What are Steel Shipping Containers Made of?

What type of steel are shipping containers made of? The corrugated wall panels, frame, cargo doors, and cross members of metal shipping containers are all made from corten steel. This special type of steel, also known as weathering steel, is the primary material in shipping containers.

Corten steel is distinguished from other types of steel in that it’s a group of steel alloys that were developed to eliminate the need for painting. Container manufacturers use this material because it possesses the physical properties that make it weldable and rust-resistant. In practice, rust resistance means that should a piece of paint chip off of the steel, a thin layer of rust will form at the surface but not go much deeper.

In addition to the main compartment of a shipping container, you may find additional shipping container components made from varying materials.

Components of a Shipping Container

Most every shipping container is manufactured to have these unique features:

Corner Castings

The reinforced corner posts of shipping containers are called corner castings. Corner castings have openings for twist lock connections that allow them to be connected to other containers or to anchor points. They’re also designed to be strong enough for crane rigging (to be lifted by rigging to a crane), even when fully loaded.

Twist Locks

Twist locks securely connect shipping containers to anchor points or to other containers. The end piece of the twist lock fits into the corner casting and then pivots to a locked position, usually via a lever.

Forklift Pockets

Standard 20-foot containers and many 40-foot containers come with two openings along the bottom edge of the structures, called forklift pockets. As their name implies, forklift pockets are reinforced slots designed to accommodate forklift tines. Forklifts can insert the tines into the pockets in order to lift and move the structures. Please note that some shipping container modifications add enough weight to the structure that it makes lifting by forklift inadvisable, especially with modified 40-foot shipping containers.

Cargo Doors

A storage container’s cargo doors are the two steel doors most often found at one end of the container (though some shipping containers have cargo door assemblies on both ends, and even have cargo door side walls). Cargo doors were designed to prevent theft and weather intrusion on long voyages and offer formidable security for the assets contained within. The door’s locking mechanism may be unfamiliar to new container users, so be sure to check out our video on how to open shipping container cargo doors.

Marine-Grade Plywood Flooring

Most shipping containers come with marine-grade plywood flooring. The flooring is infused with a small amount of insecticide to prevent six-legged stowaways from joining the container’s voyage. These insecticides do not aerosolize and are only a risk to hungry bugs, not to the people who come in contact with the flooring. We’re so confident in its safety that we even kept the original plywood flooring in our container-based Falcon Structures office.