A polyacrylamide gel electrolyte, a preparation method and application thereof

Abstract

The application discloses a polyacrylamide gel electrolyte and a preparation method and application thereof, and aims to in-situ monitor corrosion conditions of metals in the atmosphere. The sensor adopts a polyacrylamide gel added with glycerol as an electrolyte, and is prepared through the action of an initiator and a crosslinking agent. Due to the presence of the glycerol, the hydrogel electrolyte exhibits excellent moisturizing performance, significantly prolongs the time effectiveness, and can be stably stored and effectively used at normal temperature, and is suitable for long-term monitoring of corrosion conditions of metal materials.

Description

Technical Field

[0001] This invention relates to a polyacrylamide gel electrolyte, its preparation method and application, belonging to the field of metal corrosion monitoring. Background Technology

[0002] Electrochemical testing techniques have been widely applied in corrosion research. However, these techniques present unique challenges in corrosion studies of cultural buildings. Typical tests involve preparing artificial materials to mimic the original composition of metals and using traditional laboratory techniques. However, the information provided is limited because it cannot completely reproduce the compositions formed on metal buildings over long periods. Therefore, how to non-destructively monitor corrosion information has become a key research focus.

[0003] Traditional liquid electrolytes are prone to evaporation or leakage during long-term use, leading to unstable and inaccurate monitoring data.

[0004] In the field of atmospheric corrosion monitoring, the use of polymer electrolytes to replace traditional liquid electrolytes has become a common and effective method. This alternative is particularly important in the design and application of portable corrosion sensors because it effectively avoids the risks associated with liquid leakage or evaporation. However, several problems remain to be solved in the monitoring field. First, the stability and conductivity of existing polymer electrolytes under different environmental conditions still need further optimization to ensure the accuracy of long-term monitoring. Second, improving the sensitivity and response speed of sensors to capture minute changes in corrosion is also a current research focus. Summary of the Invention

[0005] Objectives of the Invention: The first objective of this invention is to provide a polyacrylamide gel electrolyte; the second objective is to provide a method for preparing the polyacrylamide gel electrolyte; the third objective is to provide the application of the polyacrylamide gel electrolyte in the preparation of a portable corrosion three-electrode sensor; and the fourth objective is to provide a portable corrosion three-electrode sensor based on the polyacrylamide gel electrolyte, so as to overcome the difficulties encountered when using liquid electrolytes for in-situ testing, especially in the field of atmospheric corrosion monitoring.

[0006] Technical solution: The present invention provides a polyacrylamide gel electrolyte, which comprises acrylamide monomer, initiator, crosslinking agent and glycerol as raw materials, wherein acrylamide monomer is dissolved under aqueous conditions, initiator and crosslinking agent are added, and acrylamide is subjected to free radical polymerization initiated by initiator under anaerobic conditions to obtain the electrolyte.

[0007] Furthermore, the initiator is ammonium persulfate or potassium persulfate.

[0008] Furthermore, the crosslinking agent is methylenebisacrylamide.

[0009] Further, the aqueous phase is a sodium sulfate solution or a rain-simulated water solution, wherein the concentration of the sodium sulfate solution is 0.002–1 mol / L, and the concentration of the total solute in the rain-simulated water solution is 0.0005–0.05 mol / L.

[0010] Furthermore, the simulated rainwater solution contains calcium sulfate, ammonium sulfate, ammonium chloride, and sodium nitrate.

[0011] Furthermore, the concentration of acrylamide monomer in the aqueous phase is 10-50%, the amount of initiator is 4-6% of the monomer mass, and the amount of crosslinking agent is 0.01-0.5% of the monomer mass.

[0012] The preparation method of the polyacrylamide gel electrolyte of the present invention includes the following steps:

[0013] Acrylamide was dissolved in the aqueous phase, and initiator, crosslinking agent, glycerol and sodium sulfate solution were added and stirred evenly. After stirring, inert gas was bubbled for 10-20 minutes, and the mixture was placed at 60-100℃ for 30-60 minutes. After cooling to room temperature, polyacrylamide gel electrolyte was obtained.

[0014] The application of the polyacrylamide gel electrolyte described in this invention in the preparation of a portable corrosion three-electrode sensor.

[0015] The present invention also includes a portable corrosion three-electrode sensor based on the polyacrylamide gel electrolyte of the present invention, comprising an outer mold, wherein the polyacrylamide gel electrolyte of the present invention is contained within the outer mold, wherein a counter electrode and a reference electrode are inserted into the polyacrylamide gel electrolyte of the present invention, and a working electrode is provided at the bottom of the polyacrylamide gel electrolyte of the present invention.

