Coating composition, metal protective coating and preparation method of metal protective coating

Abstract

The invention provides a coating composition, a metal protective coating and a preparation method of the metal protective coating. The coating composition is prepared from the following components in percentage by weight: 15 to 50 weight percent of silica sol, 3 to 25 weight percent of glass powder, 10 to 25 weight percent of silane coupling agent, 0.5 to 2 weight percent of organic acid, 2.5 to 20 weight percent of filler and the balance of water, wherein the melting point of the glass powder is 400-600 DEG C. The glass powder has the specific melting point, can soften and flow in the coating curing process, is fused with the silica sol and fills coating gaps, a more compact network structure is formed, the sealing performance and permeation resistance of a coating are improved, and corrosion of a corrosive medium to metal is blocked. The silane coupling agent is introduced, so that the interface bonding force between the coating and the metal substrate can be enhanced, and the adhesive force of the coating to the metal substrate is improved. The coating composition takes water as a solvent, so that the emission of organic volatile matters and the harm to the health of operators are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal protective coating, in particular to a coating composition, a metal protective coating and a preparation method thereof. BACKGROUND

[0002] In modern industrial applications, especially in the fields of chemical production, petroleum processing and metallurgy, the corrosion problem faced by metal equipment is becoming increasingly serious. The unique working environment of these industries, accompanied by the presence of strong acidic media such as hydrogen chloride (HCl) gas, poses a severe challenge to metal materials. Metal materials are extremely susceptible to corrosion in acidic gas environments, which not only leads to a decrease in equipment performance and a reduction in service life, but also significantly increases maintenance and repair costs, and even causes safety accidents. There are various types of anti-corrosion coatings on the current market, including epoxy resins, polyurethanes, silicones and other types, but their protective effect is usually unsatisfactory when faced with HCl gas, which is an extreme corrosive condition. This is because HCl gas has a high penetration ability, which can erode the molecular structure of the coating, causing it to gradually decompose or lose adhesion, ultimately leading to coating failure and failure to effectively protect the metal for a long time.

[0003] Silica sol is a water-soluble colloid composed of nanoscale silica particles, which has good thermal stability, chemical stability and mechanical properties, and is one of the ideal raw materials for developing new types of anti-corrosion coatings. However, coatings prepared using silica sol alone, although having good film-forming properties, still have obvious limitations in terms of resistance to HCl gas corrosion and protective effectiveness.

[0004] Therefore, it is of great significance to research and develop a coating composition that is resistant to HCl gas corrosion and does not easily peel off, a metal protective coating and a preparation method thereof, in order to improve the durability and protective effect of metal equipment in acidic media (especially HCl gas) environments, and to prolong the service life of the equipment and reduce maintenance costs. SUMMARY

[0005] The main purpose of the present application is to provide a coating composition, a metal protective coating and a preparation method thereof, in order to solve the problems of poor resistance to HCl gas corrosion and poor adhesion to metal substrates of the metal protective coating in the prior art.

[0006] In order to achieve the above-mentioned purpose, the present application provides a coating composition, which comprises, by weight percentage: 15-50wt% silica sol, 3-25wt% glass powder, 10-25wt% silane coupling agent, 0.5-2wt% organic acid, 2.5-20wt% filler and the balance water; wherein the glass powder has a melting point of 400-600℃.

[0007] Further, the coating composition comprises, by weight percentage, 30-40 wt% of silica sol, 5-10 wt% of glass powder, 15-20 wt% of silane coupling agent, 0.5-2.0 wt% of organic acid, 2.5-20 wt% of filler, and the balance of water.

[0008] Further, the weight ratio of the silica sol to the glass powder is (0.6-16.7):1, preferably (4-6):1.

[0009] Further, the silica sol comprises nano-silica particles and water, the silica sol has a solid content of 40-60 wt% and a pH value of 8-10; preferably, the nano-silica particles have an average particle size of 30-80 nm and a specific surface area of 60-100 m 2 / g.

[0010] Further, the glass powder has a softening point of 300-500℃.

[0011] Further, the glass powder has an average particle size of 10-30 μm; preferably, the components of the glass powder comprise lead oxide, boron oxide and silica, or zinc oxide, boron oxide and silica.

[0012] Further, the silane coupling agent is selected from one or more of the group consisting of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane and benzyltrimethoxysilane.

[0013] Further, the organic acid is selected from one or more of the group consisting of formic acid, acetic acid, propionic acid, butyric acid and valeric acid.

[0014] Further, the filler has an average particle size of 3-8 μm.

[0015] Further, the filler is selected from one or more of the group consisting of glass flake, mica powder, talc powder, titanium dioxide, kaolin and glass fiber; preferably, the filler is selected from a combination of glass flake, mica powder, talc powder and titanium dioxide, and the weight ratio of the four is (0.5-2):(0.5-2):(0.5-2):(2-4).

[0016] Further, the coating composition further comprises an auxiliary agent; preferably, the auxiliary agent accounts for 1-5 wt%, more preferably 2-4 wt%, of the weight percentage of the coating composition.

[0017] Further, the auxiliary agent is selected from one or more of the group consisting of dispersing agent, defoaming agent and leveling agent.

[0018] Further, the dispersant is selected from one or more of the group consisting of inorganic salt dispersants, organic dispersants and polymer dispersants; more preferably the inorganic salt dispersant is selected from one or more of the group consisting of sodium tripolyphosphate, sodium hexametaphosphate and sodium pyrophosphate; the organic dispersant is selected from one or more of the group consisting of triethylhexyl phosphoric acid, sodium dodecyl sulfate and methyl amyl alcohol; the polymer dispersant is selected from one or more of the group consisting of sodium polyacrylate, polyvinyl alcohol and polymer ketone; the defoaming agent is selected from one or more of the group consisting of silicone defoaming agent, mineral oil defoaming agent, fatty acid defoaming agent and silica defoaming agent; the leveling agent is selected from one or more of the group consisting of silicone leveling agent, acrylic leveling agent, fluorine-containing surfactant and fluorocarbon compound leveling agent.

