Method for testing fixed coupon assembly for cathodic protection of marine fuel oil pipelines

Abstract

The application discloses a test method for a fixed test piece assembly of a navigation fuel oil pipeline cathodic protection, and relates to the field of testing electric variables of fixed test pieces, and comprises the following steps: S1, synchronously connecting a test piece and a pipeline loop through a current interrupter, and setting an on-off period; S2, synchronously collecting, by a high-speed data collector, a potential signal of the test piece relative to a long-acting copper sulfate reference electrode or a soil Ag / Cl reference electrode, a current signal measured by a precision sampling resistor, and an interrupter synchronous signal, and the synchronization error between channels is less than or equal to 0.5 mu s; S3, locking a stable value before interruption as E1 based on the synchronous signal, and extracting a stable platform value after interruption as E2; S4, calculating an IR drop value of the test piece; S5, calculating a loop grounding resistance, and measuring soil resistivity p to verify the loop grounding resistance. The synchronous interruption and multi-channel synchronous collection, combined with Fourier / wavelet transform filtering processing and accurate measurement of the IR drop, solve the measurement distortion problem caused by signal asynchronization and noise interference, and provide accurate data basis for cathodic protection state evaluation.

Description

Technical Field

[0001] This invention relates to the field of testing fixed test piece electrical variables, specifically to a testing method for a fixed test piece assembly for cathodic protection of aviation kerosene pipelines. Background Technology

[0002] As a critical infrastructure component of airport apron refueling systems, the safe operation of aviation kerosene pipelines is essential for air transport. Steel aviation kerosene pipelines are susceptible to corrosion in buried environments, and current protection methods primarily combine anti-corrosion coatings with cathodic protection. Cathodic protection effectively inhibits corrosion by homogenizing the potential at all points on the metal surface, transforming the entire pipeline into a cathodic state.

[0003] In cathodic protection systems, when current flows from the auxiliary anode to the protected pipeline through media such as soil, a voltage drop, known as IR drop, is generated in the medium. The presence of IR drop interferes with the accurate measurement of the pipeline's true protective potential, thus affecting the assessment of the cathodic protection effect. When measuring IR drop, precise synchronous control and signal processing methods are often lacking, making it difficult to accurately capture the potential changes at the moment of current interruption. This leads to significant measurement errors, thereby affecting the assessment of pipeline corrosion status. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application provides a test method for a fixed test piece assembly for cathodic protection of aviation kerosene pipelines.

[0005] To achieve the above objectives, the technical solution adopted in this application is: a test method for a fixed test piece assembly for cathodic protection of aviation kerosene pipelines, characterized by comprising the following steps:

[0006] S1: The synchronous current interruptor is connected in series with the test piece and the pipeline circuit. The on-off cycle is set to (12±3) seconds on-off and (3±1) seconds off. The interrupt current is ≥30A. The temperature resistance is -40℃ to +85℃. The synchronization method adopts internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization. The synchronization accuracy is ≤1μs.

[0007] S2: The high-speed data acquisition unit synchronously acquires the potential signal of the test piece relative to the long-lasting copper sulfate reference electrode or the Ag / AgCl reference electrode for soil, the current signal measured by the precision sampling resistor, and the interrupt synchronization signal, with a synchronization error between channels ≤0.5μs;

[0008] S3: Based on the synchronization signal, lock the stable value before the interruption as E1, and extract the stable plateau value after Fourier transform filtering within the window of 0.1 seconds to 0.3 seconds after the interruption as E2, with a filtering frequency range of 50Hz±1Hz;

[0009] S4: Calculate the IR drop of the test piece using the formula IR drop = E1 - E2, with a calculation error ≤ ±2%;

[0010] S5: Combine the IR drop and the current value I to calculate the loop grounding resistance = |IR drop| / I. Use the four-electrode method to measure the soil resistivity ρ to help verify the rationality of the loop grounding resistance. The correction factor for ρ is reduced by 0.8% for every 10℃ increase in temperature.

[0011] Optionally, it also includes a synchronous current interruptor with a dynamic on / off cycle adjustment module, used to adjust the on / off cycle range online to 5-20 seconds on / 1-5 seconds off, with an adjustment step accuracy of 0.1 seconds, to adapt to the IR drop test requirements of different soil environments.

