Corten steel’s amount of aggressive agents in the air has to be taken into account. In general the covering layer offers protection against atmospheric corrosion in industrial, urban and countryside climate. When utilizing this steel in unprotected condition it is up to the designer to take into account the expected loss of thickness due to corrosion and as far as necessary, compensate for it by increasing the thickness of the material.
In cases of particular air pollution by aggressive agents conventional surface protection is recommended to the corten steel. Coating is absolutely necessary in cases of contact with water for long periods, when permanently exposed to moisture, or if it is to be used in the vicinity of the sea. The susceptibility of paint coats to under creep age by rust is less in the case of weathering steel than in the case of comparable non-weathering steel.
United States Steel Corporation (“U. S. Steel”) developed corten Steel as part of a family of proprietary High Strength Low Alloy steels for use in a wide-ranging array of applications. These steels were generically referred to as “weathering” steels. COR-TEN Steel was promoted for buildings, bridges, shipping containers, highway guide-rails as a bare weathering steel.
To use the benefits of the higher atmospheric corrosion resistance of COR-TEN in comparison to unalloyed steel it is necessary that design and execution of structures as well as the performance of maintenance works allow an impeded formation and regeneration of the protective rust layer. The methods must meet the latest requirements of technical progress and must be suited for the proposed application.
The results of tested materials showed that the corten steel has enhanced better atmospheric corrosion resistance when compared with ordinary carbon steel. On the other hand, under continuous wet or buried conditions the corrosion rate of COR-TEN may be the same as carbon steel, as the patina does not stabilize and is therefore not recommended. In marine environments stable oxide films may form on the steel, provided chlorides are washed off regularly. Normally the use of unpainted COR-TEN is not recommended for applications subjected to salt spray.