How Are Shipping Containers Made? (Step-by-Step Manufacturing Guide)

Have you ever looked at a shipping container and wondered where it came from?

These steel boxes are the building blocks of the modern world. They carry everything from the phone in your hand to the shoes on your feet. But they don't just appear out of nowhere.

Creating a container that can survive 15 years of saltwater, storms, and rough handling requires a fascinating and heavy-duty industrial process.

At TraceContainer.com, we track millions of these units, but today, let's look at how they are born.

Here is the simple, step-by-step journey of how a shipping container is manufactured.

Step 1: The Raw Material (Corten Steel)

A container isn't made of normal steel. If it were, it would rust away after a few trips across the ocean.

Manufacturers use a special type of "weathering steel" called Corten Steel.

• What is it? A high-strength steel alloy designed to resist corrosion.

• How it works: When exposed to the elements, Corten steel forms a protective layer of rust on the surface that stops deeper corrosion from eating through the metal. It’s like the container creates its own shield.

40ft standard dry container explained

Step 2: Unrolling and Corrugating

The steel arrives at the factory in massive, heavy coils.

1. Unrolling: The coils are unrolled into flat sheets.

2. Corrugating: Powerful hydraulic presses stamp the flat sheets into a wavy pattern (corrugations).

3. Why the waves? Think of a piece of paper. If you hold it flat, it bends. If you fold it into a fan shape, it becomes stiff and strong. The wavy walls give the container its incredible strength without adding extra weight.

Step 3: Assembly (Welding the Box)

Now, the parts come together in a massive jig (a frame that holds everything in place).

• The Floor Frame: Heavy steel beams are welded together to form the base.

• The Walls: The corrugated side sheets are welded vertically to the frame.

• The Corner Castings: These are the most critical parts. The four corners of the container are fitted with heavy steel blocks called "Corner Castings." These are what cranes hook onto to lift the box.

At this stage, the container looks like a container, but it is just bare, shiny metal.

Step 4: Painting and Priming

Before the floor is installed, the steel shell is prepared to face the ocean.

1. Shot Blasting: The steel is blasted with tiny metal beads to remove dust, oil, and welding slag. This makes the surface rough so the paint sticks better.

2. Priming: A zinc-rich primer is sprayed on. This is the first line of defense against rust.

3. Painting: Robots spray the final color—often blue, red, or orange—using marine-grade paint that is thick and durable.

Step 5: Installing the Flooring

You might be surprised to learn that the floor of a shipping container is usually made of wood.

• Plywood: Workers install thick sheets of marine-grade plywood (usually bamboo or tropical hardwood) over the steel floor beams.

• Treatment: The wood is treated with varnish to prevent rot and keep pests (like termites) from traveling between countries.

Step 6: The Doors and Seals

The heavy steel doors are hung on hinges.

• Rubber Seals: Thick rubber gaskets are installed around the door edges. These seals are watertight—they keep the ocean out, even during a storm.

• Locking Rods: The vertical metal bars you see on the back of trucks are installed. These "Locking Bars" clamp the doors shut tight against the frame.

Step 7: The "CSC Plate" (The Passport)

The final step is the most important for legality. A metal plate called the CSC Plate (Convention for Safe Containers) is riveted onto the left-hand door.

• What's on it? The container's ID number, manufacturing date, max weight limit, and inspection date.

• Why it matters: Without this plate, a port cannot legally load the container onto a ship. It is the container's passport.

Step 8: Testing

Before leaving the factory, a random sample of containers is tortured.

• Water Test: They are sprayed with high-pressure water to check for leaks.

• Load Test: They are loaded with massive weights to ensure they don't buckle.

Conclusion

From a roll of steel to a finished unit, the process is a marvel of efficiency. In major factories in China (where 96% of containers are made), a new container can be finished every few minutes.

Next time you pass a truck on the highway or track your shipment on TraceContainer.com, remember: that simple metal box is a masterpiece of engineering designed to survive the toughest environment on Earth.