Adaptability Calibration of Big Data Acquisition Sensors for Monitoring Carbon Steel Corrosion in Urban Atmospheric Environment
Traditional methods for monitoring and evaluating corrosion are affected by the extended experimental period and slow pace;thus,they fail to satisfy the demands for data quantity and data continuity.Techniques for online monitoring of atmospheric corrosion require large amounts of continuous and real-time data,and the obtained big data can be effectively simulated,calculated and modeled using computer software to clarify the metal corrosion process and achieve data sharing.Various techniques for detecting atmospheric corrosion have been widely used.However,the accuracy and validation of the data require further experimental verification.In this study,the corrosion rate of Q235 carbon steel in the urban atmosphere was monitored using an outdoor hanging plate,a resistance sensor,and a galvanic sensor.Subsequently,the response surface model was established,and its validity was confirmed via coupled temperature-humidity experiments and alternate drying-wetting simulation experiments.Confocal laser scanning microscope(CLSM),X-ray diffraction(XRD),scanning electron microscopy(SEM),and electrochemical testing were performed to investigate the effects of outdoor exposure and indoor simulation experiment on the surface rust layer of Q235 carbon steel.The results show that the corrosion rates of the resistance and galvanic sensors are 1.295 and 1.084 times the corrosion rate of the hanging plate,respectively.The variation trends of the corrosion rate of the sensor in the coupled temperature-humidity experiments and alternate drying-wetting simulation experiments are consistent with those of the outdoor hanging and response surface model.In the coupled temperature-humidity experiments,the corrosion rates recorded by the resistance and galvanic sensors are 1.136 and 1.018 times that of the hanging plate,respectively.In the low-temperature low-humidity environment,the corrosion rate of the galvanic sensor is similar to that of the hanging plate method.However,in the high-temperature high-humidity environment,the corrosion rate of the sensor is higher than that of the hanging plate.In the alternate drying-wetting simulation experiment,the corrosion rates of the resistance and galvanic sensors are 1.242 and 0.978 times that of the hanging plate sensor,respectively.The corrosion rate of the galvanic sensor initially increases and subsequently decreases because the salt deposited onto the surface participates during the reaction,whereas that of the resistance sensor first increases and then decreases in an alternate period.X-ray photoelectron spectroscopy analysis show that the main components of the rust layer are α-FeOOH,Fe3O4 and γ-FeOOH,withα-FeOOH being the most abundant.Indoor simulation experiments show that with an increase in temperature,the corrosion products on the carbon steel surface change from granular to massive.This is because oxygen solubility in the thin-film liquid decreases,coupled with an increase in the rate of oxygen diffusion through the thin-film liquid to the carbon steel matrix.These factors facilitate the migration rates of Fe2+and OH-in thin-film liquids and accelerates the electrode process and chemical reaction of the anode and cathode under the thin-film liquid.With the prolongation of corrosion time,the color of the carbon steel surface darkens gradually,transitioning from light yellow to reddish-brown and brown,and the corrosion products become dense and evenly distributed on the surface of the sample,relatively protecting the matrix.Because of the appearance of cracks and pits on rust layer surface,the corrosion rate determined using the sensor are higher than those obtained using the outdoor hanging plate.However,the corrosion rate of the galvanic sensor is closer to that of the hanging plate,indicating that the galvanic sensor is more suitable for use than the hanging plate in urban atmospheric environments.
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