A pipeline corrosion detection and evaluation method

Abstract

The present invention discloses a pipeline corrosion detection and evaluation method, including: pre-arranging multiple groups of corrosion metal test pieces at intervals on the outer wall of the pipeline to be tested along the axial direction of the pipeline to be tested, and measuring the potential of each corrosion metal test piece in a non-destructive state as a standard value; collecting the potential of each corrosion metal test piece at each preset time interval, determining the difference between the current collected potential of each corrosion metal test piece and the respective standard value, and determining the corrosion position and corrosion degree of the outer wall of the pipeline to be tested according to a pre-constructed database; at each preset time interval, using an ultrasonic probe to emit an ultrasonic guided wave signal at the corresponding detection point of the pipeline to be tested, and receiving the echo signal reflected at the position where the wall thickness changes during the propagation of the ultrasonic guided wave signal along the pipeline to be tested; determining the comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested according to the echo signal. The present invention can simultaneously detect the overall corrosion position and corrosion state of the inner and outer walls of the detection pipeline, and conduct a comprehensive evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline monitoring, and more particularly to a pipeline corrosion detection and evaluation method. Background Art

[0002] Gas-liquid two-phase flow is widely used in industries such as energy, chemical engineering, petrochemical engineering, and environmental engineering. During the application process, chemical reactions will occur between the pipeline and the fluid, causing corrosion or other reasons to cause corrosion, resulting in pipeline failure. After the quality of the corroded part is reduced, the pipeline wall becomes thinner, and the strength and rigidity are reduced. When the corrosion is severe, the pipeline will be damaged and perforated, resulting in fluid leakage from the perforation. Therefore, it is particularly important to detect the corrosion degree of the pipeline in a timely manner.

[0003] At present, corrosion test pieces are usually hung inside or outside the pipeline so that they are in contact with the fluid. After a certain period of time, the corrosion test pieces are taken out, cleaned, and weighed to obtain the weight of the test pieces after corrosion. The degree of corrosion of the pipeline is determined by the weight change of the corrosion test pieces and the preset time.

[0004] This method requires the corrosion test piece to be taken out from the inside of the pipeline, or dug out from the stratum where the pipeline is located. When the pipeline is located in a deep stratum, it usually takes a long time, and can only detect the overall corrosion conditions of the inner and outer walls of the pipeline at a certain point. The detection accuracy and efficiency are not high.

[0005] Therefore, how to provide a pipeline corrosion detection and evaluation method with high detection accuracy, which can simultaneously detect the corrosion location and corrosion status of the inner and outer walls of the pipeline and perform comprehensive evaluation is a problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of this, the present invention provides a pipeline corrosion detection and evaluation method, which can simultaneously detect the overall corrosion position and corrosion state of the inner and outer walls of the detection pipeline, and perform a comprehensive evaluation.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A pipeline corrosion detection and evaluation method, comprising:

[0009] Multiple sets of corrosion metal test pieces and reference electrodes are pre-buried at intervals near the outer wall of the pipeline to be tested along the axial direction, and the potential of each of the corrosion metal test pieces in a non-destructive state is measured as a standard value; wherein the corrosion metal test pieces are made of the same material as the outer wall of the pipeline to be tested;

[0010] During the operation of the pipeline to be tested, the potential of each of the corroded metal test pieces is collected at a preset time interval, the difference between the current collected potential of each of the corroded metal test pieces and the respective standard values ​​is determined, and the corrosion position and corrosion degree of the outer wall of the pipeline to be tested are determined according to a pre-constructed potential difference-corrosion degree relationship database;

[0011] At preset time intervals, an ultrasonic probe is used to transmit an ultrasonic guided wave signal at the corresponding detection point of the pipeline to be tested, and an echo signal reflected from the position where the thickness of the pipe wall changes during the propagation of the ultrasonic guided wave signal along the pipeline to be tested is received;

[0012] The comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested are determined according to the echo signal.

[0013] Furthermore, the number of the corrosion metal test pieces in each group is at least two, and they are arranged in a ring shape with equal arc lengths on the outer wall of the pipeline to be tested.

