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dc.contributorDepartment of Mechanical Engineeringen_US
dc.contributor.advisorZou, Fangxin (AAE)en_US
dc.creatorBai, Xinru-
dc.publisherHong Kong Polytechnic Universityen_US
dc.rightsAll rights reserveden_US
dc.titleAn ultrasonic testing-based research tool for real-time corrosion rate monitoringen_US
dcterms.abstractCorrosion is a metal-destructive process that can result in significant financial losses as well as harm to the environment and public safety around the world. Corrosion rate as one of the most important and fundamental factors related with the corrosion process, the measurement techniques of it has been of great attention in recent years. Ultrasonic testing is a direct and reliable approach for corrosion monitoring by continuously monitoring the wall thickness loss of components. This dissertation presents an ultrasonic testing-based research tool based on the Generalized Likelihood Ratio (GLR) algorithm to identify the corrosion rates and changes in corrosion rate in real time. The ultrasonic testing provides real-time thickness measurements while GLR algorithm can effectively identify the probability of changes of corrosion rate and linear least square regressions are then applied converts thickness measurements to real-time corrosion rates. The algorithm is systematically investigated to determine the different parameters applied to change detection on the performance of the system. The ultrasonic system was then tested on N80 carbon steel specimens readily available. The reaction was accelerated by applying a constant voltage to the cell, while the corrosion rate of specimen was logged using an ultrasound detecting system. Results reveal that an ideal match between the corrosion rate obtained by back-calculation from the measured current and corrosion rate obtained by the ultrasonic system. Besides, the steel thickness loss measured by the ultrasonic system fits the results of white light interferometer quite well. Based on this, we have also used this system to observe the natural corrosion rate of steel and its variation process in different pH hydrochloric acid solutions. The results were validated by linear polarization resistance (LPR) method and the composition and morphology of corrosion product layers in connection to corrosion rate variation in this test were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, respectively. The ultrasonic testing system based on GLR has shown to be a reliable laboratory technique for actively evaluating the corrosion rate of steel continuously and in real time.en_US
dcterms.extentxi, 85 pages : color illustrationsen_US
dcterms.isPartOfPolyU Electronic Thesesen_US
dcterms.educationalLevelAll Masteren_US
dcterms.LCSHCorrosion and anti-corrosivesen_US
dcterms.LCSHUltrasonic testingen_US
dcterms.LCSHNondestructive testingen_US
dcterms.LCSHHong Kong Polytechnic University -- Dissertationsen_US
dcterms.accessRightsrestricted accessen_US

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Please use this identifier to cite or link to this item: https://theses.lib.polyu.edu.hk/handle/200/12426