“Are shipping containers weatherproof?”
Unfortunately, the answer isn’t a simple yes or no.
People often think of this question because shipping containers are iconic symbols of durability, thanks to their rugged Corten steel construction.
Capable of handling harsh ocean voyages, these steel boxes are inherently weather-resistant, but are shipping containers weatherproof?
While Corten steel offers impressive protection, even extreme weather patterns can challenge its limits and stretch out its capability to handle any external damage.
Because of that, let’s break down how shipping containers hold up against rain, sunlight, snow, and moisture, and explore practical ways to enhance their resilience!
Also Read: Stadium Container Kitchen: Solution for Sports Event Management
Contents
Corten Steel’s Actual Protection Levels Against Weather Patterns
Corten steel (or weathering steel in other terms), the main material people use to build shipping containers, is a weathering steel alloy.
Why do people praise and use them so much when they build shipping containers?
Befitting its name, the steel has innate corrosion resistance (COR) and tensile strength (TEN) that enables protection against nearly any damage source.
When exposed to the elements, the steel forms a protective rust layer (patina) that acts like armor, slowing further corrosion.
Furthermore, corten steel also has 68-78 KSI tensile strength, which makes it even harder to break or buckle the steel construction.
However, like any steel-made object that continuously gets subjected to the elements, the steel’s effectiveness depends on the weather conditions it faces.
Against Rain
Let’s get one thing straight – Corten steel handles rain well, if the water doesn’t pool inside!
The patina thrives in environments with alternating wet and dry cycles. Rain helps the oxidation process, allowing the protective layer to stabilize.
However, standing water (e.g., puddles on the roof or around the base) can trap moisture against the steel, leading to uneven rusting or accelerated corrosion in vulnerable spots like seams and welds.
These container parts often suffer the most from waterborne damage:
- Roof corners: Poor drainage here can lead to rust streaks.
- Door seals: Worn gaskets let water seep into the floor edges.
- Floor edges: Prolonged moisture exposure can warp marine plywood.
As a result, Corten steel needs wet/dry cycles to form a stable patina. If you use or place the container in places with constant rain, you must provide proper drainage to mimic these cycles.
Against Sunlight
Sunlight isn’t a direct threat to Corten steel, but UV rays and heat cycles can indirectly cause issues.
Prolonged exposure to intense sunlight can dry out the patina prematurely, leading to flaky rust in arid climates.
This can become even worse in places with extremely hot temperatures. As it turns out, thermal expansion and contraction might stress welded joints over time.
So, what happens if your container suffers from constant sunlight exposure?
- Roofs: Direct UV exposure can fade the patina’s earthy color.
- South-facing walls: These endure the most sun in the Northern Hemisphere.
To keep your container in prime condition, apply a UV-resistant sealant to slow patina degradation.
Against Snow
With its weight and moisture, snow can be surprisingly burdensome to shipping containers. How?
Heavy snow loads can stress the container’s structure, though most containers are built to handle this.
The bigger issue is melting snow. If snow melts and refreezes repeatedly, it can seep into cracks or sit against the steel, disrupting the patina’s stability.
Even worse, in coastal or road-adjacent areas, snow mixed with de-icing salts can introduce corrosive chlorides.
After some time, snow can damage these container parts significantly:
- Roof seams: Ice dams can form here, trapping moisture.
- Door hinges: Salt-laden slush accelerates rust in these joints.
Because of what snow can do if it piles on the shipping container, you should use sand instead of de-icing salts near containers to avoid chloride corrosion.
Against Moisture
If you think of corten steel as someone like Superman, then moisture and saltwater environments are Corten steel’s kryptonite.
In coastal areas like ports or beaches, salt-laden air accelerates rusting, while high humidity can prevent the patina from fully drying, leading to porous, less protective rust.
If you don’t do something to the shipping containers that you place in moist places, these container components can degrade:
- Coastal containers: Salt spray targets the lower third of the structure.
- Floors in humid climates: Trapped moisture rots plywood and breeds mold.
So, what can you do? Easy! You can rinse containers near oceans monthly with fresh water to remove salt residue.
How to Improve Corten Steel’s Durability Against Weather Conditions
At this point, we finally know that while shipping containers are weather-resistant by design, only proactive steps can make them weather-proof.
Here’s how to fortify your container against any climate patterns and answer “Are shipping containers weatherproof?”:
Apply Protective Coatings or Sealants
- Clear Varnishes: Use UV-resistant, breathable sealants (e.g., Corten-specific varnishes) to lock in the patina and prevent flaking. These coatings shield against salt, rain, and UV rays without hiding the steel’s rustic look.
- Rust Converters: For existing rust spots, apply a converter (like phosphoric acid solutions) to stabilize the corrosion before sealing.
- Paint: If you want a non-rusty finish, use industrial enamel paints and ensure the steel is clean and primed first.
Ensure Proper Drainage and Ventilation
- Install Roof Slopes or Gutters: Prevent water pooling by adding a slight slope to the roof or fitting gutters to direct runoff.
- Elevate the Container: Place the container on gravel, piers, or blocks to keep the base dry and improve airflow underneath.
- Add Vents: Cross-ventilation reduces interior humidity, protecting the floor and walls from condensation.
Combat Salt and Chemicals
- Rinse Regularly: In coastal areas, hose down the container periodically to remove salt residue.
- Avoid De-Icing Salts: Use sand instead of salt on nearby walkways in winter. If salt exposure is unavoidable, apply a wax-based sealant to the lower third of the container.
Reinforce High-Risk Areas
- Seal Roof Seams and Door Gaskets: Use silicone caulk or EPDM rubber seals to waterproof joints.
- Install Splash Guards: In rainy or snowy climates, attach metal or plastic guards to divert water away from the base.
Perform Regular Maintenance
- Inspect Quarterly: Check for rust spots, peeling sealants, or damaged seals.
- Clean Annually: Remove dirt and debris with a soft brush or low-pressure washer. Avoid harsh chemicals.
- Reapply Sealants Every 2–3 Years: Refresh coatings to maintain protection.
Accelerate the Patina Process
If you want the protective rust layer to form up faster than its usual rate, then you can do the following:
- Mix 2 cups hydrogen peroxide, 2 tablespoons vinegar, and ½ teaspoon salt in a spray bottle.
- Mist the solution onto clean steel twice daily until the desired patina develops.
- Seal with varnish once stabilized.
Also Read: How to Clean Shipping Container Floors and the Best Tools
Conclusion
To close our explanation, what’s the answer to the question, “Are shipping containers weatherproof”? It’s yes, but only if you take the necessary measures to make them truly weatherproof. Contact Tradecorp today if you need the containers to be extremely weather-resistant, even from the start! Using industrial tools and practices to keep its containers damage-proof, Tradecorp ensures its containers to be resistant against all weather patterns.
