A method for improving the compatibility of layered bimetallic hydroxides with coatings

Abstract

This invention provides a method for improving the compatibility of layered bimetallic hydroxides with coatings, comprising the following steps: S1, using a mixed solution of divalent and trivalent metal nitrates as a precursor, preparing nitrate-intercalated layered bimetallic hydroxides via co-precipitation; S2, preparing a long-chain fatty acid sodium solution, wherein the long-chain fatty acid sodium solution is at least one selected from sodium laurate solution, sodium dodecyl sulfate solution, and sodium dodecyl sulfonate solution; S3, adding the nitrate-intercalated layered bimetallic hydroxide to the long-chain fatty acid sodium solution, magnetically stirring at room temperature, and centrifuging, washing, drying, and grinding the resulting solution. The method for improving the compatibility of layered bimetallic hydroxides with coatings described in this invention improves the compatibility of layered bimetallic hydroxides with coatings by changing the terminal functional groups of long-chain fatty acids, thereby enhancing the physical barrier effect of the layered bimetallic hydroxides in the coating and increasing the anti-corrosion performance of the coating.

Description

Technical Field

[0001] This invention relates to the field of corrosion coatings, and more specifically, to a method for improving the compatibility of layered bimetallic hydroxides with coatings. Background Technology

[0002] Layered bimetallic hydroxides (LDHs) are widely used in coating systems due to their unique layered structure and anion exchange properties. Corrosion inhibitor ions are embedded between the layers of LDHs through ion exchange reactions, acting as containers for the corrosion inhibitor. When chloride ion attack occurs, the corrosion inhibitor is gradually released through ion exchange reactions between chloride ions in the environment and the anions in the interlayer, thus inhibiting corrosion (Progress in Organic Coatings 174(2023)107299; Colloids and Surfaces A: Physicochemical and Engineering Aspects 655(2022)130339; Chemical Engineering Journal 446(2022)137078). However, LDH surfaces are rich in hydroxyl (-OH) groups, resulting in high surface energy, which makes their surface structure unstable and prone to aggregation. Furthermore, the presence of hydroxyl groups on the LDH surface facilitates the formation of hydrogen bonds between particles, also leading to the formation of aggregated particles. When added to coatings, LDH aggregation not only affects the coating's barrier properties, but its uneven distribution also impacts its corrosion resistance and self-healing effects. This directly affects its commercial application in coatings. Therefore, improving the dispersibility of LDH in coatings and reducing its aggregation are of significant theoretical and practical importance for enhancing its final corrosion protection capability in coatings.

[0003] The compatibility of LDH with coatings is a critical issue in practical applications, directly restricting the industrialization of LDH in anti-corrosion coatings. Haiyang Wang et al. modified MgAl-LDHs films on magnesium alloy surfaces with dodecyl sulfate (SDS) to obtain superhydrophobic surfaces (Corrosion Science 208(2022)110699). Similarly, Youbin Wang et al. directly added SDS to the reactant solution to synthesize superhydrophobic ZnAl-LDH films on aluminum alloy surfaces using a one-step hydrothermal method (Applied Surface Science 593(2022)153400). Kunyao Cao et al. added sodium stearate-modified MgAl-LDH to the resin, resulting in a significantly improved coating impedance, but did not analyze the effect of sodium stearate modification on the dispersibility of LDH in the coating and its compatibility with the coating (Surface & Coatings Technology 407(2021)126763). In summary, the modification of LDH by low surface energy species can significantly affect the uniform dispersion of LDH in coatings, thereby influencing the corrosion resistance of the coatings. The effects and underlying causes of long-chain aliphatic low surface energy species containing different terminal functional groups on the dispersibility of LDH in coatings and their compatibility with the coatings have not yet been reported.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to propose a method to improve the compatibility of layered bimetallic hydroxides with coatings, in order to solve the problem in the prior art that there is no modification of layered bimetallic hydroxides with long-chain sodium carboxylate salts of different functional groups, and to explore the influence of different functional groups of long-chain sodium carboxylate salts on the compatibility of layered bimetallic hydroxides with coatings.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for improving the compatibility of layered bimetallic hydroxides with coatings, the method comprising the following steps:

[0008] S1. Using a mixed solution of divalent and trivalent metal nitrates as a precursor, a layered bimetallic hydroxide with nitrate intercalation was prepared by co-precipitation.

