Polyvinyl alcohol nanofiber membrane as well as preparation method and application thereof

Abstract

The invention discloses a polyvinyl alcohol nanofiber membrane as well as a preparation method and application thereof, polyvinyl alcohol is dissolved in deionized water, citric acid, N, N-dimethylacrylamide and N, N '-methylene bisacrylamide are added, electrostatic spinning and curing are performed, an electrolyte is dripped, and drying is performed to obtain the polyvinyl alcohol nanofiber membrane. The corrosion sensor prepared by using the nanofiber membrane as an electrolyte has excellent hydrophilicity, ion transmission efficiency and mechanical stability. The sensor is convenient to mount, can realize non-destructive in-situ test, has no additional corrosion damage to the working electrode, has high detection sensitivity and reliable working electrode area calibration capability, and can accurately respond to corrosion behavior changes under different environmental conditions. And the device supports configuration of various counter electrodes and reference electrodes, has good environmental adaptability and long-term use potential, and is suitable for laboratory simulation and outdoor actual corrosion state monitoring of metal components.

Description

TECHNICAL FIELD

[0001] The present application relates to a polyvinyl alcohol nanofiber membrane and its preparation method and application, in particular to a polyvinyl alcohol nanofiber membrane and its preparation method and application as a corrosion sensor for detecting metal corrosion conditions. BACKGROUND

[0002] Electrochemical testing techniques have been widely used in corrosion research. However, most current methods are still limited to laboratory environments using simulated materials for research, making it difficult to directly apply to on-site monitoring of actual metal structures (such as sculptures and buildings). Existing corrosion sensors face a series of technical challenges in field applications, including difficulties in constructing electrochemical cells in thin liquid film environments, measurement results being easily affected by humidity fluctuations, difficulties in constructing stable test systems, limited service life of the sensor, insufficient response capability for localized corrosion, difficulties in calibrating the effective area of the working electrode, and limitations of the sensor structure on the measurement area. Existing electrochemical corrosion monitoring techniques mainly include resistance probe methods. Resistance probe methods use resistance changes caused by metal corrosion for monitoring, with the advantages of fast response speed and real-time monitoring, but in complex environments, its measurement accuracy is easily disturbed by factors such as temperature and humidity. SUMMARY

[0003] The first object of the present application is to provide a polyvinyl alcohol nanofiber membrane, the second object of the present application is to provide a preparation method of the fiber membrane, the third object of the present application is to provide a portable three-electrode corrosion sensor prepared from the polyvinyl alcohol nanofiber membrane, and the fourth object of the present application is to provide the application of the polyvinyl alcohol nanofiber membrane three-electrode corrosion sensor in metal corrosion testing.

[0004] Technical solution: The preparation method of the polyvinyl alcohol nanofiber membrane according to the present application comprises the following steps:

[0005] (1) Polyvinyl alcohol (PVA) is added to deionized water, heated and stirred to dissolve, citric acid (C6H8O7) is added, stirred to dissolve at room temperature, N,N-dimethyl acrylamide (DMA) and N,N'-methylene bisacrylamide (MBA) are added, stirred at room temperature in the dark, and bubbled to obtain a spinning solution;

[0006] (2) The nanofiber membrane is prepared by electrospinning, solidified to initiate chemical crosslinking, and dripped into an electrolyte and dried to obtain a polyvinyl alcohol nanofiber membrane.

[0007] Further, in step (1), the mass-volume ratio of polyvinyl alcohol, citric acid, N,N-dimethyl acrylamide and N,N'-methylene bisacrylamide is 50:3:50:3-50:6:50:3 g / g / mL / g. The temperature for heating and stirring to dissolve is 80-90℃, preferably 85℃, the time for heating and stirring to dissolve is 1.5-2.5h, preferably 2h. The time for stirring to dissolve at room temperature is 0.5h or more. The stirring at room temperature in the dark is wrapped with tin foil, and stirred at a speed of 400r / min or more for 30min or more at room temperature. The bubbling is bubbled with N2 for 20min or more to remove oxygen to obtain the spinning solution.

