Method for testing fixed test piece assembly for cathode protection of aviation kerosene oil delivery pipe

Abstract

The invention discloses an aviation kerosene oil conveying pipe cathode protection fixed test piece assembly testing method, and relates to the field of fixed test piece electrical variable testing. The method comprises the steps that S1, a synchronous current interrupter is connected into a test piece and a pipeline loop in series, and an on-off period is set; s2, a high-speed data collector synchronously collects a potential signal of the test piece relative to the long-acting copper sulfate reference electrode or the Ag / AgCl reference electrode for soil, a current signal measured by a precision sampling resistor and an interrupter synchronizing signal, and the synchronization error between channels is smaller than or equal to 0.5 microsecond; s3, locking a stable value before interruption as E1 based on the synchronization signal, and extracting a stable platform value after interruption as E2; s4, calculating an IR drop value of the test piece; and S5, calculating the loop grounding resistance, and measuring the soil resistivity rho to verify the loop grounding resistance. According to the method, the problem of measurement distortion caused by signal asynchronization and noise interference is solved by combining the signal synchronization, synchronous interruption and multi-channel synchronous acquisition with Fourier / wavelet transform filtering processing and accurate measurement of IR drop, and an accurate data basis is provided for cathode protection state evaluation.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of testing the electric variable of a fixed test piece, and in particular to a method for testing a fixed test piece assembly for cathodic protection of an aviation oil pipeline. BACKGROUND

[0002] The aviation oil pipeline is a key infrastructure of the airport apron refueling system, and its safe operation is crucial to air transportation. The steel aviation oil pipeline is prone to corrosion in the buried environment, and at present, the pipeline is mainly protected by combining the anticorrosion layer method and cathodic protection. Cathodic protection converts the entire pipeline into a cathode state by homogenizing the potential of each point on the metal surface, thereby effectively inhibiting corrosion.

[0003] In the cathodic protection system, when the current flows from the auxiliary anode to the protected pipeline through the medium such as soil, a certain voltage drop, namely IR drop, is generated in the medium. The existence of the IR drop interferes with the accurate measurement of the true protection potential of the pipeline, and further affects the evaluation of the cathodic protection effect. When measuring the IR drop, there is often a lack of precise synchronous control and signal processing means, and it is difficult to accurately capture the change of the potential at the moment of current interruption, resulting in a large error in the measurement result, thereby affecting the evaluation of the corrosion state of the pipeline. SUMMARY

[0004] In order to solve the technical problems existing in the prior art, the application provides a method for testing a fixed test piece assembly for cathodic protection of an aviation oil pipeline.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the application is as follows: a method for testing a fixed test piece assembly for cathodic protection of an aviation oil pipeline, characterized in that the method comprises the following steps: S1: synchronously connecting the test piece and the pipeline loop through a current interrupter, setting the on-off period to (12±3) seconds-on (3±1) seconds, interrupting the current of greater than or equal to 30 A, and resisting the temperature of-40 DEG C to +85 DEG C; the synchronous mode adopts internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization, and the synchronous precision is less than or equal to 1 mu s; S2: a high-speed data acquisition device synchronously acquires the potential signal of the test piece relative to a long-acting copper sulfate reference electrode or a soil Ag / AgCl reference electrode, the current signal measured by a precision sampling resistor, and the synchronous signal of the interrupter, and the synchronization error between channels is less than or equal to 0.5 mu s; S3: based on the synchronous signal, the stable value before interruption is locked as E1, the stable platform value in the 0.1-0.3 second window after interruption is extracted as E2 after Fourier transform filtering processing, and the filtering frequency range is 50 Hz±1 Hz; S4: the IR drop value of the test piece is calculated by the formula IR drop=E1-E2, and the calculation error is less than or equal to ±2%; S5: Calculate the loop grounding resistance = |IR drop| / I according to the IR drop and the current value I, and use the quadrupole method to measure the soil resistivity ρ to assist in verifying the rationality of the loop grounding resistance, and the correction coefficient of the ρ value is reduced by 0.8% for every 10℃ increase in temperature.

