CN116145206A - Intelligent metal frame-conductive polymer anti-corrosion coating, preparation method and application - Google Patents

Abstract

The invention discloses an intelligent metal frame-conductive polymer anti-corrosion coating and its preparation method and application. The preparation method includes: preparing metal-organic framework ZIFs by using a normal temperature synthesis method; preparing a mixed electrolyte for electrodeposition to prepare a composite coating; using a constant potential The method uses a three-electrode system, uses the mixed solution prepared in step (2) as the electrolyte, and electrodeposits a composite coating on the surface of the working electrode to obtain an electrochemically deposited metal-organic framework-conductive polymer anti-corrosion coating. The raw material of the coating in the present invention is easy to obtain and has low toxicity. It can form a film directly, quickly and in a large area on the surface of the metal substrate, and is not restricted by factors such as the shape of the substrate and the surface morphology, effectively avoiding the existing conductive polymer coating. With defects such as poor adhesion and unstable service performance, it has good application prospects in stainless steel materials and fuel cell metal plates serving in acidic soils, seawater splash areas, etc.

Description

Intelligent metal frame-conductive polymer anti-corrosion coating and its preparation method and application

technical field

The invention relates to the technical field of metal corrosion protection, in particular to an intelligent metal frame-conductive polymer anticorrosion coating, a preparation method and application thereof.

Background technique

Corrosion is a natural phenomenon in which metals undergo chemical or electrochemical reactions with media in a certain environment, resulting in deterioration or performance degradation of metals. Metal corrosion can cause irreversible damage to ships, bridges, pipelines, public buildings, household equipment, etc., seriously threatening public safety and causing huge economic losses and environmental pollution. As a commonly used metal material in industry, stainless steel is widely used in construction, shipbuilding, petrochemical, fuel cell plates and other fields. However, in the presence of corrosive media such as chloride ions and sulfur-containing compounds, the corrosion process of stainless steel materials during long-term service is still inevitable. According to statistics, about 20% of stainless steel rusts every year. In the actual environment, the corrosion of stainless steel cannot be completely stopped, but the corrosion rate of stainless steel can be reduced by various means to make the corrosion process controllable, thereby prolonging the service life of stainless steel and reducing its application cost. At present, there are many methods to prevent stainless steel corrosion, among which the coating anti-corrosion method is one of the most important methods to improve the corrosion resistance of stainless steel.

Traditional anti-corrosion coatings are mainly resinous organic coatings, and the anti-corrosion mechanism is to isolate corrosive substances by forming a physical barrier on the surface of the metal substrate. However, due to the inherent defects of the film-forming substances, there are usually micropores in the constructed coating structure, which cannot play a long-term corrosion protection role. In recent years, the construction of intelligent anti-corrosion coatings has attracted widespread attention, and it is expected to overcome the bottleneck problem that the single protection mechanism of coatings cannot meet the long-term and stable protection of stainless steel. Conductive polymers (Conductive polymers, CPs) are a special class of polymer materials. After doping, CPs can change from an insulating state to a conductive state. As a coating material, it can not only isolate the corrosive environment, but also protect the coating/metal interface. Form an oxide film at the place, maintain the corrosion potential of the protected metal in the passivation area, and further strengthen the corrosion protection function of the coating (anodic protection function). However, CPs coatings usually have defects such as micropores and cracks, and the dedoping of anions during long-term service can lead to the gradual reduction of CPs to an insulating state, weakening the anodic protection of the coating and making the coating gradually invalid. Therefore, the stability of CPs coatings during long-term service greatly limits their practical application in the field of corrosion protection.

Metal organic frameworks (Metal organic frameworks, MOFs) are organic-inorganic hybrid materials with intramolecular pores formed by the self-assembly of organic ligands and metal ions or clusters through coordination bonds. And large pore volume and abundant action sites, widely used in the fields of biosensing, drug delivery and catalysis. At present, MOFs materials have been reported as nano-microcapsule sealing corrosion inhibitors to increase the anti-corrosion performance of coatings.

In the prior art, the invention patent with the application announcement number of CN110387548A discloses a metal-organic framework-encapsulated corrosion inhibitor compound and its preparation method and application. The corrosion inhibitor is encapsulated in MOFs nanoshells to construct a new corrosion inhibition system suitable for For the corrosion environment in the seawater splash area, the characteristic of MOFs material ZIF-67 sensitive to acidic environment is used to quickly release the encapsulated corrosion inhibitor to act on the corrosion area. However, the compound is added to the acidic corrosion environment in the form of corrosion inhibitor to play a role, which limits its application range. The invention patent with application notification number CN112521837A discloses a MOF-loaded corrosion inhibitor filler, self-repairing anti-corrosion coating and its preparation method. The corrosion inhibitor is encapsulated in hmt-MOF and used as an epoxy resin filler. The protective coating endows the coating with self-healing properties, but the dispersion of MOFs encapsulated with corrosion inhibitors as fillers in the coating substrate also limits its corrosion inhibition performance.

