Environment-friendly corrosion inhibitor intercalated calcium-aluminum layered double-metal hydroxide and preparation method thereof

Abstract

The invention provides an environment-friendly corrosion inhibitor intercalated calcium-aluminum layered double hydroxide and a preparation method thereof, the preparation method comprises the following steps: S1, preparing a Ca (NO3) 2.4 H2O and Al (NO3) 3.9 H2O mixed solution marked as a solution A, and preparing a NaNO3 and NaOH mixed solution marked as a solution B; s2, dropwise adding the solution A into the solution B, carrying out a hydrothermal reaction after dropwise adding is completed, and after the reaction is completed, centrifuging, washing and drying to obtain a product C; s3, preparing an L-methionine solution, adding NaOH into the L-methionine solution with a certain volume, then adjusting the pH value of the solution, then adding the product C, stirring, centrifuging, washing and drying to obtain the environment-friendly corrosion inhibitor intercalated calcium-aluminum layered double-metal hydroxide. According to the invention, L-methionine is embedded into calcium-aluminum layered double hydroxides to obtain the green composite corrosion inhibitor, the concentration of chloride ions in a corrosive medium environment can be effectively reduced, and corrosion inhibitor ions are released, so that the corrosion of the chloride ions to a base material is reduced, and the corrosion resistance of the base material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion protection, and in particular to an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide and a preparation method thereof. Background Art

[0002] Layered double hydroxides (LDHs) are common anionic layered compounds widely used in anti-corrosion coating systems due to their unique layered structure, anion exchangeability, and tunable properties. According to literature research, LDHs can act as corrosion inhibitor containers. When chloride ions from a corrosive medium invade, the chloride ions in the environment exchange with the corrosion inhibitor anions between the LDH layers, absorbing the chloride ions while releasing the inhibitor ions, thereby protecting the substrate and achieving a corrosion inhibition effect (Coatings 12 (2022) 1631).

[0003] Currently, greening corrosion inhibitors has become a research hotspot. L-methionine, an excellent phosphorus-free corrosion inhibitor, is being used in the corrosion protection field due to its environmentally friendly, affordable, and readily available advantages. Chinese patent CN 110627097A discloses a method for preparing a material intercalated with an azole-type corrosion inhibitor, MgAl-LDH. This material is then added as a filler to a coating to produce a high-performance water-based anti-corrosion coating for use in polar low-temperature environments. The coating exhibits excellent low-temperature resistance and low-temperature application performance, and can also be used to protect engineering facilities in low-temperature environments. However, the MgAl-LDH intercalated with the azole-type corrosion inhibitor used in this method releases harmful substances during service, causing environmental pollution. Therefore, the development of an environmentally friendly modified layered double hydroxide is of great significance. Furthermore, existing work using amino acid-based corrosion inhibitors to modify calcium-aluminum LDH is limited, with most research focusing on loading LDH with traditional corrosion inhibitors. The type of amino acid corrosion inhibitor and the experimental conditions used for LDH modification have a significant impact on the loading capacity and corrosion protection performance of the LDH. Summary of the Invention

[0004] In view of this, the present invention aims to provide an environmentally friendly corrosion inhibitor-intercalated calcium aluminum layered double hydroxide and its preparation method. This aims to address the problem of azole corrosion inhibitor-intercalated MgAl-LDH materials used in the prior art, which release harmful substances during service, causing environmental pollution.

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

[0006] A method for preparing an environmentally friendly corrosion inhibitor-intercalated calcium aluminum layered double hydroxide comprises the following steps:

[0007] S1. Prepare a mixed solution of Ca(NO3)2·4H2O and Al(NO3)3·9H2O, labeled as solution A, and a mixed solution of NaNO3 and NaOH, labeled as solution B.

[0008] S2, adding solution A dropwise into solution B, and after the addition is completed, subjecting the obtained mixed slurry to a hydrothermal reaction. After the reaction is completed, centrifugation, washing, and drying are performed to obtain product C;

[0009] S3. Prepare L-methionine solution, add NaOH to a certain volume of L-methionine solution, then adjust the pH value of the solution, add product C, stir, centrifuge, wash, and dry to obtain an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide.

