A corrosion sensor and monitoring method for steel structures in ocean splash zones

Abstract

The present application relates to the technical field of testing or analyzing materials by measuring the chemical or physical properties of the materials, and specifically to a marine splash zone steel structure corrosion sensor and monitoring method, the sensor comprising a single-mode optical fiber, on which a plurality of long-period gratings and temperature compensation gratings are inscribed at intervals, the positions of the single-mode optical fiber with the long-period gratings being electroplated with an iron-carbon coating, the positions of the single-mode optical fiber with the long-period gratings being connected to a packaging protection component, and the long-period gratings and the temperature compensation gratings being connected to a demodulator via a transmission optical cable. The present application solves the problem in the prior art that optical fiber corrosion sensors for detecting steel structure corrosion have a short service life and cannot achieve multi-point monitoring.

Description

Technical Field

[0001] The present application relates to the technical field of testing or analyzing materials by means of measuring the chemical or physical properties of the materials, and in particular to a corrosion sensor and monitoring method for steel structures in an ocean splash zone. Background Art

[0002] Existing corrosion monitoring technology is mainly based on electrochemical principles, and the degree and state of corrosion of steel structures are determined by monitoring the potential changes of steel structures during the corrosion process. However, this method requires that the component to be tested and the reference electrode are placed in the electrolyte at the same time, that is, the circuit connection between the component and the electrode is kept at all times. The marine corrosion environment is divided into atmospheric zone, tidal zone, splash zone, underwater zone and other parts. Among them, the splash zone is affected by factors such as random scouring of waves, rich oxygen, and alternating dry and wet conditions. The corrosion of steel structures in this area is the most serious, threatening the safety of the structure. However, traditional electrochemical corrosion monitoring methods cannot be applied in the splash zone because the characteristics of alternating dry and wet cannot provide stable circuit connection conditions for components and electrodes. At the same time, the electrochemical method usually only monitors one measuring point, and the corrosion monitoring data obtained is difficult to fully reflect the corrosion state of the structure.

[0003] The corrosion monitoring method based on fiber grating sensors utilizes the sensitivity of long-period fiber gratings to the ambient refractive index to achieve corrosion monitoring by monitoring the refractive index changes of steel pipe piles during the corrosion process. However, the working life of this sensor is short, and this method cannot determine whether it can be used to monitor multiple corrosion points in steel pipe piles. Summary of the Invention

[0004] The purpose of this application is to provide a marine splash zone steel structure corrosion sensor and monitoring method, which solves the problem that the optical fiber corrosion sensor used in the prior art to detect steel structure corrosion has a short working life and cannot achieve multi-point monitoring.

[0005] The technical solution of this application:

[0006] The present application provides a marine splash zone steel structure corrosion sensor, which includes a single-mode optical fiber, on which a plurality of long-period gratings and temperature compensation gratings are inscribed at intervals, and the positions of the single-mode optical fiber with the long-period gratings are electroplated with an iron-carbon coating, and the positions of the single-mode optical fiber with the long-period gratings are connected to a packaging protection component, and the long-period grating and the temperature compensation grating are connected to a demodulator via a transmission optical cable.

[0007] In some embodiments, the packaging and protection assembly includes a packaging box having an opening and a sacrificial plate for closing the opening of the packaging box, and a plurality of sacrificial plates have different thicknesses.

[0008] In some embodiments, the material of the sacrificial plate and the iron-carbon coating are the same as the material of the steel structure to be inspected.

[0009] In some embodiments, the number of the long-period grating and the temperature compensation grating are both equal to the total etching depth divided by 1 mm.

[0010] According to another aspect of the present application, a method for monitoring corrosion of steel structures in an ocean splash zone comprises:

[0011] Acquire the spectral data of the long-period grating and temperature-compensated grating at the target rigid object;

[0012] Get the time t0 of corrosion penetration at the thinnest part of the sacrificial plate;

[0013] The thickness of the thinnest sacrificial plate is marked as d1;

[0014] Obtain the time t1 of spectrum drift at each point on the target steel object;

[0015] Based on t0 and t1, the average corrosion rate V1 is calculated using the following formula:

[0016] Calculate the instantaneous corrosion rate V1' based on the average corrosion rate V1;

[0017] Calculate the corrosion rate data of each point on the target steel material;

[0018] The corrosion rate data of all points were fitted with Weibull distribution to obtain the corrosion rate monitoring results corresponding to the monitoring data.

