Method for preparing a corrosion protection film of a magnesium-iron layered double hydroxide grown in situ on a steel surface

Abstract

The application discloses a preparation method of a magnesium-iron layered double hydroxide anticorrosion film grown in situ on a steel surface and belongs to the field of metal corrosion protection. 3+ The active magnesium oxide serves as an Mg 2+ ion source, and the magnesium-iron layered double metal hydroxide with hydroxyl ion intercalation is prepared in situ on the surface of the steel material by using a hydrothermal method. The preparation method is simple in process and easy to operate, involves few raw materials in the synthesis process, and can control the morphology and thickness of the film by controlling the Mg 2+ concentration, reaction temperature, reaction pH and reaction time in the synthesis process. The grown magnesium-iron layered double metal hydroxide film has a uniform and dense microstructure and has a protection and corrosion inhibition effect on the steel base material.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion protection, specifically a method for preparing a magnesium-iron layered double hydroxide anti-corrosion film grown in situ on a steel surface. Background Technology

[0002] Steel is an important engineering structural material, inexpensive, with high mechanical strength and good mechanical properties, and is widely used in the construction of marine infrastructure. However, marine corrosion is a real and serious problem, affecting not only the durability of structures but also causing significant economic losses. Common protection methods include using special steels, electrochemical cathodic protection, impressed current methods, and coating protection. Among these, surface coatings are widely used due to their good protective effect, low cost, and simple application. While conventional anti-corrosion coatings have advantages such as versatility and high efficiency, they also suffer from drawbacks such as coating aging and surface cracking, increasing the economic cost of monitoring and maintaining engineering structures. Therefore, intelligent and multifunctional anti-corrosion coating materials have promising application prospects.

[0003] Layered double hydroxides (LDHs), as a type of hydrotalcite compound, have the basic structural formula [M... 1-x 2+ M x 3+ (OH)2] X+ (A x / n n- )·mH2O, where M 2+ and M 3+ The metal ions with positive oxidation states of +2 and +3 are respectively, A n － These are the anions between the layers, where n is the charge of the interlayer anion. Due to the divalent metal ion M... 2+ It can be affected by trivalent metal ions M 3+The substitution process results in the overall electropositive nature of the hydroxide layers, allowing negatively charged anions to intercalate between the layers and balance the excess positive charge. Because different anions bind differently to the layers, LDH possesses unique ion exchange properties. This allows LDH to not only form a dense protective film on the metal substrate surface through physical barriers to block corrosive ions, but also to actively adsorb chloride ions from the environment by adjusting the anions. Methods for preparing LDH coatings on metal surfaces include in-situ hydrothermal methods, solvent evaporation methods, colloidal deposition techniques, spin coating methods, and layer-by-layer self-assembly techniques. In-situ hydrothermal methods require metal cations to dissolve from the substrate and participate in the construction of the LDH film. Compared to other methods, in-situ hydrothermal methods yield films with stronger adhesion to the substrate and allow for adjustment of the LDH film's microstructure by modifying preparation parameters.

[0004] Currently, LDH (Lithium Hydrogen Deionization) has been used as an anti-corrosion film to improve the corrosion resistance of magnesium-aluminum alloys. It achieves superhydrophobic and self-healing properties by adjusting anions. However, research on the growth of LDH films on steel surfaces is limited. The main research methods include: deposition methods, which synthesize LDH through co-precipitation and then immerse the substrate in an LDH solution for hydrothermal growth; electrodeposition methods, which first prepare an iron oxide film on a carbon steel surface using constant current electrodeposition technology and then prepare an LDH film through hydrothermal treatment; and in-situ hydrothermal methods, which provide Fe to the iron substrate. 3+ Adding divalent metal cations and an alkaline source facilitates hydrothermal reactions. Some researchers have used magnesium sulfate as the divalent metal ion source, urea as the alkaline source, and sodium carbonate and dilute nitric acid as pH adjusters to grow carbonate-intercalated Mg-Fe LDH using an in-situ hydrothermal method. However, according to the anion exchange sequence of LDH, carbonate has the strongest binding force in LDH, meaning that carbonate is difficult to displace through other ions. Therefore, it is difficult to use it as a precursor for LDH film functionalization by intercalating other functional anions to achieve film functionalization. Summary of the Invention

[0005] This invention aims to synthesize functional iron-based matrix double hydroxide film precursors, overcoming the limitation of existing research using urea as an alkali source to intercalate carbonate LDH films, which suffers from limited effectiveness. It is the first to propose using an iron matrix to provide Fe... 3+ A method for preparing a magnesium-iron layered double hydroxide anti-corrosion film grown in situ on the steel surface is presented, and the effects of divalent cation solution concentration, reaction temperature, reaction pH and reaction time on the microstructure and anti-corrosion performance of the magnesium-iron layered double hydroxide film during the growth process are further pointed out.