[0010] This green composite corrosion inhibitor, created by embedding L-methionine into a calcium-aluminum layered double hydroxide, effectively reduces chloride ion concentration in corrosive environments while simultaneously releasing inhibitor ions. This reduces chloride ion attack on the substrate and improves the corrosion resistance of the substrate. This invention is of great significance for extending the service life of the substrate, reducing the number of coating repairs, saving labor costs, improving facility safety and serviceability, and facilitating environmental sustainability.

[0011] Furthermore, in step S1, in solution A, the volume is 190-210 mL, the concentration of the Ca(NO3)2·4H2O solution is 0.4-0.6 mol / L, and the concentration of the Al(NO3)3·9H2O solution is 0.2-0.3 mol / L; in solution B, the volume is 90-110 mL, the concentration of the NaNO3 solution is 1.5-2.5 mol / L, and the concentration of the NaOH solution is 2-4 mol / L.

[0012] The calcium aluminum layered double hydroxide prepared by this setting can facilitate the intercalation of L-methionine.

[0013] Furthermore, in step S2, the hydrothermal reaction temperature is 60-70°C, and the hydrothermal reaction time is 12-36 hours.

[0014] Furthermore, in step S2, the dripping speed is one drop per second.

[0015] Furthermore, in step S2, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

[0016] Furthermore, in step S2, drying is performed in an oven, wherein the drying temperature is 40-110° C. and the drying time is 12-72 h.

[0017] Furthermore, the specific steps of step S3 are: preparing an L-methionine solution with a volume of 90-110 mL and a solution concentration of 0.005-1.0 mol / L, adding an equimolar amount of NaOH solid for deprotonation, stirring at room temperature for 10-60 min, and then adjusting the pH value of the stirred solution to 9-13 using NaOH solution.

[0018] This setting enables L-methionine to be successfully embedded into calcium aluminum layered double hydroxide, achieving a higher loading capacity while improving the anti-corrosion performance of the calcium aluminum layered double hydroxide.

[0019] Further, in step S3, the product C is weighed to 0.1-4 g, and the stirring time is 10-48 h.

[0020] Furthermore, in step S3, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

[0021] Furthermore, in step S3, drying is performed in an oven, wherein the drying temperature is 40-110° C. and the drying time is 12-72 h.

[0022] Compared with the prior art, the preparation method of the environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide described in the present invention has the following advantages:

[0023] 1) This invention embeds L-methionine into a calcium aluminum layered double hydroxide to create a green composite corrosion inhibitor. This effectively reduces chloride ion concentration in corrosive media while simultaneously releasing inhibitor ions, thereby reducing chloride ion attack on the substrate and improving the substrate's corrosion resistance. This invention is of great significance for extending the service life of the substrate, reducing the number of coating repairs, saving labor costs, improving facility safety and serviceability, and promoting environmental sustainability.

[0024] 2) The present invention modifies a specific calcium aluminum layered double hydroxide and optimizes the L-methionine concentration, volume, and processing steps to successfully embed L-methionine into the calcium aluminum layered double hydroxide, maintaining a high loading capacity. For example, when the L-methionine concentration is too high or the reaction time is too long, the loading of L-methionine between the LDH layers has reached ion exchange equilibrium. Increasing the concentration or extending the reaction time will not significantly increase the loading capacity and LDH anticorrosion performance, but will waste a lot of manpower and material resources and extend the preparation cycle. When the L-methionine concentration is too low or the reaction time is too short, the loading capacity is low and the LDH anticorrosion performance is poor.

[0025] The present invention also provides an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide, which is prepared by the above-mentioned preparation method of the environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide.

