Self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method

Abstract

This invention belongs to the field of anti-corrosion coating technology, and provides a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. Halloysite nanotubes loaded with corrosion-inhibiting components and drying oil are used as functional units. Combined with an iron tannate complex layer and silane coupling modification, functionalized fillers are prepared, and a light-colored contrast primer and a functional topcoat are constructed. A composite coating is formed through layered coating and curing. Under the action of corrosive media, the coating can provide a visual early warning of damaged areas through color changes. Simultaneously, it repairs microcracks and local defects through the release of corrosion-inhibiting components, filling with drying oil, and interfacial complexation. Furthermore, a sheet-like barrier structure extends the transmission path of corrosive media. The resulting coating combines anti-corrosion protection, damage indication, and self-healing functions, making it suitable for long-term protection of overhead pipeline surfaces.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating technology, and relates to a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. Background Technology

[0002] Overhead pipelines are exposed to various service environments, including air, rainwater, temperature variations, and industrial atmospheres. During transportation, installation, and use, the coating surface is also susceptible to scratches, impacts, and localized stress. Once microcracks, pinholes, or localized damage occur in the coating, corrosive media can penetrate the metal substrate along the defect and continue to propagate at the interface, leading to localized corrosion, coating blistering, decreased adhesion, and protective failure. For overhead pipelines, this type of damage often first occurs in localized areas. Early defects are small and difficult to detect in time through routine inspections. By the time obvious rust or coating peeling appears, the metal substrate has usually already suffered significant corrosion damage.

[0003] Existing anti-corrosion coatings for overhead pipelines primarily utilize epoxy, polyurethane, or sheet-like filler barrier systems, relying mainly on the shielding effect of the coating itself to delay the penetration of water, oxygen, and corrosive ions. While these technologies can provide corrosion protection for a certain period, their function is typically focused on passive barrier, lacking the ability to visually respond to localized damage and corrosion initiation sites, making it difficult to promptly identify early areas of coating failure. Therefore, the problem with existing technologies is that current anti-corrosion coatings for overhead pipelines cannot, while maintaining barrier performance, provide intuitive color-coded warnings of localized corrosion and coating damage, nor can they continuously repair microcracks and localized defects. This makes it difficult to identify early failure areas on the surface of overhead pipelines, and once defects form, it is difficult to promptly inhibit their further expansion. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method, thereby meeting the needs of actual production.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function, the preparation method comprising:

[0007] S1, add halloysite nanotubes to 8-hydroxyquinoline ethanol solution for vacuum impregnation to obtain 8-hydroxyquinoline-loaded halloysite nanotubes, add the 8-hydroxyquinoline-loaded halloysite nanotubes to natural linseed oil for vacuum impregnation to obtain 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes.

[0008] S2, Tannic acid solution and ferric chloride hexahydrate solution were mixed to obtain tannic acid-iron complex dispersion. Halloysite nanotubes loaded with 8-hydroxyquinoline / linseed oil were added to deionized water for dispersion and tannic acid-iron complex dispersion was added dropwise. KH-560 pre-hydrolysis solution was added and stirred to obtain functionalized halloysite nanotubes.

[0009] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly to obtain a light-colored contrast primer; epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly to obtain a functional topcoat primer.

[0010] S4. Mix the light-colored contrast primer and the functional topcoat primer with T-31 curing agent respectively. Apply the light-colored contrast primer to the carbon steel surface, and then apply the functional topcoat primer to the light-colored contrast primer surface. After curing, a self-healing anti-corrosion coating for overhead pipelines with color response warning function is obtained.

[0011] The specific methods include:

[0012] S1. Halloysite nanotubes are added to an 8-hydroxyquinoline ethanol solution and vacuum impregnated for 30-40 min. After washing and drying, 8-hydroxyquinoline-loaded halloysite nanotubes are obtained. The 8-hydroxyquinoline-loaded halloysite nanotubes are added to natural linseed oil and vacuum impregnated for 1-1.5 h. After centrifugation and drying, 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes are obtained.

[0013] S2, Tannic acid solution and ferric chloride hexahydrate solution were mixed and stirred at room temperature to obtain tannic acid-iron complex dispersion. Halloysite nanotubes loaded with 8-hydroxyquinoline / linseed oil were added to deionized water and dispersed, and the tannic acid-iron complex dispersion was added dropwise. The pH of the system was adjusted to 4.0-4.5 with 0.5-1M dilute hydrochloric acid and stirred for 1-1.5 h. After vacuum filtration, the mixture was redispersed in deionized water, KH-560 pre-hydrolysis solution was added, and the mixture was stirred for 1-2 h. After filtration and drying, functionalized halloysite nanotubes were obtained.

