A corrosion rate monitoring sensor

Abstract

The application relates to the technical field of corrosion monitoring, in particular to a corrosion rate monitoring sensor, which comprises a corrosion rate sensing probe and a reference probe; the corrosion rate sensing probe comprises a strip-shaped piezoelectric sheet and a strip-shaped corrosion sheet; the strip-shaped piezoelectric sheet and the strip-shaped corrosion sheet are bonded at the end faces in the length direction and the axes in the length direction of the two coincide, thus forming the corrosion rate sensing probe for sensing the corrosion rate of a medium; the reference probe is consistent with the main body of the corrosion rate sensing probe, and the surface of the reference probe is coated with a wear-resistant and corrosion-resistant layer; the reference probe serves as a reference datum of the corrosion sensing probe and is used for eliminating the influence of environmental factors such as temperature. The corrosion rate monitoring sensor can be applied to various corrosion conditions and environments, and has the advantages of high sensitivity, wide application range, strong anti-interference performance and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of corrosion monitoring, and in particular to a corrosion rate monitoring sensor. Background Art

[0002] Corrosion is a widespread phenomenon in the natural environment and in human daily life. Corrosion of materials is primarily caused by the presence of corrosive substances or media (such as electrolytes, acids / alkalines, and microorganisms) in their environment. This slow and persistent erosion of material structures is a potentially destructive process. Therefore, corrosion is often difficult to detect (such as corrosion within pipelines), and the resulting incidents can be sudden. Given the persistence and concealment of corrosion, as well as the suddenness of the incidents it causes, corrosion monitoring is essential for critical industrial facilities.

[0003] Currently, corrosion monitoring is mainly divided into corrosion damage monitoring and corrosion rate monitoring. Corrosion damage monitoring is to monitor the damage of the structure (such as changes in the thickness of the structure) by placing sensors on the surface of the structure; corrosion rate monitoring is to continuously sense the corrosion rate of the environment by placing corrosion rate monitoring probes in the environment where the structure is located, so as to continuously track and evaluate the corrosion status of the entire structure. The main existing corrosion rate monitoring methods and the technical problems existing in the existing monitoring methods are:

[0004] (1) Resistance method (resistance probe): The metal probe changes in size due to corrosion, resulting in changes in resistance. However, it can only measure uniform corrosion. Local corrosion and pitting corrosion will significantly interfere with the judgment of corrosion rate, and the lifespan is short.

[0005] (2) Electrochemical method (linear polarization resistance, electrochemical noise, etc.): The instantaneous corrosion rate is quantified by electrochemical means, but the corrosion sensing ability of other types is weak. It can only be used in aqueous media and is easily affected by temperature and multiphase flow erosion. The detection results are highly discrete.

[0006] (3) Corrosion test piece method: The corrosion rate is quantified by the change in the mass of the test piece. Before the emergence of other methods, it was the gold standard for evaluating the corrosion rate. However, it needs to be taken out and weighed regularly, the test cycle is long, the process is cumbersome, and the labor cost is high.

[0007] Therefore, in response to the above situation, the present invention provides a new corrosion rate online monitoring technology solution with high precision, wide application range and strong anti-interference ability. Summary of the Invention

[0008] The main purpose of the present invention is to overcome the deficiencies in the prior art and provide a corrosion rate monitoring sensor.

[0009] The technical solution adopted by the present invention to achieve its technical purpose is: a corrosion rate monitoring sensor, the sensor comprising a corrosion rate sensing probe and a reference probe;

[0010] The corrosion rate sensing probe includes a strip piezoelectric piece and a strip corrosion piece;

[0011] The strip piezoelectric sheet and the strip corrosion sheet are bonded together with their longitudinal end faces and their longitudinal axes coincide with each other, thereby forming a corrosion rate sensing probe for sensing the corrosion rate of the medium;

[0012] The reference probe is consistent with the main body of the corrosion rate sensor probe, and its surface is coated with a wear-resistant and corrosion-resistant layer. The reference probe serves as a reference benchmark for the corrosion sensor probe and is used to eliminate the influence of environmental factors such as temperature;

[0013] The strip piezoelectric piece vibrates in a longitudinal vibration mode along the length direction under the excitation of alternating current and generates longitudinal vibration coupling with the strip corrosion piece, and only longitudinal vibration coupling exists within the frequency range of the alternating current excitation;