[0014] Furthermore, the process of constructing the potential difference-corrosion degree relationship database includes:

[0015] Obtaining potential values ​​of a plurality of compensation metal test pieces made of the same material as the corroded metal test piece in a non-destructive state;

[0016] Simulating corrosion states corresponding to different corrosion levels on the compensating metal test piece, and collecting the potential values ​​of the compensating metal test piece under different corrosion states; the corrosion state includes: the corrosion depth of the corrosion point;

[0017] The potential difference-corrosion degree database is constructed according to the corrosion state simulated by each of the compensating metal test pieces and the changes in the potential values ​​before and after corrosion corresponding to different corrosion states.

[0018] Furthermore, the process of determining the corrosion position and corrosion degree of the outer wall of the pipeline to be tested includes:

[0019] Numbering each of the corrosion metal test pieces in advance, and determining the position coordinates of each of the corrosion metal test pieces on the pipeline to be tested;

[0020] The potential difference value before and after corrosion of each of the corroded metal test pieces is matched with the potential difference value-corrosion degree database to obtain the current corrosion area, corrosion thickness and corresponding corrosion degree of each of the corroded metal test pieces, and the corrosion degree of each of the corroded metal test pieces is used as the corrosion degree of the corresponding position of the outer wall of the pipeline to be tested;

[0021] A corrosion distribution map of the outer wall of the pipeline to be tested is generated according to the corrosion degree of different positions of the outer wall of the pipeline to be tested; the corrosion distribution map of the outer wall of the pipeline to be tested is updated in real time as the potential value of the corroded metal test piece changes.

[0022] Furthermore, before the pipeline to be tested is laid, it also includes: determining at least one detection point on the pipeline to be tested, and pre-arranging a plurality of ultrasonic probes at intervals in an annular direction at each detection point, and the ultrasonic guided waves emitted by each ultrasonic probe are propagated symmetrically about the axis.

[0023] Furthermore, the process of determining the comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested includes:

[0024] According to the time difference Δt between the ultrasonic guided wave emission time and the echo signal reception time and the propagation speed v of the ultrasonic guided wave signal in the pipeline to be tested, the distance between the corrosion position and the ultrasonic probe is calculated as the comprehensive corrosion position of the pipeline to be tested: Δs = v × Δt;

[0025] According to the size of the reflected echo signal, the corrosion thickness and the corresponding corrosion degree at the corrosion position of the pipeline to be tested are determined.

[0026] Furthermore, it also includes:

[0027] A three-dimensional cloud map of the pipeline to be tested is generated according to the basic parameters of the pipeline to be tested, the corrosion positions of the inner and outer walls of the pipeline to be tested are marked on the three-dimensional cloud map, and different colors are displayed according to the comprehensive corrosion degree to obtain a three-dimensional defect image of the pipeline to be tested.

[0028] Furthermore, it also includes:

[0029] According to the comprehensive corrosion degree of each corrosion position on the inner and outer walls of the pipeline to be tested and the corrosion degree at each corrosion position on the outer wall of the pipeline, the corrosion position, corrosion thickness and corresponding corrosion degree of the inner wall of the pipeline to be tested are determined.

[0030] Furthermore, according to the corrosion thickness of each corrosion position on the outer wall and the inner wall of the pipeline to be tested at different times, the corrosion rates of the inner and outer walls of the pipeline to be tested are calculated respectively.

[0031] Furthermore, it also includes:

[0032] According to the comprehensive corrosion position and corresponding corrosion thickness of the pipeline to be tested, determine whether the pipeline to be tested meets the safe service conditions;

[0033] If the number of corrosion locations exceeds the first number threshold, or the corrosion thickness at a corrosion location exceeds the first thickness threshold, it is determined to be a first-level corrosion degree, and the corroded pipeline needs to be replaced;

[0034] If the number of corrosion locations exceeds the second number threshold and is lower than the first number threshold, or if the corrosion thickness at a corrosion location exceeds the second thickness threshold and is lower than the first thickness threshold, and there is no corrosion thickness at a corrosion location that exceeds the first thickness threshold, it is determined to be a secondary corrosion degree and the pipeline corrosion status needs to be continuously observed;

[0035] If the number of corrosion locations is lower than the second number threshold, and the corrosion thickness at each corrosion location is lower than the second thickness threshold, it is determined to be level three corrosion, indicating that the pipeline is in good condition and can be operated safely.