[0009] S2. Prepare a long-chain fatty acid sodium solution, wherein the long-chain fatty acid sodium solution is at least one of sodium laurate solution, sodium dodecyl sulfate solution and sodium dodecyl sulfonate solution;

[0010] S3. Add the nitrate-intercalated layered bimetallic hydroxide to the long-chain fatty acid sodium solution, stir magnetically at room temperature, and centrifuge, wash, dry and grind the resulting solution.

[0011] This invention discloses a method for improving the compatibility of layered bimetallic hydroxides (LBHs) with coatings. By modifying the LBHs with long-chain sodium carboxylate salts of different functional groups, the influence of different functional groups of the long-chain sodium carboxylate salts on the compatibility of the LBHs with the coating is determined. This results in a smoother coating with fewer defects, better leveraging the physical barrier function of the LBHs in the coating, and endowing the coating with better barrier properties against water molecules and corrosive ions, thus exhibiting better corrosion protection performance against the substrate. This invention is of great significance for improving the service life of coatings and substrates, reducing the frequency of coating repairs, reducing labor costs, and improving facility safety.

[0012] Furthermore, in step S1, the divalent metal nitrate is at least one of Ca(NO3)2, Mg(NO3)2 and Mg(NO3)2, and the trivalent metal nitrate is at least one of Al(NO3)3 and Fe(NO3)2.

[0013] Furthermore, in step S2, the concentration of the long-chain fatty acid sodium solution is 0.02–0.06 mol / L.

[0014] Furthermore, in step S3, the mass of the nitrate-intercalated layered bimetallic hydroxide is 0.1–4 g; and the volume of the long-chain fatty acid sodium solution is 50–400 mL.

[0015] Furthermore, in step S3, the time for the room temperature magnetic stirring is 0.1 to 3 hours.

[0016] Furthermore, in step S3, the centrifuge speed is 4000-8000 r / min and the centrifugation time is 2-8 min.

[0017] Furthermore, in step S3, the drying is carried out in an oven at a temperature of 60–120°C for a time of 20–80 hours.

[0018] Furthermore, in step S1, the concentration of the divalent metal nitrate is 0.2–0.6 mol / L, and the concentration of the trivalent metal nitrate is 0.2–0.6 mol / L.

[0019] Furthermore, step S1 includes the following steps:

[0020] S11. Take 200 mL of a mixed solution of 0.5 mol / L divalent metal nitrate Ca(NO3)2 and 0.25 mol / L trivalent metal nitrate Al(NO3)3 as the precursor solution. Add the precursor solution dropwise to a mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH. The volume of the mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH is 100 mL. Carry out a coprecipitation titration reaction at a water bath temperature of 60-70℃.

[0021] S12. The reaction product of coprecipitation titration is placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 110-130°C for 23-25 ​​hours.

[0022] S13. After the hydrothermal reaction is completed, cool to room temperature, take out the reaction product, the nitrate-intercalated layered bimetallic hydroxide, and centrifuge, wash, dry and grind it.

[0023] Furthermore, in step S13, the centrifuge speed is 7000-9000 r / min and the centrifugation time is 3-7 min; the drying is carried out in an oven at a temperature of 50-70℃ for 23-25 ​​h.

[0024] Compared with the prior art, the method for improving the compatibility of layered bimetallic hydroxides with coatings described in this invention has the following beneficial effects:

[0025] This invention discloses a method for improving the compatibility of layered bimetallic hydroxides (LBHs) with coatings. By modifying the LBHs with long-chain sodium carboxylate salts of different functional groups, the influence of different functional groups of the long-chain sodium carboxylate salts on the compatibility of the LBHs with the coating is determined. This results in a smoother coating with fewer defects, better leveraging the physical barrier function of the LBHs in the coating, and endowing the coating with better barrier properties against water molecules and corrosive ions, thus exhibiting better corrosion protection performance against the substrate. This invention is of great significance for improving the service life of coatings and substrates, reducing the frequency of coating repairs, reducing labor costs, and improving facility safety. Attached Figure Description

[0026] Figure 1 The XRD pattern of the layered bimetallic hydroxide described in the embodiments of the present invention;

[0027] Figure 2 for Figure 1 Magnified XRD patterns in the 5-10° range;

[0028] Figure 3 These are SEM images of different layered bimetallic hydroxides described in the embodiments of the present invention;

[0029] Figure 4 SEM images of different layered bimetallic hydroxides added to epoxy coatings as described in embodiments of the present invention. Detailed Implementation

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. The descriptions of "first," "second," etc., mentioned in the embodiments of the present invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0031] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0032] This invention proposes a method for improving the compatibility of layered bimetallic hydroxides with coatings, the method comprising the following steps:

[0033] S1. Using a mixed solution of divalent and trivalent metal nitrates as a precursor, a layered bimetallic hydroxide with nitrate intercalation was prepared by co-precipitation.

