An optical microscope-based in-situ observation device and method for corrosion of marine engineering steel

Abstract

The application provides a kind of based on optical microscope marine engineering steel material corrosion in-situ observation device and observation method, belongs to the technical field of marine engineering material corrosion monitoring, including: optical microscope main body, high-definition camera, video storage module, corrosion-resistant quartz glass cover, corrosion-resistant clamp, reaction vessel, constant temperature water bath and environmental parameter monitor;High-definition camera is arranged in optical microscope main body, high-definition camera is connected with video storage module, and optical microscope main body and high-definition camera are placed in the inside of corrosion-resistant quartz glass cover;Reaction vessel is placed in constant temperature water bath, and simulation corrosion solution is arranged in reaction vessel;The method utilizes optical microscope and continuous video recording, realizes the whole process microscopic visualization of marine engineering steel material corrosion, accurately captures key dynamic information such as pitting corrosion initiation and crack propagation, solves the problem of missing process and destroying continuity in offline observation.

Description

Technical Field

[0001] This invention belongs to the field of corrosion monitoring technology for marine engineering materials, specifically relating to an in-situ observation device and method for corrosion of marine engineering steel based on an optical microscope. Background Technology

[0002] Marine engineering environments are characterized by high salinity, high humidity, strong ocean currents, and microbial adhesion, among other factors that induce corrosion. This leads to corrosion behaviors in steel materials used in marine engineering, such as pitting and crevice corrosion. Corrosion failure has become a core factor causing equipment malfunctions, shortened lifespans, and safety accidents in marine engineering.

[0003] Currently, the main limitations of methods for observing the corrosion process of steel used in marine engineering are as follows: Traditional methods often employ a "periodic sampling-laboratory testing" model, such as measuring the average corrosion rate using the weight loss method and observing the morphology of corrosion products using a scanning electron microscope. This model cannot capture the microscopic initiation process in the early stages of corrosion or the dynamic changes during corrosion development. It is prone to missing key instantaneous information such as pitting corrosion initiation, corrosion crack propagation, and the formation and detachment of corrosion products. Furthermore, the sampling process disrupts the continuity of corrosion, leading to a one-sided judgment of the corrosion mechanism.

[0004] Second, while commonly used electrochemical monitoring methods in marine engineering sites, such as linear polarization resistance method and electrochemical impedance spectroscopy, can achieve in-situ detection, they can only provide macroscopic electrochemical parameters and cannot directly reflect the microscopic morphological changes of the corroded area. Furthermore, portable microscopes have limited magnification and imaging quality, making it difficult to clearly identify micron-level corrosion features. More importantly, in existing observation devices, optical lenses are exposed to corrosive atmospheres or solutions for extended periods, making them susceptible to contamination or damage by corrosive media. This leads to a rapid decline in imaging quality over time, making it impossible to support long-term continuous observations of several hours to hundreds of hours.

[0005] Third, fluctuations in parameters such as seawater flow velocity and dissolved oxygen concentration in the marine environment significantly affect the corrosion process. Existing methods mostly simulate corrosion under stable laboratory conditions, which are disconnected from the dynamic nature of the actual marine environment. Furthermore, they lack continuous visual records of the corrosion process and cannot establish a real-time correlation between corrosion behavior and changes in environmental parameters. In addition, existing observation methods typically use fixed magnification and observation frequency, making it difficult to balance the high resolution required for the initial pitting corrosion and the large field of view required for the expansion of the corrosion area in the middle and later stages of corrosion, which easily leads to the loss of multi-scale corrosion information.

[0006] As marine engineering expands into deep seas, the requirements for the corrosion resistance of steel used in equipment are increasing. There is an urgent need for an observation method that can intuitively, in real time, and with high precision capture the dynamic process of microscopic corrosion of steel used in marine engineering. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide an in-situ observation device and method for corrosion of marine engineering steel based on an optical microscope. This method utilizes an optical microscope and continuous video recording to achieve full-process microscopic visualization of corrosion of marine engineering steel, accurately capturing key dynamic information such as pitting corrosion initiation and crack propagation, thus solving the problems of missed processes and disruption of continuity in offline observation. The corrosion-resistant quartz glass cover isolates the medium from damage, supporting long-term continuous observation. Furthermore, the magnification is switched according to the corrosion stage, taking into account both high resolution in the early stage and multi-scale information with a large field of view in the middle and later stages.

