A mother-of-pearl structured connecting layer for carbon steel surface, preparation method thereof, and application thereof

Abstract

The present invention provides a pearl-like structure connecting layer for carbon steel surface, a preparation method and application thereof, comprising the following steps: S1: preparing a two-dimensional sheet material CaAl-LDH-MBT; S2: preparing a PVA solution, wherein the mass fraction of PVA in water is 1-4 wt.%; S3: adding 3-aminopropyltrimethoxysilane, methanol and deionized water into a container, adding the two-dimensional sheet material CaAl-LDH-MBT in step S1 to obtain modified CaAl-LDH-MBT, and adding the modified CaAl-LDH-MBT into the carbon steel surface. aAl-LDH-MBT is added to an ethanol solution and ultrasonically dispersed to obtain a dispersion liquid. The dispersion liquid is dripped along the wall of a beaker to the water-air interface until a visible thin film is formed. Ultrasonication forms a dense monolayer on the interface; S4: The PVA solution is spin-coated onto the surface of a carbon steel plate and dried; S5: The dried carbon steel plate is slowly placed in the dense monolayer solution and dried; S6: Steps S4 and S5 constitute a cycle, and the cycle is repeated 3 to 10 times; S7: The PVA solution is spin-coated on the surface of the carbon steel plate again to obtain a mother-of-pearl structure connection layer.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coatings, and in particular to a connecting layer with an imitation mother-of-pearl structure for a carbon steel surface, and a preparation method and application thereof. Background Art

[0002] Anti-corrosion coating technology is a highly effective and low-cost corrosion protection technology commonly used to protect metal substrates from corrosion and is widely used in practical engineering environments. Currently, the development of intelligent, environmentally friendly, lightweight, and long-lasting anti-corrosion coatings has become a mainstream development trend. The adhesion between the anti-corrosion coating and the substrate is a key factor affecting its corrosion protection capabilities. Improving the adhesion between the coating and the substrate can significantly enhance the coating's long-term corrosion resistance. Lightweighting coatings is a key development trend in coatings research and development. Since coatings are used over a large surface area on ships, their usage is significant. Lightweighting coatings can contribute significantly to achieving lightweight ships. Lightweighting ships can significantly increase their cargo capacity per unit weight or their speed, effectively achieving energy savings, reducing consumption, and emissions, and significantly enhancing the long-range rapid deployment capabilities of modern naval warfare. In summary, existing technologies suffer from poor adhesion between anti-corrosion coatings and the large surface area of ​​coatings used on ships, making lightweighting difficult.

[0003] Shell nacre, with its multi-scale, highly ordered "brick-and-mortar" layered structure, can assemble fragile calcium carbonate minerals and soft polymers into advanced, strong and tough nanocomposites. Previously, researchers developed lightweight, high-strength membranes based on two-dimensional sheet materials that mimic the structure of mother-of-pearl. These membranes exhibit excellent optical, mechanical, UV-shielding, and ablation-resistant properties. However, these high-performance membranes have yet to be applied in the anti-corrosion field. Summary of the Invention

[0004] In light of this, the present invention aims to provide a connecting layer with a mother-of-pearl structure for carbon steel surfaces, as well as its preparation method and application. This approach aims to address existing issues such as poor adhesion between the anti-corrosion coating and the substrate, large coating surface area on ships, difficulty in lightweighting the anti-corrosion coating, and the lack of application of existing mother-of-pearl structures in the anti-corrosion field.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A method for preparing a connecting layer with an imitation mother-of-pearl structure for a carbon steel surface comprises the following steps:

[0007] S1: Preparation of two-dimensional sheet material CaAl-LDH-MBT;

[0008] S11, prepare a mixed solution A of 0.2-0.6 mol / L Ca(NO3)2 solution and 0.1-0.3 mol / L Al(NO3)3 solution, a mixed solution B of 1-2 mol / L NaNO3 solution and 1-3 mol / L NaOH solution, and a mixed solution C of 0.05-0.2 mol / L 2-mercaptobenzothiazole solution and 0.05-0.2 mol / L NaOH solution;

[0009] S12. Place the container containing solution B in an oil bath at a temperature of 50-70°C, and add solution A to solution B dropwise at a rate of one drop per second while stirring magnetically.

[0010] S13. After the titration is completed, the obtained suspension product is transferred to a hydrothermal kettle, which is placed in an oven at a temperature of 100-150° C. The reaction time is 12-36 h.