[0012] Optionally, the long-lasting copper sulfate reference electrode adopts a double-layer sealed structure: the outer layer is a polytetrafluoroethylene sleeve resistant to aviation kerosene corrosion, the inner layer is filled with saturated copper sulfate solution, and a platinum wire auxiliary electrode is embedded in the electrode head to ensure potential stability ≤ ±1mV at a low temperature of -40℃.

[0013] Optionally, the data acquisition system may also include an intelligent calibration module: automatically performing zero-point calibration and full-scale calibration before each test, generating a calibration curve, wherein the goodness of fit of the calibration curve satisfies the coefficient of determination R² ≥ 0.999.

[0014] Optionally, after the current interruptor is disconnected, there is a power-off potential extraction window, which lasts for 0.1-0.3 seconds. The data within the window needs to be denoised by wavelet transform to improve the signal-to-noise ratio to ≥30dB.

[0015] Optionally, the test data is also transmitted in real time to the pipeline integrity management system with encryption. The management system automatically generates an IR drop-time trend curve and a loop grounding resistance-temperature scatter plot, and sets three warning thresholds: when the IR drop is greater than 100mV or the loop grounding resistance is greater than 10Ω for three consecutive times, a red warning is triggered and pushed to the mobile terminal of the maintenance personnel.

[0016] Optionally, the fixed test piece is made of titanium alloy substrate with a composite nano-cerium oxide coating, the coating thickness is 50±5μm, and the corrosion resistance current density is ≤0.1μA / cm².

[0017] Optionally, it also includes safety interlock protection during the testing process: when the circuit current is greater than 50A or the equipment surface temperature is greater than 85°C, the power supply is automatically cut off and an audible and visual alarm is activated, and the alarm signal is simultaneously pushed to the remote monitoring center.

[0018] Optionally, the test cycle can also be set as follows: routine protection potential test is conducted once per quarter, and an additional test is conducted within 48 hours after extreme weather; fixed test pieces are excavated and inspected and their weight loss is analyzed every two years, and a test piece replacement warning is triggered when the weight loss rate is >5%.

[0019] Beneficial effects:

[0020] 1. By using high-precision synchronous interruption and multi-channel synchronous acquisition, combined with Fourier / wavelet transform filtering, accurate measurement of IR drop was achieved, completely solving the measurement distortion problem caused by signal asynchrony and noise interference in traditional methods, and providing a more accurate data foundation for cathodic protection status assessment.

[0021] 2. The dynamically adjustable on / off cycle and intelligent calibration module are adapted to different soil environments; the titanium alloy nano-coated test piece and double-sealed reference electrode ensure data reliability under extreme conditions; and the safety interlock mechanism ensures operational safety.

[0022] 3. By uploading encrypted data in real time and conducting multi-dimensional analysis, a three-level early warning mechanism and periodic detection standards have been established, achieving a leap from single-point measurement to intelligent management throughout the entire life cycle, significantly improving the predictability and reliability of corrosion protection for aviation kerosene pipelines. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of the testing method described in an embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0027] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0028] This example: Please refer to Figure 1 This embodiment provides a testing method for a fixed test piece assembly for cathodic protection of aviation kerosene pipelines, characterized by the following steps:

[0029] S1: A synchronous current interruptor is connected in series between the test piece and the pipeline circuit. The on / off cycle is set to (12±3) seconds on and (3±1) seconds off, with an interruption current ≥30A and a temperature resistance of -40℃ to +85℃. Synchronization is achieved using an internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization, with a synchronization accuracy ≤1μs. The synchronous current interruptor, through a precision control circuit, achieves periodic on / off in the test piece and pipeline circuit. The control time for this periodic on / off cycle is 12±3 seconds on and 3±1 seconds off. Internal crystal oscillator or GPS / Bluetooth dual-mode synchronization ensures strict synchronization between the interruption action and data acquisition, with an accuracy ≤1μs, avoiding timing mismatches. The temperature resistance of -40℃ to +85℃ is suitable for the extreme environment of aviation kerosene pipelines, and the interruption current ≥30A meets the requirements of high-power cathodic protection. Precise periodic control eliminates polarization interference in IR drop measurements, ensuring the capture of the true polarization potential at the moment of power failure; dual-mode synchronization technology enhances anti-interference capabilities and avoids data drift when GPS signals are lost; wide temperature and weather resistance ensures stable operation of the equipment in the cold / high temperature environment of aviation kerosene pipelines, extending the equipment's lifespan.

