Graphene nano composite material, modified anticorrosive paint thereof and preparation method of modified anticorrosive paint

Abstract

The invention discloses a graphene nano composite material, a modified anti-corrosion coating thereof and a preparation method of the modified anti-corrosion coating. The preparation method comprises the following steps: preparing a reduced graphene oxide / iron oxide / 1-hydroxyethyl-1, 1-diphosphonic acid (rGO-Fe2O3-HEDP) nano composite material by a hydrothermal method, adding the nano composite material as a filler into a coating to prepare the anticorrosive paint, and under the synergistic effect of the three components, providing excellent physical shielding and conductive connection among zinc particles for the coating and increasing the activity of zinc. Compared with a pure zinc coating, the epoxy zinc-rich anticorrosive paint containing the nano composite material is coated on a steel base material, and the coating has more excellent corrosion resistance due to strong physical shielding effect, cathode protection effect and activity regulation and self-repairing effect of an active factor 1-hydroxyethyl-1, 1-diphosphonic acid.

Description

Technical Field

[0001] The invention belongs to the field of nano materials and metal corrosion protection, and particularly relates to a graphene nano composite material and application thereof in a zinc-rich coating. Background Art

[0002] Zinc-rich epoxy primer is one of the traditional heavy-duty anti-corrosion coatings. However, the addition of high levels of zinc powder in the resin matrix can easily lead to many problems, such as zinc corrosion products encapsulating zinc particles and blocking the conductive path, poor film density, and low zinc utilization. Graphene has superb conductivity, high specific surface area, chemical stability, and thermal stability. Its sheet-like structure is hydrophobic and impermeable, and can effectively block the passage of corrosive media (water, oxygen, etc.). These characteristics make it very valuable in the field of metal corrosion protection. However, the strong van der Waals force and π-π conjugation between multi-layer stacked graphene layers make graphene difficult to disperse and easy to precipitate in solvents, which leads to a decrease in corrosion resistance. In addition, high conductivity can also promote metal corrosion. Graphene oxide contains oxygen-containing groups such as carboxyl, hydroxyl and epoxy groups, which are beneficial for modification on the carbon layer and can solve the problem of graphene agglomeration [Luo Jian, Wang Jihu, Wen Shaoguo, et al. Research progress of graphene in anti-corrosion coatings [J]. Coatings Industry, 2017, 47(11): 69-76.]. Therefore, different methods can be designed to modify graphene to improve its corrosion resistance in anti-corrosion coatings [Li Wenguan, Zhang Ruizhi, Luo Fangwei, et al. Research progress on the application of modified graphene-based fillers in anti-corrosion coatings. Coatings Industry, 2020, 50(4): 81-87.]. Inorganic nanomaterials can be used as fillers in anti-corrosion coatings to increase the shielding effect of the coating and enhance its anti-corrosion ability [Li Shaoxiang, Xue Shouwei, Wang Jiaping, et al. Preparation of graphene oxide / titanium dioxide composites and their effects on the corrosion resistance of epoxy resin coatings. Journal of Qingdao University of Science and Technology (Natural Science Edition), 2018, 39(4): 74-79.]. However, the above strategies still cannot solve the bottleneck problem of low zinc utilization rate caused by "dead zinc" produced by zinc-rich coating. Summary of the invention

[0003] The purpose of the present invention is to provide a graphene nanocomposite material, a preparation method and application thereof in a zinc-rich coating.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a graphene nanocomposite material, comprising the following steps:

[0006] The first step is to add ferrous chloride solution to the graphene oxide dispersion, ultrasonically disperse until the mixture is uniform, then adjust the pH value of the dispersion to 9-12, and then perform a hydrothermal reaction and centrifuge and wash to obtain an iron oxide / reduced graphene oxide composite material;

[0007] Step 2: Add the active factor 1-hydroxyethyl-1,1-diphosphonic acid to the iron oxide / reduced graphene oxide composite material, stir evenly, react at 80°C for 2h, and freeze-dry to obtain the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid composite material, i.e., graphene nanocomposite material.

[0008] Preferably, the ratio of ferrous chloride to graphene oxide is 100 mmol:2 g.