Contents of the invention

Aiming at the problems mentioned in the background technology, the present invention provides an intelligent metal frame-conductive polymer anti-corrosion coating and its preparation method and application, so as to overcome the inability of the existing anti-corrosion coating to meet long-term and stable corrosion protection, and the existing Defects and deficiencies in intelligent anti-corrosion technology. The intelligent metal organic framework-conductive polymer anti-corrosion coating of the present invention is composed of metal organic framework materials ZIFs and CPs materials such as polyaniline (PANI) and polypyrrole (PPY) with corrosion inhibition function, through the synergy of CPs and MOFs It can realize the targeted intelligent corrosion protection of stainless steel and other metal materials in the acid service environment.

Above-mentioned technical purpose of the present invention is achieved through the following technical solutions:

A method for preparing a metal frame-conductive polymer anticorrosion coating, comprising the following steps:

Step (1), preparing metal-organic framework ZIFs by normal temperature synthesis method, ZIFs at least including ZIF-67 and/or ZIF-8;

Step (2), preparing mixed electrolyte for electrodeposition to prepare composite coating: disperse conductive polymer monomer, sodium lauryl sulfate anionic surfactant in deionized water, then add the ZIFs prepared in step (1) , followed by ultrasonic stirring to obtain a mixed solution;

Step (3), using a three-electrode system using a constant potential method, using the mixed solution prepared in step (2) as an electrolyte, electrodepositing a composite coating on the surface of the working electrode to obtain an electrochemically deposited metal-organic framework-conductive polymer anti-corrosion coating layer.

Preferably, in step (1), the ZIFs material is provided with a metal salt as a central metal ion, and an imidazole organic compound as an organic ligand.

In any of the above schemes, preferably, the metal salt is Zn(NO ₃ ) ₂ ·6H ₂ O and/or Co(NO ₃ ) ₂ ·6H ₂ O, and the imidazole organic compound is 2-methylimidazole.

Preferably in any of the above schemes, in step (1), the preparation method of the ZIFs material is: at least one or both of Zn(NO ₃ ) ₂ ·6H ₂ O and Co(NO ₃ ) ₂ ·6H ₂ O A mixed metal salt is dissolved in water or methanol to obtain component A, and 2-methylimidazole organic ligand is dissolved in water or methanol to obtain component B. After component A and component B are fully dissolved, the component Component B was quickly poured into component A and stirred to mix the two. After standing at room temperature for reaction, the precipitate was obtained by centrifugation, and the precipitate was washed repeatedly with methanol and dried to obtain metal organic framework crystal materials ZIF-67, ZIF- 8.

In any of the above schemes, it is preferred that the mixing and stirring time of the components A and B is 30 minutes, the reaction time of standing at room temperature after mixing is 12-48 hours, and the centrifugation time after the reaction is 10-30 minutes, and wash with methanol After 3-5 times, the precipitate is vacuum-dried, the drying temperature is 50-80° C., and the drying time is 12-48 hours.

In the above steps, after component A and component B are mixed, the reaction time at room temperature is any value within the range of 12-48h, such as 12h, 15h, 20h, 25h, 30h, 35h, 40h, 48h; the centrifugation time after reaction It can be any value within the range of 10-30min, such as 10min, 20min, 30min; after washing with methanol for 3-5 times, the precipitate is vacuum-dried, and the drying temperature is any value within the range of 50-80°C, such as 50°C, 60°C ℃, 70℃, 80℃; the drying time is any value within the range of 12-48h, such as 12h, 15h, 20h, 25h, 30h, 35h, 40h, 48h.

Preferably in any of the above schemes, in step (1), during the preparation of ZIF-67 and ZIF-8, the molar ratios of the central ion and the ligand are 1:58 and 1:70, respectively.

Preferably in any of the above-mentioned schemes, in step (1), during the preparation of ZIF-67 and ZIF-8, the centrifugation speed of the product is 8000rmp, the separation time is 10-20min, and the centrifugal cleaning time of methanol is 10-20min each time . The centrifugation time of the product is any value within the range of 10-20 minutes, such as 10 minutes, 15 minutes, 20 minutes; the time of each centrifugal cleaning of methanol is 10-20 minutes, any value within the range, such as 10 minutes, 15 minutes, 20 minutes.

Preferably in any of the above schemes, in step (1), the polymer monomer (CPs monomer) includes at least one of polyaniline (PANI) and polypyrrole (PPY).

Preferably in any of the above schemes, in step (2), the mixed solution includes pyrrole or aniline monomers with a concentration of 0.1 to 0.5 mol/L, sodium lauryl sulfate of 0.05 to 0.3 mol/L and 0.5-2 mg/mL of ZIFs.

The concentration of pyrrole or aniline monomer is any value within the range of 0.1-0.5mol/L, such as 0.1mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L; lauryl sulfate The sodium concentration is any value within the range of 0.05-0.3 mol/L, such as 0.05 mol/L, 0.1 mol/L, 0.15 mol/L, 0.2 mol/L, 0.25 mol/L, 0.3 mol/L. ZIFs concentration is any value within the range of 0.5-2 mg/mL, such as 0.5 mg/mL, 1 mg/mL, 1.5 mg/mL, 2 mg/mL.

