Method for monitoring local corrosion of copper base material in real time based on discrete FBG (Fiber Bragg Grating) sensor

Abstract

The invention discloses a real-time monitoring method for local corrosion of a copper base material based on a discrete FBG sensor, and belongs to the technical field of metal corrosion monitoring. FBG strain sensors and temperature compensation sensors are distributed on the surface of the copper base material, and a temperature compensation mechanism is matched to eliminate measurement errors caused by environment temperature changes, so that the real-time monitoring of local corrosion of the copper base material is realized. Bragg wavelength drift caused by corrosion product accumulation in the corrosion process is collected in real time, and then real-time and continuous tracking of the corrosion dynamic process is obtained. The method realizes early recognition, accurate positioning and quantitative evaluation of local corrosion of the copper base material, has the advantages of non-destructiveness, high sensitivity, long-term stability and the like, and is suitable for corrosion health monitoring of copper structures such as ocean engineering, buildings, pipelines and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion monitoring technology, and relates to a real-time monitoring method for localized corrosion of copper substrates based on discrete FBG sensors. Background Technology

[0002] Copper-based materials, due to their excellent physical and mechanical properties, have been widely used in buildings, highway bridges, slope engineering, marine engineering, and natural gas pipelines. These copper-based materials typically function in highly challenging environments, including those with high humidity, microorganisms, air pollution, chemical contamination, and large temperature variations. However, throughout their service life, copper-based materials are affected by external environmental factors. Over time, corrosion damage occurs, and if not repaired or maintained promptly, it inevitably poses significant risks to the safe operation of buildings, highway bridges, slope engineering, marine engineering, and natural gas pipelines. For example, for copper-based material structures exposed to natural seawater, air, and chemical solvents, prolonged contact with corrosive liquids causes the liquid molecules to interact with the passivation layer on the copper surface, damaging the passivation layer and leading to rust formation, corrosion cracking, and further reducing the load-bearing capacity of the copper-based structural components, ultimately resulting in safety accidents. It has been reported that major safety accidents caused by corrosion of copper-based materials and other metal-based components occur worldwide every year. Therefore, corrosion monitoring and accurate corrosion behavior assessment are of great significance for providing early warning of damage to copper-based components, taking timely and effective maintenance measures, further ensuring the safe operation of infrastructure, and reducing repair or maintenance costs.

[0003] For corrosion of metal-based components such as copper-based materials, traditional measurement techniques include polarized electrochemical impedance spectroscopy (PES), acoustic emission, shock echo, and ultrasound. Different monitoring techniques or methods exhibit limitations due to their different monitoring principles; for example, PES has low measurement accuracy, while acoustic emission, shock echo, and ultrasound have high equipment costs. To achieve accurate corrosion monitoring, especially early detection and continuous improvement, advanced non-destructive technologies, such as fiber optic sensing, have become a promising tool for structural health monitoring. Compared with traditional monitoring methods, fiber optic sensing technology offers advantages such as small size, light weight, high sensitivity, high resolution, high accuracy, resistance to electromagnetic interference, and the required physical and chemical stability. It can be interconnected to form sensor networks for large-scale monitoring. Currently, fiber optic sensing technology can be divided into discrete (point) fiber optic sensing and distributed fiber optic sensing; among them, fiber Bragg grating sensors and distributed fiber optic sensors are two main types. Fiber Bragg grating sensors utilize periodic refractive index changes within the fiber core to reflect specific light wavelengths, thereby measuring strain, temperature, and other physical quantities. They have been used to monitor steel corrosion in concrete, steel plates, and steel bridges. Clearly, discrete point sensors are better suited for measuring corrosion levels at individual locations, especially for monitoring pitting corrosion. Compared to fiber Bragg grating sensors, distributed fiber optic sensing technology can achieve monitoring on a larger spatial scale along the entire length of the fiber. However, distributed fiber optic sensing technology has limited spatial resolution, lower accuracy, and higher cost, making it easier to monitor components with high elastic modulus. Furthermore, research on monitoring corrosion of copper-based materials is currently limited, and the microstructure of the corrosion layer in copper-based materials is quite complex. Therefore, choosing fiber Bragg grating sensing technology is crucial for evaluating the monitoring of corrosion behavior in copper-based materials.

