Heavy-duty anti-corrosion coating containing nano composite material and application of heavy-duty anti-corrosion coating on aluminum alloy base material

Abstract

The invention relates to the technical field of heavy anti-corrosion coatings, and discloses a heavy anti-corrosion coating containing a nano composite material and application of the heavy anti-corrosion coating on an aluminum alloy base material. 9.2 to 13.8 parts of a modified polyether amine curing agent; 1 to 5 parts of gamma-methacryloxy propyl trimethoxy silane; 0.1 to 0.5 part of a controlled hydrolysis initiator; 2 to 8 parts of graphene; 3 to 10 parts of nano silicon dioxide; 5 to 15 parts of ammonium polyphosphate; 3 to 10 parts of sodium molybdate; and 20-30 parts of a mixed solvent. The preparation method of the coating comprises the steps that all the raw materials are mixed to prepare a standby coating, the standby coating is constructed on the surface of an aluminum alloy base material, and then a double-step curing procedure is executed. Through the synergistic effect of interface chemical bonding, physical barrier and double corrosion inhibition, the obtained coating is high in adhesive force to an aluminum alloy base material and excellent in corrosion resistance, and a corrosion inhibition system does not contain toxic heavy metal and is good in environment friendliness.

Description

Technical Field

[0001] This invention relates to the field of heavy-duty anti-corrosion coating technology, and in particular to heavy-duty anti-corrosion coatings containing nanocomposite materials and their application on aluminum alloy substrates. Background Technology

[0002] Aluminum alloys, due to their low density and high strength, are widely used in marine engineering, aerospace, and automotive manufacturing. However, aluminum alloys have high chemical reactivity and are prone to localized corrosion in humid and chloride-containing environments, affecting the safety and service life of equipment structures. Therefore, developing high-performance heavy-duty anti-corrosion coatings is a key technology to ensure their long-term stable application. Introducing nanocomposite materials into coating systems and utilizing the special effects of nanounits to enhance the overall protective performance of the coating has become an important development direction in the field of heavy-duty anti-corrosion coatings.

[0003] Traditional aluminum alloy corrosion protection solutions typically rely on a composite system of chemical conversion coatings and organic coatings. Specifically, before applying the organic coating, the aluminum alloy substrate is first treated with chromate to form a chromate film. This chromate film provides passivation to the substrate and improves the adhesion of subsequent coatings. On top of this, an organic coating primarily composed of epoxy resin is applied, physically isolating the substrate to prevent the intrusion of corrosive media. This technology has been widely used in industry for a long time due to its mature process and relatively controllable cost.

[0004] However, the shortcomings of existing technologies are becoming increasingly apparent. Firstly, hexavalent chromium used in chromate treatment is a recognized highly toxic substance and a potent carcinogen. Its production and application pose a serious threat to the environment and human health, and have been strictly restricted by global environmental regulations. Secondly, the protective performance of this coating system has bottlenecks. The bonding between the coating and the substrate mainly relies on physical adsorption and mechanical locking. Under long-term humid, hot, or salt spray environments, the interface is easily penetrated and damaged by water molecules, leading to decreased coating adhesion, blistering, and even peeling. Although some studies have attempted to use chromium-free conversion agents or add functional fillers to the coating, it remains difficult to synergistically solve the three core problems of environmental protection, strong adhesion, and long-term corrosion protection.

[0005] Therefore, this invention proposes a heavy-duty anti-corrosion coating containing nanocomposite materials and its application on aluminum alloy substrates to address the shortcomings of existing technologies. Summary of the Invention

[0006] The purpose of this invention is to provide a heavy-duty anti-corrosion coating containing nanocomposite materials and its application on aluminum alloy substrates. Traditional heavy-duty anti-corrosion coatings have technical problems such as poor adhesion, insufficient anti-corrosion durability and environmental unfriendliness when applied to aluminum alloy substrates.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a heavy-duty anti-corrosion coating containing nanocomposite materials, employing the following technical solution: A heavy-duty anti-corrosion coating containing nanocomposite materials is made from raw materials comprising the following parts by weight: bisphenol A type epoxy resin: 40-60 parts; modified polyetheramine curing agent: 9.2-13.8 parts; γ-methacryloyloxypropyltrimethoxysilane: 1-5 parts; controlled hydrolysis initiator: 0.1-0.5 parts; graphene: 2-8 parts; nano silica: 3-10 parts; ammonium polyphosphate: 5-15 parts; sodium molybdate: 3-10 parts; mixed solvent: 20-30 parts.

[0008] By adopting the above technical solution, this invention establishes a multi-layered, synergistic, and layered heavy-duty anti-corrosion system. This system achieves a dense, highly adhesive composite coating with active repair capabilities through the synergistic effects of physical barriers, chemical corrosion inhibition, and interface enhancement. Its mechanism of action is specifically described below: Firstly, at the chemical corrosion inhibition level, the system constructs a dual inhibition mechanism. Sodium molybdate, as a highly efficient, low-toxicity, and environmentally friendly corrosion inhibitor, can replace traditional toxic heavy metal corrosion inhibitors such as chromates. Its molybdate ion (MoO4) 2- Ammonium polyphosphate preferentially adsorbs onto active sites on the surface of aluminum alloy substrates, forming a dense passivation film (such as Al2(MoO4)3), effectively inhibiting the anodic process of the corrosion electrochemical reaction. Ammonium polyphosphate constitutes an intumescent flame-retardant and corrosion-inhibiting system. When external corrosive media (such as water and acidic ions) penetrate into the coating, ammonium polyphosphate is activated and decomposes to produce polyphosphoric acid. On one hand, polyphosphoric acid can complex with metal ions to form a stable phosphate film; on the other hand, it acts as a dehydration catalyst, promoting localized carbonization of the epoxy resin to form a dense carbon layer. This carbon layer isolates oxygen and further corrosive media from further intrusion, playing a role in corrosion inhibition and sealing. This corrosion-inhibiting system does not contain toxic heavy metals, reducing the environmental and human health hazards of the coating during production and use.

