Shipping container homes can rust. Containers are made of corten steel, which only delays the process of corrosion but cannot prevent it completely. Non-structural rust appears on the surface and can be treated with brushing, sanding, sealing, and repainting. However, if the rust doesn’t seem to go away and has penetrated into the steel, this is known as Structural Rust. This second type of rust needs to be professionally treated to prevent further spread and damage. Rust can occur from its previous use sitting in saltwater puddles for months at sea, as well as pooling on the top from any dents in transit.
What Are Shipping Containers Made Of?
Your typical 20-foot and 40-foot shipping containers are made of “cor-ten” steel, or “weathering steel.” This type of steel comprises a mix of steel alloys and was made in the United States in 1930. The goal was to fabricate corrosion-resistant steel, corten being abbreviated of “CORrossion resistance and TENsile strength.” (1)
This does not mean Cor-ten steel will never rust or corrode. It does, however, delay the process more than regular steel.
Weathering steel develops a thin protective oxide coating to help slow down corrosion. In order to build this coating, it needs to undergo regular cycles of wet and dry environments.
The more wet and dry cycles corten steel goes through, the better the oxide later performs. This is also the reason why the kind of climate your container will be located in, greatly matters. If the environment is too wet, or too dry and without the other, the oxidation process won’t be as effective. (1)
This protective layer can also be removed due to any damage and dents during transit. Carefully inspect your container for damage before buying it and be sure to check areas of heavy use like the doors. (1)
Rust occurs when steel, water, and oxygen interact. This process is known as oxidation. Containers by the sea will rust quicker due to the salty air as it speeds up the oxidation. Some even recommend not building any container homes within three miles of the seashore. Other climates that will pose difficulty for container homes are areas with heavy rain, fog, or high humidity. (1, 2)
Beware of containers being sold at ocean ports or any of the climates previously mentioned as these containers have surely sustained some damage in the weather. (3)
Types of Shipping Container Home Rust
There are two types of rust we’ll encounter with container homes, namely non-structural and structural.
Non-structural rust appears on the surface and can be treated. One must remove it the rust patch with a wire brush or sandblasting with sandpaper, reseal it, and repaint the area. Do this until you can no longer see the rust.
Structural rust is the bigger problem as this has grown beyond the surface and into the walls, causing the structure to weaken. You may need to cut off the entire affected area in order to solve this kind of rust.
How to Remove the Rust?
If you’ve found a patch of rust, make sure you have all the safety gear of goggles, face mask, and even nylon gloves. This is to protect you from the chemicals and dust of the sandpaper. You’ll need a wire brush and can go for the silicon carbide sandpaper with no grit finer than 320. (3)
For more details and even product recommendations on the best gear and tools to get, check out this helpful piece. Do Container Homes Rust? – Live in a Container
If in sanding the area, the rust doesn’t seem to go away, this may mean it has progressed into structural rust. Structural rust needs to be professionally treated with a spot weld or be cut out and removed completely to prevent a further spread. (4)
How to Prevent Structural Rust?
Proper Landscaping and Siting of Elements
If you knew where the wind was blowing hardest, or where the sun was shining the hottest, buffer the intense wind and heat by planting your trees on that side to protect your container.
This would lessen the amount of weather exposure and prolong the container’s life. You could also apply cladding onto these sides to support the cor-ten steel from taking all the damage on its own. (1)
Aim that the smallest area is facing the side that receives the harsher weather. Make sure however that you don’t plant any plant barriers too close to your home, as this can be another source of moisture accumulation. (4)
Protect the Container Home Well
Shade the container home with a separate roof structure. A roof with an overhang protects the container shell from dealing with the weather elements directly. (4)
Ensure adequate ventilation in your home to prevent condensation. We talk about this more at length in another article, it is just important to know that condensation brings rust and mold, leading to moisture damage. Good ventilation helps keep your home cool and dry. (2)
If your soil conditions and climate allow, opt for a foundation with a crawl space, a full basement, or any system that allows you to access underneath. For this purpose, avoid having a slab foundation. (2)
Maintenance for Rust Prevention
Regularly inspect your container for any pools of water, especially after any major storm or weather event. (4)
Often, water accumulates on your roof and we don’t see this happening in our day-to-day lives, therefore needs a special check. Check for any dents that may be collecting more rainwater as this will encourage rust and corrosion. (1)
Checking the top and bottom sides is essential. The bottom side may have been sitting in salt water for months on the ship, and also have trapped moisture. This side, not being exposed to any ventilation for some time, would surely rust and corrode the under face. (3)
If you’re buying a new container or renovating an old one, have the floor replaced. Most likely the floor has suffered water damage and absorption in transit. Not only that, but the wood may also contain toxic pesticides to safely convey the goods.
You also eliminate any hazardous chemicals that the containers previously carried and may have seeped into the floors. Besides rust, for personal health and safety, it’s best to replace the floor entirely. (2, 4)
Rust on any structural members, meaning your posts, beams, and joists are a sure reject for a home. Find another container that won’t have you replace the entire structural frame. If you find patches of rust on the other wall surfaces, just scroll back up on how to remove the rust and you’re good to go. (3)
Paint is also a method of avoiding rust. Direct-to-metal, marine grade paint is the best kind to protect the container. Once the paint chips or flakes off the corten steel exposes and forms a bit of rust to prevent it from getting deeper into the steel. (1, 4)
- Shipping Container Rust Prevention Basics – Discover Containers
- How Should I Protect My Shipping Container Home from Rust? | Design Ideas for the Built World (caddetailsblog.com)
- Do Container Homes Rust? – Live in a Container
- Do Container Homes Rust? – Real Estate Info Guide