CREVICE CORROSION OF STAINLESS STEELS: ELECTROCHEMICAL NOISE ANALYSIS AT REST POTENTIAL

摘要

Thanks to a specially designed experimental device, crevice corrosion is investigated by simultaneous measurement of potential and corrosion current evolutions at rest potential. Three stages were evidenced: crevice corrosion incubation, initiation, and propagation. During the last stage, some potential and current fluctuations are observed, fairly correlated to each other (a potential drop corresponding to a current increase). Their characteristic frequency decreases drastically when the steel Cr content increases, or for a given FeCr steel, after passivation in nitric acid. It is concluded that these oscillations are correlated to passive film properties. Lastly, detailed signal analysis suggests the occurrence of deterministic chaos in the propagation stage.