Question Why own an aluminum tank?

[Cheizz]

For personal use exclusively, why would one want to own an aluminum tank?

It is not lighter than a similarly sized steel tank to carry on dry land, it doesn't carry a hugely different amount of gas. The main difference, as far as I can tell, is the buoyancy properties. And steel tanks seem to be much more consistent in that respect and need less lead weight to compensate. A steel tank, on the other hand, is more prone to corrosion, especially in saltwater. Am I missing something?

For my personal local dives (90% of which are freshwater dives), there would be no reason to buy my own aluminum tanks, it seems. If I just take proper care of my own steel tanks (as I would with all my equipment), there is no disadvantage over aluminum tanks, is there? The other way around - I think the buoyancy change of an aluminum tank during the dive would be a disadvantage over steel tanks.

 

[whynot]

Cost, availability (both new and a healthy preowned market) and distribution, #/count of manufacturers, the wetsuit/crushed neoprene + steel =‘s dangerous argument, etc.

 

[Searcaigh]

I own four AL80s as they are the common tank in my local area, and 200 bar fills are standard.

The only steel tanks I have are 10L and doubles (2 x 10L).

With hindsight I should have bought single 10L steels but the hydro is every three years compared to AL tanks at every five years, plus less weight required. I do put a 4lb weight on a cam band at the bottom of my AL80s for trim purposes, and do carry a spare cam band with a weight pouch for travel purposes.

Not all my local gas suppliers here can give me a 230 bar or higher fill.

 

[ginti]

In my experience, aluminium tanks are usually more common in warm places, where you dive in very thin suits and, therefore, you need less weight.

There are other factors, but this is by far the most important (again, in my comprehension)

 

[GF99/99]

Nope your not missing anything. And actually if properly cared for steel tanks will out last ali tanks. Reason why you see so many ali tanks is price. Think about a dive operator that has to buy a 100 tanks the price difference ads up really quick between ali and steel.

Only other reason I can think of for common use of ali tanks is deco gas. just because of the buoyancy characteristics. I really like ali s80's for this.

 

[drk5036]

There are almost no aluminum tanks in Japan

 

[ginti]

Nope your not missing anything. And actually if properly cared for steel tanks will out last ali tanks. Reason why you see so many ali tanks is price. Think about a dive operator that has to buy a 100 tanks the price difference ads up really quick between ali and steel.

Only other reason I can think of for common use of ali tanks is deco gas. just because of the buoyancy characteristics. I really like ali s80's for this.

I didn't mention my stages because I thought we were in the basic forum... But we aren't! So, let's also mention side-mount. I don't dive that way, but some friends of mine do it and they like S80 stages. That's again for the buoyancy properties, I think.

As far as I understood, an S80 bottle completely filled is roughly 1kg negative, while almost empty is roughly 1kg positive.

 

[Divin'Papaw]

AL80s are very nice in warm water with minimal exposure protection. In those instances steels can be a bit too negative. They also have better corrosion resistance to salt.

I own 4 steel 100s and 2 AL80s. I use them based upon needed gas volume for a dive, exposure protection I’ll be wearing, and sometimes it just comes down to which ones are full at the moment!

If I always wore a thick wetsuit or a drysuit, the AL80s would never get used.

 

[James79]

Reasons I like steel:

Properly taken care of, they last forever (I have a converted Navy CO2 38 from 1944 still in service).

Better buoyancy characteristics (I mainly use old school 72s... About 5 lb negative full to neutral when empty).

Metallurgy. If you have a shop that is willing or have your own compressor, a deep dive into the difference between steel and aluminum will let you make your own decisions on "cave fills" (hint, overfilling aluminum's is a bad idea). I run my 72s at 2800 psi, making them a true 80 (compared to an AL80 at about 77cf) while still having a lower dry weight than an aluminum 80.

Regards the "too negative" concern, I've only run into it in freshwater so warm I didn't need a wetsuit... So I put on my 3mm shorty and left it unzipped. Problem solved.

Respectfully,

James

 

[tbone1004]

For personal use exclusively, why would one want to own an aluminum tank?

It is not lighter than a similarly sized steel tank to carry on dry land, it doesn't carry a hugely different amount of gas. The main difference, as far as I can tell, is the buoyancy properties. And steel tanks seem to be much more consistent in that respect and need less lead weight to compensate. A steel tank, on the other hand, is more prone to corrosion, especially in saltwater. Am I missing something?

For my personal local dives (90% of which are freshwater dives), there would be no reason to buy my own aluminum tanks, it seems. If I just take proper care of my own steel tanks (as I would with all my equipment), there is no disadvantage over aluminum tanks, is there? The other way around - I think the buoyancy change of an aluminum tank during the dive would be a disadvantage over steel tanks.

I own a dozen or so of them, but they're for stage/deco use. If I was diving shallow salt water I would use them because of corrosion.

Other than that it's just a cost thing.

Why o you think the buoyancy change of an AL tank would be a disadvantage over steel? The buoyancy change of an 80cf tank is the same whether it is made out of aluminum, steel, carbon fiber, whatever. It contains roughly 6.4/2kg of gas and the shift from full to empty is 2kg. The Al tanks typically go from slightly negative to slightly positive, but that is not perceptible in the water, only on land where you have to add ballast to account for it. Steel just has that ballast built in.