I have heard this before and me thinks it is one of the famous urban legends...I'm too lazy to check it out, and even if it isn't there, maybe we should submit it.
Tank oxidation contributes to death
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I have also heard of this happening before, in the 1970's. I'll try to find a reference.
Zinc cannot be added to the interior of the cylinder using current technology, to my knowledge. Also, yes-it is toxic; ever heard of zinc fume fever? It occurs to welders, and mimics the flu.
There was a try to line steel tanks in the early 1970s with a plastic liner, but it was found to accelerate the rusting process and abandoned. No steel tank is lined with anything, to my knowledge. To do so does accelerate the corrosion, and compromises the tank. The best way to protect is only to use currently hydroed, visually inspected tanks (visual inspection was begun to answer problems with steel tank corrosion).
SeaRat
Zinc cannot be added to the interior of the cylinder using current technology, to my knowledge. Also, yes-it is toxic; ever heard of zinc fume fever? It occurs to welders, and mimics the flu.
There was a try to line steel tanks in the early 1970s with a plastic liner, but it was found to accelerate the rusting process and abandoned. No steel tank is lined with anything, to my knowledge. To do so does accelerate the corrosion, and compromises the tank. The best way to protect is only to use currently hydroed, visually inspected tanks (visual inspection was begun to answer problems with steel tank corrosion).
SeaRat
OP
I think that LUBOLD8431 was trying to flame me, and not the deceased instructor. 
The problem that I see is that zinc oxide fever occurs from (relatively) extensive inhalation of zinc oxide fumes and is an irritation in the lungs (see any MSDS). Zinc oxide is also used in sunscreen. Zinc in solution is relatively harmless and wouldn't be found in a gas canister in any appreciable amount anyway. In fact, zinc galvinization is found in many potable water containers (where zinc ions would occur in the greatest concentration). Additionally, it forms an impervious coating (ie. does not flake off like rust and is insoluble in water), which, along with its electrochemical properties with respect to iron, is why it is used to prevent rust and a coating in this case could have prevented this incident entirely (if oxidation is truely the cause). The only place where I can see there being a problem with zinc oxide dust is tank threads, but this can be avoided by drilling threads after galvanization and washing away the dust. Even then, the presence of dust in the tank would not lead to excessive inhalation. High pO2's would have no effect on this. I do not see how any of this could be a problem. If there is a reason for tanks not to be galvanized, it is most likely price (most steel tanks are not galvanized, rather painted) and the fact that incidents like this do not occur unless tanks are grossly undermaintained (because tanks are relatively dry and oxidation cannot occur readily without water and any water is usually free from ions, which are necessary for oxidation to occur, except those from carbonic acid which is rather weak, slow, and in low concentration).
brandon
ps. LUBOLD8431, please check the validity of your assumptions before questioning other's integrity, even if the technical details of making gas canisters were required of any scuba instructor.
The problem that I see is that zinc oxide fever occurs from (relatively) extensive inhalation of zinc oxide fumes and is an irritation in the lungs (see any MSDS). Zinc oxide is also used in sunscreen. Zinc in solution is relatively harmless and wouldn't be found in a gas canister in any appreciable amount anyway. In fact, zinc galvinization is found in many potable water containers (where zinc ions would occur in the greatest concentration). Additionally, it forms an impervious coating (ie. does not flake off like rust and is insoluble in water), which, along with its electrochemical properties with respect to iron, is why it is used to prevent rust and a coating in this case could have prevented this incident entirely (if oxidation is truely the cause). The only place where I can see there being a problem with zinc oxide dust is tank threads, but this can be avoided by drilling threads after galvanization and washing away the dust. Even then, the presence of dust in the tank would not lead to excessive inhalation. High pO2's would have no effect on this. I do not see how any of this could be a problem. If there is a reason for tanks not to be galvanized, it is most likely price (most steel tanks are not galvanized, rather painted) and the fact that incidents like this do not occur unless tanks are grossly undermaintained (because tanks are relatively dry and oxidation cannot occur readily without water and any water is usually free from ions, which are necessary for oxidation to occur, except those from carbonic acid which is rather weak, slow, and in low concentration).
