Comparison of Electrochemical Noise Method with the Conventional Electrochemical Techniques for Investigation of the Pitting Corrosion on Al Alloys AA6061 and AA5052

The corrosion of aluminum alloys AA6061 and AA5052 in 3.5% NaCl solution and when this solution is doped with each of acetate, chromate and citrate at 0.002 M have been investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) techniques. The goal of this paper is to compare the results obtained from polarization and EIS techniques with those acquired from the wavelet analysis of EN measurements on the pitting corrosion of Al alloys. The study of standard deviation of partial signal (SDPS) plots arising from wavelet analysis provides a convenient way of comparing the pit size and pit density in several corroding systems. The SDPS plots prove the inhibition action of acetate and chromate both on the pit size and the pit density of Al alloys. According to the SDPS plots it is possible to recognize the inhibition effect of citrate on the pit size and its acceleration effect on the pit density. Based on the calculation of the total amount of noise charges arising from all of partial signals it is possible to obtain the inhibition efficiency (IE) of an inhibitor. The IE values show a reasonable agreement with those obtained from potentiodynamic polarization and EIS methods. Therefore, the wavelet analysis of EN data seems as an alternative tool to overcome the limitations of the polarization and EIS techniques in the pitting corrosion monitoring applications.