Rapid electrochemical corrosion testing of chemically passivated aluminum alloys
Conference
·
OSTI ID:352602
- Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
- Rockwell Science Center, Thousand Oaks, CA (United States)
- Sandia National Labs., Albuquerque, NM (United States)
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.{sup 2}, 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,`` R{sub c} 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 R{sub 2} increased. In the regimes where both tests were sensitive, regression analysis showed that linear relationships could be constructed between the log of R{sub c} and the probability of a coating meeting the pass/fail criterion in salt spray. Based on these relationships, threshold R{sub c} 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.
- Research Organization:
- Sandia National Laboratory
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 352602
- Report Number(s):
- CONF-980316--
- Country of Publication:
- United States
- Language:
- English
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