[0008] Further, in step (2), during spinning, the spinning flow rate is 0.3-0.6 mL / h, the receiving distance is 10-15cm, the rotation speed is 450-550r / min, the spinning voltage is 15-25kV, the solidification temperature is 130-140℃, preferably 135℃, and the solidification time is 30min or more. The electrolyte is a sodium citrate solution, the concentration of the electrolyte is 0.50mol / L or less, the amount of the electrolyte is 3-5mL / 1cm*2cm nanofiber membrane, the drying temperature is 130-140℃, and the drying time is 2h or more.

[0009] A corrosion sensor comprising the polyvinyl alcohol nanofiber membrane prepared by the preparation method of the application. The polyvinyl alcohol nanofiber membrane is used as a solid electrolyte.

[0010] The polyvinyl alcohol nanofiber membrane prepared by the preparation method of the application or the corrosion sensor of the application is used for monitoring electrochemical corrosion in a building environment. In use, the polyvinyl alcohol nanofiber membrane is used as a solid electrolyte, a carbon rod or carbon plate is used as a counter electrode, and a saturated Ag / AgCl electrode, Ag electrode or Ag@AgCl electrode is used as a reference electrode for testing.

[0011] Further, in the electrochemical test before determining the type of electrode used by the sensor, an industrial Ag / AgCl electrode is used as a reference electrode, and a carbon rod is used as a counter electrode for easy installation to eliminate differences.

[0012] The corrosion sensor prepared by adopting the solid-state nanofiber membrane with customizable components and structure as an electrolyte has excellent hydrophilicity, ion transmission efficiency and mechanical stability, effectively solves the problems that the traditional liquid-based electrolyte is easily affected by humidity and is difficult to construct a stable thin liquid film system in outdoor application. The sensor is convenient to install, can realize non-destructive in-situ testing, has no additional corrosion damage to the working electrode, has high detection sensitivity and reliable working electrode area calibration capability, and can accurately respond to the corrosion behavior change under different environmental conditions. And support multiple configurations of counter electrodes and reference electrodes, good environmental adaptability and long-term use potential, suitable for corrosion state monitoring of laboratory simulation and outdoor actual metal components.

[0013] Beneficial effects: Compared with the prior art, the present application has the following significant advantages:

[0014] The corrosion sensor prepared by adopting the polyvinyl alcohol nanofiber membrane as an electrolyte can avoid additional corrosion damage to the working electrode during the test process; the installation process is simple and fast; it has high detection sensitivity; and the effective area of the working electrode can be accurately calibrated, thereby effectively improving the reliability and applicability of corrosion monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a three-electrode corrosion sensor structure diagram of the polyvinyl alcohol nanofiber membrane;

[0016] Figure 2 It is a contact angle test diagram of the polyvinyl alcohol nanofiber membrane prepared in Example 1; wherein, taking the mass of polyvinyl alcohol as a basis, A is 3% w / w citric acid, B is 6% w / w citric acid, C is 9% w / w citric acid, D is 12% w / w citric acid, and E is 15% w / w citric acid;

[0017] Figure 3 It is a porosity and electrolyte absorption data diagram of the polyvinyl alcohol nanofiber membrane prepared in Example 1;

[0018] Figure 4 It is an electrochemical test diagram of the polyvinyl alcohol nanofiber membrane prepared in Example 1; wherein, A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot, and D is Tafel Plot;

[0019] Figure 5 It is a contact angle test diagram of the polyvinyl alcohol nanofiber membrane prepared in Example 2; wherein, A is 15 kV, B is 20 kV, and B is 25 kV;

[0020] Figure 6 It is a porosity and electrolyte absorption data diagram of the polyvinyl alcohol nanofiber membrane prepared in Example 2;

[0021] Figure 7 Electrochemical test plots of polyvinyl alcohol nanofiber membrane prepared for Example 2; wherein A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot, D is Tafel Plot;

[0022] Figure 8 Electrochemical test plots of polyvinyl alcohol nanofiber membrane prepared for Example 3; wherein A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot, D is Tafel Plot;

[0023] Figure 9 Electrochemical test plots of sensor with different counter electrodes for Example 4; wherein A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot;

[0024] Figure 10 Electrochemical test plots of sensor with different reference electrodes for Example 4; wherein A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot;

[0025] Figure 11 Sensitivity test plots of PVA type corrosion sensor for Example 5; wherein A is Nyquist Plot, B is Tafel Plot;

[0026] Figure 12 Test object plots of application performance of PVA type corrosion sensor in actual building environment for Example 6;

[0027] Figure 13 Electrochemical test plots of application performance of PVA type corrosion sensor in actual building environment for Example 6; wherein A is Nyquist Plot, B is Bode Magnitude Plot, C is Bode Phase Plot. DETAILED DESCRIPTION

[0028] The technical solutions of the present application will be further described below in combination with the accompanying drawings.