[0009] Secondly, at the physical barrier level, the system achieves nanoscale densification. Graphene, with its two-dimensional sheet structure and extremely high aspect ratio, is interspersed throughout the coating, constructing a physical barrier that hinders media penetration and significantly extending the path of corrosive media such as water, oxygen, and chloride ions to the substrate surface. Hydrophobically modified nano-silica, with its extremely small particle size, fills the gaps between polymer chain segments in the epoxy resin curing network, increasing the crosslinking density and overall compactness of the coating, further reducing its permeability.

[0010] This invention aims to solve the problem of weak interfacial adhesion, especially poor wet adhesion, between the coating and the aluminum alloy substrate by introducing a specific combination of a "controlled hydrolysis initiator" and "γ-methacryloyloxypropyltrimethoxysilane". Its innovative principle lies in the regulation of the hydrolysis process of the silane coupling agent, the specific reaction process of which is as follows: Step 1: The controlled hydrolysis initiator in the system has a core of a water-containing metal salt encapsulated in a porous silica carrier. This structure keeps the water in a bound state, maintaining stability during paint storage and application, and preventing premature hydrolysis and condensation failure of γ-methacryloyloxypropyltrimethoxysilane due to contact with free water.

[0011] Step 2: During the initial heating stage of coating curing (60-80℃), the initiator is heated, and the crystal water inside it is slowly released at a controlled rate.

[0012] Step 3: The released trace water molecules act precisely on the γ-methacryloxypropyltrimethoxysilane molecules in the interfacial region, initiating the hydrolysis of its methoxy group (-OCH3) to generate a highly active silanol group (-Si-OH).

[0013] Step 4: The generated silanol groups undergo a dehydration condensation reaction with the hydroxyl groups (Al-OH) on the surface of the aluminum alloy substrate to form a strong covalent bond (Al-O-Si), thus achieving chemical anchoring between the coating and the metal substrate.

[0014] Step 5: Simultaneously, the methyl group (-CH3) at the other end of γ-methacryloyloxypropyltrimethoxysilane undergoes a ring-opening addition reaction with the epoxy group of the epoxy resin, tightly connecting the organic coating body with the silane molecules already anchored on the substrate.

[0015] Through this in-situ, controlled hydrolysis-condensation process, the present invention achieves chemical coupling between the organic coating substrate and the inorganic aluminum alloy substrate, which greatly improves the dry and wet adhesion of the coating and ensures that the coating will not blister or fall off due to loss of adhesion in corrosive environments, thus providing a basic guarantee for the long-term effectiveness of the entire anti-corrosion system.

[0016] Preferably, the heavy-duty anti-corrosion coating is made from raw materials comprising the following parts by weight: bisphenol A type epoxy resin: 50 parts; modified polyetheramine curing agent: 11.5 parts; γ-methacryloyloxypropyltrimethoxysilane: 3 parts; controlled hydrolysis initiator: 0.3 parts; graphene: 5 parts; nano silica: 8 parts; ammonium polyphosphate: 10 parts; sodium molybdate: 6 parts; mixed solvent: 25 parts.

[0017] By adopting the above technical solution, the component ratio achieves synergistic effect between the curing and crosslinking of epoxy resin, the physical barrier effect of functional fillers and the chemical corrosion inhibition system, so that the final comprehensive anti-corrosion performance of the coating and its adhesion to the substrate reach the optimal balance.

[0018] Preferably, the controlled hydrolysis initiator is prepared by the following method: 1. Vacuum dry the porous silica support with a pore size of 8-10 nm at 130-140℃ for 4-5 hours; 2. Load a saturated solution of a metal salt containing water of crystallization onto an activation carrier using an equal-volume impregnation method, and seal and let it stand for 3-4 hours; 3. Dry the sample at 60-70℃ for 10-12 hours. By adopting the above technical solution, this preparation method can ensure that the crystal water of the metal salt is effectively encapsulated in the nanopores of silica, forming a stable solid hydrate, which provides a structural basis for the controllable release of moisture during the subsequent curing process.

[0019] Preferably, the mixed solvent is composed of xylene and n-butanol, and the volume ratio of xylene to n-butanol is (2-3):1. By adopting the above technical solution, this solvent ratio provides good solubility for epoxy resin and controls the evaporation rate and leveling properties of the coating during construction and curing, which helps to form a smooth and defect-free coating.

[0020] Preferably, the active hydrogen equivalent of the modified polyetheramine curing agent is 100-130 g / eq. By adopting the above technical solution, this range of active hydrogen equivalents ensures that the amino groups of the curing agent can achieve a near stoichiometric match with the epoxy groups of the bisphenol A type epoxy resin, thereby forming a highly crosslinked cured network, which is crucial for the final mechanical strength and chemical resistance of the coating.

[0021] Secondly, the present invention provides a method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials, using the following technical solution: (i) Preparing the coating for use, wherein the steps for preparing the coating for use include: ① Graphene, nano-silica, and ammonium polyphosphate are dispersed in a mixed solvent to obtain a functional filler dispersion; ② Bisphenol A type epoxy resin, sodium molybdate, γ-methacryloxypropyltrimethoxysilane and hydrolysis initiator are mixed to obtain resin premix; ③ The functional filler dispersion is mixed with the resin premix to obtain the coating matrix; ④ Add the modified polyetheramine curing agent to the coating matrix and mix thoroughly to obtain the coating to be used; (ii) Apply the coating material prepared in step (1) to the surface of the aluminum alloy substrate; (iii) Perform a two-step curing process on the substrate coated with the coating to be used. The two-step curing process includes: first, holding at 60-80℃ for 60-90 min, and then raising the temperature to 120-140℃ and holding for 60-90 min.

