Electric field detection method for marine ship corrosion

Abstract

The invention discloses an electric field detection method for corrosion of a marine ship, which is used for determining whether a ship body has a corrosion spot or not according to a potential time domain oscillogram obtained by an underwater potential detection device in the process of sailing along the ship body to be detected underwater so as to complete the detection of the corrosion of the marine ship. The corrosion spot is determined based on the electric field intensity around the ship body, and the problem that a traditional corrosion spot detection method is interfered by factors such as underwater turbidity, surface cleanliness and a coating material is solved. The method does not need to adopt a reference electrode, is simple to operate, and does not generate radiation to human bodies and the environment compared with a ray detection method. The device is simple in structure, low in cost and high in reliability and accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of hull corrosion monitoring, and in particular to an electric field detection method for marine ship corrosion. Background Art

[0002] At present, the maritime transportation industry is developing rapidly. Ships are the main means of transportation at sea. Once a safety accident occurs, it will cause great casualties, economic losses and environmental pollution, causing serious negative social impact.

[0003] Corrosion is a common phenomenon of ship damage. Once a ship's hull is corroded, it will cause permanent damage to the ship's hull. More importantly, it will have a significant impact on the ship's service life, sailing speed, performance, and ship safety. The causes of hull corrosion are relatively complex. Since the hull is immersed in seawater for a long time, seawater, as a strong electrolyte, contains a large amount of salt, which promotes electrochemical reactions. The hull and propeller are made of a variety of metal materials. Due to the differences in metal activity, the potential difference between different metals will cause galvanic corrosion. The oxygen concentration in different parts of the hull is different, forming an oxygen concentration cell, which leads to corrosion. Bacteria and microorganisms in the ocean form biofilms on the hull surface, producing acidic substances, which accelerate corrosion. The impact of waves and ocean currents on the hull causes surface wear, destroying the protective layer and increasing the risk of corrosion.

[0004] Therefore, regular corrosion inspections of ship structures are necessary to ensure navigational safety. Underwater nondestructive testing (NDT) is the primary method, with commonly used methods including visual inspection, ultrasonic testing, radiographic testing, eddy current testing, potentiometric testing, and electric field characterization. However, each of these methods has its limitations, such as susceptibility to obstacles, radiation exposure to humans and the environment, expensive equipment, the need for coupling agents, reference electrodes, and limitations on the type of ship material.

[0005] In the visual inspection method, whether it is a diver going into the water or an underwater robot carrying a camera, it is affected by the underwater turbidity; the ultrasonic inspection method has high requirements for the cleanliness of the hull surface and the surface needs to be cleaned in advance; the equipment used in the radiographic inspection method is expensive, and X-rays can easily cause harm to the human body and the environment; when the eddy current inspection method encounters obstacles such as non-conductive coatings (such as epoxy resin), it will affect the eddy current penetration and can only detect damaged coatings. Summary of the Invention

[0006] The present invention discloses an electric field detection method for marine ship corrosion, so as to overcome the above technical problems.

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

[0008] An electric field detection method for marine ship corrosion comprises the following steps:

[0009] S1: Establish an underwater potential detection device including several electrode sensors;

[0010] S2: Start the underwater potential detection device and put it into the water so that the underwater potential detection device sails outside the hull to be tested along the circumference of the hull to be tested;

[0011] S3: Obtaining a time-domain waveform of the potential of the underwater potential detection device when it sails along the hull to be tested;

[0012] S4: Determine whether there are corrosion points on the hull based on the potential time domain waveform diagram to complete the detection of marine ship corrosion.

[0013] Furthermore, the underwater potential detection device includes an underwater robot body, a first electrode sensor, a second electrode sensor, a third electrode sensor, and a fourth electrode sensor;

[0014] The first electrode sensor and the second electrode sensor are respectively fixedly arranged on two sides of the underwater robot body parallel to the forward direction of the underwater potential detection device;

[0015] The third electrode sensor and the fourth electrode sensor are respectively fixedly arranged on two sides of the underwater robot body perpendicular to the forward direction of the underwater potential detection device.

[0016] Furthermore, the method used to determine whether there are corrosion points on the hull is as follows:

[0017] When the underwater potential detection device sails along the hull to be tested, the first potential and the second potential are respectively obtained by the first electrode sensor and the second electrode sensor to obtain a first potential difference time domain waveform; the third potential and the fourth potential are respectively obtained by the third electrode sensor and the fourth electrode sensor to obtain a second potential difference time domain waveform;

[0018] When there is |V 1t -V2t|>ξ and |V 3t -V4t|>ξ,

[0019] At time t, there is a corrosion point in the area of the ship to be tested corresponding to the location of the underwater potential detection device; otherwise, there is no corrosion point in the ship to be tested;

[0020] Among them, V 1t Represents the first potential at time t; V 2t Represents the second potential at time t; V 3t Represents the third potential at time t; V 4t represents the fourth potential at time t; ξ is the set potential difference threshold.