In any of the above schemes, preferably, in step (2), the mixed solution is ultrasonicated for 10-20 minutes and then magnetically stirred for 10-30 minutes to obtain a uniform mixed electrolyte.

In this step, the ultrasonic time of the mixed solution is any value within the range of 10-20 min, such as 10 min, 15 min, 20 min; the magnetic stirring time is any value within the range of 10-30 min, such as 10 min, 15 min, 20 min, 25 min, 30 min.

Preferably in any of the above-mentioned schemes, in step (3), the reference electrode and the counter electrode in the three-electrode deposition system are respectively Ag/AgCl electrodes and platinum sheet electrodes, and the working electrodes are stainless steel substrates that require corrosion protection. The chemical deposition process adopts the constant potential deposition method, and the electrodeposition time is 10 to 30 minutes.

In any of the above schemes, it is preferred that in the method of electrodeposition by constant potential method, for aniline and pyrrole monomers, the deposition voltages are respectively -1.3V and 1.4V, and the electrodeposition time is 10 to 30min. The prepared The drying temperature of the coating is 30-50°C, and the drying time is 3-5 hours. In this step, the electrodeposition time is any value within the range of 10-30min, such as 10min, 15min, 20min, 25min, 30min; the drying temperature of the prepared coating is any value within the range of 30-50°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, the drying time is any value within the range of 3-5h, such as 3h, 4h, 5h.

In any of the above schemes, it is preferred that during the electrodeposition process, the working electrode is a stainless steel substrate that requires anti-corrosion treatment, and the surface of the stainless steel substrate is a surface of any shape.

In any of the above schemes, it is preferable to encapsulate the non-coated deposition surface of the stainless steel with epoxy resin before preparing the coating, and to polish the deposition surface, followed by cleaning with deionized water, acetone, and ethanol in sequence.

Preferably in any of the above schemes, in step (3), the electrochemically deposited metal-organic framework-conductive polymer anti-corrosion coating is cleaned with deionized water and dried at a drying temperature of 30-50°C and a drying time of 3 ~5h.

The present invention also provides a metal organic framework-conductive polymer anti-corrosion coating prepared according to any one of the methods described above.

The present invention also provides a metal organic framework-conductive polymer anticorrosion coating prepared according to any one of the methods described above, which is applied to corrosion protection of stainless steel in an acidic environment.

Preferably in any of the above schemes, the acidic environment is a 0.1-0.5 mol/L sulfuric acid or hydrochloric acid solution.

The anti-corrosion effect in acidic corrosion environment was characterized by electrochemical test. The electrochemical test is carried out through a three-electrode system, in which the sample to be tested is the working electrode, the platinum sheet electrode is the counter electrode, and the Ag/AgCl electrode is the reference electrode.

Preferably, in any of the above schemes, the specific electrochemical test includes potentiodynamic polarization test, open circuit potential test and electrochemical impedance spectroscopy test.

Beneficial effect

(1) As a representative class of MOFs, zeolitic imidazolate frameworks (ZIFs) are a class of tetrahedral framework materials with imidazole esters as organic ligands. As anti-corrosion materials, ZIFs have the characteristics of stability and acid sensitivity that other types of MOFs do not have, and the imidazole ligands in the structure endow ZIFs with natural corrosion inhibition function. Therefore, the use of ZIFs and CPs in situ compounding to construct anti-corrosion coating materials can give full play to the advantages of both, and the self-healing properties of the coating can be endowed through the designability of the structure and function of ZIFs, while CPs are attached to the surface and channels of ZIFs to form a layered conductive layer. Network, give full play to the function of anodic protection and physical barrier, strengthen the anti-corrosion performance of the coating, and finally realize the intelligent protection of metals.

(2) The preparation method of the metal organic framework-conductive polymer anti-corrosion coating provided by the present invention has simple process, safety and environmental protection, low energy consumption, and is not limited by the shape of the stainless steel substrate, and can deposit functional metals quickly on the surface of stainless steel Organic Frameworks - Conductive Polymer Anticorrosion Coatings. The invention strictly controls the concentration of CPs monomer, sodium dodecyl sulfate dopant and ZIFs and electrodeposition conditions, effectively inserts the dopant into the main chain of CPs and realizes the combination of ZIFs and CPs.

(3) The present invention builds an intelligent composite anti-corrosion coating system, which overcomes the problem of poor anti-corrosion stability in the existing passive anti-corrosion coating technology. The invention uses the special metal organic framework compound ZIFs to endow the coating with self-repair function, and compound the conductive polymer to strengthen the anodic protection performance and physical barrier function of the coating. ZIFs are assembled from metal central ions such as Zn and Co and 2-methylimidazole organic ligands with corrosion inhibition function, and have abundant active sites, which are conducive to combining with conductive polymers and have good compatibility. The constructed composite coating can interact with the protected metal substrate to form metal-N/O coordination bonds, hydrogen bonds, etc., which is conducive to improving the adhesion of the coating and preventing the penetration of corrosive substances to the coating/substrate interface.