[0006] This invention proposes a method for preparing an in-situ grown magnesium-iron layered bimetallic hydroxide anti-corrosion film on a steel surface, which is carried out according to the following steps:

[0007] Step 1: Polish the steel to a mirror finish on sandpaper, and clean away any iron filings from the polishing process.

[0008] Step 2: Pickle the steel treated in Step 1, then clean and dry it;

[0009] Step 3: Place the steel treated in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.02mol / L-0.20mol / L, and control the pH of the solution to 7-13.

[0010] Step 4: Heat the high-pressure reactor from Step 3 to 80-140℃ and continue the reaction for 4-16 hours;

[0011] Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a magnesium-iron layered bimetallic hydroxide Mg-Fe LDH anti-corrosion film.

[0012] The pickling described in step 2 involves using an acid solution with a pH < 2 to pickle the steel surface to ensure that the steel surface has a uniform roughness.

[0013] The magnesium oxide mentioned in step 3 is light, active magnesium oxide.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. The reaction process is provided by the steel substrate with Fe 3+ The ion source does not require the introduction of an additional trivalent cation metal source, and the synthesis process is simple, easy to operate, and involves few raw materials.

[0016] 2. Mg can be controlled 2+ Concentration, reaction temperature, reaction pH, and reaction time control the morphology of the film.

[0017] 3. The resulting magnesium-Fe LDH layered bimetallic hydroxide film has a uniform and dense morphology and excellent corrosion protection. Attached Figure Description

[0018] Figure 1 Scanning electron microscopy (SEM) results of Mg-Fe LDH films grown on Q235 steel sheets under different magnesium oxide concentrations in Examples 1-7: (a1-a2) Example 1; (b1-b2) Example 2; (c1-c2) Example 3; (d1-d2) Example 4; (e1-e2) Example 5; (f1-f2) Example 6; (g1-g2) Example 7;

[0019] Figure 2 Electrochemical Nyquist plots of Mg-Fe LDH films grown on Q235 steel sheets in Examples 1-7 and Comparative Example 1 under different magnesium oxide concentrations in 3.5% NaCl solution;

[0020] Figure 3 Scanning electron microscopy (SEM) results of Mg-Fe LDH films grown on Q235 steel sheets under different reaction temperature conditions in Examples 8-11: (a1-a2) Example 8; (b1-b2) Example 9; (c1-c2) Example 10; (d1-d2) Example 11;

[0021] Figure 4 Electrochemical Nyquist plots of Mg-Fe LDH films grown on Q235 steel sheets in Examples 8-11 under different reaction temperature conditions in 3.5% NaCl solution;

[0022] Figure 5 Scanning electron microscopy (SEM) results of Mg-Fe LDH films grown on Q235 steel sheets under different reaction pH conditions in Examples 12-15: (a1-a2) Example 12; (b1-b2) Example 13; (c1-c2) Example 14; (d1-d2) Example 15;

[0023] Figure 6 Electrochemical Nyquist plots of Mg-Fe LDH films grown on Q235 steel sheets in Examples 12-15 under different reaction pH conditions in 3.5% NaCl solution;

[0024] Figure 7 Scanning electron microscopy results of Mg-Fe LDH films grown on Q235 steel sheets under different reaction time conditions in Examples 16-19: (a1-a2) Example 16; (b1-b2) Example 17; (c1-c2) Example 18; (d1-d2) Example 19;

[0025] Figure 8 Electrochemical Nyquist plots of Mg-Fe LDH films grown on Q235 steel sheets in Examples 16-19 under different reaction time conditions in 3.5% NaCl solution. Detailed Implementation

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

[0027] Example 1

[0028] This embodiment is an example of the method for preparing a magnesium-iron layered double hydroxide anti-corrosion film grown in situ on a steel surface according to the present invention, including the following steps:

[0029] Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process.

[0030] Step 2: Pickle the steel treated in Step 1, then clean and dry it.

[0031] Step 3: Place the steel treated in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.02 mol / L, and control the pH of the solution to 11.

[0032] Step 4: Place the high-pressure reactor from Step 3 into an oven at 120°C and react for 8 hours.

[0033] Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a Mg-Fe LDH anti-corrosion film.

