Passive low frequencey RFID for detection and monitoring of corrosion under paint and insulation

Abstract

Despite decades of research, corrosion under insulation (CUI) still presents significant challenges for non-destructive testing and evaluation (NDT&E). One of the biggest challenges posed by CUI is the inaccessibility due to the large standoff distance intro-duced by thick insulation. The hidden nature of CUI may result in it going unnoticed for long periods of time leading to potentially catastrophic failures. Electromagnetic NDT&E techniques, which are widely employed in the pipeline industries in various forms, have large decrease in sensitivity primarily due to the insulation layer. Methods to overcome this typically involve either the removal of insulation or the use of high powered and expensive equipment. Limitations of existing NDT&E techniques create opportunities for novel approaches to tackle the challenges posed by CUI. This research project, funded by the Engineering and Physical Sciences Research Coun-cil (EPSRC) CASE studentship in collaboration with International Paint®, proposes the use of passive low frequency (LF) RFID hardware for the detection and monitoring of corrosion on insulated pipes. The battery-free, low cost nature of RFID makes it attrac-tive for long term condition monitoring. Experimental studies have been conducted us-ing carefully designed samples to demonstrate the detection capabilities of the proposed system. The contribution of the research can be summarised as follows: (1) experimen-tal feasibility study demonstrating the detection capabilities at large standoff distances; (2) demonstration of the increased sensitivity of the proposed system compared to tradi-tion eddy current (EC) method; (3) use of multivariate statistical analysis to identify the most dominant features and relate them to time-domain features of the RFID waveform; (4) application of principal component analysis (PCA) to overcome the dependence of the aforementioned features on the position of the reader coil; and (5) performed accel-erated CUI testing to demonstrate the potential of the RFID system in a realistic test scenario. This work concludes that passive LF RFID hardware can be used to detect corrosion on steel under thick insulation. In comparison to traditional EC method, the RFID based method shows greater sensitivity at large standoff distances. However, significant chal-lenges, particularly the high temperature survivability of RFID tags, limit the real-world applicability.