[0014] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly to obtain a light-colored contrast primer; epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly to obtain a functional topcoat primer.

[0015] S4. Before coating, mix the light-colored contrast primer and functional topcoat primer with T-31 curing agent. Apply the light-colored contrast primer to the carbon steel surface that has been sandblasted to Sa 2.5 grade, controlling the wet film thickness of the primer to be 80-120μm. After the primer is surface dry, apply the functional topcoat primer in two coats to the surface of the light-colored contrast primer, with an interval of 1 hour between each coat. Control the wet film thickness of each functional topcoat primer to be 120-170μm. After coating, cure at 40-45℃ for 24-26 hours to obtain a self-healing anti-corrosion coating for overhead pipelines with color response warning function.

[0016] Halloysite nanotubes have an outer wall primarily composed of silanol groups, while the inner wall contains both aluminum and silanol groups. This difference in surface composition provides an interfacial basis for loading the tube cavity and sealing the outer wall. During vacuum impregnation, air is expelled from the tube cavity, and an 8-hydroxyquinoline ethanol solution enters the cavity under pressure differential. The cyclic nitrogen atom and phenolic hydroxyl oxygen atom in the 8-hydroxyquinoline molecule have coordination capabilities, allowing them to coordinate with aluminum sites on the inner wall of the tube. Simultaneously, the phenolic hydroxyl groups form hydrogen bonds with surface hydroxyl groups, enabling them to adhere to the inner wall of the tube.

[0017] Halloysite nanotubes loaded with 8-hydroxyquinoline were then subjected to vacuum impregnation with linseed oil. Under negative pressure, linseed oil entered the tube lumen and wetted the loaded 8-hydroxyquinoline, forming a composite loading structure with linseed oil as the liquid repair phase and 8-hydroxyquinoline dispersed within it. The unsaturated fatty acid glycerides in the linseed oil were retained in the tube lumen through hydrophobic interactions, van der Waals interactions, and weak hydrogen bonds between the ester groups and surface hydroxyl groups. Because 8-hydroxyquinoline first adhered to the inner wall of the tube before the lumen was filled by linseed oil, the possibility of 8-hydroxyquinoline migrating out of the lumen during subsequent impregnation was reduced.

[0018] The coordination complex formed by tannic acid and ferric ions is used to construct the external sealing layer of the tube. The tannic acid molecule contains pyrogallol and catechol groups. Under appropriate acidic conditions, the phenolic hydroxyl groups coordinate with ferric ions to form a multidentate coordination network with ferric ions as cross-linking nodes. After being dispersed in an aqueous phase, this complex comes into contact with halloysite nanotubes loaded with the repair phase. It is deposited on the tube opening and outer wall through electrostatic interactions, hydrogen bonding, and interfacial interactions with the silanol groups on the outer surface of the halloysite, forming the sealing layer.

[0019] After the above treatment, the halloysite nanotubes are loaded with linseed oil and 8-hydroxyquinoline within their lumens. The tube openings and part of the outer wall are covered by a tannic acid iron coordination network, preventing premature release of the repair components within the lumens under normal coating service conditions. Subsequently, γ-glycidyl etheroxypropyltrimethoxysilane is introduced for surface modification. This silane coupling agent is pre-hydrolyzed in a weakly acidic aqueous solution to generate silanol. The silanol condenses with residual silanols on the halloysite surface and incompletely coordinated phenolic hydroxyl groups in the tannic acid iron complex layer, forming siloxane bonds. The epoxy groups at the other end of the coupling agent can participate in the ring-opening reaction during the subsequent epoxy resin curing process, enabling interfacial bonding between the functionalized halloysite nanotubes and the epoxy matrix.

[0020] The coating matrix is ​​formed by crosslinking epoxy resin with T-31 curing agent. During curing, amine active hydrogen undergoes ring-opening addition with epoxy groups, generating a hydroxyl-containing crosslinked network. Functionalized halloysite nanotubes are embedded in this network, and the silane coupling layer improves the interfacial compatibility between the filler and the resin, reducing the tendency of functional fillers to agglomerate in the coating. The modified T-31 curing system has a low content of free small molecule amines, which can mitigate the damage of the alkaline environment to the iron tannate sealing layer in the early stage of curing, allowing the sealing structure to remain stable in an undamaged state.

