Preparation method of epoxy resin-based double-electrode-layer composite anticorrosive paint

Abstract

The invention discloses a method for enhancing the corrosion resistance of a water-borne epoxy resin coating through hydrotalcite double-electrode-layer filler. The preparation method comprises the following steps: modifying hydrotalcite by using formamide to prepare a double-electrode-layer nanosheet filler, and adding the double-electrode-layer nanosheet filler into a water-borne epoxy resin base material to prepare the epoxy resin-based double-electrode-layer coating. SEM characterization is carried out on the blank coating and the coating added with the double electric layers, AFM characterization is carried out on the double electric layer coating, and the arrangement condition of the double electric layers in the coating is detected. And carrying out salt spray resistance test on different coatings, comparing the results, and detecting the influence of adding the double-electric-layer filler on the corrosion resistance of the coatings. Results show that the hydrotalcite double-electrode-layer filler can fill fine gaps in the coating, the double-electrode-layer material is in a tiled state in the coating, and charges on a laminate repel corrosion ions, so that the corrosion ions are prevented from penetrating through the coating in the maximum area, and the corrosion resistance of the coating is enhanced.

Description

Technical Field

[0001] The invention relates to a water-based anticorrosive coating, and in particular to an epoxy resin-based double-electric layer composite anticorrosive coating and a preparation method thereof. Background Art

[0002] The use of coatings provides a long-term and simple way to protect metal materials, prolongs the service life of metals, improves the economic benefits and aesthetics of metal materials, and also plays a positive role in environmental protection. Waterborne epoxy resin has the advantages of being non-toxic, odorless, low VOC and easy to operate. It can provide an effective physical barrier between the metal substrate and the corrosive medium and is widely used on metal surfaces to inhibit metal corrosion. However, waterborne epoxy coatings still have many limitations, such as insufficient long-term salt spray resistance, brittle texture and poor wear resistance. Therefore, waterborne epoxy resins must be modified to enhance their anti-corrosion properties. The current modification methods include modifying emulsifiers and curing agents, changing the resin molecular structure and adding anti-corrosion fillers. Over the years, scientists have modified waterborne epoxy resins by adding different particles, such as graphene, polymers and organic-inorganic hybrid molecules.

[0003] Hydrotalcite (LDH) is a multifunctional two-dimensional nanomaterial with unique ion exchange properties, which can capture corrosive ions and is often used as a barrier filler to prepare anti-corrosion coatings. It has been reported that LDH without any corrosion inhibitor can be added to the coating to improve the anti-corrosion performance. The corrosion resistance of the coating modified with LDH is enhanced because the chloride at the metal-coating interface replaces the anions embedded in the LDH, prolonging the time for the corrosive substances to enter the coating and reducing the content of corrosive ions around the coating. Since hydrotalcite is a layered structure, a two-dimensional nanosheet can be obtained by peeling. The invention patent CN104924706B discloses a method of peeling hydrotalcite and montmorillonite to prepare two two-dimensional nanosheets with opposite charges, namely hydrotalcite and montmorillonite monolayers, and further compounding the two into a new type of layered material. After the hydrotalcite is peeled off, a layer of opposite charge will be adsorbed on its layer plate to prepare a double-layer nanosheet. This double-layer nanosheet can repel corrosive anions and corrosive cations due to electrostatic action, thereby preventing anions and cations from passing through the coating to achieve the purpose of anti-corrosion. Summary of the invention

[0004] In order to solve the shortcomings of existing water-based coatings, the present invention provides a double-layer water-based anti-corrosion coating. Based on the characteristics that hydrotalcite can be easily stripped and interlayer cations can be replaced, the present invention strips the hydrotalcite to prepare a double-layer nanosheet with a layer of negative charge adsorbed on the positively charged surface of the layer plate. The double-layer nanosheet is added to the water-based epoxy resin. The double-layer nanosheet will be oriented in the coating to form a double-layer coating, which has a repelling effect on corrosive anions and cations. In addition, since the double-layer nanosheet has a small particle size after stripping, it can fill the smaller gaps in the coating, thereby improving the corrosion resistance of the coating. The main invention contents are:

[0005] An epoxy resin-based double-electric layer composite anticorrosive coating comprises a base material and a filler, wherein the base material is a waterborne epoxy resin base material and the filler is a hydrotalcite-based double-electric layer nanosheet filler.

[0006] An epoxy resin-based double-electric layer composite anticorrosive coating is characterized in that the hydrotalcite is magnesium-aluminum hydrotalcite and formamide is used to peel it.

[0007] An epoxy resin-based double-electric layer composite anti-corrosion coating, characterized in that when preparing magnesium-aluminum hydrotalcite, the magnesium-aluminum ratio is 2:1-4:1 and the solution pH is 8-11.

[0008] An epoxy resin-based double-electric layer composite anticorrosive coating is characterized in that the amount of formamide used in the preparation of the hydrotalcite-based double-electric layer nanosheet filler is 10% to 30% of the mass of the hydrotalcite.