[0011] S14, after the reaction is completed, centrifuge and wash, dry at a temperature of 50-70 ° C for 24-48 hours, grind and set aside, and the obtained powder is recorded as CaAl-LDH;

[0012] S15. Adjust the pH of solution C to 10 with 0.1-1.0 mol / L NaOH solution;

[0013] S16. Add 1-3 g of CaAl-LDH in step S14 to 100 mL of the solution in step S15, stir vigorously, centrifuge, place in an oven, dry at 50-70° C. for 24-48 h, grind and set aside to obtain a two-dimensional sheet material CaAl-LDH-MBT.

[0014] S2: Prepare a PVA solution, wherein the mass fraction of PVA in water is 1-4 wt.%; the weight average molecular weight of PVA is (MW=77000); PVA is the abbreviation of polyvinyl alcohol.

[0015] S3: 3-aminopropyltrimethoxysilane, methanol, and deionized water were added to a container, mixed and stirred for 1 hour, and the two-dimensional sheet material CaAl-LDH-MBT in step S1 was added and stirred for 5 minutes, followed by centrifugation, ethanol washing, and drying to obtain modified CaAl-LDH-MBT. The modified CaAl-LDH-MBT was added to 30 mL of ethanol solution and ultrasonically dispersed to obtain a dispersion liquid. The ultrasonic time was 10 to 30 minutes. The dispersion liquid was added dropwise along the wall of the beaker to the water-air interface until a visible thin film was formed. The nanosheets were ultrasonically dispersed for 10 to 30 minutes to form a dense monolayer on the water-air interface.

[0016] The volume ratio of 3-aminopropyltrimethoxysilane, methanol, and deionized water is 1:(1-4):(5-8); preferably, the volumes of 3-aminopropyltrimethoxysilane, methanol, and deionized water are 5 mL, 12.55 mL, and 37.55 mL, respectively;

[0017] The amount of the two-dimensional sheet material CaAl-LDH-MBT added is 0.05 to 0.2 g. Preferably, the amount of the two-dimensional sheet material CaAl-LDH-MBT added is 0.11 g.

[0018] S4: Spin-coat the PVA solution in step S2 onto a carbon steel substrate at a spin-coating speed of 600-1200 rpm for 40-80 seconds, and then dry in an oven at 50-70°C for 10-20 minutes;

[0019] Wherein, the spin coating adopts a spin coater.

[0020] S5: slowly placing the carbon steel plate dried in step S4 into the solution containing the dense monolayer in step S3 to complete the self-assembly of the LDH layer, and then drying it in an oven at 50-70°C for 20-40 minutes;

[0021] S6: Steps S4 and S5 form a cycle, which is repeated 3 to 10 times;

[0022] S7: Based on step S6, the PVA solution is spin-coated on the surface of the carbon steel plate again at a spin-coating speed of 600-1200 rpm for 40-80 s, and then dried in an oven at 50-70° C. for 20-40 min to obtain a mother-of-pearl structure connection layer.

[0023] The present invention constructs a lightweight, high-strength connecting layer with a mother-of-pearl-like structure between the substrate and the conventional anti-corrosion coating, and modifies the surface of the connecting layer through a simple and mild chemical impregnation method to enhance its bonding with the anti-corrosion coating applied on the surface, thereby ultimately improving the corrosion resistance of the anti-corrosion coating. It is expected to achieve lightweight coating while maintaining the same corrosion protection capability.

[0024] Furthermore, in step S7, the following steps are also included:

[0025] S71: Prepare a dopamine solution using tris buffer at pH 8.5. The concentration of the dopamine solution is 1-8 mg / mL.

[0026] S72: Place the dried carbon steel plate in the dopamine solution, soak at room temperature for 6-24 hours, rinse with deionized water, and dry naturally.

[0027] This setting uses dopamine to enhance the interface, thereby improving the bonding strength between the imitation mother-of-pearl film layer and the anti-corrosion coating used on its surface, thereby further enhancing the corrosion resistance of the anti-corrosion coating.

[0028] Compared with the prior art, the method for preparing a connecting layer with a mother-of-pearl structure for a carbon steel surface according to the present invention has the following advantages:

[0029] 1) The imitation mother-of-pearl material obtained by the layer-by-layer self-assembly method of the present invention is used as a connecting layer between the anti-corrosion coating and the substrate, which is expected to significantly improve the long-term corrosion resistance of the anti-corrosion coating, reduce its dosage, and achieve lightweight coating. The preparation method is simple and mild, and is suitable for promotion and application in the field of anti-corrosion coatings;

[0030] 2) The present invention places carbon steel in a dopamine solution and adopts an interface enhancement method to enhance the bonding strength between the imitation mother-of-pearl film layer and the anti-corrosion coating used on its surface, thereby further enhancing the corrosion resistance of the anti-corrosion coating.