(4) The main working principle of this application is: the ZIFs material composed of organic ligands with corrosion inhibition properties exhibits water stability and acid dissociation, and is sensitive to pH changes. In acidic corrosive media, the physical barrier formed by the composite coating composed of CPs and ZIFs on the surface of metal materials can effectively prevent the inward penetration of corrosive substances. Under the condition of no corrosion, CPs can give full play to the anodic protection performance, effectively reduce the corrosion potential of the base metal material and make it in a passivation state, while ZIFs maintain a stable state, avoiding the degradation of the corrosion inhibitor active groups in the environment . When the continuous attack of corrosive substances causes local damage to the coating, while CPs play an anodic protective role, the pH change in a small range caused by the corrosion reaction stimulates the coordination bonds in ZIFs, which can promote the dissociation of ZIFs and release ligands. The bulk corrosion inhibitor acts on the damaged area of the coating, so as to realize the targeted delivery of the corrosion inhibitor to the corrosion-induced site and achieve the self-healing effect of the coating.

(5) The raw material of the coating in the present invention is easy to obtain and has low toxicity, and is easy to prepare. It can form a film directly, quickly and in a large area on the surface of the metal substrate, and is not restricted by factors such as the shape of the substrate and the surface morphology, effectively avoiding the existing The conductive polymer coating has defects such as poor adhesion and unstable service performance, and has good application prospects in stainless steel materials and fuel cell metal plates serving in acidic soils, seawater splash areas, etc. The intelligent metal-organic framework-conductive polymer anti-corrosion coating material prepared by the present invention realizes the organic combination of the anti-corrosion advantages of the metal-organic framework and the conductive polymer, and the stable and reliable anti-corrosion performance of the coating is verified by electrochemical experiments. It is suitable for corrosion protection of stainless steel materials in acidic environments such as acidic soil, inside of fuel cells, and seawater splash areas. The invention has reasonable technical route, simple and environment-friendly coating preparation process, excellent product performance and wide application prospect.

Description of drawings

Fig. 1 is the preparation flowchart of the intelligent metal organic framework-conductive polymer anticorrosion coating of the present invention;

Fig. 2 is the topography figure of the synthesized ZIF-67 nanoparticle in the embodiment of the present invention 1;

Fig. 3 is the topography figure of coating in embodiment 2 of the present invention and comparative example 2, wherein a is the topography figure of ZIF-67-PPY anticorrosion coating in embodiment 2, and b is PPY anticorrosion coating in comparative example 2 surface topography;

Fig. 4 is the change of the Nyquist figure of the electrochemical impedance spectrum with the service time when the embodiment 2 of the present invention and comparative example 2 serve for a long time in acidic corrosion environment (0.1mol/L HCl), wherein a is the ZIF- The Nyquist figure of 67-PPY anticorrosion coating, b is the Nyquist figure of PPY anticorrosion coating in comparative example 2;

Fig. 5 is the change curve of open circuit potential with sample service time when the embodiment of the present invention 2 and comparative example 2 are in service for a long time, and the potentiodynamic polarization curve of embodiment 2, comparative example 2 and 430 stainless steel bare steel;

FIG. 6 is a surface topography diagram of ZIF-8 nanoparticles synthesized in Example 4 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the present invention without any creative work by the technicians. All other obtained embodiments belong to the protection scope of the present invention. Unless otherwise specified, the relevant materials appearing in the subsequent examples are prepared from the previous examples.

A method for preparing an intelligent metal organic framework-conductive polymer anti-corrosion coating of the present invention, the preparation process is shown in Figure 1, including the following steps:

(1) Two kinds of MOFs materials with imidazole ligands ZIF-67 and ZIF-8 were prepared by normal temperature synthesis method;

(2) Disperse CPs monomer aniline or pyrrole, sodium lauryl sulfate anion dopant and ZIFs in deionized water to prepare a uniform mixed solution;

(3) Using a three-electrode system to electrodeposit a coating in the mixed solution to obtain the metal organic framework-conductive polymer anticorrosion coating.

Wherein, the ZIFs prepared by the normal temperature synthesis method are ZIF-67 and ZIF-8 materials, which specifically include processes such as crystal growth, centrifugation, washing, and vacuum drying. The more specific process of ZIF-67 crystal growth is: add a certain amount of Co(NO ₃ ) ₂ ·6H ₂ O to 50-100mL water or methanol to obtain component A, and add a certain amount of 2-methylimidazole to Obtain component B in 50-100mL of water or methanol. After A and B are fully stirred and dissolved, quickly pour B into A and stir to mix. The molar ratio of metal ion and imidazole ligand is 1:58. The mixed solution is at room temperature After stirring for 30 minutes, let it stand for 12-48 hours to make the crystal grow. The speed of centrifugation is 8000rmp, centrifuge for 10-30 minutes, use methanol to wash 3-5 times, and the lower precipitate after washing is vacuum-dried at 50-80°C for 12-48 hours; The more specific process of ZIF-8 crystal growth is: replace the nitrate that provides the central metal ion with Zn(NO ₃ ) ₂ 6H ₂ O, wherein the molar ratio of the metal ion to the imidazole ligand is 1:70, and the rest The steps are the same as ZIF-67.