[0016] Furthermore, the outer mold is made of epoxy resin and a hardener, the reference electrode is a silver / silver chloride electrode, a silver wire electrode or a silver-plated wire electrode, the electrode is a carbon rod or a carbon plate, and the working electrode is a stainless steel sheet.

[0017] Furthermore, the reference electrode and the counter electrode are arranged in parallel, and the bottom end of the reference electrode is 2 to 6 mm away from the upper surface of the working electrode.

[0018] Furthermore, the outer mold is made by mixing epoxy resin and a hardener, pouring the mixture into a silicone mold, and letting it stand for 24–48 hours.

[0019] Furthermore, the working electrode needs to undergo pretreatment. The pretreatment steps include: ultrasonically treating the working electrode in acetone, ethanol, and deionized water for 20-40 minutes each until it is clean; drying the treated working electrode at 40-60℃ for 1-2 hours; and polishing the dried working electrode with 280#, 800#, and 1200# sandpaper in sequence.

[0020] The present invention also includes the application of the polyacrylamide gel electrolyte or the portable corrosion three-electrode sensor described in the present invention in atmospheric corrosion monitoring.

[0021] The polyacrylamide gel electrolyte used in this invention enables non-destructive monitoring of metals and real-time assessment of their corrosion status, thus providing a scientific basis for the maintenance and protection of metal materials, extending their service life, and reducing potential safety risks. By adding glycerol, the electrolyte not only improves its moisturizing properties but also extends the monitoring timeliness, allowing the electrolysis to operate stably under long-term environmental conditions. This improvement not only enhances the reliability and durability of the polyacrylamide gel electrolyte-based sensor but also enables the electrolyte to continuously and effectively monitor the corrosion status of metal materials in practical applications. It provides a more effective solution for real-time monitoring of the corrosion status of metal materials in the atmosphere, provides reliable data support for the implementation of anti-corrosion measures, and ultimately ensures the safety and durability of metal structures, providing a scientific basis for the formulation of relevant anti-corrosion measures.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0023] (1) The polyacrylamide gel electrolyte of this invention has good stability and a simple preparation method, and has the following advantages: ① Electrolyte stability: The acrylamide gel electrolyte can be stored for a certain period of time, making it suitable for multiple tests and improving the flexibility and efficiency of the experiment. ② The moisturizing properties of the gel electrolyte are enhanced by adding glycerol, enabling the electrolyte to remain stable under various environmental conditions, thereby achieving long-term monitoring. This improvement enhances the reliability and durability of the sensor.

[0024] (2) The advantages of the portable corrosion three-electrode sensor provided by this invention are that it enables non-destructive testing and facilitates corrosion monitoring in different environments. Specific advantages include: ① The sensor is designed to be portable, facilitating rapid on-site detection and reducing damage to the sample. ② Good repeatability: The sensor exhibits good stability; when the same sample is tested three times consecutively, the results show little difference, demonstrating its reliable measurement capability. ③ Optimized electrode placement in the gel electrolyte, using a carbon plate as the counter electrode, helps to achieve a uniform distribution of the electric field between the electrodes, thereby reducing interference and improving measurement accuracy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the portable corrosion three-electrode sensor of the present invention;

[0026] Figure 2 Electrochemical impedance spectroscopy and Tafel comparison diagrams of five groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolyte with different sodium sulfate contents prepared in Example 2;

[0027] Figure 3 Electrochemical impedance spectroscopy and Tafel comparison diagrams of five groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolyte prepared in Example 3;

[0028] Figure 4 The effective usage time test results of 5 groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolyte prepared in Example 3 are shown in the figure.

[0029] Figure 5 Comparison of electrochemical impedance spectroscopy (EIS) of three groups of portable corrosion three-electrode sensors based on polyacrylamide gel electrolyte prepared in Example 4;

[0030] Figure 6 Comparison of electrochemical impedance spectroscopy (EIS) of three groups of portable corrosion three-electrode sensors based on polyacrylamide gel electrolyte prepared in Example 5;

[0031] Figure 7 The electrochemical impedance spectroscopy of the stability of the portable corrosion three-electrode sensor based on polyacrylamide gel electrolyte prepared in Example 6 is shown.

