Rapid electrochemical corrosion testing of chemically passivated aluminum alloys

R. G. Buchheit, M. Cunningham, H. Jensen, M. W. Kendig, M. A. Martinez

Research output: Contribution to journalConference articlepeer-review

Abstract

The corrosion resistance of 33 different conversion coatings applied to five different aluminum alloys was tested by salt spray exposure and electrochemical impedance spectroscopy (EIS). Results derived from the two tests were evaluated to determine if a relationship existed. Individual salt spray test panels, with an area of 30 in., were visually inspected at regular intervals up to 168 hours of exposure. At each inspection interval, panels were assigned a pass rank if less than 5 pits were observed, or fail rank if more than 5 pits were observed. EIS data were analyzed using a simple equivalent circuit which yielded a "coating resistance", Rc, which was used as a figure of merit to assess coating performance. Examination of the data showed that both tests could be sensitive discriminators of corrosion protection, but that EIS was more discriminating in the extremes of coating performance. Analysis showed that the probability of achieving a passing salt spray result increased as Rc increased. In the regimes where both tests were sensitive, regression analysis showed that linear relationships could be constructed between the log of Rc and the probability of a coating meeting the pass/fail criterion in salt spray. Based on these relationships, threshold Rc values have been proposed to define the minimum value for which a given coating can be expected to attain a passing result in a 168 hour salt spray test. These values ranged from 2 to 5 × 106 ohm·cm2 for 356, 2024-T3 and 7075-T6,1.5 × 107 ohm·cm2 for 7075-T6, and 2.3 × 107 ohm·cm2 for 3003.

Original languageEnglish
JournalNACE - International Corrosion Conference Series
Volume1998-March
StatePublished - 1998
EventCorrosion 1998 - San Diego, United States
Duration: Mar 22 1998Mar 27 1998

Bibliographical note

Publisher Copyright:
© 1998 by NACE International.

Keywords

  • Accelerated testing
  • Aluminum alloys
  • Conversion coatings
  • Corrosion test methods
  • Electrochemical impedance spectroscopy
  • Salt spray testing

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • General Materials Science

Fingerprint

Dive into the research topics of 'Rapid electrochemical corrosion testing of chemically passivated aluminum alloys'. Together they form a unique fingerprint.

Cite this