R/S FRACTAL ANALYSIS OF ELECTROCHEMICAL NOISE SIGNALS OF THREE ORGANIC COATING SAMPLES UNDER CORROSION CONDITIONS

This work presents the electrochemical noise results obtained under chloride corrosion conditions in three different coatings (two epoxy coatings and an epoxy/polyurethane) systems. Evaluation was performed from the fractal dimension of the electrochemical noise-time series obtained using the so called Rescale Range Analysis (RRA) proposed by Hurst. The three coatings were exposed in a chloride environment and electrochemical current noise (ECN) measurements were performed. Afterwards, the fractal dimensions were calculated from the time series obtained for the three coatings. This dimension is obtained from the empirical law R/S = (tau/2)H where R represents the difference between the maximum and minimum values of the variable, S the standard deviation of the time series, tau is the period of time measured and H the Hurst exponent between 0 < H < 1. The calculation of the Hurst exponent and fractal dimension of the time series comes from the slope of the R/S plot. The exponent may help to evaluate the coating resistance performance under corrosion conditions. [This is an unrefereed preprint].