[0032] Figure 8 Electrochemical impedance spectroscopy and TAFEL comparison diagrams of 7 groups of corrosion three-electrode sensors based on agarose gel electrolyte prepared for Comparative Example 1;

[0033] Figure 9 The graph shows the stability test results for the optimal ratio in Comparative Example 1 over two consecutive days.

[0034] Figure 10 The electrochemical impedance spectroscopy of the portable three-electrode corrosion sensor based on polyacrylamide gel electrolyte and the three-electrode corrosion sensor based on agar gel electrolyte in Example 7 shows the corrosion of different metal blocks within 24 hours.

[0035] Figure 11 This is a corrosion rate graph showing the corrosion of different metal blocks within 24 hours using the hanging plate method in Example 7. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0037] Example 1

[0038] like Figure 1 As shown, the portable corrosion three-electrode sensor based on polyacrylamide gel electrolyte of the present invention includes an outer mold 1, within which the polyacrylamide gel electrolyte 5 of the present invention is contained. A counter electrode 2 and a reference electrode 3 are inserted into the polyacrylamide gel electrolyte 5. A working electrode 4 is provided at the bottom of the polyacrylamide gel electrolyte 5 of the present invention.

[0039] The reference electrode 3 is set parallel to electrode 2, with a distance of 2 cm between them. The distance between reference electrode 3 and electrode 4 is 2–6 mm. The distance between electrode 2 and electrode 4 is slightly longer than that between reference electrode 3 and electrode 4 (approximately 1 mm longer). The outer mold 1 is made by mixing 25 mL of epoxy resin E44 (Dongguan Ailik New Materials Co., Ltd.) and 25 mL of epoxy curing agent 650 (Dongguan Ailik New Materials Co., Ltd.) and pouring the mixture into a double-layered cylindrical silicone mold with an inner diameter of 4 cm, an outer diameter of 5 cm, a height of 6 cm, and a layer thickness of 5 mm. The mixture is left to stand for 30 hours. The reference electrode 3 is a silver / silver chloride electrode, electrode 2 is a carbon rod, and the working electrode 4 is a stainless steel sheet with a length × width × thickness of 5 cm × 5 cm × 0.2 cm. The pretreatment process of the working electrode 4 is as follows: the working electrode 4 is ultrasonically treated in acetone, ethanol and deionized water for 30 minutes each until it is clean. Then, the cleaned working electrode 4 is polished with 280#, 800# and 1200# sandpaper in turn. Finally, the treated working electrode 4 is dried in an oven at 60℃ for 2 hours to obtain the working electrode 4.

[0040] Example 2: Preparation of a portable corrosion three-electrode sensor using the polyacrylamide electrolyte described in Example 1 with different sodium sulfate concentrations.

[0041] (1) Preparation of polyacrylamide gel electrolyte with sodium sulfate concentration of 0.002 mol / L

[0042] First, 2.84 mg of sodium sulfate was weighed and dissolved in 10 mL of water to obtain a sodium sulfate solution. Then, 2 g of acrylamide, 0.1 g of ammonium persulfate, and 2.5 mg of methylenebisacrylamide were weighed and dissolved in the sodium sulfate solution. The mixed solution was deoxygenated with nitrogen for 10 min, and then heated at 60 °C for 30 min to polymerize. The solution was poured into a cylindrical silicone mold with a diameter of 40 mm and a height of 40 mm and cooled to obtain polyacrylamide gel electrolyte.

[0043] (2) Pour the polyacrylamide obtained in step (1) into mold 1, which contains counter electrode 2 and silver / silver chloride as reference electrode 3. Then place the mold 1 with gel electrolyte on working electrode 4 to form a portable corrosion three-electrode sensor. The distance between reference electrode 3 and electrode 4 is 4 mm, and the distance between counter electrode 2 and electrode 4 is 5 mm.

[0044] Using the above process, four portable corrosion three-electrode sensors with sodium sulfate concentrations of 0.02 mol / L, 0.2 mol / L, 0.5 mol / L, and 1 mol / L were prepared to obtain polyacrylamide gel electrolytes.

