A coating based on ternary system layered metal hydroxide and a preparation method thereof

Abstract

This invention relates to the field of metal corrosion protection materials, specifically to a coating based on a ternary layered metal hydroxide and its preparation method. The specific technical solution is as follows: The preparation steps of the ternary layered metal hydroxide are: (1) Dissolving soluble cobalt salt, aluminum salt, and rare earth salt in water to form a mixed salt solution, then adding alkali solution to prepare a nitrate-type precursor via co-precipitation or adding urea via hydrothermal method; (2) Dispersing the obtained precursor in water, adding 2-phosphonobutane-1,2,4-tricarboxylic acid or its sodium salt, and carrying out an ion exchange reaction, followed by washing and drying to obtain the ternary layered rare earth hydroxide. This material has a regular layered structure and anion exchange performance. Cobalt ions, rare earth ions, and organophosphonates produce a synergistic anti-corrosion effect, while aluminum ions in the layers help improve structural stability. Adding this material as a filler to an organic coating can significantly improve the corrosion resistance of the metal substrate.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion protection materials, specifically to a coating based on a ternary layered metal hydroxide system and its preparation method. Background Technology

[0002] Metal corrosion is a common problem in industrial sectors, especially in harsh environments such as marine and chemical plants, where it can cause serious economic losses and safety hazards. Coating protection is one of the most widely used corrosion prevention methods. Layered bimetallic hydroxides (LDHs), due to their unique layered structure and anion exchange properties, can capture corrosive chloride ions and release interlayer corrosion-inhibiting anions, attracting widespread attention in the field of anti-corrosion coatings. Traditional LDHs typically consist of layers composed of divalent and trivalent metal ions, such as MgAl-LDH and ZnAl-LDH. In recent years, cobalt-aluminum LDHs have also begun to attract attention due to the redox activity of cobalt ions in their layers and their relatively good thermal stability.

[0003] Introducing rare earth ions into LDH layers can endow materials with additional corrosion inhibition capabilities. Rare earth ions can form a dense conversion film on the metal surface, effectively suppressing corrosion. However, existing rare earth-doped LDHs are mostly binary or ternary systems, and the interlayer anions are usually simple inorganic ions, lacking the synergistic release ability of organic corrosion inhibitors. Organophosphonic acid compounds (such as 2-phosphonobutane-1,2,4-tricarboxylic acid, PBTCA) are highly efficient metal corrosion inhibitors and scale inhibitors. Their molecules contain phosphonic acid groups and multiple carboxyl groups, which have a strong chelating ability for metal ions. Loading them into layered materials can achieve controlled release, but there is no systematic research on combining PBTCA with cobalt-aluminum rare earth multi-layered plates in the current technology.

[0004] Therefore, developing a novel layered rare earth hydroxide material with stable structure and multiple synergistic anti-corrosion functions has important application value. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a coating based on a ternary layered metal hydroxide system and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for preparing a ternary layered metal hydroxide, comprising the following steps: (1) Dissolve soluble cobalt salt, aluminum salt and rare earth salt in water to form a mixed salt solution, and then add alkaline solution to prepare nitrate type precursor by co-precipitation or by adding urea to prepare nitrate type precursor by hydrothermal method; (2) Disperse the precursor obtained in step (1) in water, add 2-phosphonobutane-1,2,4-tricarboxylic acid or its sodium salt, carry out ion exchange reaction, and obtain ternary layered rare earth hydroxide after washing and drying.

[0007] Preferably, in step (1), the rare earth salt is an erbium salt or a ytterbium salt.

[0008] Preferably, in step (1), the molar ratio of cobalt ions, aluminum ions, and rare earth ions is 0.4-0.7:0.2-0.4:0.05-0.3.

[0009] Preferably, in step (2), the conditions for the ion exchange reaction are: temperature 60℃~100℃, time 6~24 hours.

[0010] Preferably, the co-precipitation method is as follows: the mixed salt solution and the alkaline solution are simultaneously added dropwise into the reaction vessel under the conditions of a 60°C water bath and nitrogen protection, maintaining pH=8.5±0.2, adding for 1.5 h, and aging for 2 h; the solution is filtered and washed until the filtrate is neutral, and then dried at 80°C for 24 h to obtain the nitrate-type precursor.

