Self-healing coating for offshore engineering steel structure and preparation method thereof

Abstract

The present application relates to the technical field of offshore engineering steel, and proposes a kind of self-repairing coating for offshore engineering steel structure and preparation method thereof, the self-repairing coating for offshore engineering steel structure, including adhesive layer and self-repairing layer;Self-repairing layer is composed of the following mass percentage of raw materials: chitosan 24~30%, sodium alginate 10~12%, corrosion inhibitor 8~12%, microencapsulated repair agent 10~15%, and the balance is water;The core material of microencapsulated repair agent is epoxy resin, and the wall material is sodium alginate.Through the above technical scheme, the problem of insufficient corrosion resistance and self-repairing of the self-repairing coating for offshore engineering steel structure in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of marine engineering steel technology, specifically to a self-healing coating for marine engineering steel structures and its preparation method. Background Technology

[0002] Marine engineering steel structures operate under conditions of high salt spray, high humidity, strong ultraviolet radiation, seawater erosion, and alternating loads. The steel substrate is susceptible to various corrosion failures, including electrochemical corrosion, pitting corrosion, and fatigue corrosion. These problems not only reduce the service life of the marine steel structures and increase the costs of later maintenance, repair, and replacement, but also easily lead to structural failure. Coating protection is currently the most economical and commonly used anti-corrosion method for marine engineering steel structures. Self-healing coatings, with their ability to autonomously detect damage and actively repair defects, can effectively compensate for the shortcomings of traditional passive protective coatings and extend the protection period. They have now become a core research direction in the field of marine corrosion protection.

[0003] Currently, existing self-healing coatings for marine engineering have many shortcomings in industrial applications. Firstly, most coatings use chemically synthesized polymer carriers, petroleum-based repair agents, and chemical corrosion inhibitors. These materials have poor biodegradability and high environmental toxicity, and long-term use can cause irreversible pollution to the marine ecosystem, which is inconsistent with the concept of green and environmentally friendly marine development. Secondly, the coating structure is simple, relying only on a single functional layer for protection. The adhesion to the steel substrate is weak, and under the combined effects of alternating loads and salt spray corrosion, problems such as blistering, peeling, and detachment easily occur, resulting in extremely poor protective stability. Thirdly, the self-healing mechanism is imperfect, with low repair efficiency, and is mostly limited to single-time, localized repairs, unable to cope with repeated damage in the marine environment, and lacking long-term protective capabilities. Fourthly, existing technologies focus primarily on achieving the repair function, neglecting the environmental friendliness and substrate compatibility of the coating, making it difficult to simultaneously achieve the triple performance of green environmental protection, strong adhesion, and efficient self-healing. Therefore, developing a highly efficient, self-healing, and corrosion-resistant coating for marine engineering steel structures is of great significance. Summary of the Invention

[0004] This invention proposes a self-healing coating for marine engineering steel structures and its preparation method, in order to solve or alleviate at least one of the above-mentioned problems.

[0005] The technical solution of the present invention is as follows: This invention proposes a self-healing coating for marine engineering steel structures, comprising an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by mass percentage: 24%~30% chitosan, 10%~12% sodium alginate, 8%~12% corrosion inhibitor, 10%~15% microencapsulated repair agent, and the balance being water; The core material of the microencapsulated repair agent is epoxy resin, and the wall material is sodium alginate.

[0006] Preferably, the preparation method of the microencapsulated repair agent includes the following steps: A1. After dispersing the epoxy resin evenly in a mixed solution of solvent I and emulsifier, a core material dispersion is obtained. A2. After dispersing sodium alginate in solvent II evenly, a wall material dispersion is obtained; A3. The core material dispersion is added to the wall material dispersion and mixed. A crosslinking agent is added and mixing is continued. The mixture is then filtered, washed, and dried to obtain the microencapsulated repair agent.

[0007] Preferably, the corrosion inhibitor includes tea polyphenols and rosemary extract.

[0008] Preferably, the mass ratio of tea polyphenols to rosemary is 1:0.5~1.5.

[0009] Preferably, the adhesive layer is composed of the following raw materials in weight percentage: 22%~28% chitosan, 7%~10% sodium alginate, 5%~8% pectin, and the balance being water.

[0010] Preferably, the preparation method of the self-healing coating includes the following steps: adding chitosan and sodium alginate to water and dispersing them evenly, adding a corrosion inhibitor and mixing, then adding a microencapsulated repair agent and mixing again to obtain the self-healing coating.