[0006] Optionally, it also includes a dynamic on-off period adjustment module for synchronous current interrupter configuration, which is used to adjust the on-off period range to 5-20 seconds on and 1-5 seconds off, and the adjustment step precision is 0.1 second, which is suitable for different soil environment IR drop test requirements.

[0007] Optionally, the long-acting copper sulfate reference electrode adopts a double-layer sealing structure: the outer layer is a polytetrafluoroethylene sleeve resistant to coal 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 that the potential stability is ≤±1mV in a low temperature environment of-40℃.

[0008] Optionally, it also includes an intelligent calibration module configured by a data acquisition system: automatic zero point calibration and full scale calibration before each test, generating a calibration curve, and the goodness of fit of the calibration curve meets the determination coefficient R²≥0.999.

[0009] Optionally, the off potential extraction window is 0.1-0.3 seconds after the current interrupter is turned off, and the data in the window needs to be processed by wavelet transform for noise reduction, and the signal-to-noise ratio is improved to ≥30dB.

[0010] Optionally, it also includes real-time encryption transmission of test data to a pipeline integrity management system, and the management system automatically generates an IR drop-time trend curve and a loop grounding resistance-temperature scatter plot, and sets three-level early warning thresholds: when IR drop is >100mV or loop grounding resistance is >10Ω for three consecutive times, a red early warning is triggered and pushed to the mobile terminal of the operation and maintenance personnel.

[0011] Optionally, the fixed test piece adopts titanium alloy substrate surface composite nano cerium oxide coating with a coating thickness of 50±5μm and a corrosion current density of ≤0.1μA / cm².

[0012] Optionally, it also includes a safety interlock protection configured during the test process: when the loop current is >50A or the equipment surface temperature is >85℃, the power is automatically cut off and an audible and visual alarm is started, and the alarm signal is simultaneously pushed to the remote monitoring center.

[0013] Optionally, it also includes the setting of the test period: the regular protection potential test is carried out once every quarter, and the intensive test is carried out once within 48 hours after extreme weather; the fixed test piece is excavated and checked every two years for weight loss analysis, and when the weight loss rate is >5%, the test piece replacement early warning is triggered.

[0014] Beneficial effects: 1. Through high-precision synchronous interruption and multi-channel synchronous acquisition, combined with Fourier / wavelet transform filtering processing, the precise measurement of IR drop is realized, and the measurement distortion problem caused by signal asynchronization and noise interference in traditional methods is completely solved, providing more accurate data basis for cathodic protection state evaluation.

[0015] 2. The dynamically adjustable on-off period and intelligent calibration module adapt to different soil environments; the titanium alloy nano-coated test piece and the double-layer sealed reference electrode ensure the data reliability in extreme environments; the safety interlocking mechanism ensures the operation safety.

[0016] 3. Through encrypted data real-time uploading and multi-dimensional analysis, a three-level early warning mechanism and periodic detection standard are established, realizing the leap from single-point measurement to intelligent management throughout the life cycle, and significantly improving the predictability and reliability of aviation coal pipeline corrosion protection. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The flowchart of the test method of the embodiments of the present application. DETAILED DESCRIPTION

[0019] In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art based on the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0021] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0022] Embodiment: please refer to Figure 1The embodiment provides a cathodic protection fixed test piece assembly test method for aviation oil pipelines, and is characterized by comprising the following steps: S1: synchronously connect the test piece and the pipeline circuit through the current interrupter, set the on-off period to on (12±3) seconds-off (3±1) seconds, the interrupt current is greater than or equal to 30 A, the temperature resistance is-40 DEG C to +85 DEG C, the synchronization mode adopts internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization, and the synchronization accuracy is less than or equal to 1 mu s; the current interrupter is connected to the test piece and the pipeline circuit through a precision control circuit, and the periodical on-off control time of the current interrupter is on 12±3 seconds / off 3±1 seconds. The internal crystal oscillator or the GPS / Bluetooth dual-mode synchronization ensures that the interrupt action and the data acquisition are strictly synchronized, the accuracy is less than or equal to 1 mu s, time sequence mismatch is avoided, the temperature resistance of-40 DEG C to +85 DEG C is suitable for the extreme environment of the aviation pipeline, and the interrupt current greater than or equal to 30 A meets the demand of high-power cathodic protection. The precise period control eliminates the polarization effect interference in the IR drop measurement, ensures that the real polarization potential is captured at the moment of power-off, the dual-mode synchronization technology improves the anti-interference ability, data drift is avoided when the GPS signal is lost, the wide-temperature weather resistance guarantees the stable operation of the equipment in the high-cold / high-temperature environment of the aviation pipeline, and the service life of the equipment is prolonged.