[0021] When the coating is subjected to mechanical scratches, impacts, or stress, forming microcracks or defects that penetrate into the metal substrate, water, oxygen, and ions enter the defect area, and corrosion begins on the metal surface. In the anodic region, iron atoms dissolve to form ferrous ions, which then further transform into ferric ions in an oxygen-containing environment. In the cathodic region, an oxygen reduction reaction occurs, generating hydroxide ions, increasing the local alkalinity. This alkaline environment weakens the tannic acid iron coordination network, causing ferric ions to combine with hydroxide ions to form ferric hydroxide species. Tannic acid ligands are released from the complex network, loosening the sealing layer structure and re-exposing the halloysite nanotube openings. After the sealing layer at the openings is damaged, linseed oil and some 8-hydroxyquinoline within the lumen are released into the damaged area through capillary action, concentration gradients, and liquid exchange in the defect area. After entering the cracks and scratches, the linseed oil undergoes an auto-oxidation reaction with the participation of atmospheric oxygen, generating free radicals and peroxide intermediates from unsaturated fatty acid segments. This then leads to cross-linking polymerization, gradually transforming the liquid linseed oil into a solid film. The film fills the bottom and sidewalls of the defects, reducing the rate at which water and corrosive ions continue to enter the metal interface.

[0022] The released 8-hydroxyquinoline chelates with iron ions formed during corrosion. The cyclic nitrogen atom and phenolic oxygen atom in the 8-hydroxyquinoline molecule coordinate with the iron ions to form a poorly soluble iron-8-hydroxyquinoline complex. This complex deposits in the defect area and produces a greenish color change. Simultaneously, the tannic acid released from the sealing layer continues to coordinate with iron ions, reforming a dark-colored iron tannic acid complex. Both of these coordination color reactions depend on the iron ions generated in the corrosion area; therefore, the color development site corresponds to the active corrosion site.

[0023] A light-colored contrasting primer enhances the recognizability of the color response. Rutile titanium dioxide and precipitated barium sulfate in the primer provide a light-colored background; their chemical properties are stable and they do not participate in the iron ion coordination colorimetric reaction. When the functional topcoat is damaged and 8-hydroxyquinoline-iron coordination colorimetric and tannic acid-iron coordination colorimetric reactions occur, the resulting green and dark complexes create color differences against the light-colored primer background, making the locally damaged areas observable. Both the primer and functional topcoat are cured with an epoxy system, and the interlayer is co-cured with resin to form a continuous interface, reducing interference from interlayer delamination on colorimetric observation.

[0024] Preferably, in S1, the mass ratio of halloysite nanotubes, 8-hydroxyquinoline ethanol solution and natural linseed oil is 10:(20-31):(30-40).

[0025] Preferably, the halloysite nanotubes have a length of 0.5-1 μm and an inner diameter of 15-30 nm.

[0026] Preferably, the mass fraction of the 8-hydroxyquinoline ethanol solution is 0.6 to 4 wt.%.

[0027] The iodine value of the natural flaxseed oil is ≥170.

[0028] Preferably, in S2, the mass ratio of the 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes, deionized water, tannic acid-iron complex dispersion to KH-560 pre-hydrolyzed solution is 1:(8-12):(8-12):(2-3).

[0029] Preferably, the mass ratio of the tannic acid solution to the ferric chloride hexahydrate solution is (100-105):(50-52).

[0030] Preferably, the tannic acid solution has a mass fraction of 0.5-2 wt.%.

[0031] Preferably, the mass fraction of the ferric chloride hexahydrate solution is 0.6-2.4 wt.%.

[0032] Preferably, the KH-560 pre-hydrolyzed solution is a solution obtained by hydrolyzing the silane coupling agent KH-560 in an acetic acid solution with a pH of 4.5-4.8 for 1 hour, and the mass fraction of the KH-560 pre-hydrolyzed solution is 2-5 wt.%.

[0033] Preferably, in S3, the mass ratio of epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent in the light-colored contrast primer is 100: (20-30): (8-15): (10-20): (1-2): (0.3-0.5): (0.3-0.5).

[0034] Preferably, in the functional surface coating agent, the mass ratio of epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer and polyacrylate leveling agent is 100:(20-30):(5-20):(20-40):(1-2):(0.3-0.5):(0.3-0.5).

[0035] Preferably, the mass ratio of xylene to n-butanol in the mixed solvent is 4:1.

[0036] Preferably, the glass flakes have a mesh count of 200 and a diameter-to-thickness ratio of >50.

[0037] Preferably, in S4, the mass ratio of the light-colored contrast primer to the T-31 curing agent is 100:(40-50).

[0038] Preferably, the mass ratio of the functional surface coating agent to the T-31 curing agent is 100:(40-50).

[0039] Secondly, the present invention provides a self-healing anti-corrosion coating for overhead pipelines with color-response early warning function, prepared by the preparation method described in the first aspect.