[0011] Preferably, the dispersion temperature is 60~70℃ and the dispersion time is 25~35min.

[0012] This invention also proposes a method for preparing a self-healing coating for marine engineering steel structures, comprising the following steps: S1. After pretreatment, steel is obtained as pretreated steel. S2. After the raw materials of the adhesive layer are mixed evenly, they are sprayed onto the surface of the pretreated steel. When the adhesive layer is semi-cured, the self-healing coating is sprayed on, and after curing, the self-healing coating for marine engineering steel structures is obtained.

[0013] Preferably, the curing temperature is 40~50℃ and the curing time is 24~36h.

[0014] The present invention also proposes a marine engineering steel structure, comprising a steel substrate and a self-healing coating, wherein the self-healing coating comprises the self-healing coating for marine engineering steel structures described above.

[0015] The beneficial effects of this invention are as follows: This invention relates to a self-healing coating for marine engineering steel structures. The self-healing layer incorporates chitosan and sodium alginate as composite carriers, effectively improving the corrosion resistance and self-healing properties of the coating. Sodium alginate is a natural polysaccharide biomaterial with a molecular structure containing numerous hydrophilic groups such as hydroxyl and carboxyl groups. It can slowly dissolve in deionized water to form a uniform and stable viscous colloidal solution. The dissolved colloidal system exhibits excellent dispersibility and compatibility, serving as a core carrier to uniformly disperse corrosion inhibitors, microencapsulated repair agents, and other components. When combined with chitosan, the two biocarriers form a synergistic cross-linking system, further enhancing the stability and adhesion of the colloid without inhibiting the function of the corrosion inhibitors and microencapsulated repair agents, thereby effectively improving the corrosion resistance and self-healing properties of the self-healing coating for marine engineering steel structures.

[0016] In this invention, the core material of the microencapsulated repair agent is epoxy resin, and the wall material is sodium alginate. This further improves the corrosion resistance and self-healing properties of the self-healing coating for marine engineering steel structures. When the coating is damaged by external force or corrosive media, the microcapsules rupture under stress and release the epoxy resin repair agent. Through curing and cross-linking, the physical damage to the coating is healed. At the same time, the free corrosion inhibitors uniformly dispersed within the coating can quickly exert their corrosion inhibition effect. The two work synergistically to simultaneously complete the dual functions of corrosion inhibition and coating self-healing, thereby effectively improving the corrosion resistance and self-healing properties of the self-healing coating for marine engineering steel structures. Detailed Implementation

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0018] A specific embodiment of the first aspect of the present invention provides a self-healing coating for marine engineering steel structures, comprising an adhesive layer and a self-healing layer; the self-healing layer is composed of the following raw materials by mass percentage: 24%~30% chitosan, 10%~12% sodium alginate, 8%~12% corrosion inhibitor, 10%~15% microencapsulated repair agent, and the balance being water; the core material of the microencapsulated repair agent is epoxy resin, and the wall material is sodium alginate.

[0019] In one embodiment of the present invention, the preparation method of the microencapsulated repair agent includes the following steps: A1. After dispersing the epoxy resin evenly in a mixed solution of solvent I and emulsifier, a core material dispersion is obtained. A2. After dispersing sodium alginate in solvent II evenly, a wall material dispersion is obtained; A3. Add the core material dispersion to the wall material dispersion and mix. Add the crosslinking agent and continue mixing. After filtration, washing and drying, obtain the microencapsulated repair agent.

[0020] In this invention, in step A1, solvent I is water, the mass-volume ratio of epoxy resin to solvent I is 1g:2mL, the emulsifier is Tween-80, the amount of emulsifier added is 5wt% of epoxy resin, the dispersion temperature is 25℃, the dispersion time is 15min, and the dispersion rate is 500r / min.

[0021] In this invention, in step A2, the mass ratio of epoxy resin to sodium alginate is 5:4, solvent II is water, the mass-volume ratio of sodium alginate to solvent II is 2g:25mL, the dispersion temperature is 60℃, the dispersion time is 30min, and the dispersion rate is 300r / min.

[0022] In this invention, the crosslinking agent is an aqueous solution of calcium chloride, which is a 5wt% aqueous solution of calcium chloride. Calcium ions cause sodium alginate to crosslink and solidify, forming a complete microcapsule wall material that encapsulates the core material epoxy resin.

