A magnetic copper-substituted hydroxyapatite metal anticorrosive pigment and preparation method thereof

Abstract

The advantages of this solution mainly lie in the design of a magnetic copper-substituted hydroxyapatite metal anti-corrosion pigment and its preparation method to solve the problems of low efficiency and poor anti-corrosion performance of hydroxyapatite in the field of metal anti-corrosion materials. By changing the constant composition growth kinetics of hydroxyapatite to obtain Cu-HAP with different defect structures, the defect oxygen vacancies and paramagnetic radical spin polarizations within the structure optimize the spin-charge transfer kinetics at the interface, enabling the Cu 3d spin polarization to rapidly exchange spin electrons with the adsorbed oxygen to promote the capture of oxygen in the corrosion reaction and inhibiting the occurrence of the corrosion reaction where oxygen reaches the iron matrix. In addition, the HAP molecules can undergo ion exchange with Cl<supgt;‑< / supgt; ions in the corrosion environment to form a stable chlorapatite protective layer, further enhancing its barrier performance. Therefore, a strategy for preparing a magnetic copper-substituted hydroxyapatite anti-corrosion pigment is proposed, and the present invention solves the problem of only being able to improve the shielding performance singly at present.

Description

Technical Field

[0001] The invention relates to the field of hydroxyapatite in metal anticorrosion materials, and in particular to a magnetic copper-substituted hydroxyapatite metal anticorrosion pigment and a preparation method thereof. Background Art

[0002] With the further development and utilization of marine resources, the use of steel and the severity of the corrosive environment have increased, making the corrosion protection of metal materials more important. Coating technology is the most widely used corrosion protection strategy because of its simple but excellent shielding performance, which can effectively prevent the direct contact between corrosive media and metal surfaces. Phosphates are considered to be the most effective corrosion inhibitors, among which low-cost hydroxyapatite (HAP) has also been widely studied and applied in the field of biopreservation in recent years. The completely ideal periodic crystal structure of HAP does not exist, because during the crystallization process, it will be affected by the synthesis conditions, and vacancies are easily formed in the lattice, resulting in structural defects, among which oxygen vacancies and calcium vacancies are the most common. Therefore, the special properties caused by the structural design of hydroxyapatite have attracted widespread attention. Such as magnetism, corrosion resistance, photoluminescence properties, etc.

[0003] Studies have shown that hydroxyapatite is often incorporated into a polymer matrix based on its excellent anti-corrosion properties, which can provide a tortuous penetration path for corrosive media and improve the corrosion resistance of traditional organic coatings by improving the barrier properties of the coating. In addition, thanks to the low toxicity and environmental excellence of HAP, this material is expected to be used in the field of marine corrosion protection. Research on the anti-corrosion mechanism of HAP has focused on its excellent passivation film shielding effect. Due to its high structural flexibility, HAP allows deformation of various structures, resulting in different effects. For example, the formation of point defects in HAP after ion substitution will change its electronic configuration, and the presence of paramagnetic free radicals will affect the performance of HAP. Therefore, it is particularly important to explore the contribution of structural defects in HAP to anti-corrosion performance. At the same time, expanding the application of HAP in the field of steel corrosion protection is also a topic worthy of study. Summary of the invention

[0004] The present invention aims to solve the problem that the current HAP anticorrosive pigment can only improve the shielding performance in the field of metal corrosion protection, and the problem that hydroxyapatite has low efficiency and poor anticorrosion performance in the field of steel anticorrosion materials, and at the same time explores the problem of the influence of paramagnetic free radicals and lattice defects on the performance of HAP.

[0005] In order to solve the above problems, the present invention is achieved through the following technical solutions:

[0006] A method for preparing a magnetic copper-substituted hydroxyapatite metal anticorrosive pigment comprises the following steps:

[0007] The solvent, calcium source, phosphorus source and Cu(NO3)2•3H2O are mixed, and then a regulator is added to adjust the pH to alkaline, and a hydrothermal reaction is carried out under high pressure. The obtained hydroxyapatite precipitate is filtered and dried to obtain a magnetic copper-substituted hydroxyapatite metal anticorrosive pigment.

[0008] The regulator is one or more of ammonia water, hydrazine hydrate, ethylenediamine and sodium hydroxide.

