Dual active protective anticorrosive coating and method of manufacture

Abstract

This invention proposes a dual-active protective anti-corrosion coating and its preparation method. The invention uses polyurethane with disulfide bonds as a matrix and introduces modified polyaniline two-dimensional nanosheets to prepare an anti-corrosion coating, namely 2D-NACS, which achieves self-protection in seawater environments. When the coating is damaged, seawater comes into contact with the substrate, triggering a corrosion reaction that generates Fe. 2+ Triggering: ① First layer of active protection: At the metal / coating corrosion interface, C-PANI in the coating promotes Fe corrosion. 2+ Rapidly converted to Fe 3+ The coating forms an Fe2O3 passivation layer, preventing further penetration of corrosive media; secondly, the disulfide bonds at the crack heal through bond exchange, sealing the seawater diffusion path and inhibiting the penetration of corrosive media. This process mimics the migration and repair process of skin cells, ultimately leading to the gradual repair of cracks and restoration of the coating's anti-corrosion function. This solves the problem that 2D-NACS is prone to damage and cracking after long-term environmental aging and external mechanical damage, resulting in a decline in protective performance.

Description

Technical Field

[0001] This invention belongs to the field of marine anti-corrosion coating technology. Background Technology

[0002] With the rapid development of deep-sea engineering, the challenges faced by underwater equipment in extreme marine environments are becoming increasingly prominent. This equipment is typically exposed to high humidity, high salinity, and high temperatures, making it highly susceptible to pitting corrosion, crevice corrosion, and galvanic corrosion. These corrosion phenomena not only pose a serious threat to the safe operation of the equipment but may also lead to environmental pollution and resource waste. Against this backdrop, the corrosion problem of steel structures is particularly prominent, as the main structure of deep-sea engineering equipment requires a large amount of steel for support and stability. Therefore, effectively solving the corrosion problem of steel structures has become crucial to ensuring the long-term safe operation of deep-sea engineering equipment.

[0003] Currently, two-dimensional nanosheet-based anticorrosion coatings (capable of autonomous protection in seawater, 2D-NACS) play a crucial role in addressing corrosion problems in steel structures due to their superior performance. Two-dimensional nanosheets possess a large aspect ratio and excellent physical barrier properties, enabling the coating to effectively resist the penetration and diffusion of corrosive media. However, after long-term environmental aging and external mechanical damage, these coatings inevitably develop defects such as breakage and cracking, leading to a decline in protective performance and the re-emergence of corrosion problems. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a dual active protective anti-corrosion coating and its preparation method. This coating is a two-dimensional nanosheet-based anti-corrosion coating capable of self-protection in a seawater environment. The specific technical solution adopted in this invention is as follows:

[0005] A method for preparing a dual active protective anti-corrosion coating, the specific steps of which are as follows:

[0006] Step 1: Preparation of COF-modified polyaniline:

[0007] 1) Disperse 1.5g of polyaniline in 750~3000mL of acetonitrile and sonicate for 1h to obtain a polyaniline solution;

[0008] 2) Add 2 mol of 2,6-pyridinedicarboxaldehyde (PDA) and 3 mol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine (TTA) to a polyaniline solution. Under acidic conditions, the covalent organic frameworks (COF) obtained by the reaction of PDA and TTA are encapsulated on the surface of PANI by a Schiff base reaction to synthesize COF-modified polyaniline (C-PANI).

[0009] 3) The synthesized C-PANI was separated by centrifugation, washed with ethanol, and the product was collected and dried to obtain C-PANI.

[0010] Step 2: Preparation of the coating:

[0011] 1) Pour isophorone diisocyanate (IPDI) into a reaction vessel, heat to 50°C and pass through nitrogen gas. Add polytetrahydrofuran (PTMG) dropwise into the reaction vessel. The reaction is first carried out at 50°C for 30 minutes, then the temperature is raised to 80°C and the reaction is continued for 3 hours to obtain a prepolymer. Bottle and seal the prepolymer, cool to room temperature and store for later use. The molar ratio of IPDI to PTMG is 2:1.