[0022] By adopting the above technical solution, this preparation method ensures the maximization of the function of each component and constructs a stable coating-substrate interface through the design of the material mixing sequence and curing process.

[0023] The material preparation sequence in this method directly affects the uniformity and stability of the final coating. Step ① involves pre-dispersing all difficult-to-disperse solid functional fillers in a low-viscosity solvent using high-energy dispersion, which effectively breaks down filler agglomerates and achieves uniform distribution within the system. This dispersion is then mixed with the resin premix (Step ②), avoiding the inefficiency of directly dispersing solid powders in high-viscosity resin. Finally, a curing agent is added before application (Step ④), ensuring a sufficient pot life for the coating. This procedural preparation process guarantees the uniformity and stability of the final coating system.

[0024] The key innovation of this preparation method lies in the two-step curing procedure used in step (3). This procedure works synergistically with the controlled hydrolysis initiator and silane coupling agent in the coating components. The mechanism is as follows: First stage (60-80℃ holding): This low-temperature stage is mainly used for initiating interfacial reactions and initial coating formation. At this temperature, the viscosity of the coating system is low, which is beneficial for coating leveling and releasing residual solvents to form a uniform wet film. More importantly, this temperature can activate the controlled hydrolysis initiator, causing its internal water of crystallization to be released slowly at a controlled rate. The released trace water molecules can initiate the hydrolysis of γ-methacryloyloxypropyltrimethoxysilane at the interface to generate silanol groups (-Si-OH). Because the water release rate is controlled, premature self-condensation and failure of the silane in the bulk are avoided, ensuring that it preferentially reacts with the hydroxyl groups on the substrate surface.

[0025] The second stage (120-140℃ heat preservation): This high-temperature stage aims to achieve deep curing of the coating. On one hand, the high temperature significantly accelerates the cross-linking reaction between the epoxy resin and the amine curing agent, forming a dense resin network that endows the coating with excellent mechanical properties and chemical resistance. On the other hand, it provides sufficient energy for the dehydration condensation reaction between the silanol groups generated in the first stage and the hydroxyl groups (-Al-OH) on the substrate surface, forming stable Al-O-Si chemical bonds, thereby completing the chemical coupling between the organic coating and the inorganic substrate.

[0026] This two-step curing process allows the physical shaping of the coating, the chemical bonding of the interface, and the deep curing of the host resin to proceed in steps over time, ultimately resulting in a heavy-duty anti-corrosion coating with both high adhesion and high density.

[0027] Preferably, the two-step curing procedure is as follows: first, hold at 70°C for 80 minutes, then raise the temperature to 130°C and hold for 80 minutes. By adopting the above technical solution, this specific curing process curve provides a balanced reaction window for the preferred formulation of the present invention, ensuring both the full progress of silane hydrolysis and condensation reactions at the interface and the complete curing of the epoxy resin system.

[0028] Preferably, in step ①, a high-speed disperser is used to disperse the material at a speed of 1500-2500 r / min for 45-60 min. By adopting the above technical solution, this dispersion process parameter provides sufficient shear energy for the deagglomeration of nanoscale fillers (such as graphene and nano silica), ensuring that they are uniformly distributed in the coating system at a size close to their original particle size, thereby effectively exerting their physical barrier function.

[0029] Preferably, before step (ii), a sandblasting treatment of the aluminum alloy substrate surface is included. By adopting the above technical solution, sandblasting can not only remove the oxide layer and contaminants on the substrate surface, but also increase its surface roughness and specific surface area. This enhances the physical and mechanical interlocking effect between the coating and the substrate, and also increases the surface active sites (hydroxyl groups) available for the silane coupling agent to react, further improving the interfacial bonding strength.

[0030] Thirdly, the present invention provides an application of a heavy-duty anti-corrosion coating containing nanocomposite materials in the corrosion protection of aluminum alloy substrates, employing the following technical solution: The heavy-duty anti-corrosion coating containing nanocomposite materials described in the first aspect is applied to the surface of an aluminum alloy substrate to protect it from corrosion.

[0031] By adopting the above technical solution, this application achieves long-term corrosion protection for aluminum alloy substrates through the synergistic effect of the following three mechanisms: Interfacial chemical bonding: During the coating curing process, γ-methacryloxypropyltrimethoxysilane undergoes in-situ hydrolysis under controlled conditions. The resulting silanol groups condense with the hydroxyl groups on the surface of the aluminum alloy substrate, forming stable Al-O-Si chemical bonds. This chemical bonding achieves effective coupling between the organic coating and the inorganic substrate, fundamentally improving the coating's adhesion, especially its hydrolysis-resistant wet adhesion.

[0032] Dual chemical corrosion inhibition: Molybdate forms a passivation film on the substrate surface, inhibiting the anodic process of the corrosion electrochemical reaction. Simultaneously, ammonium polyphosphate decomposes to produce polyphosphoric acid upon the intrusion of corrosive media. This polyphosphoric acid reacts with corrosion products to form a dense phosphate precipitate film, sealing corrosion active sites and thus providing both corrosion inhibition and sealing effects.

[0033] Dense physical barrier: The graphene and nano-sized silica in the coating fill each other, forming a dense physical barrier layer in the epoxy resin curing network, which prevents the penetration of corrosive media such as water, oxygen and chloride ions.

[0034] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention introduces a controlled hydrolysis initiator and a silane coupling agent, combined with a two-step curing process, to initiate silane hydrolysis in situ and controllably during the low-temperature curing stage of the coating. This allows the silane to preferentially react with the hydroxyl groups on the surface of the aluminum alloy substrate, and subsequently complete cross-linking with the epoxy resin at the high-temperature stage. This design forms dense Al-O-Si chemical bonds at the interface between the coating and the metal substrate, fundamentally solving the problem of poor wet adhesion caused by weak interfacial bonding in traditional coatings, and significantly improving the bonding strength and durability between the coating and the substrate.

