Studies are made on the source mechanism and characteristics of acoustic emission (AE) signals produced by corrosion, especially pitting corrosion. Relationship between AE amplitude and corrosion depth and frequency is deduced, and the significance of the relation in estimating corrosion damage is emphasized. Theoretical basis for using modal AE to identifying corrosion-related AE and background noise is intro-duced, and methods for using modal AE to evaluate calendar damage of aircraft main structures are ...