[0004] Although fiber Bragg grating sensors have proven effective in monitoring corrosion of materials such as steel bars, their impact on the monitoring accuracy and effective monitoring range of corrosion of copper-based materials has not yet been studied. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a real-time monitoring method for localized corrosion of copper substrates based on discrete FBG sensors. This invention enables early identification, real-time monitoring, precise location, and quantitative assessment of localized corrosion of copper substrates, and features non-destructive operation, high sensitivity, and long-term stability.

[0006] To achieve the above objectives, according to the technical solution of the present invention, a method for real-time monitoring of localized corrosion of copper substrates based on a discrete FBG sensor is provided, comprising the following steps: Step S1 involves preparing a sample by taking a copper substrate, polishing the surface step by step with SiC sandpaper, cleaning it with deionized water and anhydrous ethanol, and then drying it. Step S2: After step S1, the single-mode optical fiber with 4 discrete FBG strain sensors and 1 temperature-compensated FBG sensor is bonded parallel to the surface of the copper substrate using high strain transfer adhesive to deploy the sensors. Step S3: After obtaining the copper sample, place it horizontally in an acrylic experimental cell and inject 3.5wt% NaCl solution on the surface of four small stainless steel blocks, covering the liquid surface to a height of 5cm. Simulate corrosion environment loading at room temperature. After the simulated corrosion environment loading in steps S4 and S3, the Bragg wavelength drift of each FBG sensor is acquired in real time using an FBG demodulator. Signals are collected every 10 days during the monitoring period; Step S5: Obtain the corrosion changes (Bragg wavelength shift) from step S4. The data is processed and analyzed using software. Step S6 involves collecting the copper corrosion products from step S4 and performing macroscopic and microscopic analysis of the corrosion process using a microscope to determine their morphology, elements, and structure.

[0007] Furthermore, in step S2, the center wavelengths of the four discrete FBG strain sensors are respectively =1530nm =1536nm =1539nm =1542nm, the center wavelength of the temperature-compensated FBG sensor is =1533nm and bandwidth is 0.3nm, the side mode of the single-mode fiber is greater than 15dB, the high strain transfer adhesive is ethyl cyanoacrylate, the grating length is 10mm and the grating spacing is 6cm, and the discrete FBG strain sensor and temperature compensated FBG sensor are deployed with an adhesive thickness ≤100µm.

[0008] Further, in step S3, the acrylic experimental cell has a length, width, and height of 50cm × 20cm × 5cm, and the stainless steel block is a 316 stainless steel block with a length, width, and height of 2×2×2cm. A 3.5wt% NaCl solution is injected onto the surface of the stainless steel block, and the NaCl solution covers the stainless steel block. The liquid level of the NaCl solution is any value between 4cm and 6cm. The simulated corrosion environment is loaded at room temperature.

[0009] Preferably, after step S3, step S4 uses an FBG demodulator to collect the Bragg wavelength drift of each FBG sensor in real time, with a sampling frequency of 10Hz and a wavelength resolution ≤1pm; the Bragg wavelength drift of each FBG sensor is collected in real time. The monitoring cycle involves multiple signal acquisitions every 10 days.