[0035] 2. This invention constructs a dense physical barrier layer in the coating by combining graphene with nano-silica, effectively extending the penetration path of corrosive media. Simultaneously, the synergistic effect of sodium molybdate and ammonium polyphosphate corrosion inhibitors in the system not only forms a stable passivation film on the substrate surface but also forms precipitates to block active sites when corrosion occurs. This design, combining a physical barrier with dual chemical corrosion inhibition, endows the nanocomposite coating with excellent and long-lasting heavy-duty corrosion protection.

[0036] 3. This invention successfully replaces the highly toxic heavy metal corrosion inhibitors such as chromates widely used in traditional heavy-duty anti-corrosion coatings by employing a composite corrosion inhibition system composed of sodium molybdate and ammonium polyphosphate. This design not only ensures excellent anti-corrosion performance but also avoids the introduction of toxic heavy metal elements at the source, significantly reducing the potential hazards to the environment and operators throughout the entire life cycle of the coating, including production, construction, and service. This enables the heavy-duty anti-corrosion coating to achieve the technical goals of low toxicity and environmental friendliness. Detailed Implementation

[0037] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0038] Bisphenol A type epoxy resin is an oligomer of bisphenol A diglycidyl ether, with CAS number 25068-38-6 and epoxy equivalent of 450-500 g / eq. It appears as a light yellow to brownish-yellow high-viscosity liquid or semi-solid.

[0039] Modified polyetheramine curing agent is a modified amine epoxy curing agent based on polyoxypropylene diamine structure. Its active hydrogen equivalent is 100-130 g / eq, and its appearance is a colorless to pale yellow transparent liquid.

[0040] Nanofillers: graphene and nano-silica.

[0041] Graphene, with CAS number 1034343-98-0, is a multilayer graphene sheet prepared by redox method, with an aspect ratio of 500-1000, an average sheet diameter of 5-15 μm, and a carbon content greater than 99 wt.%.

[0042] Nano-silica, whose main component is silicon dioxide (CAS No.: 7631-86-9), is a nano-sized powder prepared by a gas-phase method and then modified with silane reagents to achieve hydrophobicity. Its original particle size is 7-40 nm, and its specific surface area is 150-300 m². 2 / g.

[0043] Sodium molybdate, CAS number 7631-95-0, is an anhydrous white crystalline powder with a purity greater than 99.5%.

[0044] γ-Methacryloxypropyltrimethoxysilane, CAS No. 2530-85-0, is a colorless or slightly yellow transparent liquid with a purity greater than 98%.

[0045] The controlled hydrolysis initiator is a non-commercially available substance prepared in this invention. It consists of a metal salt containing water of crystallization and a porous silica carrier. The specific preparation method is described in subsequent preparation examples 1-2.

[0046] Ammonium polyphosphate, with CAS number 68333-79-9, is a Phase II product with a degree of polymerization (n) greater than 1000.

[0047] The mixed solvent is composed of xylene (CAS No.: 1330-20-7) and n-butanol (CAS No.: 71-36-3) in a specific volume ratio, both of which are of analytical grade.

[0048] Preparation example: Preparation of controlled hydrolysis initiator.

[0049] Preparation Example 1: This preparation example provides a method for preparing a hydrolysis initiator (P1), including the following steps: (1) 25 parts of porous silica powder with a pore size of 8 nm were placed in a vacuum oven and dried at 130°C for 5 hours to remove physically adsorbed water. After cooling to room temperature, the activated carrier was obtained for later use.

[0050] (2) Weigh 45 parts of copper sulfate pentahydrate and dissolve it in 100 parts of deionized water to prepare a saturated solution. Using the equal volume impregnation method, add the saturated solution dropwise to the activated carrier prepared in step (1) while stirring. Continue stirring at low speed (150 r / min) for 30 min to ensure that the liquid is completely absorbed. Then seal and let it stand for 3 hours to impregnate.

[0051] (3) Transfer the impregnated sample obtained in step (2) to a forced-air drying oven and dry it at 60°C for 10 hours to remove excess free water and obtain a blue powder product, which is the controlled hydrolysis initiator (P1). Seal and store it in a desiccator for later use.

[0052] Preparation Example 2: This preparation example provides a method for preparing a hydrolysis initiator (P2), including the following steps: (1) Place 30 parts of porous silica powder with a pore size of 10 nm in a vacuum oven and dry at 140 °C for 4 hours to remove physically adsorbed water. After cooling to room temperature, the activated carrier is obtained for later use.

[0053] (2) Weigh 50 parts of magnesium sulfate heptahydrate and dissolve it in 100 parts of deionized water to prepare a saturated solution. Using the equal volume impregnation method, add the saturated solution dropwise to the activated carrier prepared in step (1) while stirring. Continue stirring at low speed (150 r / min) for 30 min to ensure that the liquid is completely absorbed. Then seal and let it stand for 4 hours to impregnate.

[0054] (3) Transfer the impregnated sample obtained in step (2) to a forced-air drying oven and dry it at 70°C for 12 hours to remove excess free water and obtain a white powder product, which is the controlled hydrolysis initiator (P2). Seal and store it in a desiccator for later use.

[0055] Example: Example 1: This embodiment provides a method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials, including the following steps: (1) Add 25 parts of mixed solvent (xylene to n-butanol volume ratio of 3:1) to a container by mass, and then add 5 parts of graphene, 8 parts of nano silica and 10 parts of ammonium polyphosphate in sequence under stirring. Disperse the mixture for 50 min at 2000 r / min using a high-speed disperser to obtain functional filler dispersion A.