[0019] To achieve the above-mentioned purpose, another aspect of the present application further provides a metal protective coating prepared by coating and curing the above-mentioned coating composition provided by the present application.

[0020] Further, the thickness of the metal protective coating is 10-50 μm, preferably 20-30 μm.

[0021] Another aspect of the present application provides a preparation method of the above-mentioned metal protective coating provided by the present application, which comprises: step S1, ball milling a first mixture containing glass powder, filler and water to obtain a slurry; step S2, mixing silica sol, silane coupling agent, organic acid and the slurry to obtain a coating; step S3, coating the coating on at least one side surface of a metal substrate to obtain the metal protective coating after curing treatment.

[0022] Further, step S1 comprises: mixing the glass powder, the filler and the water to obtain the first mixture; wherein the mixing in step S1 is accompanied by first stirring; preferably the rate of the first stirring is 500-800 r / min and the time is 25-35 min.

[0023] Further, the rotation speed of the ball milling is 1200-1800 r / min and the time is 2-3 h.

[0024] Further, the ball milling is performed by using a ball milling medium, and the weight ratio of the ball milling medium to the first mixture is (0.8-1.2):1; more preferably the diameter of the ball milling medium is 1-2 mm.

[0025] Further, an auxiliary agent is introduced in the mixing in step S1.

[0026] Further, step S2 comprises: mixing the silica sol and the slurry and performing second stirring to obtain a second mixture; mixing the second mixture, the silane coupling agent and the organic acid and performing third stirring to obtain the coating.

[0027] Furthermore, the second stirring rate is 300–500 r / min, and the time is 30–40 min.

[0028] Furthermore, the third stirring rate is 300–500 r / min, and the time is 6–10 h.

[0029] Furthermore, in step S3, the coating amount of the paint on the surface of the metal substrate is 30-40 g / m². 2 .

[0030] Further, the curing process includes a first heating treatment, a second heating treatment, a third heating treatment, and a sintering treatment performed sequentially; preferably, the temperature of the first heating treatment is 50-70°C and the time is 0.4-0.6 h; preferably, the temperature of the second heating treatment is 110-130°C and the time is 0.4-0.6 h; preferably, the temperature of the third heating treatment is 200-300°C and the time is 0.5-1.5 h; preferably, the temperature of the sintering treatment is 400-600°C and the time is 2-4 h.

[0031] Applying the technical solution of this invention, a coating composition is provided, comprising silica sol, glass powder, silane coupling agent, organic acid, filler, and water. Silica sol, as a nanoscale silica dispersion system, can fill the fine pores in the metal protective coating, forming a continuous network skeleton, improving the density of the metal protective coating, and enhancing its adhesion to the metal substrate. Glass powder, possessing the aforementioned specific melting point, has a relatively low melting point, allowing it to soften and flow during the coating curing process. This enables it to fuse with the silica sol and further fill the gaps in the coating, forming a denser network structure, improving the coating's sealing and anti-permeability properties, and effectively blocking corrosive media (such as HCl gas) from eroding the metal, thus improving the coating's corrosion resistance. During the curing process, the silane coupling agent can undergo a cross-linking reaction with the silica sol and glass powder, forming a denser metal protective coating. Simultaneously, the introduction of the silane coupling agent can enhance the physical and chemical bonding between the coating and the metal substrate, establishing a stable interface layer between the metal substrate and the coating, thereby improving the coating's corrosion resistance and adhesion to the metal substrate. The introduction of organic acids can regulate the pH value of the coating system, improve the dispersibility and stability of each component, and promote the condensation reaction between hydroxyl groups in the silica sol and other components, forming a denser three-dimensional network structure and improving the coating's resistance to HCl gas corrosion. The introduction of fillers can increase the density, hardness, abrasion resistance, and hiding power of the metal protective coating, thereby improving the coating's resistance to HCl gas corrosion. The coating composition provided by this invention uses water as a solvent, which not only reduces the emission of volatile organic compounds (VOCs) but also reduces the harm to the health of operators, meeting environmental protection requirements.

[0032] Moreover, compared to other categories, the coating composition using the specific content and composition of the present invention can leverage the synergistic effect of each component to construct a dense metal protective coating on the metal surface. This coating not only effectively resists the corrosion of HCl gas but also improves the adhesion of the metal protective coating to the metal substrate, thereby providing reliable and long-lasting protection for metal equipment in an HCl corrosive environment. At the same time, the coating composition provided by the present invention produces almost no volatile organic compounds (VOCs) during production and use, which is beneficial to the environment and human health. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0034] As described in the background section, existing metal protective coatings suffer from poor resistance to HCl gas corrosion and poor adhesion to metal substrates. To address these technical problems, the first aspect of this application provides a coating composition comprising, by weight percentage: 15–50 wt% silica sol, 3–25 wt% glass powder, 10–25 wt% silane coupling agent, 0.5–2 wt% organic acid, 2.5–20 wt% filler, and the balance being water; wherein the glass powder has a melting point of 400–600°C.

[0035] The coating composition provided in this application includes silica sol, glass powder, silane coupling agent, organic acid, filler, and water. Silica sol, as a nanoscale silica dispersion system, can fill the fine pores in the metal protective coating, forming a continuous network skeleton, improving the density of the metal protective coating, and enhancing its adhesion to the metal substrate. Glass powder has the aforementioned specific melting point, which is relatively low, allowing it to soften and flow during the coating curing process. This allows it to fuse with the silica sol and further fill the gaps in the coating, forming a denser network structure, improving the sealing and impermeability of the coating, and effectively blocking corrosive media (such as HCl gas) from eroding the metal, thus improving the coating's corrosion resistance.

[0036] During the curing process, the silane coupling agent can undergo a cross-linking reaction with silica sol and glass powder to form a denser metal protective coating. At the same time, the introduction of the silane coupling agent can also enhance the physical and chemical bonding between the coating and the metal substrate, establish a stable interface layer between the metal substrate and the coating, thereby improving the corrosion resistance of the coating and its adhesion to the metal substrate.