[0023] S2: the high-speed data acquisition device synchronously collects the potential signal of the test piece relative to the long-acting copper sulfate reference electrode or the soil Ag / AgCl reference electrode, the current signal measured by the precision sampling resistor and the interrupter synchronization signal, and the synchronization error between channels is less than or equal to 0.5 mu s; the high-speed data acquisition device synchronously collects three signals at a sampling rate greater than or equal to 1 kHz and a resolution greater than or equal to 16 bits: the potential signal of the test piece relative to the reference electrode, the current signal of the precision sampling resistor and the interrupter synchronization signal, the synchronization error between channels is less than or equal to 0.5 mu s, and the time alignment of the potential, current and synchronization signal is ensured. The high sampling rate captures the millisecond-level potential fluctuation, signal distortion caused by low-speed sampling is avoided, multi-channel synchronization eliminates time sequence error, and the accurate correspondence between the stable value E1 before interruption and the filtered value E2 after interruption is ensured. The precision sampling resistor realizes high-precision conversion (error less than or equal to 0.1%) of the current signal, and provides a reliable data source for IR drop calculation.

[0024] S3: based on the synchronization signal, the stable value before interruption is locked as E1, the stable platform value in the 0.1-second to 0.3-second window after interruption is extracted as E2 after Fourier transform filtering processing, and the filtering frequency range is 50 Hz±1 Hz. Lock the stable value before the interruption as E1 based on the synchronization signal, extract the potential signal in the 0.1-0.3 second window after the interruption, and get the stable platform value E2 after Fourier transform filtering processing. The filtering eliminates power frequency interference and high frequency noise, and retains the true polarization potential characteristics. Fourier transform filtering improves the signal-to-noise ratio and ensures that E2 is stable in the 0.1-0.3 second window; strictly follow the time window set by NACE SP0169 standard to avoid the interference of depolarization process on E2; the filtering frequency band is targeted to suppress power frequency noise and improve the IR drop calculation accuracy to ≤±2%.

[0025] S4: Calculate the IR drop value of the test piece by the formula IR drop=E1-E2, and the calculation error is ≤±2%. The error boundary is realized by high-precision data acquisition, strict synchronization control and filtering algorithm. High-precision IR drop quantifies the ohmic loss of the cathodic protection circuit, and provides direct basis for evaluating the distribution efficiency of the protection current; low error calculation ensures the reliability of IR drop value, avoiding the misjudgment of cathodic protection efficiency caused by measurement error.

[0026] S5: Calculate the loop grounding resistance = |IR drop| / I combining IR drop and current value I, and use the quadrupole method to measure soil resistivity p to assist verification of the rationality of loop grounding resistance. The p value correction coefficient decreases by 0.8% for every 10℃ increase in temperature. Combine IR drop and current value I to calculate loop grounding resistance R_loop=|IR drop| / I by Ohm's law. Use the quadrupole method to measure soil resistivity p, and adjust the p value correction coefficient by 0.8% for every 10℃ increase in temperature to dynamically verify the rationality of loop grounding resistance. Loop grounding resistance quantifies the total resistance of the circuit, guiding the design and optimization of the cathodic protection system; the quadrupole method eliminates electrode polarization error and improves p measurement accuracy; the temperature compensation mechanism corrects the change of soil resistivity, ensuring the calculation accuracy of loop grounding resistance in a wide temperature environment; the calculation of loop grounding resistance and IR drop correlation analysis can be used to deduce the pipeline corrosion rate, supporting the whole life cycle corrosion management.