[0008] The specific technical solution is as follows: An in-situ corrosion observation device for marine engineering steel based on an optical microscope includes: an optical microscope body, a high-definition camera, a video recording and storage module, a corrosion-resistant quartz glass cover, a corrosion-resistant fixture, a reaction vessel, a constant-temperature water bath, and an environmental parameter monitor. The high-definition camera is housed within the optical microscope body and connected to the video recording and storage module. Both the optical microscope body and the high-definition camera are placed inside the corrosion-resistant quartz glass cover. The reaction vessel is placed inside the constant-temperature water bath and contains a simulated corrosion solution. The corrosion-resistant fixture is placed inside the reaction vessel, and the steel sample is fixed by the fixture, positioned directly below the high-definition camera. The monitoring probe of the environmental parameter monitor is immersed in the constant-temperature water bath, and the environmental parameter monitor is connected to the optical microscope body via a data cable to a data processing terminal. The steel sample is connected to an electrochemical workstation via a corrosion-resistant insulated copper wire.

[0009] An in-situ observation method for corrosion of marine engineering steel based on optical microscopy includes the following steps: S1: Preparation of steel samples. Commonly used steel in marine engineering was selected as the observation object. The surface of the sample was polished with sandpaper to remove oxide scale and processing marks. Then, it was ultrasonically cleaned with anhydrous ethanol for 5-10 minutes to remove surface oil. Finally, it was dried with nitrogen and placed in a desiccator for later use. S2: Simulation of corrosive environment; Based on the target service environment, a simulated corrosion system is built. S3: Adjusting the main body of the optical microscope. Fix the steel sample on the corrosion-resistant fixture and position it in the center of the field of view of the observation area. Adjust the focal length of the optical microscope until the microscopic morphology of the sample surface is clear. Then calibrate the video storage module and set the video recording parameters. At the same time, install a transparent corrosion-resistant quartz glass cover on the outside of the main body of the optical microscope to prevent the corrosive medium from contaminating and corroding the lens. S4: Before the sample comes into contact with the corrosive medium, take an initial microscopic image of the observation area using a microscope to identify the initial characteristics of surface scratches and grain boundaries, which will serve as a benchmark for subsequent corrosion comparison; at the same time, record the initial video recording time point. S5: Immerse the sample with the initial state recorded into the simulated corrosion solution and start the microscope's recording function. During the observation process, adjust the observation frequency and magnification according to the corrosion development stage: within 0-24 hours of corrosion, pause recording and take high-definition images every 2 hours, using a magnification of 1000x to capture the pitting corrosion initiation mechanism; within 24-168 hours of corrosion, pause recording and take high-definition images every 6 hours, using a magnification of 500x to observe the expansion of the corrosion area; after 168 hours of corrosion, pause recording and take high-definition images every 12 hours, using a magnification of 100x to record the macroscopic corrosion morphology; for areas with a fast corrosion rate, maintain image clarity through the microscope's autofocus function to avoid defocusing caused by sample surface corrosion. S6: During the observation process in step S5, key parameters of the corrosive environment are recorded simultaneously, including solution pH, temperature, dissolved oxygen concentration and pressure, to ensure that the corrosion behavior data and environmental parameter data correspond synchronously in time. S7: Image and video analysis. ImageJ image analysis software is used to process the captured images and videos. For images, the corroded and uncorroded areas are identified by grayscale threshold segmentation, and the proportion of corroded area is calculated. For pitting corrosion features, the depth and diameter of pitting corrosion pits are measured, and the density of pitting corrosion is statistically analyzed. For video data, frames at key time points are extracted to construct a dynamic sequence of the corrosion process and analyze the expansion rate of the corrosion area and the evolution law of corrosion morphology. S8: Corrosion rate calculation. Combining the corrosion area ratio and observation time, the micro corrosion rate is calculated. The formula is: Micro corrosion rate = Average corrosion depth of the corrosion area ÷ Observation time. The average corrosion depth of the corrosion area is calculated by reconstructing the three-dimensional contour of the corrosion pit using ImageJ image analysis software. At the same time, the micro corrosion rate is compared with the macro corrosion rate measured by the traditional weightlessness method to establish a correlation model between micro and macro corrosion data.

