Analysis of Electrochemical Noise (EN) Data Using MEM for Pitting Corrosion of 316 SS in Chloride Solution

Abstract

The spectral analysis of the correlated current and potential noise data record (1024 points) obtained from the stressed 316 stainless steel (SS) electrode undergoing stable pitting corrosion by using Maximum Entropy Method (MEM) are discussed in this paper. The power spectral density (PSD) data for current as well as potential were obtained using a Hanning window at different values of the coefficients (M) of the MEM to understand the influence of M on the shape of the PSD plots, roll-off slopes and spectral noise resistance at zero frequency (R°SN). The data was also analysed using the fast Fourier transform (FFT) and plotted along with the MEM data for comparison. The PSD plots obtained by the MEM retained their smooth character up to MEM = 40 became extremely noisy after M = 100. Spectral analysis using the MEM above M = 100 (about 10% of the data points in the record) was not much useful in extracting other parameters. The roll-off slopes were not true indicators of the corrosion mechanism. The optimum values of R°SN obtained by averaging the first 10 points at the lowest frequencies were found to be consistent till M = 200. The R°SN values obtained by similar methods using FFT were found to be comparable to the ones obtained by the MEM.

Keywords

• Pitting Corrosion
• Electrochemical Noise
• Stainless Steel
• MEM
• Chloride