The cathodic behavior of aluminum in seawater has been characterized with respect to divalent cations in the water and velocity of flow up to 71 cm/sec. It is shown that only 150 ppm of total analytical magnesium is needed in the water to give the previously observed noble shift in corrosion potential, and that it is the free Mg++ ions that produce the effect. The same effect is not produced by other divalent cations present in seawater. This fact supports the percarbonic acid theory of the mechanism, which is specific to magnesium. The practical significance of the "magnesium effect" is discussed in light of the observation that it tends to disappear within the first 24 hours of immersion.

An increase in speed of flow up to 71 cm/sec always produced an active shift in the corrosion potential and a decrease in the initial slope of the cathodic polarization curve. The significance of these results is discussed in regard to corrosion of aluminum in surface and deep ocean waters.

Subject
Cathodic polarization, Water, Corrosion rate, Aluminum, Sodium chloride, Seawater, Acidity, Sodium chloride solution, Magnesium, Polarization, Electrodes, Corrosion potential, Electrolytes
© 1983 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).
1983
Association for Materials Protection and Performance (AMPP)
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