[0034] S2. Prepare a long-chain fatty acid sodium solution, wherein the long-chain fatty acid sodium solution is at least one of sodium laurate solution, sodium dodecyl sulfate solution and sodium dodecyl sulfonate solution;

[0035] S3. Add the nitrate-intercalated layered bimetallic hydroxide to the long-chain fatty acid sodium solution, stir magnetically at room temperature, and centrifuge, wash, dry and grind the resulting solution.

[0036] Specifically, in step S1, the divalent metal nitrate is at least one of Ca(NO3)2, Mg(NO3)2 and Mg(NO3)2, and the trivalent metal nitrate is at least one of Al(NO3)3 and Fe(NO3)2.

[0037] Specifically, in step S2, the concentration of the long-chain fatty acid sodium solution is 0.02–0.06 mol / L.

[0038] Specifically, in step S3, the mass of the nitrate-intercalated layered bimetallic hydroxide is 0.1–4 g; and the volume of the long-chain fatty acid sodium solution is 50–400 mL.

[0039] Specifically, in step S3, the time for the room temperature magnetic stirring is 0.1 to 3 hours.

[0040] Specifically, in step S3, the centrifuge speed is 4000-8000 r / min and the centrifugation time is 2-8 min.

[0041] Specifically, in step S3, the drying process is carried out in an oven at a temperature of 60–120°C for 20–80 hours.

[0042] Specifically, in step S1, the concentration of the divalent metal nitrate is 0.2–0.6 mol / L, and the concentration of the trivalent metal nitrate is 0.2–0.6 mol / L.

[0043] Specifically, step S1 includes the following steps:

[0044] S11. Take 200 mL of a mixed solution of 0.5 mol / L divalent metal nitrate Ca(NO3)2 and 0.25 mol / L trivalent metal nitrate Al(NO3)3 as the precursor solution. Add the precursor solution dropwise to a mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH. The volume of the mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH is 100 mL. Carry out a coprecipitation titration reaction at a water bath temperature of 60-70℃.

[0045] S12. The reaction product of coprecipitation titration is placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 110-130°C for 23-25 ​​hours.

[0046] S13. After the hydrothermal reaction is completed, cool to room temperature, remove the reaction product, and centrifuge, wash, dry and grind it.

[0047] Specifically, in step S13, the centrifuge speed is 7000-9000 r / min and the centrifugation time is 3-7 min; the drying is carried out in an oven at a temperature of 50-70℃ for 23-25 ​​h.

[0048] Example 1

[0049] S1. Using a mixed solution of divalent and trivalent metal nitrates as a precursor, a layered bimetallic hydroxide with nitrate intercalation was prepared by co-precipitation.

[0050] Specifically, in step S1, the divalent metal nitrate is Ca(NO3)2, and the trivalent metal nitrate is Al(NO3)3.

[0051] S11. Take 200 mL of a mixed solution of 0.5 mol / L divalent metal nitrate Ca(NO3)2 and 0.25 mol / L trivalent metal nitrate Al(NO3)3 as the precursor solution. Add the precursor solution dropwise to a mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH. The volume of the mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH is 100 mL. Carry out a coprecipitation titration reaction at a water bath temperature of 65℃.

[0052] S12. The reaction product of coprecipitation titration is placed in a hydrothermal reactor for hydrothermal reaction at a temperature of 120°C for 24 hours.

[0053] S13. After the hydrothermal reaction is completed, cool to room temperature, take out the reaction product, the nitrate-intercalated layered bimetallic hydroxide CaAl-LDH, and centrifuge, wash, dry and grind it; the centrifuge speed is 8000 r / min and the centrifugation time is 5 min; the drying is carried out in an oven at 60℃ for 24 h.

