Anticorrosive coating as well as preparation method and application thereof

Abstract

The invention discloses an anti-corrosion coating as well as a preparation method and application thereof, and belongs to the field of anti-corrosion materials. The anti-corrosion coating is prepared from the following components in parts by weight: 40 to 45 parts of dead burnt magnesium oxide, 40 to 45 parts of monopotassium phosphate, 8 to 10 parts of a retarder and 5 to 15 parts of silver alginate microcapsules. The silver alginate microcapsule comprises a capsule material and a core material, the capsule material is silver alginate, and the core material is modified mesoporous silica and sodium aluminate. The mass ratio of the modified mesoporous silica to the sodium aluminate is 3: (6-8). The preparation method of the anti-corrosion coating comprises the following steps: adding borax and monopotassium phosphate into water, stirring, adding dead burned magnesium oxide and silver alginate microcapsules, and uniformly stirring to obtain the anti-corrosion coating. The anti-corrosion coating provided by the invention can achieve the effects of excellent anti-corrosion performance and capability of automatically repairing corrosion defects.

Description

Technical Field

[0001] This invention relates to anti-corrosion materials, and more particularly to an anti-corrosion coating, its preparation method, and its application. Background Art

[0002] In marine engineering, shipbuilding, and offshore infrastructure, metallic materials are highly susceptible to exposure to corrosive environments characterized by high salinity, high humidity, and high chloride ion content, leading to severe localized corrosion. Chloride ions are a key factor accelerating metal corrosion, penetrating the passivation film, promoting anodic dissolution, and significantly reducing the material's service life. Therefore, the control of metal corrosion is of great significance to the sustainable development of marine engineering.

[0003] Applying anti-corrosion coatings to steel substrates is an efficient and traditional method of corrosion protection, particularly suitable for protecting metal structures in marine environments. While traditional organic anti-corrosion methods such as epoxy resins and zinc-rich coatings offer some protection, their susceptibility to aging, poor weather resistance, and low environmental compatibility limit their long-term service performance. Against this backdrop, cement-based inorganic anti-corrosion coatings, due to their excellent weather resistance, barrier properties, and good compatibility with concrete substrates, have gradually become a research hotspot in the field of protective engineering. Among them, potassium magnesium phosphate cement (MKPC), as a novel fast-setting cementitious material, exhibits unique advantages in rapid repair and corrosion protection due to its characteristics such as early strength and rapid setting, good volume stability, high bond strength, high temperature resistance, and low pH buffering capacity (pH approximately 9-11).

[0004] However, the inherent brittleness of cement-based materials makes them prone to defects during service. These defects not only significantly weaken the physical barrier function of the coating, but also make them more susceptible to corrosive media (such as Cl-). - (H2O, O2) provides a channel for the penetration of substances into the metal matrix, ultimately inducing localized electrochemical corrosion. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide an anti-corrosion coating with excellent anti-corrosion performance and the ability to self-repair corrosion defects.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned anti-corrosion coating.

[0007] A third objective of this invention is to provide an application of the aforementioned anti-corrosion coating.

[0008] Technical solution: The anti-corrosion coating of the present invention comprises, by weight, 40-45 parts of calcined magnesium oxide, 40-45 parts of potassium dihydrogen phosphate, 8-10 parts of retarder, and 5-15 parts of silver alginate microcapsules.

[0009] Preferably, the silver alginate microcapsules comprise a capsule material and a core material, wherein the capsule material is silver alginate and the core material is modified mesoporous silica and sodium aluminate.

[0010] Preferably, the mass ratio of the modified mesoporous silica to sodium aluminate is 3:6-8.

[0011] Preferably, the silver alginate microcapsules are prepared as follows: sodium alginate, modified mesoporous silica, sodium aluminate and water are mixed and spray-dried; silver nitrate solution is added dropwise, stirred, centrifuged and dried to obtain silver alginate microcapsules.

[0012] Preferably, the modified mesoporous silica is prepared as follows: the mesoporous silica powder is dried and then added to a toluene solution, followed by the addition of APTES. The temperature and time are controlled and the reaction is carried out under a nitrogen atmosphere. The mixture is then washed and dried to obtain the modified mesoporous silica.