[0010] In addition, the in-situ observation method for corrosion of marine engineering steel based on optical microscope in the above-mentioned technical solution provided by the present invention may also have the following additional technical features: In the above technical solution, in step S2, the simulation of the marine corrosion environment under normal temperature and pressure is carried out by using a 3.5wt% NaCl solution to simulate seawater, and the dissolved oxygen concentration is controlled to be 8-10mg / L by an aeration device, and the temperature is maintained at 25±1℃.

[0011] In the above technical solution, in step S3, the main body of the optical microscope is a biological microscope or metallurgical microscope with a magnification of 100-1000 times, equipped with a high-definition camera and recording module with a resolution of not less than 1920×1080, and supports continuous recording at 10-30 frames / second.

[0012] In the above technical solution, in step S7, the formula for calculating the corrosion area ratio is: corrosion area ratio = corrosion area ÷ total observed area × 100%; the formula for calculating the pitting density is: pitting density = number of pits ÷ observed area.

[0013] The present invention provides an in-situ observation device and method for observing corrosion of steel used in marine engineering based on an optical microscope. Compared with the prior art, the advantages are as follows: 1. By utilizing the high magnification and continuous video recording capabilities of an optical microscope, the entire microscopic visualization of the corrosion process of steel used in marine engineering under marine conditions was achieved. It can accurately capture key dynamic information such as pitting corrosion initiation, corrosion crack propagation, and the formation and detachment of corrosion products, solving the problems of missing key processes and disrupting the continuity of corrosion in traditional offline observation methods. This provides direct and dynamic microscopic evidence for in-depth research on the mechanisms of localized corrosion such as pitting and crevice corrosion.

[0014] 2. By using the same observation object and continuous recording throughout the entire process, the time axis of microscopic corrosion morphology images, corrosion rate, environmental parameters and electrochemical signals is accurately matched and synchronously stored. This avoids the data deviation caused by different batches of samples and different detection equipment in traditional methods, making the correlation analysis between corrosion behavior and environmental factors more scientific and repeatable, and providing accurate data support for the selection and evaluation of corrosion-resistant marine engineering steels.

[0015] 3. A transparent, corrosion-resistant quartz glass cover is installed on the outside of the optical microscope body and the high-definition camera, effectively isolating the precision optical components from the contamination and corrosion of corrosive media. This solves the problems of lens damage and image quality degradation over time in traditional in-situ observation. The device can support continuous observation for several hours to hundreds of hours or more, realistically recording the complete dynamic process from pitting corrosion initiation and expansion to the formation of macroscopic corrosion morphology.

[0016] 4. By using different observation frequencies and magnifications according to the corrosion development stages, we can capture the microscopic mechanism of pitting corrosion initiation at high resolution in the early stage of corrosion, and record the expansion of the corrosion area and the evolution of the macroscopic morphology in the middle and late stages of corrosion with a large field of view, thus avoiding the loss of multi-scale information caused by a single observation strategy.

[0017] 5. By combining ImageJ image analysis software and using methods such as grayscale threshold segmentation and three-dimensional contour reconstruction of pitting pits, the corrosion area ratio, pitting depth, pitting density and micro corrosion rate can be quantitatively calculated. Furthermore, a correlation model between the micro corrosion rate and the macro corrosion rate of the traditional weightlessness method is established, thus achieving accurate quantification of corrosion behavior. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the observation device of the present invention; Figure 2 This is a schematic diagram of the structure of the constant temperature water bath and reaction vessel of the present invention; Figure 3 The images show the microstructure of Q345C marine steel in Example 1 of this invention after corrosion in 3.5wt% NaCl solution for different times. Figure 4 This is a graph showing the change of corrosion area ratio and corrosion rate of Q345C marine steel over time in an embodiment of the present invention. in, Figures 1 to 2 The correspondence between the reference numerals and component names in the attached drawings is as follows: 1. Optical microscope body, 2. High-definition camera, 3. Video storage module, 4. Corrosion-resistant quartz glass cover, 5. Steel sample, 6. Corrosion-resistant fixture, 7. Room temperature pure water, 8. Constant temperature water bath, 9. Environmental parameter monitoring instrument, 10. Data processing terminal, 11. Electrochemical workstation, 12. Simulated corrosion solution, 13. Reaction vessel, 14. Corrosion-resistant insulated copper wire. Detailed Implementation

[0019] The following are specific implementation cases and appendices. Figure 1-4 The present invention will be further described, but the present invention is not limited to these embodiments.

