The standard deviation of partial signal (SOPS) plot is obtained from wavelet analysis of electrochemical noise (EN) data. This paper employs the SOPS plots of EN current signals arising from pitting corrosion on the symmetrical and asymmetrical cells of AA6061 and AA2024 alloys in 3.5% NaCl solution with different O-2 concentrations (3-25 ppm) to obtain a better understanding of the influence of the cathodic reaction on the EN current signals. EIS measurements reveal that an increase of O-2 concentration from 3 to 5 ppm leads to the stronger passive oxide layer on the Al alloys. The time records and corresponding SOPS plots arising from symmetrical cells show an increase in the amplitude and the time width of EN current transients with increasing O-2 concentration from 3 to 5 ppm. According to an earlier modeling of EN transients this can be attributed to the enhancement of current noise detection. The EIS shows that the thickness of the passive oxide layer decreases with increasing 02 concentration from 5 to 25 ppm. Thus, an increase in the time width of EN current transients with increasing O-2 concentration from 5 to 25 ppm can be assigned to an increase in the corrosion activity. The optimal O-2 concentration for EN current measurements is 5 ppm (i.e. naturally aerated solutions). (C) 2013 Elsevier B.V. All rights reserved.