[0027] Synchronization interruption, high-precision acquisition, and filtering algorithm cooperate to compress the IR drop error to ±2%, which is much better than the traditional method; dual-mode synchronization, wide temperature and weather resistance design, and sealed reference electrode adapt to the extreme working conditions of aviation coal pipeline; real-time encrypted transmission of data, generation of trend curve, and three-level early warning realize dynamic monitoring of cathodic protection efficiency; safety interlocking protection ensures the safety and controllability of the test process.

[0028] Optionally, the synchronous current interrupter is configured with a dynamic on-off period adjustment module, which can adjust the on-off period online to 5-20 seconds on and 1-5 seconds off, with an adjustment step accuracy of 0.1 second, to adapt to the IR drop test requirements of different soil environments.

[0029] The dynamic on-off period adjustment module realizes online adjustment of the on-off period through hardware circuit and software algorithm cooperation, and its core logic is as follows: The user inputs the target on-off period through the control interface, such as on 15 seconds / off 3 seconds, and the system converts the parameters into digital signals and transmits them to the central processor. The central processor dynamically adjusts the on and off timing of the electronic switch according to the input parameters.

[0030] For example, when the on time needs to be extended, the central processor delays the triggering of the off signal, allowing the current to continue flowing for a set period of time; the off phase is achieved by quickly cutting off the switch to interrupt the current.

[0031] The system has a built-in current sensor that monitors the actual on-off state in real time. If a deviation is detected, the CPU will immediately correct the switch timing to ensure that the period accuracy is within ±0.1 seconds.

[0032] Factors such as soil resistivity and reference electrode distance can cause voltage drop during the transmission of the cathodic protection current, affecting the accuracy of the off potential measurement. For example, the IR drop decay rate differs significantly in different soil environments, such as high-resistivity sandy soil and low-resistivity clay.

[0033] Dynamic adjustment: In high-resistivity soil, extending the on time (e.g., on for 20 seconds) allows the soil medium to fully polarize, reducing the residual IR drop at the moment of turning off; shortening the off time (e.g., off for 1 second) allows the real off potential to be quickly captured, avoiding errors caused by polarization recovery.

[0034] In low-resistivity soil, shortening the on time (e.g., on for 5 seconds) prevents over-polarization, and extending the off time (e.g., off for 5 seconds) allows the IR drop to fully decay, improving measurement stability.

[0035] Optionally, the long-acting copper sulfate reference electrode adopts a double-sealed structure: the outer layer is a polytetrafluoroethylene sleeve resistant to coal 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 that the potential stability is ≤±1 mV in a low-temperature environment of -40°C.

[0036] By adjusting the on-off period, the module can optimize the measurement timing according to the IR drop decay law of different soil environments. For example, in sandy soil, the "long on and short off" mode is used, and in clay, the "short on and long off" mode is used, making the off potential measurement value closer to the true value, with an error rate of less than 5%. Precise on-off control can avoid the polarization effect of the soil medium caused by long-term on, prevent the potential from rebounding after turning off, and ensure the reliability of the measurement data.

[0037] Optionally, it also includes an intelligent calibration module for the data acquisition system: automatic zero-point calibration and full-scale calibration before each test, generating a calibration curve, and the goodness of fit of the calibration curve meets the coefficient of determination R²≥0.999.

[0038] In this embodiment, the intelligent calibration module realizes high-precision calibration of the data acquisition system through an automated process. The core logic is divided into two stages: zero-point calibration and full-scale calibration, and relies on a high-fitting-degree calibration curve to ensure data accuracy. The specific process is as follows: 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.

[0039] Specifically, the system disconnects all external signal inputs and places the sensor in an unloaded state. The acquisition module reads the output value of the sensor at this time and records it as the "zero-point offset". The original data collected subsequently is subtracted from this offset by a software algorithm to complete the zero-point correction.

[0040] A high-precision digital-to-analog converter (ADC) and a low-noise amplifier circuit are used to ensure that the resolution of the zero-point signal acquisition reaches the microvolt level (μV), avoiding the neglect of small offsets.