[0026] The advantages of the environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide and the preparation method of the environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide mentioned above over the prior art are the same and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 XRD spectra of LDH and Met-LDH according to Example 1 of the present invention;

[0028] Figure 2 1 are SEM images of LDH and Met-LDH according to Example 1 of the present invention, wherein a is the SEM image of LDH according to Example 1, and b is the SEM image of Met-LDH according to Example 1;

[0029] Figure 3 The present invention is an EIS test result diagram of Q235 steel immersed in NaCl solution with or without adding Met-LDH, wherein Met-LDH is from Example 1, a1 is the Nyquist diagram of the blank NaCl solution test, a2 is the Bode diagram of the blank NaCl solution test, b1-e1 are the Nyquist diagrams of the Met-LDH solution tests prepared in Examples 1 to 4, and b2-e2 are the Bode diagrams of the Met-LDH solution tests prepared in Examples 1 to 4. DETAILED DESCRIPTION

[0030] 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.

[0031] The present invention provides a method for preparing an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide, comprising the following steps:

[0032] S1. Prepare a mixed solution of Ca(NO3)2·4H2O and Al(NO3)3·9H2O, labeled as solution A, and a mixed solution of NaNO3 and NaOH, labeled as solution B.

[0033] S2, adding solution A dropwise into solution B, and after the addition is completed, subjecting the obtained mixed slurry to a hydrothermal reaction. After the reaction is completed, centrifugation, washing, and drying are performed to obtain product C;

[0034] S3. Prepare L-methionine solution, add NaOH solid to a certain volume of L-methionine solution, then adjust the pH value of the solution, add product C, vigorously stir, centrifuge, wash, and dry to obtain an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide, which is placed in a drying oven for storage.

[0035] Specifically, in step S1, in solution A, the volume is 190~210 mL, the concentration of Ca(NO3)2·4H2O solution is 0.4~0.6 mol / L, and the concentration of Al(NO3)3·9H2O solution is 0.2~0.3 mol / L; in solution B, the volume is 90~110 mL, the concentration of NaNO3 solution is 1.5~2.5 mol / L, and the concentration of NaOH solution is 2~4 mol / L.

[0036] Specifically, in step S2, the hydrothermal reaction temperature is 60-70°C, and the hydrothermal reaction time is 12-36 hours.

[0037] Specifically, in step S2, the dropping speed is one drop per second.

[0038] Specifically, in step S2, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

[0039] Specifically, in step S2, drying is performed in an oven, wherein the drying temperature is 40-110°C and the drying time is 12-72 hours.

[0040] Specifically, the specific steps of step S3 are: preparing an L-methionine solution with a volume of 90-110 mL and a solution concentration of 0.005-1.0 mol / L, adding an equimolar amount of NaOH solid for deprotonation, stirring at room temperature for 10-60 min, and then adjusting the pH value of the stirred solution to 9-13 using NaOH solution.

[0041] Specifically, in step S3, the concentration of the NaOH solution mentioned is 2-4 mol / L.

[0042] Specifically, in step S3, the product C is weighed to 0.1-4 g, and the stirring time is 10-48 h.

[0043] Specifically, in step S3, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

[0044] Specifically, in step S3, drying is performed in an oven, wherein the drying temperature is 40-110° C., and the drying time is 12-72 hours.

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0046] Example 1

[0047] (1) 200 mL of a mixed solution of 0.5 mol / L Ca(NO3)2·4H2O and 0.25 mol / L Al(NO3)3·9H2O was added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH at room temperature. The reaction product was then placed in a beaker for a hydrothermal reaction at a temperature of 65°C for 24 h. After the hydrothermal reaction, the product was cooled to room temperature and centrifuged and washed at a speed of 8000 r / min for 5 min. The washed product was then dried in an oven at a temperature of 65°C for 48 h. The resulting product was labeled LDH.

[0048] (2) Prepare 100 mL of 0.1 mol / L L-methionine solution, add an equimolar amount of NaOH solid, and stir at room temperature for 30 min for deprotonation. Then adjust the pH of the stirred solution to 10.8 with 3 mol / L NaOH solution. Weigh 1 g of LDH obtained in step (1) and place it in the above solution. Stir vigorously at room temperature for 24 h. Then centrifuge and wash the reaction product. The centrifuge speed is set to 8000 r / min and the centrifugation time is set to 5 min. The washed product is placed in an oven for drying. The oven temperature is set to 65 °C and the drying time is set to 48 h. The obtained product is labeled as Met-LDH.