[0009] An epoxy resin-based double-electric layer composite anticorrosive coating, characterized in that the particle size of the hydrotalcite-based double-electric layer nanosheet filler is 200-800 meshes.

[0010] An epoxy resin-based double-electric layer composite anticorrosive coating, characterized in that the dosage of the hydrotalcite-based double-electric layer nanosheet filler is 1% to 5% of the solid content of the water-based epoxy resin base material.

[0011] The present invention has the following beneficial effects:

[0012] 1. Double-layer nanosheets have a smaller particle size and can be fully filled in the gaps of the coating, providing a better physical barrier effect.

[0013] 2. Adding double-layer nanosheets to the base material forms a double-layer coating, which has a repellent effect on both corrosive anions and cations.

[0014] 3. The double-layer nanosheets are arranged in a direction in the coating to form a partition-like maze structure, which acts as a barrier to corrosive media. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the SEM image of the coating of Example 1

[0016] Figure 2 This is the SEM image of the coating of Example 2

[0017] Figure 3 This is a cross-sectional AFM image of the coating of Example 2.

[0018] Figure 4 The salt spray images of the coatings of Examples 1, 2, 3, 4, and 5 are shown in FIG. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below by way of examples.

[0020] Example 1

[0021] Add curing agent to waterborne epoxy resin at a mass ratio of 1:1 and stir evenly with a glass rod. Apply the prepared coating to the steel plate and repeat the coating 2-3 times after the coating surface is completely dry.

[0022] The scanning electron microscopy images of the obtained coatings are shown in Figure 1 As shown, the results of the 160h salt spray test are as follows Figure 4 (a) shown.

[0023] Example 2

[0024] Use a spatula to weigh 2.048 g of magnesium nitrate hexahydrate and 1.5 g of aluminum nitrate nonahydrate into a beaker, add boiling deionized water (to remove CO 2 ), stir until dissolved (code as solution A). Weigh 0.9067g of sodium hydroxide and dissolve it in boiling deionized water, slowly add the sodium hydroxide solution to solution A with a peristaltic pump, and stir for 1h under a nitrogen atmosphere. After stirring, pour the solution into a high-pressure reactor, put the reactor into an oven, set the temperature to 160°C, the time is 10h, and take it out after cooling to room temperature. Centrifuge the reaction solution, dry and grind to obtain magnesium aluminum nitrate hydrotalcite. (The molar ratio of magnesium nitrate hexahydrate to aluminum nitrate nonahydrate is 1:2, and the molar ratio of sodium hydroxide to aluminum nitrate nonahydrate is 17:3).

[0025] The synthesized magnesium aluminum nitrate hydrotalcite was passed through a 200-mesh sieve and placed in a beaker, and an appropriate amount of formamide solution was added for ultrasonic treatment. After the solution produced the Tyndall phenomenon, the reaction solution was centrifuged, dried and ground to obtain hydrotalcite double-layer nanosheets.

[0026] The prepared hydrotalcite double-layer nanomaterial is added to the water-based epoxy resin solution in an amount of 2% of the base material mass, and ultrasonically dispersed to mix evenly, and then a curing agent is added and stirred evenly with a glass rod to obtain the desired composite coating, and the prepared coating is applied to the steel plate. After the coating surface is completely dry, the coating is repeated 2-3 times.

[0027] The scanning electron microscopy images of the obtained coatings are shown in Figure 2 As shown, the AFM image of the coating cross section is Figure 3 As shown, the results of the 160h salt spray test are as follows Figure 4 (b) as shown.

[0028] Example 3

[0029] Use a spatula to weigh 2.048 g of magnesium nitrate hexahydrate and 1.5 g of aluminum nitrate nonahydrate into a beaker, add boiling deionized water (to remove CO 2 ), stir until dissolved (code as solution A). Weigh 0.9067g of sodium hydroxide and dissolve it in boiling deionized water, slowly add the sodium hydroxide solution to solution A with a peristaltic pump, and stir for 1h under a nitrogen atmosphere. After stirring, pour the solution into a high-pressure reactor, put the reactor into an oven, set the temperature to 160°C, the time is 10h, and take it out after cooling to room temperature. Centrifuge the reaction solution, dry and grind to obtain magnesium aluminum nitrate hydrotalcite. (The molar ratio of magnesium nitrate hexahydrate to aluminum nitrate nonahydrate is 1:2, and the molar ratio of sodium hydroxide to aluminum nitrate nonahydrate is 17:3).

[0030] The synthesized magnesium aluminum nitrate hydrotalcite was passed through a 200-mesh sieve and placed in a beaker, and an appropriate amount of formamide solution was added for ultrasonic treatment. After the solution produced the Tyndall phenomenon, the reaction solution was centrifuged, dried and ground to obtain hydrotalcite double-layer nanosheets.

[0031] The prepared hydrotalcite double-layer nanomaterial is added to the aqueous epoxy resin solution in an amount of 4% of the base material mass, and ultrasonically dispersed to mix evenly, and then a curing agent is added, and stirred evenly with a glass rod to obtain the desired composite coating, and the prepared coating is applied to the steel plate. After the coating surface is completely dry, the coating is repeated 2-3 times.