[0037] The introduction of organic acids can regulate the pH value of the coating system, improve the dispersibility and stability of each component, promote the condensation reaction between hydroxyl groups in silica sol and other components, forming a denser three-dimensional network structure and improving the coating's resistance to HCl gas corrosion. The introduction of fillers can increase the density, hardness, abrasion resistance, and hiding power of the metal protective coating, thereby improving the coating's resistance to HCl gas corrosion.

[0038] The coating composition provided in this application uses water as a solvent, which not only reduces the emission of volatile organic compounds (VOCs) but also reduces the harm to the health of operators, thus meeting environmental protection requirements.

[0039] Moreover, compared to other applications, the coating composition with the specific content and composition described above in this application can leverage the synergistic effect of each component to construct a dense metal protective coating on the metal surface. This coating not only effectively resists the corrosion of HCl gas but also improves the adhesion of the metal protective coating to the metal substrate, thereby providing reliable and long-lasting protection for metal equipment in an HCl corrosive environment. At the same time, the coating composition provided above in this application produces almost no volatile organic compounds (VOCs) during production and use, which is beneficial to the environment and human health.

[0040] In a preferred embodiment, the coating composition, by weight percentage, comprises: 30–40 wt% silica sol, 5–10 wt% glass powder, 15–20 wt% silane coupling agent, 0.5–2.0 wt% organic acid, 2.5–20 wt% filler, and the balance being water. The content of each component in the coating composition includes, but is not limited to, the above range. Limiting it to the above range is beneficial for improving the synergistic effect of the components in the coating composition, promoting the reaction between silica sol and other components, forming a denser network structure, thereby improving the sealing and impermeability of the coating, effectively blocking the corrosion of metals by corrosive media (such as HCl gas); it also helps to enhance the interfacial bonding between the coating and the metal substrate, thereby improving the adhesion and protective effect of the coating on the metal substrate.

[0041] In a preferred embodiment, the weight ratio of silica sol to glass powder is (0.6–16.7):1. The weight ratio of silica sol to glass powder includes, but is not limited to, the above range. Limiting it within this range helps to better leverage the synergistic effect of the two. A suitable amount of silica sol facilitates the formation of a continuous network framework, while a suitable amount of glass powder facilitates its integration with the silica sol and fills the gaps in the network structure. This results in a denser network structure, improving the sealing and impermeability of the metal protective coating, and consequently, enhancing the coating's resistance to HCl gas corrosion.

[0042] In order to construct a denser network structure, improve the sealing and anti-permeability of the metal protective coating, and further improve the resistance of the metal protective coating to HCl gas corrosion, preferably, the weight ratio of silica sol to glass powder is (4-6):1.

[0043] In order to improve the dispersion uniformity, stability and processability of the coating composition, and further improve the density of the metal protective coating and its adhesion to the metal substrate, in a preferred embodiment, the silica sol includes nano-silica particles and water, the solid content of the silica sol is 40-60 wt%, and the pH value is 8-10.

[0044] In a preferred embodiment, the average particle size of the nano-silica particles in the silica sol is 30–80 nm, and the specific surface area is 60–100 m². 2 / g. The particle size and specific surface area of ​​the nano-silica particles include, but are not limited to, the ranges mentioned above. Limiting them to the ranges above helps to inhibit the agglomeration of nano-silica particles, improve their dispersion uniformity, and facilitate their deep filling of the fine pores on the surface of the metal substrate and within the coating, thereby forming a denser metal protective coating and improving the coating's resistance to HCl gas corrosion and its adhesion to the metal substrate.

[0045] The softening point of glass powder refers to the temperature at which the glass powder begins to soften and flow when heated. In a preferred embodiment, the softening point of the glass powder is 300–500°C. Compared to other ranges, limiting the softening point of the glass powder to this range is beneficial for its softening and flow during subsequent curing processes, promoting its integration with silica sol and further filling the fine pores in the coating. This facilitates the formation of a denser network structure, improves the sealing and impermeability of the coating, and consequently helps to prevent HCl gas from corroding the metal, thus improving the coating's corrosion resistance.

[0046] In a preferred embodiment, the average particle size of the glass powder is 10–30 μm. The average particle size of the glass powder includes, but is not limited to, the above range. Limiting it to this range helps improve the uniformity of glass powder dispersion, inhibits agglomeration or precipitation due to excessively large particle size, and thus facilitates the softening and flow of the glass powder during subsequent curing processes, filling the micropores within the coating. This, in turn, improves the sealing and impermeability of the coating, and enhances its resistance to HCl gas corrosion.

[0047] To obtain glass powder with both low melting point and good chemical stability, forming a denser metallic protective coating and further improving the coating's ability to block HCl gas, in a preferred embodiment, the glass powder comprises lead oxide, boron oxide, and silicon dioxide, or zinc oxide, boron oxide, and silicon dioxide. Specifically, the glass powder includes, but is not limited to, one or more of the following: Z5140 produced by Foshan Youhe Chemical Technology Co., Ltd., GP-180 and GP-1900 produced by Shanghai Xindili New Materials Co., Ltd., and TBY-308 produced by Shandong Saikesaisi Hydrogen Energy Co., Ltd.

[0048] In a preferred embodiment, the silane coupling agent includes, but is not limited to, one or more of the group consisting of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, and benzyltrimethoxysilane. Compared to other types, using the above-mentioned silane coupling agents is beneficial for enhancing the interfacial bonding between the coating and the metal substrate, improving the adhesion of the coating to the metal substrate, and also promoting its cross-linking reaction with silica sol and glass powder, thereby facilitating the formation of a denser network structure and improving the coating's resistance to HCl gas corrosion.

[0049] In a preferred embodiment, the organic acid includes, but is not limited to, one or more of the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and valeric acid. Compared to other types, using the above-mentioned organic acids is beneficial in two ways: firstly, it promotes the reaction between the hydroxyl groups in the silica sol and other components, forming a denser three-dimensional network structure, thereby improving the coating's resistance to HCl gas corrosion; secondly, it helps maintain the pH value of the coating system within a suitable range, ensuring the stability of each component in the coating composition.