[0010] More preferably, based on the corrosion change data collected in step S4, step S5 adjusts the obtained Bragg wavelength drift. The data is processed and analyzed; the processing and analysis include: Step S51, by utilizing The sensor calculates the temperature change ΔT and performs temperature compensation to eliminate temperature cross-sensitivity. Step S52, using the initial Bragg wavelength and subsequent real-time acquisition of the Bragg wavelength drift of the FBG sensor The result after processing Perform preliminary data processing; Step S53: Following the data processing in step S52, the preliminary results are processed using the Origin software to obtain... Curve showing change over time; Step S54, through the process in S53 The time-varying curves divide the localized corrosion of copper into stages, based on... The curve characteristics divide the corrosion process into four stages: Stage I (0-2 days): the initial stage of corrosion, Slow increase; Stage II (2-4 days): Corrosion products fill the gap between the sensor and the copper substrate. Sudden increase (tensile strain, redshift); Stage III (4-8 days): Corrosion products continue to accumulate and compress the sensor. From positive to negative (compressive strain, blue shift); Stage IV (8-10 days): The corrosion product layer densifies, oxygen diffusion is hindered. It is trending towards stability.

[0011] More preferably, in step S6, the copper corrosion products after corrosion in step S4 are collected and the corrosion process is analyzed using a microscope. The specific analysis and processing methods include: Step S61: Record the corrosion status at regular intervals using microscopes of different magnifications; Step S62 involves analyzing the surface morphology, corrosion degree, compound composition, internal elemental composition, and crystal characteristics of the copper corrosion products using multiple techniques such as SEM, XRD, and TEM.

[0012] Compared with existing technologies, the advantages and positive effects of the real-time monitoring method for localized corrosion of copper substrates based on discrete FBG sensors proposed in this invention are as follows: 1. This invention utilizes a single-mode optical fiber with high sensitivity to detect micro-strain (<10με) caused by the accumulation of micron-sized corrosion products. 2. This invention is non-destructive by using a high strain transfer adhesive (ethyl cyanoacrylate) to bond parallel to the surface of a copper substrate, thus avoiding damage to the copper substrate and secondary damage. 3. This invention uses an FBG demodulator (sampling frequency = 10Hz, wavelength resolution ≤ 1pm) for monitoring, which is real-time and continuous, with a monitoring cycle as short as 100ms, enabling real-time and continuous tracking of the corrosion dynamic process; 4. This invention utilizes four discrete FBG strain sensors (center wavelength) =1530nm =1536nm =1539nm =1542nm) and a temperature-compensated FBG sensor ( Distributed monitoring is performed using single-mode optical fibers with a wavelength of 1533nm and a bandwidth of 0.3nm, and an edge mode greater than 15dB. Multi-point FBG sensors, combined with a temperature compensation mechanism, eliminate measurement errors caused by changes in ambient temperature, enabling precise location of localized corrosion areas and monitoring of corrosion status. 5. The present invention uses an FBG demodulator and a single-mode optical fiber with multiple FBG strain sensors to form a joint monitoring system, which has long-term stability. Its sensors deform in tandem with the copper substrate, making it suitable for long-term monitoring.

[0013] 6. The present invention provides a real-time monitoring method for localized corrosion of copper-based materials based on a discrete fiber Bragg grating (FBG) sensor, which is applicable to the monitoring and measurement of localized copper-based structural health in fields such as construction and marine engineering. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the real-time monitoring method and system for localized corrosion of copper substrates based on discrete FBG sensors in this embodiment. Figure 2 This is a schematic diagram showing the arrangement of some fiber Bragg gratings on a copper metal plate in this embodiment; Figure 3 This is a schematic diagram showing the drift of the Bragg wavelength in the FBG sensor of this embodiment as a function of corrosion time; Figure 4 This is a microscopic SEM image of the localized corrosion products in this embodiment. Detailed Implementation

[0015] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0016] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0017] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0018] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0019] This invention proposes a real-time monitoring method for localized corrosion of copper substrates based on discrete FBG sensors. It utilizes fiber Bragg grating sensing technology to study the dynamic corrosion behavior of copper-based materials under corrosive conditions. The invention investigates the corrosion process of copper-based materials and the changes in the microstructure of the corroded layer under corrosive conditions. It uses fiber Bragg grating sensing technology to monitor the corrosion process of copper-based materials in real time, exploring the influence of corrosion behavior on the optical sensing signal and its underlying mechanism. Furthermore, the localized corrosion monitoring system for copper substrates based on discrete fiber optic sensors, capable of covering a specific local area, provided by this invention, will offer a more solid monitoring technology foundation for the monitoring and prevention of localized corrosion on copper substrates.