[0009] Preferably, the hydrothermal reaction temperature is 180°C and the reaction time is 10 h.

[0010] Preferably, the mass ratio of graphene oxide to 1-hydroxyethyl-1,1-diphosphonic acid is (1-4):1, preferably 1:1.

[0011] In a second aspect, the present invention provides a graphene nanocomposite material prepared by the method described in the first aspect.

[0012] In a third aspect, the present invention provides a modified anti-corrosion coating, which at least includes an additive, an epoxy resin, zinc powder, and a curing agent, wherein the additive is a graphene nanocomposite material prepared by the method described in the first aspect.

[0013] Preferably, the zinc powder is spherical zinc powder particles with a particle size of 5-10 μm.

[0014] Preferably, the solid content of the additive in the modified anti-corrosion coating is 0.5% to 5%.

[0015] Preferably, the solid content of zinc powder in the modified anti-corrosion coating is 40% to 80%.

[0016] In a fourth aspect, the present invention provides a modified anti-corrosion coating, which is formed by coating the modified anti-corrosion coating described in the third aspect on a substrate.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] The two-dimensional nanostructure of the graphene nanocomposite prepared by the present invention effectively increases the impermeability and physical shielding effect of the coating; at the same time, nano iron oxide grows in situ on the reduced graphene oxide, regulates the electrical properties of the composite material, inhibits the corrosion-promoting effect of graphene, and increases the conductive path of zinc powder; the active factor 1-hydroxyethyl-1,1-diphosphonic acid in the composite material has an active regulation effect, and the strong bonding effect with zinc ions is greater than the reaction with hydroxide, which increases the activity of zinc, effectively improves the utilization rate of zinc, and prolongs the cathodic protection effect. The reactant fills the coating defects to promote self-repairing effect and improves the physical shielding effect of the coating. In the late stage of corrosion, the active factor complexes with iron ions to form an insoluble film on the surface of the metal substrate, further enhancing the physical shielding effect of the coating. The epoxy zinc-rich anticorrosion coating modified by the graphene nanocomposite synergistically shows excellent corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a transmission electron microscopy image of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite prepared in Example 1 at a size of 50 nm.

[0020] Figure 2 This is an infrared image of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material prepared in Example 1.

[0021] Figure 3 (a, b) are scanning electron micrographs of the coating prepared in Example 1 and the coating prepared in Comparative Example 1 after immersion for 30 days, respectively. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below through specific implementation examples, but the implementation examples do not limit the present invention in any form.

[0023] The two-dimensional nanostructure of the graphene nanocomposite prepared by the present invention effectively increases the impermeability and physical shielding effect of the coating; at the same time, nano iron oxide grows in situ on the reduced graphene oxide, regulates the electrical properties of the composite material, inhibits the corrosion-promoting effect of graphene, and increases the conductive path of zinc powder; the active factor 1-hydroxyethyl-1,1-diphosphonic acid in the composite material has an active regulation effect, and the strong bonding effect with zinc ions is greater than the reaction with hydroxide, which increases the activity of zinc, effectively improves the utilization rate of zinc, and prolongs the cathodic protection effect. The reactant fills the coating defects to promote self-repairing effect and improves the physical shielding effect of the coating. In the late stage of corrosion, the active factor complexes with iron ions to form an insoluble film on the surface of the metal substrate, further enhancing the physical shielding effect of the coating. The epoxy zinc-rich anticorrosion coating modified by the graphene nanocomposite synergistically shows excellent corrosion resistance.

[0024] Electrochemical performance test: The electrochemical test was carried out using the three-electrode system of the Donghua electrochemical workstation, with the coating sample as the working electrode and the test area of ​​1cm 2 , Ag / AgCl (0.197 V vs. SHE) was used as the reference electrode and platinum was used as the counter electrode. After reaching a stable open circuit potential, the frequency range of 10 5 ~10 -2 Hz EIS test. The polarization curve between -250mV and +250mV and OCP was measured, and the potential scanning rate was 0.6mV / s.