[0030] S2: The high-speed data acquisition unit synchronously acquires the potential signal of the sample relative to the long-life copper sulfate reference electrode or the Ag / AgCl reference electrode for soil, the current signal measured by the precision sampling resistor, and the interrupt synchronization signal, ensuring that the synchronization error between channels is ≤0.5μs. The high-speed data acquisition unit synchronously acquires three signals at a sampling rate ≥1kHz and a resolution ≥16 bits: the potential signal of the sample relative to the reference electrode, the current signal of the precision sampling resistor, and the interrupt synchronization signal, with an inter-channel synchronization error ≤0.5μs, ensuring time alignment of the potential, current, and synchronization signals. The high sampling rate captures millisecond-level potential fluctuations, avoiding signal distortion caused by low-speed sampling; multi-channel synchronization eliminates timing errors, ensuring accurate correspondence between the stable value E1 before interruption and the filtered value E2 after interruption; the precision sampling resistor achieves high-precision conversion of the current signal (error ≤0.1%), providing a reliable data source for IR drop calculation.

[0031] S3: Based on the synchronization signal, lock the stable value before the interruption as E1, and extract the stable plateau value after Fourier transform filtering within the window of 0.1 seconds to 0.3 seconds after the interruption as E2, with a filtering frequency range of 50Hz±1Hz;

[0032] Based on the stable value before the interruption locked by the synchronization signal as E1, the potential signal within a 0.1-0.3 second window after the interruption is extracted and obtained as the stable plateau value E2 after Fourier transform filtering. Filtering eliminates power frequency interference and high-frequency noise while preserving the true polarization potential characteristics. Fourier transform filtering improves the signal-to-noise ratio, ensuring that E2 is stable within the 0.1-0.3 second window; the time window set by the NACE SP0169 standard is strictly followed to avoid interference from the depolarization process on E2; the filtering band is specifically designed to suppress power frequency noise, improving the IR drop calculation accuracy to ≤±2%.

[0033] S4: The IR drop of the test piece is calculated using the formula IR drop = E1 - E2, with a calculation error ≤ ±2%. This error boundary is achieved through high-precision data acquisition, strict synchronous control, and filtering algorithms. High-precision IR drop quantification measures the ohmic loss of the cathodic protection circuit, providing a direct basis for evaluating the protection current distribution efficiency; low-error calculation ensures the reliability of the IR drop value, avoiding misjudgments of cathodic protection effectiveness due to measurement errors.

[0034] S5: The loop grounding resistance = |IR drop| / I is calculated by combining the IR drop and the current value I. The soil resistivity ρ is measured using the four-electrode method to assist in verifying the rationality of the loop grounding resistance. The correction factor for ρ decreases by 0.8% for every 10°C increase in temperature. The loop grounding resistance R_loop = |IR drop| / I is calculated using Ohm's law, combining the IR drop and the current value I. The soil resistivity ρ is measured using the four-electrode method, and the correction factor is adjusted by 0.8% for every 10°C increase in temperature to dynamically verify the rationality of the loop grounding resistance. The loop grounding resistance quantifies the total loop resistance, guiding the design optimization of the cathodic protection system; the four-electrode method eliminates electrode polarization errors, improving the accuracy of ρ measurement; a temperature compensation mechanism corrects for changes in soil resistivity, ensuring the accuracy of the loop grounding resistance calculation under wide temperature conditions; the correlation analysis between the calculated loop grounding resistance and IR drop can inversely deduce the pipeline corrosion rate, supporting full life-cycle corrosion management.

[0035] Synchronous interruption, high-precision acquisition, and filtering algorithms work together to reduce IR error to ±2%, which is far superior to traditional methods; dual-mode synchronization, wide temperature and weather resistance design, and sealed reference electrodes are adapted to extreme working conditions of aviation kerosene pipelines; real-time encrypted data transmission, trend curve generation, and three-level early warning enable dynamic monitoring of cathodic protection effectiveness; safety interlock protection ensures that the testing process is safe and controllable.

[0036] Optionally, the synchronous current interruptor is equipped with a dynamic on / off cycle adjustment module, which can adjust the on / off cycle range online to 5-20 seconds on / 1-5 seconds off, with an adjustment step accuracy of 0.1 seconds, to adapt to the IR drop test requirements of different soil environments.

