What Is Patination?
The key to the extraordinary durability of zinc roofs and facades, and often cited as the source of their beauty over time, is patination. Just as copper ages from orange to green, zinc over time develops its distinctive patina, going from shiny silver to matte bluish gray (depending on the precise alloy, other colors and finishes are also possible). In contact with the water, oxygen and carbon dioxide molecules in the atmosphere, the surface forms a closely adhering protective layer of zinc carbonate, which is insoluble in rainwater and will hinder any further exchanges between oxygen and zinc, thereby protecting the zinc from further corrosion. Zinc continues to renew this protective layer throughout its life, although the heaviest formation is usually complete in about five years, and will self-repair any imperfections or scratches.
