Environment-friendly composite corrosion inhibitor and preparation and application thereof

Abstract

The application belongs to the technical field of corrosion protection, and discloses a green and environment-friendly composite corrosion inhibitor, a preparation method thereof and application of the composite corrosion inhibitor in a corrosion protection coating. The composite corrosion inhibitor is prepared by mixing modified zinc oxide and Ce-MOF, and the mass ratio of the modified zinc oxide to the Ce-MOF is 1:3-3:1. By virtue of the synergistic effect of the Ce-MOF and the modified zinc oxide, the composite corrosion inhibitor is applied to the corrosion protection coating, the coating can form effective protection on the metal surface, and can block the penetration of corrosive media, so that the metal corrosion is significantly delayed. In addition, the coating has strong universality, is suitable for various metal materials and corrosive environments, and has simple preparation process and low cost, and is very suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of corrosion protection technology, and specifically relates to a green and environmentally friendly composite corrosion inhibitor, its preparation, and its application in anti-corrosion coatings. Background Technology

[0002] With the continuous operation and development of the economy and industry, equipment and devices based on carbon steel, zinc alloys, and magnesium-aluminum alloys have become an indispensable part of life and production. However, metal corrosion is a common and unavoidable phenomenon, and it can cause irreversible damage or even complete destruction to metals and their alloys. Globally, metal losses due to corrosion account for 20% to 40% of total annual metal production, approximately four times the losses caused by natural disasters. In recent years, many methods for improving the corrosion resistance of coatings have been studied, among which the addition of corrosion inhibitors is considered a very effective and cost-efficient method.

[0003] Despite significant progress in corrosion inhibitor research, current research primarily focuses on individual inhibitors, with less attention paid to composite organic corrosion inhibitors. Individual corrosion inhibitors typically suffer from low efficiency, high cost, and large consumption. By utilizing the synergistic effect between the components of composite corrosion inhibitors, the corrosion-inhibiting effect of each component can be fully utilized, and the shortcomings of individual component inhibitors can be overcome. Therefore, developing efficient, non-toxic, and widely applicable green composite organic corrosion inhibitors is of great significance for future corrosion inhibitor research. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a green and environmentally friendly composite corrosion inhibitor.

[0005] Another objective of this invention is to provide a method for preparing the aforementioned green and environmentally friendly composite corrosion inhibitor.

[0006] Another objective of this invention is to provide the application of the above-mentioned green and environmentally friendly composite corrosion inhibitor in anti-corrosion coatings.

[0007] The objective of this invention is achieved through the following solution:

[0008] A green and environmentally friendly composite corrosion inhibitor is composed of modified zinc oxide and Ce-MOF, with a mass ratio of modified zinc oxide to Ce-MOF of 1:3 to 3:1.

[0009] Preferably, the mass ratio of the modified zinc oxide to Ce-MOF is 1:1.

[0010] The modified zinc oxide is prepared by the following steps: adding nano zinc oxide and stearic acid to anhydrous ethanol, stirring and mixing the mixture, centrifuging to remove the supernatant, and drying to obtain dry modified zinc oxide micro flakes.

[0011] The ratio of the amount of nano zinc oxide, stearic acid and anhydrous ethanol is 1g:(1-2)g:(40-60)mL, and the nano zinc oxide is nano zinc oxide with an average diameter of 1-100nm.

[0012] The stirring and mixing reaction refers to a stirring and mixing reaction at 25-35℃ for 15-30 minutes, preferably an ultrasonic stirring and mixing reaction.

[0013] The centrifugation mentioned refers to centrifugation at 6000-8000 rpm for 5-10 minutes.

[0014] The Ce-MOF was prepared by the following steps:

[0015] 2-hydroxyterephthalic acid and cerium chloride heptahydrate were added to solvent 1, mixed evenly, and the pH was adjusted to 7. The mixture was stirred and reacted. After the reaction was completed, the mixture was centrifuged, washed, and purified to obtain Ce-MOF nanoparticles.