[0056] (2) Add 50 parts of bisphenol A type epoxy resin, 6 parts of sodium molybdate, 3 parts of γ-methacryloxypropyltrimethoxysilane and 0.3 parts of the controlled hydrolysis initiator (P1) prepared in Preparation Example 1 to another reactor, and mechanically stir at 600 r / min for 40 min to obtain resin premix B.

[0057] (3) While the resin premix B is being continuously stirred, the functional filler dispersion A obtained in step (1) is added to it, and then the mixture is transferred to a ball mill and ball milled for 2.5 hours to obtain the coating matrix C.

[0058] (4) Take the paint matrix C obtained in step (3), add 11.5 parts of modified polyetheramine curing agent, stir at low speed for 15 minutes until the mixture is uniform, and obtain the paint D to be used.

[0059] (5) Apply the coating D obtained in step (4) to the surface of the pretreated 6061 aluminum alloy substrate by air spraying, and control the dry film thickness to be 70 μm. Place the coated substrate in an oven and perform a two-step curing procedure: first, keep it at 70℃ for 80 min, then raise the temperature to 130℃ and keep it at 130℃ for 80 min, and then cool it with the oven to obtain a heavy-duty anti-corrosion coating.

[0060] Example 2: This embodiment provides a method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials, including the following steps: (1) By mass, 20 parts of mixed solvent (xylene and n-butanol in a volume ratio of 2:1) were added to a container, and then 2 parts of graphene, 3 parts of nano-silica and 5 parts of ammonium polyphosphate were added in sequence under stirring. The mixture was dispersed for 45 minutes at a speed of 1500 r / min using a high-speed disperser to obtain functional filler dispersion A.

[0061] (2) Add 40 parts of bisphenol A type epoxy resin, 3 parts of sodium molybdate, 1 part of γ-methacryloxypropyltrimethoxysilane and 0.1 parts of the controlled hydrolysis initiator (P1) prepared in Preparation Example 1 to another reactor, and mechanically stir at 500 r / min for 30 min to obtain resin premix B.

[0062] (3) While the resin premix B is being continuously stirred, the functional filler dispersion A obtained in step (1) is added to it, and then the mixture is transferred to a ball mill and ball milled for 2 hours to obtain the coating matrix C.

[0063] (4) Take the paint matrix C obtained in step (3), add 9.2 parts of modified polyetheramine curing agent, stir at low speed for 15 minutes until the mixture is uniform, and obtain the paint D to be used.

[0064] (5) Apply the coating D obtained in step (4) to the surface of the pretreated 6061 aluminum alloy substrate by air spraying, and control the dry film thickness to be 50 μm. Place the coated substrate in an oven and perform a two-step curing procedure: first, keep it at 60℃ for 60 min, then raise the temperature to 120℃ and keep it at 120℃ for 60 min, and then cool it with the oven to obtain a heavy-duty anti-corrosion coating.

[0065] Example 3: This embodiment provides a method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials, including the following steps: (1) By mass, 30 parts of mixed solvent (xylene and n-butanol in a volume ratio of 3:1) were added to a container, and then 8 parts of graphene, 10 parts of nano-silica and 15 parts of ammonium polyphosphate were added in sequence under stirring. The mixture was dispersed for 60 minutes at a speed of 2500 r / min using a high-speed disperser to obtain functional filler dispersion A.

[0066] (2) Add 60 parts of bisphenol A type epoxy resin, 10 parts of sodium molybdate, 5 parts of γ-methacryloxypropyltrimethoxysilane and 0.5 parts of the controlled hydrolysis initiator (P2) prepared in Preparation Example 2 to another reactor, and mechanically stir at 800 r / min for 45 min to obtain resin premix B.

[0067] (3) While the resin premix B is being continuously stirred, the functional filler dispersion A obtained in step (1) is added to it, and then the mixture is transferred to a ball mill and ball milled for 3 hours to obtain the coating matrix C.

[0068] (4) Take the paint matrix C obtained in step (3), add 13.8 parts of modified polyetheramine curing agent, stir at low speed for 15 minutes until the mixture is uniform, and obtain the paint D to be used.

[0069] (5) Apply the coating D obtained in step (4) to the surface of the pretreated 6061 aluminum alloy substrate by air spraying, and control the dry film thickness to be 100 μm. Place the coated substrate in an oven and perform a two-step curing procedure: first, keep it at 80℃ for 90 min, then raise the temperature to 140℃ and keep it at 140℃ for 90 min, and then cool it with the oven to obtain a heavy-duty anti-corrosion coating.

[0070] The pretreatment in step (5) of Examples 1-3 can be sandblasting to increase the surface roughness of the aluminum alloy substrate.

[0071] Comparative example: Comparative Example 1: Compared with Example 1, the difference is that no controlled hydrolysis initiator (P1) is added in step (2), and all other steps are the same.

[0072] Comparative Example 2: Compared with Example 1, the difference is that the curing procedure in step (5) is replaced by: placing the coated substrate directly in an oven at 130°C for 160 minutes, and the rest are the same.

[0073] Comparative Example 3: Compared with Example 1, the difference is that γ-methacryloyloxypropyltrimethoxysilane and controlled hydrolysis initiator (P1) are not added in step (2); and the curing procedure in step (5) is replaced by placing the coated substrate directly in an oven at 130°C for 160 min, and the rest are the same.

[0074] Comparative Example 4: Compared with Example 1, the difference is that: no controlled hydrolysis initiator (P1) is added in step (2); and the curing procedure in step (5) is replaced by: placing the coated substrate directly in an oven at 130°C for 160 min, and the rest are the same.

[0075] Comparative Example 5: Compared with Example 1, the difference is that ammonium polyphosphate is not added in step (1), but all other steps are the same.