[0036] It can be seen from the above technical solutions that, compared with the prior art, the present invention discloses a pipeline corrosion detection and evaluation method, which has the following beneficial effects:

[0037] 1. The present invention sets a corrosion metal test piece on the outer wall of the pipeline to be tested in advance. When the pipeline is actually in operation, for the formation pipeline, there is no need to excavate the pipeline. The corrosion metal test piece is connected to the external detection terminal to measure the potential of the corrosion metal test piece. Since the corrosion metal test piece is made of the same material as the pipeline, the corrosion degree of the corresponding position of the outer wall of the pipeline can be evaluated by the corrosion degree of the corrosion metal test piece, and the operation is simple.

[0038] 2. The present invention arranges multiple corrosion metal test pieces circumferentially on the outer wall of the pipeline, which can detect multiple corrosion data of the same detection point. By comparing the multiple data of the same detection point, the detection accuracy can be improved, and at the same time, it can avoid the situation where corrosion detection cannot be performed due to damage to a certain corrosion metal test piece.

[0039] 3. The present invention simulates the corrosion state and pre-builds a database, and can quickly obtain the corresponding corrosion degree of the corroded metal specimen according to the potential difference before and after corrosion. The method is simple and the detection result is accurate.

[0040] 4. The present invention can simultaneously detect the corrosion conditions of the inner and outer walls of the pipeline, making it easy to identify whether the pipeline corrosion factor is caused by the external environment or the internal fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0042] Figure 1 A flow chart of a pipeline corrosion detection and evaluation method in one embodiment of the present invention;

[0043] Figure 2 A distribution diagram of the corroded metal test piece and the reference electrode provided by the present invention;

[0044] Figure 3 The process of constructing the potential difference-corrosion degree relationship database provided by the present invention;

[0045] Figure 4 A flow chart of a pipeline corrosion detection and evaluation method in other embodiments provided by the present invention;

[0046] Figure 5 A flow chart of a pipeline corrosion detection and evaluation method in another embodiment provided by the present invention;

[0047] Figure 6 A flow chart of a pipeline corrosion detection and evaluation method in another embodiment provided by the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] like Figure 1 As shown, an embodiment of the present invention discloses a pipeline corrosion detection and evaluation method, comprising:

[0050] Multiple groups of corrosion metal test pieces are pre-buried at intervals near the outer wall of the pipeline to be tested along its axial direction, and the potential of each corrosion metal test piece in a non-destructive state is measured as a standard value; wherein, the corrosion metal test piece is made of the same material as the pipeline to be tested; the side of the corrosion metal test piece corresponding to the material of the inner wall of the pipeline is insulated, so that the material of the corrosion metal test piece in contact with the outside world can be made the same as the material of the pipeline to be tested in contact with the outside world, thereby ensuring the measurement accuracy;

[0051] During the operation of the pipeline to be tested, the potential of each corroded metal test piece is collected at a preset interval, the difference between the current collected potential of each corroded metal test piece and the respective standard value is determined, and the corrosion position and corrosion degree of the outer wall of the pipeline to be tested are determined based on the pre-constructed potential difference-corrosion degree relationship database;

[0052] At preset time intervals, an ultrasonic probe is used to transmit an ultrasonic guided wave signal at the corresponding detection point of the pipeline to be tested, and an echo signal reflected from the position where the thickness of the pipe wall changes during the propagation of the ultrasonic guided wave signal along the pipeline to be tested is received;

[0053] The comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested are determined according to the echo signal.

[0054] In the embodiment of the present invention, Figure 2 As shown, each group of corrosion metal test pieces has at least two pieces, and they are arranged in a ring shape with equal arc lengths on the outer wall of the pipeline to be tested. Each corrosion metal test piece corresponds to a reference electrode.

[0055] The present invention sets a corrosion metal test piece on the outer wall of the pipeline to be tested in advance, and each corrosion metal test piece is led out to the ground surface through a lead wire in the order of numbering, and connected to the detection terminal through a wiring terminal. When the pipeline is actually running, for the formation pipeline, there is no need to excavate the pipeline. The corrosion metal test piece is connected through the external detection terminal, and the potential of the corrosion metal test piece can be automatically measured at any time or according to the set time. Since the corrosion metal test piece and the pipeline are made of the same material, the corrosion degree of the corresponding position of the outer wall of the pipeline can be evaluated by the corrosion degree of the corrosion metal test piece, and the operation is simple.

