Coloration is hardly guaranteed to be consistent.
• Over the time, the replacement of a façade panel becomes challenging since it is hardly impossible to match the colour of Cor-Ten.
• Thickness of panels necessary depends on the required durability. Cladding panels may be required to account for the expected loss of thickness due to corrosion, and compensate for it by increasing the thickness of the material.
• Surface weathering of bare Cor-Ten steel typically leads to heavy rust staining on nearby surfaces like concrete, white walls, fabrics, etc.
• To maintain the material´s excellent aesthetics, proper design and management of run-off water is required to avoid staining (i.e. using gutters, drainpipes, etc.)
• All joints and profiles must be designed so that rainwater can run off – there must be no retention of water. And all contact with other materials (fixings, electrical conduits, lightings, etc.) must be avoided.
• There are not warranties for weathering steel surfaces.
• Storage in transit, at yards, or onsite should be minimised. When storage is unavoidable, uneven weathering can be minimised by positioning the material in an exposed area with good drainage.
• In industrial and marine environments the patina does not adhere as well to the steel substrate and may not protect the steel from corrosion.
The protective patina layer cannot form, however, if the surface of the steel is continuously damp or dirty. • Surfaces of weathering steel can be painted using the same methods applied in ordinary steels. As a result of the special alloying of the steel, a coating may last twice as long as a coating on ordinary steel. If Cor-Ten steel is continuously exposed to water, it is generally recommended to be painted. Nonetheless, the painting process requires the steel surface to be completely free of oxide through preferably mechanical abrasion.
• Imposed weight on building structure must be considered.
• Material should be kept as clean as possible and away from mud, grease, oil, paint, concrete, mortar and other substances to minimise cleaning costs.
• In almost all cases where the Cor-Ten steel is used as a façade cladding, this is used as rainscreen system installed on a substructure or rail system typically specified in other architectural metal. Joining different metals may induce galvanic corrosion. Galvanic corrosion occurs when two metals with different electrolytic potential come into contact in the presence of an electrolyte such as water. The table below summarises the risks of pairing Cor-Ten steels with other metals commonly used in facades. The recommended option is to use fasteners or substructure made of weathering steel. If this is not possible, it is suggested to use nylon spacers among materials to avoid direct metallic contact.