[0019] In some embodiments, the calculation of the corrosion rate data for each point on the target steel object is specifically performed by calculating the thickness of the sacrificial plate in order from thin to thick.

[0020] In some embodiments, the Weibull distribution fitting of all point corrosion rate data is specifically performed by sequentially inputting the corrosion rate data of the target steel point into the Weibull distribution model for fitting. The Weibull distribution formula is:

[0021]

[0022] Where: r(t) is the corrosion rate, d ∞ is the target steel material thickness, t is the time, T st is the translation parameter, β is the shape parameter to be fitted, and η is the scale parameter to be fitted.

[0023] In some embodiments, during the Weibull distribution fitting process, the Weibull distribution is made adaptive by changing the scale parameter and the shape parameter.

[0024] In some embodiments, when the iron-carbon coating on the surface of the single-mode optical fiber corrodes, the refractive index of the coating changes, causing the resonant wavelengths of the long-period grating and the temperature-compensated grating to drift. The corrosion monitoring process is achieved by converting spectral data of the wavelength changes of the long-period grating and the temperature-compensated grating into corrosion efficiency.

[0025] In some embodiments, the conversion of spectral data into corrosion rate is specifically as follows: a curve of the relationship between wavelength drift and time is established according to wavelength change, a curve of the relationship between corrosion rate and time is established according to electrochemical testing, and the relationship between wavelength change and corrosion rate is converted through time alignment.

[0026] The technical solution of this application has at least the following advantages and beneficial effects:

[0027] The present application provides a marine splash zone steel structure corrosion sensor, which inscribes a long-period grating and a temperature compensation grating on a single-mode optical fiber, and electroplates an iron-carbon coating on the long-period grating, thereby improving the sensitivity of the entire sensor; then, by setting a packaging protection component, the service life of the entire sensor is improved. At the same time, the set packaging protection component can also protect the long-period grating and the temperature compensation grating. By setting multiple long-period gratings and multiple temperature compensation gratings and equipping them with corresponding packaging protection components, multi-point monitoring can be achieved. At the same time, the service life of all long-period gratings and temperature compensation gratings can be effectively extended, and the monitoring time can be extended, which solves the problem in the prior art that the optical fiber corrosion sensor for detecting steel structure corrosion has a short service life and cannot achieve multi-point monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the structure of the sensor in this application;

[0029] Figure 2 This is a flow chart of the monitoring method in this application;

[0030] Figure 3 This is an example diagram of the adaptive curve of the Weibull distribution model under different corrosion intensities in the embodiment of the present application;

[0031] Figure 4 This is a graph showing the relationship between wavelength drift and time in the embodiment of the present application;

[0032] Figure 5 This is a graph showing the relationship between corrosion rate and time in the embodiment of the present application;

[0033] Figure 6 This is a graph showing the relationship between wavelength change and corrosion rate in the embodiment of this application.

[0034] In the figure: 1-single-mode optical fiber; 2-long-period grating; 3-temperature compensation grating; 4-packaging box; 5-sacrificial plate. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0036] Example 1

[0037] Please refer to Figure 1 This embodiment provides a marine splash zone steel structure corrosion sensor, which includes a single-mode optical fiber 1, on which a plurality of long-period gratings 2 and temperature compensation gratings 3 are inscribed at intervals, and the position of the single-mode optical fiber 1 with the long-period grating 2 is electroplated with an iron-carbon coating, and the position of the single-mode optical fiber 1 with the long-period grating 2 is connected to a packaging protection component, and the long-period grating 2 and the temperature compensation grating 3 are connected to a demodulator via a transmission optical cable.

