Effect of microstructure on the corrosion resistance of 2205 duplex stainless steel. Part 2: Electrochemical noise analysis of corrosion behaviors of different microstructures based on wavelet transform

Electrochemical noise has the advantage of no interference over than conventional electrochemical techniques and it shows great potential in in-situ corrosion monitoring in the future. The corrosion behaviors of 2205 duplex stainless steel (DSS) are characterized by electrochemical noise analysis based on wavelet transform. Wavelet analysis of electrochemical noise indicates that pitting occurs to the solution-annealed 2205 DSS and sample precipitating nitrides and carbides and metastable pitting occurs dramatically during the initial period and after several days amounts of stably-propagating pits will form and shelter the surrounding areas from attacks. With chi and especially plentiful sigma phase precipitating their neighboring zones get chromium and molybdenum-depleted severely in particularly the secondary austenite and act as the corrosion passages. Wavelet transform of electrochemical noise shows the characteristic of selective corrosion accordingly. SEM/EDS characterization confirms the inferences from electrochemical noise analysis and demonstrates the corrosion mechanism thoroughly.