[0012] 2) Pour the prepolymer and organic solvent into a beaker, add C-PANI, and mix to obtain coating component A;

[0013] 3) Add 4,4′-dithiodiphenylamine (DTDA) and adipic acid dihydrazide (AD) to an organic solvent and dissolve them completely to obtain coating component B;

[0014] 4) Add component B of the coating to component A of the coating and stir at 60°C for 24 hours to obtain the coating. The solid content of the coating is 20-50 wt%.

[0015] The molar ratio of IPDI and PTMG in step 1) and DTDA and AD in step 3) is 2:1:0.5:0.5; the amount of C-PANI added is 0.25-1.5 wt% of the total mass of IPDI, PTMG2000, DTDA, and AD.

[0016] Step 3: Apply the coating obtained in Step 2 to the surface of the substrate and cure it in a vacuum oven at 80°C for 24 hours to obtain a double active protective anti-corrosion coating.

[0017] Preferably, the preparation steps of polyaniline (PANI) in step one are as follows:

[0018] 1) Disperse the purified aniline and surfactant in dilute hydrochloric acid and stir to form a homogeneous solution A; the mass ratio of aniline, surfactant and dilute hydrochloric acid is 1:0.8:(240-300).

[0019] 2) Inject dilute hydrochloric acid containing 1-3 wt% ammonium sulfate into solution A to initiate polymerization and keep it at room temperature for 10 h;

[0020] 3) After centrifugation, the product was washed with ethanol and deionized water, and then collected and dried to obtain polyaniline (PANI).

[0021] Preferably, the surfactant in step 1) is hexadecyltrimethylammonium bromide (CTAB); and the concentration of dilute hydrochloric acid in steps 1) and 2) is 0.01 mol / L.

[0022] Preferably, the PTMG described in step two is poured into a rotary flask of a rotary evaporator before use, then distilled under vacuum at 120°C for 2 hours. After cooling to 60°C, it is bottled, sealed, and stored for later use.

[0023] Preferably, in steps 2) and 3) of step two, the organic solvent is N,N-dimethylformamide (DMF).

[0024] The substrate mentioned in step three is one of iron, copper, steel, magnesium, titanium, aluminum, or an alloy thereof.

[0025] The beneficial effects of this invention are:

[0026] This invention uses polyurethane with disulfide bonds as a matrix and introduces modified polyaniline two-dimensional nanosheets to prepare an anti-corrosion coating (C-PANI / PU), namely a 2D-NACS that achieves self-protection in seawater environments. When the coating is damaged, seawater comes into contact with the substrate, triggering a corrosion reaction that generates Fe. 2+ Triggering: ① First layer of active protection: At the metal / coating corrosion interface, C-PANI in the coating promotes Fe corrosion. 2+ Rapidly converted to Fe 3+ The coating forms an Fe2O3 passivation layer, preventing further penetration of corrosive media; secondly, the disulfide bonds at the crack heal through bond exchange, sealing the seawater diffusion path and inhibiting the penetration of corrosive media. This process mimics the migration and repair process of skin cells, ultimately allowing the crack to gradually repair itself and restoring the anti-corrosion function of the coating.

[0027] The 2D-NACS coating proposed in this invention, after being damaged, can effectively prevent further corrosion through self-protective mechanisms, such as self-inhibiting localized corrosion or repairing cracks, thereby significantly extending the service life of deep-sea engineering equipment. This self-healing capability not only improves the reliability of the equipment but also reduces sudden failures and safety hazards caused by corrosion. Secondly, the use of the 2D-NACS coating can significantly reduce the frequency of equipment maintenance and related costs, improving overall economic efficiency. Reduced frequency of regular maintenance and replacement of damaged parts translates to savings in operating costs and enhanced sustainability of engineering projects. Finally, by reducing the release of harmful substances during corrosion, 2D-NACS helps protect the marine environment and reduce negative impacts on marine ecosystems. This not only aligns with the concept of green development but also provides strong support for the sustainable use of marine resources.

