Method and system for predicting corrosion rate of pipeline under dynamic direct current interference

Abstract

The invention discloses a pipeline corrosion rate prediction method and system under dynamic direct current interference, and relates to the technical field of pipeline corrosion, and the method comprises the following steps: S1, obtaining pipe ground potential fluctuation parameter data and a pipeline electrochemical impedance spectrum of a to-be-predicted pipeline; s2, establishing an equivalent circuit model according to the electrochemical impedance spectrum, obtaining parameters of each electrical element, and deducing an impedance value of each electrical element combination and a Faraday current in an electrode system; s3, establishing a pipeline corrosion rate prediction model under dynamic direct current interference according to the equivalent circuit model and the Faraday law to obtain a corrosion rate; s4, comparing the corrosion data with the corrosion data obtained by the experiment to verify the accuracy of the established corrosion rate prediction model; the invention further discloses a corresponding system. According to the method and the system, a new thought can be provided for real-time prediction of the metal corrosion rate under the dynamic direct current interference, and safe and stable operation of the oil and gas pipeline under the dynamic direct current interference is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline corrosion, and in particular to a pipeline corrosion rate prediction method and system under dynamic direct current interference. Background Art

[0002] As the distance between rail transit and oil and gas pipelines continues to shorten, the urban rail transit network and the buried pipeline network present a complex cross-distribution pattern, and the operation process of rail transit will have a series of impacts on the adjacent oil and gas pipelines. In the urban rail transit system dominated by subways, DC current traction is used, powered by the positive contact network, and then returned to the negative pole by the running rail. Since the insulation of the rails is not perfect in this process, some current will leak into the ground. When cracks or damage appear in the pipeline coating, stray current will flow into the damaged part of the pipeline and then flow out from another damaged part of the pipeline. The part that flows out of the metal pipeline is prone to corrosion. This phenomenon is called dynamic DC stray current interference corrosion.

[0003] When the pipeline is subjected to dynamic DC interference, its pipe-to-ground potential will show unstable fluctuation characteristics. This change brings challenges and difficulties to the service performance testing and evaluation of the pipeline. Many people try to analyze the pipe-to-ground potential signal and use the pipe-to-ground potential as a corrosion evaluation parameter to reveal the characteristics of pipeline interference and corrosion. At present, the machine learning method is mainly used to predict the corrosion rate under dynamic DC interference. However, the accuracy of this method depends on sufficient data sample support, otherwise the reliability of the prediction result is poor. If there is a more stable and reliable method to predict the corrosion rate of the pipeline, it will be of great help to pipeline protection and avoidance of potential accidents, and it has an important value in ensuring engineering safety.

[0004] The Chinese patent with publication number CN118152992A relates to a pipeline corrosion prediction method based on machine learning, including the following steps: S1, obtain the environmental parameters and pipeline parameters of the pipeline to obtain an initial data set; S2, cluster the initial data set based on K-means to obtain the majority class and the minority class, and then use SMOTE to perform data enhancement to obtain an enhanced data set; S3, bring the enhanced data set into the SVR model for training, and use RFO to optimize the model. After the training, the optimized SVR-RFO model is obtained; S4, based on the SVR-RFO model and the parameters of the pipeline to be predicted, the corrosion of the pipeline to be tested is predicted. However, the accuracy of its prediction depends on sufficient data sample support, otherwise the reliability of the prediction result is poor. Summary of the invention

[0005] The present invention solves the problem that the existing pipeline corrosion prediction technology relies on sufficient data sample support, and proposes a pipeline corrosion rate prediction method and system under dynamic DC interference, which provides a new idea for the real-time prediction of metal corrosion rate under dynamic DC interference, and ensures the safe and stable operation of oil and gas pipelines under dynamic DC interference.