[0040] Compared with existing technologies, the beneficial effects of this invention are as follows: By sequentially loading 8-hydroxyquinoline and linseed oil into halloysite nanotubes and constructing a tannic acid-iron complex sealing layer at the tube opening and outer wall, the corrosion-inhibiting and color-developing components and the repair components are stably stored under normal service conditions of the coating, and are directionally released after local damage to the coating and contact with corrosive media. The released linseed oil can enter the crack and defect areas and oxidize to form a film, reducing the rate at which moisture, oxygen, and corrosive ions continue to penetrate into the metal matrix; 8-hydroxyquinoline and tannic acid can coordinate with iron ions generated during corrosion to develop color, creating identifiable color changes at the sites of damage and corrosion initiation; the light-colored contrasting primer enhances the recognizability of the color signal, which is beneficial for the inspection and early maintenance of overhead pipelines. Detailed Implementation

[0041] The technical solution of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific implementations of the present invention and are used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary and should not be construed as limiting the implementation of the present invention or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0042] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone any further purification treatment.

[0043] Example 1

[0044] This embodiment provides a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. The preparation method specifically includes the following steps:

[0045] S1. Halloysite nanotubes with a length of 0.5 μm and an inner diameter of 30 nm were added to a 4 wt.% 8-hydroxyquinoline ethanol solution and vacuum impregnated for 30 min. After washing and drying, 8-hydroxyquinoline-loaded halloysite nanotubes were obtained. The 8-hydroxyquinoline-loaded halloysite nanotubes were then added to natural linseed oil with an iodine value ≥170 and vacuum impregnated for 1 h. The mass ratio of halloysite nanotubes, 8-hydroxyquinoline ethanol solution and natural linseed oil was 10:20:40. After centrifugation and drying, 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes were obtained.

[0046] S2, a 0.5 wt.% tannic acid solution and a 2.4 wt.% ferric chloride hexahydrate solution were mixed and stirred at room temperature. The mass ratio of the tannic acid solution to the ferric chloride hexahydrate solution was 100:52, resulting in a tannic acid-iron complex dispersion. 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes were dispersed in deionized water, and the tannic acid-iron complex dispersion was added dropwise. The pH of the system was adjusted to 4.5 using 0.5 M dilute hydrochloric acid, and stirring was continued for 1 hour under reduced pressure. After filtration, the nanotubes were redispersed in deionized water, and 2 wt.% KH-560 pre-hydrolysate was added. The mass ratio of the 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes, deionized water, tannic acid-iron complex dispersion and KH-560 pre-hydrolysate was 1:8:12:2. The KH-560 pre-hydrolysate was a solution obtained by hydrolyzing silane coupling agent KH-560 in acetic acid solution at pH 4.8 for 1 h. The mixture was stirred for 2 h, filtered and dried to obtain functionalized halloysite nanotubes.

[0047] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent is 100:20:15:10:2:0.3:0.5 to obtain a light-colored contrast primer. Epoxy resin E-51, mixed solvent, functionalized chloroform... Halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent is 100:30:5:40:1:0.5:0.3 to obtain the functional surface coating main agent. The mass ratio of xylene to n-butanol in the mixed solvent is 4:1. The glass flakes have a mesh size of 200 mesh and an aspect ratio > 50.

[0048] S4. Before coating, mix the light-colored contrast primer and the functional topcoat primer with T-31 curing agent. The mass ratio of the light-colored contrast primer to T-31 curing agent is 100:40, and the mass ratio of the functional topcoat primer to T-31 curing agent is 100:50. Apply the light-colored contrast primer to the carbon steel surface that has been sandblasted to Sa2.5 grade, and control the wet film thickness of the primer to 80μm. After the primer is surface dry, apply the functional topcoat primer in two coats to the surface of the light-colored contrast primer, with an interval of 1 hour between each coat. Control the wet film thickness of each coat of functional topcoat primer to 170μm. After coating, the test panel is cured at 40℃ for 26 hours to obtain a self-healing anti-corrosion coating for overhead pipelines with color response warning function.

[0049] Example 2

[0050] This embodiment provides a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. The preparation method specifically includes the following steps:

[0051] S1. Halloysite nanotubes with a length of 1 μm and an inner diameter of 15 nm were added to a 0.6 wt.% 8-hydroxyquinoline ethanol solution and vacuum impregnated for 40 min. After washing and drying, 8-hydroxyquinoline-loaded halloysite nanotubes were obtained. The 8-hydroxyquinoline-loaded halloysite nanotubes were then added to natural linseed oil with an iodine value ≥170 and vacuum impregnated for 1.5 h. The mass ratio of halloysite nanotubes, 8-hydroxyquinoline ethanol solution and natural linseed oil was 10:31:30. After centrifugation and drying, 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes were obtained.

