Laboratory investigations of the behavior of high-purity zinc in dilute aqueous solutions while galvanically coupled to a 15 cm (6 inch) diameter steel pipe revealed that bicarbonates, nitrates, and/or carbonates (inhibiting anions) promote a cathodic change in the bare zinc anode potential from room temperature to 90°C. Some effects of phosphates and oxygen are considered. Chlorides and sulfates (aggressive anions) aided anodic zinc potentials and gypsum was found to be more effective than sodium chloride. Gypsum added to saturation would even revert the zinc potential to normal active values from highly ennobled values suggesting that if bare zinc underground has become cathodic and is no longer effectively protecting steel, gypsum placed around the anodes should restore the cathodic protective capability.

Subject
Noble potential, Anions, Water, Anode potential, Cathodic protection, Circuit potentials, Zinc anodes, Gypsum, Chemical inhibition, Steel, Oxygen, Zinc, Electrode potential
© 1981 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).
1981
Association for Materials Protection and Performance (AMPP)
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