[0045] Electrochemical performance tests were conducted on the five groups of polyacrylamide gel electrolyte corrosion three-electrode sensors in this example to study their impact on the working electrode. The test results are as follows: Figure 2 As shown. Figure 2 The electrochemical impedance spectroscopy (EIS) and Tafel curves are shown for five groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolytes with different sodium sulfate contents, prepared in Example 2. Figure A is the EIS, and Figure B is the Tafel curve. Figure 2 As shown in Figure A, the capacitive arc gradually decreases with increasing sodium sulfate content. The change in capacitive arc is relatively small when the sodium sulfate concentration varies between 0.2 mol / L and 1 mol / L. This phenomenon indicates that the influence of the electrolyte tends to stabilize within this concentration range. Therefore, after comprehensive consideration, 0.5 mol / L sodium sulfate was selected as the optimal electrolyte concentration. This concentration ensures good conductivity while avoiding the adverse effects of excessively high concentrations, thus providing a more reliable electrochemical environment for subsequent corrosion monitoring.

[0046] Example 3: Preparation of polyacrylamide gel electrolytes with different glycerol concentrations

[0047] The preparation process is the same as in Example 1, except that the concentration of glycerol is changed, as follows:

[0048] (1) Preparation of polyacrylamide gel electrolyte with glycerol content of 30% W / W

[0049] First, 0.710 g of sodium sulfate was weighed and dissolved in 10 mL of water to obtain a 0.5 mol / L sodium sulfate solution. Then, 2 g of acrylamide, 0.1 g of ammonium persulfate, and 2.5 mg of methylenebisacrylamide were weighed and dissolved in the sodium sulfate solution to obtain a homogeneous mixture. 30% w / w glycerol was added to the mixture, and the solution was deoxygenated using nitrogen for 10 min. Polymerization was then carried out at 60 °C for 30 min. The solution was poured into a cylindrical silicone mold with a diameter of 40 mm and a height of 40 mm and cooled to obtain a polyacrylamide gel electrolyte.

[0050] (2) Pour the polyacrylamide obtained in step (1) into the mold 1 with the counter electrode 2 and silver / silver chloride as the reference electrode 3 inserted, and then place the mold 1 with the gel electrolyte on the working electrode 4 to form a portable corrosion three-electrode sensor.

[0051] Using the above process, four portable corrosion three-electrode sensors with polyacrylamide gel electrolytes were prepared with glycerol contents of 0% W / W, 10% W / W, 20% W / W, and 40% W / W, respectively.

[0052] Electrochemical performance tests were conducted on the five sets of polyacrylamide gel electrolyte corrosion three-electrode sensors implemented in this case. The test results are as follows: Figure 3 As shown. Figure 3 The electrochemical impedance spectroscopy (EIS) and Tafel curves are shown for five groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolytes prepared in Example 3. In this diagram, A represents the EIS of polyacrylamide gel electrolytes with different glycerol contents, and B represents the Tafel curves of polyacrylamide gel electrolytes with different glycerol contents. Analysis... Figure 3 The data show that the curves for all different glycerol concentrations exhibit similar trends, indicating that the amount of glycerol added does not significantly alter the characteristics of the electrode reaction, thus supporting the validity of using this gel electrolyte for electrochemical testing.

[0053] Further analysis of the EIS and Tafel test results revealed that as the glycerol content gradually increased, the corrosive effect of the gel electrolyte on the working electrode gradually decreased, and the sensor performance improved accordingly. This phenomenon indicates that an appropriate amount of glycerol can effectively improve the stability and corrosion resistance of the electrolyte. However, when the glycerol content exceeds 40%, the electrolyte exhibits high softening properties and viscosity, making it unsuitable for experimental use. Therefore, based on the electrochemical test results and the state of the electrolyte during actual use, a gel electrolyte with a glycerol content of 30%-40% is more suitable for testing.

[0054] Figure 4 The graphs show the effective usage time test results of five groups of portable three-electrode corrosion sensors based on polyacrylamide gel electrolyte prepared in Example 3. A represents the impedance test statistics of the sensor without glycerol at different times; B represents the impedance test statistics of the sensor with 10% glycerol; C represents the impedance test statistics of the sensor with 20% glycerol; D represents the impedance test statistics of the sensor with 30% glycerol; and E represents the impedance test statistics of the sensor with 40% glycerol. Figure 4It can be clearly seen that as the glycerol content increases to 30%, the effective service life of the polyacrylamide gel electrolyte corrosion sensor also increases accordingly. For example... Figure 4 The graph in Figure E shows the impedance test statistics of a sensor with 40% glycerol added over a 30-day period. During the first 11 days of testing, the sensor's results remained stable without any change, demonstrating its effectiveness in monitoring corrosion during this time period. As time progresses, the moisturizing effect of the electrolyte gradually decreases, potentially leading to a phase transition, which in turn increases conductivity and decreases impedance, thus gradually increasing its corrosive effect on stainless steel.