[0052] S2, a 2 wt.% tannic acid solution and a 0.6 wt.% ferric chloride hexahydrate solution were mixed and stirred at room temperature. The mass ratio of the tannic acid solution to the ferric chloride hexahydrate solution was 105:50, resulting in a tannic acid-iron complex dispersion. 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes were dispersed in deionized water, and the tannic acid-iron complex dispersion was added dropwise. The pH of the system was adjusted to 4.0 using 1M dilute hydrochloric acid, and stirring was continued for 1.5 hours. The mixture was then subjected to vacuum extraction. After filtration, the nanotubes were redispersed in deionized water, and 5 wt.% KH-560 pre-hydrolyzed solution was added. The mass ratio of the 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes, deionized water, tannic acid-iron complex dispersion and KH-560 pre-hydrolyzed solution was 1:12:8:3. The KH-560 pre-hydrolyzed solution was obtained by hydrolyzing the silane coupling agent KH-560 in an acetic acid solution at pH 4.5 for 1 h. The mixture was stirred for 1 h, filtered and dried to obtain functionalized halloysite nanotubes.

[0053] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent is 100:30:8:20:1:0.5:0.3 to obtain a light-colored contrast primer. Epoxy resin E-51, mixed solvent, functionalized halloysite sodium are then mixed. The epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent are mixed evenly. The mass ratio of the epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent is 100:20:20:20:2:0.3:0.5 to obtain the functional surface coating main agent. The mass ratio of xylene to n-butanol in the mixed solvent is 4:1. The glass flakes have a mesh size of 200 mesh and an aspect ratio > 50.

[0054] S4. Before coating, mix the light-colored contrast primer and the functional topcoat primer with T-31 curing agent. The mass ratio of the light-colored contrast primer to T-31 curing agent is 100:50, and the mass ratio of the functional topcoat primer to T-31 curing agent is 100:40. Apply the light-colored contrast primer to the carbon steel surface that has been sandblasted to Sa2.5 grade, and control the wet film thickness of the primer to 120μm. After the primer is surface dry, apply the functional topcoat primer in two coats to the surface of the light-colored contrast primer, with an interval of 1 hour between each coat. Control the wet film thickness of each coat of functional topcoat primer to 120μm. After coating, the test panel is cured at 45℃ for 24 hours to obtain a self-healing anti-corrosion coating for overhead pipelines with color response warning function.

[0055] Example 3

[0056] This embodiment provides a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. The preparation method specifically includes the following steps:

[0057] S1. Halloysite nanotubes with a length of 0.7 μm and an inner diameter of 20 nm were immersed in a 1.5 wt.% 8-hydroxyquinoline ethanol solution under vacuum for 35 min. After washing and drying, 8-hydroxyquinoline-loaded halloysite nanotubes were obtained. The 8-hydroxyquinoline-loaded halloysite nanotubes were then immersed in natural linseed oil with an iodine value ≥170 under vacuum for 1.2 h. The mass ratio of halloysite nanotubes, 8-hydroxyquinoline ethanol solution and natural linseed oil was 10:25:35. After centrifugation and drying, 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes were obtained.

[0058] S2, a 1.0 wt.% tannic acid solution and a 1.5 wt.% ferric chloride hexahydrate solution were mixed and stirred at room temperature. The mass ratio of the tannic acid solution to the ferric chloride hexahydrate solution was 102:51, resulting in a tannic acid-iron complex dispersion. 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes were dispersed in deionized water, and the tannic acid-iron complex dispersion was added dropwise. The pH of the system was adjusted to 4.2 using 0.8 M dilute hydrochloric acid, and stirring was continued for 1.2 h. After vacuum filtration... The nanotubes were redispersed in deionized water, and 3.5 wt.% KH-560 pre-hydrolysate was added. The mass ratio of the 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes, deionized water, tannic acid-iron complex dispersion and KH-560 pre-hydrolysate was 1:10:10:2.5. The KH-560 pre-hydrolysate was a solution obtained by hydrolyzing silane coupling agent KH-560 in acetic acid solution at pH 4.6 for 1 h. The mixture was stirred for 1.5 h, filtered and dried to obtain functionalized halloysite nanotubes.

[0059] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent is 100:25:10:15:1.5:0.4:0.4 to obtain a light-colored contrast primer. Epoxy resin E-51, mixed solvent, functionalized chloroform... Halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent is 100:25:12:30:1.5:0.4:0.4 to obtain the functional surface coating main agent. The mass ratio of xylene to n-butanol in the mixed solvent is 4:1. The glass flakes have a mesh size of 200 mesh and an aspect ratio > 50.