[0020] An in-situ observation device for steel corrosion in marine engineering based on an optical microscope, such as... Figure 1-2 As shown, the system includes: an optical microscope body 1, a high-definition camera 2, a video recording and storage module 3, a corrosion-resistant quartz glass cover 4, a corrosion-resistant fixture 6, a reaction vessel 13, a constant temperature water bath 8, and an environmental parameter monitor 9. The optical microscope body 1 houses the high-definition camera 2, which is connected to the video recording and storage module 3. Both the optical microscope body 1 and the high-definition camera 2 are placed inside the corrosion-resistant quartz glass cover 4. The reaction vessel 13 is placed inside the constant temperature water bath 8, and a simulated corrosion solution 12 is provided inside the reaction vessel 13. The corrosion-resistant fixture 6 is placed inside the reaction vessel 13, and a steel sample 5 is fixed by the corrosion-resistant fixture 6, with the steel sample 5 positioned directly below the high-definition camera 2. The monitoring probe of the environmental parameter monitor 9 is immersed in the constant temperature water bath 8, and the environmental parameter monitor 9 is connected to the optical microscope body 1 via a data cable to a data processing terminal 10. The steel sample 5 is connected to an electrochemical workstation 11 via a corrosion-resistant insulated copper wire 14.

[0021] Specifically, the constant temperature water bath 8 is filled with 25°C room temperature purified water 7.

[0022] An in-situ observation method for corrosion of marine engineering steel based on optical microscopy includes the following steps: S1: Preparation of steel samples. Commonly used steel in marine engineering was selected as the observation object. The surface of the sample was polished with sandpaper to remove oxide scale and processing marks. Then, it was ultrasonically cleaned with anhydrous ethanol for 5-10 minutes to remove surface oil. Finally, it was dried with nitrogen and placed in a desiccator for later use. S2: Simulation of corrosive environment; Based on the target service environment, a simulated corrosion system is built. S3: Adjustment of the optical microscope body 1: Fix the steel sample on the corrosion-resistant fixture 6 and position it in the center of the field of view of the observation area. Adjust the focal length of the optical microscope until the microscopic morphology of the sample surface is clear. Then calibrate the video storage module 3 and set the video recording parameters. At the same time, install a transparent corrosion-resistant quartz glass cover 4 on the outside of the optical microscope body 1 to prevent the corrosive medium from contaminating and corroding the lens. S4: Before the sample comes into contact with the corrosive medium, take an initial microscopic image of the observation area using a microscope to identify the initial characteristics of surface scratches and grain boundaries, which will serve as a benchmark for subsequent corrosion comparison; at the same time, record the initial video recording time point. S5: Immerse the sample with the initial state recorded into the simulated corrosion solution 12 and start the microscope's recording function; during the observation process, adjust the observation frequency and magnification according to the corrosion development stage: within 0-24h of corrosion, pause recording and take high-definition images every 2h, using a magnification of 1000x to capture the pitting corrosion initiation mechanism; within 24-168h of corrosion, pause recording and take high-definition images every 6h, using a magnification of 500x to observe the expansion of the corrosion area; after 168h of corrosion, pause recording and take high-definition images every 12h, using a magnification of 100x to record the macroscopic corrosion morphology; for areas with a fast corrosion rate, maintain image clarity through the microscope's autofocus function to avoid defocusing caused by sample surface corrosion; S6: During the observation process in step S5, key parameters of the corrosive environment are recorded simultaneously, including solution pH, temperature, dissolved oxygen concentration and pressure, to ensure that the corrosion behavior data and environmental parameter data correspond synchronously in time. The pH value of the solution was measured every 4 hours.

[0023] S7: Image and video analysis. ImageJ image analysis software is used to process the captured images and videos. For images, the corroded and uncorroded areas are identified by grayscale threshold segmentation, and the proportion of corroded area is calculated. For pitting corrosion features, the depth and diameter of pitting corrosion pits are measured, and the density of pitting corrosion is statistically analyzed. For video data, frames at key time points are extracted to construct a dynamic sequence of the corrosion process and analyze the expansion rate of the corrosion area and the evolution law of corrosion morphology. S8: Corrosion rate calculation. Combining the corrosion area ratio and observation time, the micro corrosion rate is calculated. The formula is: Micro corrosion rate = Average corrosion depth of the corrosion area ÷ Observation time. The average corrosion depth of the corrosion area is calculated by reconstructing the three-dimensional contour of the corrosion pit using ImageJ image analysis software. At the same time, the micro corrosion rate is compared with the macro corrosion rate measured by the traditional weightlessness method to establish a correlation model between micro and macro corrosion data.