[0013] The method for preparing the anti-corrosion coating of the present invention includes the following steps:

[0014] Borax and potassium dihydrogen phosphate are added to water and stirred. Then, calcined magnesium oxide and silver alginate microcapsules are added and stirred evenly to obtain an anti-corrosion coating.

[0015] Preferably, the mass ratio of water to other components is 0.2-0.5.

[0016] The application of the anti-corrosion coating of the present invention in the marine engineering environment includes the following steps: applying the anti-corrosion coating to the surface of a steel substrate and allowing it to cure statically, thereby applying the anti-corrosion coating to the marine engineering environment.

[0017] Preferably, the static curing temperature is 25-35℃, the humidity is ≥90%, and the time is 5-7 days.

[0018] Invention Principle: The silver alginate microcapsules used in this invention can preserve the repair agent material for a long time. When defects appear and cracks occur in the potassium magnesium phosphate cement coating, seawater rushes into the coating defects. The capsule material in the silver alginate microcapsules dispersed on both sides of the crack area reacts chemically with chloride ions in the seawater to form silver chloride precipitate, causing the microcapsules to break and release the core material. The modified mesoporous silica in the core material adsorbs calcium and magnesium ions in the seawater, while the sodium aluminate in the core material reacts chemically with the adsorbed calcium and magnesium ions to form a layered polymetallic mineral precipitate, thereby repairing the defect. In addition, the layered polymetallic mineral also has the ability to fix corrosion ions (Cl). - SO4 2- The function of ) can effectively prevent the intrusion of corrosive ions.

[0019] The potassium magnesium phosphate cementitious material (MgKPO4·6H2O) used in this invention is a novel inorganic cementitious material, produced by the reaction of the alkali component (reburned magnesium oxide, MgO), the acid component (potassium dihydrogen phosphate, KH2PO4), and water. It features rapid setting, early strength, and high adhesion. Borax (Na2B4O7·10H2O), the retarder, is one of the most effective retarders in the MKPC system. Borax dissolves in water to form borate ions (B4O7). 2- ), which is related to Mg 2+ [Mg(B4O7)] is formed. 2- The complex forms a coating on the surface of MgO particles, hindering further dissolution of MgO and thus delaying the hydration reaction.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The anti-corrosion coating prepared by the present invention contains silver alginate microcapsules, which can quickly respond to the intrusion of chloride ions in the marine environment and release sodium aluminate as a repair agent to repair corrosion defects on its own; (2) The present invention adds silver alginate microcapsules containing sodium aluminate to the anti-corrosion coating. Sodium aluminate and calcium and magnesium ions can react chemically to generate polymetallic mineral precipitates with a layered structure. This method of repairing defects is efficient and rapid and can complete the protection of steel substrate in the early stage; (3) The polymetallic minerals with a layered structure generated during the defect repair process have the function of fixing corrosion ions, which is conducive to further improving the anti-corrosion performance of the coating; (4) The present invention uses spray drying process to prepare silver alginate microcapsules. The drying speed is fast, the product has good dispersibility, flowability and solubility, and the production process is simplified and the operation and control are convenient; (5) The coating prepared by the present invention is an inorganic anti-corrosion coating with excellent weather resistance and barrier properties. The raw material cost is low and it is more suitable for marine engineering environment. Attached Figure Description

[0021] Figure 1 This is a photograph of the anti-corrosion coating prepared in Example 1 after it has self-repaired its defects.

[0022] Figure 2 The image shows the polarization curve of the anti-corrosion coating prepared in Example 1 after immersion in artificial simulated seawater.

[0023] Figure 3 The image shows the polarization curve of the anti-corrosion coating prepared in Example 2 after immersion in simulated seawater.

[0024] Figure 4 The image shows the polarization curve of the anti-corrosion coating prepared in Example 3 after immersion in simulated seawater.

[0025] Figure 5 The polarization curve of the anti-corrosion coating prepared in Comparative Example 2 after immersion in artificial simulated seawater is shown. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the embodiments.

[0027] Example 1

[0028] The anti-corrosion coating of the present invention comprises, by weight, 44 parts of calcined magnesium oxide, 44 parts of potassium dihydrogen phosphate, 8 parts of borax, and 5 parts of silver alginate microcapsules.

[0029] The silver alginate microcapsules described herein can be prepared using existing techniques or by the method described in this invention.

