Corrosion of Mexican pipelines has been prevented by employing magnesium sacrificial anodes. This practice has identified some problems related with the operational efficiency, which by international standards remain considerably low (30 to 35%). Typically this problem has been attacked by controlling the impurity elements in magnesium, although the price concerns are of importance. In this work, it is reported that microstructural examination of specimens before and after the evaluation of magnesium sacrificial anode test specimen for underground applications has proved to be of great help in the understanding of the low efficiencies. For instance the presence of manganese-rich particles at grain boundaries are one of the main causes for the low efficiency of this sacrificial anode. Decreasing the amount of these particles will improve considerably the efficiency of this material (i.e increasing cooling rates, decreasing cell size, keeping impurities in solid solution).

Subject
Materials, Galvanic anodes, Electrochemical cells, Microstructure, Magnesium anodes, Ingots, Steel, Magnesium, Pitting, Copper, Grain boundary, Casting, Test specimen
Keywords:
magnesium, sacrificial anode, solidification, efficiency, microstructure
© 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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