The weathering steel, also know as COR-TEN steel, was invented and patented by United States Steel Corporation (U.S.S.) in 1933. COR-TEN was mainly used to build bridges and guardrails, while nowadays because of its aesthetic appeal and intrinsic properties (CORrosion resistance + TENsile strenght) many architects and designers specify it in their projects.
The metal surface naturally develops a patina of oxide “rust”, which thickens over the years, showing a chromatic variation from orange to dark-brown. During this stage, it produces a rust/drip that stains the underlying surfaces. This rust protects the metal under layer from further oxidations. Lamberti Design developed an accelerated oxidation processes that reduce the weathering process from a few years to a few months. For outdoor staging, the material is supplied in an advanced state of oxidation, without further treatments otherwise, it supplied in a raw form living it to the natural, longer weathering oxidation process. The stabilization of the oxide takes place within 12-24 months. During the maturation process, COR-TEN products release rust in the form of dripping and/or dusting, which tend to stain the underlying surfaces. The environmental conditions (dry/wet cycles, presence of corrosive pollutants, proximity to the sea and/or swimming pools, direct exposure to sunlight, etc.), the way COR-TEN is installed (under pouring rain, vertical or horizontal positioning, under sheltered conditions, possible presence of stagnations), can impact the oxidation process, its speed and the chromatic homogeneity. For indoor applications, Lamberti covers the COR-TEN surfaces with wax, which makes the surface pleasant to the touch.
Care and cleaning instructions of metals
To clean COR-TEN we recommend proceeding with a soft cloth without the use of detergents or water. For indoor applications, we recommend to re-apply every 6-12 months a protective layer of wax.