[0037] The dynamic on / off cycle adjustment module achieves online adjustment of the on / off cycle through the collaboration of hardware circuits and software algorithms. Its core logic is as follows:

[0038] The user inputs the target on / off cycle through the control interface, such as 15 seconds on / 3 seconds off. The system converts the parameters into digital signals and transmits them to the central processing unit (CPU). The CPU dynamically adjusts the on / off timing of the electronic switch based on the input parameters.

[0039] For example, when it is necessary to extend the power-on time, the central processing unit will delay triggering the shutdown signal to allow the current to continue flowing until the set time; during the power-off phase, the current is interrupted by quickly cutting off the switch.

[0040] The system has a built-in current sensor that monitors the actual on / off status in real time. If a deviation is detected, the CPU will immediately correct the switching timing to ensure that the cycle accuracy reaches ±0.1 seconds.

[0041] Factors such as soil resistivity and reference electrode distance can cause voltage drops during cathodic protection current transmission, affecting the accuracy of power-off potential measurements. For example, the IR drop decay rate differs significantly between different soil environments, such as high-resistivity sandy soil and low-resistivity clay.

[0042] When dynamically adjusted:

[0043] In high resistivity soils, extending the energizing time (e.g., 20 seconds) allows the soil medium to be fully polarized, reducing the residual IR drop at the moment of power failure; shortening the power failure time (e.g., 1 second) allows for rapid capture of the true power failure potential, avoiding errors caused by polarization recovery.

[0044] In low resistivity soils, shorten the energizing time (e.g., 5 seconds) to prevent excessive polarization, and extend the de-energizing time (e.g., 5 seconds) to allow the IR drop to decay sufficiently, thereby improving measurement stability.

[0045] Optionally, the long-lasting copper sulfate reference electrode adopts a double-layer sealed structure: the outer layer is a polytetrafluoroethylene sleeve resistant to aviation kerosene corrosion, the inner layer is filled with saturated copper sulfate solution, and a platinum wire auxiliary electrode is embedded in the electrode head to ensure potential stability ≤ ±1mV at a low temperature of -40℃.

[0046] By adjusting the on / off cycle, the module can optimize the measurement timing for different soil environments and their varying IR attenuation patterns. For example, a "long on, short off" mode is used in sandy soils, while a "short on, long off" mode is used in clay soils. This makes the measured off-voltage potential closer to the true value, reducing the error rate to within 5%. Precise on / off control avoids the polarization effect caused by prolonged energization in the soil medium, prevents potential rebound after power failure, and ensures the reliability of the measurement data.

[0047] Optionally, the data acquisition system may also include an intelligent calibration module: automatically performing zero-point calibration and full-scale calibration before each test, generating a calibration curve, and the goodness of fit of the calibration curve satisfies the coefficient of determination R² ≥ 0.999.

[0048] In this embodiment, the aforementioned intelligent calibration module achieves high-precision calibration of the data acquisition system through an automated process. Its core logic is divided into two stages: zero-point calibration and full-scale calibration, and it relies on a high-fit calibration curve to ensure data accuracy. The specific process is as follows:

[0049] Zero-point calibration: used to eliminate the initial offset of the sensor output signal and ensure that the output is zero when there is no input.

[0050] Specifically, the system disconnects all external signal inputs, placing the sensor in a no-load state. The acquisition module reads the sensor's output value at this time and records it as the "zero-point offset." A software algorithm then subtracts this offset from subsequently acquired raw data to complete the zero-point correction.

[0051] A high-precision digital-to-analog converter (ADC) and a low-noise amplifier circuit are used to ensure that the resolution of zero-point signal acquisition reaches the microvolt level (μV), avoiding the neglect of minute offsets.

[0052] Full-scale calibration: used to correct the nonlinear error of the sensor within its maximum input range, ensuring that the output signal has a strictly linear relationship with the actual physical quantity.

[0053] Specifically, the system connects to a known standard signal source and adjusts the sensor input to its full-scale value (e.g., 20mA current or 10V voltage). The acquisition module records the sensor output value at full scale and compares it with the standard value to calculate the "gain error." Subsequent data is then proportionally corrected using a software algorithm to eliminate range deviation. Combined with a piecewise linear correction algorithm, the sensor output curve is fitted at multiple points to ensure a uniform error distribution across the entire range.

[0054] Calibration curve fitting: used to quantify calibration accuracy through highly correlated calibration curves, ensuring that the output of the data acquisition system is highly consistent with the actual physical quantity.

