Enhancing Corrosion Monitoring in Bolted Steel Joints Through Ultrasonic Inspection

Abstract

Monitoring joint damage in bolted steel structures due to corrosion is a formidable challenge. The formation of rust at joint interfaces leads to significant material loss, profoundly impacting the load-bearing capacity of these structures. Therefore, early detection becomes crucial for implementing effective maintenance strategies. In this state-of-the-art ultrasonic inspection, we report our preliminary findings on joint corrosion inspection using different ultrasonic frequency signals. To study ultrasonic signal transmission across corroding bolted interfaces, we conducted laboratory experiments, employing the electrochemical corrosion technique for controlled and accelerated corrosion. Monitoring the propagation of ultrasonic signals at various corrosion stages provided initial insights into the importance of selecting the optimal inspection frequency in detecting joint corrosion. Two inspection frequencies centred at 300 and 500 kHz have been used in this study. Notably, when monitoring the bolted structure with a 300 kHz ultrasonic signal, we observed relatively insignificant changes in signal transmission energy, even at the advanced stages of corrosion. However, the 500 kHz central frequency excitation exhibited a decrease in signal energy corresponding to various stages of corrosion. This highlights the constraints and subsequent challenges associated with choosing the appropriate inspection frequency. The study concludes with the potential of using pulsed laser-based signal generation for simultaneous monitoring of a wide range of signal frequency components, offering a promising alternative to conventional piezo transducer-based setups.