Improvement of the corrosion behaviour of construction steels

The improvement of the corrosion behaviour of construction steels has been analyzed. This study followed two different lines. Firstly, the corrosion behaviour of steel directly exposed, unpainted, to the atmosphere is discussed. Weathering steels produced by the introduction of slight modifications in chemical composition and the use of alternating wetting and drying cycles exhibit a corrosion resistance that is up to eight times better than that of plain carbon steels. Moreover, the mechanical strength of these steels is higher, allowing a significant weight saving. Secondly, the protection of the steel by means of paints is considered. The use of metallic and organic coatings to protect the steel from the corrosive environment is discussed. The combination of both metallic and organic coatings that is very often used in order to provide a long term corrosion protection for steel used in building purposes has been studied by outer exposure of the samples to a marine environment. Best results were obtained by using a strontium chromate primer. A very marked influence of the inclination of these samples on the corrosion performance was observed. Those samples which have a lower inclination are corroded more easily probably due to the more difficult drainage of the rain compared to those with a higher slope, allowing its corrosive attack for a longer time.