The present work describes the corrosion studies (using electrochemical techniques) of coated and uncoated steels exposed to corrosive mixtures (including 6% ferric Chloride, alcohols, particles and water). Open Circuit Potential (OCP), Cyclic Potentiodynamic Polarization (CPP) and a modified version of the Zero Resistance Amperometry (ZRA) testing methodology were proposed to compare the corrosion resistance of several steel exposed to these environments.

The modified version of the ZRA is not only measured accurately (within 1°C) the Critical Pitting Temperature (CPT) on the different alloys studied (metallic bars exposed to 6% Ferric Chloride), but also allowed to perform the testing in a very short time. This technique is a promising way to characterize and rank different materials subjected to the same environmental conditions.

The CPP tests in 316 SS showed that the addition of the sand decreased the Pitting Potential in 316 Stainless Steels by about 130 mVSCE. However, in the 25-Cr DSS the only effect observed was an increase in the passive current (no pitting was observed at this temperature). The abrasion testing of different coated steels in 3.5% NaCl with and without additions of sand particles at very high speed (rotation experiment) was used to characterize the coating performance in these environments. As expected, the carbon steels presented very high currents (thousands of microAmps) once the coating was compromised (after the rotation started). Similarly, the Stainless Steels (SS) type 303 and 316 showed high currents (hundreds of microAmps) once the coating was compromised (after the rotation started). When the same coating (Epoxy A) is applied to 304 SS sample, exposed to a mixture of 90% Mono-Ethylene Glycol and 10% deionized water (DI H2O) (without rotation) and increased the temperature, the coating breaks down at higher temperatures (increase in the current and drop in the potential measured). Ongoing work is aiming at understanding what is the critical temperature and rotational speed for these types of coatings.

Subject
Electric current, Test methods, Materials, Abrasion, Sand, Sodium chloride, Epoxy coatings, Negative potentials, Steel, Carbon steel, Stainless steel, Epoxies, Electrode potential
© 2009 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).
2009
Association for Materials Protection and Performance (AMPP)
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