Mapping corrosion of metallic slab by thermography

Thermography is used to detect corrosion on a aluminum specimen. Two identical aluminum plates are extracted from the same base material. One of them is machined on one side, in such a way to simulate a material loss. Both the sound and damaged plate are heated on the undamaged side by a sine modulated heating source. A thermographic camera records a sequence of images of the temperature surface of both the sound and damaged sample on the heated (undamaged) sides. Several sequences are recorded with different modulation periods. By a suitable data reduction procedure, the thermographic sequence is reduced to a couple of images representing amplitude and phase of the oscillating temperature field. A perturbative method is used to solve iteratively the direct problem in the corroded domain that is confronted with the experimental data until an optimum matching is reached.