In comparison with ordinary structural steels, weathering steels, in the unpainted condition, have markedly enhanced resistance to the corrosion stress caused by changeable atmospheric conditions. The corrosion resistance of these steels is based on their chemical composition, which has been formulated so as to develop a stable non-porous oxide layer on the surface of the steel. Structures made of weathering steel need no surface treatment. The slow propagation of corrosion can be taken account of in the structural design.
When the life-time maintenance cost of the steel structure is the main criteria, the use of weathering steel is often the most cost-effi cient choice.
In the construction phase
– all the costs of surface treatment are saved
– throughput times at the workshops are shorter
– lifting and transport involve no risk of damaging the coating
– there is no need for the usual touch-up painting after erection.
In comparison with a painted structure, the saving in maintenance costs is even greater under conditions where repeated repainting is normally required. For example, pipeline bridges in an industrial atmosphere are extremely diffi cult to clean and paint after installation.