What is Weathering Steel and How does it Work?

Today, most builders take advantage of contemporary innovations in mechanised production and construction techniques that present cost-effective solutions to the concerns of safety, brisk constructions, attractive appeal, nominal maintenance, and flexibility for future use.

Because of the current variations in weather, weathering steel is perfect for someone who doesn’t want to continuously have to paint and repaint their steel.

This guide highlights the composition of weathered steel, its use in construction as an economic solution, depicts how it works exactly, and pinpoints the where it shouldn’t be put to use. Let’s kick this off by finding out what this steel industry evolution is all about.

What is Weathering Steel?

Weathering steel, officially known by its generecised U.S trademark COR-TEN®, is more or less a group of low carbon steels with extra alloying elements that are combined with the iron and carbon atoms. These additional alloying elements make this product more robust and resistant to corrosives as compared to the conventional low-carbon steel grades.

The Composition of Weathered Steel

Weathering steel is a low-carbon steel; it basically has only about 0.3% of carbon in weight. It is this low carbon count that guarantees it remains tough and ductile.

Its supplementary alloying elements  help to better its strength – but more importantly, they improve its atmospheric corrosion resistance. Even though there are many variations in the alloying elements that are used, the chief elements used to make up weathering steel alloys are copper, nickel, and chromium.

Weathered Steel Grades

Weathering steel belongs to a family of low-carbon steel alloys all of which are of different grades. Some of these weathering steel grades are proprietary. For example, COR-TEN A and COR-TEN B are proprietary grades.

Patinax, is yet another group of proprietary weathered steel grades all of which hold similarities to the American Society for Testing and Materials (ASTM) categories A 242 and A 588.

How Does Weathering Steel Work?

All low-alloy steels have the tendency to rust when they are subject to the presence of moisture and air. The rate at which a metal rusts is directly proportional to the access to moisture, oxygen and other atmospheric contaminants to its surface area.

Unlike other corrosion-resistant steels that impede the formation of rust, such as the austenitic stainless-steel, weathered steel rusts on its outer surface. With the progression of this rusting process, the outer rust layer prevents the ingress of moisture, oxygen and contaminants. Subsequently, the variations at which weathered steel rusts slows down.

In plain steel, the porous layer of rust that forms on the outer surface eventually detaches from the surface allowing for another layer of rust to form deeper into the metal. This corrosion cycle starts all over again till the plain steel is rendered useless.

On the flip side, the alloying elements in weathering steel make the initial layer of rust that forms on its surface to stick on it better. This impedes the breach of the forming rust deeper into it to weaken the metal. The adherent rust ‘patina’ eradicates the need to coat weathered steel.

Where is Weathering Steel Used?

For the very reason that weathered steel can outlive pure carbon steel in open-air conditions, it is commonly used for constructing steel structures that are out in the open. This eliminates the need to constantly repaint and re-coat these steel structures.

Case in point – It can be used in the construction of buildings and bridges. The adherent rust coating helps to considerably slow down the rate of corrosion; by the time the level of corrosion is regarded unsafe, the open-air structure will already have surpassed its design life.

Where Not to Use Weathering Steel

There still are a couple environments where weathering steel should not be used. Why? There are instances when the corrosion resistance will not be able to withstand the environmental conditions.

Case in point – weathered steel should NOT be used in environments that exhibit unusually high levels of chlorine. The adherent rust layer will not be in a position to hold out high corrosive amounts that are present in chlorine-saturated environments; this can cause an untimely failure.

What’s more? Builders shouldn’t utilise weathering steel in open-air applications that could spark off galvanic corrosion or even corrosion that is brought about by severe pH levels.

BlueScope Plate Supplies

BlueScope Plate Supplies is an innovative and dynamic Australian steel company that deals in the processing and distribution of steel plate products. We offer an assortment of steel plate products through our branches that are located all over Australia.

Our core commitment to provide our clients with a diverse range of high-quality steel products along with our allegiance to top-notch customer fulfilment is the archetypal hallmarks of BlueScope Plate Supplies.

At BlueScope Plate Supplies, we distribute an array of XLERPLATE®, TRU-SPEC®, and BISALLOY® steel brands for different exposed applications. We can cut metals to your specific requirements.

Visit one of our branches in Australia today!

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