[0031] A connecting layer with an imitation mother-of-pearl structure used on the surface of carbon steel is obtained using the above-mentioned preparation method.

[0032] An application of an imitation mother-of-pearl structural connecting layer for a carbon steel surface, using the imitation mother-of-pearl structural connecting layer described above, and an application of the imitation mother-of-pearl structural connecting layer in an anti-corrosion coating.

[0033] The advantages of the imitation mother-of-pearl structural connecting layer for carbon steel surface, the application of the imitation mother-of-pearl structural connecting layer for carbon steel surface and the preparation method of the above-mentioned imitation mother-of-pearl structural connecting layer for carbon steel surface over the prior art are the same and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a scanning electron microscope image of the two-dimensional sheet material CaAl-LDH-MBT of the present invention;

[0035] Figure 2 is the XRD pattern of the two-dimensional sheet material CaAl-LDH-MBT of the present invention;

[0036] Figure 3 The front (left) and side (right) scanning electron microscope images of the nacre-like structure connecting layer (LDH-PVA) of the present invention are shown;

[0037] Figure 4 (a) is a schematic diagram of a sample of a carbon steel surface directly coated with a varnish coating according to the present invention;

[0038] Figure 4 (b) is a schematic diagram of a sample of a varnish coating on the surface of the imitation mother-of-pearl structure connecting layer (LDH-PVA) of the present invention;

[0039] Figure 4 (c) is a schematic diagram of a sample of a varnish coating applied on the surface of the imitation mother-of-pearl structure connecting layer (LDH-PVA-Dopa) of the present invention;

[0040] Figure 5 (a) is an EIS result graph of a sample of a carbon steel surface directly coated with a varnish coating according to the present invention, immersed in a 3.5 wt.% NaCl solution for different time periods;

[0041] Figure 5 (b) is the EIS result of the sample of the LDH-PVA surface coated with varnish of the present invention immersed in 3.5wt.% NaCl solution for different time periods;

[0042] Figure 5 (c) is the EIS result of the sample of the LDH-PVA-Dopa surface coated with varnish of the present invention immersed in 3.5wt.% NaCl solution for different time periods. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0044] Example 1 (sample of clear coating directly applied on carbon steel surface)

[0045] A varnish coating is applied to the carbon steel surface by brushing. The varnish coating is a mixture of 6101 epoxy resin and 2519 curing agent (containing 100 parts of 6101 epoxy resin, 42 parts of 2519 curing agent, and 200 parts of n-butanol). The measured thickness after curing is 80μm±20μm.

[0046] Performance analysis, according to GB / T 9286-2021, the adhesion between the coating and the substrate was tested using the cross-hatch method. The results are as follows: Figure 4 As shown in (a), although the coating did not fall off obviously, the base was easily exposed at the scratches. The samples were immersed in 3.5wt.% NaCl solution for different times. The results are shown in Figure 5 As shown in (a), it can be seen that the impedance arc becomes smaller as the immersion time increases, which means that the corrosive medium erodes the substrate through the coating and induces a corrosion reaction.

[0047] Example 2 (LDH-PVA surface coated with varnish coating sample)

[0048] 1) Prepare a mixed solution A of 0.5 mol / L Ca(NO3)2 and 0.25 mol / L Al(NO3)3 solution, and prepare a mixed solution B of 2 mol / L NaNO3 and 3 mol / L NaOH solution.

[0049] 2) Solution A was added dropwise to solution B at a rate of one drop per second with magnetic stirring and the oil bath temperature set to 65°C.

[0050] 3) After the titration is completed, the obtained suspension product is transferred to a hydrothermal kettle, which is placed in an oven at 120°C for 24 hours.

[0051] 4) After the reaction is complete, centrifuge and wash, then dry at 60°C for 24 hours. Grind and set aside, labeled as CaAl-LDH.

[0052] 5) Prepare a mixed solution C of 0.1 mol / L 2-mercaptobenzothiazole (MBT) and 0.1 mol / L NaOH, then adjust its pH to 10 with 0.1 mol / L NaOH. Place 1 g of CaAl-LDH from 4) in the pH 10 solution C, stir vigorously, centrifuge, and place in an oven to dry at 60°C for 24 h. Grind and set aside for later use. Label it as CaAl-LDH-MBT.

[0053] 6) Prepare a 2 wt.% PVA (MW=77000) aqueous solution.

