When it comes to choosing materials, steel, because of its exceptional physical and mechanical characteristics, is the most popular amongst designers. It can be used to rapidly build economical, durable, and safe structures. The steel used to make hot-rolled sections, which can themselves be indefinitely recycled, is made from recycled scrap. It is particularly suitable for machining and shaping. However, it tends to react with agents in the atmosphere to form stable thermodynamic bonds – ferrous oxides and/or salts.
The ability of steel to revert to its natural or original state is called corrosion.
In layman’s terms: steel rusts!
The primary quality of steel i.e. its ability to retain its physical and mechanical strength, or in the case of a steel structure, its load bearing capacity, is generally long-lasting and is only compromised when corrosion reduces its cross section to such a degree that safety is adversely affected.
The service life of a structure depends on the rate of reaction between the steel and its environment. These reactions depend on the nature and concentration of the corrosive agents present.
Corrosion protection of structures must therefore be considered as intervening in this process in order to prevent the reaction or greatly reduce the rate.
Large numbers of steel structures, some of them a hundred years old, which have benefited from the combination of a suitable corrosion protection treatment and regular maintenance, show impressively the potential of steel. However, these types of structures, requiring high maintenance costs, are no longer acceptable today.
New requirements govern the design of the steel structures of the twenty-first century: