Electrochemical and Structural Changes in Cerium Based Conversion Coatings During Exposure to Salt Spray

Abstract

Cerium-based conversion coatings on aluminum alloy 2024-T3 substrates were characterized after various exposure times in salt spray corrosion testing. Coatings post-treated in phosphate solutions exhibited no visible corrosion after seven days. Impedances doubled for these coatings after 12 hours of testing and a ~150 nm thick alumina layer developed after 24 hours of exposure, leading to the conclusion that post-treated coatings facilitated the formation of a protective alumina layer. As-deposited coatings exhibited significant corrosion after 24 hours of exposure and had impedances that were an order of magnitude lower than post-treated coatings. Subsurface voids present underneath coatings corroded into nodules of alumina on the surface of as-deposited coatings. in contrast, the voids corroded into small pits with little corrosion product present in post-treated coatings, which was attributed to a protective oxide present around the voids.

Department(s)

Materials Science and Engineering

Keywords and Phrases

Coatings for Al Alloys

International Standard Serial Number (ISSN)

1938-5862

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2010 Wiley-Blackwell, All rights reserved.

Publication Date

01 Jan 2010

Link to Full Text

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