[0016] The solvent 1 is a mixed solution of water, ethanol and N,N-dimethylformamide, with a volume ratio of 1:(0.8-1.5):(0.8-1.5).

[0017] The amounts of 2-hydroxyterephthalic acid, cerium trichloride heptahydrate, and solvent 1 are in the ratio of 1g:(3.4-4.1)g:(100-130)ml.

[0018] The stirring reaction refers to stirring at room temperature for 20-30 hours.

[0019] The washing process refers to washing the product sequentially with N,N-dimethylformamide and ethanol to remove unreacted substances and impurities.

[0020] The purification process involves soaking the product in dichloromethane for 15-30 hours, centrifuging, washing with ethanol, and finally drying and grinding to obtain purified Ce-MOF nanoparticles. The centrifugation speed is 8000-10000 r / min, the centrifugation time is 5-15 min, the drying temperature is 50-80℃, and the drying time is 4-6 hours.

[0021] A method for preparing the above-mentioned green and environmentally friendly composite corrosion inhibitor includes the following steps: mixing modified zinc oxide and Ce-MOF evenly to obtain the green and environmentally friendly composite corrosion inhibitor.

[0022] The above-mentioned green and environmentally friendly composite corrosion inhibitors are used in the preparation of anti-corrosion coatings.

[0023] An anti-corrosion coating comprises the following components in parts by weight: 1-2 parts of composite corrosion inhibitor, 40-80 parts of epoxy resin, 70-140 parts of curing agent, and 50-100 parts of diluent.

[0024] The epoxy resin is preferably a bisphenol A type epoxy resin.

[0025] The curing agent is a water-based epoxy curing agent.

[0026] The diluent is at least one of ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, dimethyl carbonate, and propylene glycol methyl ether acetate.

[0027] A method for preparing the above-mentioned anti-corrosion coating includes the following steps: adding a composite corrosion inhibitor to a diluent and ultrasonically stirring to obtain a uniform solution; then adding epoxy resin and a curing agent to the uniform solution and stirring to form a uniformly dispersed slurry system; and then coating this slurry system onto the substrate surface to prepare an anti-corrosion epoxy resin coating.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] In the process of preparing a green and environmentally friendly composite corrosion inhibitor anti-corrosion coating, a modified zinc oxide was first prepared. This was achieved by modifying nano-zinc oxide with stearic acid. The carboxyl groups of stearic acid can undergo esterification with the hydroxyl groups on the surface of the nano-zinc oxide particles. The nano-zinc oxide is non-toxic and harmless, and in aqueous solution, it slowly releases free positively charged zinc ions, which can react with the cathodic reaction product OH. - The reaction produces insoluble Zn(OH)₂. These insoluble zinc salts can deposit on the anodic region of the metal surface, blocking the diffusion path and active sites of corrosive media, forming a protective deposition film, thereby inhibiting further corrosion. The carboxyl groups of stearic acid molecules react chemically with zinc ions on the zinc oxide surface, and their long hydrophobic alkyl chains extend outward, forming a dense "molecular brush" or "monomer film" on the zinc oxide surface. This hydrophobic film effectively repels corrosive media such as water molecules, oxygen, and chloride ions, preventing them from contacting the underlying metal substrate. This is a physical barrier effect and the most direct reason for the improved performance after modification.

[0030] In the process of preparing a green and environmentally friendly composite corrosion inhibitor anti-corrosion coating, a Ce-MOF was first prepared. Ce-MOF was synthesized at room temperature using cerium chloride heptahydrate and 2-hydroxyterephthalic acid, wherein Ce... 3+The carboxylate group in 2-hydroxyterephthalic acid is linked through a coordinate bond, ultimately forming a porous coordination polymer. Compared with traditional, toxic chromate corrosion inhibitors, cerium-based compounds are considered low-toxicity or non-toxic, environmentally friendly alternatives. When Ce-MOFs are used as corrosion inhibitors, if the coating is damaged and corrosive media (such as Cl⁻ and H₂O) come into contact with the metal substrate, the pH value of the local microenvironment will change (usually the pH in the anodic area decreases). Ce-MOFs are unstable in acidic environments and undergo controlled, slow decomposition, releasing Ce³⁺ / Ce⁻. 4 ⁺ ions migrate to the metal surface and generate insoluble Ce(OH)3 and Ce(OH)4 precipitates in a high pH environment, forming a protective film that effectively inhibits the oxygen reduction reaction at the cathode, thereby blocking the entire corrosion circuit. This "release-on-demand" characteristic makes Ce-MOF a smart corrosion inhibitor, releasing active substances only when needed (when corrosion occurs), achieving a self-healing protective effect.