[0054] 7) 5 mL of 3-aminopropyltrimethoxysilane (ATES), 12.5 mL of methanol, and 37.5 mL of deionized water were mixed and stirred for 1 hour. 0.11 g of CaAl-LDH-MBT was added and stirred for 5 minutes. The mixture was centrifuged, washed with ethanol, and dried. The dried powder was dispersed in 30 mL of ethanol and sonicated for 15 minutes. The mixture was added dropwise along the wall of the beaker to the water-air interface until a visible film formed. The mixture was sonicated for 15 minutes. After sonication, the nanosheets formed a dense monolayer at the interface.

[0055] 8) First, spin-coat PVA on a carbon steel plate as the substrate. The spin-coating parameters are set as a spin-coating speed of 1000 rpm and a spin-coating time of 60 s. Then, the plate is dried in an oven at 50° C. for 10 min.

[0056] 9) The carbon steel in 8) was slowly placed in the solution containing the dense monolayer in 7) to complete the self-assembly of the LDH layer, and then dried in an oven at 50° C. for 30 minutes.

[0057] 10) 8) and 9) constitute one cycle, and the above cycle is repeated 5 times in total.

[0058] 11) Spin-coat the PVA solution again on the carbon steel plate surface, with the specific parameters as shown in 8). The resulting sample is labeled LDH-PVA.

[0059] 12) Apply a layer of varnish to the carbon steel surface by brushing. The varnish is a mixture of 6101 epoxy resin and 2519 curing agent (containing 100 parts of 6101 epoxy resin, 42 parts of 2519 curing agent, and 200 parts of n-butanol). The measured thickness after curing is 80μm±20μm.

[0060] Performance analysis, the morphology of CaAl-LDH-MBT is as follows Figure 1 As shown in Figure 2, it presents a regular hexagonal flake morphology. The XRD results of CaAl-LDH-MBT are shown in Figure 2. Figure 2 As shown in Figure 2, the XRD pattern of the sample shows the classic (003) and (006) crystal planes, confirming the successful synthesis of LDH. At the same time, the position of the characteristic peak of the (003) crystal plane confirms the successful embedding of MBT ions. The SEM results of the front and side surfaces of the imitation mother-of-pearl layer LDH-PVA are shown in Figure 2. Figure 3 As shown in the SEM front view, the film layer is dense. As can be seen from the side view, the film layer thickness is about 2μm. According to GB / T 9286-2021, the adhesion between the coating and the substrate was tested using the cross-hatch method. The results are as follows: Figure 4 As shown in (b), like the blank sample, the coating did not fall off obviously, but the base was easily exposed at the scratches. The samples were immersed in 3.5wt.% NaCl solution for different times. The results are shown in Figure 5 As shown in (b), it can be seen that Figure 5 Compared with (a), the impedance arc is significantly larger than that of the blank sample and slowly decreases with the extension of immersion time, which confirms the important role of the LDH-PVA connecting layer with mother-of-pearl structure in improving the corrosion resistance of the coating.

[0061] Example 3 (LDH-PVA-Dopa surface coated with varnish coating sample)

[0062] 1) Prepare a 2 mg / mL dopamine solution using tris buffer at pH 8.5.

[0063] 2) The LDH-PVA sample in step 11) of Example 2 was placed in the dopamine solution obtained in step 1), soaked at room temperature for 12 hours, rinsed with deionized water, and naturally dried. The resulting sample was labeled LDH-PVA-Dopa.

[0064] 3) Apply a layer of clear coat to the surface of the LDH-PVA-Dopa by brush coating. The clear coat is a mixture of 6101 epoxy resin and 2519 curing agent (containing 100 parts of 6101 epoxy resin, 42 parts of 2519 curing agent, and 200 parts of n-butanol). The measured thickness after curing is 80 μm ± 20 μm.

[0065] Performance analysis, according to GB / T 9286-2021, the adhesion between the coating and the substrate was tested using the cross-hatch method. The results are as follows: Figure 4 As shown in (c), unlike the blank sample and LDH / PVA sample, the substrate is not easily exposed at the scratch, and the bonding strength between the coating and the substrate is significantly improved. The samples were immersed in 3.5wt.% NaCl solution for different times. The results are shown in Figure 5 As shown in (c), it can be seen that Figure 5 Compared with (b), the impedance arc further increases. Although it slowly decreases with the extension of immersion time, the impedance arc is still significantly larger than that of the LDH-PVA sample. This result confirms that surface modification can further enhance the bonding strength between the LDH-PVA connecting layer with the mother-of-pearl structure and the coating, thereby further improving the corrosion resistance of the coating.