[0029] Example 1: Effect of different citric acid addition amounts on PVA nanofiber membrane

[0030] (1) Preparation of spinning solution

[0031] Firstly, 2 g of polyvinyl alcohol (PVA) was slowly added into 18 mL of deionized water and stirred at 85 ℃ for 2 h to completely dissolve, obtaining a 10% w / v PVA solution. 0.06 g, 0.12 g, 0.18 g, 0.24 g, 0.3 g of citric acid (C6H8O7) was added to the 10% PVA solution respectively and stirred to completely dissolve (based on the mass of polyvinyl alcohol, 3%, 6%, 9%, 12%, 15% w / w respectively), 2 mL of N,N-dimethylacrylamide (DMA) and 0.12 g of N,N'-methylenebisacrylamide (MBA) were taken. A homogeneous mixture was prepared by stirring at 400 r / min for 30 min under light shielding and room temperature. Then the mixture was bubbled with nitrogen for 20 min to remove oxygen to obtain a spinning solution.

[0032] (2) Preparation of nanofiber membrane

[0033] The prepared spinning solution was poured into a 10 mL plastic syringe with a 13 G flat needle, and a nanofiber membrane was prepared by electrospinning. During the spinning process, the metal needle was connected to the positive electrode of a high-voltage power supply, and an aluminum foil was covered on the ground collection plate with a rotation speed of 500 r / min. The distance between the tip and the collector was 15 cm, the applied voltage was 20 kV, and the flow rate of the solution was controlled by a syringe pump at a speed of 0.5 mL / h. Generally, the spinning time was 12 h.

[0034] The prepared nanofiber membrane was peeled off from the collection substrate and placed in a 135 ℃ oven for 30 min to induce chemical crosslinking. Subsequently, 3 mL of 0.50 mol / L sodium citrate solution was uniformly added on the surface of the membrane with a size of 1 cm × 2 cm, and it was left to stand for 30 min to allow it to fully soak. Then the sample was transferred to a 60 ℃ oven for heating for 2 h to remove excess water, and after cooling, a PVA nanofiber membrane for sensor was obtained.

[0035] The PVA nanofiber membranes prepared from the above five groups of spinning solutions with different amounts of citric acid were tested for contact angle, and the results are shown in Figure 2 As can be seen in Figure 2 , when the amount of citric acid added is 12%, the water contact angle of the PVA nanofiber membrane reaches a maximum value of 42.48 °. Although the contact angle of the PVA nanofiber membrane gradually increases with the increase of the amount of citric acid added, it is still far below 90 °. This indicates that although the crosslinking degree increases, the PVA nanofiber membrane still has strong hydrophilicity, which indicates that even if the crosslinking degree is improved, the PVA nanofiber membrane still maintains strong hydrophilicity, which is beneficial to the full absorption of electrolyte.

[0036] The PVA nanofiber membranes prepared from the five groups of spinning solutions with different citric acid addition amounts were subjected to porosity and electrolyte absorption amount analysis, and the results are shown in Figure 3 From Figure 3 it can be seen that as the citric acid addition amount increases, the porosity and electrolyte absorption amount of the PVA nanofiber membrane also increase, and when the citric acid addition amount is 12%, the porosity and electrolyte absorption amount reach the highest values of 85% and 303%, respectively. However, when the citric acid addition amount increases to 15%, both the porosity and the absorption amount decrease. On the one hand, the relatively coarse fibers have a lower specific surface area, which limits the diffusion and absorption capacity of the electrolyte. On the other hand, high concentration of citric acid may promote partial cross-linking reaction, making the fiber network structure more dense, thereby further reducing the porosity and absorption amount. Therefore, when the citric acid addition amount is 12%, the porosity and electrolyte absorption amount reach the highest level.