[0031] A corrosion-resistant coating was prepared by mixing modified zinc oxide, Ce-MOF, epoxy resin, curing agent, and diluent in a specific ratio. This coating combines environmental friendliness with excellent metal protection performance. Its components are environmentally friendly and conform to green chemistry principles. Through the synergistic effect of Ce-MOF and modified zinc oxide, this coating can form an effective protective layer on the metal surface, blocking the penetration of corrosive media and thus significantly delaying metal corrosion. Furthermore, this coating is highly versatile and suitable for various metal materials and corrosive environments; its preparation process is simple and low-cost, making it ideal for large-scale industrial production. Attached Figure Description

[0032] Figure 1 Scanning electron microscope (SEM) images of Ce-MOF (a), modified zinc oxide (b), and composite corrosion inhibitor (c) prepared in Example 1.

[0033] Figure 2 The images show the infrared spectra of the modified zinc oxide, Ce-MOF, and composite corrosion inhibitor prepared in Example 1.

[0034] Figure 3 The potentiodynamic polarization curves of Q235 steel samples coated with epoxy resin containing corrosion inhibitors in Examples 1 and Comparative Examples 1-3 were measured after immersion in 3.5 wt.% NaCl aqueous solution for 1 h.

[0035] Figure 4 Nyquist plots of Q235 steel samples coated with an epoxy resin coating containing corrosion inhibitor, as described in Examples 1 and Comparative Examples 1-3, were obtained after immersing in a 3.5 wt.% NaCl aqueous solution for 1 h.

[0036] Figure 5Bode plots of Q235 steel samples coated with an epoxy resin coating containing corrosion inhibitor, as described in Examples 1 and Comparative Examples 1-3, were obtained by immersing them in a 3.5 wt.% NaCl aqueous solution for 1 h. Detailed Implementation

[0037] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0038] The zinc oxide used in the examples was zinc oxide with a particle size of 30 nm. The E135 epoxy resin used in the examples was purchased from Kunshan Jiulimei Electronic Materials Co., Ltd., and the DY-175 water-based epoxy curing agent used in the examples was purchased from Shenyang Dongyan Coatings & Decoration Co., Ltd.

[0039] Example 1

[0040] A method for preparing a green and environmentally friendly composite corrosion inhibitor anti-corrosion coating is proposed, the method comprising the following steps:

[0041] (1) Weigh 1 g of nano zinc oxide and 1.5 g of stearic acid and add them to 60 ml of anhydrous ethanol. Stir the mixture with ultrasound for 30 min at room temperature and remove the supernatant by centrifugation. Dry the mixture at 50 °C for 12 h to obtain dry modified zinc oxide micro flakes for coating preparation.

[0042] (2) Take 24 ml of dimethylformamide, 24 ml of ethanol and 24 ml of deionized water and mix them to form a uniform solution. Add 0.65 g of 2-hydroxyterephthalic acid and 2.4 g of cerium chloride heptahydrate to the above mixed solution and sonicate to form a uniform solution. Add triethylamine to the mixed solution and adjust the pH value of the solution until the pH value is 7. Sonicate for 2 hours and stir the mixture at 400-600 rpm at room temperature for 24 hours. Centrifuge the obtained mixture at 10000 r / min for 10 min. Wash the precipitate twice with DMF and three times with anhydrous ethanol at 10000 r / min for 10 min to remove impurities. Soak the precipitate in 25 ml of dichloromethane for 24 hours and wash it twice with anhydrous ethanol at 10000 r / min for 10 min. Dry it at 60℃ for 6 h and grind it to obtain Ce-MOF nanoparticles.