[0041] Full-scale calibration: used to correct the non-linear error of the sensor within the maximum input range and ensure that the output signal is strictly linearly related to the actual physical quantity.

[0042] Specifically, the system accesses a known standard signal source and adjusts the sensor input to the full-scale value (such as 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". The subsequent data is corrected proportionally by a software algorithm to eliminate the range deviation. Combined with the piecewise linear correction algorithm, the sensor output curve is fitted at multiple points to ensure that the error is uniformly distributed within the full-scale range.

[0043] Calibration curve fitting: used to quantify the calibration accuracy through a high-correlation calibration curve to ensure that the output of the data acquisition system is highly consistent with the actual physical quantity.

[0044] Specifically, the system selects multiple calibration points (such as 5 points, 10 points) between the zero point and the full scale, and collects the corresponding data of the sensor output and the standard value.

[0045] Linear regression analysis is performed using the least squares method to generate a calibration curve equation. The determination coefficient R² is calculated, and when R²≥0.999, it indicates that the fitting degree of the calibration curve to the actual data is extremely high, and the error can be ignored. A 32-bit floating-point operation processor is used for high-precision calculation to avoid truncation errors caused by integer operations.

[0046] Before each test, the system automatically triggers the calibration process without human intervention. The calibration parameters are stored in non-volatile memory and can be retained after power failure, ensuring long-term stability.

[0047] Optionally, the current interrupter is opened to extract the de-energized potential window, the de-energized potential extraction window is 0.1-0.3 seconds, the data in the window needs to be processed by wavelet transform denoising, and the signal-to-noise ratio is improved to ≥30dB.

[0048] The potential data is extracted in the 0.1-0.3 second period after the current interruption, avoiding polarization recovery interference and capturing the true de-energized potential. The wavelet transform algorithm is used for noise suppression on the data in the window, and the signal-to-noise ratio (SNR) is improved to ≥30dB, ensuring data reliability.

[0049] When the cathodic protection current is interrupted, the IR drop in the soil medium will decay over time, but the polarization effect on the pipeline metal surface may cause the potential to rebound. If the potential at any time point after de-energization is extracted, polarization interference may be mixed in, and the true protection effect cannot be reflected. Therefore, data needs to be extracted in a short window where IR drop has fully decayed and polarization recovery has not significantly affected the potential.

[0050] The lower limit of 0.1 seconds is used to ensure that the IR drop has decayed to more than 90% of the original value, avoiding residual IR drop errors. The upper limit of 0.3 seconds is used to prevent polarization recovery effects from causing potential rebound, ensuring that the data is close to the true de-energized potential. Through laboratory simulation of de-energization response curves in different soil environments with resistivity of 100-10,000Ω·m, it is determined that 0.1-0.3 seconds is the optimal window.

[0051] After the current interrupter triggers the de-energization signal, the data acquisition system starts a high-precision timer (resolution ≤1ms). Only potential data within 0.1-0.3 seconds is stored, and data outside the window is discarded to avoid interference.

[0052] It should be noted that the de-energized potential signal is usually accompanied by various noises, including: power system coupling-induced power frequency interference; inherent noise of sensor circuit; environmental electromagnetic interference such as lightning, radio signals, etc. Noise may mask the true potential signal and needs to be processed by denoising to improve the signal-to-noise ratio.

[0053] When wavelet transform denoising is used, wavelet transform is a time-frequency analysis method that decomposes signals into different frequency components through multi-scale decomposition, and then selectively filters out noise. The specific steps are as follows: select an appropriate wavelet basis to perform N-layer wavelet decomposition on the potential signal, obtaining low-frequency approximation components (A) and high-frequency detail components (D1, D2,..., DN). High-frequency components are processed using soft thresholding or hard thresholding to preserve significant features (such as potential mutation points) and suppress small fluctuations.