[0050] In a preferred embodiment, the average particle size of the filler is 3–8 μm. The average particle size of the filler includes, but is not limited to, the above range. Limiting it to the above range is beneficial to improving the uniformity of filler dispersion, improving the flowability and processability of the coating composition, and facilitating the formation of a denser metal protective coating. This reduces the fine pores within the coating, thereby improving the barrier effect of the coating against corrosive media such as HCl gas.

[0051] In a preferred embodiment, the filler includes, but is not limited to, one or more of the group consisting of glass flakes, mica powder, talc powder, titanium dioxide, kaolin, and glass fiber. Compared to other types, the use of fillers of the above types is beneficial to improving the hardness, wear resistance, and hiding power of the metal protective coating, thereby improving the barrier effect of the coating against corrosive media such as HCl gas. In this application, glass flakes refer to glass flakes with a thickness of 5 μm and a sheet-like structure. Introducing them into the coating composition is beneficial to forming a multi-layer barrier in the coating, thereby delaying the penetration path of corrosive media and improving the density and corrosion resistance of the metal protective coating.

[0052] In order to further improve the density, hardness, wear resistance and hiding power of the metal protective coating, thereby further improving the barrier effect of the coating against corrosive media such as HCl gas, preferably, the filler includes, but is not limited to, a composition of glass flakes, mica powder, talc powder and titanium dioxide, more preferably, the weight ratio of glass flakes, mica powder, talc powder and titanium dioxide is (0.5~2):(0.5~2):(0.5~2):(2~4).

[0053] In order to improve the dispersion uniformity of the components in the coating composition and enhance its processability, thereby obtaining a metal protective coating with higher film quality, in a preferred embodiment, the coating composition further includes additives.

[0054] In a preferred embodiment, the additives constitute 1 to 5 wt% of the coating composition by weight. The weight percentage of the additives in the coating composition includes, but is not limited to, the above range. Limiting it to this range is beneficial for improving the uniformity of dispersion of the components in the coating composition and enhancing the processability of the coating composition, thereby facilitating the acquisition of a metal protective coating with higher film quality.

[0055] To further improve the dispersion uniformity of each component in the coating composition and further improve the processability of the coating composition, thereby obtaining a metal protective coating with higher film quality, preferably, the additives account for 2 to 4 wt% of the weight of the coating composition.

[0056] Dispersants can improve the dispersion uniformity of components in a coating composition and inhibit agglomeration, thereby improving the uniformity and stability of the metal protective coating. Defoamers can effectively eliminate bubbles generated during coating preparation and application, and inhibit the appearance of micropores or defects on the surface of the metal protective coating, thereby improving the density, integrity, and aesthetics of the metal protective coating. Leveling agents enable the coating to form a smooth and continuous film on the metal substrate surface, reducing the orange peel effect, thereby improving the visual effect and actual protective effect of the metal protective coating. In a preferred embodiment, the additives include, but are not limited to, one or more of the group consisting of dispersants, defoamers, and leveling agents. Introducing the above-mentioned additives into the coating composition is beneficial for obtaining a metal protective coating with higher film quality, thereby improving the corrosion resistance of the metal protective coating and its adhesion to the metal substrate.

[0057] To obtain a metal protective coating with higher film-forming quality, thereby further improving the corrosion resistance and adhesion of the metal protective coating to the metal substrate, preferably, the dispersant includes, but is not limited to, one or more of the group consisting of inorganic salt dispersants, organic dispersants, and polymeric dispersants; wherein, the inorganic salt dispersant includes, but is not limited to, one or more of the group consisting of sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate; the organic dispersant includes, but is not limited to, one or more of the group consisting of triethylhexylphosphonic acid, sodium dodecyl sulfate, and methylpentanol; the polymeric dispersant includes, but is not limited to, one or more of the group consisting of sodium polyacrylate, polyvinyl alcohol, and polymeric ketone; the defoamer includes, but is not limited to, one or more of the group consisting of silicone defoamers, mineral oil defoamers, fatty acid defoamers, and silica defoamers; and the leveling agent includes, but is not limited to, one or more of the group consisting of silicone leveling agents, acrylic leveling agents, fluorinated surfactants, and fluorocarbon compound leveling agents.

[0058] A second aspect of this application also provides a metal protective coating, which is obtained by coating and curing the above-mentioned coating composition provided in this application.

[0059] The coating composition provided in this application comprises silica sol, glass powder, silane coupling agent, organic acid, filler, and water. The silica sol and low-melting-point glass powder work synergistically to form a denser network structure, improving the coating's sealing and impermeability, thereby effectively blocking corrosive media (such as HCl gas) from eroding the metal and enhancing the coating's corrosion resistance. The silane coupling agent can cross-link with the silica sol and glass powder to form a denser metal protective coating, while also enhancing the interfacial bonding between the coating and the metal substrate, thus improving the coating's corrosion resistance and adhesion to the metal substrate. The introduction of organic acid can regulate the pH value of the coating system, improve the dispersibility and stability of each component, and promote the condensation reaction between the hydroxyl groups in the silica sol and other components, forming a denser three-dimensional network structure and improving the coating's resistance to HCl gas corrosion. The introduction of filler can increase the density, hardness, abrasion resistance, and hiding power of the metal protective coating, improving the coating's resistance to HCl gas corrosion. Using water as a solvent in coating compositions can not only reduce the emission of volatile organic compounds (VOCs), but also reduce the harm to the health of operators, thus meeting environmental protection requirements.

[0060] In summary, the coating composition provided in this application, after coating and curing, can form a dense metal protective coating on the metal surface. This coating not only effectively resists the corrosion of HCl gas, but also improves the adhesion of the metal protective coating to the metal substrate, thereby providing reliable and long-lasting protection for metal equipment in an HCl corrosive environment. At the same time, the coating composition provided in this application produces almost no volatile organic compounds (VOCs) during production and use, which is beneficial to the environment and human health.

[0061] In a preferred embodiment, the thickness of the metal protective coating is 10–50 μm. The thickness of the metal protective coating includes, but is not limited to, the above range. Limiting it to this range is beneficial for better suppressing the corrosion of the metal by HCl gas and other corrosive media, and also for improving the density, hardness, wear resistance, and adhesion of the metal protective coating to the metal substrate.