[0055] Specifically, the system selects multiple calibration points (such as 5 points or 10 points) between zero and full scale to collect data corresponding to the sensor output and the standard value.

[0056] Linear regression analysis using the least squares method was employed to generate the calibration curve equation. The coefficient of determination R² was calculated; when R² ≥ 0.999, it indicates that the calibration curve fits the actual data extremely well, and the error is negligible. A 32-bit floating-point processor was used for high-precision calculations to avoid truncation errors caused by integer arithmetic.

[0057] Before each test, the system automatically triggers the calibration process without manual intervention. Calibration parameters are stored in non-volatile memory and are retained even after power failure, ensuring long-term stability.

[0058] Optionally, after the current interruptor is disconnected, there is a power-off potential extraction window, which lasts for 0.1-0.3 seconds. The data within the window needs to be denoised by wavelet transform to improve the signal-to-noise ratio to ≥30dB.

[0059] Potential data is extracted within a 0.1-0.3 second timeframe following the current interruption to avoid polarization recovery interference and capture the true power-off potential. Wavelet transform is applied to the data within the window to suppress noise, increasing the signal-to-noise ratio (SNR) to ≥30dB and ensuring data reliability.

[0060] When the cathodic protection current is interrupted, the IR drop in the soil medium decays over time, but the polarization effect on the pipe's metal surface may cause potential rebound. If the potential is extracted at any point in time after the power outage, polarization interference may be included, failing to reflect the true protection effect. Therefore, data should be extracted within a short window where the IR drop has sufficiently decayed and polarization recovery has not significantly affected the potential.

[0061] A lower limit of 0.1 seconds is used to ensure that the IR drop has decayed to more than 90% of its original value, avoiding residual IR drop error. An upper limit of 0.3 seconds is used to prevent potential rebound caused by polarization recovery effect, ensuring that the data is close to the actual power-off potential. Through laboratory simulation of power-off response curves in different soil environments with resistivity of 100-10,000 Ω·m, 0.1-0.3 seconds was determined to be the optimal window.

[0062] After the synchronous current interruptor triggers the power-off signal, the data acquisition system starts a high-precision timer (resolution ≤1ms). It only stores potential data within 0.1-0.3 seconds, discarding data outside the window to avoid interference.

[0063] It should be noted that power-off potential signals are usually accompanied by various types of noise, including: power frequency interference introduced by coupling from the power system; inherent noise in the sensor circuit; and environmental electromagnetic interference such as lightning and radio signals. Noise may mask the true potential signal, requiring denoising processing to improve the signal-to-noise ratio.

[0064] In wavelet transform denoising, wavelet transform is a time-frequency analysis method that decomposes the signal into different frequency components through multi-scale decomposition, and then selectively filters out noise. The specific steps are as follows: A suitable wavelet basis is selected to perform N-level wavelet decomposition on the potential signal, obtaining the low-frequency approximate component (A) and high-frequency detail components (D1, D2, ..., DN). Soft or hard thresholding is applied to the high-frequency components to preserve significant features (such as potential abrupt changes) and suppress minor fluctuations.

[0065] Threshold selection method: general threshold or Stein unbiased risk estimation. Low-frequency components reflect signal trends, while high-frequency components contain noise and abrupt changes. Wavelet reconstruction is performed on the processed low-frequency components and the thresholded high-frequency components to obtain the denoised potential signal. The original signal SNR may be as low as 10-15 dB. After wavelet transform denoising, the SNR is increased to ≥30 dB, meaning the signal power is 1000 times higher than the noise power.

[0066] Optionally, the test data is also transmitted in real time to the pipeline integrity management system with encryption. The management system automatically generates an IR drop-time trend curve and a loop grounding resistance-temperature scatter plot, and sets three warning thresholds: when the IR drop is greater than 100mV or the loop grounding resistance is greater than 10Ω for three consecutive times, a red warning is triggered and pushed to the mobile terminal of the maintenance personnel.

[0067] Test data (such as power failure potential, IR drop, loop grounding resistance, etc.) are transmitted to the Pipeline Integrity Management System (PIMS) via an encrypted protocol to ensure data security. The system automatically generates IR drop-time trend curves and loop grounding resistance-temperature scatter plots to reveal the dynamic changes in the data. A notification is triggered when three consecutive IR drop values ​​>100mV or loop grounding resistance values ​​>10Ω are detected, pushing the notification to the maintenance personnel's mobile terminal.

