Interpretation of electrochemical noise data

The measurement of the electrochemical noise associated with corroding metals places a number of requirements on the measurement system if good quality data are to be obtained. In particular, aliasing and quantization noise should be avoided. Analysis methods may ignore the ordering of the measured potential or current values by using sequence-independent parameters such as the mean, standard deviation, skew, and kurtosis, or they may take the sequencing into account by computing the autocorrelation function, power spectra, or higher-order spectra. When potential and current noise are measured simultaneously, additional methods are available, including the calculation of electrochemical noise resistance, electrochemical noise impedance, characteristic charge, characteristic frequency, and various cross-correlation methods. Newer, somewhat more speculative methods include wavelet and chaos analysts. One of the most attractive prospects of electrochemical noise measurement methods is the ability to identify the type of corrosion, something that is not possible with alternative electrochemical methods (except for methods specific to particular metal-environment systems). The characteristic frequency and characteristic charge appear to offer simple but useful parameters for this purpose.