[0028] The 2D-NACS proposed in this invention plays an important role and has far-reaching significance in the long-term corrosion protection of deep-sea engineering equipment. Attached Figure Description

[0029] Figure 1 Comparison of low-frequency modulus values ​​after 15 days of electrochemical corrosion testing. Detailed Implementation

[0030] The technical solution of the present invention will be further explained and described below with reference to specific embodiments. Example

[0031] I. Preparation of COF-modified polyaniline:

[0032] 1) Disperse 1.5g of purified aniline and 1.2g of surfactant cetyltrimethylammonium bromide (CTAB) in 450ml of HCl solution (0.01mol / l) and stir magnetically for 90 minutes to form a homogeneous solution.

[0033] 2) Inject another 60 ml HCl solution (0.01 mol / L) containing 1 g ammonium sulfate into the above solution to initiate polymerization and keep at room temperature for 10 h.

[0034] 3) After centrifugation (8000 r / min) and washing three times with ethanol and deionized water, the product was collected and further dried at 60°C to obtain polyaniline.

[0035] 4) Disperse 1.5g of polyaniline in 1500ml of acetonitrile and sonicate for 1h.

[0036] 5) Then, 2 mol of 2,6-pyridinedicarboxaldehyde (PDA) and 3 mol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine (TTA) were introduced into the above solution. Under acidic conditions, covalent organic frameworks (COF) were wrapped on the surface of PANI by Schiff base reaction to synthesize COF-modified polyaniline (C-PANI).

[0037] 6) After centrifuging the above solution (8000 r / min) and washing it three times with ethanol, the product was collected and further dried at 60°C to obtain C-PANI.

[0038] II. Preparation of Coatings:

[0039] 1) Pour PTMG2000 into a rotary flask of a rotary evaporator, and then distill under vacuum at 120°C for 2 hours. After cooling to 60°C, bottle and seal for storage.

[0040] 2) Pour 22g of isophorone diisocyanate (IPDI) into a four-necked flask, heat to 50°C and purge with nitrogen. Pour 100g of PTMG into a constant-pressure dropping funnel and add it dropwise to the flask at a rate of 4 drops per second. The reaction is carried out at 50°C for 30 minutes. Then the temperature is raised to 80°C and the reaction is continued for 3 hours to obtain the prepolymer. The prepolymer is bottled and sealed, cooled to room temperature, and stored for later use.

[0041] 3) Pour 122g of prepolymer, 1.33mg of C-PANI and 122g of solvent N,N-dimethylformamide (DMF) into a beaker and mix to obtain coating component A.

[0042] 4) Add 6.2g of 4,4′-dithiodiphenylamine and 4.35g of adipic acid dihydrazide (AD) to 122g of solvent DMF and dissolve completely to obtain coating component B.

[0043] 5) Add component B of the coating to component A of the coating and stir at 60°C for 24 hours to obtain the coating.

[0044] III. Curing of the coating:

[0045] The coating is poured into a mold and cured in a vacuum oven at 80°C for 24 hours to obtain a double active protective anti-corrosion coating.

[0046] Comparative Example 1

[0047] 1) Before the synthesis of the prepolymer, PTMG2000 was first poured into a rotary flask of a rotary evaporator and then distilled under vacuum at 120°C for 2 hours. After cooling to 60°C, it was bottled and sealed for storage.

[0048] 2) Pour 22g of IPDI into a four-necked flask, heat to 50°C, and purge with nitrogen. Pour 100g of PTMG into a constant-pressure dropping funnel and add it dropwise to the flask at a rate of 4 drops per second. The reaction is carried out at 50°C for 30 minutes. Then, the temperature is raised to 80°C, and the reaction is continued for 3 hours to obtain the prepolymer. Bottle and seal the prepolymer, cool to room temperature, and store for later use.

