A study has been made of the cathodic kinetics in CO2 containing solutions on the rotating cylinder electrode. It is shown that at pH < 4 there is a clear limiting current over a wide range of potential. Similar to rotating disc studies, this limiting current shows flow dependent and flow independent components, as observed with the rotating disc electrode at similar pH. The rotation speed independent component can be related to the slow hydration reaction of carbon dioxide and the flow dependence is due to the diffusion of protons and carbonic acid. At pH 6 a limiting current is not observed and alternative mechanisms are proposed.

It is shown that at pH 3.8 the corrosion rate is significantly less that the cathodic limiting current, and it is concluded that the cathodic process is largely under activation control at the corrosion potential, except for very low rotation speeds. At pH 6 the corrosion rate is similar to that at pH 4, although the cathodic currents away from the corrosion potential are much less than at pH 4.

Subject
Electric current, Corrosion currents, Acid concentration, Corrosion rate, Diffusion, Cathodic current, Bicarbonates, Carbonic acid, Acidity, Constants, Risk reduction, Electrodes, Corrosion potential
Keywords:
Rotating cylinder electrode, carbon dioxide corrosion, cathodic mechanisms, corrosion rates
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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