[0068] It should be noted that the three levels of warning are yellow, orange, and red, respectively.

[0069] The cathodic protection tester collects parameters such as potential, current, and grounding resistance in real time and generates raw data packets at a preset frequency. The data packets include a timestamp, device ID, measured value, and checksum to ensure data integrity and traceability.

[0070] Data packets are encrypted using the AES-256 symmetric encryption algorithm, with the key dynamically generated and periodically updated by the PIMS system. The transport protocol chosen is MQTT over TLS, with further encryption of the communication channel via an SSL / TLS layer to prevent man-in-the-middle attacks. Data is transmitted via a dedicated VPN or 4G / 5G private network to avoid exposure to the public internet. An edge computing gateway performs initial data cleaning and compression to reduce bandwidth consumption. Upon receiving the encrypted data, the PIMS server decrypts it using a pre-set key and verifies the checksum to ensure the data has not been tampered with. The decrypted data is stored in a time-series database for subsequent analysis.

[0071] The IR drop-time trend curve is used to monitor changes in IR drop over time and identify performance degradation or abnormal events in the cathodic protection system. The system plots hourly / daily average curves with time on the x-axis and IR drop value on the y-axis. A moving average algorithm is used to smooth short-term fluctuations and highlight long-term trends. A threshold line is overlaid to visually display instances of exceeding limits.

[0072] The loop grounding resistance-temperature scatter plot is used to analyze the correlation between grounding resistance and ambient temperature, and to diagnose grounding system faults. The system synchronously collects grounding resistance values ​​and temperature sensor data, and generates a scatter plot after time matching. Linear regression analysis is used to fit the resistance-temperature relationship curve, and the correlation coefficient is calculated. Outliers are marked to trigger further manual verification.

[0073] Optionally, the fixed test piece is made of titanium alloy substrate with a composite nano-cerium oxide coating, the coating thickness is 50±5μm, and the corrosion resistance current density is ≤0.1μA / cm².

[0074] Using titanium alloy as the substrate, a nano-cerium oxide (CeO2) coating with a thickness of 50±5μm is applied to the surface; its corrosion resistance current density is ≤0.1μA / cm². At room temperature, the titanium alloy reacts with oxygen to rapidly form a dense TiO2 oxide film on its surface. This film has a stable crystal structure and effectively blocks the penetration of corrosive media such as Cl⁻ and H⁺. If the passivation film is partially damaged, the high chemical reactivity of titanium will cause surrounding titanium atoms to recombine with oxygen, repairing the oxide film and maintaining long-term protective effects.

[0075] Nano-sized cerium oxide particles, typically <100 nm in diameter, are uniformly dispersed in the coating, inhibiting grain growth and forming a fine-grained or nanocrystalline structure. This fine-grained structure has a higher grain boundary density, which hinders the diffusion path of corrosive media and improves corrosion resistance. CeO2, as a rare earth oxide, has strong oxidizing properties and preferentially adsorbs at surface defects in the coating, forming stable Ce-O bonds. This chemisorption fills surface defects and reduces contact points with corrosive media. Ce³⁺ / Ce 4 The redox cycle of ⁺ can consume oxidizing substances in the corrosive medium, reduce the local corrosion potential, and inhibit electrochemical corrosion reactions. Nano-cerium oxide and the TiO2 passivation film of the titanium alloy substrate form a "double-layer protection": the outer CeO2 coating blocks the macroscopic corrosive medium, and the inner TiO2 passivation film inhibits microscopic electrochemical corrosion, achieving multi-scale protection.

[0076] Optionally, it also includes safety interlock protection during the testing process: when the circuit current is greater than 50A or the equipment surface temperature is greater than 85°C, the power supply is automatically cut off and an audible and visual alarm is activated, and the alarm signal is simultaneously pushed to the remote monitoring center.

[0077] By monitoring the circuit current and equipment surface temperature in real time, the system automatically performs protection actions when triggered by any of the following conditions: overcurrent protection when the circuit current is >50A; overheat protection when the equipment surface temperature is >85℃.

[0078] Its protective actions are: immediately cut off the power supply; activate the audible and visual alarm; and simultaneously push the alarm signal to the remote monitoring center.

