Standard ISO manufactured shipping containers are commonly known as being built from steel. There are, however, ISO units created from aluminum that have significant differences in terms of not only their structural integrity but their function in carrying cargo as well.
International cargo is carried utilizing two main types of freight containers: Dry and Refrigerated. Dry cargo, for the most part, is moved using Steel Shipping Containers. Dry Van, Open Top and Flat Rack containers are primarily built with steel and the newer steel containers have undergone a careful process of sandblasting and heavy duty coating to optimize strength as well as resistance to corrosion. Some of the older dry boxes were built from aluminum, until the industry moved to steel shipping containers which were designated as a much stronger type of unit for the heavy cargo that is typical in dry goods.
Refrigerated shipments, due to being much lighter in load capacity are developed using aluminum and stainless steel as the primary compounds. Reefer containers, as there called, need to be insulated with very thick side walls and the overall weight of aluminum is much less than that of steel making the aluminum container a much more sensible approach to transporting frozen or temperature sensitive products. The thermal efficiency and ability to maintain minimum air leakage are other positive aspects of the aluminum shipping container. With this in mind, once serviceable refrigerated containers are retired and the cooling machinery is no longer working they are very often considered for use as carrying any type of cargo, dry or frozen, that need insulation from the outside elements. In other words, steel and aluminum containers can be used for the same basic function depending on what the customer wants. When shipping goods I think the votes have been counted: steel is king with dry goods, and aluminum is the choice for frozen or refrigerated products.
So, the questions from that point remains: should someone considering a non-working refrigerated container built from aluminum vs a steel shipping container for their general portable storage needs, which one is best?
The answer is very subjective, but need also take into consideration maintenance, lifespan and of course the function required. Aluminum containers can be very expensive to repair, as the welding process is much more involved. Seams and other portions of non working reefer containers are riveted, and can be costly to re-create. However, if the environment is extreme, and the goods are sensitive to temperature, the aluminum container might be the best choice regardless of the more expensive repair costs and the shorter lifespan. Steel containers for sale are much more cost effective to repair, and performing general modifications to steel cargo boxes is a simpler procedure. The steel shipping container for sale is also more readily available, and much more durable.
Aside from shipping, due to the primary intended use for re-purposing ISO containers is for dry portable storage, it seems that the winner in this case is the steel container. It’s stronger, more diverse and more cost effective to maintain. Not to mention, the plethora of uses for steel containers far outweigh that it’s aluminum counterpart. Containerized architecture, creative structures and extensive modifications are becoming a very popular up-cycle for ocean freight containers made of steel.