[0030] The method for preparing the anti-corrosion coating of the present invention includes the following steps:

[0031] (1) Preparation of modified mesoporous silica: The mesoporous silica powder was placed in a vacuum drying oven at 100℃ and dried for 4 hours to remove the moisture adsorbed on the sample surface; 2g of dried mesoporous silica powder was placed in a reaction vessel containing 100ml toluene solution, and 2-4ml of 3-aminopropyltriethoxysilane (APTES) was added. The reaction was carried out under nitrogen atmosphere, and the temperature of the reaction vessel was controlled at 80-90℃, the stirring speed was 200-300rpm / min, and the stirring time was 10 hours; finally, it was washed with anhydrous ethanol and placed in a vacuum drying oven at 75℃ for vacuum drying to obtain modified mesoporous silica.

[0032] (2) Mix 1.5g sodium alginate, 0.3g modified mesoporous silica, 0.7g sodium aluminate with 100ml water and spray dry under magnetic stirring speed of 1000rpm / min to obtain sodium alginate microcapsules; add 4mL of 0.1mol / L silver nitrate solution, stir for 5-10 minutes, centrifuge and wash, and dry in a vacuum drying oven at 70℃ to obtain silver alginate microcapsules.

[0033] (3) According to the weight, add 8 parts of borax and 44 parts of potassium dihydrogen phosphate to 20.2 parts of water and stir thoroughly to obtain a mixed solution. Then add 44 parts of calcined magnesium oxide and 5 parts of silver alginate microcapsules and stir evenly to maintain the overall water-cement ratio (i.e. the mass ratio of water to other components) at 0.2 to obtain the anti-corrosion coating material slurry.

[0034] The application of the anti-corrosion coating of the present invention in a marine engineering environment includes the following steps:

[0035] The anti-corrosion coating is applied to the surface of Q235 steel substrate by brushing and allowed to cure for 5-7 days at 25-35℃ and humidity ≥90% before it can be applied to marine engineering environments.

[0036] Example 2

[0037] The similarities between this embodiment and Embodiment 1 will not be repeated here. The differences are as follows:

[0038] In step (3), the amount of silver alginate microcapsules added is 10 parts, and the amount of water added is 21.2 parts.

[0039] Example 3

[0040] The similarities between this embodiment and Embodiment 1 will not be repeated here. The differences are as follows:

[0041] In step (3), the amount of silver alginate microcapsules added is 15 parts, and the amount of water added is 22.2 parts.

[0042] Comparative Example 1

[0043] The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows:

[0044] In step (3), the amount of silver alginate microcapsules added is 0 parts, and the amount of water added is 19.2 parts.

[0045] Comparative Example 2

[0046] The similarities between this comparative example and Example 1 will not be repeated here; the differences are as follows:

[0047] In step (3), the amount of silver alginate microcapsules added is 20 parts, and the amount of water added is 23.2 parts.

[0048] Electrochemical polarization curve tests were performed on the anti-corrosion coatings obtained in each experiment. The test sample steel substrate had a size of 15mm×15mm×2mm. The anti-corrosion coating was applied by brushing using a fixed mold, and the coating thickness was 1mm. The coating was allowed to cure for 5-7 days under the conditions of 25-35℃ and humidity ≥90%. Finally, a crack with a width of about 0.05mm was scratched with a scalpel, and the crack did not touch the steel substrate. The test immersion solution was artificial simulated seawater, and the electrolyte for electrochemical testing was a 3.5wt% NaCl solution.

[0049] The fitting data of the electrochemical polarization curves of each sample are shown in Table 1. The fitting software was CView. The polarization resistance R is shown in the table. p The formula for calculating (Ω) is as follows: R p =B a ×B c / 2.303i corr (B a +B c ).

[0050] In the formula: B a and B c These represent the anode Tafel slope and the cathode Tafel slope, respectively; i corr (mA / cm2 ) represents the corrosion current density.

[0051] The formula for calculating the corrosion inhibition rate is as follows: η=(i corr,0 -i corr ) / i corr,0 .

[0052] In the formula: i corr，0 To compare the corrosion current density of the silver alginate-free microcapsule sample prepared in the proportion, i corr The current density is the corrosion current density for each sample.

[0053] Table 1. Fitting results of coating polarization curves

[0054]

[0055]

[0056] Note: "Time" in the table refers to the immersion time of the sample in artificial simulated seawater.

