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INSPIRE Newsletter Spring 2020
https://scholarsmine.mst.edu/inspire-newsletters/1006/thumbnail.jp
Active thermography for the investigation of corrosion in steel surfaces
The present work aims at developing an experimental methodology for the analysis
of corrosion phenomena of steel surfaces by means of Active Thermography (AT), in
reflexion configuration (RC).
The peculiarity of this AT approach consists in exciting by means of a laser source the sound
surface of the specimens and acquiring the thermal signal on the same surface, instead of the
corroded one: the thermal signal is then composed by the reflection of the thermal wave
reflected by the corroded surface. This procedure aims at investigating internal corroded
surfaces like in vessels, piping, carters etc. Thermal tests were performed in Step Heating and
Lock-In conditions, by varying excitation parameters (power, time, number of pulse, ….) to
improve the experimental set up. Surface thermal profiles were acquired by an IR
thermocamera and means of salt spray testing; at set time intervals the specimens were
investigated by means of AT. Each duration corresponded to a surface damage entity and to a
variation in the thermal response. Thermal responses of corroded specimens were related to
the corresponding corrosion level, referring to a reference specimen without corrosion. The
entity of corrosion was also verified by a metallographic optical microscope to measure the
thickness variation of the specimens
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