[0006] In order to achieve the above object, the present invention adopts the following technical solution: a pipeline corrosion rate prediction method under dynamic DC interference, comprising the following steps: S1, obtaining the pipeline ground potential fluctuation parameter data and pipeline electrochemical impedance spectrum of the pipeline to be predicted; S2, establish an equivalent circuit model based on the electrochemical impedance spectroscopy, obtain the parameters of each electrical component, and deduce the impedance value of each electrical component combination and the Faraday current in the electrode system; S3, based on the equivalent circuit model and Faraday's law, a pipeline corrosion rate prediction model under dynamic DC interference is established to obtain the corrosion rate; S4, compared with the corrosion data obtained from the experiment to verify the accuracy of the established corrosion rate prediction model.

[0007] In this technical solution, firstly, the pipeline potential fluctuation parameter data and the electrochemical impedance spectrum of the pipeline are obtained in a corresponding manner, and then an equivalent circuit model is created according to the above electrochemical impedance spectrum to obtain the parameters of each electrical component and derive the Faraday current in the electrode system. Then, a pipeline corrosion rate prediction model is established according to the equivalent circuit model, the corresponding corrosion rate is calculated, and finally the corrosion rate is verified. Based on the relationship between the interference potential fluctuation characteristic parameters and the corrosion system parameters and the corrosion rate, the present invention clarifies the theoretical corrosion rate of the pipeline under dynamic DC interference, provides a new idea for the prediction of metal corrosion rate, and helps to protect the pipeline and avoid potential accidents, and provides data support for ensuring engineering safety.

[0008] The present invention is further configured as follows: the pipeline electrochemical impedance spectrum is obtained by performing an electrochemical impedance test on a test specimen embedded in advance by an electrochemical workstation, and the electrochemical impedance spectrum test is performed to obtain a Nyquist diagram and a Bode diagram.

[0009] In this technical solution, the electrochemical impedance spectrum of the pipeline is obtained to provide a basis for the subsequent establishment of an equivalent circuit model.

[0010] The present invention is further configured as follows: Step S2 comprises: S21, based on the characteristic analysis of Nyquist diagram and Bode diagram in electrochemical impedance spectrum, the corrosion system under dynamic DC interference is obtained, and the equivalent circuit model is used to describe its corrosion process, and the parameters of each electrical component are obtained by fitting; S22, derive the equivalent circuit model to obtain the interference potential change formula, obtain the potential response formula at both ends of the double layer capacitor and the charge transfer resistor, and then obtain the corresponding Faraday current calculation formula of the charge transfer resistor.

[0011] In this technical solution, the equivalent circuit model of R(C(R(CR))) is used to describe the corrosion process, and then the solution resistance R is obtained by fitting. s , rust layer resistance R1, charge transfer resistance R dl , rust layer capacitance C1 and double layer capacitance C dl Parameter values ​​of circuit components.

[0012] The present invention is further configured as follows: Step S3 comprises: S31, the charge accumulated by the anode Faraday current is the corrosion charge, and the calculation formula for the corrosion charge accumulated by the anode current participating in the corrosion process within one cycle time is derived; S32, a corrosion rate prediction model is established based on Faraday's law. The model calculates the Faraday current value through interference potential parameters and corrosion system parameters, integrates the anode Faraday current to obtain the anode dissolved charge, and finally calculates the corrosion rate of the metal.

[0013] In this technical solution, the interference potential of the electrode system is an offset sinusoidal fluctuation curve, so the obtained Faraday current may alternate between positive and negative. Only the anode current whose Faraday current is greater than zero participates in the corrosion process, so the charge accumulated by the anode Faraday current is the corrosion charge.

[0014] The present invention is further configured as follows: Step S4 comprises: Carry out corrosion experiments under different dynamic DC interference conditions, compare the corrosion rate data obtained from the experiment with the corrosion rate calculated in step S3, and determine whether the error between the two is within a preset range.

[0015] In the present technical solution, the results are verified by corrosion experiments. If the error between the corrosion rate data of the corrosion experiment and the corrosion rate of step S3 is within a preset range, it is considered that the established corrosion rate prediction model has good accuracy.

[0016] The present invention is further configured as follows: the pipe-to-ground potential fluctuation parameter data of the pipeline to be predicted is specifically: the test piece buried in the on-site pipeline obtains the power-on and power-off potential changes of the pipeline at each moment through an automatic potential collector, and obtains the pipeline interference potential amplitude, potential frequency, potential offset and interference time through analysis.