[0076] Test example: Test Example 1: 1. Experimental Description and Test Groups This test aims to evaluate the impedance change of the coating under long-term immersion in a corrosive medium (3.5% NaCl solution) using electrochemical impedance spectroscopy (EIS). Low-frequency impedance modulus (|Z|) 0.01Hz Ohm square centimeters (Ω·cm) is a key indicator characterizing the shielding performance and protective capability of a coating, and its value is related to the coating's ability to block corrosive media. The unit of this indicator is ohm square centimeters (Ω·cm). 2 ), which is the area-normalized impedance used for standardized comparison.

[0077] There are a total of 7 groups, namely Example 1, Example 2, Example 3, and Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4.

[0078] 2. Experimental Procedure The coated and cured 6061 aluminum alloy samples (Examples 1-3 and Comparative Examples 1-4) were edge-sealed with epoxy resin, leaving only one area (e.g., 1 cm²). 2 The working area is exposed to the electrolyte. The electrochemical testing system employs a three-electrode system: the working electrode (WE) is the coating sample to be tested, the reference electrode (RE) is a saturated calomel electrode (SCE) or a silver / silver chloride electrode, and the auxiliary electrode (CE) is a large-area platinum sheet. The electrolyte solution is prepared as a 3.5% (wt.) NaCl solution using deionized water and analytical grade sodium chloride.

[0079] During testing, all working electrodes were immersed in a 3.5% NaCl solution. Open circuit potential (OCP) monitoring was performed first, and the system was considered stable when the OCP fluctuation was less than 5 mV within 30 minutes. Subsequently, a sinusoidal AC voltage perturbation with an amplitude of 10 mV was applied under the OCP, with the scan frequency range set from 100 kHz to 0.01 Hz. This procedure was executed on days 1, 15, 30, and 60 of sample immersion, and EIS data were recorded at different immersion time points. Finally, the impedance modulus value (|Z|) at a frequency of 0.01 Hz was extracted from all data. 0.01Hz Compare them.

[0080] 3. Experimental data (see Table 1) Table 1: Low-frequency impedance modulus (|Z|) of each sample after immersion in 3.5% NaCl solution for different times 0.01Hz ) Table 1 shows the electrochemical impedance spectroscopy (EIS) data, which quantitatively demonstrates the differences in the protective performance of the coatings under different preparation conditions. The samples from Examples 1-3, after being immersed in 3.5% NaCl solution for 60 days, exhibited low-frequency impedance modulus (|Z|). 0.01Hz It remains at 1.2×10 10 Ω·cm 2 Up to 5.5×10 10 Ω·cm 2 The data indicates that the coating system forms a dense physical barrier structure, effectively hindering the penetration of corrosive media. In contrast, the low-frequency impedance modulus of samples 1-4 decreased to 10 after the same test cycle. 5 Ω·cm 2 Up to 10 7 Ω·cm 2 The extent of the damage indicates that its protective structure has failed.

[0081] Correlating EIS data with various preparation conditions shows that the protective performance of this scheme depends not only on the physical barrier of the filler, but also on the chemical reaction initiated under specific process conditions. The controlled hydrolysis initiator used in the scheme provides controlled initiation conditions for subsequent reactions. This initiator and γ-methacryloyloxypropyltrimethoxysilane are introduced together into resin premix B. In the two-step curing procedure set in step (5), the lower temperature in the first stage (60℃-80℃) is conducive to the release of trace amounts of water by the initiator, preferentially initiating the hydrolysis reaction of γ-methacryloyloxypropyltrimethoxysilane to generate silanol groups (-Si-OH). The subsequent second stage of heating (120℃-140℃) promotes two condensation reactions of silanol groups: one is the dehydration between silanol groups to form a -Si-O-Si- inorganic network, which interpenetrates with the original epoxy resin network; the other is the dehydration reaction between silanol groups and hydroxyl groups on the surface of the aluminum alloy substrate to form a -Si-O-Al- chemical bond interface. The organic-inorganic hybrid network formed in the bulk phase of the coating and the chemical bonds formed at the interface constitute the stable protective system with high impedance and high adhesion in Examples 1-3.

[0082] The comparative data confirmed the above mechanism. The impedance values ​​of both Comparative Example 1 (lacking initiator) and Comparative Example 2 (lacking the two-step curing process) decreased, indicating that without either condition, the silane could not undergo sufficient hydrolysis and condensation reactions, resulting in the inability to form an effective hybrid network and chemically bonded interface. Comparative Example 5 (lacking ammonium polyphosphate) showed lower impedance in the later stages of immersion than Example 1, but higher than Comparative Examples 1-4, indicating that ammonium polyphosphate helps enhance the long-term physical shielding performance of the coating. The impedance value of Comparative Example 4 (lacking both initiator and step-curing) decreased further, confirming that the effect of adding only a silane coupling agent without specific reaction conditions is limited. Therefore, the EIS data show that the combination of a controlled hydrolysis initiator and a two-step curing process is a key technological component for achieving high impedance performance in coatings.

[0083] Test Example 2: 1. Experimental Description and Test Groups This test aims to accelerate the evaluation of the corrosion resistance of coatings in a simulated marine atmospheric environment through a neutral salt spray test, focusing on the coating's overall protection capability for the substrate and its corrosion inhibition capability at scratches and defects.

[0084] There are a total of 8 test groups, namely Example 1, Example 2, Example 3, and Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5.

[0085] 2. Experimental Procedure For coated and cured 6061 aluminum alloy samples (Examples 1-3 and Comparative Examples 1-5), cross-cuts were made on the surface using a single-edged cutting tool, with the cuts penetrating the coating to the aluminum alloy substrate. The samples were then placed in a neutral salt spray chamber for continuous spray testing according to GB / T 10125. The salt spray chamber conditions were set as follows: 5% (wt.) NaCl solution, temperature 35°C. After 2000 hours of cumulative testing, the samples were removed, rinsed with water, dried, and then rated. The rating included: measuring the maximum corrosion spread width on one side of the scratch using a graduated microscope or calipers; assessing the blistering grade of the coating (including blister density and size) according to GB / T 1766; and conducting a cross-cut adhesion test on the non-scribed areas of the sample according to GB / T 9286 and rating the grade.

