Acoustic emission signals were continuously monitored during fatigue crack propagation for LY12CZ and 7075-T6 aluminum alloys in laboratory air and 3.5% NaCl solution. The results showed that the acoustic emission count rate was as a linear function of crack propagation rate during fatigue and corrosion fatigue. The acoustic emission activity for LY12CZ was smaller in solution than that in air; but for 7075-T6, greater in solution than that in air. The acoustic emission waveform parameter, the frequency centroid ratio, was tried to use as a criterion to distinguish the corrosion fatigue crack propagation mechanism for anodic dissolution of LY12CZ and hydrogen embrittlement of 7075-T6. (c) 2005 Springer Science+ Business Media, Inc.