Most divers never give much thought to what their air cylinder is made of. Even so, it can affect aspects of your dive. Besides, it never hurts to know a little about the equipment you’re diving with.
Cylinders are made out of two types of material: steel and aluminum (actually an aluminum alloy). Each have different properties that make it appealing for different types of construction and use.
Steel cylinders are tough, making them resistant to damage. They also tend to support higher capacities, because of their increased strength. The downside to steel is that it can rust if not properly cared for.
Aluminum cylinders are softer than steel, so they’re not as tough, although they do just fine for general use. To compensate, the walls of aluminum cylinders are thicker than for steel. For this reason, an aluminum cylinder is larger and heavier than a similar capacity steel cylinder. They also don’t handle overfilling nearly as well.
I will be posting more comparisons of the physical and chemical properties of Steel vs. Aluminum in the near future, so readers can get a feel for the ability or inability for Aluminum to do damage to Steel or not or visa versa...
Just another train of research
that needs to be pursued to solve the mystery of an Aluminum (hollow) and thin walled jetliner being able to obliterate steel columns and about 6 to 8 acres (6 to 8 floors) of about 8 inches thick concrete floors with rigid steel floor pans and support trussing and the additional support of the 47 core columns of steel over those same 6 to 8 floors which are solidly attached to the 110 floor Tower plus the 6 steel basement floors.