[0055] In summary, this sensor can effectively monitor corrosion over a period of up to 11 days. This result further verifies the important role of glycerol in improving the long-term monitoring capability of polyacrylamide gel electrolytes, and provides a solid foundation for its application in atmospheric corrosion monitoring.

[0056] Example 4: Preparation of a gel-etched three-electrode sensor using different electrodes

[0057] The basic steps for preparing the polyacrylamide gel corrosion sensor are the same as in Example 3. In this example, the concentration of glycerol is set to 40% W / W. The difference is that the counter electrode 2 is a carbon plate, while the reference electrode 3 is a silver / silver chloride electrode, a silver wire electrode, and a silver wire plated with silver chloride electrode, respectively, thus preparing three different portable three-electrode corrosion sensors based on polyacrylamide gel.

[0058] Electrochemical tests were performed on these three sets of corrosion three-electrode sensors, and the results are as follows: Figure 5 As shown. Figure 5 The electrochemical impedance spectroscopy comparison diagrams of the three corrosion sensors prepared in Example 4 are shown. From Figure 5 As can be seen, the curve characteristics of these three reference electrodes are basically the same, indicating that replacing reference electrode 3 does not significantly affect the corrosion test results. This finding provides more possibilities for the flexible application of the sensor, allowing for the selection of suitable reference electrodes under different experimental conditions without affecting the accuracy of the test.

[0059] In summary, the results of this embodiment further verify the reliability and adaptability of the polyacrylamide gel corrosion sensor, laying the foundation for future research and applications.

[0060] Example 5: Different distances between the reference electrode and the working electrode for a gel corrosion three-electrode sensor

[0061] The basic steps for preparing the polyacrylamide gel corrosion sensor are the same as in Example 4. In this example, the concentration of glycerol is set to 40% W / W. The counter electrode 2 is a carbon plate, the difference being that the reference electrode 3 is a silver / silver chloride electrode. Based on practical applications, the distances between the reference electrode 3 and the working electrode 4 are selected as 2 mm, 4 mm, and 6 mm, respectively, thus preparing three different portable three-electrode corrosion sensors based on polyacrylamide gel. Electrochemical tests were performed on these three sets of corrosion three-electrode sensors, and the results are as follows: Figure 6 As shown. Figure 6 The electrochemical impedance spectroscopy (EIS) comparisons of the three corrosion sensors prepared in Example 5 are shown, where A is the Nyquist plot and B is the Bode plot. Figure 6 As can be seen from Figure A, the curve characteristics of these three reference electrodes are basically the same, indicating that the electrode spacing has little impact on the overall characteristics of the electrochemical reaction. Figure 6 The increase in impedance in the low-frequency region of the Bode plot indicates a gradual increase in electrolyte resistance, suggesting that electrolyte conductivity is affected by distance. Based on actual tests, although different distances to the reference electrode have little impact on the characteristic curves of the electrochemical reaction, the electrolyte resistance is indeed affected. Therefore, considering practical testing, choosing 4 mm as the distance between the reference and working electrodes effectively ensures the validity and repeatability of the experiment.

[0062] Example 6: Different solutions for gel corrosion three-electrode sensors

[0063] The basic steps for preparing the polyacrylamide gel corrosion sensor are the same as in Example 2. The difference is that a rain-simulated aqueous solution is used as the aqueous phase when preparing the polyacrylamide gel electrolyte, and the total solute concentration in the rain-simulated aqueous solution is 0.00073 mol / L, as detailed below.

[0064] (1) Prepare rainwater-inspired electrolyte

[0065] First, weigh 14.43 mg of calcium sulfate dihydrate (CaSO4·2H2O), 15.04 mg of ammonium sulfate [(NH4)2SO4], 19.15 mg of ammonium chloride [(NH4)Cl], and 15.13 mg of sodium nitrate (NaNO3) and dissolve them in 1000 mL of distilled water. Use this mixture as a liquid electrolyte and adjust the pH to 6.5 with 1 mol / L sodium hydroxide solution to obtain a rainwater-inspired electrolyte.

[0066] (2) Preparation of a corrosion three-electrode sensor based on polyacrylamide gel electrolyte.

