The formation of phosphate conversion coatings on mild steel has been followed using potential measurements, corrosion rate monitoring and impedance logging. Potential and corrosion rate measurements indicate the system reaches an approximate steady-state whereas impedance studies revealed further changes in the properties of the coating with increasing immersion time. The properties of the films developed at the end of coating formation, as indicated by potential and corrosion rate studies, and those produced by longer immersion times were investigated. Evaluation of performance indicates that subsequent film growth, after the end of coating formation, has a significant role in improving the protective properties of the conversion coating. The effect of chemical acceleration on coating growth and performance is also examined.

Subject
Protective coatings, Coatings, Nitrites, Corrosion rate, Impedance, Phosphates, Film formation, Immersion, Risk reduction, Polarization, Chemical conversion coatings, Polarization resistance, Corrosion potential
Keywords:
phosphate conversion coatings, impedance spectroscopy, coating performance, electrochemcial studies, chemical acceleration
© 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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