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Applied Optics

Applied Optics


  • Editor: James C. Wyant
  • Vol. 45, Iss. 7 — Mar. 1, 2006
  • pp: 1583–1593

Corrosion characterization of durable silver coatings by electrochemical impedance spectroscopy and accelerated environmental testing

Chung-Tse Chu, Peter D. Fuqua, and James D. Barrie  »View Author Affiliations

Applied Optics, Vol. 45, Issue 7, pp. 1583-1593 (2006)

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Highly reflective front-surface silver mirrors are needed for many optical applications. While various protective dielectric coating schemes have been developed, the long-term durability of Ag mirrors is still of great concern in the optics community for a variety of applications under harsh environments. The corrosion protection behavior of a SiN x -coated silver-mirror coating scheme was tested with electrochemical impedance spectroscopy (EIS) and accelerated environmental testing, including humidity and salt fog tests. The EIS data obtained were fitted with different equivalent circuit models. The results suggested that the 100 Å thick SiN x coating produced by rf magnetron sputtering was porous and acted as a leaky capacitor on the Ag film, whereas the addition of a NiCrN x interlayer as thin as 3 Å between SiN x and Ag films resulted in a much denser SiN x coating with a low-frequency impedance value of 2 orders of magnitude higher than that without the interlayer. Humidity and salt fog testing of different silver coatings showed similar results. The 100 Å SiN x / 3 Å NiCrN x / Ag coating exhibited excellent corrosion resistance against the corrosive environments used in this study.

© 2006 Optical Society of America

OCIS Codes
(310.3840) Thin films : Materials and process characterization
(310.6860) Thin films : Thin films, optical properties

ToC Category:
Stability of Coatings

Original Manuscript: March 31, 2005
Manuscript Accepted: July 20, 2005

Chung-Tse Chu, Peter D. Fuqua, and James D. Barrie, "Corrosion characterization of durable silver coatings by electrochemical impedance spectroscopy and accelerated environmental testing," Appl. Opt. 45, 1583-1593 (2006)

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