[0054] Threshold selection method: universal threshold or Stein's unbiased risk estimator. Low-frequency components reflect signal trends, while high-frequency components contain noise and abrupt change information. The processed low-frequency components and thresholded high-frequency components are reconstructed by wavelet to obtain the denoised potential signal. The original signal SNR may be as low as 10-15 dB. After denoising by wavelet transform, the SNR is improved to ≥30 dB, i.e. the signal power is 1000 times higher than the noise power.

[0055] Optionally, it also includes real-time encryption transmission of test data to the pipeline integrity management system, and the management system automatically generates an IR drop-time trend curve, a loop grounding resistance-temperature scatter plot, and sets a three-level early warning threshold: when the IR drop is >100 mV or the loop grounding resistance is >10 Ω for three consecutive times, a red early warning is triggered and pushed to the mobile terminal of the operation and maintenance personnel.

[0056] The test data (such as off-potential, IR drop, loop grounding resistance, etc.) is transmitted to the pipeline integrity management system (PIMS) through an encryption protocol to ensure data security. The system automatically generates an IR drop-time trend curve and a loop grounding resistance-temperature scatter plot to reveal the dynamic change law of the data. When the IR drop is >100 mV or the loop grounding resistance is >10 Ω for three consecutive times, a red early warning is triggered and pushed to the mobile terminal of the operation and maintenance personnel.

[0057] It should be noted that the three-level early warning is yellow / orange / red early warning in turn.

[0058] 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 packet contains a timestamp, device ID, measurement value, and a check code to ensure data integrity and traceability.

[0059] The data packet is encrypted using the AES-256 symmetric encryption algorithm, and the key is dynamically generated by the PIMS system and updated regularly. The transmission protocol is MQTT over TLS, which further encrypts the communication channel through the SSL / TLS layer to prevent man-in-the-middle attacks. Data is transmitted through a dedicated VPN or 4G / 5G private network to avoid exposure risks on the public Internet. The edge computing gateway performs preliminary cleaning and compression of the data to reduce transmission bandwidth usage. After receiving the encrypted data, the PIMS server decrypts it using the pre-set key and verifies the check code to ensure that the data has not been tampered with. The decrypted data is stored in a time series database for subsequent analysis.

[0060] The IR drop-time trend curve is used to monitor the change of IR drop with time and identify performance degradation or abnormal events of the cathodic protection system. The system uses the time axis as the horizontal coordinate and the IR drop value as the vertical coordinate to draw the hourly / daily average value curve. The moving average algorithm is used to smooth short-term fluctuations and highlight long-term trends. The threshold line is superimposed to visually display the over-standard situation.

[0061] Loop ground resistance-temperature scatter plot is used to analyze the correlation between ground resistance and ambient temperature, diagnose the fault of grounding system. The system synchronously collects ground resistance value 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. Abnormal points are marked to trigger further manual verification.

[0062] Optionally, the fixed test piece adopts titanium alloy substrate surface composite nano cerium oxide coating, the coating thickness is 50±5 μm, and the corrosion current density is ≤0.1 μA / cm².

[0063] Titanium alloy is used as the substrate, and a nano cerium oxide (CeO2) coating is compounded on the surface, with a coating thickness of 50±5 μm; and the corrosion current density is ≤0.1 μA / cm². Titanium alloy reacts with oxygen at room temperature to rapidly form a dense TiO2 oxide film on the surface, which has stable crystal structure and can effectively block the penetration of corrosion media such as Cl⁻ and H⁺. If the passive film is locally damaged, the high chemical activity of titanium will promote the recombination of surrounding titanium atoms and oxygen to repair the oxide film and maintain long-term protection effect.

[0064] The nano cerium oxide particles with a particle size usually <100 nm are uniformly dispersed in the coating, which can inhibit grain growth and form fine-grained or nanocrystalline structure. Fine-grained structure has higher grain boundary density, which can hinder the diffusion path of corrosion medium and improve corrosion resistance. As a rare earth oxide, CeO2 has strong oxidizing property and can preferentially adsorb on surface defects to form stable Ce-O bonds. This chemical adsorption can fill surface defects and reduce corrosion medium contact points. The oxidation-reduction cycle of Ce³⁺ / Ce 4 ⁺ can consume oxidizing substances in the corrosion medium, reduce the local corrosion potential, and inhibit the electrochemical corrosion reaction. Nano cerium oxide and TiO2 passivation film of titanium alloy substrate form a "double-layer protection": the outer CeO2 coating blocks macroscopic corrosion medium, and the inner TiO2 passivation film inhibits microelectrochemical corrosion, achieving multi-scale protection.