[0021] Furthermore, when the underwater potential detection device navigates outside the hull to be measured along the circumference of the hull to be measured, the distance between the underwater potential detection device and the circumference of the hull is less than 100 cm.

[0022] Furthermore, the electrode sensor uses Ag / Agcl electrode.

[0023] Beneficial effects: The electric field detection method for marine ship corrosion of the present invention determines whether there are corrosion points on the hull through the potential time domain waveform obtained by the underwater potential detection device during the navigation along the hull to be tested underwater, so as to complete the detection of marine ship corrosion. The present invention determines the corrosion points based on the electric field strength around the hull, avoiding the problem of interference from factors such as underwater turbidity, surface cleanliness, and coating materials in traditional corrosion point detection methods. The present invention does not require the use of a reference electrode and is simple to operate. Compared with the X-ray detection method, it does not generate radiation to the human body and the environment. The present invention has a simple structure, low cost, and high reliability and accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] Figure 1 This is a flow chart of the electric field detection method for marine ship corrosion of the present invention;

[0026] Figure 2 Schematic diagram of the flow of the electric field detection method for marine ship corrosion in an embodiment of the present invention;

[0027] Figure 3 Schematic diagram of the structure of an underwater potential detection device in an embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the structural framework of the marine corrosion electric field detection system in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] This embodiment introduces an electric field detection method for marine ship corrosion. Figure 1 and Figure 2 As shown, the following steps are included:

[0031] S1: Establish an underwater potential detection device including several electrode sensors;

[0032] S2: Confirm that the underwater potential detection device is correctly connected, check the fixation of the electrode sensor, turn on the power supply to the acquisition card and the underwater potential detection device, and put the underwater potential detection device into the water so that the underwater potential detection device sails outside the hull to be tested along the circumference of the hull to be tested;

[0033] S3: Acquire a potential signal of the electrode sensor to obtain a time domain waveform of the potential along the hull to be measured when the underwater potential detection device sails along the hull to be measured;

[0034] S4: Determine whether there are corrosion points on the hull based on the potential time domain waveform diagram to complete the detection of marine ship corrosion.

[0035] Preferably, when the underwater potential detection device navigates along the circumference of the hull to be measured, the distance between the underwater potential detection device and the circumference of the hull is less than 100 cm.

[0036] Preferably, if Figure 3 As shown, the underwater potential detection device includes an underwater robot body 1, a first electrode sensor 3, a second electrode sensor 4, a third electrode sensor 5, and a fourth electrode sensor 6;

[0037] The first electrode sensor 3 and the second electrode sensor 4 are respectively fixedly arranged on both sides of the underwater robot body 1 parallel to the forward direction of the underwater potential detection device;

[0038] The third electrode sensor 5 and the fourth electrode sensor 6 are respectively fixedly arranged on two sides of the underwater robot body 1 perpendicular to the forward direction of the underwater potential detection device.

[0039] Specifically, the underwater robot body 1 of this embodiment is based on existing technology in the field, and its structure will not be described in detail here.

[0040] Preferably, the method for determining whether there are corrosion points on the hull is as follows:

[0041] When the underwater potential detection device sails along the hull to be tested, the first potential and the second potential are respectively obtained by the first electrode sensor and the second electrode sensor to obtain a first potential difference time domain waveform; the third potential and the fourth potential are respectively obtained by the third electrode sensor and the fourth electrode sensor to obtain a second potential difference time domain waveform;

[0042] When there is |V 1t -V 2t |>ξ and|V 3t -V 4t When |>ξ,

[0043] At time t, there is a corrosion point in the area of the ship to be tested corresponding to the location of the underwater potential detection device; otherwise, there is no corrosion point in the ship to be tested;

[0044] Among them, V 1t Represents the first potential at time t; V 2t Represents the second potential at time t; V 3t Represents the third potential at time t; V 4t represents the fourth potential at time t; ξ is the set potential difference threshold.

[0045] Specifically, this embodiment uses two pairs of electrode sensors to jointly determine the corrosion points, so that the determined results are more reliable.

[0046] Preferably, the electrode sensor uses Ag / Agcl electrode.

