Analysis of the role of electrode capacitance on the initiation of pits for A516 carbon steel by electrochemical noise measurements

The fluctuations of potential and current of A516 carbon steel were monitor ed in chloride solution. Different noise patterns were observed during the incubation and initiation periods of pitting. During the incubation of pits , the fluctuations of potential were in phase with the current fluctuations , indicating that the faradaic current plays a major role in pit incubation . The initiation of pitting was characterized by sharp fluctuations of pote ntial and current. The slower recovery of potential always exceeded the tim e for the recovery of the current. This was attributed to the slow discharg ing of the capacitance on the electrode surface. The capacitance plays a ma jor role on potential fluctuations generated during pitting of carbon steel . (C) 1999 Elsevier Science Ltd. All rights reserved.