Pulsed Eddy Current Non-destructive Techniques for Detection and Characterization of Corrosion Under Insulation on Pipelines Structures

One of the most frequent reasons why pipeline structures fail is corrosion. Corrosion may occur on the inside, exterior, or even both surfaces of the pipeline, and it is particularly challenging for insulated pipelines. While insulation helps prevent corrosion damage, there is still a potential for corrosion under insulation (CUI). The current inspection methods require removing the insulation layer, which is time-consuming and expensive. In this research, the Pulsed Eddy Current (PEC) method was applied to detect CUI. Several factors affect PEC signals, including sample material thickness, insulation material, insulation material thickness, and coil parameters. Understanding these characteristics is crucial for designing a suitable PEC system. Comparative analysis using eddy current reveals that thicker insulation materials generally result in higher initial signal strength, with the highest values observed for 5mm insulation across all materials. However, as the carbon steel thickness increases, the signal strength consistently decreases for all insulation types. Wood insulation maintains the highest signal strength across all thicknesses, followed by acrylic, which shows higher signal strength than rubber at comparable thicknesses. Overall, increasing the thickness of the carbon steel substrate consistently reduces the signal strength. Based on error analyses, the thickness of samples and insulation should be considered carefully as they impact accuracy.