Microelectrochemical Testing of Cerium-Based Conversion Coatings

Abstract

The corrosion resistance of cerium-based conversion coatings was evaluated using a ~50 μm diameter capillary probe. The tests showed three distinct regions during electrochemical impedance spectroscopy and potentiodynamic testing: active, intermediate, and passive. Active regions had total impedance values of less than 200 Ω·cm2 and corrosion current densities (icorr) greater than 1x10-4 Amps/cm 2. Passive regions had total impedance values greater than 10 KΩ·cm2 and icorr values less than 1x10-5 Amps/cm2. The total impedance and icorr values for intermediate regions were between those for active and passive regions. Both active and intermediate regions displayed mixed open circuit potentials ranging from -0.50 V to -0.85 V vs. SCE, which showed that the coatings were susceptible to galvanic corrosion. The ability to isolate and probe specific surface features can provide insight into the corrosion mechanism as well as where corrosion is likely to initiate.

Meeting Name

Coatings for Corrosion Protection - 216th ECS Meeting (2009: Oct. 4-9, Vienna, Austria)

Department(s)

Materials Science and Engineering

Keywords and Phrases

Active regions; Conversion coatings; Corrosion current densities; Corrosion mechanisms; Galvanic corrosion; Open circuit potential; Potentiodynamic testing; Specific surface

International Standard Book Number (ISBN)

978-1566778022

International Standard Serial Number (ISSN)

1938-5862

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2010 Electrochemical Society, Inc., All rights reserved.

Publication Date

01 Jan 2010

Link to Full Text

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