[0017] In the present technical solution, the above-mentioned pipe-to-ground potential fluctuation parameter data mainly include pipeline interference potential amplitude, potential frequency, potential offset and interference time. Of course, other fluctuation parameters can also be added, which are not limited here.

[0018] The present invention is further configured as follows: the interference potential change formula is: U AB =U+U m sin(2πft) Among them, U AB is the interference potential loaded on the input terminal AB, U is the offset of the interference potential, U m is the fluctuation amplitude of the interference potential, f is the fluctuation frequency of the interference potential, and t is the interference time.

[0019] The present invention is further configured as follows: the Faraday current calculation formula is: Among them, i f is the Faraday current, R s is the solution resistance, R1 is the rust layer resistance, R dl is the charge transfer resistance, C1 is the rust layer capacitance, C dl is the double layer capacitor.

[0020] In this technical solution, the change of Faraday current is closely related to the periodic change of interference potential.

[0021] The present invention is further configured as follows: the corrosion rate calculation formula is: Among them, ν is the corrosion rate, f is the interference potential frequency, ρ is the material density, and S is the working area.

[0022] In this technical solution, Faraday's law is used to establish a theoretical method for predicting the corrosion rate of pipeline steel under dynamic DC interference. This method calculates the Faraday current from the interference potential parameters and the corrosion system parameters, and obtains the anode dissolved charge by integrating the anode Faraday current. Finally, the corrosion rate of the metal is calculated.

[0023] A pipeline corrosion rate prediction system under dynamic DC interference is applicable to the above pipeline corrosion rate prediction method under dynamic DC interference, comprising: A data acquisition unit, which acquires pipeline-ground potential fluctuation parameter data and pipeline electrochemical impedance spectrum; The equivalent circuit calculation unit establishes an equivalent circuit calculation model based on the electrochemical impedance spectrum to obtain the impedance value of each electronic component in the corrosion system and the Faraday current value at both ends of the charge transfer resistor; The corrosion rate calculation unit establishes a pipeline corrosion rate prediction model under dynamic DC interference based on the equivalent circuit model and Faraday's law to obtain the corrosion rate of the pipeline to be predicted.

[0024] The technical solution mainly includes a data acquisition unit, an equivalent circuit calculation unit and a corrosion rate calculation unit, which respectively execute the above-mentioned processes from step S1 to step S4.

[0025] The present invention can bring the following beneficial effects: The present invention relates to a pipeline corrosion rate prediction method under dynamic DC interference. Based on the relationship between interference potential fluctuation characteristic parameters and corrosion system parameters and corrosion rate, the theoretical corrosion rate of the pipeline under dynamic DC interference is clarified, which provides a new idea for metal corrosion rate prediction, helps pipeline protection and avoidance of potential accidents, and provides data support for ensuring engineering safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a pipeline corrosion rate prediction method under dynamic DC interference in the present application.

[0027] Figure 2 It is a schematic diagram of an equivalent circuit model in a pipeline corrosion rate prediction method under dynamic DC interference in the present application. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Example 1 This embodiment proposes a pipeline corrosion rate prediction method under dynamic DC interference. Figure 1 , which mainly includes the following steps.

[0030] Step S1, firstly obtain the pipeline-to-ground potential fluctuation parameter data and the pipeline electrochemical impedance spectrum of the pipeline to be predicted.

[0031] More specifically, in order to predict the corrosion rate of the pipeline, it is first necessary to collect and acquire the above-mentioned pipeline ground potential fluctuation parameter data and the pipeline electrochemical impedance spectrum.

[0032] The pipeline potential information of the pipeline to be predicted under the interference of dynamic DC stray current is obtained by the automatic potential collector installed at the test point of the pipeline. According to the pipeline-to-ground potential fluctuation curve of the pipeline to be predicted obtained by the automatic potential collector, the pipeline-to-ground potential fluctuation amplitude U is analyzed and obtained. m , its unit is V; the fluctuation frequency is f, its unit is Hz; the potential offset U, its unit is V.

