Effects of stress, defects, and layer composition on the development of corrosion features on protected silver mirrors.

The long-term environmental durability of protected silver mirror coatings is influenced by numerous factors. Here, accelerated environmental exposure testing of model silver mirror coatings illuminated the effects of stress, defects, and layer composition on the extent and mechanisms of corrosion and degradation. Experiments to reduce stress in the highest-stress layers of the mirror coatings revealed that, while stress may affect the extent of corrosion, coating defects and the composition of the mirror layers have the largest influence on corrosion feature development and growth.

Correlation of long-duration exposure and accelerated testing of protected silver mirrors.

The stability of two types of protected silver mirrors was studied by long-term exposure in a clean-room laboratory and mixed-flowing-gas (MFG) accelerated environmental test with two different gas concentrations. The two types of mirrors behaved very differently when exposed to the clean-room air for six years. The mirrors subjected to a reduced Battelle Class II MFG test protocol for 10 days exhibited similar corrosion mechanisms to those exposed to the clean-room air.

Development and growth of corrosion features on protected silver mirrors during accelerated environmental exposure.

Various layer schemes have been developed to protect thin film silver mirrors from tarnish and corrosion. However, the mechanisms by which these additional layers improve mirror durability are not fully understood. Accelerated environmental exposure testing of protected silver mirrors was used to investigate the effects of layer composition on the mechanisms of corrosion feature development and growth.

Environmental durability of protected silver mirrors prepared by plasma beam sputtering.

Various overcoat layers have been developed to protect silver mirrors from tarnish and corrosion. However, the mechanisms by which these protective layers improve mirror durability are not fully understood. Mixed flowing gas exposure was used to investigate the corrosion behavior of plasma beam sputtered silver mirrors with different adhesion layer materials.

Control of stress in protected silver mirrors prepared by plasma beam sputtering.

Plasma beam sputtering was used to deposit dielectric-protected silver mirrors that exhibited excellent durability and controlled stress. The durability of the mirrors was strongly dependent upon the presence of a very thin chromium adhesion layer between the silver layer and the dielectric overcoat. The stress of the five-layer mirror was balanced by controlling the compressive stress in the top dielectric layer, offsetting the net tensile stress of the combination of layers below.

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

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 SiNx-coated silver-mirror coating scheme was tested with electrochemical impedance spectroscopy (EIS) and accelerated environmental testing, including humidity and salt fog tests.