[0066] In summary, the connecting layer of the present invention has a mother-of-pearl-like structure, prepared on the surface of a steel substrate via a layer-by-layer self-assembly method. It exhibits excellent corrosion resistance, shielding properties, strength, and toughness. Surface modification of this connecting layer using a simple chemical impregnation method can further enhance its adhesion to the accompanying anti-corrosion coating. The excellent performance of this mother-of-pearl-like connecting layer can enhance the long-term corrosion resistance of the coating or reduce the thickness of the accompanying anti-corrosion coating, achieving lightweight coating while ensuring the service life of the anti-corrosion coating.

[0067] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for preparing a connecting layer of imitation mother-of-pearl structure for carbon steel surface, characterized in that: The steps include: S1: Preparation of two-dimensional sheet material CaAl-LDH-MBT; S2: preparing a PVA solution, wherein the mass fraction of PVA to water is 1-4 wt.%; S3: Add 3-aminopropyltrimethoxysilane, methanol, and deionized water to a container, mix and stir for 0.5 to 1.5 hours, add the two-dimensional sheet material CaAl-LDH-MBT in step S1, stir for 3 to 7 minutes, then centrifuge, wash, and dry to obtain modified CaAl-LDH-MBT, add the modified CaAl-LDH-MBT to an ethanol solution, and ultrasonically disperse it to obtain a dispersion, which is added dropwise to the water-air interface along the wall of the beaker until a visible thin film is formed, and ultrasonically disperse for 10 to 30 minutes to form a dense monolayer on the water-air interface; S4: Spin-coating the PVA solution in step S2 onto the surface of the carbon steel plate, and then drying it in an oven; S5: slowly placing the carbon steel plate dried in step S4 into the dense single layer solution of step S3, and then drying it in an oven; S6: Steps S4 and S5 form a cycle, which is repeated 3 to 10 times; S7: Based on step S6, the PVA solution is spin-coated on the surface of the carbon steel plate again, and then dried in an oven to obtain a connecting layer with an imitation mother-of-pearl structure; Step S1 includes the following steps: S11, preparing a mixed solution A of Ca(NO3)2 solution and Al(NO3)3 solution, a mixed solution B of NaNO3 solution and NaOH solution, and a mixed solution C of 2-mercaptobenzothiazole solution and NaOH solution; S12. Place the container containing solution B in an oil bath, set the temperature to 50-70°C, add solution A dropwise to solution B, and stir continuously with magnetic force; S13. After the titration is completed, the obtained suspension product is transferred to a hydrothermal kettle, which is placed in an oven at a temperature of 100-150° C. The reaction time is 12-36 h. S14, after the reaction is completed, centrifuge and wash, and dry at a temperature of 50-70 ° C for 24-48 hours. The obtained powder is recorded as CaAl-LDH; S15. Adjust the pH of solution C to 10 with 0.1-1.0 mol / L NaOH solution; S16. Add the CaAl-LDH in step S14 to the solution in step S15, continuously stir, centrifuge, dry, and grind to obtain a two-dimensional sheet material CaAl-LDH-MBT.

2. The preparation method according to claim 1, characterized in that The addition amount of the two-dimensional sheet material CaAl-LDH-MBT is 0.05 to 0.2 g.

3. The preparation method according to claim 1, characterized in that In step S3, the volume ratio of 3-aminopropyltrimethoxysilane, methanol, and deionized water is 1:(1-4):(5-8).

4. The preparation method according to claim 1, characterized in that In step S4, the spin coating speed is 600-1200 rpm, the spin coating time is 40-80 s, the drying temperature is 50-70° C., and the drying time is 10-20 min.

5. The preparation method according to claim 1, characterized in that In step S11, the concentration of Ca(NO3)2 solution is 0.2-0.6 mol / L, the concentration of Al(NO3)3 solution is 0.1-0.3 mol / L, the concentration of NaNO3 solution is 1-2 mol / L, the concentration of NaOH solution is 1-3 mol / L, the concentration of 2-mercaptobenzothiazole solution is 0.05-0.2 mol / L, and the concentration of NaOH solution is 0.05-0.2 mol / L.

6. The preparation method according to claim 1, characterized in that In step S7, the following steps are also included: S71: Prepare dopamine solution using tris buffer at pH 8.5; S72: Place the dried carbon steel plate in a dopamine solution, soak it at room temperature, then rinse it with deionized water and dry it naturally.

7. The preparation method according to claim 6, characterized in that In step S71 , the concentration of the dopamine solution is 1-8 mg / mL.

8. A connecting layer with a mother-of-pearl structure for a carbon steel surface, characterized in that: The preparation method according to claims 1 to 7 is used to obtain the product.

9. An application of a mother-of-pearl structure connecting layer on a carbon steel surface, using the mother-of-pearl structure connecting layer according to claim 8, characterized in that: Application of the imitation mother-of-pearl structure connecting layer in anti-corrosion coating.

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