Shipping containers have been the staple of logistics for decades and do not seem to change. Ideal for all kinds of transportation and storage, they are ubiquitous in several spheres - from retail to real estate. Their high-quality materials, sturdy construction, and resistance to weathering make them ideal for all kinds of applications, like temporary or permanent storage, living space extension, etc.
While they are pretty straightforward in usage, understanding what shipping units are made of can help you make more informed decisions when buying or customizing one. In this guide, we will walk you through everything you need to know if you wonder, “How are shipping containers made?”. At Midstate Containers, we know all the ins and outs of the industry’s best players, so let's get going!
What material are shipping containers made from?
When it comes to shipping container manufacturing, the material used is everything. Not only does it affect the unit’s durability, but it also determines its weather resistance and long-term performance. While steel is the most commonly used material, manufacturers also utilize aluminium and polyethylene in certain cases. Let’s learn what are shipping containers made of and where different options shine:
Steel shipping containers
Steel (especially Corten) is the backbone of the majority of commercial cargo transport. At the moment, it is the standard material for most intermodal units. Due to its superior weathering properties, Corten can develop a protective surface that is similar to rust and that helps it prevent deeper corrosion. Mix it with exceptional durability and you get an ideal option for long-term outdoor use in practically any weather.
This combination of steel strength and self-healing oxidation makes Corten containers a preferred choice for rugged environments and secure storage solutions. Its high tensile strength supports heavy loads, while the welded seams and reinforced frames ensure structural integrity during global transit.
Aluminum shipping containers
While Corten is, inarguably, the king in the sphere, aluminium shipping units also have their fair share of the market. Unlike heavy steel, they are considerably lighter, making them ideal for sea and air freight, rail transport, or temporary structures, where weight can be a real concern. Besides reducing fuel costs during transportation, it also facilitates the handling, stacking, and repositioning of the units along the way.
In addition to that, aluminium itself is a rather multifunctional container material. For instance, besides being light, it performs remarkably well in humid environments without corroding or growing mold or mildew. You’ll also often find aluminium units used for temperature-controlled units or modular offices, as the material lends itself well to insulation and energy efficiency.
Polyethylene shipping containers
While most storage and shipping units are made of metals like Corten or aluminium, the niche of polyethylene solution is here and growing. It is especially common for specialty or portable storage needs. In its essence, polyethylene is high-density plastic, meaning it does not react with many substances, making it resistant to chemical corrosion, UV degradation, and mildew. This makes for extremely high demand in the agricultural, pharmaceutical, and food industries, where cleanliness and safety are paramount.
An important feature of these units is that they are usually prefabricated in single molds. While it makes them seamless and totally leak-resistant, they are not suitable for stacking, meaning they work well only with ground-level storage or mobile setups.
Find out what shipping containers are made of with Midstate Containers – your trusted source for durable, high-quality units.
How are shipping containers made? Step by step:
Understanding how shipping containers are made gives insight into their rugged design and versatility. Here’s a breakdown of the containers fabrication process:
1. Wall Panels
The process of manufacturing containers always starts with wall panels. Sheets of thick Corten steel are rolled and pressed into a corrugated pattern. Why not just make them straight? This way, the wall gets more strength and is able to withstand more pressure and stronger impacts. The corrugation improves both vertical and horizontal load-bearing properties, a critical aspect in stacking and storage scenarios.
Once they have been formed, the panels are cut into the necessary size and prepped for welding. During this stage, the panels are typically treated with a special anti-corrosive coating to extend the life of the surface.
2. Floor Framing
The floor starts with a base frame made of reinforced steel I-beams or box tubing. This rib-looking structure provides the unit with the necessary support. The main killer feature of such a construction is that it distributes the weight of stored cargo evenly across the whole surface and makes the unit compatible with forklifts.
Forklift pockets and corner castings are integrated at this stage to prepare for eventual transport. These structural features ensure that the unit can be safely lifted and moved with machinery.
