As a diver, few gear decisions are as critical as choosing the right scuba tank. Your cylinder contains your very air supply hundreds of feet below the surface! While tank capabilities have advanced enormously since the early days of diving, one key query still roams amateur as well as veteran diving circles – steel tank or aluminum tank, which one should I choose?
Well, steel and aluminum tanks both offer unique diver-pleasing properties. But they also bear key distinctions. By examining metrics like durability, weight, buoyancy issues, air capacity, and cost, this article might help you zero in on choosing the optimal tank for your diving style.
Table of Contents
1. Durability
First, let’s pit these metals against each other for ruggedness.
Steel’s rigid atomic structure resists bending and deformation under pressure. Steel alloys have yield strengths of up to 1,000 MPa. This enables steel scuba cylinders to withstand over 3,000 PSI of internal pressure safely. You’d be hard-pressed to damage a steel tank outside of extreme trauma.
Aluminum, on the other hand, has a yield strength of 110-570 MPa making it over 4 times lighter than steel while still safely containing high-pressure gases. Although aluminum scuba tanks don’t rust they’re still less rugged and catch dent and scratch more easily from rough handling compared to hardy steel.
2. Size and Weight
Although aluminum itself is a lighter metal compared to steel, when it comes to scuba tanks aluminum tanks are comparatively heavier than their steel counterparts.
This is because what we refer to as aluminum tanks are actually made of an aluminum alloy infused with magnesium and silicon which has a low density and poor tensile strength. Hence to compensate for the weakness the Al alloy is generally folded upon itself multiple times to achieve denser tank walls, which adds to the extra mass.
A standard 80 cf aluminum tank can weigh around 30-35 pounds while a steel tank of the same internal volume will weigh 25-30 pounds depending on the manufacturer.
As for the size, steel tanks are generally small and more compact than aluminum tanks due to their sturdiness.
3. Buoyancy
In terms of buoyancy, both steel and aluminum tanks are negatively buoyant (they sink) at the beginning of your dive.
The main buoyancy difference arises after air expenditure. When tanks are almost 70-80% empty aluminum tanks start becoming positively buoyant and by the time the tank is empty aluminum tanks tend to float to the surface. So, divers are expected to tune their buoyancy with proper counterweights or BCDs to accommodate the rapid buoyancy changes in aluminum tanks.
Steel tanks on the other hand can never be positively buoyant even when the tank is empty. So it offers fewer issues with frequent buoyancy compensation mid-dive. This becomes beneficial at greater depths where even small changes in the overall buoyancy of the diver can have catastrophic results.
4. Air Capacity and Pressure
Thanks to tremendously rigid walls, steel tanks safely contain larger volumes of air at high pressures (up to 3500 psi of working pressure in case of high-pressure steel tanks) than aluminum. You’ll typically find 80 to 100 cubic-foot steel tanks holding 25-100% more air than their aluminum ones. This enables long dives and ample reserve capacity – key for deep dives.
Alternatively, with aluminum, you strategically pack just enough breathing gas needed for recreational dives. Typical Al tanks of sizes 63-80 cubic feet – require monitoring of your gas, especially when diving deep, and can last mostly up to an hour at recreational depths.
There’s no universally perfect amount of air – only the right volume for your diving objectives, experience level, and fitness. Choose wisely!
5. Cost Efficiency
Steel itself is costly, naturally, the higher cost of manufactured steel scuba tanks is passed on to the consumer. A new 100 cubic foot steel tank runs $600-1000 easily. While deals exist on second-hand tanks, steel’s initial investment and ongoing hydrostatic testing expenses add up. If you dive infrequently and primarily for recreation, steel tanks may not warrant the cost.
In contrast, aluminum scuba cylinders are cheap. As one of the earth’s most plentiful metals, raw aluminum simply costs less. A new 80 cubic foot aluminum tank can be had for $250-500 – almost half the price of an equivalent steel tank. This makes owning multiple aluminum cylinders affordable even on a modest budget. Recreational divers can be equipped cost-effectively with aluminum.
6. Maintenance
Steel tanks are more prone to corrosion due to prolonged saltwater exposure. So unless you’re ready to offer adequate after-dive care to your steel tanks it may not pass the next inspection. Special attention must be paid to make sure there are no salt crystals attached to the surface or neck of your steel tank as it can start a chain reaction of rust. Washing your steel tanks thoroughly with fresh water after each dive is a must.
On the contrary, Aluminum tanks don’t need any maintenance in terms of rust prevention since they don’t rust. But attention should be paid nevertheless to make sure no stray salt water is lingering in the neck and valve region. These tanks are prone to developing Aluminum oxide layers on the surface, which isn’t harmful for the tank per se, but can be as unsightly as a rusted steel tank.
Final Verdict
Like any complex gear choice, deciding between steel versus aluminum scuba tanks means weighing tradeoffs:
Both materials enable safely exploring the undersea realm – you can’t go wrong with either metal. Identify your priorities as a diver. Then equip yourself with cylinders appropriately matched to your needs and diving style.
If recreational diving in tropical waters at shallow depths is your purpose, aluminum tanks balance cost, weight, and capacity beautifully.
But if you have plans to advance your diving career that require greater submerged depth and durations steel becomes the obvious economic choice.
Unless your pocket is deep enough to afford both aluminum and steel, that is.
At the end of the day, whether you ultimately side with sturdy steel or trusty aluminum, wear your tank choice proudly.
