[1A1] Magnetic imaging of corrosion under insulation using quantum well Hall-effect sensors
A Lindley¹, J Sexton², R Murshudov¹ and M Missous²
¹Advanced Hall Sensors, UK
²University of Manchester, UK
Corrosion under insulation (CUI) is one of the most pressing issues facing industries that make use of cladded steel pipes, costing companies trillions of pounds every year to maintain them. Currently, while there are few devices capable of detecting corrosion under insulation, they remain expensive, bulky and difficult to utilise over kilometres of cladded steel pipe. This research presents a prototype device using novel quantum well Hall-effect (QWHE) sensors. These sensors are physically small (70-micron square), made of gallium arsenide substrates, capable of measuring magnetic fields in the tens of nanotesla and have a linear response ideally suited to imaging applications. This prototype is capable of scanning insulated or cladded steel pipes. It can detect manufactured wall thickness loss of 1 mm, 2 mm and 3 mm in a 10 mm-thick pipe, representing 10%, 20% and 30% loss, respectively, as far as 95 mm from the surface with micron-level resolution. The research presented here focuses on demonstrating the accuracy of the QWHE sensor-based prototype system by comparing the measured magnetic data to a scan of the same machined pipe acquired with a high-precision laser. Together, these two different scans demonstrate the possibility of using a QWHE sensor in future designs aimed at tackling the pressing issue of CUI.