[0011] Preferably, the hydrothermal method is as follows: the mixed salt solution and urea are mixed and reacted at 140°C for 48 hours, then naturally cooled, centrifuged, washed three times with deionized water and three times with ethanol, and dried at 60°C to obtain the nitrate-type precursor.

[0012] Accordingly, a ternary layered metal hydroxide is prepared by the preparation method described above.

[0013] Accordingly, one application of the ternary layered metal hydroxide in metal corrosion protection involves adding the ternary layered metal hydroxide as an anti-corrosion filler to organic coatings, inorganic coatings, or sol-gel coatings.

[0014] Accordingly, a coating based on a ternary layered metal hydroxide comprises the ternary layered metal hydroxide, a film-forming substance, and a curing agent, wherein the film-forming substance is at least one of epoxy resin, polyurethane, waterborne acrylic resin, silane, or silica sol; the mass ratio of the ternary layered metal hydroxide to the film-forming substance is 1:15-20, and the mass ratio of the film-forming substance to the curing agent is 2:1.

[0015] Correspondingly, a method for preventing corrosion of a metal substrate involves mixing the components of the coating and applying it to the surface of a metal substrate, then curing it at room temperature to form an anti-corrosion layer.

[0016] The present invention has the following beneficial effects: (1) This invention is the first to intercalate PBTCA into a layered metal hydroxide of cobalt aluminum erbium and cobalt aluminum ytterbium ternary system. The material structure is novel, the interlayer spacing is significantly increased, and the anion exchange capacity is improved.

[0017] (2) The material of this invention has multiple synergistic anti-corrosion mechanisms: cobalt ions can participate in the formation of the passivation film and have self-healing potential; rare earth ions (Er 3+ / Yb 3+ PBTCA can form a dense rare earth conversion film on metal surfaces; as a highly efficient corrosion inhibitor and scale inhibitor, its phosphonic acid and carboxyl groups can synergistically chelate metal ions, inhibit corrosion, and promote passivation; interlayer anion exchange can capture corrosive Cl-. - The four components work synergistically to significantly improve corrosion resistance. Attached Figure Description

[0018] Figure 1 The XRD diffraction patterns of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are shown, where: a is the XRD pattern of CoAlEr-NO3, b is the XRD pattern of CoAl-PBTCA, c is the XRD pattern of CoAlYb-PBTCA, and d is the XRD pattern of CoAlEr-PBTCA. Figure 2 The SEM image is from Example 1; Figure 3 The Nyquist plots for the corrosion resistance test in Example 3 are shown (1d and 50d represent the coating after immersion in 3.5 wt.% NaCl solution for 1 day and 50 days, respectively). Figure 4 The SEM image is from Example 2; Figure 5 The Nyquist plots for the corrosion resistance test in Example 4 are shown (1d and 50d represent the coating after immersion in 3.5 wt.% NaCl solution for 1 day and 50 days, respectively). Figure 6 The SEM image is shown in Comparative Example 1. Figure 7 The Nyquist plots for the corrosion resistance test of the coating in Comparative Example 1 are shown (1d and 50d represent the coatings after immersion in 3.5 wt.% NaCl solution for 1 day and 50 days, respectively). Figure 8 The SEM image is shown in Comparative Example 2. Figure 9 The Nyquist plots for the anti-corrosion performance test of the coating in Comparative Example 2 are shown (1d and 50d represent the coatings after immersion in 3.5 wt.% NaCl solution for 1 day and 50 days, respectively). Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.

[0021] This invention provides a method for preparing a ternary layered metal hydroxide, comprising the following steps: (1) Dissolve soluble cobalt salt, aluminum salt and rare earth salt in water to form a mixed salt solution, then add alkali solution and prepare a nitrate-type precursor by co-precipitation or by adding urea and preparing a hydrothermal method; the rare earth salt is erbium salt or ytterbium salt. The molar ratio of cobalt ions, aluminum ions and rare earth ions is 0.4-0.7:0.2-0.4:0.05-0.3.