[0049] 3) Pour 122g of prepolymer and 122g of solvent DMF into a beaker and mix to obtain coating component A.

[0050] 4) Add 6.2g of 4,4′-dithiodiphenylamine and 4.35g of adipic acid dihydrazide (AD) to 122g of solvent DMF and dissolve completely to obtain coating component B.

[0051] 5) Add component B of the coating to component A of the coating and stir at 60°C for 24 hours to obtain the coating.

[0052] 6) Pour the coating into the mold and cure it in a vacuum oven at 80°C for 24 hours.

[0053] Comparative Example 2

[0054] I. Preparation of polyaniline:

[0055] 1) Disperse 1.5g of purified aniline and 1.2g of surfactant (hexadecyltrimethylammonium bromide) in 450ml of HCl solution (0.01mol / l) and stir magnetically for 90 minutes to form a homogeneous solution.

[0056] 2) Inject another 60 ml HCl solution containing 1 g ammonium sulfate into the above solution to initiate polymerization and keep at room temperature for 10 h.

[0057] After centrifugation (8000 r / min) and washing three times with ethanol and deionized water, the product was collected and further dried at 60 °C to obtain polyaniline.

[0058] II. Preparation of Coatings:

[0059] 1) Before the synthesis of the prepolymer, PTMG2000 was first poured into a rotary flask of a rotary evaporator and then distilled under vacuum at 120°C for 2 hours. After cooling to 60°C, it was bottled and sealed for storage.

[0060] 2) Pour 22g of IPDI solution into a four-necked flask, heat to 50°C, and purge with nitrogen. Pour 100g of PTMG into a constant-pressure dropping funnel and add it dropwise to the flask at a rate of 4 drops per second. The reaction is carried out at 50°C for 30 minutes. Then, the temperature is raised to 80°C, and the reaction is continued for 3 hours to obtain the prepolymer. Bottle and seal the prepolymer, cool to room temperature, and store for later use.

[0061] 3) Pour 122g of prepolymer solution, 1.33mg of polyaniline and 122g of solvent DMF into a beaker and mix to obtain coating component A.

[0062] 4) Add 6.2g of 4,4′-dithiodiphenylamine and 4.35g of adipic acid dihydrazide (AD) to 122g of solvent DMF and dissolve completely to obtain coating component B.

[0063] 5) Add component B of the coating to component A of the coating and stir at 60°C for 24 hours to obtain the coating.

[0064] 6) Pour the coating into the mold and cure it in a vacuum oven at 80°C for 24 hours.

[0065] Effect verification:

[0066] Electrochemical impedance spectroscopy (EIS) experiments were conducted using a Shanghai Zhenhua electrochemical workstation (CHI760E). A standard three-electrode system was employed (working electrode: sample; reference electrode: Ag / AgCl electrode; auxiliary electrode: platinum electrode), with a 3.5 wt% NaCl solution as the etching medium at room temperature. The contact area between the coating under test and the etching solution was 1.00 cm². 2 The amplitude of the added sinusoidal AC signal is 20 mV, and the scanning frequency range is 10. -2 Hz~10 5 Hz. The coating thickness is 80 μm.

[0067] like Figure 1 As shown, the comparison of low-frequency modulus values ​​after 15 days of electrochemical corrosion testing reveals that the example with COF-modified polyaniline exhibits better electrochemical corrosion resistance than Comparative Example 2 (with polyaniline) and Comparative Example 1 (without any modification). This is likely because the COF-modified polyaniline surface possesses a large number of hydrogen bond acceptors, resulting in better compatibility with the coating substrate. In contrast, the unmodified polyaniline exhibits poor dispersion in the coating, ultimately leading to reduced corrosion resistance.

