Detection of Pipeline Defects Under Coatings Based on Pulsed Eddy Current Sensors and Improved SSD

Pulsed Eddy Current Testing (PECT) is an improved method derived from Eddy Current Testing (ECT). PECT uses short pulse currents as excitation currents, which allows it to detect deeper defects compared to ECT, making it more suitable for inspecting materials with coatings. This paper designs a method for detecting surface defects of coated pipelines based on a pulsed eddy current sensor and SSD. Firstly, the PECT sensor components were selected and tested for calibration, determining the precise relationship of the testing depth. In the suspected areas, lattice thickness detection was converted into defect maps, and defect target detection was performed using an improved SSD. The main improvement in SSD lies in the structure of the backbone network MobileNet2, which adopts a 4-layer depthwise separable network. In the tests, classification and localization detection were conducted for three types of defects: pits, corrosion, and cracks, achieving a relatively ideal level of accuracy.