Imaging pitting corrosion produced in salt-alcohol aqueous solution by photoacoustic microscopy

This study obtained images of pitting corrosion occurring in a salt-alcohol aqueous solution by photoacoustic microscopy (PAM). Using immersion tests and electrochemical methods, two different types of pitting corrosion were generated. Immersion testing of pure aluminum plate was conducted in sodium chloride and magnesium chloride alcohol aqueous solutions. Nondestructive measurement of pitting corrosions nas carried out using PAM. The amplitude and phase of the photoacoustic (PA) signal were measured at every point of the scan, and PA amplitude and phase images were obtained. The PA amplitude signal intensity varied with both the shape and depth of the pitting corrosion. Phase signal intensity reflected the depth and cross section of each pit.