Author: Yang, Zirui
Title: Liquid immersion based ultrasonic monitoring of electroplating process
Advisors: Zou, Fangxin (AAE)
Su, Zhongqing (ME)
Degree: M.Sc.
Year: 2021
Subject: Electroplating
Ultrasonic waves -- Industrial applications
Hong Kong Polytechnic University -- Dissertations
Department: Department of Mechanical Engineering
Pages: xii, 90 pages : color illustrations
Language: English
Abstract: Electrochemical techniques have been intensively utilized in many engineering or research areas whilst numerous issues remain to be tackled, among these issues, high accuracy electroplating of multiple steel substrates are overly concerned by related industries. For electroplated surface, uniformly layered zinc deposition is usually applied for anti-corrosion purpose. Such electrochemical process could be monitored on real time basis by implemented ultrasonic methods. The sensing network would be able to supply high accuracy time of flight (ToF) data for reconstruction of designated surface profile, which means thickness growth on substrates are being detected continuously such that change in surface condition during a specific period could be captured and analysed. The existing monitoring of plating solution and substrate can provide real-time information like ion concentration or mechanical properties that reflects the quality of plated layer. However, such means of monitoring could not provide direct information on physical change of the plated surface, and under this circumstance, a more straightforward method-ultrasonic echo measurement is induced. Ultrasonic measurement renders non-destructive, high accuracy, and as mentioned, real time monitoring on the change of surface condition during electroplating process. Being capable of propagating in both solid and aqueous media, ultrasound has been widely applied in detection of physical change within certain material without damage. Thus, an ultrasound sensor immersed in plating solvent could be inserted on plating setup to monitor the process continuously.
To acquire high precision measurement, the most influencing factor-temperature fluctuation need to be tackled by experimental compensation effectively. The measurements of temperature and sound velocity in both solid and aqueous media are showing a linear-like relation between sound velocity and the transient temperature that the sound being transmitted in the material. Also, to implement real time ultrasonic plating monitoring, coupling of both systems need to be conducted, and during this stage, technical problems including electrical interference and liquid condition change had been resolved and no sign in results showed they could still affect the monitoring. With all the preparation specified, continuous ultrasonic monitoring on plating growth with constant sampling frequency was conducted under different electrochemical conditions (plating parameters) to test the limit of proposed immersion sensing system. To verify the reliability of ultrasonic monitoring measurement, other surface examination technologies have also been applied, namely, optical surface profiling and scanning electron microscopy. With the reliable surface measuring results, surface roughness and other internal property of plated layer could be obtained. Also, from theoretical basis, Faraday's law for determination of mass transport of electrochemical reactions was utilized as a calculating verification on ultrasonic measurements. Through the analysis on all the collected information, significant finding of correlation between ultrasonic measured plating growth and plating quality was observed. Although the results may not fully support the correlation, some outstanding difference in plating results could still be reflected by ultrasonic messages. As for the most basic function that ultrasound provides, thickness measurement of the plated layer also showed acceptable compatibility with other means of detection. Consequently, with the overall performance of immersion ultrasonic monitoring method, it is noticeable that such technique could also be deployed in other fields like growth monitoring of corrosive deposition on pipeline structures under marine condition or other industrial production processes that require high precision monitoring for quality control.
Rights: All rights reserved
Access: restricted access

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