Detection of Pitting Corrosion of 316L Stainless Steel in FeCl₃ Solution by Electrochemical Noise

Electrochemical noise was used to detect the pilling corrosion of 316L stainless steel in FeCl₃ solution. The corrosion morphology was observed and the electrochemical noise characteristic parameters were analyzed. The results showed that in the initial stage of the immersion test, the fluctuation amplitude of the electrochemical noise was small and transient peaks appeared. The slope change of the current power spectrum density (PSD_I) was insignificant. It was indicated that the mela-stable pilling occurred at the electrode surface and the dissolution and restoration of passive films look place alternately. In the later period of corrosion process, a high frequency plateau of while noise appeared in the power sped rum. the amplilude of the currenl oscillation increased and the slope of PSD_I had a great change, indicating the transformation from mela-stable pilling to stable pilling corrosion.