Can Containers Rust and How to Prevent It?

AI Summary

• Shipping containers are made from weathering steel, which resists rust, but they can still corrode when paint is damaged or moisture collects.

• Common rust causes include scratches, standing water, humidity, and prolonged exposure to soil or salt.

• Preventative maintenance, such as repainting, inspecting seals, improving drainage, and treating early rust spots, extends container lifespan.

• Mann’s Cans provides durable units and guidance to help customers protect their containers from long-term rust damage.

Shipping containers are engineered to withstand harsh marine environments, extreme weather, and constant handling. However, even with their durable weathering steel construction, they are not completely immune to rust. Rust typically forms when protective coatings wear down or when moisture sits on the metal for long periods. Fortunately, rust is both manageable and preventable with the right care.

Understanding why containers rust and what you can do to prevent corrosion ensures a longer lifespan for your unit, whether it’s used for storage, a workshop, or a custom build-out. This guide breaks down the causes of rust, how to identify early signs, and the best methods to prevent long-term damage.

The Problem: Why Shipping Containers Rust

Although containers are made from corten steel (a weathering steel designed to form a protective surface layer), they still face environmental conditions that can lead to rusting. Over time, exposure to water, oxygen, and certain chemicals can break down protective coatings.

Common causes of container rust include:

• Scratches and dents exposing bare metal

• Standing water on the roof or around the base

• Humidity and condensation inside the container

• Old or damaged paint

• Soil or debris piled against the exterior walls

• Years of ocean exposure in the shipping industry

  
  

If rust is ignored, it can expand and weaken the steel. Severe rust may create pinholes, allow leaks, and compromise structural integrity, especially if it appears near doors, corners, or seams.

The Solution: Understanding Rust Types and Preventing Each One

Not all rust is the same. By identifying the type you’re dealing with, you can treat it quickly and correctly.

Surface Rust

This is the most common and least harmful type. It appears as a thin, flaky layer on the paint surface and usually forms from:

• Weather exposure

• Scratches

• Minor abrasions

  
  

Surface rust is easy to treat and rarely affects structural durability when addressed promptly.

Scale Rust

This occurs when surface rust is not removed, and the corrosion penetrates deeper. The steel becomes more brittle, and the rust is thicker and darker.

Containers with scale rust need more thorough repair, including sanding, priming, and repainting.

Structural Rust

This is the most severe form and usually affects:

• Roof edges

• Door frames

• Corners and seams

  
  

Structural rust can cause holes, weakened frame integrity, or leaks. It requires professional repair and, in some cases, replacement of steel sections.

How to Prevent Container Rust

Preventing rust is the key to ensuring your container lasts for decades. Fortunately, rust prevention is straightforward with proper care and routine inspections.

Step 1: Maintain the Paint and Exterior Coating

Paint acts as the first line of defense against rust. When the paint chips or scratches, bare steel is exposed to moisture and oxygen.

To maintain the exterior:

• Touch up chipped paint immediately

• Sand light rust spots before repainting

• Use rust-inhibiting primers

• Choose marine-grade or exterior enamel paint for maximum durability

  
  

A freshly painted container not only looks better but resists rust more effectively.

Step 2: Keep the Roof Clean and Free of Standing Water

The roof is one of the most vulnerable rust spots. Even shallow dents can collect water, accelerating corrosion.

Roof protection tips:

• Remove leaves, dirt, and debris regularly

• Check for dents and fill low spots if needed

• Ensure no tree branches hang over the container

• Inspect the roof after heavy storms

  
  

By preventing water accumulation, you significantly reduce the risk of rust.

Step 3: Improve Ground Drainage

When a container sits in a location with poor drainage, moisture can collect along the bottom edges, promoting rust.

Solutions include:

• Placing the container on gravel or compacted stone

• Using concrete pads or treated timbers

• Slope the ground away from the container

• Avoid placing containers directly on soil that traps water

  
  

Good drainage also helps prevent door misalignment by keeping the container level.

Step 4: Inspect and Maintain Door Seals

Doors are highly susceptible to rust because they contain multiple metal components and rubber seals.

Maintain door areas by:

• Cleaning and lubricating hinges

• Checking for frame rust and treating it early

• Replacing worn or cracked rubber gaskets

• Keeping the door threshold free of debris and moisture

  
  

Healthy seals prevent water intrusion, which keeps the interior dry and less prone to condensation.

Step 5: Manage Interior Condensation

Condensation is a hidden cause of interior rust. When warm, humid air meets the cool metal walls, moisture forms and drips inside.

Prevent condensation by:

• Installing passive vents

• Adding interior insulation

• Using a dehumidifier in climate-sensitive environments

• Allowing airflow around stored items

  
  

If you notice droplets on the ceiling, address the issue quickly to prevent rust from forming inside the container.

Step 6: Treat Rust Immediately When You Find It

Early rust treatment prevents larger issues later. A simple three-step process works for most cases:

1. Sand off rust until bare metal is exposed.

2. Prime the area with a rust-inhibiting primer.

3. Paint with a high-quality exterior steel coating.

   
   

For deeper rust, applying a rust converter can help neutralize corrosion before repainting.

People Also Ask

Do all containers rust eventually?

Most will develop some level of surface rust over time, but proper care prevents serious corrosion. Containers kept in dry, stable environments last much longer.

Is rust on a used container normal?

Yes. Light surface rust is common. What matters is ensuring there is no deep or structural rust, especially around doors and roof seams.

How often should I inspect my container for rust?

Twice a year is ideal, with additional inspections after extreme weather.

FAQ Section

Q: Can rust holes be repaired?

A: Yes. Small holes can be patched with steel plates and welded. Larger holes may require section replacement.

Q: Is corten steel rustproof?

A: No. It is rust-resistant and slow to corrode, but not immune. It needs protective coatings and maintenance.

Q: Does repainting really help prevent rust?

A: Absolutely. Paint seals the steel from moisture and oxygen, significantly slowing corrosion.

Q: Can containers near the coast rust faster?

A: Yes. Salt in the air accelerates corrosion, making maintenance more important in coastal environments.

Keep Your Container Rust-Free for Years

Rust prevention is simple when done consistently. Regular cleaning, paint maintenance, moisture control, and quick rust treatment all help extend your container’s life and protect your investment. Whether you're using your unit for storage, a workspace, or a custom conversion, proper care ensures long-term durability.

If you’re looking for guidance or need a reliable container to start with, Mann’s Cans provides high-quality units and support throughout your ownership.

Call 724-790-5040 or submit the online form to learn more about rust prevention or to find containers built to last.