[0020] The invention will be further described below with reference to the accompanying drawings. Please refer to the accompanying drawings. Figure 1 As shown, this is a flowchart illustrating the real-time monitoring method and system for localized corrosion of copper substrates based on discrete FBG sensors in this embodiment. The method includes: Step S1 involves preparing a sample by taking a copper substrate (preferably a Cu1100 copper plate with Cu≥99.9% and dimensions of 40cm×20cm×5mm), polishing the surface of the copper substrate step by step with SiC sandpaper until Ra≤0.1µm, cleaning it with deionized water and anhydrous ethanol, and then drying it. Step S2, four discrete FBG strain sensors (the center wavelength of the discrete FBG strain sensor is...) =1530nm =1536nm =1539nm =1542nm) and one temperature-compensated FBG sensor (the center wavelength of the temperature-compensated FBG sensor is ...). =1533nm) with a bandwidth of 0.3nm, and single-mode optical fiber with an edge mode greater than 15dB is bonded parallel to the surface of a copper substrate using a high strain transfer adhesive (ethyl cyanoacrylate), with a grating length of 10mm, a grating spacing of 6cm, and an adhesive thickness of ≤100µm for sensor deployment. Step S3: After obtaining the copper sample, place it horizontally in an acrylic test cell (the length, width and height of the acrylic test cell are 50cm×20cm×5cm). The copper sample is preferably four 2×2×2cm 316 stainless steel blocks. A 3.5wt% NaCl solution is injected into the surface of the stainless steel blocks, and the NaCl solution covers the liquid surface of the stainless steel blocks by 4cm-6cm. The simulated corrosion environment is loaded at room temperature. Step S4: Following step S3, an FBG demodulator (sampling frequency = 10Hz, wavelength resolution ≤ 1pm) is used to collect the Bragg wavelength drift of each FBG sensor in real time. Signals are collected every 10 days during the monitoring period; Step S5: Obtain the corrosion changes (Bragg wavelength shift) from step S4. The data is processed and analyzed using software. Step S6 involves collecting the copper corrosion products from step S4 and performing macroscopic and microscopic analysis of the corrosion process using a microscope to determine their morphology, elements, and structure.

[0021] Specifically, the method is implemented in a real-time corrosion monitoring terminal for copper plates (copper samples). A single-mode fiber optic grating is used to detect changes in the refractive index of the grating cladding region. The wavelength drift information of the grating cutoff cladding mode is utilized to monitor corrosion changes in the metal pipeline. This invention overcomes the shortcomings of traditional detection technologies, such as long testing cycles, inability to adapt to harsh environments, and lack of real-time monitoring capabilities. It offers advantages such as high accuracy, low cost, real-time monitoring, and high sensitivity for early corrosion detection, making it suitable for detection and prevention of metal corrosion in various scenarios, including seawater, oil, and wastewater.

[0022] The method of this invention provides accurate raw materials for the subsequent construction of the detection or monitoring system through step S1, eliminating the influence of other factors on the detection or monitoring system. Step S2 connects the temperature compensation sensor and strain sensor to the copper plate being measured, optimizing the sensor arrangement, improving detection accuracy and response speed, and ensuring real-time capture of the copper plate's corrosion status. Step S3 simulates the corrosion environment area, further determining the uniqueness of variables, allowing data to be acquired via a computer terminal connected to the FBG demodulator, providing an accurate data foundation, enabling the detection system to accurately assess the copper corrosion status, and ensuring data reliability and accuracy. In another embodiment, step S4 uses an FBG demodulator (sampling frequency = 10Hz, wavelength resolution ≤ 1pm) to collect the Bragg wavelength drift of each FBG sensor in real time. The monitoring period is 10 days for signal acquisition, and the specific corrosion situation in the corrosion area is monitored in real time. The method obtains corrosion changes (Bragg wavelength drift) through step S5. The data is processed and analyzed using software to correct possible measurement errors and determine the trend of corrosion changes. In step S6, the method of this invention collects the corrosion products of the copper after corrosion and uses a microscope to perform macroscopic and microscopic analysis of the morphology, elements, and structure of the corrosion during the corrosion process. This provides support for subsequent early maintenance and prevention, helps reduce sudden failures, and extends the service life of the copper.