[0054] S2. Prepare a long-chain fatty acid sodium solution;

[0055] Specifically, in step S2, the long-chain fatty acid sodium solution is a sodium lauryl salt solution (La), and the concentration of the long-chain fatty acid sodium solution is 0.05 mol / L.

[0056] S3. Add the nitrate-intercalated layered bimetallic hydroxide to a long-chain fatty acid sodium solution, stir magnetically at room temperature, and centrifuge, wash, dry and grind the resulting solution; the final product is sodium lauryl nitrate-intercalated layered bimetallic hydroxide (CaAl-LDH-La).

[0057] Specifically, step S3 involves adding 0.5g of nitrate-intercalated layered bimetallic hydroxide to 100mL of 0.05mol / L sodium lauryl hydroxide solution (La), stirring magnetically at room temperature for 0.5h, and then centrifuging, washing, drying, and grinding the resulting solution. The centrifuge speed is 8000r / min, and the centrifugation time is 5min. The drying is carried out in an oven at 60℃ for 24h.

[0058] Example 2

[0059] In this embodiment, unlike in Example 1, the long-chain fatty acid sodium solution is a sodium dodecyl sulfate solution (SDS); the final product is a layered bimetallic hydroxide (CaAl-LDH-SDS) modified with sodium dodecyl sulfate and intercalated with nitrate.

[0060] Comparative Example 1

[0061] In this comparative example, unlike Example 1, only step S1 of Example 1 is included; the final product is a nitrate-intercalated layered bimetallic hydroxide CaAl-LDH.

[0062] Performance testing

[0063] I. XRD pattern characterization

[0064] like Figure 1 and Figure 2 As shown, the reaction products CaAl-LDH prepared in Comparative Example 1, CaAl-LDH-La prepared in Example 1, and CaAl-LDH-SDS prepared in Example 2 were characterized by XRD patterns.

[0065] Depend on Figure 1 It can be seen that CaAl-LDH, CaAl-LDH-La, and CaAl-LDH-SDS all exhibit characteristic peaks of the (003) and (006) crystal planes at 10° and 20°, respectively. These characteristic peaks correspond to the nitrate ions embedded in the interlayer. This result also indicates that the modification with sodium lauryl sulfate and sodium dodecyl sulfate did not damage the layered structure of LDH.

[0066] Depend on Figure 2 It can be seen that CaAl-LDH-La exhibits characteristic peaks at 5.3° and 7.8°, both corresponding to the intercalated laurate ions. The leftward shift of the 2θ angle is due to the intercalation of larger laurate ions into the LDH interlayer, increasing the interlayer spacing. The presence of characteristic peaks at both 5.3° and 7.8° may be due to the different angles at which the laurate ions intercalate. CaAl-LDH-SDS exhibits a characteristic peak at 8.3°, corresponding to the intercalation of relatively large dodecyl sulfate ions.

[0067] II. SEM Image Characterization

[0068] 1. For example Figure 3 As shown, the reaction products CaAl-LDH prepared in Comparative Example 1, CaAl-LDH-La prepared in Example 1, and CaAl-LDH-SDS prepared in Example 2 were characterized by SEM spectra at different magnifications.

[0069] exist Figure 3In the figures, (a) shows the microstructure of CaAl-LDH, (b) shows the microstructure of CaAl-LDH-La, and (c) shows the microstructure of CaAl-LDH-SDS.

[0070] The results showed that CaAl-LDH, CaAl-LDH-La, and CaAl-LDH-SDS all exhibited hexagonal morphologies. However, a comparison revealed that CaAl-LDH particles were relatively small, exhibiting severe particle aggregation. The modified layered bimetallic hydroxides CaAl-LDH-La and CaAl-LDH-SDS retained their hexagonal structure and intact layered structure, with significantly reduced particle aggregation. Notably, the aggregation degree of sodium laurate-modified CaAl-LDH was much less than that of sodium dodecyl sulfate-modified CaAl-LDH.

[0071] 2. For example Figure 4 As shown, the microstructures of the reaction products CaAl-LDH prepared in Comparative Example 1, CaAl-LDH-La prepared in Example 1, and CaAl-LDH-SDS prepared in Example 2, when added to the epoxy coating, as well as the microstructure of the blank epoxy coating, were characterized by SEM images.