[0023] In this invention, the filtration is vacuum filtration, followed by washing three times with deionized water to remove unreacted sodium alginate, calcium chloride, and residual emulsifier from the surface; finally, the washed microencapsulated repair agent is placed in a constant temperature oven and dried at 40°C for 2 hours to obtain a microencapsulated repair agent with a particle size range of 5~10μm, which is then sealed and dried for later use.

[0024] In one embodiment of the present invention, the corrosion inhibitor includes tea polyphenols and rosemary extract.

[0025] In one embodiment of the present invention, the mass ratio of tea polyphenols to rosemary is 1:0.5 to 1.5, preferably 1:1.

[0026] In one embodiment of the present invention, the adhesive layer is composed of the following raw materials by mass percentage: 22%~28% chitosan, 7%~10% sodium alginate, 5%~8% pectin, and the balance being water.

[0027] In this invention, the thickness of the adhesive layer is 30~50μm, preferably 40μm, serving as a transitional bonding layer between the self-healing layer and the steel substrate. By utilizing the chemical adsorption effect between bio-based materials (chitosan, sodium alginate, pectin) and the steel surface, and in conjunction with subsequent steel surface pretreatment processes, the mechanical bonding and chemical adhesion between the overall coating and the substrate are significantly improved, thereby preventing coating peeling and detachment from the source.

[0028] In one embodiment of the present invention, the preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and dispersed evenly, then a corrosion inhibitor is added and mixed, and then a microencapsulated repair agent is added and mixed again to obtain the self-healing coating.

[0029] In this invention, the thickness of the self-healing layer is 80~120μm, preferably 100μm, and the total thickness of the coating is 110~170μm, preferably 140μm.

[0030] In this invention, the corrosion inhibitor is added in three parts, with a 5-minute interval between each addition, to avoid aggregation caused by adding it all at once.

[0031] In one embodiment of the present invention, the dispersion temperature is 60~70°C and the dispersion time is 25~35 min.

[0032] In this invention, after all the corrosion inhibitor is added, the mixing temperature is 40~45℃, the mixing rate is 400r / min, and the mixing time is 30~40min, so that the corrosion inhibitor molecules are fully dispersed in the composite carrier colloid and form hydrogen bond adsorption with the hydrophilic groups of chitosan and sodium alginate to achieve stable loading, without precipitation or stratification, and obtain a composite carrier liquid loaded with corrosion inhibitor. Subsequently, microencapsulated repair agent is directly added and mixing is continued for 20min to obtain a self-healing functional layer coating.

[0033] A second aspect of the present invention provides a method for preparing a self-healing coating for marine engineering steel structures, used to prepare the self-healing coating for marine engineering steel structures provided in the first aspect of the present invention, comprising the following steps: S1. After pretreatment, steel is obtained as pretreated steel. S2. After the raw materials of the adhesive layer are mixed evenly, they are sprayed onto the surface of the pretreated steel. When the adhesive layer is semi-cured, the self-healing coating is sprayed on. After curing, a self-healing coating for marine engineering steel structures is obtained.

[0034] In this invention, the steel used is low-alloy steel or carbon steel for marine engineering. The steel undergoes mechanical rust removal, alkaline degreasing, and acid pickling activation to thoroughly remove oxide scale, oil, rust, and impurities from the substrate surface. After rinsing with deionized water, it is dried. Subsequently, laser texture pretreatment technology is used to construct a uniform micro-nano rough structure on the substrate surface, controlling the surface roughness Ra = 0.8~1.2μm, preferably 1.0μm, to further enhance the mechanical adhesion between the coating and the substrate. After pretreatment, the coating is dried for later use.

[0035] In one embodiment of the present invention, the mixing temperature is 50~60°C and the mixing time is 30~40 min.

[0036] In one embodiment of the present invention, the curing temperature is 40~50℃ and the curing time is 24~36h.

[0037] In this invention, the curing temperature is preferably 45°C and the curing time is preferably 30h, so that the two coatings are completely cross-linked and cured to form a dense self-healing coating, resulting in a marine corrosion resistant steel structure product.