[0038] It is worth noting that the fiber Bragg grating sensors in the prior art have a short service life and the gratings are fragile and easily damaged. On the other hand, the corrosion of steel pipe piles often occurs simultaneously at multiple points, and the degree of corrosion is often different. The simultaneous corrosion of multiple points will have a direct impact on the corrosion efficiency of the entire steel pipe pile. This embodiment provides a method for monitoring the corrosion of steel structures in the ocean splash zone. A long-period grating 2 and a temperature compensation grating 3 are inscribed on a single-mode optical fiber 1, and an iron-carbon coating is electroplated on the long-period grating 2 to improve the sensitivity of the entire sensor. Then, by providing a packaging protection component, the service life of the entire sensor is improved. At the same time, the provided packaging protection component can also protect the long-period grating 2 and the temperature compensation grating 3. Furthermore, the present embodiment arranges a plurality of long-period gratings 2 and a plurality of temperature compensation gratings 3 and equips them with corresponding packaging protection components, which can realize multi-point monitoring while effectively extending the service life of all long-period gratings 2 and temperature compensation gratings 3 and extending the monitoring time. The present embodiment effectively solves the problem in the prior art that the optical fiber corrosion sensor for detecting steel structure corrosion has a short working life and cannot realize multi-point monitoring.

[0039] It is worth noting that the long-period grating 2 and the temperature compensation grating 3 are connected to a demodulator via a transmission optical cable. Compared with the prior art, the sensor provided in this embodiment can simultaneously obtain data from multiple monitoring points by connecting the entire sensor to a demodulator, thereby further realizing multi-point monitoring.

[0040] On the other hand, the corrosion monitoring method based on fiber Bragg grating sensors utilizes the strain-sensitive characteristics of fiber Bragg grating sensors to monitor the strain caused by the volume expansion of the structure caused by corrosion products, thereby realizing corrosion monitoring. However, for steel structures, the source of strain is not only corrosion, but also the load it bears under normal service, and the strain caused by the load is much larger than the corrosion strain. Therefore, this method has poor sensitivity and large errors in the monitoring results. Compared with the existing technology, this embodiment realizes corrosion monitoring by monitoring the refractive index change of the steel structure. The sensor no longer needs to monitor the strain of the steel, avoiding the errors caused by strain monitoring, and solving the problem of large errors in the monitoring results in the existing technology.

[0041] It should be noted that the arrangement of monitoring points is determined according to the shape of the steel structure being measured. For example, for a circular steel pipe pile, four measuring points can be arranged, one every 90 degrees, forming a circle.

[0042] In some embodiments, the packaging and protection assembly includes a packaging box 4 having an opening and a sacrificial plate 5 for closing the opening of the packaging box 4 , and the thicknesses of the plurality of sacrificial plates 5 are different.

[0043] It should be noted that sacrificial plate 5 is a steel sheet made of the same material and composition as the steel structure to be measured. The thickness and number of measuring points on the steel sheet sacrificial plate 5 can be adjusted based on actual monitoring needs. The steel sheet sacrificial plate 5 not only protects the long-period grating 2 and temperature-compensation grating 3, but also provides additional corrosion rate monitoring data and extends the operating life of the entire sensor. Each set of long-period grating 2 and temperature-compensation grating 3 is configured with a different sacrificial plate 5 thickness, enabling the refractive index-sensitized grating to monitor the corrosion rate of the steel structure at different corrosion depths.

[0044] It is worth noting that, under the accelerated corrosion test conditions of a current density of 500 μA per square centimeter, the corrosion life of the sacrificial plate 5, i.e., the steel plate, is extended by an average of 7 days for every 0.25 mm increase in thickness.

[0045] It is worth noting that the corrosion monitoring data is obtained from the spectral changes of the fiber Bragg grating. The extension of the service life of the long-period grating 2 and the temperature compensation grating 3 is achieved by the set sacrificial plate 5. When the sacrificial plate 5 is corroded and penetrated, the optical fiber sensor inside the box starts to work. When the iron-carbon coating electroplated on the surface of the long-period grating 2 corrodes, the refractive index of the coating will change, which will cause the resonant wavelength of the fiber Bragg grating to drift, realizing the process of monitoring corrosion through wavelength changes.

[0046] In some embodiments, the material of the sacrificial plate 5 and the iron-carbon coating are the same as that of the steel structure to be inspected. By making the material composition of the sacrificial plate 5 and the iron-carbon coating identical to that of the steel structure to be inspected, the sacrificial plate 5 and the iron-carbon coating are likely to corrode at the same rate as the steel structure, thereby avoiding the problem of large errors in monitoring results caused by the different corrosion rates of the sacrificial plate 5 and the iron-carbon coating compared to the steel structure.

[0047] Preferably, the packaging box 4 is made of acrylic.

[0048] In some embodiments, the number of the long-period gratings 2 and the temperature compensation gratings 3 are both equal to the total etching depth divided by 1 mm.