[0037] To further explore the influence of the change of citric acid addition amount on the corrosion sensor in actual testing, a carbon plate was used as a counter electrode and connected with a wire, and an Ag / AgCl electrode was used as a reference electrode. Both of them were fixed on the surface of the PVA nanofiber membrane laid on the cabinet by a clamp, and a PVA type corrosion sensor was built and subjected to electrochemical EIS and Tafel tests. The test results are shown in Figure 4 The corresponding electrochemical data are shown in Table 1.

[0038] Table 1 Electrochemical data of PVA nanofiber membranes with different citric acid addition amounts

[0039]

[0040] From Table 1, it can be seen that as the citric acid addition amount increases, the charge transfer resistance R ct gradually decreases within a certain range. When the citric acid addition amount is 12%, the fiber diameter is smaller, the porosity and electrolyte absorption amount reach the highest, the internal structure is uniform and conducive to ion transmission. Therefore, the R ct at this time is the lowest, only 358 Ω·cm², and the ion conductivity of the material is the best, and the charge transfer is smoother. However, when the citric acid addition amount increases to 15%, the R ct instead rises to 745 Ω·cm². This may be because the high concentration of citric acid increases the fiber diameter and reduces the porosity, causing the internal microstructure of the membrane to become non-uniform, thereby hindering the effective transmission of ions, affecting the permeability of the electrolyte and increasing the charge transfer resistance. The change of corrosion potential can also be seen. As the citric acid addition amount increases from 3% to 12%, E corr also rises from -0.50 V to -0.29 V, indicating that the corrosion resistance improves, which may be related to the more uniform nanofiber structure and higher porosity.

[0041] In summary, the suitable addition amount of citric acid ranges from 6% to 12%. When the addition amount is 12%, the comprehensive performance of the PVA nanofiber membrane is optimal, at which the membrane material exhibits the best hydrophilicity, the highest ion transmission efficiency and the most excellent electrochemical performance.

[0042] Example 2 Influence of different spinning voltages on PVA nanofiber membranes

[0043] Electrospinning is a process of forming fibers by the interaction of electric field force and surface tension of polymer solution in a high-voltage electrostatic field. Voltage is a key factor affecting the morphology and diameter of fibers. In the conditions of a fixed spinning flow rate of 0.5 mL / h, a receiving distance of 15 cm and a rotation speed of 500 r / min, PVA was prepared using different voltages (15 kV, 20 kV and 25 kV). The preparation process was the same as in the example, and the addition amount of citric acid was 12%. The contact angle test was performed on the three groups of PVA nanofiber membranes obtained, and the results are shown in Figure 5 From Figure 5 it can be found that when the voltage is between 15 kV and 25 kV, the contact angle of the prepared PVA nanofiber membrane is between 38° and 42°. With the increase of voltage, the contact angle gradually increases, indicating that the hydrophobicity is enhanced. The liquid absorption amount and porosity of the PVA nanofiber membrane were studied, and the results are shown in Figure 6 From the results, it can be found that when the voltage is 20 kV, the porosity and electrolyte absorption amount reach the highest values of 89% and 311%, respectively. When the voltage increases to 25 kV, the overstretching of the jet flow caused by the excessively high voltage may result in the decrease of fiber diameter, and the excessively thin fibers are more likely to form dense fibers, thereby further reducing the porosity and liquid absorption amount.

[0044] From the table, it can be seen that there are obvious differences in the electrochemical performance of the PVA fiber membranes prepared under different spinning voltages. When the voltage is 15 kV, R ct is 357.80 kΩ·cm², while it decreases to 207.71 kΩ·cm² at 20 kV, indicating that the fiber membrane prepared at 20 kV is conducive to promoting ion transmission and improving electrochemical activity. At the same time, E corr at 20 kV is -0.30 V, which is close to the corrosion potential at 15 kV, but R ct decreases significantly, indicating that the fiber membrane formed under this voltage condition has better electrolyte permeability and more uniform microstructure. In contrast, R ct at 25 kV rises sharply to 1420.00 kΩ·cm², and R s also increases significantly, indicating that the structure of PVA under this condition may be relatively dense or non-uniform, which hinders ion migration and thus affects the performance of the sensor. In addition, j corrThe j0decreased significantly, further indicating that the electrochemical activity decreased. Considering the ion transport capacity, corrosion potential and electrochemical stability, the PVA prepared at 20 kV showed the best comprehensive performance, and therefore was selected as the optimal voltage condition.