[0057] Analysis of the data in the table shows that adding silver alginate microcapsules to the anti-corrosion coating is beneficial to increasing the corrosion inhibition rate of the coating. Analysis of the polarization curve data of Examples 1-3 reveals that as the immersion time of the samples in simulated seawater increases, the corrosion inhibition rate of each coating also continuously increases. This indicates that the silver alginate microcapsules break down and release sodium aluminate, which reacts with calcium and magnesium ions in seawater to form a multi-metallic mineral with a lamellar structure, repairing defects and fixing corrosion ions. When the amount of silver alginate microcapsules added is 10 parts (Example 2), the resulting anti-corrosion coating achieves the best corrosion inhibition rate on day 28, reaching 82%. As the amount of silver alginate microcapsules added continuously increases, the porosity of the anti-corrosion coating also changes. The corrosion inhibition rate of each coating continuously decreases on the first day. When the amount of silver alginate microcapsules added is 15 parts and 20 parts (Example 3, Comparative Example 2), the corrosion inhibition rate of the coating even becomes negative. This indicates that excessive silver alginate microcapsules lead to increased coating porosity, impairing the anti-corrosion performance of the MKPC coating.

[0058] The corrosion current density of the sample without added silver alginate microcapsules (Comparative Example 1) increased from 1.896E-05 mA / cm² on day 1. 2 Increased to 3.101E-05 mA / cm 2 The polarization resistance decreased from 2.566E+06Ω to 1.703E+06Ω, indicating that the anti-corrosion performance of the coating continued to decline when the defects were not repaired.

[0059] Figure 1The image shows the actual product of the anti-corrosion coating prepared in Example 1 after it has self-repaired defects. As can be seen from the image, the defects in the coating produced a white repair product after being soaked in seawater, which prevented further corrosion of the steel substrate.

[0060] Figure 2-5 The figures show the polarization curves of each anti-corrosion coating after immersion in simulated seawater for different times, revealing the changes in the anti-corrosion performance of the coatings at different immersion times.

[0061] The experimental results above show that the present invention has successfully prepared a marine environment anti-corrosion coating. This coating has excellent anti-corrosion performance and the ability to self-repair defects, providing a new and innovative solution for the intelligentization of MKPC coatings.

Claims

1. An anti-corrosion coating, characterized in that, By weight, it includes 40-45 parts of calcined magnesium oxide, 40-45 parts of potassium dihydrogen phosphate, 8-10 parts of retarder, and 5-15 parts of silver alginate microcapsules.

2. The anti-corrosion coating according to claim 1, characterized in that, The silver alginate microcapsules comprise a capsule material and a core material, wherein the capsule material is silver alginate and the core material is modified mesoporous silica and sodium aluminate.

3. The anti-corrosion coating according to claim 2, characterized in that, The mass ratio of the modified mesoporous silica to sodium aluminate is 3:6-8.

4. The anti-corrosion coating according to claim 1, characterized in that, The preparation method of the silver alginate microcapsules is as follows: sodium alginate, modified mesoporous silica, sodium aluminate and water are mixed and spray-dried; silver nitrate solution is added dropwise, stirred, centrifuged and dried to obtain silver alginate microcapsules.

5. The anti-corrosion coating according to claim 2, characterized in that, The modified mesoporous silica is prepared as follows: the mesoporous silica powder is dried and then added to toluene solution, followed by the addition of APTES. The temperature and time are controlled and the reaction is carried out under nitrogen atmosphere. The mixture is then washed and dried to obtain the modified mesoporous silica.

6. A method for preparing the anti-corrosion coating according to claim 1, characterized in that, Includes the following steps: Borax and potassium dihydrogen phosphate are added to water and stirred. Then, calcined magnesium oxide and silver alginate microcapsules are added and stirred evenly to obtain an anti-corrosion coating.

7. The preparation method according to claim 6, characterized in that, The mass ratio of water to other components is 0.2-0.

5.

8. The application of the anti-corrosion coating of claim 1 in a marine environment.

9. The application according to claim 8, characterized in that, The process includes the following steps: applying the anti-corrosion coating to the surface of a steel substrate and allowing it to cure, thus enabling the anti-corrosion coating to be applied to marine engineering environments.

10. The application according to claim 8, characterized in that, The static curing temperature is 25-35℃, the humidity is ≥90%, and the time is 5-7 days.

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