Abstract Potentiostatic critical pitting temperature test was performed for a superduplex stainless steel. The electrochemical noise from the test was analyzed by wavelet transform and the results were compared with those by maximum entropy method. In wavelet analysis of potentiostatic electrochemical noise, the fractional energy contribution of smooth crystals to the total energy decreases in the order, general corrosion → metastable pitting → stable pitting. On the other hand, the contribution of the lowest frequency detail crystal is lower for the spectrum with general corrosion activities than that for the spectrum related with metastable pitting. The contribution is increased by the transition from metastable to stable pitting. Similar results can be obtained from the analysis of low frequency plateau height by maximum entropy method. Wavelet analysis based on the fractional energy contribution of smooth crystals and the lowest frequency detail crystal can provide information on the type and onset of corrosion like the low frequency plateau height in maximum entropy method.