Localized corrosion of stainless steels has often occurred in newsprint paper machines, despite the low chloride concentration in white water. This is now known to be due to thiosulfate ions, which can cause pitting of Type 304 steel without assistance from chloride if the sulfate-to-thiosulfate ratio is within a certain range. The effects of this ratio, of ionic strength and of inhibitive bisulfite ions have been studied.

For Type 316L, thiosulfate pitting did not occur unless the chloride concentration was fairly high (more than ˜10-2M, i.e. 350 ppm Cl–) and unless the molar concentration of chloride exceeded that of sulfate. These new results explain the previously unexpected pitting of 316L equipment in splash zones, where concentrated chloride/thiosulfate solutions can develop by evaporation.

Subject
Pits, Nickel based alloys, Sulfates, Machinery, Chloride solutions, Splash zone, Commercial alloys, Thiosulfate, Corrosion inhibitors, Steel, Pitting, Stainless steel, Chlorides
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.