Guide To Maintaining Your Shipping Container
You’ve made the investment and purchased a shipping container for storage purposes. As the new owner of a Conex container, you’re likely wondering, “How can I ensure my shipping container’s longevity and upkeep?”
Luckily, the inherent design of shipping containers makes them incredibly durable and low-maintenance, thanks to their construction from heavy gauge steel.
The Lifespan of Shipping Containers Your shipping container should serve you well for at least 15-20 years. Once a Conex container is no longer used for international cargo shipping, it’s often resold as a wind and water tight unit for storage or repurposed for various other functions.
How to Prolong the Lifespan of Your Conex Container with Preventative Maintenance and Planning
With careful planning and routine preventative maintenance, you can easily extend your sea container’s service life by an additional fifteen years or more.
Yearly Check-up for Your Storage Container Remember to conduct a thorough check-up of your storage container every year. Look out for any signs of structural rust, particularly in the box’s frame parts where water might have gathered. Examine the rubber door seals for any signs of damage. Over time, these seals may become brittle and lose their ability to create a watertight seal. As always, addressing issues promptly and carrying out basic maintenance can help you avoid costly repairs in the future. Your local climate will play a significant role in determining the type of maintenance required and the speed at which your container will deteriorate. For example, anyone who has owned a car in a damp climate knows that moisture, snow, and freezing temperatures can cause metal to deteriorate faster than in a warm, dry environment (like Arizona, for instance).
The Importance of Preventative Maintenance To ensure your cargo container storage lasts as long as possible, we’ve compiled a few tips for maintaining your container:
Shield from Water Damage and Excessive Moisture During your regular container inspections, be on the lookout for “container rain” or container condensation. Although designed to be watertight and keep outside moisture at bay, your sea container isn’t immune to the moisture present in the air and possibly within the items you’re storing.
“Container rain” refers to the condensation of airborne moisture inside closed metal structures. An extreme buildup of condensation can potentially damage certain items (like electronics or paper documents) and can hasten the oxidation process (leading to rust, which we’ll discuss later).
Understanding Condensation in Shipping Containers The metallic walls of shipping containers are excellent conductors of heat. As the external air temperature drops from day to night, the steel surfaces of the container walls cool down quickly. Once sufficiently cooled, these metal surfaces hit the ‘dew point’ – the temperature at which airborne water vapor condenses back into liquid form. When warm, humid air comes into contact with these cold metal container walls, the moisture condenses from a vapor to liquid, resulting in droplets on the metal surfaces – primarily collecting on the ceiling. In areas where there’s a significant difference between daytime and nighttime temperatures, the risk of ‘container rain’ damaging your stored items increases.
Addressing Moisture Condensation in Shipping Containers To mitigate the issue of moisture condensation in your storage container, consider these three key factors:
Lower the Humidity Level in the Conex Container Inspect the container’s ceilings and walls for visible signs of moisture condensation. Before loading the container, check the interior surfaces to ensure no water has pooled and dry any collected water. Insulation can help reduce condensation by preventing the walls from reaching the dew point.
Setting Up a Vapor Barrier A vapor barrier can significantly decrease excess moisture condensation on the container walls. This damp-proofing material, often a plastic sheet, prevents moisture diffusion through the walls, doors, or ceiling.
Using Dehumidifiers and Air Conditioning Units If you plan to store items sensitive to moisture effects, consider a more direct solution for cooling and dehumidifying the air. Air conditioners and/or dehumidifier units effectively maintain stable, dry conditions for storage containers in challenging climates or particular seasons.
For a less expensive and lower maintenance approach to managing humidity inside the container, consider using desiccants. These “hygroscopic substances” absorb atmospheric moisture.
Consider those “Do Not Eat” silica gel packets typically found in supplement bottles or product packaging – those are desiccants. They come in various forms, often as strips hung on the walls, suspended from the ceiling, or placed in bags on the container floor. Depending on the season and your local weather conditions, these desiccant bags should be replaced every 10 to 12 weeks.