[0014] The relationship between the change in the minimum impedance frequency of the strip piezoelectric sheet and the mass loss of the strip corrosion sheet is as follows;

[0015] ;

[0016] Where, is the sensitivity coefficient; is the load factor; and Respectively represent the minimum impedance frequencies of the strip piezoelectric sheet 1 when it is mechanically connected and not connected to the strip corrosion sheet 2; is the stiffness of the strip piezoelectric piece 1; is the elastic compliance constant of the strip piezoelectric piece 1; is the mass loss of the strip corrosion piece; is the change in the minimum impedance frequency of the strip piezoelectric piece caused by the mass loss of the strip corrosion piece; The mass change of the strip corrosion piece can be calculated using the above formula.

[0017] Preferably, the length of the strip piezoelectric sheet is , the width is , the thickness is , satisfying: the length of the strip piezoelectric sheet is more than 2 times greater than its own width and thickness, that is, 、 ;

[0018] The thickness of the strip piezoelectric sheet is not less than 0.5 mm, the width is greater than or equal to the thickness, and the aspect ratio is not greater than 10, that is, mm, .

[0019] Preferably, the length of the strip-shaped corrosion piece is , the width is , and the thickness is , satisfying: the length, width and thickness of the strip-shaped corrosion piece are not more than 2 times the length, width and thickness of the strip-shaped piezoelectric piece, i.e. , , .

[0020] Preferably, it further comprises a temperature sensor, a protective sleeve, a sealing cover plate, a control box, a measurement and control circuit, and a battery.

[0021] The temperature sensor is integrated in a region on the surface of the strip-shaped piezoelectric piece without electrode coverage, and is used for abnormal temperature monitoring, and also for judging whether the corrosion rate monitoring result is valid and whether additional compensation is needed; the protective sleeve provides protection for the corrosion rate sensing probe and the reference probe, and the inner bottom surface is provided with a groove and a through hole for mounting the sensing probe and the lead wire, respectively; the sealing cover plate is used for sealing and waterproofing the protective sleeve, and the center is provided with a through hole for the probe to pass through; the control box is used for mounting the measurement and control circuit and the battery; the measurement and control circuit is used for excitation and electrical impedance characteristic acquisition of the strip-shaped piezoelectric piece, temperature data acquisition of the temperature sensor, signal processing and transmission; and the battery supplies power to the measurement and control circuit.

[0022] The measurement and control circuit comprises an MCU module, a sinusoidal signal generation module, a sinusoidal signal measurement module, an impedance calculation device, a temperature monitoring module and a wireless communication module.

[0023] The MCU module is used for comprehensive control and numerical calculation of the circuit, the sinusoidal signal generation module is used for AC excitation of the strip-shaped piezoelectric pieces in the corrosion rate sensing probe and the reference probe, the sinusoidal signal measurement module is used for measuring the AC signal passing through the strip-shaped piezoelectric pieces and obtaining a digital signal, the impedance calculation device is used for calculating the electrical impedance of the strip-shaped piezoelectric pieces based on the aforementioned digital signal, the temperature monitoring module is used for acquiring temperature sensor data, and the wireless communication module is used for transmitting the final result to the terminal and also for receiving terminal signals to realize initialization and necessary control of the entire measurement and control circuit.

[0024] Preferably, the AC excitation frequency of the strip-shaped piezoelectric piece is 0.1 kHz to 300 kHz, and the parameter used for tracking and quantifying the corrosion rate is the minimum impedance frequency in the electrical impedance characteristic curve of the strip-shaped piezoelectric piece.

[0025] Preferably, the piezoelectric material of the strip piezoelectric piece is not limited, and the arrangement of the excitation electrodes on the surface of the strip piezoelectric piece depends on the conditions for the piezoelectric material used to excite the longitudinal vibration mode.

