Steel vs Aluminum Manufacturing

[Compressor]

To all the great minds in this board:

Is making a steel tank more expensive than Al tanks? Why can't there be some more competition to make the price of steels come down?
Thank you

 

[BILLB]

Good question! Unfortunately I am afraid that steel tanks and the 2 to 3 times cost factor over AL tanks is here to stay.

Competition has made steel tanks less expensive. The latest HP tanks are cheaper and in my opinon better than the LP tanks. They still cost more than AL tanks.

AL tanks are made from an alloy that is rather easy for manufactures to use. AL is also cheaper than steel on the open market for all uses. Steel on the other hand is much harder to produce, and the alloy is more expensive.

It is like owning a Mercedes or a Chevolet. Steel will last forever if properly cared for. Aluminum has a life span of around 10 to 15 years. Although, AL tanks may have nothing wrong with them, most dive shops will not fill an AL tank that is older than ten to 15 years (unless the tank is theirs).

 

[Compressor]

Thank you for your post. Besides the alloy problem of the past, why is there no AL tanks that are 10 years old ? Metal fatigue??

And is it better to have a nitrox tank with Steel or Al when considering susceptibility to oxidation (rust)?

Thank you

 

[BILLB]

Unfortunately, AL tanks have gotton a bad rap. Modern AL tanks (most manufactured after 1990) are made from an alloy that has resolved the few rouge tank explosions. All of the "fatigued" AL tanks were made from an inferior alloy which was phased out around 1990. AL tanks "stretch" more than steel. for that reason alone the stress the metal is under makes the AL tank a bit weaker with every fill. Fortunately the number of full fulls is measured in the thousands! AL tanks are "lighter" in the water and you must don additional weights.

An HP 100 steel tank weights almost the same as an AL 80 but due to it stronger and thinner construction and owning to steel's density, it can hold more air and stay "heavier" in the water.

AL tanks do corrode but once this process has covered the walls it stops! Steel tanks may rust and a higher O2 mixture will accelerate the rusting. Steel tanks do not rust if water is not allowed to enter the tank. This means that every fill needs to be done using only the best of equipment and techniques. Steel tanks that have been completely emptied are the most proned to rusting. Steel tanks should be inspected visually often. If you dive more than 50 times a year then bi-annual inspections should be considered.

Steel tanks can be '"rolled" to remove corrosion but then the tank must be hydrostatically tested befire being placed into service again.