[0045] To further explore the influence of the change of spinning voltage on the PVA nanofiber membrane used for corrosion sensor in actual test, a PVA type corrosion sensor was built (see Example 1 for details) and electrochemical EIS and Tafel tests were carried out, and the test results are shown in Figure 7 The corresponding electrochemical data are shown in Table 2.

[0046] Table 2 Electrochemical data of PVA nanofiber membranes prepared under different voltage conditions

[0047]

[0048] As can be seen from Table 2, the electrochemical performance of PVA nanofiber membranes under different spinning voltages is obviously different. When the voltage is 15 kV, R ct 357.80 kΩ·cm², while at 20 kV, it decreased to 207.71 kΩ·cm², indicating that the fiber membrane prepared at 20 kV is conducive to promoting ion transport and improving electrochemical activity. At the same time, the E corr -0.30 V, close to the corrosion potential of 15 kV, but R ct decreased significantly, indicating that the fiber membrane formed under this voltage condition has better electrolyte permeability and more uniform microstructure. In contrast, R ct rose sharply to 1420.00 kΩ·cm², and R s also increased significantly, indicating that the structure of PVA under this condition may be relatively dense or uneven, hindering ion migration and thus affecting the performance of the sensor. In addition, the j corr decreased significantly, further indicating that the electrochemical activity decreased. Considering the ion transport capacity, corrosion potential and electrochemical stability, the PVA prepared at 20 kV showed the best comprehensive performance, and therefore was selected as the optimal voltage condition.

[0049] Example 3 Influence of different concentrations of sodium citrate electrolyte on PVA nanofiber membranes

[0050] The effect of adjusting the amount of sodium citrate added on the response characteristics and corrosion behavior of PVA nanofiber membranes used in sensors was investigated to further analyze the influence of electrolyte concentration on sensor test results and provide a reference for applicability in practical application environments. Sodium citrate, as an organic salt, has good solubility and stability, which helps to enhance the adsorption capacity of the sensor membrane, thereby improving its detection performance. The PVA nanofiber membrane preparation process was the same as in Example 1, with citric acid added at 12% and spinning voltage at 20 kV. During the experiment, it was found that when the sodium citrate concentration exceeded 0.5 mol / L, salting out occurred during the drying process; therefore, the test concentration was limited to within 0.5 mol / L in this example. The assembly of PVA corrosion sensors with different concentrations of sodium citrate was the same as in the example, and their EIS tests were as follows. Figure 8 As shown, the corresponding experimental data are shown in Table 3.

[0051] Table 3 Electrochemical data of PVA nanofiber membranes prepared with different sodium citrate concentrations for use in sensors

[0052]

[0053] From Nyquist Figure 8 It can be seen that the curves corresponding to different sodium citrate contents are all single capacitive arcs, indicating that the mechanism of the interfacial electrochemical reaction has not fundamentally changed, only the reaction rate differs. Table 3 of the fitted data shows that as the concentration increases, R... s It gradually decreases, reaching 4.54 Ω·cm at 0.5 mol / L. 2 R ct The value varies with concentration, but even in R ct At lower concentrations, the reaction on the metal surface did not exhibit runaway or destructive behavior. This indicates that at this concentration, the electrolyte will not cause corrosion damage to the working electrode surface, and the sensor can still perform non-destructive testing. Since differences in temperature and humidity in the atmospheric environment may introduce additional variables, this invention selects 0.5 mol / L sodium citrate as the electrolyte. This simplifies experimental conditions, facilitates control of parameters such as ion interactions, pH value, and membrane stability, and avoids salt precipitation due to excessive concentration by using 0.5 mol / L as the upper limit, ensuring the stability and repeatability of the test results. This provides a scientific basis for the sensor's applicability in practical applications.

[0054] Example 4: The Influence of Electrode Type on the Performance of PVA-type Electrochemical Corrosion Sensor

[0055] First, industrially available Ag / AgCl was fixed as the reactive electrode (RE), and carbon rods and carbon plates were used as counter electrodes to study their differences. The assembly of the electrochemical corrosion sensor was the same as in Example 1. The PVA nanofiber membrane preparation process was the same as in Example 1, except that the citric acid addition was 12%, the spinning voltage was 20 kV, and the concentration of the sodium citrate electrolyte was 0.5 mol / L. The electrochemical corrosion sensor underwent various tests, and the results are as follows: Figure 9 As shown in the figure. The fitted data are shown in Table 4.

