Aluminum vs Steel

[boomo26]

What are the positive and negative for each?? I need to pick up two tanks, and aluminum is much cheaper, does it make a difference?? Also I am going to get nitrox certified, should this way into my decision?? Can you just switch the tank over to nitrox?? Sorry for the stupid questions, but I bought a dive computer about 3 months ago and have already sold it because I am switching to nitrox, lost some cash on the deal and do not want to make the same mistake again. Thanks for your help

Boomo

 

[RiverRat]

You already figured out steel is more expensive than AL. I'm assuming you plan on doing a bit of local diving to justify the expense? Steel has much better buoyancy characteristics than AL. Most AL tanks are positively buoyant at the end of the dive. So you need to offset with say 6# of lead. Steel tanks are "heavier" (less buoyant) at the beginning of the dive and are usually slightly negative or close to neutral at the end of the dive. This allows one to wear less lead, say 6# less (as you won't need to compensate for the extra buoyancy from an AL tank). Steel tanks can also rust inside in not properly maintained. I have PST HP100's (100 cu. ft.) and I love them. Any tank you get must be "nitrox cleaned" by a dive shop and should have a Nitrox sticker on it (to protect dumb *** divers from grabbing a nitrox filled tank and killing themselves) If you plan on drysuit diving someday you may want to seriously consider steel tanks to help offset the extra weight required for a drysuit. AL runs about $130.00 and Steel about $325.00.

 

[Tiefseetaucher]

To fill your tanks with nitrox they have to be O2 cleaned which they normally are when you buy them new. The advantage of steel is that they are heavier, which means you have to carry less weight with you. Normally they also contain more air compared to a similar sized AL tank because their walls are thinner. The advantage with AL is definatly the price. I had the same problem like you, but I got a good price on 2 steel 85's and I do not regret it.

 

[jepuskar]

Keep in mind that you do have to compensate for the weight of gas you are breathing no matter what kind of cylinder you use. As already pointed out though...steel usually ends up negative near empty, but aluminum is positive.

For example, I just bought a steel tank that starts off 9.5lbs negative filled to 3440 PSI..at 0 PSI it will be 2.5lbs negative. So on any normal dive with me its gonna be around 4 lbs negative at the end of the dive.

With my aluminum tank..it starts off at 1.5lbs negative and finishes around 4 positive or somewhere close.

Comparing the two tanks, both 80CF by the way...thats a difference of close to 8lbs. From +4 to -4 assuming I end the dive as planned. 8lbs I dont need to wear. There are other factors involved in this, but that is straight forward.

Here is the cool part...the steel tank is 6 inches shorter than the aluminum one, but holds the same volume of gas. It is also lighter to carry. It is comparable to a 63CF aluminum.

Now that is what I call HOT ACTION!!!

 

[spectrum]

To fill your tanks with nitrox they have to be O2 cleaned which they normally are when you buy them new. The advantage of steel is that they are heavier, which means you have to carry less weight with you. Normally they also contain more air compared to a similar sized AL tank because their walls are thinner. The advantage with AL is definatly the price. I had the same problem like you, but I got a good price on 2 steel 85's and I do not regret it.

The reason a steel tank lets you wear less weight is that they are less buoyant, not because they are heavier Though some may be heavier weight is irrelvant in setting dive weight.

The upshot is that some steel tanks particularly HP Steels may also weigh less topside making them more comfortable coming and going from the water.

http://home.gwi.net/~spectrum/scuba_al80.html

Pete

 

[Darnold9999]

Steel - your total weight that you carry to the dive sight can be less because the tank itself weighs less and because it is less boyant you have to carry less lead to compensate - a double bonus when diving dry. Also seems to be more choices re size. Aluminum - cheaper to buy. Depends on yur priorities is $ money more valuable to you than carrying weight.

At least this is my understanding at the moment. Would like to hear something on longevity and maintenance. However I suspect there is little difference.

 

[Rick Murchison]

Benefits of Aluminum:
1. Lower cost
2. Less susceptability to corrosion

Benefits of steel:
1. You carry less lead
2. Can actually weigh less than aluminum at the same capacity

There really isn't much more to consider. But that's enough that I much prefer steel.
Rick

 

[Wink69]

Do steel tanks tend to rust and how do you prevent them from rusting? Do you have to spend more to maintain them?

 

[jepuskar]

AFAIK just have a visual yearly and whenever your hydro is due have that done....I'm not aware of anything else special regarding steel, but someone please post if there is.

 

[Rick Murchison]

Do steel tanks tend to rust and how do you prevent them from rusting? Do you have to spend more to maintain them?

There are two basic rust issues with steel tanks.
(1) External rust - generally not a problem with hot-dipped galvanized steel tanks, but painted tanks can get rust under the paint and require a close watch on them to detect it early and take action to arrest it. Usually this isn't a problem if tanks are rinsed in fresh water after use and boots are removed.
(2) Internal rust - here's where you can get bit. Care must be taken to insure you don't get any water inside your tank. The most common cause of water intrusion is filling the tank without first blasting any residual water in the valve orifice clear. If your tank rode in on the boat in rough, windy conditions for example, there may be a drop or two of salt water that's collected in the valve. Just hooking the fill whip up and filling will blow those droplets inside the tank, and you'll get some nasty rust freckles inside. Do this enough and you can pit the tank's interior enough to ruin it. But just opening the valve for a second before filling will prevent this.
So yes, steel tanks require a little more care than aluminum, but not much more, and in my opinion their characteristics in the water make 'em well worth both the extra initial cost and the ongoing little bit of extra care.
Rick