[0026] Preferably, the strip corrosion sheet serves as a corrosion sensing test sheet, and the medium in the environment continuously corrodes the corrosion sheet, causing changes in its size and mass. The strip piezoelectric sheet mechanically connected to the corrosion sheet serves as a corrosion condition conversion element, which can convert the corrosion condition of the corrosion sheet into an electrical signal.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] In this corrosion rate monitoring sensor, the strip piezoelectric sheet and the strip corrosion sheet need to be bonded along the end faces of both along their length directions, and the axes of the two along their length directions need to coincide. The piezoelectric vibration of the strip piezoelectric sheet is a longitudinal vibration mode along the length direction, and its vibration coupling with the strip corrosion sheet is longitudinal vibration coupling, and only longitudinal vibration coupling exists within the AC excitation frequency range. The quantitative change in the mass of the strip corrosion sheet is obtained by calculating the change in the minimum impedance frequency of the strip piezoelectric sheet and a formula. It can be applied to a variety of corrosion conditions and environments, and has the advantages of high sensitivity, wide application range, and strong anti-interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 Schematic diagram of the corrosion rate sensor probe.

[0031] Figure 2 This is a data curve diagram of the theoretical results of the electrical impedance characteristics between the excitation electrodes of the piezoelectric piece in the corrosion rate sensor probe.

[0032] Figure 3 This is a data curve of the theoretical results of the relationship between the minimum impedance frequency of the piezoelectric piece in the corrosion rate sensor probe and the mass of the corrosion piece.

[0033] Figure 4 Schematic diagram of experimental verification of the sensing effect of the corrosion rate sensor probe.

[0034] Figure 5 This is the measured result of the relationship between the minimum impedance frequency of the piezoelectric piece and the mass loss of the corrosion piece in the corrosion rate sensor probe.

[0035] Figure 6 Schematic diagram of the overall structure of the corrosion rate monitoring sensor.

[0036] Figure 7 This is the measurement and control circuit and detection schematic diagram of the corrosion rate monitoring sensor.

[0037] Figure 8 This is the output result diagram of the real-time monitoring of the corrosion rate monitoring sensor.

[0038] Among them: 1. Strip piezoelectric piece; 2. Strip corrosion piece; 3. Control box; 4. Protective cover; 5. Closed cover. DETAILED DESCRIPTION

[0039] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0041] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and examples. However, it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0042] Example 1:

[0043] See also Figure 1-Figure 3 and Figure 6 , a corrosion rate monitoring sensor, the sensor includes a corrosion rate sensing probe and a reference probe.

[0044] The corrosion rate sensor probe includes a strip piezoelectric sheet 1 and a strip corrosion sheet 2. The strip piezoelectric sheet 1 and the strip corrosion sheet 2 are bonded together at their longitudinal end faces, with their longitudinal axes coinciding. This constitutes a corrosion rate sensor probe for sensing the corrosion rate of a medium. The piezoelectric material of the strip piezoelectric sheet 1 is not limited. The arrangement of the excitation electrodes on the surface of the strip piezoelectric sheet 1 depends on the conditions under which the piezoelectric material excites a longitudinal vibration mode. The strip corrosion sheet serves as a corrosion sensing test piece. The medium in the environment continuously corrodes the sheet, causing changes in its size and mass. The strip piezoelectric sheet, mechanically connected to the sheet, serves as a corrosion condition conversion element, capable of converting the corrosion condition of the sheet into an electrical signal.

[0045] The length of the strip piezoelectric piece 1 is , the width is , the thickness is , satisfying: the length of the strip piezoelectric sheet 1 is more than 2 times its own width and thickness, that is, 、 Wherein the thickness of the strip piezoelectric sheet 1 is not less than 0.5 mm, the width is greater than or equal to the thickness and the aspect ratio is not greater than 10, that is mm, .

[0046] The length of the strip corrosion plate 2 is , the width is , the thickness is , satisfying: the length, width and thickness of the strip corrosion sheet 2 are not greater than twice the length, width and thickness of the strip piezoelectric sheet 1, that is, 、 、 .

[0047] The reference probe is consistent with the corrosion rate sensor probe body, and its surface is coated with a wear-resistant and corrosion-resistant layer. The reference probe serves as a reference benchmark for the corrosion sensor probe and is used to eliminate the influence of environmental factors such as temperature.