[0056] Table 4. Results of the influence of different counter electrodes and reference electrodes on the electrochemical performance of the sensor.

[0057]

[0058] from Figure 9 As can be seen from the data, the impedance change in the low-frequency region of the Bode plot of the carbon plate is relatively gradual, indicating that the carbon plate can more effectively reduce interfacial polarization and improve charge transport efficiency, thereby enhancing the stability and sensitivity of the sensor. Meanwhile, Table 4 of the fitted data shows that the R of the carbon rod... s It is 9.04 Ω·cm², while the R of the carbon plate is... s It is 10.06 Ω·cm², although the R of the carbon plate is... s Slightly higher, but its CPE value is relatively low at 1.66×10⁻ 4 A lower capacitance value (F·cm²) and an n value closer to 1 indicate more stable interfacial capacitance characteristics of the carbon plate. A lower capacitance value may indicate less charge storage at the interface, facilitating faster electron transfer and reducing polarization effects. Therefore, although the R of the carbon plate... s It is slightly higher, but its overall performance is still better than that of carbon rods.

[0059] Based on the selection of a carbon plate as the counter electrode, the effect of changing the reference electrode was further investigated. After selecting a carbon plate as the counter electrode, saturated Ag / AgCl, Ag, and Ag@AgCl were used as reference electrodes for comparison. The experimental procedure was the same as above, and the results are shown in Figure 10. Figure 10 The trends shown in the data are basically consistent, indicating that changing the reference electrode has little impact on the overall system and both electrodes can operate stably under this system. Furthermore, the fitting data reveals that the Rg of the Ag / AgCl electrode... s The minimum is 10.06 Ω·cm², while Ag and Ag@AgCl are 14.84 Ω·cm² and 12.66 Ω·cm², respectively, indicating that the R of the saturated Ag / AgCl reference electrode is... s The lower values ​​may be more favorable for charge transport. However, the CPE and n values ​​indicate that, despite differences between different reference electrodes, the impedance characteristics of Ag and Ag@AgCl still meet the testing requirements.

[0060] In summary, in the system of PVA nanofiber membrane as electrolyte, carbon plate as counter electrode can effectively improve the stability and charge transfer capacity of the sensor, and Ag and Ag@AgCl electrodes can be used as a saturated Ag / AgCl alternative reference electrode to meet the test requirements.

[0061] Example 5 Sensitivity test of PVA type corrosion sensor

[0062] To evaluate the sensitivity of the PVA type corrosion sensor, 316L stainless steel was used as the working electrode, and the electrochemical test chart within 24 h of corrosion in a constant temperature and humidity chamber at 25°C and 60% relative humidity is shown in Figure 11 , and the corresponding electrochemical data are listed in Table 5. As can be seen from Table 5, the charge transfer resistance (R ct ) is 152.20 kΩ·cm², and the corrosion current density (j corr ) is 5.80×10⁻ 7 A / cm², indicating that the corrosion process has not started. During 1 h to 12 h, Rct decreased significantly from 130.80 kΩ·cm² to 48.01 kΩ·cm², and j corr increased from 2.66×10⁻ 6 A / cm² to 8.07×10⁻ 6 A / cm², reflecting the continuous intensification of the corrosion reaction. The corrosion potential fluctuated slightly in the range of –0.28 V to –0.30 V during this period, indicating that the corrosion driving force remained relatively stable. By 24 h, R ct rose to 161.20 kΩ·cm², and j corr decreased to 4.39×10⁻ 7 A / cm², indicating that an effective passivation film or corrosion product layer had been formed on the metal surface, significantly inhibiting the corrosion reaction. The above dynamic change process clearly reflects the high response sensitivity of the PVA type corrosion sensor to the corrosion dynamic process.

