Corrosion rates of carbon steel specimens were measured in carbon dioxide(CO2)-loaded alkanolamine(amine) solutions by weight-loss tests and by the polarization resistance method. In dilute amine solutions, lower than 10[[illegible]] M, corrosion rates were controlled by the formation of protective FeCO3 scale as in hot, CO2 -H2O environments. Tested amines inhibited CO2 induced corrosion in the concentration range between 10-2 and 2M. In concentrated amine solutions, higher than 3M, primary and tertiary amines showed markedly different effects on carbon steel corrosion. The corrosion rates of carbon steel rose with the increase in primary amine concentration, whereas the corrosion rates of carbon steel stayed low in tertiary amine solutions even at 6M, due to the formation of protective FeCO3 settle.

Tertiary amines absorb CO2 as HCO3 in the presence of water. On the contrary, primary amines absorb CO2 by two wars. One is as HCO3 like tertiary amines, and the other is direct absorption of CO2 without water, producing amine-carbamate.

The chemical substances produced due to the absorption of CO2 by amines are considered to play important roles not only on corrosion rates but also on the morphology and protectiveness of corrosion products.

Subject
Water, Absorption, Corrosion rate, Autoclaves, Corrosion testing, Protective scales, Corrosion products, Ion concentrations, Solutions, Amines, Corrosion morphology, Scale formation, Carbon steel
Keywords:
primary alkanolamines, tertiary alkanolamines, absorption of CO2, bicarbonate, amine-carbamate, protective FeCO3 scale, morphology of corrosion product
© 1996 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).
1996
Association for Materials Protection and Performance (AMPP)
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