Example 1

An intelligent metal frame-conductive polymer composite conductive anti-corrosion coating, specifically ZIF-67-PANI composite coating, the preparation method specifically includes the following steps:

Step 1: Preparation of ZIF-67 by synthetic method at room temperature: Add 2.70 g of Co(NO ₃ ) ₂ 6H ₂ O to 50 mL of methanol to obtain component A, and add 44.24 g of 2-methylimidazole to 100 mL of methanol Obtain component B. After A and B are fully stirred and dissolved, quickly pour B into A and stir to mix. Stir at room temperature for 30 minutes and then stand for reaction for 48 hours to make crystals grow. Then centrifuge at 8000rmp for 10min, collect the precipitate, wash with methanol for 5 times, 10min each time, and vacuum-dry the lower precipitate after washing at 70°C for 24h to obtain ZIF-67 nanoparticles. The surface morphology of the ZIF-67 nanoparticles in this example is shown in Figure 2, showing a rhombic dodecahedral structure with a size of 200-400 nm.

Step 2: Treatment of stainless steel substrate: use epoxy resin to encapsulate the non-deposited surface of block 430 stainless steel, leaving a 1×1cm ² deposition area and the contact area of the electrode clip, and use 240, 800, and 1500-mesh metallographic sandpaper in sequence The deposited area was sanded, then cleaned with deionized water, acetone, and ethanol in sequence, and finally dried.

The third step: the metal-organic framework-conducting polymer coating was prepared by a one-pot electrodeposition method. Add aniline monomer, sodium lauryl sulfate, and ZIF-67 into 100 mL of deionized water, sonicate for 15 minutes, and magnetically stir for 30 minutes to prepare a uniform mixed solution, in which the concentration of aniline monomer is 0.25 mol/L, dodecyl The concentration of sodium sulfate is 0.3mol/L, and the concentration of ZIF-67 is 0.5mg/mL. The treated stainless steel substrate was used as the working electrode, the platinum sheet electrode was used as the counter electrode, and the Ag/AgCl electrode was used as the reference electrode. The coating was electrodeposited on the stainless steel surface by the constant potential method. The electrodeposition time was 15 minutes and the deposition voltage was -1.3V. , the obtained coating is labeled ZIF-67-PANI coating.

The coating product obtained in this example has a dense structure and a uniform appearance, mainly showing the appearance of wrinkled PANI. The potentiodynamic polarization test can judge the corrosion behavior of the electrode surface, characterize the corrosion tendency and degree of the material, and reflect the corrosion resistance of the sample after the coating is applied. Compared with the 430 stainless steel substrate without coating, the self-corrosion voltage of the coating sample obtained in this embodiment in the corrosive environment simulated by 0.3mol/L sulfuric acid has increased by 310mV, indicating that the resistance of 430 stainless steel has been significantly improved. corrosion.

Comparative example 1

The difference from Example 1 is:

Add aniline monomer and sodium lauryl sulfate to 100 mL of deionized water, ultrasonicate for 15 minutes, and magnetically stir for 30 minutes to prepare a uniform mixed solution, wherein the concentration of aniline monomer is 0.25 mol/L, and the concentration of sodium lauryl sulfate 0.3mol/L;

Other conditions are the same as in Example 1, and the PANI coating is obtained by electrodeposition by constant potential method.

The PANI coating prepared in this comparative example has a loose structure and presents many micropores and microcracks.

Example 2

An intelligent metal frame-conductive polymer composite conductive anti-corrosion coating, specifically ZIF-67-PPY composite coating, the preparation method specifically includes the following steps:

Step 1: Preparation of ZIF-67 by synthetic method at room temperature: Add 2.70 g of Co(NO ₃ ) ₂ 6H ₂ O to 25 mL of water to obtain component A, and add 44.24 g of 2-methylimidazole to 160 mL of water to obtain component A Divide into B. After A and B are fully stirred and dissolved, quickly pour B into A and stir to mix. Stir at room temperature for 30 minutes and then let it stand for 24 hours to make the crystal grow. Then centrifuge at 8000rmp for 15min, collect the precipitate, wash with methanol for 3 times, 10min each time, and vacuum-dry the lower precipitate after washing at 60°C for 24h to obtain ZIF-67 nanoparticles. The morphology of the ZIF-67 product in this example is similar to that of Figure 2, showing a rhombic dodecahedral structure with a size of 200-300 nm.

Step 2: Treatment of stainless steel substrate: Use epoxy resin to encapsulate the non-deposited surface of 430 stainless steel sheet, leaving a 1× ^1cm2 deposition area and electrode clamp contact area, and use 240, 800, and 1500-mesh metallographic sandpaper in sequence The deposited area was sanded, then cleaned with deionized water, acetone, and ethanol in sequence, and finally dried.