[0049] Example 2

[0050] (1) 200 mL of a mixed solution of 0.5 mol / L Ca(NO3)2·4H2O and 0.25 mol / L Al(NO3)3·9H2O was added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH at room temperature. The reaction product was then placed in a beaker for hydrothermal reaction at a temperature of 65°C for 24 h. After the hydrothermal reaction, the product was cooled to room temperature and centrifuged and washed at a speed of 8000 r / min for 5 min. The washed product was then dried in an oven at a temperature of 65°C for 48 h. The resulting product was labeled LDH.

[0051] (2) Prepare 100 mL of 0.15 mol / L L-methionine solution, add an equal molar amount of NaOH solid and stir at room temperature for 40 min for deprotonation, then adjust the solution pH to 10.5 with 3 mol / L NaOH solution, weigh 3 g of LDH obtained in step (1) and place it in the above solution, vigorously stir at room temperature for 24 h, then centrifuge and wash the reaction product, set the centrifuge speed to 8000 r / min, and the centrifugation time to 5 min. Place the washed product in an oven for drying, set the oven temperature to 65°C, and set the drying time to 48 h. The obtained product is labeled as Met-LDH.

[0052] Example 3

[0053] (1) 200 mL of a mixed solution of 0.5 mol / L Ca(NO3)2·4H2O and 0.25 mol / L Al(NO3)3·9H2O was added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH at room temperature. The reaction product was then placed in a beaker for a hydrothermal reaction at a temperature of 65°C for 24 h. After the hydrothermal reaction, the product was cooled to room temperature and centrifuged and washed at a speed of 8000 r / min for 5 min. The washed product was then dried in an oven at a temperature of 65°C for 48 h. The resulting product was labeled LDH.

[0054] (2) Prepare 100 mL of 0.05 mol / L L-methionine solution, add an equal molar amount of NaOH solid and stir at room temperature for 30 min for deprotonation, then adjust the solution pH to 10.5 with 3 mol / L NaOH solution, weigh 2.5 g of LDH obtained in step (1) and place it in the above solution, vigorously stir at room temperature for 36 h, then centrifuge and wash the reaction product, set the centrifuge speed to 5000 r / min, and the centrifugation time to 10 min. Place the washed product in an oven for drying, set the oven temperature to 80°C, and set the drying time to 24 h. The obtained product is labeled as Met-LDH.

[0055] Example 4

[0056] (1) 200 mL of a mixed solution of 0.5 mol / L Ca(NO3)2·4H2O and 0.25 mol / L Al(NO3)3·9H2O was added dropwise to a mixed solution of 100 mL of 2 mol / L NaNO3 and 3 mol / L NaOH at room temperature. The reaction product was then placed in a beaker for a hydrothermal reaction at a temperature of 65°C for 24 h. After the hydrothermal reaction, the product was cooled to room temperature and centrifuged and washed at a speed of 8000 r / min for 5 min. The washed product was then dried in an oven at a temperature of 65°C for 48 h. The resulting product was labeled LDH.

[0057] (2) Prepare 100 mL of 0.02 mol / L L-methionine solution, add an equal molar amount of NaOH solid and stir at room temperature for 50 min for deprotonation, then adjust the solution pH to 10.5 with 3 mol / L NaOH solution, weigh 2 g of LDH obtained in step (1) and place it in the above solution, vigorously stir at room temperature for 24 h, then centrifuge and wash the reaction product, set the centrifuge speed to 10000 r / min, and the centrifugation time to 8 min. Place the washed product in an oven for drying, set the oven temperature to 110°C, and set the drying time to 12 h. The obtained product is labeled as Met-LDH.

