[scubazealous]

It would be cool, especially with advances in plastics you could layer over the steel to protect it from corrosion like what they do with soda cans.

For reference, a steel or aluminum SCUBA tank is usually filled to 3000psi and when I fill steel tanks I can hear and sometimes see the metal start to slightly balloon. This is normal because steel is not brittle but it is very strong.

There is a lot of rules put in place for safety though. A tank has to be visually checked by a professional every year and hydro statically tested every 5. The danger is any rust/corrosion weakening the metal and causing it to rupture. More often seen in aluminum tanks, which is one reason I prefer steel.

[marcosdumay]

Yes, in theory steel is not the best material for a high-pressure tank.

We use it because it's cheap and well tested. But we are probably better of with a layered combination of a few different materials. Steel may not even enter it.

[nradov]

Steel is the best material for certain scuba applications due more to buoyancy characteristics than strength. Firefighters typically use composite tanks for SCBA now, which are stronger but too buoyant for diving.

Layers of dissimilar materials are often problematic due to galvanic corrosion, different rates of heat expansion, and water intrusion between layers.