[0023] It should be noted that the spectral performance of fiber Bragg gratings is a result of the combined influence of multiple types of dimensional data. That is, the peak shift characteristics of the spectral data are affected by various factors such as corrosion rate, temperature, and stress, and are easily affected by the regional structure of the corrosion site. The influence of dimensional data such as temperature and stress is even greater, leading to a large error in the analysis of corrosion status. In order to reduce the influence of temperature, a temperature sensor was used.

[0024] Specifically, in step S4, the Bragg wavelength drift of each FBG sensor is acquired in real time using an FBG demodulator (sampling frequency = 10Hz, wavelength resolution ≤ 1pm). The monitoring cycle is 10 days for signal acquisition. First, a welding technique is used to connect the single-mode fiber to the jumper wire, thereby transmitting real-time corrosion data to the HG-FBG fiber optic grating sensing system on the computer for acquisition. The welding method includes: Step S41: First, use wire strippers to strip the optical fiber and pass the optical fiber through heat shrink tubing. Then, remove the coating layer wrapped on the optical fiber and clean the bare optical fiber with alcohol. Finally, cut the fiber with an optical fiber cleaver and place it into the fusion splice slot of the fusion splicer. Step S42: According to the determined fusion splicer program, after fusion splicing, the optical fiber is taken out and heated and shrunken to protect its fusion electrical connection.

[0025] Specifically, in step S5, the Bragg wavelength drift of each FBG sensor is acquired in real time by the FBG demodulator in step S4. Based on corrosion change data, the localized copper corrosion near the sensor is processed and analyzed using software.

[0026] It should be noted that the specific treatment methods for the aforementioned locally corroded areas include: Step S51, by utilizing The sensor calculates the temperature change ΔT and performs temperature compensation to eliminate temperature cross-sensitivity. Step S52, using the initial Bragg wavelength and subsequent real-time acquisition of the Bragg wavelength drift of the FBG sensor The result after processing Perform preliminary data processing; Step S53: Following the data processing in step S51, the preliminary results are processed using the Origin software to obtain... Curve showing change over time; Step S54, through the process in S52 The time-varying curves divide the localized corrosion of copper into stages, based on... The curve characteristics divide the corrosion process into four stages: Stage I (0-2 days): the initial stage of corrosion, Slow increase; Stage II (2-4 days): Corrosion products fill the gap between the sensor and the copper substrate. Sudden increase (tensile strain, redshift); Stage III (4-8 days): Corrosion products continue to accumulate and compress the sensor. From positive to negative (compressive strain, blue shift); Stage IV (8-10 days): The corrosion product layer densifies, oxygen diffusion is hindered. It is trending towards stability.

[0027] Specifically, in step S6, the copper corrosion products after corrosion in step S4 are collected, and the corrosion process is analyzed using a microscope. The specific analysis and processing methods include: Step S61: Record the corrosion status at regular intervals using microscopes of different magnifications; Step S62: The surface morphology, corrosion degree, compound composition, internal elemental composition, and crystal characteristics of the copper corrosion products were studied from multiple technical perspectives, including SEM, XRD, and TEM.

