Deterioration Of Superpolished Metal Mirrors By Blue Haze

Superpolished mirrors lose their low-scatter finish in industrial atmospheres because of a corrosion process. This degradation is investigated by exposing mirrors in controlled gaseous environments, monitoring changes with scatter measurements, and microscopically and elementally analyzing the surface films. Blue haze results when nickel from the mirror combines with airborne pollutants and water to form an amorphous salt which can coat the nickel and etch it. Preventive techniques to keep the metal clean and free of water films are also discussed.