[0038] This invention uses bio-based carriers such as chitosan, sodium alginate, and pectin, and plant-derived corrosion inhibitors such as tea polyphenols and rosemary extract. It contains no petroleum-based chemical raw materials, and the coating can be naturally degraded after disposal, without releasing any toxic or harmful substances, resulting in zero pollution to the marine ecosystem and meeting the requirements for green protection in marine engineering.

[0039] This invention features high self-healing efficiency and long-lasting protection. The dual-layer structure combined with microcapsule slow-release technology achieves a dual self-healing mechanism of "corrosion inhibition + repair," with a 24-hour repair rate of ≥90%, which is more than 50% higher than the repair efficiency of traditional self-healing coatings. It can withstand repeated damage in the marine environment, and shows no damage or peeling in a 1000-hour neutral salt spray test, significantly extending the protection period.

[0040] In this invention, the substrate has strong adhesion and is not easy to fall off; the bottom bonding layer is combined with laser texture pretreatment, and the coating has an adhesion strength of ≥15MPa to the steel substrate, which is far superior to traditional single-layer coatings. It can withstand alternating marine loads and seawater erosion, and eliminates problems such as blistering, peeling and falling off, and has extremely strong protective stability.

[0041] In this invention, the process is controllable and the cost is low; the coating preparation and coating process is simple, requiring no complex high-end equipment; the bio-based raw materials are widely available and affordable; the production cost is reduced by more than 30% compared to traditional chemically synthesized self-healing coatings; the process parameters are precise and controllable, making it suitable for large-scale industrial production; and its engineering application value and market competitiveness are outstanding.

[0042] A specific embodiment of the third aspect of the present invention provides a marine engineering steel structure, including a steel substrate and a self-healing coating.

[0043] The present invention will now be described in detail with reference to preferred embodiments and comparative examples. The preferred embodiments of the invention described below can be modified in various ways, and therefore the scope of the invention should not be construed as limited to the preferred embodiments described in detail below. Preferred embodiments are provided to help those skilled in the art to more readily understand the invention.

[0044] In the following examples and comparative examples: Epoxy resin, model E51; sodium alginate weight average molecular weight: 100,000~150,000.

[0045] Example 1 A self-healing coating for marine engineering steel structures includes an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 8%, microencapsulated repair agent 10%, and the balance is water; The adhesive layer is composed of the following raw materials by weight percentage: 22% chitosan, 10% sodium alginate, 5% pectin, and the balance being water; The preparation method of the microencapsulated repair agent includes the following steps: A1. Add epoxy resin to a mixed solution of water (the mass-volume ratio of epoxy resin to water is 1g:2mL) and Tween-80 (the amount of Tween-80 added is 5wt% of epoxy resin) and mix for 15min at 500r / min and 25℃ to disperse evenly, and then obtain the core material dispersion. A2. Sodium alginate was added to water (the mass-volume ratio of sodium alginate to water was 2g:25mL) and mixed at 300r / min and 60℃ for 30min to disperse it evenly, so as to obtain a wall material dispersion. The mass ratio of epoxy resin to sodium alginate was 5:4. A3. The core material dispersion was added to the wall material dispersion at a rate of 1 mL / min and mixed at 300 r / min for 20 min. Then, 5 wt% calcium chloride aqueous solution was added (the amount of calcium chloride aqueous solution added was 10% of the sum of the volumes of the core material dispersion and the wall material dispersion). After mixing for another 30 min, the mixture was allowed to stand for 1 h, vacuum filtered, washed three times with deionized water, and dried at 40℃ for 2 h to obtain a microencapsulated repair agent with a particle size of 5 μm. The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and mixed for 25 minutes at 300 r / min and 60℃. After being evenly dispersed, a corrosion inhibitor (composed of tea polyphenols and rosemary in a mass ratio of 1:1) is added in three batches with an interval of 5 minutes each time. The mixture is then mixed for 30 minutes at 400 r / min and 40℃. Finally, a microencapsulated repair agent is added and the mixture is mixed for another 20 minutes to obtain the self-healing coating.

[0046] A method for preparing a self-healing coating for marine engineering steel structures includes the following steps: S1 carbon steel is subjected to mechanical rust removal, alkaline degreasing, and hydrochloric acid aqueous solution pickling and activation in sequence, then rinsed with deionized water and dried; subsequently, laser texture pretreatment technology is used to make the surface roughness of carbon steel Ra=0.8μm, thus obtaining pretreated steel. S2. Mix the raw materials of the adhesive layer at 300 r / min and 50℃ for 30 min, and then spray them onto the surface of the pretreated steel to obtain an adhesive layer with a thickness of 30 μm. When the adhesive layer is in a semi-cured state, spray the self-healing coating with a thickness of 80 μm. Cure the self-healing coating for 24 h at a temperature of 40℃ and a humidity of 60% to obtain a self-healing coating for marine engineering steel structures.