[0028] In another embodiment, a real-time monitoring system for localized corrosion of copper substrate is provided for implementing the above method. The system includes a copper sample module, an FBG sensor, a corrosion environment simulation device, an FBG demodulator, and a data processing unit. The copper sample module is made of Cu1100 copper plate (40cm×20cm×5mm). The FBG sensor includes four strain sensors ( - ) +1 temperature compensation sensor ( (10mm gate length, 0.3nm bandwidth, and edge mode suppression ratio greater than 15dB; Adhesive layer: ethyl cyanoacrylate, curing time ≤30s, shear strength ≥15MPa;) The corrosion environment simulation device includes an acrylic experimental tank (50cm×20cm×5cm).

[0029] The FBG demodulator has a wavelength range of 1525-1570nm, a scanning frequency of ≥10Hz, and a wavelength accuracy of ±1pm. The data processing unit has built-in temperature compensation algorithm, strain-corrosion algorithm and early warning threshold setting module.

[0030] Please see Figure 2 As shown, this is a schematic diagram illustrating the arrangement of some single-mode optical fibers on a copper plate in this embodiment. It clearly demonstrates the specific placement of fiber optic sensors for different strain and temperature compensation in this embodiment, showing the single-mode optical fibers directly placed on the copper plate. The diagram also shows the data collection on corrosion changes starting from placing the single-mode optical fibers on the copper plate and immersing it in a corrosive environment. Specifically, from left to right, five wavelengths of reflectance spectra were obtained using center wavelengths of 1530nm, 1542nm, 1533nm, 1536nm, and 1539nm. Except for... =1533 is a temperature-compensated sensor, while the other four are strain sensors used to monitor changes in the corrosion area. Furthermore, each sensor grating is evenly spaced at 6cm intervals, and for ease of monitoring, a 2m long fiber optic pigtail is provided, which is directly fused to a jumper cable via fiber optic fusion splicing technology and connected to the input port of the grating demodulator. This embodiment does not impose specific limitations; it does not specifically limit the arrangement position and number of strain sensors in the single-mode fiber optic grating. For example, it can be set to a fiber optic grating spacing of 5cm and a number of strain sensors of 7.

[0031] Please see Figure 3 As shown, this is a schematic diagram of the Bragg wavelength change over corrosion time of one of the sensors in this embodiment of the single-mode fiber after temperature compensation treatment. Specifically, the corrosion process can be divided into four stages: Stage I: Initial corrosion stage, such as... Figure 3 As shown in 0-5000000 Slow increase; Stage II: such as Figure 3The corrosion products shown (5,000,000-7,000,000) fill the gap between the sensor and the copper substrate. Sudden increase (tensile strain, redshift); Stage III: such as Figure 3 As shown, corrosion products continuously accumulate and compress the sensor from 7,000,000 to 9,000,000. From positive to negative (compressive strain, blue shift); Stage IV: such as Figure 3 As shown, the corrosion product layer (9,000,000-1,000,000) becomes denser, hindering oxygen diffusion. It is trending towards stability.

[0032] Please see Figure 4 As shown, this is a cross-sectional SEM image of the copper corrosion product sample in this embodiment. The surface and cross-sectional morphology of the sample were analyzed using a field emission scanning electron microscope (FE-SEM, JEOL JMS-7500F, Japan) and the accompanying energy dispersive spectroscopy (EDS). It can be clearly seen that the surface is uneven, and the corrosion products are densely packed and exhibit a blocky structure, providing a reference for subsequent copper corrosion prevention.

[0033] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for real-time monitoring of localized corrosion in copper substrates based on discrete FBG sensors, characterized in that, It includes the following steps: Step S1 involves preparing a sample by taking a copper substrate, polishing the surface step by step with SiC sandpaper, cleaning it with deionized water and anhydrous ethanol, and then drying it. Step S2: After step S1, the single-mode optical fiber with 4 discrete FBG strain sensors and 1 temperature-compensated FBG sensor is bonded parallel to the surface of the copper substrate using high strain transfer adhesive to deploy the sensors. Step S3: After obtaining the copper sample, place it horizontally in an acrylic experimental cell and inject 3.5wt% NaCl solution on the surface of four small stainless steel blocks, covering the liquid surface to a height of 5cm. Simulate corrosion environment loading at room temperature. After the simulated corrosion environment loading in steps S4 and S3, the Bragg wavelength drift of each FBG sensor is acquired in real time using an FBG demodulator. Signals are collected every 10 days during the monitoring period; Step S5: Obtain the corrosion changes (Bragg wavelength shift) from step S4. The data is processed and analyzed using software. Step S6 involves collecting the copper corrosion products from step S4 and performing macroscopic and microscopic analysis of the corrosion process using a microscope to determine their morphology, elements, and structure.

