Potentiostatic Electrochemical Noise Analysis of 2101 Lean Duplex Stainless Steel in 1 mol/L NaCl

The critical pitting temperature (CPT) of 2101 lean duplex stainless steel (DSS) in 1 mol/L NaCl was investigated. Potentiostatic electrochemical noise (EN) technique coupled with scanning electron microscopy (SEM) was used to study the corrosion process of 2101 DSS at different temperatures (15, 25, 28, and 35 °C) from below CPT to above CPT. The EN data were analyzed by wavelet technique based on orthogonal db4 wavelet. The results showed that, the patterns of current noises were different at different temperatures. The characteristics of energy distribution plot (EDP) obtained from wavelet analysis technique can be used as “fingerprints” of EN signal and can be used to interpret the corrosion process. With increasing solution temperature, the maximum relative energy defined in EDP changed from the region of crystal series coefficients with smaller scales through middle scales to larger scales, which indicated the process of initiation, propagation and growth into stable pitting of metastable pitting. The results were well confirmed by the corresponding morphologies.