[0058] Performance Testing

[0059] Depend on Figure 1 It can be seen that the layered double hydroxides before and after L-methionine intercalation have (003) and (006) crystal planes, showing a typical layered double hydroxide structure, indicating the successful synthesis of calcium aluminum layered double hydroxides, and the structure of the layered double hydroxide does not change after L-methionine intercalation; Figure 1 It also shows that the (003) crystal plane diffraction peak angle of Met-LDH shifts to the right, indicating that the interlayer spacing of the layered double hydroxide is reduced, indicating that L-methionine is successfully inserted into the interlayer of the layered double hydroxide.

[0060] Depend on Figure 2 It can be seen that the layered double hydroxides before and after L-methionine intercalation have a hexagonal structure, indicating that the addition of L-methionine does not change the morphology of the layered double hydroxides.

[0061] Depend on Figure 3 (b2-c2) It can be seen that after 5 days of immersion, the |Z| 10mHz The value remains at 10 4 Ω·cm2 , indicating that Met-LDH can improve the corrosion resistance of metal substrates in salt solutions. In addition, the |Z| 10mHz The values also differed. With the increase of L-methionine concentration, |Z| 10mHz The values also increase, indicating that the corrosion inhibition effect of Met-LDH on metal substrates is affected by the concentration of L-methionine.

[0062] In summary, the present invention aims to prepare an environmentally friendly composite corrosion inhibitor comprising calcium aluminum layered double hydroxide (CaAl-LDH) intercalated with L-methionine. When a corrosive medium invades, the composite corrosion inhibitor effectively blocks the corrosive medium from invading the metal substrate through chloride ion absorption and release of the corrosion inhibitor. This can extend the service life of the substrate, save labor costs, and the raw materials are inexpensive and readily available, complying with environmentally friendly principles and having high application potential.

[0063] 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 an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide, characterized in that: The following steps are involved: S1. Prepare a mixed solution of Ca(NO3)2·4H2O and Al(NO3)3·9H2O, labeled as solution A, and a mixed solution of NaNO3 and NaOH, labeled as solution B. S2, adding solution A dropwise into solution B, and after the addition is completed, subjecting the obtained mixed slurry to a hydrothermal reaction. After the reaction is completed, centrifugation, washing, and drying are performed to obtain product C; S3. Prepare L-methionine solution, add NaOH to a certain volume of L-methionine solution, then adjust the pH value of the solution, add product C, stir, centrifuge, wash, and dry to obtain an environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide.

2. The preparation method according to claim 1, characterized in that In step S1, in solution A, the volume is 190-210 mL, the concentration of the Ca(NO3)2·4H2O solution is 0.4-0.6 mol / L, and the concentration of the Al(NO3)3·9H2O solution is 0.2-0.3 mol / L; in solution B, the volume is 90-110 mL, the concentration of the NaNO3 solution is 1.5-2.5 mol / L, and the concentration of the NaOH solution is 2-4 mol / L.

3. The preparation method according to claim 1, characterized in that In step S2, the hydrothermal reaction temperature is 60-70° C., and the hydrothermal reaction time is 12-36 hours.

4. The preparation method according to claim 1, characterized in that In step S2 , the dropping speed is one drop per second.

5. The preparation method according to claim 1, characterized in that In step S2, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

6. The preparation method according to claim 1, characterized in that The specific steps of step S3 are: preparing an L-methionine solution with a volume of 90-110 mL and a solution concentration of 0.005-1.0 mol / L, adding an equimolar amount of NaOH solid for deprotonation, stirring at room temperature for 10-60 minutes, and then adjusting the pH value of the stirred solution to 9-13 using NaOH solution.

7. The preparation method according to claim 1, characterized in that In step S3, the product C is weighed to 0.1-4 g and stirred for 10-48 h.

8. The preparation method according to claim 1, characterized in that In step S3, the centrifuge speed is set to 5000-11000 r / min, and the centrifugation time is set to 2-10 min.

9. The preparation method according to claim 1, characterized in that In step S3, drying is performed in an oven, wherein the drying temperature is 40-110° C. and the drying time is 12-72 h.

10. An environmentally friendly corrosion inhibitor intercalated calcium aluminum layered double hydroxide, characterized in that The method is described in any one of claims 1 to 9.

Images