Observation and evaluation of simulated pitting corrosion by photoacoustic imaging

Photoacoustic imaging of simulated pitting corrosions has been demonstrated. Simulated pittings, columnar holes, are fabricated on a pure aluminum plate by drilling, the diameters and depths of which are 0.2-1.0 mm and 0.5-1.5 mm, respectively. Nondestructive measurement of simulated pittings was carried out with both front and rear surface laser irradiation exitation. The signal intensity variation with hole diameter and depth is interpreted semi-quantitatively by means of a simple model. Heat flow from the bottom of a hole to the rear surface also contributes to the variation.