[0062] To further suppress the erosion of metals by HCl gas and other corrosive media, and to further improve the density, hardness, wear resistance and adhesion of the metal protective coating to the metal substrate, the thickness of the metal protective coating is preferably 20-30 μm.

[0063] The third aspect of this application also provides a method for preparing the above-mentioned metal protective coating provided in this application. The preparation method includes: step S1, ball milling a first mixture containing glass powder, filler and water to obtain a slurry; step S2, mixing silica sol, silane coupling agent, organic acid and slurry to obtain a coating; step S3, applying the coating to at least one side surface of a metal substrate, and obtaining a metal protective coating after curing treatment.

[0064] The method for preparing the above-mentioned metal protective coating provided in this application includes the following steps: In step S1, glass powder, filler, and water are mixed and ball-milled to obtain glass powder and filler with suitable particle size, improving their dispersion uniformity in water and thus obtaining a uniform and stable slurry. In step S2, silica sol, silane coupling agent, and organic acid are mixed with the above slurry to obtain a coating. The introduction of silica sol can form a continuous network skeleton, improve the density of the coating, and enhance its adhesion to the metal substrate; the silane coupling agent can undergo a cross-linking reaction with silica sol and glass powder to form a denser metal protective coating, and can also enhance the interfacial bonding force between the coating and the metal substrate, thereby improving the corrosion resistance of the coating and its adhesion to the metal substrate; the introduction of organic acid can regulate the pH value of the coating system, improve the dispersibility and stability of each component, promote the condensation reaction between the hydroxyl groups in the silica sol and other components, forming a denser three-dimensional network structure and improving the coating's resistance to HCl gas corrosion. In step S3, the coating is applied to one side of the metal substrate. During the curing process, the glass powder with a low melting point softens and flows, merging with the silica sol and further filling the gaps in the coating to form a denser network structure. This improves the sealing and impermeability of the coating, effectively blocking corrosive media (such as HCl gas) from eroding the metal and improving the corrosion resistance of the coating. At the same time, the curing process also enhances the interfacial bonding between the coating and the metal substrate, improving the adhesion of the coating to the metal substrate.

[0065] In summary, the metal protective coating preparation method provided in this application can produce a denser metal protective coating that effectively resists the corrosion of HCl gas and improves the adhesion of the metal protective coating to the metal substrate, thereby providing reliable and long-lasting protection for metal equipment in an HCl corrosive environment. At the same time, the coating composition provided in this application produces almost no volatile organic compounds (VOCs) during production and use, which is beneficial to the environment and human health.

[0066] In order to improve the dispersion uniformity of glass powder and filler in water and obtain a uniform and stable first mixture, which facilitates subsequent ball milling, in a preferred embodiment, step S1 includes: mixing glass powder, filler and water to obtain a first mixture; wherein, during the mixing process in step S1, a first stirring is performed, preferably, the first stirring rate is 500-800 r / min and the time is 25-35 min.

[0067] In a preferred embodiment, the ball milling speed is 1200–1800 r / min, and the time is 2–3 h. The ball milling speed and time include, but are not limited to, the above range. Limiting them to the above range is beneficial for obtaining glass powder and fillers with more suitable particle size, inhibiting their agglomeration, improving the uniformity and stability of the slurry, and thus facilitating the formation of a denser metal protective coating.

[0068] In a preferred embodiment, ball milling is performed using ball milling media, and the weight ratio of the ball milling media to the first mixture (i.e., the ball-to-material ratio) is (0.8–1.2):1. Using ball milling media and limiting the ball-to-material ratio within the above range improves the efficiency of ball milling, yields glass powder and fillers with more suitable particle sizes, and inhibits their agglomeration. This, in turn, improves the uniformity and stability of the slurry, and consequently facilitates the formation of a denser metal protective coating.

[0069] To further improve the efficiency of ball milling and maintain the particle size of glass powder and filler in the slurry within a more suitable range, thereby further improving the uniformity and stability of the slurry and promoting the formation of a denser metal protective coating, preferably, the diameter of the ball milling media is 1 to 2 mm.

[0070] In order to improve the processability of the coating and obtain a metal protective coating with higher film quality, in a preferred embodiment, an additive is also introduced during the mixing process in step S1.

[0071] In a preferred embodiment, the mixing process in step S2 includes: mixing the silica sol with the slurry and performing a second stirring to obtain a second mixture; mixing the second mixture, the silane coupling agent, and the organic acid and performing a third stirring to obtain a coating. Compared to other methods, using the above method for the mixing process in step S2 is beneficial to improving the dispersion uniformity of the components in the coating, improving the processability of the coating, thereby promoting the formation of a denser metal protective coating and improving the coating's barrier properties against corrosive media such as HCl gas.

[0072] To further improve the dispersion uniformity of the second mixture, preferably, the second stirring rate is 300-500 r / min and the time is 30-40 min.

[0073] To further improve the dispersion uniformity of the components in the coating, preferably, the third stirring rate is 300-500 r / min and the time is 6-10 h.

[0074] In a preferred embodiment, in step S3, the coating amount on the metal substrate surface is 30–40 g / cm³. 2 The amount of coating applied to the surface of the metal substrate includes, but is not limited to, the range described above. Limiting it to the range is beneficial for obtaining a more suitable and denser metal protective coating, thereby improving the coating's corrosion resistance and its adhesion to the metal substrate.

[0075] In a preferred embodiment, the curing process includes a first heating treatment, a second heating treatment, a third heating treatment, and a sintering treatment performed sequentially. The first heating treatment helps remove excess moisture from the coating, allowing the coating to initially cure and preparing it for subsequent processing. The second heating treatment helps enhance the adhesion between the coating and the metal substrate, improving the coating's adhesion. The third heating treatment helps promote the fusion of silica sol and glass powder, increasing the coating's density and thus improving its corrosion resistance. Sintering at higher temperatures promotes chemical reactions between silica sol, glass powder, silane coupling agents, and other components, forming a denser and more stable coating. It also helps the lower-melting-point glass powder soften and flow, fusing with the silica sol and further filling gaps in the coating to form a denser network structure, thereby improving the coating's sealing and impermeability, corrosion resistance, and adhesion to the metal substrate. Compared to other methods, the above curing process results in a denser and more stable metal protective coating, thus improving the coating's ability to block corrosive media such as HCl gas and its adhesion to the metal substrate.