[0022] The coprecipitation method is as follows: the mixed salt solution and the alkaline solution are simultaneously added dropwise into the reaction vessel under the conditions of a 60°C water bath and nitrogen protection, maintaining pH=8.5±0.2, adding for 1.5 h, and aging for 2 h; the solution is filtered and washed until it is neutral, and then dried at 80°C for 24 h to obtain the nitrate precursor.

[0023] The hydrothermal method is as follows: the mixed salt solution and urea are mixed and reacted at 140°C for 48 hours, then naturally cooled, centrifuged, washed three times with deionized water and three times with ethanol, and dried at 60°C to obtain the nitrate-type precursor.

[0024] (2) The precursor obtained in step (1) is dispersed in water, and 2-phosphonobutane-1,2,4-tricarboxylic acid or its sodium salt is added to carry out an ion exchange reaction to insert the 2-phosphonobutane-1,2,4-tricarboxylic acid ion into the interlayer. After washing and drying, a ternary layered rare earth hydroxide is obtained. The conditions for the ion exchange reaction are: temperature 60℃~100℃, time 6~24 hours.

[0025] This invention provides a ternary layered metal hydroxide prepared by the method described above. The layered metal ions of the ternary layered metal hydroxide include divalent cobalt ions, aluminum ions, and rare earth ions, and the interlayer anion is 2-phosphonobutane-1,2,4-tricarboxylate ions; the rare earth ions are erbium ions or ytterbium ions. The molar ratio of divalent cobalt ions, aluminum ions, and rare earth ions is 0.4–0.7:0.2–0.4:0.05–0.3. The ternary system is a cobalt-aluminum-erbium system or a cobalt-aluminum-ytterbium system.

[0026] This invention provides an application of the aforementioned ternary layered metal hydroxide in metal corrosion protection, wherein the ternary layered metal hydroxide is added as an anti-corrosion filler to organic coatings, inorganic coatings, or sol-gel coatings. The organic coatings, inorganic coatings, and sol-gel coatings are all existing technologies.

[0027] This invention provides a coating based on a ternary layered metal hydroxide, comprising the ternary layered metal hydroxide, a film-forming substance, and a curing agent. The film-forming substance is at least one of epoxy resin, polyurethane, waterborne acrylic resin, silane, or silica sol. The mass ratio of the ternary layered metal hydroxide to the film-forming substance is 1:15-20, and the mass ratio of the film-forming substance to the curing agent is 2:1.

[0028] This invention provides a method for corrosion protection of a metal substrate, wherein the components of the coating are mixed and applied to the surface of the metal substrate, and cured at room temperature to form an anti-corrosion layer. The amount of the ternary layered rare earth hydroxide added is 0.5% to 15% of the total mass of the coating.

[0029] Example 1: (1) Preparation of nitrate-type precursor: Weigh Co(NO3)2·6H2O (9.46 g), Al(NO3)3·9H2O (4.69 g), and Er(NO3)3·6H2O (2.27 g) in a molar ratio of Co:Al:Er=0.65:0.25:0.10, dissolve them in 100 mL of deionized water to prepare a mixed salt solution. Prepare 100 mL of 1.5 mol / L NaOH solution. Under a 60℃ water bath and N2 protection (directly introduced into the reaction flask), add the mixed salt solution and alkali solution dropwise into the reaction flask simultaneously until the pH=8.5±0.2, then stop adding. The addition time is 1.5 h, and the solution is aged for 2 h. Filter and wash until the pH of the filtrate is 7, then dry at 80℃ for 24 h to obtain CoAlEr-NO3.

[0030] (2) Ion exchange intercalation: Take 5 g of the above precursor, disperse it in 200 mL of deionized water, add 5.0 g of 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA, 50% aqueous solution), adjust the pH to 8.0 with NaOH, and stir and reflux at 80℃ for 12 h. Filter, wash 3 times each with deionized water and ethanol, and dry under vacuum at 60℃ for 24 h to obtain CoAlEr-PBTCA.

