The capacitances of passivated electrodes were investigated to aid in explaining the effect of capacitive discharging during scribing of rotating cylindrical electrodes. In scribing experiments, a capacitive current is associated with the transient current response which results from removing the passive film. The effective capacitance of the electrodes were acquired by using triangular sweep voltammetry (TSV), galvanostatic double pulse technique (GDP), and electrochemical impedance spectroscopy (EIS) conducted on Fe -16 wt%Ni -16 wt%Cr and Fe - 25 wt%Ni - 25 wt%Cr alloys immersed in 0.1 M H2SO4 - 0.01 M KCl. The TSV technique involved the electrical perturbation of an electrode/solution interface with a triangular wave potential while in the passive condition (i.e., +350 mV SCE). The TSV and GDP experiments determined that the effective capacitance of the electrode/solution interface ranged from 0.1 mF/cm2 to 0.735 mF/cm2 depending on the technique. The double layer capacitance acquired with impedance spectroscopy ranged from 47 to 100 μF/cm2. With the capacitance values, the time constant for transient response appears to occur within the range from 16 ms to less than 3 μs, depending on the dissolution (or faradaic) reaction and capacitance.

Subject
Potentiostats, Electric current, Electrochemical impedance spectroscopy, Electrochemical cells, Voltage, Perturbation method, Open circuits, Capacitance, Constants, Electrochemical current, Electrodes, Corrosion potential, Electrode potential
Keywords:
scratched electrode, ohmic potential, capacitance, impedance spectroscopy, transient current
© 1997 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1997
Association for Materials Protection and Performance (AMPP)
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