[0024] In an embodiment of the present invention, in step S2, the simulation of the marine corrosion environment under normal temperature and pressure is performed using a 3.5wt% NaCl solution to simulate seawater, and the dissolved oxygen concentration is controlled to be 8-10 mg / L by an aeration device, while the temperature is maintained at 25±1℃.

[0025] Specifically, the deep-sea environment simulation adds a high-pressure reactor to the simulation of marine corrosion environment under normal temperature and pressure, with the pressure controlled at 10-50 MPa; Specifically, the intertidal environment simulation uses a circulating lifting device to achieve alternating cycles of sample immersion in solution and exposure to air, i.e., immersion for 12 hours / exposure for 12 hours.

[0026] Specifically, for observation of actual service environments, a small observation device equipped with a microscope can be fixed in a sealed compartment to the critical corrosion area of ​​marine engineering equipment.

[0027] In an embodiment of the present invention, in step S3, the optical microscope body 1 is a biological microscope or metallurgical microscope with a magnification of 100-1000 times, equipped with a high-definition camera 2 with a resolution of not less than 1920×1080 and a recording module, supporting continuous recording at 10-30 frames per second.

[0028] In an embodiment of the present invention, in step S7, the formula for calculating the corrosion area ratio is: corrosion area ratio = corrosion area ÷ total observed area × 100%; the formula for calculating the pitting density is: pitting density = number of pits ÷ observed area.

[0029] In embodiments of the present invention, data such as corrosion area percentage, pitting density, and corrosion rate are integrated with time and environmental parameters, and dynamic change curves are plotted using Origin software to form a three-dimensional data chart of "time-environmental parameters-corrosion characteristics". All original images, videos, and processed data are stored on a dedicated server and backed up in encrypted format to ensure data integrity and traceability. Example

[0030] (I) Experimental Procedure: This embodiment takes the corrosion observation of Q345C marine steel in a shallow sea environment, i.e., a marine environment under normal temperature and pressure, as an example to explain in detail the specific implementation process of the present invention: 1. Sample preparation: Select Q345C marine steel plate, wire cut into 10mm×10mm×10mm samples, and grind them in the same direction with 400#, 800#, 1000#, 1200#, 1500# and 2000# sandpaper until the surface shows a uniform metallic luster; put the ground sample into anhydrous ethanol and ultrasonically clean it for 8 minutes, take it out and blow it dry with nitrogen to ensure that the sample surface is flat and clean and to avoid impurities interfering with the corrosion process, and finally place it in a desiccator for later use.

[0031] 2. Corrosion Environment Setup: A 500mL corrosion-resistant glass vessel was selected as reaction vessel 13. 300mL of 3.5wt% NaCl solution was added. This solution was prepared by dissolving 10.5g of NaCl in 300mL of deionized water. The reaction vessel 13 was placed in a constant temperature water bath 8, the temperature was set to 25℃, and an aeration device was inserted to introduce air into the solution at a rate of 1L / min to maintain a dissolved oxygen concentration of 9±0.5mg / L. At the same time, a pH meter probe was inserted into the solution to monitor the pH value in real time. The initial pH value was 6.8.

[0032] 3. Microscope Adjustment: An Olympus CX41 metallurgical microscope was selected, equipped with a 10-megapixel high-definition camera 2 and ToupView recording software; the sample was fixed to the stage using a PTFE corrosion-resistant clamp 6, the lens was adjusted to 500x magnification, and the focal length was adjusted to make the grain boundaries on the sample surface clear; a 50mm diameter, 2mm thick quartz glass cover was installed below the lens, ensuring a tight seal with the stage to prevent solution splashing and contamination of the lens; the recording software was started, the resolution was set to 1920×1080, the frame rate to 20 frames / second, and the storage path to a dedicated hard drive.