[0047] Specifically, after the electric field detection system of this embodiment is started, the underwater potential detection device is controlled to navigate along the hull to be tested. If there are corrosion points on the hull, when the underwater potential detection device passes through the corrosion points, a more obvious electric field signal will be generated compared to the normal area.

[0048] Specifically, the Ag / AgCl electrode of this embodiment exists as a working electrode. Since the Ag / AgCl working electrode pair is in direct contact with seawater, no salt bridge (electrode) is required, thus avoiding the problem of chloride ion contamination or dilution caused by the need for a salt bridge to isolate the reference electrode from seawater in a working mode based on a reference electrode. When Ag / AgCl is used as a working electrode, the two electrodes are in direct contact with the same medium, which can completely eliminate liquid junction potential interference. At the same time, this embodiment determines the corrosion point based on the first potential difference and the second potential difference, and directly reflects the local electrochemical activity difference (such as the anode / cathode area distribution) through the potential difference, avoiding the problem of relying more on the absolute potential of the working electrode relative to the reference electrode when using a reference electrode.

[0049] Specifically, after the analog signal measured by the sensing electrodes is transmitted to the acquisition board, it undergoes signal amplification, filtering, and analog-to-digital conversion. First, the potential signal measured by the sensing electrodes is transmitted to the acquisition board for signal amplification. The amplified potential signal is then transmitted to the host computer via the RS485 communication interface. The underwater potential detection device connects to the host computer via a USB interface, and the RS485 communication interface transmits the processed digital signal to the host computer.

[0050] The program of the host computer in this embodiment is written by LabVIEW. The uploaded data files are automatically saved on the disk. The data stored on the disk are opened with the Matlab program to draw the potential change curve along the hull to be tested, and the place where the potential curve fluctuates the most is obtained, which can determine the location of the corrosion point.

[0051] Specifically, the host computer of this embodiment can display the real-time potential waveform of the two channels. The host computer interface is provided with an indicator light. When |V 1t -V 2t |>ξ and|V 3t -V 4t When |>ξ, and significant potential fluctuations (optionally, exceeding 5000μV) are present both perpendicularly and parallel to the direction of movement of the underwater potential detection device, an indicator light will illuminate, indicating the presence of hull corrosion at that location. Simultaneously, all uploaded data files are automatically saved to disk. The stored data is opened using the MATLAB program, and a potential curve along the hull under test is plotted. By observing the areas of significant potential difference fluctuation, the location of the corrosion point can be re-identified.

[0052] Specifically, after laboratory verification, when the vertical distance between the sensor and the metal anode is within 100 cm, the potential time domain waveform displayed by the host computer has obvious fluctuations, and the range of variation is more than 5000μV. The electrode sensor uses Ag / AgCl electrodes. The solubility of AgCl in water is extremely low, and it can form a stable solid phase (AgCl) and liquid phase (Ag in the solution). + and Cl - This low solubility ensures the stability of the AgCl layer on the electrode surface, reducing potential drift caused by dissolution. Furthermore, the electrode is minimally affected by temperature, resulting in Ag / AgCl electrodes with high stability, reproducibility, fast response, and ease of maintenance.

[0053] Specifically, such as Figure 4As shown, the marine ship corrosion electric field detection system of this embodiment includes a host computer, an RS485 communication interface, an underwater potential detection device (underwater robot), a first electrode sensor, an acquisition card and a power module. Among them, the host computer is located in the water part and is connected to the RS485 communication interface. The acquisition card and the power module are placed in the sealed cabin of the underwater potential detection device. The power module supplies power to the underwater potential detection device power system and the acquisition card. The electrode sensor is fixed on the underwater potential detection device. In this embodiment, two pairs of electrode sensors are used to obtain the potential difference in two directions of the underwater potential detection device. Specifically, the electrode sensor receives the electrode induction signal, converts it into a weak voltage signal, and transmits it to the amplifier. The amplifier receives the weak voltage signal, amplifies the voltage signal through the amplifier circuit, and transmits it to the acquisition card. The acquisition card receives the amplified voltage signal and converts the voltage analog signal into a digital signal. The host computer receives the digital signal and determines whether there is a corrosion point on the hull by the two point potential differences obtained by the two pairs of electrode sensors.

[0054] This embodiment has the following beneficial effects:

[0055] 1. Simple operation, no complex equipment required: When a ship corrodes underwater, the electric field strength of the surrounding electrolyte is significantly higher than that of the seawater near uncorroded areas. The electrode sensor used in this embodiment measures the potential difference in the seawater near the hull, which is divided by the distance between the electrodes to obtain the electric field strength. Therefore, this embodiment is unaffected by factors such as underwater turbidity, surface cleanliness, and coating materials during detection. Because the propagation of the electric field is unimpeded by obstacles, underwater electric field measurement is unaffected by obstacles, resolving the problem of traditional acoustic wave detection being blocked by obstacles.

