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

Electrochemical noise was used to detect the pitting 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 (PSDI) was insignificant. It was indicated that the meta-stable pitting occurred at the electrode surface and the dissolution and restoration of passive films took place alternately. In the later period of corrosion process, a high frequency plateau of white noise appeared in the power spectrum, the amplitude of the current oscillation increased and the slope of PSDI had a great change, indicating the transformation from meta-stable pitting to stable pitting corrosion.