[0072] exist Figure 4 In the figure, (a) shows the microstructure of the blank epoxy coating without the addition of LDH powder; (b) shows the microstructure of the epoxy coating containing 2 wt.% CaAl-LDH; (c) shows the microstructure of the epoxy coating containing 2 wt.% CaAl-LDH-La; and (d) shows the microstructure of the epoxy coating containing 2 wt.% CaAl-LDH-SDS.

[0073] As shown in Figure 4, the coating became smoother and the number of pores and defects decreased after adding CaAl-LDH. The addition of CaAl-LDH-La and CaAl-LDH-SDS further reduced defects, and no LDH agglomeration was observed, demonstrating the good compatibility between the LDH modified with sodium lauryl sulfate and the coating. The coating with CaAl-LDH-La was smoother and had fewer defects than the coating with CaAl-LDH-SDS.

[0074] This invention discloses a method for improving the compatibility of layered bimetallic hydroxides (LBHs) with coatings. By modifying the LBHs with long-chain sodium carboxylate salts of different functional groups, the influence of different functional groups of the long-chain sodium carboxylate salts on the compatibility of the LBHs with the coating is determined. This results in a smoother coating with fewer defects, better leveraging the physical barrier function of the LBHs in the coating, and endowing the coating with better barrier properties against water molecules and corrosive ions, thus exhibiting better corrosion protection performance against the substrate. This invention is of great significance for improving the service life of coatings and substrates, reducing the frequency of coating repairs, reducing labor costs, and improving facility safety.

[0075] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method of improving compatibility of a layered double hydroxide with a coating, characterized by, The method for improving the compatibility of layered double hydroxides with a coating layer comprises the following steps: S1, using a mixed solution of divalent metal nitrate and trivalent metal nitrate as a precursor, and preparing a nitrate intercalated layered double hydroxide by a coprecipitation method; S2, preparing a long-chain fatty acid sodium solution, wherein the long-chain fatty acid sodium solution is a sodium laurate solution; S3, adding the nitrate intercalated layered double hydroxide into the long-chain fatty acid sodium solution, performing magnetic stirring at room temperature, and performing centrifugation, washing, drying and grinding on the obtained solution; In step S2, the concentration of the long-chain fatty acid sodium solution is 0.05 mol / L; In step S3, the mass of the nitrate intercalated layered double hydroxide is 0.5 g; and the volume of the long-chain fatty acid sodium solution is 100 mL; In step S3, the time for magnetic stirring at room temperature is 0.1-3 h; In step S3, the centrifuge speed is 4000-8000 r / min, and the centrifugation time is 2-8 min; In step S3, the drying is performed in an oven, the drying temperature is 60-120℃, and the drying time is 20-80 h.

2. The method of improving compatibility of layered double hydroxides with coating layers according to claim 1, characterized in that, In step S1, the divalent metal nitrate is at least one of Ca(NO3)2 and Mg(NO3)2, and the trivalent metal nitrate is at least one of Al(NO3)3 and Fe(NO3)2.

3. The method of improving compatibility of layered double hydroxides with coating layers according to claim 1, characterized in that, In step S1, the concentration of the divalent metal nitrate is 0.2-0.6 mol / L, and the concentration of the trivalent metal nitrate is 0.2-0.6 mol / L.

4. The method of improving compatibility of layered double hydroxides with coating layers according to claim 2, characterized in that, Step S1 comprises the following steps: S11, taking 200 mL of a mixed solution of 0.5 mol / L divalent metal nitrate Ca(NO3)2 and 0.25 mol / L trivalent metal nitrate Al(NO3)3 as a precursor solution, adding the precursor solution drop by drop into a mixed solution of 2 mol / L NaNO3 and 3 mol / L NaOH with a volume of 100 mL, and performing a coprecipitation titration reaction at a water bath temperature of 60-70℃; S12, placing the reaction product of the coprecipitation titration into an autoclave for hydrothermal reaction, wherein the hydrothermal temperature is 110-130℃, and the hydrothermal reaction time is 23-25 h; S13, after the hydrothermal reaction is completed, cooling to room temperature, taking out the reaction product, i.e., the nitrate intercalated layered double hydroxide, and performing centrifugation, washing, drying and grinding.

5. The method of improving compatibility of layered double hydroxides with coating layers according to claim 4, characterized in that, In step S13, the centrifuge speed is 7000-9000 r / min, and the centrifugation time is 3-7 min; the drying is performed in an oven, the drying temperature is 50-70℃, and the drying time is 23-25 h.

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