earth science

Weathering steel

Weathering steel is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Weathering steel rather than just read about it. In short: Weathering steel, often called corten steel (or its trademarked name, COR-TEN) is a group of steel alloys that form a stable external layer of rust that eliminates the need for painting. It was first introduced in 1933 by U.S.

Key takeaways

Weathering steel belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Weathering steel to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Weathering steel from memory before moving on to harder problems.

Reference excerpt

Weathering steel, often called corten steel (or its trademarked name, COR-TEN) is a group of steel alloys that form a stable external layer of rust that eliminates the need for painting. It was first introduced in 1933 by U.S. Steel Corporation. U.S. Steel (USS) held the registered trademark on the name COR-TEN until 2016. The name COR-TEN refers to the two distinguishing properties of this type of steel: corrosion resistance and tensile strength. Although USS sold its discrete plate business to International Steel Group (now ArcelorMittal) in 2003, it makes COR-TEN branded material in strip mill plate and sheet forms. The original COR-TEN received the standard designation A242 (COR-TEN A) from the ASTM International standards group. Newer ASTM grades are A588 (COR-TEN B) and A606 for thin sheet. All of the alloys are in common production and use. The surface oxidation generally takes six months to develop, although surface treatments can accelerate this to as little as one hour.

History The history of weathering steels began in the US in 1910s, when steels alloyed with different amounts of copper were exposed to the elements; the research continued into the 1920s and c. 1926 it was discovered that phosphorus content also helps with the corrosion resistance. In 1933 the United States Steel Corporation decided to commercialize the results of their studies and patented a steel with exceptional mechanical resistance, primarily for use in railroad hopper cars, for the handling of heavy bulk loads including coal, metal ores, other mineral products and grain. The controlled corrosion for which this material is now best known was a welcome benefit discovered soon after, prompting USS to apply the trademarked name Cor-Ten. Because of its inherent toughness, this steel is still used extensively for bulk transport, intermodal shipping containers and bulk storage. Railroad passenger cars were also being built with Cor-Ten, albeit painted, by Pullman-Standard for the Southern Pacific from 1936, continuing through commuter coaches for the Rock Island Line in 1949.

In 1964, the Moorestown Interchange was built over New Jersey Turnpike at milepost 37.02. This overpass is believed to be the first highway structure application of weathering steel. Other states including Iowa, Ohio, and Michigan followed soon after. Those were followed by University of York Footbridge in the United Kingdom in 1967. Since then, the practice of using weathering steel in bridges has expanded to many countries.

Properties Weathering refers to the chemical composition of these steels, allowing them to exhibit increased resistance to atmospheric corrosion compared to other steels. This is because the steel forms a protective layer on its surface under the influence of the weather. The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. It is not yet clear how exactly the patina formation differs from usual rusting, but it's established that drying of the wetted surface is necessary and that copper is the most important alloying element. The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather. In other words, the steel is allowed to rust in order to form the protective coating.

The mechanical properties of weathering steels depend on which alloy and how thick the material is.

ASTM A242 The original A242 alloy has a yield strength of 50 kilopounds per square inch (340 MPa) and ultimate tensile strength of 70 ksi (480 MPa) for light-medium rolled shapes and plates up to 0.75 inches (19 mm) thick. It has yield strength of 46 ksi (320 MPa) and ultimate strength of 67 ksi (460 MPa) for medium weight rolled shapes and plates 0.75–1 inch (19–25 mm) thick. The thickest rolled sections and plates – 1.5–4 in (38–102 mm) thick – have yield strength of 42 ksi (290 MPa) and ultimate strength of 63 ksi (430 MPa). ASTM A242 is available in Type 1 and Type 2. Both have different applications based on the thickness. Type 1 is often used in housing structures, construction industry and freight cars. The Type 2 steel, which is also called Corten B, is used primarily in urban furnishing, passenger ships or cranes.

ASTM A588 A588 has a yield strength of at least 50 ksi (340 MPa), and ultimate tensile strength of 70 ksi (480 MPa) for all rolled shapes and plate thicknesses up to 4 in (100 mm) thick. Plates 4–5 in (102–127 mm) thick have yield strength at least 46 ksi (320 MPa) and ultimate tensile strength at least 67 ksi (460 MPa), and plates 5–8 in (127–203 mm) thick have yield strength at least 42 ksi (290 MPa) and ultimate tensile strength at least 63 ksi (430 MPa).

Uses

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Weathering steel

Start with the simplest possible case. Write down what Weathering steel claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Weathering steel before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Weathering steel ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Weathering steel

In research: Weathering steel appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Weathering steel in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Weathering steel is common in secondary-school and first-year university syllabi. It links to neighbouring topics Sculpture materials, Structural steel, U.S. Steel, so understanding it makes those chapters shorter.
In everyday life: Look for Weathering steel outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Weathering steel in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Weathering steel means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Weathering steel out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Weathering steel in simple terms?

Why does Weathering steel matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Weathering steel?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Weathering steel.