A corrosion monitoring device for metal structures under peeling coating in wet environment

Abstract

The invention discloses a metal structure corrosion monitoring device under a stripped coating in a wet environment, which includes a sensor, a zero resistance ammeter and an industrial computer, wherein the zero resistance ammeter is connected to the industrial computer, the sensor includes a watertight joint, an electrode and a base, the electrode is arranged on the base, the electrode is connected to the watertight joint, the watertight joint is connected to the zero resistance ammeter, the base is provided with a cover plate, and a dielectric cavity is provided between the cover plate and the base. The invention can monitor the development of local corrosion of metal structures under defective coatings and optimize the selection of coating protection schemes.

Description

Technical Field

[0001] The invention belongs to the technical field of metal structure corrosion monitoring and diagnosis, and in particular relates to a metal structure corrosion monitoring device under a peeling coating in a wet environment. Background Art

[0002] Metal structures will inevitably suffer from corrosion problems in wet environments, and the use of anti-corrosion coatings is the most commonly used means of corrosion protection for metal structures. During the processing, transportation, construction and service of metal structures, anti-corrosion coatings will suffer from impact, scratching, peeling, blistering, aging and other problems, and their protective performance will be reduced. When there are defects in the coating, the metal structure under the defect will suffer from serious corrosion risks. It is particularly important to study the development characteristics of structural corrosion under coating peeling in wet environments and accurately monitor the degree of corrosion for the safety assessment of metal structures. Invention patent CN112881479A discloses a coating monitoring device and a monitoring method. By setting a sensor module, the resonant frequency caused by the change of resistance and capacitance of the coating is collected to realize the monitoring of the degree of coating aging; invention patent CN108827868A discloses a coating failure monitoring probe and a rapid monitoring method for on-site coating failure. The electrochemical impedance principle is used to realize on-site real-time monitoring of the aging state and aging speed of the coating in service. The above methods focus more on the aging performance of the coating, but the online monitoring method of corrosion of metal structures when there are coating defects is not sufficiently studied. Therefore, designing an online monitoring method and device for metal structure corrosion under stripping coating is of great significance for safety management. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned technical problems existing in the prior art and to provide a corrosion monitoring device for metal structures under peeling coatings in a wet environment, which can monitor the development of local corrosion of metal structures under defective coatings and optimize the selection of coating protection schemes.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A corrosion monitoring device for metal structures under peeling coating in a wet environment, characterized in that it includes a sensor, a zero-resistance ammeter and an industrial computer, the zero-resistance ammeter is connected to the industrial computer, the sensor includes a watertight joint, an electrode and a base, the electrode is arranged on the base, the electrode is connected to the watertight joint, the watertight joint is connected to the zero-resistance ammeter, the base is provided with a cover plate, and a dielectric cavity is provided between the cover plate and the base. The material used for the electrode is consistent with the material of the object where the sensor is arranged. For example, the monitoring device will be arranged on the pile leg of an offshore platform, so the array electrode is made of E690 steel. The peeling of defective coating is simulated by the dielectric cavity. The electrode corrosion condition is obtained by detecting the electrode current through an engineering machine and a zero-resistance ammeter. The monitoring device is arranged on a steel pile leg.

[0006] Furthermore, a multi-way switch is provided between the watertight joint and the zero-resistance ammeter. The sensor is connected to the zero-resistance ammeter through a multi-way switch matrix, and the switching time of the single-way current monitoring and the period setting of the adjacent cycle measurement of the sensor are performed through the control software installed on the industrial computer; the data obtained from the single cycle monitoring are displayed in the form of a current cloud map on the industrial computer. During each current monitoring switching process, the remaining 99 electrodes except the target electrode remain coupled, and the zero-resistance ammeter measures the current flowing between the target electrode and the remaining 99 electrodes; on the other hand, when the sensor does not perform data measurement, all switch matrices of the multi-way switch are closed, so that the 100 electrodes are coupled as a whole to simulate the electrical connection state of the entire sensor; the current monitoring of all 100 electrodes is completed as a single cycle. According to the anode and cathode current results in the current distribution cloud map, the galvanic corrosion distribution under the stripped coating and the extension of local corrosion can be determined, where the anode current represents that the galvanic corrosion in this area is more serious;

[0007] Furthermore, a copper wire is provided between the electrode and the watertight joint to achieve connection between the two.