[0076] In order to further remove moisture from the coating and allow the coating to initially cure, in a preferred embodiment, the temperature of the first heat treatment is 50-70°C and the time is 0.4-0.6 hours.

[0077] In a preferred embodiment, the temperature of the second heat treatment is 110–130°C, and the time is 0.4–0.6 h. The temperature and time of the second heat treatment include, but are not limited to, the above-mentioned ranges. Limiting them to the above-mentioned ranges is beneficial to enhancing the adhesion between the coating and the metal substrate and improving the adhesion of the coating.

[0078] In a preferred embodiment, the temperature of the third heat treatment is 200–300°C, and the time is 0.5–1.5 h. The temperature and time of the third heat treatment include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to promoting the mutual fusion of silica sol and glass powder, increasing the density of the coating, and thereby improving the coating's barrier properties against corrosive media such as HCl gas.

[0079] In a preferred embodiment, the sintering temperature is 400–600°C, and the time is 2–4 hours. The sintering temperature and time include, but are not limited to, the above ranges. Limiting them to these ranges promotes the chemical reaction between the silica sol, glass powder, silane coupling agent, and other components, forming a denser and more stable coating. Simultaneously, it facilitates the softening and flow of the lower-melting-point glass powder, allowing it to fuse with the silica sol and further fill the gaps in the coating, forming a denser network structure. This improves the coating's sealing and impermeability, enhances its corrosion resistance, and increases its adhesion to the metal substrate.

[0080] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0081] Examples 1 to 6

[0082] A method for preparing a metal protective coating specifically includes the following steps:

[0083] (1) The composition and dosage of each component of each coating composition in Examples 1 to 6 are shown in Table 1;

[0084] (2) Add the additives and water to the paint mixing tank and stir at a stirring rate of 600 r / min for 15 min to fully dissolve the additives in the water. Then add glass powder, glass flakes, titanium dioxide, mica powder and talc powder to the paint mixing tank and continue stirring for 15 min to obtain the first mixture. Add zirconium balls (zirconium balls with diameters of 1 mm and 2 mm mixed at a weight ratio of 1:1) to the paint mixing tank and ball mill at a speed of 1500 r / min for 3 h. Filter out the zirconium balls with a 200 mesh screen to obtain the slurry.

[0085] (3) At a stirring rate of 400 r / min, the slurry obtained in step (2) is mixed and dispersed with silica sol for 30 min; then formic acid and methyltrimethoxysilane (MTMS) are added, and stirring is continued for 8 h. After completion, the mixture is filtered with a 200 mesh filter cloth to remove impurity particles and obtain the coating.

[0086] (4) Apply the coating obtained in step (3) at a concentration of 30 g / m 2The coating amount was sprayed onto one side surface of a 1mm thick 316L stainless steel plate, and then heated sequentially at 60℃ for 0.5h, 120℃ for 0.5h, and 250℃ for 1h to obtain a cured coating. The cured coating was placed in an environment of 25℃ for 7 days for aging, and then sintered at 550℃ for 2h to obtain a metal protective coating.

[0087] Table 1

[0088]

[0089] The sources of the raw materials for each component in Table 1 above are as follows:

[0090] Silica sol (Nourion Chemicals Ltd., LEVASILR 1050), with a solid content of 50 wt% and a pH of 9, contains nano-silica particles with an average particle size of 60 nm and a specific surface area of ​​80 m². 2 / g;

[0091] The glass powder (Foshan Youhe Chemical Technology Co., Ltd., Z5140) has a melting point of 460℃, a softening point of 420℃, and an average particle size of 12μm. The glass powder includes zinc oxide, boron oxide, and silicon dioxide.

[0092] Glass flakes (Hebei Jiegui Mineral Products Co., Ltd., 400 mesh), with an average particle size of 37.5 μm and a thickness of 5 μm;

[0093] Mica powder (Henan Taihe Huijin Powder Technology Co., Ltd., 1250 mesh), with an average particle size of 12μm;

[0094] Talc powder (Tuoyi New Materials (Guangzhou) Co., Ltd., 1250 mesh), with an average particle size of 12μm;

[0095] Titanium dioxide (Pangang Titanium Industry, R-298), with an average particle size of 0.3 μm;

[0096] Methyltrimethoxysilane (MTMS) (Beijing Bailingwei), purity 98%;

[0097] Additives: The dispersant used is DISPERBYK-190 from BYK Chemicals; the defoamer used is Foamex 810 from Tego (Germany); and the leveling agent used is Wet 100 from Tego (Germany).

[0098] Example 7

[0099] The difference from Example 1 is that in step (4), the sintering temperature is 400°C and the time is 2 hours, while the other steps are the same as in Example 1.

[0100] Example 8

[0101] The difference from Example 1 is that in step (4), the sintering temperature is 600°C and the time is 2 hours, while the other steps are the same as in Example 1.

[0102] Example 9

[0103] The difference from Example 1 is that in step (4), the sintering temperature is 350°C and the time is 2 hours, while the other steps are the same as in Example 1.

[0104] Example 10

[0105] The difference from Example 1 is that in step (2), the ball-to-material ratio of the ball milling process is 0.8:1, the rotation speed is 1200 r / min, the ball milling time is 3 h, and the remaining steps are the same as in Example 1.

[0106] Example 11

[0107] The difference from Example 1 is that in step (2), the ball-to-material ratio of the ball milling process is 1.2:1, the rotation speed is 1800 r / min, the ball milling time is 2 h, and the remaining steps are the same as in Example 1.

[0108] Example 12

[0109] The difference from Example 1 is that in step (2), the ball-to-material ratio of the ball milling process is 0.5:1, the rotation speed is 1000 r / min, the ball milling time is 1.5 h, and the remaining steps are the same as in Example 1.

