Shipping Container Rust Prevention Tips

With their traditional purpose being to haul goods overseas, usually in rough, wet conditions, shipping containers are unfortunately always susceptible to rust. Whether you buy a used container that has had a lifetime at sea or a brand new container, rust can be a potential problem for any project. 

Most shipping containers are made from Corten steel, a strong, durable and corrosion-resistant metal also known as the ‘weathering steel’. It’s primarily used because manufacturers often guarantee a 3-5 year corrosion-free period. When it comes to rust, Corten steel is an interesting material. When exposed to air and water, it develops a thin layer of oxide (rust) which becomes corrosion protection for the steel. 

This layer of protection is important and can only be developed with a wet and dry cycle. For example, in predominantly wet climates, you won’t get the dryness and vice versa in dry climates. That’s where things get a little complicated. 

What causes shipping containers to rust?

While shipping containers need both wet and dry to develop rust, moisture is also the leading cause of rust. When containers are exposed to water, either from the sea, rain, or condensation, it is more likely to begin rusting. When at sea, saltwater can also accelerate the rusting process. 

Other contributors to shipping container rust include temperature changes that cause the container to expand and contract, abrasions that trap moisture, and certain chemicals like acids and alkalis that can react with the metal to cause rust. Additionally, a lack of regular maintenance and inspections can mean small issues go unnoticed before they cause bigger problems, such as rust.

Different types of shipping container rust

Shipping containers can develop a variety of different types of rust, depending on where it occurs and its primary cause or contributing factor. It’s important to understand different types of rust as each can have a different impact on how durable the container is. 

Surface rust is the most common type and is usually the first stage of most rust types. It forms a thin layer on the container that can be easily removed if noticed and fixed early. Pitting rust is more severe than surface rust and can create small holes in the surface that weaken the structure, potentially compromising its ability to keep out water. The most advanced type of rust is scale rust, which commonly appears as deep layers of corrosion that can cause significant damage to the steel. 

How does rust damage your shipping container?

Depending on the type of rust and its severity, it can significantly damage a shipping container by weakening its structural integrity and therefore decreasing its lifespan. Without proper maintenance and repair work early on, corrosion can cause holes in the container, compromising its ability to protect its contents from weather, pests and other external issues. 

These holes may also lead to further damage if the inside of your shipping container is constantly moist, such as damp and mould. If rust continues to worsen over time, you may not be able to use your container at all. 

Why is it important to prevent shipping container rust?

Preventing shipping container rust is highly important, no matter what you’re using your shipping container for. Rust can spread very quickly, which ultimately leads to costly repairs and could even mean you need to replace your entire container. By preventing rust, you can ensure your shipping container maintains its structural integrity for a longer period, which is especially important if your container will be used for shipping. 

How to prevent shipping containers from rusting

Whether you’ve chosen to buy a used or new shipping container for your needs, it’s important to consider rust prevention. Thankfully, there are a number of ways you can prevent rust from forming and accumulating on your shipping container, regardless of its age, condition, and size.

Keep the container dry

As we know, moisture is a key contributing factor to rust, so it’s essential to keep your container as dry as possible. Firstly, when installing your shipping container or placing it ready for shipping, you must keep it off the ground. If you’re converting a container into a living space or other project, it needs to be placed on a stable foundation. This could be concrete or railway sleepers which ensure the base of the container is protected from ground moisture and can drip dry after rain. 

While it’s not always possible to install your container under a shelter, where this is a possibility, it can be hugely beneficial in rust prevention. Another way to keep your container dry is to add guttering or a sloping roof to your project. Both options can disperse rainwater away from the container and prevent excess moisture. Depending on your build, you could even install a living roof that will absorb the water and prevent it from pooling on top. 

Keeping your container dry inside is also important in rust prevention. You can prevent condensation build-up in your shipping container with additional ventilation, ply lining, and insulation. 

Cover your shipping container

If you’re using your shipping container for infrequent shipping or storage, you may be able to simply cover it with a waterproof material to keep it dry. Tarpaulin sheets are a great option as they come in a variety of sizes to suit your container size, and are also a relatively cheap option. However, while waterproof sheets can reduce moisture, bear in mind that they may not always keep your container completely dry, especially in very wet conditions. 

