A606 weathering steel is a unique material known for its distinctive rust patina. Weathering steel arrives unrusted and will develop its rust-like appearance one it has been exposed to the elements for a period of time.
Weathering steel never completely stops rusting. The rust will form a protective coating that slows the rate of future corrosion. The rusting process will eventually decrease and from that point on the finish acts as a protective coating for the base metal.
Weathering steel requires alternating wet and dry cycles to form a properly adhered protective layer. Areas that have salt laden air, high rainfall, humidity or persistent fog are typically not the proper environment for weathering steel.