Chelating agents are organic chemicals that form coordination complexes with a wide range of metal ions in aqueous solution. These complexes are characterized by the formation of multiple rings in solution that give unusual stability to the complex. This extra stability is known as the "chelate effect." Because of their ability to solubilize and stabilize metals such as Ca2+, Fe2+, Fe3+, Cu2+, Ni2+ and Cr3+, chelating agents have found widespread use in formulations designed to clean industrial equipment fouled with metal oxides and salts. Equipment cleaned have included utility boilers and superheat/reheaters, cooling water systems, heat exchangers and many components of nuclear power plants.

This paper reviews the use of chelating agents in chemical cleaning formulations including citric acid, EDTA, HEDTA and organophosphonates. Included are discussions of the mechanisms of scale dissolution and passivation, corrosion and disposal of the waste cleaning solutions.

Subject
Acids, Ions, Iron oxide, Chelation, Solvents, Ammonium, Acidity, Corrosion inhibitors, Steel, Boilers, Magnetite, Copper, Cleaning
Keywords:
Chelant, Chemical Cleaning, Inhibitors
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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