UCLA

Highly-reflective silver mirrors are widely used in optical applications. However, silver tarnishes and corrodes in the presence of common atmospheric pollutants, which degrades its reflectivity and optical performance. Various overcoat layers have been developed to protect silver from corrosion, though the mechanisms by which these protective layers improve mirror durability are not fully understood. Accelerated environmental exposure testing was used to investigate the corrosion behavior of protected silver mirrors prepared by plasma beam sputtering. The composition and layered nanostructure of the corrosion features on mirrors with different adhesion layer materials were analyzed. A small amount of nickel in the adhesion layer had a significant impact on adhesion at the silver-dielectric interface, and directly affected the corrosion dynamics. Additionally, lateral migration of silver, not just silver corrosion, was an important factor in the corrosion process. Better adhesion at all layer interfaces is necessary to improve mirror durability.