[0086] 3. Experimental data (see Table 2) Table 2: Performance ratings of each sample after 2000 hours of salt spray testing Table 2 shows the salt spray test data, indicating that after 2000 hours of neutral salt spray testing, the coatings of Examples 1-3 did not blister (Grade 0), the scratch corrosion propagation width was less than 0.7 mm, and the adhesion was Grade 1. This result demonstrates that the coating system possesses corrosion inhibition capability and interfacial bonding strength. Comparative Examples 1-5, however, exhibited coating blistering, scratch corrosion propagation, and decreased adhesion.

[0087] This performance stems from the organic-inorganic hybrid network formed within the coating and the chemical bonds formed at the interface. Under the two-step curing process, the controlled hydrolysis initiator provides the conditions for the hydrolysis of γ-methacryloyloxypropyltrimethoxysilane. Subsequent condensation reactions form a -Si-O-Si- crosslinked network in the coating bulk phase, improving coating density, blocking chloride ion penetration, and inhibiting coating blistering. Simultaneously, the -Si-O-Al- chemical bonds formed between the silanol groups and the aluminum alloy substrate surface enhance the adhesion between the coating and the substrate. This interfacial adhesion is the structural reason why the coating maintains an adhesion grade of 1 after salt spray testing and inhibits corrosion propagation along the interface at scratches.

[0088] The comparative data verified the above-described mechanism. Comparative Examples 1 (lacking initiator) and 2 (lacking two-step curing) exhibited poor adhesion to the substrate due to the inability to form sufficient -Si-O-Si- networks and -Si-O-Al- interfacial bonds. Water and chloride ions penetrated at the interface, initiating blistering and scratch corrosion propagation. The results of Comparative Examples 3 and 4 further confirmed that the lack of the aforementioned chemical bonding mechanism reduced the coating's protective capability. Comparative Example 5 (lacking ammonium polyphosphate) showed inferior corrosion propagation width and adhesion grade compared to Example 1, indicating that both fillers also contribute to the overall protective performance of the coating.

[0089] Test Example 3: 1. Experimental Description and Test Groups This test aims to quantitatively determine the bonding strength between the coating and the 6061 aluminum alloy substrate using the pull-out method. There are eight test groups in total: Example 1, Example 2, Example 3, and Comparative Examples 1, 2, 3, 4, and 5.

[0090] 2. Experimental Procedure On the cured coating samples of Examples 1-3 and Comparative Examples 1-5, a flat area was selected and cleaned. A standard-sized dolly was vertically bonded to the coating surface using the matching high-strength adhesive. After the adhesive had fully cured under specified conditions, a special cutter was used to cut the coating down to the substrate along the edge of the dolly to isolate the test area. The pull-out device of a portable pull-off adhesion tester was connected to the dolly, and a tensile force perpendicular to the coating surface was applied at a set rate (e.g., 0.2 MPa / s) until the dolly detached from the substrate surface. The maximum tensile stress (MPa) at which the coating failed, as displayed by the instrument, was recorded. Each group was tested three times, and the average value was taken.

[0091] 3. Experimental data (see Table 3) Table 3: Adhesion test results of each sample by pull-off method sample Adhesion (MPa) Example 1 13.8 Example 2 11.5 Example 3 12.9 Comparative Example 1 6.5 Comparative Example 2 5.8 Comparative Example 3 3.2 Comparative Example 4 4.1 Comparative Example 5 9.6 The adhesion test data in Table 3 show that the adhesion values ​​of Examples 1-3 ranged from 11.5 MPa to 13.8 MPa. The adhesion values ​​of Comparative Examples 1, 2, and 4 ranged from 4.1 MPa to 6.5 MPa. The adhesion value of Comparative Example 3 was 3.2 MPa. The adhesion value of Comparative Example 5 was 9.6 MPa.

[0092] The high adhesion values ​​in Examples 1-3 are attributed to the -Si-O-Al chemical bonds formed at the interface between the coating and the 6061 aluminum alloy substrate. In the first stage of the two-step curing process, a controlled hydrolysis initiator induces the hydrolysis of γ-methacryloyloxypropyltrimethoxysilane to generate silanol groups (-Si-OH). After heating in the second stage, the generated silanol groups undergo a dehydration condensation reaction with the hydroxyl groups on the surface of the aluminum alloy substrate, forming chemical bonds at the interface.

[0093] Data analysis from comparative examples verified the above mechanism. The adhesion values ​​for Comparative Example 1 (lacking initiator) and Comparative Example 2 (lacking two-step curing) were 6.5 MPa and 5.8 MPa, respectively. This result indicates that without reaction initiation conditions or a step-by-step process, the hydrolysis and condensation reactions of silane are insufficient, and interfacial chemical bonds are not effectively formed. The adhesion of Comparative Example 3 (lacking both silane and initiator) was 3.2 MPa, reflecting the bonding strength between the epoxy resin coating and the aluminum alloy substrate, which is mainly based on physical adsorption. The adhesion of Comparative Example 5 (lacking ammonium polyphosphate) was 9.6 MPa, lower than Example 1 but higher than Comparative Examples 1-4, indicating that the interfacial chemical bonding mechanism has been formed in this component. The combined data show that the combination of controlled hydrolysis initiator and two-step curing process promotes the formation of interfacial -Si-O-Al chemical bonds, which is the technical reason for the high coating adhesion.

[0094] Test Example 4: 1. Experimental Description and Test Groups This test aims to determine the volatile organic compound (VOC) content of coatings in their applied state using gas chromatography to evaluate whether they comply with relevant environmental regulations. The test groups are Example 1, Example 2, and Example 3.