[0033] The electrochemical impedance spectrum of the pipeline is obtained by performing electrochemical impedance testing on the test specimens buried in advance through an electrochemical workstation; during the electrochemical impedance spectrum test, the amplitude of the sinusoidal wave disturbance signal is 10mV, the test frequency is between 100kHz and 10mHz, and the test obtains the Nyquist diagram and Bode diagram.

[0034] After completing the above step S1, proceed to step S2, establish an equivalent circuit model based on the electrochemical impedance spectrum, obtain grid electrical component parameters, and derive the impedance value of each partial electrical component combination and the Faraday current in the electrode system.

[0035] Step S2 mainly includes the following two sub-steps.

[0036] Step S21, performing feature analysis based on the Nyquist diagram and Bode diagram in the electrochemical impedance spectrum in step S1, and then analyzing and obtaining the corrosion system under dynamic DC interference, and using an equivalent circuit model to describe the corrosion process, and then fitting to obtain the parameters of each electrical component.

[0037] Step S22, deriving an equivalent circuit model, obtaining an interference potential change formula, then obtaining a potential response formula across the double layer capacitor and the charge transfer resistor, and then obtaining a Faraday current calculation formula for the corresponding charge transfer resistor.

[0038] More specifically, the electrochemical corrosion system under dynamic DC interference exhibits non-steady-state characteristics that change over time. In order to better describe and analyze this dynamic process, it can be abstracted into a mathematical model that can be calculated or quantitatively characterized. The commonly used method is to construct an equivalent circuit model consistent with the corrosion process, in which each process in the electrode system reaction can be characterized by a specific electrical component, thereby quantitatively describing the electrochemical corrosion process.

[0039] In this embodiment, the electrochemical impedance spectrum obtained by the test in step S1 is analyzed. There are two obvious capacitive reactance arcs in the Nyquist diagram in the entire test frequency range, and two characteristic peaks are also shown in the Bode diagram. This phenomenon reveals that there are two charge transfer processes in the pipeline corrosion process under the dynamic DC stray current interference, and further indicates that there are two time constants in the electrode reaction process. Therefore, it can be judged that pitting corrosion occurs in the test piece under dynamic DC interference and corrosion products are generated on its surface.

[0040] After the pipeline is subjected to dynamic DC interference, the electrochemical impedance spectrum can be divided into two stages. In the first stage (small semicircle), the generation of the corrosion product layer on the electrode surface is reflected; in the second stage (large semicircle), the dynamic evolution of the electrochemical reaction during the corrosion process is revealed. Comprehensive analysis shows that the corrosion system under dynamic DC interference can be described by the equivalent circuit model of R(C(R(CR))). There is a solution resistance R in the corrosion system. s , rust layer resistance R1, charge transfer resistance R dl , rust layer capacitance C1 and double layer capacitance C dl Five equivalent components, connected as follows Figure 2 According to the established equivalent circuit model, the electrochemical impedance test data was brought into the software Zsimpwin for fitting, and the fitting parameters of the five equivalent components in the equivalent circuit were obtained.

[0041] When the dynamic DC interference potential signal is loaded to both ends of the three-electrode system, it is equivalent to loading the interference potential to the input terminal AB of the equivalent circuit model, and corresponding changes will occur in the circuit. When the magnitude of the interference potential or its change formula is obtained, the potential at the double electric layer and charge transfer resistance at the electrode / solution interface (i.e., the output U CD ) is expressed by a mathematical expression related to the characteristic parameters of the interference potential. According to the change of the potential in the function, the change state of the double-layer capacitance and the charge transfer resistance can be evaluated, and then the change trend in the electrode system under dynamic DC interference can be inferred.

[0042] According to the basic principles of electronic circuits, the established equivalent circuit model is deduced, and the results are shown below. First, the change of the interference potential is shown in the following formula. The interference potential at the input end of the equivalent circuit model is the overpotential of the metal specimen, that is, the difference between the polarization potential of the specimen and the self-corrosion potential; U AB =U+U m sin(2πft) In the above formula, U AB is the interference potential loaded on the input terminal AB (V); U is the offset of the interference potential (V); U m is the fluctuation amplitude of the interference potential (V); f is the fluctuation frequency of the interference potential (Hz); t is the interference time (s).