[0031] Example 2: (1) Preparation of nitrate-type precursor: Co:Al:Yb = 0.70:0.20:0.10, weighed Co(NO3)2·6H2O (10.19 g), Al(NO3)3·9H2O (3.75 g), and Yb(NO3)3·6H2O (2.18 g), dissolved in 60 mL of deionized water, and added 7.2 g of urea. Transferred to a 100 mL hydrothermal reactor and reacted at 140 °C for 48 h. After natural cooling, centrifugation was performed, followed by washing three times with deionized water and three times with ethanol, and drying at 60 °C to obtain CoAlYb-NO3.

[0032] (2) Ion exchange intercalation: Take 5 g of the above precursor, disperse it in 200 mL of deionized water, add 5.0 g of PBTCA (50% aqueous solution), adjust the pH to 8.0 with NaOH, and stir and reflux at 80℃ for 12 h. Filter, wash 3 times each with deionized water and ethanol, and vacuum dry at 60℃ for 24 h to obtain CoAlYb-PBTCA.

[0033] Example 3: Take 5 g of CoAlEr-PBTCA powder obtained in Example 1, add it to 95 g of epoxy resin E-51, add 20 g of xylene / n-butanol mixed solvent (mass ratio 7:3), disperse at high speed for 30 min, then add curing agent polyamide 650 (epoxy resin:curing agent = 2:1, w / w), and stir evenly. After grinding, degreasing, and drying a Q235 carbon steel sheet, apply the above coating by scraping, cure at room temperature for 7 days, and the dry film thickness is 24±2 μm. The obtained coating can be used for corrosion protection of metal substrates.

[0034] Example 4: Take 5 g of CoAlYb-PBTCA powder obtained in Example 2, add it to 95 g of epoxy resin E-51, add 20 g of xylene / n-butanol mixed solvent (mass ratio 7:3), disperse at high speed for 30 min, then add curing agent polyamide 650 (epoxy resin:curing agent = 2:1, w / w), and stir evenly. After grinding, degreasing, and drying a Q235 carbon steel sheet, apply the above coating by scraping, cure at room temperature for 7 days, and the dry film thickness is 24±2 μm. The obtained coating can be used for corrosion protection of metal substrates.

[0035] Comparative Example 1: Using a molar ratio of Co:Al:Er = 0.65:0.25:0.10, weigh out 9.46 g of Co(NO3)2·6H2O, 4.69 g of Al(NO3)3·9H2O, and 2.27 g of Er(NO3)3·6H2O, dissolve them in 100 mL of deionized water to prepare a mixed salt solution. Prepare 100 mL of 1.5 mol / L NaOH solution. Under a 60℃ water bath and N2 protection, simultaneously add the salt solution and alkali solution dropwise into the reaction flask, maintaining the pH at 8.5 ± 0.2, for 1.5 h, followed by aging for 2 h. Filter and wash until the filtrate reaches pH 7, then dry at 80℃ for 24 h to obtain CoAlEr-NO3.

[0036] Comparative Example 2: (1) Preparation of nitrate-type precursor: Weigh 10.91 g of Co(NO3)2·6H2O and 4.69 g of Al(NO3)3·9H2O in a molar ratio of Co:Al = 0.75:0.25, dissolve them in 100 mL of deionized water to prepare a mixed salt solution. Prepare 100 mL of 1.5 mol / L NaOH solution. Under the protection of N2 in a 60℃ water bath, add the salt solution and alkali solution dropwise into the reaction flask simultaneously, keeping the pH at 8.5±0.2, for 1.5 h, and aging for 2 h. Filter and wash until the pH of the filtrate is 7, and dry at 80℃ for 24 h to obtain CoAl-NO3.

[0037] (2) Ion exchange intercalation: Take 5 g of the above precursor, disperse it in 200 mL of deionized water, add 5.0 g of PBTCA (50% aqueous solution), adjust the pH to 8.0 with NaOH, and stir and reflux at 80℃ for 12 h. Filter, wash 3 times each with deionized water and ethanol, and vacuum dry at 60℃ for 24 h to obtain CoAl-PBTCA.