[0095] 2. Experimental Procedure Tests were conducted according to GB / T 23985-2009 standard. Approximately 0.3 g of the coating D prepared in step (4) of each embodiment was accurately weighed and placed in a headspace vial for sealing. The headspace vial was equilibrated in a headspace furnace at 150°C for 30 min. Then, 1 mL of headspace gas was injected into a gas chromatograph equipped with a flame ionization detector (FID) for analysis. A calibration curve was constructed using standard solvents of known concentrations (xylene, n-butanol, etc.) using the external standard method to quantify each solvent component in the sample. Finally, the VOC content of the coating was calculated in g / L based on the sample mass, the content of each solvent component, and the coating density.

[0096] 3. Experimental data (see Table 4) Table 4: VOC content test results for each example sample Coating density (g / mL) VOC content (g / L) Example 1 1.48 287 Example 2 1.51 253 Example 3 1.45 311 The test data in Table 4 show that the VOC contents of Examples 1, 2, and 3 are 287 g / L, 253 g / L, and 311 g / L, respectively. The national standard GB 30981-2020 sets the VOC content limit for epoxy anticorrosive coatings at 420 g / L. The VOC contents of all examples are lower than this limit.

[0097] The anti-corrosion and adhesion properties of this coating system originate from its internal chemical bonding network, rather than the physical effects of a high proportion of solvent. As shown in the data from Test Examples 1 to 3, the combination of a controlled hydrolysis initiator and a two-step curing process induces in-situ hydrolysis and condensation of γ-methacryloyloxypropyltrimethoxysilane, forming a -Si-O-Si- hybrid network and -Si-O-Al- interfacial chemical bonds. This internal structure enables the coating to possess high impedance and high adhesion even with low solvent content. Therefore, the VOC test results combined with performance test data indicate that the formulation and preparation method of this coating, while meeting low VOC emission requirements, achieves the anti-corrosion and adhesion properties provided by the chemical bonding network.

Claims

1. A heavy-duty anti-corrosion coating containing nanocomposite materials, characterized in that, The heavy-duty anti-corrosion coating comprises the following components in parts by weight: Bisphenol A type epoxy resin: 40-60 parts; Modified polyetheramine curing agent: 9.2-13.8 parts; γ-Methacryloxypropyltrimethoxysilane: 1-5 parts; Controlled hydrolysis initiator: 0.1-0.5 parts; Graphene: 2-8 parts; Nano silica: 3-10 parts; Ammonium polyphosphate: 5-15 parts; Sodium molybdate: 3-10 parts; Mixed solvent: 20-30 parts.

2. The heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 1, characterized in that, The heavy-duty anti-corrosion coating comprises the following components in parts by weight: Bisphenol A type epoxy resin: 50 parts; Modified polyetheramine curing agent: 11.5 parts; γ-Methacryloxypropyltrimethoxysilane: 3 parts; Controlled hydrolysis initiator: 0.3 parts; Graphene: 5 parts; Nano-silica: 8 parts; Ammonium polyphosphate: 10 parts; Sodium molybdate: 6 parts; Mixed solvent: 25 parts.

3. The heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 1, characterized in that, The controlled hydrolysis initiator is prepared by a method comprising the following steps: (1) The porous silica support with a pore size of 8-10 nm is vacuum dried at 130-140℃ for 4-5 hours to obtain the activated support; (2) Dissolve the metal salt containing water of crystallization in deionized water to prepare a saturated solution, and use the equal volume impregnation method, wherein the saturated solution is added dropwise to the activated carrier obtained in step (1) under stirring, and the mixture is stirred at a low speed of 150 r / min for 30 min, and then sealed and allowed to stand for 3-4 h for impregnation. (3) Dry the impregnated sample at 60-70℃ for 10-12 h to obtain the controlled hydrolysis initiator.

4. The heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 1, characterized in that, The mixed solvent is composed of xylene and n-butanol, and the volume ratio of xylene to n-butanol is (2-3):

1.

5. The heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 1, characterized in that, The active hydrogen equivalent of the modified polyetheramine curing agent is 100-130 g / eq.

6. A method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials, used to prepare the heavy-duty anti-corrosion coating containing nanocomposite materials as described in any one of claims 1-5, characterized in that, Includes the following steps: (a) Preparing the coating for use, wherein the steps for preparing the coating for use include: ① Graphene, nano-silica, and ammonium polyphosphate are dispersed in a mixed solvent to obtain a functional filler dispersion; ② Bisphenol A type epoxy resin, sodium molybdate, γ-methacryloxypropyltrimethoxysilane and hydrolysis initiator are mixed to obtain resin premix; ③ The functional filler dispersion is mixed with the resin premix to obtain the coating matrix; ④ Add the modified polyetheramine curing agent to the coating matrix and mix thoroughly to obtain the coating to be used; (ii) Apply the coating obtained in step (1) to the surface of the aluminum alloy substrate; (iii) Perform a two-step curing process on the substrate coated with the coating to be used, the two-step curing process including: first, holding at 60-80℃ for 60-90 min, and then raising the temperature to 120-140℃ and holding for 60-90 min.

7. The method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 6, characterized in that, The two-step curing process is as follows: first, maintain the temperature at 70°C for 80 minutes, then raise the temperature to 130°C and maintain it for 80 minutes.

8. The method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 6, characterized in that, In step ①, use a high-speed disperser to disperse at a speed of 1500-2500 r / min for 45-60 min.

9. The method for preparing a heavy-duty anti-corrosion coating containing nanocomposite materials according to claim 6, characterized in that, Before step (ii), the process also includes a sandblasting process on the surface of the aluminum alloy substrate.

10. The application of the heavy-duty anti-corrosion coating containing nanocomposite materials as described in claim 1 in the corrosion protection of aluminum alloy substrates.

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