[0065] Optionally, it also includes test process configuration safety interlock protection: when the loop current > 50A or the equipment surface temperature > 85℃, the power is automatically cut off and the audible and visual alarm is started, and the alarm signal is synchronously pushed to the remote monitoring center.

[0066] By monitoring the loop current and equipment surface temperature in real time, the protection action is automatically executed when any of the following conditions is triggered: overcurrent protection loop current > 50A; overheat protection equipment surface temperature > 85℃.

[0067] The protection action is: immediately cut off the power; start audible and visual alarm; synchronously push the alarm signal to the remote monitoring center.

[0068] Specifically, current detection uses a Hall sensor or a shunt resistor to measure the loop current in real time. The Hall sensor converts the current signal into a voltage signal based on electromagnetic induction principles, and the ADC converts it into a digital signal for the control system to process. Temperature monitoring uses thermocouples or PT100 thermal resistors attached to the surface of the device at key locations. Thermocouples convert temperature differences into millivolt-level voltage signals through the Seebeck effect; PT100 achieves measurement through the characteristic of resistance value changing with temperature. The control system compares the collected current / temperature signals with the preset threshold in real time. If any parameter exceeds the limit, the protection logic is triggered immediately.

[0069] Optionally, it also includes the setting of the test period, which is: regular protection potential test every quarter, and intensive test within 48 hours after extreme weather; fixed test piece excavation inspection and weight loss analysis every two years, and test piece replacement warning triggered when the weight loss rate is >5%.

[0070] The test period setting for the corrosion protection system of the metal structure realizes dynamic management of corrosion risk through dual control of time and environment. Specifically, it includes: protection potential test period: regular test every quarter; intensive test within 48 hours after extreme weather.

[0071] Fixed test piece test period: excavation inspection and weight loss analysis every two years; test piece replacement warning triggered when the weight loss rate warning threshold is >5%.

[0072] The cathodic protection potential of the metal structure reflects whether the cathodic protection system effectively suppresses corrosion.

[0073] During regular testing, there is a nonlinear relationship between corrosion rate and potential fluctuation. Seasonal testing can capture the impact of seasonal environmental changes on potential, avoiding long-term deviation from the protection potential leading to accelerated corrosion. The specific process is: 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, start detailed investigation.

[0074] Intensive test after extreme weather: the triggering conditions are heavy rain, floods, earthquakes, and extreme temperature differences that may damage the cathodic protection system. Heavy rain may cause soil resistivity to drop suddenly, changing the current distribution and making the local area potential insufficient; floods may flood the anode bed, causing the protection current to be interrupted; earthquakes may damage the cable or the reference electrode burial position. The process of intensive test after extreme weather is: complete the full-line potential test within 48 hours after the event; focus on checking the affected areas; if potential anomalies are found, immediately repair the cathodic protection system.

[0075] The test of fixed specimens is based on the weight loss analysis of corrosion rate quantitative evaluation; through the fixed specimens buried near the oil pipeline structure, the corrosion weight loss rate is calculated by periodic excavation and weighing.

[0076] The corrosion weight loss rate Wr is a direct indicator of measuring the corrosion rate of metal, and the calculation formula is: Wherein, W0 is the initial mass of the specimen (g), W1 is the mass after corrosion (g), A is the exposed area of the specimen (m²), and t is the exposure time (years). The operation process is to excavate the specimen and remove the corrosion products; high-precision balance weighing; calculate the corrosion weight loss rate and compare the historical data to generate the corrosion weight loss rate trend chart. When the corrosion weight loss rate of the specimen exceeds 5% of the initial mass, the system automatically warns. The 5% threshold is based on engineering experience and material durability design: for example, if the initial mass of the specimen is 100g, the weight loss of 5g may have approached the critical point of the material safety reserve; after the warning, the remaining life needs to be evaluated to avoid structural failure due to corrosion.