[0033] 4. Observation Implementation: At t=0, take an initial microscopic image of the sample and start the video recording function; slowly lower the stage to completely immerse the sample in the NaCl solution, ensuring that the quartz glass cover does not touch the solution; pause the video recording at t=2h, 4h, 6h, 8h, 12h, 24h, 36h, 48h, 72h, 96h, 120h, 144h, and 168h respectively, take high-definition images, and record the pH value, temperature, and dissolved oxygen concentration of the solution at this time; stop the video recording after 168h, take out the sample, clean it, and observe the macroscopic corrosion morphology.

[0034] (II) Results and Analysis: 1. Microscopic corrosion process characteristics: Analysis of observed images and videos reveals that the corrosion process of Q345C marine steel can be divided into three stages: 1) Initial passivation stage, 0-12h: No obvious corrosion marks were found on the sample surface, with only slight gray changes at the grain boundaries, which is presumed to be the initial formation and dissolution equilibrium stage of the surface passivation film; 2) Initiation stage of pitting corrosion, 12-48h: At t=24h, pitting corrosion pits with a diameter of about 2-5μm appear at the defects on the sample surface, such as... Figure 3 As shown in (b), the pitting density is 3-5 pits / mm², and the pH value drops to 6.2 during this stage, presumably due to Cl. - The destructive effect on the passivation film; 3) Pitting corrosion propagation and product coverage stage, 48-168h: Pitting pits gradually expand and connect with each other, forming irregular corrosion areas, such as... Figure 3 As shown in (c), at t=168h, the corrosion area accounts for 18.6%, and dark gray Fe3O4 corrosion products are generated on the surface of the corrosion area, such as... Figure 3 As shown in (d), the pH value stabilizes at around 6.0 during this stage.

[0035] 2. Corrosion rate variation law: from Figure 4 It can be seen that the micro-corrosion rate increases rapidly from 0 to 0.08 μm / h within 0-24 h, mainly due to the accelerated corrosion reaction after the passivation film is destroyed; the corrosion rate remains stable in the range of 0.07-0.09 μm / h within 24-72 h, corresponding to the rapid expansion stage of pitting corrosion; after 72 h, the corrosion rate gradually decreases to 0.03 μm / h, mainly because the corrosion product layer forms a certain protective effect, slowing down the contact between the corrosive medium and the substrate. In this embodiment, the macro-weightless corrosion rate measured is 0.05 μm / h, and the average deviation from the micro-corrosion rate is only 8.3%, verifying the accuracy of the method of the present invention.

[0036] 3. Analysis of the impact of environmental parameters: Data shows that the fluctuation of dissolved oxygen concentration is negatively correlated with the pitting corrosion initiation time. When the dissolved oxygen concentration is below 7.5 mg / L, the pitting corrosion initiation time is delayed to 36 h. The decrease in pH value promotes the increase in corrosion rate. For every 0.1 pH unit decrease, the corrosion rate increases by an average of 0.01 μm / h. This provides direct data support for clarifying the influence mechanism of marine environmental parameters on steel corrosion.

[0037] Specifically, Figure 3 (a) is the initial state at t=0h; Figure 3 (b) is the pitting corrosion initiation stage at t=24h; Figure 3 (c) is the pitting corrosion propagation stage at t=72h; Figure 3 (d) is the corrosion product coverage stage at t=168h.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An in-situ observation device for corrosion of steel used in marine engineering based on an optical microscope, characterized in that, include: The optical microscope body, high-definition camera, video storage module, corrosion-resistant quartz glass cover, corrosion-resistant fixture, reaction vessel, constant temperature water bath and environmental parameter monitoring instrument; The optical microscope body is equipped with a high-definition camera, which is connected to a video recording and storage module. Both the optical microscope body and the high-definition camera are placed inside the corrosion-resistant quartz glass cover. The reaction vessel is placed in a constant-temperature water bath and contains a simulated corrosion solution. A corrosion-resistant fixture is placed inside the reaction vessel, and the steel sample is fixed by the corrosion-resistant fixture, with the steel sample located directly below the high-definition camera. The monitoring probe of the environmental parameter monitor is immersed in the constant-temperature water bath, and the environmental parameter monitor is connected to the optical microscope body via a data processing terminal. The steel sample is connected to the electrochemical workstation via a corrosion-resistant insulated copper wire.