[0025] Embodiment 1:

[0026] (1) Take 20 ml of commercially available graphene oxide slurry (10 mg / ml) and disperse it in 70 ml of deionized water. Ultrasonic dispersion is performed for 30 min to obtain a graphene oxide dispersion for use. Take 10 mmol of FeCl 2 ·4H 2 O was dispersed in 10 ml of deionized water and stirred to obtain FeCl 2 Solution, prepare FeCl 2 The solution was added to the graphene oxide dispersion, stirred for 5 minutes, and then 10 ml of 15 wt% ammonia water was added to pH = 12. The prepared solution was then transferred to a hydrothermal reactor and reacted at 180° C. for 6 hours. After the reaction was completed, the iron oxide / reduced graphene oxide composite material was obtained by washing with water.

[0027] (2) 0.2 g of active factor 1-hydroxyethyl-1,1-diphosphonic acid was added to the above iron oxide / reduced graphene oxide composite material, stirred, reacted at 80° C. for 2 h, and then separated and dried to obtain an iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material, i.e., a graphene nanocomposite material. The transmission electron microscope image thereof is shown in FIG. Figure 1 As shown in Figure 1, granular iron oxide is uniformly grown in situ on reduced graphene oxide. Its infrared spectrum is shown in Figure 1. Figure 2 As shown in the figure, as shown by the dotted line, the phosphate in hydroxyethyl diphosphonic acid undergoes an obvious displacement in the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid composite material. This is because the phosphate is complexed with the metal ions on the surface of the metal oxide during the preparation process, and at the same time, it has a strong interaction force with the functional groups on the surface of the graphene oxide, resulting in a displacement of the vibration absorption peak, which proves the strong interaction between the components of the composite material.

[0028] (3) Based on the solid content of the coating being 100 wt%, the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material (additive) accounts for 0.5 wt%, the spherical zinc powder accounts for 60 wt%, the epoxy resin E51 accounts for 19.75 wt% and the polyamide 650 curing agent 650 accounts for 19.75 wt%. The specific process is as follows: 0.05 g of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material in (2) is dissolved in 1 g of xylene solution and ultrasonically stirred for 1 h. Then, 1.975 g of epoxy resin E51 and 6.0 g of zinc powder are added and stirred for 2 h, and 1.975 g of curing agent is added and stirred for 10 min for standby use. The tinplate substrate with a size of 10×20mm was pretreated, and the substrate was polished with a roughness of 600 mesh to remove the oxide layer. The polished substrate was placed in anhydrous ethanol and ultrasonically removed the surface oil and impurities. After drying, the above coating was applied to the surface of the substrate, and the coating thickness was controlled at 50μm (±10μm). The curing process was: 70℃ curing for 6h.

[0029] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0030] Embodiment 2:

[0031] The other processes are the same as those of Example 1, except that in step (3), the amount of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material is changed to 0.2 g, that is, the solid content of the additive is 2 wt %.

[0032] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0033] Embodiment 3:

[0034] The other processes are the same as those in Example 1, except that in step (3), the amount of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material is changed to 0.5 g, that is, the solid content of the additive is 5 wt %.

[0035] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0036] Embodiment 4:

[0037] The other processes are the same as those in Example 2, except that in step (3), the zinc powder is changed to 8.0 g, that is, the solid content of the zinc powder is 80 wt%.

[0038] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0039] Embodiment 5:

[0040] The other processes are the same as those in Example 2, except that in step (3), the zinc powder is changed to 7.0 g, that is, the solid content of the zinc powder is 70 wt%.

[0041] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0042] Embodiment 6:

[0043] The other processes are the same as those in Example 2, except that in step (3), the zinc powder is changed to 4.0 g, that is, the solid content of the zinc powder is 40 wt%.

[0044] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0045] Comparative Example 1:

[0046] As a comparison, a coating without the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite additive was prepared. The process for preparing the coating was the same as step (3) of Example 4, except that the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite was changed to 0 g.

[0047] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0048] Comparative Example 2:

[0049] For comparison, a coating having an iron oxide / reduced graphene oxide composite material as an additive was prepared. The process for preparing the coating was the same as step (3) of Example 2, except that the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material was replaced with 0.2 g of the iron oxide / reduced graphene oxide composite material prepared in step (1).

