Shipping Container Exterior Finish

Exterior Finish of Cargo Shipping Containers

Do Cargo Containers Need Paint Protection?

What should the shipping container’s exterior finish look like? In general, CorTen steel does not require protective or “beautifying” paint. The patina developed after years of aging firmly bonds with steel. That leads to sealing underlayers of raw metal from exposure to the atmosphere. It also offers quite a pleasant light-reddish visual effect, exceeding what is expected from industrial-grade structures. However, due to the long and harmful exposure to highly corrosive, salty moisture and seawater, most manufacturers protect CorTen-made industrial shipping containers by marine-grade paints. Such paints have quite remarkable properties. They create very durably, waterproof and easy to clean coatings. They effectively seal the metal structure from the impact of an aggressive environment. Unfortunately, most of them contain harmful chemicals (lead, chrome, phosphorus… frankly often God only knows what, but certainly not healthy for humans). For long such paints are banned from housing applications, cargo shipping containers do not belong to such class of structures.  Any potentially toxic paints (especially these “economically advantageous”) are widely used in the transport industry.

How to Protect Recycled Cargo Shipping Containers

In many cases, the potential impact of harmful chemicals contained in industrial paints can be managed.  Assuming low concentrations of toxins, they can be “encapsulated” by coating metal surfaces with residential-type paints. They will greatly limit the off-gassing process (if any after years of service in the transport industry) and eliminate the physical contact (especially important for kids as they touch everything they can, then put hands in their mouths). Such protection is certainly valid in structures with limited (temporary) human presence (sheds, garages, storages etc…).  When it comes to habitable spaces (especially residential housing), it will be wise to check with local authorities to make sure that the refurbished structure will get pertinent certifications. As it may sound bad, let’s make it clear – it seems that encapsulating potentially toxic coatings by approved paints is widely accepted by codes governing residential buildings!

How to prepare a shipping container exterior finish?

Before applying any paint, the shipping container’s surface must be cleaned from oils, grease, flakes of old paint, rust, dirt and toxic residues (if any) … The best (and safest) way to proceed is to use pressure-washing (if possible, the best will be power-washing). The rusted areas should be cleaned using a wire brush and then sprayed with rust-inhibiting paint. The cleaning process removes loose paint chips, leaving old, strongly adhering paint intact.

Shipping Container Exterior Finish

In contrast – sandblasting, allows for the removal of questionable paint and rust, however on top of being labor-intensive and costly, it generates more environmental and health hazards by releasing minuscule particles of chemical compounds into the air. Bottom line – if sandblasting is necessary, it should be done by professionals using specialized equipment and personal protection. Note that according to environment protection law, the remains of sandblasting must be disposed of in depots intended for that purpose.  The encapsulation of potentially hazardous old paint can be also accomplished by applying (spraying) closed-cell polyurethane foam. This method has double benefits because it also creates the thermal barrier (insulation). However, you must be aware that these kinds of foams are off-gassing (releasing harmful chemical compounds in gaseous form) for several hours after application.  Care must be taken when using!

What are the best paints for container houses?

When used shipping container requires fresh paint or when you want to change its original color to the one more balanced with surroundings, or simply to match your preferences you may consider the following options:

Industrial-grade alkyd-enamel paint

Enamel belongs to the class of “hard texture” paints. It’s specifically designed for outdoor applications on surfaces of steel, wood and masonry as the protection against weather-induced wear. When dried, it’s a hard, mostly glossy, uniform finish that may last for several years.

Polyurethane paint

Polyurethane paints create durable (lasting for years), weather-resistant coatings designed for steel (metal) surfaces. Thanks to these properties, they are largely used by heavy industry. The downsides – due to their chemical composition, they may be more hazardous and so should be used only for exterior applications. There are also numerous oil and enamel-based spray paints for interior and exterior (outdoor) applications on metals. Some popular, suitable for DIY application are a series of Krylon and Rust-Oleum sprays. They offer strongly adhesive to metals, durable, UV-resistant, rust-preventing coatings that will keep for years their initial appearance. Note that both, interior and exterior walls may need similar water-resistant paint. It’s because, with an interior layer of insulation, the metal wall will have a temperature very close to outdoor conditions and so will be exposed to condensation of humidity. To some extent, the condensation effect can be reduced by using Ceramic Coating on exterior walls. This NASA-developed “Ceramic Paint Insulation” despite its thinness, creates a noticeable thermal barrier helping to slightly increase the temperature of metal walls and so decrease the condensation. When cargo shipping containers are refurbished (recycled into habitable spaces) by specialized companies, they may be able to use more robust, bonding with metal-baked enamel paints.

Shipping Container Paint

Read more about protecting shipping container home here!

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