[0047] Example 2 A self-healing coating for marine engineering steel structures includes an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance is water; The adhesive layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 8%, pectin 6%, and the balance being water; The preparation method of the microencapsulated repair agent includes the following steps: A1. Add epoxy resin to a mixed solution of water (the mass-volume ratio of epoxy resin to water is 1g:2mL) and Tween-80 (the amount of Tween-80 added is 5wt% of epoxy resin) and mix for 15min at 500r / min and 25℃ to disperse evenly, and then obtain the core material dispersion. A2. Sodium alginate was added to water (the mass-volume ratio of sodium alginate to water was 2g:25mL) and mixed at 300r / min and 60℃ for 30min to disperse it evenly, so as to obtain a wall material dispersion. The mass ratio of epoxy resin to sodium alginate was 5:4. A3. The core material dispersion was added to the wall material dispersion at a rate of 1 mL / min and mixed at 300 r / min for 20 min. Then, 5 wt% calcium chloride aqueous solution was added (the amount of calcium chloride aqueous solution added was 10% of the sum of the volumes of the core material dispersion and the wall material dispersion). After mixing for another 30 min, the mixture was allowed to stand for 1 h, vacuum filtered, washed three times with deionized water, and dried at 40℃ for 2 h to obtain a microencapsulated repair agent with a particle size of 8 μm. The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and mixed for 30 minutes at 350 r / min and 65℃. After being evenly dispersed, a corrosion inhibitor (composed of tea polyphenols and rosemary in a mass ratio of 1:1) is added in three batches with an interval of 5 minutes each time. The mixture is then mixed for 35 minutes at 400 r / min and 43℃. Finally, a microencapsulated repair agent is added and the mixture is mixed for another 20 minutes to obtain the self-healing coating.

[0048] A method for preparing a self-healing coating for marine engineering steel structures includes the following steps: S1 carbon steel is subjected to mechanical rust removal, alkaline degreasing, and hydrochloric acid aqueous solution pickling and activation in sequence, then rinsed with deionized water and dried; subsequently, laser texture pretreatment technology is used to make the surface roughness of carbon steel Ra=1.0μm, resulting in pretreated steel. S2. Mix the raw materials of the adhesive layer at 300 r / min and 55℃ for 35 min, and then spray them onto the surface of the pretreated steel to obtain an adhesive layer with a thickness of 40 μm. When the adhesive layer is in a semi-cured state, spray the self-healing coating with a thickness of 100 μm. Cure the self-healing coating for 30 h at a temperature of 45℃ and a humidity of 65% to obtain a self-healing coating for marine engineering steel structures.

[0049] Example 3 A self-healing coating for marine engineering steel structures includes an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by weight percentage: 30% chitosan, 10% sodium alginate, 12% corrosion inhibitor, 15% microencapsulated repair agent, and the balance being water; The adhesive layer is composed of the following raw materials by weight percentage: chitosan 28%, sodium alginate 7%, pectin 8%, and the balance is water; The preparation method of the microencapsulated repair agent includes the following steps: A1. Add epoxy resin to a mixed solution of water (the mass-volume ratio of epoxy resin to water is 1g:2mL) and Tween-80 (the amount of Tween-80 added is 5wt% of epoxy resin) and mix for 15min at 500r / min and 25℃ to disperse evenly, and then obtain the core material dispersion. A2. Sodium alginate was added to water (the mass-volume ratio of sodium alginate to water was 2g:25mL) and mixed at 300r / min and 60℃ for 30min to disperse it evenly, so as to obtain a wall material dispersion. The mass ratio of epoxy resin to sodium alginate was 5:4. A3. The core material dispersion was added to the wall material dispersion at a rate of 1 mL / min and mixed at 300 r / min for 20 min. Then, 5 wt% calcium chloride aqueous solution was added (the amount of calcium chloride aqueous solution added was 10% of the sum of the volumes of the core material dispersion and the wall material dispersion). After mixing for another 30 min, the mixture was allowed to stand for 1 h, vacuum filtered, washed three times with deionized water, and dried at 40℃ for 2 h to obtain a microencapsulated repair agent with a particle size of 10 μm. The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and mixed for 35 minutes at 400 r / min and 70℃. After being evenly dispersed, a corrosion inhibitor (composed of tea polyphenols and rosemary in a mass ratio of 1:1) is added in three batches with an interval of 5 minutes between each batch. The mixture is then mixed for 40 minutes at 400 r / min and 45℃. Finally, a microencapsulated repair agent is added and the mixture is mixed for another 20 minutes to obtain the self-healing coating.