The third step: the metal-organic framework-conducting polymer coating was prepared by a one-pot electrodeposition method. Add pyrrole monomer, sodium lauryl sulfate, and ZIF-67 into 100 mL of deionized water, sonicate for 10 minutes, and magnetically stir for 20 minutes to prepare a uniform mixed solution, in which the concentration of pyrrole monomer is 0.4 mol/L, dodecyl The concentration of sodium sulfate is 0.15 mol/L, and the concentration of ZIF-67 is 1 mg/mL. The treated stainless steel substrate is the working electrode, the platinum sheet electrode is the counter electrode, and the Ag/AgCl electrode is the reference electrode. The constant potential method is used to electrodeposit the coating on the surface of the stainless steel. The electrodeposition time is 10min, and the deposition voltage is 1.4V. The coating obtained is labeled ZIF-67-PPY coating.

The MOF-conductive polymer coating product obtained in this example has a compact structure and a uniform appearance, as shown in Figure 3(a).

Electrochemical impedance spectroscopy can semi-quantitatively evaluate the physical barrier performance of the coating system to the corrosive environment and the kinetic process of interfacial corrosion, thereby reflecting the anti-corrosion ability of the coating and the kinetic process of coating damage. The Nyquist figure of the electrochemical impedance spectrum in service 600h in the simulated corrosion environment of 0.1mol/L HCl is shown in accompanying drawing 4 (a), it can be seen that the impedance of this embodiment is always in the first 240h of service. It showed an increasing trend, and although the impedance decreased slightly after 240 hours of service, it was still significantly higher than that at the beginning of service. This is because PPY and ZIF-67 can play a synergistic role through the implementation of anodic protection performance and the release of corrosion inhibitors, endowing the coating with intelligent active protection capabilities, and can still maintain a high level of corrosion resistance when tiny defects appear in the long-term service of the coating. corrosion effect.

Comparative example 2

PPY coating preparation

The difference from Example 2 is:

Add pyrrole monomer and sodium lauryl sulfate to 100 mL of deionized water, ultrasonicate for 10 minutes, and magnetically stir for 20 minutes to prepare a uniform mixed solution, in which the concentration of pyrrole monomer is 0.4 mol/L, and the concentration of sodium lauryl sulfate is 0.4 mol/L. 0.15mol/L;

Other conditions are the same as in Example 2, and the PPY coating is obtained by electrodeposition by constant potential method.

The morphology of the PPY coating prepared in this comparative example is shown in Figure 3(b). The coating is composed of cauliflower-like PPY particles with micropores between the particles. The Nyquist figure of the electrochemical impedance spectrum in service 600h in the simulated corrosion environment of 0.1mol/L HCl is shown in accompanying drawing 4 (b), it can be seen that the impedance of this comparative example reaches the maximum when service 48h, shows The coating has excellent corrosion resistance in harsh corrosive environments during the 0-48h service time. However, after the coating has been in service for 48 hours, the impedance shows a linear decrease trend. It can be seen from the enlarged illustration that the impedance after 600 hours of service is even lower than the impedance value at the initial stage of service, indicating that the coating is invalid and the coating does not have a stable corrosion protection effect. , the anti-corrosion effect is significantly inferior to the anti-corrosion effect of the coating in Example 2.

The change of the open circuit potential (OCP) of the coating during long-term service in a corrosive environment can evaluate its spontaneous reaction in the form of passivation or activation in the environment, the formation of a steady-state potential and its stability, and then reflect the anti-corrosion properties of the coating. performance. Accompanying drawing 5 (a) is the variation curve of the OCP value of embodiment 2 and comparative example 2 with service time, as seen in the service time of 600h, embodiment 2 among the present invention, promptly is made of ZIF-67, PPY, dodecane The coating material constructed by sodium radical sulfate has a higher OCP value compared with Comparative Example 2, and basically maintains a relatively stable value during the entire service period, indicating that Example 2 has excellent corrosion resistance, and the coating can be used for Stainless steel provides long-lasting, stable, excellent corrosion protection.

Accompanying drawing 5 (b) is embodiment 2, comparative example 2 and the stainless steel bare steel that does not apply coating in the acid corrosion environment that the HCl of 0.1mol/L simulates the zeta potential polarization curve, it can be seen that embodiment 2 of the present invention With the highest self-corrosion potential and the lowest self-corrosion current density, compared with bare stainless steel, the self-corrosion voltage has increased by 495mV. It can be seen from the above electrochemical test results that the corrosion protection efficiency of Example 2 is higher, which is not only related to the dense structure of the coating (as shown in Figure 3 (a)), but also benefited from the combination of CPs, dopants and MOFs. The synergistic effect of the two, by giving full play to their respective advantages, endows the coating with intelligent active protection ability, and effectively improves the corrosion resistance of stainless steel.

Example 3:

An intelligent metal frame-conductive polymer composite conductive anticorrosion coating, specifically a ZIF-8-PANI composite coating, the preparation method comprising the following steps:

Step 1: Preparation of ZIF-8 by room temperature synthesis method: Add 1.17g of Zn(NO ₃ ) ₂ ·6H ₂ O to 100mL of water to obtain component A, add 22.70g of 2-methylimidazole to 100mL of water to obtain component A Divide into B. After A and B are fully stirred and dissolved, quickly pour B into A and stir to mix. Stir at room temperature for 30 minutes and then let it stand for 36 hours to make the crystal grow. Then centrifuge at 8000rmp for 20min, collect the precipitate, wash with methanol for 4 times, 10min each time, and vacuum dry the washed lower layer at 50°C for 48h to obtain ZIF-8 nanoparticles. In this embodiment, the ZIF-8 nanoparticles have a rhombic dodecahedron structure and a size of 100-150 nm.