[0048] The system also includes a temperature sensor, a protective cover 4, a closed cover plate 5, a control box 3, a measurement and control circuit, and a battery. The temperature sensor is integrated into an area of ​​the surface of the strip piezoelectric disc 1 that is not covered by electrodes. The temperature sensor is used to monitor abnormal temperatures and also to determine whether the corrosion rate monitoring results are valid and whether additional compensation is required. The protective cover 4 provides protection for the corrosion rate sensor probe and reference probe. Its inner bottom surface is provided with a groove and a through hole for installing the sensor probe and routing wires, respectively. The closed cover plate 5 is used to seal and waterproof the protective cover 4, and has a through hole in its center for the probe to pass through. The control box 3 is used to install the measurement and control circuit and battery. The measurement and control circuit is used to obtain the excitation and electrical impedance characteristics of the strip piezoelectric disc, acquire temperature data from the temperature sensor, and process and transmit signals. The battery provides power to the measurement and control circuit.

[0049] The surface of the strip piezoelectric sheet 1 is coated with two thin metal electrodes. Alternating current (AC) is applied to both electrodes. The AC excitation frequency ranges from 0.1kHz to 300kHz, and the parameter used to track and quantify the corrosion rate is the minimum impedance frequency in the electrical impedance characteristic curve of the strip piezoelectric sheet 1. Under the AC excitation, the strip piezoelectric sheet 1 vibrates in a longitudinal vibration mode along its length, generating longitudinal vibration coupling with the strip corroded sheet 2. This coupling only occurs in the longitudinal direction within the AC excitation frequency range. When the AC reaches a specific frequency, the piezoelectric sheet resonates.

[0050] Specifically, the mechanical vibration of the piezoelectric piece excites the adjacent, mechanically connected strip-shaped corroded piece 2. Conversely, the strip-shaped corroded piece 2 exerts a mechanical constraint on the piezoelectric piece. This change in constraint alters the resonant state of the piezoelectric piece, and the constraint is related to the deformation mode of the piezoelectric piece's resonance and the shape, size, and mass of the corroded piece. The corrosive medium corrodes the strip-shaped corroded piece 2, causing dimensional changes and mass loss, ultimately altering the resonant state of the piezoelectric piece mechanically connected to it. The resonant state can be reflected by the electrical impedance characteristics between the excitation electrodes.

[0051] The deformation of the piezoelectric sheet produced by the excitation of alternating current has various forms, and different single deformations will be coupled to form complex deformation modes, which will significantly reduce the accuracy and stability of corrosion rate sensing. Therefore, as a further optimization of this technical solution, the strip piezoelectric sheet 1 vibrates in a longitudinal vibration mode along the length direction under the excitation of alternating current. The vibration is transmitted into the corrosion sheet and produces longitudinal vibration coupling with the corrosion sheet, and only longitudinal vibration coupling exists within the frequency range of the AC excitation. In order to meet the above requirements, the dimensions and mechanical connection conditions of the strip piezoelectric sheet 1 and the strip corrosion sheet 2 are the same as before. At the same time, the arrangement of the excitation electrodes on the surface of the piezoelectric sheet must also meet the conditions for the piezoelectric material used to excite the longitudinal vibration mode.

[0052] The longitudinal vibration particle displacement of the strip piezoelectric piece 1 along the length direction is expressed as follows:

[0053] ;

[0054] Where, is the particle displacement function in the length direction of the strip piezoelectric piece 1; is the wave number; is the angular frequency; is the longitudinal wave velocity in the length direction of the strip piezoelectric piece 1; and are the elastic compliance constant and density of the strip piezoelectric piece 1 respectively; and is an undetermined coefficient, which is determined by the force balance condition at the mechanical connection between the piezoelectric piece and the corrosion piece. The admittance Y between the electrodes on the surface of the piezoelectric sheet is obtained from the piezoelectric constitutive equation of the piezoelectric sheet as follows:

[0055] ;

[0056] Where, is the imaginary number symbol; is the electromechanical coupling coefficient; and are the dielectric constant and piezoelectric constant of the strip piezoelectric piece 1; is the electrostatic capacitance between the excitation electrodes on the surface of the strip piezoelectric piece 1; and are the displacements at the two end points in the length direction of the strip piezoelectric piece 1; is the intensity of the excitation electric field. The electrical impedance of the piezoelectric piece and the corrosion piece after mechanical connection is obtained (The reciprocal of admittance ) Theoretical results are as follows Figure 2 As shown. The electrical impedance between the piezoelectric excitation electrodes is closely related to the frequency of AC excitation. There is a minimum point and a maximum point in the electrical impedance characteristic curve. The frequencies corresponding to the two are called the minimum impedance frequency and the maximum impedance frequency, respectively. When the frequency of AC excitation is near the minimum impedance frequency, the vibration intensity of the piezoelectric piece reaches the maximum, that is, resonance. Therefore, the minimum impedance frequency can well reflect the resonant state of the piezoelectric piece. The theoretical results of the relationship between the minimum impedance frequency and the mass of the corrosion piece are shown as follows: Figure 3 As shown in the figure, the minimum impedance frequency of the piezoelectric piece is approximately linearly related to the mass of the corrosion piece.