[0050] A method for preparing a self-healing coating for marine engineering steel structures includes the following steps: S1 carbon steel is subjected to mechanical rust removal, alkaline degreasing, and hydrochloric acid aqueous solution pickling and activation in sequence, then rinsed with deionized water and dried; subsequently, laser texture pretreatment technology is used to make the surface roughness of carbon steel Ra=1.2μm, resulting in pretreated steel. S2. Mix the raw materials of the adhesive layer at 300 r / min and 60℃ for 40 min, and then spray them onto the surface of the pretreated steel to obtain an adhesive layer with a thickness of 50 μm. When the adhesive layer is in a semi-cured state, spray the self-healing coating with a thickness of 120 μm. Cure the self-healing coating for 36 h at a temperature of 50℃ and a humidity of 70% to obtain a self-healing coating for marine engineering steel structures.

[0051] Example 4 A self-healing coating for marine engineering steel structures includes an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance is water; The adhesive layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 8%, pectin 6%, and the balance being water; The preparation method of the microencapsulated repair agent includes the following steps: A1. Add epoxy resin to a mixed solution of water (the mass-volume ratio of epoxy resin to water is 1g:2mL) and Tween-80 (the amount of Tween-80 added is 5wt% of epoxy resin) and mix for 20min at 450r / min and 25℃ to disperse evenly, and then obtain a core material dispersion. A2. Sodium alginate was added to water (the mass-volume ratio of sodium alginate to water was 2g:25mL) and mixed at 300r / min and 60℃ for 30min to disperse it evenly, so as to obtain a wall material dispersion. The mass ratio of epoxy resin to sodium alginate was 5:4. A3. The core material dispersion was added to the wall material dispersion at a rate of 1 mL / min and mixed at 300 r / min for 20 min. Then, 5 wt% calcium chloride aqueous solution was added (the amount of calcium chloride aqueous solution added was 10% of the sum of the volumes of the core material dispersion and the wall material dispersion). After mixing for another 30 min, the mixture was allowed to stand for 1 h, vacuum filtered, washed three times with deionized water, and dried at 40℃ for 2 h to obtain a microencapsulated repair agent with a particle size of 8 μm. The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and mixed for 30 minutes at 350 r / min and 65℃. After being evenly dispersed, a corrosion inhibitor (composed of tea polyphenols and rosemary in a mass ratio of 1:1) is added in three batches with an interval of 5 minutes between each batch. The mixture is then mixed for 35 minutes at 350 r / min and 43℃. Finally, a microencapsulated repair agent is added and the mixture is mixed for another 20 minutes to obtain the self-healing coating.

[0052] A method for preparing a self-healing coating for marine engineering steel structures includes the following steps: S1 carbon steel is subjected to mechanical rust removal, alkaline degreasing, and hydrochloric acid aqueous solution pickling and activation in sequence, then rinsed with deionized water and dried; subsequently, laser texture pretreatment technology is used to make the surface roughness of carbon steel Ra=1.1μm, thus obtaining pretreated steel. S2. Mix the raw materials of the adhesive layer at 300 r / min and 55℃ for 35 min, and then spray them onto the surface of the pretreated steel to obtain an adhesive layer with a thickness of 40 μm. When the adhesive layer is in a semi-cured state, spray the self-healing coating with a thickness of 100 μm. Cure the self-healing coating for 28 h at a temperature of 48℃ and a humidity of 68% to obtain a self-healing coating for marine engineering steel structures.

[0053] Comparative Example 1 Except for replacing the self-healing layer with the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water; and replacing it with the following raw materials by weight percentage: chitosan 18%, sodium alginate 18%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water, everything else is the same as in Example 2.