[0043] (3) Take the modified zinc oxide, Ce-MOF and ethyl acetate in a mass ratio of 1:1:100. Add the modified zinc oxide and Ce-MOF to ethyl acetate and stir ultrasonically for 2 minutes. Then add 80 parts of E135 epoxy resin and 140 parts of DY-175 waterborne epoxy curing agent. Stir quickly for 10 minutes to form a uniformly dispersed slurry system. After coating, dry at 60 ℃ for 3 hours to obtain a green, environmentally friendly and efficient corrosion-resistant coating.

[0044] Example 2

[0045] A method for preparing a green and environmentally friendly composite corrosion inhibitor anti-corrosion coating is proposed. In this embodiment, steps 1 and 2 are exactly the same as in Example 1, except for step 3. The specific preparation steps of step 3 are as follows:

[0046] Take modified zinc oxide, Ce-MOF and ethyl acetate in a mass ratio of 1.5:0.5:100. Add modified zinc oxide and Ce-MOF to ethyl acetate and ultrasonically stir for 2 minutes. Then add 80 parts of E135 epoxy resin and 140 parts of DY-175 water-based epoxy curing agent and stir rapidly for 10 minutes to form a uniformly dispersed slurry system. After coating, dry at 60 ℃ for 3 hours to obtain a green, environmentally friendly and efficient corrosion-resistant coating.

[0047] Example 3

[0048] A method for preparing a green and environmentally friendly composite corrosion inhibitor anti-corrosion coating is proposed. In this embodiment, steps 1 and 2 are exactly the same as in embodiment 2, except for step 3. The specific preparation steps of step 3 are as follows:

[0049] Take modified zinc oxide, Ce-MOF and ethyl acetate in a mass ratio of 0.5:1.5:100. Add modified zinc oxide and Ce-MOF to ethyl acetate and ultrasonically stir for 2 minutes. Then add 80 parts of E135 epoxy resin and 140 parts of DY-175 water-based epoxy curing agent and stir rapidly for 10 minutes to form a uniformly dispersed slurry system. After coating, dry at 60 ℃ for 3 hours to obtain a green, environmentally friendly and efficient corrosion-resistant coating.

[0050] Comparative Example 1

[0051] In this comparative example, steps 1 and 2 are exactly the same as in Example 1, the difference being step 3. The specific preparation steps for step 3 are as follows:

[0052] (3) Add 100 parts of ethyl acetate to 80 parts of E135 epoxy resin and 140 parts of DY-175 waterborne epoxy curing agent, stir quickly for 10 min to form a uniformly dispersed slurry system, and dry at 60 ℃ for 3 h after coating to obtain the coating.

[0053] Comparative Example 2

[0054] In this comparative example, steps 1 and 2 are exactly the same as in Example 1, the difference being step 3. The specific preparation steps for step 3 are as follows:

[0055] (3) Take 2 parts of modified zinc oxide and 100 parts of ethyl acetate. Add the modified nano zinc oxide to ethyl acetate and stir ultrasonically for 10 min. Then add 80 parts of E135 epoxy resin and 140 parts of DY-175 waterborne epoxy curing agent. Stir quickly for 10 min to form a uniformly dispersed slurry system. After coating, dry at 60 °C for 3 h to obtain the coating.

[0056] Comparative Example 3

[0057] In this comparative example, steps 1 and 2 are exactly the same as in Example 1, the difference being step 3. The specific preparation steps for step 3 are as follows:

[0058] (3) Take 2 parts Ce-MOF and 100 parts ethyl acetate. Add Ce-MOF to ethyl acetate and stir ultrasonically for 10 min. Then add 80 parts E135 epoxy resin and 140 parts DY-175 waterborne epoxy curing agent. Stir quickly for 10 min to form a uniformly dispersed slurry system. After coating, dry at 60 ℃ for 3 h to obtain the coating.

