AbstractThe use of electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA) for non‐destructive evaluation of corrosion processes is illustrated for three model systems. EIS can be used to detect and monitor localized corrosion of Al alloys and determine pit growth laws which can be used for lifetime prediction purposes. Electrochemical potential and current noise data can be analyzed in the time and the frequency domain. A comparison of noise data obtained for Pt and an Al 2009/SiC metal matrix composite (MMC) exposed to 0.5 N NaCl has shown that the use of potential noise data alone can lead to erroneous conclusions concerning corrosion kinetics and mechanisms. The electrochemical noise data have been evaluated using power spectral density (PSD) plots in an attempt to obtain mechanistic information. The system Fe/NaCl has been used to determine the relationship between the polarization resistance Rpobtained from EIS data and the noise resistance Rndetermined by statistical analysis of potential and current noise data. Potential and current noise can be recorded simultaneously allowing construction of noise spectra from which the spectral noise resistance R sn0can be obtained as the limit for zero frequency. Good agreement between RP, Rnand R sn0has been observed for iron exposed to NaCl solutions of different corrosivity. For polymer coated steel exposed to 0.5 N NaCl for five months analysis of EIS data allows to draw conclusions concerning the degree of disbonding of the coating and the decrease of the coating resistivity with exposure time. Rnand R sn0obtained from electrochemical noise data for an alkyd coating on cold rolled steel agree with each other and show the same time dependence as Rpand the pore resistance Rpodetermined from EIS data, but are significantly lower than Rpand Rpo. The relationships of derived noise parameters such as Rnand R sn0to coating properties and to the remaining lifetime of a polymer coating are not clear a