Ocean splash zone steel structure corrosion sensor and monitoring method

Abstract

The invention relates to the technical field of testing or analyzing materials by means of measuring chemical or physical properties of materials, in particular to an ocean splash zone steel structure corrosion sensor and a monitoring method.The sensor comprises a single-mode optical fiber, and a plurality of long-period optical gratings and temperature compensation optical gratings are inscribed on the single-mode optical fiber at intervals; the position, provided with the long-period grating, of the single-mode optical fiber is electroplated with an iron-carbon coating, the position, provided with the long-period grating, of the single-mode optical fiber is connected with a packaging protection assembly, and the long-period grating and the temperature compensation grating are connected to a demodulator through a transmission optical cable. The problems that in the prior art, an optical fiber corrosion sensor for detecting corrosion of a steel structure is short in service life and cannot achieve multi-point monitoring are solved.

Description

Technical Field

[0001] The present application relates to the technical field of testing or analyzing materials by means of determining the chemical or physical properties of 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 be 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 the 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, abundant oxygen, and alternating dry and wet. 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 sensor utilizes the sensitive property of long-period fiber grating to the environmental refractive index to realize corrosion monitoring by monitoring the refractive index change of steel pipe piles during the corrosion process. However, the working life of the sensor is short, and this method cannot determine whether it can be used to monitor multiple points of corrosion in steel pipe piles. Summary of the invention

[0004] The purpose of the present 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, an iron-carbon coating is electroplated at the position of the single-mode optical fiber with the long-period grating, a packaging protection component is connected to the position of the single-mode optical fiber with the long-period grating, 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 protection component 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 number of the temperature compensation grating are both 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 point long period grating and temperature compensation grating on 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 occurrence time t1 of the spectrum drift at each point on the target rigid 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 object;

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

[0019] In some embodiments, the calculation of the corrosion rate data of each point on the target rigid object is specifically: 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 as follows: the corrosion rate data of the points on the target rigid material are sequentially input 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 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.

[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 wavelength of the long-period grating and the temperature compensation 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 compensation 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 changes, a curve of the relationship between corrosion rate and time is established according to electrochemical tests, and the relationship between wavelength change and corrosion rate is converted through time alignment.

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

[0027] The present application provides a marine splash zone steel structure corrosion sensor, which writes 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 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, and 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 that the optical fiber corrosion sensor for detecting steel structure corrosion in the prior art has a short service life and cannot achieve multi-point monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the sensor in this application;

[0029] Figure 2 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 A curve diagram 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 an embodiment of the present 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 the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0036] Example 1

[0037] Please refer to Figure 1 The present 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 engraved at intervals, an iron-carbon coating is electroplated at the position of the long-period grating 2 on the single-mode optical fiber 1, a packaging protection component is connected to the position of the long-period grating 2 on the single-mode optical fiber 1, 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 grating sensor in the prior art has a short working life, and the grating is fragile and easily damaged. On the other hand, the corrosion of steel pipe piles is often simultaneous corrosion at multiple points, and the degree of corrosion is often different, and 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 marine splash zone steel structure corrosion monitoring, in which a long period grating 2 and a temperature compensation grating 3 are engraved on a single-mode optical fiber 1, and an iron-carbon coating is electroplated on the long period grating 2, thereby improving the sensitivity of the entire sensor; then, the packaging protection component is set to improve the working life of the entire sensor, and at the same time, the 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 expansion of the structure volume due to 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 monitoring results. Compared with the prior art, 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, thus avoiding the errors caused by strain monitoring and solving the problem of large errors in monitoring results in the prior art.

[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 protection component 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 the sacrificial plate 5 is a steel sheet, and the material and composition of the steel sheet are the same as those of the steel structure to be measured. The thickness and number of measuring points of the steel sheet sacrificial plate 5 can be adjusted according to the actual monitoring needs. The steel sheet sacrificial plate 5 not only protects the long period grating 2 and the temperature compensation grating 3, but also provides additional corrosion rate monitoring data and extends the working life of the entire sensor. The thickness of the sacrificial plate 5 configured for each group of long period grating 2 and temperature compensation grating 3 is different, and its purpose is to enable the refractive index sensitization 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 microamperes 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 mentioning that the corrosion monitoring data is obtained from the spectral changes of the fiber Bragg grating. The extension of the working 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 in 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, thereby 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 the material of the steel structure to be detected. By setting the material composition of the sacrificial plate 5 and the iron-carbon coating to be the same as that of the steel structure to be detected, the sacrificial plate 5 and the iron-carbon coating are made to have the same corrosion rate as the steel structure to the greatest extent possible, thereby avoiding the problem of large errors in the monitoring results caused by the different corrosion rates of the sacrificial plate 5 and the iron-carbon coating and the steel structure.

