10.60933/PRDR/HJYNZB YU, Samuel0000-0002-5615-9956(The Hong Kong Polytechnic University)CHUNG, Winnie Wai-sze(The Hong Kong Polytechnic University)LAU, Tom Chun-wai0000-0003-2144-659X(The Hong Kong Polytechnic University)LAI, Wallace Wai-lok0000-0002-0696-6741(The Hong Kong Polytechnic University)SHAM0000-0001-6424-5734(Janet Fung Chu)HO, Chun Yiu(The Hong Kong and China Gas Company Limited) PolyU Research Data Repository 2025 Abstract This dataset presents a thermal imaging dataset from mild steel sample that were inspected by pulsed thermography with the goal of detecting and characterizing external corrosion of metallic underground utilites (manually milled flat bottom holes representing corroded regions). The pulsed thermography experiment was applied to two mild steel plates with the dimensions of 150 mm (length) × 150 mm (width) × 10 mm (thick). The first plate contains 11 circular milled flat-bottomed holes with residual thicknesses of 1 mm 3 mm and 5 mm and lateral size of 5 mm, 10 mm, 15 mm and 20 mm while the second plates contains 9 rectangular milled flat-bottomed holes with residual thickness of 3 mm, 6 mm and 8 mm, width of 2 mm, 4 mm, 7 mm and uniform height of 20 mm. 6 sets of data were collected for both plates with half of them having steel-air interface and the other half having steel-sand interface. A pair of ZOOM PRO HD Elinchrom Digital RX photographic flashes (3 kJ per flash lamp) were used to generate the heat pulse (4 ms duration), an A655sc FLIR infrared camera using ResearchIR software to record the thermal images 450mm from the mild steel sample. Finally, the dataset proposed consists of 6 sequences of approximately 8000 images of 640 × 480 pixels each. Methods  Test Sample This dataset is collected using pulsed thermography method. Sequential IR image data were obtained using a pulsed-heating TNDT system. In the experiment, two 150 mm (length) × 150 mm (width) × 10 mm (thick) mild steel plate was machine-milled with 11 and 9 flat-bottom holes, respectively. The plate milled with circular holes had varying diameters (20 mm, 15 mm, 10 mm, 5 mm) and residual thicknesses (1 mm, 3 mm, 5 mm) while the plate milled with rectangular holes had varying width (2 mm, 4 mm, 7 mm) and residual thickness (3 mm, 6 mm, 8 mm) to imitate the various defects in a pipe wall. To model the environment of a buried metallic pipe, 3 sets of data were collected while the holes were filled with sand. Instrumentation A pair of flash lamps, which were directed towards the rear surface of the plate, was used for excitation (at t = 0 s). The plate was painted with a thin layer of black flat paint so that its emissivity was as close as possible to that of a blackbody. The change in temperature of the surface was monitored by a high-speed, long-wave infrared camera (7–14 μm) with a 640 × 480 pixel microbolometer at a frame rate of 50 Hz for 2.5 minutes after the application of the pulse. The instrument specifications and parameters used for the acquisition of the thermogram are provided in the table below. Experimental Equipment Acquisition Parameters Thermal stimulation: Sampling rate 50 Hz Photographic Flashes: ELINCHROM ZOOM Pro HD Pulse duration: 4 ms thermal pulse, Deposited energy: 3 kJ/flash (Total energy deposited 6 kJ) Acquisition duration 160 s Thermographic monitoring Time interval 20 ms FLIR A655sc, FOV 25°, 640 × 480 pixel microbolometer, 16-bit data, NETD: <30 mK, spectral range: 7.5-14.0 µm Total number of frames 8000   YU, Samuel(The Hong Kong Polytechnic University)LAI, Wallace Wai-lok(The Hong Kong Polytechnic University)