[0063] Table 5 316L stainless steel 24 h corrosion dynamic electrochemical test data

[0064]

[0065] Example 6 Application of PVA type corrosion sensor in actual building environment

[0066] To evaluate the applicability of the PVA-type corrosion sensor in actual building environment, an outdoor 304 stainless steel express cabinet was selected as the test object for on-site electrochemical testing. The specific steps are as follows: first, clean the surface of the express cabinet to remove dust; then fix the carbon plate as the counter electrode and the Ag / AgCl electrode as the reference electrode on the surface of the PVA nanofiber membrane laid on the cabinet surface (preparation process same as Example 1, citric acid addition amount 12%, spinning voltage 20 kV, sodium citrate solution concentration 0.30 mol / L) through the clamp; finally, connect the leads of the electrochemical workstation to the working electrode (express cabinet), reference electrode and counter electrode respectively to form a complete measurement circuit. (As shown in Figure 12 , to explore its actual corrosion situation. At the same time, stainless steel sheets of the same material were selected for comparison testing under ideal laboratory conditions, and the results of the two were compared and analyzed, as shown in Figure 13 .

[0067] This example mainly discusses the performance difference of the sensor in complex outdoor environment and laboratory environment to evaluate its reliability in actual application. As can be seen from Figure 13 , the test curves of the stainless steel express cabinet and the laboratory test piece are different, and the Nyquist diagram of the stainless steel cabinet shows a lower capacitance arc, which may be related to the corrosion on its surface, resulting in a decrease in electrochemical impedance. This phenomenon shows that in the actual use process, the metal surface is exposed to natural factors such as wind and sun, which is easy to produce corrosion, and the sensor can sensitively capture the change of this electrochemical parameter, showing good response ability and environmental adaptability, and further verifying the application potential of the sensor in long-term outdoor corrosion monitoring.

Claims

1. A method for preparing a polyvinyl alcohol nanofiber membrane, characterized in that, Includes the following steps: (1) Add polyvinyl alcohol to deionized water, heat and stir to dissolve, add citric acid, stir to dissolve at room temperature, then add N,N-dimethylacrylamide and N,N'-methylenebisacrylamide, stir at room temperature in the dark, and bubble to obtain spinning solution; (2) Nanofiber membranes were prepared by electrospinning, solidified to initiate chemical cross-linking, and then dried after being dripped with electrolyte to obtain polyvinyl alcohol nanofiber membranes.

2. The method for preparing the polyvinyl alcohol nanofiber membrane according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of polyvinyl alcohol, citric acid, N,N-dimethylacrylamide and N,N'-methylenebisacrylamide is 50:3:50:3-50:6:50:3 g / g / mL / g.

3. The method for preparing the polyvinyl alcohol nanofiber membrane according to claim 1, characterized in that, In step (1), the heating and stirring dissolution temperature is 80-90℃, the heating and stirring dissolution time is 1.5-2.5h, and the stirring dissolution time at room temperature is more than 0.5h.

4. The method for preparing the polyvinyl alcohol nanofiber membrane according to claim 1, characterized in that, In step (1), the mixture is stirred at a speed of 400 r / min or higher for at least 30 min at room temperature, and bubbled with N2 for at least 20 min.

5. The method for preparing the polyvinyl alcohol nanofiber membrane according to claim 1, characterized in that, In step (2), the spinning flow rate is 0.3-0.6 mL / h, the receiving distance is 10-15 cm, the rotation speed is 450-550 r / min, the spinning voltage is 15-25 kV, the curing temperature is 130-140℃, and the curing time is more than 30 min.

6. The method for preparing the polyvinyl alcohol nanofiber membrane according to claim 1, characterized in that, In step (2), the electrolyte is sodium citrate solution, the concentration of the electrolyte is less than 0.50 mol / L, the amount of electrolyte used is 3-5 mL / 1cm×2cm nanofiber membrane, the drying temperature is 130-140℃, and the drying time is more than 2 hours.

7. A corrosion sensor, characterized in that, The polyvinyl alcohol nanofiber membrane obtained by the preparation method according to any one of claims 1-6.

8. The corrosion sensor according to claim 7, characterized in that, Polyvinyl alcohol nanofiber membranes are used as solid electrolytes.

9. The application of the polyvinyl alcohol nanofiber membrane obtained by the preparation method according to any one of claims 1-6 or the corrosion sensor according to claim 7 or 8 in monitoring electrochemical corrosion in a built environment.

10. In the application according to claim 9, when in use, the polyvinyl alcohol nanofiber membrane is used as a solid electrolyte, a carbon rod or carbon plate is used as the counter electrode, and a saturated Ag / AgCl electrode, Ag electrode or Ag@AgCl electrode is used as the reference electrode for testing.

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