[0050] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0051] Comparative Example 3:

[0052] For comparison, a coating with 1-hydroxyethyl-1,1-diphosphonic acid as an additive was prepared. The process for preparing the coating was the same as step (3) of Example 2, except that the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite material was replaced with 0.2 g of 1-hydroxyethyl-1,1-diphosphonic acid.

[0053] The low-frequency impedance modulus test results of the electrochemical impedance spectroscopy of the coating after immersion in a 3.5wt% sodium chloride solution for 30 days are shown in Table 1.

[0054] Table 1 Examples and Comparative Examples with Soaking Time |Z| 0.01Hz (Ω·cm 2 ) Change graph

[0055]

[0056] As can be seen from Table 1, the test results show that for the modified anti-corrosion coating with a zinc content of 60wt%, when the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid additive content is 2wt%, the coating's |Z| 0.01Hz The lowest, the coating has the best corrosion resistance; when the additive content is 5wt%, the composite material will agglomerate to a certain extent in the coating, affecting the anti-corrosion effect of the nanocomposite material in the coating; compared with the test results of Comparative Examples 2 and 3, it can be seen that the corrosion resistance of the coating modified by adding iron oxide / reduced graphene oxide and 1-hydroxyethyl-1,1-diphosphonic acid is not as good as that of the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid composite modified coating; when the zinc content is 70 and 80wt%, compared with the test results of Comparative Example 1 without adding composite coating, |Z| 0.01Hz The increase was 1 to 2 orders of magnitude, indicating that the addition of iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid nanocomposite materials can significantly improve the corrosion resistance of the coating.

[0057] The above content only includes some implementation cases of the present invention, and does not limit the present invention in any form. Although the present invention has a better implementation case disclosed as above, it is not used to limit the present invention. Any technician familiar with this profession can use the above structure and technical content to modify or optimize it into an equivalent implementation case without departing from the scope of the technical solution of the present invention. However, any modification, equivalent change or modification made to the above implementation case based on the technical essence of the present invention without departing from the content of the technical solution of the present invention belongs to the scope of the technical solution of the present invention.

Claims

1. A method for preparing a graphene nanocomposite material, characterized in that: The following steps are involved: The first step is to add ferrous chloride solution to the graphene oxide dispersion, ultrasonically disperse until the mixture is uniform, then adjust the pH value of the dispersion to 9-12, and then perform a hydrothermal reaction and centrifuge and wash to obtain an iron oxide / reduced graphene oxide composite material; Step 2: Add the active factor 1-hydroxyethyl-1,1-diphosphonic acid to the iron oxide / reduced graphene oxide composite material, stir evenly, react at 80°C for 2h, and freeze-dry to obtain the iron oxide / reduced graphene oxide / hydroxyethyl diphosphonic acid composite material, i.e., graphene nanocomposite material.

2. The method according to claim 1, characterized in that The ratio of ferrous chloride to graphene oxide is 100 mmol:2 g.

3. The method according to claim 1, characterized in that The hydrothermal reaction temperature was 180°C and the reaction time was 10 h.

4. The method according to claim 1, characterized in that The mass ratio of graphene oxide to 1-hydroxyethyl-1,1-diphosphonic acid is (1-4):1, preferably 1:

1.

5. A graphene nanocomposite material prepared by the method according to any one of claims 1 to 4.

6. A modified anti-corrosion coating, comprising at least an additive, an epoxy resin, zinc powder, and a curing agent, characterized in that: The additive is a graphene nanocomposite material prepared by the method described in any one of claims 1 to 4.

7. The modified anticorrosive coating according to claim 6, characterized in that: The zinc powder is spherical zinc powder particles with a particle size of 5-10μm.

8. The modified anticorrosive coating according to claim 6, characterized in that: The solid content of the additive in the modified anti-corrosion coating is 0.5% to 5%.

9. The modified anticorrosive coating according to claim 6 or 7, characterized in that: The solid content of zinc powder in the modified anti-corrosion coating is 40% to 80%.

10. A modified anti-corrosion coating, characterized in that: The anti-corrosion coating is formed by coating a substrate with the modified anti-corrosion coating as described in any one of claims 6 to 9.

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