[0079] Specifically, current detection uses Hall effect sensors or shunt resistors to measure the loop current in real time. Hall effect sensors, based on the principle of electromagnetic induction, convert the current signal into a voltage signal, which is then converted into a digital signal by an ADC for processing by the control system. Temperature monitoring uses thermocouples or PT100 resistance thermometers attached to key locations on the equipment surface. Thermocouples convert temperature differences into millivolt-level voltage signals through the Seebeck effect; PT100 measures resistance based on its resistance changing with temperature. The control system compares the acquired current / temperature signals with preset thresholds in real time. If either parameter exceeds the limit, protection logic is immediately triggered.

[0080] Optionally, the test cycle can also be set as follows: routine protection potential test is conducted once per quarter, and an additional test is conducted within 48 hours after extreme weather; fixed test pieces are excavated and inspected and their weight loss is analyzed every two years, and a test piece replacement warning is triggered when the weight loss rate is >5%.

[0081] The testing cycle is set for the corrosion protection system of metal structures, achieving dynamic management of corrosion risks through dual control of time and environmental dimensions. Specifically, this includes: Protection potential testing cycle: routine testing is conducted quarterly; intensive testing following extreme weather events is completed within 48 hours.

[0082] Fixed test specimen testing cycle: excavation inspection and weight loss analysis, once every two years; a test specimen replacement warning is triggered when the weight loss rate warning threshold is >5%.

[0083] The cathodic protection potential of a metal structure reflects whether the cathodic protection system effectively inhibits corrosion.

[0084] During routine testing, the corrosion rate exhibits a non-linear relationship with potential fluctuations. Quarterly testing can capture the impact of seasonal environmental changes on the potential, preventing long-term deviations from the protection potential that could lead to accelerated corrosion. The specific procedure is as follows: use a high-impedance voltmeter to measure the potential difference between the metal structure and the reference electrode; record the data and generate a potential-time curve to analyze the trend; if the potential deviates from the standard range for two consecutive tests, a detailed investigation is initiated.

[0085] Post-extreme weather intensified testing: Triggered by environmental events such as torrential rain, floods, earthquakes, and extreme temperature differences that may damage the cathodic protection system. Torrential rain can cause a sudden drop in soil resistivity, altering current distribution and leading to insufficient potential in localized areas; floods may submerge the anode bed, causing interruption of protective current; earthquakes may damage cables or the location of reference electrodes. The procedure for post-extreme weather intensified testing is as follows: complete full-line potential testing within 48 hours of the event; focus on inspecting the affected areas; if potential anomalies are found, immediately repair the cathodic protection system.

[0086] The test on the fixed specimens is a quantitative assessment of the corrosion rate based on weight loss analysis; the corrosion weight loss rate is calculated by periodically excavating and weighing the fixed specimens buried near the oil pipeline structure.

[0087] The corrosion weight loss rate Wr is a direct indicator of the metal corrosion rate, and its calculation formula is:

[0088]

[0089] Where W0 is the initial mass of the test piece (g), W1 is the mass after corrosion (g), A is the exposed area of ​​the test piece (m²), and t is the exposure time (years).

[0090] The operational procedure is as follows: excavate the test specimen and remove corrosion products; weigh it using a high-precision balance; calculate the corrosion weight loss rate and compare it with historical data to generate a corrosion weight loss rate trend chart. The system automatically issues a warning when the corrosion weight loss rate of the test specimen exceeds 5% of its initial mass. The 5% threshold is based on engineering experience and material durability design: for example, if the initial mass of the test specimen is 100g, a weight loss of 5g may be close to the critical point of material safety reserves; after the warning, the remaining lifespan needs to be assessed to avoid structural failure due to corrosion.

[0091] Specifically, the system generates an early warning report; verifies the corrosion morphology on-site; and if replacement is confirmed, develops a test piece replacement plan and updates the corrosion database.

[0092] Quarterly testing can promptly detect cathodic protection system failures, preventing accelerated corrosion of metal structures due to insufficient protection. Intensive testing after extreme weather events allows for rapid response to sudden environmental changes, preventing unexpected corrosion incidents. Quantitative assessment of corrosion weight loss rate evaluates the degree of corrosion, and a 5% threshold warning can identify high-risk areas in advance. For example, in oil and gas pipelines, a corrosion weight loss rate >5% may correspond to a remaining pipeline wall thickness less than 70% of the design value, requiring immediate reinforcement measures.