[0008] Furthermore, the electrodes are arranged in an array of 20×5. The array electrodes are made of actual engineering steel, and the size is finely processed into a cylinder. The array electrodes are evenly distributed in 20 rows along the seam depth and 5 columns along the seam opening. The cylindrical sidewalls of the array electrodes are passivated to avoid crevice corrosion of the cylindrical sidewalls.

[0009] Furthermore, the cover plate is tilted with the bottom surface. The cover is tilted to form an opening on the base, namely the medium cavity. The opening direction of the defective coating can be arranged according to the monitoring requirements. In the implementation of other projects, the opening direction of the sensor is not restricted. It can be a horizontal coating opening, and the peeling direction is toward the ground; it can also be a longitudinal coating opening, and the peeling direction is to the right, etc. Since the opening angle of the sensor cover plate used for coating peeling simulation is small, in a wet environment, whether it is an atmospheric environment with high humidity, an immersed solution environment, or a tidal splash area, the solution or liquid film can be gathered in the peeling gap.

[0010] Furthermore, the base is provided with epoxy resin, and the epoxy resin coats the copper wire. On the back of the array electrode, a copper wire for signal transmission is connected, and the copper wire is coated with sealing epoxy in the sensor cavity to prevent corrosion of the copper wire end.

[0011] Furthermore, a seal is provided between the cover plate and the base. The seal surrounds the opening on three sides, so that the opening is in contact with the outside only at the maximum opening, ensuring that a solution or a liquid film can be gathered in the coating cavity, thereby simulating monitoring under the condition of coating peeling.

[0012] Furthermore, it also includes a support, the base is arranged on the support, the support is provided with a protective tube and a receiving cavity, and the receiving cavity is connected to the protective tube. The support can conveniently fix the sensor, and at the same time, the sensor can be conveniently connected to the multi-way switch through the protective tube.

[0013] Furthermore, a sealing gasket is provided between the support and the base. By providing the sealing gasket, no liquid penetrates into the sealed rear cavity inside the sensor support.

[0014] The present invention has the following beneficial effects due to the adoption of the above technical solution:

[0015] The metal structure corrosion monitoring device provided by the present invention has a simple structure, convenient measurement, high reliability, a long service life of the monitoring sensor, and multiple application scenarios. It is suitable for online monitoring of metal structure corrosion in humid atmospheres, submerged water bodies, and tidal splash zones; it is particularly suitable for online monitoring of metal structure corrosion with different coating peeling degrees and coating peeling opening directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings:

[0017] Figure 1 It is a schematic structural diagram of a metal structure corrosion monitoring device under a stripped coating in a wet environment according to the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of the connection between the sensor and the support in the present invention.

[0019] Figure 3 It is a schematic diagram of the structure of the connection between the electrode and the watertight joint in the present invention;

[0020] Figure 4 It is a structural schematic diagram of the sensor in the present invention;

[0021] Figure 5 This is a schematic diagram of the structure of the connection between the cover plate and the base in the present invention;

[0022] Figure 6 for Figure 4 Cross-section of the middle AA;

[0023] Figure 7 It is a schematic diagram of the structure in which the monitoring device in the present invention is arranged on a steel pile;

[0024] Figure 8 Flowchart of the use of the bit monitoring device.

[0025] In the figure, 1-sensor; 2-support; 3-sealing gasket; 4-fastener; 5-tube flange; 6-tube; 7-multi-way switch; 8-zero resistance ammeter; 9-industrial computer; 101-electrode; 102-base; 103-cover plate; 104-seal; 105-countersunk bolt; 106-epoxy resin; 107-watertight joint. DETAILED DESCRIPTION

