What is the Difference between Steel and Aluminum Tanks ?

During this blog I am going to explain the differences between a steel tank and an aluminum tank.

There are many pros and cons concerning which tank you dive with, I will try to highlight those differences do when you do decide on buying a set of tanks, you will be better informed. Of course, as always, consult you local dive shop so you can see and touch the tanks you are considering buying. They will be able to fill in the blanks for you concerning which to buy and why. I hope that this information is helpful. Now let's get on with it.

The vast majority of tanks today are either steel or aluminum.

STEEL

Most are made from chrome-molybdenum steel. Steel cylinders are hard and therefore resistant to external damage. The draw back for steel, without proper care, they may rust (A chemical reaction that forms iron oxide), not only on the outside, but inside as well. One reason to have your tanks visually inspected every year. Highly recommended.


ALUMINUM

Softer than steel, ie can become damaged for external forces. Because of this, the walls are thicker. This makes them larger, heavier, and more positively buoyant than steel. Like steel aluminum also corrodes forming aluminum oxide. Unlike the iron oxide, it actually inhibits further corrosion.



SIZE AND WEIGHT

Aluminum weighs less than steel. Because they are not as strong, tend to be larger and heavier than steel. This can concern the smaller diver.

BUOYANCY

Because aluminum is larger they displace more water and often times more buoyant. As such divers will need more weight in their belt for a diver. At the end of the dive they tend to be more positively buoyant. Where as steel is negatively buoyant after a dive. The total difference can be 4-8 pounds.

VALVE TYPES

Most steel tanks are considered high pressure tanks, which mean that they may have the plus sign after the tank allowed pressure. This as you remember means that you can fill it up to 10 % higher than what is listed. Most steel tanks have what you call a DIN valve, where the first stage of your regulator screws into the tank. This tends to get a more secure fit. While the aluminum tanks have a K valve, where the first stage just rest against the tank stem, and is held in place by sir pressure.

COST

Steel tanks cost considerably more than aluminum.