[0057] Based on the above formula, after simplification and approximation according to the resonance conditions, the relationship between the change in the minimum impedance frequency of the strip piezoelectric piece 1 and the mass loss of the strip corroded piece 2 can be obtained as follows:

[0058] ;

[0059] Where, is the sensitivity coefficient; is the load factor; and Respectively represent the minimum impedance frequencies of the strip piezoelectric sheet 1 when it is mechanically connected and not connected to the strip corrosion sheet 2; is the stiffness of the strip piezoelectric piece 1; is the mass loss of the strip corrosion piece 2; is the change in the minimum impedance frequency of the strip piezoelectric piece 1 caused by the mass loss of the strip corrosion piece 2; The mass change of the strip corrosion sheet 2 can be calculated using the above formula.

[0060] Example 2:

[0061] Referring to Figure 4-Figure 8 , on the basis of the above embodiment, the corrosion rate monitoring sensor is verified by electrochemical corrosion experiment to verify the actual effect of the present application, the experimental setup is as shown in Figure 4 . The piezoelectric material used in the piezoelectric sheet is lead zirconate titanate (PZT), thin metal electrodes are arranged on the upper and lower surfaces of the polarization direction of the strip-shaped PZT sheet, and wires are welded at the center of the electrodes. The strip-shaped PZT sheet and the strip-shaped corrosion sheet 2 are bonded by epoxy resin glue at the lengthwise end surface to form a corrosion rate sensor probe, it should be noted that the lengthwise axes of the two should coincide. The corrosion sheet end is connected to a direct current power supply and immersed in a NaCl solution, while the copper sheet is connected to a direct current power supply and immersed in a NaCl solution, the direct current power supply is turned on to realize electrochemical corrosion of the corrosion sheet. The sensor probe is taken out every certain period of time, the residues on the surface of the corrosion sheet are removed and the mass change of the corrosion sheet is obtained by a balance, the wires connected to the surface electrodes of the PZT sheet are connected to an impedance analyzer to detect the electrical impedance characteristics of the PZT sheet and obtain the minimum impedance frequency. The relationship between the minimum impedance frequency and the mass loss of the corrosion sheet is shown in Figure 5 , from the figure it can be seen that with the increase of the mass loss of the corrosion sheet, the minimum impedance frequency of the PZT sheet increases linearly with the mass loss of the corrosion sheet, which is consistent with the trend of the foregoing theoretical results.

[0062] As shown in Figure 6 , the overall structure of the corrosion rate monitoring sensor is shown. The strip-shaped piezoelectric sheet 1 and the strip-shaped corrosion sheet 2 are bonded by high-strength glue at the lengthwise end surface to form a corrosion rate sensor probe, and the temperature sensor is integrated on the surface of the strip-shaped piezoelectric sheet 1 without electrode coverage. As a further optimization of the present application, a reference probe is also needed, the difference between the reference probe and the corrosion sensor probe is that the surface of the reference probe is coated with a layer of corrosion and wear resistant layer, which is not affected by the medium corrosion effect, and is used as a reference for the corrosion sensor probe to exclude environmental interference such as temperature and fluid impact. The piezoelectric sheet ends of the corrosion sensor probe and the reference probe are respectively inserted into the grooves in the bottom surface of the protective sleeve 4, and the two are fixed by epoxy resin glue; the wires connected to the surface electrodes of the piezoelectric sheet and the wires of the temperature sensor are led out through the through holes in the bottom surface of the protective sleeve 4 and connected to the measurement and control circuit installed in the control box 3, then the control box 3 and the protective sleeve 4 are assembled; appropriate sponge is filled in the protective sleeve 4 and waterproof glue is used to realize the closure of the protective sleeve 4, the gap between the corrosion sensor probe and the reference probe and the through hole of the closure cover plate 5 is filled with waterproof glue to realize waterproof sealing.

