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A scuba tank is an essential piece of equipment for your underwater activities. It’s also a worthwhile investment that needs thoughtful consideration.
Mostly, you’ll find tanks made of steel or aluminum. But which one is better?
This article will weigh in on steel vs. aluminum scuba tanks. We’ll break down the differences between these two variations to help you decide which one to choose.
Let’s get right down to it!
Steel vs. Aluminum Scuba Tanks: What They’re Made Of
Aluminum and steel are two materials used in the manufacture of scuba tanks. So, what makes them ideal for this function?
Steel
Steel is a durable alloy, mainly composed of iron and carbon. It has high tensile strength and substantial flexibility, which is why it’s used in many applications.
Thanks to the carbon element, steel is tough and has unyielding properties.
Nevertheless, it has some weak points. The most glaring issue it presents is its highly corrosive nature. Because of that, it requires treatment, like painting or powder coating, for added protection.
Aluminum
Aluminum is lightweight, durable, and has high corrosion resistance. It’s also exceptionally malleable, so it can be easily molded into shapes and functions.
However, it’s soft, which makes it more prone to deformities.
Steel vs. Aluminum Scuba Tanks
Aluminum and steel tanks have different specifications. Both types present a set of pros and cons due to the difference in construction materials and their properties.
That said, you need to consider a few things before you decide which one to purchase.
How long will you be in the water? Will you be regularly diving? Are you a beginner and on a budget?
It’ll also help if you get a feel of both materials before investing in your equipment. If you’ll be constantly diving into a particular site, an expert’s advice in that area won’t hurt either.
With all this in mind, let’s look into the differences between aluminum and steel tanks.
1. Dry Weight
A typical scuba gear setup will weigh around 40–50 pounds on land. A huge part of that comes from the diving cylinder. That’s why this is a consideration when choosing between aluminum and steel tanks.
Aluminum is lighter than steel. However, it tends to get dented and cracked more easily. To make up for this, aluminum tanks are reinforced with thicker walls for safety.
This extra thickness makes them heavier than steel tanks of the same capacity.
Standard aluminum tanks usually weigh between 31–35 pounds, as opposed to 28–30 pounds for steel tanks.
These weights won’t matter much when in the water. But on land, that can spell a difference. After all, you’ll likely be carrying it before the dive.
Heavy tanks can also make it harder to get on and off a boat. So, your gear should be something you can comfortably lug around.
2. Size
Size is another significant consideration since it affects your comfort and safety.
A common problem for younger and shorter divers is getting a cylinder that’s too long. As a result, the tanks keep bumping with the head and restrict body movements.
So, between an aluminum and a steel tank, which one wins in this aspect?
Generally, steel tanks are slightly smaller than aluminum tanks at the same filling capacity. Again, the thickened walls of an aluminum cylinder are to blame.
On average, standard tanks are 21–26 inches long. Most steel tanks are on the lower end of that range, while most aluminum types are on the higher end. Both will work fine for beginners and recreational divers.
Nevertheless, you can use a smaller tank with an adequate capacity if you’ll be in and out of the water shortly.
3. Capacity and Pressure
Scuba tanks are offered in a range of capacities, from 50–120 cubic feet. They’re also categorized into three pressure ratings, which are:
- Low Pressure (LP): 2400–2650 psi
- Standard Pressure: 3000 psi
- High Pressure(HP): 3300–3500 psi
Standard tanks have a capacity of 5–80 cubic feet (cf). However, the most common is the 80 cf filled at 3000 psi.
This is equivalent to approximately 11.1 liters of air, which is enough for a 45-minute dive and best suited for recreational divers.
For longer dives, HP tanks are a good option. By using high pressure, more air can be contained while still keeping the size manageable.
You’ll find steel types fit for this purpose. Although, there are a few exceptions made out of aluminum.
Many HP tank users will attest to its benefits, but it comes with certain drawbacks too.
