Shipping containers are made primarily of Corten steel, a weathering steel alloy that resists corrosion, with a marine-grade plywood floor laid over a steel frame. The modern steel container was introduced in 1956 and changed the way companies moved cargo around the world. Containers let businesses ship goods safely, load and unload them quickly, and move them between ships, trains, and trucks without unpacking, while bringing much-needed standardization to the entire industry. Below, we explain what shipping containers are made of and how they are built.
What Are the Components of a Shipping Container?
Because shipping containers are designed to be stacked and exposed to harsh weather at sea, they are fully enclosed steel boxes with four walls, a roof, and a floor, with double doors on one end. A sealed container in good condition is wind and water tight, keeping rain and wind out. Reinforced steel blocks called corner castings sit at all eight corners, which allow cranes to lift containers and let them lock securely on top of one another during transport.
There are three main parts to a shipping container:
- First, exterior panels – These are what give shipping containers their box-like shape. The paneling is held in place by steel ribs that run vertically along the three sides of the containers.
- Interior flooring – The flooring of a shipping container is the majority of what the interior consists of. It’s made up of steel beams and bracing on both the top and bottom of the flooring to give it structure.
- Roof – Most of what makes up a shipping container roof is steel mesh covering what’s a “honeycomb.” These two components give shipping containers what’s “high cube storage,” meaning the roof height makes them valuable to shipping companies and allows them to store more in each container.
What Are Shipping Containers Made Of?
Shipping containers are made of Corten steel. Containers need to be weatherproof, durable, and strong enough to be stacked several high on cargo ships, so the frame, walls, roof, and doors are all built from this alloy. The only major part that isn’t steel is the floor, which is marine-grade plywood laid over steel crossmembers.
Corten steel, sometimes called weathering steel, is a group of steel alloys that contain small amounts of copper, chromium, and nickel. When exposed to the elements, Corten forms a thin, stable layer of rust on its surface that protects the steel underneath from deeper corrosion. That is why a used container can show surface rust and still be structurally sound and wind and water tight. The wall panels are typically about 1.6mm thick, while the roof and front end are usually closer to 2mm, and every panel is corrugated to add strength without adding much weight.
How Are Shipping Containers Constructed?
You may be surprised to learn that shipping container manufacturing isn’t entirely by machine. Instead, much of the process includes manual labor by teams of skilled workers. This labor ensures that each steel shipping container consistently meets the standardized specifications required to be efficient.
The first step of the process is the fabrication of the container panels.
Large rolls of steel are unrolled and cut down into sheets 1.6 to 2mm thick. Each sheet is then sandblasted and primed to remove any dust or other contaminants. Once the steel is prepared, it is pressed into corrugated panels. This makes them stronger and gives them the familiar wavy appearance of modern shipping containers.
The next step is welding together the tubular steel frame of the container.
The floor frame assembly consists of two longer I-beams laid out perpendicular to each other. They have smaller I-beams welded between them to give more strength to the structure. Once the welding is complete, a flap disc angle grinder removes any rough welding joints.
With the walls and floor complete, the next step is adding the front and back doors of the container.
Just like the rest of the container, the doors are corrugated Corten steel. Once the steel has been cut into the proper shape, it is encased in square steel tubing before sanding. This is to remove any rough welding joints.
The doors and wall panels are then attached to the floor frame. The corner posts are lined up, and everything is welded together to ensure the proper amount of strength and waterproof everything. Reinforcing braces are for extra durability and to spread any impact evenly throughout the entire frame. Next, the roof is lifted into place by a crane and welded to the whole framework.
Once quality control is done, and a final sandblasting is done, a primer layer is sprayed onto the structure before being painted.
The primer will allow the additional layers of paint to stick more effectively to the corrugated metal. After the primer dries, multiple coats of paint are sprayed on. This helps to further protect the container from the harsh elements.
A layer of 28mm marine-grade pressure-treated plywood is then attached to the floor frame. The wood is treated with EPA-approved chemicals, including pesticides and anti-decomposing agents. This will ensure the safety and longevity of the floors. Six panels of this plywood are screwed directly into the steel floor beams.
The shipping containers are now ready for company decals and logos.
They will also require labels with several unique codes. This is a system used in order for people to identify the container from anywhere in the world.
Shipping Containers In OKC
If you are ready to purchase quality shipping containers, let Twisted S Containers help you. And if you have any questions, do not hesitate to contact us today. Our experts are always happy to assist with all your shipping container needs.
Read More: How to Buy a Shipping Container: 5 Step Beginner’s Guide, How to Finish the Inside of a Shipping Container: 8 Steps
Shipping Container FAQs
What is Corten steel?
Corten steel, also called weathering steel, is a steel alloy containing small amounts of copper, chromium, and nickel. When exposed to the weather, it forms a stable layer of surface rust that protects the steel underneath from deeper corrosion, which makes it well suited for shipping containers and other outdoor structures.
Will a shipping container rust?
Yes, but slowly. The surface rust that forms on Corten steel acts as a protective barrier, so most rust on a used container is cosmetic rather than structural. Keeping the container off wet ground and touching up paint on scratches and dents will help it last much longer.
How long does a shipping container last?
A container typically spends 10 to 15 years in ocean shipping service. Once it is retired to land use as storage, a container that is kept off the ground and maintained can last 25 years or more.
Are shipping container floors safe?
They are safe for storage. Container floors are marine-grade plywood treated with pesticides at the factory to meet international quarantine rules, so if you plan to convert a container into living space, it is a good idea to seal the floor or install a new subfloor over it.