Flat coupons of Grade 2 titanium were immune to microbiologically influenced corrosion in high temperature environments (55-70°C) containing sulfur-oxidizing (SOB) and sulfate-reducing bacteria (SRB). SMO 254 was heavily pitted after similar exposure to thermophilic SRB. Hydrides did not form in titanium weld regions exposed to thermophilic hydrogen-producing bacteria. After a one-year exposure to Pacific Ocean seawater, grade 2 titanium and SMO 254 were colonized by diatoms and other algal species. Ecorr increased continuously for the stainless steel, but not for titanium. The latter result can be explained by the poor catalytic activity of the oxide layer on titanium for oxygen reduction. The capacitance obtained with electrochemical impedance spectroscopy (EIS) remained constant for both metals with titanium showing values close to the theoretical value normally observed only for inert materials. The high values of the polarization resistance (Rp) and the capacitive nature of the impedance demonstrate that the materials remained in the passive state throughout the entire exposure period.

Subject
Materials, Corrosion rate, Seawater, Bacteria, Ennoblement, Oxygen, Titanium, Corrosion resistance, Localized corrosion, Stainless steel, Titanium alloys, Microbiologically influenced corrosion, Concentration cells
Keywords:
titanium, microbiologically influenced corrosion, extreme environment
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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