Electrochemical noise analysis of corrosion behaviour of asymmetric electrodes made of mild steel in NaHCO3 solutions at different NaCl concentrations

Abstract

In this paper, the corrosion of asymmetrical electrodes made of mild steel was studied in 0.5 M NaHCO3 solutions with the addition of NaCl both before and after the immersion of electrodes. The statistical and wavelet methods were used for analysing the electrochemical current noise (ECN) signals. The ECN signals arising from asymmetric electrodes in 0.5 M NaHCO3 solution (pH 9) in the absence and presence of three different NaCl concentrations were unidirectional. This can pertain to the presence of the oxide layer. The thickness of the passive oxide layer and noise detection decreased on increasing the NaCl concentration from 0.3 to 0.7 M. The predominant transients of ECN signals and their SDPS values were lower in the case of 2 h delaying compared with simultaneous NaCl increase to 0.5 M NaHCO3 solution.