Nonlinearity of electrochemical noise caused by pitting corrosion

Measurements of statistical quantities other than spectrum or amplitude distribution can provide additional information about mechanisms of electrochemical noise generation. The third-order cumulant and bispectrum are used to determine whether the nonlinear components exist in the observed noise. The electrochemical current noise, recorded under conditions when pitting corrosion dominated, is analyzed. Transients, characteristic for metastable pitting, are observed. The recognized nonlinear components in the recorded current fluctuations characterize processes of the electrode film repassivation during metastable pitting. It is suggested that the intensity and form of the nonlinear components are related to the intensity of metal dissolution into the electrolyte.