Apply a rust converter to your container

Rust converters are chemical solutions that can be used to effectively stop rust from damaging your shipping container. They work by chemically reacting with the rust and transforming it into a stable, protective layer that prevents any further corrosion. Most rust converters can be applied like paint, either brushed or sprayed onto affected areas. It’s important to apply rust converters after cleaning and allow them to dry before applying further protection such as primer or paint.

Regularly inspect and maintain your shipping container

Regular inspections and scheduled maintenance of your shipping container are both important in your rust prevention strategy. In doing so, you can check for early signs of rust like discolouration or flaking paint before they become problematic, allowing you to address minor issues early on. As part of your inspection, you should try to determine the cause of any rust you find, which could be anything from a leak to a crack. 

While inspecting your shipping container, you should carry out several maintenance jobs, including cleaning the surfaces, touching up paint where needed, and applying protective coatings to any exposed areas. This maintenance can help to stop rust in its tracks and create a barrier against further moisture or damage.  

Take care to carefully inspect and maintain areas that are more prone to rust or moisture build-up, such as the roof and bottom of the container doors where water can puddle and encourage rusting. Container inspection and maintenance should be regularly scheduled to check for any dents, deformations, condensation or damage which could accelerate rust accumulation. This consistent upkeep will both prevent rust and extend the life of your container. 

Remove signs of rust as it forms

In line with regular inspections and maintenance, you should ensure any signs or rust are removed early to prevent further damage and spreading. To remove rust, you should use a wire brush or sandpaper to scrub the rust away, before applying a rust-inhibiting primer and paint to protect the area from future corrosion. If rust has caused holes in the steel, you can weld and seal a steel patch in line with the container corrugations to rectify the damage. 

Use a rust inhibitor and paint your container

Similarly to rust converters, rust inhibitors are chemical compounds. However, they work as a preventative measure before rust forms. You can apply them to the surface of your shipping container to create a barrier that prevents rust from forming, before applying a new coat of paint. Steel shipping containers should be regularly repainted with rubberised marine paint to extend their life and improve their appearance, especially if rust has already started forming.

How to remove rust from shipping containers

While prevention is always better than cure, sometimes rust can’t be stopped and you may already have rust on your container, especially if it’s in used condition. This means removing it is important for maintaining structural integrity and prolonging the life of your shipping container. From small patches to extensive and spreading rust, knowing how to remove it is essential for proper container maintenance.

Local treatment

For small patches of rust, or the first signs of it, you can use a wire brush and sandpaper to gently scrub the rust away without damaging the surrounding metal. The wire brush should be used first to break up and lift the rust, while the sandpaper can follow after to smooth the surface and ensure all corrosion is removed. In some cases, it may be beneficial to use abrasive pads in tight corners or uneven surfaces where you need to achieve a clean finish.

Power tool cleaning

For bigger or deeper patches, power tools such as grinders or needle scalers may be required to effectively remove rust. They also mean you can get the job done quickly with a little less elbow grease. Grinders are a good option for large surfaces as they enable you to repair rust quickly while smoothing out the metal underneath. Metal scalers are the better option for areas that are hard to reach or more intricate, letting you chip away at build-ups of rust without damaging any surrounding healthy metal.

Sandblasting

Well-used containers, or those that have been left standing for a while without proper maintenance may be subject to extensive rust accumulation. In these cases, sandblasting is an effective and powerful method for completely stripping rust away from your container’s surface and leaving it with a clean slate ready for protective treatment. 

Sandblasting involves propelling abrasive material at a high speed against the surface of the container to remove rust, old paint, and other contaminants in one go. Following the process, you’ll be left with a uniform finish, even in tight spaces or seams, enhancing the container’s appearance and ensuring it is ready for rust prevention techniques. 

Common uses of shipping containers that can lead to rusting

While any shipping container can be susceptible to rust, there are some instances that can create the ideal conditions for corrosion. With many different uses for a shipping container, and subsequently, many locations in which they can be placed, factors such as the environment, industry, and use-case can all foster rust accumulation.

Office spaces

Many people are turning to shipping containers for office space, which requires modifications including windows and doors which can compromise the container’s original seal if not converted correctly. When these openings are not sealed properly, they can create a space for moisture to enter which can lead to rusting around the edges. 

Shipping containers used as temporary construction site offices are particularly prone to rust as they are often provided without sufficient protection from the elements and can be subject to abrasions from frequent use and movement across sites. Containers used as home offices may also be more prone to rust if they are not placed on a solid foundation or do not have proper waterproofing measures in place. 