[0110] Comparative Example 1

[0111] The difference from Example 1 is that glass powder was not introduced into the coating composition, but was made up with an equal amount of silica sol, as shown in Table 2; the remaining steps are the same as in Example 1.

[0112] Comparative Example 2

[0113] The difference from Example 1 is that: no silica sol was introduced into the coating composition, and an equal amount of glass powder was used to make up the difference, as shown in Table 2; the remaining steps are the same as in Example 1.

[0114] The metal protective coating prepared in Comparative Example 2 has poor adhesion to the substrate and cannot play a role in corrosion prevention.

[0115] Comparative Examples 3 and 4

[0116] The difference from Example 1 is that the content of each component in the coating composition in Comparative Examples 3 and 4 is different from that in Example 1, as shown in Table 2; the remaining steps are the same as in Example 1.

[0117] Table 2

[0118]

[0119] Comparative Example 5

[0120] The difference from Example 1 is that in step (4), the cured coating was not sintered, and the cured coating was used as the final metal protective coating for performance testing; the remaining steps are the same as in Example 1.

[0121] Comparative Example 6

[0122] The difference from Example 1 is that in step (1), high-hardness high-temperature glass powder produced by Shijiazhuang Xianghui Technology Co., Ltd. is used to replace the glass powder in Example 1. The melting point of the high-hardness high-temperature glass powder is 750°C, and its composition includes alumina, boron oxide and silicon dioxide; the remaining steps are the same as in Example 1.

[0123] The following performance tests were performed on the metal protective coatings prepared in all the above embodiments and comparative examples of this application:

[0124] (1) Adhesion test: The adhesion test was conducted using a cross-cut tester according to the method described in the national standard GB / T 9286-2021 "Paints and Varnishes Cross-cut Test".

[0125] (2) Hardness test: The hardness of paint and varnish was determined by pencil tester (Guangzhou Biaogeda Precision Instruments, BGD 506 / 3) according to the method recorded in the national standard GB / T 6739-2022 "Determination of Hardness of Paint Film by Pencil Method".

[0126] (3) Impact strength test: The impact strength test was conducted using a paint film impact tester (Guangzhou Biaogeda Precision Instruments, BGD 304) according to the method described in the national standard GB / T 1732-2020 "Test Method for Impact Resistance of Paint Film".

[0127] (4) HCl gas corrosion resistance test: Refer to the gas corrosion test principle recorded in the industry standard HG / T 3792-2005 "Cross-linked Fluoropolymer Coatings", place the test sample in an HCl gas atmosphere (concentration maintained at 36-38 vol%) and test the HCl gas corrosion resistance of the sample.

[0128] (5) Salt water corrosion test: The test shall be conducted in accordance with the method described in the national standard GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test".

[0129] The test results are shown in Table 3.

[0130] Table 3

[0131]

[0132] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0133] Comparing Example 1 with Comparative Examples 1 and 6, it can be seen that the metal protective coatings prepared in Comparative Examples 1 and 6 have significantly shorter resistance times to HCl gas corrosion than those prepared in Example 1. Furthermore, the metal protective coating prepared in Comparative Example 6, due to poor adhesion, fails to provide corrosion protection, allowing corrosive gases or salt water to penetrate the metal surface. Therefore, introducing the glass powder with the specific melting point described above into the coating composition allows it to soften and flow during the coating curing process, fusing with the silica sol and further filling the gaps in the coating to form a denser network structure. This improves the sealing and impermeability of the coating, thereby effectively enhancing the resistance of the metal protective coating to HCl gas corrosion and salt water corrosion.

[0134] Comparing Example 1 and Comparative Example 2, it can be seen that the metal protective coating prepared in Comparative Example 2 has poor adhesion to the substrate and cannot provide corrosion protection. Therefore, it can be concluded that introducing silica sol into the coating composition can form a denser network structure, enhance the adhesion of the metal protective coating to the metal substrate, and improve the coating's resistance to HCl gas corrosion and salt water corrosion.

[0135] Comparing Examples 1 to 6 and Comparative Examples 3 and 4, where the amount of silica sol in Comparative Example 3 is outside the aforementioned specific range of this application, and the amount of silane coupling agent in Comparative Example 4 is also outside the aforementioned specific range of this application; as shown in Table 3, the metal protective coatings prepared in Comparative Examples 3 and 4 exhibit significantly shorter resistance times to HCl gas corrosion and salt water corrosion than those in Examples 1 to 6. Furthermore, due to the lower amount of silane coupling agent used in Comparative Example 4, the adhesion between the metal protective coating and the metal substrate is poor, thus failing to provide protection. Therefore, compared to other ranges, limiting the content of each component in the coating composition to the aforementioned specific range of this application allows for the synergistic effect of each component, constructing a denser metal protective coating on the metal surface, thereby effectively resisting the erosion of HCl gas and salt water, and simultaneously improving the adhesion of the metal protective coating to the metal substrate, thus providing reliable and long-lasting protection for metal equipment in acidic corrosive environments.

[0136] Comparing Examples 1, 7 to 9 and Comparative Example 5, the sintering temperatures and times in Examples 1 and 7 are within the preferred range described above, while the sintering temperature in Example 9 is outside the preferred range. Comparative Example 5 did not undergo sintering. As shown in Table 3, neither sintering (Comparative Example 5) nor sintering at a lower temperature (Example 9) significantly reduces the HCl gas corrosion resistance and salt water corrosion resistance of the metal protective coating. Therefore, sintering at the preferred temperature range described above promotes the chemical reaction between silica sol, glass powder, silane coupling agent, and other components, forming a denser and more stable coating. It also promotes the softening and flow of the lower-melting-point glass powder, allowing it to fuse with the silica sol and further fill the gaps in the coating, forming a denser network structure. This improves the coating's sealing and impermeability, enhances its resistance to HCl gas corrosion and salt water corrosion, and increases its adhesion to the metal substrate.