[0067] First, weigh 2g of acrylamide, 0.1g of ammonium persulfate, and 2.5mg of methylenebisacrylamide and dissolve them in 20mL of rainwater-inspired electrolyte to obtain a homogeneous mixture. Add 40% w / w glycerol to the mixture, deoxygenate the mixture with nitrogen for 10 minutes, and then heat at 60℃ for 30 minutes to polymerize. Pour the polymer into a cylindrical silicone mold with a diameter of 40mm and a height of 40mm, and cool to obtain polyacrylamide gel electrolyte.

[0068] (3) Pour the polyacrylamide obtained in step (2) into mold 1, which contains counter electrode 2 and silver / silver chloride as reference electrode 3. Then place the mold 1 with gel electrolyte on working electrode 4 to form a portable corrosion three-electrode sensor. The distance between reference electrode 3 and electrode 4 is 4 mm, and the distance between counter electrode 2 and electrode 4 is 5 mm.

[0069] Electrochemical tests were performed on the corrosion three-electrode sensor to verify the system and its stability. Figure 7 Three consecutive EIS measurements were performed on the same sample. The results show that the overall measurement stability is good.

[0070] Comparative Example 1: Agarose Gel Electrolyte

[0071] (1) Prepare rainwater-inspired electrolyte

[0072] First, weigh 14.43 mg of calcium sulfate dihydrate (CaSO4·2H2O), 15.04 mg of ammonium sulfate [(NH4)2SO4], 19.15 mg of ammonium chloride [(NH4)Cl], and 15.13 mg of sodium nitrate (NaNO3) and dissolve them in 1000 mL of distilled water. Use this mixture as a liquid electrolyte and adjust the pH to 6.5 with 1 mol / L sodium hydroxide solution to obtain a liquid electrolyte.

[0073] (2) Fabrication of a corrosion three-electrode sensor based on agarose gel electrolyte

[0074] Agar powder was added to 40 mL of electrolyte at a concentration of 2% W / W. The solution was stirred at room temperature for 30 min, then placed in an oil bath at 110°C for 30 min. After cooling to room temperature for a period of time, the electrolyte was poured into mold 1 containing a carbon rod as counter electrode 2 and silver / silver chloride as reference electrode 3. The solution was then cooled to solidify to obtain the corrosion three-electrode sensor. The structure of the corrosion three-electrode sensor is the same as in Example 1, except that the electrolyte is different.

[0075] Using the above process, six sets of corrosion three-electrode sensors based on agar gel electrolyte were obtained with agar contents of 3% W / W, 4% W / W, 5% W / W, 6% W / W, 8% W / W, and 10% W / W.

[0076] Electrochemical performance tests were conducted on the seven sets of agarose gel electrolyte corrosion sensors implemented in this case study, such as... Figure 8 As shown. Figure 8 The electrochemical impedance spectroscopy (EIS) and TAFEL comparison diagrams of seven groups of corrosion three-electrode sensors based on agar gel electrolytes prepared in Comparative Example 1 are shown. In the diagram, A represents the EIS of the corrosion sensors with different agar gel electrolyte contents, and B represents the corresponding TAFEL diagram. Figure 8 As shown, all the agar concentration curves exhibit similar characteristics, indicating that adding agar does not significantly alter the electrode reaction, thus supporting the use of this gel electrolyte for electrochemical testing. EIS and TAFEL test plots reveal that the gel electrolyte has the least impact on the corrosion of the working electrode at an agar content of 4% W / W. Therefore, the agar gel corrosion sensor prepared at this concentration exhibits optimal performance.

[0077] When performing aging tests on a corrosion sensor with an agar content of 4% W / W, the results showed inconsistencies in the electrochemical impedance spectroscopy results after 24 hours, such as... Figure 9 As shown, this indicates that the properties of the agarose gel electrolyte may change over time, thus affecting the stability and accuracy of the sensor.