[0063] As shown in Figure 7As shown, the measurement and control circuit and detection schematic diagram of the corrosion rate monitoring sensor. The measurement and control circuit includes: MCU module, sine signal generation module, sine signal measurement module, impedance calculation device, temperature monitoring module and wireless communication module; the MCU module is used for comprehensive control of the circuit, sends instructions to the sine signal generation module, so that it generates a sine signal that meets the requirements according to the instructions, and simultaneously excites the piezoelectric sheet in the corrosion rate sensor probe and the reference probe with alternating current in two ways; the sine signal measurement module tests the alternating current signal passing through the piezoelectric sheet and obtains a digital signal through analog-to-digital conversion, which is sent to the impedance calculation device to calculate the impedance of the corrosion rate sensor probe and the reference probe under different electric excitation frequencies, and then the MCU calculates the minimum impedance frequency of the corrosion rate sensor probe and the reference probe and the difference between them, and then calculates the mass loss of the corrosion sheet in the corrosion rate sensor probe due to corrosion based on the foregoing formula. The temperature monitoring module is used to obtain the data of the temperature sensor integrated in the corrosion rate sensor probe and the reference probe and transmit it to the MCU, and then judge whether there is an abnormal situation according to the temperature data, and whether the data obtained by the corrosion rate sensor probe and the reference probe is valid and whether additional compensation is needed. Finally, the MCU transmits the processed data to the terminal through the wireless communication module. The wireless communication module is not only used for transmitting test results to the terminal, but also used for receiving terminal signals to transmit to the MCU module to realize initialization and necessary control of the whole measurement and control circuit.

[0064] The scheme in this embodiment can be selectively combined with the scheme in other embodiments.

[0065] The working principle and specific use process of the corrosion rate monitoring sensor are as follows:

[0066] The corrosion rate monitoring sensor as shown in Figure 6 is powered on, and the sensitivity coefficient , the frequency , and the stiffness properties of the bar-shaped piezoelectric sheet 1 are input according to the type of the sensor probe . The measurement and control circuit automatically completes the sensitivity calibration of the sensor probe according to the foregoing formula; the sensor is installed at a suitable position in the area to be measured. It should be noted that the corrosion rate sensor probe and the reference probe need to be immersed in the medium to be measured at the same time. In addition, if the medium has a certain flow effect in a certain direction, the sensor probe and the reference probe need to be parallel to the direction of the medium flow. The measurement and control circuit monitors the sensor probe, the reference probe and the temperature sensor in real time for a period of time, and after confirming that the temperature and other environmental factors of the medium to be measured are in a stable state, the measurement and control circuit averages the minimum impedance frequency in this period of time, and then processes the difference between the minimum impedance frequency of the reference probe and the monitoring probe to obtain the corrosion rate of the medium to be measured , This is the initial zero point of the sensor, and the initialization of the sensor is completed. As the medium corrodes the corrosion plate of the sensor probe, it gradually loses mass, and the minimum impedance frequency of the piezoelectric plate will gradually increase. The reference probe does not lose mass because it has a wear-resistant and corrosion-resistant layer on its surface. Therefore, the change in the minimum impedance frequency of the piezoelectric plate in the reference probe is mainly caused by environmental factors such as temperature. The measurement and control circuit automatically calculates the relative change in the minimum impedance frequency of the piezoelectric plate in the sensor probe based on the minimum impedance frequency of the piezoelectric plate in the reference probe. , frequency change It is the minimum impedance frequency change caused by the mass loss of the corrosion piece in the sensor probe; the measurement and control circuit automatically detects the The mass loss of the corrosion sheet in the sensor probe due to corrosion within a certain period of time is calculated using the aforementioned formula to obtain the corrosion rate of the medium within that period of time. Finally, the temperature sensor data is combined to determine whether the result is valid and whether additional temperature compensation is required.

[0067] According to actual needs, the measurement and control circuit can detect in real time or at intervals. When the corrosion of the corrosive medium on the corrosion plate is relatively stable, the output of the sensor will be Figure 8 The results shown are as follows: the right axis is the frequency change , and the left axis is the mass loss calculated based on the above formula.