[0009] The pH is adjusted to alkaline pH 8-10.

[0010] The solvent is one of water, EDTA-2Na aqueous solution, citric acid aqueous solution and urea aqueous solution.

[0011] In terms of molar ratio, the calcium source:phosphorus source:Cu(NO3)2•3H2O=0.01:0.006:0.0008~0.002.

[0012] The calcium source is one or more of CaCl2, Ca(NO3)2•4H2O, CaCO3 and Ca(OH)2.

[0013] The phosphorus source is one or more of (NH4)2HPO4, Na2HPO4, H3PO4 and P2O5.

[0014] The high pressure has a pressure range of 10MPa to 30MPa.

[0015] The temperature of the hydrothermal reaction is 120-180° C., and the time of the hydrothermal reaction is 6-24 h.

[0016] The concentration of the solvent is 0-0.03 mol / L.

[0017] Preferably, the drying temperature is 100-180° C., and the drying time is 6-12 hours.

[0018] The preparation method of the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment of the present invention is as follows: first, a solvent is taken in a beaker, a calcium source, a phosphorus source and Cu(NO3)2•3H2O are added to the solvent, the pH is adjusted with a regulator after dissolution, and the final solution is placed in a high-pressure reactor for hydrothermal reaction to precipitate hydroxyapatite. The particles are separated from the solution by filtering through a filter, and after drying, a hydroxyapatite anticorrosive material (Cu-HAP) in which a paramagnetic free radical Cu is introduced into HAP is obtained.

[0019] The Cu-HAP pigment prepared by the present invention is respectively mixed with commercial epoxy resin ((C 11 H 12O3)N, HL-001) were mixed, and the mass ratio of Cu-HAP pigment to epoxy resin was 1:8~15, and magnetic stirring was performed to form a homogeneous suspension. Then 2-3g of polyamide curing agent (C5H 11 N3OR) in the suspension, and continue stirring. Finally, the coating is evenly coated on the smooth and clean iron substrate surface at room temperature by a one-step pulling method to form an anti-corrosion material coating with a thickness of 35-40 μm. The anti-corrosion coating is dried and cured for one week under ventilation at room temperature.

[0020] The anti-corrosion performance test method of the copper-substituted hydroxyapatite / epoxy resin anti-corrosion coating obtained by the present invention is: electrochemical impedance spectroscopy (EIS, Zahner-Electrik IM6e) and polarization test (AutoLab G1). The low-carbon steel plate covered with the anti-corrosion coating was immersed in a 3.5 wt% sodium chloride (NaCl) solution for different times (4h, 24h, 48h and 72h). The height of the coating immersed in the salt water was about 2 cm. The frequency range of the electrochemical test was 0.1 Hz-100 kHz. AutoLab G1 performed polarization tests from -0.30V to -1.20V at a scanning rate of 50 mV / s. The test system is a three-electrode system, with a low-carbon steel plate coated with Cu-HAP anti-corrosion coating as a working electrode, a saturated calomel electrode as a reference electrode, and a platinum sheet electrode (15mm×15mm×0.1mm, area of ​​2.25cm) as a counter electrode. 2 ). The impedance data were fitted and calculated by ZSimDemo software. At least three parallel EIS measurements were performed, and it was observed that the results had good repeatability.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The advantages of this scheme mainly lie in the design of a magnetic copper-substituted hydroxyapatite metal anticorrosion pigment and its preparation method, which solves the problem that the current HAP anticorrosion pigment can only improve the shielding performance in the field of metal anticorrosion, as well as the low efficiency and poor anticorrosion performance of hydroxyapatite in the field of steel anticorrosion materials. At the same time, it explores the effect of paramagnetic free radicals on the performance of HAP.

[0023] 2. This scheme changes the constant composition growth dynamics of chloroapatite by adding different buffers, regulates the crystal structure, and obtains hexagonal HAP with a higher content of hydroxyl groups. When chloride ions enter the coating, they will be transmitted along the hydroxyl channel and ion exchange will occur in the channel to form more stable chloroapatite, thereby enhancing the shielding performance of the coating.