[0026] like Figures 1 to 7 As shown, a metal structure corrosion monitoring device under peeling coating in a wet environment of the present invention includes a sensor 1, a zero resistance ammeter 8 and an industrial computer 9. The zero resistance ammeter 8 is connected to the industrial computer 9. The sensor 1 includes a watertight joint 107, an electrode 101 and a base 102. The electrode 101 is arranged on the base 102. The electrode 101 is connected to the watertight joint 107. The watertight joint 107 is connected to the zero resistance ammeter 8. The base 102 is provided with a cover plate 103. A dielectric cavity is provided between the cover plate 103 and the base 102. The material used for the electrode 101 is consistent with the material of the object where the sensor 1 is arranged. For example, the monitoring device will be arranged on the pile leg of an offshore platform. Therefore, the material of the array electrode 101 is E690 steel. The peeling condition of the defective coating is simulated by the medium cavity condition, and the corrosion condition of the electrode 101 is obtained by detecting the current of the electrode 101 through the engineering machine and the zero resistance ammeter 8. The monitoring device is arranged on the steel pile leg.

[0027] A multi-way switch 7 is provided between the watertight joint 107 and the zero resistance ammeter 8. The sensor 1 is connected to the zero resistance ammeter 8 through the matrix of the multi-way switch 7. The switching time of the single-way current monitoring and the cycle setting of the adjacent cycle measurement of the sensor 1 are performed through the control software installed on the industrial computer 9; the data obtained by the single cycle monitoring are displayed in the form of a current cloud map on the industrial computer 9. During each current monitoring switching process, the remaining 99 electrodes 101 except the target electrode 101 remain coupled, and the zero resistance ammeter 8 measures the current flowing between the target electrode 101 and the remaining 99 electrodes 101; on the other hand, when the sensor 1 does not perform data measurement, all the switch matrices of the multi-way switch 7 are closed, so that the 100 electrodes 101 are in overall coupling to simulate the electrical connection state of the entire sensor 1; the current monitoring of all 100 electrodes 101 is completed as a single cycle. According to the results of the anode and cathode currents in the current distribution cloud map, on the one hand, the galvanic corrosion distribution under the stripped coating and the extension of local corrosion can be determined, where the anode current represents that the galvanic corrosion in this area is more serious; on the other hand, according to the anode current value on each array electrode 101, the galvanic corrosion rate v of the corresponding electrode 101 can be calculated. ai,j :

[0028]

[0029] Wherein, M is the molar mass of the material used for the array electrode 101, n is the number of charge transfers when corrosion of the material used for the array electrode 101 occurs, F is the Faraday constant, and ρ m is the density of the material used for the array electrode 101, i ai,j It is the current value measured by the array electrode 101 corresponding to the single electrode 101.

[0030] A copper wire is provided between the electrode 101 and the watertight joint 107 to achieve connection between the two.

[0031] The electrodes 101 are arranged in an array of 20×5. The array electrodes 101 are made of actual engineering steel and are finely processed into a cylindrical shape. The array electrodes 101 are evenly distributed in 20 rows along the seam depth and 5 columns along the seam opening. The cylindrical sidewalls of the array electrodes 101 are passivated to prevent crevice corrosion of the cylindrical sidewalls.

[0032] The bottom surface of the cover plate 103 is tilted. The cover is tilted on the base 102 to form an opening, namely, a medium cavity. The opening direction of the defective coating can be arranged according to the monitoring requirements. In the implementation of other projects, the opening direction of the sensor 1 is not restricted. It can be a horizontal coating opening, and the peeling direction is toward the ground; it can also be a longitudinal coating opening, and the peeling direction is to the right, etc. Since the opening angle of the sensor 1 cover plate 103 used for coating peeling simulation is small, in a wet environment, whether it is an atmospheric environment with high humidity, an immersed solution environment, or a tidal splash area, a solution or liquid film can be gathered in the peeling gap.

[0033] The base 102 is provided with epoxy resin 106, and the epoxy resin 106 covers the copper wire. On the back of the array electrode 101, a copper wire for signal transmission is connected, and the copper wire is covered with sealing epoxy in the sensor 1 cavity to prevent corrosion of the copper wire end.

[0034] A seal 104 is provided between the cover plate 103 and the base 102. The seal 104 surrounds the opening on three sides, so that the opening is in contact with the outside only at the maximum opening, ensuring that a solution or a liquid film can be gathered in the coating cavity, thereby simulating monitoring under the condition of coating peeling.