[0068] It should be noted that although the above embodiments have been described herein, this does not limit the scope of patent protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structures, equivalent processes, or equivalent functional transformations made using the contents of the present invention's specification and drawings, and direct or indirect application of the above technical solutions to other related technical fields, are all included in the scope of protection of the present invention's patent.

Claims

1. A corrosion rate monitoring sensor, characterized in that: The sensor comprises a corrosion rate sensing probe, a reference probe, a temperature sensor, a protective cover (4), a sealing cover (5), a control box (3), a measurement and control circuit, and a battery; The corrosion rate sensing probe comprises a strip piezoelectric piece (1) and a strip corrosion piece (2); The strip-shaped piezoelectric sheet (1) and the strip-shaped corrosion sheet (2) are bonded together with their end faces in the longitudinal direction, and their longitudinal axes coincide with each other; The reference probe is consistent with the corrosion rate sensor probe body, and its surface is coated with a wear-resistant and corrosion-resistant layer; The strip piezoelectric sheet (1) vibrates in a longitudinal vibration mode along the length direction under the excitation of alternating current and generates longitudinal vibration coupling with the strip corrosion sheet (2), and only longitudinal vibration coupling exists within the frequency range of the alternating current excitation; The relationship between the change in the minimum impedance frequency of the strip piezoelectric piece (1) and the mass loss of the strip corrosion piece (2) is as follows; ； Where, is the sensitivity coefficient; is the load factor; and represent the minimum impedance frequencies of the strip piezoelectric piece (1) when it is mechanically connected and when it is not connected to the strip corrosion piece (2); is the stiffness of the strip piezoelectric piece (1); is the elastic compliance constant of the strip piezoelectric piece (1); 、 、 are the length, width and thickness of the strip piezoelectric sheet (1) respectively; is the mass loss of the strip corrosion piece (2); is the change in the minimum impedance frequency of the strip piezoelectric piece (1) caused by the mass loss of the strip corrosion piece (2); The mass change of the strip corrosion piece (2) can be calculated by the above formula; The length of the strip piezoelectric piece (1) is , the width is , the thickness is ,satisfy: 、 ;in mm, ; The length of the strip corrosion sheet (2) is , the width is , the thickness is ,satisfy: 、 、 .

2. A corrosion rate monitoring sensor according to claim 1, characterized in that: The temperature sensor is integrated in an area of ​​the surface of the strip piezoelectric piece (1) that is not covered by electrodes; the protective cover (4) provides protection for the corrosion rate sensing probe and the reference probe, and its inner bottom surface is provided with a groove and a through hole for installing the sensing probe and leading the wire respectively; the closed cover (5) is used to seal and waterproof the protective cover (4), and a through hole is provided in the center thereof for the probe to pass through; the control box (3) is used to install a measurement and control circuit and a battery; the measurement and control circuit is used to obtain the excitation and electrical impedance characteristics of the strip piezoelectric piece (1), obtain temperature data of the temperature sensor, and process and transmit signals; the battery supplies power to the measurement and control circuit.

3. A corrosion rate monitoring sensor according to claim 1, characterized in that: The measurement and control circuit includes: an MCU single chip computer module, a sinusoidal signal generating module, a sinusoidal signal measuring module, an impedance calculating device, a temperature monitoring module and a wireless communication module; The MCU single-chip computer module is used for comprehensive control and numerical calculation of the circuit, the sinusoidal signal generating module is used to perform AC excitation on the strip piezoelectric pieces in the corrosion rate sensing probe and the reference probe, the sinusoidal signal measuring module is used to measure the AC signal passing through the strip piezoelectric piece and obtain a digital signal, the impedance calculating device is used to calculate the electrical impedance of the strip piezoelectric piece based on the aforementioned digital signal, the temperature monitoring module is used to obtain temperature sensor data, the wireless communication module is used to transmit the final result to the terminal, and is also used to receive terminal signals to realize initialization and control of the entire measurement and control circuit.

4. The corrosion rate monitoring sensor according to claim 1, characterized in that: The AC excitation frequency of the strip piezoelectric piece (1) is 0.1 kHz to 300 kHz, and the parameter used to track and quantify the corrosion rate is the minimum impedance frequency in the electrical impedance characteristic curve of the strip piezoelectric piece (1).

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