Steel that is prolongly exposed in the natural environment can withstand and do so for a very long time. It is much safer than iron, which rusts eventually and breaks apart. Steel however, when placed in the comfort of concrete, is much more protected and can withstand for hundreds of years without rusting.
Steel is suceptible to rusting and deterioration over time, and is not the best selection of material for protecting from wind/rain/snow exposure. It may seem like a strong material, but it is a metal that suffers from oxidizing and in protecting buildings, construction workers and architects are better off selecting materials like concrete and brick.