[0035] The support 2 is also included, and the base 102 is arranged on the support 2. The support 2 is provided with a protective tube 6 and a receiving cavity, and the receiving cavity is connected to the protective tube 6. The support 2 can conveniently fix the sensor 1, and at the same time, the sensor 1 can be conveniently connected to the multi-way switch 7 through the protective tube 6. The bottom of the support 2 can be fixed to the target platform structure by bolt connection or welding. The support 2 is provided with a protective tube flange for connecting with the protective tube 6.

[0036] A sealing gasket 3 is provided between the support 2 and the base 102. The sensor 1 base 102 and the sensor 1 support 2 are fastened and sealed by the fastener 4 and the bracket sealing gasket 3, so that no liquid penetrates into the sealed rear cavity of the support 2.

[0037] like Figure 8 FIG. 1 is a flow chart of a method for monitoring corrosion of a metal structure under a peeling coating in a wet environment. The method is implemented by the above-mentioned monitoring device and comprises the following steps:

[0038] S1: Processing of sensor 1: Determine the opening angle and depth of the stripping coating gap according to design requirements, and process the array electrode 101 and the sensor 1 base 102;

[0039] S2: Assemble the sensor 1, encapsulate the processed components of the sensor 1, lead out the signal line, fasten and seal the sensor 1 base 102 and the sensor 1 support 2 through the fastener 4 and the bracket sealing gasket 3, wherein the simulated peeling coating sealing direction is adjusted according to the needs;

[0040] S3: The sensor 1 is fixed and arranged on the target structure by bolt connection or welding, and the arrangement and docking of the protective pipe flange and the protective pipe 6 are completed. The signal line passes through the protective pipe flange and the protective pipe 6 and is connected to the multi-way switch 7, the zero resistance ammeter 8 and the industrial computer 9;

[0041] S4: monitoring setting control, setting the industrial computer 9 to measure the cycle interval and the switching time of the multi-way switch 7, controlling the multi-way switch 7, so that the array electrode 101 probe of the sensor 1 is connected to the zero resistance ammeter 8 in sequence, and measuring the current data;

[0042] S5: Draw a current distribution cloud map, and draw the measured current data into a 20×5 current distribution cloud map;

[0043] S6: Perform data processing and analysis based on the current distribution cloud diagram.

[0044] The metal structure corrosion monitoring device provided by the present invention has a simple structure, convenient measurement, and high reliability. The monitoring sensor 1 has a long service life and multiple application scenarios. It is suitable for online monitoring of metal structure corrosion in humid atmospheres, submerged water bodies, and tidal splash zones; it is particularly suitable for online monitoring of metal structure corrosion with different coating peeling degrees and coating peeling opening directions.

[0045] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.

Claims

1. A corrosion monitoring device for metal structures under peeling coating in a wet environment, characterized in that: It includes a sensor, a zero-resistance ammeter and an industrial computer, wherein the zero-resistance ammeter is connected to the industrial computer, the sensor includes a watertight joint, an electrode and a base, the electrode is arranged on the base, the electrode is connected to the watertight joint, the watertight joint is connected to the zero-resistance ammeter, the base is provided with a cover plate, a medium cavity is arranged between the cover plate and the base, and the bottom surface of the cover plate is inclined; a sealing member is arranged between the cover plate and the base, the sealing member surrounds the opening on three sides, so that the opening is in contact with the outside only at the maximum opening, ensuring that the solution or liquid film can be gathered in the coating cavity, thereby simulating the monitoring under the condition of coating peeling.

2. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 1, characterized in that: A multi-way switch is provided between the watertight joint and the zero-resistance ammeter.

3. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 1, characterized in that: The electrodes are arranged in a 20×5 array.

4. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 1, characterized in that: A copper wire is arranged between the electrode and the watertight joint to achieve connection between the two.

5. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 4, characterized in that: The base is provided with epoxy resin, and the epoxy resin covers the copper wire.

6. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 1, characterized in that: It also includes a support, the base is arranged on the support, the support is provided with a protective tube and a containing cavity, and the containing cavity is communicated with the protective tube.

7. The device for monitoring corrosion of metal structures under peeling coating in a wet environment according to claim 6, characterized in that: A sealing gasket is provided between the support and the base.

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