For one, not all dive shops have the correct equipment to refill an HP tank. You’ll need to upgrade your regulator setup as well, so the tank doesn’t implode.
Lastly, be prepared for the cost as an HP tank is more expensive than its counterparts.
If going for shorter dives, a low-pressure tank will do just fine. It’s also slightly smaller, so you can move better.
4. Durability and Longevity
Steel scuba tanks are likely to last longer than aluminum tanks since they’re more damage resistant. Proper care and maintenance are required, though.
Remember, steel is susceptible to oxidation, which results in rust. When exposed to saltwater, corrosion speeds up.
That’s why tank owners practice a routine check through periodic tumbling. This is a process of removing rust from the inside of the tank.
Additionally, avoid water entry into the tank at all costs. So, special attention is needed when refilling the tank.
Moisture in the interior hastens oxidation and weakens the material. It also contaminates the air.
The same applies to aluminum tanks. The product of oxidation is a thin powdery layer of aluminum oxide, which protects the surface from further oxidation.
While this doesn’t damage the material itself, regulator interiors are at risk. So, getting rid of this powder is still your best move.
Again, aluminum tanks are softer and may be scratched and dented more quickly. That said, extra care during handling is advisable.
Nevertheless, steel and aluminum tanks need to undergo hydrostatic tests and visual inspections regularly. That includes initial tests from the manufacturer.
Doing so ensures the integrity of the equipment and avoids untoward incidents.
Take note: These routine tests are covered by the U.S. Code of Federal Regulations under 49 CFR 180.209. This law doesn’t apply to private owners, though, but is highly recommended for safety reasons.
All the same, scuba tanks will last longer when properly maintained.
5. Buoyancy
Choosing between an aluminum tank and a steel tank is also a matter of buoyancy.
Check out the product specifications and zoom into the buoyancy values before purchasing one. You’ll likely find two figures. There’s one for when the cylinder is full and another for when it’s empty.
If you see a negative value, that means a negative buoyancy. In other words, the tank is heavier than the displaced water and so it’ll sink.
On the other hand, a positively-buoyant tank is lighter than the water and tends to float.
These values impact your overall buoyancy in the water and the preparations you need to do before a dive.
For example, steel tanks have negative values, whether full or empty. Although there are buoyancy changes, you’ll hardly feel them.
On the contrary, an aluminum tank starts with a negative buoyancy.As you consume air from the container, however, it slowly changes. The tank may become positively buoyant during the dive.
This tendency to float should be addressed by putting on additional weight in your gear. Otherwise, it can contribute to you ascending sooner than necessary.
Remember, that isn’t advisable because it can lead to decompression sickness (DCS). This condition results from a sudden increase in surrounding pressure, where the nitrogen absorbed in the blood aren’t cleared out in time.
If you experience DCS, you may feel muscle pains and nausea. In some cases, it may be deadly.
For safety purposes, divers follow decompression tables and make necessary stops, depending on the depth of the water.
6. Price
Aluminum tanks normally cost less than steel tanks. That’s why you’d typically see them in dive stores.
This option will do just fine if you’re going for recreational dives or are on a tight budget.
However, if you plan on longer dives and going scuba diving regularly, a steel tank is a worthwhile investment. But you’d have to shell out a bit more for it.
Conclusion
After weighing in on steel vs. aluminum scuba tanks, you already know that both present their own set of advantages and disadvantages.
Properly maintained steel scuba tanks are likely to last longer. They also remain negatively buoyant underwater. Plus, they have a capacity and size advantage over aluminum tanks since they can be filled at higher pressures.
However, steel tanks are prone to corrosion and more costly than comparable aluminum tanks.
On the other hand, aluminum tanks are cheaper and highly resistant to corrosion.
That said, they should be handled carefully because of their susceptibility to dents, scratches, and cracks. Additionally, you’ll be needing extra weight on your gear to counter the positive buoyancy that it can give you.