[0024] 3. The presence of defective oxygen vacancies and paramagnetic radical spin polarization in the Cu-HAP structure optimize the spin charge transfer dynamics of the interface, so that the Cu 3d spin polarization can quickly exchange spin electrons with the adsorbed oxygen to promote the capture of oxygen in the corrosion reaction, inhibiting the occurrence of corrosion reactions in which oxygen reaches the iron matrix. The formation of the chlorapatite passivation film and the improvement of its compatibility and dispersibility in the epoxy matrix give it excellent anti-corrosion properties.

[0025] 4. A method for preparing a magnetic copper-substituted hydroxyapatite anticorrosive pigment is proposed. The present invention helps to solve the problem that currently only the shielding performance can be improved.

[0026] 5. The present invention prepares a copper-substituted hydroxyapatite anticorrosive pigment having a point defect structure and spin polarization effect generated by the introduction of paramagnetic free radicals, namely, Cu 3d spin polarization effect, which is beneficial to improving the anticorrosion performance of the material.

[0027] 6. Copper-substituted hydroxyapatite anticorrosive pigment has a point defect structure, which effectively inhibits the transfer of oxygen and has a certain corrosion inhibitory effect.

[0028] 7. The combined effect of the spin polarization and defective oxygen vacancies of copper-substituted hydroxyapatite pigments can hinder the corrosion reaction between corrosive ions and metal surfaces, thereby exhibiting extremely excellent anti-corrosion properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 (a) is a SEM morphology image of Cu-HAP#1 of Example 1;

[0030] Figure 1 (b) is a SEM morphology image of Cu-HAP#2 of Example 2;

[0031] Figure 1 (c) is a SEM morphology image of Cu-HAP#3 of Example 3;

[0032] Figure 1 (d) is a SEM morphology image of Cu-HAP#4 of Example 4;

[0033] Figure 2 is the Bode plot of the iron block coated with the Cu-HAP coating in Examples 1 to 4 immersed in a 3.5wt% NaCl solution for 72 h;

[0034] Figure 3 It is the Nyquist plot of the iron block coated with Cu-HAP coating in Examples 1 to 4 immersed in 3.5wt% NaCl solution for 72 h. DETAILED DESCRIPTION

[0035] The medicines in the following examples, epoxy resin (C 11 H 12 O3)N, model HL-001; purchased from Xinletian brand (Shanghai Caoying E-commerce Co., Ltd.); polyamide curing agent is C5H 11 N3OR, model HL-001, was purchased from Xinletian brand (Shanghai Caoying E-Commerce Co., Ltd.).

[0036] Example 1

[0037] First, take 100 mL of 0.01 mol / L EDTA-2Na (disodium ethylenediaminetetraacetate) aqueous solution in a beaker, add 0.010 mol CaCl2, 0.002 mol Cu(NO3)2•3H2O and 0.006 mol Na2HPO4 to the EDTA-2Na solution, stir and mix thoroughly, and then adjust the pH to 8 with hydrazine hydrate. The mixed solution is placed in a high-pressure reactor and heated to 120°C in an oven for hydrothermal reaction for 24 h to precipitate hydroxyapatite. The microparticles are separated by filtration and dried at 180°C for 6 h to obtain a thin-flaked magnetic copper-substituted hydroxyapatite anticorrosive pigment (Cu-HAP#1), as shown in the SEM image. Figure 1 (a).

[0038] Example 2

[0039] First, take 100 mL of 0.02 mol / L citric acid aqueous solution in a beaker, add 0.010 mol CaCO3, 0.0015 mol Cu(NO3)2•3H2O and 0.006 mol P2O5 to the citric acid solution, stir and mix thoroughly, and then adjust the pH to 8.5 with ammonia water. The mixed solution is placed in a high-pressure reactor and heated to 140°C in an oven for hydrothermal reaction for 20 hours to precipitate hydroxyapatite. The microparticles are separated by filtration and dried at 160°C for 8 hours to obtain a needle-shaped magnetic copper-substituted hydroxyapatite anticorrosive pigment (Cu-HAP#2), as shown in the SEM image. Figure 1 (b).