[0038] Spectral analysis: From Figure 1 The XRD patterns show that the (003) diffraction peak of Example 1 (CoAlEr-PBTCA) and Example 2 (CoAlYb-PBTCA) is significantly shifted to the left, and the interlayer spacing is greater than that of Comparative Example 1 (CoAlEr-NO3) and Comparative Example 2 (CoAl-PBTCA), indicating that PBTCA was successfully intercalated and that rare earth ions (Er) were present. 3+ The introduction of ) further increased the interlayer spacing and resulted in good crystallinity.

[0039] Figure 2 and Figure 4 The SEM images show that Examples 1 and 2 have regular sheet-like morphology and are evenly dispersed.

[0040] Figure 3 , Figure 5 , Figure 7 , Figure 9 The Nyquist plot comparison shows that Examples 3 and 4 have the largest capacitive arc radius and maintain high impedance after immersion for 50 days, and their anti-corrosion performance is significantly better than the two comparative examples.

[0041] Figure 6 and Figure 8 The morphology shows that Comparative Example 1 has a densely packed layered structure, while Comparative Example 2 has more interlayer voids, neither of which is as structurally regular as Example 1. In summary, the CoAlEr-PBTCA and CoAlYb-PBTCA ternary system layered rare earth hydroxides exhibit excellent synergistic corrosion protection effects.

[0042] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a ternary layered metal hydroxide, characterized in that: Includes the following steps: (1) Dissolve soluble cobalt salt, aluminum salt and rare earth salt in water to form a mixed salt solution, and then add alkaline solution to prepare nitrate type precursor by co-precipitation or by adding urea to prepare nitrate type precursor by hydrothermal method; (2) Disperse the precursor obtained in step (1) in water, add 2-phosphonobutane-1,2,4-tricarboxylic acid or its sodium salt, carry out ion exchange reaction, and obtain ternary layered rare earth hydroxide after washing and drying.

2. The preparation method according to claim 1, characterized in that: In step (1), the rare earth salt is erbium salt or ytterbium salt.

3. The preparation method according to claim 2, characterized in that: In step (1), the molar ratio of cobalt ions, aluminum ions, and rare earth ions is 0.4-0.7:0.2-0.4:0.05-0.

3.

4. The preparation method according to claim 1, characterized in that: In step (2), the conditions for the ion exchange reaction are: temperature 60℃~100℃, time 6~24 hours.

5. The preparation method according to claim 1, characterized in that: The coprecipitation method is as follows: the mixed salt solution and the alkaline solution are simultaneously added dropwise into the reaction vessel under the conditions of a 60°C water bath and nitrogen protection, maintaining pH=8.5±0.2, adding for 1.5 h, and aging for 2 h; the solution is filtered and washed until it is neutral, and then dried at 80°C for 24 h to obtain the nitrate precursor.

6. The preparation method according to claim 1, characterized in that: The hydrothermal method is as follows: the mixed salt solution and urea are mixed and reacted at 140°C for 48 hours, then naturally cooled, centrifuged, washed three times with deionized water and three times with ethanol, and dried at 60°C to obtain the nitrate-type precursor.

7. A ternary layered metal hydroxide prepared by the preparation method according to claims 1-6.

8. The application of the ternary layered metal hydroxide of claim 7 in metal corrosion protection, characterized in that: The ternary layered metal hydroxide is added as an anti-corrosion filler to organic coatings, inorganic coatings, or sol-gel coatings.

9. A coating based on a ternary layered metal hydroxide system, characterized in that: The ternary system comprises the layered metal hydroxide of claim 7, a film-forming substance, and a curing agent, wherein the film-forming substance is at least one of epoxy resin, polyurethane, waterborne acrylic resin, silane, or silica sol; the mass ratio of the layered metal hydroxide to the film-forming substance is 1:15-20, and the mass ratio of the film-forming substance to the curing agent is 2:

1.

10. A method for corrosion protection of a metal substrate, characterized in that: The components of the coating described in claim 9 are mixed and applied to the surface of a metal substrate, and cured at room temperature to form an anti-corrosion layer.

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