Brownian approximation around

Figures 7.36 to 7.39 contain the measurements obtained during four consecutive experiments made with these S30400 steel cylindrical specimens equipped with the crevice collar and the results obtained by analyzing the voltage fluctuations by the SPD and R/S techniques. At the end of these tests, the specimens were removed from the electrolyte, the PTFE collar was removed, and the severity of the corrosion attack was assessed. In all four cases, severe crevice attack was observed beneath the collar around the majority of the circumference. Knowing that a Brownian motion behavior is equivalent to a fractal dimension of 1.5, as can be verified by the R/S technique, while the presence of persistence causes an increase in D, it is possible to divide the results presented in Figs. 7.36 to 7.39 into two zones those with D < 1.5, and those where D > 1.5. The transition between these two zones is quite evident in all four experiments carried out during this study. In the first experiment (Fig. 7.36), it occurred at approximately 4.5 h in the test, whereas it occurred at 3.1 h for the second experiment (Fig. 7.37), 3.2 h for the third (Fig. 7.38), and 4.1 h during the fourth (Fig. 7.39).

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