[0060] S4. Before coating, mix the light-colored contrast primer and the functional topcoat primer with T-31 curing agent. The mass ratio of the light-colored contrast primer to T-31 curing agent is 100:45, and the mass ratio of the functional topcoat primer to T-31 curing agent is 100:45. Apply the light-colored contrast primer to the carbon steel surface that has been sandblasted to Sa2.5 grade, and control the wet film thickness of the primer to 100μm. After the primer is surface dry, apply the functional topcoat primer in two coats to the surface of the light-colored contrast primer, with an interval of 1 hour between each coat. Control the wet film thickness of each coat of functional topcoat primer to 140μm. After coating, the test panel is cured at 42℃ for 25 hours to obtain a self-healing anti-corrosion coating for overhead pipelines with color response warning function.

[0061] Example 4

[0062] This embodiment provides a self-healing anti-corrosion coating for overhead pipelines with color-responsive early warning function and its preparation method. The preparation method specifically includes the following steps:

[0063] S1. Halloysite nanotubes with a length of 0.9 μm and an inner diameter of 25 nm were immersed in a 2.5 wt.% 8-hydroxyquinoline ethanol solution under vacuum for 38 min. After washing and drying, 8-hydroxyquinoline-loaded halloysite nanotubes were obtained. The 8-hydroxyquinoline-loaded halloysite nanotubes were then immersed in natural linseed oil with an iodine value ≥170 under vacuum for 1.4 h. The mass ratio of halloysite nanotubes, 8-hydroxyquinoline ethanol solution and natural linseed oil was 10:28:38. After centrifugation and drying, 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes were obtained.

[0064] S2, a 1.5 wt.% tannic acid solution and a 2.0 wt.% ferric chloride hexahydrate solution were mixed and stirred at room temperature. The mass ratio of the tannic acid solution to the ferric chloride hexahydrate solution was 103:51, resulting in a tannic acid-iron complex dispersion. 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes were dispersed in deionized water, and the tannic acid-iron complex dispersion was added dropwise. The pH of the system was adjusted to 4.4 using 0.7 M dilute hydrochloric acid, and stirring was continued for 1.3 h. The mixture was then subjected to vacuum extraction. After filtration, the nanotubes were redispersed in deionized water, and 4 wt.% KH-560 pre-hydrolyzed solution was added. The mass ratio of the 8-hydroxyquinoline / linseed oil-supported halloysite nanotubes, deionized water, tannic acid-iron complex dispersion and KH-560 pre-hydrolyzed solution was 1:11:9:2.8. The KH-560 pre-hydrolyzed solution was obtained by hydrolyzing the silane coupling agent KH-560 in an acetic acid solution at pH 4.7 for 1 h. The mixture was stirred for 1.8 h, filtered and dried to obtain functionalized halloysite nanotubes.

[0065] S3, epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, polysiloxane defoamer and polyacrylate leveling agent is 100:28:12:18:1.8:0.45:0.4 to obtain a light-colored contrast primer. Epoxy resin E-51, mixed solvent, functionalized chloroform... Halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent are mixed evenly. The mass ratio of epoxy resin E-51, mixed solvent, functionalized halloysite nanotubes, glass flakes, KH-560, polysiloxane defoamer, and polyacrylate leveling agent is 100:28:18:35:1.8:0.4:0.45 to obtain the functional surface coating main agent. The mass ratio of xylene to n-butanol in the mixed solvent is 4:1. The glass flakes have a mesh size of 200 mesh and an aspect ratio > 50.

[0066] S4. Before coating, mix the light-colored contrast primer and the functional topcoat with T-31 curing agent. The mass ratio of the light-colored contrast primer to T-31 curing agent is 100:48, and the mass ratio of the functional topcoat to T-31 curing agent is 100:42. Apply the light-colored contrast primer to the carbon steel surface that has been sandblasted to Sa2.5 grade, and control the wet film thickness of the primer to 110μm. After the primer is surface dry, apply the functional topcoat in two coats to the surface of the light-colored contrast primer, with an interval of 1 hour between each coat. Control the wet film thickness of each coat of the functional topcoat to 150μm. After coating, the test panel is cured at 43℃ for 25 hours to obtain a self-healing anti-corrosion coating for overhead pipelines with color response warning function.

[0067] Comparative Example 1

[0068] This comparative example provides a self-healing anti-corrosion coating for overhead pipelines with color-response early warning function and its preparation method. The difference between this example and Example 1 is that in S1, 8-hydroxyquinoline ethanol solution is not used to vacuum impregnate halloysite nanotubes. Instead, halloysite nanotubes are loaded with natural linseed oil. Other process parameters and operating conditions are exactly the same as in Example 1.

[0069] Comparative Example 2

[0070] This comparative example provides a self-healing anti-corrosion coating for overhead pipelines with color-response early warning function and its preparation method. The difference between this example and Example 1 is that in S1, natural linseed oil is not used to perform secondary vacuum impregnation of 8-hydroxyquinoline-loaded halloysite nanotubes. Only 8-hydroxyquinoline-loaded halloysite nanotubes are prepared. Other process parameters and operating conditions are exactly the same as in Example 1.