[0043] Calculate the linear equivalent circuit model and get the impedance value of each electrical component combination in the circuit, which can be mathematically expressed by the following formula. dl and C dlThe parallel impedance of Z2 is the series impedance of R1 and Z1, and Z3 is the parallel impedance of Z2 and C1. Finally, the total resistance value Z in the equivalent circuit model is obtained. 总 ;

[0044] From this, the total current in the electrode system can be obtained as shown in the following formula:

[0045] At the same time, a quantitative relationship between the output potential and the input potential at both ends of the required electrical components is established, where the potential at both ends of the double-layer capacitor and the charge transfer resistor can be expressed by the following formula:

[0046] The double layer current i for double layer charging and discharging c , also known as capacitive current or non-Faraday current. When deriving its current change equation, the potential at both ends of the double-layer capacitor is partially differentiated with respect to time to obtain the current change equation through the double-layer capacitor, as shown in the following formula:

[0047] The response voltage formula across the charge transfer resistor is known, so the corresponding Faraday current i can be obtained f , as shown in the following formula, its change is closely related to the periodic change of the interference potential;

[0048] In one embodiment, a dynamic DC interference is applied to X70 steel in a standard soil simulation solution to conduct an indoor simulated corrosion experiment.

[0049] When the interference potential at both ends of the working electrode changes periodically, the response voltage and current at both ends of the electrode / solution double layer interface also change periodically, but the non-Faraday current and potential change are not synchronized. In the positive half-cycle of the interference potential, the electrons in the double layer flow away through the wire, resulting in a gradual decrease in the number of electrons, and the potential gradually becomes positively biased. Since a certain amount of electrons accumulate in the working electrode, the potential gradually increases from zero to the peak value; at the end of the entire positive half-cycle, the number of positive charges reaches the maximum value, and the potential is also the maximum; in the negative half-cycle of the interference potential, external electrons flow into the double layer through the wire, resulting in an increase in the number of electrons and a negative potential bias. Due to the accumulation of positive charges in the positive half-cycle, the potential decreases from the peak value to the minimum value. When the interference potential fluctuates periodically, the electron transfer between the positive half-cycle and the negative half-cycle also occurs periodically. It can be found that the fluctuation mode of the potential and current obtained by theoretical calculation is consistent with the corresponding form actually observed.

[0050] Therefore, under the established equivalent circuit model, the electrochemical parameters of all electrical components can be accurately expressed through mathematical expressions, which means that the potential and current change response formula derived in this application can more accurately describe the change trend of the electrode system.

[0051] Step S3, establishing a pipeline corrosion rate prediction model under dynamic DC interference according to the equivalent circuit model and Faraday's law to obtain the corrosion rate.

[0052] Step S3 mainly includes the following two sub-steps.

[0053] Step S31, the charge accumulated by the anode Faraday current is the corrosion charge, and a calculation formula for the corrosion charge accumulated by the anode current participating in the corrosion process within one cycle is derived; Step S32, a corrosion rate prediction model is established according to Faraday's law. The model calculates the Faraday current value through interference potential parameters and corrosion system parameters, integrates the anode Faraday current to obtain the anode dissolved charge, and finally calculates the corrosion rate of the metal.

[0054] On the basis of step S2, when the characteristic parameters of the applied interference potential and the corrosion system parameters change, the current value at both ends of the charge transfer resistor, i.e., the Faraday current, is calculated using i f Calculated in the form of a mathematical function;

[0055] Since the equation involves the interference potential of the electrode system ΔU+U m sin(2πft) is a sinusoidal wave curve with an offset, so the obtained Faraday current may have alternating positive and negative conditions. In the corrosion system, only the Faraday current i f>0 anode current participates in corrosion, so the charge accumulated by the anode Faraday current is the charge involved in corrosion. In a cycle, not all Faraday currents are greater than zero under the change of interference potential, and different situations need to be discussed to quantitatively describe the charge amount of the corrosion process.

