How Should I Protect My Shipping Container Home from Rust?
Shipping containers can be expendable, at least in the United States. The country tends to import more goods carried by container than export. It’s less costly to ship goods in new containers than to ship empty ones back to the exporting country.
The empty shipping containers, thus, are available to be repurposed. One growing market for used containers is architecture—they are used to build homes. Both 20’ and 40’ containers can be combined to form a larger structure, or a single container can serve as a “tiny home.”
All homes need to be protected from the elements. Wood rots; mortar between bricks or stone crumbles. Container homes are no different—they are at risk of rusting if they are not handled carefully.
As with many things, prevention is the first—and best—step in solving a problem. Most shipping containers are made from COR-TEN steel, which is strong, durable, and resistant to corrosion. Cor-ten steel is also known as the “weathering steel.”
Cor-ten develops a thin layer of oxide—rust—when exposed to air and water. That layer is the corrosion protection for the steel. Cor-ten needs a wet and dry cycle to develop this protective coating. If your climate is mainly wet, then you won’t get the dryness. If you’re in a dry climate, you won’t get the wetness.
Cor-ten steel is used on containers because manufacturers guarantee 3-5-year corrosion-free period. Given the abuse containers can suffer at sea, that might seem like a long time, but homes should last longer than that, and any container home must take many factors into consideration.
First off, make sure you’ve designed your container home well. Minimize the exposure of the containers to weather, and be aware of your physical situation. If the weather mainly comes from the west, for example, plan on more plantings or shelter to the west side of the house to manage the amount of water getting on the house.
Plan on using shade to help keep the home cooler in summer. Not only will the occupants be more comfortable, but the house will not have as much condensation. Condensation causes both rust and mold and can also damage insulation. Ventilation will also keep the container cooler and dryer.
People building in coastal areas need to be aware that salt-laden air is not the best for Cor-ten steel—it will speed up the oxidizing and corrosion which does occur. Some recommend not using containers to build homes within three miles of the shore.
Most locations will require a foundation for the home. Don’t place a container on a slab. Either a full basement or crawl space will be better, especially since either one allows access to the underside of the container.
During the design process, make sure any areas which might catch water are either eliminated or covered. Places where containers are joined could become corrosion traps. If leaves can be trapped in a spot, find ways to correct them.
Inspections: Container Condition
Home builders should thoroughly inspect their containers—top, bottom, and sides. Pay close attention to the area under the floor. This space may have been exposed to excess water and the elements. The cross-members supporting the floor may be badly corroded, as may be the side rails.
Replace the floor. The hardwood floor of the container may have suffered water damage. Also, the wood was probably treated with some harsh pesticides. Take it all away and start again. You will find the new floor more than worth the extra cost and time.
Thorough cleaning of the container is essential, not only for corrosion protection but to eliminate any traces of harmful chemicals which may have been present in the container at some time.
Containers are best painted with a ceramic insulating paint. While the insulating effects of the paint have been questioned, it does keep the risks of further corrosion down as much as possible.
Builders should also plan insulation of container homes carefully. Insulation should be considered carefully, as too much will take up room inside the container. In cold climates, the insulation is needed to keep the home warm and to protect it from condensation. Several insulation choices are available:
Spray Foam—This insulation forms a vapor barrier with the container, thus reducing condensation and mold. It can be applied to the exterior and then painted, keeping the appearance of the container and the convenience of the insulation.
Insulation panels—These panels provide excellent insulation for their thickness.
Blanket insulation—These rolls require stud walls for placement, which will decrease floor space. It is the least expensive form of insulation, however.
Eco-friendly—Since one reason for living in container homes is eco-friendliness, eco-friendly insulation is consistent with your philosophy; wool or cotton insulation is effective but expensive.
The design of the home is key, also. If you are in a rainy area, you should consider water run-off. A shed roof over the top of the container would be advisable—perhaps enclosed but ventilated to allow more insulation as well.
Shed roofs will also be excellent places to install solar panels, as well as to catch rainwater for later use.
Knowing the Signs of Possible Corrosion
Regular inspection is key for a container home (it probably is a good idea for any home).
The most likely place for undue rust/corrosion is where the container has been dented or damaged. Check the roof and walls after storms. Branches and acorns can cause dings, which break the paint or the oxidation layer. Repair any dents you find.
Check also for standing water on the roof. Letting water stand on the roof will endanger your container faster than any other risk.
Take pictures of any cosmetic rust spots found on the container. While at first they may be harmless, they may also grow and impair the integrity of the home.
Container homes are ideal in storms. They are sturdy and should last through hurricane or earthquake. That said, inspect a container home after any major weather event. Flying debris can cause the dings and dents which lead to corrosion.
Treatment, of course, should begin when the containers are on site. Sandblasting any rust off and getting down to the bare metal is advisable. After it’s clear, the container is ready for priming, sealing, and painting.
If the container develops rust areas over time, clearing the rust with a wire brush and sandpaper works best. Once the area is clear of rust, apply vinegar and let it dry. Painting with an appropriate paint, either the ceramic paint or a direct-to-metal paint will protect the container from further corrosion.