[0137] Comparing Examples 1, 10, and 12, the ball milling speed and ball-to-material ratio in Examples 1, 10, and 11 are all within the preferred range described above, while Example 12 is outside the range. As shown in Table 3, the metal protective coating obtained in Example 12 exhibits significantly worse resistance to HCl gas corrosion and salt water corrosion than that in Examples 1, 10, and 11. Therefore, compared to other ranges, limiting the ball-to-material ratio, speed, and time of ball milling within the preferred range described above is beneficial for obtaining glass powder and fillers with more suitable particle sizes, inhibiting their agglomeration, and improving the uniformity and stability of the slurry. This, in turn, facilitates the formation of a denser metal protective coating, thereby improving the resistance of the metal protective coating to HCl gas corrosion and salt water corrosion.

[0138] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coating composition, characterized in that, The coating composition comprises, by weight percentage: 15-50 wt% silica sol, 3-25 wt% glass powder, 10-25 wt% silane coupling agent, 0.5-2 wt% organic acid, 2.5-20 wt% filler and balance water; wherein the glass powder has a melting point of 400-600°C.

2. The coating composition according to claim 1, characterized in that, The coating composition comprises, by weight percentage: 30-40 wt% of the silica sol, 5-10 wt% of the glass powder, 15-20 wt% of the silane coupling agent, 0.5-2.0 wt% of the organic acid, 2.5-20 wt% of the filler, and the balance being water; Preferably, the weight ratio of the silica sol to the glass powder is (0.6-16.7):1, more preferably (4-6):1; Preferably, the silica sol comprises nano-silica particles and water, the silica sol having a solid content of 40–60 wt% and a pH value of 8–10; more preferably, the nano-silica particles have an average particle size of 30–80 nm and a specific surface area of ​​60–100 m². 2 / g; Preferably, the softening point of the glass powder is 300–500°C; Preferably, the average particle size of the glass powder is 10-30 μm; more preferably, the glass powder comprises lead oxide, boron oxide and silicon dioxide, or zinc oxide, boron oxide and silicon dioxide.

3. The coating composition according to claim 1 or 2, characterized in that, The silane coupling agent is selected from one or more of the group consisting of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, and benzyltrimethoxysilane; Preferably, the organic acid is selected from one or more of the group consisting of formic acid, acetic acid, propionic acid, butyric acid, and valeric acid; Preferably, the average particle size of the filler is 3–8 μm; Preferably, the filler is selected from one or more of the group consisting of glass flakes, mica powder, talc powder, titanium dioxide, kaolin and glass fiber; more preferably, the filler is selected from a composition of glass flakes, mica powder, talc powder and titanium dioxide; and even more preferably, the weight ratio of the glass flakes, the mica powder, the talc powder and the titanium dioxide is (0.5-2):(0.5-2):(0.5-2):(2-4).

4. The coating composition according to any one of claims 1 to 3, characterized in that, The coating composition further includes additives; Preferably, the additive accounts for 1-5 wt% of the weight of the coating composition, more preferably 2-4 wt%. Preferably, the additive is selected from one or more of the group consisting of dispersants, defoamers, and leveling agents; More preferably, the dispersant is selected from one or more of the group consisting of inorganic salt dispersants, organic dispersants, and polymeric dispersants; even more preferably, the inorganic salt dispersant is selected from one or more of the group consisting of sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate; the organic dispersant is selected from one or more of the group consisting of triethylhexylphosphate, sodium dodecyl sulfate, and methylpentanol; and the polymeric dispersant is selected from one or more of the group consisting of sodium polyacrylate, polyvinyl alcohol, and polymeric ketones. More preferably, the defoamer is selected from one or more of the group consisting of silicone defoamers, mineral oil defoamers, fatty acid defoamers and silica defoamers; More preferably, the leveling agent is selected from one or more of the group consisting of silicone leveling agents, acrylic leveling agents, fluorinated surfactants and fluorocarbon leveling agents.

5. A metal protective coating, characterized in that, The metal protective coating is obtained by coating and curing the coating composition according to any one of claims 1 to 4.

6. The metal protective coating according to claim 5, characterized in that, The thickness of the metal protective coating is 10–50 μm, more preferably 20–30 μm.

7. A method for preparing the metal protective coating according to claim 5, characterized in that, The preparation method includes: Step S1: The first mixture containing glass powder, filler and water is ball-milled to obtain a slurry; Step S2: Mix the silica sol, silane coupling agent, organic acid and the slurry to obtain a coating. Step S3: Apply the coating to at least one side of the metal substrate and cure it to obtain the metal protective coating.

8. The method for preparing a metal protective coating according to claim 7, characterized in that, Step S1 includes: mixing the glass powder, the filler and the water to obtain the first mixture; wherein, during the mixing process in step S1, a first stirring is performed; preferably, the first stirring rate is 500-800 r / min and the time is 25-35 min; Preferably, the ball mill rotates at a speed of 1200–1800 r / min for 2–3 hours. Preferably, ball milling is performed using ball milling media, and the weight ratio of the ball milling media to the first mixture is (0.8-1.2):1; more preferably, the diameter of the ball milling media is 1-2 mm. Preferably, an auxiliary agent is also introduced during the mixing process in step S1.

9. The method for preparing a metal protective coating according to claim 7, characterized in that, Step S2 includes: mixing the silica sol with the slurry and performing a second stirring to obtain a second mixture; mixing the second mixture, the silane coupling agent, and the organic acid and performing a third stirring to obtain the coating. Preferably, the second stirring rate is 300-500 r / min, and the time is 30-40 min; Preferably, the third stirring rate is 300-500 r / min, and the time is 6-10 h.

10. The method for preparing a metal protective coating according to any one of claims 7 to 9, characterized in that, In step S3, the coating amount on the metal substrate surface is 30-40 g / m². 2 ; Preferably, the curing process includes a first heating treatment, a second heating treatment, a third heating treatment, and a sintering treatment performed sequentially; More preferably, the temperature of the first heat treatment is 50-70°C, and the time is 0.4-0.6 h; More preferably, the temperature of the second heat treatment is 110–130°C, and the time is 0.4–0.6 h; More preferably, the temperature of the third heating treatment is 200–300°C, and the time is 0.5–1.5 h; More preferably, the sintering treatment is performed at a temperature of 400–600°C for 2–4 hours.

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