase was then added dropwise to an aqueous solution of gelatin and gum arabic at a water bath of 40°C. The mass ratio of gelatin to gum arabic was 5:1, the total concentration was 3%, and the pH was 4.

0. The oil phase and aqueous solution volume ratio is 1:

5. The mixture is stirred at high speed to emulsify and form an emulsion. Then the temperature is lowered to 10°C. Finally, 6% to 8% glutaraldehyde (by weight of gelatin) is added to crosslink and cure the capsule wall. After centrifugation, washing, and drying, type B catalyst microcapsules are obtained. S43: Take 100 parts by weight of waterborne epoxy resin main agent, add 8 to 12 parts of the above type A microcapsules and 4 to 6 parts of type B microcapsules, and ultrasonically disperse for 5 to 10 minutes. Add 18 to 22 parts of waterborne amine curing agent and 0.5 to 1.5 parts of BYK-024 defoamer, and stir quickly and evenly to obtain a self-healing coating. Then spray and let stand for 15 minutes. Place the sample at 60°C and dry for 4 hours to obtain a microcapsule self-healing layer. S5: Preparation of wear-resistant superhydrophobic top layer S51: Take nano alumina and nano silica powder in a 1:1 mass ratio, and ultrasonically disperse in a mixed solvent of anhydrous ethanol and deionized water in a 4:1 volume ratio to prepare a nanoparticle suspension with a solid content of 5%. Then, 5% tridecafluorooctyltriethoxysilane (based on the total mass of the nanoparticles) was added to the suspension. The mixture was heated to 70°C and refluxed for 4 hours. The modified nanoparticles were separated by centrifugation, washed with anhydrous ethanol, and dried to obtain hydrophobic nanoparticles with long-chain fluorinated organic groups grafted onto their surface. S52: 100 parts of organosilicon resin containing phenyl and vinyl functional groups were used as the film-forming agent. 180-200 parts of a xylene / butyl acetate mixed solvent were added for dilution, followed by 18-22 parts of the hydrophobic nanoparticles. The mixture was stirred and placed in a ball mill jar, using ceramic balls as the grinding medium, and ball-milled at 200 rpm for 2 hours to obtain a superhydrophobic coating. The coating was then allowed to stand to remove bubbles. S53: The coating was applied using an airless spraying method at a pressure of 80 bar, maintaining a spray gun distance of 25 cm from the sample. After spraying, the coating was dried at 90°C for 3 hours to obtain a robust, wear-resistant, superhydrophobic top layer, which is the corrosion-resistant coating for aluminum formwork of this invention.

4. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The micro-arc oxidation electrolyte described in step S1 specifically comprises: 10 g / L sodium metasilicate, 2 g / L potassium hydroxide, 2 g / L sodium tungstate, 1.5 g / L sodium hexametaphosphate, and 1.5 g / L sodium tetraborate.

5. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The parameters of the bipolar pulse power supply mentioned in step S1 are set as follows: upper limit of anode voltage 450V, lower limit of cathode voltage 150V, pulse frequency 800Hz, duty cycle +30% / -20%, and oxidation time 6-10 minutes.

6. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The organosilicon hybrid sol described in step S2 has the following composition and dosage: 8-12 parts of γ-glycidoxypropyltrimethoxysilane, 10-12 parts of methyltriethoxysilane, and 10-11 parts of tetraethoxysilane are added to 70 parts of an aqueous ethanol solution, and the volume ratio of ethanol to water is 1:

1. The mixture is hydrolyzed for 8 hours.

7. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The spray gun described in step S33 has the following parameters: nozzle diameter 1.0 mm, spraying pressure 6 bar, and spraying distance 15 cm.

8. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The aqueous phase described in step S41 contains 2 wt% urea, 1 wt% formaldehyde and 1 wt% OP-10 surfactant.

9. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The spraying described in step S43 has the following parameters: air pressure 4 bar and nozzle distance 20 cm from the surface.

10. The method for preparing a corrosion-resistant coating for building aluminum formwork according to claim 3, characterized in that, The xylene / butyl acetate mixed solvent mentioned in step S52 is specifically: xylene and butyl acetate in a volume ratio of 1:1.

Images