2. A method for in-situ observation of corrosion of marine engineering steel based on an optical microscope, wherein the in-situ observation device for corrosion of marine engineering steel based on an optical microscope as described in claim 1 is characterized in that, Includes the following steps: S1: Preparation of steel samples. Commonly used steel in marine engineering was selected as the observation object. The surface of the sample was polished with sandpaper to remove oxide scale and processing marks. Then, it was ultrasonically cleaned with anhydrous ethanol for 5-10 minutes to remove surface oil. Finally, it was dried with nitrogen and placed in a desiccator for later use. S2: Simulation of corrosive environment; Based on the target service environment, a simulated corrosion system is built. S3: Adjusting the main body of the optical microscope. Fix the steel sample on the corrosion-resistant fixture and position it in the center of the field of view of the observation area. Adjust the focal length of the optical microscope until the microscopic morphology of the sample surface is clear. Subsequently, the video storage module was calibrated and the video recording parameters were set. At the same time, a transparent and corrosion-resistant quartz glass cover was installed on the outside of the optical microscope body to prevent the lens from being contaminated and corroded by corrosive media. S4: Before the sample comes into contact with the corrosive medium, take an initial microscopic image of the observation area using a microscope to identify the initial characteristics of surface scratches and grain boundaries, which will serve as a benchmark for subsequent corrosion comparison; at the same time, record the initial video recording time point. S5: Immerse the sample with the initial state recorded into the simulated corrosion solution and start the microscope's recording function. During the observation process, adjust the observation frequency and magnification according to the corrosion development stage: within 0-24 hours of corrosion, pause recording and take high-definition images every 2 hours, using a magnification of 1000x to capture the pitting corrosion initiation mechanism; within 24-168 hours of corrosion, pause recording and take high-definition images every 6 hours, using a magnification of 500x to observe the expansion of the corrosion area; after 168 hours of corrosion, pause recording and take high-definition images every 12 hours, using a magnification of 100x to record the macroscopic corrosion morphology; for areas with a fast corrosion rate, maintain image clarity through the microscope's autofocus function to avoid defocusing caused by sample surface corrosion. S6: During the observation process in step S5, key parameters of the corrosive environment are recorded simultaneously, including solution pH, temperature, dissolved oxygen concentration and pressure, to ensure that the corrosion behavior data and environmental parameter data correspond synchronously in time. S7: Image and video analysis. ImageJ image analysis software is used to process the captured images and videos. For images, the corroded and uncorroded areas are identified by grayscale threshold segmentation, and the proportion of corroded area is calculated. For pitting corrosion features, the depth and diameter of pitting corrosion pits are measured, and the density of pitting corrosion is statistically analyzed. For video data, frames at key time points are extracted to construct a dynamic sequence of the corrosion process and analyze the expansion rate of the corrosion area and the evolution law of corrosion morphology. S8: Corrosion rate calculation. Combining the corrosion area ratio and observation time, the micro corrosion rate is calculated. The formula is: Micro corrosion rate = Average corrosion depth of the corrosion area ÷ Observation time. The average corrosion depth of the corrosion area is calculated by reconstructing the three-dimensional contour of the corrosion pit using ImageJ image analysis software. At the same time, the micro corrosion rate is compared with the macro corrosion rate measured by the traditional weightlessness method to establish a correlation model between micro and macro corrosion data.

3. The in-situ observation method for corrosion of marine engineering steel based on optical microscopy according to claim 2, characterized in that, In step S2, the simulation of the marine corrosion environment under normal temperature and pressure uses a 3.5wt% NaCl solution to simulate seawater, and the dissolved oxygen concentration is controlled at 8-10mg / L by an aeration device, while the temperature is maintained at 25±1℃.

4. The in-situ observation method for corrosion of marine engineering steel based on optical microscopy according to claim 2, characterized in that, In step S3, the main body of the optical microscope is a biological microscope or metallurgical microscope with a magnification of 100-1000x, equipped with a high-definition camera and recording module with a resolution of not less than 1920×1080, and supports continuous recording at 10-30 frames per second.

5. The in-situ observation method for corrosion of marine engineering steel based on optical microscopy according to claim 2, characterized in that, In step S7, the formula for calculating the corrosion area percentage is: corrosion area percentage = corrosion area ÷ total observed area × 100%; the formula for calculating the pitting density is: pitting density = number of pits ÷ observed area.

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