[0049] It should be noted that the number of groups of the long-period grating 2 and the temperature compensation grating 3 is determined by dividing the total corrosion depth by 1 mm. For example, if a corrosion depth of 5 mm needs to be monitored, a total of five groups are set up, that is, every time 1 mm of corrosion occurs, the sensor will return a change in the monitoring value, and the system will know that the steel at that location has corroded by one millimeter.

[0050] Example 2

[0051] Please refer to Figure 2 and Figure 3 In order to better illustrate the present application and facilitate understanding, the present application also proposes a method for monitoring corrosion of steel structures in an ocean splash zone, comprising:

[0052] Acquire spectral data of the long-period grating 2 and the temperature compensation grating 3 at a point on the target rigid object;

[0053] Obtain the time t0 of corrosion penetration at the thinnest part of the sacrificial plate 5;

[0054] The sacrificial plate 5 with the thinnest thickness is marked as d1;

[0055] Obtain the time t1 of spectrum drift at each point on the target steel object;

[0056] Based on t0 and t1, the average corrosion rate V1 is calculated using the following formula:

[0057] Calculate the instantaneous corrosion rate V1' based on the average corrosion rate V1;

[0058] Calculate the corrosion rate data of each point on the target steel material;

[0059] The corrosion rate data of all points were fitted with Weibull distribution to obtain the corrosion rate monitoring results corresponding to the monitoring data.

[0060] It should be noted that the specific working process of this method is:

[0061] When the sensor is placed in a corrosive environment, the entire monitoring system begins to monitor corrosion. This time point is t0, at which point all the sacrificial steel plates 5 begin to corrode. When the thinnest sacrificial steel plate 5 (thickness d1) is corroded through, the corrosion depth is recorded as d1. Then, the iron-carbon coated long-period grating 2 inside it contacts the corrosive environment of the splash zone and starts working, and the spectrum begins to drift. The time point of spectrum drift is t1. Based on t0, t1, and d1, the average corrosion rate V1 from t0 to t1 can be obtained. The specific formula for the average corrosion rate V1 is:

[0062] Then, the instantaneous corrosion rate V1' of the iron-carbon coated long period grating 2 inside the packaging box 4 after the time point t1 can be measured, and the instantaneous corrosion rate V1' of the remaining iron-carbon coated long period grating 2 points after the time point t1 can be calculated in the same way;

[0063] Finally, the Weibull distribution was fitted to the corrosion rate data at all points to obtain the corrosion rate monitoring results corresponding to the monitoring data, realizing high-sensitivity multi-point corrosion monitoring of steel structures in the splash zone, further effectively solving the problem that multi-point monitoring of steel structure corrosion cannot be achieved in the existing technology.

[0064] In some embodiments, the corrosion rate data for each point on the target steel material is calculated by calculating the thickness of the sacrificial plate 5 from thinnest to thickest. Specifically, the instantaneous corrosion rate V1' of the iron-carbon-coated long-period grating 2 within the packaging box 4 after time point t1 can be measured. Similarly, the instantaneous corrosion rate V1' of the remaining iron-carbon-coated long-period grating 2 points is calculated in ascending order of the thickness of the sacrificial plate 5 on the steel sheet. This method not only simultaneously monitors the corrosion status of multiple points but also determines the order in which each point corrodes, thereby improving monitoring effectiveness.

[0065] In some embodiments, the Weibull distribution fitting of all point corrosion rate data is specifically performed by sequentially inputting the corrosion rate data of the target steel point into the Weibull distribution model for fitting. The Weibull distribution formula is:

[0066]

[0067] Where: r(t) is the corrosion rate; d ∞ is the target rigid material thickness; t is the time; T st is the translation parameter; β is the shape parameter to be fitted, and η is the scale parameter to be fitted

[0068] Detailed, T st is the translation parameter, i.e. the starting time when the corrosion sacrificial plate 5 fails or is penetrated. For the target rigid object without sacrificial plate 5, T st=0.

[0069] In some embodiments, during the Weibull distribution fitting process, the Weibull distribution is made adaptive by changing the scale parameter and the shape parameter.