[0077] Specifically, the system generates a warning report; the corrosion morphology is reviewed on site; if it is confirmed that it needs to be replaced, the specimen replacement plan is developed and the corrosion database is updated.

[0078] Quarterly testing can discover the failure of the cathodic protection system in time to avoid accelerated corrosion of the metal structure due to insufficient protection. The encrypted test after extreme weather can quickly respond to environmental mutations to prevent sudden corrosion accidents. The corrosion weight loss rate quantitative evaluation of corrosion degree, 5% threshold warning can identify high-risk areas in advance. For example, in oil and gas pipelines, the corrosion weight loss rate of the specimen > 5% may correspond to the remaining wall thickness of the pipeline being less than 70% of the design value, and reinforcement measures need to be taken immediately.

[0079] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various changes and modifications to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. Testing method for cathodic protection fixed test piece assembly of aviation kerosene oil pipeline, characterized in that: The following steps are involved: S1: A synchronous current interrupter is connected in series between the test piece and the pipeline loop. The on-off cycle is set to (12±3) seconds on and (3±1) seconds off. The interruption current is ≥30A. The temperature resistance is -40℃ to +85℃. The synchronization method uses an internal crystal oscillator or external GPS / Bluetooth dual-mode synchronization. The synchronization accuracy is ≤1μs. S2: The high-speed data acquisition device synchronously collects the potential signal of the test piece relative to the long-acting copper sulfate reference electrode or the soil Ag / AgCl reference electrode, the current signal measured by the precision sampling resistor, and the interrupter synchronization signal. The synchronization error between channels is ≤0.5μs; S3: Based on the synchronization signal, the stable value before the interruption is locked as E1, and the stable platform value processed by Fourier transform filtering within the window of 0.1 second to 0.3 second after the interruption is extracted as E2. The filtering frequency range is 50Hz±1Hz; S4: Calculate the IR drop value of the test piece using the formula IR drop = E1-E2, with a calculation error of ≤±2%; S5: Calculate the loop grounding resistance by combining IR drop and current value I. Loop grounding resistance = |IR drop| / I. Use the four-pole method to measure the soil resistivity ρ to assist in verifying the rationality of the loop grounding resistance. The correction factor of soil resistivity ρ decreases by 0.8% for every 10°C increase in temperature.

2. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 1, characterized in that: It also includes a dynamic on-off cycle adjustment module for the synchronous current interrupter, which is 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 second to adapt to the IR drop test requirements of different soil environments.

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

4. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 1, characterized in that: The data acquisition system is also provided with an intelligent calibration module: zero point calibration and full scale calibration are automatically performed before each test to generate a calibration curve, the goodness of fit of the calibration curve meeting the determination coefficient R² ≥ 0.

999.

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

6. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 5, characterized in that: It also includes real-time encrypted transmission of test data to a pipeline integrity management system, which automatically generates an IR drop-time trend curve, a loop ground resistance-temperature scatter plot, and sets three-level warning thresholds; When the IR drop is greater than 100mV or the loop ground resistance is greater than 10Ω for three consecutive times, a red alert is triggered and pushed to the operation and maintenance personnel's mobile terminal.

7. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 1, characterized in that: The fixed test piece adopts a composite nano-cerium oxide coating on the surface of a titanium alloy substrate, the coating thickness is 50±5μm, and the corrosion resistance current density is ≤0.1μA / cm².

8. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 1, characterized in that: It also includes safety interlock protection configured during the test process: when the loop current is greater than 50A or the surface temperature of the equipment 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.

9. The method for testing the cathodic protection fixed test piece assembly of aviation kerosene oil pipeline according to claim 1, characterized in that: It also includes the setting of the test cycle, which is: routine protection potential testing once a quarter, and intensified testing within 48 hours after extreme weather; fixed test pieces are excavated and inspected and weight loss analyzed every two years, and a test piece replacement warning is triggered when the weight loss rate is greater than 5%.

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