Analysis of pitting corrosion behavior of pure Al in sodium chloride solution with the wavelet technique

The potential electrochemical noise (EN) measurements in conjunction with the scanning electron microscopy (SEM) technique have been used to study the corrosion behavior of pure aluminum in neutral 3.0 wt% sodium chloride solution. EN information on the evolution of pitting corrosion over a period of five days has been obtained and analyzed with a wavelet transform technique. The results show that the EN signal was composed of a distinct type of events characterized by small scaling values, i.e., their time constants, and the wavelet transform technique is a useful alternative tool to overcome the limitations of FFT. Meanwhile, it is found that the energy distribution plots (EDP) can be used as “fingerprints” of EN signals, and good correspondence between the characteristics of EDP and the material corrosion type/severity has been obtained. Finally, the relationship between the EN features and the corrosion morphologies has been elucidated according to the “autoacceleration” and “cathodic protection” mechanisms of the corrosion process.