[0093] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A test method for a fixed test piece assembly for cathodic protection of aviation kerosene pipelines, characterized in that, Includes the following steps: S1: The test piece is made of titanium alloy substrate with a composite nano-cerium oxide coating on the surface. The coating thickness is 50±5μm. The corrosion resistance current density is ≤0.1μA / cm². The synchronous current interruptor is connected in series with the test piece and the pipeline circuit. The on-off cycle is set to (12±3) seconds on-off (3±1) seconds off. The interruption current is ≥30A. The temperature resistance is -40℃ to +85℃. The synchronization method adopts internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization. The synchronization accuracy is ≤1μs. S2: The high-speed data acquisition unit synchronously acquires the potential signal of the test piece relative to the long-lasting copper sulfate reference electrode or the Ag / AgCl reference electrode for soil, the current signal measured by the precision sampling resistor, and the interrupt synchronization signal, with a synchronization error between channels ≤0.5μs; S3: Based on the synchronization signal, lock the stable value before the interruption as E1, and extract the stable plateau value after Fourier transform filtering within the window of 0.1 seconds to 0.3 seconds after the interruption as E2, with a filtering frequency range of 50Hz±1Hz; S4: Calculate the IR drop of the test piece using the formula IR drop = E1 - E2, with a calculation error ≤ ±2%; S5: Calculate the loop grounding resistance by combining IR drop and current value I. Loop grounding resistance = |IR drop| / I. Use the four-electrode method to measure soil resistivity ρ to help verify the rationality of the loop grounding resistance. For every 10℃ increase in temperature, the correction factor for soil resistivity ρ decreases by 0.8%.

2. The test method for the fixed test piece assembly of cathodic protection for aviation kerosene pipelines according to claim 1, characterized in that, It also includes a synchronous current interruptor with a dynamic on / off cycle adjustment module, which is used to adjust the on / off cycle range online to 5-20 seconds on and 1-5 seconds off, with an adjustment step accuracy of 0.1 seconds, to adapt to the IR drop test requirements of different soil environments.

3. The test method for the fixed test piece assembly for cathodic protection of aviation kerosene pipelines according to claim 1, characterized in that, The long-lasting copper sulfate reference electrode adopts a double-layer sealed structure: the outer layer is a polytetrafluoroethylene sleeve resistant to aviation kerosene corrosion, the inner layer is filled with saturated copper sulfate solution, and the electrode head is embedded with a platinum wire auxiliary electrode to ensure potential stability ≤±1mV at a low temperature of -40℃.

4. The testing method for the fixed test piece assembly of cathodic protection for aviation kerosene pipelines according to claim 1, characterized in that, It also includes a data acquisition system configuration intelligent calibration module: automatically performs zero-point calibration and full-scale calibration before each test, and generates a calibration curve, wherein the goodness of fit of the calibration curve satisfies the coefficient of determination R²≥0.

999.

5. The testing method for the fixed test piece assembly for cathodic protection of aviation kerosene pipelines according to claim 1, characterized in that, After the current interruptor is disconnected, there is a power-off potential extraction window, which is 0.1-0.3 seconds. The data within the window is processed by wavelet transform for noise reduction, and the signal-to-noise ratio is improved to ≥30dB.

6. The test method for the fixed test piece assembly for cathodic protection of aviation kerosene pipelines according to claim 5, characterized in that, It also includes real-time encrypted transmission of test data to the pipeline integrity management system, which automatically generates IR drop-time trend curves, loop grounding resistance-temperature scatter plots, and sets three-level early warning thresholds; A red alert is triggered when the IR drop exceeds 100mV three times consecutively or the loop grounding resistance exceeds 10Ω, and the alert is sent to the mobile terminal of the maintenance personnel.

7. The test method for the fixed test piece assembly of cathodic protection for aviation kerosene pipelines according to claim 1, characterized in that, It also includes safety interlock protection during the testing process: when the circuit current is greater than 50A or the equipment surface temperature is greater than 85℃, the power supply is automatically cut off and an audible and visual alarm is activated, and the alarm signal is simultaneously pushed to the remote monitoring center.

8. The test method for the fixed test piece assembly for cathodic protection of aviation kerosene pipelines according to claim 1, characterized in that, It also includes the setting of the test cycle, which is as follows: the routine protection potential test is conducted once every quarter, and the test is intensified once within 48 hours after extreme weather; the fixed test piece is excavated and inspected and weight loss analysis is performed every two years, and a test piece replacement warning is triggered when the weight loss rate is >5%.

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