COR-TEN® FACT SHEET

COR-TEN® Steel is a durable, weathering steel that starts out a typical steely gray colour and develops a warm, rust-coloured patina over time. Unlike rust, however, this patina is non-corrosive and doesn't affect the steel's integrity.

To maintain an even colour it is recommended that water can run freely from the surface.

In a sheltered environment your COR-TEN® product may not adopt the intended colour and protective patina. Direct contact with earth, snow or vegetation may also affect the colour and it is therefore not recommended for building foundations. Prolonged contact with wood, copper, chemicals or de-icing salts is not advised.

COR-TEN® can be perforated for aesthetic purposes. In these cases, it is possible that run-off from these holes can affect the colour of the patina.

During installation, you should ensure free airflow and allow water to run off freely so that moisture can escape from the surfaces. The back-side ventilation space should run the full length and be 30 mm wide. Fitting screws should be made of acid-proof stainless steel and include an EPDM or neoprene gasket to prevent galvanic corrosion. At surface lap joints, direct contact between steel surfaces should be avoided, and a ventilation gap should be left between the sheets.

Primarily the steel begins to rust in the same fashion as ordinary steel when exposed to wet and dry conditions. However, as time passes, the rust layer transforms into a patina layer, and the colour changes from fresh, newly developed orange-brown, to light or dark brown. The speed of change and the final colour of the steel depends on the atmospheric conditions of the site and the surrounding air quality. Sulfur dense atmospheres will speed up the oxidation process and result in a darker patina. Frequent cycles of wet and dry conditions will also speed up oxidation.