[0059] The prepared coating was applied to the surface of the pretreated epoxy resin-encapsulated Q235 steel sample, with the coating thickness controlled at approximately 100 μm. The pretreated epoxy resin-encapsulated Q235 was obtained through the following steps: A Q235 carbon steel column with a diameter of 12 mm and a height of 10 mm was selected and smoothed using 240, 500, and 800 grit sandpaper, then connected to a copper wire and fixed with conductive copper glue. The carbon steel column was placed in a mold, the wire position was adjusted to ensure it was upright, and pre-mixed and thoroughly stirred sealing resin was poured into the mold to encapsulate the sample. The sealing resin consisted of epoxy resin M01-A and curing agent M01-B in a 10:3 mass ratio. After the sealing resin dried and solidified, the sample was removed and its working surface was sanded using 240, 500, 800, and 1000 grit SiC sandpaper to remove excess resin and fully expose the working surface. Finally, ultrasonic cleaning was performed using anhydrous ethanol, and the product was then placed in a drying oven to dry for later use.

[0060] Figure 1 Scanning electron microscopy (SEM) images of the modified zinc oxide and Ce-MOF prepared in Example 1, and the composite corrosion inhibitor prepared in Example 1 (the composite corrosion inhibitor is a homogeneous mixture of modified zinc oxide and Ce-MOF in a mass ratio of 1:1). Figure 2 Infrared spectral analysis was performed on the modified zinc oxide and Ce-MOF prepared in Example 1, as well as the composite corrosion inhibitor prepared in Example 1. Ce-MOF showed a value at 3325.3 cm⁻¹.- The strong, broad peak at ¹ is attributed to the OH stretching vibration of the ligand H₂BDC-OH, 528.5 cm⁻¹ - The band at ¹ proves that Ce 3+ Successful coordination with the oxygen atom in the organic ligand. 1541.1 cm - ¹, 1465.9 cm - ¹ and 1400.3 cm - The characteristic peaks at ¹ correspond to the asymmetric and symmetric stretching vibrations of the carboxylate group (-COO⁻), respectively. Ce-MOF and Ce-MOF / ZnO-SA show peaks at 1658.8 cm⁻¹. - The peak shift at ¹ may be due to Ce 3+ This is due to the enhanced attraction to CO bonds. ZnO-SA at 2848.9 cm⁻¹ - ¹ and 2918.3 cm - The absorption peak at ¹ clearly indicates the presence of the CH2 methylene group. Comparative results show that the characteristic peaks of Ce-MOF and ZnO-SA did not change significantly after mixing, indicating that the composite process did not destroy the original structures of either.

[0061] Figure 3 The coatings prepared in Examples 1 and Comparative Examples 1-3 were applied to Q235 steel and then immersed in a 3.5 wt.% NaCl aqueous solution (pH=5.5) for 1 h. The potentiodynamic polarization curves were measured. The addition of modified zinc oxide did not significantly shift the curve to the left, while the addition of Ce-MOF significantly shifted the curve to the upper left, with the corrosion potential increasing significantly to approximately −0.24 V. However, the addition of the composite corrosion inhibitor to the resin resulted in the greatest reduction in corrosion current density and the best corrosion protection performance.

[0062] Figure 4 and Figure 5 The Nyquist and Bode plots were obtained after the coatings prepared for Examples 1 and Comparative Examples 1-3 were applied to Q235 steel and then immersed in a 3.5 wt.% NaCl aqueous solution (pH=5.5) for 1 h.

[0063] from Figure 4 It can be seen that the coating with modified zinc oxide has a compressive arc radius of approximately 10. 6 The capacitive arc radius of Ce-MOF coatings reaches 10 on the order of magnitude. 9 The coating exhibits good corrosion resistance, but is still inferior to composite corrosion inhibitor coatings, with its compressive arc radius increased to approximately 10. 10 The magnitude indicates that composite corrosion inhibitors are more effective in improving the corrosion resistance of coatings.