[0040] Example 3

[0041] First, take 100 mL of 0.03 mol / L CO(NH2)2 (urea) aqueous solution in a beaker, add 0.010 mol Ca(NO3)2•4H2O, 0.0010 mol Cu(NO3)2•3H2O and 0.006 mol (NH4)2HPO4 to the urea solution, stir and mix thoroughly, and then adjust the pH to 9 with ethylenediamine. The mixed solution is placed in a high-pressure reactor and heated to 160°C in an oven for hydrothermal reaction for 12 h to precipitate hydroxyapatite. The microparticles are separated by filtration and dried at 120°C for 10 h to obtain a magnetic copper-substituted flake hydroxyapatite anticorrosive pigment (Cu-HAP#3), SEM image shown in Figure 2. Figure 1 (c).

[0042] Example 4

[0043] First, take 100 mL of pure water in a beaker, add 0.010 mol Ca(OH)2, 0.0008 mol Cu(NO3)2•3H2O and 0.006 mol H3PO4, stir and mix thoroughly, and then adjust the pH to 10 with sodium hydroxide. The mixed solution is placed in a high-pressure reactor and heated to 180°C in an oven for hydrothermal reaction for 6 h to precipitate hydroxyapatite. The microparticles are separated by filtration and dried at 100°C for 12 h to obtain a spherical needle-shaped magnetic copper-substituted hydroxyapatite anticorrosive pigment (Cu-HAP#4), SEM image is shown in Figure 1 (d).

[0044] Example 5

[0045] The iron blocks coated with Cu-HAP#1~Cu-HAP#4 coating materials were immersed in 3.5wt%NaCl solution for 72 h, and the Bode and Nyquist plots were shown in Fig. Figure 2 and Figure 3 . Figure 3 In the figure, Z is the electrochemical impedance, which is a vector, Z′ is the real part, and Z″ is the imaginary part. The real part is the horizontal axis and the imaginary part is the vertical axis. The plotted graph is the Nyquist diagram.

[0046] The surface morphology of Cu-HAP was studied by SEM. Figure 1 As shown. The sample morphology is uniform. The addition of different buffers will affect the constant composition growth dynamics of hydroxyapatite, causing lattice defects and leading to changes in the lattice parameters of HAP. The nanosheet structure presented in Example 1 is more likely to form pores on the surface, providing abundant electroactive sites and promoting spin-polarized electron exchange with oxygen. EIS characterization obtained the Nyquist and Bode plots of the coating, as shown Figure 2 and Figure 3As shown, the Cu-HAP synthesized by low-temperature hydrothermal method in Example 1 has the highest impedance value and the best anti-corrosion performance. The hydroxyapatite synthesized by the present invention tends to be hexagonal and has a higher content of hydroxyl groups. When chloride ions enter the coating, they will be transmitted along the hydroxyl channel and ion exchange will occur in the channel to form more stable chlorapatite, thereby enhancing the shielding performance of the coating.

Claims

1. A method for preparing a magnetic copper-substituted hydroxyapatite metal anticorrosive pigment, characterized in that: The following steps are involved: The solvent, calcium source, phosphorus source and Cu(NO3)2•3H2O are mixed, and then a regulator is added to adjust the pH to alkaline, and a hydrothermal reaction is carried out under high pressure. The obtained hydroxyapatite precipitate is filtered and dried to obtain a magnetic copper-substituted hydroxyapatite metal anticorrosive pigment. The calcium source is one or more of CaCl2, Ca(NO3)2•4H2O, CaCO3 and Ca(OH)2. The regulator is hydrazine hydrate, The solvent is EDTA-2Na aqueous solution.

2. The method for preparing the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment according to claim 1, characterized in that: The pH is adjusted to 8-10.

3. The method for preparing the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment according to claim 1, characterized in that: In terms of molar ratio, the calcium source:phosphorus source:Cu(NO3)2•3H2O=0.01:0.006:0.0008~0.

002.

4. The method for preparing the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment according to claim 1, characterized in that: The phosphorus source is one or more of (NH4)2HPO4, Na2HPO4, H3PO4 and P2O5.

5. The method for preparing the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment according to claim 1, characterized in that: The high pressure has a pressure range of 10MPa to 30MPa.

6. The method for preparing the magnetic copper-substituted hydroxyapatite metal anticorrosive pigment according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 120-180° C., and the time of the hydrothermal reaction is 6-24 hours.

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