Keep a Shipping Container Dry for Sea Freight

Did you know that about 10 percent of all seagoing sea freight is unusable due to moisture damage according to TradeRisk Guarantee, an international shipping surety company.

Imagine that. A full ten percent of all ocean-going shipping has to be discarded due to moisture damage. That is tens of millions of dollars worth of unusable goods.

Why is moisture a problem in shipping?

To paraphrase Shakespeare, let us count the ways.

First, there is the disruption caused by moisture destroying or causing shipping labels to fall off. Imagine the chaos when an entire container of goods has its shipping labels peeled off?

In addition, moisture causes many problems with products.

Wood tends to warp. Dry goods tend to clump with too much moisture.

Mold and mildew may develop, which among other things, tends to cause bad odors in goods such as textiles, which makes them virtually unsaleable.

Microscopic corrosion and rust may attack products, in particular, computer and electronic products.

In addition, protective cardboard boxes may become soggy, requiring at the very least repackaging. And mind you, those at a port will not do the repackaging.

So where does water come from in shipping containers?

Most people imagine the obvious answer is that seawater leaks into the container. However not only are modern cargo containers airtight, but they often sit high in the air relative to the sea.

The first answer is humidity.

If all shipping originated in Antarctica, which has only .2 percent relative humidity, there would be much fewer humidity problems. However, in places such as the Philippines and Thailand, up to 4 percent of the air in a shipping container can contain water.

And gradually, this humidity condenses, causing problems in the shipping.

Another water source is pallets. If the pallets are made of greenwood, a single pallet can contain up to 10 pounds of water. So using the wrong type of pallets can greatly accelerate moisture problems.

In addition, many organic products are called hygroscopic, having a tendency to hold and draw moisture to the products.

Remedies for moisture problems. How to keep a shipping container dry.

Since shipping container condensation and how to keep moisture out of storage containers is so important, what are the common remedies?

  • Venting

How to ventilate a shipping container is essential knowledge for shippers.

The first remedy is ventilation. Vents can draw moisture out of the air and disperse them outwardly from the shipping container.

Believe it or not, the American Institute of Marine Underwriters has a handy slogan to determine whether venting will assist in combating moisture or not.

The slogan is: “Hot to cold, ventilate boldly. Cold to hot, ventilate NOT.”

Meaning if the temperature inside the container is warm, and the outside temperature of the sea air surrounding the ship is significantly colder, ventilation will tend to help.

However, ventilation is for most, just a partial solution. But humidity controlled containers are possible with ventilation. Or, choose thermal containers suitable for international ocean freight.

  • Desiccants

Desiccants such as silica, charcoal, or calcium sulfate, or calcium chloride are used, inside the product itself (not the container as a whole) to keep moisture out of a product.

If you have ever bought a pair of shoes or even a simple food item like beef jerky, you will usually find a desiccant pack to keep the item moisture-free.

  • Shrink wrap and vapor barriers

When they are shipped, computers and electronic parts tend to be protected with shrink wrapping, using foil, and usually with a small added desiccant.

With shrink wrapping, which does tend to be a little expensive and time-consuming, no matter how high the humidity level in a container itself, valuable electronics that can be sensitive to the corrosion of humidity are protected.

As a result, although expensive, and as mentioned, require additional time to prepare, shrink wrapping is one of the most efficient ways of controlling moisture.

  • The use of non-wood pallets

Although non-wood pallets are more expensive, using polymer-made plastic pallets offers a great advantage for many.

Polymer pallets contain no water, and as said before greenwood pallets can contain a substantial amount of water.

In addition, polymer pallets can last as long as 10 years, 10 years, or more.

In addition, there are no sharp nails in a polymer pallet. It is all one piece.

However, there are disadvantages, the primary one being those wooden pallets have the capability of handling a much greater load.

Wooden pallets are also cheaper, and when they become unusable, they can be disposed of much easier than a plastic pallet.

But for ocean carrier goods, in particular sensitive electronics as well as food products, plastic pallets tend to be essential.

  • Data loggers

Most shippers now use data loggers to determine how much moisture is within a shipping container.

Through the use of data loggers, shippers are not only able to determine the humidity and temperature inside a container, but they have an extensive database to warn shippers what to expect inside an ocean container and to take remedial action ahead of time to avoid usable cargo being delivered.


Keeping moisture out of air and sea containers is vitally important. As long as you are able to store your product correctly, shipping safely with no damage is possible.

If you’re a business owner who ships temperature-sensitive items in large quantities regularly, Astro Asia can provide custom solutions for your shipping requirement. Need a thermal box, cold box or an insulated shipping blanket? Get in touch today for a custom quote.

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