[0064] from Figure 5 It can be seen that the impedance modulus of the blank coating is only 10 in the low-frequency region (0.01 Hz).4 The low-frequency impedance modulus of the coating with added modified zinc oxide and Ce-MOF was significantly improved to 10. 9 The magnitude is on the order of magnitude; while the coating with added composite corrosion inhibitor has a maximum |Z| of 0.01 Hz, reaching 10. 10 The magnitude indicates that, under the synergistic effect of modified zinc oxide and Ce-MOF nanoparticles, the coating has the best physical barrier ability against corrosive media, the fewest internal defects, and the best density. This shows that the composite corrosion inhibitor can play the best role in blocking corrosive media.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A green and environmentally friendly composite corrosion inhibitor, characterized in that... It is composed of modified zinc oxide and Ce-MOF, with a mass ratio of modified zinc oxide to Ce-MOF of 1:3 to 3:1; The modified zinc oxide is prepared by the following steps: adding nano zinc oxide and stearic acid to anhydrous ethanol, stirring and mixing the mixture, centrifuging to remove the supernatant, and drying to obtain dry modified zinc oxide.

2. The green and environmentally friendly composite corrosion inhibitor according to claim 1, characterized in that: The mass ratio of the modified zinc oxide to Ce-MOF is 1:

1.

3. The green and environmentally friendly composite corrosion inhibitor according to claim 1, characterized in that: In the preparation steps of modified zinc oxide, the ratio of the amount of nano zinc oxide, stearic acid and anhydrous ethanol is 1g:(1-2)g:(40-60)mL, and the nano zinc oxide is nano zinc oxide with an average diameter of 1-100nm. The stirring and mixing reaction mentioned refers to stirring and mixing at 25-35℃ for 15-30 minutes.

4. The green and environmentally friendly composite corrosion inhibitor according to claim 1, characterized in that: The Ce-MOF was prepared by the following steps: 2-hydroxyterephthalic acid and cerium chloride heptahydrate were added to solvent 1, mixed evenly, pH was adjusted to 7 and the mixture was stirred to react. After the reaction was completed, the mixture was centrifuged, washed and purified to obtain Ce-MOF nanoparticles.

5. The green and environmentally friendly composite corrosion inhibitor according to claim 4, characterized in that: Solvent 1 is a mixed solution of water, ethanol, and N,N-dimethylformamide, with a volume ratio of 1:(0.8-1.5):(0.8-1.5). The amounts of 2-hydroxyterephthalic acid, cerium trichloride heptahydrate, and solvent 1 meet the ratio of 1g:(3.4-4.1)g:(100-130)ml; The stirring reaction refers to stirring at room temperature for 20-30 hours.

6. The green and environmentally friendly composite corrosion inhibitor according to claim 4, characterized in that: The washing mentioned refers to washing with N,N-dimethylformamide and ethanol in sequence; The purification process involves soaking the product in dichloromethane for 15-30 hours, centrifuging it, washing it with ethanol, and finally drying and grinding it to obtain purified Ce-MOF nanoparticles.

7. The application of the green and environmentally friendly composite corrosion inhibitor according to any one of claims 1-6 in the preparation of anti-corrosion coatings.

8. A corrosion-resistant coating, characterized in that... The product comprises the following components in parts by weight: 1-2 parts of the green and environmentally friendly composite corrosion inhibitor as described in any one of claims 1-6, 40-80 parts of epoxy resin, 70-140 parts of curing agent, and 50-100 parts of diluent.

9. The anti-corrosion coating according to claim 8, characterized in that: The epoxy resin is a bisphenol A type epoxy resin; The curing agent is a water-based epoxy curing agent; The diluent is at least one of ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, dimethyl carbonate, and propylene glycol methyl ether acetate.

10. A method for preparing an anti-corrosion coating according to claim 8 or 9, characterized in that... Includes the following steps: The green and environmentally friendly composite corrosion inhibitor described in any one of claims 1-6 is added to a diluent and ultrasonically stirred to obtain a uniform solution. Then, epoxy resin and curing agent are added to the uniform solution and stirred to form a uniformly dispersed slurry system. This slurry system is then coated onto the substrate surface to prepare an anti-corrosion epoxy resin coating.

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