[0034] Example 2

[0035] This embodiment is another example of the method for preparing a magnesium-iron layered double hydroxide anti-corrosion film grown in situ on a steel surface according to the present invention, the difference being the concentration of the active magnesium oxide solution.

[0036] In Example 1, step 3, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.04 mol / L", while all other steps remain the same.

[0037] Example 3

[0038] The difference between this embodiment and Example 1 lies in the concentration of the active magnesium oxide solution. In step 3 of Example 1, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.06 mol / L", while the other steps remain the same.

[0039] Example 4

[0040] The difference between this embodiment and Example 1 lies in the concentration of the active magnesium oxide solution. In step 3 of Example 1, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.08 mol / L", while the other steps remain the same.

[0041] Example 5

[0042] The difference between this embodiment and Example 1 lies in the concentration of the active magnesium oxide solution. In step 3 of Example 1, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.10 mol / L", while the other steps remain the same.

[0043] Example 6

[0044] The difference between this embodiment and Example 1 lies in the concentration of the active magnesium oxide solution. In step 3 of Example 1, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.15 mol / L", while the other steps remain the same.

[0045] Example 7

[0046] The difference between this embodiment and Example 1 lies in the concentration of the active magnesium oxide solution. In step 3 of Example 1, "pour in an active magnesium oxide solution with a concentration of 0.02 mol / L" is changed to "pour in an active magnesium oxide solution with a concentration of 0.20 mol / L", while the other steps remain the same.

[0047] Example 8

[0048] Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process.

[0049] Step 2: Pickle the steel treated in Step 1, then clean and dry it.

[0050] Step 3: Place the steel treated in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.10 mol / L, and control the pH of the solution to 11.

[0051] Step 4: Place the high-pressure reactor from Step 3 into an oven at 80°C and react for 8 hours.

[0052] Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a Mg-Fe LDH anti-corrosion film.

[0053] Example 9

[0054] The difference between this embodiment and Embodiment 8 lies in the reaction temperature. In Embodiment 8, step 4, "placing the high-pressure reactor from step 3 in an oven at 80°C for 8 hours" is changed to "placing the high-pressure reactor from step 3 in an oven at 100°C for 8 hours". All other steps remain the same.

[0055] Example 10

[0056] The difference between this embodiment and Embodiment 8 lies in the reaction temperature. In Embodiment 8, step 4, "place the high-pressure reactor from step 3 into an oven at 80°C for 8 hours" is modified to "place the high-pressure reactor from step 3 into an oven at 120°C for 8 hours". All other steps remain the same.

[0057] Example 11

[0058] The difference between this embodiment and Embodiment 8 lies in the reaction temperature. In Embodiment 8, step 4, "placing the high-pressure reactor from step 3 in an oven at 80°C for 8 hours" is changed to "placing the high-pressure reactor from step 3 in an oven at 140°C for 8 hours". All other steps remain the same.

[0059] Example 12

[0060] Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process.

[0061] Step 2: Pickle the steel treated in Step 1, then clean and dry it.

[0062] Step 3: Place the steel treated in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.10 mol / L, and control the pH of the solution to 7.

[0063] Step 4: Place the high-pressure reactor from Step 3 into an oven at 120°C and react for 8 hours.

[0064] Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a Mg-Fe LDH anti-corrosion film.

[0065] Example 13

[0066] The difference between this embodiment and Example 12 lies in the reaction pH. In step 3 of Example 12, "control the solution pH = 7" is changed to "control the solution pH = 9", while the other steps remain the same.

[0067] Example 14

[0068] The difference between this embodiment and Example 12 lies in the reaction pH. In step 3 of Example 12, "control the solution pH = 7" is changed to "control the solution pH = 11", while the other steps remain the same.

[0069] Example 15

[0070] The difference between this embodiment and Example 12 lies in the reaction pH. In step 3 of Example 12, "control the solution pH = 7" is changed to "control the solution pH = 13", while the other steps remain the same.

[0071] Example 16

[0072] Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process.

[0073] Step 2: Pickle the steel treated in Step 1, then clean and dry it.

[0074] Step 3: Place the steel treated in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.10 mol / L, and control the pH of the solution to 11.

[0075] Step 4: Place the high-pressure reactor from Step 3 into an oven at 120°C and react for 4 hours.

[0076] Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a Mg-Fe LDH anti-corrosion film.

[0077] Example 17

[0078] The difference between this embodiment and Embodiment 16 lies in the reaction time. In Embodiment 16, step 4, "placing the high-pressure reactor from step 3 in an oven at 120°C for 4 hours" is changed to "placing the high-pressure reactor from step 3 in an oven at 120°C for 8 hours". All other steps remain the same.