[0054] Comparative Example 2 Except for replacing the self-healing layer with the following raw material composition by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water; the self-healing layer is composed of the following raw material composition by weight percentage: chitosan 28.8%, sodium alginate 7.2%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water, the rest is the same as in Example 2.

[0055] Comparative Example 3 Except for replacing the self-healing layer with the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water; and replacing it with the following raw materials by weight percentage: chitosan 36%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water, the rest is the same as in Example 2.

[0056] Comparative Example 4 Except for replacing the self-healing layer with the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water; and replacing it with the following raw materials by weight percentage: sodium alginate 36%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance being water, the rest is the same as in Example 2.

[0057] Comparative Example 5 A self-healing coating for marine engineering steel structures, comprising a self-healing layer; The self-healing layer is composed of the following raw materials by weight percentage: chitosan 24%, sodium alginate 12%, corrosion inhibitor 10%, microencapsulated repair agent 12%, and the balance is water; The preparation method of the microencapsulated repair agent includes the following steps: A1. Add epoxy resin to a mixed solution of water (the mass-volume ratio of epoxy resin to water is 1g:2mL) and Tween-80 (the amount of Tween-80 added is 5wt% of epoxy resin) and mix for 15min at 500r / min and 25℃ to disperse evenly, and then obtain the core material dispersion. A2. Sodium alginate was added to water (the mass-volume ratio of sodium alginate to water was 2g:25mL) and mixed at 300r / min and 60℃ for 30min to disperse it evenly, so as to obtain a wall material dispersion. The mass ratio of epoxy resin to sodium alginate was 5:4. A3. The core material dispersion was added to the wall material dispersion at a rate of 1 mL / min and mixed at 300 r / min for 20 min. Then, 5 wt% calcium chloride aqueous solution was added (the amount of calcium chloride aqueous solution added was 10% of the sum of the volumes of the core material dispersion and the wall material dispersion). After mixing for another 30 min, the mixture was allowed to stand for 1 h, vacuum filtered, washed three times with deionized water, and dried at 40℃ for 2 h to obtain a microencapsulated repair agent with a particle size of 8 μm. The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and mixed for 30 minutes at 350 r / min and 65℃. After being evenly dispersed, a corrosion inhibitor (composed of tea polyphenols and rosemary in a mass ratio of 1:1) is added in three batches with an interval of 5 minutes each time. The mixture is then mixed for 35 minutes at 400 r / min and 43℃. Finally, a microencapsulated repair agent is added and the mixture is mixed for another 20 minutes to obtain the self-healing coating.

[0058] A method for preparing a self-healing coating for marine engineering steel structures includes the following steps: S1 carbon steel is subjected to mechanical rust removal, alkaline degreasing, and hydrochloric acid aqueous solution pickling and activation in sequence, then rinsed with deionized water and dried; subsequently, laser texture pretreatment technology is used to make the surface roughness of carbon steel Ra=1.0μm, resulting in pretreated steel. S2. Spray a self-healing coating with a thickness of 100μm. Cur the coating for 30 hours at a temperature of 45℃ and a humidity of 65% to obtain a self-healing coating for marine engineering steel structures.

[0059] The self-healing coatings for marine engineering steel structures in Examples 1-4 and Comparative Examples 1-5 were subjected to the following performance tests: (1) Bond strength between coating and substrate: The adhesion test was conducted according to GB / T 31586.1 "Evaluation and acceptance criteria for adhesion / cohesion (breaking strength) of protective coating system to steel structure anti-corrosion protective coating - Part 1: Pull-off test". A standard test column with a diameter of 20 mm was used to bond with the coating surface with high strength. The universal testing machine pulled the test column vertically upward at a uniform constant rate. The critical load when the coating peeled off or the cohesive failure occurred was recorded, and the bond strength between the coating and the steel structure substrate was calculated. (2) Corrosion resistance: Neutral salt spray accelerated corrosion test was carried out in accordance with GB / T 10125 "Artificial Atmosphere Corrosion Test - Salt Spray Test", and the harsh service conditions of nearshore marine structures were simulated according to ISO 12944-9:2018 "Paints and Varnishes - Protective Coating Systems for Steel Structures - Part 9: Coating Systems for Offshore and Marine Structures - Laboratory Test Methods". Uniform scratches penetrating the coating to the steel substrate were pre-made on the coating surface using a special scratching tool. The test plate was placed in a 5% NaCl neutral salt spray test chamber, and the temperature was controlled at 35℃. During the test, the blistering, rusting and peeling of the coating at the scratches were observed regularly. (3) 24h self-healing performance: The 24h self-healing effect of the coating was evaluated according to T / CSCP 0003 "Evaluation Method for Self-Healing Performance of Organic Coatings". A straight scratch with a width of 100μm was prepared on the intact coating surface using a standard scratcher, penetrating the coating and reaching the steel structure substrate. The scratched test plate was placed in a standard environment of 23℃ and 50% relative humidity for 24h to complete the self-healing process. After the standing period, the scratch closure morphology was observed by optical microscope and the scratch healing coverage was statistically analyzed.