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

[0048] In some embodiments, the number of the long-period grating 2 and the number of the temperature compensation grating 3 are both the total corrosion 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 has been 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 the spectral data of the point long period grating 2 and the temperature compensation grating 3 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 occurrence time t1 of the spectrum drift at each point on the target rigid 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 object;

[0059] The Weibull distribution was fitted to the corrosion rate data of all points 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. The time point is t0. At this time, all the sacrificial steel plates 5 begin to corrode. When the thinnest sacrificial steel plate 5 (thickness d1) is corroded and penetrated, 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 to work, and the spectrum begins to drift. At this moment, the time point of spectrum drift is t1. At this point, according to t0, t1, and d1, the average corrosion rate V1 in the time period from t0 to t1 can be obtained. The specific formula of 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 other iron-carbon coated long period grating 2 points after the time point t1 can be calculated by analogy;

[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 calculation of the corrosion rate data of each point on the target rigid object is specifically as follows: the thickness of the sacrificial plate 5 is calculated in order from thin to thick. In detail, the iron-carbon coated long period grating 2 inside the packaging box 4 can measure the instantaneous corrosion rate V1' after the time point t1, and so on, according to the order of the thickness of the steel sheet sacrificial plate 5 from small to large, the instantaneous corrosion rate V1' of the remaining iron-carbon coated long period grating 2 points is calculated. This method can not only detect the corrosion conditions of multiple points at the same time, but also determine the order in which each point is corroded, thereby improving the monitoring effect.

[0065] In some embodiments, the Weibull distribution fitting of all point corrosion rate data is specifically: the corrosion rate data of the points on the target rigid material are sequentially input 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, 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 give corrosion rate monitoring results through changes in scale parameters and shape parameters. Figure 3 As shown, 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 good fitting effects are 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 compensation 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 compensation 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 according to wavelength changes, a curve of the relationship between corrosion rate and time is established according to electrochemical tests, and the relationship between wavelength changes and corrosion rates 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. For those skilled in the art, it is obvious that the present application is not limited to the details of the above exemplary embodiments, and 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 attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present application. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0074] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description 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 may also be appropriately combined to form other implementation modes 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), wherein a plurality of long-period gratings (2) and temperature compensation gratings (3) are inscribed at intervals on the single-mode optical fiber (1), an iron-carbon coating is electroplated at a position on the single-mode optical fiber (1) where the long-period grating (2) is present, a packaging protection component is connected to a position on the single-mode optical fiber (1) where the long-period grating (2) is present, and the long-period grating (2) and the temperature compensation grating (3) are connected to a demodulator via a transmission optical cable.

2. The sensor according to claim 1, characterized in that The packaging protection component comprises a packaging box (4) having an opening and a sacrificial plate (5) for closing the opening of the packaging box (4); the thicknesses of the plurality of sacrificial plates (5) are different.

3. The sensor according to claim 2, characterized in that The material of the sacrificial plate (5) and the iron-carbon coating are the same as the material of the steel structure to be inspected.

4. The sensor according to claim 2, characterized in that The number of the long-period grating (2) and the number of the temperature compensation grating (3) are both the total corrosion depth divided by 1 millimeter.

5. A method for monitoring corrosion of steel structures in ocean splash zones, characterized in that: include: Acquiring spectral data of a point long period grating (2) and a temperature compensation grating (3) on a target rigid object; Obtain the time t0 of corrosion penetration at the thinnest part of the sacrificial plate (5); The sacrificial plate (5) with the thinnest thickness is marked as d1; Obtain the occurrence time t1 of the spectrum drift at each point on the target rigid object; Based on t0 and t1, the average corrosion rate V1 is calculated using the following formula: Calculate the instantaneous corrosion rate V1' based on the average corrosion rate V1; Calculate the corrosion rate data of each point on the target steel object; The Weibull distribution was fitted to the corrosion rate data of all points to obtain the corrosion rate monitoring results corresponding to the monitoring data.

6. The monitoring method according to claim 5, characterized in that: The calculation of the corrosion rate data of each point on the target rigid object is specifically as follows: the thickness of the sacrificial plate (5) is calculated in order from thin to thick.

7. The monitoring method according to claim 5, characterized in that: The Weibull distribution fitting of all the point corrosion rate data is specifically as follows: the corrosion rate data of the points on the target rigid material are sequentially input into the Weibull distribution model for fitting. The Weibull distribution formula is: 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.

8. The monitoring method according to claim 6, characterized in that: In the Weibull distribution fitting process, the Weibull distribution is made adaptive by changing the scale parameter and the shape parameter.

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

10. The monitoring method according to claim 9, characterized in that: The conversion of spectral data into corrosion rate is specifically as follows: a curve of wavelength drift and time is established according to wavelength change, a curve of corrosion rate and time is established according to electrochemical test, and the relationship between wavelength change and corrosion rate is converted through time alignment.

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