Gold-coated mirrors are widely used in infrared optics for industrial, space, and military applications. These mirrors are often made of aluminum or beryllium substrates with polished nickel plating. Gold is deposited on the nickel layer by either electroplating or vacuum deposition processes. Atmospheric corrosion of gold-coated electrical connectors and contacts was a well-known problem in the electronic industry and studied extensively. However, there is limited literature data that correlates atmospheric corrosion to the optical properties of gold mirror coatings. In this paper, the atmospheric corrosion of different electroplated gold mirror coatings were investigated with an accelerated mixed flowing gas (MFG) test for up to 50 days. The MFG test utilizes a combination of low-level air pollutants, humidity, and temperatures to achieve a simulated indoor environment. Depending on the gold coating thickness, pore corrosion started to appear on samples after about 10 days of the MFG exposure. The corrosion behavior of the gold mirror coatings demonstrated the porous nature of the electroplated gold coatings as well as the variation of porosity to the coating thickness. The changes of optical properties of the gold mirrors were correlated to the morphology of corrosion features on the mirror surface.

Date Published: 19 August 2010
PDF: 8 pages
Proc. SPIE 7786, Current Developments in Lens Design and Optical Engineering XI; and Advances in Thin Film Coatings VI, 77860J (19 August 2010); doi: 10.1117/12.858779

Published in SPIE Proceedings Vol. 7786:
Current Developments in Lens Design and Optical Engineering XI; and Advances in Thin Film Coatings VI
R. Barry Johnson; Virendra N. Mahajan; Simon Thibault, Editor(s)