Steel Tank idea

[doos]

Has anyone ever heard of or tried a steel tank lined with aluminum? This would give the advantage of extra wieght (for us cold water divers), and the rust protection of the aluminum lining. I think the big concern would be the different coefficients of expansion for the metals. Aluminum expands at about double the rate of steel, but being a liner I wonder if that would be a concern.

Any thoughts?

 

[Wayward Son]

I don't think it's either needed nor a good idea. Any moisture that gets trapped under the AL can cause the steel to rust out, but you'd never see it until it was too late.

Properly maintained steel tanks should not be rusting on the inside, anyway. I have one I bought in 1978, making it over 27 years old. At the last VIP trace amounts of surface rust were observed in the bottom, not even enough to do anything about yet. It may need to be tumbled this year.

 

[phylo]

If you check out allot of the older tanks they had a vynal coating on the inside. The same idea you had except much cheaper and you dont have to worry about the expansion issues. The only problem is that once a crack developes and any moisture gets in there you cant see it rusting through your tank.. Vynal lined tanks dont pass visual any more, at least not at the shop I work with.


Phil

 

[DA Aquamaster]

Vinyl coating worked fine until the coating developed pin holes that would trap water against the side of the tank. Pits would then form before the problem became visible. The thing is that coating the tank solved a problem that did not really exist and created new problems in its place and an aluminum liner would be colving the same non existant problem.

If the air going into the tank is dry, you have no moisture and rusting will not occur. So prevention in terms of keeping water out of the tank by ensuring the tank is always stored with at least some pressure in it, that the air put in it is dry, and that no water is present on the valve or on the fill whip when the tank is filled (the most common way for water to enter a tank) is far more effective than a liner.

 

[steveann]

With the two metals, you would also have to worry about galvanic corrosion, which would eat your tank away far faster than normal oxidation would. I don't know which material would go first (I'd have to look at the materials' properties), but in an electrolytic solution (saltwater, even freshwater) galvanic corrosion would be your biggest worry. Of course, you could put something like zincs on the tanks, that might alleviate that problem. Although, then you'd have to change zincs out a lot.