Three sets of polymer coated steel were exposed to Pacific ocean water (NS) and artificial (AS) sea water. Each set had a different primer - metallic zinc, IVD-Al or phosphate. Within each set one group of samples had an epoxy coating, the other set had an additional layer of polyurethane as a topcoat. Degradation of the protective properties of the polymer coating was followed by recording impedance spectra and electrochemical potential and current noise data as well as by visual observation. Statistical analyses concerning the effects of the nature of the primer, presence of a topcoat and exposure medium (biotic vs. abiotic) were performed based on the breakpoint frequency fb obtained from impedance data and the noise resistance Rn and the spectral noise resistance Rosn obtained from noise data. Samples exposed to three different colonies of microorganisms containing sulfate reducing-bacteria (SRB) and a control solution were evaluated using electrochemical impedance spectroscopy (EIS). All samples were examined by environmental scanning electron microscopy (ESEM) to determine biofilm distribution and spatial relationships between coating damage and microorganisms.

Subject
Primers, Coating performance, Zinc rich coatings, Top coats, Electrochemical noise, Impedance, Polyurethanes, Coating degradation, Polyurethane coatings, Electrochemical data, Epoxies, Coating systems, Samples
Keywords:
polymer coatings, natural seawater, microbial corrosion, EIS, ENA, laboratory tests, surface analysis
© 1996 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).
1996
Association for Materials Protection and Performance (AMPP)
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