Internal corrosion of dry sales gas pipelines is normally overlooked due to the perceived absence of condensed water. However, periodic cleaning of sales gas lines yield large quantities of sludge that is composed of corrosion products known as black powder mixed with other contaminants such as hydrocarbons (mainly TEG), elemental sulfur, sand, salts, water, and metal debris. Two potential sources of water in the sludge are: (1) treated natural gas whose water dew point exceeds the temperature of the pipeline, (2) water absorbed with TEG carryovers or co-condenses with triethylene glycol (TEG) vapor.

In the present paper, the corrosion rate of carbon steel samples fully immersed in sales gas pipelines black powder sludge containing high amounts of TEG was investigated after long periods of exposure of 355days in oxygen-rich atmospheric environment and 100 days in simulated sales gas compositions.

The steel samples immersed in the sales gas sludge showed no or extremely low corrosion rates. In contrast, steel samples immersed in pure condensed deionized water showed significantly higher corrosion rates of 1.0 mpy to 4.0 mpy. These results show that sales gas black powder sludge has an inhibiting effect on the corrosion of these lines.

Subject
Water, Composition, Salts, Corrosion rate, Pipelines, Bottles, Mixtures, Black powder, Sludge, Steel, Carbon steel, Immersion, Samples
Keywords:
black powder, sludge, TEG, corrosion, sales gas, pitting
© 2011 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).
2011
Association for Materials Protection and Performance (AMPP)
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