In facilities operating in a sour environment, oxygen ingress converts the H2S to thiosulfate ions, whose oxidizing effect can induce pitting attack in the presence of certain corrosion inhibitors. The present paper shows that this process involves a slight increase in the corrosion potential, associated with the existence of a critical pitting potential.

The critical potential has been identified either with the aid of "pseudo-polarization" curves, corresponding to the locus of the free corrosion point, Ucorr(t) = f(log icorr(t)), in the presence of thiosulfate but without applied polarization, or by plotting conventional polarization curves U = f(log i), in the absence of thiosulfate, but at extremely slow scanning rates.

Subject
Pits, Water, Corrosion rate, Uniform corrosion rate, Free corrosion potential, Polarization curves, Thiosulfate, Corrosion inhibitors, Pitting, Stainless steel, Critical pitting potential, Electrode potential, Oil
© 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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