[0071] Comparative Example 3

[0072] This comparative example provides a self-healing anti-corrosion coating for overhead pipelines with color-response early warning function and its preparation method. The difference between this example and Example 1 is that in S2, instead of using tannic acid solution and ferric chloride hexahydrate solution to complex and block 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes, the 8-hydroxyquinoline / linseed oil-loaded halloysite nanotubes are directly modified with KH-560. Other process parameters and operating conditions are exactly the same as in Example 1.

[0073] Performance testing:

[0074] The scratch and salt spray corrosion test method is as follows:

[0075] The coating was tested after being left at room temperature for 7 days. Before testing, the surface of the test panel was cleaned with deionized water and allowed to air dry. Then, a straight scratch was made in the center of the coating using a single-edged scratching tool. The scratch was 50 mm long and 1 mm wide, penetrating the coating and exposing the carbon steel substrate. After scratching, loose debris at the edges of the scratch was removed with a soft brush. The scratched area was not sanded again. The scratched test panel was placed in a salt spray test chamber at a 20° angle to the vertical, with the scratched side facing upwards. The test medium was a 5 wt.% sodium chloride aqueous solution. The temperature of the salt spray chamber was controlled at 35℃, and the salt spray deposition rate was controlled at 1.0-2.0 mL / (80 cm²). 2The solution pH was 6.5-7.2, and the continuous spraying time was 720 h. After the experiment, the test plates were removed, and the surface salts were gently rinsed with deionized water. After drying at room temperature, the rust, blistering, peeling, and corrosion expansion in the scratched area were observed. The maximum width of corrosion expansion on both sides of the scratch was measured using vernier calipers or microscopic measurement software. Five locations were selected at equal intervals along the scratch length of each test plate, and the average value was taken as the scratch corrosion expansion width.

[0076] The color response warning test method is as follows:

[0077] The coating was tested after being left at room temperature for 7 days. Artificial defects were created on the coating surface using a needle tip or scratcher, with a length of 20 mm, a width of 0.5 mm, and a depth sufficient to expose the carbon steel substrate. After cleaning and drying the defect areas with deionized water, 0.2 mL of a 3.5 wt.% sodium chloride aqueous solution was added to each defect, ensuring complete coverage. The test plates were then exposed in a constant temperature and humidity chamber at 40°C and 95% relative humidity. Color changes in the defect areas were observed at 0.5 h, 1 h, 2 h, 4 h, 8 h, and 24 h. The time when the first green, bluish-black, or dark color appeared at the defect was recorded as the color response time. Color changes could be observed using a combination of visual observation and photographic recording. When photographing, the light source, shooting distance, and background should be consistent.

[0078] The self-healing performance testing method is as follows:

[0079] The coating was tested after being left at room temperature for 7 days. Micro-scratches were prepared on the coating surface using a micro-scratcher or blade. The scratch length was 20 mm, the initial scratch width was controlled to be 80-120 μm, and the scratch depth was controlled to penetrate the functional topcoat but not completely destroy the light-colored contrast primer. Immediately after scratch preparation, the scratched area was photographed using an optical microscope, and the initial scratch width was measured and recorded as W0. The test panel was then placed in an air environment with a temperature of 25℃ and a relative humidity of 60% for 24 hours, and then placed in a humid heat environment with a temperature of 40℃ and a relative humidity of 95% for 24 hours. After treatment, the scratched area was photographed again at the same magnification and the same position, and the remaining width of the scratch after repair was measured and recorded as W. t According to the formula H = (W0 - W) t The scratch repair rate is calculated as H / W0×100%, where H is the scratch repair rate, W0 is the initial scratch width, and W... t The remaining width of the scratch after repair. At least 5 measurement locations should be selected for each test plate, and the average value should be taken as the scratch repair rate of that test plate.

[0080] The test results are shown in Table 1.

[0081] Table 1. Test results of self-healing anti-corrosion coatings in Examples 1-4 and Comparative Examples 1-3

[0082]

[0083] As shown in Table 1, compared to Example 1, Comparative Example 1 showed an increase in scratch corrosion spread width, an increase in color response time, and a decrease in scratch repair rate; Comparative Example 2 showed an increase in scratch corrosion spread width, no change in color response time, and a decrease in scratch repair rate; and Comparative Example 3 showed an increase in scratch corrosion spread width, an increase in color response time, and a decrease in scratch repair rate. This is because Comparative Example 1 did not contain 8-hydroxyquinoline, and the defect lacked an active component that could rapidly chelate with iron ions for color development and corrosion inhibition. It relied solely on the ferric tannate system to produce a dark response, resulting in a slower color development speed. Comparative Example 2 did not contain natural linseed oil, and the 8-hydroxyquinoline and ferric tannate system could still complex with the iron ions generated by corrosion for color development. Therefore, the color response time did not change significantly, but the defect area lacked a flowable and oxidatively cured repair phase, making it difficult to effectively fill and seal the scratches. Water and ions continued to enter the metal interface, exacerbating corrosion spread. Comparative Example 3 did not construct a ferric tannate complex plugging layer. 8-hydroxyquinoline and linseed oil in the lumen were more likely to migrate and be lost during preparation or early service. After damage, there were insufficient components to be released. At the same time, the lack of ferric tannate's dark color synergistic color development and triggering plugging structure resulted in delayed color response and decreased self-healing rate.