Claims

1. A method for preparing a dual active protective anti-corrosion coating, characterized in that, The specific steps of this method are as follows: Step 1: Preparation of COF-modified polyaniline: 1) Disperse 1.5g of polyaniline in 750~3000mL of acetonitrile and sonicate for 1h to obtain a polyaniline solution; 2) 2 mol of 2,6-pyridinedicarboxaldehyde and 3 mol of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine were added to a polyaniline solution. Under acidic conditions, the covalent organic framework obtained from the reaction of 2,6-pyridinedicarboxaldehyde and 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine was encapsulated on the surface of polyaniline via a Schiff base reaction, thus synthesizing COF-modified polyaniline. 3) The synthesized COF-modified polyaniline was separated by centrifugation, washed with ethanol, and the product was collected and dried to obtain COF-modified polyaniline; Step 2: Preparation of the coating: 1) Pour isophorone diisocyanate into a reaction vessel, heat to 50°C and pass through nitrogen gas. Add polytetrahydrofuran dropwise into the reaction vessel. The reaction is first carried out at 50°C for 30 minutes, then the temperature is raised to 80°C and the reaction is continued for 3 hours to obtain a prepolymer. Bottle and seal the prepolymer, cool to room temperature and store for later use. The molar ratio of isophorone diisocyanate to polytetrahydrofuran is 2:

1. 2) Pour the prepolymer and organic solvent into a beaker, add COF-modified polyaniline, and mix to obtain coating component A; 3) Add 4,4'-dithiodiphenylamine and adipic acid dihydrazide to an organic solvent and dissolve them completely to obtain coating component B; 4) Add component B of the coating to component A of the coating and stir at 60°C for 24 hours to obtain the coating. The solid content of the coating is 20-50 wt%. In step 1), the molar ratio of isophorone diisocyanate, polytetrahydrofuran, and in step 3), 4,4'-dithiodiphenylamine and adipic acid dihydrazide is 2:1:0.5:0.5; the amount of COF-modified polyaniline added is 0.25-1.5 wt% of the total mass of isophorone diisocyanate, polytetrahydrofuran, 4,4'-dithiodiphenylamine, and adipic acid dihydrazide. Step 3: Apply the coating obtained in Step 2 to the surface of the substrate and cure it in a vacuum oven at 80°C for 24 hours to obtain a double active protective anti-corrosion coating.

2. The method for preparing the dual active protective anti-corrosion coating according to claim 1, characterized in that, The preparation steps of polyaniline in step one are as follows: 1) Disperse the purified aniline and surfactant in dilute hydrochloric acid and stir to form a homogeneous solution A; the mass ratio of aniline, surfactant and dilute hydrochloric acid is 1:0.8:(240-300). 2) Inject dilute hydrochloric acid containing 1-3 wt% ammonium sulfate into solution A to initiate polymerization and keep it at room temperature for 10 h; 3) After centrifugation, the product was washed with ethanol and deionized water respectively, collected and dried to obtain polyaniline.

3. The method for preparing a dual active protective anti-corrosion coating according to claim 2, characterized in that, The surfactant mentioned in step 1) of step one is hexadecyltrimethylammonium bromide.

4. The method for preparing a dual active protective anti-corrosion coating according to claim 2, characterized in that, In steps 1 and 2), the concentration of dilute hydrochloric acid is 0.01 mol / L.

5. The method for preparing a dual active protective anti-corrosion coating according to claim 1, characterized in that, Before use, the polytetrahydrofuran described in step two is poured into a rotary flask of a rotary evaporator and then distilled under vacuum at 120°C for 2 hours. After cooling to 60°C, it is bottled, sealed, and stored for later use.

6. The method for preparing a dual active protective anti-corrosion coating according to claim 1, characterized in that, The molecular weight of polytetrahydrofuran is 2000.

7. The method for preparing a dual active protective anti-corrosion coating according to claim 1, characterized in that, In steps 2) and 3), the organic solvent is N,N-dimethylformamide.

8. The method for preparing a dual active protective anti-corrosion coating according to claim 1, characterized in that, The substrate mentioned in step three is one of iron, copper, steel, magnesium, titanium, aluminum, or an alloy thereof.

9. The dual active protective anti-corrosion coating prepared by the method according to any one of claims 1 to 8.

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