Storage units

Typically, shipping containers used for storage are not always well maintained or protected, which can lead to rust occurring. This is especially true if they are not ventilated correctly. If you’re using a shipping container for storage, particularly for storing textiles or materials that can absorb humidity, condensation can cause more of a problem with rust formation. 

Workshops or studios

Containers converted into workshops and studios, whether for professional or recreational use, can also be more susceptible to rust if they are frequently exposed to chemicals, tools, or spills which could promote corrosion. If you are creating a container workshop or studio, it’s essential that you have appropriate protective and preventative measures in place to prevent rust formation. 

Food and beverage outlets

Proper care and attention should be taken in containers converted into food or beverage outlets, particularly in ensuring spills and leaks are promptly cleaned from the surfaces of the container. Outlets providing hot or fried food should take extra care to ensure hot oils do not remain on surfaces as they can be hard to remove and over time, result in rust formation. 

Container homes

For shipping container home conversions it’s vital that care is taken to modify them properly to avoid rust accumulation. With exposure to moisture from rain or humidity, shipping container homes may be more susceptible to rust, especially if appropriate ventilation and insulation have not been installed. Without ventilation and insulation, moisture can become trapped inside the container, leading to interior rust and potential damage to structural components over time.

How to keep a shipping container home from rusting

If you’re choosing to build a home with a shipping container, it’s important to prevent rust from the outset. The last thing you want for your new living space is to be troubled with rust and any potential issues or damage that could come with it. Implementing an effective strategy to prevent rust is vital, and could include anything from regular inspections to protective measures.

Design your container home well

The first step in rust prevention for a container home is ensuring it is designed well and to a high standard. As part of the design process, you should minimise the exposure of your unit to weather and ensure you understand the environment it’s placed within. As an example, if the container is placed in a north-facing location that is more susceptible to extreme weather and rain, you could use this to inform the container design and add more shelter to this side. 

It’s also important to incorporate proper ventilation to keep your container home cool and dry, especially if it’s located in a damp environment. If you’re joining containers together, be sure to consider areas where water or debris could be caught or trapped as this can also lead to corrosion.

Plan insulation of container homes carefully

Insulating a shipping container home is highly important, not just for comfort and warmth, but also to keep rust accumulation at bay. However, insulation can be bulky and take up quite a bit of space, especially if you’re using smaller containers. As part of your container home design process, you will need to allow space for insulation, and keep this in mind when choosing the size and layout of your home.

Coat your container with corrosion protection

No matter what final design you’ve chosen for your container home, corrosion protection is a must. It’s not enough to simply paint your shipping container in a colour of your choice, you need to choose a corrosion protection paint to help prevent rust and extend the life of your unit. Different corrosion coatings can be applied, including zinc, aluminium, or zinc-aluminium blends, each providing sacrificial corrosion to protect the steel exterior.

Add cladding to the exterior

Cladding the outside of your shipping container is an effective way to prevent rust from forming, while also enhancing its durability. You can choose a variety of cladding materials to protect your container home, from wood and vinyl to metal and plastic. This ensures you can also nail the aesthetic of your home while protecting it. Installing cladding offers a protective barrier from various factors that can lead to corrosion, including moisture, UV rays, and harsh weather conditions. Cladding also helps to maintain the container’s structural integrity and can improve energy efficiency.

Position your container properly

Container positioning is also important for your home when it comes to rust prevention. For example, it’s worth considering which way the wind blows in your intended location so you can put measures in place to increase the container’s stability and weather protection. Your shipping container home should also be situated on a proper base to avoid excess moisture seeping in and decrease the chance of your container sliding. 

Place your container home on a stable foundation

Proper foundations for your shipping container home, such as a concrete base, are important to ensure it is not affected by groundwater which could lead to rust. You may also want to consider incorporating a crawl space so the underside of the container can be accessed for maintenance. If you place your container home on soft or wet ground, it’s important to lift it off the ground to allow airflow and prevent direct moisture on your container. 

The bottom line

No matter what you’re using your shipping container for, rust prevention is key. Whether you’ve opted to buy a used container that requires rust removal, or you’ve decided to get a new shipping container and want to prevent rust from forming, taking proactive steps like applying protective coatings and ensuring proper ventilation will help extend the container’s lifespan and keep it in top condition. And don’t forget, our team is on hand to help you with any customisations, conversions, or advice on ensuring your container is maintained to effectively prevent rust.