[0070] It is worth noting that the Weibull distribution has adaptive characteristics and can adaptively monitor data and provide corrosion rate monitoring results through changes in scale parameters and shape parameters. Figure 3 As shown in the figure, a, b, and c represent three different corrosion intensities. When the corrosion intensities are different, the Weibull distribution can be adaptively fitted by changing the scale parameter and shape parameter. The specific parameters are 0.0156, 0.0164 and 1.25, 1.29. It can be seen that a good fitting effect is achieved under different corrosion intensities.

[0071] In some embodiments, when the iron-carbon coating on the surface of the single-mode optical fiber 1 corrodes, the refractive index of the coating changes, causing the resonant wavelengths of the long-period grating 2 and the temperature-compensating grating 3 to drift. The corrosion monitoring process is achieved by converting the spectral data of the wavelength changes of the long-period grating 2 and the temperature-compensating grating 3 into corrosion efficiency.

[0072] In some embodiments, the conversion of spectral data into corrosion rate is specifically as follows: a curve of the relationship between wavelength drift and time is established based on wavelength changes, a curve of the relationship between corrosion rate and time is established based on electrochemical testing, and the relationship between wavelength change and corrosion rate is converted through time alignment.

[0073] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic features of the present application. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and range of equivalents of the claims are included in the present application. Any figure mark in the claims should not be construed as limiting the claim to which it relates.

[0074] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A marine splash zone steel structure corrosion sensor, characterized in that: include: A single-mode optical fiber (1) is provided, wherein a plurality of long-period gratings (2) and temperature compensation gratings (3) are inscribed on the single-mode optical fiber (1) at intervals, wherein the number of the long-period gratings (2) and the temperature compensation gratings (3) is equal to the total corrosion depth divided by 1 mm, wherein the position of the long-period grating (2) on the single-mode optical fiber (1) is electroplated with an iron-carbon coating, and the position of the long-period grating (2) on the single-mode optical fiber (1) is connected with a packaging protection component; the packaging protection component comprises a packaging box (4) with an opening and a sacrificial plate (5) for sealing the opening of the packaging box (4), wherein the thickness of the plurality of sacrificial plates (5) is different, and the material of the sacrificial plate (5) and the iron-carbon coating are the same as the material of the steel structure to be detected; the long-period grating (2) and the temperature compensation grating (3) are connected to a demodulator via a transmission optical cable.

2. A method for monitoring corrosion of steel structures in the ocean splash zone based on the ocean splash zone steel structure corrosion sensor according to claim 1, characterized in that: include: Acquiring spectral data of a point-position long-period grating (2) and a temperature compensation grating (3) on a steel structure corrosion sensor in an ocean splash zone; Obtain the time of corrosion penetration at the thinnest point of the sacrificial plate (5) ; The thickness of the thinnest sacrificial plate (5) is ; Obtain the time when spectral drift occurs at each point on the steel structure corrosion sensor in the ocean splash zone ; based on and , calculate the average corrosion rate , the specific formula is: ; Based on average corrosion rate Calculate the instantaneous corrosion rate ; Calculate the corrosion rate data of each point on the steel structure corrosion sensor in the ocean splash zone; The corrosion rate data of all points were fitted with Weibull distribution to obtain the corrosion rate monitoring results corresponding to the monitoring data.

3. The monitoring method according to claim 2, characterized in that: The calculation of the corrosion rate data of each point on the steel structure corrosion sensor in the ocean splash zone is specifically as follows: the thickness of the sacrificial plate (5) is calculated in order from thin to thick.

4. The monitoring method according to claim 3, characterized in that: During the Weibull distribution fitting process, the Weibull distribution is made self-adaptive by changing the scale parameter and the shape parameter.

5. The monitoring method according to claim 2, characterized in that: When the iron-carbon coating on the surface of the single-mode optical fiber (1) corrodes, the coating's refractive index changes, causing the resonance wavelengths of the long-period grating (2) and the temperature-compensating grating (3) to drift. The corrosion monitoring process is achieved by converting spectral data of the wavelength changes of the long-period grating (2) and the temperature-compensating grating (3) into corrosion efficiency.

6. The monitoring method according to claim 5, characterized in that: The conversion of spectral data into corrosion rate is specifically as follows: establishing a wavelength drift versus time curve based on wavelength change, establishing a corrosion rate versus time curve based on electrochemical testing, and converting the wavelength change versus corrosion rate relationship through time alignment.

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