A corrosion resistant chemical conversion coating on aluminum alloys was developed using a trivalent chromium bath. Electrochemical impedance spectroscopy and dc-polarization measurements were made to determine the nature of the surface films formed. The results showed a 10 to 100 fold increase in the polarization resistance of the surface films compared to the untreated aluminum alloy. These electrochemical results compared well with the corrosion behavior in salt spray tests. The trivalent chromium-treated surfaces showed no corrosion for up to 200 hours in 5% salt spray. A post-treatment with an oxidizer even further improved its resistance which almost doubled its corrosion protection.

Subject
Electrochemical impedance spectroscopy, Coatings, Aluminum, Chromium, Impedance, Capacitance, Sodium chloride solution, Salt spray corrosion testing, Corrosion protection, Corrosion resistance, Aluminum alloys, Chemical conversion coatings, Polarization resistance
Keywords:
corrosion protection, conversion coatings, ac-impedance, trivalent chromium, aluminum alloys, salt spray tests
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.