The corrosion processes can be estimated by measurements of electrochemical noise. Noise can be observed as current and voltage fluctuations in a three-electrode setup. The presence of pitting corrosion is manifested as transients in current and voltage fluctuations. For an estimation of the pitting corrosion presence in the recorded current fluctuations, the detection of the characteristic transients has been performed. For the determination of transient occurrence, a detection algorithm of the local changes in a spectrogram of the current fluctuations has been used. The spectrogram has been derived using short-time Fourier transform (STFT). The detected transients, characteristic of pitting corrosion, have been filtered. A time-varying filtering has been performed using an iterative algorithm, presented in the paper.