[0056] ΔU+U m When sin(2πft) is less than 0, part of the Faraday current participates in the corrosion process: (1) There exist t1 and t2 (t1<t2<T / 2) such that ΔU+U m sin(2πft)=0. At this time, the calculation formula for the accumulated corrosion charge is as follows: (2) There exist t1 and t2 (T / 2<t1<t2) such that ΔU+U m sin(2πft)=0. At this time, the calculation formula for the accumulated corrosion charge is as follows:

[0057] ΔU+U m When sin(2πft) is always greater than 0, that is, all Faraday currents participate in the corrosion process of the electrode, so the calculation formula for the accumulated corrosion charge in one cycle is as follows:

[0058] In the electrochemical corrosion process, the anode dissolves and causes the metal to corrode. According to Faraday's law, for every 1 farad of electricity passed, the amount of metal dissolved at the anode is 1g. From this, the amount of metal corrosion under dynamic DC interference can be calculated as follows: Where m is the amount of metal corrosion (g); M is the atomic weight of the metal (55.85 g / mol for iron); Q is the charge dissolved at the anode (C); n is the valence of the metal after the chemical reaction (Fe is 2); and F is the Faraday constant (F = 96500 C / mol).

[0059] In summary, the following formula is used to establish the corrosion rate prediction method of pipeline steel under dynamic DC interference under theoretical conditions using Faraday's law. This method calculates the Faraday current from the interference potential parameters and the corrosion system parameters, and obtains the anode dissolved charge by integrating the anode Faraday current. Finally, the corrosion rate of the metal is calculated; Where ν is the corrosion rate (mm·a -1 ), f is the interference potential frequency (Hz), ρ is the material density (g·cm -3); S is the working area (cm 2 ).

[0060] Step S4, compare with the corrosion data obtained from the experiment to verify the accuracy of the corrosion rate prediction model established. Specifically, this step is to compare the corrosion rate data obtained from the corrosion experiment under different dynamic DC interference conditions with the corrosion rate calculated in step S3, and determine whether the error between the two is within a preset range, so as to evaluate the accuracy and reliability of the corrosion rate prediction model established.

[0061] In one embodiment, a dynamic DC interference corrosion experiment is conducted with different interference times (1d, 3d, 5d, 7d), different interference potential amplitudes (0.1V, 1V, 5V, 10V), different interference potential frequencies (1mHz, 5mHz, 20mHz, 100Hz) and different interference potential offsets (-0.4V, -0.2V, 0V, 0.2V, 0.4V). In the experiment, the initial values ​​of the parameters under different interference conditions are: interference time is 1d; interference potential amplitude is 1V; interference potential frequency is 10mHz; interference potential offset is 0V, and the corrosion rate under various working conditions is obtained by this experiment.

[0062] Taking the interference time of 1 day, the interference potential amplitude of 0.1V, the interference potential frequency of 10mHz, and the interference potential offset of 0V as an example, the polarization potential and self-corrosion potential of the metal specimen are tested, and the overpotential of the specimen is calculated. The input potential of the equivalent circuit model is obtained, and the input potential and the fitting parameters of the equivalent circuit model measured experimentally are substituted into the corrosion rate prediction model to compare the actual corrosion rate with the theoretically calculated corrosion rate.

[0063] The comparison results of the actual corrosion rate of the metal test piece under different interference conditions and the corrosion rate calculated by the prediction model are shown in Table 1. In this embodiment, the generally acceptable error is within 20%. It can be seen that the error between the corrosion rate obtained by the experiment and the corrosion rate obtained by the theoretical calculation is acceptable within 15%. Therefore, it is believed that the established corrosion rate prediction model has good prediction accuracy and can be used in the actual corrosion rate prediction of metal pipelines; Table 1 Comparison of corrosion rates under different interference conditions

[0064] This example involves a pipeline corrosion rate prediction method under dynamic DC interference. By obtaining the pipe-to-ground potential fluctuation parameter data and the pipeline electrochemical impedance spectrum of the pipeline to be predicted, an equivalent circuit model is established and the mathematical expression of the Faraday current at both ends of the charge transfer resistor is derived. The pipeline corrosion rate prediction model is established by combining the equivalent circuit diagram and Faraday's law, and the corrosion rate is finally obtained. The accuracy of the predicted corrosion rate is verified. This method provides a new idea for the prediction of metal pipeline corrosion rate and provides data support for pipeline safety protection and management.