[0078] Example 7: Practical Application of Polyacrylamide Gel Corrosion Sensor

[0079] The polyacrylamide gel corrosion sensor prepared in Example 6 and the agar gel corrosion sensor prepared in Comparative Example 1 were used to detect the corrosion of different metal blocks over 24 hours. Details are as follows:

[0080] Using 316L stainless steel plates (5cm long, 5cm wide, and 0.2cm thick), 201 stainless steel plates, and Q235 steel plates as working electrodes, respectively, the electrodes were ultrasonically treated for 30 minutes each in acetone, ethanol, and deionized water until clean. The cleaned working electrodes were then polished sequentially with 280#, 800#, and 1200# sandpaper and dried. The treated 316L, 201, and Q235 stainless steel plates were placed in a constant temperature and humidity test chamber and subjected to corrosion for 1 hour, 4 hours, 8 hours, and 24 hours at 15℃ and 100% humidity. The polyacrylamide gel corrosion sensor prepared in Example 6 and the agar gel corrosion sensor prepared in Comparative Example 1 were placed on the above steel plate samples and connected to an electrochemical workstation for testing. Electrochemical impedance spectroscopy was performed to test the corrosion of the 316L, 201, and Q235 stainless steel plates over 1-24 hours. The results are as follows: Figure 10 As shown.

[0081] Figure 10The images show the electrochemical impedance spectroscopy (EIS) spectra of different metal blocks under 24 hours of corrosion using the portable three-electrode corrosion sensor based on polyacrylamide gel electrolyte and the three-electrode corrosion sensor based on agar gel electrolyte in Example 7. Specifically, A represents the EIS spectrum of 316L stainless steel using the polyacrylamide gel corrosion sensor; B represents the EIS spectrum of 201 stainless steel using the polyacrylamide gel corrosion sensor; C represents the EIS spectrum of Q235 steel using the polyacrylamide gel corrosion sensor; D represents the EIS spectrum of 316L stainless steel using the agar gel corrosion sensor; E represents the EIS spectrum of 201 stainless steel using the agar gel corrosion sensor; F represents the EIS spectrum of Q235 steel using the agar gel corrosion sensor; G represents a comparative EIS spectrum of 316L stainless steel, 201 stainless steel, and Q235 steel under 24 hours of corrosion using the polyacrylamide gel corrosion sensor; and H represents a comparative EIS spectrum of 316L stainless steel, 201 stainless steel, and Q235 steel under 24 hours of corrosion using the agar gel corrosion sensor. Figure 10 Significant impedance changes were observed in samples A, B, and C, demonstrating that the polyacrylamide gel sensor clearly reflects the corrosion status of different materials at different time points. This indicates that the polyacrylamide gel sensor has high sensitivity to metal corrosion and can effectively capture the electrochemical changes during the corrosion process. (Test results of the agar gel corrosion sensor are also provided.) Figure 10 The D, E, and F components showed weaker electrochemical responses, making it difficult to distinguish corrosion differences at different time points. Therefore, polyacrylamide gel provides clearer results when assessing metal corrosion over a short period.

[0082] pass Figure 10 Analysis of G and H values ​​revealed that, at the same time interval, both polyacrylamide gel and agar gel showed lower impedance for Q235, while 316L exhibited higher impedance, indicating better corrosion resistance of 316L. This further validates the superiority of polyacrylamide gel sensors in metal corrosion assessment.

[0083] The commonly used method is the hanging plate method to determine the corrosion status of samples. Specific procedures: 316L stainless steel, 201 stainless steel, and Q235 steel are sequentially ultrasonically treated in acetone, ethanol, and deionized water for 30 minutes each until thoroughly cleaned. The cleaned working electrodes are then polished sequentially with 280#, 800#, and 1200# sandpaper, and dried before use. The treated 316L stainless steel, 201 stainless steel, and Q235 steel are placed in a constant temperature and humidity test chamber and subjected to corrosion at 15℃ and 100% humidity. The corrosion status of the samples within 24 hours is determined by the difference in mass. The results are as follows: Figure 11 As shown.

[0084] Figure 11This is a corrosion rate graph showing the corrosion of different metal blocks within 24 hours using the hanging plate method in Example 7. In the graph, A is the sample image before corrosion, from left to right: 316L stainless steel, 201 stainless steel, and Q235 steel; B is the sample image after 24 hours of corrosion, from left to right: 316L stainless steel, 201 stainless steel, and Q235 steel; C is the mass loss graph for 316L stainless steel; D is the mass loss graph for 201 stainless steel; and E is the mass loss graph for Q235 steel. Figure 11 In the comparison between A and B, visual observation of sample changes cannot accurately determine the degree of corrosion, especially when there are no obvious signs of corrosion on the surface. Data on mass loss ( Figure 11 Using C, D, and E (corresponding to C, D, and E), the degree of corrosion of each material can be assessed more objectively. From Figure 10 It can be seen that Q235 steel has the greatest mass loss and a high corrosion rate, while 316L stainless steel exhibits better corrosion resistance.