Step 2: Treatment of stainless steel substrate: use epoxy resin to encapsulate the non-deposition surface of block 304 stainless steel, leaving a 1×1cm ² deposition area and electrode clamp contact area, and use 240, 800, 1500 mesh metallographic sandpaper in sequence The deposited area was sanded, then cleaned with deionized water, acetone, and ethanol in sequence, and finally dried.

The third step: the metal-organic framework-conducting polymer coating was prepared by a one-pot electrodeposition method. Add aniline monomer, sodium lauryl sulfate, and ZIF-8 into 100 mL of deionized water, sonicate for 20 minutes, and magnetically stir for 20 minutes to prepare a uniform mixed solution, in which the concentration of aniline monomer is 0.5 mol/L, dodecyl The concentration of sodium sulfate is 0.25mol/L, and the concentration of ZIF-8 is 2mg/mL. The treated stainless steel substrate is the working electrode, the platinum sheet electrode is the counter electrode, and the Ag/AgCl electrode is the reference electrode. The constant potential method is used to electrodeposit the coating on the surface of the stainless steel. The electrodeposition time is 30 minutes and the deposition voltage is -1.3V. , the obtained coating is labeled ZIF-67-PANI coating.

The appearance of the coating product obtained in this example is similar to the appearance of the coating in Example 1 shown in Figure 3(a), with a dense structure and uniform appearance, showing a more complex micro-morphology. Compared with the uncoated stainless steel substrate, its self-corrosion voltage increased by 298mV in the corrosive environment simulated by 0.5mol/L hydrochloric acid.

Comparative example 3

The difference with embodiment 3 is:

Add the aniline monomer and sodium lauryl sulfate into 100 mL of deionized water, ultrasonicate for 20 min, and magnetically stir for 20 min to prepare a uniform mixed solution, in which the concentration of aniline monomer is 0.5 mol/L, and the concentration of sodium lauryl sulfate is 0.5 mol/L. 0.25mol/L;

Other conditions are the same as in Example 3, and the PANI coating is obtained by electrodeposition by constant potential method.

The PANI coating prepared in this comparative example has a loose structure and presents more micropores and microcracks.

Example 4

An intelligent metal frame-conductive polymer composite conductive anticorrosion coating, specifically a preparation method for a ZIF-8-PPY composite coating, comprising the following steps:

Step 1: Preparation of ZIF-8 by synthetic method at room temperature: Add 1.17g of Zn(NO ₃ ) ₂ ·6H ₂ O to 20mL of methanol to obtain component A, and add 22.70g of 2-methylimidazole to 100mL of methanol Obtain component B. After A and B are fully stirred and dissolved, quickly pour B into A and stir to mix. Stir at room temperature for 30 minutes and then stand for reaction for 24 hours to make crystals grow. Then, centrifuge at 8000rmp for 15min, collect the precipitate, wash with methanol for 3 times, each time for 15min, and vacuum dry the lower precipitate after washing at 60°C for 48h to obtain ZIF-8 nanoparticles. The morphology of ZIF-8 nanoparticles in this example is shown in Figure 6, and the product has a rhombic dodecahedral structure with a size of 70-100 nm.

Step 2: Treatment of stainless steel substrate: use epoxy resin to encapsulate the non-deposition surface of 304 stainless steel sheet, leaving a 1×1cm ² deposition area and electrode clamp contact area, and use 240, 800, 1500 mesh metallographic sandpaper in sequence The deposited area was sanded, then cleaned with deionized water, acetone, and ethanol in sequence, and finally dried.

The third step: the metal-organic framework-conducting polymer coating was prepared by a one-pot electrodeposition method. Add pyrrole monomer, sodium lauryl sulfate, and ZIF-8 into 100 mL of deionized water, sonicate for 10 minutes, and magnetically stir for 20 minutes to prepare a uniform mixed solution, wherein the concentration of pyrrole monomer is 0.2 mol/L, dodecyl The concentration of sodium sulfate was 0.1 mol/L (SDS), and the concentration of ZIF-8 was 1.5 mg/mL. The treated stainless steel substrate is the working electrode, the platinum sheet electrode is the counter electrode, and the Ag/AgCl electrode is the reference electrode. The constant potential method is used to electrodeposit the coating on the surface of the stainless steel. The electrodeposition time is 20 minutes and the deposition voltage is 1.4V. , the obtained coating is labeled ZIF-8-PPY coating.

The MOF-conductive polymer coating product obtained in this example has a compact structure and a uniform appearance. Compared with the uncoated 304 stainless steel substrate, its self-corrosion voltage increased by 463mV in the corrosive environment simulated by 0.5mol/L sulfuric acid.