[0060] The test results are shown in Table 1 below.

[0061] Table 1 Performance test results of coatings in Examples 1-4 and Comparative Examples 1-5

[0062] The bonding strength, corrosion resistance, and 24-hour repair rate of the coating and substrate in Examples 1-4 were all higher than those in Comparative Examples 1-4, indicating that the present invention effectively improves the bonding strength, corrosion resistance, and 24-hour repair rate of the coating and substrate by adding chitosan and sodium alginate as composite carriers for the self-healing layer, and limiting the chitosan content to 24%-30% and the sodium alginate content to 10%-12%.

[0063] Example 2 shows that the bonding strength between the coating and the substrate, corrosion resistance, and 24-hour repair rate are all higher than those of Comparative Example 5, indicating that the present invention effectively improves the coating adhesion and overall protective performance by adding an adhesive layer and a self-healing layer.

[0064] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A self-healing coating for marine engineering steel structures, characterized in that, Includes an adhesive layer and a self-healing layer; The self-healing layer is composed of the following raw materials by mass percentage: 24%~30% chitosan, 10%~12% sodium alginate, 8%~12% corrosion inhibitor, 10%~15% microencapsulated repair agent, and the balance being water; The core material of the microencapsulated repair agent is epoxy resin, and the wall material is sodium alginate.

2. The self-healing coating for marine engineering steel structures according to claim 1, characterized in that, The preparation method of the microencapsulated repair agent includes the following steps: A1. After dispersing the epoxy resin evenly in a mixed solution of solvent I and emulsifier, a core material dispersion is obtained. A2. After dispersing sodium alginate in solvent II evenly, a wall material dispersion is obtained; A3. The core material dispersion is added to the wall material dispersion and mixed. A crosslinking agent is added and the mixture is continued. After filtration, washing and drying, the microencapsulated repair agent is obtained.

3. The self-healing coating for marine engineering steel structures according to claim 1, characterized in that, The corrosion inhibitors include tea polyphenols and rosemary extract.

4. The self-healing coating for marine engineering steel structures according to claim 3, characterized in that, The mass ratio of tea polyphenols to rosemary is 1:0.5~1.

5.

5. The self-healing coating for marine engineering steel structures according to claim 1, characterized in that, The adhesive layer is composed of the following raw materials by mass percentage: 22%~28% chitosan, 7%~10% sodium alginate, 5%~8% pectin, and the balance being water.

6. The self-healing coating for marine engineering steel structures according to claim 1, characterized in that, The preparation method of the self-healing coating includes the following steps: chitosan and sodium alginate are added to water and dispersed evenly, then a corrosion inhibitor is added and mixed, and then a microencapsulated repair agent is added and mixed again to obtain the self-healing coating.

7. A self-healing coating for marine engineering steel structures according to claim 6, characterized in that, The dispersion temperature is 60~70℃, and the dispersion time is 25~35min.

8. A method for preparing a self-healing coating for marine engineering steel structures, used to prepare the self-healing coating for marine engineering steel structures as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. After pretreatment, steel is obtained as pretreated steel. S2. After the raw materials of the adhesive layer are mixed evenly, they are sprayed onto the surface of the pretreated steel. When the adhesive layer is semi-cured, the self-healing coating is sprayed on, and after curing, the self-healing coating for marine engineering steel structures is obtained.

9. A method for preparing a coating for marine engineering steel structures according to claim 8, characterized in that, The curing temperature is 40~50℃, and the curing time is 24~36h.

10. A marine engineering steel structure, characterized in that, It includes a steel substrate and a self-healing coating, wherein the self-healing coating includes the self-healing coating for marine engineering steel structures as described in any one of claims 1 to 7.

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