3. Doors
Well-made doors ensure both accessibility and security of the unit. Typically, they are made from the same steel and mounted on one end, similar to regular doors. Many modern units feature doors with rubber gaskets for creating a tighter and more weather-resistant environment inside. Additionally, most options include sturdy locking mechanisms for protection.
For customized access, it also uses man doors, which are smaller, single-leaf doors that can be added to the side or rear of a unit. These are popular in-office conversions or modified retail setups, offering easier daily access while maintaining a secure enclosure.
4. Corner Posts
The main load-bearing components of each unit are the four vertical corner posts. These have castings on top and bottom to attach to vehicles, cranes, and rail equipment and to enable stacking.
Because each corner post is welded straight to the wall and frame sections, the unit will remain structurally sound even when fully loaded or under strain.
5. Assembly
Once individual components like walls, doors, flooring, and corner posts are ready, they are assembled in sequence. Welding teams secure each piece to form a rigid, sealed structure. Precision is crucial here; any misalignment could affect waterproofing and load distribution.
The roof is added last, completing the box-like design. Before moving on to painting, every joint and weld is inspected to meet international standards for container manufacturing.
6. Painting
After assembly, the entire unit is prepped for coating. A primer layer is applied to protect against corrosion, followed by one or more layers of industrial-grade paint.
Painting not only serves a protective function—it also allows for branding or visual identification. You can learn more about this process in painting a shipping container, where we break down best practices for long-term results.
Painting is useful not only when assembling a new container, but also in restoring an old one. It is the need to use a custom color or finish. Paint modifications significantly extend the container service life.
7. Flooring
The flooring is secured into the steel floor frame and is typically made from marine plywood or sustainable bamboo. These materials are chosen for their moisture resistance and strength under compression.
Plywood is treated to prevent rot and termite damage, while bamboo offers a green alternative with excellent durability. Both options can withstand heavy loads and environmental shifts without warping or splitting.
Need specialized flooring? Midstate offers tailored flooring modifications to accommodate various industrial and residential uses.
8. Hardware
Next, additional hardware like hinges, locking bars, vents, and handles are installed. This step is critical to make the unit functional and secure.
To enhance theft prevention and tamper resistance, we recommend our lock boxes. These steel covers protect the padlock from bolt cutters and crowbars — an essential feature for construction sites, farms, and remote storage.
9. Labels
The outside is labeled with operating and regulatory information. Along with any necessary serial numbers and branding, this also includes the CSC (Convention for Safe Containers) plate, which attests to the unit's suitability for international shipment.
Labels provide traceability and attest to the unit's compliance with international handling and safety regulations.
10. Waterproofing
In the final phase, the unit is sealed against the elements. Waterproof gaskets are added around doors, and sealants are applied to joints and seams.
Proper waterproofing ensures long-term performance in all climates. Learn more in our blog, The impact of water on shipping containers, where we explore how water damage can affect storage conditions and structural integrity.
Need a shipping container? Understand what goes into making one, and get yours from Midstate Containers today!
Summary
While they may not seem like it, storage units are complex structures where every step in the manufacturing process matters. Whether made from Corten, aluminium, or polyethylene, today’s shipping units are more than just cargo boxes - they’re smart, modular solutions for storage, offices, retail, and beyond.
And if you are looking for the highest-grade units form the most reliable container manufacturers, Midstate Containers is your destination.
FAQ
How thick is the steel on a shipping container?
Typical shipping container wall thickness is between 1.6mm and 2.0mm for walls, doors, and roof panels.
Where Can You Get a Shipping Container?
Midstate Containers proudly serves California and beyond. As a leading container provider, we offer new, used, and custom units tailored to your needs. Reach out for inventory, pricing, or design support.
What is Corten Steel?
Corten is a weathering steel designed to form a stable, rust-like appearance that protects the metal beneath from corrosion. It's ideal for outdoor applications and is commonly used in shipping container manufacturing due to its long-lasting properties and low maintenance requirements.
