What is COR-TEN Steel?

Nearly all current shipping containers are built from Corten Steel, often referred to as weathering steel or COR-TEN steel. Slow to rust, strong and durable it is the ideal for shipping containers

blue 20ft shipping container with little to no damageWhat is COR-TEN Steel?

Corten steel is a special alloy of steel, approx. 85% steel with the remaining elements made up from Phosphorus, Copper, Chromium and Nickel-Molybdenum.

COR-TEN A Grade steel has phosphorus in it, whereas COR-TEN B grade steel does not. All shipping containers use COR-TEN A grade steel as standard. As best we understand COR-TEN B grade steel is more widely used in aesthetic and cosmetic fittings and fixtures as well as artworks.

Why is COR-TEN Steel Used in Shipping Containers

Put very simply, its been tried and tested, as have other options. COR-TEN steel offers the best mix of durability (perhaps going as far as abuse-ability), weather resistance and strength. These qualities make it an ideal material for use in shipping containers.

COR-TEN steel is such a popular material for use in shipping containers as it has proven itself to offer the best balance of value, lifespan and strength. You can give it a knock or a bump and it will still work just as well.

Rust

used 20ft container with some surface rust

Rust forms very slowly on shipping containers when made with COR-TEN steel. When it rusts, the rust layer itself is not porous. This means it doesn’t let water through the rust layer. This is the property that means this alloy of steel is perfect for shipping containers.

Longevity

The side walls of a shipping container are generally 1.6-1.8mm thick, depending on factory and when it was built. We receive all our used shipping containers with a broad average of 15 years old.

The chances of this 1.6-1.8mm thick steel having rusted through during its lifespan are near zero. We suggest you expect a minimum of 10 more year use out of your shipping container with minimal to no maintenance required.

Weather Proof

A typical shipping container is built to survive a 15+ year life in service. It will spend a lot of time in some of the harshest weather environments the globe has to offer. Commonly surrounded by saltwater. If not on the high seas, a shipping container is still likely to be on or near a docks.

Durable

Shipping containers are serviced by ports and depots around the world. Each port is different, they may have different cranes and handling equipment. They won’t all handle a shipping container in the same way to each other. Some terminals will be rougher or harsher than others. (often the age of the port equipment in use plays a big factor here!)

Can Shipping Containers be Made of Anything Else?

Over the years other materials have been tried and will continue to be tried and tested out, but so far Corten steel has won out.

Galvanised Containers

Galvanised shipping containers have been in circulation before. They worked well, as long as they didn’t receive damage that would break or crack the external galvanisation layer. Damage was very easy to do as a shipping container will receive a bump or knock fairly regularly.

Galvanisation is a fantastic quality weather proofing process, but the galvanisation layer is (compared to steel) relatively brittle and can break or crack on impact.

The main reason we believe these were not more widely adopted is due to maintenance. During its lifetime a shipping container will require maintaining, which commonly involves welding. Galvanised steel gives off some nasty gasses when its welded. Its more specialist then welding mild or COR-TEN steel and it needs specialist equipment. It make it much more expensive to maintain a galvanized shipping container over a lifetime of use in the shipping industry.

Although galvanised containers that are suitable for shipping are no longer available, we do offer a range of galvanised storage containers. These are great options for storage as the galvanisation provides fantastic weatherproofing. As storage units, if sat static, they will not endure as many knocks and bumps as a shipping container.

Aluminium

For some time aluminium shipping containers were used. Aluminium does not rust at all and is has to be said, used examples that we have seen have generally been in very good condition. However, these are no longer widely used. We are unaware of any factory offering aluminium shipping containers in the current market.

Aluminium shipping containers that we have seen were built with largely flat riveted sides that were not corrugated. We assume this was to reduce the amount of aluminium needed in the construction. Unfortunately, this also means its relatively easy to pop these rivets with a crowbar or similar.

How Long Does Corten Steel Last?

We regularly see very old shipping containers, well over 25 years old still without signs that they are rusting through. Obviously the degree of corrosion depends a lot of location and how well its been looked after when at the previous owners site. If a 1.6mm sheet of steel can normally last 25 years plus, this offers the casual user an idea of just how good the in-built protection of Corten steel is.

40ft used container with some surface rustWhen untreated / not painted or similar the surface will evenly rust over a few years and offer a reddy brown rusty oxidised appearance. There are some great example photos of cosmetic use for Corten steel in some of our reference & credit links below.

With shipping container traders and those in the shipping industry, looks and appearance of a shipping container generally have a much lower priority. The aim being to get the customer’s goods from A to B as cheaply as possible, on time and safely.

Contact Us

Budgetshippingcontainers.co.uk offer the UK’s largest online range of shipping containers for sale with a nationwide network of storage and conversion yards and crane equipped delivery vehicles.

If you need a shipping container feel free to browse our online range of shipping containers for sale. You can also call us on freephone 0808 1234 215 any time 9am – 5pm weekdays and our team will be happy to discuss your requirements. Alternatively, you can use our online shipping container quote form or request a telephone callback. In both cases we aim to get back to you within 1-2 working hours (may take longer for more detailed quotes).

Sources and Credits for this article

Background info about COR-TEN steel has been taken from:

https://masteel.co.uk/products/weathering-steel

https://www.john-steel.com/en/blog/metal-advice/corten-steel-naturally-rusted-steel

For more information on What is COR-TEN Steel? talk to Budget Shipping Containers