[0056] For each detection point, at least two corrosion metal test pieces are set, so that multiple positions of the same detection point can be detected. By comparing the data of multiple corrosion metal test pieces at the same detection point, the numerical values ​​can be compared with each other. Specifically, the average value can be taken to determine the potential value of the detection point, which can improve the detection accuracy. At the same time, it can also avoid the situation where corrosion detection cannot be carried out due to damage to a certain corrosion metal test piece.

[0057] In a specific embodiment, Figure 3 As shown in FIG. 1 , the process of constructing the potential difference-corrosion degree relationship database includes:

[0058] Obtaining potential values ​​of a plurality of compensating metal test pieces of the same material as the corroded metal test piece in a non-destructive state;

[0059] The corrosion states corresponding to different corrosion levels are simulated on the compensating metal test pieces respectively, and the potential values ​​of the compensating metal test pieces under different corrosion states are collected; the corrosion states include: pitting radius and pitting depth of the corrosion point;

[0060] According to the corrosion state simulated by each compensation metal test piece and the change of the potential value before and after corrosion corresponding to different corrosion states, a potential difference value-corrosion degree database is constructed.

[0061] Specifically, the process of determining the corrosion location and corrosion degree of the outer wall of the pipeline to be tested includes:

[0062] Number each corrosion metal test piece in advance, and determine the position coordinates of each corrosion metal test piece on the pipeline to be tested;

[0063] The potential difference value before and after corrosion of each corroded metal test piece is matched with the potential difference value-corrosion degree database to obtain the current corrosion area, corrosion thickness and corresponding corrosion degree of each corroded metal test piece, and the corrosion degree of each corroded metal test piece is used as the corrosion degree of the corresponding position of the outer wall of the pipeline to be tested;

[0064] A corrosion distribution map of the outer wall of the pipeline to be tested is generated according to the corrosion degree of different positions of the outer wall of the pipeline to be tested; the corrosion distribution map of the outer wall of the pipeline to be tested is updated in real time as the potential value of the corroded metal test piece changes.

[0065] The embodiment of the present invention simulates a large number of different corrosion states for the measuring electrode in advance to determine the electrode potential under different corrosion states, analyzes the corresponding relationship between the corrosion degree and the potential value, and then constructs a database. When the pipeline is actually operated subsequently, the corrosion data in the database can be retrieved according to the actual potential difference value, and the corrosion data corresponding to the current potential value can be quickly matched, so that the corrosion area, corrosion depth and corresponding corrosion degree of the corroded metal test piece at each detection point can be understood in real time.

[0066] Specifically, the corrosion depth of the corroded metal test piece can be directly used as the corrosion depth of the outer wall of the pipeline within a certain range before and after the detection point. For example, the range can be half of the distance between the current detection point and the two groups of corroded metal test pieces before and after. The corrosion area in the range before and after the current detection point can be calculated based on the corrosion area in the database corresponding to the average value of the potential difference value detected by each corroded metal test piece at the current detection point, and the ratio of the corroded metal test piece to the outer wall area of ​​the pipeline in the range.

[0067] In a specific embodiment, before the pipeline to be tested is laid, it also includes: determining at least one detection point on the pipeline to be tested, and pre-arranging multiple ultrasonic probes at intervals in an annular direction at each detection point, and the ultrasonic guided waves emitted by each ultrasonic probe are symmetrically propagated about the axis.

[0068] In one embodiment, the calculation process of the comprehensive corrosion position and corrosion degree of the pipeline is:

[0069] According to the time difference Δt between the ultrasonic guided wave emission time and the echo signal reception time and the propagation speed v of the ultrasonic guided wave signal in the pipeline to be tested, the distance between the corrosion position and the ultrasonic probe is calculated as the comprehensive corrosion position of the pipeline to be tested: Δs = v × Δt;

[0070] According to the size of the reflected echo signal, the corrosion thickness and the corresponding corrosion degree at the corrosion position of the pipeline to be tested are determined.

[0071] like Figure 4 As shown, in other embodiments, the method of the present invention further includes:

[0072] S5. Generate a three-dimensional cloud map of the pipeline to be tested according to the basic parameters of the pipeline to be tested (inner diameter, outer diameter, pipe length, etc.), mark the comprehensive corrosion positions of the inner and outer walls of the pipeline to be tested on the three-dimensional cloud map, and display different colors according to the comprehensive corrosion degree to obtain a three-dimensional defect image of the pipeline to be tested.