Comparative example 4

The difference with embodiment 4 is:

Add pyrrole monomer and sodium lauryl sulfate to 100 mL of deionized water, ultrasonicate for 10 min, and magnetically stir for 20 min to prepare a uniform mixed solution, wherein the concentration of pyrrole monomer is 0.2 mol/L, and the concentration of sodium lauryl sulfate is 0.2 mol/L. 0.1mol/L;

Other conditions are the same as in Example 1, and the PPY coating is obtained by electrodeposition by constant potential method.

The morphology of the PPY coating prepared in this comparative example is similar to that of the comparative example 2 shown in Figure 3(b). The coating is composed of cauliflower-like PPY particles with micropores between the particles.

From Examples 1 to 4, it can be seen that the preparation method of the intelligent metal organic framework-conductive polymer anti-corrosion coating material of the present invention is simple and low in energy consumption, and a composite with dense structure and uniform appearance can be obtained by adjusting the ratio of each component. The structure of the coating, and the construction of the coating is not limited by the morphology and shape of the metal substrate. In addition to having a good physical barrier effect, the obtained coating material can also give full play to the advantages of conductive polymers and metal-organic frameworks. Metal provides anodic protection and intelligent self-healing function where the coating is slightly damaged. Therefore, in an acidic corrosion environment, the intelligent metal organic framework-conductive polymer anticorrosion coating in the present invention can provide stable and long-term protection for stainless steel materials. The invention has great significance for corrosion protection of stainless steel materials in acidic environments such as acidic soil, fuel cell interior, and seawater splashing area.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (10)

1. the preparation method of intelligent metal frame-conductive polymer anticorrosion coating, it is characterized in that: comprise the following steps: Step (1), preparing metal-organic framework ZIFs by normal temperature synthesis method, ZIFs at least including ZIF-67 and/or ZIF-8; Step (2), preparing mixed electrolyte for electrodeposition to prepare composite coating: disperse conductive polymer monomer, sodium lauryl sulfate anionic surfactant in deionized water, then add the ZIFs prepared in step (1) , followed by ultrasonic stirring to obtain a mixed solution; Step (3), using a three-electrode system using a constant potential method, using the mixed solution prepared in step (2) as an electrolyte, electrodepositing a composite coating on the surface of the working electrode to obtain an electrochemically deposited metal-organic framework-conductive polymer anti-corrosion coating layer. 2. the preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 1 is characterized in that: in step (1), described ZIFs material provides central metal ion by metal salt, and imidazole organic matter provides organic Ligand. 3. The preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 2, characterized in that: the metal salt is Zn(NO ₃ ) ₂ 6H ₂ O and/or Co(NO ₃ ) ₂ ·6H ₂ O, the imidazole organic compound is 2-methylimidazole. 4. The preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 1, characterized in that: in step (1), the preparation method of ZIFs material is: Zn(NO ₃ ) ₂ ·6H ₂ O, Co(NO ₃ ) ₂ ·6H ₂ O at least one or two mixed metal salts are dissolved in water or methanol to obtain component A, and 2-methylimidazole organic ligands are dissolved in water or methanol to obtain Component B, after component A and component B are fully dissolved, quickly pour component B into component A and stir to mix the two, after standing at room temperature for reaction, centrifuge to obtain precipitate, and wash repeatedly with methanol Afterwards, the precipitate is dried to obtain the metal organic framework crystal material ZIF-67 or ZIF-8. 5. the preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 4 is characterized in that: the mixing time of described component A and component B is 30min, and the reaction time of standing at room temperature after mixing is 12~48h, after the reaction, the centrifugation time is 10~30min, and the precipitate is washed with methanol for 3~5 times, and then the precipitate is vacuum-dried at a drying temperature of 50~80°C, and the drying time is 12~48h; ZIF-67 and ZIF-8 During the preparation process, the molar ratios of central ions and ligands were 1:58 and 1:70, respectively. 6. The preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 1, characterized in that: in step (2), the mixed solution includes pyrrole or aniline with a concentration of 0.1-0.5mol/L Monomer, 0.05-0.3mol/L sodium lauryl sulfate and 0.5-2mg/mL ZIFs. 7. the preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 1 is characterized in that: in step (3), reference electrode and counter electrode are Ag/AgCl electrode respectively in the three-electrode deposition system And platinum sheet electrode, the working electrode is a stainless steel sample that needs to be protected against corrosion, the electrochemical deposition process is deposited by a constant potential method, and the electrodeposition time is 10 to 30 minutes. 8. the preparation method of intelligent metal frame-conductive polymer anticorrosion coating according to claim 1 is characterized in that: in step (3), the metal organic framework after electrochemical deposition-conductive polymer anticorrosion coating is used Wash and dry with ion water, the drying temperature is 30-50°C, and the drying time is 3-5 hours. 9. A metal organic framework-conductive polymer anti-corrosion coating prepared by the method according to any one of claims 1-8. 10. A metal organic framework-conductive polymer anticorrosion coating prepared by the method according to any one of claims 1 to 8 is applied to corrosion protection of stainless steel in an acidic environment.

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