2. The method for real-time monitoring of localized corrosion of copper substrate based on a discrete FBG sensor according to claim 1, characterized in that, In step S2, the center wavelengths of the four discrete FBG strain sensors are respectively =1530nm =1536nm =1539nm =1542nm, the center wavelength of the temperature-compensated FBG sensor is =1533nm and bandwidth is 0.3nm, the side mode of the single-mode fiber is greater than 15dB, the high strain transfer adhesive is ethyl cyanoacrylate, the grating length is 10mm and the grating spacing is 6cm, and the discrete FBG strain sensor and temperature compensated FBG sensor are deployed with an adhesive thickness ≤100µm.

3. The method for real-time monitoring of localized corrosion of copper substrates based on discrete FBG sensors according to claim 1, characterized in that, In step S3, the acrylic experimental cell has a length, width, and height of 50cm × 20cm × 5cm, and the stainless steel block is a 316 stainless steel block with a length, width, and height of 2×2×2cm. A 3.5wt% NaCl solution is injected onto the surface of the stainless steel block, covering the stainless steel block. The NaCl solution level is any value between 4cm and 6cm. The simulated corrosion environment is loaded at room temperature.

4. The method for real-time monitoring of localized corrosion of copper substrate based on a discrete FBG sensor according to claim 3, characterized in that, Following step S3, step S4 uses an FBG demodulator to acquire the Bragg wavelength drift of each FBG sensor in real time, with a sampling frequency of 10Hz and a wavelength resolution ≤1pm; the Bragg wavelength drift of each FBG sensor is acquired in real time. The monitoring cycle involves multiple signal acquisitions every 10 days.

5. The method for real-time monitoring of localized corrosion of copper substrate based on a discrete FBG sensor according to claim 4, characterized in that, Based on the corrosion change data collected in step S4, step S5 calculates the obtained Bragg wavelength drift. The data is processed and analyzed; the processing and analysis include: Step S51, by utilizing The sensor calculates the temperature change ΔT and performs temperature compensation to eliminate temperature cross-sensitivity. Step S52, using the initial Bragg wavelength and subsequent real-time acquisition of the Bragg wavelength drift of the FBG sensor The result after processing Perform preliminary data processing; Step S53: Following the data processing in step S52, the preliminary results are processed using the Origin software to obtain... Curve showing change over time; Step S54, through the process in S53 The time-varying curves divide the localized corrosion of copper into stages, based on... The curve characteristics divide the corrosion process into four stages: Stage I (0-2 days): the initial stage of corrosion, Slow increase; Stage II (2-4 days): Corrosion products fill the gap between the sensor and the copper substrate. Sudden increase (tensile strain, redshift); Stage III (4-8 days): Corrosion products continue to accumulate and compress the sensor. From positive to negative (compressive strain, blue shift); Stage IV (8-10 days): The corrosion product layer densifies, oxygen diffusion is hindered. It is trending towards stability.

6. The method for real-time monitoring of localized corrosion of copper substrate based on a discrete FBG sensor according to claim 1, characterized in that, In step S6, the copper corrosion products after corrosion in step S4 are collected, and the corrosion process is analyzed using a microscope. The specific analysis and processing methods include: Step S61: Record the corrosion status at regular intervals using microscopes of different magnifications; Step S62 involves analyzing the surface morphology, corrosion degree, compound composition, internal elemental composition, and crystal characteristics of the copper corrosion products using multiple techniques such as SEM, XRD, and TEM.

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