Materials selection in HF-alkylation units is mostly based on long time experience. The most widely used material in the alkylation units is standard carbon steel, because it is capable to form a thick protective FeF2 layer in concentrated or anhydrous hydrofluoric acid. The corrosion resistance decreases, when the acid is dilute (less than 64% HF) or the temperature is above 160 °F (70 °C). The composition and metallurgical state are also suspected to affect the corrosion resistance of carbon steel. The effect of composition appears more complicated than believed, especially the A-106 specification on the total amount of Cr+Ni+Cu+Mo+V <1% should be studied more closely from the corrosion point of view. Laboratory tests showed that the uniform corrosion rate may be 100 times higher in galvanic contact of two dissimilar steels. The effect of galvanic contacts can neither be excluded in the process equipment corrosion cases.

Subject
Water, Materials, Piping, Composition, Corrosion currents, Corrosion rate, Density, Hydrofluoric acid, Steel, Corrosion resistance, Elements, Tafel slope, Samples
Keywords:
Oil refining, HF-alkylation, carbon steel, fluoride scale, residual elements
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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