[0085] While the plate-mounted method is an effective corrosion assessment method, its complex operation and long waiting time may not be suitable for applications requiring rapid evaluation. Compared to the plate-mounted method, the polyacrylamide gel electrolyte sensor of this invention provides a more efficient detection method. By directly performing electrochemical tests, we can quickly obtain electrochemical impedance spectroscopy data, thereby comparing the corrosion resistance of different metals. Experimental results show that the results of the gel sensor are consistent with those of the plate-mounted method, demonstrating its accuracy and reliability.

[0086] In summary, gel corrosion sensors are simpler and faster to operate, effectively reducing experimental waiting time and making them suitable for applications requiring rapid assessment of metal corrosion performance. Therefore, gel electrolyte sensors are a corrosion detection method worthy of widespread adoption.

Claims

1. The application of a polyacrylamide gel electrolyte in the preparation of a portable corrosion three-electrode sensor, characterized in that, The polyacrylamide gel electrolyte is prepared by dissolving acrylamide monomer, initiator, crosslinking agent and glycerol as raw materials in an aqueous phase, adding initiator and crosslinking agent, and then initiating free radical polymerization of acrylamide under anaerobic conditions.

2. The application according to claim 1, characterized in that, The initiator is ammonium persulfate or potassium persulfate, the crosslinking agent is methylenebisacrylamide, the concentration of acrylamide monomer in the aqueous phase is 10-50%, the amount of initiator is 4-6% of the monomer mass, and the amount of crosslinking agent is 0.01-0.5% of the monomer mass.

3. The application according to claim 1, characterized in that, The aqueous phase is a sodium sulfate solution or a rain-simulated water solution, wherein the concentration of the sodium sulfate solution is 0.002~1 mol / L and the concentration of the total solute in the rain-simulated water solution is 0.0005~0.05 mol / L.

4. The application according to any one of claims 1 to 3, characterized in that, The preparation method of polyacrylamide gel electrolyte includes the following steps: dissolving acrylamide in an aqueous phase, adding an initiator, crosslinking agent, glycerol and sodium sulfate solution, stirring evenly, bubbling with inert gas for 10-20 min, placing at 60-100 ℃ for 30-60 min, and cooling to room temperature to obtain polyacrylamide gel electrolyte.

5. A portable corrosion three-electrode sensor, comprising an outer mold (1), characterized in that, The outer mold (1) contains a polyacrylamide gel electrolyte (5), and the polyacrylamide gel electrolyte (5) has a counter electrode (2) and a reference electrode (3) inserted inside. The bottom of the polyacrylamide gel electrolyte (5) is provided with a working electrode (4). The polyacrylamide gel electrolyte is made by dissolving acrylamide monomer, initiator, crosslinking agent and glycerol as raw materials, adding initiator and crosslinking agent, and initiating free radical polymerization of acrylamide under anaerobic conditions.

6. The portable corrosion three-electrode sensor according to claim 5, characterized in that, The outer mold (1) is made of epoxy resin and hardener. The reference electrode (3) is a silver / silver chloride electrode, a silver wire electrode or a silver-plated wire electrode. The electrode (2) is a carbon rod or a carbon plate. The working electrode (4) is a stainless steel sheet.

7. The portable corrosion three-electrode sensor according to claim 5, characterized in that, The reference electrode (3) is set in parallel with the counter electrode (2), and the bottom of the reference electrode (3) is 2-6 mm away from the upper surface of the working electrode (4).

8. The portable corrosion three-electrode sensor according to claim 5, characterized in that, The outer mold (1) is made by mixing epoxy resin and hardener and pouring it into a silicone mold and letting it stand for 24-48 hours. The working electrode (4) needs to be pretreated. The pretreatment steps include: ultrasonically treating the working electrode (4) in acetone, ethanol and deionized water for 20-40 minutes each until it is clean; polishing the cleaned working electrode (4) with 280#, 800# and 1200# sandpaper in turn; and drying the polished working electrode (4) at 40-60 ℃ for 1-2 hours.

9. The application of polyacrylamide gel electrolyte or the portable corrosion three-electrode sensor according to any one of claims 5 to 8 in atmospheric corrosion monitoring, wherein the polyacrylamide gel electrolyte is prepared by dissolving acrylamide monomer, initiator, crosslinking agent and glycerol as raw materials, adding initiator and crosslinking agent, and initiating free radical polymerization of acrylamide under anaerobic conditions.

Images