Neutral salt spray aging effect on low emissivity coating

While Low-E coatings have already reached very good optical properties, their durability in a salt chemical environment has not been largely studied. Therefore the degradation of Low-E coatings deposited by magnetron sputtering with “AZO/Ti/Ag/AZO/substrate” structure has been investigated as a function of exposure time to a salt spray. A mechanism of degradation is proposed; the degradation step is initiated by the diffusion of water and salt through the top layer. We clearly show that those contaminants reach the metallic interfaces of Ag and Ti. During the delamination step, the AZO top layer reacts with contaminants, and Zn and O are evacuated in the environment by water droplets. Despite this delamination of the top layer, the Low-E coatings keep their optical properties with an emissivity of ∼0.08. At further delamination step, the silver layer agglomerates to form larger crystallite and the optical properties of Low-E coatings drastically deteriorate.