M60 1QD UK. 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 ob-tained. 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 devia-tion, 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 meth-ods are available, including the calculation of electrochemical noise resistance, electrochemical noise impedance, character-istic charge, characteristic frequency, and various cross-correlation methods. Newer, somewhat more speculative methods include wavelet and chaos analysis. One of the most attractive prospects of electrochemical noise measure-ment methods is the ability to identify the type of corrosion, something that is not possible with alternative electrochemi-cal 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. KEY WORDS: chaos, characteristic charge, characteristic frequency, coefficient of variation, corrosion fatigue, crevic