Stackable shipping containers have been used to transport cargo for more than half a century, and nothing much has changed in terms of their construction. Most are made of corrugated steel and incorporate floors made from strong planking or plywood. But while steel is not the only material used for shipping containers, steel containers are the most common type for various reasons including security, mobility, accessibility, and lifespan.
Since 1969, steel containers have been standardized in terms of the material used for construction and their size, as well as the patented design of the corner posts incorporated in the design of these mobile containers.
Standardization of steel containers used for overland and ocean shipping is in accordance with the Swiss-based International Organization for Standardization (ISO) that develops and publishes international standards on just about everything.
ISO standards specify the type of steel containers should be made from. Essentially, it is a “weathering steel” that is resistant to corrosion and commonly referred to as Cor-ten steel. It is the same type of steel used in the many industries that utilize steel sections like bridges, facades and building panels that are left exposed to the elements.
When it comes to size, ISO standards specify both the internal and external dimensions of steel containers, which is why standard size lengths are the same worldwide, the most common being 10 ft, 20 ft, and 40 ft. Most are 8 ft wide, and the height of steel containers ranges from 4 ft to 9 ft 6 ins though most are 8 ft 6 ins high.
But containers aren’t only made from steel, some are made from aluminium and sometimes stainless steel too – usually a combination of the two metals.
Significantly different to steel containers, shipping containers are also made from aluminium according to ISO specifications.
For some years, both steel and aluminium were used for mobile containers that would carry dry cargo. But steel was stronger and therefore became the preferred material. At the same time, because refrigerated products are generally a lot lighter than dry cargo, a combination of aluminium and stainless steel continued to be used for refrigerated shipping containers. Generally, the walls of these aluminium containers are considerably thinner than those of steel containers, and their thermal insulation is increased by the use of other materials on the inside of their walls.
Steel containers and those made of aluminium cannot be used interchangeably. Apart from anything else, the latter isn’t constructed for stacking, and they are generally used domestically, within countries of origin, rather than for shipping cargo across the sea or across continents.
Of course, refrigerated containers aren’t only made of aluminium. Today reefers (the term for refrigerated containers) are commonly made from steel.
Almar Container group specialises in steel shipping containers and has the full range of sizes. Our mobile containers are suitable for dry and refrigerated freight, depending on your needs. They may also be used for storage. Contact us to discuss your needs. We are ready to help.