[0032] The results of the 160h salt spray test are as follows: Figure 4 (c) as shown.

[0033] Example 4

[0034] Use a spatula to weigh 2.048 g of magnesium nitrate hexahydrate and 1.5 g of aluminum nitrate nonahydrate into a beaker, add boiling deionized water (to remove CO 2), stir until dissolved (code as solution A). Weigh 0.9067g of sodium hydroxide and dissolve it in boiling deionized water, slowly add the sodium hydroxide solution to solution A with a peristaltic pump, and stir for 1h under a nitrogen atmosphere. After stirring, pour the solution into a high-pressure reactor, put the reactor into an oven, set the temperature to 160°C, the time is 10h, and take it out after cooling to room temperature. Centrifuge the reaction solution, dry and grind to obtain magnesium aluminum nitrate hydrotalcite. (The molar ratio of magnesium nitrate hexahydrate to aluminum nitrate nonahydrate is 1:2, and the molar ratio of sodium hydroxide to aluminum nitrate nonahydrate is 17:3).

[0035] The synthesized magnesium aluminum nitrate hydrotalcite was passed through a 200-mesh sieve and placed in a beaker, and an appropriate amount of formamide solution was added for ultrasonic treatment. After the solution produced the Tyndall phenomenon, the reaction solution was centrifuged, dried and ground to obtain hydrotalcite double-layer nanosheets.

[0036] The prepared hydrotalcite double-layer nanomaterial is added to the water-based epoxy resin solution in an amount of 6% of the base material mass, and ultrasonic dispersion is performed to mix the mixture evenly. Then, a curing agent is added and stirred evenly with a glass rod to obtain the desired composite coating. The prepared coating is applied to the steel plate. After the coating surface is completely dry, the coating is repeated 2-3 times.

[0037] The results of the 160h salt spray test are as follows: Figure 4 (d) as shown.

[0038] Example 5

[0039] Use a spatula to weigh 2.048 g of magnesium nitrate hexahydrate and 1.5 g of aluminum nitrate nonahydrate into a beaker, add boiling deionized water (to remove CO 2 ), stir until dissolved (code as solution A). Weigh 0.9067g of sodium hydroxide and dissolve it in boiling deionized water, slowly add the sodium hydroxide solution to solution A with a peristaltic pump, and stir for 1h under a nitrogen atmosphere. After stirring, pour the solution into a high-pressure reactor, put the reactor into an oven, set the temperature to 160°C, the time is 10h, and take it out after cooling to room temperature. Centrifuge the reaction solution, dry and grind to obtain magnesium aluminum nitrate hydrotalcite. (The molar ratio of magnesium nitrate hexahydrate to aluminum nitrate nonahydrate is 1:2, and the molar ratio of sodium hydroxide to aluminum nitrate nonahydrate is 17:3).

[0040] The synthesized magnesium aluminum nitrate hydrotalcite was passed through a 200-mesh sieve and placed in a beaker, and an appropriate amount of formamide solution was added for ultrasonic treatment. After the solution produced the Tyndall phenomenon, the reaction solution was centrifuged, dried and ground to obtain hydrotalcite double-layer nanosheets.

[0041] The prepared hydrotalcite double-layer nanomaterial is added to the water-based epoxy resin solution in an amount of 8% of the base material mass, and ultrasonic dispersion is performed to mix the mixture evenly. Then, a curing agent is added and stirred evenly with a glass rod to obtain the desired composite coating. The prepared coating is applied to the steel plate. After the coating surface is completely dry, the coating is repeated 2-3 times.

[0042] The results of the 160h salt spray test are as follows: Figure 4 (e) as shown.

Claims

1. An epoxy resin-based double-electric layer composite anticorrosive coating, comprising a base material and a filler, characterized in that: The base material is a water-based epoxy resin base material, and the filler is a hydrotalcite-based double-electric-layer nanosheet filler.

2. The hydrotalcite-based double-electric-layer nanosheet filler according to claim 1, characterized in that: The hydrotalcite is magnesium aluminum hydrotalcite, and formamide is used to exfoliate it.

3. The magnesium-aluminum hydrotalcite according to claim 2, characterized in that: When preparing magnesium aluminum hydrotalcite, the magnesium aluminum ratio is 2:1-4:1 and the solution pH is 8-11.

4. The epoxy resin-based double-electric layer composite anticorrosive coating according to claim 1, characterized in that: The amount of formamide used in the preparation of the hydrotalcite-based double-electric-layer nanosheet filler is 10% to 30% of the mass of the hydrotalcite.

5. The hydrotalcite-based double-electric-layer nanosheet filler according to claim 1, characterized in that: The particle size of the hydrotalcite-based double-electric-layer nanosheet filler is 200-800 meshes.

6. The epoxy resin-based double-electric layer composite anticorrosive coating according to claim 1, characterized in that: The dosage of the hydrotalcite-based double-electric-layer nanosheet filler is 1% to 5% of the solid content of the waterborne epoxy resin base material.

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