How to Prevent Your Shipping Container From Rusting in the Winter
Dec 2020

How to Prevent Your Shipping Container From Rusting in the Winter

Posted By   |  0 Comment

Shipping containers are designed to withstand the extreme conditions at sea for many years when ferrying cargo. In this environment, they’re exposed to an assortment of corrosive elements that range from rain and saltwater to airborne salt and industrial pollutants.

These containers are subjected to physical damage during loading and unloading from ships and trucks, which may breach the paint coating and contribute to corrosion. Ultimately, these containers have a shortened useful life and may require expensive repairs to keep them fully functional in the transport industry.

Rust is dangerous because it causes the metal to corrode and disintegrate, affecting your shipping container’s structural integrity. This may compromise the safety of the contents within, exposing them to insects and vermin, and the elements.

Even non-structural rust, which is not as harmful, will negatively affect the container’s appearance and resale value. It may even affect the image of your business if the rust patches are visible to your customers. Companies should exercise vigilant and regular maintenance and address problem areas as soon as they emerge.

Used Shipping Container Grades

Most of the used shipping containers in Ontario are repurposed after making only one trip. A single trip is barely enough to cause significant damage to the container, compared to used containers that make multiple trips at sea for several years, causing them to appear bruised and battered. Regardless of how long a shipping container has been at sea, all repurposed shipping containers for sale in Ontario will protect whatever is inside, whether used for storage or modified into living or commercial space.

The extent of abuse that a shipping container has gone through at sea determines the grade of containers for sale or rent. Single-trip containers are like new with very minimal dings or dents from handling.

Even the paint coating on these containers makes them shine like new. These containers are of the highest grade and are the most expensive option. But once the container leaves the harsh sea environment, it is likely to withstand the most brutal winters for 25 years or longer with good maintenance.

Other used containers are graded based on the amount of surface damage such as dings, dents, and rust patches and the condition of the doors, floors, and paint condition. Containers at the lowest end of the grading scale usually have many and large patches of surface rust. But even these worn containers are wind and watertight and safe from extreme weather.

Why Shipping Containers Rust

Rust forms when iron readily combines with oxygen in the atmosphere. Rust is a form of corrosion. Corten steel — the material used in shipping container construction — is considered an ‘Atmospheric Corrosion Resistant Steel.’ That means it’s incredibly resistant to atmospheric weathering compared to other unalloyed steels. But because it contains some iron, the metal is still prone to rust.

Once the containers get to dry land and are opened, the risk of rusting from the inside increases. When opened, wet air may get trapped in the container. The condensation can cause surfaces with chipped paint to rust. As such, it becomes necessary to ventilate shipping containers on dry land to prevent rust.

Your shipping container home, office, kiosk, or store is prone to rusting due to exposure to the elements. But this process takes a very long time, and the effects can be successfully mitigated in various ways:

Corrosion Coatings for Shipping Containers

Paint is not enough to adequately protect containers against the harsh conditions at sea. To reduce liability, maintenance and replacement costs, and depreciation, transport companies, usually apply corrosion protection using thermal spray equipment and materials. These corrosion coatings galvanically protect the steel surfaces, maintaining a clean appearance for longer, with no surface rust.

The types of corrosion coatings applied include zinc, aluminum, or zinc-aluminum blends, which increase container service life by providing sacrificial corrosion to protect the steel surfaces. The coating has a thickness of about 100 µm, which provides lasting protection for 15 to 25 years, depending on the environment. You can then apply an overcoat of paint immediately after the corrosion coating without affecting the corrosion protection properties.

Other Rust Prevention Methods for Shipping Containers

Generally, shipping container corrosion is mitigated using corten steel alloy in the construction process and special paints to prevent rust. Some companies go the extra mile to apply a zinc-aluminum coating to enhance the reduce the risk of corrosion for a couple of decades.

Once you purchase your used shipping container in Toronto, you have the responsibility to maintain your unit and protect it from rust. There’re various ways to protect your container from rust in winter, including:

1. Inspecting the container regularly

When purchasing a used container in Toronto, scrutinize it for any signs of rust. Even after transporting it to your property, regularly check the container’s base, the bottom area of the doors, and other places where water seems to be trapped for signs of rust to initiate remedies as soon as possible. Keep your eyes on areas with dents and deformations because damage to the paint can cause the rust to develop more rapidly.

2. Avoiding constant contact with snow/ice/water

Moisture initiates oxidation of the steel metal, leading to the formation of rust. So, it’s essential to keep your container as dry as possible. Consider using a raised platform for your container’s foundation, so it’s not in contact with groundwater, snow, or ice. The bottom surface of container doors is also prone to rusting because water collects in that area. You should clean and dry your container floor thoroughly every day.

3. Improving ventilation

Condensation can also form inside the container because it’s airtight and watertight, creating the risk of oxidation and condensation. This problem can be addressed by improving the ventilation of your container.

4. Apply zinc paint

Consider applying a coat of zinc paint to slow down corrosion. Quality zinc paint containing over 90 percent dry zinc powder provides ‘cathodic protection,’ which significantly reduces rust formation.

5. Local treatment of rust patches

If you notice some spots where rust is forming, but the problem is not too severe, it can be successfully treated by sandblasting or grinding or chipping down the rust in that area to the bare metal, and then painting over the surface with a primer and topcoat.

Shipping Containers Can Rust Without Care

Although used shipping containers for sale in Ontario are in good condition and are incredibly durable with proper maintenance, you should keep in mind that they have a lifespan. The constant exposure to winter and summer weather conditions will eventually wear it down, resulting in structural damage. At this point, you should take it out of service.

If you spot patches of rust and corrosion on your used container, get in touch with your dealer in Toronto as soon as possible to get it fixed.

To learn more about how to prevent your shipping container from rusting in the winter, call Sigma Container at (416) 366-7762 or contact us here.

Tom Bray is a freelance writer with over five years experience writing for online publications and over ten years in business and sales. He studied journalism and media and has written for various online outlets on multiple topics. His specialty subjects are shipping containers and transport logistics.

Tom’s passion for writing and transport logistics motivates him to provide frequent direct marketing content that can show you how a shipping container can be effectively utilized and modified to each person’s needs.

You can connect with Tom via email at