brandon
ps. LUBOLD8431, please check the validity of your assumptions before questioning other's integrity, even if the technical details of making gas canisters were required of any scuba instructor.
steeldiver
Contributor
The diver in question is responsible for his accident ,
NOT keeping your equipment in order ie.visuals and hydro,s
is criminal.especialy a dive concern that could allow the refilling and use of such equipment.
If you own your own gear have it serviced reguarlly,
or if diving nitrox have dedicated or reguarlly oxygen cleaned gear
you dont need specialised coatings inside steel cylinders
Howard
NOT keeping your equipment in order ie.visuals and hydro,s
is criminal.especialy a dive concern that could allow the refilling and use of such equipment.
If you own your own gear have it serviced reguarlly,
or if diving nitrox have dedicated or reguarlly oxygen cleaned gear
you dont need specialised coatings inside steel cylinders
Howard
The only "gross internal oxidation" case that I know to be true is one where a poorly maintained tank (steel 72), one that had been completely emptied in salt water and had managed to get some salt water in it, after several years sitting upright, corroded so badly that the bottom blew off the tank, sending the tank through the owner's garage roof. I have also heard of tanks stored horizontally that have had sidewall failures, but none so dramatic as the "through the roof" one. All these incidents say "you just can't 'rust' all the O2 out of the gas without a tank failure."
-----------------------
There may have been a fatality; there may have been less than 1% O2 in the tank; there may have been some rust in the tank - but if the story is true, my bet is that that tank had been used for, and started out with something other than air in it. Nitrogen, most likely, or if the guy was a homebrewer, helium.
Rick
DameDykker
Guest
You'r right. But he won't ever do this again! However, I think that the punisment was somewhat over the top for the offence.
I also agree that the chemistry doesn't add up. The cylinder which lost the bottom would have had severe pitting just at the surface of the saline water. This means that reallatively little material was rusted away. Postulating pits with a 2mm diameter, a inner diameter of 20 cm and a wall thickness of 8 mm the amount of metal turned into rust would in that case be some 5 cm3 in rough numbers assuming that half the wall thickness had to go before the tank failed. That is VERY far from the numbers NetDoctor gives for the O2 calculations. Something else must have happpend.
I remember a similar story from 20+ years ago, but I can't back it up with a specific incident. That said, and considering the source, I tend to believe it is in fact an actual event.
As for water in tanks, I have been in many places where some water in the tank is not unheard of. Yes of course it rusts or corrodes the tank and there are myriad potential consequences, but it does happen
As for water in tanks, I have been in many places where some water in the tank is not unheard of. Yes of course it rusts or corrodes the tank and there are myriad potential consequences, but it does happen
leadweight
Contributor
If oxidation had contributed to O2 depletion why did'nt the rust in the tank cause the diver's regulator to fail? That might have caused an out of air situation and response before the diver died from breathing a low O2 mixture.
"one of the two tanks the decedent had been
using contained less than 1 percent oxygen.
... Contributing factor/significant diagnosis included obesity."
What a crock of BS. You breathe "less than 1 percent oxygen" at recreational dive depths and you're dead!. To drag any other physiological attribute into the equation is assinine, pointless, irrelevant and smacks of an agenda other than truth.
In addition to that, I don't believe the story anyway.
E. itajara
using contained less than 1 percent oxygen.
... Contributing factor/significant diagnosis included obesity."
What a crock of BS. You breathe "less than 1 percent oxygen" at recreational dive depths and you're dead!. To drag any other physiological attribute into the equation is assinine, pointless, irrelevant and smacks of an agenda other than truth.
In addition to that, I don't believe the story anyway.
E. itajara
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