[0084] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing an overhead pipeline self-repairing anticorrosive coating with color response warning function, characterized in that, The preparation method comprises: S1, vacuum impregnation of adding halloysite nanotubes into 8-hydroxyquinoline ethanol solution to obtain 8-hydroxyquinoline loaded halloysite nanotubes, and vacuum impregnation of adding the 8-hydroxyquinoline loaded halloysite nanotubes into natural linseed oil to obtain 8-hydroxyquinoline / linseed oil loaded halloysite nanotubes; S2, mixing of a tannic acid solution and a ferric chloride hexahydrate solution to obtain a tannic acid-iron complex dispersion liquid, dispersion of adding the 8-hydroxyquinoline / linseed oil loaded halloysite nanotubes into deionized water and dropwise addition of the tannic acid-iron complex dispersion liquid, and stirring of adding a KH-560 pre-hydrolysis liquid to obtain functionalized halloysite nanotubes; S3, uniform mixing of epoxy resin E-51, a mixed solvent, rutile titanium dioxide and precipitated barium sulfate, KH-560, a polysiloxane defoaming agent and a polyacrylate leveling agent to obtain a light-colored contrast primer main agent, and uniform mixing of epoxy resin E-51, a mixed solvent, the functionalized halloysite nanotubes, glass flake, KH-560, a polysiloxane defoaming agent and a polyacrylate leveling agent to obtain a functional topcoat main agent; S4, mixing of the light-colored contrast primer main agent and the functional topcoat main agent with T-31 curing agent respectively, coating of the light-colored contrast primer main agent on the surface of carbon steel, and then applying the functional topcoat main agent on the surface of the light-colored contrast primer to obtain an aerial pipeline self-repairing anti-corrosion coating with color response early warning function.

2. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response early warning function according to claim 1, characterized in that, In S1: The mass ratio of the halloysite nanotubes, the 8-hydroxyquinoline ethanol solution and the natural linseed oil is 10:(20-31):(30-40). The halloysite nanotubes have a tube length of 0.5-1 μm and an inner diameter of 15-30 nm.

3. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S2: The mass ratio of the 8-hydroxyquinoline / linseed oil loaded halloysite nanotubes, the deionized water, the tannic acid-iron complex dispersion liquid and the KH-560 pre-hydrolysis liquid is 1:(8-12):(8-12):(2-3).

4. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S2: The mass ratio of the tannic acid solution and the ferric chloride hexahydrate solution is (100-105):(50-52).

5. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S2: The KH-560 pre-hydrolysis liquid is a solution obtained by hydrolyzing silane coupling agent KH-560 in an acetic acid solution with pH of 4.5-4.8 for 1 h, and the mass fraction of the KH-560 pre-hydrolysis liquid is 2-5 wt.%.

6. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S3: In the light-colored contrast primer main agent, the mass ratio of the epoxy resin E-51, the mixed solvent, the rutile titanium dioxide and precipitated barium sulfate, the KH-560, the polysiloxane defoaming agent and the polyacrylate leveling agent is 100:(20-30):(8-15):(10-20):(1-2):(0.3-0.5):(0.3-0.5).

7. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S3: In the functional topcoat main agent, the mass ratio of the epoxy resin E-51, the mixed solvent, the functionalized halloysite nanotubes, the glass flake, the KH-560, the polysiloxane defoaming agent and the polyacrylic acid ester leveling agent is 100:(20-30):(5-20):(20-40):(1-2):(0.3-0.5):(0.3-0. 5); The mass ratio of xylene and n-butanol in the mixed solvent is 4:

1.

8. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S4: The mass ratio of the light-colored contrast primer to the T-31 curing agent is 100:(40-50).

9. The method for preparing the overhead pipeline self-repairing anticorrosive coating with color response warning function according to claim 1, characterized in that, In S4: The mass ratio of the functional surface coating agent to the T-31 curing agent is 100:(40-50).

10. An overhead pipeline self-repairing anticorrosive coating with color response warning function, characterized in that, It is obtained by the preparation method according to any one of claims 1-9.

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