COR-TEN® is a proprietary weathering steel similar to those listed in EN10025-5. The anti-corrosive properties are better than those found in other structural steels. Alloying elements form a tight oxide layer or patina that constantly regenerates under the effects of the weather protecting the steel slow down the corrosion process. This usually takes around 18 – 36 months.
The tight rust layer or patina that forms is aesthetically pleasing and has been used famously in large sculptures such as the Chicago Picasso and Anthony Gormley’s Angel of the North. COR-TEN® reaches a “stable” oxidation point where further oxidation may occur, but never impedes the quality of the steel. Staining will occur on the areas where there is runoff, even if you pre-rust the material.