Scuba Tanks: Steel vs. Aluminum

All scuba tanks in use today are made of either aluminum or steel, and both metals have their own set of advantages and disadvantages. However, which tank is better is a complicated question. Aluminum tanks are more common, mostly because of their lower price tag and advantages that appeal to scuba diving schools and tour operators, but this does not necessarily mean that an aluminum tank is ideal for everyone.

  1. Features

    • Aluminum is the big loser when it comes to durability. It is easier to both dent and scratch, and suffers more from metal fatigue. In a cart crash or bad fall, aluminum tanks are more likely to suffer damage than steel. A well-cared-for steel tank will virtually last forever, while an aluminum tank will eventually wear out. On the other hand, aluminum is cheaper than steel.

    Hazards

    • Metal fatigue is a serious potential hazard for aluminum tanks, as the aluminum may develop hairline cracks. While scuba tanks are subject to inspection and hydrostatic testing once every five years, nascent cracking is hard to detect. An undetectable crack poses no problem at the time it is tested, but it may grow into a problem before the next testing date five years later.

    Misconceptions

    • A common mistake made when comparing steel and aluminum tanks is that aluminum does not corrode in saltwater. This is in error. Both steel and aluminum corrode, although steel is more prone to corrosion.

    Buoyancy

    • Most of the time, steel scuba tanks are heavier than their aluminum counterparts. Some especially well-made steel tanks are actually lighter than aluminum, however, because much less of that stronger metal is used in their manufacturing process. Either way, a lighter tank is easier to handle on land, but becomes awkward toward the end of the dive. As the tank empties of air, it becomes more buoyant, especially a lighter tank. Because aluminum tanks are almost always lighter, this is a particular problem for them. However, some scuba tanks--both steel and aluminum--are specifically designed for neutral buoyancy while empty.

    Size

    • Because aluminum tanks use more metal in their construction than steel tanks, they are usually a little bigger. This is not much of a problem for recreational divers, who often dive with only a single scuba tank strapped to their back. A technical diver, on the other hand, may dive with as many as five tanks strapped to his back and sides. In that case, small differences in size might add up to a big difference, and many technical divers use a mix of steel and aluminum tanks.

    Availability

    • If you are buying scuba tanks, a wide selection of makes and models for both steel and aluminum tanks is available. When it comes to renting a tank, however, aluminum tanks are usually the only choice. As aluminum tanks are cheaper and less prone to corrosion, these tanks are the format of choice for schools and tour operators, who must keep and maintain a large inventory of rental equipment.