[0079] Example 18

[0080] The difference between this embodiment and Embodiment 16 lies in the reaction time. In Embodiment 16, step 4, "place the high-pressure reactor from step 3 in an oven at 120°C for 4 hours" is modified to "place the high-pressure reactor from step 3 in an oven at 120°C for 12 hours". All other steps remain the same.

[0081] Example 19

[0082] The difference between this embodiment and Embodiment 16 lies in the reaction time. In Embodiment 16, step 4, "placing the high-pressure reactor from step 3 in an oven at 120°C for 4 hours" is changed to "placing the high-pressure reactor from step 3 in an oven at 120°C for 16 hours". All other steps remain the same.

[0083] Comparative Example 1

[0084] Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process.

[0085] Step 2: Pickle the steel treated in Step 1, then clean and dry it.

[0086] Performance testing:

[0087] (1) The microstructure of the Mg-Fe LDH film surface was observed using a field emission scanning electron microscope (FEI Quattro S, USA, Czech Republic).

[0088] (2) The electrochemical impedance spectroscopy of Mg-Fe LDH thin films in 3.5% NaCl solution was determined using a CS3004 electrochemical workstation. A 15mm × 15mm Q235 steel sheet was used as the working electrode, a saturated calomel electrode as the reference electrode, and a platinum electrode as the auxiliary electrode.

[0089] The specific experimental results are as follows:

[0090] (1) Field emission scanning electron microscope, such as Figure 1 The results showed that when the magnesium oxide concentration was 0.02-0.2 mol / L, the reaction temperature was 80-140℃, the reaction pH was 7-13, and the reaction time was 4-16 h, a lamellar structure of LDH was observed on the surface of Q235 steel. With increasing magnesium oxide concentration, the porosity of the film on the steel surface gradually decreased, and the density increased. The structure was most dense when the magnesium oxide concentration was 0.1 mol / L; further increases in concentration did not significantly change the density. With increasing reaction temperature, reaction pH, and reaction time, the film density first increased and then decreased. At a temperature of 120℃, reaction pH = 11, and reaction time of 8 h, the film surface had the fewest pores and the best structural density. As the reaction process continued to increase the temperature, pH, and reaction time, cracks began to appear in the LDH film.

[0091] (2) Electrochemical results are as follows Figure 2 As shown in Figures 4, 6, and 8, the results indicate that the impedance arc radius of the sample coated with the LDH film is significantly larger than that of the bare carbon steel sample, demonstrating the significant corrosion resistance of the LDH film. The corrosion resistance gradually improves with increasing magnesium oxide concentration, reaching a stable value at 0.1 mol / L. With increasing reaction temperature, the impedance arc radius first increases and then decreases, reaching its maximum at 120℃. With increasing reaction pH, the impedance arc radius first increases and then decreases, reaching its maximum at pH = 11. With increasing reaction time, the impedance arc radius first increases and then decreases, reaching its maximum at a reaction time of 8 h. Therefore, the film exhibits the best corrosion resistance when the magnesium oxide concentration is 0.10 mol / L, the reaction temperature is 120℃, the reaction solution pH is 11, and the reaction time is 8 h.

Claims

1. A method for preparing an in-situ grown magnesium-iron layered bimetallic hydroxide anti-corrosion film on a steel surface, characterized in that, Prepare according to the following steps: Step 1: Polish the Q235 steel sheet to a mirror finish on sandpaper, and clean it to remove iron filings from the polishing process; Step 2: Pickle the Q235 steel sheet processed in Step 1, then clean and dry it; The pickling process involves using an acid solution with a pH < 2 to pickle the surface of Q235 steel sheets to ensure that the steel surface has a uniform roughness. Step 3: Place the Q235 steel sheet processed in Step 2 into a high-pressure reactor, pour in an active magnesium oxide solution with a concentration of 0.1 mol / L, and control the pH of the solution to 11. Step 4: Heat the high-pressure reactor from Step 3 to 120°C and continue the reaction for 8 hours; Step 5: Cool the high-pressure reactor from Step 4 to room temperature, clean the sample and dry it to obtain a magnesium-iron layered bimetallic hydroxide Mg-Fe LDH anti-corrosion film.

2. The method for preparing an in-situ grown magnesium-iron layered bimetallic hydroxide anti-corrosion film on a steel surface according to claim 1, characterized in that, The magnesium oxide mentioned in step 3 is light, active magnesium oxide.

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