[0056] 2. Although both methods rely on underwater electric field measurement to detect hull corrosion, this embodiment, unlike the potentiometric method, does not require a fixed reference electrode. There's no need to connect the reference electrode to the positive terminal of the potentiometer via a shielded cable. Instead, the electrode pair is directly fixed to the underwater robot, enabling measurement of the electric field around the robot's path. This simplifies and streamlines the operation. Compared to the electric field signature method, this method does not require current to the hull; compared to the ultrasonic method, it does not require a coupling agent; and compared to the radiographic method, it does not generate radiation to the human body or the environment, and its operation is simple and convenient.

[0057] 3. The detection route is flexible and the detection results can be obtained immediately: The detection device of this embodiment is to fix two pairs of electrodes on an underwater robot, and control the detection route by remote control of the underwater robot. The obtained electric field signal enters the acquisition board, is amplified and filtered, and is connected to the host computer through the RS485 communication interface. The program of the host computer is written in Labview, which can display the real-time waveform of the potential difference between the two channels. When the potential difference exceeds the threshold set by the program (5000μV), the indicator light in the host computer window will light up, indicating that corrosion exists at that location.

[0058] 3. The test results are stored and can be confirmed: After a single test is completed, the potential difference data obtained is stored on the disk. The file can be opened through MATLAB to directly draw the waveform of the potential difference. The area with large potential difference fluctuations can be used to identify the corrosion point, and the immediate results can be confirmed.

[0059] 4. Compared with traditional ultrasonic testing, the corrosion detection of this embodiment does not require the use of coupling agents. In addition, the sensor of this embodiment is an Ag / AgCl electrode sensor, which is low in cost.

[0060] In summary, this embodiment detects corrosion on the hull surface by detecting underwater electric fields. The electrode sensors use Ag / AgCl electrodes, which have excellent anti-interference properties. The signals are amplified and filtered by the acquisition board and transmitted to the host computer via the RS485 communication interface. This method detects hull corrosion points with high reliability and accuracy.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electric field detection method for marine ship corrosion, characterized in that: The steps include: S1: Establish an underwater potential detection device including several electrode sensors; S2: Start the underwater potential detection device and put it into the water so that the underwater potential detection device sails outside the hull to be tested along the circumference of the hull to be tested; S3: Obtaining a time-domain waveform of the potential of the underwater potential detection device when it sails along the hull to be tested; S4: Determine whether there are corrosion points on the hull based on the potential time domain waveform diagram to complete the detection of marine ship corrosion.

2. The electric field detection method for marine ship corrosion according to claim 1, characterized in that: The underwater potential detection device comprises an underwater robot body (1), a first electrode sensor (3), a second electrode sensor (4), a third electrode sensor (5), and a fourth electrode sensor (6); The first electrode sensor (3) and the second electrode sensor (4) are respectively fixedly arranged on two sides of the underwater robot body (1) parallel to the forward direction of the underwater potential detection device; The third electrode sensor (5) and the fourth electrode sensor (6) are respectively fixedly arranged on two sides of the underwater robot body (1) perpendicular to the forward direction of the underwater potential detection device.

3. The electric field detection method for marine ship corrosion according to claim 2, characterized in that: The method used to determine whether there are corrosion points on the hull is as follows: When the underwater potential detection device sails along the hull to be tested, the first potential and the second potential are respectively obtained through the first electrode sensor and the second electrode sensor to obtain a first potential difference time domain waveform; Obtaining a third potential and a fourth potential through the third electrode sensor and the fourth electrode sensor respectively, so as to obtain a second potential difference time domain waveform; When there is |V 1t -V 2t |>ξ and|V 3t -V 4t When |>ξ, At time t, there is a corrosion point in the area of the ship to be tested corresponding to the location of the underwater potential detection device; otherwise, there is no corrosion point in the ship to be tested; Among them, V 1t Represents the first potential at time t; V 2t Represents the second potential at time t; V 3t Represents the third potential at time t; V 4t represents the fourth potential at time t; ξ is the set potential difference threshold.

4. The electric field detection method for marine ship corrosion according to claim 1, characterized in that: When the underwater potential detection device navigates outside the hull to be measured along the circumference of the hull to be measured, the distance between the underwater potential detection device and the circumference of the hull is less than 100 cm.

5. The electric field detection method for marine ship corrosion according to claim 1, characterized in that: The electrode sensor adopts Ag / Agcl electrode.

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