[0073] The embodiment of the present invention draws a three-dimensional defect image of the pipeline to be tested and updates it according to real-time detection data to visualize the corrosion condition of the pipeline, so that the staff can intuitively know the corrosion degree of different positions of the pipeline to be tested.

[0074] like Figure 5 As shown, in another embodiment, the following steps are also included:

[0075] S5. Determine the corrosion position, corrosion thickness and corresponding corrosion degree of the inner wall of the pipeline to be tested according to the comprehensive corrosion degree of each corrosion position on the inner and outer walls of the pipeline to be tested and the corrosion degree at each corrosion position on the outer wall of the pipeline.

[0076] Specifically, the corrosion location map of the pipeline can be subtracted from the corrosion location of the outer wall of the pipeline to obtain the distribution of the corrosion location of the inner wall of the pipeline; the corrosion thickness corresponding to the comprehensive corrosion location of the pipeline minus the corrosion thickness corresponding to each corrosion location on the outer wall of the pipeline can be obtained to obtain the corrosion thickness corresponding to the corrosion location on the inner wall of the pipeline.

[0077] The present invention can simultaneously detect the corrosion conditions of the inner and outer walls of the pipeline, making it easy to identify whether the pipeline corrosion factor is caused by the external environment or the internal fluid.

[0078] In another embodiment, the steps are further included:

[0079] According to the corrosion thickness of each corrosion position on the outer wall and inner wall of the tested pipeline at different times, the corrosion rate of the inner and outer walls of the tested pipeline is calculated respectively. The staff can evaluate the service life of the pipeline according to the corrosion rate, so as to maintain or replace the pipeline in time when the pipeline life is about to end.

[0080] In yet another embodiment, Figure 6 As shown, the steps include:

[0081] S5. According to the comprehensive corrosion position and corresponding corrosion thickness of the pipeline to be tested, determine whether the pipeline to be tested meets the safe service conditions;

[0082] If the number of corrosion locations exceeds the first number threshold, or the corrosion thickness at a corrosion location exceeds the first thickness threshold, it is determined to be a first-level corrosion degree, and the corroded pipeline needs to be replaced;

[0083] If the number of corrosion locations exceeds the second number threshold and is lower than the first number threshold, or if the corrosion thickness at a corrosion location exceeds the second thickness threshold and is lower than the first thickness threshold, and there is no corrosion thickness at a corrosion location that exceeds the first thickness threshold, it is determined to be a secondary corrosion degree and the pipeline corrosion status needs to be continuously observed;

[0084] If the number of corrosion locations is lower than the second number threshold, and the corrosion thickness at each corrosion location is lower than the second thickness threshold, it is determined to be level three corrosion, indicating that the pipeline is in good condition and can be operated safely.

[0085] The embodiments of the present invention can also provide early warnings in different ways according to the degree of corrosion.

[0086] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0087] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A pipeline corrosion detection and evaluation method, characterized in that: include: Before laying the pipeline to be tested, at least one detection point on the pipeline to be tested is determined, and a plurality of ultrasonic probes are pre-arranged at intervals in a circumferential direction at each detection point; the ultrasonic guided waves emitted by each ultrasonic probe are propagated symmetrically to the axis; Multiple sets of corrosion metal test pieces and reference electrodes are pre-buried at intervals near the outer wall of the pipeline to be tested along the axial direction, and the potential of each of the corrosion metal test pieces in a non-destructive state is measured as a standard value; wherein the corrosion metal test pieces are made of the same material as the outer wall of the pipeline to be tested; During the operation of the pipeline to be tested, the potential of each of the corroded metal test pieces is collected by the detection terminal at a preset interval, the difference between the current collected potential of each of the corroded metal test pieces and the respective standard values ​​is determined, and the corrosion position and corrosion degree of the outer wall of the pipeline to be tested are determined according to the pre-constructed potential difference-corrosion degree relationship database; the construction process of the potential difference-corrosion degree relationship database includes: Obtaining potential values ​​of a plurality of compensation metal test pieces made of the same material as the corroded metal test piece in a non-destructive state; Simulating corrosion states corresponding to different corrosion levels on the compensating metal test piece, and collecting the potential values ​​of the compensating metal test piece under different corrosion states; the corrosion state includes: the corrosion depth of the corrosion point; Constructing the potential difference-corrosion degree database according to the corrosion state simulated by each of the compensating metal test pieces and the changes in the potential values ​​before and after corrosion corresponding to different corrosion states; At preset time intervals, an ultrasonic probe is used to transmit an ultrasonic guided wave signal at the corresponding detection point of the pipeline to be tested, and an echo signal reflected from the position where the thickness of the pipe wall changes during the propagation of the ultrasonic guided wave signal along the pipeline to be tested is received; Determine the comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested according to the echo signal; The corrosion position, corrosion thickness and corresponding corrosion degree of the inner wall of the pipeline to be tested are determined according to the comprehensive corrosion degree of each corrosion position on the inner and outer walls of the pipeline to be tested and the corrosion degree at each corrosion position on the outer wall of the pipeline; the corrosion thickness corresponding to the corrosion position of the pipeline on the inner wall is subtracted from the corrosion thickness corresponding to each corrosion position on the outer wall of the pipeline to obtain the corrosion thickness corresponding to the corrosion position on the inner wall of the pipeline.

2. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: The number of the corrosion metal test pieces in each group is at least two, and they are arranged in a ring shape with equal arc lengths at intervals on the outer wall of the pipeline to be tested.

3. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: The process of determining the corrosion location and corrosion degree of the outer wall of the pipeline to be tested includes: Numbering each of the corrosion metal test pieces in advance, and determining the position coordinates of each of the corrosion metal test pieces on the pipeline to be tested; The potential difference value before and after corrosion of each of the corroded metal test pieces is matched with the potential difference value-corrosion degree database to obtain the current corrosion area, corrosion thickness and corresponding corrosion degree of each of the corroded metal test pieces, and the corrosion degree of each of the corroded metal test pieces is used as the corrosion degree of the corresponding position of the outer wall of the pipeline to be tested; A corrosion distribution map of the outer wall of the pipeline to be tested is generated according to the corrosion degree of different positions of the outer wall of the pipeline to be tested; the corrosion distribution map of the outer wall of the pipeline to be tested is updated in real time as the potential value of the corroded metal test piece changes.

4. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: The process of determining the comprehensive corrosion position and the corresponding comprehensive corrosion degree of the pipeline to be tested includes: According to the time difference Δt between the ultrasonic guided wave emission time and the echo signal reception time and the propagation speed v of the ultrasonic guided wave signal in the pipeline to be tested, the distance between the corrosion position and the ultrasonic probe is calculated as the comprehensive corrosion position of the pipeline to be tested: Δs=v×Δt; According to the size of the reflected echo signal, the corrosion thickness and the corresponding corrosion degree at the corrosion position of the pipeline to be tested are determined.

5. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: Also includes: A three-dimensional cloud map of the pipeline to be tested is generated according to the basic parameters of the pipeline to be tested, the corrosion positions of the inner and outer walls of the pipeline to be tested are marked on the three-dimensional cloud map, and different colors are displayed according to the comprehensive corrosion degree to obtain a three-dimensional defect image of the pipeline to be tested.

6. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: According to the corrosion thickness of each corrosion position on the outer wall and inner wall of the pipeline to be tested at different times, the corrosion rates of the inner and outer walls of the pipeline to be tested are calculated respectively.

7. A pipeline corrosion detection and evaluation method according to claim 1, characterized in that: Also includes: According to the comprehensive corrosion position and corresponding corrosion thickness of the pipeline to be tested, determine whether the pipeline to be tested meets the safe service conditions; If the number of corrosion locations exceeds the first number threshold, or the corrosion thickness at a corrosion location exceeds the first thickness threshold, it is determined to be a first-level corrosion degree, and the corroded pipeline needs to be replaced; If the number of corrosion locations exceeds the second number threshold and is lower than the first number threshold, or if the corrosion thickness at a corrosion location exceeds the second thickness threshold and is lower than the first thickness threshold, and there is no corrosion thickness at a corrosion location that exceeds the first thickness threshold, it is determined to be a secondary corrosion degree and the pipeline corrosion status needs to be continuously observed; If the number of corrosion locations is lower than the second number threshold, and the corrosion thickness at each corrosion location is lower than the second thickness threshold, it is determined to be level three corrosion, indicating that the pipeline is in good condition and can be operated safely.

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