Implement Ventilation to Allow Warm, Humid Air to Exit Consider the climate where your container will be stored. If significant temperature fluctuations between day and night are common, you might need to take extra measures to prevent “container rain.” To encourage air circulation and prevent heat build-up, containers are often retrofitted with vents. This straightforward measure can significantly reduce the impact of condensation.
Ensure Only Completely Dry Items Are Stored It’s crucial to store only thoroughly dry goods in the storage container. Keep in mind that some materials, such as freshly cut wood, may inherently contain high moisture levels. This means these items can release moisture into the air, potentially increasing humidity levels within the container. Avoid placing objects sensitive to moisture (like furniture or cardboard boxes) directly against the walls where water droplets are most likely to condense and accumulate. Be mindful that certain items (e.g., electronics, dried foodstuffs, or cardboard boxes of paper documents susceptible to mold) may be vulnerable to the effects of moisture accumulation, and plan accordingly.
Rust Prevention: How to Safeguard Shipping Containers Against Rust
Although Conex containers are engineered to be waterproof and withstand all weather conditions, they are made of steel and, as such, can rust.
Fortunately, most shipping containers are constructed from corrosion-resistant Cor-Ten steel, and steps can be taken to both prevent the onset of rust and slow down its corrosive effects. If you’ve bought a container “as is,” it’s highly likely that the used shipping container has been heavily exposed to saltwater and salty air, both of which expedite corrosion. However, a one-trip or new container will not have this level of corrosion.
What triggers rust in shipping containers? Rust forms when iron reacts with oxygen in the air or chloride in water. While marine-grade steel has anti-corrosive qualities, the harsh maritime environments that containers endure mean that rust will eventually appear.
When a shipping container comes into contact with both oxygen and water, an oxidation chemical reaction takes place. This reaction between the steel, water, and oxygen forms hydrated iron (III) oxide, which manifests as rust. Shipping containers can also begin to rust if their metal surface is damaged during transit. If the container’s protective coating is compromised due to impact during loading, it exposes the bare metal, providing an opportunity for oxidation to commence.
Identifying Two Distinct Types of Rust in Shipping Containers The most noticeable rust on a container’s exterior walls is classified as “non-structural” rust because it develops on the wall surfaces. While this surface rust is unsightly and can stain items that touch it, it also diminishes the resale value of a container. A visibly rusty container might not pose any risk to its users, but few individuals are interested in seeing (or purchasing) a rusty steel box.
The second, more harmful type of container rust is termed “structural rust”. This advanced stage of corrosion begins to undermine the container’s structural integrity. Major structural rust can make a container unfit for many uses due to structural instability. Significant structural rust may also impede the owner from obtaining CSC certification for the container. According to portshippingcontainers.com, CSC stands for ‘Container Safe Convention’, indicating that the container is safe for use, capable of enduring the stresses of cross-country and overseas shipping, and needs to be inspected and certified according to international regulations.
Treating Early Indications of Rust Address minor surface rust issues promptly when they initially emerge. If caught early, the rusted area can be easily treated and cleaned. Any signs of damage such as scrapes, dents, and scratches should be dealt with before they start to rust, preventing further corrosion that could escalate the problem from a non-structural issue to a structural one.
The first signs of rust should be eliminated. Begin by preparing the affected area using a wire brush or sandpaper to grind down any visible rusted surfaces.
For effective rust removal, it’s essential to sand down to the bare metal until no traces of rust are visible. After completely eradicating the surface rust, cleanse the exposed area with vinegar and let it dry. Once the vinegar has dried, you can apply a layer of rust-inhibiting primer or use marine-grade Direct-To-Metal (DTM) paint to cover the area. If the surface rust problem is more severe, the solution involves fully sandblasting the exterior container walls and subsequently sealing and repainting the container. However, for most storage purposes, the costly procedure of sandblasting and total refurbishment of the container is unnecessary.
How do I prepare my container for painting over rust?
As a basic rule of thumb, repainting a 20-foot container would require around four gallons of paint, while a 40-foot container would need approximately eight gallons.
