Why Use Weathering Steel for Outdoor Structures

All over the Asia-Pacific region there are thousands of bridges as well as road and rail networks. The different designs and building materials for these assets present a diverse range of hurdles for all those who manage and maintain them.

This guide is meant to highlight reasons for using weathered steel and to retard the proliferation of prestressed concrete beam systems that play a crucial role in impeding the use of steel for structural constructions all across Australia.

5 Reasons for Using Weathering Steel

Nominal Maintenance

The annual cost of asset maintenance in Australia is approximately $32 billion. Of this figure, the needless corrosion damage amounts to about $8 billion and continually has a major economic effect on the industry as well as the greater community. The comparative costs and corrosion effects are alike for all the Asia-Pacific countries.

Weathering steel structures only require an intervallic check up and maintenance to ensure that they uphold satisfactory performance. Therefore, they are perfect where access for imminent maintenance purposes is strenuous or hazardous and where traffic interruptions need to be reduced.

Anti-Corrosive Aspects

Corrosion affects all types of metals to variant extents of severity. If not for the development and implementation of comprehensive management strategies, steel and other types of metals will surely rust.

The environment and the existent climatic conditions also play part in the degradation of open-air structures. The prime cities in Australia are either in the tropical or coastal zones – some are even exposed to both. For example, bridges in Brisbane and Darwin are subject to extreme tropical storms and toxic counts of airborne salt that are present in coastal regions.

Weathered steel is officially known as structural steel that has enhanced atmospheric corrosion resistance. It is robust, low-alloy steel that is ideal for environments that are exposed to high counts of pollutants and salinity. You can leave the weathering steel structure, for example an outdoor sculpture, unpainted to allow for the formation of the adherent rust ‘patina’ to lessen further corrosion.

Every type of structural steel rusts at a rate dependent on the amount of oxygen and moisture that the metallic iron is subjected to. As this rusting process continues, the oxide layer acts as a barrier that restricts further ingress of the oxygen and moisture to the underlying metal. Thus, the corrosion rate slows down.

The oxide layer that forms on the surface of most conventional carbon-manganese sheets is quite porous and it eventually flakes off; this allows for the occurrence of a fresh corrosion cycle.

However, the alloying elements of weathering steel create a sturdy rust layer that is less porous and one that is adherent to the base metal. This oxide layer stays sufficiently impermeable to oxygen and moisture. As a result, the rate of corrosion may diminish to extremely low levels.

Weathering Steel is Economical

Even though weathered steel is somewhat pricier than conventional structural steel, the savings from the eliminated paint system offset the extra material expenses. The initial cost of an outdoor weathering steel structure is rather similar to that of a typical painted-steel alternative. But in fact weathering steel is worth investing in for the long run, as Australian’s are faced with variations in weathering which can’t be controlled, and therefore would damage structures that aren’t made from weathered steel.

Weathered Steel is Sturdy for Heavy-Duty Structures

In the construction and building industry, a material’s tensile strength and overall yield is critical – especially in buildings and bridges. Weathering steel presents these aspects to supplement its toughness and ductility.

For the reason that COR-TEN® is chemically calibrated, it instantaneously begins to create a rust layer on its outer surface. According to Wikipedia, this patina layer constantly develops and regenerates to act as an adherent coating that shields the inner alloys from toxic corrosion levels.


The protective patina layer of weathered structural steel has an aesthetic-pleasing orange-red colouring that enriches with the age of a structure. This distinct look is at times the sole reason why most opt to use weathered steel.

Case in point – the Echigo-Matsunoyama Museum of Natural science is the perfect epitome of a building that was built using COR-TEN® for aesthetic purposes. The designer of this museum wanted the building to come across as a ruin and to contrast the snowy environment.


The contemporaneous innovation of weathering steel products can assist Australian builders in the construction and management of bridges, open-air sculptures, as well as road and rail infrastructure.

It is formidably recommended that a durability plan is a decisive tool in the support of an all-inclusive asset management plan.

Weathering steel is perfect to combat the variations in weather conditions, as there’s no need to paint or repaint the steel.


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