[0065] Example 2 On the basis of Example 1, this example further proposes a pipeline corrosion rate prediction system under dynamic DC interference, which mainly includes a data acquisition unit, an equivalent circuit calculation unit and a corrosion rate calculation unit.

[0066] The data acquisition unit mainly performs the following functions: obtaining pipeline ground potential fluctuation parameter data and pipeline electrochemical impedance spectrum.

[0067] In the above data acquisition unit, for the test piece of the buried pipeline on site, the on-off potential change of the pipeline at each moment is obtained by an automatic potential acquisition instrument, and the pipeline interference potential amplitude, potential frequency, potential offset and interference time are analyzed and obtained as an input parameter of the pipeline velocity prediction device, and the input U AB The calculation formula obtains the change of interference potential loaded in the corrosion system. The electrochemical impedance test is performed on the test piece through the electrochemical workstation to obtain the electrochemical impedance spectrum.

[0068] For a more specific process of the data acquisition unit, reference may be made to the process of step S1 in embodiment 1.

[0069] Among them, the main functions of the equivalent circuit calculation unit are: establishing an equivalent circuit calculation model based on the electrochemical impedance spectrum, obtaining the impedance values ​​of each part of the electronic components in the corrosion system and the Faraday current values ​​at both ends of the charge transfer resistor.

[0070] The Nyquist and Bode diagrams of the electrochemical impedance spectrum were analyzed to determine the circuit elements contained in the corrosion system, and an equivalent circuit model was established. The solution resistance R was obtained by fitting analysis based on the equivalent circuit model. s , rust layer resistance R1, charge transfer resistance R dl , rust layer capacitance C1 and double layer capacitance C dl The parameter values ​​of the five circuit components. AB Input the potential response formula across the charge transfer resistor to obtain U CD Change equation. Continue to enter the corresponding Faraday current response formula, and the obtained i f Change equation.

[0071] For a more specific process of the equivalent circuit calculation unit, reference may be made to the process of step S2 in embodiment 1.

[0072] Among them, the corrosion rate calculation unit mainly performs the following functions: establishing a pipeline corrosion rate prediction model under dynamic DC interference according to the equivalent circuit model and Faraday's law, and obtaining the corrosion rate of the pipeline to be predicted.

[0073] In the corrosion system, only the anode current with Faraday current greater than zero participates in corrosion, so the Faraday current is analyzed to calculate the amount of corrosion charge accumulated by the anode current participating in the corrosion process in one cycle. The corrosion charge is fed into the pipeline corrosion rate prediction model established based on Faraday's law to calculate the predicted corrosion rate of the metal.

[0074] For a more specific process of the corrosion rate calculation unit, reference may be made to the process of step S3 in Example 1.

[0075] In addition, this embodiment also includes a verification unit, which mainly performs the function of comparing the corrosion rate obtained by the corrosion rate prediction model with the corrosion rate obtained by the experiment, thereby verifying the accuracy of the corrosion rate prediction model.

[0076] For a more specific process of the verification unit, reference may be made to the process of step S4 in Example 1.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A pipeline corrosion rate prediction method under dynamic DC interference, characterized in that: The following steps are involved: S1, obtaining the pipeline ground potential fluctuation parameter data and pipeline electrochemical impedance spectrum of the pipeline to be predicted; S2, establish an equivalent circuit model based on the electrochemical impedance spectroscopy, obtain the parameters of each electrical component, and deduce the impedance value of each electrical component combination and the Faraday current in the electrode system; S3, based on the equivalent circuit model and Faraday's law, a pipeline corrosion rate prediction model under dynamic DC interference is established to obtain the corrosion rate; S4, compared with the corrosion data obtained from the experiment to verify the accuracy of the established corrosion rate prediction model.

2. According to the method for predicting pipeline corrosion rate under dynamic DC interference according to claim 1, it is characterized in that: The pipeline electrochemical impedance spectrum is obtained by performing an electrochemical impedance test on a test specimen embedded in advance using an electrochemical workstation, and the electrochemical impedance spectrum test is performed to obtain a Nyquist diagram and a Bode diagram.

3. The method for predicting pipeline corrosion rate under dynamic DC interference according to claim 1 or 2 is characterized in that: The step S2 comprises: S21, based on the characteristic analysis of Nyquist diagram and Bode diagram in electrochemical impedance spectrum, the corrosion system under dynamic DC interference is obtained, and the equivalent circuit model is used to describe its corrosion process, and the parameters of each electrical component are obtained by fitting; S22, derive the equivalent circuit model to obtain the interference potential change formula, obtain the potential response formula at both ends of the double layer capacitor and the charge transfer resistor, and then obtain the corresponding Faraday current calculation formula of the charge transfer resistor.

4. The method for predicting pipeline corrosion rate under dynamic DC interference according to claim 3 is characterized in that: The step S3 comprises: S31, the charge accumulated by the anode Faraday current is the corrosion charge, and the calculation formula for the corrosion charge accumulated by the anode current participating in the corrosion process within one cycle time is derived; S32, a corrosion rate prediction model is established based on Faraday's law. The model calculates the Faraday current value through interference potential parameters and corrosion system parameters, integrates the anode Faraday current to obtain the anode dissolved charge, and finally calculates the corrosion rate of the metal.

5. A pipeline corrosion rate prediction method under dynamic DC interference according to claim 1, 2 or 4, characterized in that: The step S4 comprises: Carry out corrosion experiments under different dynamic DC interference conditions, compare the corrosion rate data obtained from the experiment with the corrosion rate calculated in step S3, and determine whether the error between the two is within a preset range.

6. A pipeline corrosion rate prediction method under dynamic DC interference according to claim 1 or 2, characterized in that: The pipeline-to-ground potential fluctuation parameter data to be predicted are specifically as follows: the test piece buried in the on-site pipeline obtains the power-on and power-off potential changes of the pipeline at each moment through an automatic potential collector, and obtains the pipeline interference potential amplitude, potential frequency, potential offset and interference time through analysis.

7. The method for predicting pipeline corrosion rate under dynamic DC interference according to claim 3 is characterized in that: The interference potential change formula is: U AB =U+U m sin(2πft) Among them, U AB is the interference potential loaded on the input terminal AB, U is the offset of the interference potential, U m is the fluctuation amplitude of the interference potential, f is the fluctuation frequency of the interference potential, and t is the interference time.

8. The method for predicting pipeline corrosion rate under dynamic DC interference according to claim 3 is characterized in that: The Faraday current calculation formula is: Among them, i f is the Faraday current, R s is the solution resistance, R1 is the rust layer resistance, R dl is the charge transfer resistance, C1 is the rust layer capacitance, C dl is the double layer capacitor.

9. The method for predicting pipeline corrosion rate under dynamic DC interference according to claim 4 is characterized in that: The corrosion rate calculation formula is: Among them, ν is the corrosion rate, f is the interference potential frequency, ρ is the material density, and S is the working area.

10. A pipeline corrosion rate prediction system under dynamic DC interference, applicable to a pipeline corrosion rate prediction method under dynamic DC interference according to any one of claims 1 to 9, characterized in that it comprises: A data acquisition unit, which acquires pipeline-ground potential fluctuation parameter data and pipeline electrochemical impedance spectrum; The equivalent circuit calculation unit establishes an equivalent circuit calculation model based on the electrochemical impedance spectrum to obtain the impedance value of each electronic component in the corrosion system and the Faraday current value at both ends of the charge transfer resistor; The corrosion rate calculation unit establishes a pipeline corrosion rate prediction model under dynamic DC interference based on the equivalent circuit model and Faraday's law to obtain the corrosion rate of the pipeline to be predicted.

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