The first step in preparing your container for primer and/or paint application is to sand down any visible rust patches. A pressure washer is perfect for removing layers of dirt and dust. Use a wire wheel or sandpaper to grind down rust patches.
It’s advisable to apply a coat of rust-inhibiting primer to the area first. This ensures that the top coat of paint sticks properly to the metal. Consult your local paint vendor to determine which primer they carry is best suited for outdoor metal surfaces. Allow adequate time for the primer coat to thoroughly dry before applying the final, top coat of paint.
So, what type of paint should you use for rust-proofing your shipping container? There are several options available to match your requirements, paint availability, and budget. According to various sources, marine-grade Direct-To-Metal (DTM) waterborne paint is highly recommended for shipping containers. Ceramic insulating paint is another good choice, despite some questions about its insulating effects. Other options include water-borne paint, alkyd enamel paint, acrylic paint, polyurethane paint, and rust primer. Additionally, Rust Grip® offers one of the most effective anti-rust/anti-corrosion coatings for shipping containers with a 15,000 hour salt spray test rating. Applying a coat of zinc paint can also significantly slow down the process of shipping container rust through ‘cathodic protection’.
Shipping Container Paint Selection
Choosing the right paint for your shipping container largely depends on your intended use.
- Water-based paints are environmentally friendly with lower VOC levels. When applied correctly and after thorough preparation, these paints can be equally or even more effective in preventing rust compared to traditional oil-based paints.
- Industrial-grade alkyd enamel paints are quite cost-effective and user-friendly for non-professionals. You can expect the finish from these paints to last anywhere between five to ten years.
- Polyurethane paint is a heavy-duty type commonly used in industrial settings. However, it’s important to note that this paint contains chemicals that may pose hazards during use. As there are specific procedures involved in mixing and applying polyurethane paint, you might consider hiring a professional for this task.
- Zinc paint. Application of zinc-based paint effectively slows down the onset of rust on shipping containers. This is due to a process known as ‘cathodic protection’, where the zinc in the paint decelerates the rusting of the underlying steel.
Sandblasting the entire exterior of the container is typically not recommended. It’s an expensive procedure that requires professional assistance and equipment. Moreover, sandblasting can strip away the original high-quality marine-grade paint, which provides robust rust protection. Since a home paint job may not offer the same rust resistance as the original paint, it’s advisable to prime and paint over the existing marine paint.
Position the Container on a Level Foundation
One of the simplest measures you can take to guard against water damage and rust is to position your shipping container on level ground, rather than in a low-lying area where rainwater tends to accumulate. If water pools under or around the container, it creates an environment conducive to rapid rust development. If your container is placed directly on the ground, the bottom comes into contact with ground moisture, making it more prone to rust.
Firstly, choose a location that is elevated and flat. It’s advised by builders to set up your Conex container on a basic foundation using either concrete blocks or railroad ties. This not only provides stability but also improves air circulation underneath the container, which helps prevent moisture buildup and subsequent rusting. Pay special attention to the bottom of the container doors, as water often accumulates in this area.
Maintain Door Hinges and Gaskets of the Container
Despite their simplicity, shipping containers do require some maintenance, particularly on the doors.
One of the most straightforward and necessary tasks is lubricating the door hinges. Over time and with disuse, these metal hinges can become stiff and seize up. Regular application of an all-purpose lubricant, such as WD40 or 3-in-1 oil, during routine container checks can prevent the hinges from rusting, ensure their smooth operation, and keep the doors functioning properly.
Replacing Worn Rubber Seals on Shipping Container Doors
Shipping containers are designed to provide a sealed, watertight environment, and this is achieved in part through the use of rubber gaskets on the metal doors. These gaskets play a crucial role in preventing moisture ingress.
However, these rubber seals typically have a lifespan of about 10 years, after which they begin to crack and degrade, compromising their sealing effectiveness. If the seals are significantly worn or damaged, it’s advisable to replace them. Door gasket kits for shipping containers are readily available online and can be used to restore the door’s sealing capability, ensuring the container remains watertight.
By adhering to these guidelines, you can enhance the longevity of your shipping container storage unit, ensuring it safeguards your belongings for decades.
